Characterization of Asymptomatic Bacteriuria Escherichia coli Isolates in Search of Alternative Strains for Efficient Bacterial Interference against Uropathogens

PubMed Central

Stork, Christoph; Kovács, Beáta; Rózsai, Barnabás; Putze, Johannes; Kiel, Matthias; Dorn, Ágnes; Kovács, Judit; Melegh, Szilvia; Leimbach, Andreas; Kovács, Tamás; Schneider, György; Kerényi, Monika; Emödy, Levente; Dobrindt, Ulrich

2018-01-01

Asymptomatic bacterial colonization of the urinary bladder (asymptomatic bacteriuria, ABU) can prevent bladder colonization by uropathogens and thus symptomatic urinary tract infection (UTI). Deliberate bladder colonization with Escherichia coli ABU isolate 83972 has been shown to outcompete uropathogens and prevent symptomatic UTI by bacterial interference. Many ABU isolates evolved from uropathogenic ancestors and, although attenuated, may still be able to express virulence-associated factors. Our aim was to screen for efficient and safe candidate strains that could be used as alternatives to E. coli 83972 for preventive and therapeutic bladder colonization. To identify ABU E. coli strains with minimal virulence potential but maximal interference efficiency, we compared nine ABU isolates from diabetic patients regarding their virulence- and fitness-associated phenotypes in vitro, their virulence in a murine model of sepsis and their genome content. We identified strains in competitive growth experiments, which successfully interfere with colonization of ABU isolate 83972 or uropathogenic E. coli strain 536. Six isolates were able to outcompete E. coli 83972 and two of them also outcompeted UPEC 536 during growth in urine. Superior competitiveness was not simply a result of better growth abilities in urine, but seems also to involve expression of antagonistic factors. Competitiveness in urine did not correlate with the prevalence of determinants coding for adhesins, iron uptake, toxins, and antagonistic factors. Three ABU strains (isolates 61, 106, and 123) with superior competitiveness relative to ABU model strain 83972 display low in vivo virulence in a murine sepsis model, and susceptibility to antibiotics. They belong to different phylogroups and differ in the presence of ExPEC virulence- and fitness-associated genes. Importantly, they all lack marked cytotoxic activity and exhibit a high LD50 value in the sepsis model. These strains represent promising candidates for a more detailed assessment of relevant fitness traits in urine and their suitability for therapeutic bladder colonization. PMID:29491858

L-fucose utilization provides Campylobacter jejuni with a competitive advantage.

PubMed

Stahl, Martin; Friis, Lorna M; Nothaft, Harald; Liu, Xin; Li, Jianjun; Szymanski, Christine M; Stintzi, Alain

2011-04-26

Campylobacter jejuni is a prevalent gastrointestinal pathogen in humans and a common commensal of poultry. When colonizing its hosts, C. jejuni comes into contact with intestinal carbohydrates, including L-fucose, released from mucin glycoproteins. Several strains of C. jejuni possess a genomic island (cj0480c-cj0490) that is up-regulated in the presence of both L-fucose and mucin and allows for the utilization of L-fucose as a substrate for growth. Strains possessing this genomic island show increased growth in the presence of L-fucose and mutation of cj0481, cj0486, and cj0487 results in the loss of the ability to grow on this substrate. Furthermore, mutants in the putative fucose permease (cj0486) are deficient in fucose uptake and demonstrate a competitive disadvantage when colonizing the piglet model of human disease, which is not paralleled in the colonization of poultry. This identifies a previously unrecorded metabolic pathway in select strains of C. jejuni associated with a virulent lifestyle.

l-Fucose utilization provides Campylobacter jejuni with a competitive advantage

PubMed Central

Stahl, Martin; Friis, Lorna M.; Nothaft, Harald; Liu, Xin; Li, Jianjun; Szymanski, Christine M.; Stintzi, Alain

2011-01-01

Campylobacter jejuni is a prevalent gastrointestinal pathogen in humans and a common commensal of poultry. When colonizing its hosts, C. jejuni comes into contact with intestinal carbohydrates, including l-fucose, released from mucin glycoproteins. Several strains of C. jejuni possess a genomic island (cj0480c–cj0490) that is up-regulated in the presence of both l-fucose and mucin and allows for the utilization of l-fucose as a substrate for growth. Strains possessing this genomic island show increased growth in the presence of l-fucose and mutation of cj0481, cj0486, and cj0487 results in the loss of the ability to grow on this substrate. Furthermore, mutants in the putative fucose permease (cj0486) are deficient in fucose uptake and demonstrate a competitive disadvantage when colonizing the piglet model of human disease, which is not paralleled in the colonization of poultry. This identifies a previously unrecorded metabolic pathway in select strains of C. jejuni associated with a virulent lifestyle. PMID:21482772

Transient dynamics of invasive competition: barred owls, spotted owls, habitat, and the demons of competition present.

PubMed

Dugger, Katie M; Anthony, Robert G; Andrews, Lawrence S

2011-10-01

The recent range expansion of Barred Owls (Strix varia) into the Pacific Northwest, where the species now co-occurs with the endemic Northern Spotted Owl (Strix occidentalis caurina), resulted in a unique opportunity to investigate potential competition between two congeneric, previously allopatric species. The primary criticism of early competition research was the use of current species' distribution patterns to infer past processes; however, the recent expansion of the Barred Owl and the ability to model the processes that result in site occupancy (i.e., colonization and extinction) allowed us to address the competitive process directly rather than inferring past processes through current patterns. The purpose of our study was to determine whether Barred Owls had any negative effects on occupancy dynamics of nesting territories by Northern Spotted Owls and how these effects were influenced by habitat characteristics of Spotted Owl territories. We used single-species, multi-season occupancy models and covariates quantifying Barred Owl detections and habitat characteristics to model extinction and colonization rates of Spotted Owl pairs in southern Oregon, USA. We observed a strong, negative association between Barred Owl detections and colonization rates and a strong positive effect of Barred Owl detections on extinction rates of Spotted Owls. We observed increased extinction rates in response to decreased amounts of old forest at the territory core and higher colonization rates when old-forest habitat was less fragmented. Annual site occupancy for pairs reflected the strong effects of Barred Owls on occupancy dynamics with much lower occupancy rates predicted for territories where Barred Owls were detected. The strong Barred Owl and habitat effects on occupancy dynamics of Spotted Owls provided evidence of interference competition between the species. These effects increase the importance of conserving large amounts of contiguous, old-forest habitat to maintain Northern Spotted Owls in the landscape.

Tomato seed and root exudate sugars: composition, utilization by Pseudomonas biocontrol strains and role in rhizosphere colonization.

PubMed

Lugtenberg, B J; Kravchenko, L V; Simons, M

1999-10-01

The role of tomato seed and root exudate sugars as nutrients for Pseudomonas biocontrol bacteria was studied. To this end, the major exudate sugars of tomato seeds, seedlings and roots were identified and quantified using high-performance liquid chromatographic (HPLC) analysis. Glucose, fructose and maltose were present in all studied growth stages of the plant, but the ratios of these sugars were strongly dependent on the developmental stage. In order to study the putative role of exudate sugar utilization in rhizosphere colonization, two approaches were adopted. First, after co-inoculation on germinated tomato seeds, the root-colonizing ability of the efficient root-colonizing P. fluorescens strain WCS365 in a gnotobiotic quartz sand-plant nutrient solution system was compared with that of other Pseudomonas biocontrol strains. No correlation was observed between the colonizing ability of a strain and its ability to use the major exudate sugars as the only carbon and energy source. Secondly, a Tn5lacZ mutant of P. fluorescens strain WCS365, strain PCL1083, was isolated, which is impaired in its ability to grow on simple sugars, including those found in exudate. The mutation appeared to reside in zwf, which encodes glucose-6-phosphate dehydrogenase. The mutant grows as well as the parental strain on other media, including tomato root exudate. After inoculation of germinated sterile tomato seeds, the mutant cells reached the same population levels at the root tip as the wild-type strain, both alone and in competition, indicating that the ability to use exudate sugars does not play a major role in tomato root colonization, despite the fact that sugars have often been reported to represent the major exudate carbon source. This conclusion is supported by the observation that the growth of mutant PCL1083 in vitro is inhibited by glucose, a major exudate sugar, at a concentration of 0.001%, which indicates that the glucose concentration in the tomato rhizosphere is very low.

Host-Derived Sialic Acids Are an Important Nutrient Source Required for Optimal Bacterial Fitness In Vivo

PubMed Central

McDonald, Nathan D.; Lubin, Jean-Bernard; Chowdhury, Nityananda

2016-01-01

ABSTRACT A major challenge facing bacterial intestinal pathogens is competition for nutrient sources with the host microbiota. Vibrio cholerae is an intestinal pathogen that causes cholera, which affects millions each year; however, our knowledge of its nutritional requirements in the intestinal milieu is limited. In this study, we demonstrated that V. cholerae can grow efficiently on intestinal mucus and its component sialic acids and that a tripartite ATP-independent periplasmic SiaPQM strain, transporter-deficient mutant NC1777, was attenuated for colonization using a streptomycin-pretreated adult mouse model. In in vivo competition assays, NC1777 was significantly outcompeted for up to 3 days postinfection. NC1777 was also significantly outcompeted in in vitro competition assays in M9 minimal medium supplemented with intestinal mucus, indicating that sialic acid uptake is essential for fitness. Phylogenetic analyses demonstrated that the ability to utilize sialic acid was distributed among 452 bacterial species from eight phyla. The majority of species belonged to four phyla, Actinobacteria (members of Actinobacillus, Corynebacterium, Mycoplasma, and Streptomyces), Bacteroidetes (mainly Bacteroides, Capnocytophaga, and Prevotella), Firmicutes (members of Streptococcus, Staphylococcus, Clostridium, and Lactobacillus), and Proteobacteria (including Escherichia, Shigella, Salmonella, Citrobacter, Haemophilus, Klebsiella, Pasteurella, Photobacterium, Vibrio, and Yersinia species), mostly commensals and/or pathogens. Overall, our data demonstrate that the ability to take up host-derived sugars and sialic acid specifically allows V. cholerae a competitive advantage in intestinal colonization and that this is a trait that is sporadic in its occurrence and phylogenetic distribution and ancestral in some genera but horizontally acquired in others. PMID:27073099

Inhibition of fungal colonization by Pseudoalteromonas tunicata provides a competitive advantage during surface colonization.

PubMed

Franks, A; Egan, S; Holmström, C; James, S; Lappin-Scott, H; Kjelleberg, S

2006-09-01

The marine epiphytic bacterium Pseudoalteromonas tunicata produces a range of extracellular secondary metabolites that inhibit an array of common fouling organisms, including fungi. In this study, we test the hypothesis that the ability to inhibit fungi provides P. tunicata with an advantage during colonization of a surface. Studies on a transposon-generated antifungal-deficient mutant of P. tunicata, FM3, indicated that a long-chain fatty acid-coenzyme A ligase is involved in the production of a broad-range antifungal compound by P. tunicata. Flow cell experiments demonstrated that production of an antifungal compound provided P. tunicata with a competitive advantage against a marine yeast isolate during surface colonization. This compound enabled P. tunicata to disrupt an already established fungal biofilm by decreasing the number of yeast cells attached to the surface by 66% +/- 9%. For in vivo experiments, the wild-type and FM3 strains of P. tunicata were used to inoculate the surface of the green alga Ulva australis. Double-gradient denaturing gradient gel electrophoresis analysis revealed that after 48 h, the wild-type P. tunicata had outcompeted the surface-associated fungal community, whereas the antifungal-deficient mutant had no effect on the fungal community. Our data suggest that P. tunicata is an effective competitor against fungal surface communities in the marine environment.

Competition for space during bacterial colonization of a surface.

PubMed

Lloyd, Diarmuid P; Allen, Rosalind J

2015-09-06

Competition for space is ubiquitous in the ecology of both microorganisms and macro-organisms. We introduce a bacterial model system in which the factors influencing competition for space during colonization of an initially empty habitat can be tracked directly. Using fluorescence microscopy, we follow the fate of individual Escherichia coli bacterial cell lineages as they undergo expansion competition (the race to be the first to colonize a previously empty territory), and as they later compete at boundaries between clonal territories. Our experiments are complemented by computer simulations of a lattice-based model. We find that both expansion competition, manifested as differences in individual cell lag times, and boundary competition, manifested as effects of neighbour cell geometry, can play a role in colonization success, particularly when lineages expand exponentially. This work provides a baseline for investigating how ecological interactions affect colonization of space by bacterial populations, and highlights the potential of bacterial model systems for the testing and development of ecological theory. © 2015 The Authors.

Competition for space during bacterial colonization of a surface

PubMed Central

Lloyd, Diarmuid P.; Allen, Rosalind J.

2015-01-01

Competition for space is ubiquitous in the ecology of both microorganisms and macro-organisms. We introduce a bacterial model system in which the factors influencing competition for space during colonization of an initially empty habitat can be tracked directly. Using fluorescence microscopy, we follow the fate of individual Escherichia coli bacterial cell lineages as they undergo expansion competition (the race to be the first to colonize a previously empty territory), and as they later compete at boundaries between clonal territories. Our experiments are complemented by computer simulations of a lattice-based model. We find that both expansion competition, manifested as differences in individual cell lag times, and boundary competition, manifested as effects of neighbour cell geometry, can play a role in colonization success, particularly when lineages expand exponentially. This work provides a baseline for investigating how ecological interactions affect colonization of space by bacterial populations, and highlights the potential of bacterial model systems for the testing and development of ecological theory. PMID:26333814

The role of competition – colonization tradeoffs and spatial heterogeneity in promoting trematode coexistence

USGS Publications Warehouse

Mordecai, Erin A.; Jaramillo, Alejandra G.; Ashford, Jacob E.; Hechinger, Ryan F.; Lafferty, Kevin D.

2016-01-01

Competition – colonization tradeoffs occur in many systems, and theory predicts that they can strongly promote species coexistence. However, there is little empirical evidence that observed competition – colonization tradeoffs are strong enough to maintain diversity in natural systems. This is due in part to a mismatch between theoretical assumptions and biological reality in some systems. We tested whether a competition – colonization tradeoff explains how a diverse trematode guild coexists in California horn snail populations, a system that meets the requisite criteria for the tradeoff to promote coexistence. A field experiment showed that subordinate trematode species tended to have higher colonization rates than dominant species. This tradeoff promoted coexistence in parameterized models but did not fully explain trematode diversity and abundance, suggesting a role of additional diversity maintenance mechanisms. Spatial heterogeneity is an alternative way to promote coexistence if it isolates competing species. We used scale transition theory to expand the competition – colonization tradeoff model to include spatial variation. The parameterized model showed that spatial variation in trematode prevalence did not isolate most species sufficiently to explain the overall high diversity, but could benefit some rare species. Together, the results suggest that several mechanisms combine to maintain diversity, even when a competition – colonization tradeoff occurs.

Gastrointestinal Tract Colonization Dynamics by Different Enterococcus faecium Clades

PubMed Central

Montealegre, Maria Camila; Singh, Kavindra V.; Murray, Barbara E.

2016-01-01

Colonization of the gastrointestinal tract (GIT) generally precedes infection with antibiotic-resistant Enterococcus faecium. We used a mouse GIT colonization model to test differences in the colonization levels by strains from different E. faecium lineages: clade B, part of the healthy human microbiota; subclade A1, associated with infections; and subclade A2, primarily associated with animals. After mono-inoculation, there was no significant difference in colonization (measured as the geometric mean number of colony-forming units per gram) by the E. faecium clades at any time point (P > .05). However, in competition assays, with 6 of the 7 pairs, clade B strains outcompeted clade A strains in their ability to persist in the GIT; this difference was significant in some pairs by day 2 and in all pairs by day 14 (P < .0008–.0283). This observation may explain the predominance of clade B in the community and why antibiotic-resistant hospital-associated E. faecium are often replaced by clade B strains once patients leave the hospital. PMID:26671890

The Candida albicans Pho4 Transcription Factor Mediates Susceptibility to Stress and Influences Fitness in a Mouse Commensalism Model

PubMed Central

Urrialde, Verónica; Prieto, Daniel; Pla, Jesús; Alonso-Monge, Rebeca

2016-01-01

The Pho4 transcription factor is required for growth under low environmental phosphate concentrations in Saccharomyces cerevisiae. A characterization of Candida albicans pho4 mutants revealed that these cells are more susceptible to both osmotic and oxidative stress and that this effect is diminished in the presence of 5% CO2 or anaerobiosis, reflecting the relevance of oxygen metabolism in the Pho4-mediated response. A pho4 mutant was as virulent as wild type strain when assayed in the Galleria mellonella infection model and was even more resistant to murine macrophages in ex vivo killing assays. The lack of Pho4 neither impairs the ability to colonize the murine gut nor alters the localization in the gastrointestinal tract. However, we found that Pho4 influenced the colonization of C. albicans in the mouse gut in competition assays; pho4 mutants were unable to attain high colonization levels when inoculated simultaneously with an isogenic wild type strain. Moreover, pho4 mutants displayed a reduced adherence to the intestinal mucosa in a competitive ex vivo assays with wild type cells. In vitro competitive assays also revealed defects in fitness for this mutant compared to the wild type strain. Thus, Pho4, a transcription factor involved in phosphate metabolism, is required for adaptation to stress and fitness in C. albicans. PMID:27458452

Competitive interactions are mediated in a sex-specific manner by arbuscular mycorrhiza in Antennaria dioica.

PubMed

Varga, S; Vega-Frutis, R; Kytöviita, M-M

2017-03-01

Plants usually interact with other plants, and the outcome of such interaction ranges from facilitation to competition depending on the identity of the plants, including their sexual expression. Arbuscular mycorrhizal (AM) fungi have been shown to modify competitive interactions in plants. However, few studies have evaluated how AM fungi influence plant intraspecific and interspecific interactions in dioecious species. The competitive abilities of female and male plants of Antennaria dioica were examined in a greenhouse experiment. Females and males were grown in the following competitive settings: (i) without competition, (ii) with intrasexual competition, (iii) with intersexual competition, and (iv) with interspecific competition by Hieracium pilosella - a plant with similar characteristics to A. dioica. Half of the pots were grown with Claroideoglomus claroideum, an AM fungus isolated from the same habitat as the plant material. We evaluated plant survival, growth, flowering phenology, and production of AM fungal structures. Plant survival was unaffected by competition or AM fungi. Competition and the presence of AM fungi reduced plant biomass. However, the sexes responded differently to the interaction between fungal and competition treatments. Both intra- and interspecific competition results were sex-specific, and in general, female performance was reduced by AM colonization. Plant competition or sex did not affect the intraradical structures, extraradical hyphae, or spore production of the AM fungus. These findings suggest that plant sexual differences affect fundamental processes such as competitive ability and symbiotic relationships with AM fungi. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

Beyond the competition-colonization trade-off: linking multiple trait response to disturbance characteristics.

PubMed

Seifan, Merav; Seifan, Tal; Schiffers, Katja; Jeltsch, Florian; Tielbörger, Katja

2013-02-01

Disturbances' role in shaping communities is well documented but highly disputed. We suggest replacing the overused two-trait trade-off approach with a functional group scheme, constructed from combinations of four key traits that represent four classes of species' responses to disturbances. Using model results and field observations from sites affected by two highly different disturbances, we demonstrated that popular dichotomous trade-offs are not sufficient to explain community dynamics, even if some emerge under certain conditions. Without disturbances, competition was only sufficient to predict species survival but not relative success, which required some escape mechanism (e.g., long-term dormancy). With highly predictable and large-scale disturbances, successful species showed a combination of high individual tolerance to disturbance and, more surprisingly, high competitive ability. When disturbances were less predictable, high individual tolerance and long-term seed dormancy were favored, due to higher environmental uncertainty. Our study demonstrates that theories relying on a small number of predefined trade-offs among traits (e.g., competition-colonization trade-off) may lead to unrealistic results. We suggest that the understanding of disturbance-community relationships can be significantly improved by employing sets of relevant trait assemblies instead of the currently common approach in which trade-offs are assumed in advance.

An Invasive Plant Promotes Its Arbuscular Mycorrhizal Symbioses and Competitiveness through Its Secondary Metabolites: Indirect Evidence from Activated Carbon

PubMed Central

Yuan, Yongge; Tang, Jianjun; Leng, Dong; Hu, Shuijin; Yong, Jean W. H.; Chen, Xin

2014-01-01

Secondary metabolites released by invasive plants can increase their competitive ability by affecting native plants, herbivores, and pathogens at the invaded land. Whether these secondary metabolites affect the invasive plant itself, directly or indirectly through microorganisms, however, has not been well documented. Here we tested whether activated carbon (AC), a well-known absorbent for secondary metabolites, affect arbuscular mycorrhizal (AM) symbioses and competitive ability in an invasive plant. We conducted three experiments (experiments 1–3) with the invasive forb Solidago canadensis and the native Kummerowia striata. Experiment 1 determined whether AC altered soil properties, levels of the main secondary metabolites in the soil, plant growth, and AMF communities associated with S. canadensis and K. striata. Experiment 2 determined whether AC affected colonization of S. canadensis by five AMF, which were added to sterilized soil. Experiment 3 determined the competitive ability of S. canadensis in the presence and absence of AMF and AC. In experiment 1, AC greatly decreased the concentrations of the main secondary metabolites in soil, and the changes in concentrations were closely related with the changes of AMF in S. canadensis roots. In experiment 2, AC inhibited the AMF Glomus versiforme and G. geosporum but promoted G. mosseae and G. diaphanum in the soil and also in S. canadensis roots. In experiment 3, AC reduced S. canadensis competitive ability in the presence but not in the absence of AMF. Our results provided indirect evidence that the secondary metabolites (which can be absorbed by AC) of the invasive plant S. canadensis may promote S. canadensis competitiveness by enhancing its own AMF symbionts. PMID:24817325

An invasive plant promotes its arbuscular mycorrhizal symbioses and competitiveness through its secondary metabolites: indirect evidence from activated carbon.

PubMed

Yuan, Yongge; Tang, Jianjun; Leng, Dong; Hu, Shuijin; Yong, Jean W H; Chen, Xin

2014-01-01

Secondary metabolites released by invasive plants can increase their competitive ability by affecting native plants, herbivores, and pathogens at the invaded land. Whether these secondary metabolites affect the invasive plant itself, directly or indirectly through microorganisms, however, has not been well documented. Here we tested whether activated carbon (AC), a well-known absorbent for secondary metabolites, affect arbuscular mycorrhizal (AM) symbioses and competitive ability in an invasive plant. We conducted three experiments (experiments 1-3) with the invasive forb Solidago canadensis and the native Kummerowia striata. Experiment 1 determined whether AC altered soil properties, levels of the main secondary metabolites in the soil, plant growth, and AMF communities associated with S. canadensis and K. striata. Experiment 2 determined whether AC affected colonization of S. canadensis by five AMF, which were added to sterilized soil. Experiment 3 determined the competitive ability of S. canadensis in the presence and absence of AMF and AC. In experiment 1, AC greatly decreased the concentrations of the main secondary metabolites in soil, and the changes in concentrations were closely related with the changes of AMF in S. canadensis roots. In experiment 2, AC inhibited the AMF Glomus versiforme and G. geosporum but promoted G. mosseae and G. diaphanum in the soil and also in S. canadensis roots. In experiment 3, AC reduced S. canadensis competitive ability in the presence but not in the absence of AMF. Our results provided indirect evidence that the secondary metabolites (which can be absorbed by AC) of the invasive plant S. canadensis may promote S. canadensis competitiveness by enhancing its own AMF symbionts.

Competition-Colonization Trade-Offs, Competitive Uncertainty, and the Evolutionary Assembly of Species

PubMed Central

Pillai, Pradeep; Guichard, Frédéric

2012-01-01

We utilize a standard competition-colonization metapopulation model in order to study the evolutionary assembly of species. Based on earlier work showing how models assuming strict competitive hierarchies will likely lead to runaway evolution and self-extinction for all species, we adopt a continuous competition function that allows for levels of uncertainty in the outcome of competition. We then, by extending the standard patch-dynamic metapopulation model in order to include evolutionary dynamics, allow for the coevolution of species into stable communities composed of species with distinct limiting similarities. Runaway evolution towards stochastic extinction then becomes a limiting case controlled by the level of competitive uncertainty. We demonstrate how intermediate competitive uncertainty maximizes the equilibrium species richness as well as maximizes the adaptive radiation and self-assembly of species under adaptive dynamics with mutations of non-negligible size. By reconciling competition-colonization tradeoff theory with co-evolutionary dynamics, our results reveal the importance of intermediate levels of competitive uncertainty for the evolutionary assembly of species. PMID:22448253

Porphyromonas gingivalis displays a competitive advantage over Aggregatibacter actinomycetemcomitans in co-cultured biofilm.

PubMed

Takasaki, K; Fujise, O; Miura, M; Hamachi, T; Maeda, K

2013-06-01

Biofilm formation occurs through the events of cooperative growth and competitive survival among multiple species. Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans are important periodontal pathogens. The aim of this study was to demonstrate competitive or cooperative interactions between these two species in co-cultured biofilm. P. gingivalis strains and gingipain mutants were cultured with or without A. actinomycetemcomitans. Biofilms formed on glass surfaces were analyzed by crystal violet staining and colony counting. Preformed A. actinomycetemcomitans biofilms were treated with P. gingivalis culture supernatants. Growth and proteolytic activities of gingipains were also determined. Monocultured P. gingivalis strains exhibited a range of biofilm-formation abilities and proteolytic activities. The ATCC33277 strain, noted for its high biofilm-formation ability and proteolytic activity, was found to be dominant in biofilm co-cultured with A. actinomycetemcomitans. In a time-resolved assay, A. actinomycetemcomitans was primarily the dominant colonizer on a glass surface and subsequently detached in the presence of increasing numbers of ATCC33277. Detachment of preformed A. actinomycetemcomitans biofilm was observed by incubation with culture supernatants from highly proteolytic strains. These results suggest that P. gingivalis possesses a competitive advantage over A. actinomycetemcomitans. As the required biofilm-formation abilities and proteolytic activities vary among P. gingivalis strains, the diversity of the competitive advantage is likely to affect disease recurrence during periodontal maintenance. © 2012 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The evolution of dispersal in a Levins' type metapopulation model.

PubMed

Jansen, Vincent A A; Vitalis, Renaud

2007-10-01

We study the evolution of the dispersal rate in a metapopulation model with extinction and colonization dynamics, akin to the model as originally described by Levins. To do so we extend the metapopulation model with a description of the within patch dynamics. By means of a separation of time scales we analytically derive a fitness expression from first principles for this model. The fitness function can be written as an inclusive fitness equation (Hamilton's rule). By recasting this equation in a form that emphasizes the effects of competition we show the effect of the local competition and the local population size on the evolution of dispersal. We find that the evolution of dispersal cannot be easily interpreted in terms of avoidance of kin competition, but rather that increased dispersal reduces the competitive ability. Our model also yields a testable prediction in term of relatedness and life-history parameters.

Fecundity of trees and the colonization-competition hypothesis

Treesearch

James S. Clark; Shannon LaDeau; Ines Ibanez

2004-01-01

Colonization-competition trade-offs represent a stabilizing mechanism that is thought to maintain diversity of forest trees. If so, then early-successional species should benefit from high capacity to colonize new sites, and late-successional species should be good competitors. Tests of this hypothesis in forests have been precluded by an inability to estimate...

Host-Derived Sialic Acids Are an Important Nutrient Source Required for Optimal Bacterial Fitness In Vivo.

PubMed

McDonald, Nathan D; Lubin, Jean-Bernard; Chowdhury, Nityananda; Boyd, E Fidelma

2016-04-12

A major challenge facing bacterial intestinal pathogens is competition for nutrient sources with the host microbiota.Vibrio cholerae is an intestinal pathogen that causes cholera, which affects millions each year; however, our knowledge of its nutritional requirements in the intestinal milieu is limited. In this study, we demonstrated that V. cholerae can grow efficiently on intestinal mucus and its component sialic acids and that a tripartite ATP-independent periplasmic SiaPQM strain, transporter-deficient mutant NC1777, was attenuated for colonization using a streptomycin-pretreated adult mouse model. In in vivo competition assays, NC1777 was significantly outcompeted for up to 3 days postinfection. NC1777 was also significantly outcompeted in in vitro competition assays in M9 minimal medium supplemented with intestinal mucus, indicating that sialic acid uptake is essential for fitness. Phylogenetic analyses demonstrated that the ability to utilize sialic acid was distributed among 452 bacterial species from eight phyla. The majority of species belonged to four phyla, Actinobacteria (members of Actinobacillus, Corynebacterium, Mycoplasma, and Streptomyces), Bacteroidetes (mainly Bacteroides, Capnocytophaga, and Prevotella), Firmicutes (members of Streptococcus, Staphylococcus, Clostridium, and Lactobacillus), and Proteobacteria (including Escherichia, Shigella, Salmonella, Citrobacter, Haemophilus, Klebsiella, Pasteurella, Photobacterium, Vibrio, and Yersinia species), mostly commensals and/or pathogens. Overall, our data demonstrate that the ability to take up host-derived sugars and sialic acid specifically allows V. cholerae a competitive advantage in intestinal colonization and that this is a trait that is sporadic in its occurrence and phylogenetic distribution and ancestral in some genera but horizontally acquired in others. Sialic acids are nine carbon amino sugars that are abundant on all mucous surfaces. The deadly human pathogen Vibrio cholerae contains the genes required for scavenging, transport, and catabolism of sialic acid. We determined that the V. cholerae SiaPQM transporter is essential for sialic acid transport and that this trait allows the bacterium to outcompete noncatabolizers in vivo. We also showed that the ability to take up and catabolize sialic acid is prevalent among both commensals and pathogens that colonize the oral cavity and the respiratory, intestinal, and urogenital tracts. Phylogenetic analysis determined that the sialic acid catabolism phenotype is ancestral in some genera such as Yersinia, Streptococcus, and Staphylococcus and is acquired by horizontal gene transfer in others such as Vibrio, Aeromonas, and Klebsiella. The data demonstrate that this trait has evolved multiple times in different lineages, indicating the importance of specialized metabolism to niche expansion. Copyright © 2016 McDonald et al.

Methylotrophic metabolism is advantageous for Methylobacterium extorquens during colonization of Medicago truncatula under competitive conditions.

PubMed

Sy, Abdoulaye; Timmers, Antonius C J; Knief, Claudia; Vorholt, Julia A

2005-11-01

Facultative methylotrophic bacteria of the genus Methylobacterium are commonly found in association with plants. Inoculation experiments were performed to study the importance of methylotrophic metabolism for colonization of the model legume Medicago truncatula. Competition experiments with Methylobacterium extorquens wild-type strain AM1 and methylotrophy mutants revealed that the ability to use methanol as a carbon and energy source provides a selective advantage during colonization of M. truncatula. Differences in the fitness of mutants defective in different stages of methylotrophic metabolism were found; whereas approximately 25% of the mutant incapable of oxidizing methanol to formaldehyde (deficient in methanol dehydrogenase) was recovered, 10% or less of the mutants incapable of oxidizing formaldehyde to CO2 (defective in biosynthesis of the cofactor tetrahydromethanopterin) was recovered. Interestingly, impaired fitness of the mutant strains compared with the wild type was found on leaves and roots. Single-inoculation experiments showed, however, that mutants with defects in methylotrophy were capable of plant colonization at the wild-type level, indicating that methanol is not the only carbon source that is accessible to Methylobacterium while it is associated with plants. Fluorescence microscopy with a green fluorescent protein-labeled derivative of M. extorquens AM1 revealed that the majority of the bacterial cells on leaves were on the surface and that the cells were most abundant on the lower, abaxial side. However, bacterial cells were also found in the intercellular spaces inside the leaves, especially in the epidermal cell layer and immediately underneath this layer.

Trade-off between competition and facilitation defines gap colonization in mountains

PubMed Central

Lembrechts, Jonas J.; Milbau, Ann; Nijs, Ivan

2015-01-01

Recent experimental observations show that gap colonization in small-stature (e.g. grassland and dwarf shrubs) vegetation strongly depends on the abiotic conditions within them. At the same time, within-gap variation in biotic interactions such as competition and facilitation, caused by distance to the gap edge, would affect colonizer performance, but a theoretical framework to explore such patterns is missing. Here, we model how competition, facilitation and environmental conditions together determine the small-scale patterns of gap colonization along a cold gradient in mountains, by simulating colonizer survival in gaps of various sizes. Our model adds another dimension to the known effects of biotic interactions along a stress gradient by focussing on the trade-off between competition and facilitation in the within-gap environment. We show that this trade-off defines a peak in colonizer survival at a specific distance from the gap edge, which progressively shifts closer to the edge as the environment gets colder, ultimately leaving a large fraction of gaps unsuitable for colonization in facilitation-dominated systems. This is reinforced when vegetation size and temperature amelioration are manipulated simultaneously with temperature in order to simulate an elevational gradient more realistically. Interestingly, all other conditions being equal, the magnitude of the realized survival peak was always lower in large than in small gaps, making large gaps harder to colonize. The model is relevant to predict effects of non-native plant invasions and climate warming on colonization processes in mountains. PMID:26558706

Role of Mrx Fimbriae of Xenorhabdus nematophila in Competitive Colonization of the Nematode Host ▿

PubMed Central

Snyder, Holly; He, Hongjun; Owen, Heather; Hanna, Chris; Forst, Steven

2011-01-01

Xenorhabdus nematophila engages in mutualistic associations with the infective juvenile (IJ) stage of specific entomopathogenic nematodes. Mannose-resistant (Mrx) chaperone-usher-type fimbriae are produced when the bacteria are grown on nutrient broth agar (NB agar). The role of Mrx fimbriae in the colonization of the nematode host has remained unresolved. We show that X. nematophila grown on LB agar produced flagella rather than fimbriae. IJs propagated on X. nematophila grown on LB agar were colonized to the same extent as those propagated on NB agar. Further, progeny IJs were normally colonized by mrx mutant strains that lacked fimbriae both when bacteria were grown on NB agar and when coinjected into the insect host with aposymbiotic nematodes. The mrx strains were not competitively defective for colonization when grown in the presence of wild-type cells on NB agar. In addition, a phenotypic variant strain that lacked fimbriae colonized as well as the wild-type strain. In contrast, the mrx strains displayed a competitive colonization defect in vivo. IJ progeny obtained from insects injected with comixtures of nematodes carrying either the wild-type or the mrx strain were colonized almost exclusively with the wild-type strain. Likewise, when insects were coinjected with aposymbiotic IJs together with a comixture of the wild-type and mrx strains, the resulting IJ progeny were predominantly colonized with the wild-type strain. These results revealed that Mrx fimbriae confer a competitive advantage during colonization in vivo and provide new insights into the role of chaperone-usher fimbriae in the life cycle of X. nematophila. PMID:21856828

Disturbance facilitates the coexistence of antagonistic ecosystem engineers in California estuaries.

PubMed

Castorani, Max C N; Hovel, Kevin A; Williams, Susan L; Baskett, Marissa L

2014-08-01

Ecological theory predicts that interactions between antagonistic ecosystem engineers can lead to local competitive exclusion, but disturbance can facilitate broader coexistence. However, few empirical studies have tested the potential for disturbance to mediate competition between engineers. We examined the capacity for disturbance and habitat modification to explain the disjunct distributions of two benthic ecosystem engineers, eelgrass Zostera marina and the burrowing ghost shrimp Neotrypaea californiensis, in two California estuaries. Sediment sampling in eelgrass and ghost shrimp patches revealed that ghost shrimp change benthic biogeochemistry over small scales (centimeters) but not patch scales (meters to tens of meters), suggesting a limited capacity for sediment modification to explain species distributions. To determine the relative competitive abilities of engineers, we conducted reciprocal transplantations of ghost shrimp and eelgrass. Local ghost shrimp densities declined rapidly following the addition of eelgrass, and transplanted eelgrass expanded laterally into the surrounding ghost shrimp-dominated areas. When transplanted into eelgrass patches, ghost shrimp failed to persist. Ghost shrimp were also displaced from plots with structural mimics of eelgrass rhizomes and roots, suggesting that autogenic habitat modification by eelgrass is an important mechanism determining ghost shrimp distributions. However, ghost shrimp were able to rapidly colonize experimental disturbances to eelgrass patch edges, which are common in shallow estuaries. We conclude that coexistence in this system is maintained by spatiotemporally asynchronous disturbances and a competition-colonization trade-off: eelgrass is a competitively superior ecosystem engineer, but benthic disturbances permit the coexistence of ghost shrimp at the landscape scale by modulating the availability of space.

Extracellular Polymeric Substance Production and Aggregated Bacteria Colonization Influence the Competition of Microbes in Biofilms.

PubMed

Jayathilake, Pahala G; Jana, Saikat; Rushton, Steve; Swailes, David; Bridgens, Ben; Curtis, Tom; Chen, Jinju

2017-01-01

The production of extracellular polymeric substance (EPS) is important for the survival of biofilms. However, EPS production is costly for bacteria and the bacterial strains that produce EPS (EPS+) grow in the same environment as non-producers (EPS-) leading to competition between these strains for nutrients and space. The outcome of this competition is likely to be dependent on factors such as initial attachment, EPS production rate, ambient nutrient levels and quorum sensing. We use an Individual-based Model (IbM) to study the competition between EPS+ and EPS- strains by varying the nature of initial colonizers which can either be in the form of single cells or multicellular aggregates. The microbes with EPS+ characteristics obtain a competitive advantage if they initially colonize the surface as smaller aggregates and are widely spread-out between the cells of EPS-, when both are deposited on the substratum. Furthermore, the results show that quorum sensing-regulated EPS production may significantly reduce the fitness of EPS producers when they initially deposit as aggregates. The results provide insights into how the distribution of bacterial aggregates during initial colonization could be a deciding factor in the competition among different strains in biofilms.

Trade-off between competition and facilitation defines gap colonization in mountains.

PubMed

Lembrechts, Jonas J; Milbau, Ann; Nijs, Ivan

2015-11-10

Recent experimental observations show that gap colonization in small-stature (e.g. grassland and dwarf shrubs) vegetation strongly depends on the abiotic conditions within them. At the same time, within-gap variation in biotic interactions such as competition and facilitation, caused by distance to the gap edge, would affect colonizer performance, but a theoretical framework to explore such patterns is missing. Here, we model how competition, facilitation and environmental conditions together determine the small-scale patterns of gap colonization along a cold gradient in mountains, by simulating colonizer survival in gaps of various sizes. Our model adds another dimension to the known effects of biotic interactions along a stress gradient by focussing on the trade-off between competition and facilitation in the within-gap environment. We show that this trade-off defines a peak in colonizer survival at a specific distance from the gap edge, which progressively shifts closer to the edge as the environment gets colder, ultimately leaving a large fraction of gaps unsuitable for colonization in facilitation-dominated systems. This is reinforced when vegetation size and temperature amelioration are manipulated simultaneously with temperature in order to simulate an elevational gradient more realistically. Interestingly, all other conditions being equal, the magnitude of the realized survival peak was always lower in large than in small gaps, making large gaps harder to colonize. The model is relevant to predict effects of non-native plant invasions and climate warming on colonization processes in mountains. Published by Oxford University Press on behalf of the Annals of Botany Company.

Gastrointestinal Tract Colonization Dynamics by Different Enterococcus faecium Clades.

PubMed

Montealegre, Maria Camila; Singh, Kavindra V; Murray, Barbara E

2016-06-15

Colonization of the gastrointestinal tract (GIT) generally precedes infection with antibiotic-resistant Enterococcus faecium We used a mouse GIT colonization model to test differences in the colonization levels by strains from different E. faecium lineages: clade B, part of the healthy human microbiota; subclade A1, associated with infections; and subclade A2, primarily associated with animals. After mono-inoculation, there was no significant difference in colonization (measured as the geometric mean number of colony-forming units per gram) by the E. faecium clades at any time point (P > .05). However, in competition assays, with 6 of the 7 pairs, clade B strains outcompeted clade A strains in their ability to persist in the GIT; this difference was significant in some pairs by day 2 and in all pairs by day 14 (P < .0008-.0283). This observation may explain the predominance of clade B in the community and why antibiotic-resistant hospital-associated E. faecium are often replaced by clade B strains once patients leave the hospital. © The Author 2015. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.

Competitive interactions between a nonmycorrhizal invasive plant, Alliaria petiolata, and a suite of mycorrhizal grassland, old field, and forest species.

PubMed

Poon, Gary T; Maherali, Hafiz

2015-01-01

The widespread invasion of the nonmycorrhizal biennial plant, Alliaria petiolata in North America is hypothesized to be facilitated by the production of novel biochemical weapons that suppress the growth of mycorrhizal fungi. As a result, A. petiolata is expected to be a strong competitor against plant species that rely on mycorrhizal fungi for nutrient uptake services. If A. petiolata is also a strong competitor for soil resources, it should deplete nutrients to levels lower than can be tolerated by weaker competitors. Because the negative effect of losing the fungal symbiont for mycorrhizal plants is greatest when nutrients are low, the ability of A. petiolata to simultaneously suppress fungi and efficiently take up soil nutrients should further strengthen its competitive ability against mycorrhizal plants. To test this hypothesis, we grew 27 mycorrhizal tree, forb and grass species that are representative of invaded habitats in the absence or presence of competition with A. petiolata in soils that had previously been experimentally planted with the invader or left as a control. A history of A. petiolata in soil reduced plant available forms of nitrogen by >50% and phosphorus by 17% relative to control soil. Average mycorrhizal colonization of competitor species was reduced by >50% in A. petiolata history versus control soil. Contrary to expectations, competition between A. petiolata and other species was stronger in control than history soil. The invader suppressed the biomass of 70% of competitor species in control soil but only 26% of species in history soil. In addition, A. petiolata biomass was reduced by 56% in history versus control soil, whereas the average biomass of competitor species was reduced by 15%. Thus, our results suggest that the negative effect of nutrient depletion on A. petiolata was stronger than the negative effect of suppressing mycorrhizal colonization on competitor species. These findings indicate that the inhibitory potential of A. petiolata on competitor species via mycorrhizal suppression is not enhanced under nutrient limitation.

Competitive interactions between a nonmycorrhizal invasive plant, Alliaria petiolata, and a suite of mycorrhizal grassland, old field, and forest species

PubMed Central

Poon, Gary T.

2015-01-01

The widespread invasion of the nonmycorrhizal biennial plant, Alliaria petiolata in North America is hypothesized to be facilitated by the production of novel biochemical weapons that suppress the growth of mycorrhizal fungi. As a result, A. petiolata is expected to be a strong competitor against plant species that rely on mycorrhizal fungi for nutrient uptake services. If A. petiolata is also a strong competitor for soil resources, it should deplete nutrients to levels lower than can be tolerated by weaker competitors. Because the negative effect of losing the fungal symbiont for mycorrhizal plants is greatest when nutrients are low, the ability of A. petiolata to simultaneously suppress fungi and efficiently take up soil nutrients should further strengthen its competitive ability against mycorrhizal plants. To test this hypothesis, we grew 27 mycorrhizal tree, forb and grass species that are representative of invaded habitats in the absence or presence of competition with A. petiolata in soils that had previously been experimentally planted with the invader or left as a control. A history of A. petiolata in soil reduced plant available forms of nitrogen by >50% and phosphorus by 17% relative to control soil. Average mycorrhizal colonization of competitor species was reduced by >50% in A. petiolata history versus control soil. Contrary to expectations, competition between A. petiolata and other species was stronger in control than history soil. The invader suppressed the biomass of 70% of competitor species in control soil but only 26% of species in history soil. In addition, A. petiolata biomass was reduced by 56% in history versus control soil, whereas the average biomass of competitor species was reduced by 15%. Thus, our results suggest that the negative effect of nutrient depletion on A. petiolata was stronger than the negative effect of suppressing mycorrhizal colonization on competitor species. These findings indicate that the inhibitory potential of A. petiolata on competitor species via mycorrhizal suppression is not enhanced under nutrient limitation. PMID:26213654

Differences in competitive ability for the occupancy of shelters in triatomines.

PubMed

Zacharias, C A; Minoli, S A; Manrique, G

2017-09-01

Triatomines (Hemiptera: Reduviidae: Triatominae) are nocturnal blood-sucking insects. During daylight hours they remain in an akinetic state inside their shelters, whereas at dusk they become active and move outside. When they are outside their shelters during the photophase, triatomines are vulnerable to diurnal predators and the period just before dawn is critical to their survival. This work analyses the existence of competitive interactions involved in the occupancy of shelters by triatomines. Behavioural assays were performed in which nymphs of different stages, nutritional status or species were released in an experimental arena containing a space-limited artificial shelter. The proportions of individuals occupying the shelter during the photophase were quantified to estimate the competitive abilities of each stage and species. Intraspecific comparisons showed higher levels of shelter occupancy for fourth over fifth instars and fed over unfed nymphs of Triatoma infestans. Interspecific comparisons showed higher rates of shelter occupancy for Triatoma sordida in comparison with T. infestans, and for T. infestans over Rhodnius prolixus. Arrival order was also relevant to determining shelter occupancy levels: early arrival was advantageous in comparison with later arrival. The study of intra- and interspecific competitive interactions for shelter occupancy provides relevant information about colonization and recolonization processes in the natural environments of triatomines. © 2017 The Royal Entomological Society.

The trehalose utilization gene thuA ortholog in Mesorhizobium loti does not influence competitiveness for nodulation on Lotus spp.

PubMed

Ampomah, Osei Yaw; Jensen, John Beck

2014-03-01

Competitiveness for nodulation is a desirable trait in rhizobia strains used as inoculant. In Sinorhizobium meliloti 1021 mutation in either of the trehalose utilization genes thuA or thuB influences its competitiveness for root colonization and nodule occupancy depending on the interacting host. We have therefore investigated whether mutation in the thuA ortholog in Mesorhizobium loti MAFF303099 also leads to a similar competitive phenotype on its hosts. The results show that M. loti thuA mutant Ml7023 was symbiotically effective and was as competitive as the wild type in colonization and nodule occupancy on Lotus corniculatus and Lotus japonicus. The thuA gene in M. loti was not induced during root colonization or in the infection threads unlike in S. meliloti, despite its induction by trehalose and high osmolarity in in vitro assays.

Antagonistic mechanisms of synbiosis between Lactobacillus plantarum CIF17AN2 and green banana starch in the proximal colon model challenged with Salmonella Typhimurium.

PubMed

Uraipan, Supansa; Brigidi, Patrizia; Hongpattarakere, Tipparat

2014-08-01

Antagonistic mechanisms of Lactobacillus plantarum CIF17AN2 (an infant isolate), saba starch, and their synbiotic combination against Salmonella Typhimurium SA2093 were evaluated. The anti-Salmonella activity was investigated under the competitive niche of fecal microbiota using the simulated proximal colon model. The alterations of the dominant fecal microbiota and beneficial bacteria were also displayed using FISH and PCR-DGGE techniques. L. plantarum CIF17AN2 exhibited anti-Salmonella mechanisms through secretion of antimicrobial compounds, adhesion ability and competitive adhesion to mucin and HT-29 cell line. However, the Salmonella inhibition was significantly reduced in the presence of human fecal microflora. The combination of saba starch with L. plantarum CIF17AN2 showed the greatest inhibition against Sal. Typhimurium SA2093 in the simulated colon model. The enhancement of anti-Salmonella activity due to the addition of saba starch corresponded to a significant decrease in pH and an increase of lactic acid and short chain fatty acids. According to PCR-DGGE analysis, L. plantarum CIF17AN2 was able to survive and effectively compete with fecal microflora. Saba starch supplement modified bifidobacterial profile but had a slight impact on the profile of lactic acid bacteria. This prebiotic approach alleviated the nutrient limitation in the proximal colon model leading to the selective stimulation of beneficial lactobacilli and bifidobacteria, hence the enhancement of anti-Salmonella activity. Copyright © 2014 Elsevier Ltd. All rights reserved.

Biocontrol ability and action mechanism of food-isolated yeast strains against Botrytis cinerea causing post-harvest bunch rot of table grape.

PubMed

Parafati, Lucia; Vitale, Alessandro; Restuccia, Cristina; Cirvilleri, Gabriella

2015-05-01

Strains belonging to the species Saccharomyces cerevisiae, Wickerhamomyces anomalus, Metschnikowia pulcherrima and Aureobasidium pullulans, isolated from different food sources, were tested in vitro as biocontrol agents (BCAs) against the post-harvest pathogenic mold Botrytis cinerea. All yeast strains demonstrated antifungal activity at different levels depending on species and medium. Killer strains of W. anomalus and S. cerevisiae showed the highest biocontrol in vitro activity, as demonstrated by largest inhibition halos. The competition for iron and the ability to form biofilm and to colonize fruit wounds were hypothesized as the main action mechanisms for M. pulcherrima. The production of hydrolytic enzymes and the ability to colonize the wounds were the most important mechanisms for biocontrol activity in A. pullulans and W. anomalus, which also showed high ability to form biofilm. The production of volatile organic compounds (VOCs) with in vitro and in vivo inhibitory effect on pathogen growth was observed for the species W. anomalus, S. cerevisiae and M. pulcherrima. Our study clearly indicates that multiple modes of action may explain as M. pulcherrima provide excellent control of postharvest botrytis bunch rot of grape. Copyright © 2014 Elsevier Ltd. All rights reserved.

Inhibition of Fungal Colonization by Pseudoalteromonas tunicata Provides a Competitive Advantage during Surface Colonization†

PubMed Central

Franks, A.; Egan, S.; Holmström, C.; James, S.; Lappin-Scott, H.; Kjelleberg, S.

2006-01-01

The marine epiphytic bacterium Pseudoalteromonas tunicata produces a range of extracellular secondary metabolites that inhibit an array of common fouling organisms, including fungi. In this study, we test the hypothesis that the ability to inhibit fungi provides P. tunicata with an advantage during colonization of a surface. Studies on a transposon-generated antifungal-deficient mutant of P. tunicata, FM3, indicated that a long-chain fatty acid-coenzyme A ligase is involved in the production of a broad-range antifungal compound by P. tunicata. Flow cell experiments demonstrated that production of an antifungal compound provided P. tunicata with a competitive advantage against a marine yeast isolate during surface colonization. This compound enabled P. tunicata to disrupt an already established fungal biofilm by decreasing the number of yeast cells attached to the surface by 66% ± 9%. For in vivo experiments, the wild-type and FM3 strains of P. tunicata were used to inoculate the surface of the green alga Ulva australis. Double-gradient denaturing gradient gel electrophoresis analysis revealed that after 48 h, the wild-type P. tunicata had outcompeted the surface-associated fungal community, whereas the antifungal-deficient mutant had no effect on the fungal community. Our data suggest that P. tunicata is an effective competitor against fungal surface communities in the marine environment. PMID:16957232

Composition of an avian guild in spatially structured habitats supports a competition–colonization trade-off

PubMed Central

Rodríguez, Alejandro; Jansson, Gunnar; Andrén, Henrik

2007-01-01

Assuming better colonization abilities of inferior competitors, the competition–colonization trade-off (CCTO) is one of the hypotheses that explains spatial variation of species composition in fragmented habitats. Whereas this mechanism may structure some plant and insect communities, ecologists have failed to document its operation in other natural systems, and its generality has been questioned. We combined fieldwork and published data to study the composition of a guild of passerines (Parus cristatus, Parus montanus, Parus ater and Regulus regulus) inhabiting 10 landscapes that differed in the amount of forest habitat. The species were ordered in a stable, well-defined competitive hierarchy, and the dispersal ability of each species was inversely correlated with its position in this hierarchy. In functionally continuous landscapes, superior competitors occupied most fragments and all guild members commonly occurred. The relative incidences of superior and inferior competitors were reversed, and differences amplified, in landscapes where patches were physically (distance) or functionally (matrix hardness) isolated. We found little support for two competing hypotheses, namely reduced habitat quality in isolated patches and lower abundance of a keystone predator (Glaucidium passerinum) in fragmented landscapes. We concluded that the CCTO offered the most probable explanation for variation in the composition of the Parus guild across landscapes. PMID:17389222

Assessing the efficacy of co-inoculation of wheat seedlings with the associative bacteria Paenibacillus polymyxa 1465 and Azospirillum brasilense Sp245.

PubMed

Yegorenkova, Irina V; Tregubova, Kristina V; Burygin, Gennady L; Matora, Larisa Y; Ignatov, Vladimir V

2016-03-01

Co-inoculation of associative bacteria, which have high nitrogen-fixing activity, tolerance for environmental conditions, and the ability to compete with the natural microflora, is used widely to enhance the growth and yields of agricultural plants. We evaluated the ability of 2 co-inoculated plant-growth-promoting rhizobacteria, Paenibacillus polymyxa 1465 and Azospirillum brasilense Sp245, to colonize roots of wheat (Triticum aestivum L. 'Saratovskaya 29') seedlings, and we assessed the morphometric parameters of wheat early in its development. Analysis by ELISA with polyclonal antibodies raised against the exopolysaccharide of P. polymyxa 1465 and the lipopolysaccharide of A. brasilense Sp245 demonstrated that the root-colonizing activity of A. brasilense was higher when the bacterium was co-inoculated with P. polymyxa than when it was inoculated singly. Immunofluorescence microscopy with Alexa Fluor 532-labeled antibodies revealed sites of attachment of co-inoculated P. polymyxa and A. brasilense and showed that the 2 bacteria colonized similar regions of the roots. Co-inoculation exerted a negative effect on wheat seedling development, inhibiting root length by 17.6%, total root weight by 11%, and total shoot weight by 12%. Under certain conditions, dual inoculation of wheat may prove ineffective, apparently owing to the competition between the rhizobacteria for colonization sites on the plant roots. The findings from this study may aid in developing techniques for mixed bacterial inoculation of cultivated plants.

Factors affecting the conversion of apple polyphenols to phenolic acids and fruit matrix to short-chain fatty acids by human faecal microbiota in vitro.

PubMed

Bazzocco, Sarah; Mattila, Ismo; Guyot, Sylvain; Renard, Catherine M G C; Aura, Anna-Marja

2008-12-01

Proanthocyanidins (PAs) in apples are condensed tannins comprised mostly of (-)-epicatechin units with some terminal (+)-catechins. PAs, especially those having a long chain-length, are absorbed in the upper intestine only to a small extent and are passed to the colon. In the colon they are subjected to microbial metabolism by colonic microbiota. In the present article, the ability of human microbiota to ferment apple PAs is studied. Freeze-dried fruit preparations (apple, enzymatically digested apple, isolated cell-walls, isolated PAs or ciders) from two varieties, Marie Ménard and Avrolles, containing PAs of different chain lengths, were compared. Fermentation studies were performed in an in vitro colon model using human faecal microbiota as an inoculum. The maximal extent of conversion to known microbial metabolites, was observed at late time point for Marie Ménard cider, having short PAs. In this case, the initial dose also contributed to the extent of conversion. Long-chain PAs were able to inhibit the in vitro microbial metabolism of PAs shown as low maxima at early time points. Presence of isolated PAs also suppressed SCFA formation from carbohydrates as compared with that from apple cell wall or faecal suspension without substrates. The low maximal extents at early time points suggest that there is a competition between the inhibitory effect of the PAs on microbial activity, and the ability to convert PAs by the microbiota.

Survival of Potentially Pathogenic Human-Associated Bacteria in the Rhizosphere of Hydroponically Grown Wheat

NASA Technical Reports Server (NTRS)

Morales, Anabelle; Garland, Jay L.; Lim, Daniel V.

1996-01-01

Plants may serve as reservoirs for human-associated bacteria (H-AB) in long-term space missions containing bioregenerative life support systems. The current study examined the abilities of five human-associated potential pathogens, Pseudomonas aeruginosa, Pseudomonas cepacia, Staphylococcus aureus, Streptococcus pyogenes, and Escherichia coli, to colonize and grow in the rhizosphere of hydroponically grown wheat, a candidate crop for life support. All of these bacteria have been recovered from past NASA missions and present potential problems for future missions. The abilities of these organisms to adhere to the roots of axenic five-day-old wheat (Triticum aestivum L. cv. Yecora rojo) were evaluated by enumeration of the attached organisms after a one hour incubation of roots in a suspension (approximately 10(exp 8 cu/ml)) of the H-AB. Results showed that a greater percentage of P. aeruginosa cells adhered to the wheat roots than the other four H-AB. Similarly incubated seedlings were also grown under attempted axenic conditions for seven days to examine the potential of each organism to proliferate in the rhizosphere (root colonization capacity). P. cepacia and P. aeruginosa showed considerable growth. E. coli and S. aureus showed no significant growth, and S. pyogenes died off in the wheat rhizosphere. Studies examining the effects of competition on the survival of these microorganisms indicated that P. aeruginosa was the only organism that survived in the rhizosphere of hydroponically grown wheat in the presence of different levels of microbial competition.

Effect of Serotype on Pneumococcal Competition in a Mouse Colonization Model.

PubMed

Trzciński, Krzysztof; Li, Yuan; Weinberger, Daniel M; Thompson, Claudette M; Cordy, Derrick; Bessolo, Andrew; Malley, Richard; Lipsitch, Marc

2015-09-15

Competitive interactions between Streptococcus pneumoniae strains during host colonization could influence the serotype distribution in nasopharyngeal carriage and pneumococcal disease. We evaluated the competitive fitness of strains of serotypes 6B, 14, 19A, 19F, 23F, and 35B in a mouse model of multiserotype carriage. Isogenic variants were constructed using clinical strains as the capsule gene donors. Animals were intranasally inoculated with a mixture of up to six pneumococcal strains of different serotypes, with separate experiments involving either clinical isolates or isogenic capsule-switch variants of clinical strain TIGR4. Upper-respiratory-tract samples were repeatedly collected from animals in order to monitor changes in the serotype ratios using quantitative PCR. A reproducible hierarchy of capsular types developed in the airways of mice inoculated with multiple strains. Serotype ranks in this hierarchy were similar among pneumococcal strains of different genetic backgrounds in different strains of mice and were not altered when tested under a range of host conditions. This rank correlated with the measure of the metabolic cost of capsule synthesis and in vitro measure of pneumococcal cell surface charge, both parameters considered to be predictors of serotype-specific fitness in carriage. This study demonstrates the presence of a robust competitive hierarchy of pneumococcal serotypes in vivo that is driven mainly, but not exclusively, by the capsule itself. Streptococcus pneumoniae (pneumococcus) is the leading cause of death due to respiratory bacterial infections but also a commensal frequently carried in upper airways. Available vaccines induce immune responses against polysaccharides coating pneumococcal cells, but with over 90 different capsular types (serotypes) identified, they can only target strains of the selected few serotypes most prevalent in disease. Vaccines not only protect vaccinated individuals against disease but also protect by reducing carriage of vaccine-targeted strains to induce herd effects across whole populations. Unfortunately, reduction in the circulation of vaccine-type strains is offset by increase in carriage and disease from nonvaccine strains, indicating the importance of competitive interactions between pneumococci in shaping the population structure of this pathogen. Here, we showed that the competitive ability of pneumococcal strains to colonize the host strongly depends on the type of capsular polysaccharide expressed by pneumococci and only to a lesser degree on strain or host genetic backgrounds or on variation in host immune responses. Copyright © 2015 Trzciński et al.

Salmonella enterica Serovar Typhimurium Exploits Inflammation to Modify Swine Intestinal Microbiota.

PubMed

Drumo, Rosanna; Pesciaroli, Michele; Ruggeri, Jessica; Tarantino, Michela; Chirullo, Barbara; Pistoia, Claudia; Petrucci, Paola; Martinelli, Nicola; Moscati, Livia; Manuali, Elisabetta; Pavone, Silvia; Picciolini, Matteo; Ammendola, Serena; Gabai, Gianfranco; Battistoni, Andrea; Pezzotti, Giovanni; Alborali, Giovanni L; Napolioni, Valerio; Pasquali, Paolo; Magistrali, Chiara F

2015-01-01

Salmonella enterica serovar Typhimurium is an important zoonotic gastrointestinal pathogen responsible for foodborne disease worldwide. It is a successful enteric pathogen because it has developed virulence strategies allowing it to survive in a highly inflamed intestinal environment exploiting inflammation to overcome colonization resistance provided by intestinal microbiota. In this study, we used piglets featuring an intact microbiota, which naturally develop gastroenteritis, as model for salmonellosis. We compared the effects on the intestinal microbiota induced by a wild type and an attenuated S. Typhimurium in order to evaluate whether the modifications are correlated with the virulence of the strain. This study showed that Salmonella alters microbiota in a virulence-dependent manner. We found that the wild type S. Typhimurium induced inflammation and a reduction of specific protecting microbiota species (SCFA-producing bacteria) normally involved in providing a barrier against pathogens. Both these effects could contribute to impair colonization resistance, increasing the host susceptibility to wild type S. Typhimurium colonization. In contrast, the attenuated S. Typhimurium, which is characterized by a reduced ability to colonize the intestine, and by a very mild inflammatory response, was unable to successfully sustain competition with the microbiota.

Salmonella enterica Serovar Typhimurium Exploits Inflammation to Modify Swine Intestinal Microbiota

PubMed Central

Drumo, Rosanna; Pesciaroli, Michele; Ruggeri, Jessica; Tarantino, Michela; Chirullo, Barbara; Pistoia, Claudia; Petrucci, Paola; Martinelli, Nicola; Moscati, Livia; Manuali, Elisabetta; Pavone, Silvia; Picciolini, Matteo; Ammendola, Serena; Gabai, Gianfranco; Battistoni, Andrea; Pezzotti, Giovanni; Alborali, Giovanni L.; Napolioni, Valerio; Pasquali, Paolo; Magistrali, Chiara F.

2016-01-01

Salmonella enterica serovar Typhimurium is an important zoonotic gastrointestinal pathogen responsible for foodborne disease worldwide. It is a successful enteric pathogen because it has developed virulence strategies allowing it to survive in a highly inflamed intestinal environment exploiting inflammation to overcome colonization resistance provided by intestinal microbiota. In this study, we used piglets featuring an intact microbiota, which naturally develop gastroenteritis, as model for salmonellosis. We compared the effects on the intestinal microbiota induced by a wild type and an attenuated S. Typhimurium in order to evaluate whether the modifications are correlated with the virulence of the strain. This study showed that Salmonella alters microbiota in a virulence-dependent manner. We found that the wild type S. Typhimurium induced inflammation and a reduction of specific protecting microbiota species (SCFA-producing bacteria) normally involved in providing a barrier against pathogens. Both these effects could contribute to impair colonization resistance, increasing the host susceptibility to wild type S. Typhimurium colonization. In contrast, the attenuated S. Typhimurium, which is characterized by a reduced ability to colonize the intestine, and by a very mild inflammatory response, was unable to successfully sustain competition with the microbiota. PMID:26835435

Strategies of offspring investment and dispersal in a spatially structured environment: a theoretical study using ants.

PubMed

Cronin, Adam L; Loeuille, Nicolas; Monnin, Thibaud

2016-02-05

Offspring investment strategies vary markedly between and within taxa, and much of this variation is thought to stem from the trade-off between offspring size and number. While producing larger offspring can increase their competitive ability, this often comes at a cost to their colonization ability. This competition-colonization trade-off (CCTO) is thought to be an important mechanism supporting coexistence of alternative strategies in a wide range of taxa. However, the relative importance of an alternative and possibly synergistic mechanism-spatial structuring of the environment-remains the topic of some debate. In this study, we explore the influence of these mechanisms on metacommunity structure using an agent-based model built around variable life-history traits. Our model combines explicit resource competition and spatial dynamics, allowing us to tease-apart the influence of, and explore the interaction between, the CCTO and the spatial structure of the environment. We test our model using two reproductive strategies which represent extremes of the CCTO and are common in ants. Our simulations show that colonisers outperform competitors in environments subject to higher temporal and spatial heterogeneity and are favoured when agents mature late and invest heavily in reproduction, whereas competitors dominate in low-disturbance, high resource environments and when maintenance costs are low. Varying life-history parameters has a marked influence on coexistence conditions and yields evolutionary stable strategies for both modes of reproduction. Nonetheless, we show that these strategies can coexist over a wide range of life-history and environmental parameter values, and that coexistence can in most cases be explained by a CCTO. By explicitly considering space, we are also able to demonstrate the importance of the interaction between dispersal and landscape structure. The CCTO permits species employing different reproductive strategies to coexist over a wide range of life-history and environmental parameters, and is likely to be an important factor in structuring ant communities. Our consideration of space highlights the importance of dispersal, which can limit the success of low-dispersers through kin competition, and enhance coexistence conditions for different strategies in spatially structured environments.

Novel Two-Step Hierarchical Screening of Mutant Pools Reveals Mutants under Selection in Chicks

PubMed Central

Yang, Hee-Jeong; Bogomolnaya, Lydia M.; Elfenbein, Johanna R.; Endicott-Yazdani, Tiana; Reynolds, M. Megan; Porwollik, Steffen; Cheng, Pui; Xia, Xiao-Qin

2016-01-01

Contaminated chicken/egg products are major sources of human salmonellosis, yet the strategies used by Salmonella to colonize chickens are poorly understood. We applied a novel two-step hierarchical procedure to identify new genes important for colonization and persistence of Salmonella enterica serotype Typhimurium in chickens. A library of 182 S. Typhimurium mutants each containing a targeted deletion of a group of contiguous genes (for a total of 2,069 genes deleted) was used to identify regions under selection at 1, 3, and 9 days postinfection in chicks. Mutants in 11 regions were under selection at all assayed times (colonization mutants), and mutants in 15 regions were under selection only at day 9 (persistence mutants). We assembled a pool of 92 mutants, each deleted for a single gene, representing nearly all genes in nine regions under selection. Twelve single gene deletion mutants were under selection in this assay, and we confirmed 6 of 9 of these candidate mutants via competitive infections and complementation analysis in chicks. STM0580, STM1295, STM1297, STM3612, STM3615, and STM3734 are needed for Salmonella to colonize and persist in chicks and were not previously associated with this ability. One of these key genes, STM1297 (selD), is required for anaerobic growth and supports the ability to utilize formate under these conditions, suggesting that metabolism of formate is important during infection. We report a hierarchical screening strategy to interrogate large portions of the genome during infection of animals using pools of mutants of low complexity. Using this strategy, we identified six genes not previously known to be needed during infection in chicks, and one of these (STM1297) suggests an important role for formate metabolism during infection. PMID:26857572

Role of ptsP, orfT, and sss recombinase genes in root colonization by Pseudomonas fluorescens Q8r1-96.

PubMed

Mavrodi, Olga V; Mavrodi, Dmitri V; Weller, David M; Thomashow, Linda S

2006-11-01

Pseudomonas fluorescens Q8r1-96 produces 2,4-diacetylphloroglucinol (2,4-DAPG), a polyketide antibiotic that suppresses a wide variety of soilborne fungal pathogens, including Gaeumannomyces graminis var. tritici, which causes take-all disease of wheat. Strain Q8r1-96 is representative of the D-genotype of 2,4-DAPG producers, which are exceptional because of their ability to aggressively colonize and maintain large populations on the roots of host plants, including wheat, pea, and sugar beet. In this study, three genes, an sss recombinase gene, ptsP, and orfT, which are important in the interaction of Pseudomonas spp. with various hosts, were investigated to determine their contributions to the unusual colonization properties of strain Q8r1-96. The sss recombinase and ptsP genes influence global processes, including phenotypic plasticity and organic nitrogen utilization, respectively. The orfT gene contributes to the pathogenicity of Pseudomonas aeruginosa in plants and animals and is conserved among saprophytic rhizosphere pseudomonads, but its function is unknown. Clones containing these genes were identified in a Q8r1-96 genomic library, sequenced, and used to construct gene replacement mutants of Q8r1-96. Mutants were characterized to determine their 2,4-DAPG production, motility, fluorescence, colony morphology, exoprotease and hydrogen cyanide (HCN) production, carbon and nitrogen utilization, and ability to colonize the rhizosphere of wheat grown in natural soil. The ptsP mutant was impaired in wheat root colonization, whereas mutants with mutations in the sss recombinase gene and orfT were not. However, all three mutants were less competitive than wild-type P. fluorescens Q8r1-96 in the wheat rhizosphere when they were introduced into the soil by paired inoculation with the parental strain.

Role of ptsP, orfT, and sss Recombinase Genes in Root Colonization by Pseudomonas fluorescens Q8r1-96▿

PubMed Central

Mavrodi, Olga V.; Mavrodi, Dmitri V.; Weller, David M.; Thomashow, Linda S.

2006-01-01

Pseudomonas fluorescens Q8r1-96 produces 2,4-diacetylphloroglucinol (2,4-DAPG), a polyketide antibiotic that suppresses a wide variety of soilborne fungal pathogens, including Gaeumannomyces graminis var. tritici, which causes take-all disease of wheat. Strain Q8r1-96 is representative of the D-genotype of 2,4-DAPG producers, which are exceptional because of their ability to aggressively colonize and maintain large populations on the roots of host plants, including wheat, pea, and sugar beet. In this study, three genes, an sss recombinase gene, ptsP, and orfT, which are important in the interaction of Pseudomonas spp. with various hosts, were investigated to determine their contributions to the unusual colonization properties of strain Q8r1-96. The sss recombinase and ptsP genes influence global processes, including phenotypic plasticity and organic nitrogen utilization, respectively. The orfT gene contributes to the pathogenicity of Pseudomonas aeruginosa in plants and animals and is conserved among saprophytic rhizosphere pseudomonads, but its function is unknown. Clones containing these genes were identified in a Q8r1-96 genomic library, sequenced, and used to construct gene replacement mutants of Q8r1-96. Mutants were characterized to determine their 2,4-DAPG production, motility, fluorescence, colony morphology, exoprotease and hydrogen cyanide (HCN) production, carbon and nitrogen utilization, and ability to colonize the rhizosphere of wheat grown in natural soil. The ptsP mutant was impaired in wheat root colonization, whereas mutants with mutations in the sss recombinase gene and orfT were not. However, all three mutants were less competitive than wild-type P. fluorescens Q8r1-96 in the wheat rhizosphere when they were introduced into the soil by paired inoculation with the parental strain. PMID:16936061

Bioprotective Role of Yeasts

PubMed Central

Muccilli, Serena; Restuccia, Cristina

2015-01-01

The yeasts constitute a large group of microorganisms characterized by the ability to grow and survive in different and stressful conditions and then to colonize a wide range of environmental and human ecosystems. The competitive traits against other microorganisms have attracted increasing attention from scientists, who proposed their successful application as bioprotective agents in the agricultural, food and medical sectors. These antagonistic activities rely on the competition for nutrients, production and tolerance of high concentrations of ethanol, as well as the synthesis of a large class of antimicrobial compounds, known as killer toxins, which showed clearly a large spectrum of activity against food spoilage microorganisms, but also against plant, animal and human pathogens. This review describes the antimicrobial mechanisms involved in the antagonistic activity, their applications in the processed and unprocessed food sectors, as well as the future perspectives in the development of new bio-drugs, which may overcome the limitations connected to conventional antimicrobial and drug resistance. PMID:27682107

Nanocoatings for Chronic Wound Repair-Modulation of Microbial Colonization and Biofilm Formation.

PubMed

Mihai, Mara Mădălina; Preda, Mădălina; Lungu, Iulia; Gestal, Monica Cartelle; Popa, Mircea Ioan; Holban, Alina Maria

2018-04-12

Wound healing involves a complex interaction between immunity and other natural host processes, and to succeed it requires a well-defined cascade of events. Chronic wound infections can be mono- or polymicrobial but their major characteristic is their ability to develop a biofilm. A biofilm reduces the effectiveness of treatment and increases resistance. A biofilm is an ecosystem on its own, enabling the bacteria and the host to establish different social interactions, such as competition or cooperation. With an increasing incidence of chronic wounds and, implicitly, of chronic biofilm infections, there is a need for alternative therapeutic agents. Nanotechnology shows promising openings, either by the intrinsic antimicrobial properties of nanoparticles or their function as drug carriers. Nanoparticles and nanostructured coatings can be active at low concentrations toward a large variety of infectious agents; thus, they are unlikely to elicit emergence of resistance. Nanoparticles might contribute to the modulation of microbial colonization and biofilm formation in wounds. This comprehensive review comprises the pathogenesis of chronic wounds, the role of chronic wound colonization and infection in the healing process, the conventional and alternative topical therapeutic approaches designed to combat infection and stimulate healing, as well as revolutionizing therapies such as nanotechnology-based wound healing approaches.

Competition-colonization dynamics: An ecology approach to quasispecies dynamics and virulence evolution in RNA viruses.

PubMed

Ojosnegros, Samuel; Beerenwinkel, Niko; Domingo, Esteban

2010-07-01

A single and purified clone of foot-and-mouth disease virus diversified in cell culture into two subpopulations that were genetically distinct. The subpopulation with higher virulence was a minority and was suppressed by the dominant but less virulent one. These two populations follow the competitioncolonization dynamics described in ecology. Virulent viruses can be regarded as colonizers because they killed the cells faster and they spread faster. The attenuated subpopulation resembles competitors because of its higher replication efficiency in coinfected cells. Our results suggest a new model for the evolution of virulence which is based on interactions between components of the quasispecies. Competition between viral mutants takes place at two levels, intracellular competition and competition for new cells. The two strategies are subjected to densitydependent selection.

Acarbose: a new option in the treatment of ulcerative colitis by increasing hydrogen production.

PubMed

Zhang, De-Qing; Zhu, Jian-Hong; Chen, Wei-Chang

2012-01-01

Acarbose, which is clinically widely used to treat Type 2 Diabetes, is thought to act at the small intestine by competitively inhibiting enzymes that delay the release of glucose from complex carbohydrates, thereby specifically reducing post prandial glucose excursion. The major side-effect of treatment with acarbose, flatulence, occurs when undigested carbohydrates are fermented by colonic bacteria, resulting in considerable amount of hydrogen. We propose that enteric benefits of acarbose is partly attributable to be their ability to neutralise oxidative stress via increased production of H2 in the gastrointestinal tract. Therefore, symptoms of ulcerative colitis in human beings can be ameliorated by acarbose.

Endophytic colonization and in planta nitrogen fixation by a diazotrophic Serratia sp. in rice.

PubMed

Sandhiya, G S; Sugitha, T C K; Balachandar, D; Kumar, K

2005-09-01

Nitrogen fixing endophytic Serratia sp. was isolated from rice and characterized. Re-colonization ability of Serratia sp. in the rice seedlings as endophyte was studied under laboratory condition. For detecting the re-colonization potential in the rice seedlings, Serratia sp. was marked with reporter genes (egfp and Kmr) using transposon mutagenesis. The conjugants were screened for re-colonization ability and presence of nif genes using PCR. Further, the influence of flavonoids and growth hormones on the endophytic colonization and in planta nitrogen fixation of Serratia was also investigated. The flavonoids, quercetin (3 microg/ml) and diadzein (2 microg/ml) significantly increased the re-colonization ability of the endophytic Serratia, whereas the growth hormones like IAA and NAA (5 microg/ml) reduced the endophytic colonization ability of Serratia sp. Similarly, the in planta nitrogen fixation by Serratia sp. in rice was significantly increased due to flavonoids. The inoculation of endophytic diazotrophs increased the plant biomass and biochemical constituents.

Evolution of dispersal and life history strategies – Tetrahymena ciliates

PubMed Central

Fjerdingstad, Else J; Schtickzelle, Nicolas; Manhes, Pauline; Gutierrez, Arnaud; Clobert, Jean

2007-01-01

Background Considerable attention has focused on how selection on dispersal and other core life-history strategies (reproductive effort, survival ability, colonization capacity) may lead to so-called dispersal syndromes. Studies on genetic variation in these syndromes within species could importantly increase our understanding of their evolution, by revealing whether traits co-vary across genetic lineages in the manner predicted by theoretical models, and by stimulating further hypotheses for experimental testing. Yet such studies remain scarce. Here we studied the ciliated protist Tetrahymena thermophila, a particularly interesting organism due to cells being able to transform into morphs differing dramatically in swim-speed. We investigated dispersal, morphological responses, reproductive performance, and survival in ten different clonal strains. Then, we examined whether life history traits co-varied in the manner classically predicted for ruderal species, examined the investment of different strains into short- and putative long-distance dispersal, while considering also the likely impact of semi-sociality (cell aggregation, secretion of 'growth factors') on dispersal strategies. Results Very significant among-strain differences were found with regard to dispersal rate, morphological commitment and plasticity, and almost all core life-history traits (e.g. survival, growth performance and strategy), with most of these traits being significantly intercorrelated. Some strains showed high short-distance dispersal rates, high colonization capacity, bigger cell size, elevated growth performance, and good survival abilities. These well performing strains, however, produced fewer fast-swimming dispersal morphs when subjected to environmental degradation than did philopatric strains performing poorly under normal conditions. Conclusion Strong evidence was found for a genetic covariation between dispersal strategies and core life history traits in T. thermophila, with a fair fit of observed trait associations with classic colonizer models. However, the well performing strains with high colonization success and short-distance dispersal likely suffered under a long-distance dispersal disadvantage, due to producing fewer fast-swimming dispersal morphs than did philopatric strains. The smaller cell size at carrying capacity of the latter strains and their poor capacity to colonize as individual cells suggest that they may be adapted to greater levels of dependency on clone-mates (stronger sociality). In summary, differential exposure to selection on competitive and cooperative abilities, in conjunction with selective factors targeting specifically dispersal distance, likely contributed importantly to shaping T. thermophila dispersal and life history evolution. PMID:17683620

Production of the antimicrobial secondary metabolite indigoidine contributes to competitive surface colonization by the marine roseobacter Phaeobacter sp. strain Y4I.

PubMed

Cude, W Nathan; Mooney, Jason; Tavanaei, Arash A; Hadden, Mary K; Frank, Ashley M; Gulvik, Christopher A; May, Amanda L; Buchan, Alison

2012-07-01

Members of the Roseobacter lineage of marine bacteria are prolific surface colonizers in marine coastal environments, and antimicrobial secondary metabolite production has been hypothesized to provide a competitive advantage to colonizing roseobacters. Here, we report that the roseobacter Phaeobacter sp. strain Y4I produces the blue pigment indigoidine via a nonribosomal peptide synthase (NRPS)-based biosynthetic pathway encoded by a novel series of genetically linked genes: igiBCDFE. A Tn5-based random mutagenesis library of Y4I showed a perfect correlation between indigoidine production by the Phaeobacter strain and inhibition of Vibrio fischeri on agar plates, revealing a previously unrecognized bioactivity of this molecule. In addition, igiD null mutants (igiD encoding the indigoidine NRPS) were more resistant to hydrogen peroxide, less motile, and faster to colonize an artificial surface than the wild-type strain. Collectively, these data provide evidence for pleiotropic effects of indigoidine production in this strain. Gene expression assays support phenotypic observations and demonstrate that igiD gene expression is upregulated during growth on surfaces. Furthermore, competitive cocultures of V. fischeri and Y4I show that the production of indigoidine by Y4I significantly inhibits colonization of V. fischeri on surfaces. This study is the first to characterize a secondary metabolite produced by an NRPS in roseobacters.

Tumor evolution in space: the effects of competition colonization tradeoffs on tumor invasion dynamics.

PubMed

Orlando, Paul A; Gatenby, Robert A; Brown, Joel S

2013-01-01

We apply competition colonization tradeoff models to tumor growth and invasion dynamics to explore the hypothesis that varying selection forces will result in predictable phenotypic differences in cells at the tumor invasive front compared to those in the core. Spatially, ecologically, and evolutionarily explicit partial differential equation models of tumor growth confirm that spatial invasion produces selection pressure for motile phenotypes. The effects of the invasive phenotype on normal adjacent tissue determine the patterns of growth and phenotype distribution. If tumor cells do not destroy their environment, colonizer and competitive phenotypes coexist with the former localized at the invasion front and the latter, to the tumor interior. If tumors cells do destroy their environment, then cell motility is strongly selected resulting in accelerated invasion speed with time. Our results suggest that the widely observed genetic heterogeneity within cancers may not be the stochastic effect of random mutations. Rather, it may be the consequence of predictable variations in environmental selection forces and corresponding phenotypic adaptations.

Tumor Evolution in Space: The Effects of Competition Colonization Tradeoffs on Tumor Invasion Dynamics

PubMed Central

Orlando, Paul A.; Gatenby, Robert A.; Brown, Joel S.

2013-01-01

We apply competition colonization tradeoff models to tumor growth and invasion dynamics to explore the hypothesis that varying selection forces will result in predictable phenotypic differences in cells at the tumor invasive front compared to those in the core. Spatially, ecologically, and evolutionarily explicit partial differential equation models of tumor growth confirm that spatial invasion produces selection pressure for motile phenotypes. The effects of the invasive phenotype on normal adjacent tissue determine the patterns of growth and phenotype distribution. If tumor cells do not destroy their environment, colonizer and competitive phenotypes coexist with the former localized at the invasion front and the latter, to the tumor interior. If tumors cells do destroy their environment, then cell motility is strongly selected resulting in accelerated invasion speed with time. Our results suggest that the widely observed genetic heterogeneity within cancers may not be the stochastic effect of random mutations. Rather, it may be the consequence of predictable variations in environmental selection forces and corresponding phenotypic adaptations. PMID:23508890

Field Assessment of Non-toxigenic Aspergillus flavus Strain K49 in Competitive Displacement of Toxigenic Isolates

USDA-ARS?s Scientific Manuscript database

Non-toxigenic strains of Aspergillus flavus offer the potential to control aflatoxin contamination by competitive displacement of indigenous populations of A. flavus colonizing corn grain. Two sets of experiments were conducted to assess the competitiveness of strain K49 when challenged against two...

Ectomycorrhizal fungi and interspecific competition: species interactions, community structure, coexistence mechanisms, and future research directions.

PubMed

Kennedy, Peter

2010-09-01

The field of ectomycorrhizal fungal (EMF) ecology has largely developed outside the ecological mainstream, owing in large part to the challenges in studying the structure and dynamics of EMF communities. With advances in molecular identification and other research techniques, however, there has been growing interest among mycologists and ecologists in understanding how different ecological factors affect EMF community structure and diversity. While factors such as soil chemistry and host specificity have long been considered important, an increasing number of laboratory and field studies have documented that interspecific competition also has a major impact on EMF species interactions and may significantly influence EMF community structure. In this review, I examine the progress that has been made in understanding the nature of EMF competition. Currently, there are four conclusions that can be drawn: negative competitive effects are rarely reciprocal; competitive outcomes are environmentally context-dependent; field distributions often reflect competitive interactions; and timing of colonization influences competitive success. In addition, I highlight recent studies documenting links between competitive coexistence and EMF community structure, including checkerboard distributions, lottery models, storage effects, and colonization-competition tradeoffs. Finally, I discuss several aspects of EMF competition needing further investigation and some newer methods with which to address them.

Interactive effects of juvenile defoliation, light conditions, and interspecific competition on growth and ectomycorrhizal colonization of Fagus sylvatica and Pinus sylvestris seedlings.

PubMed

Trocha, Lidia K; Weiser, Ewa; Robakowski, Piotr

2016-01-01

Seedlings of forest tree species are exposed to a number of abiotic (organ loss or damage, light shortage) and biotic (interspecific competition) stress factors, which may lead to an inhibition of growth and reproduction and, eventually, to plant death. Growth of the host and its mycorrhizal symbiont is often closely linked, and hence, host damage may negatively affect the symbiont. We designed a pot experiment to study the response of light-demanding Pinus sylvestris and shade-tolerant Fagus sylvatica seedlings to a set of abiotic and biotic stresses and subsequent effects on ectomycorrhizal (ECM) root tip colonization, seedling biomass, and leaf nitrogen content. The light regime had a more pronounced effect on ECM colonization than did juvenile damage. The interspecific competition resulted in higher ECM root tip abundance for Pinus, but this effect was insignificant in Fagus. Low light and interspecific competition resulted in lower seedling biomass compared to high light, and the effect of the latter was partially masked by high light. Leaf nitrogen responded differently in Fagus and Pinus when they grew in interspecific competition. Our results indicated that for both light-demanding (Pinus) and shade-tolerant (Fagus) species, the light environment was a major factor affecting seedling growth and ECM root tip abundance. The light conditions favorable for the growth of seedlings may to some extent compensate for the harmful effects of juvenile organ loss or damage and interspecific competition.

Interference competition and invasion: spatial structure, novel weapons and resistance zones.

PubMed

Allstadt, Andrew; Caraco, Thomas; Molnár, F; Korniss, G

2012-08-07

Certain invasive plants may rely on interference mechanisms (e.g., allelopathy) to gain competitive superiority over native species. But expending resources on interference presumably exacts a cost in another life-history trait, so that the significance of interference competition for invasion ecology remains uncertain. We model ecological invasion when combined effects of preemptive and interference competition govern interactions at the neighborhood scale. We consider three cases. Under "novel weapons," only the initially rare invader exercises interference. For "resistance zones" only the resident species interferes, and finally we take both species as interference competitors. Interference increases the other species' mortality, opening space for colonization. However, a species exercising greater interference has reduced propagation, which can hinder its colonization of open sites. Interference never enhances a rare invader's growth in the homogeneously mixing approximation to our model. But interference can significantly increase an invader's competitiveness, and its growth when rare, if interactions are structured spatially. That is, interference can increase an invader's success when colonization of open sites depends on local, rather than global, species densities. In contrast, interference enhances the common, resident species' resistance to invasion independently of spatial structure, unless the propagation-cost is too great. The particular combination of propagation and interference producing the strongest biotic resistance in a resident species depends on the shape of the tradeoff between the two traits. Increases in background mortality (i.e., mortality not due to interference) always reduce the effectiveness of interference competition. Copyright © 2012 Elsevier Ltd. All rights reserved.

Does polyembryony confer a competitive advantage to the invasive perennial vine Vincetoxicum rossicum (Apocynaceae)?

PubMed

Blanchard, Megan L; Barney, Jacob N; Averill, Kristine M; Mohler, Charles L; Ditommaso, Antonio

2010-02-01

Determining which traits may allow some introduced plant species to become invasive in their new environment continues to be a key question in invasion biology. Vincetoxicum rossicum is an invasive, perennial vine colonizing natural and seminatural habitats primarily in the northeastern United States and southeastern Canada. More than half its seeds exhibit polyembryony, a relatively uncommon condition in which a single seed produces multiple seedlings. For evaluating the potential consequences of polyembryony on invasiveness, V. rossicum plants derived from seeds of three embryonic classes-singlets, doublets, and triplets (one, two, and three seedlings per seed, respectively)-were paired in all combinations intraspecifically and with the co-occurring native herbs Solidago canadensis and Asclepias syriaca in a greenhouse study. Vincetoxicum rossicum biomass was 25-55% greater and follicle production 55-100% greater under intraspecific competition compared with interspecific competition. However, within a competitive environment, follicle production varied little. Regardless of competitive environment, V. rossicum originating from seeds with a greater number of embryos typically performed no better than plants arising from seed with fewer embryos (singlets = doublets = triplets)-except intraspecifically where doublets outperformed singlets, and with S. canadensis where triplets outperformed singlets. Our findings suggest that overall performance and fitness of V. rossicum is higher in monocultures than in mixed stands and that its ability to invade new habitats may not be attributable to the production of polyembryonic seeds.

Temperature-specific competition between invasive mosquitofish and an endangered cyprinodontid fish.

PubMed

Carmona-Catot, Gerard; Magellan, Kit; García-Berthou, Emili

2013-01-01

Condition-specific competition is widespread in nature. Species inhabiting heterogeneous environments tend to differ in competitive abilities depending on environmental stressors. Interactions between these factors can allow coexistence of competing species, which may be particularly important between invasive and native species. Here, we examine the effects of temperature on competitive interactions between invasive mosquitofish, Gambusia holbrooki, and an endemic Iberian toothcarp, Aphanius iberus. We compare the tendency to approach heterospecifics and food capture rates between these two species, and examine differences between sexes and species in aggressive interactions, at three different temperatures (19, 24 and 29°C) in three laboratory experiments. Mosquitofish exhibit much more aggression than toothcarp. We show that mosquitofish have the capacity to competitively displace toothcarp through interference competition and this outcome is more likely at higher temperatures. We also show a reversal in the competitive hierarchy through reduced food capture rate by mosquitofish at lower temperatures and suggest that these two types of competition may act synergistically to deprive toothcarp of food at higher temperatures. Males of both species carry out more overtly aggressive acts than females, which is probably related to the marked sexual dimorphism and associated mating systems of these two species. Mosquitofish may thus impact heavily on toothcarp, and competition from mosquitofish, especially in warmer summer months, may lead to changes in abundance of the native species and displacement to non-preferred habitats. Globally increasing temperatures mean that highly invasive, warm-water mosquitofish may be able to colonize environments from which they are currently excluded through reduced physiological tolerance to low temperatures. Research into the effects of temperature on interactions between native and invasive species is thus of fundamental importance.

Temperature-Specific Competition between Invasive Mosquitofish and an Endangered Cyprinodontid Fish

PubMed Central

Carmona-Catot, Gerard; Magellan, Kit; García-Berthou, Emili

2013-01-01

Condition-specific competition is widespread in nature. Species inhabiting heterogeneous environments tend to differ in competitive abilities depending on environmental stressors. Interactions between these factors can allow coexistence of competing species, which may be particularly important between invasive and native species. Here, we examine the effects of temperature on competitive interactions between invasive mosquitofish, Gambusia holbrooki, and an endemic Iberian toothcarp, Aphanius iberus. We compare the tendency to approach heterospecifics and food capture rates between these two species, and examine differences between sexes and species in aggressive interactions, at three different temperatures (19, 24 and 29°C) in three laboratory experiments. Mosquitofish exhibit much more aggression than toothcarp. We show that mosquitofish have the capacity to competitively displace toothcarp through interference competition and this outcome is more likely at higher temperatures. We also show a reversal in the competitive hierarchy through reduced food capture rate by mosquitofish at lower temperatures and suggest that these two types of competition may act synergistically to deprive toothcarp of food at higher temperatures. Males of both species carry out more overtly aggressive acts than females, which is probably related to the marked sexual dimorphism and associated mating systems of these two species. Mosquitofish may thus impact heavily on toothcarp, and competition from mosquitofish, especially in warmer summer months, may lead to changes in abundance of the native species and displacement to non-preferred habitats. Globally increasing temperatures mean that highly invasive, warm-water mosquitofish may be able to colonize environments from which they are currently excluded through reduced physiological tolerance to low temperatures. Research into the effects of temperature on interactions between native and invasive species is thus of fundamental importance. PMID:23382951

Conditions Promoting Mycorrhizal Parasitism Are of Minor Importance for Competitive Interactions in Two Differentially Mycotrophic Species

PubMed Central

Friede, Martina; Unger, Stephan; Hellmann, Christine; Beyschlag, Wolfram

2016-01-01

Interactions of plants with arbuscular mycorrhizal fungi (AMF) may range along a broad continuum from strong mutualism to parasitism, with mycorrhizal benefits received by the plant being determined by climatic and edaphic conditions affecting the balance between carbon costs vs. nutritional benefits. Thus, environmental conditions promoting either parasitism or mutualism can influence the mycorrhizal growth dependency (MGD) of a plant and in consequence may play an important role in plant-plant interactions. In a multifactorial field experiment we aimed at disentangling the effects of environmental and edaphic conditions, namely the availability of light, phosphorus and nitrogen, and the implications for competitive interactions between Hieracium pilosella and Corynephorus canescens for the outcome of the AMF symbiosis. Both species were planted in single, intraspecific and interspecific combinations using a target-neighbor approach with six treatments distributed along a gradient simulating conditions for the interaction between plants and AMF ranking from mutualistic to parasitic. Across all treatments we found mycorrhizal association of H. pilosella being consistently mutualistic, while pronounced parasitism was observed in C. canescens, indicating that environmental and edaphic conditions did not markedly affect the cost:benefit ratio of the mycorrhizal symbiosis in both species. Competitive interactions between both species were strongly affected by AMF, with the impact of AMF on competition being modulated by colonization. Biomass in both species was lowest when grown in interspecific competition, with colonization being increased in the less mycotrophic C. canescens, while decreased in the obligate mycotrophic H. pilosella. Although parasitism-promoting conditions negatively affected MGD in C. canescens, these effects were small as compared to growth decreases related to increased colonization levels in this species. Thus, the lack of plant control over mycorrhizal colonization was identified as a possible key factor for the outcome of competition, while environmental and edaphic conditions affecting the mutualism-parasitism continuum appeared to be of minor importance. PMID:27729924

Contribution of Urease to Colonization by Shiga Toxin-Producing Escherichia coli

PubMed Central

Steyert, Susan R.

2012-01-01

Shiga toxin-producing Escherichia coli (STEC) is a food-borne pathogen with a low infectious dose that colonizes the colon in humans and can cause severe clinical manifestations such as hemolytic-uremic syndrome. The urease enzyme, encoded in the STEC chromosome, has been demonstrated to act as a virulence factor in other bacterial pathogens. The NH3 produced as urease hydrolyzes urea can aid in buffering bacteria in acidic environments as well as provide an easily assimilated source of nitrogen that bacteria can use to gain a metabolic advantage over intact microflora. Here, we explore the role of urease in STEC pathogenicity. The STEC urease enzyme exhibited maximum activity near neutral pH and during the stationary-growth phase. Experiments altering growth conditions performed with three phylogenetically distinct urease-positive strains demonstrated that the STEC ure gene cluster is inducible by neither urea nor pH but does respond to nitrogen availability. Quantitative reverse transcription-PCR (qRT-PCR) data indicate that nitrogen inhibits the transcriptional response. The deletion of the ure gene locus was constructed in STEC strain 88-0643, and the ure mutant was used with the wild-type strain in competition experiments in mouse models to examine the contribution of urease. The wild-type strain was twice as likely to survive passage through the acidic stomach and demonstrated an enhanced ability to colonize the intestinal tract compared to the ure mutant strain. These in vivo experiments reveal that, although the benefit STEC gains from urease expression is modest and not absolutely required for colonization, urease can contribute to the pathogenicity of STEC. PMID:22665380

Evaluating Darwin’s Naturalization Hypothesis in Experimental Plant Assemblages: Phylogenetic Relationships Do Not Determine Colonization Success

PubMed Central

Castro, Sergio A.; Escobedo, Victor M.; Aranda, Jorge; Carvallo, Gastón O.

2014-01-01

Darwin’s naturalization hypothesis (DNH) proposes that colonization is less likely when the colonizing species is related to members of the invaded community, because evolutionary closeness intensifies competition among species that share similar resources. Studies that have evaluated DNH from correlational evidence have yielded controversial results with respect to its occurrence and generality. In the present study we carried out a set of manipulative experiments in which we controlled the phylogenetic relatedness of one colonizing species (Lactuca sativa) with five assemblages of plants (the recipient communities), and evaluated the colonizing success using five indicators (germination, growth, flowering, survival, and recruitment). The evolutionary relatedness was calculated as the mean phylogenetic distance between Lactuca and the members of each assemblage (MPD) and by the mean phylogenetic distance to the nearest neighbor (MNND). The results showed that the colonization success of Lactuca was not affected by MPD or MNND values, findings that do not support DNH. These results disagree with experimental studies made with communities of microorganisms, which show an inverse relation between colonization success and phylogenetic distances. We suggest that these discrepancies may be due to the high phylogenetic distance used, since in our experiments the colonizing species (Lactuca) was a distant relative of the assemblage members, while in the other studies the colonizing taxa have been related at the congeneric and conspecific levels. We suggest that under field conditions the phylogenetic distance is a weak predictor of competition, and it has a limited role in determining colonization success, contrary to prediction of the DNH. More experimental studies are needed to establish the importance of phylogenetic distance between colonizing species and invaded community on colonization success. PMID:25141013

Effects of available water on growth and competition of southern pine beetle associated fungi

Treesearch

Kier D. Klepzig; J. Flores-Otero; R.W. Hofstetter; M.P. Ayers

2004-01-01

Competitive interactions among bark beetle associated fungi are potentially influenced by abiotic factors. Water potential, in particular, undergoes marked changes over the course of beetle colonization of tree hosts. To investigate the impact of water potential on competition among three southern pine beetle associated fungi, Ophiostoma minus,

COMPETITIVE ABILITY IN MALE HOUSE MICE (Mus musculus): GENETIC INFLUENCES

PubMed Central

Cunningham, Christopher B.; Ruff, James S.; Chase, Kevin; Potts, Wayne K.; Carrier, David R.

2013-01-01

Conspecifics of many animal species physically compete to gain reproductive resources and thus fitness. Despite the importance of competitive ability across the animal kingdom, specific traits that influence or underpin competitive ability are poorly characterized. Here, we investigate whether there are genetic influences on competitive ability within male house mice. Additionally, we examined if litter demographics (litter size and litter sex ratio) influence competitive ability. We phenotyped two generations for a male s ability to possess a reproductive resource--a prime nesting site--using semi-natural enclosures with mixed sex groupings. We used the animal model coupled with an extensive pedigree to estimate several genetic parameters. Competitive ability was found to be highly heritable, but only displayed a moderate genetic correlation to body mass. Interestingly, litter sex ratio had a weak negative influence on competitive ability. Litter size had no significant influence on competitive ability. Our study also highlights how much remians unknown about the proximal causes of competitive ability. PMID:23291957

Host Defense Peptide Resistance Contributes to Colonization and Maximal Intestinal Pathology by Crohn's Disease-Associated Adherent-Invasive Escherichia coli

PubMed Central

McPhee, Joseph B.; Small, Cherrie L.; Reid-Yu, Sarah A.; Brannon, John R.; Le Moual, Hervé

2014-01-01

Host defense peptides secreted by colonocytes and Paneth cells play a key role in innate host defenses in the gut. In Crohn's disease, the burden of tissue-associated Escherichia coli commonly increases at epithelial surfaces where host defense peptides concentrate, suggesting that this bacterial population might actively resist this mechanism of bacterial killing. Adherent-invasive E. coli (AIEC) is associated with Crohn's disease; however, the colonization determinants of AIEC in the inflamed gut are undefined. Here, we establish that host defense peptide resistance contributes to host colonization by Crohn's-associated AIEC. We identified a plasmid-encoded genomic island (called PI-6) in AIEC strain NRG857c that confers high-level resistance to α-helical cationic peptides and α- and β-defensins. Deletion of PI-6 sensitized strain NRG857c to these host defense molecules, reduced its competitive fitness in a mouse model of infection, and attenuated its ability to induce cecal pathology. This phenotype is due to two genes in PI-6, arlA, which encodes a Mig-14 family protein implicated in defensin resistance, and arlC, an OmpT family outer membrane protease. Implicit in these findings are new bacterial targets whose inhibition might limit AIEC burden and disease in the gut. PMID:24866805

Personality and problem-solving performance explain competitive ability in the wild.

PubMed

Cole, Ella F; Quinn, John L

2012-03-22

Competitive ability is a major determinant of fitness, but why individuals vary so much in their competitiveness remains only partially understood. One increasingly prevalent view is that realized competitive ability varies because it represents alternative strategies that arise because of the costs associated with competitiveness. Here we use a population of great tits (Parus major) to explore whether individual differences in competitive ability when foraging can be explained by two traits that have previously been linked to alternative behavioural strategies: the personality trait 'exploration behaviour' and a simple cognitive trait, 'innovative problem-solving performance'. We assayed these traits under standardized conditions in captivity and then measured competitive ability at feeders with restricted access in the wild. Competitive ability was repeatable within individual males across days and correlated positively with exploration behaviour, representing the first such demonstration of a link between a personality trait and both competitive ability and food intake in the wild. Competitive ability was also simultaneously negatively correlated with problem-solving performance; individuals who were poor competitors were good at problem-solving. Rather than being the result of variation in 'individual quality', our results support the hypothesis that individual variation in competitive ability can be explained by alternative behavioural strategies.

Production of a fungistatic substance by Pseudallescheria boydii isolated from soil amended with vegetable tissues and its significance.

PubMed

Ko, Wen-Hsiung; Tsou, Yi-Jung; Ju, Yu-Ming; Hsieh, Huei-Mei; Ann, Pao-Jen

2010-02-01

Four fungal isolates that were able to use vegetable tissues for multiplication in soil were isolated and identified as Pseudallescheria boydii based on morphological characteristics and ITS sequence similarity. When grown in broth prepared from the same vegetable tissues used in soil amendment, all these isolates of P. boydii produced a substance capable of reducing the disease incidence of black leaf spot of spoon cabbage caused by Alternaria brassicicola and inhibiting the germination of A. brassicicola conidia. The substance, which was fungistatic, was very stable under high temperature and high or low pH value. It was soluble in polar solvents and insoluble in non-polar solvents. Molecular weight estimation and ion exchange ability tests suggest that the fungistatic compound has a molecular weight between 500 and 1,000 and has no charge on its molecule. Results from this study suggest the possession of a strong competitive saprophytic ability by P. boydii, which in turn may explain the widespread occurrence of this human pathogen in soil. Production of a fungistatic substance when P. boydii was grown in broth prepared from vegetable tissues suggests the importance of antibiotic production in its competitive saprophytic colonization of organic matters in soil.

Ecological interactions in Aedes species on Reunion Island.

PubMed

Bagny Beilhe, L; Delatte, H; Juliano, S A; Fontenille, D; Quilici, S

2013-12-01

Two invasive, container-breeding mosquito species, Aedes aegypti (Stegomyia aegypti) and Aedes albopictus (Stegomyia albopicta) (Diptera: Culicidae), have different distribution patterns on Reunion Island. Aedes albopictus occurs in all areas and Ae. aegypti colonizes only some restricted areas already occupied by Ae. albopictus. This study investigates the abiotic and biotic ecological mechanisms that determine the distribution of Aedes species on Reunion Island. Life history traits (duration of immature stages, survivorship, fecundity, estimated finite rate of increase) in Ae. aegypti and Ae. albopictus were compared at different temperatures. These fitness measures were characterized in both species in response to competitive interactions among larvae. Aedes aegypti was drastically affected by temperature, performing well only at around 25 °C, at which it achieved its highest survivorship and greatest estimated rate of increase. The narrow distribution of this species in the field on Reunion Island may thus relate to its poor ability to cope with unfavourable temperatures. Aedes aegypti was also more negatively affected by high population densities and to some extent by interactions with Ae. albopictus, particularly in the context of limited food supplies. Aedes albopictus exhibited better population performance across a range of environmental conditions. Its ecological plasticity and its superior competitive ability relative to its congener may further enhance its invasion success on Reunion Island. © 2012 The Royal Entomological Society.

Intraspecific Competition Impacts Vibrio fischeri Strain Diversity during Initial Colonization of the Squid Light Organ

PubMed Central

Sun, Yan; LaSota, Elijah D.; Cecere, Andrew G.; LaPenna, Kyle B.; Larios-Valencia, Jessie; Wollenberg, Michael S.

2016-01-01

ABSTRACT Animal development and physiology depend on beneficial interactions with microbial symbionts. In many cases, the microbial symbionts are horizontally transmitted among hosts, thereby making the acquisition of these microbes from the environment an important event within the life history of each host. The light organ symbiosis established between the Hawaiian squid Euprymna scolopes and the bioluminescent bacterium Vibrio fischeri is a model system for examining how hosts acquire horizontally transmitted microbial symbionts. Recent studies have revealed that the light organ of wild-caught E. scolopes squid contains polyclonal populations of V. fischeri bacteria; however, the function and development of such strain diversity in the symbiosis are unknown. Here, we report our phenotypic and phylogenetic characterizations of FQ-A001, which is a V. fischeri strain isolated directly from the light organ of an E. scolopes individual. Relative to the type strain ES114, FQ-A001 exhibits similar growth in rich medium but displays increased bioluminescence and decreased motility in soft agar. FQ-A001 outcompetes ES114 in colonizing the crypt spaces of the light organs. Remarkably, we find that animals cocolonized with FQ-A001 and ES114 harbor singly colonized crypts, in contrast to the cocolonized crypts observed from competition experiments involving single genotypes. The results with our two-strain system suggest that strain diversity within the squid light organ is a consequence of diversity in the single-strain colonization of individual crypt spaces. IMPORTANCE The developmental programs and overall physiologies of most animals depend on diverse microbial symbionts that are acquired from the environment. However, the basic principles underlying how microbes colonize their hosts remain poorly understood. Here, we report our findings of bacterial strain competition within the coevolved animal-microbe symbiosis composed of the Hawaiian squid and bioluminescent bacterium Vibrio fischeri. Using fluorescent proteins to differentially label two distinct V. fischeri strains, we find that the strains are unable to coexist in the same niche within the host. Our results suggest that strain competition for distinct colonization sites dictates the strain diversity associated with the host. Our study provides a platform for studying how strain diversity develops within a host. PMID:27016564

Personality and problem-solving performance explain competitive ability in the wild

PubMed Central

Cole, Ella F.; Quinn, John L.

2012-01-01

Competitive ability is a major determinant of fitness, but why individuals vary so much in their competitiveness remains only partially understood. One increasingly prevalent view is that realized competitive ability varies because it represents alternative strategies that arise because of the costs associated with competitiveness. Here we use a population of great tits (Parus major) to explore whether individual differences in competitive ability when foraging can be explained by two traits that have previously been linked to alternative behavioural strategies: the personality trait ‘exploration behaviour’ and a simple cognitive trait, ‘innovative problem-solving performance’. We assayed these traits under standardized conditions in captivity and then measured competitive ability at feeders with restricted access in the wild. Competitive ability was repeatable within individual males across days and correlated positively with exploration behaviour, representing the first such demonstration of a link between a personality trait and both competitive ability and food intake in the wild. Competitive ability was also simultaneously negatively correlated with problem-solving performance; individuals who were poor competitors were good at problem-solving. Rather than being the result of variation in ‘individual quality’, our results support the hypothesis that individual variation in competitive ability can be explained by alternative behavioural strategies. PMID:21937498

Competition between Vibrio fischeri strains during initiation and maintenance of a light organ symbiosis.

PubMed

Lee, K H; Ruby, E G

1994-04-01

Colonization of the light-emitting organ of the Hawaiian squid Euprymna scolopes is initiated when the nascent organ of a newly hatched squid becomes inoculated with Vibrio fischeri cells present in the ambient seawater. Although they are induced for luminescence in the light organ, these symbiotic strains are characteristically non-visibly luminous (NVL) when grown in laboratory culture. The more typical visibly luminous (VL) type of V. fischeri co-occurs in Hawaiian seawater with these NVL strains; thus, two phenotypically distinct groups of this species potentially have access to the symbiotic niche, yet only the NVL ones are found there. In laboratory inoculation experiments, VL strains, when presented in pure culture, showed the same capability for colonizing the light organ as NVL strains. However, in experiments with mixed cultures composed of both VL and NVL strains, the VL ones were unable to compete with the NVL ones and did not persist within the light organ as the symbiosis became established. In addition, NVL strains entered light organs that had already been colonized by VL strains and displaced them. The mechanism underlying the symbiotic competitiveness exhibited by NVL strains remains unknown; however, it does not appear to be due to a higher potential for siderophore activity. While a difference in luminescence phenotype between VL and NVL strains in culture is not likely to be significant in the symbiosis, it has helped identify two distinct groups of V. fischeri that express different colonization capabilities in the squid light organ. This competitive difference provides a useful indication of important traits in light organ colonization.

Competition between Vibrio fischeri strains during initiation and maintenance of a light organ symbiosis.

PubMed Central

Lee, K H; Ruby, E G

1994-01-01

Colonization of the light-emitting organ of the Hawaiian squid Euprymna scolopes is initiated when the nascent organ of a newly hatched squid becomes inoculated with Vibrio fischeri cells present in the ambient seawater. Although they are induced for luminescence in the light organ, these symbiotic strains are characteristically non-visibly luminous (NVL) when grown in laboratory culture. The more typical visibly luminous (VL) type of V. fischeri co-occurs in Hawaiian seawater with these NVL strains; thus, two phenotypically distinct groups of this species potentially have access to the symbiotic niche, yet only the NVL ones are found there. In laboratory inoculation experiments, VL strains, when presented in pure culture, showed the same capability for colonizing the light organ as NVL strains. However, in experiments with mixed cultures composed of both VL and NVL strains, the VL ones were unable to compete with the NVL ones and did not persist within the light organ as the symbiosis became established. In addition, NVL strains entered light organs that had already been colonized by VL strains and displaced them. The mechanism underlying the symbiotic competitiveness exhibited by NVL strains remains unknown; however, it does not appear to be due to a higher potential for siderophore activity. While a difference in luminescence phenotype between VL and NVL strains in culture is not likely to be significant in the symbiosis, it has helped identify two distinct groups of V. fischeri that express different colonization capabilities in the squid light organ. This competitive difference provides a useful indication of important traits in light organ colonization. PMID:8144466

Efficacy and putative mode of action of native and commercial antagonistic yeasts against postharvest pathogens of pear.

PubMed

Lutz, M Cecilia; Lopes, Christian A; Rodriguez, M Eugenia; Sosa, M Cristina; Sangorrín, Marcela P

2013-06-17

Putative mechanisms of action associated with the biocontrol capacity of four yeast strains (Cryptoccocus albidus NPCC 1248, Pichia membranifaciens NPCC 1250, Cryptoccocus victoriae NPCC 1263 and NPCC 1259) against Penicillium expansum and Botrytis cinerea were studied by means of in vitro and in situ assays. C. albidus(YP), a commercial yeast was also evaluated for comparative purposes. The yeast strains exhibited a variety of different mechanisms including: wound colonization, germination inhibition, biofilm formation, secretion of killer toxins, competition for nutrient and secretion of hydrolytic enzymes (protease, chitinase and glucanase). The relationship between strains (and their associated antagonist mechanisms) and in situ antagonist activity was also evaluated. Results indicate that mechanisms such as production of hydrolytic enzymes, the ability for colonization of wounds, production of killer toxin and inhibition of germination are the most important for biocontrol activity. Our study indicate that multiple modes of action may explain why P. membranifaciens NPCC 1250 and C. victoriae NPCC 1263 provided excellent control of postharvest pears disease. Copyright © 2013 Elsevier B.V. All rights reserved.

Managing ulcerative colitis by increasing hydrogen production via oral administration of Acarbose.

PubMed

Zhu, Jian-Hong; Zhang, De-Qing; Chen, Wei-Chang

2013-01-01

The objective of the study was to investigate ulcerative colitis management through oral administration of acarbose. Acarbose has gained importance as a drug used widely to treat Diabetes Mellitus Type 2,as it acts on the small intestine by competitively inhibiting enzymes that delay the release of glucose from complex carbohydrates, thereby specifically reducing postprandial glucose excursion. The main side-effect of treatment with Acarbose, flatulence, occurs when undigested carbohydrates are fermented by colonic bacteria, resulting in considerable amounts of hydrogen. We found that the enteric benefits of Acarbose are partly due to be their ability to neutralise oxidative stress via increased production of H₂ in the gastrointestinal tract. Therefore, some symptoms of ulcerative colitis in human beings can be ameliorated by Acarbose.

Ecological studies on the revegetation process of surface coal mined areas in North Dakota. 4. Soil and vegetation development on topsoiled areas. Final report Aug 75-Jun 82

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iverson, L.R.; Wali, M.K.

1982-06-01

Four North Dakota reclaimed mined sites one to four years in age were studied for patterns of species colonization, biochemical interaction among species, competitive phenomena, and management applications. Kochia scoparia, a colonizer, was the dominant species for the first two years, but was completely eliminated by the fourth year; the planted Agropyron grasses concomitantly increased during this four year period. Competition experiments between Kochia and Agropyron revealed that Kochia initially acted as a 'nurse' crop for Agropyron establishment. Mowing of the first year colonizing species (especially Kochia) just prior to seed set proved to be very effective at reducing weedmore » populations and improving planted Agropyron populations in the second year. This method is highly recommended for use in hastening the establishment of planted species after mining.« less

Colon cancer cells colonize the lung from established liver metastases through p38 MAPK signalling and PTHLH.

PubMed

Urosevic, Jelena; Garcia-Albéniz, Xabier; Planet, Evarist; Real, Sebastián; Céspedes, María Virtudes; Guiu, Marc; Fernandez, Esther; Bellmunt, Anna; Gawrzak, Sylwia; Pavlovic, Milica; Mangues, Ramon; Dolado, Ignacio; Barriga, Francisco M; Nadal, Cristina; Kemeny, Nancy; Batlle, Eduard; Nebreda, Angel R; Gomis, Roger R

2014-07-01

The mechanisms that allow colon cancer cells to form liver and lung metastases, and whether KRAS mutation influences where and when metastasis occurs, are unknown. We provide clinical and molecular evidence showing that different MAPK signalling pathways are implicated in this process. Whereas ERK2 activation provides colon cancer cells with the ability to seed and colonize the liver, reduced p38 MAPK signalling endows cancer cells with the ability to form lung metastasis from previously established liver lesions. Downregulation of p38 MAPK signalling results in increased expression of the cytokine PTHLH, which contributes to colon cancer cell extravasation to the lung by inducing caspase-independent death in endothelial cells of the lung microvasculature. The concerted acquisition of metastatic traits in the colon cancer cells together with the sequential colonization of liver and lung highlights the importance of metastatic lesions as a platform for further dissemination.

Campylobacter jejuni CsrA Regulates Metabolic and Virulence Associated Proteins and Is Necessary for Mouse Colonization.

PubMed

Fields, Joshua A; Li, Jiaqi; Gulbronson, Connor J; Hendrixson, David R; Thompson, Stuart A

2016-01-01

Campylobacter jejuni infection is a leading bacterial cause of gastroenteritis and a common antecedent leading to Gullian-Barré syndrome. Our previous data suggested that the RNA-binding protein CsrA plays an important role in regulating several important phenotypes including motility, biofilm formation, and oxidative stress resistance. In this study, we compared the proteomes of wild type, csrA mutant, and complemented csrA mutant C. jejuni strains in an effort to elucidate the mechanisms by which CsrA affects virulence phenotypes. The putative CsrA regulon was more pronounced at stationary phase (111 regulated proteins) than at mid-log phase (25 regulated proteins). Proteins displaying altered expression in the csrA mutant included diverse metabolic functions, with roles in amino acid metabolism, TCA cycle, acetate metabolism, and various other cell processes, as well as pathogenesis-associated characteristics such as motility, chemotaxis, oxidative stress resistance, and fibronectin binding. The csrA mutant strain also showed altered autoagglutination kinetics when compared to the wild type. CsrA specifically bound the 5' end of flaA mRNA, and we demonstrated that CsrA is a growth-phase dependent repressor of FlaA expression. Finally, the csrA mutant exhibited reduced ability to colonize in a mouse model when in competition with the wild type, further underscoring the role of CsrA in C. jejuni colonization and pathogenesis.

Campylobacter jejuni CsrA Regulates Metabolic and Virulence Associated Proteins and Is Necessary for Mouse Colonization

PubMed Central

Fields, Joshua A.; Li, Jiaqi; Gulbronson, Connor J.; Hendrixson, David R.

2016-01-01

Campylobacter jejuni infection is a leading bacterial cause of gastroenteritis and a common antecedent leading to Gullian-Barré syndrome. Our previous data suggested that the RNA-binding protein CsrA plays an important role in regulating several important phenotypes including motility, biofilm formation, and oxidative stress resistance. In this study, we compared the proteomes of wild type, csrA mutant, and complemented csrA mutant C. jejuni strains in an effort to elucidate the mechanisms by which CsrA affects virulence phenotypes. The putative CsrA regulon was more pronounced at stationary phase (111 regulated proteins) than at mid-log phase (25 regulated proteins). Proteins displaying altered expression in the csrA mutant included diverse metabolic functions, with roles in amino acid metabolism, TCA cycle, acetate metabolism, and various other cell processes, as well as pathogenesis-associated characteristics such as motility, chemotaxis, oxidative stress resistance, and fibronectin binding. The csrA mutant strain also showed altered autoagglutination kinetics when compared to the wild type. CsrA specifically bound the 5’ end of flaA mRNA, and we demonstrated that CsrA is a growth-phase dependent repressor of FlaA expression. Finally, the csrA mutant exhibited reduced ability to colonize in a mouse model when in competition with the wild type, further underscoring the role of CsrA in C. jejuni colonization and pathogenesis. PMID:27257952

In vitro selection of enteric microflora for potential use as a competitive exclusion culture against Campylobacter in poultry

USDA-ARS?s Scientific Manuscript database

The administration of nonpathogenic microflora in neonatal poultry has been employed to reduce or eliminate the colonization of enteric pathogens. This concept, also called competitive exclusion (CE), although effective against Salmonella, has not consistently worked against Campylobacter. Most CE...

Simulating the Interacting Effects of Intraspecific Variation, Disturbance, and Competition on Climate-Driven Range Shifts in Trees.

PubMed

Moran, Emily V; Ormond, Rhys A

2015-01-01

Climate change is expected to favor shifts in plant distributions; some such shifts are already being observed along elevation gradients. However, the rate of such shifts may be limited by their ability to reach newly suitable areas and by competition from resident species. The degree of local adaptation and genetic variation may also play a role in the interaction between migrants and residents by affecting relative fitness. We used a simulation model to explore the interacting effects of dispersal, fecundity, disturbance, and genetic variation on range-edge dynamics between a pair of demographically similar tree species. Ideal climate for an individual is determined by genotype. The simulated landscape undergoes an 80-year period of climate change in which climate bands shift upslope; subsequently, climate is held constant for 300 years. The presence of a high-elevation competitor caused a significant lag in the range shift of the low-elevation species relative to competition-free scenarios. Increases in fecundity and dispersal distance both helped to speed up the replacement of the high-elevation species by the low-elevation species at their range boundary. While some disturbance scenarios facilitated this transition, frequent canopy disturbance inhibited colonization by removing reproductive adults and led to range contractions in both species. Differences between dispersal scenarios were more pronounced when disturbance was frequent (15 vs. 25 year return interval) and dispersal was limited. When the high-elevation species lacked genetic variation, its range was more-easily invaded by the low-elevation species, while a similar lack of variation in the low-elevation species inhibited colonization-but only when this lack of variation decreased the fitness of the affected species near the range boundary. Our model results support the importance of measuring and including dispersal/fecundity, disturbance type and frequency, and genetic variation when assessing the potential for range shifts and species vulnerability to climate change.

A comprehensive test of evolutionarily increased competitive ability in a highly invasive plant species

PubMed Central

Joshi, Srijana; Gruntman, Michal; Bilton, Mark; Seifan, Merav; Tielbörger, Katja

2014-01-01

Background and Aims A common hypothesis to explain plants' invasive success is that release from natural enemies in the introduced range selects for reduced allocation to resistance traits and a subsequent increase in resources available for growth and competitive ability (evolution of increased competitive ability, EICA). However, studies that have investigated this hypothesis have been incomplete as they either did not test for all aspects of competitive ability or did not select appropriate competitors. Methods Here, the prediction of increased competitive ability was examined with the invasive plant Lythrum salicaria (purple loosestrife) in a set of common-garden experiments that addressed these aspects by carefully distinguishing between competitive effect and response of invasive and native plants, and by using both intraspecific and interspecific competition settings with a highly vigorous neighbour, Urtica dioica (stinging nettle), which occurs in both ranges. Key Results While the intraspecific competition results showed no differences in competitive effect or response between native and invasive plants, the interspecific competition experiment revealed greater competitive response and effect of invasive plants in both biomass and seed production. Conclusions The use of both intra- and interspecific competition experiments in this study revealed opposing results. While the first experiment refutes the EICA hypothesis, the second shows strong support for it, suggesting evolutionarily increased competitive ability in invasive populations of L. salicaria. It is suggested that the use of naturally co-occurring heterospecifics, rather than conspecifics, may provide a better evaluation of the possible evolutionary shift towards greater competitive ability. PMID:25301818

Curcuma longa extract exerts a myorelaxant effect on the ileum and colon in a mouse experimental colitis model, independent of the anti-inflammatory effect.

PubMed

Aldini, Rita; Budriesi, Roberta; Roda, Giulia; Micucci, Matteo; Ioan, Pierfranco; D'Errico-Grigioni, Antonia; Sartini, Alessandro; Guidetti, Elena; Marocchi, Margherita; Cevenini, Monica; Rosini, Francesca; Montagnani, Marco; Chiarini, Alberto; Mazzella, Giuseppe

2012-01-01

Curcuma has long been used as an anti-inflammatory agent in inflammatory bowel disease. Since gastrointestinal motility is impaired in inflammatory states, the aim of this work was to evaluate if Curcuma Longa had any effect on intestinal motility. The biological activity of Curcuma extract was evaluated against Carbachol induced contraction in isolated mice intestine. Acute and chronic colitis were induced in Balb/c mice by Dextran Sulphate Sodium administration (5% and 2.5% respectively) and either Curcuma extract (200 mg/kg/day) or placebo was thereafter administered for 7 and 21 days respectively. Spontaneous contractions and the response to Carbachol and Atropine of ileum and colon were studied after colitis induction and Curcuma administration. Curcuma extract reduced the spontaneous contractions in the ileum and colon; the maximal response to Carbachol was inhibited in a non-competitive and reversible manner. Similar results were obtained in ileum and colon from Curcuma fed mice. DSS administration decreased the motility, mainly in the colon and Curcuma almost restored both the spontaneous contractions and the response to Carbachol after 14 days assumption, compared to standard diet, but a prolonged assumption of Curcuma decreased the spontaneous and Carbachol-induced contractions. Curcuma extract has a direct and indirect myorelaxant effect on mouse ileum and colon, independent of the anti-inflammatory effect. The indirect effect is reversible and non-competitive with the cholinergic agent. These results suggest the use of curcuma extract as a spasmolytic agent.

A comprehensive test of evolutionarily increased competitive ability in a highly invasive plant species.

PubMed

Joshi, Srijana; Gruntman, Michal; Bilton, Mark; Seifan, Merav; Tielbörger, Katja

2014-12-01

A common hypothesis to explain plants' invasive success is that release from natural enemies in the introduced range selects for reduced allocation to resistance traits and a subsequent increase in resources available for growth and competitive ability (evolution of increased competitive ability, EICA). However, studies that have investigated this hypothesis have been incomplete as they either did not test for all aspects of competitive ability or did not select appropriate competitors. Here, the prediction of increased competitive ability was examined with the invasive plant Lythrum salicaria (purple loosestrife) in a set of common-garden experiments that addressed these aspects by carefully distinguishing between competitive effect and response of invasive and native plants, and by using both intraspecific and interspecific competition settings with a highly vigorous neighbour, Urtica dioica (stinging nettle), which occurs in both ranges. While the intraspecific competition results showed no differences in competitive effect or response between native and invasive plants, the interspecific competition experiment revealed greater competitive response and effect of invasive plants in both biomass and seed production. The use of both intra- and interspecific competition experiments in this study revealed opposing results. While the first experiment refutes the EICA hypothesis, the second shows strong support for it, suggesting evolutionarily increased competitive ability in invasive populations of L. salicaria. It is suggested that the use of naturally co-occurring heterospecifics, rather than conspecifics, may provide a better evaluation of the possible evolutionary shift towards greater competitive ability. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Competitive outcome of Daphnia-Simocephalus experimental microcosms: salinity versus priority effects.

PubMed

Loureiro, Cláudia; Pereira, Joana L; Pedrosa, M Arminda; Gonçalves, Fernando; Castro, Bruno B

2013-01-01

Competition is a major driving force in freshwaters, especially given the cyclic nature and dynamics of pelagic food webs. Competition is especially important in the initial species assortment during colonization and re-colonization events, which depends strongly on the environmental context. Subtle changes, such as saline intrusion, may disrupt competitive relationships and, thus, influence community composition. Bearing this in mind, our objective was to assess whether low salinity levels (using NaCl as a proxy) alter the competitive outcome (measured as the rate of population biomass increase) of Daphnia-Simocephalus experimental microcosms, taking into account interactions with priority effects (sequential species arrival order). With this approach, we aimed to experimentally demonstrate a putative mechanism of differential species sorting in brackish environments or in freshwaters facing secondary salinization. Experiments considered three salinity levels, regarding NaCl added (0.00, 0.75 and 1.50 g L(-1)), crossed with three competition scenarios (no priority, priority of Daphnia over Simocephalus, and vice-versa). At lower NaCl concentrations (0.00 and 0.75 g L(-1)), Daphnia was a significantly superior competitor, irrespective of the species inoculation order, suggesting negligible priority effects. However, the strong decrease in Daphnia population growth at 1.50 g L(-1) alleviated the competitive pressure on Simocephalus, causing an inversion of the competitive outcome in favour of Simocephalus. The intensity of this inversion depended on the competition scenario. This salinity-mediated disruption of the competitive outcome demonstrates that subtle environmental changes produce indirect effects in key ecological mechanisms, thus altering community composition, which may lead to serious implications in terms of ecosystem functioning (e.g. lake regime shifts due to reduced grazing) and biodiversity.

The relative nature of fertilization success: Implications for the study of post-copulatory sexual selection

PubMed Central

2008-01-01

Background The determination of genetic variation in sperm competitive ability is fundamental to distinguish between post-copulatory sexual selection models based on good-genes vs compatible genes. The sexy-sperm and the good-sperm hypotheses for the evolution of polyandry require additive (intrinsic) effects of genes influencing sperm competitiveness, whereas the genetic incompatibility hypothesis invokes non-additive genetic effects. A male's sperm competitive ability is typically estimated from his fertilization success, a measure that is dependent on the ability of rival sperm competitors to fertilize the ova. It is well known that fertilization success may be conditional to genotypic interactions among males as well as between males and females. However, the consequences of effects arising from the random sampling of sperm competitors upon the estimation of genetic variance in sperm competitiveness have been overlooked. Here I perform simulations of mating trials performed in the context of sibling analysis to investigate whether the ability to detect additive genetic variance underlying the sperm competitiveness phenotype is hindered by the relative nature of fertilization success measurements. Results Fertilization success values render biased sperm competitive ability values. Furthermore, asymmetries among males in the errors committed when estimating sperm competitive abilities are likely to exist as long as males exhibit variation in sperm competitiveness. Critically, random effects arising from the relative nature of fertilization success lead to an underestimation of underlying additive genetic variance in sperm competitive ability. Conclusion The results show that, regardless of the existence of genotypic interactions affecting the output of sperm competition, fertilization success is not a perfect predictor of sperm competitive ability because of the stochasticity of the background used to obtain fertilization success measures. Random effects need to be considered in the debate over the maintenance of genetic variation in sperm competitiveness, and when testing good-genes and compatible-genes processes as explanations of polyandrous behaviour using repeatability/heritability data in sperm competitive ability. These findings support the notion that the genetic incompatibility hypothesis needs to be treated as an alternative hypothesis, rather than a null hypothesis, in studies that fail to detect intrinsic sire effects on the sperm competitiveness phenotype. PMID:18474087

The PapG-adhesin at the tip of P-fimbriae provides Escherichia coli with a competitive edge in experimental bladder infections of cynomolgus monkeys

PubMed Central

1995-01-01

Human urinary tract infection is an infectious disease that depends on a series of host-microbial interactions. The bacteria first colonize the colon and then the periurethral/vaginal areas; they ascend to and infect first the bladder and then the kidneys. Expression of Escherichia coli P-fimbriae constitutes the strongest correlation to renal pathogenicity, but is also related to first-time cystitis in children. The role of P-fimbriae in the preceding steps in the infectious process is unknown. To examine this, we constructed, from a P-fimbriated E. coli strain with a class II G-adhesin preferentially binding to globoside, one isogenic mutant lacking the G-adhesin and another isogenic mutant in which we replaced the papG class II allele with a class III adhesin preferentially binding to the Forssman antigen. We report here the comparison of the adhesin knockout mutant (DS17-8) and the class-switch mutant (DS17-1) with the wild-type (DS17) for in vivo colonization of the gut, vagina, and bladder of cynomolgus monkeys. It was recently shown that the class II tip G-adhesin is a prerequisite for acute pyelonephritis to occur in the monkey model in the absence of other kidney-specific adhesins or obstruction of the urinary flow. Here we show that it is not required for bladder infection but gives a competitive advantage in mixed infections. In the vagina and colon, the G-adhesin gives no competitive advantage. PMID:7500014

Clarifying Baker's Law

PubMed Central

Cheptou, P.-O.

2012-01-01

Background Baker's Law states that colonization by self-compatible organisms is more likely to be successful than colonization by self-incompatible organisms because of the ability for self-compatible organisms to produce offspring without pollination agents. This simple model has proved very successful in plant ecology and has been applied to various contexts, including colonizing or ruderal species, islands colonizers, invasive species or mating system variation across distribution ranges. Moreover, it is one of the only models in population biology linking two traits of major importance in ecology, namely dispersal and mating system. Although Baker's Law has stimulated a large number of empirical studies reporting the association of self-fertilization and colonizing ability in various contexts, the data have not established a general pattern for the association of traits. Scope In this paper, a critical position is adopted to discuss and clarify Baker's Law. From the literature referring to Baker's Law, an analysis made regarding how mating success is considered in such studies and discrepancies with population genetics theory of mating systems are highlighted. The data reporting the association of self-fertilization and colonizing ability are also briefly reviewed and the potential bias in interpretation is discussed. Lastly, a recent theoretical model analysing the link between colonizing ability and self-fertilization is considered. Conclusions Evolutionary predictions are actually more complex than Baker's intuitive arguments. It appears that Baker's Law encompasses a variety of ecological scenarios, which cannot be considered a priori as equivalent. Questioning what has been considered as self-evident for more than 50 years seems a reasonable objective to analyse in-depth dispersal and mating system traits. PMID:21685434

An Ribonuclease T2 Family Protein Modulates Acinetobacter baumannii Abiotic Surface Colonization

PubMed Central

Jacobs, Anna C.; Blanchard, Catlyn E.; Catherman, Seana C.; Dunman, Paul M.; Murata, Yoshihiko

2014-01-01

Acinetobacter baumannii is an emerging bacterial pathogen of considerable medical concern. The organism's transmission and ability to cause disease has been associated with its propensity to colonize and form biofilms on abiotic surfaces in health care settings. To better understand the genetic determinants that affect biomaterial attachment, we performed a transposon mutagenesis analysis of abiotic surface-colonization using A. baumannii strain 98-37-09. Disruption of an RNase T2 family gene was found to limit the organism's ability to colonize polystyrene, polypropylene, glass, and stainless steel surfaces. DNA microarray analyses revealed that in comparison to wild type and complemented cells, the RNase T2 family mutant exhibited reduced expression of 29 genes, 15 of which are predicted to be associated with bacterial attachment and surface-associated motility. Motility assays confirmed that RNase T2 mutant displays a severe motility defect. Taken together, our results indicate that the RNase T2 family protein identified in this study is a positive regulator of A. baumannii's ability to colonize inanimate surfaces and motility. Moreover, the enzyme may be an effective target for the intervention of biomaterial colonization, and consequently limit the organism's transmission within the hospital setting. PMID:24489668

Role of luxS in Stress Tolerance and Adhesion Ability in Lactobacillus plantarum KLDS1.0391

PubMed Central

Jia, Fang-Fang; Zheng, Hui-Qi; Sun, Si-Rui; Pang, Xue-Hui; Liang, Yu; Shang, Jia-Cui; Zhu, Zong-Tao

2018-01-01

Lactobacillus plantarum, a probiotic, has a high survival rate and high colonization ability in the gastrointestinal tract. Tolerance to the gastrointestinal environment and adhesion to intestinal epithelial cells by some Lactobacillus species (excluding L. plantarum) are related to luxS/AI-2. Here, the role of luxS in tolerance to simulated digestive juice (SDJ) and adhesion to Caco-2 cells by L. plantarum KLDS1.0391 (hereafter, KLDS1.0391) was investigated. The KLDS1.0391 luxS mutant strain was constructed by homologous recombination. When luxS was deleted, acid and bile salt tolerance and survival rates in SDJ significantly decreased (p < 0.05 for all). The ability of the luxS deletion strain to adhere to Caco-2 cells was markedly lower than that of the wild-type strain (p < 0.05). The ability of the luxS mutant strain to adhere (competition, exclusion, and displacement) to Escherichia coli ATCC 25922 was significantly lower than that of the wild-type strain (p < 0.05 for all). A significant decrease was noted only in the exclusion adhesion inhibition of the luxS mutant strain to Salmonella typhimurium ATCC 14028 (p < 0.05). These results indicate that the luxS gene plays an important role in the gastrointestinal environment tolerance and adhesion ability of KLDS1.0391. PMID:29651434

Curcuma longa Extract Exerts a Myorelaxant Effect on the Ileum and Colon in a Mouse Experimental Colitis Model, Independent of the Anti-Inflammatory Effect

PubMed Central

Roda, Giulia; Micucci, Matteo; Ioan, Pierfranco; D’Errico-Grigioni, Antonia; Sartini, Alessandro; Guidetti, Elena; Marocchi, Margherita; Cevenini, Monica; Rosini, Francesca; Montagnani, Marco; Chiarini, Alberto; Mazzella, Giuseppe

2012-01-01

Background Curcuma has long been used as an anti-inflammatory agent in inflammatory bowel disease. Since gastrointestinal motility is impaired in inflammatory states, the aim of this work was to evaluate if Curcuma Longa had any effect on intestinal motility. Methods The biological activity of Curcuma extract was evaluated against Carbachol induced contraction in isolated mice intestine. Acute and chronic colitis were induced in Balb/c mice by Dextran Sulphate Sodium administration (5% and 2.5% respectively) and either Curcuma extract (200 mg/kg/day) or placebo was thereafter administered for 7 and 21 days respectively. Spontaneous contractions and the response to Carbachol and Atropine of ileum and colon were studied after colitis induction and Curcuma administration. Results Curcuma extract reduced the spontaneous contractions in the ileum and colon; the maximal response to Carbachol was inhibited in a non-competitive and reversible manner. Similar results were obtained in ileum and colon from Curcuma fed mice. DSS administration decreased the motility, mainly in the colon and Curcuma almost restored both the spontaneous contractions and the response to Carbachol after 14 days assumption, compared to standard diet, but a prolonged assumption of Curcuma decreased the spontaneous and Carbachol-induced contractions. Conclusions Curcuma extract has a direct and indirect myorelaxant effect on mouse ileum and colon, independent of the anti-inflammatory effect. The indirect effect is reversible and non-competitive with the cholinergic agent. These results suggest the use of curcuma extract as a spasmolytic agent. PMID:22984538

Comparison of tachykinin NK1 and NK2 receptors in the circular muscle of the guinea-pig ileum and proximal colon.

PubMed Central

Maggi, C. A.; Patacchini, R.; Meini, S.; Quartara, L.; Sisto, A.; Potier, E.; Giuliani, S.; Giachetti, A.

1994-01-01

1. The aim of this study was the pharmacological characterization of tachykinin NK1 and NK2 receptors mediating contraction in the circular muscle of the guinea-pig ileum and proximal colon. The action of substance P (SP), neurokinin A (NKA) and of the synthetic agonists [Sar9]SP sulphone, [Glp6,Pro9]SP(6-11) (septide) and [beta Ala8]NKA(4-10) was investigated. The affinities of various peptide and nonpeptide antagonists for the NK1 and NK2 receptor was estimated by use of receptor selective agonists. 2. The natural agonists, SP and NKA, produced concentration-dependent contraction in both preparations. EC50 values were 100 pM and 5 nM for SP, 1.2 nM and 19 nM for NKA in the ileum and colon, respectively. The action of SP and NKA was not significantly modified by peptidase inhibitors (bestatin, captopril and thiorphan, 1 microM each). 3. Synthetic NK1 and NK2 receptor agonists produced concentration-dependent contraction of the circular muscle of the ileum and proximal colon. EC50 values were 83 pM, 36 pM and 10 nM in the ileum, 8 nM, 0.7 nM and 12 nM in the colon for [Sar9]SP sulphone, septide and [beta Ala8]NKA-(4-10), respectively. The pseudopeptide derivative of NKA(4-10), MDL 28,564 behaved as a full or near-to-full agonist in both preparations, its EC50s being 474 nM and 55 nM in the ileum and colon, respectively. 4. Nifedipine (1 microM) abolished the response to septide and [Sar9]SP sulphone in the ileum and produced a rightward shift and large depression of the response in the colon. The response to [beta Ala8]NKA(4-10) was abolished in the ileum and largely unaffected in the colon. 5. The NK1 receptor antagonists, (+/-)-CP 96,34, FK 888 and GR 82,334 competitively antagonized the response to septide and [Sar9]SP sulphone in both preparations without affecting that to [beta Ala8]NKA(4-10). In general, the NK1 receptor antagonists were significantly more potent toward septide than [Sar9]SP sulphone in both preparations. 6. The NK2 receptor antagonists, GR 94,800 and SR 48,968 selectively antagonized the response to [beta Ala8]NKA(4-10) without affecting that to [Sar9]SP sulphone or septide in the ileum and colon. SR 48,968 produced noncompetitive antagonism of the response to the NK2 receptor agonist in the ileum and competitive antagonism in the colon. 7. MEN 10,376 and the cyclic pseudopeptide MEN 10,573 antagonized in a competitive manner the response to [beta Ala8]NKA(4-10) in the ileum and colon.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:7518302

Time-restricted flight ability influences dispersal and colonization rates in a group of freshwater beetles.

PubMed

Iversen, Lars Lønsmann; Rannap, Riinu; Briggs, Lars; Sand-Jensen, Kaj

2017-02-01

Variation in the ability to fly or not is a key mechanism for differences in local species occurrences. It is increasingly acknowledged that physiological or behavioral mechanisms rather than morphological differences may drive flight abilities. However, our knowledge on the seasonal variability and stressors creating nonmorphological differences in flight abilities and how it scales to local and regional occurrences is very limited particularly for small, short-lived species such as insects. Here, we examine how flight ability might vary across seasons and between two closely related genera of freshwater beetles with similar geographical ranges, life histories, and dispersal-related morphology. By combining flight experiments of >1,100 specimens with colonization rates in a metacommunity of 54 ponds in northern and eastern Europe, we have analyzed the relationship between flight ability and spatio-environmental distribution of the study genera. We find profound differences in flight ability between the two study genera across seasons. High flight ability for Acilius (97% of the tested individuals flew during the experiments) and low for Graphoderus (14%) corresponded to the different colonization rates of newly created ponds. Within a 5-year period, 81 and 31% of the study ponds were colonized by Acilius and Graphoderus , respectively. While Acilius dispersed throughout the season, flight activity in Graphoderus was restricted to stressed situations immediately after the emergence of adults. Regional colonization ability of Acilius was independent of spatial connectivity and mass effect from propagule sources. In contrast, Graphoderus species were closely related to high connectivity between ponds in the landscape. Our data suggest that different dispersal potential can account for different local occurrences of Acilius and Graphoderus . In general, our findings provide some of the first insights into the understanding of seasonal restrictions in flight patterns of aquatic beetles and their consequences for species distributions.

Neutral competition of stem cells is skewed by proliferative changes downstream of Hh and Hpo.

PubMed

Amoyel, Marc; Simons, Benjamin D; Bach, Erika A

2014-10-16

Neutral competition, an emerging feature of stem cell homeostasis, posits that individual stem cells can be lost and replaced by their neighbors stochastically, resulting in chance dominance of a clone at the niche. A single stem cell with an oncogenic mutation could bias this process and clonally spread the mutation throughout the stem cell pool. The Drosophila testis provides an ideal system for testing this model. The niche supports two stem cell populations that compete for niche occupancy. Here, we show that cyst stem cells (CySCs) conform to the paradigm of neutral competition and that clonal deregulation of either the Hedgehog (Hh) or Hippo (Hpo) pathway allows a single CySC to colonize the niche. We find that the driving force behind such behavior is accelerated proliferation. Our results demonstrate that a single stem cell colonizes its niche through oncogenic mutation by co-opting an underlying homeostatic process. © 2014 The Authors.

The introduced tree Prosopis juliflora is a serious threat to native species of the Brazilian Caatinga vegetation.

PubMed

de Souza Nascimento, Clóvis Eduardo; Tabarelli, Marcelo; da Silva, Carlos Alberto Domingues; Leal, Inara Roberta; de Souza Tavares, Wagner; Serrão, José Eduardo; Zanuncio, José Cola

2014-05-15

Despite its economic importance in the rural context, the Prosopis juliflora tree species has already invaded millions of hectares globally (particularly rangelands), threatening native biodiversity and rural sustainability. Here we examine seedling growth (leaf area, stem diameter, plant height) and seedling mortality across five native plant species of the Caatinga vegetation in response to competition with P. juliflora. Two sowing treatments with 10 replications were adopted within a factorial 2 × 5 randomized block design. Treatments consisted of P. juliflora seeds sowed with seeds of Caesalpinia ferrea, Caesalpinia microphylla, Erythrina velutina, Mimosa bimucronata and Mimosa tenuiflora (one single native species per treatment), while seeds of native species sowed without P. juliflora were adopted as controls. Overall, our results suggest that P. juliflora can reduce seedling growth by half and cause increased seedling mortality among woody plant species. Moreover, native species exhibit different levels of susceptibility to competition with P. juliflora, particularly in terms of plant growth. Such a superior competitive ability apparently permits P. juliflora to establish monospecific stands of adult trees, locally displacing native species or limiting their recruitment. The use of less sensitive species, such as C. ferrea and M. tenuiflora, to restore native vegetation before intensive colonization by P. juliflora should be investigated as an effective approach for avoiding its continuous spread across the Caatinga region. Copyright © 2014 Elsevier B.V. All rights reserved.

Alternaria in Food: Ecophysiology, Mycotoxin Production and Toxicology

PubMed Central

Patriarca, Andrea; Magan, Naresh

2015-01-01

Alternaria species are common saprophytes or pathogens of a wide range of plants pre- and post-harvest. This review considers the relative importance of Alternaria species, their ecology, competitiveness, production of mycotoxins and the prevalence of the predominant mycotoxins in different food products. The available toxicity data on these toxins and the potential future impacts of Alternaria species and their toxicity in food products pre- and post-harvest are discussed. The growth of Alternaria species is influenced by interacting abiotic factors, especially water activity (aw), temperature and pH. The boundary conditions which allow growth and toxin production have been identified in relation to different matrices including cereal grain, sorghum, cottonseed, tomato, and soya beans. The competitiveness of Alternaria species is related to their water stress tolerance, hydrolytic enzyme production and ability to produce mycotoxins. The relationship between A. tenuissima and other phyllosphere fungi has been examined and the relative competitiveness determined using both an Index of Dominance (ID) and the Niche Overlap Index (NOI) based on carbon-utilisation patterns. The toxicology of some of the Alternaria mycotoxins have been studied; however, some data are still lacking. The isolation of Alternaria toxins in different food products including processed products is reviewed. The future implications of Alternaria colonization/infection and the role of their mycotoxins in food production chains pre- and post-harvest are discussed. PMID:26190916

Pharmacological identification of β-adrenoceptor subtypes mediating isoprenaline-induced relaxation of guinea pig colonic longitudinal smooth muscle.

PubMed

Chino, Daisuke; Sone, Tomoyo; Yamazaki, Kumi; Tsuruoka, Yuri; Yamagishi, Risa; Shiina, Shunsuke; Obara, Keisuke; Yamaki, Fumiko; Higai, Koji; Tanaka, Yoshio

2018-01-01

Object We aimed to identify the β-adrenoceptor (β-AR) subtypes involved in isoprenaline-induced relaxation of guinea pig colonic longitudinal smooth muscle using pharmacological and biochemical approaches. Methods Longitudinal smooth muscle was prepared from the male guinea pig ascending colon and contracted with histamine prior to comparing the relaxant responses to three catecholamines (isoprenaline, adrenaline, and noradrenaline). The inhibitory effects of subtype-selective β-AR antagonists on isoprenaline-induced relaxation were then investigated. Results The relaxant potencies of the catecholamines were ranked as: isoprenaline > noradrenaline ≈ adrenaline, whereas the rank order was isoprenaline > noradrenaline > adrenaline in the presence of propranolol (a non-selective β-AR antagonist; 3 × 10 -7 M). Atenolol (a selective β 1 -AR antagonist; 3 × 10 -7 -10 -6  M) acted as a competitive antagonist of isoprenaline-induced relaxation, and the pA 2 value was calculated to be 6.49 (95% confidence interval: 6.34-6.83). The relaxation to isoprenaline was not affected by ICI-118,551 (a selective β 2 -AR antagonist) at 10 -9 -10 -8  M, but was competitively antagonized by 10 -7 -3 × 10 -7  M, with a pA 2 value of 7.41 (95% confidence interval: 7.18-8.02). In the presence of propranolol (3 × 10 -7 M), the relaxant effect of isoprenaline was competitively antagonized by bupranolol (a non-selective β-AR antagonist), with a pA 2 value of 5.90 (95% confidence interval: 5.73-6.35). Conclusion These findings indicated that the β-AR subtypes involved in isoprenaline-induced relaxation of colonic longitudinal guinea pig muscles are β 1 -AR and β 3 -AR.

Potential probiotic characteristics of Lactobacillus and Enterococcus strains isolated from traditional dadih fermented milk against pathogen intestinal colonization.

PubMed

Collado, M Carmen; Surono, Ingrid S; Meriluoto, Jussi; Salminen, Seppo

2007-03-01

Traditional fermented buffalo milk in Indonesia (dadih) has been believed to have a beneficial impact on human health, which could be related to the properties of the lactic acid bacteria (LAB) involved in its fermentation process. In previous studies, it was discovered that strains of dadih lactic isolates possessed some beneficial properties in vitro. In the present study, the adhesion capacity of specific LAB isolates from dadih to intestinal mucus was analyzed. Further, the ability to inhibit model human pathogens and displace them from mucus was assessed. The adhesion of tested LAB strains was strain-dependent and varied from 1.4 to 9.8%. The most adhesive Lactobacillus plantarum strain was IS-10506, with 9.8% adhesion. The competition assay between dadih LAB isolates and pathogens showed that a 2-h preincubation with L. plantarum at 37 degrees C significantly reduced pathogen adhesion to mucus. All tested LAB strains displaced and inhibited pathogen adhesion, but the results were strain-specific and dependent on time and pathogen strains. In general, L. plantarum IS-10506 showed the best ability against pathogen adhesion.

Are sick individuals weak competitors? Competitive ability of snails parasitized by a gigantism-inducing trematode.

PubMed

Seppälä, Otto; Karvonen, Anssi; Kuosa, Marja; Haataja, Maarit; Jokela, Jukka

2013-01-01

Parasitized individuals are often expected to be poor competitors because they are weakened by infections. Many trematode species, however, although extensively exploiting their mollusc hosts, also induce gigantism (increased host size) by diverting host resources towards growth instead of reproduction. In such systems, alternatively to reduced competitive ability due to negative effects of parasitism on host performance, larger size could allow more efficient resource acquisition and thus increase the relative competitive ability of host individuals. We addressed this hypothesis by testing the effect of a trematode parasite Diplostomum pseudospathaceum on the competitive ability of its snail host Lymnaea stagnalis. We experimentally examined the growth of snails kept in pairs in relation to their infection status and intensity of resource competition (i.e. food availability). We found that parasitized snails grew faster and their reproduction was reduced compared to unparasitized individuals indicating parasite-induced gigantism. However, growth of the snails was faster when competing with parasitized individuals compared to unparasitized snails indicating reduced competitive ability due to parasitism. The latter effect, however, was relatively weak suggesting that the effects of the parasite on snail physiology may partly override each other in determining competitive ability.

Are Sick Individuals Weak Competitors? Competitive Ability of Snails Parasitized by a Gigantism-Inducing Trematode

PubMed Central

Seppälä, Otto; Karvonen, Anssi; Kuosa, Marja; Haataja, Maarit; Jokela, Jukka

2013-01-01

Parasitized individuals are often expected to be poor competitors because they are weakened by infections. Many trematode species, however, although extensively exploiting their mollusc hosts, also induce gigantism (increased host size) by diverting host resources towards growth instead of reproduction. In such systems, alternatively to reduced competitive ability due to negative effects of parasitism on host performance, larger size could allow more efficient resource acquisition and thus increase the relative competitive ability of host individuals. We addressed this hypothesis by testing the effect of a trematode parasite Diplostomum pseudospathaceum on the competitive ability of its snail host Lymnaea stagnalis. We experimentally examined the growth of snails kept in pairs in relation to their infection status and intensity of resource competition (i.e. food availability). We found that parasitized snails grew faster and their reproduction was reduced compared to unparasitized individuals indicating parasite-induced gigantism. However, growth of the snails was faster when competing with parasitized individuals compared to unparasitized snails indicating reduced competitive ability due to parasitism. The latter effect, however, was relatively weak suggesting that the effects of the parasite on snail physiology may partly override each other in determining competitive ability. PMID:24205383

Kinetics and Strain Specificity of Rhizosphere and Endophytic Colonization by Enteric Bacteria on Seedlings of Medicago sativa and Medicago truncatula

PubMed Central

Dong, Yuemei; Iniguez, A. Leonardo; Ahmer, Brian M. M.; Triplett, Eric W.

2003-01-01

The presence of human-pathogenic, enteric bacteria on the surface and in the interior of raw produce is a significant health concern. Several aspects of the biology of the interaction between these bacteria and alfalfa (Medicago sativa) seedlings are addressed here. A collection of enteric bacteria associated with alfalfa sprout contaminations, along with Escherichia coli K-12, Salmonella enterica serotype Typhimurium strain ATCC 14028, and an endophyte of maize, Klebsiella pneumoniae 342, were labeled with green fluorescent protein, and their abilities to colonize the rhizosphere and the interior of the plant were compared. These strains differed widely in their endophytic colonization abilities, with K. pneumoniae 342 and E. coli K-12 being the best and worst colonizers, respectively. The abilities of the pathogens were between those of K. pneumoniae 342 and E. coli K-12. All Salmonella bacteria colonized the interiors of the seedlings in high numbers with an inoculum of 102 CFU, although infection characteristics were different for each strain. For most strains, a strong correlation between endophytic colonization and rhizosphere colonization was observed. These results show significant strain specificity for plant entry by these strains. Significant colonization of lateral root cracks was observed, suggesting that this may be the site of entry into the plant for these bacteria. At low inoculum levels, a symbiosis mutant of Medicago truncatula, dmi1, was colonized in higher numbers on the rhizosphere and in the interior by a Salmonella endophyte than was the wild-type host. Endophytic entry of M. truncatula appears to occur by a mechanism independent of the symbiotic infections by Sinorhizobium meliloti or mycorrhizal fungi. PMID:12620870

No difference in the competitive ability of introduced and native Trifolium provenances when grown with soil biota from their introduced and native ranges

PubMed Central

Shelby, Natasha; Hulme, Philip E.; van der Putten, Wim H.; McGinn, Kevin J.; Weser, Carolin; Duncan, Richard P.

2016-01-01

The evolution of increased competitive ability (EICA) hypothesis could explain why some introduced plant species perform better outside their native ranges. The EICA hypothesis proposes that introduced plants escape specialist pathogens or herbivores leading to selection for resources to be reallocated away from defence and towards greater competitive ability. We tested the hypothesis that escape from soil-borne enemies has led to increased competitive ability in three non-agricultural Trifolium (Fabaceae) species native to Europe that were introduced to New Zealand in the 19th century. Trifolium performance is intimately tied to rhizosphere biota. Thus, we grew plants from one introduced (New Zealand) and two native (Spain and the UK) provenances for each of three species in pots inoculated with soil microbiota collected from the rhizosphere beneath conspecifics in the introduced and native ranges. Plants were grown singly and in competition with conspecifics from a different provenance in order to compare competitive ability in the presence of different microbial communities. In contrast to the predictions of the EICA hypothesis, we found no difference in the competitive ability of introduced and native provenances when grown with soil microbiota from either the native or introduced range. Although plants from introduced provenances of two species grew more slowly than native provenances in native-range soils, as predicted by the EICA hypothesis, plants from the introduced provenance were no less competitive than native conspecifics. Overall, the growth rate of plants grown singly was a poor predictor of their competitive ability, highlighting the importance of directly quantifying plant performance in competitive scenarios, rather than relying on surrogate measures such as growth rate. PMID:26969431

Competitive Exclusion of Heterologous Campylobacter spp. in Chicks

PubMed Central

Chen, Hui-Cheng; Stern, Norman J.

2001-01-01

Chicken and human isolates of Campylobacter jejuni were used to provide oral challenge of day-old broiler chicks. The isolation ratio of the competing challenge strains was monitored and varied, depending upon the isolates used. A PCR-restriction fragment length polymorphism assay of the flagellin gene (flaA) was used to discriminate between the chick-colonizing isolates. Our observations indicated that the selected C. jejuni colonizers dominated the niche provided by the chicken ceca. Chicken isolates from the flaA type 7 grouping generally had numerical superiority over the human isolates when they were administered in our 1-day-old chick model. Our results suggest that it is possible to use combinations of C. jejuni chicken isolates as a defined bacterial preparation for the competitive exclusion of human-pathogenic C. jejuni in poultry. PMID:11157253

Diversifying evolution of competitiveness.

PubMed

Baldauf, Sebastian A; Engqvist, Leif; Weissing, Franz J

2014-10-29

In many species, individuals express phenotypic characteristics that enhance their competitiveness, that is, the ability to acquire resources in competition with others. Moreover, the degree of competitiveness varies considerably across individuals and in time. By means of an evolutionary model, we provide an explanation for this finding. We make the assumption that investment into competitiveness enhances the probability to acquire a high-quality resource, but at the same time reduces the ability of exploiting acquired resources with maximal efficiency. The model reveals that under a broad range of conditions competitiveness either converges to a polymorphic state, where individuals differing in competitive ability stably coexist, or is subject to perpetual transitions between periods of high and low competitiveness. The dynamics becomes even more complex if females can evolve preferences for (or against) competitive males. In extreme cases, such preferences can even drive the population to extinction.

Occupancy of yellow-billed and Pacific loons: evidence for interspecific competition and habitat mediated co-occurrence

USGS Publications Warehouse

Haynes, Trevor B.; Schmutz, Joel A.; Lindberg, Mark S.; Wright, Kenneth G.; Uher-Koch, Brian D.; Rosenberger, Amanda E.

2014-01-01

Interspecific competition is an important process structuring ecological communities, however, it is difficult to observe in nature. We used an occupancy modelling approach to evaluate evidence of competition between yellow-billed (Gavia adamsii) and Pacific (G. pacifica) loons for nesting lakes on the Arctic Coastal Plain of Alaska. With multiple years of data and survey platforms, we estimated dynamic occupancy states (e.g. rates of colonization or extinction from individual lakes) and controlled for detection differences among aircraft platforms and ground survey crews. Results indicated that yellow-billed loons were strong competitors and negatively influenced the occupancy of Pacific loons by excluding them from potential breeding lakes. Pacific loon occupancy was conditional on the presence of yellow-billed loons, with Pacific loons having almost a tenfold decrease in occupancy probability when yellow-billed loons were present and a threefold decrease in colonization probability when yellow-billed loons were present in the current or previous year. Yellow-billed and Pacific loons co-occurred less than expected by chance except on very large lakes or lakes with convoluted shorelines; variables which may decrease the cost of maintaining a territory in the presence of the other species. These results imply the existence of interspecific competition between yellow-billed and Pacific loons for nesting lakes; however, habitat characteristics which facilitate visual and spatial separation of territories can reduce competitive interactions and promote species co-occurrence.

Numerical assessment affects aggression and competitive ability: a team-fighting strategy for the ant Formica xerophila.

PubMed

Tanner, Colby J

2006-11-07

The relationship between numerical advantage and competitive ability is a fundamental component in contests between groups of social animals. An individual's ability to correctly assess the numerical state of its group is of vital importance. In addition to numerical dominance, the group's fighting ability also plays an important role in competitive interactions. By staging experimental fights between two Formica ant species, I show that Formica xerophila are able to assess their own group's strength prior to any competitive encounter. Ants that perceive themselves as part of a large group act more aggressively toward a competitor than ants that perceive themselves as isolated individuals. This increase in aggression improves F. xerophila's competitive ability. Furthermore, the number of individuals in a contest was found to affect competitive ability. In contests with equal number of competitors, groups of F. xerophila were more successful than individual F. xerophila. Contrary to previous predictions using Lanchester's laws of fighting, F. xerophila's ability to kill competitors increased nonlinearly with group size. This nonlinearity was due to the collective fighting strategy of an F. xerophila group isolating and engaging a single Formica integroides competitors.

Numerical assessment affects aggression and competitive ability: a team-fighting strategy for the ant Formica xerophila

PubMed Central

Tanner, Colby J

2006-01-01

The relationship between numerical advantage and competitive ability is a fundamental component in contests between groups of social animals. An individual's ability to correctly assess the numerical state of its group is of vital importance. In addition to numerical dominance, the group's fighting ability also plays an important role in competitive interactions. By staging experimental fights between two Formica ant species, I show that Formica xerophila are able to assess their own group's strength prior to any competitive encounter. Ants that perceive themselves as part of a large group act more aggressively toward a competitor than ants that perceive themselves as isolated individuals. This increase in aggression improves F. xerophila's competitive ability. Furthermore, the number of individuals in a contest was found to affect competitive ability. In contests with equal number of competitors, groups of F. xerophila were more successful than individual F. xerophila. Contrary to previous predictions using Lanchester's laws of fighting, F. xerophila's ability to kill competitors increased nonlinearly with group size. This nonlinearity was due to the collective fighting strategy of an F. xerophila group isolating and engaging a single Formica integroides competitors. PMID:17015327

Co-inoculation of aflatoxigenic and non-aflatoxigenic strains of Aspergillus flavus to study fungal invasion, colonization, and competition in maize kernels

PubMed Central

Hruska, Zuzana; Rajasekaran, Kanniah; Yao, Haibo; Kincaid, Russell; Darlington, Dawn; Brown, Robert L.; Bhatnagar, Deepak; Cleveland, Thomas E.

2014-01-01

A currently utilized pre-harvest biocontrol method involves field inoculations with non-aflatoxigenic Aspergillus flavus strains, a tactic shown to strategically suppress native aflatoxin-producing strains and effectively decrease aflatoxin contamination in corn. The present in situ study focuses on tracking the invasion and colonization of an aflatoxigenic A. flavus strain (AF70), labeled with green fluorescent protein (GFP), in the presence of a non-aflatoxigenic A. flavus biocontrol strain (AF36), to better understand the competitive interaction between these two strains in seed tissue of corn (Zea mays). Corn kernels that had been co-inoculated with GFP-labeled AF70 and wild-type AF36 were cross-sectioned and observed under UV and blue light to determine the outcome of competition between these strains. After imaging, all kernels were analyzed for aflatoxin levels. There appeared to be a population difference between the co-inoculated AF70-GFP+AF36 and the individual AF70-GFP tests, both visually and with pixel count analysis. The GFP allowed us to observe that AF70-GFP inside the kernels was suppressed up to 82% when co-inoculated with AF36 indicating that AF36 inhibited progression of AF70-GFP. This was in agreement with images taken of whole kernels where AF36 exhibited a more robust external growth compared to AF70-GFP. The suppressed growth of AF70-GFP was reflected in a corresponding (upto 73%) suppression in aflatoxin levels. Our results indicate that the decrease in aflatoxin production correlated with population depression of the aflatoxigenic fungus by the biocontrol strain supporting the theory of competitive exclusion through robust propagation and fast colonization by the non-aflatoxigenic fungus. PMID:24734028

Co-inoculation of aflatoxigenic and non-aflatoxigenic strains of Aspergillus flavus to study fungal invasion, colonization, and competition in maize kernels.

PubMed

Hruska, Zuzana; Rajasekaran, Kanniah; Yao, Haibo; Kincaid, Russell; Darlington, Dawn; Brown, Robert L; Bhatnagar, Deepak; Cleveland, Thomas E

2014-01-01

A currently utilized pre-harvest biocontrol method involves field inoculations with non-aflatoxigenic Aspergillus flavus strains, a tactic shown to strategically suppress native aflatoxin-producing strains and effectively decrease aflatoxin contamination in corn. The present in situ study focuses on tracking the invasion and colonization of an aflatoxigenic A. flavus strain (AF70), labeled with green fluorescent protein (GFP), in the presence of a non-aflatoxigenic A. flavus biocontrol strain (AF36), to better understand the competitive interaction between these two strains in seed tissue of corn (Zea mays). Corn kernels that had been co-inoculated with GFP-labeled AF70 and wild-type AF36 were cross-sectioned and observed under UV and blue light to determine the outcome of competition between these strains. After imaging, all kernels were analyzed for aflatoxin levels. There appeared to be a population difference between the co-inoculated AF70-GFP+AF36 and the individual AF70-GFP tests, both visually and with pixel count analysis. The GFP allowed us to observe that AF70-GFP inside the kernels was suppressed up to 82% when co-inoculated with AF36 indicating that AF36 inhibited progression of AF70-GFP. This was in agreement with images taken of whole kernels where AF36 exhibited a more robust external growth compared to AF70-GFP. The suppressed growth of AF70-GFP was reflected in a corresponding (upto 73%) suppression in aflatoxin levels. Our results indicate that the decrease in aflatoxin production correlated with population depression of the aflatoxigenic fungus by the biocontrol strain supporting the theory of competitive exclusion through robust propagation and fast colonization by the non-aflatoxigenic fungus.

Competitive effects of introduced annual weeds on some native and reclamation species in the Powder River Basin, Wyoming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, E.B.; Knight, D.H.

1980-01-01

Four experiments were conducted to examine the competitive effects of introduced annual weeds on certain native and reclamation species. The first experiment was initiated by discing three sites in the Powder River Basin, Wyoming, at three distances from introduced weed seed sources. Introduced weed colonization was greatest when a seed source was located nearby. Higher weed cover resulted in reductions of percent cover, density, and richness of the native species. The second experiment was conducted in the greenhouse and was designed to determine if there are changes in response of S. kali and the native grasses Agropyron smithii and Boutelouamore » gracilis to competition and water regime. Both grass species had lower biomass and higher stomatal resistance when growing in mixed culture with S. kali than in pure culture in the dry regime, but there were no significant differences in the wet regime. In general, the difference in plant response between mixed and pure cultures was more pronounced in the dry than in the wet regime. The third study was a greenhouse experiment on germination and competition of S. kali (a C/sub 4/ species) with native species Lepidium densiflorum (C/sub 3/), Chenopodium pratericola (C/sub 3/), A. smithii (C/sub 3/), and B. gracilis (C/sub 4/) under May, June, and July temperature regimes. Salsola kali germinated equally well in all three regimes, but the other C/sub 4/ species had highest germination in the July regime and the C/sub 3/ species in the May and June regimes. The fourth study was designed to examine the effect of weed colonization on the success of mine reclamation. Little effect was observed, but colonization by introduced annuals was very low. (ERB)« less

A mannose-specific adherence mechanism in Lactobacillus plantarum conferring binding to the human colonic cell line HT-29.

PubMed

Adlerberth, I; Ahrne, S; Johansson, M L; Molin, G; Hanson, L A; Wold, A E

1996-07-01

Two Lactobacillus plantarum strains of human intestinal origin, strains 299 (= DSM 6595) and 299v (= DSM 9843), have proved to be efficient colonizers of the human intestine under experimental conditions. These strains and 17 other L. plantarum strains were tested for the ability to adhere to cells of the human colonic cell line HT-29.L.plantarum 299 and 299v and nine other L. plantarum strains, including all six strains that belong to the same genetic subgroup as L. plantarum 299 and 299v, adhered to HT-29 cells in a manner that could be inhibited by methyl-alpha-D-mannoside. The ability to adhere to HT-29 cells correlated with an ability to agglutinate cells of Saccharomyces cerevisiae and erythrocytes in a mannose-sensitive manner and with adherence to D-mannose-coated agarose beads. L. plantarum 299 and 299v adhered to freshly isolated human colonic and ileal enterocytes, but the binding was not significantly inhibited by methyl-alpha-D-mannoside. Periodate treatment of HT-29 cells abolished mannose-sensitive adherence, confirming that the cell-bound receptor was of carbohydrate nature. Proteinase K treatment of the bacteria also abolished adherence, indicating that the binding involved protein structures on the bacterial cell surface. Thus, a mannose-specific adhesin has been identified in L. plantarum; this adhesin could be involved in the ability to colonize the intestine.

Microbial competition between Bacillus subtilis and Staphylococcus aureus monitored by imaging mass spectrometry

PubMed Central

Gonzalez, David J.; Haste, Nina M.; Hollands, Andrew; Fleming, Tinya C.; Hamby, Matthew; Pogliano, Kit; Nizet, Victor

2011-01-01

Microbial competition exists in the general environment, such as soil or aquatic habitats, upon or within unicellular or multicellular eukaryotic life forms. The molecular actions that govern microbial competition, leading to niche establishment and microbial monopolization, remain undetermined. The emerging technology of imaging mass spectrometry (IMS) enabled the observation that there is directionality in the metabolic output of the organism Bacillus subtilis when co-cultured with Staphylococcus aureus. The directionally released antibiotic alters S. aureus virulence factor production and colonization. Therefore, IMS provides insight into the largely hidden nature of competitive microbial encounters and niche establishment, and provides a paradigm for future antibiotic discovery. PMID:21719540

Differences in Competitive Ability between Plants from Nonnative and Native Populations of a Tropical Invader Relates to Adaptive Responses in Abiotic and Biotic Environments

PubMed Central

Liao, Zhi-Yong; Zhang, Ru; Barclay, Gregor F.; Feng, Yu-Long

2013-01-01

The evolution of competitive ability of invasive plant species is generally studied in the context of adaptive responses to novel biotic environments (enemy release) in introduced ranges. However, invasive plants may also respond to novel abiotic environments. Here we studied differences in competitive ability between Chromolaena odorata plants of populations from nonnative versus native ranges, considering biogeographical differences in both biotic and abiotic environments. An intraspecific competition experiment was conducted at two nutrient levels in a common garden. In both low and high nutrient treatments, C. odorata plants from nonnative ranges showed consistently lower root to shoot ratios than did plants from native ranges grown in both monoculture and competition. In the low nutrient treatment, C. odorata plants from nonnative ranges showed significantly lower competitive ability (competition-driven decreases in plant height and biomass were more), which was associated with their lower root to shoot ratios and higher total leaf phenolic content (defense trait). In the high nutrient treatment, C. odorata plants from nonnative ranges showed lower leaf toughness and cellulosic contents (defense traits) but similar competitive ability compared with plants from native ranges, which was also associated with their lower root to shoot ratios. Our results indicate that genetically based shifts in biomass allocation (responses to abiotic environments) also influence competitive abilities of invasive plants, and provide a first potential mechanism for the interaction between range and environment (environment-dependent difference between ranges). PMID:23977140

Are invasive plants more competitive than native conspecifics? Patterns vary with competitors.

PubMed

Zheng, Yulong; Feng, Yulong; Valiente-Banuet, Alfonso; Li, Yangping; Liao, Zhiyong; Zhang, Jiaolin; Chen, Yajun

2015-10-22

Invasive plants are sometimes considered to be more competitive than their native conspecifics, according to the prediction that the invader reallocates resources from defense to growth due to liberation of natural enemies ['Evolution of Increased Competitive Ability' (EICA) hypothesis]. However, the differences in competitive ability may depend on the identity of competitors. In order to test the effects of competitors, Ageratina adenophora plants from both native and invasive ranges competed directly, and competed with native residents from both invasive (China) and native (Mexico) ranges respectively. Invasive A. adenophora plants were more competitive than their conspecifics from native populations when competing with natives from China (interspecific competition), but not when competing with natives from Mexico. Invasive A. adenophora plants also showed higher competitive ability when grown in high-density monoculture communities of plants from the same population (intrapopulation competition). In contrast, invasive A. adenophora plants showed lower competitive ability when competing with plants from native populations (intraspecific competition). Our results indicated that in the invasive range A. adenophora has evolved to effectively cope with co-occurring natives and high density environments, contributing to invasion success. Here, we showed the significant effects of competitors, which should be considered carefully when testing the EICA hypothesis.

Foci of aberrant crypts in the colons of mice and rats exposed to carcinogens associated with foods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tudek, B.; Bird, R.P.; Bruce, W.R.

1989-03-01

Aberrant crypt foci can be identified in the colons of rodents treated 3 wk earlier with azoxymethane, a known colon carcinogen. These crypts can easily be visualized in the unsectioned methylene blue-stained colons under light microscopy, where they are distinguished by their increased size, more prominent epithelial cells, and pericryptal space. They occur as single aberrant crypts or as two, three, or four aberrant crypts in a cluster. We compared the reported ability of carcinogens associated with the human diet to induce colon cancer with the measured rate of induction of aberrant crypts in female CF1 mice and Sprague-Dawley rats.more » The carcinogens used were 1,2-dimethylhydrazine, methyl nitrosourea, N-nitrosodimethylamine, benzo(a)pyrene, aflatoxin B1, 2-amino-6-methyldipyrido(1,2-alpha:3',2'-d)imidazole, 2-amino-3-methylimidazo(4,5-P)quinoline, 2-amino-3,4-dimethylimidazo(4,5-P)quinoline, and 3-amino-1-methyl-5H-pyrido(4,3-b)indole. Graded doses of these compounds were given to the animals by gavage twice with a 4-day interval, and the animals were terminated 3 wk later. All colon carcinogens induced aberrant crypts in a dose-related fashion. N-Nitrosodimethylamine and 3-amino-1-methyl-5H-pyrido(4,3-b)indole, carcinogenic compounds that do not induce colon cancer, did not induce them. The ability of the studied compounds to induce aberrant crypts was species specific; e.g., aflatoxin B1 and 2-amino-3,4-dimethylimidazo(4,5-P)quinoline induce about 20 times more in rats than mice. This relationship was consistent with their reported ability to induce colon cancer in these species. Results of the present study support the use of the aberrant crypt assays to screen colon-specific carcinogens and to study the process of colon carcinogenesis.« less

Intraspecies Competition for Niches in the Distal Gut Dictate Transmission during Persistent Salmonella Infection

PubMed Central

Lam, Lilian H.; Monack, Denise M.

2014-01-01

In order to be transmitted, a pathogen must first successfully colonize and multiply within a host. Ecological principles can be applied to study host-pathogen interactions to predict transmission dynamics. Little is known about the population biology of Salmonella during persistent infection. To define Salmonella enterica serovar Typhimurium population structure in this context, 129SvJ mice were oral gavaged with a mixture of eight wild-type isogenic tagged Salmonella (WITS) strains. Distinct subpopulations arose within intestinal and systemic tissues after 35 days, and clonal expansion of the cecal and colonic subpopulation was responsible for increases in Salmonella fecal shedding. A co-infection system utilizing differentially marked isogenic strains was developed in which each mouse received one strain orally and the other systemically by intraperitoneal (IP) injection. Co-infections demonstrated that the intestinal subpopulation exerted intraspecies priority effects by excluding systemic S. Typhimurium from colonizing an extracellular niche within the cecum and colon. Importantly, the systemic strain was excluded from these distal gut sites and was not transmitted to naïve hosts. In addition, S. Typhimurium required hydrogenase, an enzyme that mediates acquisition of hydrogen from the gut microbiota, during the first week of infection to exert priority effects in the gut. Thus, early inhibitory priority effects are facilitated by the acquisition of nutrients, which allow S. Typhimurium to successfully compete for a nutritional niche in the distal gut. We also show that intraspecies colonization resistance is maintained by Salmonella Pathogenicity Islands SPI1 and SPI2 during persistent distal gut infection. Thus, important virulence effectors not only modulate interactions with host cells, but are crucial for Salmonella colonization of an extracellular intestinal niche and thereby also shape intraspecies dynamics. We conclude that priority effects and intraspecies competition for colonization niches in the distal gut control Salmonella population assembly and transmission. PMID:25474319

Genome-wide identification of bacterial plant colonization genes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cole, Benjamin J.; Feltcher, Meghan E.; Waters, Robert J.

Diverse soil-resident bacteria can contribute to plant growth and health, but the molecular mechanisms enabling them to effectively colonize their plant hosts remain poorly understood. We used randomly barcoded transposon mutagenesis sequencing (RB-TnSeq) in Pseudomonas simiae, a model root-colonizing bacterium, to establish a genome-wide map of bacterial genes required for colonization of the Arabidopsis thaliana root system. We identified 115 genes (2% of all P. simiae genes) with functions that are required for maximal competitive colonization of the root system. Among the genes we identified were some with obvious colonization-related roles in motility and carbon metabolism, as well as 44more » other genes that had no or vague functional predictions. Independent validation assays of individual genes confirmed colonization functions for 20 of 22 (91%) cases tested. To further characterize genes identified by our screen, we compared the functional contributions of P. simiae genes to growth in 90 distinct in vitro conditions by RB-TnSeq, highlighting specific metabolic functions associated with root colonization genes. Here, our analysis of bacterial genes by sequence-driven saturation mutagenesis revealed a genome-wide map of the genetic determinants of plant root colonization and offers a starting point for targeted improvement of the colonization capabilities of plant-beneficial microbes.« less

Genome-wide identification of bacterial plant colonization genes

DOE PAGES

Cole, Benjamin J.; Feltcher, Meghan E.; Waters, Robert J.; ...

2017-09-22

Diverse soil-resident bacteria can contribute to plant growth and health, but the molecular mechanisms enabling them to effectively colonize their plant hosts remain poorly understood. We used randomly barcoded transposon mutagenesis sequencing (RB-TnSeq) in Pseudomonas simiae, a model root-colonizing bacterium, to establish a genome-wide map of bacterial genes required for colonization of the Arabidopsis thaliana root system. We identified 115 genes (2% of all P. simiae genes) with functions that are required for maximal competitive colonization of the root system. Among the genes we identified were some with obvious colonization-related roles in motility and carbon metabolism, as well as 44more » other genes that had no or vague functional predictions. Independent validation assays of individual genes confirmed colonization functions for 20 of 22 (91%) cases tested. To further characterize genes identified by our screen, we compared the functional contributions of P. simiae genes to growth in 90 distinct in vitro conditions by RB-TnSeq, highlighting specific metabolic functions associated with root colonization genes. Here, our analysis of bacterial genes by sequence-driven saturation mutagenesis revealed a genome-wide map of the genetic determinants of plant root colonization and offers a starting point for targeted improvement of the colonization capabilities of plant-beneficial microbes.« less

Cyclic RGD peptide-modified liposomal drug delivery system for targeted oral apatinib administration: enhanced cellular uptake and improved therapeutic effects.

PubMed

Song, Zhiwang; Lin, Yun; Zhang, Xia; Feng, Chan; Lu, Yonglin; Gao, Yong; Dong, Chunyan

2017-01-01

Apatinib is an oral tyrosine kinase inhibitor, which selectively targets vascular endothelial growth factor receptor 2 and has the potential to treat many tumors therapeutically. Cyclic arginylglycylaspartic acid (cRGD)- and polyethylene glycol (PEG)-modified liposomes (cRGD-Lipo-PEG) were constructed to act as a targeted delivery system for the delivery of apatinib to the human colonic cancer cell line, HCT116. These cRGD-modified liposomes specifically recognized integrin α v β 3 and exhibited greater uptake efficiency with respect to delivering liposomes into HCT116 cells when compared to nontargeted liposomes (Lipo-PEG), as well as greater death of tumor cells and apoptosis. The mechanism by which cRGD-Lipo-PEG targets cells was elucidated further with competition assays. To determine the anticancer efficacy in vivo, nude mice were implanted with HCT116 xenografts and treated with apatinib-loaded liposomes or free apatinib intravenously or via intragastric administration. The active and passive targeting of cRGD-Lipo-PEG led to significant tumor treatment targeting ability, better inhibition of tumor growth, and less toxicity when compared with treatments using uncombined apatinib. The results presented strongly support the case for cRGD-Lipo-PEG representing a targeted delivery system for apatinib in the treatment of colonic cancer.

Cyclic RGD peptide-modified liposomal drug delivery system for targeted oral apatinib administration: enhanced cellular uptake and improved therapeutic effects

PubMed Central

Song, Zhiwang; Lin, Yun; Zhang, Xia; Feng, Chan; Lu, Yonglin; Gao, Yong; Dong, Chunyan

2017-01-01

Apatinib is an oral tyrosine kinase inhibitor, which selectively targets vascular endothelial growth factor receptor 2 and has the potential to treat many tumors therapeutically. Cyclic arginylglycylaspartic acid (cRGD)- and polyethylene glycol (PEG)-modified liposomes (cRGD-Lipo-PEG) were constructed to act as a targeted delivery system for the delivery of apatinib to the human colonic cancer cell line, HCT116. These cRGD-modified liposomes specifically recognized integrin αvβ3 and exhibited greater uptake efficiency with respect to delivering liposomes into HCT116 cells when compared to nontargeted liposomes (Lipo-PEG), as well as greater death of tumor cells and apoptosis. The mechanism by which cRGD-Lipo-PEG targets cells was elucidated further with competition assays. To determine the anticancer efficacy in vivo, nude mice were implanted with HCT116 xenografts and treated with apatinib-loaded liposomes or free apatinib intravenously or via intragastric administration. The active and passive targeting of cRGD-Lipo-PEG led to significant tumor treatment targeting ability, better inhibition of tumor growth, and less toxicity when compared with treatments using uncombined apatinib. The results presented strongly support the case for cRGD-Lipo-PEG representing a targeted delivery system for apatinib in the treatment of colonic cancer. PMID:28331317

Competitive Dominance among Strains of Luminous Bacteria Provides an Unusual Form of Evidence for Parallel Evolution in Sepiolid Squid-Vibrio Symbioses

PubMed Central

Nishiguchi, Michele K.; Ruby, Edward G.; McFall-Ngai, Margaret J.

1998-01-01

One of the principal assumptions in symbiosis research is that associated partners have evolved in parallel. We report here experimental evidence for parallel speciation patterns among several partners of the sepiolid squid-luminous bacterial symbioses. Molecular phylogenies for 14 species of host squids were derived from sequences of both the nuclear internal transcribed spacer region and the mitochondrial cytochrome oxidase subunit I; the glyceraldehyde phosphate dehydrogenase locus was sequenced for phylogenetic determinations of 7 strains of bacterial symbionts. Comparisons of trees constructed for each of the three loci revealed a parallel phylogeny between the sepiolids and their respective symbionts. Because both the squids and their bacterial partners can be easily cultured independently in the laboratory, we were able to couple these phylogenetic analyses with experiments to examine the ability of the different symbiont strains to compete with each other during the colonization of one of the host species. Our results not only indicate a pronounced dominance of native symbiont strains over nonnative strains, but also reveal a hierarchy of symbiont competency that reflects the phylogenetic relationships of the partners. For the first time, molecular systematics has been coupled with experimental colonization assays to provide evidence for the existence of parallel speciation among a set of animal-bacterial associations. PMID:9726861

Bacterial virulence phenotypes of Escherichia coli and host susceptibility determines risk for urinary tract infections

PubMed Central

Schreiber, Henry L.; Conover, Matt S.; Chou, Wen-Chi; Hibbing, Michael E.; Manson, Abigail L.; Dodson, Karen W.; Hannan, Thomas J.; Roberts, Pacita L.; Stapleton, Ann E.; Hooton, Thomas M.; Livny, Jonathan; Earl, Ashlee M.; Hultgren, Scott J.

2017-01-01

Urinary tract infections (UTIs) are caused by uropathogenic Escherichia coli (UPEC) strains. In contrast to many enteric E. coli pathogroups, no genetic signature has been identified for UPEC strains. We conducted a high-resolution comparative genomic study using E. coli isolates collected from the urine of women suffering from frequent recurrent UTIs. These isolates were genetically diverse and varied in urovirulence, or the ability to infect the bladder of a mouse model of cystitis. Importantly, we found no set of genes, including previously defined putative urovirulence factors (PUFs), that were predictive of urovirulence. In addition, in some patients, the E. coli strain causing a recurrent UTI had fewer PUFs than the supplanted strain. In competitive experimental infections in mice, the supplanting strain was more efficient at colonizing the mouse bladder than the supplanted strain. Despite the lack of a clear genomic signature for urovirulence, comparative transcriptomic and phenotypic analyses revealed that the expression of key conserved functions during culture, such as motility and sugar metabolism, could be used to predict subsequent mouse bladder colonization. Taken together, our findings suggest that UTI risk and outcome may be determined by complex interactions between host susceptibility and the urovirulence potential of diverse bacterial strains. PMID:28330863

Significant competitive advantage conferred by meiosis and syngamy in the yeast Saccharomyces cerevisiae.

PubMed Central

Birdsell, J; Wills, C

1996-01-01

The presumed advantages of genetic recombinations are difficult to demonstrate directly. To investigate the effects of recombination and background heterozygosity on competitive ability, we have performed serial-transfer competition experiments between isogenic sexual and asexual strains of the yeast Saccharomyces cerevisiae. The members of these diploid pairs of strains differed only in being heterozygous (sexual) or homozygous (asexual) at the mating type or MAT locus. Competing pairs had either a completely homozygous or a heterozygous genetic background, the latter being heterozygous at many different loci throughout the genome. A round of meiotic recombination (automixis) conferred a large and statistically significant enhancement of competitive ability on sexual strains with a heterozygous genetic background. By contrast, in homozygous background competitions, meiosis decreased the sexual strains' initial relative competitive ability. In all cases, however, the sexual strains outcompeted their isogenic asexual counterparts, whether meiotic recombination had occurred or not. In some genetic backgrounds, this was due in part to an overdominance effect on competitive advantage of heterozygosity at the MAT locus. The advantage of the sexual strains also increased significantly during the course of the homozygous background competitions, particularly when meiosis had occurred. This latter effect either did not occur or was very weak in heterozygous background competitions. Overall, sexual strains with heterozygous genetic backgrounds had a significantly higher initial relative competitive ability than those with homozygous backgrounds. The advantage of mating type heterozygosity in this organism extends far beyond the ability to recombine meiotically. PMID:8570658

Complete genome sequence of Lactobacillus johnsonii FI9785, a competitive exclusion agent against pathogens in poultry.

PubMed

Wegmann, Udo; Overweg, Karin; Horn, Nikki; Goesmann, Alexander; Narbad, Arjan; Gasson, Michael J; Shearman, Claire

2009-11-01

Lactobacillus johnsonii is a member of the acidophilus group of lactobacilli. Because of their probiotic properties, including attachment to epithelial cells, immunomodulation, and competitive exclusion of pathogens, representatives of this group are being intensively studied. Here we report the complete annotated genome sequence of Lactobacillus johnsonii FI9785, a strain which prevents the colonization of specific-pathogen-free chicks by Clostridium perfringens.

Dispersal-competition tradeoff in microbiomes in the quest for land colonization.

PubMed

Dini-Andreote, Francisco; van Elsas, Jan Dirk; Olff, Han; Salles, Joana Falcão

2018-06-21

Ancestor microbes started colonizing inland habitats approximately 2.7 to 3.5 billion years ago. With some exceptions, the key physiological adaptations of microbiomes associated with marine-to-land transitions have remained elusive. This is essentially caused by the lack of suitable systems that depict changes in microbiomes across sufficiently large time scales. Here, we investigate the adaptive routes taken by microbiomes along a contemporary gradient of land formation. Using functional trait-based metagenomics, we show that a switch from a microbial 'dispersal' to a 'competition' response modus best characterizes the microbial trait changes during this eco-evolutionary trajectory. The 'dispersal' modus prevails in microbiomes at the boundary sites between land and sea. It encompasses traits conferring cell chemosensory and motile behaviors, thus allowing the local microbes to exploit short-lived nutritional patches in high-diffusion microhabitats. A systematic transition towards the 'competition' modus occurs progressively as the soil matures, which is likely due to forces of viscosity or strain that favor traits for competition and chemical defense. Concomitantly, progressive increases in the abundances of genes encoding antibiotic resistance and complex organic substrate degradation were found. Our findings constitute a novel perspective on the ecology and evolution of microbiome traits, tracking back one of the most seminal transitions in the evolutionary history of life.

Demographic consequences of invasion by a native, controphic competitor to an insular bird population.

PubMed

Johnson, K M; Germain, R R; Tarwater, C E; Reid, J M; Arcese, P

2018-05-01

Species invasions and range shifts can lead to novel competitive interactions between historically resident and colonizing species, but the demographic consequences of such interactions remain controversial. We present results from field experiments and 45 years of demographic monitoring to test the hypothesis that the colonization of Mandarte Is., BC, Canada, by fox sparrows (Passerella iliaca) caused the long-term decline of the resident population of song sparrows (Melospiza melodia). Several lines of evidence indicate that competition with fox sparrows for winter food reduced over-winter survival in juvenile song sparrows by 48% from 1960 to 2015, enforcing population decline despite an increase in annual reproductive rate in song sparrows over the same period. Preference for locally abundant seeds presented at experimental arenas suggested complete overlap in diet in song and fox sparrows, and observations at arenas baited with commercial seed showed that fox sparrows displaced song sparrows in 91-100% of interactions in two periods during winter. In contrast, we found no evidence of interspecific competition for resources during the breeding season. Our results indicate that in the absence of marked shifts in niche dimension, range expansions by dominant competitors have the potential to cause the extirpation of historically resident species when competitive interactions between them are strong and resources not equitably partitioned.

In vivo characterization of Lactobacillus johnsonii FI9785 for use as a defined competitive exclusion agent against bacterial pathogens in poultry.

PubMed

La Ragione, R M; Narbad, A; Gasson, M J; Woodward, M J

2004-01-01

To test the efficacy of Lactobacillus johnsonii FI9785 in reducing the colonization and shedding of Salmonella enterica serotype Enteritidis, Escherichia coli O78:K80 and Clostridium perfringens in poultry. Specific pathogen-free chicks (1 day old) were dosed with a single oral inoculum of 1x10(9) CFU. Lactobacillus johnsonii FI9785 and 24 h later were challenged in separate experiments with S. Enteritidis (S1400, nalr) and E. coli O78:K80 (EC34195, nalr). There were no significant effects against S. Enteritidis whereas colonization of the small intestine by E. coli O78:K80 was reduced significantly. Both S. Enteritidis and E. coli colonized the caeca and colon to levels equivalent to control birds and there was no reduction in shedding as assessed by a semi-quantitative cloacal swabbing technique. Specific pathogen-free chicks (20 day old) were dosed with a single oral inoculum of 1x10(9) CFU L. johnsonii FI9785 and 24 h later were challenged with C. perfringens. A single oral dose of L. johnsonii FI9785 was sufficient to suppress all aspects of colonization and persistence of C. perfringens. Lactobacillus johnsonii FI9785 may be given to poultry for use as a competitive exclusion agent to control C. perfringens. Lactobacillus johnsonii FI9785 may be a valuable tool to control the endemic disease of necrotic enteritis, thereby reducing economic losses associated with reduced use of antimicrobials in the poultry industry.

Selfing ability and dispersal are positively related, but not affected by range position: a multispecies study on southern African Asteraceae.

PubMed

de Waal, C; Rodger, J G; Anderson, B; Ellis, A G

2014-05-01

Dispersal and breeding system traits are thought to affect colonization success. As species have attained their present distribution ranges through colonization, these traits may vary geographically. Although several theories predict associations between dispersal ability, selfing ability and the relative position of a population within its geographic range, there is little theoretical or empirical consensus on exactly how these three variables are related. We investigated relationships between dispersal ability, selfing ability and range position across 28 populations of 13 annual, wind-dispersed Asteraceae species from the Namaqualand region of South Africa. Controlling for phylogeny, relative dispersal ability--assessed from vertical fall time of fruits--was positively related to an index of autofertility--determined from hand-pollination experiments. These findings support the existence of two discrete syndromes: high selfing ability associated with good dispersal and obligate outcrossing associated with lower dispersal ability. This is consistent with the hypothesis that selection for colonization success drives the evolution of an association between these traits. However, no general effect of range position on dispersal or breeding system traits was evident. This suggests selection on both breeding system and dispersal traits acts consistently across distribution ranges. © 2014 The Authors. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Control of Salmonella Enteritidis in turkeys using organic acids and competitive exclusion product.

PubMed

Milbradt, E L; Zamae, J R; Araújo Júnior, J P; Mazza, P; Padovani, C R; Carvalho, V R; Sanfelice, C; Rodrigues, D M; Okamoto, A S; Andreatti Filho, R L

2014-08-01

To evaluate the use of organic acids (OAs) and competitive exclusion (CE) product administered continuously in the feed and transiently in drinking water on the control of Salmonella enterica subspecie enterica serotype Enteritidis (SE) prior to slaughter. The influence of treatments were evaluated on pH, population of the lactic acid bacteria (LAB) and bacteria of the family Enterobacteriaceae, concentration of volatile fatty acids and SE colonization in the crop and caecum. The birds were challenged with SE 24 h before being slaughtered, and then, the caeca and crop were removed and subjected to SE counts. Continuous administration of OAs reduced the population of bacteria from the Enterobacteriaceae family in both crop and caecum, positively influenced the butyric acid concentration and reduced SE colonization in the caecum. The diet supplemented with CE product positively influenced the quantity of LAB in the crop and caecum, elevated the butyric acid concentration and reduced both Enterobacteriaceae quantity and SE colonization in the caecum. There was no effect from administering the treatments via drinking water on the variables measured. Continuous supplementation in feed with OAs and CE product reduced SE colonization of the caeca. Supplementation of OAs and CE product in diet to turkeys can reduce the SE load, potentially leading to a lower contamination risk of meat during slaughter. © 2014 The Society for Applied Microbiology.

What Kind of Capsule Endoscope Is Suitable for a Controllable Self-Propelling Capsule Endoscope? Experimental Study Using a Porcine Stomach Model for Clinical Application (with Videos)

PubMed Central

Ota, Kazuhiro; Nouda, Sadaharu; Takeuchi, Toshihisa; Iguchi, Munetaka; Kojima, Yuichi; Kuramoto, Takanori; Inoue, Takuya; Shindo, Yasunori; Uesugi, Kenshiro; Fujito, Yoshiaki; Nishihara, Hironori; Ohtsuka, Naotake; Higuchi, Kazuhide

2015-01-01

Background We have been developing the Self-Propelling Capsule Endoscope (SPCE) that allows for controllability from outside of the body and real-time observation. What kind of capsule endoscope (CE) is suitable for a controllable SPCE is unclear and a very critical point for clinical application. We compared observing ability of three kinds of SPCEs with different viewing angles and frame rates. Methods Eleven buttons were sewed in an excised porcine stomach. Four examiners controlled the SPCE using PillCamSB2, -ESO2, and -COLON2 (Given Imaging Ltd., Israel), for 10 minutes each with the aim of detecting as many buttons and examining them as closely as possible. The ability to find lesions was assessed based on the number of detected buttons. The SPCE-performance score (SPS) was used to evaluate the ability to examine the lesions in detail. Results The SPCE-ESO2, -COLON2, and -SB2 detected 11 [interquartile range (IQR): 0], 10.5 (IQR, 0.5), and 8 (IQR, 1.0) buttons, respectively. The SPCE-ESO2 and -COLON2 had a significantly better ability to detect lesions than the -SB2 (p < 0.05). The SPCE-ESO2, -COLON2, and -SB2 had significantly different SPS values of 22 (IQR, 0), 16.5 (IQR, 1.5), and 14 (IQR, 1.0), respectively (p < 0.05 for all comparisons; SPCE-SB2 vs. -ESO2, -SB2 vs. -COLON2, and -ESO2 vs. -COLON2). Conclusions PillCamESO2 is most suitable in different three CEs for SPCE for examining lesions in detail of the stomach. PMID:26447694

What Kind of Capsule Endoscope Is Suitable for a Controllable Self-Propelling Capsule Endoscope? Experimental Study Using a Porcine Stomach Model for Clinical Application (with Videos).

PubMed

Ota, Kazuhiro; Nouda, Sadaharu; Takeuchi, Toshihisa; Iguchi, Munetaka; Kojima, Yuichi; Kuramoto, Takanori; Inoue, Takuya; Shindo, Yasunori; Uesugi, Kenshiro; Fujito, Yoshiaki; Nishihara, Hironori; Ohtsuka, Naotake; Higuchi, Kazuhide

2015-01-01

We have been developing the Self-Propelling Capsule Endoscope (SPCE) that allows for controllability from outside of the body and real-time observation. What kind of capsule endoscope (CE) is suitable for a controllable SPCE is unclear and a very critical point for clinical application. We compared observing ability of three kinds of SPCEs with different viewing angles and frame rates. Eleven buttons were sewed in an excised porcine stomach. Four examiners controlled the SPCE using PillCamSB2, -ESO2, and -COLON2 (Given Imaging Ltd., Israel), for 10 minutes each with the aim of detecting as many buttons and examining them as closely as possible. The ability to find lesions was assessed based on the number of detected buttons. The SPCE-performance score (SPS) was used to evaluate the ability to examine the lesions in detail. The SPCE-ESO2, -COLON2, and -SB2 detected 11 [interquartile range (IQR): 0], 10.5 (IQR, 0.5), and 8 (IQR, 1.0) buttons, respectively. The SPCE-ESO2 and -COLON2 had a significantly better ability to detect lesions than the -SB2 (p < 0.05). The SPCE-ESO2, -COLON2, and -SB2 had significantly different SPS values of 22 (IQR, 0), 16.5 (IQR, 1.5), and 14 (IQR, 1.0), respectively (p < 0.05 for all comparisons; SPCE-SB2 vs. -ESO2, -SB2 vs. -COLON2, and -ESO2 vs. -COLON2). PillCamESO2 is most suitable in different three CEs for SPCE for examining lesions in detail of the stomach.

The role of reproductive plant traits and biotic interactions in the dynamics of semi-arid plant communities.

PubMed

Pueyo, Y; Kéfi, S; Díaz-Sierra, R; Alados, C L; Rietkerk, M

2010-12-01

The dynamics of semi-arid plant communities are determined by the interplay between competition and facilitation among plants. The sign and strength of these biotic interactions depend on plant traits. However, the relationships between plant traits and biotic interactions, and the consequences for plant communities are still poorly understood. Our objective here was to investigate, with a modelling approach, the role of plant reproductive traits on biotic interactions, and the consequences for processes such as plant succession and invasion. The dynamics of two plant types were modelled with a spatially-explicit integrodifferential model: (1) a plant with seed dispersal (colonizer of bare soil) and (2) a plant with local vegetative propagation (local competitor). Both plant types were involved in facilitation due to a local positive feedback between vegetation biomass and soil water availability, which promoted establishment and growth. Plants in the system also competed for limited water. The efficiency in water acquisition (dependent on reproductive and growth plant traits) determined which plant type dominated the community at the steady state. Facilitative interactions between plant types also played an important role in the community dynamics, promoting establishment in the driest conditions and recovery from low biomass. Plants with vegetative propagation took advantage of the ability of seed dispersers to establish on bare soil from a low initial biomass. Seed dispersers were good invaders, maintained high biomass at intermediate and high rainfall and showed a high ability in taking profit from the positive feedback originated by plants with vegetative propagation under the driest conditions. However, seed dispersers lost competitiveness with an increasing investment in fecundity. All together, our results showed that reproductive plant traits can affect the balance between facilitative and competitive interactions. Understanding this effect of plant traits on biotic interactions provides insights in processes such as plant succession and shrub encroachment. Copyright © 2010 Elsevier Inc. All rights reserved.

Ability of a Generalist Seed Beetle to Colonize an Exotic Host: Effects of Host Plant Origin and Oviposition Host.

PubMed

Amarillo-Suárez, A; Repizo, A; Robles, J; Diaz, J; Bustamante, S

2017-08-01

The colonization of an exotic species by native herbivores is more likely to occur if that herbivore is a generalist. There is little information on the life-history mechanisms used by native generalist insects to colonize exotic hosts and how these mechanisms are affected by host properties. We examined the ability of the generalist seed beetle Stator limbatus Horn to colonize an exotic species. We compared its host preference, acceptability, performance, and egg size when ovipositing and developing on two native (Pithecellobium dulce (Roxb.) Benth and Senegalia riparia (Kunth)) and one exotic legume species (Leucaena leucocephala (Lam.)). We also analyzed the seed chemistry. We found that females recognize the exotic species as an unfavorable host for larval development and that they delayed oviposition and laid fewer and larger eggs on the exotic species than on the native species. Survivorship on the exotic host was 0%. Additionally, seeds of the native species contain five chemical compounds that are absent in the exotic species, and the exotic species contains three sterols, which are absent in the native legumes. Genetically based differences between beetles adapted to different hosts, plastic responses toward new hosts, and chemical differences among seeds are important in host colonization and recognition of the exotic host. In conclusion, the generalist nature of S. limbatus does not influence its ability to colonize L. leucocephala. Explanations for the colonization of exotic hosts by generalist native species and for the success of invasive species must be complemented with studies measuring local adaptation and plasticity.

Fungal symbiosis from mutualism to parasitism: who controls the outcome, host or invader?

USGS Publications Warehouse

Redman, R.S.; Dunigan, D.D.; Rodriguez, R.J.

2001-01-01

Plant symbiotic fungi are generally thought to express a single lifestyle that might increase (mutualism), decrease (parasitism), or have no influence (commensalism) on host fitness. However, data are presented here demonstrating that plant pathogenic Colletotrichum species are able to asymptomatically colonize plants and express nonpathogenic lifestyles. Experiments were conducted in growth chambers and plant colonization was assessed by emergence of fungi from surface sterilized plant tissues. Expression of symbiotic lifestyles was assessed by monitoring the ability of fungi to confer disease resistance, drought tolerance and growth enhancement. Several pathogenic Colletotrichum species expressed either mutualistic or commensal lifestyles in plants not known to be hosts. Mutualists conferred disease resistance, drought tolerance, and/or growth enhancement to host plants. Lifestyle-altered mutants expressing nonpathogenic lifestyles had greater host ranges than the parental wildtype isolate. Successive colonization studies indicated that the ability of a symbiont to colonize a plant was dependent on previous colonization events and the lifestyles expressed by the initial colonizing fungus. The results indicate that the outcome of symbiosis is controlled by the plant's physiology. ?? New Phytologist.

Competitive Traits Are More Important than Stress-Tolerance Traits in a Cadmium-Contaminated Rhizosphere: A Role for Trait Theory in Microbial Ecology.

PubMed

Wood, Jennifer L; Tang, Caixian; Franks, Ashley E

2018-01-01

Understanding how biotic and abiotic factors govern the assembly of rhizosphere-microbial communities is a long-standing goal in microbial ecology. In phytoremediation research, where plants are used to remediate heavy metal-contaminated soils, a deeper understanding of rhizosphere-microbial ecology is needed to fully exploit the potential of microbial-assisted phytoremediation. This study investigated whether Grime's competitor/stress-tolerator/ruderal (CSR) theory could be used to describe the impact of cadmium (Cd) and the presence of a Cd-accumulating plant, Carpobrotus rossii (Haw.) Schwantes, on the assembly of soil-bacterial communities using Illumina 16S rRNA profiling and the predictive metagenomic-profiling program, PICRUSt. Using predictions based on CSR theory, we hypothesized that Cd and the presence of a rhizosphere would affect community assembly. We predicted that the additional resource availability in the rhizosphere would enrich for competitive life strategists, while the presence of Cd would select for stress-tolerators. Traits identified as competitive followed CSR predictions, discriminating between rhizosphere and bulk-soil communities whilst stress-tolerance traits increased with Cd dose, but only in bulk-soil communities. These findings suggest that a bacterium's competitive attributes are critical to its ability to occupy and proliferate in a Cd-contaminated rhizosphere. Ruderal traits, which relate to community re-colonization potential, were synergistically decreased by the presence of the rhizosphere and Cd dose. Taken together this microcosm study suggests that the CSR theory is broadly applicable to microbial communities. Further work toward developing a simplified and robust strategy for microbial CSR classification will provide an ecologically meaningful framework to interpret community-level changes across a range of biomes.

Salt tolerant Methylobacterium mesophilicum showed viable colonization abilities in the plant rhizosphere

PubMed Central

Egamberdieva, Dilfuza; Wirth, Stephan; Alqarawi, Abdulaziz A.; Abd_Allah, E.F.

2015-01-01

The source of infection has always been considered as an important factor in epidemiology and mostly linked to environmental source such as surface water, soil, plants and also animals. The activity of the opportunistic pathogens associated with plant root, their adaptation and survival under hostile environmental condition is poorly understood. In this study the salt tolerance ability of Methylobacterium mesophilicum and its colonization in the root and shoot of plants under severe drought and salt stress conditions were investigated. The colonization of plant by M. mesophilicum was investigated in a gnotobiotic sand system, and their survival in pots with saline soil. Bacterial strain was found to colonize rhizosphere of cucumber, tomato and paprika grown under normal and salt stress condition and reached up to 6.4 × 104 and 2.6 × 104 CFU/g root. The strain was resistant to Gentamicin, Ampicillin, Amoxicillin plus Clavulanic acid, Cefotaxime, neomycin, penicillin and was also tolerant to salinity stress (up to 6% NaCl). These abilities play important roles in enabling persistent colonization of the plant surface by M. mesophilicum strains. In conclusion, this study provides background information on the behaviour of opportunistic pathogen M. mesophilicum on plants and their survival in harsh environmental conditions. PMID:26288563

Simulated Warming Differentially Affects the Growth and Competitive Ability of Centaurea maculosa Populations from Home and Introduced Ranges

PubMed Central

He, Wei-Ming; Li, Jing-Ji; Peng, Pei-Hao

2012-01-01

Climate warming may drive invasions by exotic plants, thereby raising concerns over the risks of invasive plants. However, little is known about how climate warming influences the growth and competitive ability of exotic plants from their home and introduced ranges. We conducted a common garden experiment with an invasive plant Centaurea maculosa and a native plant Poa pratensis, in which a mixture of sand and vermiculite was used as a neutral medium, and contrasted the total biomass, competitive effects, and competitive responses of C. maculosa populations from Europe (home range) and North America (introduced range) under two different temperatures. The warming-induced inhibitory effects on the growth of C. maculosa alone were stronger in Europe than in North America. The competitive ability of C. maculosa plants from North America was greater than that of plants from Europe under the ambient condition whereas this competitive ability followed the opposite direction under the warming condition, suggesting that warming may enable European C. maculosa to be more invasive. Across two continents, warming treatment increased the competitive advantage instead of the growth advantage of C. maculosa, suggesting that climate warming may facilitate C. maculosa invasions through altering competitive outcomes between C. maculosa and its neighbors. Additionally, the growth response of C. maculosa to warming could predict its ability to avoid being suppressed by its neighbors. PMID:22303485

Simulated warming differentially affects the growth and competitive ability of Centaurea maculosa populations from home and introduced ranges.

PubMed

He, Wei-Ming; Li, Jing-Ji; Peng, Pei-Hao

2012-01-01

Climate warming may drive invasions by exotic plants, thereby raising concerns over the risks of invasive plants. However, little is known about how climate warming influences the growth and competitive ability of exotic plants from their home and introduced ranges. We conducted a common garden experiment with an invasive plant Centaurea maculosa and a native plant Poa pratensis, in which a mixture of sand and vermiculite was used as a neutral medium, and contrasted the total biomass, competitive effects, and competitive responses of C. maculosa populations from Europe (home range) and North America (introduced range) under two different temperatures. The warming-induced inhibitory effects on the growth of C. maculosa alone were stronger in Europe than in North America. The competitive ability of C. maculosa plants from North America was greater than that of plants from Europe under the ambient condition whereas this competitive ability followed the opposite direction under the warming condition, suggesting that warming may enable European C. maculosa to be more invasive. Across two continents, warming treatment increased the competitive advantage instead of the growth advantage of C. maculosa, suggesting that climate warming may facilitate C. maculosa invasions through altering competitive outcomes between C. maculosa and its neighbors. Additionally, the growth response of C. maculosa to warming could predict its ability to avoid being suppressed by its neighbors.

An exotic invasive plant selects for increased competitive tolerance, but not competitive suppression, in a native grass.

PubMed

Fletcher, Rebecca A; Callaway, Ragan M; Atwater, Daniel Z

2016-06-01

Exotic invasive plants can exert strong selective pressure for increased competitive ability in native plants. There are two fundamental components of competitive ability: suppression and tolerance, and the current paradigm that these components have equal influences on a species' overall competitive ability has been recently questioned. If these components do not have equal influences on overall ability, then selection on competitive tolerance and suppression may be disproportionate. We used naturally invaded communities to study the effects of selection caused by an invasive forb, Centaurea stoebe, on a native grass, Pseudoroegneria spicata. P. spicata plants were harvested from within dense C. stoebe patches and from nearby uninvaded areas, divided clonally into replicates, then transplanted into a common garden where they grew alone or competed with C. stoebe. We found that P. spicata plants collected from within C. stoebe patches were significantly more tolerant of competition with C. stoebe than P. spicata plants collected from uninvaded areas, but plants from inside invaded patches were not superior at suppressing C. stoebe. These results are consistent with the hypothesis that strong competitors may select for tolerance to competition more than for the ability to suppress neighbors. This has important implications for how native plant communities may respond to invasion over time, and how invasive and native species may ultimately coexist.

Unique Metabolic Adaptations Dictate Distal Organ-Specific Metastatic Colonization

PubMed Central

Schild, Tanya; Low, Vivien; Blenis, John; Gomes, Ana P.

2018-01-01

Summary Metastases arising from tumors have the proclivity to colonize specific organs, suggesting that they must rewire their biology to meet the demands of the organ colonized, thus altering their primary properties. Each metastatic site presents distinct metabolic challenges to a colonizing cancer cell, ranging from fuel and oxygen availability to oxidative stress. Here, we discuss the organ-specific metabolic adaptations cancer cells must undergo, which provide the ability to overcome the unique barriers to colonization in foreign tissues and establish the metastatic tissue tropism phenotype. PMID:29533780

In vitro analysis of age-related changes in the developmental potential of bone marrow thymocyte progenitors.

PubMed

Sharp, A; Kukulansky, T; Globerson, A

1990-12-01

Mechanisms underlying the age-related decrease in the developmental capacity of thymocyte progenitors from the bone marrow (BM) were analyzed, focussing on interaction of these cells with the thymic microenvironment. We employed the experimental model in which mixtures of young and old mouse BM cells, congenic for the Thy-1 marker, were seeded onto fetal thymus (FT) explains depleted of self lymphocytes and the levels of Thy-1+ cells developing from each of the two donor types were measured. When cells from young and old BM donors were seeded simultaneously, in saturating quantities, a higher level of T cells developed from the young donors. To find out whether there were originally more thymocyte progenitors in the young BM, we carried out the competitive colonization under limiting dilution conditions and found that the advantage of the young had diminished under these conditions, thus suggesting that the age-related changes could not be related solely to quantitative differences. We then incubated the FT sequentially with old donor cells for 24 h, followed by young for an additional 48 h and found that the advantage of the young progenitors was eliminated. We thus established that the initial stage of colonization of the FT was important in determining the outcome of the subsequent development. The kinetics of simultaneous competition within the FT, however, revealed that the advantage of the young BM-derived cells became significant only from day 7 in organ culture, thus suggesting that sequential divisions of these cells were at a higher level than those of the old. Recolonization of FT explants by young or old BM-derived thymocytes obtained from the first colonization of the FT stroma showed a reduced, but still significant advantage for the young BM-derived cells over the old. Thus, we concluded that the old BM thymocyte progenitors manifested a qualitative disadvantage which became apparent during competitive colonization of the FT.

A review of the potential for competitive cereal cultivars as a tool in integrated weed management.

PubMed

Andrew, I K S; Storkey, J; Sparkes, D L

2015-06-01

Competitive crop cultivars offer a potentially cheap option to include in integrated weed management strategies (IWM). Although cultivars with high competitive potential have been identified amongst cereal crops, competitiveness has not traditionally been considered a priority for breeding or farmer cultivar choice. The challenge of managing herbicide-resistant weed populations has, however, renewed interest in cultural weed control options, including competitive cultivars. We evaluated the current understanding of the traits that explain variability in competitive ability between cultivars, the relationship between suppression of weed neighbours and tolerance of their presence and the existence of trade-offs between competitive ability and yield in weed-free scenarios. A large number of relationships between competitive ability and plant traits have been reported in the literature, including plant height, speed of development, canopy architecture and partitioning of resources. There is uncertainty over the relationship between suppressive ability and tolerance, although tolerance is a less stable trait over seasons and locations. To realise the potential of competitive crop cultivars as a tool in IWM, a quick and simple-to-use protocol for assessing the competitive potential of new cultivars is required; it is likely that this will not be based on a single trait, but will need to capture the combined effect of multiple traits. A way needs to be found to make this information accessible to farmers, so that competitive cultivars can be better integrated into their weed control programmes.

Cross-feeding between bifidobacteria and butyrate-producing colon bacteria explains bifdobacterial competitiveness, butyrate production, and gas production.

PubMed

De Vuyst, Luc; Leroy, Frédéric

2011-09-01

Inulin-type fructans are not digested and reach the human colon intact, where they are selectively fermented by the colon microbiota, in particular bifidobacteria. As a result, they are converted, directly or indirectly, to short-chain fatty acids and other organic acids, as well as gases, and lead to both bifidogenic and butyrogenic health-promoting effects. Bifidobacteria display phenotypic variation on strain level as to their capacity to degrade inulin-type fructans. Also, different chain lengths of inulin-type fructans may stimulate different subgroups within the bifidobacterial population. The end-metabolites of inulin-type fructan degradation by bifidobacteria reflect their growth rates on these polymers. Other colon bacteria are also able to degrade inulin-type fructans, as is the case for lactobacilli, Bacteroides, certain enterobacteria, and butyrate producers. Bacterial cross-feeding mechanisms in the colon lay at the basis of overall butyrate production, a functional characteristic of several colon bacteria that is always accompanied by gas production. Finally, specificity of polysaccharide use by the colon microbiota may determine diet-induced alterations in the microbiota and consequent metabolic effects. Copyright © 2011 Elsevier B.V. All rights reserved.

Distinct stages during colonization of the mouse gastrointestinal tract by Candida albicans

PubMed Central

Prieto, Daniel; Pla, Jesús

2015-01-01

Candida albicans is a member of the human microbiota, colonizing both the vaginal and gastrointestinal tracts. This yeast is devoid of a life style outside the human body and the mechanisms underlying the adaptation to the commensal status remain to be determined. Using a model of mouse gastrointestinal colonization, we show here that C. albicans stably colonizes the mouse gut in about 3 days starting from a dose as low as 100 cells, reaching steady levels of around 107 cells/g of stools. Using fluorescently labeled strains, we have assessed the competition between isogenic populations from different sources in cohoused animals. We show that long term (15 days) colonizing cells have increased fitness in the gut niche over those grown in vitro or residing in the gut for 1–3 days. Therefore, two distinct states, proliferation and adaptation, seem to exist in the adaptation of this fungus to the mouse gut, a result with potential significance in the prophylaxis and treatment of Candida infections. PMID:26300861

Correlation between the methylation of APC gene promoter and colon cancer.

PubMed

Li, Bing-Qiang; Liu, Peng-Peng; Zhang, Cai-Hua

2017-08-01

The present study was planned to explore the correlation between the methylation of APC (adenomatous polyposis coli) and colon carcinogenesis. Colon cancer tissues and tumor-adjacent normal tissues of 60 colon cancer patients (who received surgical operation in our hospital from January 2012 to December 2014) were collected. SW1116 cells in human colon cancer tissues were selected for culturing. 5-aza-2c-deoxycytidine (5-aza-dC) was utilized as an inhibitor of the methylation for APC gene. Methylation specific PCR (MSP) was utilized for detection of APC methylation in SW1116 cells. The MTT and Transwell assays were performed to detect the effect of the methylation of APC gene on the proliferation and invasive abilities of SW1116 cells. The correlation between the methylation of APC gene and pathological parameters of colon cancer patients was analyzed. MSP results revealed that 41 cases (68.33%) showed methylation of APC gene in colon cancer tissues. No methylation of APC gene was found in tumor-adjacent normal tissues. 5-aza-dC was able to inhibit the methylation of APC gene in SW1116 cells. APC gene methylation was correlated with tumor size, differentiation degree, lymph node metastasis and Dukes staging. In conclusion, the levels of the methylation of APC in colon cancer tissues and SW1116 cells are relatively high. The methylation of APC promoted the proliferation and invasion abilities of SW1116 cells. Furthermore, methylation is correlated with a variety of clinicopathological features of colon cancer patients.

Modelling the multidimensional niche by linking functional traits to competitive performance

PubMed Central

Maynard, Daniel S.; Leonard, Kenneth E.; Drake, John M.; Hall, David W.; Crowther, Thomas W.; Bradford, Mark A.

2015-01-01

Linking competitive outcomes to environmental conditions is necessary for understanding species' distributions and responses to environmental change. Despite this importance, generalizable approaches for predicting competitive outcomes across abiotic gradients are lacking, driven largely by the highly complex and context-dependent nature of biotic interactions. Here, we present and empirically test a novel niche model that uses functional traits to model the niche space of organisms and predict competitive outcomes of co-occurring populations across multiple resource gradients. The model makes no assumptions about the underlying mode of competition and instead applies to those settings where relative competitive ability across environments correlates with a quantifiable performance metric. To test the model, a series of controlled microcosm experiments were conducted using genetically related strains of a widespread microbe. The model identified trait microevolution and performance differences among strains, with the predicted competitive ability of each organism mapped across a two-dimensional carbon and nitrogen resource space. Areas of coexistence and competitive dominance between strains were identified, and the predicted competitive outcomes were validated in approximately 95% of the pairings. By linking trait variation to competitive ability, our work demonstrates a generalizable approach for predicting and modelling competitive outcomes across changing environmental contexts. PMID:26136444

The Janus face of Darwinian competition

PubMed Central

Hintze, Arend; Phillips, Nathaniel; Hertwig, Ralph

2015-01-01

Without competition, organisms would not evolve any meaningful physical or cognitive abilities. Competition can thus be understood as the driving force behind Darwinian evolution. But does this imply that more competitive environments necessarily evolve organisms with more sophisticated cognitive abilities than do less competitive environments? Or is there a tipping point at which competition does more harm than good? We examine the evolution of decision strategies among virtual agents performing a repetitive sampling task in three distinct environments. The environments differ in the degree to which the actions of a competitor can affect the fitness of the sampling agent, and in the variance of the sample. Under weak competition, agents evolve decision strategies that sample often and make accurate decisions, which not only improve their own fitness, but are good for the entire population. Under extreme competition, however, the dark side of the Janus face of Darwinian competition emerges: Agents are forced to sacrifice accuracy for speed and are prevented from sampling as often as higher variance in the environment would require. Modest competition is therefore a good driver for the evolution of cognitive abilities and of the population as a whole, whereas too much competition is devastating. PMID:26354182

The Janus face of Darwinian competition.

PubMed

Hintze, Arend; Phillips, Nathaniel; Hertwig, Ralph

2015-09-10

Without competition, organisms would not evolve any meaningful physical or cognitive abilities. Competition can thus be understood as the driving force behind Darwinian evolution. But does this imply that more competitive environments necessarily evolve organisms with more sophisticated cognitive abilities than do less competitive environments? Or is there a tipping point at which competition does more harm than good? We examine the evolution of decision strategies among virtual agents performing a repetitive sampling task in three distinct environments. The environments differ in the degree to which the actions of a competitor can affect the fitness of the sampling agent, and in the variance of the sample. Under weak competition, agents evolve decision strategies that sample often and make accurate decisions, which not only improve their own fitness, but are good for the entire population. Under extreme competition, however, the dark side of the Janus face of Darwinian competition emerges: Agents are forced to sacrifice accuracy for speed and are prevented from sampling as often as higher variance in the environment would require. Modest competition is therefore a good driver for the evolution of cognitive abilities and of the population as a whole, whereas too much competition is devastating.

Role of NleH, a type III secreted effector from attaching and effacing pathogens, in colonization of the bovine, ovine, and murine gut.

PubMed

Hemrajani, Cordula; Marches, Olivier; Wiles, Siouxsie; Girard, Francis; Dennis, Alison; Dziva, Francis; Best, Angus; Phillips, Alan D; Berger, Cedric N; Mousnier, Aurelie; Crepin, Valerie F; Kruidenier, Laurens; Woodward, Martin J; Stevens, Mark P; La Ragione, Roberto M; MacDonald, Thomas T; Frankel, Gad

2008-11-01

The human pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7 colonizes human and animal gut via formation of attaching and effacing lesions. EHEC strains use a type III secretion system to translocate a battery of effector proteins into the mammalian host cell, which subvert diverse signal transduction pathways implicated in actin dynamics, phagocytosis, and innate immunity. The genomes of sequenced EHEC O157:H7 strains contain two copies of the effector protein gene nleH, which share 49% sequence similarity with the gene for the Shigella effector OspG, recently implicated in inhibition of migration of the transcriptional regulator NF-kappaB to the nucleus. In this study we investigated the role of NleH during EHEC O157:H7 infection of calves and lambs. We found that while EHEC DeltanleH colonized the bovine gut more efficiently than the wild-type strain, in lambs the wild-type strain exhibited a competitive advantage over the mutant during mixed infection. Using the mouse pathogen Citrobacter rodentium, which shares many virulence factors with EHEC O157:H7, including NleH, we observed that the wild-type strain exhibited a competitive advantage over the mutant during mixed infection. We found no measurable differences in T-cell infiltration or hyperplasia in colons of mice inoculated with the wild-type or the nleH mutant strain. Using NF-kappaB reporter mice carrying a transgene containing a luciferase reporter driven by three NF-kappaB response elements, we found that NleH causes an increase in NF-kappaB activity in the colonic mucosa. Consistent with this, we found that the nleH mutant triggered a significantly lower tumor necrosis factor alpha response than the wild-type strain.

Spatial and temporal patterns of coexistence between competing Aedes mosquitoes in urban Florida.

PubMed

Leisnham, Paul T; Juliano, S A

2009-05-01

Understanding mechanisms fostering coexistence between invasive and resident species is important in predicting ecological, economic, or health impacts of invasive species. The mosquito Aedes aegypti coexists at some urban sites in southeastern United States with invasive Aedes albopictus, which is often superior in interspecific competition. We tested predictions for three hypotheses of species coexistence: seasonal condition-specific competition, aggregation among individual water-filled containers, and colonization-competition tradeoff across spatially partitioned habitat patches (cemeteries) that have high densities of containers. We measured spatial and temporal patterns of abundance for both species among water-filled resident cemetery vases and experimentally positioned standard cemetery vases and ovitraps in metropolitan Tampa, Florida. Consistent with the seasonal condition-specific competition hypothesis, abundances of both species in resident and standard cemetery vases were higher early in the wet season (June) versus late in the wet season (September), but the proportional increase of A. albopictus was greater than that of A. aegypti, presumably due to higher dry-season egg mortality and strong wet-season competitive superiority of larval A. albopictus. Spatial partitioning was not evident among cemeteries, a result inconsistent with the colonization-competition tradeoff hypothesis, but both species were highly independently aggregated among standard cemetery vases and ovitraps, which is consistent with the aggregation hypothesis. Densities of A. aegypti but not A. albopictus differed among land use categories, with A. aegypti more abundant in ovitraps in residential areas compared to industrial and commercial areas. Spatial partitioning among land use types probably results from effects of land use on conditions in both terrestrial and aquatic-container environments. These results suggest that both temporal and spatial variation may contribute to local coexistence between these Aedes in urban areas.

Colonization of chicken cecae by Escherichia coli associated with hemorrhagic colitis.

PubMed Central

Beery, J T; Doyle, M P; Schoeni, J L

1985-01-01

Bacterial enumeration, histologic examination, and immunoperoxidase staining demonstrated the ability of an Escherichia coli strain associated with hemorrhagic colitis (serotype O157:H7) to colonize chicken cecae for up to 90 days postinoculation after a peroral challenge at 1 day of age. The bacteria induced mild, transient, mucous membrane damage confined to the proximal cecae of healthy, normal-appearing chickens, principally at 14 to 28 days postinoculation. Attachment, effacement, and penetration of the cecal surface epithelium by E. coli O157:H7 were observed. With the exception of splenic, hepatic, and cecal tonsil immune-related changes and cecal damage and colonization, no other organ systems or portions of the gastrointestinal tract were affected by the bacteria. Bacterial counts indicated that E. coli O157:H7 was predominantly present in the cecae (often at levels greater than 10(6) CFU/g of tissue and contents) and to a lesser extent in the colon. Our results suggest that E. coli O157:H7 colonizes chicken cecae and is passed through the colon with fecal excrement. The ability of this organism to colonize chicken cecae indicates that chickens may serve as hosts and possibly as reservoirs for E. coli O157:H7. Images PMID:3885853

Longer growing seasons shift grassland vegetation towards more-productive species

NASA Astrophysics Data System (ADS)

Fridley, Jason D.; Lynn, Josh S.; Grime, J. P.; Askew, A. P.

2016-09-01

Despite advances in plant functional ecology that provide a framework for predicting the responses of vegetation to environmental change, links between plant functional strategies and elevated temperatures are poorly understood. Here, we analyse the response of a species-rich grassland in northern England to two decades of temperature and rainfall manipulations in the context of the functional attributes of 21 coexisting species that represent a large array of resource-use strategies. Three principal traits, including body size (canopy height), tissue investment (leaf construction cost), and seed size, varied independently across species and reflect tradeoffs associated with competitiveness, stress tolerance, and colonization ability. Unlike past studies, our results reveal a strong association between functional traits and temperature regime; species favoured by extended growing seasons have taller canopies and faster assimilation rates, which has come at the expense of those species of high tissue investment. This trait-warming association was three times higher in deep soils, suggesting species shifts have been strongly mediated by competition. In contrast, vegetation shifts from rainfall manipulations have been associated only with tissue investment. Functional shifts towards faster growing species in response to warming may be responsible for a marginal increase in productivity in a system that was assumed to be nutrient-limited.

Interspecific Relationships in Benthic Assemblages of a Large Lowland River : Co-existence or Competition as a Result of Habitat Characteristics

NASA Astrophysics Data System (ADS)

Akopian, M.; Usseglio-Polatera, P.

2005-05-01

Macrobenthic assemblages of the lower, regulated and canalized Marne River (France) are dominated by several "exotic", recently introduced species. Arrival, installation and spread of such alien species were certainly promoted by (1) the close connection between French and other European river systems (Rhine, Danube), (2) the modification of natural river flow and benthic habitats. Both habitat characteristics (e.g. granulometric composition, organic content) and corresponding benthic assemblage structure were analysed to identify the substrate affinity of major taxa in the lower Marne River. The main aim of the study was to evaluate the possible biotic interactions (i.e. competition for food and/or space) among dominant taxa as function of habitat features and to predict the future development of newly established species, already known as potential invaders: Corbicula fluminea (Bivalvia), Hypania invalida (Polychaeta), Chelicorophium curvispinum (Amphipoda), etc. Most of the newly established species, coming from the same biogeographical area ("invasional meltdown" hypothesis?), are eurytopic, with high fecundity and large food spectrum. First results demonstrated the co-existence of such species in the Marne River. But the future ecological importance of these organisms in benthic assemblages of the river depends on their present population size, population dynamics, and ability to colonize bottom substrates.

Development of a competitive exclusion product for poultry meeting the regulatory requirements for registration in the European Union.

PubMed

Klose, Viviana; Mohnl, Michaela; Plail, Regina; Schatzmayr, Gerd; Loibner, Andreas-Paul

2006-05-01

Competitive exclusion treatment is able to increase the pathogen colonization resistance of day-old chicks by applying probiotic bacteria stabilizing the indigenous microflora. In order to develop a safe microbial feed additive, various bacterial strains were isolated out of the gastrointestinal tract of healthy chickens. One hundred twenty-one representatives were selected based on differences in whole-cell protein patterns and screened for antagonistic properties. Five effective strains (Pediococcus acidilactici, Enterococcus faecium, Bifidobacterium animalis ssp. animalis, Lactobacillus reuteri, and Lactobacillus salivarius ssp. salivarius) exhibited in vitro the ability to inhibit a range of common pathogens and were evaluated with regard to the risks associated with genetic transfer of antibiotic resistances from animals to humans via the food chain. The probiotic strains were sensitive to several clinically effective antibiotics, though some of them showed single resistances. None of the vancomycin-resistant (R) strains carried the enterococcal vanA gene. Two tetracycline R strains were shown to harbor a tet(M)-associated resistance. The strains contained no extrachromosomal DNA and were not able to transfer the resistance by means of conjugation. On basis of the collected data the presence of easy transferable resistances was excluded and the chicken strains were considered to be suitable for the use as feed additive.

Electroactive Mg2+-Hydroxyapatite Nanostructured Networks against Drug-Resistant Bone Infection Strains.

PubMed

Andrés, Nancy C; Sieben, Juan M; Baldini, Mónica; Rodríguez, Carlos H; Famiglietti, Ángela; Messina, Paula V

2018-06-13

Surface colonization competition between bacteria and host cells is one of the critical factors involved in tissue/implant integration. Current biomaterials are evaluated for their ability both of withstanding favorable responses of host tissue cells and of resisting bacterial contamination. In this work, the antibacterial ability of biocompatible Mg 2+ -substituted nanostructured hydroxyapatite (HA) was investigated. The densities of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli strains were significantly decreased after culture in the presence of Mg-substituted HA materials in direct correlation with Mg 2+ -Ca 2+ switch in the HA lattice. It was noticed that this decrease was accompanied by a minimal alteration of bacterial environments; therefore, the Mg 2+ -HA antibacterial effect was associated with the material surface topography and it electroactive behavior. It was observed that 2.23 wt % Mg 2+ -HA samples exhibited the best antibacterial performance; it decreased 2-fold the initial population of E. coli, P. aeruginosa, and S. aureus at the intermediate concentration (50 mg mL -1 of broth). Our results reinforce the potential of Mg-HA nanostructured materials to be used in antibacterial coatings for implantable devices and/or medicinal materials to prevent bone infection and to promote wound healing.

Is parental competitive ability in winter negatively affected by previous springs' family size?

PubMed

Fokkema, Rienk W; Ubels, Richard; Tinbergen, Joost M

2017-03-01

Reproductive behavior cannot be understood without taking the local level of competition into account. Experimental work in great tits ( Parus major ) showed that (1) a survival cost of reproduction was paid in environments with high levels of competition during the winter period and (2) experimentally manipulated family size negatively affected the ability of parents to compete for preferred breeding boxes in the next spring. The fact that survival was affected in winter suggests that the competitive ability of parents in winter may also be affected by previous reproductive effort. In this study, we aim to investigate whether (1) such carryover effects of family size on the ability of parents to compete for resources in the winter period occurred and (2) this could explain the occurrence of a survival cost of reproduction under increased competition. During two study years, we manipulated the size of in total 168 great tit broods. Next, in winter, we induced competition among the parents by drastically reducing the availability of roosting boxes in their local environment for one week. Contrary to our expectation, we found no negative effect of family size manipulation on the probability of parents to obtain a roosting box. In line with previous work, we did find that a survival cost of reproduction was paid only in plots in which competition for roosting boxes was shortly increased. Our findings thus add to the scarce experimental evidence that survival cost of reproduction are paid under higher levels of local competition but this could not be linked to a reduced competitive ability of parents in winter.

Equal Opportunity Tactic: Redesigning and Applying Competition Games in Classrooms

ERIC Educational Resources Information Center

Cheng, Hercy N. H.; Wu, Winston M. C.; Liao, Calvin C. Y.; Chan, Tak-Wai

2009-01-01

Competition, despite its potential drawbacks, is an easily adopted and frequently used motivator in classrooms. Individual abilities, in the years of schooling, are inevitably different, and performance in competition is heavily ability dependent, resulting that more-able students always win while less-able students always lose. Students easily…

EVOLUTIONARY PERSPECTIVES IN A MUTUALISM OF SEPIOLID SQUID AND BIOLUMINESCENT BACTERIA: COMBINED USAGE OF MICROBIAL EXPERIMENTAL EVOLUTION AND TEMPORAL POPULATION GENETICS

PubMed Central

Soto, W.; Punke, E. B.; Nishiguchi, M. K.

2013-01-01

The symbiosis between marine bioluminescent Vibrio bacteria and the sepiolid squid Euprymna is a model for studying animal–bacterial Interactions. Vibrio symbionts native to particular Euprymna species are competitively dominant, capable of outcompeting foreign Vibrio strains from other Euprymna host species. Despite competitive dominance, secondary colonization events by invading nonnative Vibrio fischeri have occurred. Competitive dominance can be offset through superior nonnative numbers and advantage of early start host colonization by nonnatives, granting nonnative vibrios an opportunity to establish beachheads in foreign Euprymna hosts. Here, we show that nonnative V. fischeri are capable of rapid adaptation to novel sepiolid squid hosts by serially passaging V. fischeri JRM200 (native to Hawaiian Euprymna scolopes) lines through the novel Australian squid host E. tasmanica for 500 generations. These experiments were complemented by a temporal population genetics survey of V. fischeri, collected from E. tasmanica over a decade, which provided a perspective from the natural history of V. fischeri evolution over 15,000–20,000 generations in E. tasmanica. No symbiont anagenic evolution within squids was observed, as competitive dominance does not purge V. fischeri genetic diversity through time. Instead, abiotic factors affecting abundance of V. fischeri variants in the planktonic phase sustain temporal symbiont diversity, a property itself of ecological constraints imposed by V. fischeri host adaptation. PMID:22519773

Removal and prevention of dental plaque with d-tagatose.

PubMed

Lu, Y; Levin, G V

2002-08-01

Dental plaque develops when early bacterial colonizers adhere to the acquired pellicle (saliva-derived proteinous coating on the tooth surface) followed by adhesion of late interspecies colonizers to form this type of biofilm (coaggregation). In developing a d-tagatose-based toothpaste, we examined 15 oral isolates, including both early colonizers (Streptococcus and Actinomyces) and late colonizers (Fusobacterium, Porphyromonas, Prevotella, Veillonella, Capnocytophaga, and Actinobacillus), and tested them for their ability to coaggregate with each other. We then tested the ability of d-tagatose to reverse any such coaggregations. Coaggregation was examined visually and scored by using a system ranging from 0, for no visible coaggregation to 4, for maximum coaggregation. d-Tagatose, at a concentration of less than 750 mm, completely reversed the coaggregation of 17 (60%) of 28 strongly coaggregating pairs (coaggregation score = 2 or higher) tested. In contrast, d-sorbitol had little reversal effect. d-Tagatose-sensitive coaggregations were d-galactose-reversible as well. d-Tagatose acted on both early and late colonizers; both groups, especially the late colonizers, were frequently involved in periodontal diseases. Thus, d-tagatose has the potential for preventing and removing plaque development and for altering the subgingival microbiota. These effective qualities offer conservative control of gingival and periodontal disease.

Pre-treatment with Bifidobacterium breve UCC2003 modulates Citrobacter rodentium-induced colonic inflammation and organ specificity.

PubMed

Collins, James W; Akin, Ali R; Kosta, Artemis; Zhang, Ning; Tangney, Mark; Francis, Kevin P; Frankel, Gad

2012-11-01

Citrobacter rodentium, which colonizes the gut mucosa via formation of attaching and effacing (A/E) lesions, causes transmissible colonic hyperplasia. The aim of this study was to evaluate whether prophylactic treatment with Bifidobacterium breve UCC2003 can improve the outcome of C. rodentium infection. Six-week-old albino C57BL/6 mice were pre-treated for 3 days with B. breve, challenged with bioluminescent C. rodentium and administered B. breve or PBS-C for 8 days post-infection; control mice were either administered B. breve and mock-infected with PBS, or mock-treated with PBS-C and mock-infected with PBS. C. rodentium colonization was monitored by bacterial enumeration from faeces and by a combination of both 2D bioluminescence imaging (BLI) and composite 3D diffuse light imaging tomography with µCT imaging (DLIT-µCT). At day 8 post-infection, colons were removed and assessed for crypt hyperplasia, histology by light microscopy, bacterial colonization by immunofluorescence, and A/E lesion formation by electron microscopy. Prophylactic administration of B. breve did not prevent C. rodentium colonization or A/E lesion formation. However, this treatment did alter C. rodentium distribution within the large intestine and significantly reduced colonic crypt hyperplasia at the peak of bacterial infection. These results show that B. breve could not competitively exclude C. rodentium, but reduced pathogen-induced colonic inflammation.

Larval competition of Chrysomya megacephala and Chrysomya rufifacies (Diptera: Calliphoridae): behavior and ecological studies of two blow fly species of forensic significance.

PubMed

Shiao, Shiuh-Feng; Yeh, Ta-Chuan

2008-07-01

Chrysomya megacephala and Chrysomya rufifacies are two predominant necrophagous species in Taiwan. Larvae of the latter can prey on other maggots, including that of their own species as facultative food. This facultative characteristic of C. rufifacies may enhance its competitive advantage over other maggots and could also change the situation of other coexisting colonies. In this study, these two species were colonized in the laboratory, and the main objective was to try to understand the effect of competition on larval development. According to our results, intraspecific competition mostly occurred as competition for food; when the rearing density was increased, larvae pupated earlier, resulting in a lighter adult dry weight. The tendencies were similar in both species, but C. megacephala developed smaller viable adults and had higher survivorship at high densities. Although C. rufifacies could use the food resource of cannibalism, its survivorship was still low. Our results also showed there were significant interactions between intraspecific competition and the density factor. However, with interspecific competition, the first-instar larvae of C. rufifacies invaded maggot masses of C. megacephala to feed together. The third instars of C. rufifacies were able to expel C. megacephala larvae from food by using a fleshy protrusion on their body surface; C. megacephala was usually forced to pupate earlier by shortening its larval stages. The results indicated that a temporary competitive advantage could only be obtained by C. rufifacies under a proper larval density. In addition, the effects on different larval stages, the responses to different competition intensities, and the temperature-dependent effects on interspecific competition are also discussed. In general, under mixed-species rearing at different temperatures and densities, larval duration, adult dry weight, and survivorship of both species decreased. However, our results did not completely agree with previous studies, and we suspect that the difference was partially caused by different experimental designs and different biological characters of different blow fly colonies. Our results also suggest that both the predation ability and defense or escape activity should be taken into account when evaluating larval competitive advantages. The durations of larval stages of these two species could be decreased by approximately 54 h when a single species was reared alone and food was limited; the largest reduction in larval duration, approximately 25 h in C. megacephala and 34 h in C. rufifacies, caused by interspecific competition was under a high larval density. In conclusion, competition decreased the larval duration of these two species by up to 2 d; this also draws attention to justifying the postmortem interval estimation of using larval developmental data when larval competition exists.

Competitive Abilities in Experimental Microcosms Are Accurately Predicted by a Demographic Index for R*

PubMed Central

Murrell, Ebony G.; Juliano, Steven A.

2012-01-01

Resource competition theory predicts that R*, the equilibrium resource amount yielding zero growth of a consumer population, should predict species' competitive abilities for that resource. This concept has been supported for unicellular organisms, but has not been well-tested for metazoans, probably due to the difficulty of raising experimental populations to equilibrium and measuring population growth rates for species with long or complex life cycles. We developed an index (Rindex) of R* based on demography of one insect cohort, growing from egg to adult in a non-equilibrium setting, and tested whether Rindex yielded accurate predictions of competitive abilities using mosquitoes as a model system. We estimated finite rate of increase (λ′) from demographic data for cohorts of three mosquito species raised with different detritus amounts, and estimated each species' Rindex using nonlinear regressions of λ′ vs. initial detritus amount. All three species' Rindex differed significantly, and accurately predicted competitive hierarchy of the species determined in simultaneous pairwise competition experiments. Our Rindex could provide estimates and rigorous statistical comparisons of competitive ability for organisms for which typical chemostat methods and equilibrium population conditions are impractical. PMID:22970128

Are invasive plants more competitive than native conspecifics? Patterns vary with competitors

NASA Astrophysics Data System (ADS)

Zheng, Yulong; Feng, Yulong; Valiente-Banuet, Alfonso; Li, Yangping; Liao, Zhiyong; Zhang, Jiaolin; Chen, Yajun

2015-10-01

Invasive plants are sometimes considered to be more competitive than their native conspecifics, according to the prediction that the invader reallocates resources from defense to growth due to liberation of natural enemies [‘Evolution of Increased Competitive Ability’ (EICA) hypothesis]. However, the differences in competitive ability may depend on the identity of competitors. In order to test the effects of competitors, Ageratina adenophora plants from both native and invasive ranges competed directly, and competed with native residents from both invasive (China) and native (Mexico) ranges respectively. Invasive A. adenophora plants were more competitive than their conspecifics from native populations when competing with natives from China (interspecific competition), but not when competing with natives from Mexico. Invasive A. adenophora plants also showed higher competitive ability when grown in high-density monoculture communities of plants from the same population (intrapopulation competition). In contrast, invasive A. adenophora plants showed lower competitive ability when competing with plants from native populations (intraspecific competition). Our results indicated that in the invasive range A. adenophora has evolved to effectively cope with co-occurring natives and high density environments, contributing to invasion success. Here, we showed the significant effects of competitors, which should be considered carefully when testing the EICA hypothesis.

Isolation and Characterization of a Phosphorus-Solubilizing Bacterium from Rhizosphere Soils and Its Colonization of Chinese Cabbage (Brassica campestris ssp. chinensis)

PubMed Central

Wang, Zhen; Xu, Guoyi; Ma, Pengda; Lin, Yanbing; Yang, Xiangna; Cao, Cuiling

2017-01-01

Phosphate-solubilizing bacteria (PSB) can promote the dissolution of insoluble phosphorus (P) in soil, enhancing the availability of soluble P. Thus, their application can reduce the consumption of fertilizer and aid in sustainable agricultural development. From the rhizosphere of Chinese cabbage plants grown in Yangling, we isolated a strain of PSB (YL6) with a strong ability to dissolve P and showed that this strain promoted the growth of these plants under field conditions. However, systematic research on the colonization of bacteria in the plant rhizosphere remains deficient. Thus, to further study the effects of PSB on plant growth, in this study, green fluorescent protein (GFP) was used to study the colonization of YL6 on Chinese cabbage roots. GFP expression had little effect on the ability of YL6 to grow and solubilize P. In addition, the GFP-expressing strain stably colonized the Chinese cabbage rhizosphere (the number of colonizing bacteria in the rhizosphere soil was 4.9 lg CFU/g). Using fluorescence microscopy, we observed a high abundance of YL6-GFP bacteria at the Chinese cabbage root cap and meristematic zone, as well as in the root hairs and hypocotyl epidermal cells. High quantities of GFP-expressing bacteria were recovered from Chinese cabbage plants during different planting periods for further observation, indicating that YL6-GFP had the ability to endogenously colonize the plants. This study has laid a solid and significant foundation for further research on how PSB affects the physiological processes in Chinese cabbage to promote plant growth. PMID:28798725

Live and heat-killed Lactobacillus spp. interfere with Streptococcus mutans and Streptococcus oralis during biofilm development on titanium surface.

PubMed

Ciandrini, E; Campana, R; Baffone, W

2017-06-01

This research investigates the ability of live and heat-killed (HK) Lactic Acid Bacteria (LAB) to interfere with Streptococcus mutans ATCC 25175 and Streptococcus oralis ATCC 9811 during biofilm formation. Eight Lactobacillus spp. and two oral colonizers, pathogenic Streptococcus mutans and resident Streptococcus oralis, were characterized for their aggregation abilities, cell surface properties and biofilm formation ability on titanium surface. Then, the interference activity of selected live and HK Lactobacillus spp. during S. mutans and S. oralis biofilm development were performed. The cell-free culture supernatants (CFCS) anti-biofilm activity was also determined. LAB possess good abilities of auto-aggregation (from 14.19 to 28.97%) and of co-aggregation with S. oralis. The cell-surfaces characteristics were most pronounced in S. mutans and S. oralis, while the highest affinities to xylene and chloroform were observed in Lactobacillus rhamnosus ATCC 53103 (56.37%) and Lactobacillus paracasei B21060 (43.83%). S. mutans and S. oralis developed a biofilm on titanium surface, while LAB showed a limited or no ability to create biofilm. Live and HK L. rhamnosus ATCC 53103 and L. paracasei B21060 inhibited streptococci biofilm formation by competition and displacement mechanisms with no substantial differences. The CFCSs of both LAB strains, particularly the undiluted one of L. paracasei B21060, decreased S. mutans and S. oralis biofilm formation. This study evidenced the association of LAB aggregation abilities and cell-surface properties with the LAB-mediated inhibition of S. mutans and S. oralis biofilm formation. Lactobacilli showed different mechanisms of action and peculiar strain-specific characteristics, maintained also in the heat-killed LAB. Copyright © 2017 Elsevier Ltd. All rights reserved.

Examining the interaction between developmental toxicity and microbiota colonization

EPA Science Inventory

There is growing evidence that microbiota can modify the toxicokinetics and/or toxicodynamics of environmental chemicals. Commonly used mammalian systems have limited ability to link phenotypic effects in exposed animals to colonization status. Here, we used gnotobiotic zebrafish...

Establishment of ectomycorrhizal fungal community on isolated Nothofagus cunninghamii seedlings regenerating on dead wood in Australian wet temperate forests: does fruit-body type matter?

PubMed

Tedersoo, Leho; Gates, Genevieve; Dunk, Chris W; Lebel, Teresa; May, Tom W; Kõljalg, Urmas; Jairus, Teele

2009-08-01

Decaying wood provides an important habitat for animals and forms a seed bed for many shade-intolerant, small-seeded plants, particularly Nothofagus. Using morphotyping and rDNA sequence analysis, we compared the ectomycorrhizal fungal community of isolated N. cunninghamii seedlings regenerating in decayed wood against that of mature tree roots in the forest floor soil. The /cortinarius, /russula-lactarius, and /laccaria were the most species-rich and abundant lineages in forest floor soil in Australian sites at Yarra, Victoria and Warra, Tasmania. On root tips of seedlings in dead wood, a subset of the forest floor taxa were prevalent among them species of /laccaria, /tomentella-thelephora, and /descolea, but other forest floor dominants were rare. Statistical analyses suggested that the fungal community differs between forest floor soil and dead wood at the level of both species and phylogenetic lineage. The fungal species colonizing isolated seedlings on decayed wood in austral forests were taxonomically dissimilar to the species dominating in similar habitats in Europe. We conclude that formation of a resupinate fruit body type on the underside of decayed wood is not necessarily related to preferential root colonization in decayed wood. Rather, biogeographic factors as well as differential dispersal and competitive abilities of fungal taxa are likely to play a key role in structuring the ectomycorrhizal fungal community on isolated seedlings in decaying wood.

The Intersection Between Colonization Resistance, Antimicrobial Stewardship, and Clostridium difficile.

PubMed

Rosa, Rossana; Donskey, Curtis J; Munoz-Price, L Silvia

2018-06-07

Colonization resistance refers to the innate defense provided by the indigenous microbiota against colonization by pathogenic organisms. We aim to describe how this line of defense is deployed against Clostridium difficile and what the implications are for interventions directed by Antimicrobial Stewardship Programs. The indigenous microbiota provides colonization resistance through depletion of nutrients, prevention of access to adherence sites within the gut mucosa, production of inhibitory substances, and stimulation of the host's immune system. The ability to quantify colonization resistance could provide information regarding periods of maximal vulnerability to colonization with pathogens and also allow the identification of mechanisms of restoration of colonization resistance. Methods utilized to determine the composition of the gut microbiota include sequencing technologies and measurement of concentration of specific bacterial metabolites. Use of innovations in the quantification of colonization resistance can expand the role of Antimicrobial Stewardship from prevention of disruption of the indigenous microbiota to restoration of colonization resistance.

Rapid Diversity Loss of Competing Animal Species in Well-Connected Landscapes

PubMed Central

Schippers, Peter; Hemerik, Lia; Baveco, Johannes M.; Verboom, Jana

2015-01-01

Population viability of a single species, when evaluated with metapopulation based landscape evaluation tools, always increases when the connectivity of the landscape increases. However, when interactions between species are taken into account, results can differ. We explore this issue using a stochastic spatially explicit meta-community model with 21 competing species in five different competitive settings: (1) weak, coexisting competition, (2) neutral competition, (3) strong, excluding competition, (4) hierarchical competition and (5) random species competition. The species compete in randomly generated landscapes with various fragmentation levels. With this model we study species loss over time. Simulation results show that overall diversity, the species richness in the entire landscape, decreases slowly in fragmented landscapes whereas in well-connected landscapes rapid species losses occur. These results are robust with respect to changing competitive settings, species parameters and spatial configurations. They indicate that optimal landscape configuration for species conservation differs between metapopulation approaches, modelling species separately and meta-community approaches allowing species interactions. The mechanism behind this is that species in well-connected landscapes rapidly outcompete each other. Species that become abundant, by chance or by their completive strength, send out large amounts of dispersers that colonize and take over other patches that are occupied by species that are less abundant. This mechanism causes rapid species loss. In fragmented landscapes the colonization rate is lower, and it is difficult for a new species to establish in an already occupied patch. So, here dominant species cannot easily take over patches occupied by other species and higher diversity is maintained for a longer time. These results suggest that fragmented landscapes have benefits for species conservation previously unrecognized by the landscape ecology and policy community. When species interactions are important, landscapes with a low fragmentation level can be better for species conservation than well-connected landscapes. Moreover, our results indicate that metapopulation based landscape evaluation tools may overestimate the value of connectivity and should be replaced by more realistic meta-community based tools. PMID:26218682

Arbuscular mycorrhizal fungi alter the competitive hierarchy among old-field plant species.

PubMed

Stanescu, Sabina; Maherali, Hafiz

2017-02-01

Inoculation with arbuscular mycorrhizal (AM) fungi is known to increase the species diversity of plant communities. One mechanism that can increase the likelihood of species co-existence, and thus species diversity, is a trade-off between competitive ability and the magnitude of plant growth response to AM fungal inoculation. By suppressing the growth of strong competitors while simultaneously enhancing the growth of weak competitors, this trade-off would cause the competitive hierarchy to be less pronounced in soil inoculated with AM fungi relative to non-inoculated conditions. To test whether such a trade-off exists, we quantified competitive abilities and mycorrhizal growth response (MGR) among 21 species that co-occur in old fields in southern Ontario. Competitive ability was determined by calculating competitive effect (CE), or the degree to which each species suppressed the biomass of a common phytometer species, Plantago lanceolata. Higher CE values represent stronger competitive ability. Old-field species varied in their ability to suppress the biomass of the phytometer and MGR was generally positive. There was a statistically significant negative correlation between CE in non-inoculated soil and MGR (r = -0.49, P = 0.02). In addition, variance in CE was 73% lower in soil inoculated with AM fungi compared to non-inoculated soil (P = 0.0023). These findings support the hypothesis that AM fungi weaken strong competitors while enhancing the performance of weak competitors. Because this trade-off compressed the competitive hierarchy among old-field species in soil inoculated with AM fungi, it may be a mechanism by which mycorrhizal fungi enhance species evenness and diversity.

Epidemiology, Relative Invasive Ability, Molecular Characterization, and Competitive Performance of Campylobacter jejuni Strains in the Chicken Gut▿

PubMed Central

Pope, Christopher; Wilson, Janet; Taboada, Eduardo N.; MacKinnon, Joanne; Felipe Alves, Cristiano A.; Nash, John H. E.; Rahn, Kris; Tannock, Gerald W.

2007-01-01

One hundred forty-one Campylobacter jejuni isolates from humans with diarrhea and 100 isolates from retailed poultry meat were differentiated by flaA typing. The bacteria were isolated in a specific geographical area (Dunedin) in New Zealand over a common time period. Twenty nine flaA types were detected, one of which (flaA restriction fragment length polymorphism type 15 [flaA-15]) predominated among isolates from humans (∼30% of isolates). This strain was of low prevalence (5% of isolates) among poultry isolates. flaA-15 strains were five to six times more invasive of HEp2 cells in an in vitro assay than a flaA type (flaA-3) that was commonly encountered on poultry meat (23% of isolates) but was seldom associated with human illness (5%). Competitive-exclusion experiments with chickens, utilizing real-time quantitative PCR to measure the population sizes of specific strains representing flaA-15 (T1016) and flaA-3 (Pstau) in digesta, were carried out. These experiments showed that T1016 always outcompeted Pstau in the chicken intestine. Genomic comparisons of T1016 and Pstau were made using DNA microarrays representing the genome of C. jejuni NCTC 11168. These comparisons revealed differences between the strains in the gene content of the Cj1417c-to-Cj1442c region of the genome, which is associated with the formation of capsular polysaccharide. The strains differed in Penner type (T1016, O42; Pstau, O53). It was concluded that poultry meat was at least one source of human infection with C. jejuni, that some Campylobacter strains detected in poultry meat are of higher virulence for humans than others, and that bacterial attributes affecting strain virulence and commensal colonization ability may be linked. PMID:17921281

Compartment-specific immunity in the human gut: properties and functions of dendritic cells in the colon versus the ileum.

PubMed

Mann, Elizabeth R; Bernardo, David; English, Nicholas R; Landy, Jon; Al-Hassi, Hafid O; Peake, Simon T C; Man, Ripple; Elliott, Timothy R; Spranger, Henning; Lee, Gui Han; Parian, Alyssa; Brant, Steven R; Lazarev, Mark; Hart, Ailsa L; Li, Xuhang; Knight, Stella C

2016-02-01

Dendritic cells (DC) mediate intestinal immune tolerance. Despite striking differences between the colon and the ileum both in function and bacterial load, few studies distinguish between properties of immune cells in these compartments. Furthermore, information of gut DC in humans is scarce. We aimed to characterise human colonic versus ileal DC. Human DC from paired colonic and ileal samples were characterised by flow cytometry, electron microscopy or used to stimulate T cell responses in a mixed leucocyte reaction. A lower proportion of colonic DC produced pro-inflammatory cytokines (tumour necrosis factor-α and interleukin (IL)-1β) compared with their ileal counterparts and exhibited an enhanced ability to generate CD4(+)FoxP3(+)IL-10(+) (regulatory) T cells. There were enhanced proportions of CD103(+)Sirpα(-) DC in the colon, with increased proportions of CD103(+)Sirpα(+) DC in the ileum. A greater proportion of colonic DC subsets analysed expressed the lymph-node-homing marker CCR7, alongside enhanced endocytic capacity, which was most striking in CD103(+)Sirpα(+) DC. Expression of the inhibitory receptor ILT3 was enhanced on colonic DC. Interestingly, endocytic capacity was associated with CD103(+) DC, in particular CD103(+)Sirpα(+) DC. However, expression of ILT3 was associated with CD103(-) DC. Colonic and ileal DC differentially expressed skin-homing marker CCR4 and small-bowel-homing marker CCR9, respectively, and this corresponded to their ability to imprint these homing markers on T cells. The regulatory properties of colonic DC may represent an evolutionary adaptation to the greater bacterial load in the colon. The colon and the ileum should be regarded as separate entities, each comprising DC with distinct roles in mucosal immunity and imprinting. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

L-Fucose metabolism in camplobacter jejuni

USDA-ARS?s Scientific Manuscript database

Campylobacter jejuni is a gastrointestinal pathogen once considered asaccharolytic, but now known to metabolize fucose. Strains with the fuc locus encode enzymes for fucose uptake and metabolism and show a competitive colonization advantage in the piglet disease model. C. jejuni NCTC11168 shows redu...

Fungal Lactamases, Their Occurrence and Function

USDA-ARS?s Scientific Manuscript database

Fungi are absorptive feeders and thus must colonize and ramify through their substrate to survive. In so doing they are in competition, particularly in the soil, with myriad microbes. Additionally, these microbes use xenobiotic compounds as offensive weapons to compete for nutrition, and fungi must ...

Neighbour tolerance, not suppression, provides competitive advantage to non-native plants.

PubMed

Golivets, Marina; Wallin, Kimberly F

2018-05-01

High competitive ability has often been invoked as a key determinant of invasion success and ecological impacts of non-native plants. Yet our understanding of the strategies that non-natives use to gain competitive dominance remains limited. Particularly, it remains unknown whether the two non-mutually exclusive competitive strategies, neighbour suppression and neighbour tolerance, are equally important for the competitive advantage of non-native plants. Here, we analyse data from 192 peer-reviewed studies on pairwise plant competition within a Bayesian multilevel meta-analytic framework and show that non-native plants outperform their native counterparts due to high tolerance of competition, as opposed to strong suppressive ability. Competitive tolerance ability of non-native plants was driven by neighbour's origin and was expressed in response to a heterospecific native but not heterospecific non-native neighbour. In contrast to natives, non-native species were not more suppressed by hetero- vs. conspecific neighbours, which was partially due to higher intensity of intraspecific competition among non-natives. Heterogeneity in the data was primarily associated with methodological differences among studies and not with phylogenetic relatedness among species. Altogether, our synthesis demonstrates that non-native plants are competitively distinct from native plants and challenges the common notion that neighbour suppression is the primary strategy for plant invasion success. © 2018 John Wiley & Sons Ltd/CNRS.

Are invasive plants more competitive than native conspecifics? Patterns vary with competitors

PubMed Central

Zheng, Yulong; Feng, Yulong; Valiente-Banuet, Alfonso; Li, Yangping; Liao, Zhiyong; Zhang, Jiaolin; Chen, Yajun

2015-01-01

Invasive plants are sometimes considered to be more competitive than their native conspecifics, according to the prediction that the invader reallocates resources from defense to growth due to liberation of natural enemies [‘Evolution of Increased Competitive Ability’ (EICA) hypothesis]. However, the differences in competitive ability may depend on the identity of competitors. In order to test the effects of competitors, Ageratina adenophora plants from both native and invasive ranges competed directly, and competed with native residents from both invasive (China) and native (Mexico) ranges respectively. Invasive A. adenophora plants were more competitive than their conspecifics from native populations when competing with natives from China (interspecific competition), but not when competing with natives from Mexico. Invasive A. adenophora plants also showed higher competitive ability when grown in high-density monoculture communities of plants from the same population (intrapopulation competition). In contrast, invasive A. adenophora plants showed lower competitive ability when competing with plants from native populations (intraspecific competition). Our results indicated that in the invasive range A. adenophora has evolved to effectively cope with co-occurring natives and high density environments, contributing to invasion success. Here, we showed the significant effects of competitors, which should be considered carefully when testing the EICA hypothesis. PMID:26489964

Phenotypic variation of Pseudomonas brassicacearum as a plant root-colonization strategy.

PubMed

Achouak, Wafa; Conrod, Sandrine; Cohen, Valérie; Heulin, Thierry

2004-08-01

Pseudomonas brassicacearum was isolated as a major root-colonizing population from Arabidopsis thaliana. The strain NFM421 of P. brassicacearum undergoes phenotypic variation during A. thaliana and Brassica napus root colonization in vitro as well as in soil, resulting in different colony appearance on agar surfaces. Bacteria forming translucent colonies (phase II cells) essentially were localized at the surface of young roots and root tips, whereas wild-type cells (phase I cells) were localized at the basal part of roots. The ability of phase II cells to spread and colonize new sites on root surface correlates with over-production of flagellin as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of surface proteins and microsequencing. Moreover, phase II cells showed a higher ability to swim and to swarm on semisolid agar medium. Phase I and phase II cells of P. brassicacearum NFM421 were tagged genetically with green fluorescent protein and red fluorescent protein. Confocal scanning laser microscopy was used to localize phase II cells on secondary roots and root tips of A. thaliana, whereas phase I cells essentially were localized at the basal part of roots. These experiments were conducted in vitro and in soil. Phenotypic variation on plant roots is likely to be a colonization strategy that may explain the high colonization power of P. brassicacearum.

Microbiota colonization status influences developmental toxicity of bisphenol A in embryonic zebrafish

EPA Science Inventory

There is growing evidence that microbiota can modify the toxicokinetics and/or toxicodynamics of environmental chemicals. Commonly used mammalian systems have limited ability to link phenotypic effects in exposed animals to colonization status. Here, we used gnotobiotic zebrafish...

Sperm Competitive Ability in Drosophila melanogaster Associated With Variation in Male Reproductive Proteins

PubMed Central

Fiumera, Anthony C.; Dumont, Bethany L.; Clark, Andrew G.

2005-01-01

Multiple mating by females establishes the opportunity for postcopulatory sexual selection favoring males whose sperm is preferentially employed in fertilizations. Here we use natural variation in a wild population of Drosophila melanogaster to investigate the genetic basis of sperm competitive ability. Approximately 101 chromosome 2 substitution lines were scored for components of sperm competitive ability (P1′, P2′, fecundity, remating rate, and refractoriness), genotyped at 70 polymorphic markers in 10 male reproductive genes, and measured for transcript abundance of those genes. Permutation tests were applied to quantify the statistical significance of associations between genotype and phenotype. Nine significant associations were identified between polymorphisms in the male reproductive genes and sperm competitive ability and 13 were identified between genotype and transcript abundance, but no significant associations were found between transcript abundance and sperm competitive ability. Pleiotropy was evident in two genes: a polymorphism in Acp33A associated with both P1′ and P2′ and a polymorphism in CG17331 associated with both elevated P2′ and reduced refractoriness. The latter case is consistent with antagonistic pleiotropy and may serve as a mechanism maintaining genetic variation. PMID:15466425

Azospirillum brasilense Chemotaxis Depends on Two Signaling Pathways Regulating Distinct Motility Parameters

PubMed Central

Mukherjee, Tanmoy; Kumar, Dhivya; Burriss, Nathan; Xie, Zhihong

2016-01-01

ABSTRACT The genomes of most motile bacteria encode two or more chemotaxis (Che) systems, but their functions have been characterized in only a few model systems. Azospirillum brasilense is a motile soil alphaproteobacterium able to colonize the rhizosphere of cereals. In response to an attractant, motile A. brasilense cells transiently increase swimming speed and suppress reversals. The Che1 chemotaxis pathway was previously shown to regulate changes in the swimming speed, but it has a minor role in chemotaxis and root surface colonization. Here, we show that a second chemotaxis system, named Che4, regulates the probability of swimming reversals and is the major signaling pathway for chemotaxis and wheat root surface colonization. Experimental evidence indicates that Che1 and Che4 are functionally linked to coordinate changes in the swimming motility pattern in response to attractants. The effect of Che1 on swimming speed is shown to enhance the aerotactic response of A. brasilense in gradients, likely providing the cells with a competitive advantage in the rhizosphere. Together, the results illustrate a novel mechanism by which motile bacteria utilize two chemotaxis pathways regulating distinct motility parameters to alter movement in gradients and enhance the chemotactic advantage. IMPORTANCE Chemotaxis provides motile bacteria with a competitive advantage in the colonization of diverse niches and is a function enriched in rhizosphere bacterial communities, with most species possessing at least two chemotaxis systems. Here, we identify the mechanism by which cells may derive a significant chemotactic advantage using two chemotaxis pathways that ultimately regulate distinct motility parameters. PMID:27068592

Azospirillum brasilense Chemotaxis Depends on Two Signaling Pathways Regulating Distinct Motility Parameters.

PubMed

Mukherjee, Tanmoy; Kumar, Dhivya; Burriss, Nathan; Xie, Zhihong; Alexandre, Gladys

2016-06-15

The genomes of most motile bacteria encode two or more chemotaxis (Che) systems, but their functions have been characterized in only a few model systems. Azospirillum brasilense is a motile soil alphaproteobacterium able to colonize the rhizosphere of cereals. In response to an attractant, motile A. brasilense cells transiently increase swimming speed and suppress reversals. The Che1 chemotaxis pathway was previously shown to regulate changes in the swimming speed, but it has a minor role in chemotaxis and root surface colonization. Here, we show that a second chemotaxis system, named Che4, regulates the probability of swimming reversals and is the major signaling pathway for chemotaxis and wheat root surface colonization. Experimental evidence indicates that Che1 and Che4 are functionally linked to coordinate changes in the swimming motility pattern in response to attractants. The effect of Che1 on swimming speed is shown to enhance the aerotactic response of A. brasilense in gradients, likely providing the cells with a competitive advantage in the rhizosphere. Together, the results illustrate a novel mechanism by which motile bacteria utilize two chemotaxis pathways regulating distinct motility parameters to alter movement in gradients and enhance the chemotactic advantage. Chemotaxis provides motile bacteria with a competitive advantage in the colonization of diverse niches and is a function enriched in rhizosphere bacterial communities, with most species possessing at least two chemotaxis systems. Here, we identify the mechanism by which cells may derive a significant chemotactic advantage using two chemotaxis pathways that ultimately regulate distinct motility parameters. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Endophytic Ability of Different Isolates of Entomopathogenic Fungi Beauveria bassiana (Balsamo) Vuillemin in Stem and Leaf Tissues of Maize (Zea mays L.).

PubMed

Renuka, S; Ramanujam, B; Poornesha, B

2016-06-01

The present study was conducted to examine the ability of six promising indigenous isolates of Beauveria bassiana (NBAII-Bb-5a, 7, 14, 19, 23 and 45) as an endophyte in maize stem and leaf tissues. Maize seedlings (var. Nithyashree) were inoculated with conidial suspensions and were examined for endophytic establishment in leaf and stems at different intervals during 15-90 days after treatment. All six isolates showed colonization in stem and leaf tissues with varying abilities of colonization and persistence. The mean percent colonization ranged from 7.41 to 20.37 % in older stem tissues and 3.70 to 21.29 % in young stem tissues and in leaf, it ranged from 6.46 to 27.78 % in older leaf tissues and 11.11 to 26.85 % in young leaf tissues. Among six isolates tested, Bb-23 isolate recorded the maximum mean colonization in older stem (20.37 %), older leaf (27.78 %) and in young stem (21.29 %). Bb-5a isolate showed maximum mean colonization in young leaf tissues (26.85 %). Persistence of inoculated fungal isolates decreased with increase in age of the plant. No physical symptoms of damage were observed in any of the B. bassiana treated plants. No colonization of B. bassiana was observed in the untreated control maize plants. The results obtained in plating and PCR techniques were similar with regard to the confirmation of endophytic establishment of B. bassiana. This study indicated the possibility of using B. bassiana as an endophyte in maize for management of maize stem borer, Chilo partellus.

Comparison of tachykinin NK1 and NK2 receptors in the circular muscle of the guinea-pig ileum and proximal colon.

PubMed

Maggi, C A; Patacchini, R; Meini, S; Quartara, L; Sisto, A; Potier, E; Giuliani, S; Giachetti, A

1994-05-01

1. The aim of this study was the pharmacological characterization of tachykinin NK1 and NK2 receptors mediating contraction in the circular muscle of the guinea-pig ileum and proximal colon. The action of substance P (SP), neurokinin A (NKA) and of the synthetic agonists [Sar9]SP sulphone, [Glp6,Pro9]SP(6-11) (septide) and [beta Ala8]NKA(4-10) was investigated. The affinities of various peptide and nonpeptide antagonists for the NK1 and NK2 receptor was estimated by use of receptor selective agonists. 2. The natural agonists, SP and NKA, produced concentration-dependent contraction in both preparations. EC50 values were 100 pM and 5 nM for SP, 1.2 nM and 19 nM for NKA in the ileum and colon, respectively. The action of SP and NKA was not significantly modified by peptidase inhibitors (bestatin, captopril and thiorphan, 1 microM each). 3. Synthetic NK1 and NK2 receptor agonists produced concentration-dependent contraction of the circular muscle of the ileum and proximal colon. EC50 values were 83 pM, 36 pM and 10 nM in the ileum, 8 nM, 0.7 nM and 12 nM in the colon for [Sar9]SP sulphone, septide and [beta Ala8]NKA-(4-10), respectively. The pseudopeptide derivative of NKA(4-10), MDL 28,564 behaved as a full or near-to-full agonist in both preparations, its EC50s being 474 nM and 55 nM in the ileum and colon, respectively. 4. Nifedipine (1 microM) abolished the response to septide and [Sar9]SP sulphone in the ileum and produced a rightward shift and large depression of the response in the colon. The response to [beta Ala8]NKA(4-10) was abolished in the ileum and largely unaffected in the colon. 5. The NK1 receptor antagonists, (+/-)-CP 96,34, FK 888 and GR 82,334 competitively antagonized the response to septide and [Sar9]SP sulphone in both preparations without affecting that to [beta Ala8]NKA(4-10). In general, the NK1 receptor antagonists were significantly more potent toward septide than [Sar9]SP sulphone in both preparations. 6. The NK2 receptor antagonists, GR 94,800 and SR 48,968 selectively antagonized the response to [beta Ala8]NKA(4-10) without affecting that to [Sar9]SP sulphone or septide in the ileum and colon. SR 48,968 produced noncompetitive antagonism of the response to the NK2 receptor agonist in the ileum and competitive antagonism in the colon. 7. MEN 10,376 and the cyclic pseudopeptide MEN 10,573 antagonized in a competitive manner the response to [beta Ala8]NKA(4-10) in the ileum and colon. While MEN 10,573 was equipotent in both preparations, MEN 10,376 was significantly more potent in the colon than in the ileum. MEN 10,376was also effective against septide in both preparations, without affecting the response to [Sar9] SP sulphone. MEN 10,573 antagonized the response to [Sar9]SP sulphone and septide in both preparations,pKB values against septide being intermediate, and significantly different from, those measured against[Beta Ala 8]NKA(4-10) and [Sa9]lSP sulphone.8. These findings show that tachykinin NK1 and NK2 receptors mediate contraction of the circular muscle of the guinea-pig ileum and colon. In both preparations NK1 receptor antagonists display higher apparent affinity when tested against septide than [Sar9]SP sulphone. These findings are compatible with the proposed existence of NK1 receptor subtypes in guinea-pig, although alternative explanations (e.g.agonist binding to different epitopes of the same receptor protein) cannot be excluded at present.Furthermore, an intraspecies heterogeneity of the NK2 receptor in the circular muscle of the guinea-pig ileum and colon is suggested.

Genetic Control of Plant Root Colonization by the Biocontrol agent, Pseudomonas fluorescens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cole, Benjamin J.; Fletcher, Meghan; Waters, Jordan

Plant growth promoting rhizobacteria (PGPR) are a critical component of plant root ecosystems. PGPR promote plant growth by solubilizing inaccessible minerals, suppressing pathogenic microorganisms in the soil, and directly stimulating growth through hormone synthesis. Pseudomonas fluorescens is a well-established PGPR isolated from wheat roots that can also colonize the root system of the model plant, Arabidopsis thaliana. We have created barcoded transposon insertion mutant libraries suitable for genome-wide transposon-mediated mutagenesis followed by sequencing (TnSeq). These libraries consist of over 105 independent insertions, collectively providing loss-of-function mutants for nearly all genes in the P.fluorescens genome. Each insertion mutant can be unambiguouslymore » identified by a randomized 20 nucleotide sequence (barcode) engineered into the transposon sequence. We used these libraries in a gnotobiotic assay to examine the colonization ability of P.fluorescens on A.thaliana roots. Taking advantage of the ability to distinguish individual colonization events using barcode sequences, we assessed the timing and microbial concentration dependence of colonization of the rhizoplane niche. These data provide direct insight into the dynamics of plant root colonization in an in vivo system and define baseline parameters for the systematic identification of the bacterial genes and molecular pathways using TnSeq assays. Having determined parameters that facilitate potential colonization of roots by thousands of independent insertion mutants in a single assay, we are currently establishing a genome-wide functional map of genes required for root colonization in P.fluorescens. Importantly, the approach developed and optimized here for P.fluorescens>A.thaliana colonization will be applicable to a wide range of plant-microbe interactions, including biofuel feedstock plants and microbes known or hypothesized to impact on biofuel-relevant traits including biomass productivity and pathogen resistance.« less

Ceratocystis smalleyi colonization of bitternut hickkory and host responses in the xylem

Treesearch

J.-H. Park; J. Juzwik

2014-01-01

Colonization of Carya cordiformis sapwood by Ceratocystis smalleyi and subsequent host defence responses following artificial inoculation were investigated using anatomical and histological techniques. Hyphae of C. smalleyi were observed in all sapwood xylem features confirming the ability of the pathogen to...

Relative size predicts competitive outcome through 2 million years.

PubMed

Liow, Lee Hsiang; Di Martino, Emanuela; Krzeminska, Malgorzata; Ramsfjell, Mali; Rust, Seabourne; Taylor, Paul D; Voje, Kjetil L

2017-08-01

Competition is an important biotic interaction that influences survival and reproduction. While competition on ecological timescales has received great attention, little is known about competition on evolutionary timescales. Do competitive abilities change over hundreds of thousands to millions of years? Can we predict competitive outcomes using phenotypic traits? How much do traits that confer competitive advantage and competitive outcomes change? Here we show, using communities of encrusting marine bryozoans spanning more than 2 million years, that size is a significant determinant of overgrowth outcomes: colonies with larger zooids tend to overgrow colonies with smaller zooids. We also detected temporally coordinated changes in average zooid sizes, suggesting that different species responded to a common external driver. Although species-specific average zooid sizes change over evolutionary timescales, species-specific competitive abilities seem relatively stable, suggesting that traits other than zooid size also control overgrowth outcomes and/or that evolutionary constraints are involved. © 2017 John Wiley & Sons Ltd/CNRS.

Differential effects of ephemeral colonization by arbuscular mycorrhizal fungi in two Cuscuta species with different ecology.

PubMed

Behdarvandi, Behrang; Guinel, Frédérique C; Costea, Mihai

2015-10-01

Seedlings of parasitic Cuscuta species are autotrophic but can survive only a short period of time, during which they must locate and attach to a suitable host. They have an ephemeral root-like organ considered not a "true" root by most studies. In the present study, two species with contrasting ecology were examined: Cuscuta gronovii, a North American riparian species, and Cuscuta campestris, an invasive dodder that thrives in disturbed habitats. The morphology, structure, and absorptive capability of their root-like organ were compared, their potential for colonization by two species of arbuscular mycorrhizal fungi (AMF) was assessed, and the effect of the AMF on seedling growth and survival was determined. The root of both species absorbed water and interacted with AMF, but the two species exhibited dissimilar growth and survival patterns depending on the colonization level of their seedlings. The extensively colonized seedlings of C. gronovii grew more and survived longer than non-colonized seedlings. In contrast, the scarce colonization of C. campestris seedlings did not increase their growth or longevity. The differential growth responses of the AMF-colonized and non-colonized Cuscuta species suggest a mycorrhizal relationship and reflect their ecology. While C. gronovii roots have retained a higher ability to interact with AMF and are likely to take advantage of fungal communities in riparian habitats, the invasive C. campestris has largely lost this ability possibly as an adaptation to disturbed ecosystems. These results indicate that dodders have a true root, even if much reduced and ephemeral, that can interact with AMF.

Resource competition in plant invasions: emerging patterns and research needs

PubMed Central

Gioria, Margherita; Osborne, Bruce A.

2014-01-01

Invasions by alien plants provide a unique opportunity to examine competitive interactions among plants. While resource competition has long been regarded as a major mechanism responsible for successful invasions, given a well-known capacity for many invaders to become dominant and reduce plant diversity in the invaded communities, few studies have measured resource competition directly or have assessed its importance relative to that of other mechanisms, at different stages of an invasion process. Here, we review evidence comparing the competitive ability of invasive species vs. that of co-occurring native plants, along a range of environmental gradients, showing that many invasive species have a superior competitive ability over native species, although invasive congeners are not necessarily competitively superior over native congeners, nor are alien dominants are better competitors than native dominants. We discuss how the outcomes of competition depend on a number of factors, such as the heterogeneous distribution of resources, the stage of the invasion process, as well as phenotypic plasticity and evolutionary adaptation, which may result in increased or decreased competitive ability in both invasive and native species. Competitive advantages of invasive species over natives are often transient and only important at the early stages of an invasion process. It remains unclear how important resource competition is relative to other mechanisms (competition avoidance via phenological differences, niche differentiation in space associated with phylogenetic distance, recruitment and dispersal limitation, indirect competition, and allelopathy). Finally, we identify the conceptual and methodological issues characterizing competition studies in plant invasions, and we discuss future research needs, including examination of resource competition dynamics and the impact of global environmental change on competitive interactions between invasive and native species. PMID:25324851

Resource competition in plant invasions: emerging patterns and research needs.

PubMed

Gioria, Margherita; Osborne, Bruce A

2014-01-01

Invasions by alien plants provide a unique opportunity to examine competitive interactions among plants. While resource competition has long been regarded as a major mechanism responsible for successful invasions, given a well-known capacity for many invaders to become dominant and reduce plant diversity in the invaded communities, few studies have measured resource competition directly or have assessed its importance relative to that of other mechanisms, at different stages of an invasion process. Here, we review evidence comparing the competitive ability of invasive species vs. that of co-occurring native plants, along a range of environmental gradients, showing that many invasive species have a superior competitive ability over native species, although invasive congeners are not necessarily competitively superior over native congeners, nor are alien dominants are better competitors than native dominants. We discuss how the outcomes of competition depend on a number of factors, such as the heterogeneous distribution of resources, the stage of the invasion process, as well as phenotypic plasticity and evolutionary adaptation, which may result in increased or decreased competitive ability in both invasive and native species. Competitive advantages of invasive species over natives are often transient and only important at the early stages of an invasion process. It remains unclear how important resource competition is relative to other mechanisms (competition avoidance via phenological differences, niche differentiation in space associated with phylogenetic distance, recruitment and dispersal limitation, indirect competition, and allelopathy). Finally, we identify the conceptual and methodological issues characterizing competition studies in plant invasions, and we discuss future research needs, including examination of resource competition dynamics and the impact of global environmental change on competitive interactions between invasive and native species.

Interactions among filamentous fungi Aspergillus niger, Fusarium verticillioides and Clonostachys rosea: fungal biomass, diversity of secreted metabolites and fumonisin production.

PubMed

Chatterjee, Subhankar; Kuang, Yi; Splivallo, Richard; Chatterjee, Paramita; Karlovsky, Petr

2016-05-10

Interactions among fungi colonizing dead organic matter involve exploitation competition and interference competition. Major mechanism of interference competition is antibiosis caused by secreted secondary metabolites. The effect of competition on secondary metabolite production by fungi is however poorly understood. Fungal biomass was rarely monitored in interaction studies; it is not known whether dominance in pairwise interactions follows congruent patterns. Pairwise interactions of three fungal species with different life styles were studied. The saprophyte Aspergillus niger (A.n.), the plant pathogen Fusarium verticillioides (F.v.), and the mycoparasite Clonostachys rosea (C.r.) were grown in single and dual cultures in minimal medium with asparagine as nitrogen source. Competitive fitness shifted with time: in dual C.r./F.v. cultures after 10 d F.v. grew well while C.r. was suppressed; after 20 d C.r. recovered while F.v. became suppressed; and after 30 d most F.v. was destroyed. At certain time points fungal competitive fitness exhibited a rock-paper-scissors pattern: F.v. > A.n., A.n. > C.r., and C.r. > F.v. Most metabolites secreted to the medium at early stages in single and dual cultures were not found at later times. Many metabolites occurring in supernatants of single cultures were suppressed in dual cultures and many new metabolites not occurring in single cultures were found in dual cultures. A. niger showed the greatest ability to suppress the accumulation of metabolites produced by the other fungi. A. niger was also the species with the largest capacity of transforming metabolites produced by other fungi. Fumonisin production by F. verticillioides was suppressed in co-cultures with C. rosea but fumonisin B1 was not degraded by C. rosea nor did it affect the growth of C. rosea up to a concentration of 160 μg/ml. Competitive fitness in pairwise interactions among fungi is incongruent, indicating that species-specific factors and/or effects are involved. Many metabolites secreted by fungi are catabolized by their producers at later growth stages. Diversity of metabolites accumulating in the medium is stimulated by fungus/fungus interactions. C. rosea suppresses the synthesis of fumonisins by F. verticillioides but does not degrade fumonisins.

Relative competitive ability of rice with strawhull and blackhull red rice biotypes

USDA-ARS?s Scientific Manuscript database

Weed interference depends largely upon the species composition of the weed community and an ability to compete with the cultured crop. Weedy red rice is a major weed pest of rice in the southern U.S. The focus of this study was to evaluate the competitive ability of rice against common, genetically ...

Proteus mirabilis and Urinary Tract Infections

PubMed Central

Schaffer, Jessica N.; Pearson, Melanie M.

2015-01-01

Proteus mirabilis is a Gram-negative bacterium which is well-known for its ability to robustly swarm across surfaces in a striking bulls’-eye pattern. Clinically, this organism is most frequently a pathogen of the urinary tract, particularly in patients undergoing long-term catheterization. This review covers P. mirabilis with a focus on urinary tract infections (UTI), including disease models, vaccine development efforts, and clinical perspectives. Flagella-mediated motility, both swimming and swarming, is a central facet of this organism. The regulation of this complex process and its contribution to virulence is discussed, along with the type VI-secretion system-dependent intra-strain competition which occurs during swarming. P. mirabilis uses a diverse set of virulence factors to access and colonize the host urinary tract, including urease and stone formation, fimbriae and other adhesins, iron and zinc acquisition, proteases and toxins, biofilm formation, and regulation of pathogenesis. While significant advances in this field have been made, challenges remain to combatting complicated UTI and deciphering P. mirabilis pathogenesis. PMID:26542036

Proteus mirabilis and Urinary Tract Infections.

PubMed

Schaffer, Jessica N; Pearson, Melanie M

2015-10-01

Proteus mirabilis is a Gram-negative bacterium and is well known for its ability to robustly swarm across surfaces in a striking bulls'-eye pattern. Clinically, this organism is most frequently a pathogen of the urinary tract, particularly in patients undergoing long-term catheterization. This review covers P. mirabilis with a focus on urinary tract infections (UTI), including disease models, vaccine development efforts, and clinical perspectives. Flagella-mediated motility, both swimming and swarming, is a central facet of this organism. The regulation of this complex process and its contribution to virulence is discussed, along with the type VI-secretion system-dependent intra-strain competition, which occurs during swarming. P. mirabilis uses a diverse set of virulence factors to access and colonize the host urinary tract, including urease and stone formation, fimbriae and other adhesins, iron and zinc acquisition, proteases and toxins, biofilm formation, and regulation of pathogenesis. While significant advances in this field have been made, challenges remain to combatting complicated UTI and deciphering P. mirabilis pathogenesis.

Endophytic colonization and biocontrol performance of Pseudomonas fluorescens PICF7 in olive (Olea europaea L.) are determined neither by pyoverdine production nor swimming motility.

PubMed

Maldonado-González, M Mercedes; Schilirò, Elisabetta; Prieto, Pilar; Mercado-Blanco, Jesús

2015-09-01

Pseudomonas fluorescens PICF7 is an indigenous inhabitant of olive (Olea europaea L.) rhizosphere, able to display endophytic lifestyle in roots, to induce a wide range of defence responses upon colonization of this organ and to exert effective biological control against Verticillium wilt of olive (VWO) (Verticillium dahliae). We aimed to evaluate the involvement of specific PICF7 phenotypes in olive root colonization and VWO biocontrol effectiveness by generating mutants impaired in swimming motility (fliI) or siderophore pyoverdine production (pvdI). Besides, the performance of mutants with diminished in vitro growth in potato dextrose agar medium (gltA) and cysteine (Cys) auxotrophy was also assessed. Results showed that olive root colonization and VWO biocontrol ability of the fliI, pvdI and gltA mutants did not significantly differ from that displayed by the parental strain PICF7. Consequently, altered in vitro growth, swimming motility and pyoverdine production contribute neither to PICF7 VWO suppressive effect nor to its colonization ability. In contrast, the Cys auxotroph mutant showed reduced olive root colonization capacity and lost full biocontrol efficacy. Moreover, confocal laser scanning microscopy revealed that all mutants tested were able to endophytically colonize root tissue to the same extent as wild-type PICF7, discarding these traits as relevant for its endophytic lifestyle. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

Marine worms (genus Osedax) colonize cow bones

PubMed Central

Jones, William J; Johnson, Shannon B; Rouse, Greg W; Vrijenhoek, Robert C

2007-01-01

Bone-eating worms of the genus Osedax colonized and grew on cow bones deployed at depths ranging from 385 to 2893 m in Monterey Bay, California. Colonization occurred as rapidly as two months following deployment of the cow bones, similar to the time it takes to colonize exposed whalebones. Some Osedax females found on the cow bones were producing eggs and some hosted dwarf males in their tubes. Morphological and molecular examinations of these worms confirmed the presence of six Osedax species, out of the eight species presently known from Monterey Bay. The ability of Osedax species to colonize, grow and reproduce on cow bones challenges previous notions that these worms are ‘whale-fall specialists.’ PMID:18077256

Marine worms (genus Osedax) colonize cow bones.

PubMed

Jones, William J; Johnson, Shannon B; Rouse, Greg W; Vrijenhoek, Robert C

2008-02-22

Bone-eating worms of the genus Osedax colonized and grew on cow bones deployed at depths ranging from 385 to 2893m in Monterey Bay, California. Colonization occurred as rapidly as two months following deployment of the cow bones, similar to the time it takes to colonize exposed whalebones. Some Osedax females found on the cow bones were producing eggs and some hosted dwarf males in their tubes. Morphological and molecular examinations of these worms confirmed the presence of six Osedax species, out of the eight species presently known from Monterey Bay. The ability of Osedax species to colonize, grow and reproduce on cow bones challenges previous notions that these worms are 'whale-fall specialists.'

Effects of mycorrhizal species on colonization, polyphenol levels, and growth characteristics of Allium porrum

USDA-ARS?s Scientific Manuscript database

The effects of different mycorrhizal fungi species (Rhizopus intraradices, Gigapora margarita, Glomus geosporum, Paraglomus occultum, Claroideoglomus claroideum, white Glomus species) on their ability to colonize leek roots (Allium porrum) and the effect of symbiosis on changes in the levels of poly...

The role of growth form and correlated traits in competitive ranking of six perennial ruderal plant species grown in unbalanced mixtures

NASA Astrophysics Data System (ADS)

Dietz, Hansjörg; Steinlein, Thomas; Ullmann, Isolde

1998-02-01

The competitive abilities of six perennial ruderal plants of three different growth forms were compared via yield measures using an additive diallel experimental design with unbalanced mixtures (9:3 or 3:9 plants per pot, respectively). Thus, in a given mixture species A was grown in two configurations: three individuals in centre position of the pot together with nine plants of species B in border position and vice versa. Effect competitive abilities as well as response competitive abilities of the species were significantly related to canopy height and plant biomass. The species with lower rosette growth form and smaller biomasses were weaker competitors than the species possessing elevated canopies along with higher biomasses, whereas total leaf area was not significantly correlated with competitive ability between species. Species differences in competitive ability were stronger between the plants grown in the central position than between those grown in the border position. Furthermore, interactions between species-specific traits and configuration could be observed, indicating the importance of species proportions and arrangement patterns for evaluation of competitive outcome in the field. The degree of complete transitivity of the competitive network of the six ruderal species, which was significantly higher than expected under the null model in our experimental design, also seemed to depend on species proportions in mixture. Shifts in root:shoot ratio of the centre plants when faced with competition by the border plants were in the direction of higher shoot allocation for the weak competitors with rosette growth form irrespective of the neighbour species, except for Bunias orientalis, which showed a more plastic response. The stronger competitors showed higher root allocation ( Urtica dioica) or were hardly affected at all. Consistent with the results of our experiment, the weaker competitors occur at rather frequently disturbed and therefore transient field sites whereas the stronger competitors predominate at infrequently disturbed sites during several phases of succession.

Improving Genomic Prediction in Cassava Field Experiments by Accounting for Interplot Competition

PubMed Central

Elias, Ani A.; Rabbi, Ismail; Kulakow, Peter; Jannink, Jean-Luc

2018-01-01

Plants competing for available resources is an unavoidable phenomenon in a field. We conducted studies in cassava (Manihot esculenta Crantz) in order to understand the pattern of this competition. Taking into account the competitive ability of genotypes while selecting parents for breeding advancement or commercialization can be very useful. We assumed that competition could occur at two levels: (i) the genotypic level, which we call interclonal, and (ii) the plot level irrespective of the type of genotype, which we call interplot competition or competition error. Modification in incidence matrices was applied in order to relate neighboring genotype/plot to the performance of a target genotype/plot with respect to its competitive ability. This was added into a genomic selection (GS) model to simultaneously predict the direct and competitive ability of a genotype. Predictability of the models was tested through a 10-fold cross-validation method repeated five times. The best model was chosen as the one with the lowest prediction root mean squared error (pRMSE) compared to that of the base model having no competitive component. Results from our real data studies indicated that <10% increase in accuracy was achieved with GS-interclonal competition model, but this value reached up to 25% with a GS-competition error model. We also found that the competitive influence of a cassava clone is not just limited to the adjacent neighbors but spreads beyond them. Through simulations, we found that a 26% increase of accuracy in estimating trait genotypic effect can be achieved even in the presence of high competitive variance. PMID:29358232

Improving Genomic Prediction in Cassava Field Experiments by Accounting for Interplot Competition.

PubMed

Elias, Ani A; Rabbi, Ismail; Kulakow, Peter; Jannink, Jean-Luc

2018-03-02

Plants competing for available resources is an unavoidable phenomenon in a field. We conducted studies in cassava ( Manihot esculenta Crantz) in order to understand the pattern of this competition. Taking into account the competitive ability of genotypes while selecting parents for breeding advancement or commercialization can be very useful. We assumed that competition could occur at two levels: (i) the genotypic level, which we call interclonal, and (ii) the plot level irrespective of the type of genotype, which we call interplot competition or competition error. Modification in incidence matrices was applied in order to relate neighboring genotype/plot to the performance of a target genotype/plot with respect to its competitive ability. This was added into a genomic selection (GS) model to simultaneously predict the direct and competitive ability of a genotype. Predictability of the models was tested through a 10-fold cross-validation method repeated five times. The best model was chosen as the one with the lowest prediction root mean squared error (pRMSE) compared to that of the base model having no competitive component. Results from our real data studies indicated that <10% increase in accuracy was achieved with GS-interclonal competition model, but this value reached up to 25% with a GS-competition error model. We also found that the competitive influence of a cassava clone is not just limited to the adjacent neighbors but spreads beyond them. Through simulations, we found that a 26% increase of accuracy in estimating trait genotypic effect can be achieved even in the presence of high competitive variance. Copyright © 2018 Elias et al.

The effect of invasive hybrid taxa on the ecological succession of coastal marshes

USDA-ARS?s Scientific Manuscript database

Hybridization following colonization of invasive species in novel environments frequently results in offspring with improved biological and competitive functions referred to as heterosis or hybrid vigor. However, little is known about the effect of these invasive hybrids on the structuring and funct...

Interactions between Streptomyces coelicolor and Bacillus subtilis: Role of surfactants in raising aerial structures.

PubMed

Straight, Paul D; Willey, Joanne M; Kolter, Roberto

2006-07-01

Using mixed-species cultures, we have undertaken a study of interactions between two common spore-forming soil bacteria, Bacillus subtilis and Streptomyces coelicolor. Our experiments demonstrate that the development of aerial hyphae and spores by S. coelicolor is inhibited by surfactin, a lipopeptide surfactant produced by B. subtilis. Current models of aerial development by sporulating bacteria and fungi postulate a role for surfactants in reducing surface tension at air-liquid interfaces, thereby removing the major barrier to aerial growth. S. coelicolor produces SapB, an amphipathic peptide that is surface active and required for aerial growth on certain media. Loss of aerial hyphae in developmental mutants can be rescued by addition of purified SapB. While a surfactant from a fungus can substitute for SapB in a mutant that lacks aerial hyphae, not all surfactants have this effect. We show that surfactin is required for formation of aerial structures on the surface of B. subtilis colonies. However, in contrast to this positive role, our experiments reveal that surfactin acts antagonistically by arresting S. coelicolor aerial development and causing altered expression of developmental genes. Our observations support the idea that surfactants function specifically for a given organism regardless of their shared ability to reduce surface tension. Production of surfactants with antagonistic activity could provide a powerful competitive advantage during surface colonization and in competition for resources.

Role of NleH, a Type III Secreted Effector from Attaching and Effacing Pathogens, in Colonization of the Bovine, Ovine, and Murine Gut▿

PubMed Central

Hemrajani, Cordula; Marches, Olivier; Wiles, Siouxsie; Girard, Francis; Dennis, Alison; Dziva, Francis; Best, Angus; Phillips, Alan D.; Berger, Cedric N.; Mousnier, Aurelie; Crepin, Valerie F.; Kruidenier, Laurens; Woodward, Martin J.; Stevens, Mark P.; La Ragione, Roberto M.; MacDonald, Thomas T.; Frankel, Gad

2008-01-01

The human pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7 colonizes human and animal gut via formation of attaching and effacing lesions. EHEC strains use a type III secretion system to translocate a battery of effector proteins into the mammalian host cell, which subvert diverse signal transduction pathways implicated in actin dynamics, phagocytosis, and innate immunity. The genomes of sequenced EHEC O157:H7 strains contain two copies of the effector protein gene nleH, which share 49% sequence similarity with the gene for the Shigella effector OspG, recently implicated in inhibition of migration of the transcriptional regulator NF-κB to the nucleus. In this study we investigated the role of NleH during EHEC O157:H7 infection of calves and lambs. We found that while EHEC ΔnleH colonized the bovine gut more efficiently than the wild-type strain, in lambs the wild-type strain exhibited a competitive advantage over the mutant during mixed infection. Using the mouse pathogen Citrobacter rodentium, which shares many virulence factors with EHEC O157:H7, including NleH, we observed that the wild-type strain exhibited a competitive advantage over the mutant during mixed infection. We found no measurable differences in T-cell infiltration or hyperplasia in colons of mice inoculated with the wild-type or the nleH mutant strain. Using NF-κB reporter mice carrying a transgene containing a luciferase reporter driven by three NF-κB response elements, we found that NleH causes an increase in NF-κB activity in the colonic mucosa. Consistent with this, we found that the nleH mutant triggered a significantly lower tumor necrosis factor alpha response than the wild-type strain. PMID:18725419

The ability to use nitrate confers advantage to Dekkera bruxellensis over S. cerevisiae and can explain its adaptation to industrial fermentation processes.

PubMed

de Barros Pita, Will; Leite, Fernanda Cristina Bezerra; de Souza Liberal, Anna Theresa; Simões, Diogo Ardaillon; de Morais, Marcos Antonio

2011-06-01

The yeast Dekkera bruxellensis has been regarded as a contamination problem in industrial ethanol production because it can replace the originally inoculated Saccharomyces cerevisiae strains. The present study deals with the influence of nitrate on the relative competitiveness of D. bruxellensis and S. cerevisiae in sugar cane ethanol fermentations. The industrial strain D. bruxellensis GDB 248 showed higher growth rates than S. cerevisiae JP1 strain in mixed ammonia/nitrate media, and nitrate assimilation genes were only slightly repressed by ammonia. These characteristics rendered D. bruxellensis cells with an ability to overcome S. cerevisiae populations in both synthetic medium and in sugar cane juice. The results were corroborated by data from industrial fermentations that showed a correlation between high nitrate concentrations and high D. bruxellensis cell counts. Moreover, the presence of nitrate increased fermentation efficiency of D. bruxellensis cells in anaerobic conditions, which may explain the maintenance of ethanol production in the presence of D. bruxellensis in industrial processes. The presence of high levels of nitrate in sugar cane juice may be due to its inefficient conversion by plant metabolism in certain soil types and could explain the periodical episodes of D. bruxellensis colonization of Brazilian ethanol plants.

Group B Streptococcus β-hemolysin/Cytolysin Breaches Maternal-Fetal Barriers to Cause Preterm Birth and Intrauterine Fetal Demise in Vivo

PubMed Central

Randis, Tara M.; Gelber, Shari E.; Hooven, Thomas A.; Abellar, Rosanna G.; Akabas, Leor H.; Lewis, Emma L.; Walker, Lindsay B.; Byland, Leah M.; Nizet, Victor; Ratner, Adam J.

2014-01-01

Background. Maternal vaginal colonization with Streptococcus agalactiae (Group B Streptococcus [GBS]) is a precursor to chorioamnionitis, fetal infection, and neonatal sepsis, but the understanding of specific factors in the pathogenesis of ascending infection remains limited. Methods. We used a new murine model to evaluate the contribution of the pore-forming GBS β-hemolysin/cytolysin (βH/C) to vaginal colonization, ascension, and fetal infection. Results. Competition assays demonstrated a marked advantage to βH/C-expressing GBS during colonization. Intrauterine fetal demise and/or preterm birth were observed in 54% of pregnant mice colonized with wild-type (WT) GBS and 0% of those colonized with the toxin-deficient cylE knockout strain, despite efficient colonization and ascension by both strains. Robust placental inflammation, disruption of maternal-fetal barriers, and fetal infection were more frequent in animals colonized with WT bacteria. Histopathologic examination revealed bacterial tropism for fetal lung and liver. Conclusions. Preterm birth and fetal demise are likely the direct result of toxin-induced damage and inflammation rather than differences in efficiency of ascension into the upper genital tract. These data demonstrate a distinct contribution of βH/C to GBS chorioamnionitis and subsequent fetal infection in vivo and showcase a model for this most proximal step in GBS pathogenesis. PMID:24474814

Nutraceuticals as potential therapeutic agents for colon cancer: a review

PubMed Central

Kuppusamy, Palaniselvam; Yusoff, Mashitah M.; Maniam, Gaanty Pragas; Ichwan, Solachuddin Jauhari Arief; Soundharrajan, Ilavenil; Govindan, Natanamurugaraj

2014-01-01

Colon cancer is a world-wide health problem and the second-most dangerous type of cancer, affecting both men and women. The modern diet and lifestyles, with high meat consumption and excessive alcohol use, along with limited physical activity has led to an increasing mortality rate for colon cancer worldwide. As a result, there is a need to develop novel and environmentally benign drug therapies for colon cancer. Currently, nutraceuticals play an increasingly important role in the treatment of various chronic diseases such as colon cancer, diabetes and Alzheimer׳s disease. Nutraceuticals are derived from various natural sources such as medicinal plants, marine organisms, vegetables and fruits. Nutraceuticals have shown the potential to reduce the risk of colon cancer and slow its progression. These dietary substances target different molecular aspects of colon cancer development. Accordingly, this review briefly discusses the medicinal importance of nutraceuticals and their ability to reduce the risk of colorectal carcinogenesis. PMID:26579381

Nutraceuticals as potential therapeutic agents for colon cancer: a review.

PubMed

Kuppusamy, Palaniselvam; Yusoff, Mashitah M; Maniam, Gaanty Pragas; Ichwan, Solachuddin Jauhari Arief; Soundharrajan, Ilavenil; Govindan, Natanamurugaraj

2014-06-01

Colon cancer is a world-wide health problem and the second-most dangerous type of cancer, affecting both men and women. The modern diet and lifestyles, with high meat consumption and excessive alcohol use, along with limited physical activity has led to an increasing mortality rate for colon cancer worldwide. As a result, there is a need to develop novel and environmentally benign drug therapies for colon cancer. Currently, nutraceuticals play an increasingly important role in the treatment of various chronic diseases such as colon cancer, diabetes and Alzheimer׳s disease. Nutraceuticals are derived from various natural sources such as medicinal plants, marine organisms, vegetables and fruits. Nutraceuticals have shown the potential to reduce the risk of colon cancer and slow its progression. These dietary substances target different molecular aspects of colon cancer development. Accordingly, this review briefly discusses the medicinal importance of nutraceuticals and their ability to reduce the risk of colorectal carcinogenesis.

Preferential Edge Habitat Colonization by a Specialist Weevil, Rhinoncomimus latipes (Coleoptera: Curculionidae)

USDA-ARS?s Scientific Manuscript database

Understanding the behavioral basis of dispersal and colonization is critical in biological control systems, where success of a natural enemy depends in part on its ability to find and move to new host patches. We studied behavior of the specialist weevil Rhinoncomimus latipes Korotyaev, a biological...

Infection of Helicoverpa armigera by endophytic Beauveria bassiana colonizing tomato plants

USDA-ARS?s Scientific Manuscript database

A novel endophytic strain of Beauveria bassiana was isolated from leaf tissue of a wild tomato plant. This strain and two B. bassiana strains previously isolated from soil were evaluated for their ability to endophytically colonize tomatoes and subsequent in planta efficacy against Helicoverpa armig...

Suture marker lesion detection in the colon by self-stabilizing and unmodified capsule endoscopes: pilot study in acute canine models.

PubMed

Filip, Dobromir; Yadid-Pecht, Orly; Muench, Gregory; Mintchev, Martin P; Andrews, Christopher N

2013-02-01

Capsule endoscopy is a noninvasive method for examining the small intestine. Recently, this method has been used to visualize the colon. However, the capsule often tumbles in the wider colon lumen, resulting in potentially missed pathology. In addition, the capsule does not have the ability to distend collapsed segments of the organ. Self-stabilizing capsule endoscopy is a new method of visualizing the colon without tumbling and with the ability to passively distend colon walls. To quantitatively compare the detection rate of intraluminal suture marker lesions for colonoscopy by using a custom-modified, self-stabilizing capsule endoscope (SCE); an unmodified capsule endoscope (CE) of the same brand; and a standard colonoscope. Four mongrel dogs underwent laparotomy and the implantation of 5 to 8 suture markers to approximate colon lesions. Each dog had both capsule endoscopy and self-stabilizing capsule endoscopy, administered consecutively in random order. In each case, the capsule was inserted endoscopically into the proximal lumen of the colon followed by pharmacologically induced colon peristalsis to propel it distally through the colon. Blinded standard colonoscopy was performed by an experienced gastroenterologist after the capsule endoscopies. Experimental study in a live canine model. Four dogs. Laparotomy, capsule endoscopy, colonoscopy. Comparison of the marker detection rate of the SCE to that of the unmodified MiroCam CE and a colonoscope. The average percentages of the marker detection rate for unmodified capsule endoscopy, self-stabilizing capsule endoscopy, and colonoscopy, respectively, were 31.1%, 86%, and 100% (P < .01), with both self-stabilizing capsule endoscopy and colonoscopy performing significantly better than the unmodified capsule endoscopy. Acute canine model, suture markings poorly representative of epithelial polyps, limited number of animals. The proposed self-stabilizing capsule endoscope delivered a significant improvement in detection rates of colon suture markings when compared with the unmodified capsule endoscope. Copyright © 2013 American Society for Gastrointestinal Endoscopy. Published by Mosby, Inc. All rights reserved.

A disparity between locomotor economy and territory-holding ability in male house mice.

PubMed

Morris, Jeremy S; Ruff, James S; Potts, Wayne K; Carrier, David R

2017-07-15

Both economical locomotion and physical fighting are important performance traits to many species because of their direct influence on components of Darwinian fitness. Locomotion represents a substantial portion of the total daily energy budget of many animals. Fighting performance often determines individual reproductive fitness through the means of resource control, social dominance and access to mates. However, phenotypic traits that improve either locomotor economy or fighting ability may diminish performance in the other. Here, we tested for a predicted disparity between locomotor economy and competitive ability in wild-derived house mice ( Mus musculus ). We used 8 week social competition trials in semi-natural enclosures to directly measure male competitive ability through territorial control and female occupancy within territories. We also measured oxygen consumption during locomotion for each mouse using running trials in an enclosed treadmill and open-flow respirometry. Our results show that territory-holding males have higher absolute and mass-specific oxygen consumption when running (i.e. reduced locomotor economy) compared with males that do not control territories. This relationship was present both before and after 8 week competition trials in semi-natural enclosures. This disparity between physical competitive ability and economical locomotion may impose viability costs on males in species for which competition over mates is common and may constrain the evolution of behavioral and phenotypic diversity, particularly in natural settings with environmental and resource variability. © 2017. Published by The Company of Biologists Ltd.

Relation between extinction and assisted colonization of plants in the arctic-alpine and boreal regions.

PubMed

Pykälä, Juha

2017-06-01

Assisted colonization of vascular plants is considered by many ecologists an important tool to preserve biodiversity threatened by climate change. I argue that assisted colonization may have negative consequences in arctic-alpine and boreal regions. The observed slow movement of plants toward the north has been an argument for assisted colonization. However, these range shifts may be slow because for many plants microclimatic warming (ignored by advocates of assisted colonization) has been smaller than macroclimatic warming. Arctic-alpine and boreal plants may have limited possibilities to disperse farther north or to higher elevations. I suggest that arctic-alpine species are more likely to be driven to extinction because of competitive exclusion by southern species than by increasing temperatures. If so, the future existence of arctic-alpine and boreal flora may depend on delaying or preventing the migration of plants toward the north to allow northern species to evolve to survive in a warmer climate. In the arctic-alpine region, preventing the dispersal of trees and shrubs may be the most important method to mitigate the negative effects of climate change. The purported conservation benefits of assisted colonization should not be used to promote the migration of invasive species by forestry. © 2016 Society for Conservation Biology.

Isolation and characterisation of new putative probiotic bacteria from human colonic flora.

PubMed

Raz, Irit; Gollop, Natan; Polak-Charcon, Sylvie; Schwartz, Betty

2007-04-01

The present study describes a novel bacterial isolate exhibiting high ability to synthesise and secrete butyrate. The novel isolated bacterium was obtained from human faeces and grown in selective liquid intestinal microflora medium containing rumen fluid under microaerobic conditions. Its probiotic properties were demonstrated by the ability of the isolate to survive high acidity and medium containing bile acids and the ability to adhere to colon cancer cells (Caco-2) in vitro. Phylogenetic identity to Enterococcus durans was established using specific primers for 16S rRNA (99% probability). PCR analyses with primers to the bacterial gene encoding butyrate kinase, present in the butyrogenic bacteria Clostridium, showed that this gene is present in E. durans. The in vivo immunoprotective and anti-inflammatory effects of E. durans were assessed in dextran sodium sulfate (DSS)-induced colitis in Balb/c mice. Administration of E. durans ameliorated histological, clinical and biochemical scores directly related to intestinal inflammation whereas the lactic acid bacterium Lactobacillus delbrueckii was ineffective in this regard. Colonic cDNA concentrations of IL-1beta and TNF-alpha were significantly down regulated in DSS-treated E. durans-fed mice but not in control or DSS-treated L. delbrueckii- fed mice. Fluorescent in situ hybridisation analyses of colonic tissue from mice fed E. durans, using a butyrate kinase probe, demonstrated that E. durans significantly adheres to the colonic tissue. The novel isolated bacterium described in the present paper, upon further characterisation, can be developed into a useful probiotic aimed at the treatment of patients suffering from ulcerative colitis.

The chicken or the egg? Adaptation to desiccation and salinity tolerance in a lineage of water beetles.

PubMed

Pallarés, Susana; Arribas, Paula; Bilton, David T; Millán, Andrés; Velasco, Josefa; Ribera, Ignacio

2017-10-01

Transitions from fresh to saline habitats are restricted to a handful of insect lineages, as the colonization of saline waters requires specialized mechanisms to deal with osmotic stress. Previous studies have suggested that tolerance to salinity and desiccation could be mechanistically and evolutionarily linked, but the temporal sequence of these adaptations is not well established for individual lineages. We combined molecular, physiological and ecological data to explore the evolution of desiccation resistance, hyporegulation ability (i.e., the ability to osmoregulate in hyperosmotic media) and habitat transitions in the water beetle genus Enochrus subgenus Lumetus (Hydrophilidae). We tested whether enhanced desiccation resistance evolved before increases in hyporegulation ability or vice versa, or whether the two mechanisms evolved in parallel. The most recent ancestor of Lumetus was inferred to have high desiccation resistance and moderate hyporegulation ability. There were repeated shifts between habitats with differing levels of salinity in the radiation of the group, those to the most saline habitats generally occurring more rapidly than those to less saline ones. Significant and accelerated changes in hyporegulation ability evolved in parallel with smaller and more progressive increases in desiccation resistance across the phylogeny, associated with the colonization of meso- and hypersaline waters during global aridification events. All species with high hyporegulation ability were also desiccation-resistant, but not vice versa. Overall, results are consistent with the hypothesis that desiccation resistance mechanisms evolved first and provided the physiological basis for the development of hyporegulation ability, allowing these insects to colonize and diversify across meso- and hypersaline habitats. © 2017 John Wiley & Sons Ltd.

Pathogen re-colonization of in-house composted and non-composted broiler litter

USDA-ARS?s Scientific Manuscript database

“In-house” litter composting has been reintroduced to the industry and shown to reduce bacteria by as much as two orders of magnitude. Other industries have demonstrated that pathogens can recolonize a waste-residual when microbial competition has been reduced or inhibited following composting. Po...

Living on the edge: Emergence of spontaneous gac mutations in Pseudomonas protegens during swarming motility

USDA-ARS?s Scientific Manuscript database

Swarming motility is a flagella-driven multicellular behavior that allows bacteria to colonize new niches and escape competition. Here, we investigated the spatial distribution and evolution of ‘social cheaters’ in swarming colonies of Pseudomonas protegens Pf-5. Lipopeptide surfactants in the orfam...

Quantifying competitive ability of perennial grasses to inhibit Scotch broom

Treesearch

Timothy Harrington

2011-01-01

Greenhouse pot studies were conducted to quantify the competitive abilities of three native perennial grass species to inhibit development of Scotch broom (Cytisus scoparius (L.) Link ) seedlings: spike bentgrass (Agrostis exarata Trin. ), blue wildrye (Elymus glaucus Buckley), and western fescue (

An integrated analysis of the effects of past land use on forest herb colonization at the landscape scale

USGS Publications Warehouse

Verheyen, K.; Guntenspergen, Glenn R.; Biesbrouck, B.; Hermy, M.

2003-01-01

A framework that summarizes the direct and indirect effects of past land use on forest herb recolonization is proposed, and used to analyse the colonization patterns of forest understorey herbaceous species in a 360-ha mixed forest, grassland and arable landscape in the Dijle river valley (central Belgium).Fine-scale distribution maps were constructed for 14 species. The species were mapped in 15 946 forest plots and outside forests (along parcel margins) in 5188 plots. Forest stands varied in age between 1 and more than 224 years. Detailed land-use history data were combined with the species distribution maps to identify species-specific colonization sources and to calculate colonization distances.The six most frequent species were selected for more detailed statistical analysis.Logistic regression models indicated that species frequency in forest parcels was a function of secondary forest age, distance from the nearest colonization source and their interaction. Similar age and distance effects were found within hedgerows.In 199 forest stands, data about soils, canopy structure and the cover of competitive species were collected. The relative importance of habitat quality and spatio-temporal isolation for the colonization of the forest herb species was quantified using structural equation modelling (SEM), within the framework proposed for the effects of past land use.The results of the SEM indicate that, except for the better colonizing species, the measured habitat quality variables are of minor importance in explaining colonization patterns, compared with the combination of secondary forest age and distance from colonization sources.Our results suggest the existence of a two-stage colonization process in which diaspore availability determines the initial pattern, which is affected by environmental sorting at later stages.

Anaerobic respiration of Escherichia coli in the mouse intestine.

PubMed

Jones, Shari A; Gibson, Terri; Maltby, Rosalie C; Chowdhury, Fatema Z; Stewart, Valley; Cohen, Paul S; Conway, Tyrrell

2011-10-01

The intestine is inhabited by a large microbial community consisting primarily of anaerobes and, to a lesser extent, facultative anaerobes, such as Escherichia coli, which we have shown requires aerobic respiration to compete successfully in the mouse intestine (S. A. Jones et al., Infect. Immun. 75:4891-4899, 2007). If facultative anaerobes efficiently lower oxygen availability in the intestine, then their sustained growth must also depend on anaerobic metabolism. In support of this idea, mutants lacking nitrate reductase or fumarate reductase have extreme colonization defects. Here, we further explore the role of anaerobic respiration in colonization using the streptomycin-treated mouse model. We found that respiratory electron flow is primarily via the naphthoquinones, which pass electrons to cytochrome bd oxidase and the anaerobic terminal reductases. We found that E. coli uses nitrate and fumarate in the intestine, but not nitrite, dimethyl sulfoxide, or trimethylamine N-oxide. Competitive colonizations revealed that cytochrome bd oxidase is more advantageous than nitrate reductase or fumarate reductase. Strains lacking nitrate reductase outcompeted fumarate reductase mutants once the nitrate concentration in cecal mucus reached submillimolar levels, indicating that fumarate is the more important anaerobic electron acceptor in the intestine because nitrate is limiting. Since nitrate is highest in the absence of E. coli, we conclude that E. coli is the only bacterium in the streptomycin-treated mouse large intestine that respires nitrate. Lastly, we demonstrated that a mutant lacking the NarXL regulator (activator of the NarG system), but not a mutant lacking the NarP-NarQ regulator, has a colonization defect, consistent with the advantage provided by NarG. The emerging picture is one in which gene regulation is tuned to balance expression of the terminal reductases that E. coli uses to maximize its competitiveness and achieve the highest possible population in the intestine.

The roles of competition and habitat in the dynamics of populations and species distributions

USGS Publications Warehouse

Yackulic, Charles Brandon; Reid, Janice; Nichols, James D.; Hines, James E.; Davis, Raymond; Forsman, Eric

2014-01-01

The role of competition in structuring biotic communities at fine spatial scales is well known from detailed process-based studies. Our understanding of competition's importance at broader scales is less resolved and mainly based on static species distribution maps. Here, we bridge this gap by examining the joint occupancy dynamics of an invading (barred owl: Strix varia) and a resident species (Northern spotted owl: Strix occidentalis caurina) in a 1000 km2 study area over a 22 - year period. Past studies of these competitors have focused on the dynamics of one species at a time, hindering efforts to parse out the roles of habitat and competition and to forecast the future of the resident species. In addition, while these studies accounted for the imperfect detection of the focal species, no multiseason analysis of these species has accounted for the imperfect detection of the secondary species, potentially biasing inference. We analyze survey data using models that combine the general multistate-multiseason occupancy modeling framework with autologistic modeling - allowing us to account for important aspects of our study system. We find that local extinction probability increases for each species when the other is present; however, the effect of the invader on the resident is greater. Although the species prefer different habitats, these habitats are highly correlated at the patch scale and the impacts of invader on the resident are greatest in patches that would otherwise be optimal. As a consequence, competition leads to a weaker relationship between habitat and Northern spotted owl occupancy. Colonization and extinction rates of the invader are closely related to neighborhood occupancy, and over the first half of the study the availability of colonists limited the rate of population growth. Competition is likely to exclude the resident species both through its immediate effects on local extinction, and by indirectly lowering colonization rates as Northern spotted owl occupancy declines. Our analysis suggests that dispersal limitation affects both the invasion dynamics and the scale at which the effects of competition are observed. We also provide predictions regarding the potential costs and benefits of managing barred owl populations at different target levels.

Multi level ecological fitting: indirect life cycles are not a barrier to host switching and invasion.

PubMed

Malcicka, Miriama; Agosta, Salvatore J; Harvey, Jeffrey A

2015-09-01

Many invasive species are able to escape from coevolved enemies and thus enjoy a competitive advantage over native species. However, during the invasion phase, non-native species must overcome many ecological and/or physiological hurdles before they become established and spread in their new habitats. This may explain why most introduced species either fail to establish or remain as rare interstitials in their new ranges. Studies focusing on invasive species have been based on plants or animals where establishment requires the possession of preadapted traits from their native ranges that enables them to establish and spread in their new habitats. The possession of preadapted traits that facilitate the exploitation of novel resources or to colonize novel habitats is known as 'ecological fitting'. Some species have evolved traits and life histories that reflect highly intimate associations with very specific types of habitats or niches. For these species, their phenological windows are narrow, and thus the ability to colonize non-native habitats requires that a number of conditions need to be met in accordance with their more specialized life histories. Some of the strongest examples of more complex ecological fitting involve invasive parasites that require different animal hosts to complete their life cycles. For instance, the giant liver fluke, Fascioloides magna, is a major parasite of several species of ungulates in North America. The species exhibits a life cycle whereby newly hatched larvae must find suitable intermediate hosts (freshwater snails) and mature larvae, definitive hosts (ungulates). Intermediate and definitive host ranges of F. magna in its native range are low in number, yet this parasite has been successfully introduced into Europe where it has become a parasite of native European snails and deer. We discuss how the ability of these parasites to overcome multiple ecophysiological barriers represents an excellent example of 'multiple-level ecological fitting'. © 2015 John Wiley & Sons Ltd.

Multifunctional pH sensitive 3D scaffolds for treatment and prevention of bone infection.

PubMed

Cicuéndez, Mónica; Doadrio, Juan C; Hernández, Ana; Portolés, M Teresa; Izquierdo-Barba, Isabel; Vallet-Regí, María

2018-01-01

Multifunctional-therapeutic three-dimensional (3D) scaffolds have been prepared. These biomaterials are able to destroy the S. aureus bacterial biofilm and to allow bone regeneration at the same time. The present study is focused on the design of pH sensitive 3D hierarchical meso-macroporous 3D scaffolds based on MGHA nanocomposite formed by a mesostructured glassy network with embedded hydroxyapatite nanoparticles, whose mesopores have been loaded with levofloxacin (Levo) as antibacterial agent. These 3D platforms exhibit controlled and pH-dependent Levo release, sustained over time at physiological pH (7.4) and notably increased at infection pH (6.7 and 5.5), which is due to the different interaction rate between diverse Levo species and the silica matrix. These 3D systems are able to inhibit the S. aureus growth and to destroy the bacterial biofilm without cytotoxic effects on human osteoblasts and allowing an adequate colonization and differentiation of preosteoblastic cells on their surface. These findings suggest promising applications of these hierarchical MGHA nanocomposite 3D scaffolds for the treatment and prevention of bone infection. Multifunctional 3D nanocomposite scaffolds with the ability for loading and sustained delivery of an antimicrobial agent, to eliminate and prevent bone infection and at the same time to contribute to bone regeneration process without cytotoxic effects on the surrounding tissue has been proposed. These 3D scaffolds exhibit a sustained levofloxacin delivery at physiological pH (pH 7.4), which increasing notably when pH decreases to characteristic values of bone infection process (pH 6.7 and pH 5.5). In vitro competitive assays between preosteoblastic and bacteria onto the 3D scaffold surface demonstrated an adequate osteoblast colonization in entire scaffold surface together with the ability to eliminate bacteria contamination. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Man and his spaceships: Vehicles for extraterrestrial colonization?

PubMed

Siefert, Janet L

2012-11-01

The resiliency and adaptive ability of microbial life in real time on Earth relies heavily upon horizontal gene transfer. Based on that knowledge, how likely is earth based microbial life to colonize extraterrestrial targets such as Mars? To address this question, we consider manned and unmanned space exploration, the resident microbiota that is likely to inhabit those vehicles, the adaptive potential of that microbiota in an extraterrestrial setting especially with regards to mobile genetic elements, and the likelihood that Mars like environments could initiate and sustain colonization.

The Importance of Species Traits for Species Distribution on Oceanic Islands

PubMed Central

Vazačová, Kristýna; Münzbergová, Zuzana

2014-01-01

Understanding species' ability to colonize new habitats is a key knowledge allowing us to predict species' survival in the changing landscapes. However, most studies exploring this topic observe distribution of species in landscapes which are under strong human influence being fragmented only recently and ignore the fact that the species distribution in these landscapes is far from equilibrium. Oceanic islands seem more appropriate systems for studying the relationship between species traits and its distribution as they are fragmented without human contribution and as they remained unchanged for a long evolutionary time. In our study we compared the values of dispersal as well as persistence traits among 18 species pairs from the Canary Islands differing in their distribution within the archipelago. The data were analyzed both with and without phylogenetic correction. The results demonstrate that no dispersal trait alone can explain the distribution of the species in the system. They, however, also suggest that species with better dispersal compared to their close relatives are better colonizers. Similarly, abundance of species in the archipelago seems to be an important predictor of species colonization ability only when comparing closely related species. This implies that analyses including phylogenetic correction may provide different insights than analyses without such a correction and both types of analyses should be combined to understand the importance of various plant traits for species colonization ability. PMID:25003737

Cell wars: regulation of cell survival and proliferation by cell competition

PubMed Central

Vivarelli, Silvia; Wagstaff, Laura; Piddini, Eugenia

2012-01-01

During cell competition fitter cells take over the tissue at the expense of viable, but less fit, cells, which are eliminated by induction of apoptosis or senescence. This probably acts as a quality-control mechanism to eliminate suboptimal cells and safeguard organ function. Several experimental conditions have been shown to trigger cell competition, including differential levels in ribosomal activity or in signalling pathway activation between cells, although it is unclear how those differences are sensed and translated into fitness levels. Many of the pathways implicated in cell competition have been previously linked with cancer, and this has led to the hypothesis that cell competition could play a role in tumour formation. Cell competition could be co-opted by cancer cells to kill surrounding normal cells and boost their own tissue colonization. However, in some cases, cell competition could have a tumour suppressor role, as cells harbouring mutations in a subset of tumour suppressor genes are killed by wild-type cells. Originally described in developing epithelia, competitive interactions have also been observed in some stem cell niches, where they play a role in regulating stem cell selection, maintenance and tissue repopulation. Thus competitive interactions could be relevant to the maintenance of tissue fitness and have a protective role against aging. PMID:22928509

Inhibition of fungal colonization on the rhizoplane of the CS2 - producing plant, Mimosa pudica L.

Treesearch

Z. Feng; P.G. Hartel; R.W. Roncadori; Shi-Jean S. Sung

1998-01-01

Carbon disulfide (CS2) is a colorless, volatile, foul-smelling, fungicidal liquid that is produced by some plants. The authors determined the ability of a model CS2-producing plant, Mimosa pudica, to affect the rhizoplane colonization of six species of soil fungi. Tomato (Lycopersicon esculentum...

Helicobacter pylori protein oxidation influences the colonization process.

PubMed

Godlewska, Renata; Dzwonek, Artur; Mikuła, Michał; Ostrowski, Jerzy; Pawłowski, Marcin; Bujnicki, Janusz M; Jagusztyn-Krynicka, Elzbieta K

2006-08-01

Dsb proteins control the formation and rearrangement of disulfide bonds during the folding of membrane and exported proteins. Here we examined the role of DsbI protein in Helicobacter pylori pathogenesis and demonstrated that a dsbI mutant impaired in disulfide bond formation revealed a greatly reduced ability to colonize mice gastric mucosa.

Algal ancestor of land plants was preadapted for symbiosis.

PubMed

Delaux, Pierre-Marc; Radhakrishnan, Guru V; Jayaraman, Dhileepkumar; Cheema, Jitender; Malbreil, Mathilde; Volkening, Jeremy D; Sekimoto, Hiroyuki; Nishiyama, Tomoaki; Melkonian, Michael; Pokorny, Lisa; Rothfels, Carl J; Sederoff, Heike Winter; Stevenson, Dennis W; Surek, Barbara; Zhang, Yong; Sussman, Michael R; Dunand, Christophe; Morris, Richard J; Roux, Christophe; Wong, Gane Ka-Shu; Oldroyd, Giles E D; Ané, Jean-Michel

2015-10-27

Colonization of land by plants was a major transition on Earth, but the developmental and genetic innovations required for this transition remain unknown. Physiological studies and the fossil record strongly suggest that the ability of the first land plants to form symbiotic associations with beneficial fungi was one of these critical innovations. In angiosperms, genes required for the perception and transduction of diffusible fungal signals for root colonization and for nutrient exchange have been characterized. However, the origin of these genes and their potential correlation with land colonization remain elusive. A comprehensive phylogenetic analysis of 259 transcriptomes and 10 green algal and basal land plant genomes, coupled with the characterization of the evolutionary path leading to the appearance of a key regulator, a calcium- and calmodulin-dependent protein kinase, showed that the symbiotic signaling pathway predated the first land plants. In contrast, downstream genes required for root colonization and their specific expression pattern probably appeared subsequent to the colonization of land. We conclude that the most recent common ancestor of extant land plants and green algae was preadapted for symbiotic associations. Subsequent improvement of this precursor stage in early land plants through rounds of gene duplication led to the acquisition of additional pathways and the ability to form a fully functional arbuscular mycorrhizal symbiosis.

Language Learning and Control in Monolinguals and Bilinguals

ERIC Educational Resources Information Center

Bartolotti, James; Marian, Viorica

2012-01-01

Parallel language activation in bilinguals leads to competition between languages. Experience managing this interference may aid novel language learning by improving the ability to suppress competition from known languages. To investigate the effect of bilingualism on the ability to control native-language interference, monolinguals and bilinguals…

Assessing the competitive ability of Japanese stilt grass, Microstegium vimineum (Trin.) A. Camus

USGS Publications Warehouse

Leicht, S.A.; Silander, J.A.; Greenwood, K.

2005-01-01

Microstegium vimineum (Japanese stilt grass) is an invasive grass in the eastern half of the United States which can form dense monocultures in forest understories, displacing native species. Although the loss of native species has been observed in the field, the actual competitive ability of this grass has not been examined. Microstegium vimineum was grown under controlled environment, greenhouse conditions in competition with Lolium perenne ssp. multiflorum (annual rye grass) and Muhlenbergia mexicana (Mexican muhly) in varying density ratios in full and low light treatments. Microstegium vimineum had a greater aboveground biomass, relative growth rate, and reproductive output than both competitors in both light treatments. The high competitive ability of Microstegium vimineum, especially in low light conditions, reflects its highly aggressive nature in forested or other landscapes of eastern North America.

Effect of the Level of Coordinated Motor Abilities on Performance in Junior Judokas

PubMed Central

Lech, Grzegorz; Jaworski, Janusz; Lyakh, Vladimir; Krawczyk, Robert

2011-01-01

The main focus of this study was to identify coordinated motor abilities that affect fighting methods and performance in junior judokas. Subjects were selected for the study in consideration of their age, competition experience, body mass and prior sports level. Subjects’ competition history was taken into consideration when analysing the effectiveness of current fight actions, and individual sports level was determined with consideration to rank in the analysed competitions. The study sought to determine the level of coordinated motor abilities of competitors. The scope of this analysis covered the following aspects: kinaesthetic differentiation, movement frequency, simple and selective reaction time (evoked by a visual or auditory stimulus), spatial orientation, visual-motor coordination, rhythmization, speed, accuracy and precision of movements and the ability to adapt movements and balance. A set of computer tests was employed for the analysis of all of the coordination abilities, while balance examinations were based on the Flamingo Balance Test. Finally, all relationships were determined based on the Spearman’s rank correlation coefficient. It was observed that the activity of the contestants during the fight correlated with the ability to differentiate movements and speed, accuracy and precision of movement, whereas the achievement level during competition was connected with reaction time. PMID:23486723

Evaluating plant-soil feedback together with competition in a serpentine grassland.

PubMed

Casper, Brenda B; Castelli, Jeffrey P

2007-05-01

Plants can alter biotic and abiotic soil characteristics in ways that feedback to change the performance of that same plant species relative to co-occurring plants. Most evidence for this plant-soil feedback comes from greenhouse studies of potted plants, and consequently, little is known about the importance of feedback in relation to other biological processes known to structure plant communities, such as plant-plant competition. In a field experiment with three C4 grasses, negative feedback was expressed through reduced survival and shoot biomass when seedlings were planted within existing clumps of conspecifics compared with clumps of heterospecifics. However, the combined effects of feedback and competition were species-specific. Only Andropogon gerardii exhibited feedback when competition with the clumps was allowed. For Sorghastrum nutans, strong interspecific competition eliminated the feedback expressed in the absence of competition, and Schizachyrium scoparium showed no feedback at all. That arbuscular mycorrhizal (AM) fungi may play a role in the feedback was indicated by higher AM root colonization with conspecific plant neighbours. We suggest that feedback and competition should not be viewed as entirely separate processes and that their importance in structuring plant communities cannot be judged in isolation from each other.

Genetic labelling and application of the isoproturon-mineralizing Sphingomonas sp. strain SRS2 in soil and rhizosphere.

PubMed

Kristensen, K E; Jacobsen, C S; Hansen, L H; Aamand, J; Morgan, J A W; Sternberg, C; Sørensen, S R

2006-09-01

To construct a luxAB-labelled Sphingomonas sp. strain SRS2 maintaining the ability to mineralize the herbicide isoproturon and usable for monitoring the survival and distribution of strain SRS2 on plant roots in laboratory systems. We inserted the mini-Tn5-luxAB marker into strain SRS2 using conjugational mating. In the transconjugant mutants luciferase was produced in varying levels. The mutants showed significant differences in their ability to degrade isoproturon. One luxAB-labelled mutant maintained the ability to mineralize isoproturon and was therefore selected for monitoring colonization of barley roots. We successfully constructed a genetically labelled isoproturon-mineralizing-strain SRS2 and demonstrated its ability to survive in soil and its colonization of rhizosphere. The construction of a luxAB-labelled strain SRS2 maintaining the degradative ability, provides a powerful tool for ecological studies serving as the basis for evaluating SRS2 as a bioremediation agent.

Investigating differences in driver accident involvement : the influence of perceptual motor competence, competitive athletics, and gender

DOT National Transportation Integrated Search

1999-04-01

This report presents the results of a study to determine if skills developed in competitive athletics transfer to driving ability, and whether such transfer is mediated by gender. To test these questions, the authors compared the driving ability of m...

Sport in the People's Republic of China: Selected Issues.

ERIC Educational Resources Information Center

Chu, Donald

Marxist/Maoist interpretations of sport in China differ significantly from the functional and meritocratic perspectives in the West which emphasize competition and personal reward. The latter school stresses the ability of the upwardly mobile aspirant to prove ability through competition. Individuals with talent are placed in valued positions in…

Isolation and identification of amylase-producing, endospore-forming bacteria from the alimentary tract of commercially processed broilers

USDA-ARS?s Scientific Manuscript database

Bacterial cultures of crop and cecal contents of adult poultry contain beneficial bacteria that reduce colonization of young poultry by Salmonella. Since endospore-forming bacteria may play a role in competitive exclusion of Salmonella in poultry, 3 trials were conducted to isolate these bacteria fr...

Are insular populations of the Philippine falconet (Microhierax erythrogenys) steps in a cline?

Treesearch

Todd E. Katzner; Nigel J. Collar

2013-01-01

Founder effects, new environments, and competition often produce changes in species colonizing islands, although the resulting endemism sometimes requires molecular identification. One method to identify fruitful areas for more detailed genetic study is through comparative morphological analyses. We measured 210 museum specimens to evaluate the potential morphological...

To promote the engineering innovative abilities of undergraduates by taking projects as the guidance and competitions as the promotion

NASA Astrophysics Data System (ADS)

Xu, Yishen; Wu, Di; Chen, Daqing; Gu, Jihua; Gao, Lei

2017-08-01

According to the inherent requirements of education for talents' knowledge, quality and comprehensive ability and the major training goals of optoelectronics information science and engineering, in order to enhance the undergraduates' comprehensive practical ability and consciousness of innovation, we carried out the reforms of teaching method and teaching mode, which took the training programs of innovation and entrepreneurship for undergraduates, extracurricular academic research fund, "Chun-Tsung Scholar" program or research projects of their tutors as the guidance, and took the all levels of relevant discipline competitions as the promotion. And the training mainline of engineering innovation talents as "undergraduate's tutorial system ->innovative training program or tutor's research project ->academic competition ->graduation projects (thesis)" was constructed stage by stage by combining the undergraduates' graduation projects and their participated academic competition into one for improving the quality of the graduation projects (thesis). The practical results of the last several years illuminate that the proposed training model can effectively stimulate the students' awareness of autonomous learning, enhance their comprehensive ability of analyzing and solving problems and improve their ability of engineering practice and innovation as well as their teamwork spirit.

Automated virtual colonoscopy

NASA Astrophysics Data System (ADS)

Hunt, Gordon W.; Hemler, Paul F.; Vining, David J.

1997-05-01

Virtual colonscopy (VC) is a minimally invasive alternative to conventional fiberoptic endoscopy for colorectal cancer screening. The VC technique involves bowel cleansing, gas distension of the colon, spiral computed tomography (CT) scanning of a patient's abdomen and pelvis, and visual analysis of multiplanar 2D and 3D images created from the spiral CT data. Despite the ability of interactive computer graphics to assist a physician in visualizing 3D models of the colon, a correct diagnosis hinges upon a physician's ability to properly identify small and sometimes subtle polyps or masses within hundreds of multiplanar and 3D images. Human visual analysis is time-consuming, tedious, and often prone to error of interpretation.We have addressed the problem of visual analysis by creating a software system that automatically highlights potential lesions in the 2D and 3D images in order to expedite a physician's interpretation of the colon data.

The influence of dibutyryl adenosine cyclic monophosphate on cell proliferation in the epithelium of the jejunal crypts, the colonic crypts and in colonic carcinomata of rat.

PubMed

Tutton, P J; Barkla, D H

1980-01-01

1. Cell proliferation in the jejunal crypts, the colonic crypts and in dimethylhydrazine (DMH)-induced adenocarcinomata of rat colon was measured using a stathmokinetic technique. 2. Dibutryl cyclic adneosine monophosphate (dibutyryl cAMP) was found to inhibit cell proliferation in colonic crypts and in colonic adenocarcinomata. 3. Dibutryl cAMP at very high doses was found to inhibit jejunal crypt cell proliferation but at lower doses was found to accelerate jejunal crypt cell proliferation. 4. Neither bilateral adrenalectomy nor chemical sympathectomy was found to abolish the ability of dibutryl cAMP to stimulate jejunal crypt cell proliferation. 5. The present results are difficult to interpret in terms of known hormonal influences on cell proliferation in the tissues examined and of established actions, of these hormones on cyclic nucleotide metabolism in other tissues.

Fitness consequences of plants growing with siblings: reconciling kin selection, niche partitioning and competitive ability

PubMed Central

File, Amanda L.; Murphy, Guillermo P.; Dudley, Susan A.

2012-01-01

Plant studies that have investigated the fitness consequences of growing with siblings have found conflicting evidence that can support different theoretical frameworks. Depending on whether siblings or strangers have higher fitness in competition, kin selection, niche partitioning and competitive ability have been invoked. Here, we bring together these processes in a conceptual synthesis and argue that they can be co-occurring. We propose that these processes can be reconciled and argue for a trait-based approach of measuring natural selection instead of the fitness-based approach to the study of sibling competition. This review will improve the understanding of how plants interact socially under competitive situations, and provide a framework for future studies. PMID:22072602

Cognitive Capitalism: Economic Freedom Moderates the Effects of Intellectual and Average Classes on Economic Productivity.

PubMed

Coyle, Thomas R; Rindermann, Heiner; Hancock, Dale

2016-10-01

Cognitive ability stimulates economic productivity. However, the effects of cognitive ability may be stronger in free and open economies, where competition rewards merit and achievement. To test this hypothesis, ability levels of intellectual classes (top 5%) and average classes (country averages) were estimated using international student assessments (Programme for International Student Assessment; Trends in International Mathematics and Science Study; and Progress in International Reading Literacy Study) (N = 99 countries). The ability levels were correlated with indicators of economic freedom (Fraser Institute), scientific achievement (patent rates), innovation (Global Innovation Index), competitiveness (Global Competitiveness Index), and wealth (gross domestic product). Ability levels of intellectual and average classes strongly predicted all economic criteria. In addition, economic freedom moderated the effects of cognitive ability (for both classes), with stronger effects at higher levels of freedom. Effects were particularly robust for scientific achievements when the full range of freedom was analyzed. The results support cognitive capitalism theory: cognitive ability stimulates economic productivity, and its effects are enhanced by economic freedom. © The Author(s) 2016.

Competition between the phytophagous stink bugs Euschistus heros and Piezodorus guildinii in soybeans.

PubMed

Tuelher, Edmar S; Silva, Éder H; Hirose, Edson; Guedes, Raul Narciso C; Oliveira, Eugênio E

2016-10-01

The abundance and contribution of the neotropical brown stink bug, Euschistus heros (F.), and the redbanded stink bug, Piezodorus guildinii (West.), to the composition of insect pests of soybean, Glycine max (L.), fields have changed both spatially and temporally in neotropical soybean production areas. Therefore, we assessed the competitiveness of each species in direct competition experiments following an additive series. We performed mixed (adult) insect infestations in soybean plants and evaluated the fitness of each species and the soybean yield. While the competitive ability of E. heros was significantly compromised by increments in conspecifics and heterospecifics (i.e. P. guildinii), the competitive ability of P. guildinii was compromised by the presence of heterospecifics (i.e. E. heros). The reproductive output of P. guildinii remained unaffected by increments in E. heros or of P. guildinii. Intriguingly, despite the fact that P. guildinii apparently lost the competition with E. heros, almost no pod production was observed in any plant colonised by the former. The higher abundance of E. heros in neotropical soybean fields seems to result from higher competitive ability than its heterospecific competitor P. guildinii, which may prevent the higher losses caused by P. guildinii. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Bacterial growth, flow, and mixing shape human gut microbiota density and composition.

PubMed

Arnoldini, Markus; Cremer, Jonas; Hwa, Terence

2018-03-13

The human gut microbiota is highly dynamic, and host physiology and diet exert major influences on its composition. In our recent study, we integrated new quantitative measurements on bacterial growth physiology with a reanalysis of published data on human physiology to build a comprehensive modeling framework. This can generate predictions of how changes in different host factors influence microbiota composition. For instance, hydrodynamic forces in the colon, along with colonic water absorption that manifests as transit time, exert a major impact on microbiota density and composition. This can be mechanistically explained by their effect on colonic pH which directly affects microbiota competition for food. In this addendum, we describe the underlying analysis in more detail. In particular, we discuss the mixing dynamics of luminal content by wall contractions and its implications for bacterial growth and density, as well as the broader implications of our insights for the field of gut microbiota research.

Ecological Release from Aquatic Predation Is Associated with the Emergence of Marine Blenny Fishes onto Land.

PubMed

Ord, Terry J; Summers, Thomas C; Noble, Mae M; Fulton, Christopher J

2017-05-01

An ecological release from competition or predation is a frequent adaptive explanation for the colonization of novel environments, but empirical data are limited. On the island of Rarotonga, several blenny fish species appear to be in the process of colonizing land. Anecdotal observations have implied that aquatic predation is an important factor in prompting such amphibious fish behavior. We provide evidence supporting this hypothesis by demonstrating that amphibious blennies shift their abundance up and down the shoreline to remain above predatory fishes that periodically move into intertidal areas during high tide. A predation experiment using blenny mimics confirmed a high risk of aquatic predation for blennies, significantly higher than predation experienced on land. These data suggest that predation has played an active role in promoting terrestrial activity in amphibious blennies and provide a rare example of how ecological release from predation could drive the colonization of a novel environment.

Preferential edge habitat colonization by a specialist weevil, Rhinoncomimus latipes (Coleoptera: Curculionidae)

Treesearch

J.A. Hough-Goldstein; E. Lake; V. D' Amico; S.H. Berg

2012-01-01

Understanding the behavioral basis of dispersal and colonization is critical in biological control systems, where success of a natural enemy depends in part on its ability to find and move to new host patches. We studied behavior of the specialist weevil Rhinoncomimus latipes Korotyaev, a biological control agent of mile-a-minute weed, ...

The secreted form of the p40 subunit of interleukin (IL)-12 inhibits IL-23 functions and abrogates IL-23-mediated antitumour effects

PubMed Central

Shimozato, Osamu; Ugai, Shin-ichi; Chiyo, Masako; Takenobu, Hisanori; Nagakawa, Hiroyasu; Wada, Akihiko; Kawamura, Kiyoko; Yamamoto, Hiroshi; Tagawa, Masatoshi

2006-01-01

Interleukin (IL)-23 is a heterodimeric cytokine consisting of a novel p19 molecule and the p40 subunit of IL-12. Since secreted p40 can act as an antagonist for IL-12, we investigated whether p40 also inhibited IL-23-mediated immunological functions. p40 did not induce interferon (IFN)-γ or IL-17 production from splenocytes but impaired IL-23-induced cytokine production by competitive binding to the IL-23 receptors. Furthermore, a mixed population of murine colon carcinoma Colon 26 cells transduced with the p40 gene and those transduced with the IL-23 gene developed tumours in syngenic mice, whereas the IL-23-expressing Colon 26 cells were completely rejected. p40 also suppressed IFN-γ production of antigen-stimulated splenocytes and IL-23-mediated cytotoxic T-lymphocyte activities in the mice that rejected Colon 26 cells expressing IL-23. p40 can thereby antagonize IL-23 and is a possible therapeutic agent for suppression of IL-23 functions. PMID:16423037

Evaluation of quantitative PCR measurement of bacterial colonization of epithelial cells.

PubMed

Schmidt, Marcin T; Olejnik-Schmidt, Agnieszka K; Myszka, Kamila; Borkowska, Monika; Grajek, Włodzimierz

2010-01-01

Microbial colonization is an important step in establishing pathogenic or probiotic relations to host cells and in biofilm formation on industrial or medical devices. The aim of this work was to verify the applicability of quantitative PCR (Real-Time PCR) to measure bacterial colonization of epithelial cells. Salmonella enterica and Caco-2 intestinal epithelial cell line was used as a model. To verify sensitivity of the assay a competition of the pathogen cells to probiotic microorganism was tested. The qPCR method was compared to plate count and radiolabel approach, which are well established techniques in this area of research. The three methods returned similar results. The best quantification accuracy had radiolabel method, followed by qPCR. The plate count results showed coefficient of variation two-times higher than this of qPCR. The quantitative PCR proved to be a reliable method for enumeration of microbes in colonization assay. It has several advantages that make it very useful in case of analyzing mixed populations, where several different species or even strains can be monitored at the same time.

Safe caves and dangerous forests? Predation risk may contribute to salamander colonization of subterranean habitats

NASA Astrophysics Data System (ADS)

Salvidio, Sebastiano; Palumbi, Giulia; Romano, Antonio; Costa, Andrea

2017-04-01

Recent studies suggest that many organisms actively colonize the subterranean environment to avoid climatic stress, exploit new ecological opportunities and reduce competition and predation. Terrestrial salamanders are known to colonize the more stable subterranean habitats mainly to escape external climatic extremes, while the role of predation avoidance remains untested. To better understand the importance of predation, we used clay models of the cave salamander Speleomantes strinatii to compare the predation occurring in woodland and subterranean habitats. Models were positioned in three forests and in three caves in NW Italy. One-hundred eighty-four models were retrieved from the field and 59 (32%) were attacked by predators. Models were attacked on their head more often than expected by chance and, therefore, were perceived by predators as real prey items. In the woodlands, clay models showed a four-time higher probability of being attacked in comparison to caves, suggesting a different level of potential predation risk in these surface habitats. These findings are one of the first experimental evidences that, in terrestrial ecosystems, predation avoidance may contribute to the salamander underground colonization process.

Ecology of Root Colonizing Massilia (Oxalobacteraceae)

PubMed Central

Ofek, Maya; Hadar, Yitzhak; Minz, Dror

2012-01-01

Background Ecologically meaningful classification of bacterial populations is essential for understanding the structure and function of bacterial communities. As in soils, the ecological strategy of the majority of root-colonizing bacteria is mostly unknown. Among those are Massilia (Oxalobacteraceae), a major group of rhizosphere and root colonizing bacteria of many plant species. Methodology/Principal Findings The ecology of Massilia was explored in cucumber root and seed, and compared to that of Agrobacterium population, using culture-independent tools, including DNA-based pyrosequencing, fluorescence in situ hybridization and quantitative real-time PCR. Seed- and root-colonizing Massilia were primarily affiliated with other members of the genus described in soil and rhizosphere. Massilia colonized and proliferated on the seed coat, radicle, roots, and also on hyphae of phytopathogenic Pythium aphanidermatum infecting seeds. High variation in Massilia abundance was found in relation to plant developmental stage, along with sensitivity to plant growth medium modification (amendment with organic matter) and potential competitors. Massilia absolute abundance and relative abundance (dominance) were positively related, and peaked (up to 85%) at early stages of succession of the root microbiome. In comparison, variation in abundance of Agrobacterium was moderate and their dominance increased at later stages of succession. Conclusions In accordance with contemporary models for microbial ecology classification, copiotrophic and competition-sensitive root colonization by Massilia is suggested. These bacteria exploit, in a transient way, a window of opportunity within the succession of communities within this niche. PMID:22808103

Ecology of root colonizing Massilia (Oxalobacteraceae).

PubMed

Ofek, Maya; Hadar, Yitzhak; Minz, Dror

2012-01-01

Ecologically meaningful classification of bacterial populations is essential for understanding the structure and function of bacterial communities. As in soils, the ecological strategy of the majority of root-colonizing bacteria is mostly unknown. Among those are Massilia (Oxalobacteraceae), a major group of rhizosphere and root colonizing bacteria of many plant species. The ecology of Massilia was explored in cucumber root and seed, and compared to that of Agrobacterium population, using culture-independent tools, including DNA-based pyrosequencing, fluorescence in situ hybridization and quantitative real-time PCR. Seed- and root-colonizing Massilia were primarily affiliated with other members of the genus described in soil and rhizosphere. Massilia colonized and proliferated on the seed coat, radicle, roots, and also on hyphae of phytopathogenic Pythium aphanidermatum infecting seeds. High variation in Massilia abundance was found in relation to plant developmental stage, along with sensitivity to plant growth medium modification (amendment with organic matter) and potential competitors. Massilia absolute abundance and relative abundance (dominance) were positively related, and peaked (up to 85%) at early stages of succession of the root microbiome. In comparison, variation in abundance of Agrobacterium was moderate and their dominance increased at later stages of succession. In accordance with contemporary models for microbial ecology classification, copiotrophic and competition-sensitive root colonization by Massilia is suggested. These bacteria exploit, in a transient way, a window of opportunity within the succession of communities within this niche.

Inactivation of gacS Does Not Affect the Competitiveness of Pseudomonas chlororaphis in the Arabidopsis thaliana Rhizosphere

PubMed Central

Schmidt-Eisenlohr, Heike; Gast, Astrid; Baron, Christian

2003-01-01

Quorum-sensing-controlled processes are considered to be important for the competitiveness of microorganisms in the rhizosphere. They affect cell-cell communication, biofilm formation, and antibiotic production, and the GacS-GacA two-component system plays a role as a key regulator. In spite of the importance of this system for the regulation of various processes, strains with a Gac− phenotype are readily recovered from natural habitats. To analyze the influence of quorum sensing and the influence of the production of the antibiotic phenazine-1-carboxamide on rhizosphere colonization by Pseudomonas chlororaphis, a gnotobiotic system based on Arabidopsis thaliana seedlings in soil was investigated. Transposon insertion mutants of P. chlororaphis isolate SPR044 carrying insertions in different genes required for the production of N-acyl-homoserine lactones and phenazine-1-carboxamide were generated. Analysis of solitary rhizosphere colonization revealed that after prolonged growth, the population of the wild type was significantly larger than that of the homoserine lactone-negative gacS mutant and that of a phenazine-1-carboxamide-overproducing strain. In cocultivation experiments, however, the population size of the gacS mutant was similar to that of the wild type after extended growth in the rhizosphere. A detailed analysis of growth kinetics was performed to explain this phenomenon. After cells grown to the stationary phase were transferred to fresh medium, the gacS mutant had a reduced lag phase, and production of the stationary-phase-specific sigma factor RpoS was strongly reduced. This may provide a relative competitive advantage in cocultures with other bacteria, because it permits faster reinitiation of growth after a change to nutrient-rich conditions. In addition, delayed entry into the stationary phase may allow more efficient nutrient utilization. Thus, GacS-GacA-regulated processes are not absolutely required for efficient rhizosphere colonization in populations containing the wild type and Gac− mutants. PMID:12620875

Chemopreventive potential of β-Sitosterol in experimental colon cancer model - an In vitro and In vivo study

PubMed Central

2010-01-01

Background Asclepias curassavica Linn. is a traditional medicinal plant used by tribal people in the western ghats, India, to treat piles, gonorrhoea, roundworm infestation and abdominal tumours. We have determined the protective effect of β-sitosterol isolated from A. curassavica in colon cancer, using in vitro and in vivo models. Methods The active molecule was isolated, based upon bioassay guided fractionation, and identified as β-sitosterol on spectral evidence. The ability to induce apoptosis was determined by its in vitro antiradical activity, cytotoxic studies using human colon adenocarcinoma and normal monkey kidney cell lines, and the expression of β-catenin and proliferating cell nuclear antigen (PCNA) in human colon cancer cell lines (COLO 320 DM). The chemopreventive potential of β-sitosterol in colon carcinogenesis was assessed by injecting 1,2-dimethylhydrazine (DMH, 20 mg/kg b.w.) into male Wistar rats and supplementing this with β-sitosterol throughout the experimental period of 16 weeks at 5, 10, and 20 mg/kg b.w. Results β-sitosterol induced significant dose-dependent growth inhibition of COLO 320 DM cells (IC50 266.2 μM), induced apoptosis by scavenging reactive oxygen species, and suppressed the expression of β-catenin and PCNA antigens in human colon cancer cells. β-sitosterol supplementation reduced the number of aberrant crypt and crypt multiplicity in DMH-initiated rats in a dose-dependent manner with no toxic effects. Conclusion We found doses of 10-20 mg/kg b.w. β-sitosterol to be effective for future in vivo studies. β-sitosterol had chemopreventive potential by virtue of its radical quenching ability in vitro, with minimal toxicity to normal cells. It also attenuated β-catenin and PCNA expression, making it a potential anticancer drug for colon carcinogenesis. PMID:20525330

Competitions for Showcasing Innovative and Creative Talents

ERIC Educational Resources Information Center

Riley, Tracy L.

2011-01-01

Competitions are recommended for identifying and providing for the exceptional talents of young people. Competitions have been a cornerstone of gifted education, putting talents to the test by enabling gifted students to showcase their abilities and receive acknowledgement and recognition for their talents. Competitions have been noted as "a…

Meta-analysis reveals evolution in invasive plant species but little support for Evolution of Increased Competitive Ability (EICA).

PubMed

Felker-Quinn, Emmi; Schweitzer, Jennifer A; Bailey, Joseph K

2013-03-01

Ecological explanations for the success and persistence of invasive species vastly outnumber evolutionary hypotheses, yet evolution is a fundamental process in the success of any species. The Evolution of Increased Competitive Ability (EICA) hypothesis (Blossey and Nötzold 1995) proposes that evolutionary change in response to release from coevolved herbivores is responsible for the success of many invasive plant species. Studies that evaluate this hypothesis have used different approaches to test whether invasive populations allocate fewer resources to defense and more to growth and competitive ability than do source populations, with mixed results. We conducted a meta-analysis of experimental tests of evolutionary change in the context of EICA. In contrast to previous reviews, there was no support across invasive species for EICA's predictions regarding defense or competitive ability, although invasive populations were more productive than conspecific native populations under noncompetitive conditions. We found broad support for genetically based changes in defense and competitive plant traits after introduction into new ranges, but not in the manner suggested by EICA. This review suggests that evolution occurs as a result of plant introduction and population expansion in invasive plant species, and may contribute to the invasiveness and persistence of some introduced species.

Meta-analysis reveals evolution in invasive plant species but little support for Evolution of Increased Competitive Ability (EICA)

PubMed Central

Felker-Quinn, Emmi; Schweitzer, Jennifer A; Bailey, Joseph K

2013-01-01

Ecological explanations for the success and persistence of invasive species vastly outnumber evolutionary hypotheses, yet evolution is a fundamental process in the success of any species. The Evolution of Increased Competitive Ability (EICA) hypothesis (Blossey and Nötzold 1995) proposes that evolutionary change in response to release from coevolved herbivores is responsible for the success of many invasive plant species. Studies that evaluate this hypothesis have used different approaches to test whether invasive populations allocate fewer resources to defense and more to growth and competitive ability than do source populations, with mixed results. We conducted a meta-analysis of experimental tests of evolutionary change in the context of EICA. In contrast to previous reviews, there was no support across invasive species for EICA's predictions regarding defense or competitive ability, although invasive populations were more productive than conspecific native populations under noncompetitive conditions. We found broad support for genetically based changes in defense and competitive plant traits after introduction into new ranges, but not in the manner suggested by EICA. This review suggests that evolution occurs as a result of plant introduction and population expansion in invasive plant species, and may contribute to the invasiveness and persistence of some introduced species. PMID:23531703

Mineralogical controls on surface colonization by sulfur-metabolizing microbial communities

NASA Astrophysics Data System (ADS)

Jones, A. A.; Bennett, P.

2012-12-01

When characterizing microbial diversity and the microbial ecosystem of the shallow subsurface the mineral matrix is generally assumed to be homogenous and unreactive. We report here experimental evidence that microorganisms colonize rock surfaces according to the rock's chemistry and the organism's metabolic requirements and tolerances. We investigated this phenomenon using laboratory biofilm reactors with both a pure culture of sulfur-oxidizing Thiothrix unzii and a mixed environmental sulfur-metabolizing community from Lower Kane, Cave, WY, USA. Reactors contained rock and mineral chips (calcite, albite, microcline, quartz, chert, Madison Limestone (ML), Madison Dolostone (MD), and basalt) amended with one of the two inoculants. Biomass of attached microorganisms on each mineral surface was quantified. The 16S rRNA of attached microbial communities were compared using Roche FLX and Titanium 454 next generation pyrosequencing. A primary controlling factor on taxonomy of attached microorganisms in both pure and mixed culture experiments was mineral buffering capacity. In mixed culture experiments acid-buffering carbonates were preferentially colonized by neutrophilic sulfur-oxidizing microorganisms (~18% to ~27% of microorganisms), while acidophilic sulfur-oxidizing microorganisms colonized non-buffering quartz exclusively (~46% of microorganisms). The nutrient content of the rock was a controlling factor on biomass accumulation, with neutrophilic organisms selecting between carbonate surfaces of equivalent buffer capacities according to the availability of phosphate. Dry biomass on ML was 17.8 ± 2.3 mg/cm2 and MD was 20.6 ± 6.8 mg/cm2; while nutrient poor calcite accumulated 2.4 ± 0.3 mg/cm2. Biomass accumulation was minimal on non-buffering nutrient-limited surfaces. These factors are countered by the competitive exclusion of some populations. A pure culture of T. unzii preferentially colonizes carbonates while a very closely related Thiothrix spp is excluded from these same rock samples in a mixed culture. Diversity analysis reveals that ML, MD, and calcite have >98% of sequences belonging to shared OTUs. The carbonates have <3% of sequences belonging to OTUs shared with any silicate mineral surface with the exception of basalt (~85% similarity). These four surfaces were host to the least diverse microbial communities, suggesting that competitive exclusion of microorganisms not adapted to these surfaces is a controlling variable on taxonomy. Furthermore, the microorganisms on basalt reveal an unique association between Thiothrix unzii (often found in mid-ocean ridge environments) and basalt, where it excludes other sulfur oxidizers and accumulates the highest non-carbonate biomass in both pure (3.5 ± 1.0 mg/cm2) and mixed culture (5.4 ± 1.4 mg/cm2) experiments. This association suggests that adaptations to specific rocks may be retained even when the organism is displaced from an ancestral rock/mineral surface habitat. Combined, these variables (buffering capacity, nutrient availability, competitive exclusion, tolerance of surface geochemistry, and latent adaptations) affect biomass density, local diversity, and global diversity of the attached communities on mineral and rock surfaces and suggest that different populations are more tolerant of, and more competitive on, specific rock/mineral types.

The Mere Exposure Effect: Relationship to Response Competition and Imagery Ability.

ERIC Educational Resources Information Center

Vrana, Scott R.

Exposure to novel stimuli increases one's liking for such stimuli. Response competition is one theory attempting to account for this effect: as a stimulus becomes more familiar, competing responses drop out in favor of one dominant response and the stimulus becomes better liked. Imagery ability refers to the regeneration of responses during…

The Interaction between Root Herbivory and Competitive Ability of Native and Invasive-Range Populations of Brassica nigra

PubMed Central

Oduor, Ayub M. O.; Stift, Marc; van Kleunen, Mark

2015-01-01

The evolution of increased competitive ability (EICA) hypothesis predicts that escape from intense herbivore damage may enable invasive plants to evolve higher competitive ability in the invasive range. Below-ground root herbivory can have a strong impact on plant performance, and invasive plants often compete with multiple species simultaneously, but experimental approaches in which EICA predictions are tested with root herbivores and in a community setting are rare. Here, we used Brassica nigra plants from eight invasive- and seven native-range populations to test whether the invasive-range plants have evolved increased competitive ability when competing with Achillea millefolium and with a community (both with and without A. millefolium). Further, we tested whether competitive interactions depend on root herbivory on B. nigra by the specialist Delia radicum. Without the community, competition with A. millefolium reduced biomass of invasive- but not of native-range B. nigra. With the community, invasive-range B. nigra suffered less than native-range B. nigra. Although the overall effect of root herbivory was not significant, it reduced the negative effect of the presence of the community. The community produced significantly less biomass when competing with B. nigra, irrespective of the range of origin, and independent of the presence of A. millefolium. Taken together, these results offer no clear support for the EICA hypothesis. While native-range B. nigra plants appear to be better in dealing with a single competitor, the invasive-range plants appear to be better in dealing with a more realistic multi-species community. Possibly, this ability of tolerating multiple competitors simultaneously has contributed to the invasion success of B. nigra in North America. PMID:26517125

The effects of increased CO[sub 2] on the competitive ability of Lupinus arboreus, a dominant nitrogen-fixing shrub

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallace, A.M.

Plant responses to increased atmospheric CO[sub 2] have been shown to be both species-specific and dependent on other environmental factors, potentially changing competitive interactions and altering community structure. The competitive response of a dominant nitrogen-fixing shrub to an introduced annual (Bromus diandrus) and a native perennial grass (Bromus carinatus) was measured under ambient and high CO[sub 2] and two nitrogen levels. These species coexist in a generally nitrogen-limited coastal grassland reserve besieged with alien species. The relative competitive ability of the lupin increased with CO[sub 2] for all treatments, with the largest difference occurring at low nitrogen in competition withmore » the introduced annual. This study provides a global change perspective for those interested in conserving native Californian grassland species, as well as the first data on the competitive response of nitrogen-fixers to high CO[sub 2].« less

The impact of nursing students' chemistry learning performance assessment in Taiwan: competitive versus non-competitive student team achievement division approaches

NASA Astrophysics Data System (ADS)

Wang, Kai-Ping

2012-07-01

Purpose: The purpose of this study was to determine the effectiveness of competitive Student Team Achievement Division (STAD), non-competitive STAD, and traditional learning on chemistry learning and learning perceptions. Sample, design and methods: By adopting the STAD approach, this study examined 144 nursing students at a five-year junior college in northern Taiwan during the first semester (totaling 18 weeks) of the 2008 academic year. Results: The findings reveal that both a heterogeneous group with external pressure (involving competitive STAD) and a friendship group with affective pressure (involving traditional learning) enhance group cohesion and assist students' meaningful learning; the heterogeneous group without extra pressure (involving non-competitive STAD), by contrast, fails because of apathy and lassitude. Moreover, learning effectiveness will obviously predominate until the learning strategy continues for a long period or at least one semester. Conclusions: This study revealed that the learning performance level of the competitive STAD group is significantly different from that of the non-competitive STAD group; and the learning performance level of the traditional group is significantly different from that of the non-competitive STAD group. Both the competitive STAD group and traditional group of medium ability students are significantly different from the non-competitive STAD group. Low-ability students from the competitive STAD group are significantly different from those of the non-competitive STAD, though no significant differences were found in learning perception. However, both a lack of friendship and a lack of ability in using algorithms may affect students' chemistry learning. Furthermore, gender imbalance, educational culture, and group emotions are factors that may influence student learning performance. Further study should focus on the use of grouping, improve responsibility in group discussion, and investigate group interaction patterns to determine the factors that influence learning performance of students working in groups.

Competition between Naegleria fowleri and Free Living Amoeba Colonizing Laboratory Scale and Operational Drinking Water Distribution Systems.

PubMed

Miller, Haylea C; Wylie, Jason T; Kaksonen, Anna H; Sutton, David; Puzon, Geoffrey J

2018-03-06

Free living amoebae (FLA), including pathogenic Naegleria fowleri, can colonize and grow within pipe wall biofilms of drinking water distribution systems (DWDSs). Studies on the interactions between various FLA species in biofilms are limited. Understanding the interaction between FLA and the broader biofilm ecology could help better predict DWDS susceptibility to N. fowleri colonization. The aim of this study was to determine if N. fowleri and other FLAs ( Naegleria, Vermamoeba, Willaertia, and Vahlkampfia spp.) cocolonize DWDS biofilm. FLAs commonly isolated from DWDSs ( N. fowleri, V. vermiformis, and N. lovaniensis) were introduced into laboratory-scale biomonitors to determine the impact of these amoebae on N. fowleri's presence and viability. Over 18 months, a single viable amoebae ( N. fowleri, N. lovaniensis, or V. vermiformis) was detected in each biofilm sample, with the exception of N. lovaniensis and N. fowleri, which briefly cocolonized biofilm following their coinoculation. The analysis of biofilm and bulk water samples from operational DWDSs revealed a similar lack of cocolonization with a single FLA detected in 99% ( n = 242) of samples. Interestingly, various Naegleria spp. did colonize the same DWDS locations but at different times. This knowledge furthers the understanding of ecological factors which enable N. fowleri to colonize and survive within operational DWDSs and could aid water utilities to control its occurrence.

Delineating the roles of males and females in sperm competition

PubMed Central

Evans, Jonathan P.; Rosengrave, Patrice; Gasparini, Clelia; Gemmell, Neil J.

2013-01-01

Disentangling the relative roles of males, females and their interactive effects on competitive fertilization success remains a challenge in sperm competition. In this study, we apply a novel experimental framework to an ideally suited externally fertilizing model system in order to delineate these roles. We focus on the chinook salmon, Oncorhynchus tshawytscha, a species in which ovarian fluid (OF) has been implicated as a potential arbiter of cryptic female choice for genetically compatible mates. We evaluated this predicted sexually selected function of OF using a series of factorial competitive fertilization trials. Our design involved a series of 10 factorial crosses, each involving two ‘focal’ rival males whose sperm competed against those from a single ‘standardized’ (non-focal) rival for a genetically uniform set of eggs in the presence of OF from two focal females. This design enabled us to attribute variation in competitive fertilization success among focal males, females (OF) and their interacting effects, while controlling for variation attributable to differences in the sperm competitive ability of rival males, and male-by-female genotypic interactions. Using this experimental framework, we found that variation in sperm competitiveness could be attributed exclusively to differences in the sperm competitive ability of focal males, a conclusion supported by subsequent analyses revealing that variation in sperm swimming velocity predicts paternity success. Together, these findings provide evidence that variation in paternity success can be attributed to intrinsic differences in the sperm competitive ability of rival males, and reveal that sperm swimming velocity is a key target of sexual selection. PMID:24266039

The outcome of alien tree invasions in Puerto Rico

Treesearch

Ariel E. Lugo

2004-01-01

Invasive alien tree species in Puerto Rico often form monospecific stands on deforested lands that were previously used for agriculture and then abandoned. Most native pioneer species are incapable of colonizing these sites, and thus introduced species have little competition from native trees. Alien trees may dominate sites for 30 to 40 years, but by that time native...

Plant competition, facilitation, and other overstory-understory interactions in longleaf pine ecosystems.

Treesearch

Timothy B. Harrington

2006-01-01

Many of the stand structural characteristics of longleaf pine (Pinus palustris Mill.) forests that existed prior to European colonization have been altered or lost from past disturbance histories (Frost this volume). For example, often missing are the widely spaced, large-diameter trees, the all-aged stand structure that included a vigorous cohort...

Impact of diversity of colonizing strains on strategies for sampling Escherichia coli from fecal specimens.

PubMed

Lautenbach, Ebbing; Bilker, Warren B; Tolomeo, Pam; Maslow, Joel N

2008-09-01

Of 49 subjects, 21 were colonized with more than one strain of Escherichia coli and 12 subjects had at least one strain present in fewer than 20% of colonies. The ability to accurately characterize E. coli strain diversity is directly related to the number of colonies sampled and the underlying prevalence of the strain.

Campylobacter protein oxidation influences epithelial cell invasion or intracellular survival as well as intestinal tract colonization in chickens.

PubMed

Lasica, A M; Wyszynska, A; Szymanek, K; Majewski, P; Jagusztyn-Krynicka, E K

2010-01-01

The Dsb family of redox proteins catalyzes disulfide bond formation and isomerization. Since mutations in dsb genes change the conformation and stability of many extracytoplasmic proteins, and since many virulence factors of pathogenic bacteria are extracytoplasmic, inactivation of dsb genes often results in pathogen attenuation. This study investigated the role of 2 membrane-bound oxidoreductases, DsbB and DsbI, in the Campylobacter jejuni oxidative Dsb pathway. Campylobacter mutants, lacking DsbB or DsbI or both, were constructed by allelic replacement and used in the human intestinal epithelial T84 cell line for the gentamicin protection assay (invasion assay) and chicken colonization experiments. In C. coli strain 23/1, the inactivation of the dsbB or dsbI gene separately did not significantly affect the colonization process. However, simultaneous disruption of both membrane-bound oxidoreductase genes significantly decreased the strain’s ability to colonize chicken intestines. Moreover, C. jejuni strain 81-176 with mutated dsbB or dsbI genes showed reduced invasion/intracellular survival abilities. No cells of the double mutants (dsbB⁻ dsbI⁻) of C. jejuni 81-176 were recovered from human cells after 3 h of invasion.

Franchise competition in the electric utility industry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vince, C.A.; Fogel, J.C.

Franchise competition is - and should be - an integral part of enhanced competition. It serves the traditional goal of encouraging lower costs through the threat of takeover or purchase. However, the issue of utility recovery for stranded costs stands as a major unresolved question affecting customers` ability to partake of this central aspect of competition.

Evolution of competitive ability within Lonicera japonica's invaded range

Treesearch

Gregory A. Evans; Francis F. Kilkenny; Laura F. Galloway

2013-01-01

Factors influencing invasive taxa may change during the course of an invasion. For example, intraspecific competition is predicted to be more important in areas with older stands of dense monospecific invaders than at the margins of an invaded range. We evaluated evolution in response to predicted changes in competition by comparing the intraspecific competitive...

Competitive ability, stress tolerance and plant interactions along stress gradients.

PubMed

Qi, Man; Sun, Tao; Xue, SuFeng; Yang, Wei; Shao, DongDong; Martínez-López, Javier

2018-04-01

Exceptions to the generality of the stress-gradient hypothesis (SGH) may be reconciled by considering species-specific traits and stress tolerance strategies. Studies have tested stress tolerance and competitive ability in mediating interaction outcomes, but few have incorporated this to predict how species interactions shift between competition and facilitation along stress gradients. We used field surveys, salt tolerance and competition experiments to develop a predictive model interspecific interaction shifts across salinity stress gradients. Field survey and greenhouse tolerance tests revealed tradeoffs between stress tolerance and competitive ability. Modeling showed that along salinity gradients, (1) plant interactions shifted from competition to facilitation at high salinities within the physiological limits of salt-intolerant plants, (2) facilitation collapsed when salinity stress exceeded the physiological tolerance of salt-intolerant plants, and (3) neighbor removal experiments overestimate interspecific facilitation by including intraspecific effects. A community-level field experiment, suggested that (1) species interactions are competitive in benign and, facilitative in harsh condition, but fuzzy under medium environmental stress due to niche differences of species and weak stress amelioration, and (2) the SGH works on strong but not weak stress gradients, so SGH confusion arises when it is applied across questionable stress gradients. Our study clarifies how species interactions vary along stress gradients. Moving forward, focusing on SGH applications rather than exceptions on weak or nonexistent gradients would be most productive. © 2018 by the Ecological Society of America.

A canopy architectural model to study the competitive ability of chickpea with sowthistle.

PubMed

Cici, S-Zahra-Hosseini; Adkins, Steve; Hanan, Jim

2008-06-01

Improving the competitive ability of crops is a sustainable method of weed management. This paper shows how a virtual plant model of competition between chickpea (Cicer arietinum) and sowthistle (Sonchus oleraceus) can be used as a framework for discovering and/or developing more competitive chickpea cultivars. The virtual plant models were developed using the L-systems formalism, parameterized according to measurements taken on plants at intervals during their development. A quasi-Monte Carlo light-environment model was used to model the effect of chickpea canopy on the development of sowthistle. The chickpea-light environment-sowthistle model (CLES model) captured the hypothesis that the architecture of chickpea plants modifies the light environment inside the canopy and determines sowthistle growth and development pattern. The resulting CLES model was parameterized for different chickpea cultivars (viz. 'Macarena', 'Bumper', 'Jimbour' and '99071-1001') to compare their competitive ability with sowthistle. To validate the CLES model, an experiment was conducted using the same four chickpea cultivars as different treatments with a sowthistle growing under their canopy. The growth of sowthistle, both in silico and in glasshouse experiments, was reduced most by '99071-1001', a cultivar with a short phyllochron. The second rank of competitive ability belonged to 'Macarena' and 'Bumper', while 'Jimbour' was the least competitive cultivar. The architecture of virtual chickpea plants modified the light inside the canopy, which influenced the growth and development of the sowthistle plants in response to different cultivars. This is the first time that a virtual plant model of a crop-weed interaction has been developed. This virtual plant model can serve as a platform for a broad range of applications in the study of chickpea-weed interactions and their environment.

Severe sepsis facilitates intestinal colonization by extended-spectrum-β-lactamase-producing Klebsiella pneumoniae and transfer of the SHV-18 resistance gene to Escherichia coli during antimicrobial treatment.

PubMed

Guan, Jun; Liu, Shaoze; Lin, Zhaofen; Li, Wenfang; Liu, Xuefeng; Chen, Dechang

2014-01-01

Infections caused by multidrug-resistant pathogens are frequent and life threatening in critically ill patients. To investigate whether severe sepsis affects gut colonization by resistant pathogens and genetic exchange between opportunistic pathogens, we tested the intestinal-colonization ability of an extended-spectrum beta-lactamase-producing Klebsiella pneumoniae strain carrying the SHV-18 resistance gene and the transfer ability of the resistance gene to endogenous Escherichia coli under ceftriaxone treatment in rats with burn injury only or severe sepsis induced by burns plus endotoxin exposure. Without ceftriaxone treatment, the K. pneumoniae strain colonized the intestine in both septic and burned rats for a short time, with clearance occurring earlier in burn-only rats but never in sham burn rats. In both burned and septic rats, the colonization level of the challenge strain dropped at the beginning and then later increased during ceftriaxone treatment, after which it declined gradually. This pattern coincided with the change in resistance of K. pneumoniae to ceftriaxone during and after ceftriaxone treatment. Compared with burn-only injury, severe sepsis had a more significant effect on the change in antimicrobial resistance to ceftriaxone. Only in septic rats was the resistance gene successfully transferred from the challenge strain to endogenous E. coli during ceftriaxone treatment; the gene persisted for at least 4 weeks after ceftriaxone treatment. We concluded that severe sepsis can facilitate intestinal colonization by an exogenous resistant pathogen and the transfer of the resistance gene to a potential endogenous pathogen during antimicrobial treatment.

Evolution of the mating system in colonizing plants.

PubMed

Pannell, John R

2015-05-01

Colonization is likely to be more successful for species with an ability to self-fertilize and thus to establish new populations as single individuals. As a result, self-compatibility should be common among colonizing species. This idea, labelled 'Baker's law', has been influential in discussions of sexual-system and mating-system evolution. However, its generality has been questioned, because models of the evolution of dispersal and the mating system predict an association between high dispersal rates and outcrossing rather than selfing, and because of many apparent counter examples to the law. The contrasting predictions made by models invoking Baker's law versus those for the evolution of the mating system and dispersal urges a reassessment of how we should view both these traits. Here, I review the literature on the evolution of mating and dispersal in colonizing species, with a focus on conceptual issues. I argue for the importance of distinguishing between the selfing or outcrossing rate and a simple ability to self-fertilize, as well as for the need for a more nuanced consideration of dispersal. Colonizing species will be characterized by different phases in their life pattern: dispersal to new habitat, implying an ecological sieve on dispersal traits; establishment and a phase of growth following colonization, implying a sieve on reproductive traits; and a phase of demographic stasis at high density, during which new trait associations can evolve through local adaptation. This dynamic means that the sorting of mating-system and dispersal traits should change over time, making simple predictions difficult. © 2015 John Wiley & Sons Ltd.

A greater foraging scale, not a higher foraging precision, may facilitate invasion by exotic plants in nutrient-heterogeneous conditions.

PubMed

Chen, Bao-Ming; Su, Jin-Quan; Liao, Hui-Xuan; Peng, Shao-Lin

2018-03-05

Soil nutrient heterogeneity has been proposed to influence competitive outcomes among different plant species. Thus, it is crucial to understand the effects of environmental heterogeneity on competition between exotic invasive and native species. However, the effects of soil nutrient heterogeneity on the competition between invasive and native plants have rarely been linked to root foraging behaviour. In this study, a competition experiment was performed with two invasive-native species pairs (BP-VC, Bidens pilosa vs. Vernonia cinerea; MM-PS, Mikania micrantha vs. Paederia scandens) grown under homogeneous and heterogeneous conditions in a common greenhouse environment. Root activity was assessed by determining the amount of strontium (Sr) taken up by the shoot of each species. The invasive species exhibited a greater foraging scale, whereas the native species exhibited a higher foraging precision. A trade-off between foraging scale and precision was observed within each pair of invasive-native species. Compared with soil homogeneity, soil heterogeneity significantly increased the biomass of the two invasive species, B. pilosa and M. micrantha, under competitive conditions. Within each pair, the invasive species exhibited greater relative competitive ability with respect to shoot mass, and considerably more Sr taken up by the invasive species compared with the native species. The Sr acquisition results indicate that nutrient-poor conditions may facilitate the competitive ability of the native species V. cinerea, whereas M. micrantha may possess a stronger competitive ability regardless of soil nutrient conditions. Soil nutrient heterogeneity has the potential to promote the invasion of these two exotic species due to their larger foraging scale, stronger competitive ability and greater root activity relative to their counterpart native species. The present work highlights the importance of soil heterogeneity in plant invasion, particularly with regards to root foraging traits and competition between invasive and native plants. © The Author(s) 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Molecular characterization of group A Streptococcus maltodextrin catabolism and its role in pharyngitis

PubMed Central

Shelburne, Samuel A.; Keith, David B.; Davenport, Michael T.; Horstmann, Nicola; Brennan, Richard G.; Musser, James M.

2008-01-01

Summary We previously demonstrated that the cell-surface lipoprotein MalE contributes to GAS maltose/maltodextrin utilization, but MalE inactivation does not completely abrogate GAS catabolism of maltose or maltotriose. Using a genome-wide approach, we identified the GAS phosphotransferase system (PTS) responsible for non-MalE maltose/maltotriose transport. This PTS is encoded by an open reading frame (M5005_spy1692) previously annotated as ptsG based on homology with the glucose PTS in Bacillus subtilis. Genetic inactivation of M5005_spy1692 significantly reduced transport rates of radiolabeled maltose and maltotriose, but not glucose, leading us to propose its reannotation as malT for maltose transporter. The ΔmalT, ΔmalE, and ΔmalE:malT strains were significantly attenuated in their growth in human saliva and in their ability to catabolize α-glucans digested by purified human salivary α-amylase. Compared to wild-type, the three isogenic mutant strains were significantly impaired in their ability to colonize the mouse oropharynx. Finally, we discovered that the transcript levels of maltodextrin utilization genes are regulated by competitive binding of the maltose repressor MalR and catabolite control protein A. These data provide novel insights into regulation of the GAS maltodextrin genes and their role in GAS host-pathogen interaction, thereby increasing the understanding of links between nutrient acquisition and virulence in common human pathogens. PMID:18485073

Hierarchical classification with a competitive evolutionary neural tree.

PubMed

Adams, R G.; Butchart, K; Davey, N

1999-04-01

A new, dynamic, tree structured network, the Competitive Evolutionary Neural Tree (CENT) is introduced. The network is able to provide a hierarchical classification of unlabelled data sets. The main advantage that the CENT offers over other hierarchical competitive networks is its ability to self determine the number, and structure, of the competitive nodes in the network, without the need for externally set parameters. The network produces stable classificatory structures by halting its growth using locally calculated heuristics. The results of network simulations are presented over a range of data sets, including Anderson's IRIS data set. The CENT network demonstrates its ability to produce a representative hierarchical structure to classify a broad range of data sets.

Intrasexual competition enhances reproductive isolation between locally adapted populations

PubMed Central

Arias-Rodriguez, Lenin; Plath, Martin

2018-01-01

Abstract During adaptation to different habitat types, both morphological and behavioral traits can undergo divergent selection. Males often fight for status in dominance hierarchies and rank positions predict reproductive success. Ecotypes with reduced fighting abilities should have low reproductive success when migrating into habitats that harbor ecotypes with superior fighting abilities. Livebearing fishes in the Poecilia mexicana-species complex inhabit not only regular freshwater environments, but also independently colonized sulfidic (H2S-containing) habitats in three river drainages. In the current study, we found fighting intensities in staged contests to be considerably lower in some but not all sulfidic surface ecotypes and the sulfidic cave ecotype compared with populations from non-sulfidic surface sites. This is perhaps due to selection imposed by H2S, which hampers oxygen uptake and transport, as well as cellular respiration. Furthermore, migrants from sulfidic habitats may lose fights even if they do not show overall reduced aggressiveness, as physiological performance is likely to be challenged in the non-sulfidic environment to which they are not adapted. To test this hypothesis, we simulated migration of H2S-adapted males into H2S-free waters, as well as H2S-adapted cave-dwelling males into sulfidic surface waters. We found that intruders established dominance less often than resident males, independent of whether or not they showed reduced aggressiveness overall. Our study shows that divergent evolution of male aggressive behavior may also contribute to the maintenance of genetic differentiation in this system and we call for more careful evaluation of male fighting abilities in studies on ecological speciation. PMID:29492045

Reproductive efficiency and shade avoidance plasticity under simulated competition.

PubMed

Fazlioglu, Fatih; Al-Namazi, Ali; Bonser, Stephen P

2016-07-01

Plant strategy and life-history theories make different predictions about reproductive efficiency under competition. While strategy theory suggests under intense competition iteroparous perennial plants delay reproduction and semelparous annuals reproduce quickly, life-history theory predicts both annual and perennial plants increase resource allocation to reproduction under intense competition. We tested (1) how simulated competition influences reproductive efficiency and competitive ability (CA) of different plant life histories and growth forms; (2) whether life history or growth form is associated with CA; (3) whether shade avoidance plasticity is connected to reproductive efficiency under simulated competition. We examined plastic responses of 11 herbaceous species representing different life histories and growth forms to simulated competition (spectral shade). We found that both annual and perennial plants invested more to reproduction under simulated competition in accordance with life-history theory predictions. There was no significant difference between competitive abilities of different life histories, but across growth forms, erect species expressed greater CA (in terms of leaf number) than other growth forms. We also found that shade avoidance plasticity can increase the reproductive efficiency by capitalizing on the early life resource acquisition and conversion of these resources into reproduction. Therefore, we suggest that a reassessment of the interpretation of shade avoidance plasticity is necessary by revealing its role in reproduction, not only in competition of plants.

Microbial community composition affects soil fungistasis.

PubMed

de Boer, Wietse; Verheggen, Patrick; Klein Gunnewiek, Paulien J A; Kowalchuk, George A; van Veen, Johannes A

2003-02-01

Most soils inhibit fungal germination and growth to a certain extent, a phenomenon known as soil fungistasis. Previous observations have implicated microorganisms as the causal agents of fungistasis, with their action mediated either by available carbon limitation (nutrient deprivation hypothesis) or production of antifungal compounds (antibiosis hypothesis). To obtain evidence for either of these hypotheses, we measured soil respiration and microbial numbers (as indicators of nutrient stress) and bacterial community composition (as an indicator of potential differences in the composition of antifungal components) during the development of fungistasis. This was done for two fungistatic dune soils in which fungistasis was initially fully or partly relieved by partial sterilization treatment or nutrient addition. Fungistasis development was measured as restriction of the ability of the fungi Chaetomium globosum, Fusarium culmorum, Fusarium oxysporum, and Trichoderma harzianum to colonize soils. Fungistasis did not always reappear after soil treatments despite intense competition for carbon, suggesting that microbial community composition is important in the development of fungistasis. Both microbial community analysis and in vitro antagonism tests indicated that the presence of pseudomonads might be essential for the development of fungistasis. Overall, the results lend support to the antibiosis hypothesis.

Co-occurrence of invasive Cuban Treefrogs and native treefrogs in PVC pipe refugia

USGS Publications Warehouse

Elston, Laura M.; Waddle, J. Hardin; Rice, Kenneth G.; Percival, H. Franklin

2013-01-01

The Cuban Treefrog (Osteopilus septentrionalis) was first introduced to Florida at Key West. Since this introduction, Cuban Treefrogs have spread to Miami and are now established throughout most of peninsular Florida. Cuban Treefrogs can become very abundant in areas they colonize. Several reasons contribute to their success, including a generalist diet, high fecundity and the ability to reproduce year-round, and use of disturbed or human-modified habitats. Scientists and managers are concerned that Cuban Treefrogs may contribute to the decline of native treefrogs. Cuban Treefrogs may exclude native treefrogs through both competition and predation. Because the evidence from our study and others suggests that Green and Squirrel Treefrogs do not alter their behavior to avoid Cuban Treefrogs, there is cause for concern that sampling with PVC pipes may increase the vulnerability of the native species to predation. This possibility needs further research, including whether other species of native treefrogs sympatric to where Cuban Treefrogs have invaded are also naïve to the possible threat posed by these frogs, and also if native treefrogs eventually learn to avoid Cuban Treefrogs.

pH feedback and phenotypic diversity within bacterial functional groups of the human gut.

PubMed

Kettle, Helen; Donnelly, Ruairi; Flint, Harry J; Marion, Glenn

2014-02-07

Microbial diversity in the human colon is very high with apparently large functional redundancy such that within each bacterial functional group there are many coexisting strains. Modelling this mathematically is problematic since strains within a functional group are often competing for the same limited number of resources and therefore competitive exclusion theory predicts a loss of diversity over time. Here we investigate, through computer simulation, a fluctuation dependent mechanism for the promotion of diversity. A variable pH environment caused by acidic by-products of bacterial growth on a fluctuating substrate coupled with small differences in acid tolerance between strains promotes diversity under both equilibrium and far-from-equilibrium conditions. Under equilibrium conditions pH fluctuations and relative nonlinearity in pH limitation among strains combine to prevent complete competitive exclusion. Under far-from-equilibrium conditions, loss of diversity through extinctions is made more difficult because pH cycling leads to fluctuations in the competitive ranking of strains, thereby helping to equalise fitness. We assume a trade-off between acid tolerance and maximum growth rate so that our microbial system consists of strains ranging from specialists to generalists. By altering the magnitude of the effect of the system on its pH environment (e.g. the buffering capacity of the colon) and the pattern of incoming resource we explore the conditions that promote diversity. © 2013 Elsevier Ltd. Published by Elsevier Ltd. All rights reserved.

Customizing chemotherapy for colon cancer: the potential of gene expression profiling.

PubMed

Mariadason, John M; Arango, Diego; Augenlicht, Leonard H

2004-06-01

The value of gene expression profiling, or microarray analysis, for the classification and prognosis of multiple forms of cancer is now clearly established. For colon cancer, expression profiling can readily discriminate between normal and tumor tissue, and to some extent between tumors of different histopathological stage and prognosis. While a definitive in vivo study demonstrating the potential of this methodology for predicting response to chemotherapy is presently lacking, the ability of microarrays to distinguish other subtleties of colon cancer phenotype, as well as recent in vitro proof-of-principle experiments utilizing colon cancer cell lines, illustrate the potential of this methodology for predicting the probability of response to specific chemotherapeutic agents. This review discusses some of the recent advances in the use of microarray analysis for understanding and distinguishing colon cancer subtypes, and attempts to identify challenges that need to be overcome in order to achieve the goal of using gene expression profiling for customizing chemotherapy in colon cancer.

Triclosan Promotes Staphylococcus aureus Nasal Colonization

PubMed Central

Syed, Adnan K.; Ghosh, Sudeshna; Love, Nancy G.; Boles, Blaise R.

2014-01-01

ABSTRACT The biocide triclosan is used in many personal care products, including toothpastes, soaps, clothing, and medical equipment. Consequently, it is present as a contaminant in the environment and has been detected in some human fluids, including serum, urine, and milk. Staphylococcus aureus is an opportunistic pathogen that colonizes the noses and throats of approximately 30% of the population. Colonization with S. aureus is known to be a risk factor for several types of infection. Here we demonstrate that triclosan is commonly found in the nasal secretions of healthy adults and the presence of triclosan trends positively with nasal colonization by S. aureus. We demonstrate that triclosan can promote the binding of S. aureus to host proteins such as collagen, fibronectin, and keratin, as well as inanimate surfaces such as plastic and glass. Lastly, triclosan-exposed rats are more susceptible to nasal colonization with S. aureus. These data reveal a novel factor that influences the ability of S. aureus to bind surfaces and alters S. aureus nasal colonization. PMID:24713325

Differential regulation of EGFR-MAPK signaling by deoxycholic acid (DCA) and ursodeoxycholic acid (UDCA) in colon cancer.

PubMed

Centuori, Sara M; Martinez, Jesse D

2014-10-01

A high-fat diet coincides with increased levels of bile acids. This increase in bile acids, particularly deoxycholic acid (DCA), has been strongly associated with the development of colon cancer. Conversely, ursodeoxycholic acid (UDCA) may have chemopreventive properties. Although structurally similar, DCA and UDCA present different biological and pathological effects in colon cancer progression. The differential regulation of cancer by these two bile acids is not yet fully understood. However, one possible explanation for their diverging effects is their ability to differentially regulate signaling pathways involved in the multistep progression of colon cancer, such as the epidermal growth factor receptor (EGFR)-mitogen-activated protein kinase (MAPK) pathway. This review will examine the biological effects of DCA and UDCA on colon cancer development, as well as the diverging effects of these bile acids on the oncogenic signaling pathways that play a role in colon cancer development, with a particular emphasis on bile acid regulation of the EGFR-MAPK pathway.

Differential regulation of EGFR-MAPK signaling by deoxycholic acid (DCA) and ursodeoxycholic acid (UDCA) in colon cancer

PubMed Central

Centuori, Sara M.; Martinez, Jesse D.

2014-01-01

A high fat diet coincides with elevated levels of bile acids. This elevation of bile acids, particularly deoxycholic acid (DCA), has been strongly associated with the development of colon cancer. Conversely, ursodeoxycholic acid (UDCA) may have chemopreventive properties. Although structurally similar, DCA and UDCA present different biological and pathological effects in colon cancer progression. The differential regulation of cancer by these two bile acids is not yet fully understood. However, one possible explanation for their diverging effects is their ability to differentially regulate signaling pathways involved in the multistep progression of colon cancer, such as the epidermal growth factor receptor (EGFR) mitogen-activated protein kinase (MAPK) pathway. This review will examine the biological effects of DCA and UDCA on colon cancer development, as well as the diverging effects of these bile acids on the oncogenic signaling pathways that play a role in colon cancer development, with a particular emphasis on bile acid regulation of the EGFR-MAPK pathway. PMID:25027205

Plasmid-controlled colonization factor associated with virulence in Esherichia coli enterotoxigenic for humans.

PubMed Central

Evans, D G; Silver, R P; Evans, D J; Chase, D G; Gorbach, S L

1975-01-01

An enterotoxin-producing strain of Escherichia coli isolated from a case of cholera-like diarrhea (E. coli strain H-10407) was found to possess a surface-associated colonization factor. Colonization was manifested as the ability of small inocula (10(5) bacteria) to attain large (10(9)) populations in the infant rabbit intestine with a concomitant diarrheal response. A laboratory-passed derivative of E. coli H-10407, designated H-10407-P, failed to exhibit an increase in population in the infant rabbit and also failed to induce diarrhea. Cell-free culture supernatant fluids of E. coli H-10407 and H-10407-P produced equivalent enterotoxic responses in infant and in adult rabbits. Specific anti-colonization factor antiserum was produced by adsorbing hyperimmune anti-H-10407 serum with both heat-killed and living cells E. coli H-10407-P. This specific adsorbed serum protected infant rabbits from challenge with living E. coli H-10407 although the serum did not possess bactericidal activity. The anti-colonization factor serum did not agglutinate a strain of E. coli K-12 possessing the K88 colonization factor peculiar to E. coli enterotoxigenic for swine. By electron microscopy it was demonstrated that E. coli H-10407, but not H10407-, possessed pilus-like surface structures which agglutinated with the specific adsorbed (anti-colonization factor) antiserum. E. coli H-10407 possessed three species of plasmid deoxyribonucleic acid, measuring 60 X 10(6), 42 X 10(6), and 3.7 X 10(6) daltons, respectively. E. coli H-10407-P possessed only the 42 X 10(6)- and the 3.7 X 10(6)-dalton plasmid species. Spontaneous loss of the specific H-10407 surface-associated antigen was accompanied by loss of the 60 X 10(6)-dalton species of plasmid deoxyribonucleic acid and loss of colonizing ability. Thus, it is concluded that the E. coli colonization factor described here is a virulence factor which may play an important and possibly essential role in naturally occurring E. coli enterotoxic diarrhea in man. Images PMID:1100526

Plasmid-controlled colonization factor associated with virulence in Esherichia coli enterotoxigenic for humans.

PubMed

Evans, D G; Silver, R P; Evans, D J; Chase, D G; Gorbach, S L

1975-09-01

An enterotoxin-producing strain of Escherichia coli isolated from a case of cholera-like diarrhea (E. coli strain H-10407) was found to possess a surface-associated colonization factor. Colonization was manifested as the ability of small inocula (10(5) bacteria) to attain large (10(9)) populations in the infant rabbit intestine with a concomitant diarrheal response. A laboratory-passed derivative of E. coli H-10407, designated H-10407-P, failed to exhibit an increase in population in the infant rabbit and also failed to induce diarrhea. Cell-free culture supernatant fluids of E. coli H-10407 and H-10407-P produced equivalent enterotoxic responses in infant and in adult rabbits. Specific anti-colonization factor antiserum was produced by adsorbing hyperimmune anti-H-10407 serum with both heat-killed and living cells E. coli H-10407-P. This specific adsorbed serum protected infant rabbits from challenge with living E. coli H-10407 although the serum did not possess bactericidal activity. The anti-colonization factor serum did not agglutinate a strain of E. coli K-12 possessing the K88 colonization factor peculiar to E. coli enterotoxigenic for swine. By electron microscopy it was demonstrated that E. coli H-10407, but not H10407-, possessed pilus-like surface structures which agglutinated with the specific adsorbed (anti-colonization factor) antiserum. E. coli H-10407 possessed three species of plasmid deoxyribonucleic acid, measuring 60 X 10(6), 42 X 10(6), and 3.7 X 10(6) daltons, respectively. E. coli H-10407-P possessed only the 42 X 10(6)- and the 3.7 X 10(6)-dalton plasmid species. Spontaneous loss of the specific H-10407 surface-associated antigen was accompanied by loss of the 60 X 10(6)-dalton species of plasmid deoxyribonucleic acid and loss of colonizing ability. Thus, it is concluded that the E. coli colonization factor described here is a virulence factor which may play an important and possibly essential role in naturally occurring E. coli enterotoxic diarrhea in man.

Bacillus spore-based oral carriers loading curcumin for the therapy of colon cancer.

PubMed

Yin, Liang; Meng, Zhan; Zhang, Yuxiao; Hu, Kaikai; Chen, Wuya; Han, Kaibin; Wu, Bao-Yan; You, Rong; Li, Chu-Hua; Jin, Ying; Guan, Yan-Qing

2018-02-10

Oral drug delivery has attracted substantial attention due to its advantages over other administration routes. Bacillus spores, as oral probiotic agents, are applied widely. In this paper, a novel Bacillus spore-based oral colon targeted carrier loading curcumin was developed for colon cancer treatment. Curcumin was linked covalently with the outer coat of Bacillus spore and folate, respectively (SPORE-CUR-FA). Bacillus spores are capable of delivering drugs to the colon area through gastric barrier, taking the advantage of its tolerance to the harsh conditions and disintegration of the outer coat of spores after germination in the colon. The drug release in vitro and in vivo of SPORE-CUR-FA was investigated. Results showed that SPORE-CUR-FA had the characteristics of colon-targeted drug release. Pharmacokinetic studies confirmed that Bacillus spore-based carriers could efficiently improve the oral bioavailability of curcumin. In vitro and in vivo anti-tumor studies showed that SPORE-CUR-FA had substantial ability for inhibiting colon cancer cells. These findings suggest that this Bacillus spore-based oral drug delivery system has a great potential for the treatment of colon cancer. Copyright © 2017 Elsevier B.V. All rights reserved.

Electronic Commerce and Competitive Procurement

DTIC Science & Technology

1991-06-01

electronic commerce techniques ( electronic Jata interchange (EDI). electronic mail ( E -mail), electronic bulletin boards and facsimile] to competitive ...The ability to conduct discussions and negotiations with offerors electronically by E -mail supports the competitive proposal solicitation method...software vendors understand the dimensions of the DoD electronic commerce market , they may through competitive forces provide EDI capability. If their

76 FR 37191 - Notice of Competition for University Transportation Centers (UTC) Program Grants

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-24

... Competition for University Transportation Centers (UTC) Program Grants AGENCY: Research and Innovative... conduct a competition for University Transportation Centers (UTC) Program grants for the purpose of... of demonstrated ability, research, technology and education resources, leadership, multi-modal...

Online resources for the identification of North American wood decay fungi

Treesearch

Jessie A. Glaeser

2012-01-01

The ability to identify wood decay fungi is an important skill for an arborist. Knowing which fungus is colonizing a tree can be used to better assess the type, amount, and position of decay in the tree, and its subsequent effects on wood strength. Distinguishing species of fungi that colonize sapwood, heartwood, or roots can provide information to improve the quality...

Impact of Diversity of Colonizing Strains on Strategies for Sampling Escherichia coli from Fecal Specimens ▿

PubMed Central

Lautenbach, Ebbing; Bilker, Warren B.; Tolomeo, Pam; Maslow, Joel N.

2008-01-01

Of 49 subjects, 21 were colonized with more than one strain of Escherichia coli and 12 subjects had at least one strain present in fewer than 20% of colonies. The ability to accurately characterize E. coli strain diversity is directly related to the number of colonies sampled and the underlying prevalence of the strain. PMID:18650357

Growth and intraspecific competitive abilities of the dioecious Lindera melissifolia (Lauraceae) in varied flooding regimes

Treesearch

Tracy S. Hawkins; Nathan M. Schiff; Theodor D. Leininger; Emile S Gardiner; Margaret S. Devall; Paul B. Hamel; A. Dan Wilson; Kristina F. Connor

2009-01-01

Forest Service, Southern Research Station, Stoneville, MS 38776). Growth and intraspecific competitive abilities of the dioecious Lindera melissifolia (Lauraceae) in varied flooding regimes. J. Torrey Bot. Soc. 136: 91–101. 2009.—The contribution of sexual dimorphism to malebiased colony ratios observed in field populations of the federally...

University Rankings in Action? The Importance of Rankings and an Excellence Competition for University Choice of High-Ability Students

ERIC Educational Resources Information Center

Horstschraer, Julia

2012-01-01

This paper analyzes how high-ability students respond to different indicators of university quality when applying for a university. Are prospective students influenced by quality indicators of a university ranking or by an excellence status awarded within a nationwide competition? And if so, are some quality dimensions, e.g. research reputation,…

Oral administration of a recombinant cholera toxin B subunit promotes mucosal healing in the colon.

PubMed

Baldauf, K J; Royal, J M; Kouokam, J C; Haribabu, B; Jala, V R; Yaddanapudi, K; Hamorsky, K T; Dryden, G W; Matoba, N

2017-07-01

Cholera toxin B subunit (CTB) is a component of a licensed oral cholera vaccine. However, CTB has pleiotropic immunomodulatory effects whose impacts on the gut are not fully understood. Here, we found that oral administration in mice of a plant-made recombinant CTB (CTBp) significantly increased several immune cell populations in the colon lamina propria. Global gene expression analysis revealed that CTBp had more pronounced impacts on the colon than the small intestine, with significant activation of TGFβ-mediated pathways in the colon epithelium. The clinical relevance of CTBp-induced impacts on colonic mucosa was examined. In a human colon epithelial model using Caco2 cells, CTBp, but not the non-GM1-binding mutant G33D-CTBp, induced TGFβ-mediated wound healing. In a dextran sodium sulfate (DSS) acute colitis mouse model, oral administration of CTBp protected against colon mucosal damage as manifested by mitigated body weight loss, decreased histopathological scores, and blunted escalation of inflammatory cytokine levels while inducing wound healing-related genes. Furthermore, biweekly oral administration of CTBp significantly reduced disease severity and tumorigenesis in the azoxymethane/DSS model of ulcerative colitis and colon cancer. Altogether, these results demonstrate CTBp's ability to enhance mucosal healing in the colon, highlighting its potential application in ulcerative colitis therapy besides cholera vaccination.

Induction of KIAA1199/CEMIP is associated with colon cancer phenotype and poor patient survival

PubMed Central

Fink, Stephen P.; Myeroff, Lois L.; Kariv, Revital; Platzer, Petra; Xin, Baozhong; Mikkola, Debra; Lawrence, Earl; Morris, Nathan; Nosrati, Arman; Willson, James K. V.; Willis, Joseph; Veigl, Martina; Barnholtz-Sloan, Jill S.; Wang, Zhenghe; Markowitz, Sanford D.

2015-01-01

Genes induced in colon cancer provide novel candidate biomarkers of tumor phenotype and aggressiveness. We originally identified KIAA1199 (now officially called CEMIP) as a transcript highly induced in colon cancer: initially designating the transcript as Colon Cancer Secreted Protein 1. We molecularly characterized CEMIP expression both at the mRNA and protein level and found it is a secreted protein induced an average of 54-fold in colon cancer. Knockout of CEMIPreduced the ability of human colon cancer cells to form xenograft tumors in athymic mice. Tumors that did grow had increased deposition of hyaluronan, linking CEMIP participation in hyaluronan degradation to the modulation of tumor phenotype. We find CEMIP mRNA overexpression correlates with poorer patient survival. In stage III only (n = 31) or in combined stage II plus stage III colon cancer cases (n = 73), 5-year overall survival was significantly better (p = 0.004 and p = 0.0003, respectively) among patients with low CEMIP expressing tumors than those with high CEMIP expressing tumors. These results demonstrate that CEMIP directly facilitates colon tumor growth, and high CEMIP expression correlates with poor outcome in stage III and in stages II+III combined cohorts. We present CEMIP as a candidate prognostic marker for colon cancer and a potential therapeutic target. PMID:26437221

Novel weapons and invasion: biogeographic differences in the competitive effects of Centaurea maculosa and its root exudate (+/-)-catechin.

PubMed

He, Wei-Ming; Feng, Yulong; Ridenour, Wendy M; Thelen, Giles C; Pollock, Jarrod L; Diaconu, Alecu; Callaway, Ragan M

2009-04-01

Recent studies suggest that the invasive success of Centaurea maculosa may be related to its stronger allelopathic effects on native North American species than on related European species, one component of the "novel weapons" hypothesis. Other research indicates that C. maculosa plants from the invasive range in North America have evolved to be larger and better competitors than conspecifics from the native range in Europe, a component of the "evolution of increased competitive ability" hypothesis. These hypotheses are not mutually exclusive, but this evidence sets the stage for comparing the relative importance of evolved competitive ability to inherent competitive traits. In a competition experiment with a large number of C. maculosa populations, we found no difference in the competitive effects of C. maculosa plants from North America and Europe on other species. However, both North American and European C. maculosa were much better competitors against plants native to North America than congeners native to Romania, collected in areas where C. maculosa is also native. These results are consistent with the novel weapons hypothesis. But, in a second experiment using just one population from North America and Europe, and where North American and European species were collected from a broader range of sites, competitive interactions were weaker overall, and the competitive effects of C. maculosa were slightly stronger against European species than against North American species. Also consistent with the novel weapons hypothesis, (+/-)-catechin had stronger effects on native North American species than on native European species in two experiments. Our results suggest that the regional composition of the plant communities being invaded by C. maculosa may be more important for invasive success than the evolution of increased size and competitive ability.

Apparent plasticity in functional traits determining competitive ability and spatial distribution: a case from desert.

PubMed

Xie, Jiang-Bo; Xu, Gui-Qing; Jenerette, G Darrel; Bai, Yong-fei; Wang, Zhong-Yuan; Li, Yan

2015-07-20

Species competitive abilities and their distributions are closely related to functional traits such as biomass allocation patterns. When we consider how nutrient supply affects competitive abilities, quantifying the apparent and true plasticity in functional traits is important because the allometric relationships among traits are universal in plants. We propose to integrate the notion of allometry and the classical reaction norm into a composite theoretical framework that quantifies the apparent and true plasticity. Combining the framework with a meta-analysis, a series of field surveys and a competition experiment, we aimed to determine the causes of the dune/interdune distribution patterns of two Haloxylon species in the Gurbantonggut Desert. We found that (1) the biomass allocation patterns of both Haloxylon species in responses to environmental conditions were apparent rather than true plasticity and (2) the allometric allocation patterns affected the plants' competition for soil nutrient supply. A key implication of our results is that the apparent plasticity in functional traits of plants determines their response to environmental change. Without identifying the apparent and true plasticity, we would substantially overestimate the magnitude, duration and even the direction of plant responses in functional traits to climate change.

Apparent plasticity in functional traits determining competitive ability and spatial distribution: a case from desert

PubMed Central

Xie, Jiang-Bo; Xu, Gui-Qing; Jenerette, G. Darrel; Bai, Yong-fei; Wang, Zhong-Yuan; Li, Yan

2015-01-01

Species competitive abilities and their distributions are closely related to functional traits such as biomass allocation patterns. When we consider how nutrient supply affects competitive abilities, quantifying the apparent and true plasticity in functional traits is important because the allometric relationships among traits are universal in plants. We propose to integrate the notion of allometry and the classical reaction norm into a composite theoretical framework that quantifies the apparent and true plasticity. Combining the framework with a meta-analysis, a series of field surveys and a competition experiment, we aimed to determine the causes of the dune/interdune distribution patterns of two Haloxylon species in the Gurbantonggut Desert. We found that (1) the biomass allocation patterns of both Haloxylon species in responses to environmental conditions were apparent rather than true plasticity and (2) the allometric allocation patterns affected the plants’ competition for soil nutrient supply. A key implication of our results is that the apparent plasticity in functional traits of plants determines their response to environmental change. Without identifying the apparent and true plasticity, we would substantially overestimate the magnitude, duration and even the direction of plant responses in functional traits to climate change. PMID:26190745

Predicting coexistence of plants subject to a tolerance-competition trade-off.

PubMed

Haegeman, Bart; Sari, Tewfik; Etienne, Rampal S

2014-06-01

Ecological trade-offs between species are often invoked to explain species coexistence in ecological communities. However, few mathematical models have been proposed for which coexistence conditions can be characterized explicitly in terms of a trade-off. Here we present a model of a plant community which allows such a characterization. In the model plant species compete for sites where each site has a fixed stress condition. Species differ both in stress tolerance and competitive ability. Stress tolerance is quantified as the fraction of sites with stress conditions low enough to allow establishment. Competitive ability is quantified as the propensity to win the competition for empty sites. We derive the deterministic, discrete-time dynamical system for the species abundances. We prove the conditions under which plant species can coexist in a stable equilibrium. We show that the coexistence conditions can be characterized graphically, clearly illustrating the trade-off between stress tolerance and competitive ability. We compare our model with a recently proposed, continuous-time dynamical system for a tolerance-fecundity trade-off in plant communities, and we show that this model is a special case of the continuous-time version of our model.

Diversity begets diversity in competition for space

Treesearch

Daniel S. Maynard; Mark A. Bradford; Daniel L. Lindner; Linda T. A. van Diepen; Serita D. Frey; Jessie A. Glaeser; Thomas W. Crowther

2017-01-01

Competition can profoundly affect biodiversity patterns by determining whether similar species are likely to coexist. When species compete directly for space, competitive ability differences should theoretically promote trait and phylogenetic clustering, provided that niche differences are otherwise minimal. Yet many sessile communities exhibit high biodiversity...

Competitive interactions between forest trees are driven by species' trait hierarchy, not phylogenetic or functional similarity: implications for forest community assembly.

PubMed

Kunstler, Georges; Lavergne, Sébastien; Courbaud, Benoît; Thuiller, Wilfried; Vieilledent, Ghislain; Zimmermann, Niklaus E; Kattge, Jens; Coomes, David A

2012-08-01

The relative importance of competition vs. environmental filtering in the assembly of communities is commonly inferred from their functional and phylogenetic structure, on the grounds that similar species compete most strongly for resources and are therefore less likely to coexist locally. This approach ignores the possibility that competitive effects can be determined by relative positions of species on a hierarchy of competitive ability. Using growth data, we estimated 275 interaction coefficients between tree species in the French mountains. We show that interaction strengths are mainly driven by trait hierarchy and not by functional or phylogenetic similarity. On the basis of this result, we thus propose that functional and phylogenetic convergence in local tree community might be due to competition-sorting species with different competitive abilities and not only environmental filtering as commonly assumed. We then show a functional and phylogenetic convergence of forest structure with increasing plot age, which supports this view. © 2012 Blackwell Publishing Ltd/CNRS.

Quantitative measurement of feline colonic transit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krevsky, B.; Somers, M.B.; Maurer, A.H.

1988-10-01

Colonic transit scintigraphy, a method for quantitatively evaluating the movement of the fecal stream in vivo, was employed to evaluate colonic transit in the cat. Scintigraphy was performed in duplicate in five cats and repeated four times in one cat. After instillation of an 111In marker into the cecum through a surgically implanted silicone cecostomy tube, colonic movement of the instillate was quantitated for 24 h using gamma scintigraphy. Antegrade and retrograde motion of radionuclide was observed. The cecum and ascending colon emptied rapidly, with a half-emptying time of 1.68 +/- 0.56 h (mean +/- SE). After 24 h, 25.1more » +/- 5.2% of the activity remained in the transverse colon. The progression of the geometric center was initially rapid, followed later by a delayed phase. Geometric center reproducibility was found to be high when analyzed using simple linear regression (slope = 0.92; r = 0.73; P less than 0.01). Atropine (0.1 mg/kg im) was found to delay cecum and ascending colon emptying and delay progression of the geometric center. These results demonstrate both 1) the ability of colonic transit scintigraphy to detect changes in transit induced by pharmacological manipulation and 2) the fact that muscarinic blockade inhibits antegrade transit of the fecal stream. We conclude that feline colonic transit may be studied in a quantitative and reproducible manner with colonic transit scintigraphy.« less

Salmonella enterica Serovar Typhimurium Exploits Inflammation to Compete with the Intestinal Microbiota

PubMed Central

Stecher, Bärbel; Westendorf, Astrid M; Barthel, Manja; Kremer, Marcus; Chaffron, Samuel; Macpherson, Andrew J; Buer, Jan; Parkhill, Julian; Dougan, Gordon; von Mering, Christian; Hardt, Wolf-Dietrich

2007-01-01

Most mucosal surfaces of the mammalian body are colonized by microbial communities (“microbiota”). A high density of commensal microbiota inhabits the intestine and shields from infection (“colonization resistance”). The virulence strategies allowing enteropathogenic bacteria to successfully compete with the microbiota and overcome colonization resistance are poorly understood. Here, we investigated manipulation of the intestinal microbiota by the enteropathogenic bacterium Salmonella enterica subspecies 1 serovar Typhimurium (S. Tm) in a mouse colitis model: we found that inflammatory host responses induced by S. Tm changed microbiota composition and suppressed its growth. In contrast to wild-type S. Tm, an avirulent invGsseD mutant failing to trigger colitis was outcompeted by the microbiota. This competitive defect was reverted if inflammation was provided concomitantly by mixed infection with wild-type S. Tm or in mice (IL10−/−, VILLIN-HACL4-CD8) with inflammatory bowel disease. Thus, inflammation is necessary and sufficient for overcoming colonization resistance. This reveals a new concept in infectious disease: in contrast to current thinking, inflammation is not always detrimental for the pathogen. Triggering the host's immune defence can shift the balance between the protective microbiota and the pathogen in favour of the pathogen. PMID:17760501

Genes Contributing to Porphyromonas gingivalis Fitness in Abscess and Epithelial Cell Colonization Environments.

PubMed

Miller, Daniel P; Hutcherson, Justin A; Wang, Yan; Nowakowska, Zuzanna M; Potempa, Jan; Yoder-Himes, Deborah R; Scott, David A; Whiteley, Marvin; Lamont, Richard J

2017-01-01

Porphyromonas gingivalis is an important cause of serious periodontal diseases, and is emerging as a pathogen in several systemic conditions including some forms of cancer. Initial colonization by P. gingivalis involves interaction with gingival epithelial cells, and the organism can also access host tissues and spread haematogenously. To better understand the mechanisms underlying these properties, we utilized a highly saturated transposon insertion library of P. gingivalis , and assessed the fitness of mutants during epithelial cell colonization and survival in a murine abscess model by high-throughput sequencing (Tn-Seq). Transposon insertions in many genes previously suspected as contributing to virulence showed significant fitness defects in both screening assays. In addition, a number of genes not previously associated with P. gingivalis virulence were identified as important for fitness. We further examined fitness defects of four such genes by generating defined mutations. Genes encoding a carbamoyl phosphate synthetase, a replication-associated recombination protein, a nitrosative stress responsive HcpR transcription regulator, and RNase Z, a zinc phosphodiesterase, showed a fitness phenotype in epithelial cell colonization and in a competitive abscess infection. This study verifies the importance of several well-characterized putative virulence factors of P. gingivalis and identifies novel fitness determinants of the organism.

Plant Size and Competitive Dynamics along Nutrient Gradients.

PubMed

Goldberg, Deborah E; Martina, Jason P; Elgersma, Kenneth J; Currie, William S

2017-08-01

Resource competition theory in plants has focused largely on resource acquisition traits that are independent of size, such as traits of individual leaves or roots or proportional allocation to different functions. However, plants also differ in maximum potential size, which could outweigh differences in module-level traits. We used a community ecosystem model called mondrian to investigate whether larger size inevitably increases competitive ability and how size interacts with nitrogen supply. Contrary to the conventional wisdom that bigger is better, we found that invader success and competitive ability are unimodal functions of maximum potential size, such that plants that are too large (or too small) are disproportionately suppressed by competition. Optimal size increases with nitrogen supply, even when plants compete for nitrogen only in a size-symmetric manner, although adding size-asymmetric competition for light does substantially increase the advantage of larger size at high nitrogen. These complex interactions of plant size and nitrogen supply lead to strong nonlinearities such that small differences in nitrogen can result in large differences in plant invasion success and the influence of competition along productivity gradients.

Inter-specific competition: Spartina alterniflora is replacing Spartina anglica in coastal China

NASA Astrophysics Data System (ADS)

Zhi, Yingbiao; Li, Hongli; An, Shuqing; Zhao, Lei; Zhou, Changfang; Deng, Zifa

2007-09-01

Spartina anglica C. E Hubbard, an invasive species world wide, underwent rapid invasion before the 1990s and followed by a drastic decline in costal China since its first introduction from Europe in 1963. It was hypothesized that the competition with Spartina alterniflora Loisel., introduced into China in 1979, might play an important role in this decline due to their overlapping niche existed in the field. In this paper, we evaluated relative competitive ability using the Relative Neighbour Effect (RNE) index and the growth responses of the two species under both independent and mixed planting experiments. Several performance indices, including culm height, as well as above-ground, below-ground and spike biomass, were significantly higher in S. alterniflora than S. anglica. The relative inter-specific competitive ability of S. alterniflora was significantly greater than that of S. anglica and S. alterniflora exerted an asymmetric, competitive dominance over S. anglica. The competition remarkably reduced several performance parameters in S. anglica including: above-ground biomass, culm height, stalk diameter, number of leaves, number of roots, max root length, leaf area, leaf thickness; numbers of ramets, rhizomes, internodes of total rhizomes, vegetative tillers (and consequently total tillers), and total length of rhizomes. This substantial growth advantage of S. alterniflora might explain its greater inter-specific competitive ability, and suggests a mechanism by which S. alterniflora has been able to replace S. anglica and quickly invade the natural salt marsh communities of coastal China.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dufour, Marc, E-mail: Marc.dufour@chuv.ch; Faes, Seraina, E-mail: Seraina.faes@chuv.ch; Dormond-Meuwly, Anne, E-mail: Anne.meuwly-Dormond@chuv.ch

Highlights: • PGE{sub 2} activates mTORC1 in colon cancer cells. • Inhibition of mTORC1 blocks PGE{sub 2} induced colon cancer cell growth. • mTORC1 is a signaling intermediary in PGE{sub 2} induced colon cancer cell responses. - Abstract: The inflammatory prostaglandin E{sub 2} (PGE{sub 2}) cytokine plays a key role in the development of colon cancer. Several studies have shown that PGE{sub 2} directly induces the growth of colon cancer cells and furthermore promotes tumor angiogenesis by increasing the production of the vascular endothelial growth factor (VEGF). The signaling intermediaries implicated in these processes have however not been fully characterized.more » In this report, we show that the mechanistic target of rapamycin complex 1 (mTORC1) plays an important role in PGE{sub 2}-induced colon cancer cell responses. Indeed, stimulation of LS174T cells with PGE{sub 2} increased mTORC1 activity as observed by the augmentation of S6 ribosomal protein phosphorylation, a downstream effector of mTORC1. The PGE{sub 2} EP{sub 4} receptor was responsible for transducing the signal to mTORC1. Moreover, PGE{sub 2} increased colon cancer cell proliferation as well as the growth of colon cancer cell colonies grown in matrigel and blocking mTORC1 by rapamycin or ATP-competitive inhibitors of mTOR abrogated these effects. Similarly, the inhibition of mTORC1 by downregulation of its component raptor using RNA interference blocked PGE{sub 2}-induced LS174T cell growth. Finally, stimulation of LS174T cells with PGE{sub 2} increased VEGF production which was also prevented by mTORC1 inhibition. Taken together, these results show that mTORC1 is an important signaling intermediary in PGE{sub 2} mediated colon cancer cell growth and VEGF production. They further support a role for mTORC1 in inflammation induced tumor growth.« less

Virulence and competitive ability in genetically diverse malaria infections

PubMed Central

de Roode, Jacobus C.; Pansini, Riccardo; Cheesman, Sandra J.; Helinski, Michelle E. H.; Huijben, Silvie; Wargo, Andrew R.; Bell, Andrew S.; Chan, Brian H. K.; Walliker, David; Read, Andrew F.

2005-01-01

Explaining parasite virulence is a great challenge for evolutionary biology. Intuitively, parasites that depend on their hosts for their survival should be benign to their hosts, yet many parasites cause harm. One explanation for this is that within-host competition favors virulence, with more virulent strains having a competitive advantage in genetically diverse infections. This idea, which is well supported in theory, remains untested empirically. Here we provide evidence that within-host competition does indeed select for high parasite virulence. We examine the rodent malaria Plasmodium chabaudi in laboratory mice, a parasite–host system in which virulence can be easily monitored and competing strains quantified by using strain-specific real-time PCR. As predicted, we found a strong relationship between parasite virulence and competitive ability, so that more virulent strains have a competitive advantage in mixed-strain infections. In transmission experiments, we found that the strain composition of the parasite populations in mosquitoes was directly correlated with the composition of the blood-stage parasite population. Thus, the outcome of within-host competition determined relative transmission success. Our results imply that within-host competition is a major factor driving the evolution of virulence and can explain why many parasites harm their hosts. PMID:15894623

Growth and Competitive Effects of Centaurea stoebe Populations in Response to Simulated Nitrogen Deposition

PubMed Central

He, Wei-Ming; Montesinos, Daniel; Thelen, Giles C.; Callaway, Ragan M.

2012-01-01

Increased resource availability can promote invasion by exotic plants, raising concerns over the potential effects of global increases in the deposition of nitrogen (N). It is poorly understood why increased N favors exotics over natives. Fast growth may be a general trait of good invaders and these species may have exceptional abilities to increase growth rates in response to N deposition. Additionally, invaders commonly displace locals, and thus may have inherently greater competitive abilities. The mean growth response of Centaurea stoebe to two N levels was significantly greater than that of North American (NA) species. Growth responses to N did not vary among C. stoebe populations or NA species. Without supplemental N, NA species were better competitors than C. stoebe, and C. stoebe populations varied in competitive effects. The competitive effects of C. stoebe populations increased with N whereas the competitive effects of NA species decreased, eliminating the overall competitive advantage demonstrated by NA species in soil without N added. These results suggest that simulated N deposition may enhance C. stoebe invasion through increasing its growth and relative competitive advantage, and also indicate the possibility of local adaptation in competitive effects across the introduced range of an invader. PMID:22563451

Growth and competitive effects of Centaurea stoebe populations in response to simulated nitrogen deposition.

PubMed

He, Wei-Ming; Montesinos, Daniel; Thelen, Giles C; Callaway, Ragan M

2012-01-01

Increased resource availability can promote invasion by exotic plants, raising concerns over the potential effects of global increases in the deposition of nitrogen (N). It is poorly understood why increased N favors exotics over natives. Fast growth may be a general trait of good invaders and these species may have exceptional abilities to increase growth rates in response to N deposition. Additionally, invaders commonly displace locals, and thus may have inherently greater competitive abilities. The mean growth response of Centaurea stoebe to two N levels was significantly greater than that of North American (NA) species. Growth responses to N did not vary among C. stoebe populations or NA species. Without supplemental N, NA species were better competitors than C. stoebe, and C. stoebe populations varied in competitive effects. The competitive effects of C. stoebe populations increased with N whereas the competitive effects of NA species decreased, eliminating the overall competitive advantage demonstrated by NA species in soil without N added. These results suggest that simulated N deposition may enhance C. stoebe invasion through increasing its growth and relative competitive advantage, and also indicate the possibility of local adaptation in competitive effects across the introduced range of an invader.

Grazer-induced morphological defense in Scenedesmus obliquus is affected by competition against Microcystis aeruginosa

PubMed Central

Zhu, Xuexia; Wang, Jun; Lu, Yichun; Chen, Qinwen; Yang, Zhou

2015-01-01

The green alga Scenedesmus is known for its phenotypic plasticity in response to grazing risk. However, the benefits of colony formation induced by infochemicals from zooplankton should come with costs. That is, a tradeoff in benefit-to-cost ratios is likely under complex environmental conditions. In this study, we hypothesized that the coexistence of Scenedesmus and its competitors decreases the formation of anti-grazer colonies in Scenedesmus. Results demonstrated that the presence of a competitor Microcystis aeruginosa inhibited inducible defensive colony formation of Scenedesmus obliquus, and the established defensive colonies negatively affected the competitive ability of S. obliquus. The proportion of induced defensive colonies in cultures was dependent on the relative abundance of competitors. Under low competition intensity, large amount of eight-celled colonies were formed but at the cost of decreased competitive inhibition on M. aeruginosa. By contrast, defensive colony formation of S. obliquus slacked in the presence of high competition intensity to maintain a high displacement rate (competitive ability). In conclusion, S. obliquus exhibited different responses to potential grazing pressure under different intensities of competition, i.e., Scenedesmus morphological response to grazing infochemicals was affected by competition against Microcystis. PMID:26224387

Grazer-induced morphological defense in Scenedesmus obliquus is affected by competition against Microcystis aeruginosa.

PubMed

Zhu, Xuexia; Wang, Jun; Lu, Yichun; Chen, Qinwen; Yang, Zhou

2015-07-30

The green alga Scenedesmus is known for its phenotypic plasticity in response to grazing risk. However, the benefits of colony formation induced by infochemicals from zooplankton should come with costs. That is, a tradeoff in benefit-to-cost ratios is likely under complex environmental conditions. In this study, we hypothesized that the coexistence of Scenedesmus and its competitors decreases the formation of anti-grazer colonies in Scenedesmus. Results demonstrated that the presence of a competitor Microcystis aeruginosa inhibited inducible defensive colony formation of Scenedesmus obliquus, and the established defensive colonies negatively affected the competitive ability of S. obliquus. The proportion of induced defensive colonies in cultures was dependent on the relative abundance of competitors. Under low competition intensity, large amount of eight-celled colonies were formed but at the cost of decreased competitive inhibition on M. aeruginosa. By contrast, defensive colony formation of S. obliquus slacked in the presence of high competition intensity to maintain a high displacement rate (competitive ability). In conclusion, S. obliquus exhibited different responses to potential grazing pressure under different intensities of competition, i.e., Scenedesmus morphological response to grazing infochemicals was affected by competition against Microcystis.

Development of the initial diatom microfouling layer on antifouling and fouling-release surfaces in temperate and tropical Australia.

PubMed

Molino, Paul J; Campbell, Ewan; Wetherbee, Richard

2009-11-01

Diatoms are a major component of the slime layers that form on artificial surfaces in marine environments. In this article, the role played by diatoms during the pioneering stages of colonization of three marine antifouling (AF) coatings, viz Intersmooth 360, Super Yacht 800 and a fouling-release (FR) coating Intersleek 700, was investigated. The study was conducted over three distinct seasons in two very different marine environments in Australia, ie temperate Williamstown, Victoria and tropical Cairns, Queensland. Diatom fouling occurred more rapidly on the FR coating Intersleek 700, compared to both biocidal AF paints. However, colonization by diatoms on all three coatings was generally slow during the 16-day study. Benthic diatoms do not subsist by floating around in the water column, rather they only gain the opportunity to colonize new surfaces when they either voluntarily release or are displaced from their benthic habitat, thereafter entering the water column where the opportunity to adhere to a new surface presents itself. However, once settled, fouling diatoms grow exponentially from the site of attachment, spreading out until they populate large areas of the surface. This mode of surface colonization correlates more with an 'infection' type, epidemiology model, a mechanism that accounts for the colonization of significant regions of the coating surface from a single fouling diatom cell, forming 'clonal patches'. This is in comparison to the bacterial colonization of the surface, which exhibits far more rapid recruitment and growth of cells on the substratum surface. Therefore, it is hypothesized that fouling diatoms may be characterized more by their ability to adhere and grow on surfaces already modified by bacterial biofilms, rather than on their strength of adhesion. Cell morphology and the ability to avoid shear may also be an important factor.

The Effects of Peer Competition-Based Science Learning Game on Secondary Students' Performance, Achievement Goals, and Perceived Ability

ERIC Educational Resources Information Center

Chen, Ching-Huei; Law, Victor; Chen, Wei-Yu

2018-01-01

The purpose of this study is to examine the effects of different modes of competition on science learning in a game-based learning (GBL) environment. Some key motivational constructs such as learning goals, performance goals, and perceived ability were also investigated. One hundred ninety-five students from a secondary school in Taiwan were…

Real-Time Tracking of Motor Response Activation and Response Competition in a Stroop Task in Young Children: A Lateralized Readiness Potential Study

ERIC Educational Resources Information Center

Szucs, Denes; Soltesz, Fruzsina; Bryce, Donna; Whitebread, David

2009-01-01

The ability to select an appropriate motor response by resolving competition among alternative responses plays a major role in cognitive performance. fMRI studies suggest that the development of this skill is related to the maturation of the frontal cortex that underlies the improvement of motor inhibition abilities. However, fMRI cannot…

Consequences of pre-inoculation with native arbuscular mycorrhizae on root colonization and survival of Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush) seedlings after transplanting

Treesearch

Bill Eugene Davidson

2015-01-01

Inoculation of seedlings with arbuscular mycorrhizal fungi (AMF) is a common practice aimed at improving seedling establishment. The success of this practice largely depends on the ability of the inoculum to multiply and colonize the growing root system after transplanting. These events were investigated in Artemisia tridentata ssp. wyomingensis (Wyoming big sagebrush...

Free radical scavenging and COX-2 inhibition by simple colon metabolites of polyphenols: A theoretical approach.

PubMed

Amić, Ana; Marković, Zoran; Marković, Jasmina M Dimitrić; Jeremić, Svetlana; Lučić, Bono; Amić, Dragan

2016-12-01

Free radical scavenging and inhibitory potency against cyclooxygenase-2 (COX-2) by two abundant colon metabolites of polyphenols, i.e., 3-hydroxyphenylacetic acid (3-HPAA) and 4-hydroxyphenylpropionic acid (4-HPPA) were theoretically studied. Different free radical scavenging mechanisms are investigated in water and pentyl ethanoate as a solvent. By considering electronic properties of scavenged free radicals, hydrogen atom transfer (HAT) and sequential proton loss electron transfer (SPLET) mechanisms are found to be thermodynamically probable and competitive processes in both media. The Gibbs free energy change for reaction of inactivation of free radicals indicates 3-HPAA and 4-HPPA as potent scavengers. Their reactivity toward free radicals was predicted to decrease as follows: hydroxyl>alkoxyls>phenoxyl≈peroxyls>superoxide. Shown free radical scavenging potency of 3-HPAA and 4-HPPA along with their high μM concentration produced by microbial colon degradation of polyphenols could enable at least in situ inactivation of free radicals. Docking analysis with structural forms of 3-HPAA and 4-HPPA indicates dianionic ligands as potent inhibitors of COX-2, an inducible enzyme involved in colon carcinogenesis. Obtained results suggest that suppressing levels of free radicals and COX-2 could be achieved by 3-HPAA and 4-HPPA indicating that these compounds may contribute to reduced risk of colon cancer development. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interactions between abundant fungal species influence the fungal community assemblage on limestone

PubMed Central

Morón-Ríos, Alejandro; Ortega-Morales, Benjamin Otto; De la Rosa-García, Susana; Partida-Martínez, Laila Pamela; Quintana, Patricia; Alayón-Gamboa, José Armando; Cappello-García, Silvia; González-Gómez, Santiago

2017-01-01

The assembly of fungal communities on stone materials is mainly influenced by the differential bioreceptivity of such materials and environmental conditions. However, little is known about the role of fungal interactions in the colonization and establishment of fungal species. We analyzed the effects of intra- and interspecific interactions between 11 species of fungi in oligotrophic and copiotrophic media and on limestone coupons. In a previous study, these species were the most frequently isolated in the epilithic biofilms of limestone walls exposed to a subtropical climate. In the culture media, we found a greater frequency of intra- and interspecific inhibitory effects in the oligotrophic medium than in the copiotrophic medium. On the limestone coupons, all fungi were able to establish; however, the colonization success rate varied significantly. Cladosporium cladosporioides had a less extensive colonization in isolation (control) than in dual interactions (coexistence) with other species. Phoma eupyrena exhibited the highest colonization success rate and competitive dominance among all tested species. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses revealed that Pestalotiopsis maculans and Paraconiothyrium sp. produced calcium oxalate crystals during their growth on coupon surfaces, both in isolation and in dual interactions. Our results demonstrate that interactions between abundant fungal species influence the fungal colonization on substrates, the biomineralization and the fungal community assemblage growing in limestone biofilms. PMID:29211748

Microbial Surface Colonization and Biofilm Development in Marine Environments

PubMed Central

2015-01-01

SUMMARY Biotic and abiotic surfaces in marine waters are rapidly colonized by microorganisms. Surface colonization and subsequent biofilm formation and development provide numerous advantages to these organisms and support critical ecological and biogeochemical functions in the changing marine environment. Microbial surface association also contributes to deleterious effects such as biofouling, biocorrosion, and the persistence and transmission of harmful or pathogenic microorganisms and their genetic determinants. The processes and mechanisms of colonization as well as key players among the surface-associated microbiota have been studied for several decades. Accumulating evidence indicates that specific cell-surface, cell-cell, and interpopulation interactions shape the composition, structure, spatiotemporal dynamics, and functions of surface-associated microbial communities. Several key microbial processes and mechanisms, including (i) surface, population, and community sensing and signaling, (ii) intraspecies and interspecies communication and interaction, and (iii) the regulatory balance between cooperation and competition, have been identified as critical for the microbial surface association lifestyle. In this review, recent progress in the study of marine microbial surface colonization and biofilm development is synthesized and discussed. Major gaps in our knowledge remain. We pose questions for targeted investigation of surface-specific community-level microbial features, answers to which would advance our understanding of surface-associated microbial community ecology and the biogeochemical functions of these communities at levels from molecular mechanistic details through systems biological integration. PMID:26700108

Microbial Surface Colonization and Biofilm Development in Marine Environments.

PubMed

Dang, Hongyue; Lovell, Charles R

2016-03-01

Biotic and abiotic surfaces in marine waters are rapidly colonized by microorganisms. Surface colonization and subsequent biofilm formation and development provide numerous advantages to these organisms and support critical ecological and biogeochemical functions in the changing marine environment. Microbial surface association also contributes to deleterious effects such as biofouling, biocorrosion, and the persistence and transmission of harmful or pathogenic microorganisms and their genetic determinants. The processes and mechanisms of colonization as well as key players among the surface-associated microbiota have been studied for several decades. Accumulating evidence indicates that specific cell-surface, cell-cell, and interpopulation interactions shape the composition, structure, spatiotemporal dynamics, and functions of surface-associated microbial communities. Several key microbial processes and mechanisms, including (i) surface, population, and community sensing and signaling, (ii) intraspecies and interspecies communication and interaction, and (iii) the regulatory balance between cooperation and competition, have been identified as critical for the microbial surface association lifestyle. In this review, recent progress in the study of marine microbial surface colonization and biofilm development is synthesized and discussed. Major gaps in our knowledge remain. We pose questions for targeted investigation of surface-specific community-level microbial features, answers to which would advance our understanding of surface-associated microbial community ecology and the biogeochemical functions of these communities at levels from molecular mechanistic details through systems biological integration. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Extinction Debt and Colonizer Credit on a Habitat Perturbed Fishing Bank.

PubMed

Duplisea, Daniel E; Frisk, Michael G; Trenkel, Verena M

2016-01-01

Temporal changes in occupancy of the Georges Bank (NE USA) fish and invertebrate community were examined and interpreted in the context of systems ecological theory of extinction debt (EDT). EDT posits that in a closed system with a mix of competitor and colonizer species and experiencing habitat fragmentation and loss, the competitor species will show a gradual decline in fitness (occupancy) eventually leading to their extinction (extirpation) over multiple generations. A corollary of this is a colonizer credit, where colonizer species occupancy may increase with fragmentation because the disturbance gives that life history a transient relative competitive advantage. We found that competitor species occupancy decreased in time concomitant with an increase in occupancy of colonizer species and this may be related to habitat fragmentation or loss owing to industrialized bottom trawl fishing. Mean species richness increased over time which suggests less specialization (decreased dominance) of the assemblage that may result from habitat homogenization. These analyses also showed that when abundance of species was decreased by fishing but eventually returned to previous levels, on average it had a lower occupancy than earlier in the series which could increase their vulnerability to depletion by fishing. Changing occupancy and diversity patterns of the community over time is consistent with EDT which can be exacerbated by direct impacts of fishery removals as well as climate change impacts on the fish community assemblage.

Lack of Host Specialization in Aspergillus flavus

PubMed Central

St. Leger, Raymond J.; Screen, Steven E.; Shams-Pirzadeh, Bijan

2000-01-01

Aspergillus spp. cause disease in a broad range of organisms, but it is unknown if strains are specialized for particular hosts. We evaluated isolates of Aspergillus flavus, Aspergillus fumigatus, and Aspergillus nidulans for their ability to infect bean leaves, corn kernels, and insects (Galleria mellonella). Strains of A. flavus did not affect nonwounded bean leaves, corn kernels, or insects at 22°C, but they killed insects following hemocoelic challenge and caused symptoms ranging from moderate to severe in corn kernels and bean leaves injured during inoculation. The pectinase P2c, implicated in aggressive colonization of cotton bolls, is produced by most A. flavus isolates, but its absence did not prevent colonization of bean leaves. Proteases have been implicated in colonization of animal hosts. All A. flavus strains produced very similar patterns of protease isozymes when cultured on horse lung polymers. Quantitative differences in protease levels did not correlate with the ability to colonize insects. In contrast to A. flavus, strains of A. nidulans and A. fumigatus could not invade living insect or plant tissues or resist digestion by insect hemocytes. Our results indicate that A. flavus has parasitic attributes that are lacking in A. fumigatus and A. nidulans but that individual strains of A. flavus are not specialized to particular hosts. PMID:10618242

How chimpanzees cooperate in a competitive world

PubMed Central

Suchak, Malini; Eppley, Timothy M.; Campbell, Matthew W.; Feldman, Rebecca A.; Quarles, Luke F.; de Waal, Frans B. M.

2016-01-01

Our species is routinely depicted as unique in its ability to achieve cooperation, whereas our closest relative, the chimpanzee (Pan troglodytes), is often characterized as overly competitive. Human cooperation is assisted by the cost attached to competitive tendencies through enforcement mechanisms, such as punishment and partner choice. To examine if chimpanzees possess the same ability to mitigate competition, we set up a cooperative task in the presence of the entire group of 11 adults, which required two or three individuals to pull jointly to receive rewards. This open-group set-up provided ample opportunity for competition (e.g., freeloading, displacements) and aggression. Despite this unique set-up and initial competitiveness, cooperation prevailed in the end, being at least five times as common as competition. The chimpanzees performed 3,565 cooperative acts while using a variety of enforcement mechanisms to overcome competition and freeloading, as measured by (attempted) thefts of rewards. These mechanisms included direct protest by the target, third-party punishment in which dominant individuals intervened against freeloaders, and partner choice. There was a marked difference between freeloading and displacement; freeloading tended to elicit withdrawal and third-party interventions, whereas displacements were met with a higher rate of direct retaliation. Humans have shown similar responses in controlled experiments, suggesting shared mechanisms across the primates to mitigate competition for the sake of cooperation. PMID:27551075

The evolution of increased competitive ability, innate competitive advantages, and novel biochemical weapons act in concert for a tropical invader.

PubMed

Qin, Rui-Min; Zheng, Yu-Long; Valiente-Banuet, Alfonso; Callaway, Ragan M; Barclay, Gregor F; Pereyra, Carlos Silva; Feng, Yu-Long

2013-02-01

There are many non-mutually exclusive mechanisms for exotic invasions but few studies have concurrently tested more than one hypothesis for the same species. Here, we tested the evolution of increased competitive ability (EICA) hypothesis in two common garden experiments in which Chromolaena odorata plants originating from native and nonnative ranges were grown in competition with natives from each range, and the novel weapons hypothesis in laboratory experiments with leachates from C. odorata. Compared with conspecifics originating from the native range, C. odorata plants from the nonnative range were stronger competitors at high nutrient concentrations in the nonnative range in China and experienced far more herbivore damage in the native range in Mexico. In both China and Mexico, C. odorata was more suppressed by species native to Mexico than by species native to China. Species native to China were much more inhibited by leaf extracts from C. odorata than species from Mexico, and this difference in allelopathic effects may provide a possible explanation for the biogeographic differences in competitive ability. Our results indicate that EICA, innate competitive advantages, and novel biochemical weapons may act in concert to promote invasion by C. odorata, and emphasize the importance of exploring multiple, non-mutually exclusive mechanisms for invasions. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

The Vibrio parahaemolyticus ToxRS Regulator Is Required for Stress Tolerance and Colonization in a Novel Orogastric Streptomycin-Induced Adult Murine Model

PubMed Central

Whitaker, W. Brian; Parent, Michelle A.; Boyd, Aoife; Richards, Gary P.

2012-01-01

Vibrio parahaemolyticus, a marine bacterium, is the causative agent of gastroenteritis associated with the consumption of seafood. It contains a homologue of the toxRS operon that in V. cholerae is the key regulator of virulence gene expression. We examined a nonpolar mutation in toxRS to determine the role of these genes in V. parahaemolyticus RIMD2210633, an O3:K6 isolate, and showed that compared to the wild type, ΔtoxRS was significantly more sensitive to acid, bile salts, and sodium dodecyl sulfate stresses. We demonstrated that ToxRS is a positive regulator of ompU expression, and that the complementation of ΔtoxRS with ompU restores stress tolerance. Furthermore, we showed that ToxRS also regulates type III secretion system genes in chromosome I via the regulation of the leuO homologue VP0350. We examined the effect of ΔtoxRS in vivo using a new orogastric adult murine model of colonization. We demonstrated that streptomycin-treated adult C57BL/6 mice experienced prolonged intestinal colonization along the entire intestinal tract by the streptomycin-resistant V. parahaemolyticus. In contrast, no colonization occurred in non-streptomycin-treated mice. A competition assay between the ΔtoxRS and wild-type V. parahaemolyticus strains marked with the β-galactosidase gene lacZ demonstrated that the ΔtoxRS strain was defective in colonization compared to the wild-type strain. This defect was rescued by ectopically expressing ompU. Thus, the defect in stress tolerance and colonization in ΔtoxRS is solely due to OmpU. To our knowledge, the orogastric adult murine model reported here is the first showing sustained intestinal colonization by V. parahaemolyticus. PMID:22392925

High Colonization Possibility of Some Species of Weeds in Suaeda salsa Community: From an Ecological Stoichiometry Perspective

PubMed Central

Ge, Changzi; Wang, Renqing; Chai, Yanchao; Wang, Haiqing; Kan, Manman; Liu, Jian

2017-01-01

Suaeda salsa community is a vegetation type in saline-alkali areas. Weed invasion and colonization in S. salsa communities lead to fragmentationsof S. salsa communities. The colonization of invaded weeds in S. salsa communities is related to community succession of saline-alkali zones. The fragmented S. salsa community may be restored if the mechanism of invaded weed colonization in S. salsa communities is clearly elucidated. Thus, we studied the ecological stoichiometric characteristics of soils and plants in a salt marsh to explain the high colonization possibility of invaded weeds in S. salsa communities. In October 2014, soils and plants were collected from Dongfeng Salt Marsh, Jiaozhou Bay, Shandong Province, China. The ratio of Ex-N/Ex-P in soil was less than 13, which suggests a relative nitrogen limitation for the primary production in the zone. The minimum phosphorus content in plants was higher than 1 mg g-1, whereas the maximum nitrogen content in plants was less than 13 mg g-1. These results imply that phosphorus was abundant, whereas nitrogen was deficient in the area. The plants in the salt marsh may be limited by nitrogen. Given the relatively lower nitrogen contents in Cyperus glomeratus, Echinochloa crusgalli, and Aster subulatus than that in S. salsa, these three species exhibited higher competitiveness than S. salsa did when nitrogen was limited in primary production. These weed species may colonize highly in S. salsa communities. Moreover, nitrogen fertilization might be effective to maintain S. salsa community in Dongfeng Salt Marsh, whereas its effects on controlling weeds colonization in S. salsa communities need more studies to verify. PMID:28135313

High Colonization Possibility of Some Species of Weeds in Suaeda salsa Community: From an Ecological Stoichiometry Perspective.

PubMed

Ge, Changzi; Wang, Renqing; Chai, Yanchao; Wang, Haiqing; Kan, Manman; Liu, Jian

2017-01-01

Suaeda salsa community is a vegetation type in saline-alkali areas. Weed invasion and colonization in S. salsa communities lead to fragmentationsof S. salsa communities. The colonization of invaded weeds in S. salsa communities is related to community succession of saline-alkali zones. The fragmented S. salsa community may be restored if the mechanism of invaded weed colonization in S. salsa communities is clearly elucidated. Thus, we studied the ecological stoichiometric characteristics of soils and plants in a salt marsh to explain the high colonization possibility of invaded weeds in S. salsa communities. In October 2014, soils and plants were collected from Dongfeng Salt Marsh, Jiaozhou Bay, Shandong Province, China. The ratio of Ex-N/Ex-P in soil was less than 13, which suggests a relative nitrogen limitation for the primary production in the zone. The minimum phosphorus content in plants was higher than 1 mg g-1, whereas the maximum nitrogen content in plants was less than 13 mg g-1. These results imply that phosphorus was abundant, whereas nitrogen was deficient in the area. The plants in the salt marsh may be limited by nitrogen. Given the relatively lower nitrogen contents in Cyperus glomeratus, Echinochloa crusgalli, and Aster subulatus than that in S. salsa, these three species exhibited higher competitiveness than S. salsa did when nitrogen was limited in primary production. These weed species may colonize highly in S. salsa communities. Moreover, nitrogen fertilization might be effective to maintain S. salsa community in Dongfeng Salt Marsh, whereas its effects on controlling weeds colonization in S. salsa communities need more studies to verify.

Belowground Controls on the Dynamics of Plant Communities

NASA Astrophysics Data System (ADS)

Sivandran, G.

2013-12-01

Arid regions are characterized by high variability in the arrival of rainfall, and species found in these areas have adapted mechanisms to ensure the capture of this scarce resource. In particular, the rooting strategies employed by vegetation can be critical to their survival. These rooting strategies also dictate the competitive outcomes within plant communities. A dynamic rooting scheme was incorporated into tRIBS+VEGGIE (a physically-based, distributed ecohydrologic model). The dynamic rooting scheme allows vegetation the freedom to alter its rooting profile in response to changes in rainfall and soil conditions, in a way that more closely mimics observed phenotypic plasticity. A simple competition-colonization model was combined with the new dynamic root scheme to explore the role of root adaptability in plant competition and landscape evolution in semi-arid environments. The influence of model representation of rooting strategy on the long term plant community composition

Academic Competition: Rating Race

ERIC Educational Resources Information Center

Rogach, Olga V.; Frolova, Elena V.; Ryabova, Tatyana M.

2017-01-01

The purpose of the study is to identify the factors of competitiveness among university teachers through an assessment of a modern teacher desire and abilities to be demanded professionally. Three hypotheses were put forward: about the impact of a teacher's qualification level on his competitiveness, about the motivational component role of the…

Competitive Embeddedness and the Emergence of Interfirm Cooperation

ERIC Educational Resources Information Center

Trapido, Denis

2007-01-01

How does a history of competition between two economic actors affect their willingness and ability to work together for mutual benefit? Existing theory and research offer mixed predictions and answers. The competitive embeddedness hypothesis suggested here postulates that the likelihood of cooperation between two firms is positively related to the…

Plants promote mating and dispersal of the human pathogenic fungus Cryptococcus

PubMed Central

Mohan, Rajinikanth; Heitman, Joseph

2017-01-01

Infections due to Cryptococcus are a leading cause of fungal infections worldwide and are acquired as a result of environmental exposure to desiccated yeast or spores. The ability of Cryptococcus to grow, mate, and produce infectious propagules in association with plants is important for the maintenance of the genetic diversity and virulence factors important for infection of animals and humans. In the Western United States and Canada, Cryptococcus has been associated with conifers and tree species other than Eucalyptus; however, to date Cryptococcus has only been studied on live Arabidopsis thaliana, Eucalyptus sp., and Terminalia catappa (almond) seedlings. Previous research has demonstrated the ability of Cryptococcus to colonize live plants, leaves, and vasculature. We investigated the ability of Cryptococcus to grow on live seedlings of the angiosperms, A. thaliana, Eucalyptus camaldulensis, Colophospermum mopane, and the gymnosperms, Pseudotsuga menziesii (Douglas fir), and Tsuga heterophylla (Western hemlock). We observed a broad-range ability of Cryptococcus to colonize both traditional infection models as well as newly tested conifer species. Furthermore, C. neoformans, C. deneoformans, C. gattii (VGI), C. deuterogattii (VGII) and C. bacillisporus (VGIII) were able to colonize live plant leaves and needles but also undergo filamentation and mating on agar seeded with plant materials or in saprobic association with dead plant materials. The ability of Cryptococcus to grow and undergo filamentation and reproduction in saprobic association with both angiosperms and gymnosperms highlights an important role of plant debris in the sexual cycle and exposure to infectious propagules. This study highlights the broad importance of plants (and plant debris) as the ecological niche and reservoirs of infectious propagules of Cryptococcus in the environment. PMID:28212396

Plants promote mating and dispersal of the human pathogenic fungus Cryptococcus.

PubMed

Springer, Deborah J; Mohan, Rajinikanth; Heitman, Joseph

2017-01-01

Infections due to Cryptococcus are a leading cause of fungal infections worldwide and are acquired as a result of environmental exposure to desiccated yeast or spores. The ability of Cryptococcus to grow, mate, and produce infectious propagules in association with plants is important for the maintenance of the genetic diversity and virulence factors important for infection of animals and humans. In the Western United States and Canada, Cryptococcus has been associated with conifers and tree species other than Eucalyptus; however, to date Cryptococcus has only been studied on live Arabidopsis thaliana, Eucalyptus sp., and Terminalia catappa (almond) seedlings. Previous research has demonstrated the ability of Cryptococcus to colonize live plants, leaves, and vasculature. We investigated the ability of Cryptococcus to grow on live seedlings of the angiosperms, A. thaliana, Eucalyptus camaldulensis, Colophospermum mopane, and the gymnosperms, Pseudotsuga menziesii (Douglas fir), and Tsuga heterophylla (Western hemlock). We observed a broad-range ability of Cryptococcus to colonize both traditional infection models as well as newly tested conifer species. Furthermore, C. neoformans, C. deneoformans, C. gattii (VGI), C. deuterogattii (VGII) and C. bacillisporus (VGIII) were able to colonize live plant leaves and needles but also undergo filamentation and mating on agar seeded with plant materials or in saprobic association with dead plant materials. The ability of Cryptococcus to grow and undergo filamentation and reproduction in saprobic association with both angiosperms and gymnosperms highlights an important role of plant debris in the sexual cycle and exposure to infectious propagules. This study highlights the broad importance of plants (and plant debris) as the ecological niche and reservoirs of infectious propagules of Cryptococcus in the environment.

[Nodulation competitiveness of nodule bacteria: Genetic control and adaptive significance].

PubMed

Onishchuk, O P; Vorobyov, N I; Provorov, N A

2017-01-01

The most recent data on the system of cmp (competitiveness) genes that determine the nodulation competitiveness of rhizobial strains, i.e., the ability to compete for nodule formation in leguminous plants, is analyzed. Three genetic approaches for the construction of economically valuable strains of rhizobia are proposed: the amplification of positive regulators of competitiveness, the inactivation of the negative regulators of this trait, and the introduction of efficient competitiveness factors into strains capable of active nitrogen fixation.

Evolution of increased competitiveness in cows trades off with reduced milk yield, fertility and more masculine morphology.

PubMed

Sartori, Cristina; Mazza, Serena; Guzzo, Nadia; Mantovani, Roberto

2015-08-01

In some species females compete for food, foraging territories, mating, and nesting sites. Competing females can exhibit morphological, physiological, and behavioral adaptations typical of males, which are commonly considered as secondary sexual traits. Competition and the development of traits increasing competitiveness require much energy and may exert adverse effects on fecundity and survival. From an evolutionary perspective, positive selection for increased competitiveness would then result in evolution of reduced values for traits related to fitness such as fecundity and survival. There is recent evidence for such evolutionary trade-offs involving male competition, but no study has considered competing females so far. Using data from competitions for dominance in cows (Bos taurus), we found negative genetic correlations between traits providing success in competition, that is, fighting ability and fitness traits related to milk production and with fertility (the inverse of parity-conception interval). Fighting ability also showed low but positive genetic correlations with "masculine" morphological traits, and negative correlations with "feminine" traits. A genetic change in traits over time has occurred due to selection on competitiveness, corresponding to an evolutionary process of "masculinization" counteracting the official selection for milk yield. Similar evolutionary trade-off between success in competition and fitness components may be present in various species experiencing female competition. © 2015 The Author(s). Evolution © 2015 The Society for the Study of Evolution.

Effect of pentoxifylline and vinpocetine on the healing of ischemic colon anastomosis: an experimental study.

PubMed

Sümer, Aziz; Altınlı, Ediz; Senger, Serkan; Köksal, Neşet; Onur, Ender; Eroğlu, Ersan; Güneş, Pembegül

2011-11-01

In the current study, we aimed to investigate the influences of pentoxifylline, which increases the flexibility, deformability and viscosity of the erythrocytes while reducing the aggregation abilities of the platelets, and vinpocetine, which has neuroprotective and antioxidant effects, on healing of colonic anastomoses. We used 30 Albino Wistar rats. Subjects were divided into three groups of 10 rats each. Colonic ischemia was established in all the groups. Following colonic transection, anastomosis was performed. Group A received intraperitoneal saline, whereas Group B and Group C received pentoxifylline and vinpocetine, respectively. The subjects were sacrificed on the postoperative 5th day by ether anesthesia, and their colonic bursting pressures were measured. The anastomotic area was excised for hydroxyproline assay and histopathologic examination. According to intergroup comparisons, colonic bursting pressure was found to be higher in the treatment groups than in the control group; however, the difference was not statistically significant. Intergroup comparisons regarding tissue hydroxyproline levels showed statistically significant differences between Groups A and B, Groups A and C and Groups B and C. Similar to pentoxifylline, vinpocetine was also shown to have a beneficial effect over ischemic colon anastomoses.

Mechanisms linking dietary fiber, gut microbiota and colon cancer prevention.

PubMed

Zeng, Huawei; Lazarova, Darina L; Bordonaro, Michael

2014-02-15

Many epidemiological and experimental studies have suggested that dietary fiber plays an important role in colon cancer prevention. These findings may relate to the ability of fiber to reduce the contact time of carcinogens within the intestinal lumen and to promote healthy gut microbiota, which modifies the host's metabolism in various ways. Elucidation of the mechanisms by which dietary fiber-dependent changes in gut microbiota enhance bile acid deconjugation, produce short chain fatty acids, and modulate inflammatory bioactive substances can lead to a better understanding of the beneficial role of dietary fiber. This article reviews the current knowledge concerning the mechanisms via which dietary fiber protects against colon cancer.

Frequent long-distance plant colonization in the changing Arctic.

PubMed

Alsos, Inger Greve; Eidesen, Pernille Bronken; Ehrich, Dorothee; Skrede, Inger; Westergaard, Kristine; Jacobsen, Gro Hilde; Landvik, Jon Y; Taberlet, Pierre; Brochmann, Christian

2007-06-15

The ability of species to track their ecological niche after climate change is a major source of uncertainty in predicting their future distribution. By analyzing DNA fingerprinting (amplified fragment-length polymorphism) of nine plant species, we show that long-distance colonization of a remote arctic archipelago, Svalbard, has occurred repeatedly and from several source regions. Propagules are likely carried by wind and drifting sea ice. The genetic effect of restricted colonization was strongly correlated with the temperature requirements of the species, indicating that establishment limits distribution more than dispersal. Thus, it may be appropriate to assume unlimited dispersal when predicting long-term range shifts in the Arctic.

Probiotics and Diverticular Disease: Evidence-based?

PubMed

Lahner, Edith; Annibale, Bruno

Diverticular disease (DD) is a common gastrointestinal condition. Clinical spectrum ranges from asymptomatic diverticulosis to symptomatic uncomplicated or complicated DD. Symptoms related to uncomplicated DD are not specific and may be indistinguishable from those of irritable bowel syndrome. Low-grade inflammation, altered intestinal microbiota, visceral hypersensitivity, and abnormal colonic motility have been identified as factors potentially contributing to symptoms. Probiotics may modify the gut microbial balance leading to health benefits. Probiotics, due to their anti-inflammatory effects and ability to maintain an adequate bacterial colonization in the colon, are promising treatment options for DD. This review focuses on the available evidence on the efficacy of prebiotics in uncomplicated DD.

Pharmacokinetics of colon-specific pH and time-dependent flurbiprofen tablets.

PubMed

Vemula, Sateesh Kumar; Veerareddy, Prabhakar Reddy; Devadasu, Venkat Ratnam

2015-09-01

Present research deals with the development of compression-coated flurbiprofen colon-targeted tablets to retard the drug release in the upper gastro intestinal system, but progressively release the drug in the colon. Flurbiprofen core tablets were prepared by direct compression method and were compression coated using sodium alginate and Eudragit S100. The formulation is optimized based on the in vitro drug release study and further evaluated by X-ray imaging and pharmacokinetic studies in healthy humans for colonic delivery. The optimized formulation showed negligible drug release (4.33 ± 0.06 %) in the initial lag period followed by progressive release (100.78 ± 0.64 %) for 24 h. The X-ray imaging in human volunteers showed that the tablets reached the colon without disintegrating in the upper gastrointestinal tract. The C max of colon-targeted tablets was 12,374.67 ng/ml at T max 10 h, where as in case of immediate release tablets the C max was 15,677.52 ng/ml at T max 3 h, that signifies the ability of compression-coated tablets to target the colon. Development of compression-coated tablets using combination of time-dependent and pH-sensitive approaches was suitable to target the flurbiprofen to colon.

Smart nanocomposite hydrogels based on azo crosslinked graphene oxide for oral colon-specific drug delivery

NASA Astrophysics Data System (ADS)

Hou, Lin; Shi, Yuyang; Jiang, Guixiang; Liu, Wei; Han, Huili; Feng, Qianhua; Ren, Junxiao; Yuan, Yujie; Wang, Yongchao; Shi, Jinjin; Zhang, Zhenzhong

2016-08-01

A safe and efficient nanocomposite hydrogel for colon cancer drug delivery was synthesized using pH-sensitive and biocompatible graphene oxide (GO) containing azoaromatic crosslinks as well as poly (vinyl alcohol) (PVA) (GO-N=N-GO/PVA composite hydrogels). Curcumin (CUR), an anti-cancer drug, was encapsulated successfully into the hydrogel through a freezing and thawing process. Fourier transform infrared spectroscopy, scanning electron microscopy and Raman spectroscopy were performed to confirm the formation and morphological properties of the nanocomposite hydrogel. The hydrogels exhibited good swelling properties in a pH-sensitive manner. Drug release studies under conditions mimicking stomach to colon transit have shown that the drug was protected from being released completely into the physiological environment of the stomach and small intestine. In vivo imaging analysis, pharmacokinetics and a distribution of the gastrointestinal tract experiment were systematically studied and evaluated as colon-specific drug delivery systems. All the results demonstrated that GO-N=N-GO/PVA composite hydrogels could protect CUR well while passing through the stomach and small intestine to the proximal colon, and enhance the colon-targeting ability and residence time in the colon site. Therefore, CUR loaded GO-N=N-GO/PVA composite hydrogels might potentially provide a theoretical basis for the treatment of colon cancer with high efficiency and low toxicity.

Simulating the Interacting Effects of Intraspecific Variation, Disturbance, and Competition on Climate-Driven Range Shifts in Trees

PubMed Central

2015-01-01

Climate change is expected to favor shifts in plant distributions; some such shifts are already being observed along elevation gradients. However, the rate of such shifts may be limited by their ability to reach newly suitable areas and by competition from resident species. The degree of local adaptation and genetic variation may also play a role in the interaction between migrants and residents by affecting relative fitness. We used a simulation model to explore the interacting effects of dispersal, fecundity, disturbance, and genetic variation on range-edge dynamics between a pair of demographically similar tree species. Ideal climate for an individual is determined by genotype. The simulated landscape undergoes an 80-year period of climate change in which climate bands shift upslope; subsequently, climate is held constant for 300 years. The presence of a high-elevation competitor caused a significant lag in the range shift of the low-elevation species relative to competition-free scenarios. Increases in fecundity and dispersal distance both helped to speed up the replacement of the high-elevation species by the low-elevation species at their range boundary. While some disturbance scenarios facilitated this transition, frequent canopy disturbance inhibited colonization by removing reproductive adults and led to range contractions in both species. Differences between dispersal scenarios were more pronounced when disturbance was frequent (15 vs. 25 year return interval) and dispersal was limited. When the high-elevation species lacked genetic variation, its range was more-easily invaded by the low-elevation species, while a similar lack of variation in the low-elevation species inhibited colonization—but only when this lack of variation decreased the fitness of the affected species near the range boundary. Our model results support the importance of measuring and including dispersal/fecundity, disturbance type and frequency, and genetic variation when assessing the potential for range shifts and species vulnerability to climate change. PMID:26560869

A Canopy Architectural Model to Study the Competitive Ability of Chickpea with Sowthistle

PubMed Central

Cici, S-Zahra-Hosseini; Adkins, Steve; Hanan, Jim

2008-01-01

Background and Aims Improving the competitive ability of crops is a sustainable method of weed management. This paper shows how a virtual plant model of competition between chickpea (Cicer arietinum) and sowthistle (Sonchus oleraceus) can be used as a framework for discovering and/or developing more competitive chickpea cultivars. Methods The virtual plant models were developed using the L-systems formalism, parameterized according to measurements taken on plants at intervals during their development. A quasi-Monte Carlo light-environment model was used to model the effect of chickpea canopy on the development of sowthistle. The chickpea–light environment–sowthistle model (CLES model) captured the hypothesis that the architecture of chickpea plants modifies the light environment inside the canopy and determines sowthistle growth and development pattern. The resulting CLES model was parameterized for different chickpea cultivars (viz. ‘Macarena’, ‘Bumper’, ‘Jimbour’ and ‘99071-1001’) to compare their competitive ability with sowthistle. To validate the CLES model, an experiment was conducted using the same four chickpea cultivars as different treatments with a sowthistle growing under their canopy. Results and Conclusions The growth of sowthistle, both in silico and in glasshouse experiments, was reduced most by ‘99071-1001’, a cultivar with a short phyllochron. The second rank of competitive ability belonged to ‘Macarena’ and ‘Bumper’, while ‘Jimbour’ was the least competitive cultivar. The architecture of virtual chickpea plants modified the light inside the canopy, which influenced the growth and development of the sowthistle plants in response to different cultivars. This is the first time that a virtual plant model of a crop–weed interaction has been developed. This virtual plant model can serve as a platform for a broad range of applications in the study of chickpea–weed interactions and their environment. PMID:18375962

Interference competition between an invasive parakeet and native bird species at feeding sites.

PubMed

Le Louarn, Marine; Couillens, Bertrand; Deschamps-Cottin, Magali; Clergeau, Philippe

2016-01-01

Interference competition has proved to be a factor of successful establishment of invasive species. This type of competition may have a stronger impact when native species have temporal niche overlap with the invasive species. The ring-necked parakeet Psittacula krameri has been successfully introduced in many countries and its interspecific agonistic behavior has already been reported. The purpose of this study is to analyze the territorial and preemptive interference competition between the ring-necked parakeet and native bird species in a recently colonized area. We used an empirical approach by recording video sequences in gardens equipped with bird feeders in winter. Our results showed that the ring-necked parakeet was the most frequent species at the feeders. Several native species showed temporal niche overlap with the ring-necked parakeet, the highest overlap being with the starling Sturnus vulgaris . The starling was also the species most impacted by interference competition with the parakeet. Our study suggests that, by being most frequently present at the feeders, by demonstrating the most agonistic behavior and by hindering access to food of the other species, the ring-necked parakeet is a superior competitor and may compete with native bird species.

Effects of intraspecific phenotypic variation on species coexistence.

PubMed

Hausch, Stephen; Vamosi, Steven M; Fox, Jeremy W

2018-06-01

Intraspecific variation can promote or inhibit species coexistence, both by increasing species' competitive abilities, and by altering the relative strengths of intraspecific and interspecific competition. Effects of intraspecific variation on coexistence can occur via complementarity of different variants, and via a selection effect: initially-variable populations are more likely to contain highly competitive variants that might determine the ability of the population as a whole to both invade and resist invasion. We tested the effects of intraspecific variation and composition on coexistence by assaying the mutual invasibility of populations of two competing bean weevil species (Callosobruchus maculatus and C. chinensis) when each was initiated with one, three, or five genetically- and phenotypically-distinct lineages. Our results reveal that intraspecific variation is a double-edged sword for species coexistence. Increasing intraspecific variation increased species' abilities to invade, and to resist invasion, via selection effects and intraspecific niche complementarity among conspecific lineages, thereby creating the potential for exclusion among mismatched competitors. But intraspecific variation also increased the scope for resource partitioning, creating the potential for stable coexistence. Stable coexistence occurred only when intraspecific variation caused species to exhibit both relatively evenly-matched competitive abilities and sufficiently-strong resource partitioning. Our work explains the conflicting results of previous studies. © 2018 by the Ecological Society of America.

Fierce Competition between Toxoplasma and Chlamydia for Host Cell Structures in Dually Infected Cells

PubMed Central

Romano, Julia D.; de Beaumont, Catherine; Carrasco, Jose A.; Ehrenman, Karen; Bavoil, Patrik M.

2013-01-01

The prokaryote Chlamydia trachomatis and the protozoan Toxoplasma gondii, two obligate intracellular pathogens of humans, have evolved a similar modus operandi to colonize their host cell and salvage nutrients from organelles. In order to gain fundamental knowledge on the pathogenicity of these microorganisms, we have established a cell culture model whereby single fibroblasts are coinfected by C. trachomatis and T. gondii. We previously reported that the two pathogens compete for the same nutrient pools in coinfected cells and that Toxoplasma holds a significant competitive advantage over Chlamydia. Here we have expanded our coinfection studies by examining the respective abilities of Chlamydia and Toxoplasma to co-opt the host cytoskeleton and recruit organelles. We demonstrate that the two pathogen-containing vacuoles migrate independently to the host perinuclear region and rearrange the host microtubular network around each vacuole. However, Toxoplasma outcompetes Chlamydia to the host microtubule-organizing center to the detriment of the bacterium, which then shifts to a stress-induced persistent state. Solely in cells preinfected with Chlamydia, the centrosomes become associated with the chlamydial inclusion, while the Toxoplasma parasitophorous vacuole displays growth defects. Both pathogens fragment the host Golgi apparatus and recruit Golgi elements to retrieve sphingolipids. This study demonstrates that the productive infection by both Chlamydia and Toxoplasma depends on the capability of each pathogen to successfully adhere to a finely tuned developmental program that aims to remodel the host cell for the pathogen's benefit. In particular, this investigation emphasizes the essentiality of host organelle interception by intravacuolar pathogens to facilitate access to nutrients. PMID:23243063

Fierce competition between Toxoplasma and Chlamydia for host cell structures in dually infected cells.

PubMed

Romano, Julia D; de Beaumont, Catherine; Carrasco, Jose A; Ehrenman, Karen; Bavoil, Patrik M; Coppens, Isabelle

2013-02-01

The prokaryote Chlamydia trachomatis and the protozoan Toxoplasma gondii, two obligate intracellular pathogens of humans, have evolved a similar modus operandi to colonize their host cell and salvage nutrients from organelles. In order to gain fundamental knowledge on the pathogenicity of these microorganisms, we have established a cell culture model whereby single fibroblasts are coinfected by C. trachomatis and T. gondii. We previously reported that the two pathogens compete for the same nutrient pools in coinfected cells and that Toxoplasma holds a significant competitive advantage over Chlamydia. Here we have expanded our coinfection studies by examining the respective abilities of Chlamydia and Toxoplasma to co-opt the host cytoskeleton and recruit organelles. We demonstrate that the two pathogen-containing vacuoles migrate independently to the host perinuclear region and rearrange the host microtubular network around each vacuole. However, Toxoplasma outcompetes Chlamydia to the host microtubule-organizing center to the detriment of the bacterium, which then shifts to a stress-induced persistent state. Solely in cells preinfected with Chlamydia, the centrosomes become associated with the chlamydial inclusion, while the Toxoplasma parasitophorous vacuole displays growth defects. Both pathogens fragment the host Golgi apparatus and recruit Golgi elements to retrieve sphingolipids. This study demonstrates that the productive infection by both Chlamydia and Toxoplasma depends on the capability of each pathogen to successfully adhere to a finely tuned developmental program that aims to remodel the host cell for the pathogen's benefit. In particular, this investigation emphasizes the essentiality of host organelle interception by intravacuolar pathogens to facilitate access to nutrients.

Fermentation of mucin and plant polysaccharides by strains of Bacteroides from the human colon.

PubMed Central

Salyers, A A; Vercellotti, J R; West, S E; Wilkins, T D

1977-01-01

Ten Bacteroides species found in the human colon were surveyed for their ability to ferment mucins and plant polysaccharides ("dietary fiber"). A number of strains fermented mucopolysaccharides (heparin, hyaluronate, and chondroitin sulfate) and ovomucoid. Only 3 of the 188 strains tested fermented beef submaxillary mucin, and none fermented porcine gastric mucin. Many of the Bacteroides strains tested were also able to ferment a variety of plant polysaccharides, including amylose, dextran, pectin, gum tragacanth, gum guar, larch arabinogalactan, alginate, and laminarin. Some plant polysaccharides such as gum arabic, gum karaya, gum ghatti and fucoidan, were not utilized by any of the strains tested. The ability to utilize mucins and plant polysaccharides varied considerably among the Bacteroides species tested. PMID:848954

The HOG pathway is critical for the colonization of the mouse gastrointestinal tract by Candida albicans.

PubMed

Prieto, Daniel; Román, Elvira; Correia, Inês; Pla, Jesus

2014-01-01

The opportunistic pathogen Candida albicans is a frequent inhabitant of the human gastrointestinal tract where it usually behaves as a harmless commensal. In this particular niche, it needs to adapt to the different micro environments that challenge its survival within the host. In order to determine those factors involved in gut adaptation, we have used a gastrointestinal model of colonization in mouse to trace the behaviour of fungal cells. We have developed a genetic labelling system based on the complementary spectral properties of the fluorescent proteins GFP and a new C. albicans codon-adapted RFP (dTOM2) that allow a precise quantification of the fungal population in the gut via standard in vitro cultures or flow cytometry. This methodology has allowed us to determine the role of the three MAP kinase pathways of C. albicans (mediated by the MAPK Mkc1, Cek1 or Hog1) in mouse gut colonization via competitive assays with MAPK pathway mutants and their isogenic wild type strain. This approach reveals the signalling through HOG pathway as a critical factor influencing the establishment of C. albicans in the mouse gut. Less pronounced effects for mkc1 or cek1 mutants were found, only evident after 2-3 weeks of colonization. We have also seen that hog1 mutants is defective in adhesion to the gut mucosa and sensitive to bile salts. Finally, we have developed a genetic strategy for the in vivo excision (tetracycline-dependent) of any specific gene during the course of colonization in this particular niche, allowing the analysis of its role during gut colonization.

EGFR Overexpressed in Colonic Neoplasia Can be Detected on Wide-Field Endoscopic Imaging.

PubMed

Zhou, Juan; Joshi, Bishnu P; Duan, Xiyu; Pant, Asha; Qiu, Zhen; Kuick, Rork; Owens, Scott R; Wang, Thomas D

2015-07-16

Colorectal cancer initially lies dormant as dysplasia, a premalignant state that provides an opportunity for early cancer detection. Dysplasia can be flat in morphology, focal in size, and patchy in distribution, and thus it appears "invisible" on conventional wide-field endoscopy. We aim to develop and validate a peptide that is specific for epidermal growth factor receptor (EGFR), a cell surface target that is overexpressed in colonic adenomas and is readily accessible for imaging. We expressed and purified the extracellular domain of EGFR for use with phage display to identify a peptide QRHKPRE that binds to domain 2 of this target. A near-infrared fluorescence endoscope was used to perform in vivo imaging to validate specific peptide binding to spontaneous colonic adenomas in a mouse model with topical administration. We also validated specific peptide binding to human colonic adenomas on immunohistochemistry and immunofluorescence. After labeling with Cy5.5, we validated specific peptide binding to EGFR on knockdown and competition studies. Peptide binding to cells occurred within 2.46 min and had an affinity of 50 nm. No downstream signaling was observed. We measured a target-to-background ratio of 4.0±1.7 and 2.7±0.7, for polyps and flat lesions, respectively. On immunofluorescence of human colonic specimens, greater intensity from peptide binding to dysplasia than normal was found with a 19.4-fold difference. We have selected and validated a peptide that can be used as a specific contrast agent to identify colonic adenomas that overexpress EGFR in vivo on fluorescence endoscopy.

Few Differences in Metabolic Network Use Found Between Salmonella enterica Colonization of Plants and Typhoidal Mice.

PubMed

Kwan, Grace; Plagenz, Brett; Cowles, Kimberly; Pisithkul, Tippapha; Amador-Noguez, Daniel; Barak, Jeri D

2018-01-01

The human enteric pathogen Salmonella enterica leads a cross-kingdom lifestyle, actively colonizing and persisting on plants in between animal hosts. One of the questions that arises from this dual lifestyle is how S. enterica is able to adapt to such divergent hosts. Metabolic pathways required for S. enterica animal colonization and virulence have been previously identified, but the metabolism of this bacterium on plants is poorly understood. To determine the requirements for plant colonization by S. enterica , we first screened a library of metabolic mutants, previously examined in a systemic mouse typhoidal model, for competitive plant colonization fitness on alfalfa seedlings. By comparing our results to those reported in S. enterica -infected murine spleens, we found that the presence of individual nutrients differed between the two host niches. Yet, similar metabolic pathways contributed to S. enterica colonization of both plants and animals, such as the biosynthesis of amino acids, purines, and vitamins and the catabolism of glycerol and glucose. However, utilization of at least three metabolic networks differed during the bacterium's plant- and animal-associated lifestyles. Whereas both fatty acid biosynthesis and degradation contributed to S. enterica animal colonization, only fatty acid biosynthesis was required during plant colonization. Though serine biosynthesis was required in both hosts, S. enterica used different pathways within the serine metabolic network to achieve this outcome. Lastly, the metabolic network surrounding manA played different roles during colonization of each host. In animal models of infection, O-antigen production downstream of manA facilitates immune evasion. We discovered that manA contributed to S. enterica attachment, to seeds and germinated seedlings, and was essential for growth in early seedling exudates, when mannose is limited. However, only seedling attachment was linked to O-antigen production, indicating that manA played additional roles critical for plant colonization that were independent of surface polysaccharide production. The integrated view of S. enterica metabolism throughout its life cycle presented here provides insight on how metabolic versatility and adaption of known physiological pathways for alternate functions enable a zoonotic pathogen to thrive in niches spanning across multiple kingdoms of life.

OpnS, an outer membrane porin of Xenorhabdus nematophila, confers a competitive advantage for growth in the insect host.

PubMed

van der Hoeven, Ransome; Forst, Steven

2009-09-01

The gammaproteobacterium Xenorhabdus nematophila engages in a mutualistic association with an entomopathogenic nematode and also functions as a pathogen toward different insect hosts. We studied the role of the growth-phase-regulated outer membrane protein OpnS in host interactions. OpnS was shown to be a 16-stranded beta-barrel porin. opnS was expressed during growth in insect hemolymph and expression was elevated as the cell density increased. When wild-type and opnS deletion strains were coinjected into insects, the wild-type strain was predominantly recovered from the insect cadaver. Similarly, an opnS-complemented strain outcompeted the DeltaopnS strain. Coinjection of the wild-type and DeltaopnS strains together with uncolonized nematodes into insects resulted in nematode progeny that were almost exclusively colonized with the wild-type strain. Likewise, nematode progeny recovered after coinjection of a mixture of nematodes carrying either the wild-type or DeltaopnS strain were colonized by the wild-type strain. In addition, the DeltaopnS strain displayed a competitive growth defect when grown together with the wild-type strain in insect hemolymph but not in defined culture medium. The DeltaopnS strain displayed increased sensitivity to antimicrobial compounds, suggesting that deletion of OpnS affected the integrity of the outer membrane. These findings show that the OpnS porin confers a competitive advantage for the growth and/or the survival of X. nematophila in the insect host and provides a new model for studying the biological relevance of differential regulation of porins in a natural host environment.

The nasal microbiota of dairy farmers is more complex than oral microbiota, reflects occupational exposure, and provides competition for staphylococci

PubMed Central

Sandberg, Scott; Reyes, Iris; Fritsche, Thomas R.

2017-01-01

Allergic and autoimmune diseases had been attributed to lack of exposure to biodiversity, an important factor in regulating immune homeostasis in a healthy host. We posit that the microbiome of healthy dairy farmers (DF) will be richer than non-farmers (NF) living in urban settings due to exposure to a greater biodiversity in the dairy environment. However, no studies have investigated the relationships between microbiota of dairy farmers (DF) compared with urban non-farmers (NF). We compared the nasal and oral microbiota of dairy farmers (N_DF, O_DF, respectively) with nasal and oral microbiota of NF in the same geographical area. The N_DF showed high microbial diversity with hundreds of unique genera that reflected environmental/occupational exposures. The nasal and oral microbiomes clustered separately from each other using Principal Coordinate Analysis, and with DF harboring two-fold and 1.5-fold greater exclusive genera in their nose and mouth respectively, than did non-farmers. Additionally, the N_DF group had a lower burden of Staphylococcus spp. suggesting a correlation between higher microbial diversity and competition for colonization by staphylococci. The N_DF samples were negative for the mecA gene, a marker of methicillin-resistance in staphylococci. The lower burden of staphylococci was found to be independent of the abundance of Corynebacterium spp. Exposure to greater biodiversity could enhance microbial competition, thereby reducing colonization with opportunistic pathogens. Future studies will analyze whether exposure to livestock microbiomes offers protection from acute and chronic diseases. PMID:28850578

The nasal microbiota of dairy farmers is more complex than oral microbiota, reflects occupational exposure, and provides competition for staphylococci.

PubMed

Shukla, Sanjay K; Ye, Zhan; Sandberg, Scott; Reyes, Iris; Fritsche, Thomas R; Keifer, Matthew

2017-01-01

Allergic and autoimmune diseases had been attributed to lack of exposure to biodiversity, an important factor in regulating immune homeostasis in a healthy host. We posit that the microbiome of healthy dairy farmers (DF) will be richer than non-farmers (NF) living in urban settings due to exposure to a greater biodiversity in the dairy environment. However, no studies have investigated the relationships between microbiota of dairy farmers (DF) compared with urban non-farmers (NF). We compared the nasal and oral microbiota of dairy farmers (N_DF, O_DF, respectively) with nasal and oral microbiota of NF in the same geographical area. The N_DF showed high microbial diversity with hundreds of unique genera that reflected environmental/occupational exposures. The nasal and oral microbiomes clustered separately from each other using Principal Coordinate Analysis, and with DF harboring two-fold and 1.5-fold greater exclusive genera in their nose and mouth respectively, than did non-farmers. Additionally, the N_DF group had a lower burden of Staphylococcus spp. suggesting a correlation between higher microbial diversity and competition for colonization by staphylococci. The N_DF samples were negative for the mecA gene, a marker of methicillin-resistance in staphylococci. The lower burden of staphylococci was found to be independent of the abundance of Corynebacterium spp. Exposure to greater biodiversity could enhance microbial competition, thereby reducing colonization with opportunistic pathogens. Future studies will analyze whether exposure to livestock microbiomes offers protection from acute and chronic diseases.

Gamma (γ) tocopherol upregulates peroxisome proliferator activated receptor (PPAR) gamma (γ) expression in SW 480 human colon cancer cell lines

PubMed Central

Campbell, Sharon E; Stone, William L; Whaley, Sarah G; Qui, Min; Krishnan, Koyamangalath

2003-01-01

Background Tocopherols are lipid soluble antioxidants that exist as eight structurally different isoforms. The intake of γ-tocopherol is higher than α-tocopherol in the average US diet. The clinical results of the effects of vitamin E as a cancer preventive agent have been inconsistent. All published clinical trials with vitamin E have used α-tocopherol. Recent epidemiological, experimental and molecular studies suggest that γ-tocopherol may be a more potent chemopreventive form of vitamin E compared to the more-studied α-tocopherol. γ-Tocopherol exhibits differences in its ability to detoxify nitrogen dioxide, growth inhibitory effects on selected cancer cell lines, inhibition of neoplastic transformation in embryonic fibroblasts, and inhibition of cyclooxygenase-2 (COX-2) activity in macrophages and epithelial cells. Peroxisome proliferator activator receptor γ (PPARγ) is a promising molecular target for colon cancer prevention. Upregulation of PPARγ activity is anticarcinogenic through its effects on downstream genes that affect cellular proliferation and apoptosis. The thiazolidine class of drugs are powerful PPARγ ligands. Vitamin E has structural similarity to the thiazolidine, troglitazone. In this investigation, we tested the effects of both α and γ tocopherol on the expression of PPARγ mRNA and protein in SW 480 colon cancer cell lines. We also measured the intracellular concentrations of vitamin E in SW 480 colon cancer cell lines. Results We have discovered that the α and γ isoforms of vitamin E upregulate PPARγ mRNA and protein expression in the SW480 colon cancer cell lines. γ-Tocopherol is a better modulator of PPARγ expression than α-tocopherol at the concentrations tested. Intracellular concentrations increased as the vitamin E concentration added to the media was increased. Further, γ-tocopherol-treated cells have higher intracellular tocopherol concentrations than those treated with the same concentrations of α-tocopherol. Conclusion Our data suggest that both α and γ tocopherol can upregulate the expression of PPARγ which is considered an important molecular target for colon cancer chemoprevention. We show that the expression of PPARγ mRNA and protein are increased and these effects are more pronounced with γ-tocopherol. γ-Tocopherol's ability to upregulate PPARγ expression and achieve higher intracellular concentrations in the colonic tissue may be relevant to colon cancer prevention. We also show that the intracellular concentrations of γ-tocopherol are several fold higher than α-tocopherol. Further work on other colon cancer cell lines are required to quantitate differences in the ability of these forms of vitamin E to induce apoptosis, suppress cell proliferation and act as PPAR ligands as well as determine their effects in conjunction with other chemopreventive agents. Upregulation of PPARγ by the tocopherols and in particular by γ-tocopherol may have relevance not only to cancer prevention but also to the management of inflammatory and cardiovascular disorders. PMID:14521714

Major role for FeoB in Campylobacter jejuni ferrous iron acquisition, gut colonization, and intracellular survival.

PubMed

Naikare, Hemant; Palyada, Kiran; Panciera, Roger; Marlow, Denver; Stintzi, Alain

2006-10-01

To assess the importance of ferrous iron acquisition in Campylobacter physiology and pathogenesis, we disrupted and characterized the Fe2+ iron transporter, FeoB, in Campylobacter jejuni NCTC 11168, 81-176, and ATCC 43431. The feoB mutant was significantly affected in its ability to transport 55Fe2+. It accumulated half the amount of iron than the wild-type strain during growth in an iron-containing medium. The intracellular iron of the feoB mutant was localized in the periplasmic space versus the cytoplasm for the wild-type strain. These results indicate that the feoB gene of C. jejuni encodes a functional ferrous iron transport system. Reverse transcriptase PCR analysis revealed the cotranscription of feoB and Cj1397, which encodes a homolog of Escherichia coli feoA. C. jejuni 81-176 feoB mutants exhibited reduced ability to persist in human INT-407 embryonic intestinal cells and porcine IPEC-1 small intestinal epithelial cells compared to the wild type. C. jejuni NCTC 11168 feoB mutant was outcompeted by the wild type for colonization and/or survival in the rabbit ileal loop. The feoB mutants of the three C. jejuni strains were significantly affected in their ability to colonize the chick cecum. And finally, the three feoB mutants were outcompeted by their respective wild-type strains for infection of the intestinal tracts of colostrum-deprived piglets. Taken together, these results demonstrate that FeoB-mediated ferrous iron acquisition contributes significantly to colonization of the gastrointestinal tract during both commensal and infectious relationship, and thus it plays an important role in Campylobacter pathogenesis.

Evolution of increased larval competitive ability in Drosophila melanogaster without increased larval feeding rate.

PubMed

Sarangi, Manaswini; Nagarajan, Archana; Dey, Snigdhadip; Bose, Joy; Joshi, Amitabh

2016-09-01

Multiple experimental evolution studies on Drosophila melanogaster in the 1980s and 1990s indicated that enhanced competitive ability evolved primarily through increased larval tolerance to nitrogenous wastes and increased larval feeding and foraging rate, at the cost of efficiency of food conversion to biomass, and this became the widely accepted view of how adaptation to larval crowding evolves in fruitflies.We recently showed that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolved greater competitive ability without evolving higher feeding rates, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater efficiency of food conversion to biomass, increased pupation height and, perhaps, greater urea/ammonia tolerance. This was a very different suite of traits than that seen to evolve under similar selection in D. melanogaster and was closer to the expectations from the theory of K-selection. At that time, we suggested two possible reasons for the differences in the phenotypic correlates of greater competitive ability seen in the studies with D. melanogaster and the other two species. First, that D. ananassae and D. n. nasuta had a very different genetic architecture of traits affecting competitive ability compared to the long-term laboratory populations of D. melanogaster used in the earlier studies, either because the populations of the former two species were relatively recently wild-caught, or by virtue of being different species. Second, that the different evolutionary trajectories in D. ananassae and D. n. nasuta versus D. melanogaster were a reflection of differences in the manner in which larval crowding was imposed in the two sets of selection experiments. The D. melanogaster studies used a higher absolute density of eggs per unit volume of food, and a substantially larger total volume of food, than the studies on D. ananassae and D. n. nasuta. Here, we show that long-term laboratory populations of D. melanogaster, descended from some of the populations used in the earlier studies, evolve essentially the same set of traits as the D. ananassae and D. n. nasuta crowding-adapted populations when subjected to a similar larval density at low absolute volumes of food. As in the case of D. ananassae and D. n. nasuta, and in stark contrast to earlier studies with D. melanogaster, these crowding-adapted populations of D. melanogaster did not evolve greater larval feeding rates as a correlate of increased competitive ability. The present results clearly suggest that the suite of phenotypes through which the evolution of greater competitive ability is achieved in fruitflies depends critically not just on larval density per unit volume of food, but also on the total amount of food available in the culture vials. We discuss these results in the context of an hypothesis about how larval density and the height of the food column in culture vials might interact to alter the fitness costs and benefits of increased larval feeding rates, thus resulting in different routes to the evolution of greater competitive ability, depending on the details of exactly how the larval crowding was implemented.

Colonic Absorption of Low-Molecular-Weight Metabolites Influenced by the Intestinal Microbiome: A Pilot Study.

PubMed

Matsumoto, Mitsuharu; Ooga, Takushi; Kibe, Ryoko; Aiba, Yuji; Koga, Yasuhiro; Benno, Yoshimi

2017-01-01

Low-molecular-weight metabolites produced by the intestinal microbiome play a direct role in health and disease. However, little is known about the ability of the colon to absorb these metabolites. It is also unclear whether these metabolites are bioavailable. Here, metabolomics techniques (capillary electrophoresis with time-of-flight mass spectrometry, CE-TOFMS), germ-free (GF) mice, and colonized (Ex-GF) mice were used to identify the colonic luminal metabolites transported to colonic tissue and/or blood. We focused on the differences in each metabolite between GF and Ex-GF mice to determine the identities of metabolites that are transported to the colon and/or blood. CE-TOFMS identified 170, 246, 166, and 193 metabolites in the colonic feces, colonic tissue, portal plasma, and cardiac plasma, respectively. We classified the metabolites according to the following influencing factors: (i) the membrane transport system of the colonocytes, (ii) metabolism during transcellular transport, and (iii) hepatic metabolism based on the similarity in the ratio of each metabolite between GF and Ex-GF mice and found 62 and 22 metabolites that appeared to be absorbed from the colonic lumen to colonocytes and blood, respectively. For example, 11 basic amino acids were transported to the systemic circulation from the colonic lumen. Furthermore, many low-molecular-weight metabolites influenced by the intestinal microbiome are bioavailable. The present study is the first to report the transportation of metabolites from the colonic lumen to colonocytes and somatic blood in vivo, and the present findings are critical for clarifying host-intestinal bacterial interactions.

Sales Role-Plays and Mock Interviews: An Investigation of Student Performance in Sales Competitions

ERIC Educational Resources Information Center

Mani, Sudha; Kothandaraman, Prabakar; Kashyap, Rajiv; Ashnai, Bahar

2016-01-01

Sales competitions provide students with opportunities to apply their understanding of sales. Despite a long tradition of scholarship on sales role-plays, the answer to what drives student performance in sales competitions remains elusive. In this research, we examine how motivation (work engagement) and ability (cognitive aptitude and…

Rhizosphere Colonization and Control of Meloidogyne spp. by Nematode-trapping Fungi

PubMed Central

Persson, Christina; Jansson, Hans-Börje

1999-01-01

The ability of nematode-trapping fungi to colonize the rhizosphere of crop plants has been suggested to be an important factor in biological control of root-infecting nematodes. In this study, rhizosphere colonization was evaluated for 38 isolates of nematode-trapping fungi representing 11 species. In an initial screen, Arthrobotrys dactyloides, A. superba, and Monacrosporium ellipsosporum were most frequently detected in the tomato rhizosphere. In subsequent pot experiments these fungi and the non-root colonizing M. geophyropagum were introduced to soil in a sodium alginate matrix, and further tested both for establishment in the tomato rhizosphere and suppression of root-knot nematodes. The knob-forming M. ellipsosporum showed a high capacity to colonize the rhizosphere both in the initial screen and the pot experiments, with more than twice as many fungal propagules in the rhizosphere as in the root-free soil. However, neither this fungus nor the other nematode-trapping fungi tested reduced nematode damage to tomato plants. PMID:19270886

Ecological Interactions of Bacteria in the Human Gut

NASA Astrophysics Data System (ADS)

Falony, Gwen; de Vuyst, Luc

The colon or large intestine is one of the most important organs of the human body (Macfarlane and Cummings, 1991). Moreover, its inhabitants, the colon microbiota, are the key elements of the human digestive ecosystem. The vast complexity of the human large-intestinal microbiota has inspired researchers to consider it as an organ itself, located inside the colon and acquired postnatally (Bäckhed et al., 2005; Zocco et al., 2007). From a physiologist's point of view, this image of the colon microbiota is relevant: like an organ, it is composed of different cell lineages that communicate with both one another and the host; it consumes, stores, and redistributes energy; it mediates physiologically important chemical transformations; and it is able to maintain and repair itself through self-replication (Bäckhed et al., 2005). As a microbial organ, the human colon community does not only broaden the digestive abilities of the host (Gill et al., 2006), but also influences body processes far beyond digestion (Roberfroid, 2005b; Turnbaugh et al., 2007).

Supercritical carbon dioxide-developed silk fibroin nanoplatform for smart colon cancer therapy.

PubMed

Xie, Maobin; Fan, Dejun; Li, Yi; He, Xiaowen; Chen, Xiaoming; Chen, Yufeng; Zhu, Jixiang; Xu, Guibin; Wu, Xiaojian; Lan, Ping

2017-01-01

To deliver insoluble natural compounds into colon cancer cells in a controlled fashion. Curcumin (CM)-silk fibroin (SF) nanoparticles (NPs) were prepared by solution-enhanced dispersion by supercritical CO 2 (SEDS) (20 MPa pressure, 1:2 CM:SF ratio, 1% concentration), and their physicochemical properties, intracellular uptake efficiency, in vitro anticancer effect, toxicity, and mechanisms were evaluated and analyzed. CM-SF NPs (<100 nm) with controllable particle size were prepared by SEDS. CM-SF NPs had a time-dependent intracellular uptake ability, which led to an improved inhibition effect on colon cancer cells. Interestingly, the anticancer effect of CM-SF NPs was improved, while the side effect on normal human colon mucosal epithelial cells was reduced by a concentration of ~10 μg/mL. The anticancer mechanism involves cell-cycle arrest in the G 0 /G 1 and G 2 /M phases in association with inducing apoptotic cells. The natural compound-loaded SF nanoplatform prepared by SEDS indicates promising colon cancer-therapy potential.

Selective suppression of in situ proliferation of scyphozoan polyps by biofouling.

PubMed

Feng, Song; Wang, Shi-Wei; Zhang, Guang-Tao; Sun, Song; Zhang, Fang

2017-01-30

An increase in marine artificial constructions has been proposed as a major cause of jellyfish blooms, because these constructions provide additional substrates for organisms at the benthic stage (polyps), which proliferate asexually and release a large amount of free-swimming medusae. These hard surfaces are normally covered by fouling communities, the components of which have the potential to impede the proliferation of polyps. In this study, we report an in situ experiment of polyp survival of four large scyphozoan species found in East Asian marginal seas that were exposed to biofouling, a universal phenomenon occurring on marine artificial constructions. Our results showed that the polyps of three species (Nemopilema nomurai, Cyanea nozaki, and Rhopilema esculentum) attached to the artificial surfaces were completely eliminated by biofouling within 7-8months, and only those of moon jellyfish (Aurelia sp.1) in the upper layers could multiply on both artificial materials and other organisms (e.g., ascidians and bryozoans). Fouling-associated competition and predation and suppressed asexual reproduction of podocysts were observed to contribute to the loss of polyps. This study shows that the natural distribution of polyps is defined by the biofouling community that colonizes the surfaces of artificial constructions. Consequently, the contribution of marine constructions to jellyfish bloom is limited only to the ability of the jellyfish species to reproduce asexually through budding and inhabit solid surfaces of fouling organisms in addition to inhabiting original artificial materials. We anticipate that fragile polyps will colonize and proliferate in harsh environments that are deleterious to biofouling, and we propose special attention to polyps in antifouling practices for excluding the possibility that they occupy the available ecological space. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ruminococcus bromii is a keystone species for the degradation of resistant starch in the human colon

PubMed Central

Ze, Xiaolei; Duncan, Sylvia H; Louis, Petra; Flint, Harry J

2012-01-01

The release of energy from particulate substrates such as dietary fiber and resistant starch (RS) in the human colon may depend on the presence of specialist primary degraders (or ‘keystone species') within the microbial community. We have explored the roles of four dominant amylolytic bacteria found in the human colon in the degradation and utilization of resistant starches. Eubacterium rectale and Bacteroides thetaiotaomicron showed limited ability to utilize RS2- and RS3-resistant starches by comparison with Bifidobacterium adolescentis and Ruminococcus bromii. In co-culture, however, R. bromii proved unique in stimulating RS2 and RS3 utilization by the other three bacterial species, even in a medium that does not permit growth of R. bromii itself. Having previously demonstrated low RS3 fermentation in vivo in two individuals with undetectable populations of R. bromii-related bacteria, we show here that supplementation of mixed fecal bacteria from one of these volunteers with R. bromii, but not with the other three species, greatly enhanced the extent of RS3 fermentation in vitro. This argues strongly that R. bromii has a pivotal role in fermentation of RS3 in the human large intestine, and that variation in the occurrence of this species and its close relatives may be a primary cause of variable energy recovery from this important component of the diet. This work also indicates that R. bromii possesses an exceptional ability to colonize and degrade starch particles when compared with previously studied amylolytic bacteria from the human colon. PMID:22343308

Water-use efficiency and relative growth rate mediate competitive interactions in Sonoran Desert winter annual plants.

PubMed

Gremer, Jennifer R; Kimball, Sarah; Keck, Katie R; Huxman, Travis E; Angert, Amy L; Venable, D Lawrence

2013-10-01

A functional approach to investigating competitive interactions can provide a mechanistic understanding of processes driving population dynamics, community assembly, and the maintenance of biodiversity. In Sonoran Desert annual plants, a trade-off between relative growth rate (RGR) and water-use efficiency (WUE) contributes to species differences in population dynamics that promote long-term coexistence. Traits underlying this trade-off explain variation in demographic responses to precipitation as well as life history and phenological patterns. Here, we ask how these traits mediate competitive interactions. • We conducted competition trials for three species occupying different positions along the RGR-WUE trade-off axis and compared the effects of competition at high and low soil moisture. We compared competitive effect (ability to suppress neighbors) and competitive response (ability to withstand competition from neighbors) among species. • The RGR-WUE trade-off predicted shifts in competitive responses at different soil moistures. The high-RGR species was more resistant to competition in high water conditions, while the opposite was true for the high-WUE species. The intermediate RGR species tended to have the strongest impact on all neighbors, so competitive effects did not scale directly with differences in RGR and WUE among competitors. • Our results reveal mechanisms underlying long-term variation in fitness: high-RGR species perform better in years with large, frequent rain events and can better withstand competition under wetter conditions. The opposite is true for high-WUE species. Such resource-dependent responses strongly influence community dynamics and can promote coexistence in variable environments.

Habitat preferences and intraspecific competition in black-footed ferrets

USGS Publications Warehouse

Biggins, Dean E.; Godbey, Jerry L.; Matchett, Marc R.; Livieri, Travis M.

2006-01-01

We used radio-telemetry data (28,560 positional fixes) collected on 153 black-footed ferrets (Mustela nigripes) to (1) reexamine the assumed obligate relationship of these ferrets to prairie dogs (Cynomys spp.), (2) investigate habitat preferences of ferrets at a small scale (1 year (P = 0.048). Also, preference was stronger for wild-born young ferrets than for young captive-born ferrets released to augment the wild population (P = 0.040). This additional evidence for competition among ferrets, and for an advantage of prior residency, raises conservation concerns. The energetics-based model commonly used to predict ferret densities at reintroduction sites does not consider competition, which likely leads to overestimation of the densities of ferrets attainable in high-quality habitat. During sequential releases of ferrets, prior residency may handicap success of newcomers, even though the latter may have higher potential fitness. Although the manner of initial colonization of available habitat by blackfooted ferrets, and their subsequent competition for it, was suggestive of an ideal despotic distribution, we did not assess effects of prey density or burrow density on fitness.

Elucidating the Role of Effectors in Plant-Fungal Interactions: Progress and Challenges

PubMed Central

Selin, Carrie; de Kievit, Teresa R.; Belmonte, Mark F.; Fernando, W. G. Dilantha

2016-01-01

Pathogenic fungi have diverse growth lifestyles that support fungal colonization on plants. Successful colonization and infection for all lifestyles depends upon the ability to modify living host plants to sequester the necessary nutrients required for growth and reproduction. Secretion of virulence determinants referred to as “effectors” is assumed to be the key governing factor that determines host infection and colonization. Effector proteins are capable of suppressing plant defense responses and alter plant physiology to accommodate fungal invaders. This review focuses on effector molecules of biotrophic and hemibiotrophic plant pathogenic fungi, and the mechanism required for the release and uptake of effector molecules by the fungi and plant cells, respectively. We also place emphasis on the discovery of effectors, difficulties associated with predicting the effector repertoire, and fungal genomic features that have helped promote effector diversity leading to fungal evolution. We discuss the role of specific effectors found in biotrophic and hemibiotrophic fungi and examine how CRISPR/Cas9 technology may provide a new avenue for accelerating our ability in the discovery of fungal effector function. PMID:27199930

A native plant competitor mediates the impact of above- and belowground damage on an invasive tree.

PubMed

Carrillo, Juli; Siemann, Evan

2016-10-01

Plant competition may mediate the impacts of herbivory on invasive plant species through effects on plant growth and defense. This may predictably depend on whether herbivory occurs above or below ground and on relative plant competitive ability. We simulated the potential impact of above- or belowground damage by biocontrol agents on the growth of a woody invader (Chinese tallow tree, Triadica sebifera) through artificial herbivory, with or without competition with a native grass, little bluestem (Schizachyrium scoparium). We measured two defense responses of Triadica through quantifying constitutive and induced extrafloral nectar production and tolerance of above- and belowground damage (root and shoot biomass regrowth). We examined genetic variation in plant growth and defense across native (China) and invasive (United States) Triadica populations. Without competition, aboveground damage had a greater impact than belowground damage on Triadica performance, whereas with competition and above- and belowground damage impacted Triadica similarly. Whole plant tolerance to damage below ground was negatively associated with tolerance to grass competitors indicating tradeoffs in the ability to tolerate herbivory vs. compete. Competition reduced investment in defensive extrafloral nectar (EFN) production. Aboveground damage inhibited rather than induced EFN production while belowground plant damage did not impact aboveground nectar production. We found some support for the evolution of increased competitive ability hypothesis for invasive plants as United States plants were larger than native China plants and were more plastic in their response to biotic stressors than China plants (they altered their root to shoot ratios dependent on herbivory and competition treatments). Our results indicate that habitat type and the presence of competitors may be a larger determinant of herbivory impact than feeding mode and suggest that integrated pest management strategies including competitive dynamics of recipient communities should be incorporated into biological control agent evaluation at earlier stages. © 2016 by the Ecological Society of America.

SpxB is a suicide gene of Streptococcus pneumoniae and confers a selective advantage in an in vivo competitive colonization model.

PubMed

Regev-Yochay, Gili; Trzcinski, Krzysztof; Thompson, Claudette M; Lipsitch, Marc; Malley, Richard

2007-09-01

The human bacterial pathogen Streptococcus pneumoniae dies spontaneously upon reaching stationary phase. The extent of S. pneumoniae death at stationary phase is unusual in bacteria and has been conventionally attributed to autolysis by the LytA amidase. In this study, we show that spontaneous pneumococcal death is due to hydrogen peroxide (H(2)O(2)), not LytA, and that the gene responsible for H(2)O(2) production (spxB) also confers a survival advantage in colonization. Survival of S. pneumoniae in stationary phase was significantly prolonged by eliminating H(2)O(2) in any of three ways: chemically by supplementing the media with catalase, metabolically by growing the bacteria under anaerobic conditions, or genetically by constructing DeltaspxB mutants that do not produce H(2)O(2). Likewise, addition of H(2)O(2) to exponentially growing S. pneumoniae resulted in a death rate similar to that of cells in stationary phase. While DeltalytA mutants did not lyse at stationary phase, they died at a rate similar to that of the wild-type strain. Furthermore, we show that the death process induced by H(2)O(2) has features of apoptosis, as evidenced by increased annexin V staining, decreased DNA content, and appearance as assessed by transmission electron microscopy. Finally, in an in vivo rat model of competitive colonization, the presence of spxB conferred a selective advantage over the DeltaspxB mutant, suggesting an explanation for the persistence of this gene. We conclude that a suicide gene of pneumococcus is spxB, which induces an apoptosis-like death in pneumococci and confers a selective advantage in nasopharyngeal cocolonization.

SpxB Is a Suicide Gene of Streptococcus pneumoniae and Confers a Selective Advantage in an In Vivo Competitive Colonization Model▿

PubMed Central

Regev-Yochay, Gili; Trzcinski, Krzysztof; Thompson, Claudette M.; Lipsitch, Marc; Malley, Richard

2007-01-01

The human bacterial pathogen Streptococcus pneumoniae dies spontaneously upon reaching stationary phase. The extent of S. pneumoniae death at stationary phase is unusual in bacteria and has been conventionally attributed to autolysis by the LytA amidase. In this study, we show that spontaneous pneumococcal death is due to hydrogen peroxide (H2O2), not LytA, and that the gene responsible for H2O2 production (spxB) also confers a survival advantage in colonization. Survival of S. pneumoniae in stationary phase was significantly prolonged by eliminating H2O2 in any of three ways: chemically by supplementing the media with catalase, metabolically by growing the bacteria under anaerobic conditions, or genetically by constructing ΔspxB mutants that do not produce H2O2. Likewise, addition of H2O2 to exponentially growing S. pneumoniae resulted in a death rate similar to that of cells in stationary phase. While ΔlytA mutants did not lyse at stationary phase, they died at a rate similar to that of the wild-type strain. Furthermore, we show that the death process induced by H2O2 has features of apoptosis, as evidenced by increased annexin V staining, decreased DNA content, and appearance as assessed by transmission electron microscopy. Finally, in an in vivo rat model of competitive colonization, the presence of spxB conferred a selective advantage over the ΔspxB mutant, suggesting an explanation for the persistence of this gene. We conclude that a suicide gene of pneumococcus is spxB, which induces an apoptosis-like death in pneumococci and confers a selective advantage in nasopharyngeal cocolonization. PMID:17631628

Metabolic pathways of Pseudomonas aeruginosa involved in competition with respiratory bacterial pathogens

PubMed Central

Beaume, Marie; Köhler, Thilo; Fontana, Thierry; Tognon, Mikael; Renzoni, Adriana; van Delden, Christian

2015-01-01

Background: Chronic airway infection by Pseudomonas aeruginosa considerably contributes to lung tissue destruction and impairment of pulmonary function in cystic-fibrosis (CF) patients. Complex interplays between P. aeruginosa and other co-colonizing pathogens including Staphylococcus aureus, Burkholderia sp., and Klebsiella pneumoniae may be crucial for pathogenesis and disease progression. Methods: We generated a library of PA14 transposon insertion mutants to identify P. aeruginosa genes required for exploitative and direct competitions with S. aureus, Burkholderia cenocepacia, and K. pneumoniae. Results: Whereas wild-type PA14 inhibited S. aureus growth, two transposon insertions located in pqsC and carB, resulted in reduced growth inhibition. PqsC is involved in the synthesis of 4-hydroxy-2-alkylquinolines (HAQs), a family of molecules having antibacterial properties, while carB is a key gene in pyrimidine biosynthesis. The carB mutant was also unable to grow in the presence of B. cepacia and K. pneumoniae but not Escherichia coli and S. epidermidis. We further identified a transposon insertion in purF, encoding a key enzyme of purine metabolism. This mutant displayed a severe growth deficiency in the presence of Gram-negative but not of Gram-positive bacteria. We identified a beneficial interaction in a bioA transposon mutant, unable to grow on rich medium. This growth defect could be restored either by addition of biotin or by co-culturing the mutant in the presence of K. pneumoniae or E. coli. Conclusion: Complex interactions take place between the various bacterial species colonizing CF-lungs. This work identified both detrimental and beneficial interactions occurring between P. aeruginosa and three other respiratory pathogens involving several major metabolic pathways. Manipulating these pathways could be used to interfere with bacterial interactions and influence the colonization by respiratory pathogens. PMID:25954256

Maternal experience and soil origin influence interactions between resident species and a dominant invasive species.

PubMed

Stotz, Gisela C; Gianoli, Ernesto; Cahill, James F

2018-01-01

Invasive species dominance in invaded communities may not be long-lasting due to regulatory processes, such as plant-soil feedbacks and neighboring species adaptation. Further, the change in species competitive ability may be contingent upon neighbor identity (i.e., specialized response) or consistent across neighbors (i.e., generalized response). Specialized responses can facilitate overall coexistence, while generalized responses may result in competitive exclusion. We set up a greenhouse experiment to test, in three species, the effect of soil conditions (non-invaded vs. invaded soil) and maternal experience (offspring of maternal plants from invaded vs. non-invaded areas) on species competitive ability against the invader Bromus inermis and conspecifics. If changes in species competitive ability against B. inermis were also evident when interacting with conspecifics, it would suggest a generalized increased/decreased competitive ability. Maternal experience resulted in reduced suppression of B. inermis in the three species and no change in tolerance. On the other hand, tolerance to B. inermis was enhanced when plants grew in soil from invaded areas, compared to non-brome soil. Importantly, both the decreased suppression due to maternal experience with B. inermis and the increased tolerance in invaded soil appear to be invader specific, as no such effects were observed when interacting with conspecifics. Specialized responses should facilitate coexistence, as no individual/species is a weaker or stronger competitor against all other neighbors or under all local soil conditions. Further, the negative plant-soil feedback for B. inermis should facilitate native species recovery in invaded areas and result in lower B. inermis performance and dominance over time.

Plant protection by the recombinant, root-colonizing Pseudomonas fluorescens F113rifPCB strain expressing arsenic resistance: improving rhizoremediation.

PubMed

Ryan, R P; Ryan, D; Dowling, D N

2007-12-01

The present study was designed to evaluate the stable insertion and expression of an arsenic resistance operon in the rhizosphere competent, PCB degrading strain Pseudomonas fluorescens F113rifPCB (F113rifPCB) and to investigate its ability to protect plants from arsenic. Introduction of the clone pUM3 (arsRDABC) into F113rifPCB was carried out by triparental conjugation. The resultant arsenic resistant strain was screened through a number of phenotypic tests including ability to grow on biphenyl, its rhizosphere competence and plant protection potential. Insertion and expression of arsenic resistant operon arsRDABC (from plasmid R773) into F113rifPCB strain has allowed this strain to grow, colonize the root and degrade biphenyl (100 mmol l(-1)) in the presence of sodium arsenate concentrations of up to 11.5 mmol l(-1). The strain retains its ability to colonize the rhizosphere of plants and appears to provide seed germination protection to arsenic which is not seen by the wild type. Owing to the significantly improved growth characteristics of both this rhizobacterium and plant species, the use of F113rifPCB-ars endowed with arsenic resistance capabilities may be a promising strategy to remediate mixed organic metal-contaminated sites. These types of strain could be used in the inoculation of metal accumulation plants for phytoremediation.

Genes Contributing to Porphyromonas gingivalis Fitness in Abscess and Epithelial Cell Colonization Environments

PubMed Central

Miller, Daniel P.; Hutcherson, Justin A.; Wang, Yan; Nowakowska, Zuzanna M.; Potempa, Jan; Yoder-Himes, Deborah R.; Scott, David A.; Whiteley, Marvin; Lamont, Richard J.

2017-01-01

Porphyromonas gingivalis is an important cause of serious periodontal diseases, and is emerging as a pathogen in several systemic conditions including some forms of cancer. Initial colonization by P. gingivalis involves interaction with gingival epithelial cells, and the organism can also access host tissues and spread haematogenously. To better understand the mechanisms underlying these properties, we utilized a highly saturated transposon insertion library of P. gingivalis, and assessed the fitness of mutants during epithelial cell colonization and survival in a murine abscess model by high-throughput sequencing (Tn-Seq). Transposon insertions in many genes previously suspected as contributing to virulence showed significant fitness defects in both screening assays. In addition, a number of genes not previously associated with P. gingivalis virulence were identified as important for fitness. We further examined fitness defects of four such genes by generating defined mutations. Genes encoding a carbamoyl phosphate synthetase, a replication-associated recombination protein, a nitrosative stress responsive HcpR transcription regulator, and RNase Z, a zinc phosphodiesterase, showed a fitness phenotype in epithelial cell colonization and in a competitive abscess infection. This study verifies the importance of several well-characterized putative virulence factors of P. gingivalis and identifies novel fitness determinants of the organism. PMID:28900609

Colonization of the Cecal Mucosa by Helicobacter hepaticus Impacts the Diversity of the Indigenous Microbiota

PubMed Central

Kuehl, Carole J.; Wood, Heather D.; Marsh, Terence L.; Schmidt, Thomas M.; Young, Vincent B.

2005-01-01

Establishment of mucosal and/or luminal colonization is the first step in the pathogenesis of many gastrointestinal bacterial pathogens. The pathogen must be able to establish itself in the face of competition from the complex microbial community that is already in place. We used culture-independent methods to monitor the colonization of the cecal mucosa of Helicobacter-free mice following experimental infection with the pathogen Helicobacter hepaticus. Two days after infection, H. hepaticus comprised a minor component of the mucosa-associated microbiota, but within 14 days, it became the dominant member of the community. Colonization of the mucosa by H. hepaticus was associated with a decrease in the overall diversity of the microbial community, in large part due to changes in evenness resulting from the relative dominance of H. hepaticus as a member of the community. Our results demonstrate that invasion of the complex gastrointestinal microbial community by a pathogenic microorganism causes reproducible and significant disturbances in the community structure. The use of non-culture-based methods to monitor these changes should lead to a greater understanding of the ecological principles that govern pathogen invasion and may lead to novel methods for the prevention and control of gastrointestinal pathogens. PMID:16177375

Activities of free and encapsulated Lactobacillus acidophilus LA5 or Lactobacillus casei 01 in processed longan juices on exposure to simulated gastrointestinal tract.

PubMed

Chaikham, Pittaya; Apichartsrangkoon, Arunee; Worametrachanon, Srivilai; Supraditareporn, Wissanee; Chokiatirote, Ekachai; Van der Wiele, Tom

2013-07-01

Fruit drinks containing probiotics are gaining interest in the global marketplace. For example, longan juice, containing carbohydrate and various bioactive components, is a potentially health-promoting beverage as well as probiotic carrier for human consumption. In this study, high-pressure and thermal processes were applied to eliminate competitive micro-organisms in longan juice prior to the addition of Lactobacillus acidophilus LA5 or Lactobacillus casei 01. The activities of these probiotics in a simulated gastrointestinal tract were also investigated. Encapsulated probiotics could survive in the acidic environment of the stomach and small intestine, while the free cells were completely eliminated. In the colon experiment, the influence of encapsulated L. casei 01 on colon lactobacilli was significantly greater than that of encapsulated L. acidophilus LA5. Both encapsulated probiotics suspended in processed longan juices led to extensive increases in the formation of lactic acid and short-chain fatty acids (SCFA). Acetate was the major SCFA produced by colon bacteria, followed by propionate and butyrate. The discernible clear zone suggested that L. casei 01 provided greater antibacterial activity than L. acidophilus LA5. Both encapsulated probiotics along with processed longan juice led to significant increases in colon lactobacilli, lactic acid and SCFA formation. © 2012 Society of Chemical Industry.

Lactate has the potential to promote hydrogen sulphide formation in the human colon.

PubMed

Marquet, Perrine; Duncan, Sylvia H; Chassard, Christophe; Bernalier-Donadille, Annick; Flint, Harry J

2009-10-01

High concentrations of sulphide are toxic for the gut epithelium and may contribute to bowel disease. Lactate is a favoured cosubstrate for the sulphate-reducing colonic bacterium Desulfovibrio piger, as shown here by the stimulation of sulphide formation by D. piger DSM749 by lactate in the presence of sulphate. Sulphide formation by D. piger was also stimulated in cocultures with the lactate-producing bacterium Bifidobacterium adolescentis L2-32. Other lactate-utilizing bacteria such as the butyrate-producing species Eubacterium hallii and Anaerostipes caccae are, however, expected to be in competition with the sulphate-reducing bacteria (SRB) for the lactate formed in the human colon. Strains of E. hallii and A. caccae produced 65% and 96% less butyrate from lactate, respectively, in a coculture with D. piger DSM749 than in a pure culture. In triculture experiments involving B. adolescentis L2-32, up to 50% inhibition of butyrate formation by E. hallii and A. caccae was observed in the presence of D. piger DSM749. On the other hand, sulphide formation by D. piger was unaffected by E. hallii or A. caccae in these cocultures and tricultures. These experiments strongly suggest that lactate can stimulate sulphide formation by SRB present in the colon, with possible consequences for conditions such as colitis.

In vivo molecular imaging of colorectal cancer using quantum dots targeted to vascular endothelial growth factor receptor 2 and optical coherence tomography/laser-induced fluorescence dual-modality imaging

NASA Astrophysics Data System (ADS)

Carbary-Ganz, Jordan L.; Welge, Weston A.; Barton, Jennifer K.; Utzinger, Urs

2015-09-01

Optical coherence tomography/laser induced fluorescence (OCT/LIF) dual-modality imaging allows for minimally invasive, nondestructive endoscopic visualization of colorectal cancer in mice. This technology enables simultaneous longitudinal tracking of morphological (OCT) and biochemical (fluorescence) changes as colorectal cancer develops, compared to current methods of colorectal cancer screening in humans that rely on morphological changes alone. We have shown that QDot655 targeted to vascular endothelial growth factor receptor 2 (QD655-VEGFR2) can be applied to the colon of carcinogen-treated mice and provides significantly increased contrast between the diseased and undiseased tissue with high sensitivity and specificity ex vivo. QD655-VEGFR2 was used in a longitudinal in vivo study to investigate the ability to correlate fluorescence signal to tumor development. QD655-VEGFR2 was applied to the colon of azoxymethane (AOM-) or saline-treated control mice in vivo via lavage. OCT/LIF images of the distal colon were taken at five consecutive time points every three weeks after the final AOM injection. Difficulties in fully flushing unbound contrast agent from the colon led to variable background signal; however, a spatial correlation was found between tumors identified in OCT images, and high fluorescence intensity of the QD655 signal, demonstrating the ability to detect VEGFR2 expressing tumors in vivo.

Mechanisms linking dietary fiber, gut microbiota and colon cancer prevention

PubMed Central

Zeng, Huawei; Lazarova, Darina L; Bordonaro, Michael

2014-01-01

Many epidemiological and experimental studies have suggested that dietary fiber plays an important role in colon cancer prevention. These findings may relate to the ability of fiber to reduce the contact time of carcinogens within the intestinal lumen and to promote healthy gut microbiota, which modifies the host’s metabolism in various ways. Elucidation of the mechanisms by which dietary fiber-dependent changes in gut microbiota enhance bile acid deconjugation, produce short chain fatty acids, and modulate inflammatory bioactive substances can lead to a better understanding of the beneficial role of dietary fiber. This article reviews the current knowledge concerning the mechanisms via which dietary fiber protects against colon cancer. PMID:24567795

Do plant traits predict the competitive abilities of closely related species?

PubMed Central

Schwartz, Lauren M.; Gibson, David J.; Young, Bryan G.

2016-01-01

Invasive species are a threat to every ecosystem. There is a strong incentive to predict which species will become invasive before they become too widespread and unmanageable. Different approaches have been advocated to assess invasive species potential. These include examining plant functional traits, quantifying competitive ability and phylogenetic comparison. In this study, we conducted experiments based on the above approaches in a multi-year, temporally replicated, set of experiments to compare these assessment methods to determine the invasive potential of Japanese chaff flower (Achyranthes japonica). We compared plant traits and competitive ability of Japanese chaff flower with two agricultural invasive species, Palmer amaranth (Amaranthus palmeri) and tall waterhemp (Amaranthus tuberculatus), and one endangered plant species, bloodleaf (Iresine rhizomatosa), in the Amaranthaceae. Additionally, we assessed the invasive potential based on each of these approaches and determined the degree of agreement between them. A relatively conservative assessment integrating all three approaches would be that the competitive ability of closely related individuals with similar functional traits would share invasive potential. In a greenhouse experiment, each of the study species and soya beans were grown as monocultures and were evaluated to assess the drawdown of an aboveground (light) and a belowground (nitrogen) resource. In a field experiment, each study species was grown at varying densities per 15-cm-diameter pot with or without one or two soya bean plants, to simulate relative densities for soya beans grown in 38- and 76-cm-wide row spacing, respectively. In addition, Japanese chaff flower seedlings were planted either as un-manipulated seedlings or as a seedling cut back to the soil surface at the four-node stage (cut Japanese chaff flower) at which point seedlings have reached a perennial growth stage. The greenhouse experiment showed that each species drew down light differently, but not nitrogen. Shading decreased the aboveground biomass of the species in comparison with unshaded controls. Nitrogen, however, increased the aboveground biomass of Palmer amaranth and Japanese chaff flower. In the field experiment, a competitive effect ranking was determined to be: tall waterhemp ≥ Palmer amaranth = cut Japanese chaff flower ≥ uncut Japanese chaff flower ≥ bloodleaf, with the competitive response ranking being the inverse. These results suggest that under specific conditions, these closely related species do exhibit similar competitive abilities. Furthermore, the invasiveness and not the life history or habitat of these closely related species appeared to be the driving factor of competitiveness. PMID:26722108

The effects of chemical interactions and culture history on the colonization of structured habitats by competing bacterial populations.

PubMed

van Vliet, Simon; Hol, Felix J H; Weenink, Tim; Galajda, Peter; Keymer, Juan E

2014-05-07

Bacterial habitats, such as soil and the gut, are structured at the micrometer scale. Important aspects of microbial life in such spatial ecosystems are migration and colonization. Here we explore the colonization of a structured ecosystem by two neutrally labeled strains of Escherichia coli. Using time-lapse microscopy we studied the colonization of one-dimensional arrays of habitat patches linked by connectors, which were invaded by the two E. coli strains from opposite sides. The two strains colonize a habitat from opposite sides by a series of traveling waves followed by an expansion front. When population waves collide, they branch into a continuing traveling wave, a reflected wave and a stationary population. When the two strains invade the landscape from opposite sides, they remain segregated in space and often one population will displace the other from most of the habitat. However, when the strains are co-cultured before entering the habitats, they colonize the habitat together and do not separate spatially. Using physically separated, but diffusionally coupled, habitats we show that colonization waves and expansion fronts interact trough diffusible molecules, and not by direct competition for space. Furthermore, we found that colonization outcome is influenced by a culture's history, as the culture with the longest doubling time in bulk conditions tends to take over the largest fraction of the habitat. Finally, we observed that population distributions in parallel habitats located on the same device and inoculated with cells from the same overnight culture are significantly more similar to each other than to patterns in identical habitats located on different devices inoculated with cells from different overnight cultures, even tough all cultures were started from the same -80°C frozen stock. We found that the colonization of spatially structure habitats by two interacting populations can lead to the formation of complex, but reproducible, spatiotemporal patterns. Furthermore, we showed that chemical interactions between two populations cause them to remain spatially segregated while they compete for habitat space. Finally, we observed that growth properties in bulk conditions correlate with the outcome of habitat colonization. Together, our data show the crucial roles of chemical interactions between populations and a culture's history in determining the outcome of habitat colonization.

The effects of chemical interactions and culture history on the colonization of structured habitats by competing bacterial populations

PubMed Central

2014-01-01

Background Bacterial habitats, such as soil and the gut, are structured at the micrometer scale. Important aspects of microbial life in such spatial ecosystems are migration and colonization. Here we explore the colonization of a structured ecosystem by two neutrally labeled strains of Escherichia coli. Using time-lapse microscopy we studied the colonization of one-dimensional arrays of habitat patches linked by connectors, which were invaded by the two E. coli strains from opposite sides. Results The two strains colonize a habitat from opposite sides by a series of traveling waves followed by an expansion front. When population waves collide, they branch into a continuing traveling wave, a reflected wave and a stationary population. When the two strains invade the landscape from opposite sides, they remain segregated in space and often one population will displace the other from most of the habitat. However, when the strains are co-cultured before entering the habitats, they colonize the habitat together and do not separate spatially. Using physically separated, but diffusionally coupled, habitats we show that colonization waves and expansion fronts interact trough diffusible molecules, and not by direct competition for space. Furthermore, we found that colonization outcome is influenced by a culture’s history, as the culture with the longest doubling time in bulk conditions tends to take over the largest fraction of the habitat. Finally, we observed that population distributions in parallel habitats located on the same device and inoculated with cells from the same overnight culture are significantly more similar to each other than to patterns in identical habitats located on different devices inoculated with cells from different overnight cultures, even tough all cultures were started from the same −80°C frozen stock. Conclusions We found that the colonization of spatially structure habitats by two interacting populations can lead to the formation of complex, but reproducible, spatiotemporal patterns. Furthermore, we showed that chemical interactions between two populations cause them to remain spatially segregated while they compete for habitat space. Finally, we observed that growth properties in bulk conditions correlate with the outcome of habitat colonization. Together, our data show the crucial roles of chemical interactions between populations and a culture’s history in determining the outcome of habitat colonization. PMID:24884963

Transactional Influences of Infants' Orienting Ability and Maternal Cooperation on Competition in Three-Year-Old Children.

ERIC Educational Resources Information Center

Lutkenhaus, Paul; And Others

1985-01-01

Describes how three-year-olds regulate their effort during competition and compares their facial expressions after failure and success, demonstrating the operation of a display rule in competition. Explores the cross-situational stability of subjects' regulation of behavior, as well as the relationship between factors influencing mother-child…

Comparison of traditional culture and molecular qPCR for detection of simultaneous carriage of multiple pneumococcal serotypes in African children.

PubMed

Olwagen, Courtney P; Adrian, Peter V; Madhi, Shabir A

2017-07-05

S. pneumoniae is a common colonizer of the human nasopharynx in high income and low-middle income countries. Due to limitations of standard culture methods, the prevalence of concurrent colonization with multiple serotypes is unclear. We evaluated the use of multiplex quantitative PCR (qPCR) to detect multiple pneumococcal serotypes/group colonization in archived nasopharyngeal swabs of pneumococcal conjugate vaccine naive children who had previously been investigated by traditional culture methods. Overall the detection of pneumococcal colonization was higher by qPCR (82%) compared to standard culture (71%; p < 0.001), with a high concordance (kappa = 0.73) of serotypes/groups identified by culture also being identified by qPCR. Also, qPCR was more sensitive in detecting multiple serotype/groups among colonized cases (28.7%) compared to culture (4.5%; p < 0.001). Of the additional serotypes detected only by qPCR, the majority were of lower density (<10 4 CFU/ml) than the dominant colonizing serotype, with serotype/group 6A/B, 19B/F and 23F being the highest density colonizers, followed by serotype 5 and serogroup 9A/L/N/V being the most common second and third colonizers respectively. The ability of qPCR to detect multiple pneumococcal serotypes at a low carriage density might provide better insight into underlying mechanism for changes in serotype colonization in PCV vaccinated children.

Campylobacter jejuni host tissue tropism: a consequence of its low-carb lifestyle?

PubMed

Thompson, Stuart A; Gaynor, Erin C

2008-11-13

Mechanisms underlying virulence properties of Campylobacter jejuni have historically been difficult to identify. In this issue of Cell Host & Microbe, Hofreuter et al. (2008) show that C. jejuni's ability to metabolize glutamine, glutathione, and asparagine affects its ability to colonize specific host tissues. These findings reflect the emerging theme of bacterial physiology directly impacting pathogenesis.

Assessing the ability of Salmonella enterica to translocate Type III effectors into plant cells

USDA-ARS?s Scientific Manuscript database

Salmonella enterica, a human enteric pathogen, has the ability to multiply and survive endophytically in plants, and mutations in genes encoding the type III secretion system (T3SS) or its effectors (T3Es) may contribute to this colonization. Two reporter plasmids for T3E translocation into plant ce...

Growth rates of rhizosphere microorganisms depend on competitive abilities of plants for nitrogen

NASA Astrophysics Data System (ADS)

Blagodatskaya, Evgenia; Littschwager, Johanna; Lauerer, Marianna; Kuzyakov, Yakov

2010-05-01

Rhizosphere - one of the most important ‘hot spots' in soil - is characterized not only by accelerated turnover of microbial biomass and nutrients but also by strong intra- and inter-specific competition. Intra-specific competition occurs between individual plants of the same species, while inter-specific competition can occur both at population level (plant species-specific, microbial species-specific interactions) and at community level (plant - microbial interactions). Such plant - microbial interactions are mainly governed by competition for available N sources, since N is one of the main growth limiting nutrients in natural ecosystems. Functional structure and activity of microbial community in rhizosphere is not uniform and is dependent on quantity and quality of root exudates which are plant specific. It is still unclear how microbial growth and turnover in the rhizosphere are dependent on the features and competitive abilities of plants for N. Depending on C and N availability, acceleration and even retardation of microbial activity and carbon mineralization can be expected in the rhizosphere of plants with high competitive abilities for N. We hypothesized slower microbial growth rates in the rhizosphere of plants with smaller roots, as they usually produce less exudates compared to plants with small shoot-to-root ratio. As the first hypothesis is based solely on C availability, we also expected the greater effect of N availability on microbial growth in rhizosphere of plants with smaller root mass. These hypothesis were tested for two plant species of strawberry: Fragaria vesca L. (native species), and Duchesnea indica (Andrews) Focke (an invasive plant in central Europe) growing in intraspecific and interspecific competition. Microbial biomass and the kinetic parameters of microbial growth in the rhizosphere were estimated by dynamics of CO2 emission from the soil amended with glucose and nutrients. Specific growth rate (µ) of soil microorganisms was estimated by fitting the parameters of the equation: CO2(t) = A + B × exp(µ×t), to the measured CO2 production rate (CO2(t)) after glucose addition, where A is the initial respiration rate uncoupled from ATP production, B the initial rate of the growing fraction of total respiration coupled with ATP generation and cell growth, and t time. Our study revealed the linkage between growth strategies of rhizosphere microorganisms and different adaptation strategies of F. vesca and D. indica to N limitation. Plant - strong competitor for N (D. indica) did not change root mass under N limitation causing the deficit of N in the rhizosphere and altering the structure of rhizosphere microbial community. Benefiting of slow growing microorganisms with K-strategy under N limiting conditions was indicated by strong decrease in specific microbial growth rates in the rhizosphere of D. indica. Root mass of the plant with weak competitive abilities for N (F. vesca) increased under lack of N to compensate the lack of nutrients. The increase in root mass and possible increase in amount of root exudates coincided with no structural changes in microbial community in rhizosphere of F. vesca. By intraspecific competition at low N level a 2.4-fold slower microbial specific growth rates were observed under D. indica (0.09 h-1) characterized by smaller root biomass and lower N content in roots compared with F. vesca. The generation time of actively growing microbial biomass was for the 6 hours longer in rhizosphere of D. indica than under F. vesca (10.7 to 4.6 h, respectively). Thus, under N limitation the strong competition for N between plant and microorganisms decreased microbial growth rates and carbon turnover in rhizosphere. By interspecific competition of both plants at low N level, microbial growth rates were similar to those for D. indica indicating that plant with stronger competitive abilities for N controls microbial community in the rhizosphere. At high N availability the root biomass did not differ significantly between both plants. This resulted in similar microbial growth rates for intra- and interspecific plant competition. Since high N level smoothed the differences between plant species in root and microbial biomass as well as in microbial growth rates, we conclude that competitive abilities of plant species were responsible for microbial growth in rhizosphere only under N imitation. As it is common that fine root proliferation and root exudation decrease at high N level, N addition smoothed the differences in microbial growth independently on plant competitive abilities.

Streptococcus pneumoniae Colonization Is Required To Alter the Nasal Microbiota in Cigarette Smoke-Exposed Mice

PubMed Central

Shen, Pamela; Whelan, Fiona J.; Schenck, L. Patrick; McGrath, Joshua J. C.; Vanderstocken, Gilles; Bowdish, Dawn M. E.; Surette, Michael G.

2017-01-01

ABSTRACT Smokers have nasal microbiota dysbiosis, with an increased frequency of colonizing bacterial pathogens. It is possible that cigarette smoke increases pathogen acquisition by perturbing the microbiota and decreasing colonization resistance. However, it is difficult to disentangle microbiota dysbiosis due to cigarette smoke exposure from microbiota changes caused by increased pathogen acquisition in human smokers. Using an experimental mouse model, we investigated the impact of cigarette smoke on the nasal microbiota in the absence and presence of nasal pneumococcal colonization. We observed that cigarette smoke exposure alone did not alter the nasal microbiota composition. The microbiota composition was also unchanged at 12 h following low-dose nasal pneumococcal inoculation, suggesting that the ability of the microbiota to resist initial nasal pneumococcal acquisition was not impaired in smoke-exposed mice. However, nasal microbiota dysbiosis occurred as a consequence of established high-dose nasal pneumococcal colonization at day 3 in smoke-exposed mice. Similar to clinical reports on human smokers, an enrichment of potentially pathogenic bacterial genera such as Fusobacterium, Gemella, and Neisseria was observed. Our findings suggest that cigarette smoke exposure predisposes to pneumococcal colonization independent of changes to the nasal microbiota and that microbiota dysbiosis observed in smokers may occur as a consequence of established pathogen colonization. PMID:28760931

Streptococcus pneumoniae Colonization Is Required To Alter the Nasal Microbiota in Cigarette Smoke-Exposed Mice.

PubMed

Shen, Pamela; Whelan, Fiona J; Schenck, L Patrick; McGrath, Joshua J C; Vanderstocken, Gilles; Bowdish, Dawn M E; Surette, Michael G; Stämpfli, Martin R

2017-10-01

Smokers have nasal microbiota dysbiosis, with an increased frequency of colonizing bacterial pathogens. It is possible that cigarette smoke increases pathogen acquisition by perturbing the microbiota and decreasing colonization resistance. However, it is difficult to disentangle microbiota dysbiosis due to cigarette smoke exposure from microbiota changes caused by increased pathogen acquisition in human smokers. Using an experimental mouse model, we investigated the impact of cigarette smoke on the nasal microbiota in the absence and presence of nasal pneumococcal colonization. We observed that cigarette smoke exposure alone did not alter the nasal microbiota composition. The microbiota composition was also unchanged at 12 h following low-dose nasal pneumococcal inoculation, suggesting that the ability of the microbiota to resist initial nasal pneumococcal acquisition was not impaired in smoke-exposed mice. However, nasal microbiota dysbiosis occurred as a consequence of established high-dose nasal pneumococcal colonization at day 3 in smoke-exposed mice. Similar to clinical reports on human smokers, an enrichment of potentially pathogenic bacterial genera such as Fusobacterium , Gemella , and Neisseria was observed. Our findings suggest that cigarette smoke exposure predisposes to pneumococcal colonization independent of changes to the nasal microbiota and that microbiota dysbiosis observed in smokers may occur as a consequence of established pathogen colonization. Copyright © 2017 American Society for Microbiology.

Influence of Salmonella enterica Serovar Typhimurium ssrB on Colonization of Eastern Oysters (Crassostrea virginica) as Revealed by a Promoter Probe Screen

PubMed Central

Cox, Clayton E.; Wright, Anita C.; McClelland, Michael

2015-01-01

Although Salmonella has been isolated from 7.4 to 8.6% of domestic raw oysters, representing a significant risk for food-borne illness, little is known about the factors that influence their initial colonization by Salmonella. This study tested the hypothesis that specific regulatory changes enable a portion of the invading Salmonella population to colonize oysters. An in vivo promoter probe library screen identified 19 unique regions as regulated during colonization. The mutants in the nearest corresponding downstream genes were tested for colonization defects in oysters. Only one mutation, in ssrB, resulted in a significantly reduced ability to colonize oysters compared to that of wild-type Salmonella. Because ssrB regulates Salmonella pathogenicity island 2 (SPI-2)-dependent infections in vertebrate macrophages, the possibility that ssrB mediated colonization of oyster hemocytes in a similar manner was examined. However, no difference in hemocyte colonization was observed. The complementary hypothesis that signal exchange between Salmonella and the oyster's native microbial community aids colonization was also tested. Signals that triggered responses in quorum sensing (QS) reporters were shown to be produced by oyster-associated bacteria and present in oyster tissue. However, no evidence for signal exchange was observed in vivo. The sdiA reporter responded to salinity, suggesting that SdiA may also have a role in environmental sensing. Overall, this study suggests the initial colonization of live oysters by Salmonella is controlled by a limited number of regulators, including ssrB. PMID:26497459

Contribution of Asparagine Catabolism to Salmonella Virulence

PubMed Central

McLaughlin, Patrick A.; McClelland, Michael; Yang, Hee-Jeong; Porwollik, Steffen; Bogomolnaya, Lydia; Chen, Juei-Suei; Andrews-Polymenis, Helene

2016-01-01

ABSTRACT Salmonellae are pathogenic bacteria that cause significant morbidity and mortality in humans worldwide. Salmonellae establish infection and avoid clearance by the immune system by mechanisms that are not well understood. We previously showed that l-asparaginase II produced by Salmonella enterica serovar Typhimurium (S. Typhimurium) inhibits T cell responses and mediates virulence. In addition, we previously showed that asparagine deprivation such as that mediated by l-asparaginase II of S. Typhimurium causes suppression of activation-induced T cell metabolic reprogramming. Here, we report that STM3997, which encodes a homolog of disulfide bond protein A (dsbA) of Escherichia coli, is required for l-asparaginase II stability and function. Furthermore, we report that l-asparaginase II localizes primarily to the periplasm and acts together with l-asparaginase I to provide S. Typhimurium the ability to catabolize asparagine and assimilate nitrogen. Importantly, we determined that, in a murine model of infection, S. Typhimurium lacking both l-asparaginase I and II genes competes poorly with wild-type S. Typhimurium for colonization of target tissues. Collectively, these results indicate that asparagine catabolism contributes to S. Typhimurium virulence, providing new insights into the competition for nutrients at the host-pathogen interface. PMID:27849183

Contribution of Asparagine Catabolism to Salmonella Virulence.

PubMed

McLaughlin, Patrick A; McClelland, Michael; Yang, Hee-Jeong; Porwollik, Steffen; Bogomolnaya, Lydia; Chen, Juei-Suei; Andrews-Polymenis, Helene; van der Velden, Adrianus W M

2017-02-01

Salmonellae are pathogenic bacteria that cause significant morbidity and mortality in humans worldwide. Salmonellae establish infection and avoid clearance by the immune system by mechanisms that are not well understood. We previously showed that l-asparaginase II produced by Salmonella enterica serovar Typhimurium (S Typhimurium) inhibits T cell responses and mediates virulence. In addition, we previously showed that asparagine deprivation such as that mediated by l-asparaginase II of S Typhimurium causes suppression of activation-induced T cell metabolic reprogramming. Here, we report that STM3997, which encodes a homolog of disulfide bond protein A (dsbA) of Escherichia coli, is required for l-asparaginase II stability and function. Furthermore, we report that l-asparaginase II localizes primarily to the periplasm and acts together with l-asparaginase I to provide S Typhimurium the ability to catabolize asparagine and assimilate nitrogen. Importantly, we determined that, in a murine model of infection, S Typhimurium lacking both l-asparaginase I and II genes competes poorly with wild-type S Typhimurium for colonization of target tissues. Collectively, these results indicate that asparagine catabolism contributes to S Typhimurium virulence, providing new insights into the competition for nutrients at the host-pathogen interface. Copyright © 2017 American Society for Microbiology.

Spatial variability in oviposition damage by periodical cicadas in a fragmented landscape.

PubMed

Cook, William M; Holt, Robert D; Yao, Jin

2001-03-01

Effects of the periodical cicada (Magicicada spp.) on forest dynamics are poorly documented. A 1998 emergence of M. cassini in eastern Kansas led to colonization of a fragmented experimental landscape undergoing secondary succession. We hypothesized that per-tree rates of oviposition damage by cicadas would reflect: (1) distance from the source of the emergence, (2) patch size, and (3) local tree density. Ovipositing females displayed clear preferences for host species and damage incidence showed predictable spatial patterns. Two species (smooth sumac, Rhus glabra, and eastern red cedar, Juniperus virginiana) were rarely attacked, whereas others (rough-leaved dogwood, Cornus drummondii; slippery elm, Ulmus rubra; box elder, Acer negundo, and honey locust, Gleditsia triacanthos) were strongly attacked. The dominant early successional tree, dogwood, received on average the most attacks. As predicted, attacks per stem declined strongly with distance from the emergence source, and with local stem density (a "dilution" effect). Contrary to expectations, there were more attacks per stem on larger patches. Because ovipositing cicadas cut damaging slits in host tree branches, potentially affecting tree growth rate, competitive ability, and capacity to reproduce, cicada damage could potentially influence spatial variation in secondary succession.

Microbial Community Composition Affects Soil Fungistasis†

PubMed Central

de Boer, Wietse; Verheggen, Patrick; Klein Gunnewiek, Paulien J. A.; Kowalchuk, George A.; van Veen, Johannes A.

2003-01-01

Most soils inhibit fungal germination and growth to a certain extent, a phenomenon known as soil fungistasis. Previous observations have implicated microorganisms as the causal agents of fungistasis, with their action mediated either by available carbon limitation (nutrient deprivation hypothesis) or production of antifungal compounds (antibiosis hypothesis). To obtain evidence for either of these hypotheses, we measured soil respiration and microbial numbers (as indicators of nutrient stress) and bacterial community composition (as an indicator of potential differences in the composition of antifungal components) during the development of fungistasis. This was done for two fungistatic dune soils in which fungistasis was initially fully or partly relieved by partial sterilization treatment or nutrient addition. Fungistasis development was measured as restriction of the ability of the fungi Chaetomium globosum, Fusarium culmorum, Fusarium oxysporum, and Trichoderma harzianum to colonize soils. Fungistasis did not always reappear after soil treatments despite intense competition for carbon, suggesting that microbial community composition is important in the development of fungistasis. Both microbial community analysis and in vitro antagonism tests indicated that the presence of pseudomonads might be essential for the development of fungistasis. Overall, the results lend support to the antibiosis hypothesis. PMID:12571002

Oxalobacter formigenes Colonization and Oxalate Dynamics in a Mouse Model

PubMed Central

Li, Xingsheng; Ellis, Melissa L.

2015-01-01

Animal and human studies have provided compelling evidence that colonization of the intestine with Oxalobacter formigenes reduces urinary oxalate excretion and lowers the risk of forming calcium oxalate kidney stones. The mechanism providing protection appears to be related to the unique ability of O. formigenes to rely on oxalate as a major source of carbon and energy for growth. However, much is not known about the factors that influence colonization and host-bacterium interactions. We have colonized mice with O. formigenes OxCC13 and systematically investigated the impacts of diets with different levels of calcium and oxalate on O. formigenes intestinal densities and urinary and intestinal oxalate levels. Measurement of intestinal oxalate levels in mice colonized or not colonized with O. formigenes demonstrated the highly efficient degradation of soluble oxalate by O. formigenes relative to other microbiota. The ratio of calcium to oxalate in diets was important in determining colonization densities and conditions where urinary oxalate and fecal oxalate excretion were modified, and the results were consistent with those from studies we have performed with colonized and noncolonized humans. The use of low-oxalate purified diets showed that 80% of animals retained O. formigenes colonization after a 1-week dietary oxalate deprivation. Animals not colonized with O. formigenes excreted two times more oxalate in feces than they had ingested. This nondietary source of oxalate may play an important role in the survival of O. formigenes during periods of dietary oxalate deprivation. These studies suggest that the mouse will be a useful model to further characterize interactions between O. formigenes and the host and factors that impact colonization. PMID:25979889

A submarine volcanic eruption leads to a novel microbial habitat.

PubMed

Danovaro, Roberto; Canals, Miquel; Tangherlini, Michael; Dell'Anno, Antonio; Gambi, Cristina; Lastras, Galderic; Amblas, David; Sanchez-Vidal, Anna; Frigola, Jaime; Calafat, Antoni M; Pedrosa-Pàmies, Rut; Rivera, Jesus; Rayo, Xavier; Corinaldesi, Cinzia

2017-04-24

Submarine volcanic eruptions are major catastrophic events that allow investigation of the colonization mechanisms of newly formed seabed. We explored the seafloor after the eruption of the Tagoro submarine volcano off El Hierro Island, Canary Archipelago. Near the summit of the volcanic cone, at about 130 m depth, we found massive mats of long, white filaments that we named Venus's hair. Microscopic and molecular analyses revealed that these filaments are made of bacterial trichomes enveloped within a sheath and colonized by epibiotic bacteria. Metagenomic analyses of the filaments identified a new genus and species of the order Thiotrichales, Thiolava veneris. Venus's hair shows an unprecedented array of metabolic pathways, spanning from the exploitation of organic and inorganic carbon released by volcanic degassing to the uptake of sulfur and nitrogen compounds. This unique metabolic plasticity provides key competitive advantages for the colonization of the new habitat created by the submarine eruption. A specialized and highly diverse food web thrives on the complex three-dimensional habitat formed by these microorganisms, providing evidence that Venus's hair can drive the restart of biological systems after submarine volcanic eruptions.

Increased Virulence and Competitive Advantage of a/α Over a/a or α/α Offspring Conserves the Mating System of Candida albicans

PubMed Central

Lockhart, Shawn R.; Wu, Wei; Radke, Joshua B.; Zhao, Rui; Soll, David R.

2005-01-01

The majority of Candida albicans strains in nature are a/α and must undergo homozygosis to a/a or α/α to mate. Here we have used a mouse model for systemic infection to test the hypothesis that a/α strains predominate in nature because they have a competitive advantage over a/a and α/α offspring in colonizing hosts. Single-strain injection experiments revealed that a/α strains were far more virulent than either their a/a or α/α offspring. When equal numbers of parent a/α and offspring a/a or α/α cells were co-injected, a/α always exhibited a competitive advantage at the time of extreme host morbidity or death. When equal numbers of an engineered a/a/α2 strain and its isogenic a/a parent strain were co-injected, the a/a/α2 strain exhibited a competitive advantage at the time of host morbidity or death, suggesting that the genotype of the mating-type (MTL) locus, not associated genes on chromosome 5, provides a competitive advantage. We therefore propose that heterozygosity at the MTL locus not only represses white-opaque switching and genes involved in the mating process, but also affects virulence, providing a competitive advantage to the a/α genotype that conserves the mating system of C. albicans in nature. PMID:15695357

Increased virulence and competitive advantage of a/alpha over a/a or alpha/alpha offspring conserves the mating system of Candida albicans.

PubMed

Lockhart, Shawn R; Wu, Wei; Radke, Joshua B; Zhao, Rui; Soll, David R

2005-04-01

The majority of Candida albicans strains in nature are a/alpha and must undergo homozygosis to a/a or alpha/alpha to mate. Here we have used a mouse model for systemic infection to test the hypothesis that a/alpha strains predominate in nature because they have a competitive advantage over a/a and alpha/alpha offspring in colonizing hosts. Single-strain injection experiments revealed that a/alpha strains were far more virulent than either their a/a or alpha/alpha offspring. When equal numbers of parent a/alpha and offspring a/a or alpha/alpha cells were co-injected, a/alpha always exhibited a competitive advantage at the time of extreme host morbidity or death. When equal numbers of an engineered a/a/alpha2 strain and its isogenic a/a parent strain were co-injected, the a/a/alpha2 strain exhibited a competitive advantage at the time of host morbidity or death, suggesting that the genotype of the mating-type (MTL) locus, not associated genes on chromosome 5, provides a competitive advantage. We therefore propose that heterozygosity at the MTL locus not only represses white-opaque switching and genes involved in the mating process, but also affects virulence, providing a competitive advantage to the a/alpha genotype that conserves the mating system of C. albicans in nature.

Obesity-related colon cancer: dietary factors and their mechanisms of anticancer action.

PubMed

Zeng, Huawei; Lazarova, Darina L

2012-02-01

Overweight/obesity is an epidemic in the US as well as in other developed countries, affecting two-thirds of Americans and an estimated 2.3 billion people worldwide. Obesity increases the risk for Type 2 diabetes, cardiovascular disease and cancer. For example, epidemiological studies have established a strong association between obesity and colon cancer. It is generally accepted that metabolic changes associated with overweight/obesity, particularly abdominal obesity and changes in adipocyte function, contribute to the increased risk of colon cancer. Understanding the mechanisms underlying this association is important for the development of preventive strategies for colon cancer. Part of these preventive strategies may be based on dietary factors, such as vitamins, minerals (e.g. selenium), fibre, phytochemicals and phenolic compounds. These anticancer nutrients may counteract the molecular changes associated with obesity. The present article reviews the evidence that inflammation and insulin resistance induced by obesity are the molecular mediators of the association between obesity and colon cancer. We also evaluate the evidence for the ability of dietary factors to target the obesity-induced changes and, thus, protect against colon cancer. © 2011 The Authors. Clinical and Experimental Pharmacology and Physiology © 2011 Blackwell Publishing Asia Pty Ltd.

Proteome Analysis Identifies the Dpr Protein of Streptococcus mutans as an Important Factor in the Presence of Early Streptococcal Colonizers of Tooth Surfaces

PubMed Central

Yoshida, Akihiro; Niki, Mamiko; Yamamoto, Yuji; Yasunaga, Ai; Ansai, Toshihiro

2015-01-01

Oral streptococci are primary colonizers of tooth surfaces and Streptococcus mutans is the principal causative agent of dental caries in humans. A number of proteins are involved in the formation of monospecies biofilms by S. mutans. This study analyzed the protein expression profiles of S. mutans biofilms formed in the presence or absence of S. gordonii, a pioneer colonizer of the tooth surface, by two-dimensional gel electrophoresis (2-DE). After identifying S. mutans proteins by Mass spectrometric analysis, their expression in the presence of S. gordonii was analyzed. S. mutans was inoculated with or without S. gordonii DL1. The two species were compartmentalized using 0.2-μl Anopore membranes. The biofilms on polystyrene plates were harvested, and the solubilized proteins were separated by 2-DE. When S. mutans biofilms were formed in the presence of S. gordonii, the peroxide resistance protein Dpr of the former showed 4.3-fold increased expression compared to biofilms that developed in the absence of the pioneer colonizer. In addition, we performed a competition assay using S. mutans antioxidant protein mutants together with S. gordonii and other initial colonizers. Growth of the dpr-knockout S. mutans mutant was significantly inhibited by S. gordonii, as well as by S. sanguinis. Furthermore, a cell viability assay revealed that the viability of the dpr-defective mutant was significantly attenuated compared to the wild-type strain when co-cultured with S. gordonii. Therefore, these results suggest that Dpr might be one of the essential proteins for S. mutans survival on teeth in the presence of early colonizing oral streptococci. PMID:25816242

The HOG Pathway Is Critical for the Colonization of the Mouse Gastrointestinal Tract by Candida albicans

PubMed Central

Prieto, Daniel; Román, Elvira; Correia, Inês; Pla, Jesus

2014-01-01

The opportunistic pathogen Candida albicans is a frequent inhabitant of the human gastrointestinal tract where it usually behaves as a harmless commensal. In this particular niche, it needs to adapt to the different micro environments that challenge its survival within the host. In order to determine those factors involved in gut adaptation, we have used a gastrointestinal model of colonization in mouse to trace the behaviour of fungal cells. We have developed a genetic labelling system based on the complementary spectral properties of the fluorescent proteins GFP and a new C. albicans codon-adapted RFP (dTOM2) that allow a precise quantification of the fungal population in the gut via standard in vitro cultures or flow cytometry. This methodology has allowed us to determine the role of the three MAP kinase pathways of C. albicans (mediated by the MAPK Mkc1, Cek1 or Hog1) in mouse gut colonization via competitive assays with MAPK pathway mutants and their isogenic wild type strain. This approach reveals the signalling through HOG pathway as a critical factor influencing the establishment of C. albicans in the mouse gut. Less pronounced effects for mkc1 or cek1 mutants were found, only evident after 2–3 weeks of colonization. We have also seen that hog1 mutants is defective in adhesion to the gut mucosa and sensitive to bile salts. Finally, we have developed a genetic strategy for the in vivo excision (tetracycline-dependent) of any specific gene during the course of colonization in this particular niche, allowing the analysis of its role during gut colonization. PMID:24475243

Platinum(IV) complex LA-12 exerts higher ability than cisplatin to enhance TRAIL-induced cancer cell apoptosis via stimulation of mitochondrial pathway.

PubMed

Jelínková, Iva; Šafaříková, Barbora; Vondálová Blanářová, Olga; Skender, Belma; Hofmanová, Jiřina; Sova, Petr; Moyer, Mary Pat; Kozubík, Alois; Kolář, Zdeněk; Ehrmann, Jiří; Hyršlová Vaculová, Alena

2014-12-01

In search for novel strategies in colon cancer treatment, we investigated the unique ability of platinum(IV) complex LA-12 to efficiently enhance the killing effects of tumor necrosis factor-related apoptosis inducing ligand (TRAIL), and compared it with the sensitizing action of cisplatin. We provide the first evidence that LA-12 primes human colon cancer cells for TRAIL-induced cytotoxicity by p53-independent activation of the mitochondrial apoptotic pathway. The cooperative action of LA-12 and TRAIL was associated with stimulation of Bax/Bak activation, drop of mitochondrial membrane potential, caspase-9 activation, and a shift of the balance among Bcl-2 family proteins in favor of the pro-apoptotic members. In contrast to cisplatin, LA-12 was a potent inducer of ERK-mediated Noxa and BimL protein upregulation, and more effectively enhanced TRAIL-induced apoptosis in the absence of Bax. The cooperative action of LA-12 and TRAIL was augmented following the siRNA-mediated silencing of Mcl-1 in both Bax proficient/deficient cells. We newly demonstrated that LA-12 induced ERK-mediated c-Myc upregulation, and proved that c-Myc silencing inhibited the mitochondrial activation and apoptosis in colon cancer cells treated with LA-12 and TRAIL. The LA-12-mediated sensitization to TRAIL-induced apoptosis was demonstrated in several colon cancer cell lines, further underscoring the general relevance of our findings. The selective action of LA-12 was documented by preferential priming of cancer but not normal colon cancer cells to TRAIL killing effects. Our work highlights the promising potential of LA-12 over cisplatin to enhance the colon cancer cell sensitivity to TRAIL-induced apoptosis, and provides new mechanistic insights into their cooperative action. Copyright © 2014 Elsevier Inc. All rights reserved.

Genetic diversity in Campylobacter jejuni is associated with differential colonization of broiler chickens and C57BL/6J IL10-deficient mice

PubMed Central

Wilson, David L.; Rathinam, Vijay A. K.; Qi, Weihong; Wick, Lukas M.; Landgraf, Jeff; Bell, Julia A.; Plovanich-Jones, Anne; Parrish, Jodi; Finley, Russell L.; Mansfield, Linda S.; Linz, John E.

2010-01-01

Previous studies have demonstrated that Campylobacter jejuni, the leading causative agent of bacterial food-borne disease in the USA, exhibits high-frequency genetic variation that is associated with changes in cell-surface antigens and ability to colonize chickens. To expand our understanding of the role of genetic diversity in the disease process, we analysed the ability of three C. jejuni human disease isolates (strains 11168, 33292 and 81-176) and genetically marked derivatives to colonize Ross 308 broilers and C57BL/6J IL10-deficient mice. C. jejuni colonized broilers at much higher efficiency (all three strains, 23 of 24 broilers) than mice (11168 only, 8 of 24 mice). C. jejuni 11168 genetically marked strains colonized mice at very low efficiency (2 of 42 mice); however, C. jejuni reisolated from mice colonized both mice and broilers at high efficiency, suggesting that this pathogen can adapt genetically in the mouse. We compared the genome composition in the three wild-type C. jejuni strains and derivatives by microarray DNA/DNA hybridization analysis; the data demonstrated a high degree of genetic diversity in three gene clusters associated with synthesis and modification of the cell-surface structures capsule, flagella and lipo-oligosaccharide. Finally, we analysed the frequency of mutation in homopolymeric tracts associated with the contingency genes wlaN (GC tract) and flgR (AT tracts) in culture and after passage through broilers and mice. C. jejuni adapted genetically in culture at high frequency and the degree of genetic diversity was increased by passage through broilers but was nearly eliminated in the gastrointestinal tract of mice. The data suggest that the broiler gastrointestinal tract provides an environment which promotes outgrowth and genetic variation in C. jejuni; the enhancement of genetic diversity at this location may contribute to its importance as a human disease reservoir. PMID:20360176

Size evolution in microorganisms masks trade-offs predicted by the growth rate hypothesis.

PubMed

Gounand, Isabelle; Daufresne, Tanguy; Gravel, Dominique; Bouvier, Corinne; Bouvier, Thierry; Combe, Marine; Gougat-Barbera, Claire; Poly, Franck; Torres-Barceló, Clara; Mouquet, Nicolas

2016-12-28

Adaptation to local resource availability depends on responses in growth rate and nutrient acquisition. The growth rate hypothesis (GRH) suggests that growing fast should impair competitive abilities for phosphorus and nitrogen due to high demand for biosynthesis. However, in microorganisms, size influences both growth and uptake rates, which may mask trade-offs and instead generate a positive relationship between these traits (size hypothesis, SH). Here, we evolved a gradient of maximum growth rate (μ max ) from a single bacterium ancestor to test the relationship among μ max , competitive ability for nutrients and cell size, while controlling for evolutionary history. We found a strong positive correlation between μ max and competitive ability for phosphorus, associated with a trade-off between μ max and cell size: strains selected for high μ max were smaller and better competitors for phosphorus. Our results strongly support the SH, while the trade-offs expected under GRH were not apparent. Beyond plasticity, unicellular populations can respond rapidly to selection pressure through joint evolution of their size and maximum growth rate. Our study stresses that physiological links between these traits tightly shape the evolution of competitive strategies. © 2016 The Author(s).

Man and his spaceships

PubMed Central

Siefert, Janet L.

2012-01-01

The resiliency and adaptive ability of microbial life in real time on Earth relies heavily upon horizontal gene transfer. Based on that knowledge, how likely is earth based microbial life to colonize extraterrestrial targets such as Mars? To address this question, we consider manned and unmanned space exploration, the resident microbiota that is likely to inhabit those vehicles, the adaptive potential of that microbiota in an extraterrestrial setting especially with regards to mobile genetic elements, and the likelihood that Mars like environments could initiate and sustain colonization. PMID:23481263

Common mycorrhizal networks amplify competition by preferential mineral nutrient allocation to large host plants.

PubMed

Weremijewicz, Joanna; Sternberg, Leonel da Silveira Lobo O'Reilly; Janos, David P

2016-10-01

Arbuscular mycorrhizal (AM) fungi interconnect plants in common mycorrhizal networks (CMNs) which can amplify competition among neighbors. Amplified competition might result from the fungi supplying mineral nutrients preferentially to hosts that abundantly provide fixed carbon, as suggested by research with organ-cultured roots. We examined whether CMNs supplied (15) N preferentially to large, nonshaded, whole plants. We conducted an intraspecific target-neighbor pot experiment with Andropogon gerardii and several AM fungi in intact, severed or prevented CMNs. Neighbors were supplied (15) N, and half of the target plants were shaded. Intact CMNs increased target dry weight (DW), intensified competition and increased size inequality. Shading decreased target weight, but shaded plants in intact CMNs had mycorrhizal colonization similar to that of sunlit plants. AM fungi in intact CMNs acquired (15) N from the substrate of neighbors and preferentially allocated it to sunlit, large, target plants. Sunlit, intact CMN, target plants acquired as much as 27% of their nitrogen from the vicinity of their neighbors, but shaded targets did not. These results suggest that AM fungi in CMNs preferentially provide mineral nutrients to those conspecific host individuals best able to provide them with fixed carbon or representing the strongest sinks, thereby potentially amplifying asymmetric competition below ground. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Nutritional basis for colonization resistance by human commensal Escherichia coli strains HS and Nissle 1917 against E. coli O157:H7 in the mouse intestine.

PubMed

Maltby, Rosalie; Leatham-Jensen, Mary P; Gibson, Terri; Cohen, Paul S; Conway, Tyrrell

2013-01-01

Escherichia coli is a single species consisting of many biotypes, some of which are commensal colonizers of mammals and others that cause disease. Humans are colonized on average with five commensal biotypes, and it is widely thought that the commensals serve as a barrier to infection by pathogens. Previous studies showed that a combination of three pre-colonized commensal E. coli strains prevents colonization of E. coli O157:H7 in a mouse model (Leatham, et al., 2010, Infect Immun 77: 2876-7886). The commensal biotypes included E. coli HS, which is known to successfully colonize humans at high doses with no adverse effects, and E. coli Nissle 1917, a human commensal strain that is used in Europe as a preventative of traveler's diarrhea. We hypothesized that commensal biotypes could exert colonization resistance by consuming nutrients needed by E. coli O157:H7 to colonize, thus preventing this first step in infection. Here we report that to colonize streptomycin-treated mice E. coli HS consumes six of the twelve sugars tested and E. coli Nissle 1917 uses a complementary yet divergent set of seven sugars to colonize, thus establishing a nutritional basis for the ability of E. coli HS and Nissle 1917 to occupy distinct niches in the mouse intestine. Together these two commensals use the five sugars previously determined to be most important for colonization of E. coli EDL933, an O157:H7 strain. As predicted, the two commensals prevented E. coli EDL933 colonization. The results support a model in which invading pathogenic E. coli must compete with the gut microbiota to obtain the nutrients needed to colonize and establish infection; accordingly, the outcome of the challenge is determined by the aggregate capacity of the native microbiota to consume the nutrients required by the pathogen.

Interspecific interactions through 2 million years: are competitive outcomes predictable?

PubMed Central

Di Martino, Emanuela; Rust, Seabourne

2016-01-01

Ecological interactions affect the survival and reproduction of individuals. However, ecological interactions are notoriously difficult to measure in extinct populations, hindering our understanding of how the outcomes of interactions such as competition vary in time and influence long-term evolutionary changes. Here, the outcomes of spatial competition in a temporally continuous community over evolutionary timescales are presented for the first time. Our research domain is encrusting cheilostome bryozoans from the Wanganui Basin of New Zealand over a ca 2 Myr time period (Pleistocene to Recent). We find that a subset of species can be identified as consistent winners, and others as consistent losers, in the sense that they win or lose interspecific competitive encounters statistically more often than the null hypothesis of 50%. Most species do not improve or worsen in their competitive abilities through the 2 Myr period, but a minority of species are winners in some intervals and losers in others. We found that conspecifics tend to cluster spatially and interact more often than expected under a null hypothesis: most of these are stand-off interactions where the two colonies involved stopped growing at edges of encounter. Counterintuitively, competitive ability has no bearing on ecological dominance. PMID:27581885

Genetic Considerations for the Restoration of Smooth Cordgrass (Spartina alterniflora) Within Its Native Range

USGS Publications Warehouse

Travis, Steven E.; Proffitt, C. Edward; Edwards, Keith R.

2006-01-01

In order to remain viable over many generations, plant populations require the ability to respond adaptively to a changing environment. Such adaptive potential is directly controlled by underlying genetic variation, which can be measured in terms of both heterozygosity at the individual level and clonal, or genotypic diversity at the population level. This report summarizes research relating to the importance of genetic diversity in the restoration of salt marsh smooth cordgrass, Spartina alterniflora, a dominant member of low elevation intertidal marshes throughout the northern Gulf of Mexico and Atlantic Coasts of North America. Recent research has indicated that S. alterniflora is a partially clonal species characterized by the recruitment of seedlings exclusively during the initial colonization phase of population establishment. A major consequence of this finding is that clonal diversity generally peaks rather early in the development of a restored marsh, depending on the rate of natural immigration and/or the clonal diversity of planting units, and then undergoes a steady decline over geological time spans because of stochastic mortality and intraspecific competition. Low levels of clonal diversity resulting from restricted immigration or clonally depauperate planting materials in turn places strict limits on opportunities for outcrossing in a species known to suffer from severe inbreeding depression. Low clonal diversity may further lead to declining levels of heterozyosity of individual clones, which directly affects competitive ability. In addition, the planting of genetically diverse plant materials should take into account the genetic and adaptive differentiation that takes place when plant populations are widely separated in space and/or dwell under varying sets of environmental conditions. Thus, steps should be taken to ensure that S. alterniflora clones developed for restorative plantings are both genetically diverse and sufficiently pre-adapted to environmental conditions at the proposed restoration site. This can be achieved by growing plant materials collected from local sources and by either taking care to maintain relatively high levels of clonal diversity or by planting clones at sufficiently low densities that they will not quickly grow to monopolize a restoration site without first producing several generations of sexual recruits through crosses with nearby native populations.

In Silico Analysis of Usher Encoding Genes in Klebsiella pneumoniae and Characterization of Their Role in Adhesion and Colonization

PubMed Central

Khater, Fida; Balestrino, Damien; Charbonnel, Nicolas; Dufayard, Jean François; Brisse, Sylvain; Forestier, Christiane

2015-01-01

Chaperone/usher (CU) assembly pathway is used by a wide range of Enterobacteriaceae to assemble adhesive surface structures called pili or fimbriae that play a role in bacteria-host cell interactions. In silico analysis revealed that the genome of Klebsiella pneumoniae LM21 harbors eight chromosomal CU loci belonging to γκп and ϭ clusters. Of these, only two correspond to previously described operons, namely type 1 and type 3-encoding operons. Isogenic usher deletion mutants of K. pneumoniae LM21 were constructed for each locus and their role in adhesion to animal (Intestine 407) and plant (Arabidopsis thaliana) cells, biofilm formation and murine intestinal colonization was investigated. Type 3 pili usher deleted mutant was impaired in all assays, whereas type 1 pili usher deleted mutant only showed attenuation in adhesion to plant cells and in intestinal colonization. The LM21ΔkpjC mutant was impaired in its capacity to adhere to Arabidopsis cells and to colonize the murine intestine, either alone or in co-inoculation experiments. Deletion of LM21kpgC induced a significant decrease in biofilm formation, in adhesion to animal cells and in colonization of the mice intestine. The LM21∆kpaC and LM21∆kpeC mutants were only attenuated in biofilm formation and the adhesion abilities to Arabidopsis cells, respectively. No clear in vitro or in vivo effect was observed for LM21∆kpbC and LM21∆kpdC mutants. The multiplicity of CU loci in K. pneumoniae genome and their specific adhesion pattern probably reflect the ability of the bacteria to adhere to different substrates in its diverse ecological niches. PMID:25751658

Cholinergic interactions between donepezil and prucalopride in human colon: potential to treat severe intestinal dysmotility

PubMed Central

Broad, J; Kung, V W S; Boundouki, G; Aziz, Q; De Maeyer, J H; Knowles, C H; Sanger, G J

2013-01-01

BACKGROUND AND PURPOSE Cholinesterase inhibitors such as neostigmine are used for acute colonic pseudo-obstruction, but cardio-bronchial side-effects limit use. To minimize side-effects, lower doses could be combined with a 5-HT4 receptor agonist, which also facilitates intestinal cholinergic activity. However, safety concerns, especially in the elderly, require drugs with good selectivity of action. These include the AChE inhibitor donepezil (used for Alzheimer's disease, with reduced cardio-bronchial liability) and prucalopride, the first selective, clinically available 5-HT4 receptor agonist. This study examined their individual and potential synergistic activities in human colon. EXPERIMENTAL APPROACH Neuronally mediated muscle contractions and relaxations of human colon were evoked by electrical field stimulation (EFS) and defined phenotypically as cholinergic, nitrergic or tachykinergic using pharmacological tools; the effects of drugs were determined as changes in ‘area under the curve’. KEY RESULTS Prucalopride increased cholinergically mediated contractions (EC50 855 nM; 33% maximum increase), consistent with its ability to stimulate intestinal motility; donepezil (477%) and neostigmine (2326%) had greater efficacy. Concentrations of donepezil (30–100 nM) found in venous plasma after therapeutic doses had minimal ability to enhance cholinergic activity. However, donepezil (30 nM) together with prucalopride (3, 10 μM) markedly increased EFS-evoked contractions compared with prucalopride alone (P = 0.04). For example, the increases observed with donepezil and prucalopride 10 μM together or alone were, respectively, 105 ± 35%, 4 ± 6% and 35 ± 21% (n = 3–7, each concentration). CONCLUSIONS AND IMPLICATIONS Potential synergy between prucalopride and donepezil activity calls for exploration of this combination as a safer, more effective treatment of colonic pseudo-obstruction. PMID:24032987

OpnS, an Outer Membrane Porin of Xenorhabdus nematophila, Confers a Competitive Advantage for Growth in the Insect Host▿ †

PubMed Central

van der Hoeven, Ransome; Forst, Steven

2009-01-01

The gammaproteobacterium Xenorhabdus nematophila engages in a mutualistic association with an entomopathogenic nematode and also functions as a pathogen toward different insect hosts. We studied the role of the growth-phase-regulated outer membrane protein OpnS in host interactions. OpnS was shown to be a 16-stranded β-barrel porin. opnS was expressed during growth in insect hemolymph and expression was elevated as the cell density increased. When wild-type and opnS deletion strains were coinjected into insects, the wild-type strain was predominantly recovered from the insect cadaver. Similarly, an opnS-complemented strain outcompeted the ΔopnS strain. Coinjection of the wild-type and ΔopnS strains together with uncolonized nematodes into insects resulted in nematode progeny that were almost exclusively colonized with the wild-type strain. Likewise, nematode progeny recovered after coinjection of a mixture of nematodes carrying either the wild-type or ΔopnS strain were colonized by the wild-type strain. In addition, the ΔopnS strain displayed a competitive growth defect when grown together with the wild-type strain in insect hemolymph but not in defined culture medium. The ΔopnS strain displayed increased sensitivity to antimicrobial compounds, suggesting that deletion of OpnS affected the integrity of the outer membrane. These findings show that the OpnS porin confers a competitive advantage for the growth and/or the survival of X. nematophila in the insect host and provides a new model for studying the biological relevance of differential regulation of porins in a natural host environment. PMID:19465651

Sialic Acid Catabolism Confers a Competitive Advantage to Pathogenic Vibrio cholerae in the Mouse Intestine▿

PubMed Central

Almagro-Moreno, Salvador; Boyd, E. Fidelma

2009-01-01

Sialic acids comprise a family of nine-carbon ketosugars that are ubiquitous on mammalian mucous membranes. However, sialic acids have a limited distribution among Bacteria and are confined mainly to pathogenic and commensal species. Vibrio pathogenicity island 2 (VPI-2), a 57-kb region found exclusively among pathogenic strains of Vibrio cholerae, contains a cluster of genes (nan-nag) putatively involved in the scavenging (nanH), transport (dctPQM), and catabolism (nanA, nanE, nanK, and nagA) of sialic acid. The capacity to utilize sialic acid as a carbon and energy source might confer an advantage to V. cholerae in the mucus-rich environment of the gut, where sialic acid availability is extensive. In this study, we show that V. cholerae can utilize sialic acid as a sole carbon source. We demonstrate that the genes involved in the utilization of sialic acid are located within the nan-nag region of VPI-2 by complementation of Escherichia coli mutants and gene knockouts in V. cholerae N16961. We show that nanH, dctP, nanA, and nanK are highly expressed in V. cholerae grown on sialic acid. By using the infant mouse model of infection, we show that V. cholerae ΔnanA strain SAM1776 is defective in early intestinal colonization stages. In addition, SAM1776 shows a decrease in the competitive index in colonization-competition assays comparing the mutant strain with both O1 El Tor and classical strains. Our data indicate an important relationship between the catabolism of sialic acid and bacterial pathogenesis, stressing the relevance of the utilization of the resources found in the host's environment. PMID:19564383

The effect of inbreeding and larval feeding regime on immature development of Aedes albopictus.

PubMed

Jong, Zheng-Wei; Kassim, Nur Faeza A; Naziri, Muhammad Aiman; Webb, Cameron E

2017-06-01

The fundamental approach to the biological control of Aedes albopictus requires the mass rearing of mosquitoes and the release of highly competitive adults in the field. As the fitness of adults is highly dependent on the development of immatures, we aimed to identify the minimum feeding regime required to produce viable and competitive adults by evaluating three response parameters: development duration, immature mortality, and adult wing length. Our study suggests at least 0.60 mg/larva/day of larval diet composed of dog food, dried beef liver, yeast, and milk powder in a weight ratio of 2:1:1:1 is required to maximize adult fitness. With standardized protocols in mass rearing, intensive studies can be readily conducted on mosquito colonies to facilitate comparisons across laboratories. This study also evaluated the differences in response of laboratory and field strains under different feeding regimes. We found that strain alone did not exert substantial effects on all response parameters. However, the field strain exhibited significantly lower immature mortality than the laboratory strain under the minimum feeding regime. Females and males of the laboratory strain had longer wing lengths under nutritional constraint due to the higher mortality that resulted in reduced interactions with the remaining larvae. Meanwhile, the field strain exhibited heterogeneous duration of immature development compared with the laboratory strain. The disparities demonstrated by the two strains in this study suggest the effect of inbreeding surfaced after a long term of laboratory colonization. Despite the trade-offs resulting from laboratory colonization, the competitiveness of the laboratory strain of Ae. albopictus is comparable to the field strain, provided the larvae are fed optimally. © 2017 The Society for Vector Ecology.

Sialic acid catabolism confers a competitive advantage to pathogenic vibrio cholerae in the mouse intestine.

PubMed

Almagro-Moreno, Salvador; Boyd, E Fidelma

2009-09-01

Sialic acids comprise a family of nine-carbon ketosugars that are ubiquitous on mammalian mucous membranes. However, sialic acids have a limited distribution among Bacteria and are confined mainly to pathogenic and commensal species. Vibrio pathogenicity island 2 (VPI-2), a 57-kb region found exclusively among pathogenic strains of Vibrio cholerae, contains a cluster of genes (nan-nag) putatively involved in the scavenging (nanH), transport (dctPQM), and catabolism (nanA, nanE, nanK, and nagA) of sialic acid. The capacity to utilize sialic acid as a carbon and energy source might confer an advantage to V. cholerae in the mucus-rich environment of the gut, where sialic acid availability is extensive. In this study, we show that V. cholerae can utilize sialic acid as a sole carbon source. We demonstrate that the genes involved in the utilization of sialic acid are located within the nan-nag region of VPI-2 by complementation of Escherichia coli mutants and gene knockouts in V. cholerae N16961. We show that nanH, dctP, nanA, and nanK are highly expressed in V. cholerae grown on sialic acid. By using the infant mouse model of infection, we show that V. cholerae DeltananA strain SAM1776 is defective in early intestinal colonization stages. In addition, SAM1776 shows a decrease in the competitive index in colonization-competition assays comparing the mutant strain with both O1 El Tor and classical strains. Our data indicate an important relationship between the catabolism of sialic acid and bacterial pathogenesis, stressing the relevance of the utilization of the resources found in the host's environment.

New opioid receptor antagonist: Naltrexone-14-O-sulfate synthesis and pharmacology.

PubMed

Zádor, Ferenc; Király, Kornél; Váradi, András; Balogh, Mihály; Fehér, Ágnes; Kocsis, Dóra; Erdei, Anna I; Lackó, Erzsébet; Zádori, Zoltán S; Hosztafi, Sándor; Noszál, Béla; Riba, Pál; Benyhe, Sándor; Fürst, Susanna; Al-Khrasani, Mahmoud

2017-08-15

Opioid antagonists, naloxone and naltrexone have long been used in clinical practice and research. In addition to their low selectivity, they easily pass through the blood-brain barrier. Quaternization of the amine group in these molecules, (e.g. methylnaltrexone) results in negligible CNS penetration. In addition, zwitterionic compounds have been reported to have limited CNS access. The current study, for the first time gives report on the synthesis and the in vitro [competition binding, G-protein activation, isolated mouse vas deferens (MVD) and mouse colon assay] pharmacology of the zwitterionic compound, naltrexone-14-O-sulfate. Naltrexone, naloxone, and its 14-O-sulfate analogue were used as reference compounds. In competition binding assays, naltrexone-14-O-sulfate showed lower affinity for µ, δ or κ opioid receptor than the parent molecule, naltrexone. However, the μ/κ opioid receptor selectivity ratio significantly improved, indicating better selectivity. Similar tendency was observed for naloxone-14-O-sulfate when compared to naloxone. Naltrexone-14-O-sulfate failed to activate [ 35 S]GTPγS-binding but inhibit the activation evoked by opioid agonists (DAMGO, Ile 5,6 deltorphin II and U69593), similarly to the reference compounds. Schild plot constructed in MVD revealed that naltrexone-14-O-sulfate acts as a competitive antagonist. In mouse colon, naltrexone-14-O-sulfate antagonized the inhibitory effect of morphine with lower affinity compared to naltrexone and higher affinity when compared to naloxone or naloxone-14-O-sulfate. In vivo (mouse tail-flick test), subcutaneously injected naltrexone-14-O-sulfate antagonized morphine's antinociception in a dose-dependent manner, indicating it's CNS penetration, which was unexpected from such zwitter ionic structure. Future studies are needed to evaluate it's pharmacokinetic profile. Copyright © 2017 Elsevier B.V. All rights reserved.

Invasion resistance arises in strongly interacting species-rich model competition communities.

PubMed Central

Case, T J

1990-01-01

I assemble stable multispecies Lotka-Volterra competition communities that differ in resident species number and average strength (and variance) of species interactions. These are then invaded with randomly constructed invaders drawn from the same distribution as the residents. The invasion success rate and the fate of the residents are determined as a function of community-and species-level properties. I show that the probability of colonization success for an invader decreases with community size and the average strength of competition (alpha). Communities composed of many strongly interacting species limit the invasion possibilities of most similar species. These communities, even for a superior invading competitor, set up a sort of "activation barrier" that repels invaders when they invade at low numbers. This "priority effect" for residents is not assumed a priori in my description for the individual population dynamics of these species; rather it emerges because species-rich and strongly interacting species sets have alternative stable states that tend to disfavor species at low densities. These models point to community-level rather than invader-level properties as the strongest determinant of differences in invasion success. The probability of extinction for a resident species increases with community size, and the probability of successful colonization by the invader decreases. Thus an equilibrium community size results wherein the probability of a resident species' extinction just balances the probability of an invader's addition. Given the distribution of alpha it is now possible to predict the equilibrium species number. The results provide a logical framework for an island-biogeographic theory in which species turnover is low even in the face of persistent invasions and for the protection of fragile native species from invading exotics. PMID:11607132

Azo polymeric micelles designed for colon-targeted dimethyl fumarate delivery for colon cancer therapy.

PubMed

Ma, Zhen-Gang; Ma, Rui; Xiao, Xiao-Lin; Zhang, Yong-Hui; Zhang, Xin-Zi; Hu, Nan; Gao, Jin-Lai; Zheng, Yu-Feng; Dong, De-Li; Sun, Zhi-Jie

2016-10-15

Colon-targeted drug delivery and circumventing drug resistance are extremely important for colon cancer chemotherapy. Our previous work found that dimethyl fumarate (DMF), the approved drug by the FDA for the treatment of multiple sclerosis, exhibited anti-tumor activity on colon cancer cells. Based on the pharmacological properties of DMF and azo bond in olsalazine chemical structure, we designed azo polymeric micelles for colon-targeted dimethyl fumarate delivery for colon cancer therapy. We synthesized the star-shape amphiphilic polymer with azo bond and fabricated the DMF-loaded azo polymeric micelles. The four-arm polymer star-PCL-azo-mPEG (sPCEG-azo) (constituted by star-shape PCL (polycaprolactone) and mPEG (methoxypolyethylene glycols)-olsalazine) showed self-assembly ability. The average diameter and polydispersity index of the DMF-loaded sPCEG-azo polymeric micelles were 153.6nm and 0.195, respectively. In vitro drug release study showed that the cumulative release of DMF from the DMF-loaded sPCEG-azo polymeric micelles was no more than 20% in rat gastric fluid within 10h, whereas in the rat colonic fluids, the cumulative release of DMF reached 60% in the initial 2h and 100% within 10h, indicating that the DMF-loaded sPCEG-azo polymeric micelles had excellent colon-targeted property. The DMF-loaded sPCEG-azo polymeric micelles had no significant cytotoxicity on colon cancer cells in phosphate buffered solution (PBS) and rat gastric fluid. In rat colonic fluid, the micelles showed significant cytotoxic effect on colon cancer cells. The blank sPCEG-azo polymeric micelles (without DMF) showed no cytotoxic effect on colon cancer cells in rat colonic fluids. In conclusion, the DMF-loaded sPCEG-azo polymeric micelles show colon-targeted DMF release and anti-tumor activity, providing a novel approach potential for colon cancer therapy. Colon-targeted drug delivery and circumventing drug resistance are extremely important for colon cancer chemotherapy. Our previous work found that dimethyl fumarate (DMF), the approved drug by the FDA for the treatment of multiple sclerosis, exhibited anti-tumor activities on colon cancer cells (Br J Pharmacol. 2015 172(15):3929-43.). Based on the pharmacological properties of DMF and azo bond in olsalazine chemical structure, we designed azo polymeric micelles for colon-targeted dimethyl fumarate delivery for colon cancer therapy. We found that the DMF-loaded sPCEG-azo polymeric micelles showed colon-targeted DMF release and anti-tumor activities, providing a novel approach potential for colon cancer therapy. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Resource competition model predicts zonation and increasing nutrient use efficiency along a wetland salinity gradient

USGS Publications Warehouse

Schoolmaster, Donald; Stagg, Camille L.

2018-01-01

A trade-off between competitive ability and stress tolerance has been hypothesized and empirically supported to explain the zonation of species across stress gradients for a number of systems. Since stress often reduces plant productivity, one might expect a pattern of decreasing productivity across the zones of the stress gradient. However, this pattern is often not observed in coastal wetlands that show patterns of zonation along a salinity gradient. To address the potentially complex relationship between stress, zonation, and productivity in coastal wetlands, we developed a model of plant biomass as a function of resource competition and salinity stress. Analysis of the model confirms the conventional wisdom that a trade-off between competitive ability and stress tolerance is a necessary condition for zonation. It also suggests that a negative relationship between salinity and production can be overcome if (1) the supply of the limiting resource increases with greater salinity stress or (2) nutrient use efficiency increases with increasing salinity. We fit the equilibrium solution of the dynamic model to data from Louisiana coastal wetlands to test its ability to explain patterns of production across the landscape gradient and derive predictions that could be tested with independent data. We found support for a number of the model predictions, including patterns of decreasing competitive ability and increasing nutrient use efficiency across a gradient from freshwater to saline wetlands. In addition to providing a quantitative framework to support the mechanistic hypotheses of zonation, these results suggest that this simple model is a useful platform to further build upon, simulate and test mechanistic hypotheses of more complex patterns and phenomena in coastal wetlands.

PhaR, a Negative Regulator of PhaP, Modulates the Colonization of a Burkholderia Gut Symbiont in the Midgut of the Host Insect, Riptortus pedestris.

PubMed

Jang, Seong Han; Jang, Ho Am; Lee, Junbeom; Kim, Jong Uk; Lee, Seung Ah; Park, Kyoung-Eun; Kim, Byung Hyun; Jo, Yong Hun; Lee, Bok Luel

2017-06-01

Five genes encoding PhaP family proteins and one phaR gene have been identified in the genome of Burkholderia symbiont strain RPE75. PhaP proteins function as the surface proteins of polyhydroxyalkanoate (PHA) granules, and the PhaR protein acts as a negative regulator of PhaP biosynthesis. Recently, we characterized one phaP gene to understand the molecular cross talk between Riptortus insects and Burkholderia gut symbionts. In this study, we constructed four other phaP gene-depleted mutants (Δ phaP1 , Δ phaP2 , Δ phaP3 , and Δ phaP4 mutants), one phaR gene-depleted mutant, and a phaR -complemented mutant (Δ phaR/phaR mutant). To address the biological roles of four phaP family genes and the phaR gene during insect-gut symbiont interaction, these Burkholderia mutants were fed to the second-instar nymphs, and colonization ability and fitness parameters were examined. In vitro , the Δ phaP3 and Δ phaR mutants cannot make a PHA granule normally in a stressful environment. Furthermore, the Δ phaR mutation decreased the colonization ability in the host midgut and negatively affected the host insect's fitness compared with wild-type Burkholderia -infected insects. However, other phaP family gene-depleted mutants colonized well in the midgut of the fifth-instar nymph insects. However, in the case of females, the colonization rate of the Δ phaP3 mutant was decreased and the host's fitness parameters were decreased compared with the wild-type-infected host, suggesting that the environment of the female midgut may be more hostile than that of the male midgut. These results demonstrate that PhaR plays an important role in the biosynthesis of PHA granules and that it is significantly related to the colonization of the Burkholderia gut symbiont in the host insects' midgut. IMPORTANCE Bacterial polyhydroxyalkanoate (PHA) biosynthesis is a complex process requiring several enzymes. The biological roles of PHA granule synthesis enzymes and the surface proteins of PHA granules during host-gut symbiont interactions are not fully understood. Here, we report the effects on colonization ability in the host midguts and the fitness of host insects after feeding Burkholderia mutant cells (four phaP -depleted mutants and one phaR -depleted mutant) to the host insects. Analyses of both synthesized PHA granule amounts and CFU numbers suggest that the phaR gene is closely related to synthesis of the PHA granule and the colonization of the Burkholderia gut symbiont in the host insect's midgut. Like our previous report, this study also supports the idea that the environment of the host midgut may not be favorable to symbiotic Burkholderia cells and that PHA granules may be required to adapt in the host midgut. Copyright © 2017 American Society for Microbiology.

PhaR, a Negative Regulator of PhaP, Modulates the Colonization of a Burkholderia Gut Symbiont in the Midgut of the Host Insect, Riptortus pedestris

PubMed Central

Jang, Seong Han; Jang, Ho Am; Lee, Junbeom; Kim, Jong Uk; Lee, Seung Ah; Park, Kyoung-Eun; Kim, Byung Hyun; Jo, Yong Hun

2017-01-01

ABSTRACT Five genes encoding PhaP family proteins and one phaR gene have been identified in the genome of Burkholderia symbiont strain RPE75. PhaP proteins function as the surface proteins of polyhydroxyalkanoate (PHA) granules, and the PhaR protein acts as a negative regulator of PhaP biosynthesis. Recently, we characterized one phaP gene to understand the molecular cross talk between Riptortus insects and Burkholderia gut symbionts. In this study, we constructed four other phaP gene-depleted mutants (ΔphaP1, ΔphaP2, ΔphaP3, and ΔphaP4 mutants), one phaR gene-depleted mutant, and a phaR-complemented mutant (ΔphaR/phaR mutant). To address the biological roles of four phaP family genes and the phaR gene during insect-gut symbiont interaction, these Burkholderia mutants were fed to the second-instar nymphs, and colonization ability and fitness parameters were examined. In vitro, the ΔphaP3 and ΔphaR mutants cannot make a PHA granule normally in a stressful environment. Furthermore, the ΔphaR mutation decreased the colonization ability in the host midgut and negatively affected the host insect's fitness compared with wild-type Burkholderia-infected insects. However, other phaP family gene-depleted mutants colonized well in the midgut of the fifth-instar nymph insects. However, in the case of females, the colonization rate of the ΔphaP3 mutant was decreased and the host's fitness parameters were decreased compared with the wild-type-infected host, suggesting that the environment of the female midgut may be more hostile than that of the male midgut. These results demonstrate that PhaR plays an important role in the biosynthesis of PHA granules and that it is significantly related to the colonization of the Burkholderia gut symbiont in the host insects' midgut. IMPORTANCE Bacterial polyhydroxyalkanoate (PHA) biosynthesis is a complex process requiring several enzymes. The biological roles of PHA granule synthesis enzymes and the surface proteins of PHA granules during host-gut symbiont interactions are not fully understood. Here, we report the effects on colonization ability in the host midguts and the fitness of host insects after feeding Burkholderia mutant cells (four phaP-depleted mutants and one phaR-depleted mutant) to the host insects. Analyses of both synthesized PHA granule amounts and CFU numbers suggest that the phaR gene is closely related to synthesis of the PHA granule and the colonization of the Burkholderia gut symbiont in the host insect's midgut. Like our previous report, this study also supports the idea that the environment of the host midgut may not be favorable to symbiotic Burkholderia cells and that PHA granules may be required to adapt in the host midgut. PMID:28341680

Minority Undergraduate Research in Prostate Cancer: Bridging Opportunities for Postbaccalaureate Education

DTIC Science & Technology

2012-03-01

students  were  assigned  to  read  both  popular  and   scientific  literature  regarding  the   genetic ,  socio...Biochemistry, Soma Jobbagy, BS Biochemistry, and Erica Boetefuer, Biological Sciences Judging Rubrics for the ASBMB Undergraduate Poster Competition 2007...Bruce Boman, Biological Sciences Role of miRNAs in Regulating Colon Cancer Stem Cells 37) Carrie Barnum and Jennifer Sabatino, Genetics Zohra Ali-Khan

Internalization property of intestinal bacteria in colon cancer and HIV/AIDS patients.

PubMed

Wachsmannova, Lenka; Ciernikova, Sona; Majek, Juraj; Mego, Michal; Stevurkova, Viola; Zajac, Vladimir

2016-07-01

Bacteria from the intestinal tract of Slovak and American HIV/AIDS patients and Slovak colon cancer patients were tested for the capacity to be internalized by cells of the HL-60 cell line as well as by normal human lymphocytes. They were anticipated to possess a specific characteristic, i.e. a vigorous ability to be internalized by HL-60 cells and human lymphocytes. This assumption was confirmed by gentamicin protection assay. Internalization of bacteria from HIV/AIDS patients frequently resulted in partial (patients SKM1, SKM22) or complete lysis (patients SKK1-1, SKM12) of HL-60 cells. In comparison with intramucosal bacteria isolated from patients with colorectal cancer (TSG, 883, 660, 838, 536, MZRa), their capacity to internalize HL-60 cells was found to be 15-20 times higher (USP15/7, USP1/4, USP3/3, SK725/5). Partial lysis (patients USP15/7, USP3/3 and SKM22) and complete lysis (patients USP1/4, SKK1-1/1, SKM1/6, SKM12/5) were detected also after internalization of bacteria by normal human lymphocytes. Compared to the amount of intracellular bacteria isolated from patients with HIV/AIDS, the ability of bacteria from patients with colorectal cancer to internalize normal human lymphocytes was significantly lower (10-15 times), yet still higher than that of bacteria isolated from healthy people. Our results present the ability of bacteria of colon cancer patients and HIV/AIDS patients to internalize HL-60 cells and normal human lymphocytes. The findings underline the potentially important function of bacteria in the induction of colorectal cancer and immunodeficiency. The particularly high detection ability of bacteria from HIV/AIDS patients to internalize normal human cells emphasizes their potentially important role in the process of AIDS.

Judging the Ability of Friends and Foes.

PubMed

Cook, Jennifer L; Murphy, Jennifer; Bird, Geoffrey

2016-10-01

Collaboration leads us to judge our own ability to be more similar to our collaborators and their ability to be more similar to our own, while competition leads us to exaggerate the gap between our abilities. How does this happen and what does it mean? Copyright © 2016 Elsevier Ltd. All rights reserved.

Research and Practice on Basic Composition and Cultivation Pattern of College Students' Innovative Ability

ERIC Educational Resources Information Center

Xu, Zhenhui; Chen, Hanlin

2010-01-01

Facing the increasingly fierce international competition, it has been the core of higher education to explore how to cultivate college students with innovative ability. College students' innovative ability is mainly composed of basic ability, innovative thinking and innovative actions. In conformity to the above composition, the cultivation…

Accuracy of colonoscopy in localizing colonic cancer.

PubMed

Stanciu, C; Trifan, Anca; Khder, Saad Alla

2007-01-01

It is important to establish the precise localization of colonic cancer preoperatively; while colonoscopy is regarded as the diagnostic gold standard for colorectal cancer, its ability to localize the tumor is less reliable. To define the accuracy of colonoscopy in identifying the location of colonic cancer. All of the patients who had a colorectal cancer diagnosed by colonoscopy at the Institute of Gastroenterology and Hepatology, Iaşi and subsequently received a surgical intervention at three teaching hospitals in Iaşi, between January 2001 and December 2005, were included in this study. Endoscopic records and operative notes were carefully reviewed, and tumor localization was recorded. There were 161 patients (89 men, 72 women, aged 61.3 +/- 12.8 years) who underwent conventional surgery for colon cancer detected by colonoscopy during the study period. Twenty-two patients (13.66%) had erroneous colonoscopic localization of the tumors. The overall accuracy of preoperative colonoscopic localization was 87.58%. Colonoscopy is an accurate, reliable method for locating colon cancer, although additional techniques (i.e., endoscopic tattooing) should be performed at least for small lesions.

Supercritical carbon dioxide-developed silk fibroin nanoplatform for smart colon cancer therapy

PubMed Central

Li, Yi; He, Xiaowen; Chen, Xiaoming; Chen, Yufeng; Zhu, Jixiang; Xu, Guibin; Wu, Xiaojian; Lan, Ping

2017-01-01

Purpose To deliver insoluble natural compounds into colon cancer cells in a controlled fashion. Materials and methods Curcumin (CM)–silk fibroin (SF) nanoparticles (NPs) were prepared by solution-enhanced dispersion by supercritical CO2 (SEDS) (20 MPa pressure, 1:2 CM:SF ratio, 1% concentration), and their physicochemical properties, intracellular uptake efficiency, in vitro anticancer effect, toxicity, and mechanisms were evaluated and analyzed. Results CM-SF NPs (<100 nm) with controllable particle size were prepared by SEDS. CM-SF NPs had a time-dependent intracellular uptake ability, which led to an improved inhibition effect on colon cancer cells. Interestingly, the anticancer effect of CM-SF NPs was improved, while the side effect on normal human colon mucosal epithelial cells was reduced by a concentration of ~10 μg/mL. The anticancer mechanism involves cell-cycle arrest in the G0/G1 and G2/M phases in association with inducing apoptotic cells. Conclusion The natural compound-loaded SF nanoplatform prepared by SEDS indicates promising colon cancer-therapy potential. PMID:29118580

Evaluation of the potential carcinogenic activity of Senna and Cascara glycosides for the rat colon.

PubMed

Mereto, E; Ghia, M; Brambilla, G

1996-03-19

Anthraquinone glycosides of Senna and Cascara were investigated for their ability to induce aberrant crypt foci (ACF) in the rat colon mucosa, which are considered putative preneoplastic lesions. Dietary exposure to high doses of these glycosides for 56 successive days did not cause the appearance of ACF or increase in incidence of ACF induced by 1,2-dimethyl-hydrazine (DMH). However, in rats treated with both DMH and the highest dose of glycosides, the average number of aberrant crypts per focus, considered a consistent predictor of tumor outcome, was higher than in rats given DMH alone. These findings suggest that Senna and Cascara glycoside might behave as weak promoters in rat colon carcinogenesis.

On a collision course: competition and dispersal differences create no-analogue communities and cause extinctions during climate change

PubMed Central

Urban, Mark C.; Tewksbury, Josh J.; Sheldon, Kimberly S.

2012-01-01

Most climate change predictions omit species interactions and interspecific variation in dispersal. Here, we develop a model of multiple competing species along a warming climatic gradient that includes temperature-dependent competition, differences in niche breadth and interspecific differences in dispersal ability. Competition and dispersal differences decreased diversity and produced so-called ‘no-analogue’ communities, defined as a novel combination of species that does not currently co-occur. Climate change altered community richness the most when species had narrow niches, when mean community-wide dispersal rates were low and when species differed in dispersal abilities. With high interspecific dispersal variance, the best dispersers tracked climate change, out-competed slower dispersers and caused their extinction. Overall, competition slowed the advance of colonists into newly suitable habitats, creating lags in climate tracking. We predict that climate change will most threaten communities of species that have narrow niches (e.g. tropics), vary in dispersal (most communities) and compete strongly. Current forecasts probably underestimate climate change impacts on biodiversity by neglecting competition and dispersal differences. PMID:22217718

Efficient zinc uptake is critical for the ability of Pseudomonas aeruginosa to express virulence traits and colonize the human lung.

PubMed

Mastropasqua, Maria Chiara; Lamont, Iain; Martin, Lois W; Reid, David W; D'Orazio, Melania; Battistoni, Andrea

2018-07-01

We have recently shown that Pseudomonas aeruginosa, an opportunistic pathogen that chronically infects the lungs of patients with cystic fibrosis (CF) and other forms of lung disease, is extremely efficient in recruiting zinc from the environment and that this capability is required for its ability to cause acute lung infections in mice. To verify that P. aeruginosa faces zinc shortage when colonizing the lungs of human patients, we analyzed the expression of three genes that are highly induced under conditions of zinc deficiency (zrmA, dksA2 and rpmE2), in bacteria in the sputum of patients with inflammatory lung disease. All three genes were expressed in all the analyzed sputum samples to a level much higher than that of bacteria grown in zinc-containing laboratory medium, supporting the hypothesis that P. aeruginosa is under zinc starvation during lung infections. We also found that the expression of several virulence traits that play a central role in the ability of P. aeruginosa to colonize the lung is affected by disruption of the most important zinc importing systems. Virulence features dependent on zinc intake include swarming and swimming motility and the ability to form biofilms. Furthermore, alterations in zinc assimilation interfere with the synthesis of the siderophore pyoverdine, suggesting that zinc recruitment could modulate iron uptake and affect siderophore-mediated cell signaling. Our results reveal that zinc uptake is likely to play a key role in the ability of P. aeruginosa to cause chronic lung infections and strongly modulates critical virulence traits of the pathogen. Taking into account the recent discovery that zinc uptake in P. aeruginosa is promoted by the release of a small molecular weight molecule showing high affinity for zinc, our data suggest novel and effective possibilities to control lung infections by these bacteria. Copyright © 2018 Elsevier GmbH. All rights reserved.

Adipocytes activate mitochondrial fatty acid oxidation and autophagy to promote tumor growth in colon cancer.

PubMed

Wen, Yang-An; Xing, Xiaopeng; Harris, Jennifer W; Zaytseva, Yekaterina Y; Mitov, Mihail I; Napier, Dana L; Weiss, Heidi L; Mark Evers, B; Gao, Tianyan

2017-02-02

Obesity has been associated with increased incidence and mortality of a wide variety of human cancers including colorectal cancer. However, the molecular mechanism by which adipocytes regulate the metabolism of colon cancer cells remains elusive. In this study, we showed that adipocytes isolated from adipose tissues of colon cancer patients have an important role in modulating cellular metabolism to support tumor growth and survival. Abundant adipocytes were found in close association with invasive tumor cells in colon cancer patients. Co-culture of adipocytes with colon cancer cells led to a transfer of free fatty acids that released from the adipocytes to the cancer cells. Uptake of fatty acids allowed the cancer cells to survive nutrient deprivation conditions by upregulating mitochondrial fatty acid β-oxidation. Mechanistically, co-culture of adipocytes or treating cells with fatty acids induced autophagy in colon cancer cells as a result of AMPK activation. Inhibition of autophagy attenuated the ability of cancer cells to utilize fatty acids and blocked the growth-promoting effect of adipocytes. In addition, we found that adipocytes stimulated the expression of genes associated with cancer stem cells and downregulated genes associated with intestinal epithelial cell differentiation in primary colon cancer cells and mouse tumor organoids. Importantly, the presence of adipocytes promoted the growth of xenograft tumors in vivo. Taken together, our results show that adipocytes in the tumor microenvironment serve as an energy provider and a metabolic regulator to promote the growth and survival of colon cancer cells.

Adipocytes activate mitochondrial fatty acid oxidation and autophagy to promote tumor growth in colon cancer

PubMed Central

Wen, Yang-An; Xing, Xiaopeng; Harris, Jennifer W; Zaytseva, Yekaterina Y; Mitov, Mihail I; Napier, Dana L; Weiss, Heidi L; Mark Evers, B; Gao, Tianyan

2017-01-01

Obesity has been associated with increased incidence and mortality of a wide variety of human cancers including colorectal cancer. However, the molecular mechanism by which adipocytes regulate the metabolism of colon cancer cells remains elusive. In this study, we showed that adipocytes isolated from adipose tissues of colon cancer patients have an important role in modulating cellular metabolism to support tumor growth and survival. Abundant adipocytes were found in close association with invasive tumor cells in colon cancer patients. Co-culture of adipocytes with colon cancer cells led to a transfer of free fatty acids that released from the adipocytes to the cancer cells. Uptake of fatty acids allowed the cancer cells to survive nutrient deprivation conditions by upregulating mitochondrial fatty acid β-oxidation. Mechanistically, co-culture of adipocytes or treating cells with fatty acids induced autophagy in colon cancer cells as a result of AMPK activation. Inhibition of autophagy attenuated the ability of cancer cells to utilize fatty acids and blocked the growth-promoting effect of adipocytes. In addition, we found that adipocytes stimulated the expression of genes associated with cancer stem cells and downregulated genes associated with intestinal epithelial cell differentiation in primary colon cancer cells and mouse tumor organoids. Importantly, the presence of adipocytes promoted the growth of xenograft tumors in vivo. Taken together, our results show that adipocytes in the tumor microenvironment serve as an energy provider and a metabolic regulator to promote the growth and survival of colon cancer cells. PMID:28151470

Broad-Spectrum Suppression of Innate Immunity Is Required for Colonization of Arabidopsis Roots by the Fungus Piriformospora indica1[C][W

PubMed Central

Jacobs, Sophie; Zechmann, Bernd; Molitor, Alexandra; Trujillo, Marco; Petutschnig, Elena; Lipka, Volker; Kogel, Karl-Heinz; Schäfer, Patrick

2011-01-01

Piriformospora indica is a root-colonizing basidiomycete that confers a wide range of beneficial traits to its host. The fungus shows a biotrophic growth phase in Arabidopsis (Arabidopsis thaliana) roots followed by a cell death-associated colonization phase, a colonization strategy that, to our knowledge, has not yet been reported for this plant. P. indica has evolved an extraordinary capacity for plant root colonization. Its broad host spectrum encompasses gymnosperms and monocotyledonous as well as dicotyledonous angiosperms, which suggests that it has an effective mechanism(s) for bypassing or suppressing host immunity. The results of our work argue that P. indica is confronted with a functional root immune system. Moreover, the fungus does not evade detection but rather suppresses immunity triggered by various microbe-associated molecular patterns. This ability to suppress host immunity is compromised in the jasmonate mutants jasmonate insensitive1-1 and jasmonate resistant1-1. A quintuple-DELLA mutant displaying constitutive gibberellin (GA) responses and the GA biosynthesis mutant ga1-6 (for GA requiring 1) showed higher and lower degrees of colonization, respectively, in the cell death-associated stage, suggesting that P. indica recruits GA signaling to help establish proapoptotic root cell colonization. Our study demonstrates that mutualists, like pathogens, are confronted with an effective innate immune system in roots and that colonization success essentially depends on the evolution of strategies for immunosuppression. PMID:21474434

Development of an ion-pair to improve the colon permeability of a low permeability drug: Atenolol.

PubMed

Lozoya-Agullo, Isabel; González-Álvarez, Isabel; González-Álvarez, Marta; Merino-Sanjuán, Matilde; Bermejo, Marival

2016-10-10

To ensure the optimal performance of oral controlled release formulations, drug colon permeability is one of the critical parameters. Consequently developing this kind of formulations for low permeability molecules requires strategies to increase their ability to cross the colonic membrane. The objective of this work is to show if an ion-pair formation can improve the colon permeability of atenolol as a low permeability drug model. Two counter ions have been tested: brilliant blue and bromophenol blue. The Distribution coefficients at pH7.00 (DpH7) of atenolol, atenolol + brilliant blue and atenolol + bromophenol blue were experimentally determined in n-octanol. Moreover, the colonic permeability was determined in rat colon using in situ closed loop perfusion method based in Doluisio's Technique. To check the potential effects of the counter ions on the membrane integrity, a histological assessment of colonic tissue was done. The results of the partitioning studies were inconclusive about ion-pair formation; nevertheless colon permeability was significantly increased by both counter ions (from 0.232±0.021cm/s to 0.508±0.038cm/s in the presence of brilliant blue and to 0.405±0.044cm/s in the presence of bromophenol blue). Neither damage on the membrane was observed on the histological studies, nor any change on paracellular permeability suggesting that the permeability enhancement could be attributed to the ion-pair formation. Copyright © 2016 Elsevier B.V. All rights reserved.

Citrinin as an accessory establishment factor of P. expansum for the colonization of apples.

PubMed

Touhami, Najim; Soukup, Sebastian T; Schmidt-Heydt, Markus; Kulling, Sabine E; Geisen, Rolf

2018-02-02

Penicillium expansum is the causal agent of blue mold decay of apples. This fungal species can produce the two important mycotoxins patulin and citrinin. It was previously shown that patulin represents a colonization factor for the infection of apples. No definitive information about the importance of citrinin for the colonization of apples is currently available. The pksCT gene of the citrinin cluster codes for the citrinin polyketide synthase. Mutants of P. expansum in which the pksCT was inactivated showed a drastic decrease in the citrinin production. In addition, the pksCT mutants were also reduced in the ability to colonize apples. Externally added citrinin restored the capacity of the mutants to colonize apples roughly to that of the wild type. A kinetic analysis of the expression of the two respective pks genes of patulin (patK) and citrinin (pksCT) revealed that both genes are highly expressed in the first phase during the colonization process. The production of patulin in the apple matrix coincides with the expression of the patK gene. Almost no citrinin could be identified analytically during the first phase but only at a later stage of the colonization. It could be demonstrated that citrinin is degraded in apples and can tightly be bound to pectin. Overall the results suggest that citrinin may have an accessory function for the establishment of the colonization guided by other factors. Copyright © 2017 Elsevier B.V. All rights reserved.

Carryover effects from natal habitat type upon competitive ability lead to trait divergence or source-sink dynamics.

PubMed

Kristensen, Nadiah Pardede; Johansson, Jacob; Chisholm, Ryan A; Smith, Henrik G; Kokko, Hanna

2018-06-25

Local adaptation to rare habitats is difficult due to gene flow, but can occur if the habitat has higher productivity. Differences in offspring phenotypes have attracted little attention in this context. We model a scenario where the rarer habitat improves offspring's later competitive ability - a carryover effect that operates on top of local adaptation to one or the other habitat type. Assuming localised dispersal, so the offspring tend to settle in similar habitat to the natal type, the superior competitive ability of offspring remaining in the rarer habitat hampers immigration from the majority habitat. This initiates a positive feedback between local adaptation and trait divergence, which can thereafter be reinforced by coevolution with dispersal traits that match ecotype to habitat type. Rarity strengthens selection on dispersal traits and promotes linkage disequilibrium between locally adapted traits and ecotype-habitat matching dispersal. We propose that carryover effects may initiate isolation by ecology. © 2018 The Authors. Ecology Letters published by CNRS and John Wiley & Sons Ltd.

Development of a Phage Cocktail to Control Proteus mirabilis Catheter-associated Urinary Tract Infections

PubMed Central

Melo, Luís D. R.; Veiga, Patrícia; Cerca, Nuno; Kropinski, Andrew M.; Almeida, Carina; Azeredo, Joana; Sillankorva, Sanna

2016-01-01

Proteus mirabilis is an enterobacterium that causes catheter-associated urinary tract infections (CAUTIs) due to its ability to colonize and form crystalline biofilms on the catheters surface. CAUTIs are very difficult to treat, since biofilm structures are highly tolerant to antibiotics. Phages have been used widely to control a diversity of bacterial species, however, a limited number of phages for P. mirabilis have been isolated and studied. Here we report the isolation of two novel virulent phages, the podovirus vB_PmiP_5460 and the myovirus vB_PmiM_5461, which are able to target, respectively, 16 of the 26 and all the Proteus strains tested in this study. Both phages have been characterized thoroughly and sequencing data revealed no traces of genes associated with lysogeny. To further evaluate the phages’ ability to prevent catheter’s colonization by Proteus, the phages adherence to silicone surfaces was assessed. Further tests in phage-coated catheters using a dynamic biofilm model simulating CAUTIs, have shown a significant reduction of P. mirabilis biofilm formation up to 168 h of catheterization. These results highlight the potential usefulness of the two isolated phages for the prevention of surface colonization by this bacterium. PMID:27446059

Genetics of mycorrhizal symbiosis in winter wheat (Triticum aestivum).

PubMed

Lehnert, Heike; Serfling, Albrecht; Enders, Matthias; Friedt, Wolfgang; Ordon, Frank

2017-07-01

Bread wheat (Triticum aestivum) is a major staple food and therefore of prime importance for feeding the Earth's growing population. Mycorrhiza is known to improve plant growth, but although extensive knowledge concerning the interaction between mycorrhizal fungi and plants is available, genotypic differences concerning the ability of wheat to form mycorrhizal symbiosis and quantitative trait loci (QTLs) involved in mycorrhization are largely unknown. Therefore, a diverse set of 94 bread wheat genotypes was evaluated with regard to root colonization by arbuscular mycorrhizal fungi. In order to identify genomic regions involved in mycorrhization, these genotypes were analyzed using the wheat 90k iSelect chip, resulting in 17 823 polymorphic mapped markers, which were used in a genome-wide association study. Significant genotypic differences (P < 0.0001) were detected in the ability to form symbiosis and 30 significant markers associated with root colonization, representing six QTL regions, were detected on chromosomes 3A, 4A and 7A, and candidate genes located in these QTL regions were proposed. The results reported here provide key insights into the genetics of root colonization by mycorrhizal fungi in wheat. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Analysis of students’ self-determination in learning mathematics

NASA Astrophysics Data System (ADS)

Wilujeng, H.

2018-01-01

Self-determination (SDT) is the ability in identifying and achieving the purpose based on knowledge and the assessment of the individual against himself. Three aspects in the SDT includes autonomy, competence and relationships become an important part for students to be able to understand the capabilities of themselves, having a positive competitiveness to other students and can interact well between friends. Therefore, teachers need to know the ability of students SDT after making the learning process. This research was conducted to improve the process of learning mathematics by knowing the ability of students SDT. The researcher gave the question form to 38 students and analyzed the ability of SDT. The Results of the study showed that the student SDT ability is still poor. Students were lack of confidence to solve math problems. In addition, the competitiveness of students was low that have made them looked lazy. This can be resolved by making learning more interesting for students so that it can increase the student SDT ability.

Tracking microbial colonization in fecal microbiota transplantation experiments via genome-resolved metagenomics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Sonny T. M.; Kahn, Stacy A.; Delmont, Tom O.

Fecal microbiota transplantation (FMT) is an effective treatment for recurrent Clostridium difficile infection and shows promise for treating other medical conditions associated with intestinal dysbioses. However, we lack a sufficient understanding of which microbial populations successfully colonize the recipient gut, and the widely used approaches to study the microbial ecology of FMT experiments fail to provide enough resolution to identify populations that are likely responsible for FMT-derived benefits. Here, we used shotgun metagenomics together with assembly and binning strategies to reconstruct metagenome-assembled genomes (MAGs) from fecal samples of a single FMT donor. We then used metagenomic mapping to track themore » occurrence and distribution patterns of donor MAGs in two FMT recipients. Our analyses revealed that 22% of the 92 highly complete bacterial MAGs that we identified from the donor successfully colonized and remained abundant in two recipients for at least 8 weeks. Most MAGs with a high colonization rate belonged to the order Bacteroidales. The vast majority of those that lacked evidence of colonization belonged to the order Clostridiales, and colonization success was negatively correlated with the number of genes related to sporulation. Our analysis of 151 publicly available gut metagenomes showed that the donor MAGs that colonized both recipients were prevalent, and the ones that colonized neither were rare across the participants of the Human Microbiome Project. Although our dataset showed a link between taxonomy and the colonization ability of a given MAG, we also identified MAGs that belong to the same taxon with different colonization properties, highlighting the importance of an appropriate level of resolution to explore the functional basis of colonization and to identify targets for cultivation, hypothesis generation, and testing in model systems. Lastly, the analytical strategy adopted in our study can provide genomic insights into bacterial populations that may be critical to the efficacy of FMT due to their success in gut colonization and metabolic properties, and guide cultivation efforts to investigate mechanistic underpinnings of this procedure beyond associations.« less

Tracking microbial colonization in fecal microbiota transplantation experiments via genome-resolved metagenomics

DOE PAGES

Lee, Sonny T. M.; Kahn, Stacy A.; Delmont, Tom O.; ...

2017-05-04

Fecal microbiota transplantation (FMT) is an effective treatment for recurrent Clostridium difficile infection and shows promise for treating other medical conditions associated with intestinal dysbioses. However, we lack a sufficient understanding of which microbial populations successfully colonize the recipient gut, and the widely used approaches to study the microbial ecology of FMT experiments fail to provide enough resolution to identify populations that are likely responsible for FMT-derived benefits. Here, we used shotgun metagenomics together with assembly and binning strategies to reconstruct metagenome-assembled genomes (MAGs) from fecal samples of a single FMT donor. We then used metagenomic mapping to track themore » occurrence and distribution patterns of donor MAGs in two FMT recipients. Our analyses revealed that 22% of the 92 highly complete bacterial MAGs that we identified from the donor successfully colonized and remained abundant in two recipients for at least 8 weeks. Most MAGs with a high colonization rate belonged to the order Bacteroidales. The vast majority of those that lacked evidence of colonization belonged to the order Clostridiales, and colonization success was negatively correlated with the number of genes related to sporulation. Our analysis of 151 publicly available gut metagenomes showed that the donor MAGs that colonized both recipients were prevalent, and the ones that colonized neither were rare across the participants of the Human Microbiome Project. Although our dataset showed a link between taxonomy and the colonization ability of a given MAG, we also identified MAGs that belong to the same taxon with different colonization properties, highlighting the importance of an appropriate level of resolution to explore the functional basis of colonization and to identify targets for cultivation, hypothesis generation, and testing in model systems. Lastly, the analytical strategy adopted in our study can provide genomic insights into bacterial populations that may be critical to the efficacy of FMT due to their success in gut colonization and metabolic properties, and guide cultivation efforts to investigate mechanistic underpinnings of this procedure beyond associations.« less

Propolis from Different Geographic Origins Suppress Intestinal Inflammation in a Model of DSS-Induced Colitis is Associated with Decreased Bacteroides spp. in the Gut.

PubMed

Wang, Kai; Jin, Xiaolu; Li, Qiangqiang; Sawaya, Alexandra Christine Helena Frankland; Leu, Richard K Le; Conlon, Michael A; Wu, Liming; Hu, Fuliang

2018-06-11

Dietary supplementation with polyphenol-rich propolis can protect against experimentally-induced colitis. We examined whether different polyphenol compositions of Chinese propolis (CP) and Brazilian propolis (BP) influences their ability to protect against dextran sulfate sodium (DSS)-induced colitis in rats. HPLC-DAD/Q-TOF-MS analysis confirmed that polyphenol compositions of CP and BP were dissimilar. Rats were given CP or BP by gavage (300 mg/kg body weight) throughout the study, starting 1 week prior to DSS treatment for 1 week followed by 3 d without DSS. CP and BP significantly reduced the colitis disease activity index relative to controls not receiving propolis, prevented significant DSS-induced colonic tissue damage and increased resistance to DSS-induced colonic oxidative stress as shown by reduced malonaldehyde levels and increased T-AOC levels. CP and BP significantly reduced DSS-induced colonic apoptosis. Colonic inflammatory markers IL-1β, IL-6 and MCP-1 were suppressed by CP and BP, whereas only BP induced expression of TGF-β. CP, not BP, increased the diversity and richness of gut microbiota populations. Both forms of propolis significantly reduced populations of Bacteroides spp. Despite the dissimilar polyphenol compositions of CP and BP, their ability to protect against DSS-induced colitis is similar. Nevertheless, some different physiological impacts were observed. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Cultured representatives of two major phylogroups of human colonic Faecalibacterium prausnitzii can utilize pectin, uronic acids, and host-derived substrates for growth.

PubMed

Lopez-Siles, Mireia; Khan, Tanweer M; Duncan, Sylvia H; Harmsen, Hermie J M; Garcia-Gil, L Jesús; Flint, Harry J

2012-01-01

Faecalibacterium prausnitzii is one of the most abundant commensal bacteria in the healthy human large intestine, but information on genetic diversity and substrate utilization is limited. Here, we examine the phylogeny, phenotypic characteristics, and influence of gut environmental factors on growth of F. prausnitzii strains isolated from healthy subjects. Phylogenetic analysis based on the 16S rRNA sequences indicated that the cultured strains were representative of F. prausnitzii sequences detected by direct analysis of fecal DNA and separated the available isolates into two phylogroups. Most F. prausnitzii strains tested grew well under anaerobic conditions on apple pectin. Furthermore, F. prausnitzii strains competed successfully in coculture with two other abundant pectin-utilizing species, Bacteroides thetaiotaomicron and Eubacterium eligens, with apple pectin as substrate, suggesting that this species makes a contribution to pectin fermentation in the colon. Many F. prausnitzii isolates were able to utilize uronic acids for growth, an ability previously thought to be confined to Bacteroides spp. among human colonic anaerobes. Most strains grew on N-acetylglucosamine, demonstrating an ability to utilize host-derived substrates. All strains tested were bile sensitive, showing at least 80% growth inhibition in the presence of 0.5 μg/ml bile salts, while inhibition at mildly acidic pH was strain dependent. These attributes help to explain the abundance of F. prausnitzii in the colonic community but also suggest factors in the gut environment that may limit its distribution.

Cultured Representatives of Two Major Phylogroups of Human Colonic Faecalibacterium prausnitzii Can Utilize Pectin, Uronic Acids, and Host-Derived Substrates for Growth

PubMed Central

Lopez-Siles, Mireia; Khan, Tanweer M.; Duncan, Sylvia H.; Harmsen, Hermie J. M.; Garcia-Gil, L. Jesús

2012-01-01

Faecalibacterium prausnitzii is one of the most abundant commensal bacteria in the healthy human large intestine, but information on genetic diversity and substrate utilization is limited. Here, we examine the phylogeny, phenotypic characteristics, and influence of gut environmental factors on growth of F. prausnitzii strains isolated from healthy subjects. Phylogenetic analysis based on the 16S rRNA sequences indicated that the cultured strains were representative of F. prausnitzii sequences detected by direct analysis of fecal DNA and separated the available isolates into two phylogroups. Most F. prausnitzii strains tested grew well under anaerobic conditions on apple pectin. Furthermore, F. prausnitzii strains competed successfully in coculture with two other abundant pectin-utilizing species, Bacteroides thetaiotaomicron and Eubacterium eligens, with apple pectin as substrate, suggesting that this species makes a contribution to pectin fermentation in the colon. Many F. prausnitzii isolates were able to utilize uronic acids for growth, an ability previously thought to be confined to Bacteroides spp. among human colonic anaerobes. Most strains grew on N-acetylglucosamine, demonstrating an ability to utilize host-derived substrates. All strains tested were bile sensitive, showing at least 80% growth inhibition in the presence of 0.5 μg/ml bile salts, while inhibition at mildly acidic pH was strain dependent. These attributes help to explain the abundance of F. prausnitzii in the colonic community but also suggest factors in the gut environment that may limit its distribution. PMID:22101049

Up-regulation of CHAF1A, a poor prognostic factor, facilitates cell proliferation of colon cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Zehua; Cui, Feifei; Yu, Fudong

2014-06-27

Highlights: • We identified that CHAF1A was up-regulated in colon tumor mucosa in TMA. • The expression pattern of CHAF1A was validated with qPCR and western-blot. • CHAF1A overexpression is an independent indicator for poor colon cancer survival. • CHAF1A facilitates cell proliferation of colon cancer both in vitro and in vivo. - Abstract: Deregulation of chromatin assembly factor 1, p150 subunit A (CHAF1A) has recently been reported to be involved in the development of some cancer types. In this study, we identified that the frequency of positive CHAF1A staining in primary tumor mucosa (45.8%, 93 of 203 samples) wasmore » significantly elevated compared to that in paired normal mucosa (18.7%, 38 of 203 samples). The increased expression was strongly associated with cancer stage, tumor invasion, and histological grade. The five-year survival rate of patients with CHAF1A-positive tumors was remarkably lower than that of patients with CHAF1A-negative tumors. Colon cancer cells with CHAF1A knockdown exhibited decreased cell growth index, reduction in colony formation ability, elevated cell apoptosis rate as well as impaired colon tumorigenicity in nude mice. Hence, CHAF1A upregulation functions as a poor prognostic indicator of colon cancer, potentially contributing to its progression by mediating cancer cell proliferation.« less

Left colonic graft in esophageal reconstruction for caustic stricture: mortality and morbidity.

PubMed

Boukerrouche, A

2013-01-01

The adequacy of the blood supply to the left colon graft and its ability to transport food effectively from pharynx to stomach made it an esophageal substitute of choice, particularly in esophageal caustic stricture. From 1999 to 2009, 60 patients underwent colon interposition for esophageal caustic stricture (n= 57) and cancer (n= 3). An isoperistaltic colonic graft based on the left colonic artery could be used in all of these patients. The substernal route was used exclusively, and upper thoracic inlet was opened when necessary. The isoperistaltic left colonic graft interposed by substernal route represents the surgical procedure of choice in all operations performed for esophageal substitution during the study period. The operative mortality rate was 3.3%. A cervical fistula occurred in 10 patients (16.6%) and cervical anastomotic stricture in five patients (8.3%). Dilation was required in all the stricture of the esophageal colonic anastomosis with good response. The isoperistaltic left colic transplant supplied by the left colic pedicle is an excellent long-term replacement organ for the esophageal caustic stenosis. When performed by experienced surgeons, the left isoperistaltic esophagocoloplasty is a satisfactory surgical method for esophageal reconstruction with acceptable early morbidity and good long-term functional results. © 2012 Copyright the Authors. Journal compilation © 2012, Wiley Periodicals, Inc. and the International Society for Diseases of the Esophagus.

Characterization of Thymic Settling Progenitors in the Mouse Embryo Using In Vivo and In Vitro Assays

PubMed Central

Ramond, Cyrille; Bandeira, Antonio; Berthault, Claire; Pereira, Pablo; Cumano, Ana; Burlen-Defranoux, Odile

2015-01-01

Characterizing thymic settling progenitors is important to understand the pre-thymic stages of T cell development, essential to devise strategies for T cell replacement in lymphopenic patients. We studied thymic settling progenitors from murine embryonic day 13 and 18 thymi by two complementary in vitro and in vivo techniques, both based on the “hanging drop” method. This method allowed colonizing irradiated fetal thymic lobes with E13 and/or E18 thymic progenitors distinguished by CD45 allotypic markers and thus following their progeny. Colonization with mixed populations allows analyzing cell autonomous differences in biologic properties of the progenitors while colonization with either population removes possible competitive selective pressures. The colonized thymic lobes can also be grafted in immunodeficient male recipient mice allowing the analysis of the mature T cell progeny in vivo, such as population dynamics of the peripheral immune system and colonization of different tissues and organs. Fetal thymic organ cultures revealed that E13 progenitors developed rapidly into all mature CD3+ cells and gave rise to the canonical γδ T cell subset, known as dendritic epithelial T cells. In comparison, E18 progenitors have a delayed differentiation and were unable to generate dendritic epithelial T cells. The monitoring of peripheral blood of thymus-grafted CD3-/- mice further showed that E18 thymic settling progenitors generate, with time, larger numbers of mature T cells than their E13 counterparts, a feature that could not be appreciated in the short term fetal thymic organ cultures. PMID:26131754

Genomic analysis reveals the major driving forces of bacterial life in the rhizosphere

PubMed Central

Matilla, Miguel A; Espinosa-Urgel, Manuel; Rodríguez-Herva, José J; Ramos, Juan L; Ramos-González, María Isabel

2007-01-01

Background Mutualistic interactions less well known than those between rhizobia and legumes are commonly found between plants and bacteria, frequently pseudomonads, which colonize roots and adjacent soil areas (the rhizosphere). Results A global analysis of Pseudomonas putida genes expressed during their interaction with maize roots revealed how a bacterial population adjusts its genetic program to this lifestyle. Differentially expressed genes were identified by comparing rhizosphere-colonizing populations with three distinct controls covering a variety of nutrients, growth phases and life styles (planktonic and sessile). Ninety rhizosphere up-regulated (rup) genes, which were induced relative to all three controls, were identified, whereas there was no repressed gene in common between the experiments. Genes involved in amino acid uptake and metabolism of aromatic compounds were preferentially expressed in the rhizosphere, which reflects the availability of particular nutrients in root exudates. The induction of efflux pumps and enzymes for glutathione metabolism indicates that adaptation to adverse conditions and stress (oxidative) response are crucial for bacterial life in this environment. The finding of a GGDEF/EAL domain response regulator among the induced genes suggests a role for the turnover of the secondary messenger c-diGMP in root colonization. Several mutants in rup genes showed reduced fitness in competitive root colonization. Conclusion Our results show the importance of two selective forces of different nature to colonize the rhizosphere: stress adaptation and availability of particular nutrients. We also identify new traits conferring bacterial survival in this niche and open a way to the characterization of specific signalling and regulatory processes governing the plant-Pseudomonas association. PMID:17784941

In silico prediction of escherichia coli proteins targeting the host cell nucleus, with special reference to their role in colon cancer etiology.

PubMed

Khan, Abdul Arif

2014-06-01

The potential role of Escherichia coli in the development of colorectal carcinoma (CRC) has been investigated in many studies. Although the exact mechanism is not clear, chronic inflammation caused by E. coli and other related events are suggested as possible causes behind E. coli-induced colon cancer. It has been found that CRC cells, but not normal cells, are colonized by an intracellular form of E. coli. We predicted nuclear targeting of bacterial proteins in the host cell through computational tools nuclear localization signal (NLS) mapper and balanced subcellular localization predictor (BaCeILo). During intracellular E. coli residence, such targeting is highly likely and may have a possible role in colon cancer etiology. We observed that several gene expression-associated proteins of E. coli can migrate to the host nucleus during intracellular infections. This situation provides an opportunity for competitive interaction of host and pathogen proteins with similar cellular substrates, thereby increasing the chances of development of colon cancer. Moreover, the results indicated that proteins localized in the membrane of E. coli mostly act as secretary proteins in host cells. No exact correlation was observed between NLS prediction and nuclear localization prediction by BaCeILo. This is partly because of a number of reasons, including that only 30% of nuclear proteins carry NLS and that proteins <40 kDa molecular weight can passively target the host nucleus. This study concludes that detection of gene expression-specific E. coli proteins and their targeting of the nucleus may have a profound impact on CRC etiology.

The Colonization History of Juniperus brevifolia (Cupressaceae) in the Azores Islands

PubMed Central

Rumeu, Beatriz; Caujapé-Castells, Juli; Blanco-Pastor, José Luis; Jaén-Molina, Ruth; Nogales, Manuel; Elias, Rui B.; Vargas, Pablo

2011-01-01

Background A central aim of island biogeography is to understand the colonization history of insular species using current distributions, fossil records and genetic diversity. Here, we analyze five plastid DNA regions of the endangered Juniperus brevifolia, which is endemic to the Azores archipelago. Methodology/Principal Findings The phylogeny of the section Juniperus and the phylogeographic analyses of J. brevifolia based on the coalescence theory of allele (plastid) diversity suggest that: (1) a single introduction event likely occurred from Europe; (2) genetic diversification and inter-island dispersal postdated the emergence of the oldest island (Santa Maria, 8.12 Ma); (3) the genetic differentiation found in populations on the islands with higher age and smaller distance to the continent is significantly higher than that on the younger, more remote ones; (4) the high number of haplotypes observed (16), and the widespread distribution of the most frequent and ancestral ones across the archipelago, are indicating early diversification, demographic expansion, and recurrent dispersal. In contrast, restriction of six of the seven derived haplotypes to single islands is construed as reflecting significant isolation time prior to colonization. Conclusions/Significance Our phylogeographic reconstruction points to the sequence of island emergence as the key factor to explain the distribution of plastid DNA variation. The reproductive traits of this juniper species (anemophily, ornithochory, multi-seeded cones), together with its broad ecological range, appear to be largely responsible for recurrent inter-island colonization of ancestral haplotypes. In contrast, certain delay in colonization of new haplotypes may reflect intraspecific habitat competition on islands where this juniper was already present. PMID:22110727

Serine-rich repeat proteins and pili promote Streptococcus agalactiae colonization of the vaginal tract.

PubMed

Sheen, Tamsin R; Jimenez, Alyssa; Wang, Nai-Yu; Banerjee, Anirban; van Sorge, Nina M; Doran, Kelly S

2011-12-01

Streptococcus agalactiae (group B streptococcus [GBS]) is a Gram-positive bacterium found in the female rectovaginal tract and is capable of producing severe disease in susceptible hosts, including newborns and pregnant women. The vaginal tract is considered a major reservoir for GBS, and maternal vaginal colonization poses a significant risk to the newborn; however, little is known about the specific bacterial factors that promote GBS colonization and persistence in the female reproductive tract. We have developed in vitro models of GBS interaction with the human female cervicovaginal tract using human vaginal and cervical epithelial cell lines. Analysis of isogenic mutant GBS strains deficient in cell surface organelles such as pili and serine-rich repeat (Srr) proteins shows that these factors contribute to host cell attachment. As Srr proteins are heavily glycosylated, we confirmed that carbohydrate moieties contribute to the effective interaction of Srr-1 with vaginal epithelial cells. Antibody inhibition assays identified keratin 4 as a possible host receptor for Srr-1. Our findings were further substantiated in an in vivo mouse model of GBS vaginal colonization, where mice inoculated with an Srr-1-deficient mutant exhibited decreased GBS vaginal persistence compared to those inoculated with the wild-type (WT) parental strain. Furthermore, competition experiments in mice showed that WT GBS exhibited a significant survival advantage over the ΔpilA or Δsrr-1 mutant in the vaginal tract. Our results suggest that these GBS surface proteins contribute to vaginal colonization and may offer new insights into the mechanisms of vaginal niche establishment.

Serine-Rich Repeat Proteins and Pili Promote Streptococcus agalactiae Colonization of the Vaginal Tract ▿

PubMed Central

Sheen, Tamsin R.; Jimenez, Alyssa; Wang, Nai-Yu; Banerjee, Anirban; van Sorge, Nina M.; Doran, Kelly S.

2011-01-01

Streptococcus agalactiae (group B streptococcus [GBS]) is a Gram-positive bacterium found in the female rectovaginal tract and is capable of producing severe disease in susceptible hosts, including newborns and pregnant women. The vaginal tract is considered a major reservoir for GBS, and maternal vaginal colonization poses a significant risk to the newborn; however, little is known about the specific bacterial factors that promote GBS colonization and persistence in the female reproductive tract. We have developed in vitro models of GBS interaction with the human female cervicovaginal tract using human vaginal and cervical epithelial cell lines. Analysis of isogenic mutant GBS strains deficient in cell surface organelles such as pili and serine-rich repeat (Srr) proteins shows that these factors contribute to host cell attachment. As Srr proteins are heavily glycosylated, we confirmed that carbohydrate moieties contribute to the effective interaction of Srr-1 with vaginal epithelial cells. Antibody inhibition assays identified keratin 4 as a possible host receptor for Srr-1. Our findings were further substantiated in an in vivo mouse model of GBS vaginal colonization, where mice inoculated with an Srr-1-deficient mutant exhibited decreased GBS vaginal persistence compared to those inoculated with the wild-type (WT) parental strain. Furthermore, competition experiments in mice showed that WT GBS exhibited a significant survival advantage over the ΔpilA or Δsrr-1 mutant in the vaginal tract. Our results suggest that these GBS surface proteins contribute to vaginal colonization and may offer new insights into the mechanisms of vaginal niche establishment. PMID:21984789

Competitive interactions between native and invasive exotic plant species are altered under elevated carbon dioxide.

PubMed

Manea, Anthony; Leishman, Michelle R

2011-03-01

We hypothesized that the greater competitive ability of invasive exotic plants relative to native plants would increase under elevated CO(2) because they typically have traits that confer the ability for fast growth when resources are not limiting and thus are likely to be more responsive to elevated CO(2). A series of competition experiments under ambient and elevated CO(2) glasshouse conditions were conducted to determine an index of relative competition intensity for 14 native-invasive exotic species-pairs. Traits including specific leaf area, leaf mass ratio, leaf area ratio, relative growth rate, net assimilation rate and root weight ratio were measured. Competitive rankings within species-pairs were not affected by CO(2) concentration: invasive exotic species were more competitive in 9 of the 14 species-pairs and native species were more competitive in the remaining 5 species-pairs, regardless of CO(2) concentration. However, there was a significant interaction between plant type and CO(2) treatment due to reduced competitive response of native species under elevated compared with ambient CO(2) conditions. Native species had significantly lower specific leaf area and leaf area ratio under elevated compared with ambient CO(2). We also compared traits of more-competitive with less-competitive species, regardless of plant type, under both CO(2) treatments. More-competitive species had smaller leaf weight ratio and leaf area ratio, and larger relative growth rate and net assimilation rate under both ambient and elevated CO(2) conditions. These results suggest that growth and allocation traits can be useful predictors of the outcome of competitive interactions under both ambient and elevated CO(2) conditions. Under predicted future atmospheric CO(2) conditions, competitive rankings among species may not change substantially, but the relative success of invasive exotic species may be increased. Thus, under future atmospheric CO(2) conditions, the ecological and economic impact of some invasive exotic plants may be even greater than under current conditions.

Contractor responses of the isolated colon of the mouse to morphine and some opioid peptides.

PubMed Central

Fontaine, J.; Reuse, J.

1985-01-01

Morphine (1 X 10(-8) - 1 X 10(-4)M), fentanyl (1 X 10(-9) - 1 X 10(-5)M) and alfentanyl (1 X 10(-10) - 1 X 10(-5)M) as well as methionine enkephalin [Met5]enkephalin (1 X 10(-11) - 1 X 10(-8)M), [D-Ala2, Met5]enkephalin (1 X 10(-12) - 1 X 10(-8)M) and dynorphin A(1 - 13) (1 X 10(-9) - 1 X 10(-6)M) caused a contractor response of the longitudinal musculature of the terminal colon of the mouse. These effects were competitively antagonized by naloxone. The pA2 values obtained for naloxone antagonism of morphine and opioid peptides and the high sensitivity of the preparation to enkephalins suggest the presence of delta-opiate receptors in this preparation but mu- and kappa-receptors may also be present. Opiate-induced contractions in the mouse colon were abolished by tetrodotoxin and after incubation with indomethacin. It is concluded that the excitatory actions of the opiates in the mouse colon are mediated via opiate receptors located on nerves which do not release acetylcholine, noradrenaline or 5-hydroxytryptamine. The opiates may produce their action by removing an inhibitory neural influence (the nature of which remains to be elucidated) allowing a prostaglandin-mediated effect to predominate, thereby increasing muscle tone. PMID:2864095

The role of drought- and disturbance-mediated competition in shaping community responses to varied environments.

PubMed

Napier, Joseph D; Mordecai, Erin A; Heckman, Robert W

2016-06-01

By altering the strength of intra- and interspecific competition, droughts may reshape plant communities. Furthermore, species may respond differently to drought when other influences, such as herbivory, are considered. To explore this relationship, we conducted a greenhouse experiment measuring responses to inter- and intraspecific competition for two grasses, Schedonorus arundinaceus and Paspalum dilatatum, while varying water availability and simulating herbivory via clipping. We then parameterized population growth models to examine the long-term outcome of competition under these conditions. Under drought, S. arundinaceus was less water stressed than P. dilatatum, which exhibited severe water stress; clipping alleviated this stress, increasing the competitive ability of P. dilatatum relative to S. arundinaceus. Although P. dilatatum competed weakly under drought, clipping reduced water stress in P. dilatatum, thereby enhancing its ability to compete with S. arundinaceus under drought. Supporting these observations, population growth models predicted that P. dilatatum would exclude S. arundinaceus when clipped under drought, while S. arundinaceus would exclude P. dilatatum when unclipped under drought. When the modeled environment varied temporally, environmental variation promoted niche differences that, though insufficient to maintain stable coexistence, prevented unconditional competitive exclusion by promoting priority effects. Our results suggest that it is important to consider how species respond not just to stable, but also to variable, environments. When species differ in their responses to drought, competition, and simulated herbivory, stable environments may promote competitive exclusion, while fluctuating environments may promote coexistence. These interactions are critical to understanding how species will respond to global change.

Growing Competition for Libraries.

ERIC Educational Resources Information Center

Gibbons, Susan

2001-01-01

Describes the Questia subscription-based online academic digital books library. Highlights include weaknesses of the collection; what college students want from a library; importance of marketing; competition for traditional academic libraries that may help improve library services; and the ability of Questia to overcome barriers and…

Detection of the Entomopathogenic Fungus Beauveria bassiana in the Rhizosphere of Wound-Stressed Zea mays Plants

PubMed Central

McKinnon, Aimee C.; Glare, Travis R.; Ridgway, Hayley J.; Mendoza-Mendoza, Artemio; Holyoake, Andrew; Godsoe, William K.; Bufford, Jennifer L.

2018-01-01

Entomopathogenic fungi from the genus Beauveria (Vuillemin) play an important role in controlling insect populations and have been increasingly utilized for the biological control of insect pests. Various studies have reported that Beauveria bassiana (Bals.), Vuill. also has the ability to colonize a broad range of plant hosts as endophytes without causing disease but while still maintaining the capacity to infect insects. Beauveria is often applied as an inundative spore application, but little research has considered how plant colonization may alter the ability to persist in the environment. The aim of this study was to investigate potential interactions between B. bassiana and Zea mays L. (maize) in the rhizosphere following inoculation, in order to understand the factors that may affect environmental persistence of the fungi. The hypothesis was that different isolates of B. bassiana have the ability to colonize maize roots and/or rhizosphere soil, resulting in effects to the plant microbiome. To test this hypothesis, a two-step nested PCR protocol was developed to find and amplify Beauveria in planta or in soil; based on the translation elongation factor 1-alpha (ef1α) gene. The nested protocol was also designed to enable Beauveria species differentiation by sequence analysis. The impact of three selected B. bassiana isolates applied topically to roots on the rhizosphere soil community structure and function were consequently assessed using denaturing gradient gel electrophoresis (DGGE) and MicroRespTM techniques. The microbial community structure and function were not significantly affected by the presence of the isolates, however, retention of the inocula in the rhizosphere at 30 days after inoculation was enhanced when plants were subjected to intensive wounding of foliage to crudely simulate herbivory. The plant defense response likely changed under wound stress resulting in the apparent recruitment of Beauveria in the rhizosphere, which may be an indirect defensive strategy against herbivory and/or the result of induced systemic susceptibility in maize enabling plant colonization. PMID:29942287

The Rewiring of Ubiquitination Targets in a Pathogenic Yeast Promotes Metabolic Flexibility, Host Colonization and Virulence

PubMed Central

Childers, Delma S.; Raziunaite, Ingrida; Mol Avelar, Gabriela; Mackie, Joanna; Budge, Susan; Stead, David; Gow, Neil A. R.; Lenardon, Megan D.; Ballou, Elizabeth R.; MacCallum, Donna M.; Brown, Alistair J. P.

2016-01-01

Efficient carbon assimilation is critical for microbial growth and pathogenesis. The environmental yeast Saccharomyces cerevisiae is “Crabtree positive”, displaying a rapid metabolic switch from the assimilation of alternative carbon sources to sugars. Following exposure to sugars, this switch is mediated by the transcriptional repression of genes (carbon catabolite repression) and the turnover (catabolite inactivation) of enzymes involved in the assimilation of alternative carbon sources. The pathogenic yeast Candida albicans is Crabtree negative. It has retained carbon catabolite repression mechanisms, but has undergone posttranscriptional rewiring such that gluconeogenic and glyoxylate cycle enzymes are not subject to ubiquitin-mediated catabolite inactivation. Consequently, when glucose becomes available, C. albicans can continue to assimilate alternative carbon sources alongside the glucose. We show that this metabolic flexibility promotes host colonization and virulence. The glyoxylate cycle enzyme isocitrate lyase (CaIcl1) was rendered sensitive to ubiquitin-mediated catabolite inactivation in C. albicans by addition of a ubiquitination site. This mutation, which inhibits lactate assimilation in the presence of glucose, reduces the ability of C. albicans cells to withstand macrophage killing, colonize the gastrointestinal tract and cause systemic infections in mice. Interestingly, most S. cerevisiae clinical isolates we examined (67%) have acquired the ability to assimilate lactate in the presence of glucose (i.e. they have become Crabtree negative). These S. cerevisiae strains are more resistant to macrophage killing than Crabtree positive clinical isolates. Moreover, Crabtree negative S. cerevisiae mutants that lack Gid8, a key component of the Glucose-Induced Degradation complex, are more resistant to macrophage killing and display increased virulence in immunocompromised mice. Thus, while Crabtree positivity might impart a fitness advantage for yeasts in environmental niches, the more flexible carbon assimilation strategies offered by Crabtree negativity enhance the ability of yeasts to colonize and infect the mammalian host. PMID:27073846

Suppression of epithelial ovarian cancer invasion into the omentum by 1α,25-dihydroxyvitamin D3 and its receptor.

PubMed

Lungchukiet, Panida; Sun, Yuefeng; Kasiappan, Ravi; Quarni, Waise; Nicosia, Santo V; Zhang, Xiaohong; Bai, Wenlong

2015-04-01

Epithelial ovarian cancer (EOC) is the leading cause of gynecological cancer death in women, mainly because it has spread to intraperitoneal tissues such as the omentum in the peritoneal cavity by the time of diagnosis. In the present study, we established in vitro assays, ex vivo omental organ culture system and syngeneic animal tumor models using wild type (WT) and vitamin D receptor (VDR) null mice to investigate the effects of 1α,25-dihydroxyvitamin D3 (1,25D3) and VDR on EOC invasion. Treatment of human EOC cells with 1,25D3 suppressed their migration and invasion in monolayer scratch and transwell assays and ability to colonize the omentum in the ex vivo system, supporting a role for epithelial VDR in interfering with EOC invasion. Furthermore, VDR knockdown in OVCAR3 cells increased their ability to colonize the omentum in the ex vivo system in the absence of 1,25D3, showing a potential ligand-independent suppression of EOC invasion by epithelial VDR. In syngeneic models, ID8 tumors exhibited an increased ability to colonize omenta of VDR null over that of WT mice; pre-treatment of WT, not VDR null, mice with EB1089 reduced ID8 colonization, revealing a role for stromal VDR in suppressing EOC invasion. These studies are the first to demonstrate a role for epithelial and stromal VDR in mediating the activity of 1,25D3 as well as a 1,25D3-independent action of the VDR in suppressing EOC invasion. The data suggest that VDR-based drug discovery may lead to the development of new intervention strategies to improve the survival of patients with EOC at advanced stages. This article is part of a Special Issue entitled "Vitamin D Workshop". Copyright © 2014 Elsevier Ltd. All rights reserved.

Response to competition of bulbous geophyte Allium oleraceum differing in ploidy level.

PubMed

Fialová, M; Duchoslav, M

2014-01-01

Experimental studies that explore the possible causes of ploidy distributions and niche differentiation are rare. Increased competitive ability may be advantageous for survival in dense vegetation and may strongly affect local and regional abundances of cytotypes and potentially contribute to invasion success. We compared survival, growth and reproduction of plants originating from bulbils of three cytotypes (2n = 4x, 5x, 6x) of Allium oleraceum growing with and without a competitor (Arrhenatherum elatius). There was a strong negative effect of competition but no effect of ploidy or ploidy × competition on survivorship, height and total dry mass of A. oleraceum, i.e. no support for different competitive abilities of the ploidy levels. However, slightly different responses of populations to competition treatments within all cytotypes suggest differentiation within cytotypes. Under competition, plant survivorship was low, surviving plants were small, had low dry mass and produced neither sexual nor asexual propagules. Without competition, plant survivorship was high, and cytotypes differed in three traits after 2 year's growth: dry mass of flowers, number of flowers and ratio of the dry mass of sexual to asexual propagules all decreased with increasing ploidy level. We additionally tested tetra- and pentaploids as to whether plants originating from different types of propagule (bulbils, seeds) differ in survivorship, growth and reproduction when growing with and without a competitor. Plants originating from bulbils had higher survivorship, were more robust, flowered earlier and produced more propagules when compared to plants originating from seeds and grown without competition. Under competition, differences in performance between plants originating from seeds and bulbils mostly disappeared, with higher survivorship only for plants originating from bulbils. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands.

Metabolic scope and interspecific competition in sculpins of Greenland are influenced by increased temperatures due to climate change.

PubMed

Seth, Henrik; Gräns, Albin; Sandblom, Erik; Olsson, Catharina; Wiklander, Kerstin; Johnsson, Jörgen I; Axelsson, Michael

2013-01-01

Ongoing climate change has led to an increase in sea surface temperatures of 2-4°C on the west coast of Greenland. Since fish are ectothermic, metabolic rate increases with ambient temperature. This makes these animals particularly sensitive to changes in temperature; subsequently any change may influence their metabolic scope, i.e. the physiological capacity to undertake aerobically challenging activities. Any temperature increase may thus disrupt species-specific temperature adaptations, at both the molecular level as well as in behavior, and concomitant species differences in the temperature sensitivity may shift the competitive balance among coexisting species. We investigated the influence of temperature on metabolic scope and competitive ability in three species of marine sculpin that coexist in Greenland coastal waters. Since these species have different distribution ranges, we hypothesized that there should be a difference in their physiological response to temperature; hence we compared their metabolic scope at three temperatures (4, 9 and 14°C). Their competitive ability at the ambient temperature of 9°C was also tested in an attempt to link physiological capacity with behaviour. The Arctic staghorn sculpin, the species with the northernmost distribution range, had a lower metabolic scope in the higher temperature range compared to the other two species, which had similar metabolic scope at the three temperatures. The Arctic staghorn sculpin also had reduced competitive ability at 9°C and may thus already be negatively affected by the current ocean warming. Our results suggest that climate change can have effects on fish physiology and interspecific competition, which may alter the species composition of the Arctic fish fauna.

Interspecific interactions between Phragmites australis and Spartina alterniflora along a tidal gradient in the Dongtan wetland, Eastern China.

PubMed

Yuan, Yue; Wang, Kaiyun; Li, Dezhi; Pan, Yu; Lv, Yuanyuan; Zhao, Meixia; Gao, JinJin

2013-01-01

The invasive species Spartina alterniora Loisel was introduced to the eastern coast of China in the 1970s and 1980s for the purposes of land reclamation and the prevention of soil erosion. The resulting interspecific competition had an important influence on the distribution of native vegetation, which makes studying the patterns and mechanisms of the interactions between Spartina alterniora Loisel and the native species Phragmites australis (Cav.) Trin ex Steud in this region very important. There have been some researches on the interspecific interactions between P. australis and S. alterniora in the Dongtan wetland of Chongming, east China, most of which has focused on the comparison of their physiological characteristics. In this paper, we conducted a neighbor removal experiment along a tidal gradient to evaluate the relative competitive abilities of the two species by calculating their relative neighbor effect (RNE) index. We also looked at the influence of environmental stress and disturbance on the competitive abilities of the two species by comparing interaction strength (I) among different tidal zones both for P. australis and S. alterniora. Finally, we measured physiological characteristics of the two species to assess the physiological mechanisms behind their different competitive abilities. Both negative and positive interactions were found between P. australis and S. alterniora along the environmental gradient. When the direction of the competitive intensity index for P. australis and S. alterniora was consistent, the competitive or facilitative effect of S. alterniora on P. australis was stronger than that of P. australis on S. alterniora. The interspecific interactions of P. australis and S. alterniora varied with environmental conditions, as well as with the method used, to measure interspecific interactions.

The contribution of aerobic and anaerobic respiration to intestinal colonization and virulence for Salmonella typhimurium in the chicken.

PubMed

Barrow, Paul Andrew; Berchieri, Angelo; Freitas Neto, Oliveiro Caetano de; Lovell, Margaret

2015-10-01

The basic mechanism whereby Salmonella serovars colonize the chicken intestine remains poorly understood. Previous studies have indicated that proton-translocating proteins utilizing oxygen as terminal electron acceptor do not appear to be of major importance in the gut of the newly hatched chicken and consequently they would be even less significant during intestinal colonization of more mature chickens where the complex gut microflora would trap most of the oxygen in the lumen. Consequently, alternative electron acceptors may be more significant or, in their absence, substrate-level phosphorylation may also be important to Salmonella serovars in this environment. To investigate this we constructed mutants of Salmonella enterica serovar Typhimurium defective in various aspects of oxidative or substrate-level phosphorylation to assess their role in colonization of the chicken intestine, assessed through faecal shedding, and virulence. Mutations affecting use of oxygen or alternative electron acceptors did not eliminate faecal shedding. By contrast mutations in either pta (phosphotransacetylase) or ackA (acetate kinase) abolished shedding. The pta but not the ackA mutation also abolished systemic virulence for chickens. An additional ldhA (lactate dehydrogenase) mutant also showed poor colonizing ability. We hypothesise that substrate-level phosphorylation may be more important than respiration using oxygen or alternative electron acceptors for colonization of the chicken caeca.

Pharmacokinetics of ketorolac tromethamine compression-coated tablets for colon delivery.

PubMed

Vemula, Sateesh Kumar; Veerareddy, Prabhakar Reddy; Devadasu, Venkat Ratnam

2014-08-01

Present research efforts are focused in developing compression-coated ketorolac tromethamine tablets to improve the drug levels in colon by retarding the drug release in the stomach and small intestine. To achieve this objective, core tablets containing ketorolac tromethamine were prepared by direct compression and compression coated with sodium alginate. The developed tablets were evaluated for physical properties, in vitro drug release, X-ray imaging, and pharmacokinetic studies in human volunteers. Based on the in vitro drug release study, the optimized formulation showed very little drug release (6.75 ± 0.49 %) in the initial lag period of 5 h, followed by progressive release up to 97.47 ± 0.93 % within 24 h. The X-ray imaging of tablets in human volunteers showed that the tablets reached the colon without disintegrating in the upper gastrointestinal tract. From the pharmacokinetic study, the C max of colon-targeted tablets was 3,486.70 ng/ml at T max 10 h, whereas in the case of immediate-release tablets, the C max of 4,506.31 ng/ml at T max 2 h signifies the ability of compression-coated tablets to target the colon. In conclusion, compression-coated tablets are suitable to deliver ketorolac tromethamine to the colon.

Campylobacter jejuni Colonization in Wild Birds: Results from an Infection Experiment

PubMed Central

Waldenström, Jonas; Axelsson-Olsson, Diana; Olsen, Björn; Hasselquist, Dennis; Griekspoor, Petra; Jansson, Lena; Teneberg, Susann; Svensson, Lovisa; Ellström, Patrik

2010-01-01

Campylobacter jejuni is a common cause of bacterial gastroenteritis in most parts of the world. The bacterium has a broad host range and has been isolated from many animals and environments. To investigate shedding patterns and putative effects on an avian host, we developed a colonization model in which a wild bird species, the European Robin Erithacus rubecula, was inoculated orally with C. jejuni from either a human patient or from another wild bird species, the Song Thrush Turdus philomelos. These two isolates were genetically distinct from each other and provoked very different host responses. The Song Thrush isolate colonized all challenged birds and colonization lasted 6.8 days on average. Birds infected with this isolate also showed a transient but significant decrease in body mass. The human isolate did not colonize the birds and could be detected only in the feces of the birds shortly after inoculation. European Robins infected with the wild bird isolate generated a specific antibody response to C. jejuni membrane proteins from the avian isolate, which also was cross-reactive to membrane proteins of the human isolate. In contrast, European Robins infected with the human isolate did not mount a significant response to bacterial membrane proteins from either of the two isolates. The difference in colonization ability could indicate host adaptations. PMID:20140204

Study of the Ability of Bifidobacteria of Human Origin to Prevent and Treat Rotavirus Infection Using Colonic Cell and Mouse Models

PubMed Central

Darveau, André; Fliss, Ismaïl

2016-01-01

Rotavirus is the leading cause of severe acute gastroenteritis among children worldwide. Despite effective vaccines, inexpensive alternatives such as probiotics are needed. The aim of this study was to assess the ability of probiotic candidate Bifidobacterium thermophilum RBL67 to inhibit rotavirus infection. Bacterial adhesion to intestinal cells and interference with viral attachment were evaluated in vitro. B. thermophilum RBL67 displayed adhesion indexes of 625 ± 84 and 1958 ± 318 on Caco-2 and HT-29 cells respectively and was comparable or superior to four other bifidobacteria, including B. longum ATCC 15707 and B. pseudolongum ATCC 25526 strains. Incubation of B. thermophilum RBL67 for 30 min before (exclusion) and simultaneously (competition) with human rotavirus strain Wa decreased virus attachment by 2.0 ± 0.1 and 1.5 ± 0.1 log10 (by 99.0% and 96.8% respectively). Displacement of virus already present was negligible. In CD-1 suckling mice fed B. thermophilum RBL67 challenged with simian rotavirus SA-11, pre-infection feeding with RBL 67 was more effective than post-infection feeding, reducing the duration of diarrhea, limiting epithelial lesions, reducing viral replication in the intestine, accelerating recovery, and stimulating the humoral specific IgG and IgM response, without inducing any adverse effect. B. thermophilum RBL67 had little effect on intestinal IgA titer. These results suggest that humoral immunoglobulin might provide protection against the virus and that B. thermophilum RBL67 has potential as a probiotic able to inhibit rotavirus infection and ultimately reduce its spread. PMID:27727323

Order of arrival affects competition in two reef fishes.

PubMed

Geange, Shane W; Stier, Adrian C

2009-10-01

Many communities experience repeated periods of colonization due to seasonally regenerating habitats or pulsed arrival of young-of-year. When an individual's persistence in a community depends upon the strength of competitive interactions, changes in the timing of arrival relative to the arrival of a competitor can modify competitive strength and, ultimately, establishment in the community. We investigated whether the strength of intracohort competitive interactions between recent settlers of the reef fishes Thalassoma hardwicke and T. quinquevittatum are dependent on the sequence and temporal separation of their arrival into communities. To achieve this, we manipulated the sequence and timing of arrival of each species onto experimental patch reefs by simulating settlement pulses and monitoring survival and aggressive interactions. Both species survived best in the absence of competitors, but when competitors were present, they did best when they arrived at the same time. Survival declined as each species entered the community progressively later than its competitor and as aggression by its competitor increased. Intraspecific effects of resident T. hardwicke were similar to interspecific effects. This study shows that the strength of competition depends not only on the identity of competitors, but also on the sequence and timing of their interactions, suggesting that when examining interaction strengths, it is important to identify temporal variability in the direction and magnitude of their effects. Furthermore, our findings provide empirical evidence for the importance of competitive lotteries in the maintenance of species diversity in demographically open marine systems.

Global-scale relationships between colonization ability and range size in marine and freshwater fish.

PubMed

Strona, Giovanni; Galli, Paolo; Montano, Simone; Seveso, Davide; Fattorini, Simone

2012-01-01

Although fish range sizes are expected to be associated with species dispersal ability, several studies failed to find a clear relationship between range size and duration of larval stage as a measure of dispersal potential. We investigated how six characteristics of the adult phase of fishes (maximum body length, growth rate, age at first maturity, life span, trophic level and frequency of occurrence) possibly associated with colonization ability correlate with range size in both freshwater and marine species at global scale. We used more than 12 million point records to estimate range size of 1829 freshwater species and 10068 marine species. As measures of range size we used both area of occupancy and extent of occurrence. Relationships between range size and species traits were assessed using Canonical Correlation Analysis. We found that frequency of occurrence and maximum body length had a strong influence on range size measures, which is consistent with patterns previously found (at smaller scales) in several other taxa. Freshwater and marine fishes showed striking similarities, suggesting the existence of common mechanisms regulating fish biogeography in the marine and freshwater realms.

Hypervirulent (hypermucoviscous) Klebsiella pneumoniae

PubMed Central

Shon, Alyssa S.; Bajwa, Rajinder P.S.; Russo, Thomas A.

2013-01-01

A new hypervirulent (hypermucoviscous) variant of Klebsiella pneumoniae has emerged. First described in the Asian Pacific Rim, it now increasingly recognized in Western countries. Defining clinical features are the ability to cause serious, life-threatening community-acquired infection in younger healthy hosts, including liver abscess, pneumonia, meningitis and endophthalmitis and the ability to metastatically spread, an unusual feature for enteric Gram-negative bacilli in the non-immunocompromised. Despite infecting a healthier population, significant morbidity and mortality occurs. Although epidemiologic features are still being defined, colonization, particularly intestinal colonization, appears to be a critical step leading to infection. However the route of entry remains unclear. The majority of cases described to date are in Asians, raising the issue of a genetic predisposition vs. geospecific strain acquisition. The traits that enhance its virulence when compared with “classical” K. pneumoniae are the ability to more efficiently acquire iron and perhaps an increase in capsule production, which confers the hypermucoviscous phenotype. An objective diagnostic test suitable for routine use in the clinical microbiology laboratory is needed. If/when these strains become increasingly resistant to antimicrobials, we will be faced with a frightening clinical scenario. PMID:23302790

Insect herbivores drive real-time ecological and evolutionary change in plant populations.

PubMed

Agrawal, Anurag A; Hastings, Amy P; Johnson, Marc T J; Maron, John L; Salminen, Juha-Pekka

2012-10-05

Insect herbivores are hypothesized to be major factors affecting the ecology and evolution of plants. We tested this prediction by suppressing insects in replicated field populations of a native plant, Oenothera biennis, which reduced seed predation, altered interspecific competitive dynamics, and resulted in rapid evolutionary divergence. Comparative genotyping and phenotyping of nearly 12,000 O. biennis individuals revealed that in plots protected from insects, resistance to herbivores declined through time owing to changes in flowering time and lower defensive ellagitannins in fruits, whereas plant competitive ability increased. This independent real-time evolution of plant resistance and competitive ability in the field resulted from the relaxation of direct selective effects of insects on plant defense and through indirect effects due to reduced herbivory on plant competitors.

Disruptive Challenges and Accelerating Force Transformation

DTIC Science & Technology

2006-01-01

strategy and the military transformation process. The ability to maintain a competitive advantage depends not only on the Nation’s manpower, fiscal...rapid change and ambiguity are the norm, this competitive advantage often depends on the availability of multiple effective options. If U.S. military

76 FR 23971 - Proposed Information Collection; Comment Request; Competitive Enhancement Needs Assessment Survey...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-29

... DEPARTMENT OF COMMERCE Bureau of Industry and Security Proposed Information Collection; Comment Request; Competitive Enhancement Needs Assessment Survey Program AGENCY: Bureau of Industry and Security... their abilities to meet defense program needs. The information collected from voluntary surveys will be...

DSM and electric utility competitiveness: An Illinois perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, P.W.

1994-12-31

A predominant theme in the current electric utility industry literature is that competitive forces have emerged and may become more prominent. The wholesale bulk power market is alreadly competitive, as non-utility energy service providers already have had a significant impact on that market; this trend was accelerated by the Energy Policy Act of 1992. Although competition at the retail level is much less pervasive, electric utility customers increasingly have greater choice in selecting energy services. These choices may include, depending on the customer, the ability to self-generate, switch fuels, move to a new location, or rely more heavily on demand-sidemore » management as a means of controlling electric energy use. This paper explores the subject of how demand-side management (DSM) programs, which are often developed by a utility to satisfy resource requirements as a part of its least-cost planning process, can affect the utility`s ability to compete in the energy services marketplace. In this context, the term `DSM` is used in this paper to refer to those demand-side services and programs which provide resources to the utility`s system. Depending on one`s perspective, DSM programs (so defined) can be viewed either as an enhancement to the competitive position of a utility by enabling it to provide its customers with a broader menu of energy services, simultaneously satisfying the objectives of the utility as well as those of the customers, or as a detractor to a utility`s ability to compete. In the latter case, the concern is with respect to the potential for adverse rate impacts on customers who are not participants in DSM programs. The paper consists of an identification of the pros and cons of DSM as a competitive strategy, the tradeoff which can occur between the cost impacts and rate impacts of DSM, and an examination of alternative strategies for maximizing the utilization of DSM both as a resource and as a competitive strategy.« less

Morphological Differentiation of Colon Carcinoma Cell Lines in Rotating Wall Vessels

NASA Technical Reports Server (NTRS)

Jessup, J. M.

1994-01-01

The objectives of this project were to determine whether (1) microgravity permits unique, three-dimensional cultures of neoplastic human colon tissues and (2) this culture interaction produces novel intestinal growth and differentiation factors. The initial phase of this project tested the efficacy of simulated microgravity for the cultivation and differentiation of human colon carcinoma in rotating wall vessels (RWV's) on microcarrier beads. The RWV's simulate microgravity by randomizing the gravity vector in an aqueous medium under a low shear stress environment in unit gravity. This simulation achieves approximately a one-fifth g environment that allows cells to 'float' and form three-dimensional relationships with less shear stress than in other stirred aqueous medium bioreactors. In the second phase of this project we assessed the ability of human colon carcinoma lines to adhere to various substrates because adhesion is the first event that must occur to create three-dimensional masses. Finally, we tested growth factor production in the last phase of this project.

Murine immune responses to oral BCG immunization in the presence or absence of prior BCG sensitization.

PubMed

Cross, Martin L; Lambeth, Matthew R; Aldwell, Frank E

2010-02-01

Oral delivery of live Mycobacterium bovis BCG in a lipid matrix invokes cell-mediated immune (CMI) responses in mice and consequent protection against pulmonary challenge with virulent mycobacteria. To investigate the influence of prior BCG sensitization on oral vaccine efficacy, we assessed CMI responses and BCG colonization of the alimentary tract lymphatics 5 months after oral vaccination, in both previously naive mice and in mice that had been sensitized to BCG by injection 6 months previously. CMI responses did not differ significantly between mice that received subcutaneous BCG followed by oral BCG and those that received either injected or oral BCG alone. In vivo BCG colonization was predominant in the mesenteric lymph nodes after oral vaccination; this colonizing ability was not influenced by prior BCG sensitization. From this murine model study, we conclude that although prior parenteral-route BCG sensitization does not detrimentally affect BCG colonization after oral vaccination, there is no significant immune-boosting effect of the oral vaccine either.

Increased Chain Length Promotes Pneumococcal Adherence and Colonization

PubMed Central

Rodriguez, Jesse L.; Dalia, Ankur B.

2012-01-01

Streptococcus pneumoniae is a mucosal pathogen that grows in chains of variable lengths. Short-chain forms are less likely to activate complement, and as a consequence they evade opsonophagocytic clearance more effectively during invasive disease. When grown in human nasal airway surface fluid, pneumococci exhibited both short- and long-chain forms. Here, we determined whether longer chains provide an advantage during colonization when the organism is attached to the epithelial surface. Chain-forming mutants and the parental strain grown under conditions to promote chain formation showed increased adherence to human epithelial cells (A549 cells) in vitro. Additionally, adherence to A549 cells selected for longer chains within the wild-type strain. In vivo in a murine model of colonization, chain-forming mutants outcompeted the parental strain. Together, our results demonstrate that morphological heterogeneity in the pneumococcus may promote colonization of the upper respiratory tract by enhancing the ability of the organism to bind to the epithelial surface. PMID:22825449

Effect of Fungal Colonization of Wheat Grains with Fusarium spp. on Food Choice, Weight Gain and Mortality of Meal Beetle Larvae (Tenebrio molitor)

PubMed Central

Guo, Zhiqing; Döll, Katharina; Dastjerdi, Raana; Karlovsky, Petr; Dehne, Heinz-Wilhelm; Altincicek, Boran

2014-01-01

Species of Fusarium have significant agro-economical and human health-related impact by infecting diverse crop plants and synthesizing diverse mycotoxins. Here, we investigated interactions of grain-feeding Tenebrio molitor larvae with four grain-colonizing Fusarium species on wheat kernels. Since numerous metabolites produced by Fusarium spp. are toxic to insects, we tested the hypothesis that the insect senses and avoids Fusarium-colonized grains. We found that only kernels colonized with F. avenaceum or Beauveria bassiana (an insect-pathogenic fungal control) were avoided by the larvae as expected. Kernels colonized with F. proliferatum, F. poae or F. culmorum attracted T. molitor larvae significantly more than control kernels. The avoidance/preference correlated with larval feeding behaviors and weight gain. Interestingly, larvae that had consumed F. proliferatum- or F. poae-colonized kernels had similar survival rates as control. Larvae fed on F. culmorum-, F. avenaceum- or B. bassiana-colonized kernels had elevated mortality rates. HPLC analyses confirmed the following mycotoxins produced by the fungal strains on the kernels: fumonisins, enniatins and beauvericin by F. proliferatum, enniatins and beauvericin by F. poae, enniatins by F. avenaceum, and deoxynivalenol and zearalenone by F. culmorum. Our results indicate that T. molitor larvae have the ability to sense potential survival threats of kernels colonized with F. avenaceum or B. bassiana, but not with F. culmorum. Volatiles potentially along with gustatory cues produced by these fungi may represent survival threat signals for the larvae resulting in their avoidance. Although F. proliferatum or F. poae produced fumonisins, enniatins and beauvericin during kernel colonization, the larvae were able to use those kernels as diet without exhibiting increased mortality. Consumption of F. avenaceum-colonized kernels, however, increased larval mortality; these kernels had higher enniatin levels than F. proliferatum or F. poae-colonized ones suggesting that T. molitor can tolerate or metabolize those toxins. PMID:24932485

How recent advances in molecular tests could impact the diagnosis of pneumonia.

PubMed

Murdoch, David R

2016-01-01

Molecular diagnostic tests have been the single major development in pneumonia diagnostics over recent years. Nucleic acid detection tests (NATs) have greatly improved the ability to detect respiratory viruses and bacterial pathogens that do not normally colonize the respiratory tract. In contrast, NATs do not yet have an established role for diagnosing pneumonia caused by bacteria that commonly colonize the nasopharynx due to difficulties discriminating between pathogens and coincidental carriage strains. New approaches are needed to distinguish infection from colonization, such as through use of quantitative methods and identification of discriminating cut-off levels. The recent realization that the lung microbiome exists has provided new insights into the pathogenesis of pneumonia involving the interaction between multiple microorganisms. New developments in molecular diagnostics must account for this new paradigm.