Science.gov

Sample records for microbial growth determination

  1. Solutes determine the temperature windows for microbial survival and growth

    PubMed Central

    Chin, Jason P.; Megaw, Julianne; Magill, Caroline L.; Nowotarski, Krzysztof; Williams, Jim P.; Bhaganna, Prashanth; Linton, Mark; Patterson, Margaret F.; Underwood, Graham J. C.; Mswaka, Allen Y.; Hallsworth, John E.

    2010-01-01

    Microbial cells, and ultimately the Earth's biosphere, function within a narrow range of physicochemical conditions. For the majority of ecosystems, productivity is cold-limited, and it is microbes that represent the failure point. This study was carried out to determine if naturally occurring solutes can extend the temperature windows for activity of microorganisms. We found that substances known to disorder cellular macromolecules (chaotropes) did expand microbial growth windows, fungi preferentially accumulated chaotropic metabolites at low temperature, and chemical activities of solutes determined microbial survival at extremes of temperature as well as pressure. This information can enhance the precision of models used to predict if extraterrestrial and other hostile environments are able to support life; furthermore, chaotropes may be used to extend the growth windows for key microbes, such as saprotrophs, in cold ecosystems and manmade biomes. PMID:20404182

  2. Determination of Microbial Growth by Protein Assay in an Air-Cathode Single Chamber Microbial Fuel Cell.

    PubMed

    Li, Na; Kakarla, Ramesh; Moon, Jung Mi; Min, Booki

    2015-07-01

    Microbial fuel cells (MFCs) have gathered attention as a novel bioenergy technology to simultaneously treat wastewater with less sludge production than the conventional activated sludge system. In two different operations of the MFC and aerobic process, microbial growth was determined by the protein assay method and their biomass yields using real wastewater were compared. The biomass yield on the anode electrode of the MFC was 0.02 g-COD-cell/g- COD-substrate and the anolyte planktonic biomass was 0.14 g-COD-cell/g-COD-substrate. An MFC without anode electrode resulted in the biomass yield of 0.07 ± 0.03 g-COD-cell/g-COD-substrate, suggesting that oxygen diffusion from the cathode possibly supported the microbial growth. In a comparative test, the biomass yield under aerobic environment was 0.46 ± 0.07 g-COD-cell/g-COD-substrate, which was about 3 times higher than the total biomass value in the MFC operation.

  3. Scaling and optimal synergy: Two principles determining microbial growth in complex media

    NASA Astrophysics Data System (ADS)

    Massucci, Francesco Alessandro; Guimerà, Roger; Nunes Amaral, Luís A.; Sales-Pardo, Marta

    2015-06-01

    High-throughput experimental techniques and bioinformatics tools make it possible to obtain reconstructions of the metabolism of microbial species. Combined with mathematical frameworks such as flux balance analysis, which assumes that nutrients are used so as to maximize growth, these reconstructions enable us to predict microbial growth. Although such predictions are generally accurate, these approaches do not give insights on how different nutrients are used to produce growth, and thus are difficult to generalize to new media or to different organisms. Here, we propose a systems-level phenomenological model of metabolism inspired by the virial expansion. Our model predicts biomass production given the nutrient uptakes and a reduced set of parameters, which can be easily determined experimentally. To validate our model, we test it against in silico simulations and experimental measurements of growth, and find good agreement. From a biological point of view, our model uncovers the impact that individual nutrients and the synergistic interaction between nutrient pairs have on growth, and suggests that we can understand the growth maximization principle as the optimization of nutrient synergies.

  4. New microbial growth factor

    NASA Technical Reports Server (NTRS)

    Bok, S. H.; Casida, L. E., Jr.

    1977-01-01

    A screening procedure was used to isolate from soil a Penicillium sp., two bacterial isolates, and a Streptomyces sp. that produced a previously unknown microbial growth factor. This factor was an absolute growth requirement for three soil bacteria. The Penicillium sp. and one of the bacteria requiring the factor, an Arthrobacter sp., were selected for more extensive study concerning the production and characteristics of the growth factor. It did not seem to be related to the siderochromes. It was not present in soil extract, rumen fluid, or any other medium component tested. It appears to be a glycoprotein of high molecular weight and has high specific activity. When added to the diets for a meadow-vole mammalian test system, it caused an increased consumption of diet without a concurrent increase in rate of weight gain.

  5. Teaching Microbial Growth by Simulation.

    ERIC Educational Resources Information Center

    Ruiz, A. Fernandez; And Others

    1989-01-01

    Presented is a simulation program for Apple II computer which assays the effects of a series of variables on bacterial growth and interactions between microbial populations. Results of evaluation of the program with students are summarized. (CW)

  6. Modeling microbial growth and dynamics.

    PubMed

    Esser, Daniel S; Leveau, Johan H J; Meyer, Katrin M

    2015-11-01

    Modeling has become an important tool for widening our understanding of microbial growth in the context of applied microbiology and related to such processes as safe food production, wastewater treatment, bioremediation, or microbe-mediated mining. Various modeling techniques, such as primary, secondary and tertiary mathematical models, phenomenological models, mechanistic or kinetic models, reactive transport models, Bayesian network models, artificial neural networks, as well as agent-, individual-, and particle-based models have been applied to model microbial growth and activity in many applied fields. In this mini-review, we summarize the basic concepts of these models using examples and applications from food safety and wastewater treatment systems. We further review recent developments in other applied fields focusing on models that explicitly include spatial relationships. Using these examples, we point out the conceptual similarities across fields of application and encourage the combined use of different modeling techniques in hybrid models as well as their cross-disciplinary exchange. For instance, pattern-oriented modeling has its origin in ecology but may be employed to parameterize microbial growth models when experimental data are scarce. Models could also be used as virtual laboratories to optimize experimental design analogous to the virtual ecologist approach. Future microbial growth models will likely become more complex to benefit from the rich toolbox that is now available to microbial growth modelers.

  7. Modeling microbial growth and dynamics.

    PubMed

    Esser, Daniel S; Leveau, Johan H J; Meyer, Katrin M

    2015-11-01

    Modeling has become an important tool for widening our understanding of microbial growth in the context of applied microbiology and related to such processes as safe food production, wastewater treatment, bioremediation, or microbe-mediated mining. Various modeling techniques, such as primary, secondary and tertiary mathematical models, phenomenological models, mechanistic or kinetic models, reactive transport models, Bayesian network models, artificial neural networks, as well as agent-, individual-, and particle-based models have been applied to model microbial growth and activity in many applied fields. In this mini-review, we summarize the basic concepts of these models using examples and applications from food safety and wastewater treatment systems. We further review recent developments in other applied fields focusing on models that explicitly include spatial relationships. Using these examples, we point out the conceptual similarities across fields of application and encourage the combined use of different modeling techniques in hybrid models as well as their cross-disciplinary exchange. For instance, pattern-oriented modeling has its origin in ecology but may be employed to parameterize microbial growth models when experimental data are scarce. Models could also be used as virtual laboratories to optimize experimental design analogous to the virtual ecologist approach. Future microbial growth models will likely become more complex to benefit from the rich toolbox that is now available to microbial growth modelers. PMID:26298697

  8. Conditioning biomass for microbial growth

    DOEpatents

    Bodie, Elizabeth A; England, George

    2015-03-31

    The present invention relates to methods for improving the yield of microbial processes that use lignocellulose biomass as a nutrient source. The methods comprise conditioning a composition comprising lignocellulose biomass with an enzyme composition that comprises a phenol oxidizing enzyme. The conditioned composition can support a higher rate of growth of microorganisms in a process. In one embodiment, a laccase composition is used to condition lignocellulose biomass derived from non-woody plants, such as corn and sugar cane. The invention also encompasses methods for culturing microorganisms that are sensitive to inhibitory compounds in lignocellulose biomass. The invention further provides methods of making a product by culturing the production microorganisms in conditioned lignocellulose biomass.

  9. Well having inhibited microbial growth

    DOEpatents

    Lee, Brady D.; Dooley, Kirk J.

    2006-08-15

    The invention includes methods of inhibiting microbial growth in a well. A packing material containing a mixture of a first material and an antimicrobial agent is provided to at least partially fill a well bore. One or more access tubes are provided in an annular space around a casing within the well bore. The access tubes have a first terminal opening located at or above a ground surface and have a length that extends from the first terminal opening at least part of the depth of the well bore. The access tubes have a second terminal opening located within the well bore. An antimicrobial material is supplied into the well bore through the first terminal opening of the access tubes. The invention also includes well constructs.

  10. A thermodynamic theory of microbial growth.

    PubMed

    Desmond-Le Quéméner, Elie; Bouchez, Théodore

    2014-08-01

    Our ability to model the growth of microbes only relies on empirical laws, fundamentally restricting our understanding and predictive capacity in many environmental systems. In particular, the link between energy balances and growth dynamics is still not understood. Here we demonstrate a microbial growth equation relying on an explicit theoretical ground sustained by Boltzmann statistics, thus establishing a relationship between microbial growth rate and available energy. The validity of our equation was then questioned by analyzing the microbial isotopic fractionation phenomenon, which can be viewed as a kinetic consequence of the differences in energy contents of isotopic isomers used for growth. We illustrate how the associated theoretical predictions are actually consistent with recent experimental evidences. Our work links microbial population dynamics to the thermodynamic driving forces of the ecosystem, which opens the door to many biotechnological and ecological developments. PMID:24522260

  11. A thermodynamic theory of microbial growth

    PubMed Central

    Desmond-Le Quéméner, Elie; Bouchez, Théodore

    2014-01-01

    Our ability to model the growth of microbes only relies on empirical laws, fundamentally restricting our understanding and predictive capacity in many environmental systems. In particular, the link between energy balances and growth dynamics is still not understood. Here we demonstrate a microbial growth equation relying on an explicit theoretical ground sustained by Boltzmann statistics, thus establishing a relationship between microbial growth rate and available energy. The validity of our equation was then questioned by analyzing the microbial isotopic fractionation phenomenon, which can be viewed as a kinetic consequence of the differences in energy contents of isotopic isomers used for growth. We illustrate how the associated theoretical predictions are actually consistent with recent experimental evidences. Our work links microbial population dynamics to the thermodynamic driving forces of the ecosystem, which opens the door to many biotechnological and ecological developments. PMID:24522260

  12. Substrate and nutrient limitation regulating microbial growth in soil

    NASA Astrophysics Data System (ADS)

    Bååth, Erland

    2015-04-01

    Microbial activity and growth in soil is regulated by several abiotic factors, including temperature, moisture and pH as the most important ones. At the same time nutrient conditions and substrate availability will also determine microbial growth. Amount of substrate will not only affect overall microbial growth, but also affect the balance of fungal and bacterial growth. The type of substrate will also affect the latter. Furthermore, according to Liebig law of limiting factors, we would expect one nutrient to be the main limiting one for microbial growth in soil. When this nutrient is added, the initial second liming factor will become the main one, adding complexity to the microbial response after adding different substrates. I will initially describe different ways of determining limiting factors for bacterial growth in soil, especially a rapid method estimating bacterial growth, using the leucine incorporation technique, after adding C (as glucose), N (as ammonium nitrate) and P (as phosphate). Scenarios of different limitations will be covered, with the bacterial growth response compared with fungal growth and total activity (respiration). The "degree of limitation", as well as the main limiting nutrient, can be altered by adding substrate of different stoichiometric composition. However, the organism group responding after alleviating the nutrient limitation can differ depending on the type of substrate added. There will also be situations, where fungi and bacteria appear to be limited by different nutrients. Finally, I will describe interactions between abiotic factors and the response of the soil microbiota to alleviation of limiting factors.

  13. Microbial growth responses upon rewetting dry soil

    NASA Astrophysics Data System (ADS)

    Meisner, Annelein; Rousk, Johannes; Bååth, Erland

    2015-04-01

    Increased rainfall and drought periods are expected to occur with current climate change, leading to fluctuations in soil moisture. Changes in soil moisture are known to affect carbon cycling. A pulse of carbon dioxide release (respiration) is often observed after rewetting a dry soil and a drying threshold is observed before this pulse emerges. Increased microbial activity is often assumed to be the cause for the pulse in respiration. Yet, the microbial growth responses that underlie this pulse are often not studied. The following questions will be addressed in this presentation. 1) Do fungal and bacterial growth explain the pulse in respiration upon rewetting a dry soil? 2) How does microbial growth respond to different drying intensities before rewetting? To answer the research questions, soils from Sweden, U.K. and Greenland were put in microcosms, air-dried for four days, a prolonged period or to different moisture content before rewetting. We measured soil respiration, fungal growth rates and/or bacterial growth rates at high temporal resolution during one week after rewetting. Our results suggest that the respiration pulse upon rewetting dry soil is not due to high microbial growth rates. During the first hours after rewetting, bacterial and fungal growth rates were low whereas the respiration rates were high. As such, there was a decoupling between the pulse in respiration and microbial growth rates. Two patterns of bacterial growth were observed upon rewetting the three different soils. In "pattern 1", bacteria started growing immediately in a linear pattern up to values similar as the moist control. In "pattern 2", bacteria started growing exponentially after a lag period of no growth with a second pulse of respiration occurring at the start of bacterial growth. Manipulating the drying intensity changed the patterns. Soils with "pattern 1" were changed to "pattern 2" when subjected to more extensive drying periods whereas soils with "pattern 2" were

  14. Susceptibility of green and conventional building materials to microbial growth.

    PubMed

    Mensah-Attipoe, J; Reponen, T; Salmela, A; Veijalainen, A-M; Pasanen, P

    2015-06-01

    Green building materials are becoming more popular. However, little is known about their ability to support or limit microbial growth. The growth of fungi was evaluated on five building materials. Two green, two conventional building materials and wood as a positive control were selected. The materials were inoculated with Aspergillus versicolor, Cladosporium cladosporioides and Penicillium brevicompactum, in the absence and presence of house dust. Microbial growth was assessed at four different time points by cultivation and determining fungal biomass using the N-acetylhexosaminidase (NAHA) enzyme assay. No clear differences were seen between green and conventional building materials in their susceptibility to support microbial growth. The presence of dust, an external source of nutrients, promoted growth of all the fungal species similarly on green and conventional materials. The results also showed a correlation coefficient ranging from 0.81 to 0.88 between NAHA activity and culturable counts. The results suggest that the growth of microbes on a material surface depends on the availability of organic matter rather than the classification of the material as green or conventional. NAHA activity and culturability correlated well indicating that the two methods used in the experiments gave similar trends for the growth of fungi on material surfaces.

  15. Microbial growth in small-volume pharmaceuticals.

    PubMed

    Whyte, W; Niven, L; Bell, N D

    1989-01-01

    The ability of aseptically filled pharmaceuticals to support microbial growth was tested on 43 small-volume products (mainly parenterals). These were inoculated with a variety of microorganisms which were known to be associated with contamination of pharmaceutical products. In general, Gram-negative bacteria were found to be much more likely to grow than Gram-positive. It was possible for an inoculum of a few cells to multiply to levels up to 10(7)/mL. The presence of preservatives also influenced the likelihood of growth, 12 out of 19 (63%) of the pharmaceuticals without preservatives supporting growth of one or more microorganisms; only 3 out of 24 (12%) of those with preservatives supported growth. The importance of these observations is discussed with reference to formulation of aseptically filled products, environmental sampling and the quality of cleanroom conditions necessary for production. It is suggested that those pharmaceuticals which are designed to be sterile but not to be terminally sterilized, should be tested before production begins, for their ability to support microbial growth. In this way, the risks involved in aseptically filling can be ascertained. A test is proposed in which "indicator" microorganisms would predict the likelihood of pharmaceutical formulations supporting growth.

  16. Microbial Growth under Supercritical CO2

    PubMed Central

    Peet, Kyle C.; Freedman, Adam J. E.; Hernandez, Hector H.; Britto, Vanya; Boreham, Chris; Ajo-Franklin, Jonathan B.

    2015-01-01

    Growth of microorganisms in environments containing CO2 above its critical point is unexpected due to a combination of deleterious effects, including cytoplasmic acidification and membrane destabilization. Thus, supercritical CO2 (scCO2) is generally regarded as a sterilizing agent. We report isolation of bacteria from three sites targeted for geologic carbon dioxide sequestration (GCS) that are capable of growth in pressurized bioreactors containing scCO2. Analysis of 16S rRNA genes from scCO2 enrichment cultures revealed microbial assemblages of varied complexity, including representatives of the genus Bacillus. Propagation of enrichment cultures under scCO2 headspace led to isolation of six strains corresponding to Bacillus cereus, Bacillus subterraneus, Bacillus amyloliquefaciens, Bacillus safensis, and Bacillus megaterium. Isolates are spore-forming, facultative anaerobes and capable of germination and growth under an scCO2 headspace. In addition to these isolates, several Bacillus type strains grew under scCO2, suggesting that this may be a shared feature of spore-forming Bacillus spp. Our results provide direct evidence of microbial activity at the interface between scCO2 and an aqueous phase. Since microbial activity can influence the key mechanisms for permanent storage of sequestered CO2 (i.e., structural, residual, solubility, and mineral trapping), our work suggests that during GCS microorganisms may grow and catalyze biological reactions that influence the fate and transport of CO2 in the deep subsurface. PMID:25681188

  17. Impact of warm winters on microbial growth

    NASA Astrophysics Data System (ADS)

    Birgander, Johanna; Rousk, Johannes; Axel Olsson, Pål

    2014-05-01

    Growth of soil bacteria has an asymmetrical response to higher temperature with a gradual increase with increasing temperatures until an optimum after which a steep decline occurs. In laboratory studies it has been shown that by exposing a soil bacterial community to a temperature above the community's optimum temperature for two months, the bacterial community grows warm-adapted, and the optimum temperature of bacterial growth shifts towards higher temperatures. This result suggests a change in the intrinsic temperature dependence of bacterial growth, as temperature influenced the bacterial growth even though all other factors were kept constant. An intrinsic temperature dependence could be explained by either a change in the bacterial community composition, exchanging less tolerant bacteria towards more tolerant ones, or it could be due to adaptation within the bacteria present. No matter what the shift in temperature tolerance is due to, the shift could have ecosystem scale implications, as winters in northern Europe are getting warmer. To address the question of how microbes and plants are affected by warmer winters, a winter-warming experiment was established in a South Swedish grassland. Results suggest a positive response in microbial growth rate in plots where winter soil temperatures were around 6 °C above ambient. Both bacterial and fungal growth (leucine incorporation, and acetate into ergosterol incorporation, respectively) appeared stimulated, and there are two candidate explanations for these results. Either (i) warming directly influence microbial communities by modulating their temperature adaptation, or (ii) warming indirectly affected the microbial communities via temperature induced changes in bacterial growth conditions. The first explanation is in accordance with what has been shown in laboratory conditions (explained above), where the differences in the intrinsic temperature relationships were examined. To test this explanation the

  18. Nanomechanical sensors for single microbial cell growth monitoring

    NASA Astrophysics Data System (ADS)

    Maloney, Niall; Lukacs, Gyongyi; Jensen, Jason; Hegner, Martin

    2014-06-01

    A nanomechanical technique for rapid real time detection and monitoring of microorganism growth will significantly reduce costs and diagnosis times in industrial and clinical settings. Owing to their label free detection mechanism and unprecedented sensitivity to the mass and elastic modulus of biological structures, dynamically operated cantilever arrays provide an opportunity to rapidly detect and track the evolution of microbial growth. Here we report the monitoring of the growth of single Aspergillus niger spores via the multimode response of microcantilevers. The fungal hyphal structure affects the cantilevers' nanomechanical properties as it propagates along the sensor. We demonstrate, for the first time, the mapping of cellular events with great accuracy using a cantilever frequency response. Imaging of growth conditions on the cantilever, which is performed in parallel, allows for verification of these results. Theoretical comparison and finite element modelling confirm experimental findings and allow for determination of the hyphal elastic modulus.A nanomechanical technique for rapid real time detection and monitoring of microorganism growth will significantly reduce costs and diagnosis times in industrial and clinical settings. Owing to their label free detection mechanism and unprecedented sensitivity to the mass and elastic modulus of biological structures, dynamically operated cantilever arrays provide an opportunity to rapidly detect and track the evolution of microbial growth. Here we report the monitoring of the growth of single Aspergillus niger spores via the multimode response of microcantilevers. The fungal hyphal structure affects the cantilevers' nanomechanical properties as it propagates along the sensor. We demonstrate, for the first time, the mapping of cellular events with great accuracy using a cantilever frequency response. Imaging of growth conditions on the cantilever, which is performed in parallel, allows for verification of these

  19. Bioflumology: Microbial mat growth in flumes

    NASA Astrophysics Data System (ADS)

    Airo, A.; Weigert, S.; Beck, C.

    2014-04-01

    The emergence of oxygenic photosynthesis resulted in a transformational change of Earth's geochemical cycles and the subsequent evolution of life. However, it remains vigorously debated when this metabolic ability had evolved in cyanobacteria. This is largely because studies of Archean microfossil morphology, molecular biomarkers, and isotopic characteristics are frequently ambiguous. However, the high degree of morphological similarities between modern photosynthetic and Archean fossil mats has been interpreted to indicate phototactic microbial behavior or oxygenic photosynthesis. In order to better evaluate the relationship between mat morphology and metabolism, we here present a laboratory set-up for conducting month-long experiments in several sterilizable circular flumes designed to allow single-species cyanobacterial growth under adjustable fluid-flow conditions and protected from contamination.

  20. Interspecies interactions are an integral determinant of microbial community dynamics.

    PubMed

    Aziz, Fatma A A; Suzuki, Kenshi; Ohtaki, Akihiro; Sagegami, Keita; Hirai, Hidetaka; Seno, Jun; Mizuno, Naoko; Inuzuka, Yuma; Saito, Yasuhisa; Tashiro, Yosuke; Hiraishi, Akira; Futamata, Hiroyuki

    2015-01-01

    This study investigated the factors that determine the dynamics of bacterial communities in a complex system using multidisciplinary methods. Since natural and engineered microbial ecosystems are too complex to study, six types of synthetic microbial ecosystems (SMEs) were constructed under chemostat conditions with phenol as the sole carbon and energy source. Two to four phenol-degrading, phylogenetically and physiologically different bacterial strains were used in each SME. Phylogeny was based on the nucleotide sequence of 16S rRNA genes, while physiologic traits were based on kinetic and growth parameters on phenol. Two indices, J parameter and "interspecies interaction," were compared to predict which strain would become dominant in an SME. The J parameter was calculated from kinetic and growth parameters. On the other hand, "interspecies interaction," a new index proposed in this study, was evaluated by measuring the specific growth activity, which was determined on the basis of relative growth of a strain with or without the supernatant prepared from other bacterial cultures. Population densities of strains used in SMEs were enumerated by real-time quantitative PCR (qPCR) targeting the gene encoding the large subunit of phenol hydroxylase and were compared to predictions made from J parameter and interspecies interaction calculations. In 4 of 6 SEMs tested the final dominant strain shown by real-time qPCR analyses coincided with the strain predicted by both the J parameter and the interspecies interaction. However, in SMEII-2 and SMEII-3 the final dominant Variovorax strains coincided with prediction of the interspecies interaction but not the J parameter. These results demonstrate that the effects of interspecies interactions within microbial communities contribute to determining the dynamics of the microbial ecosystem.

  1. Interspecies interactions are an integral determinant of microbial community dynamics.

    PubMed

    Aziz, Fatma A A; Suzuki, Kenshi; Ohtaki, Akihiro; Sagegami, Keita; Hirai, Hidetaka; Seno, Jun; Mizuno, Naoko; Inuzuka, Yuma; Saito, Yasuhisa; Tashiro, Yosuke; Hiraishi, Akira; Futamata, Hiroyuki

    2015-01-01

    This study investigated the factors that determine the dynamics of bacterial communities in a complex system using multidisciplinary methods. Since natural and engineered microbial ecosystems are too complex to study, six types of synthetic microbial ecosystems (SMEs) were constructed under chemostat conditions with phenol as the sole carbon and energy source. Two to four phenol-degrading, phylogenetically and physiologically different bacterial strains were used in each SME. Phylogeny was based on the nucleotide sequence of 16S rRNA genes, while physiologic traits were based on kinetic and growth parameters on phenol. Two indices, J parameter and "interspecies interaction," were compared to predict which strain would become dominant in an SME. The J parameter was calculated from kinetic and growth parameters. On the other hand, "interspecies interaction," a new index proposed in this study, was evaluated by measuring the specific growth activity, which was determined on the basis of relative growth of a strain with or without the supernatant prepared from other bacterial cultures. Population densities of strains used in SMEs were enumerated by real-time quantitative PCR (qPCR) targeting the gene encoding the large subunit of phenol hydroxylase and were compared to predictions made from J parameter and interspecies interaction calculations. In 4 of 6 SEMs tested the final dominant strain shown by real-time qPCR analyses coincided with the strain predicted by both the J parameter and the interspecies interaction. However, in SMEII-2 and SMEII-3 the final dominant Variovorax strains coincided with prediction of the interspecies interaction but not the J parameter. These results demonstrate that the effects of interspecies interactions within microbial communities contribute to determining the dynamics of the microbial ecosystem. PMID:26539177

  2. Interspecies interactions are an integral determinant of microbial community dynamics

    PubMed Central

    Aziz, Fatma A. A.; Suzuki, Kenshi; Ohtaki, Akihiro; Sagegami, Keita; Hirai, Hidetaka; Seno, Jun; Mizuno, Naoko; Inuzuka, Yuma; Saito, Yasuhisa; Tashiro, Yosuke; Hiraishi, Akira; Futamata, Hiroyuki

    2015-01-01

    This study investigated the factors that determine the dynamics of bacterial communities in a complex system using multidisciplinary methods. Since natural and engineered microbial ecosystems are too complex to study, six types of synthetic microbial ecosystems (SMEs) were constructed under chemostat conditions with phenol as the sole carbon and energy source. Two to four phenol-degrading, phylogenetically and physiologically different bacterial strains were used in each SME. Phylogeny was based on the nucleotide sequence of 16S rRNA genes, while physiologic traits were based on kinetic and growth parameters on phenol. Two indices, J parameter and “interspecies interaction,” were compared to predict which strain would become dominant in an SME. The J parameter was calculated from kinetic and growth parameters. On the other hand, “interspecies interaction,” a new index proposed in this study, was evaluated by measuring the specific growth activity, which was determined on the basis of relative growth of a strain with or without the supernatant prepared from other bacterial cultures. Population densities of strains used in SMEs were enumerated by real-time quantitative PCR (qPCR) targeting the gene encoding the large subunit of phenol hydroxylase and were compared to predictions made from J parameter and interspecies interaction calculations. In 4 of 6 SEMs tested the final dominant strain shown by real-time qPCR analyses coincided with the strain predicted by both the J parameter and the interspecies interaction. However, in SMEII-2 and SMEII-3 the final dominant Variovorax strains coincided with prediction of the interspecies interaction but not the J parameter. These results demonstrate that the effects of interspecies interactions within microbial communities contribute to determining the dynamics of the microbial ecosystem. PMID:26539177

  3. Minimal models of growth and decline of microbial populations.

    PubMed

    Juška, Alfonsas

    2011-01-21

    Dynamics of growth and decline of microbial populations were analysed and respective models were developed in this investigation. Analysis of the dynamics was based on general considerations concerning the main properties of microorganisms and their interactions with the environment which was supposed to be affected by the activity of the population. Those considerations were expressed mathematically by differential equations or systems of the equations containing minimal sets of parameters characterizing those properties. It has been found that: (1) the factors leading to the decline of the population have to be considered separately, namely, accumulation of metabolites (toxins) in the medium and the exhaustion of resources; the latter have to be separated again into renewable ('building materials') and non-renewable (sources of energy); (2) decline of the population is caused by the exhaustion of sources of energy but no decline is predicted by the model because of the exhaustion of renewable resources; (3) the model determined by the accumulation of metabolites (toxins) in the medium does not suggest the existence of a separate 'stationary phase'; (4) in the model determined by the exhaustion of energy resources the 'stationary' and 'decline' phases are quite discernible; and (5) there is no symmetry in microbial population dynamics, the decline being slower than the rise. Mathematical models are expected to be useful in getting insight into the process of control of the dynamics of microbial populations. The models are in agreement with the experimental data. PMID:21036180

  4. Microbial growth and transport in saturated and unsaturated porous media

    NASA Astrophysics Data System (ADS)

    Hron, Pavel; Jost, Daniel; Bastian, Peter; Ippisch, Olaf

    2014-05-01

    There is a considerable ongoing effort aimed at understanding the behavior of microorganisms in porous media. Microbial activity is of significant interest in various environmental applications such as in situ bioremediation, protection of drinking water supplies and for subsurface geochemistry in general. The main limiting factors for bacterial growth are the availability of electron acceptors, nutrients and bio-available water. The capillary fringe, defined - in a wider sense than usual - as the region of the subsurface above the groundwater table, but still dominated by capillary rise, is a region where all these factors are abundantly available. It is thus a region where high microbial activity is to be expected. In a research unit 'Dynamic Capillary Fringes - A Multidisciplinary Approach (DyCap)' founded by the German Research Foundation (DFG), the growth of microorganisms in the capillary fringe was studied experimentally and with numerical simulations. Processes like component transport and diffusion, exchange between the liquid phase and the gas phase, microbial growth and cell attachment and detachment were incorporated into a numerical simulator. The growth of the facultative anaerobic Escherichia coli as a function of nutrient availability and oxygen concentration in the liquid phase is modeled with modified Monod-type models and modifications for the switch between aerobic and anaerobic growth. Laboratory batch experiments with aqueous solutions of bacteria have been carried out under various combinations of oxygen concentrations in the gas phase and added amounts of dissolved organic carbon to determine the growth model parameters by solution of a parameter estimation problem. For the transport of bacteria the adhesion to phase boundaries is also very important. As microorganisms are transported through porous media, they are removed from the pore fluid by physicochemical filtration (attachment to sediment grain surfaces) or are adhering to gas

  5. 21 CFR 866.2560 - Microbial growth monitor.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Microbial growth monitor. 866.2560 Section 866.2560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2560 Microbial...

  6. 21 CFR 866.2560 - Microbial growth monitor.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Microbial growth monitor. 866.2560 Section 866.2560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2560 Microbial...

  7. 21 CFR 866.2560 - Microbial growth monitor.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Microbial growth monitor. 866.2560 Section 866.2560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2560 Microbial...

  8. 21 CFR 866.2560 - Microbial growth monitor.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Microbial growth monitor. 866.2560 Section 866.2560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2560 Microbial...

  9. 21 CFR 866.2560 - Microbial growth monitor.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Microbial growth monitor. 866.2560 Section 866.2560 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices § 866.2560 Microbial...

  10. Spatial & Temporal Geophysical Monitoring of Microbial Growth and Biofilm Formation

    EPA Science Inventory

    Previous studies have examined the effect of biogenic gases and biomineralization on the acoustic properties of porous media. In this study, we investigated the spatiotemporal effect of microbial growth and biofilm formation on compressional waves and complex conductivity in sand...

  11. Microbial growth on respirator filters from improper storage.

    PubMed

    Pasanen, A L; Keinänen, J; Kalliokoski, P; Martikainen, P I; Ruuskanen, J

    1993-12-01

    Microbiological contamination and particle penetration were studied in two respirator filters with high efficiency. Microbial growth in filter materials during storage under conditions and the passing of microorganisms through the filters were particularly examined. Filters with different fiberglass and cellulose proportions were loaded in environments containing high microbial levels and incubated at a relative humidity of 98%. Particle penetration through loaded and incubated filters and carbon, nitrogen and microbial content were measured. After incubation, considerable particle penetration and the passing of fungal spores were observed for filters composed mainly of cellulose, probably because of humid conditions, which stimulated fungi to grow and extend mycelia and spores through the filter. Microbial activity, microorganism concentrations, and the chemical properties of the filter materials also supported this hypothesis. Storing used respirators in humid environments may result in heavy microbial contamination of the filters, especially if the filter material is biodegradable by microorganisms. PMID:8153595

  12. Microbial growth and physiology in space - A review

    NASA Technical Reports Server (NTRS)

    Cioletti, Louis A.; Mishra, S. K.; Pierson, Duane L.

    1991-01-01

    An overview of microbial behavior in closed environments is given with attention to data related to simulated microgravity and actual space flight. Microbes are described in terms of antibiotic sensitivity, subcellular structure, and physiology, and the combined effects are considered of weightlessness and cosmic radiation on human immunity to such microorganisms. Space flight results report such effects as increased phage induction, accelerated microbial growth rates, and the increased risk of disease communication and microbial exchange aboard confining spacecraft. Ultrastructural changes are also noted in the nuclei, cell membranes, and cytoplasmic streaming, and it appears that antibiotic sensitivity is reduced under both actual and simulated conditions of spaceflight.

  13. Estimating phosphorus availability for microbial growth in an emerging landscape

    USGS Publications Warehouse

    Schmidt, S.K.; Cleveland, C.C.; Nemergut, D.R.; Reed, S.C.; King, A.J.; Sowell, P.

    2011-01-01

    Estimating phosphorus (P) availability is difficult—particularly in infertile soils such as those exposed after glacial recession—because standard P extraction methods may not mimic biological acquisition pathways. We developed an approach, based on microbial CO2 production kinetics and conserved carbon:phosphorus (C:P) ratios, to estimate the amount of P available for microbial growth in soils and compared this method to traditional, operationally-defined indicators of P availability. Along a primary succession gradient in the High Andes of Perú, P additions stimulated the growth-related (logistic) kinetics of glutamate mineralization in soils that had been deglaciated from 0 to 5 years suggesting that microbial growth was limited by soil P availability. We then used a logistic model to estimate the amount of C incorporated into biomass in P-limited soils, allowing us to estimate total microbial P uptake based on a conservative C:P ratio of 28:1 (mass:mass). Using this approach, we estimated that there was < 1 μg/g of microbial-available P in recently de-glaciated soils in both years of this study. These estimates fell well below estimates of available soil P obtained using traditional extraction procedures. Our results give both theoretical and practical insights into the kinetics of C and P utilization in young soils, as well as show changes in microbial P availability during early stages of soil development.

  14. Optimization of biomass composition explains microbial growth-stoichiometry relationships

    USGS Publications Warehouse

    Franklin, O.; Hall, E.K.; Kaiser, C.; Battin, T.J.; Richter, A.

    2011-01-01

    Integrating microbial physiology and biomass stoichiometry opens far-reaching possibilities for linking microbial dynamics to ecosystem processes. For example, the growth-rate hypothesis (GRH) predicts positive correlations among growth rate, RNA content, and biomass phosphorus (P) content. Such relationships have been used to infer patterns of microbial activity, resource availability, and nutrient recycling in ecosystems. However, for microorganisms it is unclear under which resource conditions the GRH applies. We developed a model to test whether the response of microbial biomass stoichiometry to variable resource stoichiometry can be explained by a trade-off among cellular components that maximizes growth. The results show mechanistically why the GRH is valid under P limitation but not under N limitation. We also show why variability of growth rate-biomass stoichiometry relationships is lower under P limitation than under N or C limitation. These theoretical results are supported by experimental data on macromolecular composition (RNA, DNA, and protein) and biomass stoichiometry from two different bacteria. In addition, compared to a model with strictly homeostatic biomass, the optimization mechanism we suggest results in increased microbial N and P mineralization during organic-matter decomposition. Therefore, this mechanism may also have important implications for our understanding of nutrient cycling in ecosystems.

  15. Dynamic speckle study of microbial growth

    NASA Astrophysics Data System (ADS)

    Vincitorio, F. M.; Mulone, C.; Marcuzzi, P. A.; Budini, N.; Freyre, C.; Lopez, A. J.; Ramil, A.

    2015-08-01

    In this work we present a characterization of yeast dynamic speckle activity during growth in an isolated agar culture medium. We found that it is possible to detect the growth of the microorganisms even before they turn out to be visible. By observing the time evolution of the speckle activity at different regions of the culture medium we could extract a map of the growth process, which served to analyze how the yeast develops and spreads over the agar's medium. An interesting point of this study concerns with the influence of the laser light on the yeast growth rate. We have found that yeast finds hard to develop at regions with higher laser light illumination, although we used a synchronous system to capture the speckle pattern. The results obtained in this work would serve us as a starting point to fabricate a detector of growing microorganism colonies, with obvious interesting applications in diverse areas.

  16. Acoustic and Electrical Property Changes Due to Microbial Growth and Biofilm Formation in Porous Media

    EPA Science Inventory

    A laboratory study was conducted to investigate the effect of microbial growth and biofilm formation on compressional waves, and complex conductivity during stimulated microbial growth. Over the 29 day duration of the experiment, compressional wave amplitudes and arrival times f...

  17. Microbial physiology and ecology of slow growth.

    PubMed Central

    Koch, A L

    1997-01-01

    The uptake capabilities of the cell have evolved to permit growth at very low external nutrient concentrations. How are these capabilities controlled when the substrate concentrations are not extremely low and the uptake systems could import substrate much more rapidly than the metabolic capabilities of the cell might be able to handle? To answer this question, earlier theories for the kinetics of uptake through the cell envelope and steady-state systems of metabolic enzymes are discussed and a computer simulation is presented. The problems to the cell of fluctuating levels of nutrient and too much substrate during continuous culture are discussed. Too much substrate can lead to oligotrophy, substrate-accelerated death, entry into the viable but not culturable state, and lactose killing. The relationship between uptake and growth is considered. Finally, too little substrate may lead to catastrophic attempts at mounting molecular syntheses that cannot be completed. PMID:9293184

  18. Calorimetric versus Growth Microbial Analysis of Cellulase Enzymes Acting on Cellulose

    PubMed Central

    Lovrien, Rex E.; Williams, Karl K.; Ferrey, Mark L.; Ammend, David A.

    1987-01-01

    Assay of cellulase enzymology on cellulose was investigated by two methods: (i) plate colony counting to determine microbial growth and (ii) microbial calorimetry. These methods were chosen because they accept raw samples and have the potential to be far more specific than spectrophotometric reducing sugar assays. Microbial calorimetry requires ca. 0.5 to 1 h and 10 to 100 μM concentrations of cellulolytic lower sugars (glucose and cellobiose). Growth assay (liquid culture, plating, colony counting) requires 15 to 20 h and ca. 0.5 mM sugars. Microbial calorimetry requires simply aerobic metabolism, whereas growth assay requires completion of the cell cycle. A stripping technique is described for use in conjunction with the calorimetric method to enable separate analysis of the two sugars. Mixtures of glucose and cellobiose are equilibrated with Escherichia coli and spun out to remove glucose. The supernatant is calorimetrically combusted with Klebsiella sp. to quantitate cellobiose, and the same organism combusting the nonstripped mixture gives heat proportional to the sum of the two sugars. Calorimetry of cellulolysis products from individual exo- and endocellulases, and from their reconstituted mixture, was carried out to develop a microbial calorimetric means for demonstrating enzyme synergism. PMID:16347508

  19. Biodegradation during contaminant transport in porous media: 4. Impact of microbial lag and bacterial cell growth

    NASA Astrophysics Data System (ADS)

    Sandrin, Susannah K.; Jordan, Fiona L.; Maier, Raina M.; Brusseau, Mark L.

    2001-08-01

    Miscible-displacement experiments were conducted to examine the impact of microbial lag and bacterial cell growth on the transport of salicylate, a model hydrocarbon compound. The impacts of these processes were examined separately, as well as jointly, to determine their relative effects on biodegradation dynamics. For each experiment, a column was packed with porous medium that was first inoculated with bacteria that contained the NAH plasmid encoding genes for the degradation of naphthalene and salicylate, and then subjected to a step input of salicylate solution. The transport behavior of salicylate was non-steady for all cases examined, and was clearly influenced by a delay (lag) in the onset of biodegradation. This microbial lag, which was consistent with the results of batch experiments, is attributed to the induction and synthesis of the enzymes required for biodegradation of salicylate. The effect of microbial lag on salicylate transport was eliminated by exposing the column to two successive pulses of salicylate, thereby allowing the cells to acclimate to the carbon source during the first pulse. Elimination of microbial lag effects allowed the impact of bacterial growth on salicylate transport to be quantified, which was accomplished by determining a cell mass balance. Conversely, the impact of microbial lag was further investigated by performing a similar double-pulse experiment under no-growth conditions. Significant cell elution was observed and quantified for all conditions/systems. The results of these experiments allowed us to differentiate the effects associated with microbial lag and growth, two coupled processes whose impacts on the biodegradation and transport of contaminants can be difficult to distinguish.

  20. Using coagulation to restrict microbial re-growth in tap water by phosphate limitation in water treatment.

    PubMed

    Wen, Gang; Ma, Jun; Huang, Ting-Lin; Egli, Thomas

    2014-09-15

    Extensive microbial re-growth in a drinking water distribution system can deteriorate water quality. The limiting factor for microbial re-growth in a tap water produced by a conventional drinking water treatment plant in China was identified by determining the microbial re-growth potential (MRP) by adding different nutrients to stimulate growth of a natural microbial consortium as inoculum and flow-cytometric enumeration. No obvious change of MRP was found in tap water after addition of carbon, whereas, a 1- to 2-fold increase of MRP was observed after addition of phosphate (P). This clearly demonstrated that microbial re-growth in this tap water was limited by P. Most of the re-grown microbial flora (>85%) consisted of high nucleic acid content cells. A subsequent investigation of the MRP in the actual water treatment plant demonstrated that coagulation was the crucial step for decreasing MRP and producing P-limited water. Therefore, a comparison concerning the control of MRP by three different coagulants was conducted. It showed that all the three coagulants efficiently reduced the MRP and shifted the limitation regime from C to P, but the required dose was different. The study shows that it is feasible to restrict microbial re-growth by P limitation using coagulation in water treatment.

  1. Determination of cyanide using a microbial sensor

    SciTech Connect

    Nakanishi, Keijiro; Ikebukuro, Kazunori; Karube, Isao

    1996-08-01

    A microbial cyanide sensor was prepared, consisting of immobilized Saccharomyces cerevisiae and an oxygen electrode. When the electrode was inserted into a solution containing glucose, the respiration activity of the microorganisms increased. The change in the respiration activity is monitored with the oxygen electrode. When cyanide is added to the sample solution, the electron transport chain reaction of the respiration system in the mitochondria is inhibited, resulting in a decrease in respiration. The inhibition is caused by cyanide binding with respiration enzymes such as the cytochrome oxidase complex in the mitochondrial inner membrane. Therefore, the cyanide concentration can be measured from the change in the respiration rate. When the sensor was applied to a batch system at pH 8.0 and 30{degrees}C, the cyanide calibration curve showed linearity in the concentration range between 0.3 pM and 150 {mu}m CN{sup -}. 13 refs., 8 figs., 1 tab.

  2. Microbial growth and biofilm formation in geologic media is detected with complex conductivity measurements

    NASA Astrophysics Data System (ADS)

    Davis, Caroline A.; Atekwana, Estella; Atekwana, Eliot; Slater, Lee D.; Rossbach, Silvia; Mormile, Melanie R.

    2006-09-01

    Complex conductivity measurements (0.1-1000 Hz) were obtained from biostimulated sand-packed columns to investigate the effect of microbial growth and biofilm formation on the electrical properties of porous media. Microbial growth was verified by direct microbial counts, pH measurements, and environmental scanning electron microscope imaging. Peaks in imaginary (interfacial) conductivity in the biostimulated columns were coincident with peaks in the microbial cell concentrations extracted from sands. However, the real conductivity component showed no discernible relationship to microbial cell concentration. We suggest that the observed dynamic changes in the imaginary conductivity (σ″) arise from the growth and attachment of microbial cells and biofilms to sand surfaces. We conclude that complex conductivity techniques, specifically imaginary conductivity measurements are a proxy indicator for microbial growth and biofilm formation in porous media. Our results have implications for microbial enhanced oil recovery, CO2 sequestration, bioremediation, and astrobiology studies.

  3. INVESTIGATING THE EFFECT OF MICROBIAL GROWTH AND BIOFILM FORMATION ON SEISMIC WAVE PROPAGATION IN SEDIMENT

    EPA Science Inventory

    Previous laboratory investigations have demonstrated that the seismic methods are sensitive to microbially-induced changes in porous media through the generation of biogenic gases and biomineralization. The seismic signatures associated with microbial growth and biofilm formation...

  4. Spatial & Temporal Geophysical Monitoring of Microbial Growth and Biofilm Formation

    NASA Astrophysics Data System (ADS)

    Davis, C. A.; Pyrak-Nolte, L. J.; Atekwana, E. A.; Werkema, D. D.; Haugen, M. E.

    2009-12-01

    Previous studies have examined the effect of biogenic gases and biomineralization on the acoustic properties of porous media. In this study, we investigated the spatiotemporal effect of microbial growth and biofilm formation on compressional waves and complex conductivity in sand columns. A control column (non-biostimulated) and a biostimulated column were studied in a 2D acoustic scanning apparatus, and a second set of columns were constructed with Ag-AgCl electrodes for complex conductivity measurements. At the completion of the 29-day experiment, compressional wave amplitudes and arrival times for the control column were observed to be relatively uniform over the scanned 2D region. However, the biostimulated sample exhibited a high degree of spatial variability within the column for both the amplitude and arrival times. Furthermore, portions of the sample exhibited increased attenuation (~ 80%) concurrent with an increase in the arrival times, while other portions exhibited decreased attenuation (~ 45%) and decreased arrival time. The acoustic amplitude and arrival times changed significantly in the biostimulated column between Days 5 and 7 of the experiment and are consistent with a peak in the imaginary conductivity (σ”) values. The σ” response corresponds to different stages of biofilm development. That is, we interpret the peak σ” with the maximum biofilm thickness and decreasing σ” due to cell death or detachment. Environmental scanning electron microscope (ESEM) imaging confirmed microbial cell attachment to sand surfaces in the biostimulated columns, showed apparent differences in the morphology of attached biomass between regions of increased and decreased attenuation, and indicated no mineral precipitation or biomineralization. The heterogeneity in the elastic properties arises from the differences in the morphology and structure of attached biofilms. These results suggest that combining acoustic imaging and complex conductivity techniques

  5. Arsenic as an energy source for microbial growth. (Invited)

    NASA Astrophysics Data System (ADS)

    Oremland, R. S.

    2009-12-01

    Arsenic, although known for millenia to be a potent poison, can also constitute the basis for energy metabolism by a number of Bacteria and Archaea. Hence, the oxyanion arsenate [As(V)] can serve as a respiratory electron acceptor for the growth of anaerobes, resulting in the accumulation of arsenite [As(III)]. Conversely, As(III) can serve as an electron donor for the growth of aerobic and anaerobic (e.g., nitrate-respiring) chemoautotrophs, as well as photoautotrophs that grow via anoxygenic photosynthesis. Collectively, these microbes carry out these redox reactions between the +3 and +5 oxidation states that have profound importance for the mobility of As in the environment, and perhaps for the pattern of microbial evolution on Earth. I will focus upon the occurrence of these microbes in extreme environments that are rich in naturally-occurring arsenic.

  6. Microbial growth and macromolecular synthesis in the northwestern Atlantic Ocean

    SciTech Connect

    Cuhel, R.L.; Jannasch, H.W.; Taylor, C.D.

    1983-01-01

    Simultaneous time-course measurements of /sup 35/SO/sub 4//sup 2 -/, /sup 32/PO/sup 43 -/, /sup 15/NH/sub 4//sup +/, and (/sup 14/C)acetate, glucose, and glutamate uptake were made at three stations in the northwestern Atlantic Ocean, using water samples taken from well below the euphotic zone. Marked deviations from linearity were observed in 14 of the 15 cases. At the two most inshore stations uptake of /sup 15/NH/sub 4//sup +/ or incorporation of /sup 35/SO/sub 4//sup 2 -/ into protein was undetectable for 16-30 h, followed by very rapid increases in the rates of activity. The sudden burst of SO/sub 4//sup 2 -/and NH/sub 4//sup +/ uptake was accompanied by a major increase in the incorporation of /sup 32/P into RNA and lipid fractions of the microbial population at a continental slope station. At a station in Sargasso Sea, all substrates were taken up without lag. Extended incubations led to a growth plateau which may be a measure of the total biologically labile organic nutrient supply. In all cases tested, chloramphenicol severely restricted uptake. One of the inshore stations was revisited a year later with similar results. The combined data demonstrate the utility of using inorganic nutrient uptake and subcellular incorporation patterns to measure microbial growth and metabolism and stress the necessity of time-course rather than end-point incubations.

  7. Macroalgae Decrease Growth and Alter Microbial Community Structure of the Reef-Building Coral, Porites astreoides

    PubMed Central

    Vega Thurber, Rebecca; Burkepile, Deron E.; Correa, Adrienne M. S.; Thurber, Andrew R.; Shantz, Andrew A.; Welsh, Rory; Pritchard, Catharine; Rosales, Stephanie

    2012-01-01

    With the continued and unprecedented decline of coral reefs worldwide, evaluating the factors that contribute to coral demise is of critical importance. As coral cover declines, macroalgae are becoming more common on tropical reefs. Interactions between these macroalgae and corals may alter the coral microbiome, which is thought to play an important role in colony health and survival. Together, such changes in benthic macroalgae and in the coral microbiome may result in a feedback mechanism that contributes to additional coral cover loss. To determine if macroalgae alter the coral microbiome, we conducted a field-based experiment in which the coral Porites astreoides was placed in competition with five species of macroalgae. Macroalgal contact increased variance in the coral-associated microbial community, and two algal species significantly altered microbial community composition. All macroalgae caused the disappearance of a γ-proteobacterium previously hypothesized to be an important mutualist of P. astreoides. Macroalgal contact also triggered: 1) increases or 2) decreases in microbial taxa already present in corals, 3) establishment of new taxa to the coral microbiome, and 4) vectoring and growth of microbial taxa from the macroalgae to the coral. Furthermore, macroalgal competition decreased coral growth rates by an average of 36.8%. Overall, this study found that competition between corals and certain species of macroalgae leads to an altered coral microbiome, providing a potential mechanism by which macroalgae-coral interactions reduce coral health and lead to coral loss on impacted reefs. PMID:22957055

  8. Macroalgae decrease growth and alter microbial community structure of the reef-building coral, Porites astreoides.

    PubMed

    Vega Thurber, Rebecca; Burkepile, Deron E; Correa, Adrienne M S; Thurber, Andrew R; Shantz, Andrew A; Welsh, Rory; Pritchard, Catharine; Rosales, Stephanie

    2012-01-01

    With the continued and unprecedented decline of coral reefs worldwide, evaluating the factors that contribute to coral demise is of critical importance. As coral cover declines, macroalgae are becoming more common on tropical reefs. Interactions between these macroalgae and corals may alter the coral microbiome, which is thought to play an important role in colony health and survival. Together, such changes in benthic macroalgae and in the coral microbiome may result in a feedback mechanism that contributes to additional coral cover loss. To determine if macroalgae alter the coral microbiome, we conducted a field-based experiment in which the coral Porites astreoides was placed in competition with five species of macroalgae. Macroalgal contact increased variance in the coral-associated microbial community, and two algal species significantly altered microbial community composition. All macroalgae caused the disappearance of a γ-proteobacterium previously hypothesized to be an important mutualist of P. astreoides. Macroalgal contact also triggered: 1) increases or 2) decreases in microbial taxa already present in corals, 3) establishment of new taxa to the coral microbiome, and 4) vectoring and growth of microbial taxa from the macroalgae to the coral. Furthermore, macroalgal competition decreased coral growth rates by an average of 36.8%. Overall, this study found that competition between corals and certain species of macroalgae leads to an altered coral microbiome, providing a potential mechanism by which macroalgae-coral interactions reduce coral health and lead to coral loss on impacted reefs. PMID:22957055

  9. Monitoring microbial growth and activity using spectral induced polarization and low-field nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Keating, Kristina; Revil, Andre

    2015-04-01

    Microbes and microbial activities in the Earth's subsurface play a significant role in shaping subsurface environments and are involved in environmental applications such as remediation of contaminants in groundwater and oil fields biodegradation. Stimulated microbial growth in such applications could cause wide variety of changes of physical/chemical properties in the subsurface. It is critical to monitor and determine the fate and transportation of microorganisms in the subsurface during such applications. Recent geophysical studies demonstrate the potential of two innovative techniques, spectral induced polarization (SIP) and low-field nuclear magnetic resonance (NMR), for monitoring microbial growth and activities in porous media. The SIP measures complex dielectric properties of porous media at low frequencies of exciting electric field, and NMR studies the porous structure of geologic media and characterizes fluids subsurface. In this laboratory study, we examined both SIP and NMR responses from bacterial growth suspension as well as suspension mixed with silica sands. We focus on the direct contribution of microbes to the SIP and NMR signals in the absence of biofilm formation or biomineralization. We used Zymomonas mobilis and Shewanella oneidensis (MR-1) for SIP and NMR measurements, respectively. The SIP measurements were collected over the frequency range of 0.1 - 1 kHz on Z. mobilis growth suspension and suspension saturated sands at different cell densities. SIP data show two distinct peaks in imaginary conductivity spectra, and both imaginary and real conductivities increased as microbial density increased. NMR data were collected using both CPMG pulse sequence and D-T2 mapping to determine the T2-distribution and diffusion properties on S. oneidensis suspension, pellets (live and dead), and suspension mixed with silica sands. NMR data show a decrease in the T2-distribution in S. oneidensis suspension saturated sands as microbial density increase. A

  10. Optimising Microbial Growth with a Bench-Top Bioreactor

    ERIC Educational Resources Information Center

    Baker, A. M. R.; Borin, S. L.; Chooi, K. P.; Huang, S. S.; Newgas, A. J. S.; Sodagar, D.; Ziegler, C. A.; Chan, G. H. T.; Walsh, K. A. P.

    2006-01-01

    The effects of impeller size, agitation and aeration on the rate of yeast growth were investigated using bench-top bioreactors. This exercise, carried out over a six-month period, served as an effective demonstration of the importance of different operating parameters on cell growth and provided a means of determining the optimisation conditions…

  11. SELECTIVE REVERSIBLE INHIBITION OF MICROBIAL GROWTH WITH PYRITHIAMINE

    PubMed Central

    Woolley, D. W.; White, A. G. C.

    1943-01-01

    Growth of many microbial species was inhibited by pyrithiamine, the pyridine analog of thiamine. Growth of many other species was not influenced. In a series of bacteria, yeasts, and molds, it was found that inhibition of growth occurred only in those in which growth was stimulated by thiamine or its component pyrimidine and thiazole portions. The amount of pyrithiamine required for inhibition was correlated with the type of thiamine requirements of various species. The least amount was needed to inhibit organisms which required intact thiamine. Those which could use the pyrimidine and thiazole portions were not so readily inhibited. In the case of the former organisms, half maximal inhibition was produced by as little as 0.03 γ per cc. In all instances, the inhibition was overcome by sufficient amounts of thiamine. The synthesis of thiamine by insusceptible species was studied, and it was concluded that formation of thiamine or other antagonistic substance did not provide an adequate explanation of the resistance of these species to the action of pyrithiamine. PMID:19871344

  12. Microbial growth on pall rings: a problem when upgrading biogas with the water-wash absorption technique.

    PubMed

    Tynell, Asa; Börjesson, Gunnar; Persson, Margareta

    2007-01-01

    Biogas is upgraded using an absorption with water-wash technique by 11 of a total of 14 upgrading plants in Sweden. However, problems with microbial growth on the pall rings in the absorption column, and in one case in the desorption column, have a negative impact on the upgrading of raw gas to vehicle gas. Five of the nine biogas plants studied here have experienced problems with microbial growth. The objectives of this study were to identify such microbial growth and to determine possible factors for its control, in order to provide recommendations for process management. A questionnaire was sent out and visits were made to the upgrading plants to collect information about the upgrading process. Phospholipid fatty acid (PLFA) analysis was performed to determine microbial biomass and community structure in samples from four upgrading plants. In samples from two of the plants, methane-oxidizing bacteria (type I methanotrophs) were indicated, while samples from one of the other plants showed biomarkers indicating actinomycetes. Factors affecting development of microbial growth were found to be water quality and the pH and temperature of the process water. Plants that used wastewater in the upgrading process experienced far more problems than those using clean water of drinking quality.

  13. Detecting Microbial Growth and Metabolism in Geologic Media with Complex Conductivity Measurements

    NASA Astrophysics Data System (ADS)

    Davis, C. A.; Atekwana, E. A.; Slater, L. D.; Bottrell, P. M.; Chasten, L. E.; Heidenreich, J. D.

    2006-05-01

    Complex conductivity measurements between 0.1-1000 Hz were obtained from biostimulated sand-packed (coarse and mixed fine and medium grain) columns to investigate microbial growth, biofilm formation, and microbial metabolism on the electrical properties of porous media. Microbial growth and metabolism was verified by direct microbial counts, pH changes, and environmental scanning electron microscope imaging. Peaks in imaginary (interfacial) conductivity in the coarse grain columns occurred concurrently with peaks in the microbial cell concentrations. The magnitude of the imaginary conductivity response in the mixed fine and medium grain columns, however, was low compared to the coarse grain sand columns, consistent with lower microbial cell concentrations. It is possible that the pore size in the mixed fine and medium grain sand restricted bacteria cell division, inhibiting microbial growth, and thus the smaller magnitude imaginary conductivity response. The biostimulated columns for both grain sizes displayed similar trends and showed an increase in the real (electrolytic) conductivity and decrease in pH over time. Dynamic changes in the imaginary conductivity arises from the growth and attachment of microbial cells and biofilms to surfaces, whereas, changes in the real conductivity arises from the release of byproducts (ionic species) of microbial metabolism. We conclude that complex conductivity techniques are feasible sensors for detecting microbial growth (imaginary conductivity measurements) and metabolism (real conductivity measurements) with implications for bioremediation and astrobiology studies.

  14. Elevated atmospheric CO2 increases microbial growth rates and enzymes activity in soil

    NASA Astrophysics Data System (ADS)

    Blagodatskaya, Evgenia; Blagodatsky, Sergey; Dorodnikov, Maxim; Kuzyakov, Yakov

    2010-05-01

    Increasing the belowground translocation of assimilated carbon by plants grown under elevated CO2 can cause a shift in the structure and activity of the microbial community responsible for the turnover of organic matter in soil. We investigated the long-term effect of elevated CO2 in the atmosphere on microbial biomass and specific growth rates in root-free and rhizosphere soil. The experiments were conducted under two free air carbon dioxide enrichment (FACE) systems: in Hohenheim and Braunschweig, as well as in the intensively managed forest mesocosm of the Biosphere 2 Laboratory (B2L) in Oracle, AZ. Specific microbial growth rates (μ) were determined using the substrate-induced respiration response after glucose and/or yeast extract addition to the soil. We evaluated the effect of elevated CO2 on b-glucosidase, chitinase, phosphatase, and sulfatase to estimate the potential enzyme activity after soil amendment with glucose and nutrients. For B2L and both FACE systems, up to 58% higher μ were observed under elevated vs. ambient CO2, depending on site, plant species and N fertilization. The μ-values increased linearly with atmospheric CO2 concentration at all three sites. The effect of elevated CO2 on rhizosphere microorganisms was plant dependent and increased for: Brassica napus=Triticum aestivummicrobial growth rates directly (N limitation) and indirectly (changing the quantity of fine roots). So, 50% decrease in N fertilization caused the overall increase or decrease of microbial growth rates depending on plant species. The μ-value increase was lower for microorganisms growing on yeast extract then for those growing on glucose, i.e. the effect of elevated CO2 was smoothed on rich vs. simple substrate. So, the r/K strategies ratio can be better revealed by studying growth on simple (glucose) than on rich substrate mixtures (yeast extract). After adding glucose, enzyme activities under elevated CO2 were

  15. Teaching the Microbial Growth Curve Concept Using Microalgal Cultures and Flow Cytometry

    ERIC Educational Resources Information Center

    Forget, Nathalie; Belzile, Claude; Rioux, Pierre; Nozais, Christian

    2010-01-01

    The microbial growth curve is widely studied within microbiology classes and bacteria are usually the microbial model used. Here, we describe a novel laboratory protocol involving flow cytometry to assess the growth dynamics of the unicellular microalgae "Isochrysis galbana." The algal model represents an appropriate alternative to bacteria…

  16. Inhibition of microbial growth on air cathodes of single chamber microbial fuel cells by incorporating enrofloxacin into the catalyst layer.

    PubMed

    Liu, Weifeng; Cheng, Shaoan; Sun, Dan; Huang, Haobin; Chen, Jie; Cen, Kefa

    2015-10-15

    The inevitable growth of aerobic bacteria on the surface of air cathodes is an important factor reducing the performance stability of air cathode single-chamber membrane-free microbial fuel cells (MFCs). Thus searching for effective methods to inhibit the cathodic microbial growth is critical for the practical application of MFCs. In this study, enrofloxacin (ENR), a broad spectrum fluoroquinolone antibiotic, was incorporated into the catalyst layer of activated carbon air cathodes (ACACs) to inhibit the cathodic microbial growth. The biomass content on ACACs was substantially reduced by 60.2% with ENR treatment after 91 days of MFCs operation. As a result of the inhibited microbial growth, the oxygen reduction catalytic performance of the ENR treated ACACs was much stable compared to the fast performance decline of the untreated control. Consequently, a quite stable electricity production was obtained for the MFCs with the ENR treated ACACs, in contrast with a 22.5% decrease in maximum power density of the MFCs with the untreated cathode. ENR treatment of ACACs showed minimal effects on the anode performance. These results indicate that incorporating antibiotics into ACACs should be a simple and effective strategy to inhibit the microbial growth and improve the long-term stability of the performance of air cathode and the electricity production of MFCs.

  17. EFFECT OF TEMPERATURE ON THE C ISOTOPIC VALUE OF MICROBIAL LIPIDS APPLIED TO DETERMINE C USAGE IN MICROBIAL COMMUNITIES

    EPA Science Inventory

    The combination of compound specific stable isotopic analysis with phospholipid fatty acid (PLFAS) analysis is useful in determining the source of organic carbon used by groups of a microbial community. Determination of the effect of certain environmental parameters is important ...

  18. The role of microbial signals in plant growth and development.

    PubMed

    Ortíz-Castro, Randy; Contreras-Cornejo, Hexon Angel; Macías-Rodríguez, Lourdes; López-Bucio, José

    2009-08-01

    Plant growth and development involves a tight coordination of the spatial and temporal organization of cell division, cell expansion and cell differentiation. Orchestration of these events requires the exchange of signaling molecules between the root and shoot, which can be affected by both biotic and abiotic factors. The interactions that occur between plants and their associated microorganisms have long been of interest, as knowledge of these processes could lead to the development of novel agricultural applications. Plants produce a wide range of organic compounds including sugars, organic acids and vitamins, which can be used as nutrients or signals by microbial populations. On the other hand, microorganisms release phytohormones, small molecules or volatile compounds, which may act directly or indirectly to activate plant immunity or regulate plant growth and morphogenesis. In this review, we focus on recent developments in the identification of signals from free-living bacteria and fungi that interact with plants in a beneficial way. Evidence has accumulated indicating that classic plant signals such as auxins and cytokinins can be produced by microorganisms to efficiently colonize the root and modulate root system architecture. Other classes of signals, including N-acyl-L-homoserine lactones, which are used by bacteria for cell-to-cell communication, can be perceived by plants to modulate gene expression, metabolism and growth. Finally, we discuss the role played by volatile organic compounds released by certain plant growth-promoting rhizobacteria in plant immunity and developmental processes. The picture that emerges is one in which plants and microbes communicate themselves through transkingdom signaling systems involving classic and novel signals.

  19. The role of microbial signals in plant growth and development

    PubMed Central

    Ortíz-Castro, Randy; Contreras-Cornejo, Hexon Angel; Macías-Rodríguez, Lourdes

    2009-01-01

    Plant growth and development involves a tight coordination of the spatial and temporal organization of cell division, cell expansion and cell differentiation. Orchestration of these events requires the exchange of signaling molecules between the root and shoot, which can be affected by both biotic and abiotic factors. The interactions that occur between plants and their associated microorganisms have long been of interest, as knowledge of these processes could lead to the development of novel agricultural applications. Plants produce a wide range of organic compounds including sugars, organic acids and vitamins, which can be used as nutrients or signals by microbial populations. On the other hand, microorganisms release phytohormones, small molecules or volatile compounds, which may act directly or indirectly to activate plant immunity or regulate plant growth and morphogenesis. In this review, we focus on recent developments in the identification of signals from free-living bacteria and fungi that interact with plants in a beneficial way. Evidence has accumulated indicating that classic plant signals such as auxins and cytokinins can be produced by microorganisms to efficiently colonize the root and modulate root system architecture. Other classes of signals, including N-acyl-L-homoserine lactones, which are used by bacteria for cell-to-cell communication, can be perceived by plants to modulate gene expression, metabolism and growth. Finally, we discuss the role played by volatile organic compounds released by certain plant growth-promoting rhizobacteria in plant immunity and developmental processes. The picture that emerges is one in which plants and microbes communicate themselves through transkingdom signaling systems involving classic and novel signals. PMID:19820333

  20. Impact of microbial growth on water flow and solute transport in unsaturated porous media

    SciTech Connect

    Yarwood, R. R.; Rockhold, M. L.; Niemet, M. R.; Selker, John S.; Bottomley, Peter J.

    2006-10-05

    A novel analytical method was developed that permitted real-time, noninvasive measurements of microbial growth and associated changes in hydrodynamic properties in porous media under unsaturated flowing conditions. Salicylate-induced, lux gene-based bioluminescence was used to quantify the temporal and spatial development of colonization over a seven day time course. Water contents were determined daily by measuring light transmission through the system. Hydraulic flow paths were determined daily by pulsing a bromophenol blue dye solution through the colonized region of the sand. Bacterial growth and accumulation had a significant impact on the hydraulic properties of the porous media. Microbial colonization caused localized drying within the colonized zone, with decreases in saturation approaching 50% of antecedent values, and a 25% lowering of the capillary fringe height. Flow was retarded within the colonized zone and diverted around it. The apparent solute velocity through the colonized region was reduced from 0.41 cm min 1 (R2 = 0.99) to 0.25 cm min 1 (R2 = 0.99) by the sixth day of the experiment, associated with maximum population densities that would occupy about 7% of the available pore space within the colonized region. Changes in the extent of colonization occurred over the course of the experiment, including upward migration against flow. The distribution of cells was not determined by water flow alone, but rather by a dynamic interaction between water flow and microbial growth. This experimental system provides rich data sets for the testing of conceptualizations expressed through numerical modeling.

  1. Prediction of microbial growth rate versus biomass yield by a metabolic network with kinetic parameters.

    PubMed

    Adadi, Roi; Volkmer, Benjamin; Milo, Ron; Heinemann, Matthias; Shlomi, Tomer

    2012-01-01

    Identifying the factors that determine microbial growth rate under various environmental and genetic conditions is a major challenge of systems biology. While current genome-scale metabolic modeling approaches enable us to successfully predict a variety of metabolic phenotypes, including maximal biomass yield, the prediction of actual growth rate is a long standing goal. This gap stems from strictly relying on data regarding reaction stoichiometry and directionality, without accounting for enzyme kinetic considerations. Here we present a novel metabolic network-based approach, MetabOlic Modeling with ENzyme kineTics (MOMENT), which predicts metabolic flux rate and growth rate by utilizing prior data on enzyme turnover rates and enzyme molecular weights, without requiring measurements of nutrient uptake rates. The method is based on an identified design principle of metabolism in which enzymes catalyzing high flux reactions across different media tend to be more efficient in terms of having higher turnover numbers. Extending upon previous attempts to utilize kinetic data in genome-scale metabolic modeling, our approach takes into account the requirement for specific enzyme concentrations for catalyzing predicted metabolic flux rates, considering isozymes, protein complexes, and multi-functional enzymes. MOMENT is shown to significantly improve the prediction accuracy of various metabolic phenotypes in E. coli, including intracellular flux rates and changes in gene expression levels under different growth rates. Most importantly, MOMENT is shown to predict growth rates of E. coli under a diverse set of media that are correlated with experimental measurements, markedly improving upon existing state-of-the art stoichiometric modeling approaches. These results support the view that a physiological bound on cellular enzyme concentrations is a key factor that determines microbial growth rate. PMID:22792053

  2. Prediction of microbial growth rate versus biomass yield by a metabolic network with kinetic parameters.

    PubMed

    Adadi, Roi; Volkmer, Benjamin; Milo, Ron; Heinemann, Matthias; Shlomi, Tomer

    2012-01-01

    Identifying the factors that determine microbial growth rate under various environmental and genetic conditions is a major challenge of systems biology. While current genome-scale metabolic modeling approaches enable us to successfully predict a variety of metabolic phenotypes, including maximal biomass yield, the prediction of actual growth rate is a long standing goal. This gap stems from strictly relying on data regarding reaction stoichiometry and directionality, without accounting for enzyme kinetic considerations. Here we present a novel metabolic network-based approach, MetabOlic Modeling with ENzyme kineTics (MOMENT), which predicts metabolic flux rate and growth rate by utilizing prior data on enzyme turnover rates and enzyme molecular weights, without requiring measurements of nutrient uptake rates. The method is based on an identified design principle of metabolism in which enzymes catalyzing high flux reactions across different media tend to be more efficient in terms of having higher turnover numbers. Extending upon previous attempts to utilize kinetic data in genome-scale metabolic modeling, our approach takes into account the requirement for specific enzyme concentrations for catalyzing predicted metabolic flux rates, considering isozymes, protein complexes, and multi-functional enzymes. MOMENT is shown to significantly improve the prediction accuracy of various metabolic phenotypes in E. coli, including intracellular flux rates and changes in gene expression levels under different growth rates. Most importantly, MOMENT is shown to predict growth rates of E. coli under a diverse set of media that are correlated with experimental measurements, markedly improving upon existing state-of-the art stoichiometric modeling approaches. These results support the view that a physiological bound on cellular enzyme concentrations is a key factor that determines microbial growth rate.

  3. Factors Limiting Microbial Growth and Activity at a Proposed High-Level Nuclear Repository, Yucca Mountain, Nevada

    PubMed Central

    Kieft, T. L.; Kovacik, W. P.; Ringelberg, D. B.; White, D. C.; Haldeman, D. L.; Amy, P. S.; Hersman, L. E.

    1997-01-01

    As part of the characterization of Yucca Mountain, Nev., as a potential repository for high-level nuclear waste, volcanic tuff was analyzed for microbial abundance and activity. Tuff was collected aseptically from nine sites along a tunnel in Yucca Mountain. Microbial abundance was generally low: direct microscopic cell counts were near detection limits at all sites (3.2 x 10(sup4) to 2.0 x 10(sup5) cells g(sup-1) [dry weight]); plate counts of aerobic heterotrophs ranged from 1.0 x 10(sup1) to 3.2 x 10(sup3) CFU g(sup-1) (dry weight). Phospholipid fatty acid concentrations (0.1 to 3.7 pmol g(sup-1)) also indicated low microbial biomasses; diglyceride fatty acid concentrations, indicative of dead cells, were in a similar range (0.2 to 2.3 pmol g(sup-1)). Potential microbial activity was quantified as (sup14)CO(inf2) production in microcosms containing radiolabeled substrates (glucose, acetate, and glutamic acid); amendments with water and nutrient solutions (N and P) were used to test factors potentially limiting this activity. Similarly, the potential for microbial growth and the factors limiting growth were determined by performing plate counts before and after incubating volcanic tuff samples for 24 h under various conditions: ambient moisture, water-amended, and amended with various nutrient solutions (N, P, and organic C). A high potential for microbial activity was demonstrated by high rates of substrate mineralization (as much as 70% of added organic C in 3 weeks). Water was the major limiting factor to growth and microbial activity, while amendments with N and P resulted in little further stimulation. Organic C amendments stimulated growth more than water alone. PMID:16535670

  4. Microbial growth and carbon use efficiency in the rhizosphere and root-free soil.

    PubMed

    Blagodatskaya, Evgenia; Blagodatsky, Sergey; Anderson, Traute-Heidi; Kuzyakov, Yakov

    2014-01-01

    Plant-microbial interactions alter C and N balance in the rhizosphere and affect the microbial carbon use efficiency (CUE)-the fundamental characteristic of microbial metabolism. Estimation of CUE in microbial hotspots with high dynamics of activity and changes of microbial physiological state from dormancy to activity is a challenge in soil microbiology. We analyzed respiratory activity, microbial DNA content and CUE by manipulation the C and nutrients availability in the soil under Beta vulgaris. All measurements were done in root-free and rhizosphere soil under steady-state conditions and during microbial growth induced by addition of glucose. Microorganisms in the rhizosphere and root-free soil differed in their CUE dynamics due to varying time delays between respiration burst and DNA increase. Constant CUE in an exponentially-growing microbial community in rhizosphere demonstrated the balanced growth. In contrast, the CUE in the root-free soil increased more than three times at the end of exponential growth and was 1.5 times higher than in the rhizosphere. Plants alter the dynamics of microbial CUE by balancing the catabolic and anabolic processes, which were decoupled in the root-free soil. The effects of N and C availability on CUE in rhizosphere and root-free soil are discussed. PMID:24722409

  5. Inhibition of microbial growth, study of solution stability, growth and characterization of potassium fluoride mixed ?-arginine phosphate single crystals

    NASA Astrophysics Data System (ADS)

    Haja Hameed, A. S.; Ravi, G.; Ramasamy, P.

    2001-07-01

    In order to alleviate the major problem of microbial growth and colouration in L-arginine phosphate (LAP), the use of potassium fluoride (KF), a new additive having higher dipole moment, has been proposed. The stabilities of the pure and KF mixed LAP solution at different temperatures have been determined. Pure and KF mixed LAP crystals were grown by the temperature lowering technique. The presence of potassium in the crystal was identified by inductively coupled plasma analysis (ICP). The lattice parameters for the grown crystals were determined from X-ray powder diffraction. The molecular vibration and thermal behaviour of KF mixed LAP were found from Fourier transform infrared (FTIR) spectroscopy and thermal analysis (DTA &TGA) respectively.

  6. Soil degradation and amendment effects on soil properties, microbial communities, and plant growth

    NASA Astrophysics Data System (ADS)

    Gebhardt, M.; Fehmi, J. S.; Rasmussen, C.; Gallery, R. E.

    2015-12-01

    Human activities that disrupt soil properties are fundamentally changing ecosystems. Soil degradation, caused by anthropogenic disturbance can decrease microbial abundance and activity, leading to changes in nutrient availability, soil organic matter, and plant establishment. The addition of amendments to disturbed soils have the potential ameliorate these negative consequences. We studied the effects of soil degradation, via an autoclave heat shock method, and the addition of amendments (biochar and woodchips) on microbial activity, soil carbon and nitrogen availability, microbial biomass carbon and nitrogen content, and plant growth of ten plant species native to the semi-arid southwestern US. Relative to non-degraded soils, microbial activity, measured via extracellular enzyme assays, was significantly lower for all seven substrates assayed. These soils also had significantly lower amounts of carbon assimilated into microbial biomass but no change in microbial biomass nitrogen. Soil degradation had no effect on plant biomass. Amendments caused changes in microbial activity: biochar-amended soils had significant increases in potential activity with five of the seven substrates measured; woodchip amended soils had significant increases with two. Soil carbon increased with both amendments but this was not reflected in a significant change in microbial biomass carbon. Biochar-amended soils had increases in soil nitrogen availability but neither amendment caused changes in microbial biomass nitrogen. Biochar amendments had no significant effect on above- or belowground plant biomass while woodchips significantly decreased aboveground plant biomass. Results show that soil degradation decreases microbial activity and changes nutrient dynamics, but these are not reflected in changes in plant growth. Amendments provide nutrient sources and change soil pore space, which cause microbial activities to fluctuate and may, in the case of woodchips, increase plant drought

  7. Carbon nanotubes as plant growth regulators: effects on tomato growth, reproductive system, and soil microbial community.

    PubMed

    Khodakovskaya, Mariya V; Kim, Bong-Soo; Kim, Jong Nam; Alimohammadi, Mohammad; Dervishi, Enkeleda; Mustafa, Thikra; Cernigla, Carl E

    2013-01-14

    Multi-walled carbon nanotubes (CNTs) can affect plant phenotype and the composition of soil microbiota. Tomato plants grown in soil supplemented with CNTs produce two times more flowers and fruit compared to plants grown in control soil. The effect of carbon nanotubes on microbial community of CNT-treated soil is determined by denaturing gradient gel electrophoresis and pyrosequencing analysis. Phylogenetic analysis indicates that Proteobacteria and Bacteroidetes are the most dominant groups in the microbial community of soil. The relative abundances of Bacteroidetes and Firmicutes are found to increase, whereas Proteobacteria and Verrucomicorbia decrease with increasing concentration of CNTs. The results of comparing diversity indices and species level phylotypes (OTUs) between samples showed that there is not a significant affect on bacterial diversity.

  8. Biochar and microbial signaling: production conditions determine effects on microbial communication

    PubMed Central

    Masiello, Caroline A.; Chen, Ye; Gao, Xiaodong; Liu, Shirley; Cheng, Hsiao-Ying; Bennett, Matthew R.; Rudgers, Jennifer A.; Wagner, Daniel S.; Zygourakis, Kyriacos; Silberg, Jonathan J.

    2013-01-01

    Charcoal has a long soil residence time, which has resulted in its production and use as a carbon sequestration technique (biochar). A range of biological effects can be triggered by soil biochar that can positively and negatively influence carbon storage, such as changing the decomposition rate of organic matter and altering plant biomass production. Sorption of cellular signals has been hypothesized to underlie some of these effects, but it remains unknown whether the binding of biochemical signals occurs, and if so, on time scales relevant to microbial growth and communication. We examined biochar sorption of N-3-oxo-dodecanoyl-L-homoserine lactone, an acyl-homoserine lactone (AHL) intercellular signaling molecule used by many gram-negative soil microbes to regulate gene expression. We show that wood biochars disrupt communication within a growing multicellular system that is made up of sender cells that synthesize AHL and receiver cells that express green fluorescent protein in response to an AHL signal. However, biochar inhibition of AHL-mediated cell-cell communication varied, with the biochar prepared at 700°C (surface area of 301 m2/g) inhibiting cellular communication 10-fold more than an equivalent mass of biochar prepared at 300°C (surface area of 3 m2/g). These findings provide the first direct evidence that biochars elicit a range of effects on gene expression dependent on intercellular signaling, implicating the method of biochar preparation as a parameter that could be tuned to regulate microbial-dependent soil processes, like nitrogen fixation and pest attack of root crops. PMID:24066613

  9. Maximising electricity production by controlling the biofilm specific growth rate in microbial fuel cells.

    PubMed

    Ledezma, Pablo; Greenman, John; Ieropoulos, Ioannis

    2012-08-01

    The aim of this work is to study the relationship between growth rate and electricity production in perfusion-electrode microbial fuel cells (MFCs), across a wide range of flow rates by co-measurement of electrical output and changes in population numbers by viable counts and optical density. The experiments hereby presented demonstrate, for the first time to the authors' knowledge, that the anodic biofilm specific growth rate can be determined and controlled in common with other loose matrix perfusion systems. Feeding with nutrient-limiting conditions at a critical flow rate (50.8 mL h(-1)) resulted in the first experimental determination of maximum specific growth rate μ(max) (19.8 day(-1)) for Shewanella spp. MFC biofilms, which is considerably higher than those predicted or assumed via mathematical modelling. It is also shown that, under carbon-energy limiting conditions there is a strong direct relationship between growth rate and electrical power output, with μ(max) coinciding with maximum electrical power production.

  10. Growth Kinetics of Suspended Microbial Cells: From Single-Substrate-Controlled Growth to Mixed-Substrate Kinetics

    PubMed Central

    Kovárová-Kovar, Karin; Egli, Thomas

    1998-01-01

    Growth kinetics, i.e., the relationship between specific growth rate and the concentration of a substrate, is one of the basic tools in microbiology. However, despite more than half a century of research, many fundamental questions about the validity and application of growth kinetics as observed in the laboratory to environmental growth conditions are still unanswered. For pure cultures growing with single substrates, enormous inconsistencies exist in the growth kinetic data reported. The low quality of experimental data has so far hampered the comparison and validation of the different growth models proposed, and only recently have data collected from nutrient-controlled chemostat cultures allowed us to compare different kinetic models on a statistical basis. The problems are mainly due to (i) the analytical difficulty in measuring substrates at growth-controlling concentrations and (ii) the fact that during a kinetic experiment, particularly in batch systems, microorganisms alter their kinetic properties because of adaptation to the changing environment. For example, for Escherichia coli growing with glucose, a physiological long-term adaptation results in a change in KS for glucose from some 5 mg liter−1 to ca. 30 μg liter−1. The data suggest that a dilemma exists, namely, that either “intrinsic” KS (under substrate-controlled conditions in chemostat culture) or μmax (under substrate-excess conditions in batch culture) can be measured but both cannot be determined at the same time. The above-described conventional growth kinetics derived from single-substrate-controlled laboratory experiments have invariably been used for describing both growth and substrate utilization in ecosystems. However, in nature, microbial cells are exposed to a wide spectrum of potential substrates, many of which they utilize simultaneously (in particular carbon sources). The kinetic data available to date for growth of pure cultures in carbon-controlled continuous culture

  11. An investigation of the sensitivity of low-field nuclear magnetic resonance to microbial growth and activity

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Keating, K.

    2014-12-01

    Microbes and microbial processes play a significant role in shaping subsurface environments and are involved in applications ranging from microbially enhanced oil recovery to soil and groundwater contaminant remediation. Stimulated microbial growth in such applications could cause wide variety of changes of physical/chemical properties in the subsurface; however, due to the complexity of subsurface systems,it is difficult to monitor the growth of microbes and microbial activity in porous media. The focus of this research is to determine if low-field nuclear magnetic resonance (NMR), a method used in well logging to characterize fluids in hydrocarbon reservoirs or water in aquifers, can be used to directly detect the presence and the growth of microbes in geologic media. In this laboratory study, low-field NMR (2 MHz) relaxation measurements were collected on microbial suspensions with measured densities (i.e. biomasses), microbial pellets (live and dead), and inoculated silica. We focus on the direct contribution of microbes to the NMR signals in the absence of biomineralization. Shewanella oneidensis (MR-1), a facultative metal reducer known to play an important role in subsurface environments, were used as a model organism and were inoculated under aerobic condition. Data were collected using a CPMG pulse sequence, which was to determine the T2-distribution, and using a gradient spin-echo (PGSE) plus CPMG pulse sequence, which was used to encode diffusion properties and determine the effective diffusion-spin-spin relaxation correlation (D-T2) plot. Our data show no obvious change in the T2-distribution as S. oneidensis density varied in suspension, but show a clear distinction in the T2-distribution and D-T2 plots between live and dead cell pellets. A decrease in the T2-distribution is observed in the inoculated sand column. These results will provide a basis for understanding the effect of microbes within geologic media on low-field NMR measurements. This

  12. Microbial Biofilm Growth on Irradiated, Spent Nuclear Fuel Cladding

    SciTech Connect

    S.M. Frank

    2009-02-01

    A fundamental criticism regarding the potential for microbial influenced corrosion in spent nuclear fuel cladding or storage containers concerns whether the required microorganisms can, in fact, survive radiation fields inherent in these materials. This study was performed to unequivocally answer this critique by addressing the potential for biofilm formation, the precursor to microbial-influenced corrosion, in radiation fields representative of spent nuclear fuel storage environments. This study involved the formation of a microbial biofilm on irradiated spent nuclear fuel cladding within a hot cell environment. This was accomplished by introducing 22 species of bacteria, in nutrient-rich media, to test vessels containing irradiated cladding sections and that was then surrounded by radioactive source material. The overall dose rate exceeded 2 Gy/h gamma/beta radiation with the total dose received by some of the bacteria reaching 5 × 103 Gy. This study provides evidence for the formation of biofilms on spent-fuel materials, and the implication of microbial influenced corrosion in the storage and permanent deposition of spent nuclear fuel in repository environments.

  13. Comparison of Primary Models to Predict Microbial Growth by the Plate Count and Absorbance Methods.

    PubMed

    Pla, María-Leonor; Oltra, Sandra; Esteban, María-Dolores; Andreu, Santiago; Palop, Alfredo

    2015-01-01

    The selection of a primary model to describe microbial growth in predictive food microbiology often appears to be subjective. The objective of this research was to check the performance of different mathematical models in predicting growth parameters, both by absorbance and plate count methods. For this purpose, growth curves of three different microorganisms (Bacillus cereus, Listeria monocytogenes, and Escherichia coli) grown under the same conditions, but with different initial concentrations each, were analysed. When measuring the microbial growth of each microorganism by optical density, almost all models provided quite high goodness of fit (r(2) > 0.93) for all growth curves. The growth rate remained approximately constant for all growth curves of each microorganism, when considering one growth model, but differences were found among models. Three-phase linear model provided the lowest variation for growth rate values for all three microorganisms. Baranyi model gave a variation marginally higher, despite a much better overall fitting. When measuring the microbial growth by plate count, similar results were obtained. These results provide insight into predictive microbiology and will help food microbiologists and researchers to choose the proper primary growth predictive model. PMID:26539483

  14. Comparison of Primary Models to Predict Microbial Growth by the Plate Count and Absorbance Methods

    PubMed Central

    Pla, María-Leonor; Oltra, Sandra; Esteban, María-Dolores; Andreu, Santiago; Palop, Alfredo

    2015-01-01

    The selection of a primary model to describe microbial growth in predictive food microbiology often appears to be subjective. The objective of this research was to check the performance of different mathematical models in predicting growth parameters, both by absorbance and plate count methods. For this purpose, growth curves of three different microorganisms (Bacillus cereus, Listeria monocytogenes, and Escherichia coli) grown under the same conditions, but with different initial concentrations each, were analysed. When measuring the microbial growth of each microorganism by optical density, almost all models provided quite high goodness of fit (r2 > 0.93) for all growth curves. The growth rate remained approximately constant for all growth curves of each microorganism, when considering one growth model, but differences were found among models. Three-phase linear model provided the lowest variation for growth rate values for all three microorganisms. Baranyi model gave a variation marginally higher, despite a much better overall fitting. When measuring the microbial growth by plate count, similar results were obtained. These results provide insight into predictive microbiology and will help food microbiologists and researchers to choose the proper primary growth predictive model. PMID:26539483

  15. Comparison of Primary Models to Predict Microbial Growth by the Plate Count and Absorbance Methods.

    PubMed

    Pla, María-Leonor; Oltra, Sandra; Esteban, María-Dolores; Andreu, Santiago; Palop, Alfredo

    2015-01-01

    The selection of a primary model to describe microbial growth in predictive food microbiology often appears to be subjective. The objective of this research was to check the performance of different mathematical models in predicting growth parameters, both by absorbance and plate count methods. For this purpose, growth curves of three different microorganisms (Bacillus cereus, Listeria monocytogenes, and Escherichia coli) grown under the same conditions, but with different initial concentrations each, were analysed. When measuring the microbial growth of each microorganism by optical density, almost all models provided quite high goodness of fit (r(2) > 0.93) for all growth curves. The growth rate remained approximately constant for all growth curves of each microorganism, when considering one growth model, but differences were found among models. Three-phase linear model provided the lowest variation for growth rate values for all three microorganisms. Baranyi model gave a variation marginally higher, despite a much better overall fitting. When measuring the microbial growth by plate count, similar results were obtained. These results provide insight into predictive microbiology and will help food microbiologists and researchers to choose the proper primary growth predictive model.

  16. Sensitive determination of L-lysine with a new amperometric microbial biosensor based on Saccharomyces cerevisiae yeast cells.

    PubMed

    Akyilmaz, Erol; Erdoğan, Ali; Oztürk, Ramazan; Yaşa, Ihsan

    2007-01-15

    A new amperometric microbial biosensor based on Saccharomyces cerevisiae NRRL-12632 cells, which had been induced for lysine oxidase enzyme and immobilized in gelatin by a cross-linking agent was developed for the sensitive determination of L-lysine amino acid. To construct the microbial biosensor S. cerevisiae cells were activated and cultured in a suitable culture medium. By using gelatine (8.43 mg cm(-2)) and glutaraldehyde (0.25%), cells obtained in the logarithmic phase of the growth curve at the end of a 14 h period were immobilized and fixed on a pretreated oxygen sensitive Teflon membrane of a dissolved oxygen probe. The assay procedure of the microbial biosensor is based on the determination of the differences of the respiration activity of the cells on the oxygenmeter in the absence and the presence of L-lysine. According to the end point measurement technique used in the experiments it was determined that the microbial biosensor response depended linearly on L-lysine concentrations between 1.0 and 10.0 microM with a 1 min response time. In optimization studies of the microbial biosensor, the most suitable microorganism quantities were found to be 0.97x10(5)CFU cm(-2). In addition phosphate buffer (pH 7.5; 50 mM) and 30 degrees C were obtained as the optimum working conditions. In characterization studies of the microbial biosensor some parameters such as substrate specificity, interference effects of some substances on the microbial biosensor responses, reproducibility of the biosensor and operational and storage stability were investigated.

  17. Growth performance and intestinal microbial populations of growing pigs fed diets containing sucrose thermal oligosaccharide caramel.

    PubMed

    Orban, J I; Patterson, J A; Adeola, O; Sutton, A L; Richards, G N

    1997-01-01

    Four experiments were conducted to determine growth performance and changes in intestinal microbial populations of growing pigs fed diets containing sucrose thermal oligosaccharide caramel (STOC). Ninety-six barrows and 96 gilts were group-fed experimental nursery diets for 32 d after weaning in both Exp. 1 and 2. For each experiment, pigs were divided into four groups of 48 pigs and were fed either control, antibiotic (Apramycin sulfate, 34 mg/kg), 1% STOC, or 2% STOC diets for 32 d after weaning. Each diet was replicated six times with eight pigs per replication. Pigs were either orally gavaged (Exp 1) with water of STOC (2 g per pig) or pigs were creep-fed (Exp 2) either a control diet or a 2% STOC diet for 5 d before weaning (33 d). At the end of Exp 1 and 2, cecal material was collected for enumeration of total aerobes, total anaerobes, coliforms, lactobacilli, and bifidobacteria. Gilts (96 per experiment) used in Exp. 3 and 4 were weaned at 26 d and fed experimental nursery diets for 32 d. They were fed either a control or 1% STOC diet and were otherwise treated as previously described. There were no significant effects of STOC or antibiotic on ADG, ADFI, feed efficiency, or cecal microbial populations in pigs in this study. Feeding diets containing either antibiotic of STOC did not improve animal performance or change intestinal bacterial populations in the present study. PMID:9027562

  18. Microbial Patterns Signaling via Toll-Like Receptors 2 and 5 Contribute to Epithelial Repair, Growth and Survival

    PubMed Central

    Shaykhiev, Renat; Behr, Jürgen; Bals, Robert

    2008-01-01

    Epithelial cells (ECs) continuously interact with microorganisms and detect their presence via different pattern-recognition receptors (PRRs) including Toll-like receptors (TLRs). Ligation of epithelial TLRs by pathogens is usually associated with the induction of pro-inflammatory mediators and antimicrobial factors. In this study, using human airway ECs as a model, we found that detection of microbial patterns via epithelial TLRs directly regulates tissue homeostasis. Staphylococcus aureus (S. aureus) and microbial patterns signaling via TLR2 and TLR5 induce a set of non-immune epithelial responses including cell migration, wound repair, proliferation, and survival of primary and cancerous ECs. Using small interfering RNA (siRNA) gene targeting, receptor-tyrosine kinase microarray and inhibition studies, we determined that TLR and the epidermal growth factor receptor (EGFR) mediate the stimulating effect of microbial patterns on epithelial repair. Microbial patterns signaling via Toll-like receptors 2 and 5 contribute to epithelial repair, growth and survival. This effect is independent of hematopoietic and other cells as well as inflammatory cytokines suggesting that epithelia are able to regulate their integrity in an autonomous non-inflammatory manner by sensing microbes directly via TLRs. PMID:18167552

  19. Prediction of microbial growth in mixed culture with a competition model.

    PubMed

    Fujikawa, Hiroshi; Sakha, Mohammad Z

    2014-01-01

    Prediction of microbial growth in mixed culture was studied with a competition model that we had developed recently. The model, which is composed of the new logistic model and the Lotka-Volterra model, is shown to successfully describe the microbial growth of two species in mixed culture using Staphylococcus aureus, Escherichia coli, and Salmonella. With the parameter values of the model obtained from the experimental data on monoculture and mixed culture with two species, it then succeeded in predicting the simultaneous growth of the three species in mixed culture inoculated with various cell concentrations. To our knowledge, it is the first time for a prediction model for multiple (three) microbial species to be reported. The model, which is not built on any premise for specific microorganisms, may become a basic competition model for microorganisms in food and food materials. PMID:24975413

  20. Modeling Microbial Growth Dynamics, Patterns, and Coexistence on Partially Saturated Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Long, T.; Or, D.

    2005-12-01

    A new modeling tool was developed to study the impact of variations in matric potential on aquatic pathways and substrate diffusion, and on microbial growth and movement on unsaturated rough surfaces. The modeling domain is composed of prescribed distributions of conical pits (sites) connected by prismatic channels (bonds) representing rough surfaces of soils or rocks. The well-defined geometry facilitates exact description of aqueous phase distribution within the roughness for a given matric potential. Microbial growth within the resulting highly variable diffusion network architectures (vary with matric potential) and interactions with nutrient diffusion patterns are simulated by coupling Reaction-Diffusion Method (RDM) and the Active Walker Method (AWM). Simulation results show direct impact of wetness conditions (matric potential values) on microbial growth rates and expansion patters for the same surface roughness. In addition to modification of mean diffusion rates for drier or wetter conditions, the network connectivity may induce significant changes in spatial patters of microbial growth. Impact of these changes on coexistence of two competing microbial species will be discussed.

  1. Growth and element flux at fine taxonomic resolution in natural microbial communities

    NASA Astrophysics Data System (ADS)

    Hungate, Bruce; Mau, Rebecca; Schwartz, Egbert; Caporaso, J. Gregory; Dijkstra, Paul; van Gestel, Natasja; Koch, Benjamin J.; Liu, Cindy M.; McHugh, Theresa; Marks, Jane C.; Morrissey, Ember; Price, Lance B.

    2015-04-01

    Microorganisms are the engines of global biogeochemical cycles, driving half of all photosynthesis and nearly all decomposition. Yet, quantifying the rates at which uncultured microbial taxa grow and transform elements in intact and highly diverse natural communities in the environment remains among the most pressing challenges in microbial ecology today. Here, we show how shifts in the density of DNA caused by stable isotope incorporation can be used to estimate the growth rates of individual bacterial taxa in intact soil communities. We found that the distribution of growth rates followed the familiar lognormal distribution observed for the abundances, biomasses, and traits of many organisms. Growth rates of most bacterial taxa increased in response to glucose amendment, though the increase in growth observed for many taxa was larger than could be explained by direct utilization of the added glucose for growth, illustrating that glucose addition indirectly stimulated the utilization of other substrates. Variation in growth rates and phylogenetic distances were quantitatively related, connecting evolutionary history and biogeochemical function in intact soil microbial communities. Our approach has the potential to identify biogeochemically significant taxa in the microbial community and quantify their contributions to element transformations and ecosystem processes.

  2. Bioenergetic Limitations on Slow Microbial Growth in the Subsurface: What is the Burden of Maintenance on the Overall Energy Budget?

    NASA Astrophysics Data System (ADS)

    Smeaton, C. M.; Bajracharya, B. M.; Ridenour, C.; Van Cappellen, P.

    2014-12-01

    In low energy environments such as the subsurface, the minimum energy required to maintain cellular integrity and function (maintenance energy) may represent a significant fraction of the total energy available to microbial communities. However, traditional kinetic and thermodynamic models incorporating key microbial processes are often developed using data collected in nutrient rich growth media. In this study, slow microbial growth in the subsurface was simulated using a flow through bioreactor system in experiments designed to determine the maintenance energy requirement of the model subsurface bacterium Shewanella oneidensis. An existing bioreactor system (Applikon EZ-control®, 2.4 L) was modified to include a biomass retention filtration unit (retentostat) resulting in biomass accumulation over time. An artificial low-nutrient groundwater medium was optimized for slow S. oneidensis growth and was supplied and removed from the reactor at flow rates on the order of 1 mL min-1 with a dilution rate of 0.025 h-1. The retentostat was run under electron donor limited conditions with nitrate, a common groundwater contaminant, supplied at 0.025 mM h-1 and lactate supplied in excess at 0.125 mM h-1. Respiratory ammonification of nitrate by S. oneidensis and cell growth was monitored over time (40 days) and compared to parallel incubations in batch reactors. Initial rates of ammonification were similar in the bioreactor and batch reactors, however, optical density and ATP measurements showed slow yet increasing microbial growth over time (generation time = 17 days) in the retentostat. In contrast, cells in the batch reactors did not grow significantly and died within 2 weeks of inoculation. A maintenance energy demand was estimated (2.5 kJ C-mol biomass h-1) by fitting the biomass production rates to the van Verseveld equation. The low maintenance energy demand of S. oneidensis as compared to typical maintenance energies reported in the literature (>10 kJ C-mol biomass

  3. Thermodynamics of Microbial Growth Coupled to Metabolism of Glucose, Ethanol, Short-Chain Organic Acids, and Hydrogen ▿ †

    PubMed Central

    Roden, Eric E.; Jin, Qusheng

    2011-01-01

    A literature compilation demonstrated a linear relationship between microbial growth yield and the free energy of aerobic and anaerobic (respiratory and/or fermentative) metabolism of glucose, ethanol, formate, acetate, lactate, propionate, butyrate, and H2. This relationship provides a means to estimate growth yields for modeling microbial redox metabolism in soil and sedimentary environments. PMID:21216913

  4. Connection between stochastic and deterministic modelling of microbial growth.

    PubMed

    Kutalik, Zoltán; Razaz, Moe; Baranyi, József

    2005-01-21

    We present in this paper various links between individual and population cell growth. Deterministic models of the lag and subsequent growth of a bacterial population and their connection with stochastic models for the lag and subsequent generation times of individual cells are analysed. We derived the individual lag time distribution inherent in population growth models, which shows that the Baranyi model allows a wide range of shapes for individual lag time distribution. We demonstrate that individual cell lag time distributions cannot be retrieved from population growth data. We also present the results of our investigation on the effect of the mean and variance of the individual lag time and the initial cell number on the mean and variance of the population lag time. These relationships are analysed theoretically, and their consequence for predictive microbiology research is discussed.

  5. Evaluation of the microbial growth response to inorganic nanoparticles

    PubMed Central

    Williams, Darryl N; Ehrman, Sheryl H; Pulliam Holoman, Tracey R

    2006-01-01

    In order to enhance the utilization of inorganic nanoparticles in biological systems, it is important to develop a fundamental understanding of the influence they have on cellular health and function. Experiments were conducted to test silica, silica/iron oxide, and gold nanoparticles for their effects on the growth and activity of Escherichia coli (E. coli). Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to characterize the morphology and quantify size distribution of the nanoparticles, respectively. TEM was also used to verify the interactions between composite iron oxide nanoparticles and E. coli. The results from DLS indicated that the inorganic nanoparticles formed small aggregates in the growth media. Growth studies measured the influence of the nanoparticles on cell proliferation at various concentrations, showing that the growth of E. coli in media containing the nanoparticles indicated no overt signs of toxicity. PMID:16507102

  6. Soil C and N availability determine the priming effect: microbial N mining and stoichiometric decomposition theories

    NASA Astrophysics Data System (ADS)

    Chen, Ruirui; Senbayram, Mehmet; Blagodatsky, Sergey; Dittert, Klaus; Lin, Xiangui; Blagodatskaya, Evgenia; Kuzyakov, Yakov

    2014-05-01

    The increasing input of anthropogenically derived nitrogen (N) to ecosystems raises a crucial question: how does available N modify the decomposer community and thus affects the mineralization of soil organic matter (SOM). Moreover, N input modifies the priming effect (PE), that is, the effect of fresh organics on the microbial decomposition of SOM. We studied the interactive effects of C and N on SOM mineralization (by natural 13C labelling adding C4-sucrose or C4-maize straw to C3-soil) in relation to microbial growth kinetics and to the activities of five hydrolytic enzymes. This encompasses the groups of parameters governing two mechanisms of priming effects - microbial N mining and stoichiometric decomposition theories. In sole C treatments, positive PE was accompanied by a decrease in specific microbial growth rates, confirming a greater contribution of K-strategists to the decomposition of native SOM. Sucrose addition with N significantly accelerated mineralization of native SOM, whereas mineral N added with plant residues accelerated decomposition of plant residues. This supports the microbial mining theory in terms of N limitation. Sucrose addition with N was accompanied by accelerated microbial growth, increased activities of β-glucosidase and cellobiohydrolase, and decreased activities of xylanase and leucine amino peptidase. This indicated an increased contribution of r-strategists to the PE and to decomposition of cellulose but the decreased hemicellulolytic and proteolytic activities. Thus, the acceleration of the C cycle was primed by exogenous organic C and was controlled by N. This confirms the stoichiometric decomposition theory. Both K- and r-strategists were beneficial for priming effects, with an increasing contribution of K-selected species under N limitation. Thus, the priming phenomenon described in 'microbial N mining' theory can be ascribed to K-strategists. In contrast, 'stoichiometric decomposition' theory, that is, accelerated OM

  7. Soil C and N availability determine the priming effect: microbial N mining and stoichiometric decomposition theories.

    PubMed

    Chen, Ruirui; Senbayram, Mehmet; Blagodatsky, Sergey; Myachina, Olga; Dittert, Klaus; Lin, Xiangui; Blagodatskaya, Evgenia; Kuzyakov, Yakov

    2014-07-01

    The increasing input of anthropogenically derived nitrogen (N) to ecosystems raises a crucial question: how does available N modify the decomposer community and thus affects the mineralization of soil organic matter (SOM). Moreover, N input modifies the priming effect (PE), that is, the effect of fresh organics on the microbial decomposition of SOM. We studied the interactive effects of C and N on SOM mineralization (by natural (13) C labelling adding C4 -sucrose or C4 -maize straw to C3 -soil) in relation to microbial growth kinetics and to the activities of five hydrolytic enzymes. This encompasses the groups of parameters governing two mechanisms of priming effects - microbial N mining and stoichiometric decomposition theories. In sole C treatments, positive PE was accompanied by a decrease in specific microbial growth rates, confirming a greater contribution of K-strategists to the decomposition of native SOM. Sucrose addition with N significantly accelerated mineralization of native SOM, whereas mineral N added with plant residues accelerated decomposition of plant residues. This supports the microbial mining theory in terms of N limitation. Sucrose addition with N was accompanied by accelerated microbial growth, increased activities of β-glucosidase and cellobiohydrolase, and decreased activities of xylanase and leucine amino peptidase. This indicated an increased contribution of r-strategists to the PE and to decomposition of cellulose but the decreased hemicellulolytic and proteolytic activities. Thus, the acceleration of the C cycle was primed by exogenous organic C and was controlled by N. This confirms the stoichiometric decomposition theory. Both K- and r-strategists were beneficial for priming effects, with an increasing contribution of K-selected species under N limitation. Thus, the priming phenomenon described in 'microbial N mining' theory can be ascribed to K-strategists. In contrast, 'stoichiometric decomposition' theory, that is, accelerated OM

  8. Dynamical Allocation of Cellular Resources as an Optimal Control Problem: Novel Insights into Microbial Growth Strategies.

    PubMed

    Giordano, Nils; Mairet, Francis; Gouzé, Jean-Luc; Geiselmann, Johannes; de Jong, Hidde

    2016-03-01

    Microbial physiology exhibits growth laws that relate the macromolecular composition of the cell to the growth rate. Recent work has shown that these empirical regularities can be derived from coarse-grained models of resource allocation. While these studies focus on steady-state growth, such conditions are rarely found in natural habitats, where microorganisms are continually challenged by environmental fluctuations. The aim of this paper is to extend the study of microbial growth strategies to dynamical environments, using a self-replicator model. We formulate dynamical growth maximization as an optimal control problem that can be solved using Pontryagin's Maximum Principle. We compare this theoretical gold standard with different possible implementations of growth control in bacterial cells. We find that simple control strategies enabling growth-rate maximization at steady state are suboptimal for transitions from one growth regime to another, for example when shifting bacterial cells to a medium supporting a higher growth rate. A near-optimal control strategy in dynamical conditions is shown to require information on several, rather than a single physiological variable. Interestingly, this strategy has structural analogies with the regulation of ribosomal protein synthesis by ppGpp in the enterobacterium Escherichia coli. It involves sensing a mismatch between precursor and ribosome concentrations, as well as the adjustment of ribosome synthesis in a switch-like manner. Our results show how the capability of regulatory systems to integrate information about several physiological variables is critical for optimizing growth in a changing environment.

  9. Dynamical Allocation of Cellular Resources as an Optimal Control Problem: Novel Insights into Microbial Growth Strategies

    PubMed Central

    Giordano, Nils; Mairet, Francis; Gouzé, Jean-Luc

    2016-01-01

    Microbial physiology exhibits growth laws that relate the macromolecular composition of the cell to the growth rate. Recent work has shown that these empirical regularities can be derived from coarse-grained models of resource allocation. While these studies focus on steady-state growth, such conditions are rarely found in natural habitats, where microorganisms are continually challenged by environmental fluctuations. The aim of this paper is to extend the study of microbial growth strategies to dynamical environments, using a self-replicator model. We formulate dynamical growth maximization as an optimal control problem that can be solved using Pontryagin’s Maximum Principle. We compare this theoretical gold standard with different possible implementations of growth control in bacterial cells. We find that simple control strategies enabling growth-rate maximization at steady state are suboptimal for transitions from one growth regime to another, for example when shifting bacterial cells to a medium supporting a higher growth rate. A near-optimal control strategy in dynamical conditions is shown to require information on several, rather than a single physiological variable. Interestingly, this strategy has structural analogies with the regulation of ribosomal protein synthesis by ppGpp in the enterobacterium Escherichia coli. It involves sensing a mismatch between precursor and ribosome concentrations, as well as the adjustment of ribosome synthesis in a switch-like manner. Our results show how the capability of regulatory systems to integrate information about several physiological variables is critical for optimizing growth in a changing environment. PMID:26958858

  10. Effect of temperature on microbial growth rate - thermodynamic analysis, the arrhenius and eyring-polanyi connection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this work is to develop a new thermodynamic mathematical model for evaluating the effect of temperature on the rate of microbial growth. The new mathematical model is derived by combining the Arrhenius equation and the Eyring-Polanyi transition theory. The new model, suitable for ...

  11. Influence of different buffers (HEPES/MOPS) on keratinocyte cell viability and microbial growth.

    PubMed

    Dias, Kássia de Carvalho; Barbugli, Paula Aboud; Vergani, Carlos Eduardo

    2016-06-01

    This study assessed the effect of the buffers 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) and 3-(N-morpholino) propanesulfonic acid (MOPS) on keratinocyte cell viability and microbial growth. It was observed that RPMI buffered with HEPES, supplemented with l-glutamine and sodium bicarbonate, can be used as a more suitable medium to promote co-culture. PMID:27060444

  12. Determining potential for microbial atrazine degradation in agricultural drainage ditches

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Passage of agricultural runoff through vegetated drainage ditches has been shown to reduce the amount of pesticides, such as atrazine, exiting agricultural watersheds. Previous studies found that microbial communities in soil from fields treated with atrazine display enhanced rates of atrazine degr...

  13. What is Growth? Concurrent determination of a bacterial population's many shades of growth

    NASA Astrophysics Data System (ADS)

    Lambert, Guillaume; Kussell, Edo

    2013-03-01

    One of the most exciting developments in the study of the physics of microbial life is the ability to precisely monitor stochastic variations of gene expression in individual cells. A fundamental question is whether these variations improve the long-term ability of a population to adapt to new environments. While variations in gene expression in bacteria are easily measured through the use of reporter systems such as green fluorescent proteins and its variants, precise determination of a cell's growth rate, and how it is influenced by its immediate environment, remains challenging. Here, we show that many conflicting and ambiguous definitions of bacterial growth can actually be used interchangeably in E. coli. Indeed, by monitoring small populations of E. coli bacteria inside a microfluidic device, we show that seemingly independent measurements of growth (elongation rate and the average division time, for instance) agree very precisely with one another. We combine these definitions with the population's length and age distribution to very precisely quantify the influence of temperature variations on a population's growth rate. We conclude by using coalescence theory to describe the evolution of a population's genetic structure over time.

  14. Modeling microbial dynamics in heterogeneous environments: Growth on soil carbon sources

    SciTech Connect

    Resat, Haluk; Bailey, Vanessa L.; McCue, Lee Ann; Konopka, Allan

    2012-01-01

    We have developed a new hybrid model to study how microbial dynamics are affected by the heterogeneity in the physical structure of the environment. The modeling framework can represent porous media such as soil. The individual based biological model can explicitly simulate microbial diversity, and cell metabolism is regulated via optimal allocation of cellular resources to enzyme synthesis, control of growth rate by protein synthesis capacity, and shifts to dormancy. This model was developed to study how microbial community functioning is influenced by local environmental conditions and by the functional attributes of individual microbes. Different strategies for acquisition of carbon from polymeric cellulose were investigated. Bacteria that express membrane-associated hydrolase had different growth and survival dynamics in soil pores than bacteria that release extracellular hydrolases. The kinetic differences may suggest different functional roles for these two classes of microbes in cellulose utilization. Our model predicted an emergent behavior in which co-existence led to higher cellulose utilization efficiency and reduced stochasticity. Microbial community dynamics were simulated at two spatial scales: micro-pores that resemble 6-20 {micro}m size portions of the soil physical structure and in 111 {micro}m size soil aggregates with a random pore structure. Trends in dynamic properties were very similar at these two scales, implying that micro-scale studies can be useful approximations to aggregate scale studies when local effects on microbial dynamics are studied.

  15. Microbial contamination associated with consumption and the growth in plastic bottled beverage.

    PubMed

    Ohnishi, Takahiro; Goto, Keiichi; Kanda, Takashi; Kanazawa, Yuji; Ozawa, Kazuhiro; Sugiyama, Kanji; Watanabe, Maiko; Konuma, Hirotaka; Hara-Kudo, Yukiko

    2013-01-01

    Plastic bottles enable the storage of unfinished beverages, and most of microbial contamination has occurred in the unfinished beverage that was left. Therefore, we investigated microorganisms in various beverages contaminated by pouring and drinking directly by mouth from the bottle, and analyzed the growth of microorganisms in the beverages at room temperature. In the pouring test, microbial growth was detected in 60 of 320 samples, and 13 bacterial strains, 49 mold strains, and 8 yeast strains were isolated. Molds including Cladosporium spp., Tramets spp., Bjerkandera spp., and Penicillium spp. accounted for the majority of isolated microorganisms. In the drinking test, microbial growth was detected in 181 of 352 samples, and 225 bacterial strains, 27 mold strains and 77 yeast strains were isolated. Bacteria including Streptococcus spp. such as S. salivarius and Staphylococcus spp. such as S. aureus accounted for the majority of isolated microorganisms. Enterotoxin-producing S. aureus and Bacillus cereus were also isolated. The pH of the beverage influenced the growth of bacteria. The Brix values of the beverage did not correlate with the growth of microorganisms. These results revealed that various microorganisms including foodborne pathogens were able to grow in numerous types of beverages and that the storage of unfinished beverage in inappropriate condition, such as the storage at room temperature led microorganism to grow easily in beverage. Therefore, it is necessary to consume beverages as soon as possible after opening the bottle.

  16. Biological management of Sclerotinia sclerotiorum in pea using plant growth promoting microbial consortium.

    PubMed

    Jain, Akansha; Singh, Akanksha; Singh, Surendra; Singh, Harikesh Bahadur

    2015-08-01

    The beneficial plant-microbe interactions play crucial roles in protection against large number of plant pathogens causing disease. The present study aims to investigate the growth promoting traits induced by beneficial microbes namely Pseudomonas aeruginosa PJHU15, Trichoderma harzianum TNHU27, and Bacillus subtilis BHHU100 treated singly and in combinations under greenhouse and field conditions to control Sclerotinia sclerotiorum. Plants treated with three microbe consortium enhanced plant growth maximally both in the presence and absence of the pathogen. Increase in plant length, total biomass, number of leaves, nodules and secondary roots, total chlorophyll and carotenoid content, and yield were recorded in plants treated with microbial consortia. Also, a decrease in plant mortality was observed in plants treated with microbial consortia in comparison to untreated control plants challenged with S. sclerotiorum. Furthermore, the decrease in disease of all the treatments can be associated with differential improvement of growth induced in pea. PMID:25727183

  17. Biological management of Sclerotinia sclerotiorum in pea using plant growth promoting microbial consortium.

    PubMed

    Jain, Akansha; Singh, Akanksha; Singh, Surendra; Singh, Harikesh Bahadur

    2015-08-01

    The beneficial plant-microbe interactions play crucial roles in protection against large number of plant pathogens causing disease. The present study aims to investigate the growth promoting traits induced by beneficial microbes namely Pseudomonas aeruginosa PJHU15, Trichoderma harzianum TNHU27, and Bacillus subtilis BHHU100 treated singly and in combinations under greenhouse and field conditions to control Sclerotinia sclerotiorum. Plants treated with three microbe consortium enhanced plant growth maximally both in the presence and absence of the pathogen. Increase in plant length, total biomass, number of leaves, nodules and secondary roots, total chlorophyll and carotenoid content, and yield were recorded in plants treated with microbial consortia. Also, a decrease in plant mortality was observed in plants treated with microbial consortia in comparison to untreated control plants challenged with S. sclerotiorum. Furthermore, the decrease in disease of all the treatments can be associated with differential improvement of growth induced in pea.

  18. Numerical solution of a microbial growth model applied to dynamic environments.

    PubMed

    Zhu, Si; Chen, Guibing

    2015-05-01

    The Baranyi and Roberts model is one of the most frequently used microbial growth models. It has been successfully applied to numerous studies of various microorganisms in different food products. Under dynamic conditions, the model is implicitly formulated as a set of two coupled differential equations which could be numerically solved using the Runge-Kutta method. In this study, a simplified numerical solution of the coupled differential equations was derived and used to simulate microbial growth under dynamic conditions in Microsoft Excel. As expected, the results obtained were the same as those from solving the coupled differential equations using a MATLAB Solver. In addition, model parameters were accurately identified by fitting the numerical solution to simulated growth curves under dynamic (time-varying) temperature conditions using the Microsoft Excel Solver.

  19. Prevention of Acid Mine Drainage Through Complexation of Ferric Iron by Soluble Microbial Growth Products

    NASA Astrophysics Data System (ADS)

    Pandey, S.; Yacob, T. W.; Silverstein, J.; Rajaram, H.; Minchow, K.; Basta, J.

    2011-12-01

    Acid mine drainage (AMD) is a widespread environmental problem with deleterious impacts on water quality in streams and watersheds. AMD is generated largely by the oxidation of metal sulfides (i.e. pyrite) by ferric iron. This abiotic reaction is catalyzed by conversion of ferrous to ferric iron by iron and sulfur oxidizing microorganisms. Biostimulation is currently being investigated as an attempt to inhibit the oxidation of pyrite and growth of iron oxidizing bacteria through addition of organic carbon. This may stimulate growth of indigenous communities of acidophilic heterotrophic bacteria to compete for oxygen. The goal of this research is to investigate a secondary mechanism associated with carbon addition: complexation of free Fe(III) by soluble microbial growth products (SMPs) produced by microorganisms growing in waste rock. Exploratory research at the laboratory scale examined the effect of soluble microbial products (SMPs) on the kinetics of oxidation of pure pyrite during shaker flask experiments. The results confirmed a decrease in the rate of pyrite oxidation that was dependent upon the concentration of SMPs in solution. We are using these data to verify results from a pyrite oxidation model that accounts for SMPs. This reactor model involves differential-algebraic equations incorporating total component mass balances and mass action laws for equilibrium reactions. Species concentrations determined in each time step are applied to abiotic pyrite oxidation rate expressions from the literature to determine the evolution of total component concentrations. The model was embedded in a parameter estimation algorithm to determine the reactive surface area of pyrite in an abiotic control experiment, yielding an optimized value of 0.0037 m2. The optimized model exhibited similar behavior to the experiment for this case; the root mean squared of residuals for Fe(III) was calculated to be 7.58 x 10-4 M, which is several orders of magnitude less than the actual

  20. Growth dynamic of Naegleria fowleri in a microbial freshwater biofilm.

    PubMed

    Goudot, Sébastien; Herbelin, Pascaline; Mathieu, Laurence; Soreau, Sylvie; Banas, Sandrine; Jorand, Frédéric

    2012-09-01

    The presence of pathogenic free-living amoebae (FLA) such as Naegleria fowleri in freshwater environments is a potential public health risk. Although its occurrence in various water sources has been well reported, its presence and associated factors in biofilm remain unknown. In this study, the density of N. fowleri in biofilms spontaneously growing on glass slides fed by raw freshwater were followed at 32 °C and 42 °C for 45 days. The biofilms were collected with their substrata and characterized for their structure, numbered for their bacterial density, thermophilic free-living amoebae, and pathogenic N. fowleri. The cell density of N. fowleri within the biofilms was significantly affected both by the temperature and the nutrient level (bacteria/amoeba ratio). At 32 °C, the density remained constantly low (1-10 N. fowleri/cm(2)) indicating that the amoebae were in a survival state, whereas at 42 °C the density reached 30-900 N. fowleri/cm(2) indicating an active growth phase. The nutrient level, as well, strongly affected the apparent specific growth rate (μ) of N. fowleri in the range of 0.03-0.23 h(-1). At 42 °C a hyperbolic relationship was found between μ and the bacteria/amoeba ratio. A ratio of 10(6) to 10(7) bacteria/amoeba was needed to approach the apparent μ(max) value (0.23 h(-1)). Data analysis also showed that a threshold for the nutrient level of close to 10(4) bacteria/amoeba is needed to detect the growth of N. fowleri in freshwater biofilm. This study emphasizes the important role of the temperature and bacteria as prey to promote not only the growth of N. fowleri, but also its survival.

  1. Impacts of Microbial Growth on the Air Quality of the International Space Station

    NASA Technical Reports Server (NTRS)

    Macatangay, Ariel V.; Bruce, Rebekah J.

    2010-01-01

    An understanding of the various sources of non-methane volatile organic compounds (NMVOCs) is one facet to ensuring the habitability of crewed spacecraft. Even though the International Space Station (ISS) atmosphere is relatively well characterized in terms of what is in the atmosphere and approximately how much, linking the majority of these trace contaminants detected to their source is virtually impossible. Albeit a few of can be associated to a single source, the majority of these trace contaminants have their origins from multiple sources. On crewed spacecraft such as ISS, trace contaminants are broadly categorized as either coming from equipment, which includes systems and payloads, or from the metabolic processes of the crew members. Such widely encompassing categories clearly illustrate the difficulty in linking air contaminants to their source(s). It is well known that microbial growth in ISS can flourish if left unchecked. Although processes are in place to limit microbial growth, in reality, microbial growth has pervaded the habitable environment of ISS. This is simply a consequence of having crewed spacecraft, as humans are the largest contributor to the bioload. As with crew members, microbes also have metabolic processes which, in many ways, are comparable to human metabolism. As such, it can be expected that microbial growth can lead to the release of volatile organic compounds into the ISS atmosphere. Given a large enough microbial population, the impact to the air quality of ISS can be potentially large. A survey of the microbiology found in ISS will be presented as well as the possible types of volatile organic compounds that can result from such organisms. This will be correlated to the observations provided by ground-based analysis of ISS atmosphere samples

  2. Impacts of Microbial Growth on the Air Quality of the International Space Station

    NASA Technical Reports Server (NTRS)

    Macatangay, Ariel V.; Bruce, Rebekah J.

    2009-01-01

    An understanding of the various sources of non-methane volatile organic compounds (NMVOCs) is one facet to ensuring the habitability of crewed spacecraft. Even though the International Space Station (ISS) atmosphere is relatively well characterized in terms of what is in the atmosphere and approximately how much, linking the majority of these trace contaminants detected to their source is virtually impossible. Albeit a few of can be associated to a single source, the majority of these trace contaminants have their origins from multiple sources. On crewed spacecraft such as ISS, trace contaminants are broadly categorized as either coming from equipment, which includes systems and payloads, or from the metabolic processes of the crew members. Such widely encompassing categories clearly illustrate the difficulty in linking air contaminants to their source(s). It is well known that microbial growth in ISS can flourish if left unchecked. Although processes are in place to limit microbial growth, in reality, microbial growth has pervaded the habitable environment of ISS. This is simply a consequence of having crewed spacecraft, as humans are the largest contributor to the bioload. As with crew members, microbes also have metabolic processes which, in many ways, are comparable to human metabolism. As such, it can be expected that microbial growth can lead to the release of volatile organic compounds into the ISS atmosphere. Given a large enough microbial population, the impact to the air quality of ISS can be potentially large. A survey of the microbiology found in ISS will be presented as well as the possible types of volatile organic compounds that can result from such organisms. This will be correlated to the observations provided by ground-based analysis of ISS atmosphere samples.

  3. Effect of refrigeration on microbial growth in the Blairex Water Purifier.

    PubMed

    Harris, M G; Meng, K E; Frank, L J; Mamalis, G

    1987-05-01

    The Blairex Water Purifier is designed to make tap water into purified water that can be used to make saline solution for soft contact lens disinfection and rinsing. The micropore filters of eight Purifiers were perforated to allow a controlled contamination by either Pseudomonas aeruginosa or Serratia marcescens. The bacterial growth was evaluated in these altered Blairex Water Purifiers under refrigerated and unrefrigerated conditions. Those Purifiers that were refrigerated showed significantly less bacterial growth than those Purifiers that were kept at room temperature between samplings. Our findings imply that soft contact lens wearers may reduce the level of microbial growth in undamaged Purifiers by refrigerating the Purifiers between uses. PMID:3111265

  4. Green tea yogurt: major phenolic compounds and microbial growth.

    PubMed

    Amirdivani, Shabboo; Baba, Ahmad Salihin Hj

    2015-07-01

    The purpose of this study was to evaluate fermentation of milk in the presence of green tea (Camellia sinensis) with respect to changes in antioxidant activity, phenolic compounds and the growth of lactic acid bacteria. Pasteurized full fat cow's milk and starter culture were incubated at 41 °C in the presence of two different types of green tea extracts. The yogurts formed were refrigerated (4 °C) for further analysis. The total phenolic content was highest (p < 0.05) in air-dried green tea-yogurt (MGT) followed by steam-treated green tea (JGT) and plain yogurts. Four major compounds in MGTY and JGTY were detected. The highest concentration of major phenolic compounds in both samples was related to quercetin-rhamnosylgalactoside and quercetin-3-O-galactosyl-rhamnosyl-glucoside for MGTY and JGTY respectively during first 7 day of storage. Diphenyl picrylhydrazyl and ferric reducing antioxidant power methods showed highest antioxidant capacity in MGTY, JGTY and PY. Streptococcus thermophillus and Lactobacillus spp. were highest in MGTY followed by JGTY and PY. This paper evaluates the implementation of green tea yogurt as a new product with functional properties and valuable component to promote the growth of beneficial yogurt bacteria and prevention of oxidative stress by enhancing the antioxidant activity of yogurt. PMID:26139940

  5. Genetic and Nongenetic Determinants of Cell Growth Variation Assessed by High-Throughput Microscopy

    PubMed Central

    Ziv, Naomi; Siegal, Mark L.; Gresham, David

    2013-01-01

    In microbial populations, growth initiation and proliferation rates are major components of fitness and therefore likely targets of selection. We used a high-throughput microscopy assay, which enables simultaneous analysis of tens of thousands of microcolonies, to determine the sources and extent of growth rate variation in the budding yeast (Saccharomyces cerevisiae) in different glucose environments. We find that cell growth rates are regulated by the extracellular concentration of glucose as proposed by Monod (1949), but that significant heterogeneity in growth rates is observed among genetically identical individuals within an environment. Yeast strains isolated from different geographic locations and habitats differ in their growth rate responses to different glucose concentrations. Inheritance patterns suggest that the genetic determinants of growth rates in different glucose concentrations are distinct. In addition, we identified genotypes that differ in the extent of variation in growth rate within an environment despite nearly identical mean growth rates, providing evidence that alleles controlling phenotypic variability segregate in yeast populations. We find that the time to reinitiation of growth (lag) is negatively correlated with growth rate, yet this relationship is strain-dependent. Between environments, the respirative activity of individual cells negatively correlates with glucose abundance and growth rate, but within an environment respirative activity and growth rate show a positive correlation, which we propose reflects differences in protein expression capacity. Our study quantifies the sources of genetic and nongenetic variation in cell growth rates in different glucose environments with unprecedented precision, facilitating their molecular genetic dissection. PMID:23938868

  6. Comparative analysis of some models of gene regulation in mixed-substrate microbial growth.

    PubMed

    Narang, Atul

    2006-09-21

    Mixed-substrate microbial growth is of fundamental interest in microbiology and bioengineering. Several mathematical models have been developed to account for the genetic regulation of such systems, especially those resulting in diauxic growth. In this work, we compare the dynamics of three such models (Narang, 1998a. The dynamical analogy between microbial growth on mixtures of substrates and population growth of competing species. Biotechnol. Bioeng. 59, 116-121; Thattai and Shraiman, 2003. Metabolic switching in the sugar phosphotransferase system of Escherichia coli. Biophys. J. 85(2), 744-754; Brandt et al., 2004. Modelling microbial adaptation to changing availability of substrates. Water Res. 38, 1004-1013). We show that these models are dynamically similar--the initial motion of the inducible enzymes in all the models is described by the Lotka-Volterra equations for competing species. In particular, the prediction of diauxic growth corresponds to "extinction" of one of the enzymes during the first few hours of growth. The dynamic similarity occurs because in all the models, the inducible enzymes possess properties characteristic of competing species: they are required for their own synthesis, and they inhibit each other. Despite this dynamic similarity, the models vary with respect to the range of dynamics captured. The Brandt et al. model always predicts the diauxic growth pattern, whereas the remaining two models exhibit both diauxic and non-diauxic growth patterns. The models also differ with respect to the mechanisms that generate the mutual inhibition between the enzymes. In the Narang model, mutual inhibition occurs because the enzymes for each substrate enhance the dilution of the enzymes for the other substrate. The Brandt et al. model superimposes upon this dilution effect an additional mechanism of mutual inhibition. In the Thattai and Shraiman model, the mutual inhibition is entirely due to competition for the phosphoryl groups. For quantitative

  7. Effect of different film packaging on microbial growth in minimally processed cactus pear (Opuntia ficus-indica).

    PubMed

    Palma, A; Mangia, N P; Fadda, A; Barberis, A; Schirra, M; D'Aquino, S

    2013-01-01

    Microorganisms are natural contaminants of fresh produce and minimally processed products, and contamination arises from a number of sources, including the environment, postharvest handling and processing. Fresh-cut products are particularly susceptible to microbial contaminations because of the changes occurring in the tissues during processing. In package gas composition of modified atmosphere packaging (MAP) in combination with low storage temperatures besides reducing physiological activity of packaged produce, can also delay pathogen growth. Present study investigated on the effect of MAPs, achieved with different plastic films, on microbial growth of minimally processed cactus pear (Opuntio ficus-indica) fruit. Five different plastic materials were used for packaging the manually peeled fruit. That is: a) polypropylene film (Termoplast MY 40 micron thickness, O2 transmission rate 300 cc/m2/24h); b) polyethylene film (Bolphane BHE, 11 micron thickness, O2 transmission rate 19000 cc/m2/24h); c) polypropylene laser-perforated films (Mach Packaging) with 8, 16 or 32 100-micron holes. Total aerobic psychrophilic, mesophilic microorganisms, Enterobacteriaceae, yeast, mould populations and in-package CO2, O2 and C2H4 were determined at each storage time. Different final gas compositions, ranging from 7.8 KPa to 17.1 KPa O2, and 12.7 KPa to 2.6 KPa CO2, were achieved with MY and micro perforated films, respectively. Differences were detected in the mesophilic, Enterobacteriaceae and yeast loads, while no difference was detected in psychrophilic microorganisms. At the end of storage, microbial load in fruits sealed with MY film was significantly lower than in those sealed with BHE and micro perforated films. Furthermore, fruits packed with micro-perforated films showed the highest microbial load. This occurrence may in part be related to in-package gas composition and in part to a continuous contamination of microorganisms through micro-holes.

  8. Adapting isostatic microbial growth parameters into non-isostatic models for use in dynamic ecosystems

    NASA Astrophysics Data System (ADS)

    Spangler, J.; Schulz, C. J.; Childers, G. W.

    2009-12-01

    Modeling microbial respiration and growth is an important tool for understanding many geochemical systems. The estimation of growth parameters relies on fitting experimental data to a selected model, such as the Monod equation or some variation, most often under batch or continuous culture conditions. While continuous culture conditions can be analogous to some natural environments, it often isn’t the case. More often, microorganisms are subject to fluctuating temperature, substrate concentrations, pH, water activity, and inhibitory compounds, to name a few. Microbial growth estimation under non-isothermal conditions has been possible through use of numerical solutions and has seen use in the field of food microbiology. In this study, numerical solutions were used to extend growth models under more non-isostatic conditions using momentary growth rate estimates. Using a model organism common in wastewater (Paracoccus denitrificans), growth and respiration rate parameters were estimated under varying static conditions (temperature, pH, electron donor/acceptor concentrations) and used to construct a non-isostatic growth model. After construction of the model, additional experiments were conducted to validate the model. These non-isostatic models hold the potential for allowing the prediction of cell biomass and respiration rates under a diverse array of conditions. By not restricting models to constant environmental conditions, the general applicability of the model can be greatly improved.

  9. Bifunctional silver nanoparticle cathode in microbial fuel cells for microbial growth inhibition with comparable oxygen reduction reaction activity.

    PubMed

    An, Junyeong; Jeon, Hongrae; Lee, Jaeyoung; Chang, In Seop

    2011-06-15

    Organic contamination of water bodies in which benthic microbial fuel cells (benthic MFCs) are installed, and organic crossover from the anode to the cathode of membraneless MFCs, is a factor causing oxygen depletion and substrate loss in the cathode due to the growth of heterotrophic aerobic bacteria. This study examines the possible use of silver nanoparticles (AgNPs) as a cathodic catalyst for MFCs suffering from organic contamination and oxygen depletion. Four treated cathodes (AgNPs-coated, Pt/C-coated, Pt/C+AgNPs-coated, and plain graphite cathodes) were prepared and tested under high levels of organics loading. During operation (fed with 50 mM acetate), the AgNPs-coated system showed the highest DO concentration (0.8 mg/L) in the cathode area as well as the highest current (ranging from 0.04 to 0.12 mA). Based on these results, we concluded that (1) the growth of oxygen-consuming heterotrophic microbes could be inhibited by AgNPs, (2) the function of AgNPs as a bacterial growth inhibitor resulted in a greater increase of DO concentration in the cathode than the other tested cathode systems, (3) AgNPs could be applied as a cathode catalyst for oxygen reduction, and as a result (4) the MFC with the AgNPs-coated cathode led to the highest current generation among the tested MFCs. PMID:21585217

  10. Microbial growth and the effects of mild acidification and preservatives in refrigerated sweet potato puree.

    PubMed

    Pérez-Díaz, Ilenys M; Truong, Van-Den; Webber, Ashlee; McFeeters, Roger F

    2008-03-01

    Refrigerated sweet potato puree is a convenient form of sweet potato that can be used as an ingredient in formulated foods. The microbiology of refrigerated sweet potato puree during storage for up to 5 weeks was evaluated. Because the puree was made by comminuting steam-cooked sweet potatoes before refrigeration, no naturally occurring vegetative bacterial cells were detected during a 4-week period of refrigerated storage at 4 degrees C. However, if postprocessing microbial contamination of the puree were to occur, contaminating microorganisms such as Listeria monocytogenes could grow during refrigerated storage. The effects of acidification or the addition of potassium sorbate and sodium benzoate on a population of L. monocytogenes inoculated into refrigerated (4 degrees C) sweet potato puree were determined. Inoculation of the refrigerated puree with L. monocytogenes at 10(6) CFU/ml resulted in a 3-log increase after 3 weeks storage of nonsupplemented puree. Supplementation of the sweet potato puree with 0.06% (wt/vol) sorbic acid or benzoic acid plus mild acidification of the sweet potato puree with citric acid to pH 4.2 prevented growth of L. monocytogenes during storage at 4 degrees C.

  11. ATP monitoring technology for microbial growth control in potable water systems

    NASA Astrophysics Data System (ADS)

    Whalen, Patrick A.; Whalen, Philip J.; Cairns, James E.

    2006-05-01

    ATP (Adenosine Triphosphate) is the primary energy transfer molecule present in all living biological cells on Earth. ATP cannot be produced or maintained by anything but a living organism, and as such, its measurement is a direct indication of biological activity. The main advantage of ATP as a biological indicator is the speed of the analysis - from collecting the sample to obtaining the result, only minutes are required. The technology to measure ATP is already widely utilized to verify disinfection efficacy in the food industry and is also commonly applied in industrial water processes such as cooling water systems to monitor microbial growth and biocide applications. Research has indicated that ATP measurement technology can also play a key role in such important industries as potable water distribution and biological wastewater treatment. As will be detailed in this paper, LuminUltra Technologies has developed and applied ATP measurement technologies designed for any water type, and as such can provide a method to rapidly and accurately determine the level of biological activity in drinking water supplies. Because of its speed and specificity to biological activity, ATP measurement can play a key role in defending against failing drinking water quality, including those encountered during routine operation and also bioterrorism.

  12. Structural effects of ionic liquids on microalgal growth inhibition and microbial degradation.

    PubMed

    Pham, Thi Phuong Thuy; Cho, Chul-Woong; Yun, Yeoung-Sang

    2016-03-01

    In the present study, we investigated structural effects of various ionic liquids (ILs) on microalgal growth inhibition and microbial biodegradability. For this, we tested pyridinium- and pyrrolidinium-based ILs with various alkyl chain lengths and bromide anion, and compared the toxicological effects with log EC50 values of imidazolium-based IL with the same alkyl chains and anion from literature. Comparing determined EC50 values of cationic moieties with the same alkyl chain length, pyridinium-based ILs were found to be slightly more toxic towards the freshwater green alga, Pseudokirchneriella subcapitata, than a series of pyrrolidinium and imidazolium except to 1-octyl-3-methylimidazolium bromide. Concerning the biodegradation study of 12 ILs using the activated sludge microorganisms, the results showed that the pyridinium derivatives except to 1-propyl-3-methylpyridinium cation were degraded. Whereas in case of imidazolium- and pyrrolidinium-based compounds, only n-hexyl and n-octyl substituted cations were fully degraded but no significant biodegradation was observed for the short chains (three and four alkyl chains).

  13. Waste water derived electroactive microbial biofilms: growth, maintenance, and basic characterization.

    PubMed

    Gimkiewicz, Carla; Harnisch, Falk

    2013-12-29

    The growth of anodic electroactive microbial biofilms from waste water inocula in a fed-batch reactor is demonstrated using a three-electrode setup controlled by a potentiostat. Thereby the use of potentiostats allows an exact adjustment of the electrode potential and ensures reproducible microbial culturing conditions. During growth the current production is monitored using chronoamperometry (CA). Based on these data the maximum current density (jmax) and the coulombic efficiency (CE) are discussed as measures for characterization of the bioelectrocatalytic performance. Cyclic voltammetry (CV), a nondestructive, i.e. noninvasive, method, is used to study the extracellular electron transfer (EET) of electroactive bacteria. CV measurements are performed on anodic biofilm electrodes in the presence of the microbial substrate, i.e. turnover conditions, and in the absence of the substrate, i.e. nonturnover conditions, using different scan rates. Subsequently, data analysis is exemplified and fundamental thermodynamic parameters of the microbial EET are derived and explained: peak potential (Ep), peak current density (jp), formal potential (E(f)) and peak separation (ΔEp). Additionally the limits of the method and the state-of the art data analysis are addressed. Thereby this video-article shall provide a guide for the basic experimental steps and the fundamental data analysis.

  14. A comparison of additional treatment processes to limit particle accumulation and microbial growth during drinking water distribution.

    PubMed

    Liu, G; Lut, M C; Verberk, J Q J C; Van Dijk, J C

    2013-05-15

    Water quality changes, particle accumulation and microbial growth occurring in pilot-scale water distribution systems fed with normally treated and additional treated groundwater were monitored over a period of almost one year. The treatment processes were ranked in the following order: nanofiltration (NF) > (better than) ultrafiltration (UF) > ion exchange (IEX) for limiting particle accumulation. A different order was found for limiting overall microbial growth: NF > IEX > UF. There were strong correlations between particle load and particle accumulation, and between nutrient load and microbial growth. It was concluded that particle accumulation can be controlled by reducing the particle load in water treatment plants; and the microbial growth can be better controlled by limiting organic nutrients rather than removing biomass in water treatment plants. The major focus of this study was on microbial growth. The results demonstrated that growth occurred in all types of treated water, including the phases of bulk water, biofilm and loose deposits. Considering the growth in different phases, similar growth in bulk water was observed for all treatments; NF strongly reduced growth both in loose deposits and in biofilm; UF promoted growth in biofilm, while strongly limiting growth in loose deposits. IEX had good efficiency in between UF and NF, limiting both growths in loose deposits and in biofilm. Significant growth was found in loose deposits, suggesting that loose deposit biomass should be taken into account for growth evaluation and/or prediction. Strong correlations were found between microbial growth and pressure drop in a membrane fouling simulator which proved that a membrane fouling simulator can be a fast growth predictor (within a week). Different results obtained by adenosine triphosphate and flow cytometry cell counts revealed that ATP can accurately describe both suspended and particle-associated biomass, and flow cytometry files of TCC measurements needs

  15. Methods for Facilitating Microbial Growth on Pulp Mill Waste Streams and Characterization of the Biodegradation Potential of Cultured Microbes

    PubMed Central

    Mathews, Stephanie L.; Ayoub, Ali S.; Pawlak, Joel; Grunden, Amy M.

    2013-01-01

    The kraft process is applied to wood chips for separation of lignin from the polysaccharides within lignocellulose for pulp that will produce a high quality paper. Black liquor is a pulping waste generated by the kraft process that has potential for downstream bioconversion. However, the recalcitrant nature of the lignocellulose resources, its chemical derivatives that constitute the majority of available organic carbon within black liquor, and its basic pH present challenges to microbial biodegradation of this waste material. Methods for the collection and modification of black liquor for microbial growth are aimed at utilization of this pulp waste to convert the lignin, organic acids, and polysaccharide degradation byproducts into valuable chemicals. The lignocellulose extraction techniques presented provide a reproducible method for preparation of lignocellulose growth substrates for understanding metabolic capacities of cultured microorganisms. Use of gas chromatography-mass spectrometry enables the identification and quantification of the fermentation products resulting from the growth of microorganisms on pulping waste. These methods when used together can facilitate the determination of the metabolic activity of microorganisms with potential to produce fermentation products that would provide greater value to the pulping system and reduce effluent waste, thereby increasing potential paper milling profits and offering additional uses for black liquor. PMID:24378616

  16. Response of microbial growth to orthophosphate and organic carbon influx in copper and plastic based plumbing water systems.

    PubMed

    Park, Se-Keun; Kim, Yeong-Kwan; Choi, Sung-Chan

    2008-07-01

    Consequences of orthophosphate addition for corrosion control in water distribution pipes with respect to microbial growth were investigated using batch and dynamic tests. Batch tests showed that the release of copper in either low or high organic carbon content water was decreased by 69% and 56% with addition 206 microg PO(4)-P, respectively. Dosing of orthophosphate against corrosion did not increase microbial growth potential in the water and in the biofilm in both corroded and uncorroded systems receiving tap water with a low content of organic carbon and of biodegradable organic fraction. However, in tap water having a high concentration of organic carbon from acetate addition, orthophosphate addition promoted the growth of bacteria, allowed more bacteria to assemble on corroded and uncorroded surfaces, and increased the consumption of organic carbon. Orthophosphate consumption did not exceed 1% of the amount of easily biodegradable organic carbon required for microbial growth, and the orthophosphate demand for corrosion control greatly exceeded the nutritional requirement of microbial growth. The results of the dynamic tests demonstrated that there was a significant effect of interaction between biodegradable organic carbon and orthophosphate on biofilm growth, whereby the effect of orthophosphate flux on microbial growth was dependent on the levels of biodegradable organic carbon. Controlling an easily biodegradable organic carbon would be therefore necessary to minimize the microbial growth potential induced by orthophosphate-based anticorrosion treatment.

  17. Response of microbial growth to orthophosphate and organic carbon influx in copper and plastic based plumbing water systems.

    PubMed

    Park, Se-Keun; Kim, Yeong-Kwan; Choi, Sung-Chan

    2008-07-01

    Consequences of orthophosphate addition for corrosion control in water distribution pipes with respect to microbial growth were investigated using batch and dynamic tests. Batch tests showed that the release of copper in either low or high organic carbon content water was decreased by 69% and 56% with addition 206 microg PO(4)-P, respectively. Dosing of orthophosphate against corrosion did not increase microbial growth potential in the water and in the biofilm in both corroded and uncorroded systems receiving tap water with a low content of organic carbon and of biodegradable organic fraction. However, in tap water having a high concentration of organic carbon from acetate addition, orthophosphate addition promoted the growth of bacteria, allowed more bacteria to assemble on corroded and uncorroded surfaces, and increased the consumption of organic carbon. Orthophosphate consumption did not exceed 1% of the amount of easily biodegradable organic carbon required for microbial growth, and the orthophosphate demand for corrosion control greatly exceeded the nutritional requirement of microbial growth. The results of the dynamic tests demonstrated that there was a significant effect of interaction between biodegradable organic carbon and orthophosphate on biofilm growth, whereby the effect of orthophosphate flux on microbial growth was dependent on the levels of biodegradable organic carbon. Controlling an easily biodegradable organic carbon would be therefore necessary to minimize the microbial growth potential induced by orthophosphate-based anticorrosion treatment. PMID:18495203

  18. Methods for determining the abundance, diversity and activity of soil microbial communities

    NASA Astrophysics Data System (ADS)

    Pereg, Lily

    2014-05-01

    The diversity and abundance of soil microbial communities play important roles in determining soil structure, quality and productivity. The past decade has seen an increase in the number and efficiency of methods for determining microbial diversity, abundance and function. Recognising that only a very small proportion of the soil microbial community can be cultured, most current studies use molecular techniques based on the 16S and 18S rRNA encoding sequences (DGGE, TRFLP, OFRG, ARISA, SSCP) as well as techniques based on the cellular composition of the microbes (PLFA composition). Recent developments include high-throughput sequencing and microarrays, representing major advances in microbial community analysis. While the diversity of microbes can be determined using DNA-based techniques, microbial activity changes under various conditions. Therefore, the analysis of soil function at any given time requires the analysis of gene expression using RNA-based techniques. Molecular techniques have tremendously advanced our knowledge in the field of soil microbiology, however, the limitations should not be underestimated. This presentation will critically review both the advantages and the limitations of techniques used in soil microbial analysis.

  19. Phenolic-rich leaf carbon fractions differentially influence microbial respiration and plant growth.

    PubMed

    Meier, Courtney L; Bowman, William D

    2008-11-01

    Phenolics can reduce soil nutrient availability, either indirectly by stimulating microbial nitrogen (N) immobilization or directly by enhancing physical protection within soil. Phenolic-rich plants may therefore negatively affect neighboring plant growth by restricting the N supply. We used a slow-growing, phenolic-rich alpine forb, Acomastylis rossii, to test the hypothesis that phenolic-rich carbon (C) fractions stimulate microbial population growth and reduce plant growth. We generated low-molecular-weight (LMW) fractions, tannin fractions, and total soluble C fractions from A. rossii and measured their effects on soil respiration and growth of Deschampsia caespitosa, a fast-growing, co-dominant grass. Fraction effects fell into two distinct categories: (1) fractions did not increase soil respiration and killed D. caespitosa plants, or (2) fractions stimulated soil respiration and reduced plant growth and plant N concentration while simultaneously inhibiting root growth. The LMW phenolic-rich fractions increased soil respiration and reduced plant growth more than tannins. These results suggest that phenolic compounds can inhibit root growth directly as well as indirectly affect growth by reducing pools of plant available N by stimulating soil microbes. Both mechanisms illustrate how below-ground phenolic effects may influence the growth of neighboring plants. We also examined patterns of foliar phenolic concentrations among populations of A. rossii across a natural productivity gradient (productivity was used as a proxy for competition intensity). Concentrations of some LMW phenolics increased significantly in more productive sites where A. rossii is a competitive equal with the faster growing D. caespitosa. Taken together, our results contribute important information to the growing body of evidence indicating that the quality of C moving from plants to soils can have significant effects on neighboring plant performance, potentially associated with phytoxic

  20. Growth-inhibitory activity of natural and synthetic isothiocyanates against representative human microbial pathogens

    PubMed Central

    Kurepina, Natalia; Kreiswirth, Barry N.; Mustaev, Arkady

    2013-01-01

    Aims The aim of this study was to test the growth inhibition activity of isothiocyanates (ITC), defense compounds of plants, against common human microbial pathogens. Methods and Results In this study we have tested the growth inhibitory activity of a diverse collection of new and previously known representative ITC of various structural classes against pathogenic bacteria, fungi and molds by a serial dilution method. Generally, the compounds were more active against Gram-positive bacteria and fungi exhibiting species-specific bacteriostatic or bactericidal effect. The most active compounds inhibited the growth of both drug-susceptible and multi drug resistant (MDR) pathogens at micromolar concentrations. In the case of Mycobacterium tuberculosis some compounds were more active against MDR, rather than against susceptible strains. The average anti-microbial activity for some of new derivatives was significantly higher than previously reported for the most active ITC compounds. The structure-activity relationship (SAR) established for various classes of ITC with Bacillus cereus (model organism for B. anthracis) followed a distinct pattern, thereby enabling prediction of new more efficient inhibitors. Remarkably, tested bacteria failed to develop resistance to ITC. While effectively inhibiting microbial growth, ITCs displayed moderate toxicity towards eukaryotic cells. Conclusions High antimicrobial activity coupled with moderate toxicity grants further thorough studies of the ITC compounds aimed at elucidation of their cellular targets and inhibitory mechanism. Significance and impact of the study This systematic study identified new ITC compounds highly active against common human microbial pathogens at the concentrations comparable with those for currently used antimicrobial drugs (e.g. rifampicin, fluconazole). Tested representative pathogens do not develop resistance to the inhibitors. These properties justify further evaluation of ITC compounds as potential

  1. Measurement of microbial growth in the low nutrient conditions of a simulated subsurface environment

    NASA Astrophysics Data System (ADS)

    Hand, V. L.; Boult, S.; Vaughan, D. J.; Beadle, I. R.; Humphreys, P.; Wogelius, R. A.

    2003-04-01

    The growth of bacteria in natural porous media may alter porosity and permeability, and therefore hydraulic conductivity. Changes are due both to pore clogging caused by the production of bacterial extracellular polysaccharides (EPS) and the formation of secondary mineral precipitates. Pore clogging has implications not only for fluid flow, but also for contaminant transport. Most biofilm research has been conducted under nutrient rich conditions, quite different from the actual subsurface environment. There is therefore a general need for studies under environmentally relevant conditions. The main objectives were to determine growth under environmental conditions and to produce reproducible homogeneously coated columns of porous media for further experiments on metal transport. Six short columns (length 25mm; diameter 20mm) instrumented with pressure, pH and dissolved oxygen sensors were used. Growth and reproducibility of the biofilm are related to the flow rate, the concentration of the nutrients and the grain size of the porous medium substrate. Two types of porous media were used; a single mineral quartz media with a constant grain size and a natural mixed mineral assemblage of non-uniform grain size. Nutrient used was a landfill derived carbon source present in synthetic trench leachate (STL) diluted with synthetic groundwater (SGW) by a factor of 100. The STL was pumped through each column at a constant, environmentally relevant flow rate of 0.109 ml/min. Experiments were performed under both aerobic and anaerobic conditions contained in a temperature-controlled room at 10^oC. Measurement of the pressure increase within the column apparatus was made, as an increase in pressure is relative to the resistance of the media to flow and indicates biofilm formation and pore clogging within the column. Monitoring of dissolved oxygen shows the metabolic conditions of the bacteria and also the biological oxygen demand. Column effluent was analysed for changes in

  2. Microbial Communities: Tracing Growth Processes from Antarctic Lakes to Early Earth to Other Planets

    NASA Astrophysics Data System (ADS)

    Sumner, D. Y.

    2014-12-01

    Life in the Universe is dominated by microbes: they are numerically the most abundant cells in our bodies and in Earth's biosphere, and they are the only life that might be present elsewhere in our solar system. Life beyond our solar system could include macroscopic organisms, but everything we understand about the origin of life suggests it must start with microbes. Thus, understanding microbial ecosystems, in the absence of macroscopic organisms, is critical to understanding early life on Earth and life elsewhere in the Universe - if it exists. But what are the general principles of microbial ecology in the absence of predation? What happens when each cell is a chemical factory that can swap among metabolic processes in response to environmental and emergent cues? Geobiologists and astrobiologists are addressing these questions in diverse ways using both Earth's modern biosphere and its fossil record. Modern microbial communities in shallow, ice-covered lakes, Antarctica (Fig.), provide a model for high productivity microbial ecosystems with no to low predation. In these lakes, photosynthetic communities create macroscopic pinnacles and domes, sometime lithified into stromatolites. They provide an ecological, geochemical and morphological model for Precambrian microbial communities in low sedimentation, low current environments. Insights from these communities include new growth processes for ancient mats, especially some that grew prior to the oxidation of Earth's atmosphere. The diversity of biosignatures created in these communities also provides context for models of life under ice elsewhere in our solar system such as paleolakes on Mars and on icy moons. Results from the Mars Science Laboratory (MSL) team document formerly habitable fluvial and lacustrine environments. Lacustrine environments, in particular, are favorable for preserving biosignatures, and continued investigations by MSL will provide a deeper understanding of the duration of habitable

  3. Extraction of solubles from plant biomass for use as microbial growth stimulant and methods related thereto

    DOEpatents

    Lau, Ming Woei

    2015-12-08

    A method for producing a microbial growth stimulant (MGS) from a plant biomass is described. In one embodiment, an ammonium hydroxide solution is used to extract a solution of proteins and ammonia from the biomass. Some of the proteins and ammonia are separated from the extracted solution to provide the MGS solution. The removed ammonia can be recycled and the proteins are useful as animal feeds. In one embodiment, the method comprises extracting solubles from pretreated lignocellulosic biomass with a cellulase enzyme-producing growth medium (such T. reesei) in the presence of water and an aqueous extract.

  4. Influence of mechanical disintegration on the microbial growth of aerobic sludge biomass: A comparative study of ultrasonic and shear gap homogenizers by oxygen uptake measurements.

    PubMed

    Divyalakshmi, P; Murugan, D; Sivarajan, M; Saravanan, P; Lajapathi Rai, C

    2015-11-01

    Wastewater treatment plant incorporates physical, chemical and biological processes to treat and remove the contaminants. The main drawback of conventional activated sludge process is the huge production of excess sludge, which is an unavoidable byproduct. The treatment and disposal of excess sludge costs about 60% of the total operating cost. The ideal way to reduce excess sludge production during wastewater treatment is by preventing biomass formation within the aerobic treatment train rather than post treatment of the generated sludge. In the present investigation two different mechanical devices namely, Ultrasonic and Shear Gap homogenizers have been employed to disintegrate the aerobic biomass. This study is intended to restrict the multiplication of microbial biomass and at the same time degrade the organics present in wastewater by increasing the oxidative capacity of microorganisms. The disintegrability on biomass was determined by biochemical methods. Degree of inactivation provides the information on inability of microorganisms to consume oxygen upon disruption. The soluble COD quantifies the extent of release of intra cellular compounds. The participation of disintegrated microorganism in wastewater treatment process was carried out in two identical respirometeric reactors. The results show that Ultrasonic homogenizer is very effective in the disruption of microorganisms leading to a maximum microbial growth reduction of 27%. On the other hand, Shear gap homogenizer does not favor the sludge growth reduction rather it facilitates the growth. This study also shows that for better microbial growth reduction, floc size reduction alone is not sufficient but also microbial disruption is essential.

  5. DNA-based determination of microbial biomass suitable for frozen and alkaline soil samples

    NASA Astrophysics Data System (ADS)

    Semenov, Mikhail; Blagodatskaya, Evgeniya; Kogut, Boris; Kuzyakov, Yakov

    2015-04-01

    Microbial biomass is a sensitive indicator of changes due to soil management, long before other basic soil measures such as Corg or Ntot. Improvement of methods for determination of microbial biomass still remains relevant, and these methods should be correctly applicable for the soil samples being in various state. This study was designed to demonstrate the applicability of DNA-based determination of microbial biomass under conditions when the common basic approaches, namely chloroform fumigation-extraction (CFE) and substrate-induced respiration (SIR), are restricted by certain soil properties, experimental designs or research needs, e.g. in frozen, alkaline or carbonaceous soils. We compared microbial biomass determined by CFE, SIR and by DNA approaches in the range of neutral and slightly alkaline Chernozem and alkaline Calcisol of semi-arid climate. The samples of natural and agricultural ecosystems were taken throughout the soil profile from long-term static field experiments in the European part of Russia. Extraction and subsequent quantification of dsDNA revealed a strong agreement with SIR and CFE when analyzing the microbial biomass content in soils with pH below 8. The conversion factors (FDNA) from dsDNA to SIR-Cmic (5.10) and CFE-Cmic (4.41) were obtained by testing a range of the soil samples down to 1.5 m depth and indicated a good reproducibility of DNA-based estimations. In alkaline soils (pH > 8), CO2 retention due to alkaline pH and exchange with carbonates resulted in a strong underestimation of soil microbial biomass by SIR or even in the absence of any CO2 emission, especially at low absolute values of microbial biomass in subsoil. Correction of CO2 efflux by theoretical retention pH-dependent factors caused overestimation of SIR-biomass. In alkaline conditions, DNA extraction proved to be a reliable alternative for microbial biomass determination. Moreover, the DNA-based approach can serve as an excellent alternative enabling correct

  6. Soil pH determines microbial diversity and composition in the park grass experiment.

    PubMed

    Zhalnina, Kateryna; Dias, Raquel; de Quadros, Patricia Dörr; Davis-Richardson, Austin; Camargo, Flavio A O; Clark, Ian M; McGrath, Steve P; Hirsch, Penny R; Triplett, Eric W

    2015-02-01

    The Park Grass experiment (PGE) in the UK has been ongoing since 1856. Its purpose is to study the response of biological communities to the long-term treatments and associated changes in soil parameters, particularly soil pH. In this study, soil samples were collected across pH gradient (pH 3.6-7) and a range of fertilizers (nitrogen as ammonium sulfate, nitrogen as sodium nitrate, phosphorous) to evaluate the effects nutrients have on soil parameters and microbial community structure. Illumina 16S ribosomal RNA (rRNA) amplicon sequencing was used to determine the relative abundances and diversity of bacterial and archaeal taxa. Relationships between treatments, measured soil parameters, and microbial communities were evaluated. Clostridium, Bacteroides, Bradyrhizobium, Mycobacterium, Ruminococcus, Paenibacillus, and Rhodoplanes were the most abundant genera found at the PGE. The main soil parameter that determined microbial composition, diversity, and biomass in the PGE soil was pH. The most probable mechanism of the pH impact on microbial community may include mediation of nutrient availability in the soil. Addition of nitrogen to the PGE plots as ammonium sulfate decreases soil pH through increased nitrification, which causes buildup of soil carbon, and hence increases C/N ratio. Plant species richness and plant productivity did not reveal significant relationships with microbial diversity; however, plant species richness was positively correlated with soil microbial biomass. Plants responded to the nitrogen treatments with an increase in productivity and a decrease in the species richness.

  7. Assessment of Heterotrophic Growth Supported by Soluble Microbial Products in Anammox Biofilm using Multidimensional Modeling

    PubMed Central

    Liu, Yiwen; Sun, Jing; Peng, Lai; Wang, Dongbo; Dai, Xiaohu; Ni, Bing-Jie

    2016-01-01

    Anaerobic ammonium oxidation (anammox) is known to autotrophically convert ammonium to dinitrogen gas with nitrite as the electron acceptor, but little is known about their released microbial products and how these are relative to heterotrophic growth in anammox system. In this work, we applied a mathematical model to assess the heterotrophic growth supported by three key microbial products produced by bacteria in anammox biofilm (utilization associated products (UAP), biomass associated products (BAP), and decay released substrate). Both One-dimensional and two-dimensional numerical biofilm models were developed to describe the development of anammox biofilm as a function of the multiple bacteria–substrate interactions. Model simulations show that UAP of anammox is the main organic carbon source for heterotrophs. Heterotrophs are mainly dominant at the surface of the anammox biofilm with small fraction inside the biofilm. 1-D model is sufficient to describe the main substrate concentrations/fluxes within the anammox biofilm, while the 2-D model can give a more detailed biomass distribution. The heterotrophic growth on UAP is mainly present at the outside of anammox biofilm, their growth on BAP (HetB) are present throughout the biofilm, while the growth on decay released substrate (HetD) is mainly located in the inner layers of the biofilm. PMID:27273460

  8. Assessment of Heterotrophic Growth Supported by Soluble Microbial Products in Anammox Biofilm using Multidimensional Modeling.

    PubMed

    Liu, Yiwen; Sun, Jing; Peng, Lai; Wang, Dongbo; Dai, Xiaohu; Ni, Bing-Jie

    2016-01-01

    Anaerobic ammonium oxidation (anammox) is known to autotrophically convert ammonium to dinitrogen gas with nitrite as the electron acceptor, but little is known about their released microbial products and how these are relative to heterotrophic growth in anammox system. In this work, we applied a mathematical model to assess the heterotrophic growth supported by three key microbial products produced by bacteria in anammox biofilm (utilization associated products (UAP), biomass associated products (BAP), and decay released substrate). Both One-dimensional and two-dimensional numerical biofilm models were developed to describe the development of anammox biofilm as a function of the multiple bacteria-substrate interactions. Model simulations show that UAP of anammox is the main organic carbon source for heterotrophs. Heterotrophs are mainly dominant at the surface of the anammox biofilm with small fraction inside the biofilm. 1-D model is sufficient to describe the main substrate concentrations/fluxes within the anammox biofilm, while the 2-D model can give a more detailed biomass distribution. The heterotrophic growth on UAP is mainly present at the outside of anammox biofilm, their growth on BAP (HetB) are present throughout the biofilm, while the growth on decay released substrate (HetD) is mainly located in the inner layers of the biofilm. PMID:27273460

  9. Plant growth in Arabidopsis is assisted by compost soil-derived microbial communities.

    PubMed

    Carvalhais, Lilia C; Muzzi, Frederico; Tan, Chin-Hong; Hsien-Choo, Jin; Schenk, Peer M

    2013-01-01

    Plants in natural and agricultural environments are continuously exposed to a plethora of diverse microorganisms resulting in microbial colonization of roots and the rhizosphere. This process is believed to be accompanied by an intricate network of ongoing simultaneous interactions. In this study, we examined Arabidopsis thaliana roots and shoots in the presence or absence of whole microbial communities extracted from compost soil. The results show a clear growth promoting effect on Arabidopsis shoots in the presence of soil microbes compared to plants grown in microbe-free soil under otherwise identical conditions. Element analyses showed that iron uptake was facilitated by these mixed microbial communities which also led to transcriptional downregulation of genes required for iron transport. In addition, soil microbial communities suppressed the expression of marker genes involved in nitrogen uptake, oxidative stress/redox signaling, and salicylic acid (SA)-mediated plant defense while upregulating jasmonate (JA) signaling, cell wall organization/biosynthesis and photosynthesis. Multi-species analyses such as simultaneous transcriptional profiling of plants and their interacting microorganisms (metatranscriptomics) coupled to metagenomics may further increase our understanding of the intricate networks underlying plant-microbe interactions.

  10. Plant growth in Arabidopsis is assisted by compost soil-derived microbial communities

    PubMed Central

    Carvalhais, Lilia C.; Muzzi, Frederico; Tan, Chin-Hong; Hsien-Choo, Jin; Schenk, Peer M.

    2013-01-01

    Plants in natural and agricultural environments are continuously exposed to a plethora of diverse microorganisms resulting in microbial colonization of roots and the rhizosphere. This process is believed to be accompanied by an intricate network of ongoing simultaneous interactions. In this study, we examined Arabidopsis thaliana roots and shoots in the presence or absence of whole microbial communities extracted from compost soil. The results show a clear growth promoting effect on Arabidopsis shoots in the presence of soil microbes compared to plants grown in microbe-free soil under otherwise identical conditions. Element analyses showed that iron uptake was facilitated by these mixed microbial communities which also led to transcriptional downregulation of genes required for iron transport. In addition, soil microbial communities suppressed the expression of marker genes involved in nitrogen uptake, oxidative stress/redox signaling, and salicylic acid (SA)-mediated plant defense while upregulating jasmonate (JA) signaling, cell wall organization/biosynthesis and photosynthesis. Multi-species analyses such as simultaneous transcriptional profiling of plants and their interacting microorganisms (metatranscriptomics) coupled to metagenomics may further increase our understanding of the intricate networks underlying plant-microbe interactions. PMID:23847639

  11. Determination of the microbial origin of geosmin in Chinese liquor.

    PubMed

    Du, Hai; Xu, Yan

    2012-03-01

    Geosmin is the major cause of the common earthy off-flavor in light-aroma type Chinese liquor and, thus, highly detrimental to the aromatic quality. To find out its origin, the evolving process of geosmin in light-aroma type liquor making was monitored, and microbial analysis of Daqu containing geosmin was carried out. The results showed that geosmin appeared in all the fermented sorghums at different fermentation periods. About 57% geosmin in the fermented sorghums was distilled into liquor. During the distillation process, the peak of geosmin concentration appeared when alcohol content was 50-60% vol. More importantly, high geosmin content was observed during the Daqu-making process. Furthermore, five Streptomyces strains were isolated from different types of Daqu used for the fermentation of light-aroma type liquor. All of them produced only geosmin as the main volatile metabolite but no 2-methylisoborneol (2-MIB). It appears that microorganisms developing in Daqu are responsible for the presence of geosmin in liquor. Because of the relatively low detection threshold estimated at 110 ng/L in 46 vol % hydroalcoholic solution, the presence of geosmin in Daqu may pose a risk for Chinese liquor producers.

  12. Modeling microbial dynamics in heterogeneous environments: growth on soil carbon sources.

    PubMed

    Resat, Haluk; Bailey, Vanessa; McCue, Lee Ann; Konopka, Allan

    2012-05-01

    We have developed a new kinetic model to study how microbial dynamics are affected by the heterogeneity in the physical structure of the environment and by different strategies for hydrolysis of polymeric carbon. The hybrid model represented the dynamics of substrates and enzymes using a continuum representation and the dynamics of the cells were modeled individually. Individual-based biological model allowed us to explicitly simulate microbial diversity, and to model cell physiology as regulated via optimal allocation of cellular resources to enzyme synthesis, control of growth rate by protein synthesis capacity, and shifts to dormancy. This model was developed to study how microbial community functioning is influenced by local environmental conditions in heterogeneous media such as soil and by the functional attributes of individual microbes. Microbial community dynamics were simulated at two spatial scales: micro-pores that resemble 6-20-μm size portions of the soil physical structure and in 111-μm size soil aggregates with a random pore structure. Different strategies for acquisition of carbon from polymeric cellulose were investigated. Bacteria that express membrane-associated hydrolase had different growth and survival dynamics in soil pores than bacteria that release extracellular hydrolases. The kinetic differences suggested different functional niches for these two microbe types in cellulose utilization. Our model predicted an emergent behavior in which co-existence of membrane-associated hydrolase and extracellular hydrolases releasing organisms led to higher cellulose utilization efficiency and reduced stochasticity. Our analysis indicated that their co-existence mutually benefits these organisms, where basal cellulose degradation activity by membrane-associated hydrolase-expressing cells shortened the soluble hydrolase buildup time and, when enzyme buildup allowed for cellulose degradation to be fast enough to sustain exponential growth, all the

  13. Biohydrogen production in the suspended and attached microbial growth systems from waste pastry hydrolysate.

    PubMed

    Han, Wei; Hu, Yunyi; Li, Shiyi; Li, Feifei; Tang, Junhong

    2016-10-01

    Waste pastry was hydrolyzed by glucoamylase and protease which were obtained from solid state fermentation of Aspergillus awamori and Aspergillus oryzae to produce waste pastry hydrolysate. Then, the effects of hydraulic retention times (HRTs) (4-12h) on hydrogen production rate (HPR) in the suspended microbial growth system (continuous stirred tank reactor, CSTR) and attached microbial growth system (continuous mixed immobilized sludge reactor, CMISR) from waste pastry hydrolysate were investigated. The maximum HPRs of CSTR (201.8mL/(h·L)) and CMISR (255.3mL/(h·L)) were obtained at HRT of 6h and 4h, respectively. The first-order reaction could be used to describe the enzymatic hydrolysis of waste pastry. The carbon content of the waste pastry remained 22.8% in the undigested waste pastry and consumed 77.2% for carbon dioxide and soluble microbial products. To our knowledge, this is the first study which reports biohydrogen production from waste pastry. PMID:27416509

  14. Biohydrogen production in the suspended and attached microbial growth systems from waste pastry hydrolysate.

    PubMed

    Han, Wei; Hu, Yunyi; Li, Shiyi; Li, Feifei; Tang, Junhong

    2016-10-01

    Waste pastry was hydrolyzed by glucoamylase and protease which were obtained from solid state fermentation of Aspergillus awamori and Aspergillus oryzae to produce waste pastry hydrolysate. Then, the effects of hydraulic retention times (HRTs) (4-12h) on hydrogen production rate (HPR) in the suspended microbial growth system (continuous stirred tank reactor, CSTR) and attached microbial growth system (continuous mixed immobilized sludge reactor, CMISR) from waste pastry hydrolysate were investigated. The maximum HPRs of CSTR (201.8mL/(h·L)) and CMISR (255.3mL/(h·L)) were obtained at HRT of 6h and 4h, respectively. The first-order reaction could be used to describe the enzymatic hydrolysis of waste pastry. The carbon content of the waste pastry remained 22.8% in the undigested waste pastry and consumed 77.2% for carbon dioxide and soluble microbial products. To our knowledge, this is the first study which reports biohydrogen production from waste pastry.

  15. Microbial Communities in Biofilms of an Acid Mine Drainage Site Determined by Phospholipid Analysis

    NASA Astrophysics Data System (ADS)

    Das Gupta, S.; Fang, J.

    2008-12-01

    Phospholipids were extracted to determine the microbial biomass and community structure of biofims from an acid mine drainage (AMD) at the Green Valley coal mine site (GVS) in western Indiana. The distribution of specific biomarkers indicated the presence of a variety of microorganisms. Phototrophic microeukaryotes, which include Euglena mutabilis, algae, and cyanobacteria were the most dominant organisms, as indicated by the presence of polyunsaturated fatty acids. The presence of terminally methyl branched fatty acids suggests the presence of Gram-positive bacteria, and the mid-methyl branched fatty acids indicates the presence of sulfate-reducing bacteria. Fungi appear to also be an important part of the AMD microbial communities as suggested by the presence of 18:2 fatty acid. The acidophilic microeukaryotes Euglena dominated the biofilm microbial communities. These microorganisms appear to play a prominent role in the formation and preservation of stromatolites and in releasing oxygen to the atmosphere by oxygenic photosynthesis. Thus, the AMD environment comprises a host of microorganisms spreading out within the phylogenetic tree of life. Novel insights on the roles of microbial consortia in the formation and preservation of stromatolites and the production of oxygen through photosynthesis in AMD systems may have significance in the understanding of the interaction of Precambrian microbial communities in environments that produced microbially-mediated sedimentary structures and that caused oxygenation of Earth's atmosphere.

  16. Measurement of Microbial Activity and Growth in the Ocean by Rates of Stable Ribonucleic Acid Synthesis

    PubMed Central

    Karl, David M.

    1979-01-01

    A relatively simple and extremely sensitive technique for measuring rates of stable ribonucleic acid (RNA) synthesis was devised and applied to bacterial cultures and seawater samples. The procedure is based upon the uptake and incorporation of exogenous radiolabeled adenine into cellular RNA. To calculate absolute rates of synthesis, measurements of the specific radioactivity of the intracellular adenosine 5′-triphosphate pools (precursor to RNA) and of the total amount of radioactivity incorporated into stable cellular RNA per unit time are required. Since the rate of RNA synthesis is positively correlated with growth rate, measurements of RNA synthesis should be extremely useful for estimating and comparing the productivities of microbial assemblages in nature. Adenosine 5′-triphosphate, adenylate energy charge, and rates of stable RNA synthesis have been measured at a station located in the Columbian Basin of the Caribbean Sea. A subsurface peak in RNA synthesis (and therefore growth) was located within the dissolved oxygen minimum zone (450 m), suggesting in situ microbiological utilization of dissolved molecular oxygen. Calculations of the specific rates of RNA synthesis (i.e., RNA synthesis per unit of biomass) revealed that the middepth maximum corresponded to the highest specific rate of growth (420 pmol of adenine incorporated into RNA·day−1) of all depths sampled, including the euphotic zone. The existence of an intermediate depth zone of active microbial growth may be an important site for nutrient regeneration and may serve as a source of reduced carbon for mesopelagic and deep sea environments. PMID:16345461

  17. Quantum dots conjugated zinc oxide nanosheets: Impeder of microbial growth and biofilm

    NASA Astrophysics Data System (ADS)

    Patil, Rajendra; Gholap, Haribhau; Warule, Sambhaji; Banpurkar, Arun; Kulkarni, Gauri; Gade, Wasudeo

    2015-01-01

    The grieving problem of the 21st century has been the antimicrobial resistance in pathogenic microorganisms to conventional antibiotics. Therefore, developments of novel antibacterial materials which effectively inhibit or kill such resistant microorganisms have become the need of the hour. In the present study, we communicate the synthesis of quantum dots conjugated zinc oxide nanostructures (ZnO/CdTe) as an impeder of microbial growth and biofilm. The as-synthesized nanostructures were characterized by X-ray diffraction, ultraviolet-visible spectroscopy, photoluminescence spectroscopy, field emission scanning electron microscopy and high resolution transmission electron microscopy. The growth impedance property of ZnO and ZnO/CdTe on Gram positive organism, Bacillus subtilis NCIM 2063 and Gram negative, Escherichia coli NCIM 2931 and biofilm impedance activity in Pseudomonas aeruginosa O1 was found to occur due to photocatalytical action on the cell biofilm surfaces. The impedance in microbial growth and biofilm formation was further supported by ruptured appearances of cells and dettrered biofilm under field emission scanning electron and confocal laser scanning microscope. The ZnO/CdTe nanostructures array synthesized by hydrothermal method has an advantage of low growth temperature, and opportunity to fabricate inexpensive material for nano-biotechnological applications.

  18. Marine microbial ecology off East Antarctica (30 - 80°E): Rates of bacterial and phytoplankton growth and grazing by heterotrophic protists

    NASA Astrophysics Data System (ADS)

    Pearce, Imojen; Davidson, Andrew T.; Thomson, Paul G.; Wright, Simon; van den Enden, Rick

    2010-05-01

    Marine microbes (<200 μm) contribute most of the living matter and carbon flow in the Southern Ocean, yet the factors that control the composition and function of these microbial communities are not well understood. To determine the importance of microbial grazers in controlling microbial abundance, we determined microbial standing stocks and rates of herbivory and bacterivory in relation to the physical environment off East Antarctica during the Baseline Research on Oceanography, Krill and the Environment: West (BROKE-West) survey, which covered waters from the Polar Front to the coast between 30 and 80°E. Concentrations of heterotrophic nanoflagellates (HNF) (˜2 to 20 μm), microzooplankton (˜20 to 200 μm), bacteria, and chlorophyll a (Chl a) were determined and the growth and grazing mortality of phytoplankton and bacteria were estimated using the grazing dilution technique at 22 sites along the survey. Results showed that microzooplankton and HNF consumed on average 52% of bacterial production d -1 and 62% primary production d -1 but consumed >100% d -1 at the western ice-edge sites. Rates of bacterivory ranged from 0.4 - 2.6 d -1 and were correlated with bacterial concentrations, bacterial growth rates and longitude. Rates were highest in the eastern-most part of the survey, which was sampled last, reflecting the transition along the successional continuum toward a respiration-based, senescent, microbial community. Rates of herbivory ranged from 0.3 to 2.4 d -1 and were correlated with concentrations of microzooplankton and HNF combined, rates of phytoplankton growth, and latitude. Rates were highest at southern ice edge sites where concentrations of prey (as represented by Chl a) and microzooplankton were also highest. Cluster analysis of the concentrations of marine microbes and their rates of growth and grazing mortality identified 5 groups of sample sites that conveniently summarised the variability in the composition and function of the microbial

  19. Chemical diversity of microbial volatiles and their potential for plant growth and productivity

    PubMed Central

    Kanchiswamy, Chidananda Nagamangala; Malnoy, Mickael; Maffei, Massimo E.

    2015-01-01

    Microbial volatile organic compounds (MVOCs) are produced by a wide array of microorganisms ranging from bacteria to fungi. A growing body of evidence indicates that MVOCs are ecofriendly and can be exploited as a cost-effective sustainable strategy for use in agricultural practice as agents that enhance plant growth, productivity, and disease resistance. As naturally occurring chemicals, MVOCs have potential as possible alternatives to harmful pesticides, fungicides, and bactericides as well as genetic modification. Recent studies performed under open field conditions demonstrate that efficiently adopting MVOCs may contribute to sustainable crop protection and production. We review here the chemical diversity of MVOCs by describing microbial–plants and microbial–microbial interactions. Furthermore, we discuss MVOCs role in inducing phenotypic plant responses and their potential physiological effects on crops. Finally, we analyze potential and actual limitations for MVOC use and deployment in field conditions as a sustainable strategy for improving productivity and reducing pesticide use. PMID:25821453

  20. Determinants of Growth Hormone Resistance in Malnutrition

    PubMed Central

    Fazeli, Pouneh K.; Klibanski, Anne

    2014-01-01

    States of under-nutrition are characterized by growth hormone resistance. Decreased total energy intake, as well as isolated protein-calorie malnutrition and isolated nutrient deficiencies result in elevated growth hormone levels and low levels of IGF-I. We review various states of malnutrition and a disease state characterized by chronic under-nutrition -- anorexia nervosa -- and discuss possible mechanisms contributing to the state of growth hormone resistance, including FGF-21 and SIRT1. We conclude by examining the hypothesis that growth hormone resistance is an adaptive response to states of under-nutrition, in order to maintain euglycemia and preserve energy. PMID:24363451

  1. Rumen degradable protein supply affects microbial efficiency in continuous culture and growth in steers.

    PubMed

    Brooks, M A; Harvey, R M; Johnson, N F; Kerley, M S

    2012-12-01

    We hypothesized that microbial efficiency and output from fermentation in the rumen would be optimized when peptide supply was balanced with peptide requirement of ruminal microflora. This study was conducted to measure response of varying rumen degradable peptide (RDPep) supply on ruminal fermentation characteristics and steer growth. A continuous culture experiment was conducted with diets formulated to achieve a predicted RDPep balance (RDPep supplied above RDPep required) of -0.30 to 1.45% CP with rumen degradable N (RDN) balance (RDN supplied above RDN required) above dietary ammonia-N requirement of microbes. Two additional treatments had RDPep balances of -0.30 and 0.78% CP with insufficient ammonia-N supply to meet microbial requirements. Single-flow fermenters (N = 24; n = 6) were inoculated with rumen fluid and maintained anaerobically at 39°C with a 0.06 h(-1) dilution rate. Inadequate RDN decreased OM digestion and microbial N flow, and increased rumen undegradable N (P < 0.01). Microbial efficiency decreased in RDN-deficient diets and was greatest when RDPep balance did not excessively exceed microbial requirement of RDPep predicted (P < 0.01). A growth study was conducted with 49 yearling, crossbred, Angus steers (initial BW 370 ± 34 kg). Animals were assigned to 1 of 4 treatment groups by BW and further divided into 3 pens with 4 steers per pen to achieve similar initial pen weights. Treatments consisted of 4 isonitrogenous diets balanced for RDN but varying in predicted RDPep balance (0.55%, -0.02%, -0.25%, and -0.65% CP). Animals were maintained on treatment for 70 d with individual BW taken on d 0, 1, 21, 42, 70, and 71. Final BW decreased linearly with decreasing RDPep (P = 0.05). Average daily gain and G:F displayed a quadratic effect with greater ADG and G:F at greater and lesser RDPep levels (P = 0.02). We concluded that balancing RDPep supply to predicted requirement improved fermentation efficiency and microbial output, which in turn

  2. Determination of carbon and nitrogen in microbial biomass of southern-Taiga soils by different methods

    NASA Astrophysics Data System (ADS)

    Makarov, M. I.; Malysheva, T. I.; Maslov, M. N.; Kuznetsova, E. Yu.; Menyailo, O. V.

    2016-06-01

    The results of methods for determining microbial biomass carbon vary in reproducibility among soils. The fumigation-extraction and substrate-induced respiration methods give similar results for Albic Luvisol and Gleyic Fluvisol, while the results of the rehydration method are reliably higher. In Histic Fluvisol, relatively similar results are obtained using the fumigation-extraction and rehydration methods, and the substrate-induced respiration method gives almost halved results. The seasonal dynamics of microbial biomass carbon also varies depending on the method used. The highest difference is typical for the warm period, when the concentrations found by the extraction and substrate-induced methods poorly agree between two out of three soils studied. The concentration of microbial biomass nitrogen is less sensitive to the analytical method: the differences between the results of the fumigation-extraction and rehydration methods are statistically insignificant in the all soils. To reveal stable relationships between the results of determining microbial carbon and the soil properties and analytical method, a large diversity of soils should be studied. This will allow for proposing of conversion factors for the recalculation of the obtained values to the concentrations of carbon and nitrogen in microbial biomass for different soils (or soil groups) and, hence, the more correct comparison of the results obtained by different methods.

  3. Biomechanical ordering and buckling due to microbial growth confined at oil-water interfaces

    NASA Astrophysics Data System (ADS)

    Juarez, Gabriel; Stocker, Roman

    2015-11-01

    Bacteria are unicellular organisms that often exist as densely populated, surface-associated communities. Bacteria are also environmental colloids and spontaneously attach and self-assemble at liquid-liquid interfaces. Here, we present results on the growth dynamics of individual rod-shaped bacteria confined to finite oil-water interfaces of varying curvature. Through experiments using microfluidic chambers and time-lapse microscopy, we study the formation of macroscopic structures observed as adsorbed bacteria grow, divide, and self-assemble in a nematic phase due to biomechanical interactions. The continued growth at the interface leads to a jammed monolayer of cells, which then causes the interface to buckle and undergo large deformations including wrinkling and tubulation. These observations highlight the interplay between physical environment, such as confinement and interface curvature, and active biological processes, such as growth, at the scale of individual agents and shape our understanding of macroscale processes such as microbial degradation of oil in the ocean.

  4. Development of a competition model for microbial growth in mixed culture.

    PubMed

    Fujikawa, Hiroshi; Munakata, Kanako; Sakha, Mohammad Z

    2014-01-01

    A novel competition model for describing bacterial growth in mixed culture was developed in this study. Several model candidates were made with our logistic growth model that precisely describes the growth of a monoculture of bacteria. These candidates were then evaluated for the usefulness in describing growth of two competing species in mixed culture using Staphylococcus aureus, Escherichia coli, and Salmonella. Bacterial cells of two species grew at initial doses of 10(3), 10(4), and 10(5) CFU/g at 28ºC. Among the candidates, a model where the Lotka-Volterra model, a general competition model in ecology, was incorporated as a new term in our growth model was the best for describing all types of growth of two competitors in mixed culture. Moreover, the values for the competition coefficient in the model were stable at various combinations of the initial populations of the species. The Baranyi model could also successfully describe the above types of growth in mixed culture when it was coupled with the Gimenez and Dalgaard model. However, the values for the competition coefficients in the competition model varied with the conditions. The present study suggested that our model could be a basic model for describing microbial competition.

  5. Development of a competition model for microbial growth in mixed culture.

    PubMed

    Fujikawa, Hiroshi; Munakata, Kanako; Sakha, Mohammad Z

    2014-01-01

    A novel competition model for describing bacterial growth in mixed culture was developed in this study. Several model candidates were made with our logistic growth model that precisely describes the growth of a monoculture of bacteria. These candidates were then evaluated for the usefulness in describing growth of two competing species in mixed culture using Staphylococcus aureus, Escherichia coli, and Salmonella. Bacterial cells of two species grew at initial doses of 10(3), 10(4), and 10(5) CFU/g at 28ºC. Among the candidates, a model where the Lotka-Volterra model, a general competition model in ecology, was incorporated as a new term in our growth model was the best for describing all types of growth of two competitors in mixed culture. Moreover, the values for the competition coefficient in the model were stable at various combinations of the initial populations of the species. The Baranyi model could also successfully describe the above types of growth in mixed culture when it was coupled with the Gimenez and Dalgaard model. However, the values for the competition coefficients in the competition model varied with the conditions. The present study suggested that our model could be a basic model for describing microbial competition. PMID:24975409

  6. GEOELECTRICAL EVIDENCE OF MICROBIAL DEGRADATION OF DIESEL CONTAMINATED SEDIMENTS

    EPA Science Inventory

    The alteration of physical properties by microbial activity in petroleum contaminated sediments was investigated using geophysical techniques in laboratory column experiments. Microbial population growth was determined by the Most Probable Number technique (MPN), community dynami...

  7. Long-term tracking of microbial survivability and growth in a controlled environment

    NASA Astrophysics Data System (ADS)

    Sutandar, Andiyanto; Abdiel Foo, Jong Yong; Lim, Chu Sing; Hsu, Li-Yang

    2008-04-01

    The ecological and histological study of a microbial population in a given environment provides important information leading to its survivability and growth. Current standard laboratory practices adopt culture on a medium housed in an incubated environment. However, large numbers of cultures are usually required to investigate the effects of variations in parametric conditions on the microbes. This can result in a high use of resources such as consumables and man-hours. Automated systems that are able to replenish fresh nutrients and extract metabolic waste for long-term monitoring are also limited. In this study, a system capable of real-time monitoring of microbe survival and providing a suitable environment for their growth is presented. Housed within its structure is a customized chamber with temperature control, pH regulation, nutrient providence and metabolic waste removal functions. To assess the reliability of the system, five sets of Staphylococcus aureus ATCC 29213 strains are cultured and monitored continuously for 96 consecutive hours. The survival and growth of the pathogens are verified by standard laboratory techniques such as viable plate count after each successive 24 h of monitoring. The findings herein suggest that the system is able to monitor the microbial population with minimal human intervention and can be a valuable long-term tracking tool.

  8. The determinants of HMO enrollment and growth.

    PubMed Central

    Goldberg, L G; Greenberg, W

    1981-01-01

    This paper analyzes why HMO enrollment and growth have varied greatly among states. Using Tobit analysis, a number of variables are related to state HMO market share in 1976 and the change in HMO market share from 1966 to 1976. Higher hospital costs and mobile populations are shown to have encouraged HMO development. There is some evidence that the extent of unionization and the presence of group practices encourages HMO enrollment and growth. Legal restrictions on HMO development imposed at the state level appear to have had little effect upon HMOs. In particular, certificate-of-need laws have not impeded HMO enrollment and growth. Consequently, our results suggest that the enrollment and growth of HMOs respond more to impersonal market and demographic conditions than to certain legal restrictions. PMID:7327943

  9. The determinants of HMO enrollment and growth.

    PubMed

    Goldberg, L G; Greenberg, W

    1981-01-01

    This paper analyzes why HMO enrollment and growth have varied greatly among states. Using Tobit analysis, a number of variables are related to state HMO market share in 1976 and the change in HMO market share from 1966 to 1976. Higher hospital costs and mobile populations are shown to have encouraged HMO development. There is some evidence that the extent of unionization and the presence of group practices encourages HMO enrollment and growth. Legal restrictions on HMO development imposed at the state level appear to have had little effect upon HMOs. In particular, certificate-of-need laws have not impeded HMO enrollment and growth. Consequently, our results suggest that the enrollment and growth of HMOs respond more to impersonal market and demographic conditions than to certain legal restrictions.

  10. Soil microbial biomass and root growth in Bt and non-Bt cotton

    NASA Astrophysics Data System (ADS)

    Tan, D. K. Y.; Broughton, K.; Knox, O. G.; Hulugalle, N. R.

    2012-04-01

    The introduction of transgenic Bacillus thuringiensis (Bt) cotton (Gossypium hirsutum L.) has had a substantial impact on pest management in the cotton industry. While there has been substantial research done on the impact of Bt on the above-ground parts of the cotton plant, less is known about the effect of Bt genes on below ground growth of cotton and soil microbial biomass. The aim of this research was to test the hypothesis that Bt [Sicot 80 BRF (Bollgard II Roundup Ready Flex®)] and non-Bt [Sicot 80 RRF (Roundup Ready Flex®)] transgenic cotton varieties differ in root growth and root turnover, carbon indices and microbial biomass. A field experiment was conducted in Narrabri, north-western NSW. The experimental layout was a randomised block design and used minirhizotron and core break and root washing methods to measure cotton root growth and turnover during the 2008/09 season. Root growth in the surface 0-0.1 m of the soil was measured using the core break and root washing methods, and that in the 0.1 to 1 m depth was measured with a minirhizotron and an I-CAP image capture system. These measurements were used to calculate root length per unit area, root carbon added to the soil through intra-seasonal root death, carbon in roots remaining at the end of the season and root carbon potentially added to the soil. Microbial biomass was also measured using the ninhydrin reactive N method. Root length densities and length per unit area of non-Bt cotton were greater than Bt cotton. There were no differences in root turnover between Bt and non-Bt cotton at 0-1 m soil depth, indicating that soil organic carbon stocks may not be affected by cotton variety. Cotton variety did not have an effect on soil microbial biomass. The results indicate that while there are differences in root morphology between Bt and non-Bt cotton, these do not change the carbon turnover dynamics in the soil.

  11. Total soil DNA quantification as an alternative microbial biomass determination approach

    NASA Astrophysics Data System (ADS)

    Semenov, Mikhail

    2015-04-01

    Many studies on geographically widespread soils from arctic permafrost to arid and tropical soils, as well as those studies on extreme events, such as freezing-thawing and drying-rewetting of soils, require immediate freezing of soil after sampling. The two common basic approaches, such as chloroform fumigation-extraction (CFE) and substrate-induced respiration (SIR), however, are not applicable in frozen or dry soil samples due to a partial destruction of microbial cells during freezing-thawing and drying-rewetting. This calls for approaches enabling correct estimation of microbial biomass in frozen or dried soil samples. This study was aimed to compare commonly used SIR and CFE techniques with total soil DNA quantification and demonstrate the applicability of DNA-based determination of microbial biomass in carbonate-containing, slightly (Chernozem) and strongly alkaline (Calcisol) soils of semi-arid climates. The samples of natural and agricultural ecosystems were taken throughout the soil profile from long-term static field experiments in the European part of Russia. The linear regression between SIR-Cmic and total soil dsDNA for the Chernozem showed very strong correlation. From the regression equation, the conversion factor of 5.10 with R2 = 0.96 was obtained. The effect of CO2 retention at alkaline pH (>8) and low microbial biomass-C resulted in an inability to obtain any SIR-CO2 release at deeper horizons of Calcisol, i.e. the CO2 retention potential was higher that the CO2 evolution. As a consequence, the values of SIR-Cmic of Calcisol at the horizons with pH > 8.0 were strongly underestimated (by a factor of 2-3). This smoothed the differences in Cmic between soil horizons. Nevertheless, reliable dsDNA values obtained for these soils demonstrated well-pronounced changes in microbial biomass within soil profile. The CFE and DNA-based approaches showed a good correspondence, with R2 = 0.96 for both soil types. The CFE-Cmic to DNA-Cmic factor of 0

  12. A Bayesian approach to analyzing phenotype microarray data enables estimation of microbial growth parameters.

    PubMed

    Gerstgrasser, Matthias; Nicholls, Sarah; Stout, Michael; Smart, Katherine; Powell, Chris; Kypraios, Theodore; Stekel, Dov

    2016-06-01

    Biolog phenotype microarrays (PMs) enable simultaneous, high throughput analysis of cell cultures in different environments. The output is high-density time-course data showing redox curves (approximating growth) for each experimental condition. The software provided with the Omnilog incubator/reader summarizes each time-course as a single datum, so most of the information is not used. However, the time courses can be extremely varied and often contain detailed qualitative (shape of curve) and quantitative (values of parameters) information. We present a novel, Bayesian approach to estimating parameters from Phenotype Microarray data, fitting growth models using Markov Chain Monte Carlo (MCMC) methods to enable high throughput estimation of important information, including length of lag phase, maximal "growth" rate and maximum output. We find that the Baranyi model for microbial growth is useful for fitting Biolog data. Moreover, we introduce a new growth model that allows for diauxic growth with a lag phase, which is particularly useful where Phenotype Microarrays have been applied to cells grown in complex mixtures of substrates, for example in industrial or biotechnological applications, such as worts in brewing. Our approach provides more useful information from Biolog data than existing, competing methods, and allows for valuable comparisons between data series and across different models. PMID:26762475

  13. A thermodynamically-based model for predicting microbial growth and community composition coupled to system geochemistry: Application to uranium bioreduction

    SciTech Connect

    Istok, Jonathan D.; Park, Melora M.; Michalsen, Mandy M.; Spain, A. M.; Krumholz, Lee R.; Liu, Chongxuan; McKinley, James P.; Long, Philip E.; Roden, Eric E.; Peacock, Aaron D.; Baldwin, Brett R.

    2010-04-01

    ‘Bioimmobilization’ of redox-sensitive heavy metals and radionuclides is being investigated as a way to remediate contaminated groundwater and sediments. In one approach, growth-limiting substrates are added to the subsurface to stimulate the activity of targeted groups of indigenous microorganisms and create conditions favorable for the microbially-mediated reductive precipitation (‘bioreduction’) of targeted contaminants. We present a theoretical framework for modeling this process that modifies conventional geochemical reaction path modeling to include thermodynamic descriptions for microbial growth and may be called biogeochemical reaction path modeling. In this approach, the actual microbial community is represented by a synthetic microbial community consisting of a collection of microbial groups; each with a unique growth equation that couples a specific pair of energy yielding redox reactions. The growth equations and their computed standard-state free energy yields are appended to the thermodynamic databasse used in conventional geochemical reaction path modeling, providing a direct coupling between chemical species participating in both microbial growth and geochemical reactions. To compute the biogeochemical reaction paths, growth substrates are added incrementally to a defined geochemical environment and the coupled equations are solved simultaneously to predict microbial biomass, community composition (i.e. the fraction of total biomass in each microbial group), and the aqueous and mineral composition of the system, including aqueous speciation and oxidation state of the targeted contaminants. The approach, with growth equations derived from the literature using well known bioenergetics principles, was used to predict the results of a laboratory microcosm experiment and an in situ field experiment that investigated the bioreduction of uranium. Predicted effects of ethanol or acetate addition on uranium concentration and speciation, major ion

  14. Complex conductivity response to microbial growth and biofilm formation on phenanthrene spiked medium

    NASA Astrophysics Data System (ADS)

    Albrecht, Remy; Gourry, Jean Christophe; Simonnot, Marie-Odile; Leyval, Corinne

    2011-11-01

    Several laboratory studies have recently demonstrated the utility of geophysical methods for the investigation of microbial-induced changes over contaminated sites. However, it remains difficult to distinguish the effects due to the new physical properties imparted by microbial processes, to bacterial growth, or to the development of bacterial biofilm. We chose to study the influence of biofilm formation on geophysical response using complex conductivity measurements (0.1-1000 Hz) in phenanthrene-contaminated media. Biotic assays were conducted with two phenanthrene (PHE) degrading bacterial strains: Burkholderia sp (NAH1), which produced biofilm and Stenophomonas maltophilia (MATE10), which did not, and an abiotic control. Results showed that bacterial densities for NAH1 and MATE10 strains continuously increased at the same rate during the experiment. However, the complex conductivity signature showed noticeable differences between the two bacteria, with a phase shift of 50 mrad at 4 Hz for NAH1, which produced biofilm. Biofilm volume was quantified by Scanning Confocal Laser Microscopy (SCLM). Significant correlations were established between phase shift decrease and biofilm volume for NAH1 assays. Results suggest that complex conductivity measurements, specifically phase shift, can be a useful indicator of biofilm formation inside the overall signal of microbial activity on contaminated sites.

  15. Activity and growth of microbial populations in pressurized deep-sea sediment and animal gut samples.

    PubMed

    Tabor, P S; Deming, J W; Ohwada, K; Colwell, R R

    1982-08-01

    Benthic animals and sediment samples were collected at deep-sea stations in the northwest (3,600-m depth) and southeast (4,300- and 5200-m depths) Atlantic Ocean. Utilization rates of [14C]glutamate (0.67 to 0.74 nmol) in sediment suspensions incubated at in situ temperatures and pressures (3 to 5 degrees C and 360, 430, or 520 atmospheres) were relatively slow, ranging from 0.09 to 0.39 nmol g-1 day-1, whereas rates for pressurized samples of gut suspensions varied widely, ranging from no detectable activity to a rapid rate of 986 nmol g-1 day-1. Gut flora from a holothurian specimen and a fish demonstrated rapid, barophilic substrate utilization, based on relative rates calculated for pressurized samples and samples held at 1 atm (101.325 kPa). Substrate utilization by microbial populations in several sediment samples was not inhibited by in situ pressure. Deep-sea pressures did not restrict growth, measured as doubling time, of culturable bacteria present in a northwest Atlantic sediment sample and in a gut suspension prepared from an abyssal scavenging amphipod. From the results of this study, it was concluded that microbial populations in benthic environments can demonstrate significant metabolic activity under deep-ocean conditions of temperature and pressure. Furthermore, rates of microbial activity in the guts of benthic macrofauna are potentially more rapid than in surrounding deep-sea sediments. PMID:6127054

  16. Turnover of microbial lipids in the deep biosphere and growth of benthic archaeal populations.

    PubMed

    Xie, Sitan; Lipp, Julius S; Wegener, Gunter; Ferdelman, Timothy G; Hinrichs, Kai-Uwe

    2013-04-01

    Deep subseafloor sediments host a microbial biosphere with unknown impact on global biogeochemical cycles. This study tests previous evidence based on microbial intact polar lipids (IPLs) as proxies of live biomass, suggesting that Archaea dominate the marine sedimentary biosphere. We devised a sensitive radiotracer assay to measure the decay rate of ([(14)C]glucosyl)-diphytanylglyceroldiether (GlcDGD) as an analog of archaeal IPLs in continental margin sediments. The degradation kinetics were incorporated in model simulations that constrained the fossil fraction of subseafloor IPLs and rates of archaeal turnover. Simulating the top 1 km in a generic continental margin sediment column, we estimated degradation rate constants of GlcDGD being one to two orders of magnitude lower than those of bacterial IPLs, with half-lives of GlcDGD increasing with depth to 310 ky. Given estimated microbial community turnover times of 1.6-73 ky in sediments deeper than 1 m, 50-96% of archaeal IPLs represent fossil signals. Consequently, previous lipid-based estimates of global subseafloor biomass probably are too high, and the widely observed dominance of archaeal IPLs does not rule out a deep biosphere dominated by Bacteria. Reverse modeling of existing concentration profiles suggest that archaeal IPL synthesis rates decline from around 1,000 pg⋅mL(-1) sediment⋅y(-1) at the surface to 0.2 pg⋅mL(-1)⋅y(-1) at 1 km depth, equivalent to production of 7 × 10(5) to 140 archaeal cells⋅mL(-1) sediment⋅y(-1), respectively. These constraints on microbial growth are an important step toward understanding the relationship between the deep biosphere and the carbon cycle.

  17. Carbon stabilization and microbial growth in acidic mine soils after addition of different amendments for soil reclamation

    NASA Astrophysics Data System (ADS)

    Zornoza, Raúl; Acosta, Jose; Ángeles Muñoz, María; Martínez-Martínez, Silvia; Faz, Ángel; Bååth, Erland

    2016-04-01

    The extreme soil conditions in metalliferous mine soils have a negative influence on soil biological activity and therefore on soil carbon estabilization. Therefore, amendments are used to increase organic carbon content and activate microbial communities. In order to elucidate some of the factors controlling soil organic carbon stabilization in reclaimed acidic mine soils and its interrelationship with microbial growth and community structure, we performed an incubation experiment with four amendments: pig slurry (PS), pig manure (PM) and biochar (BC), applied with and without marble waste (MW; CaCO3). Results showed that PM and BC (alone or together with MW) contributed to an important increment in recalcitrant organic C, C/N ratio and aggregate stability. Bacterial and fungal growths were highly dependent on pH and labile organic C. PS supported the highest microbial growth; applied alone it stimulated fungal growth, and applied with MW it stimulated bacterial growth. BC promoted the lowest microbial growth, especially for fungi, with no significant increase in fungal biomass. MW+BC increased bacterial growth up to values similar to PM and MW+PM, suggesting that part of the biochar was degraded, at least in short-term mainly by bacteria rather than fungi. PM, MW+PS and MW+PM supported the highest microbial biomass and a similar community structure, related with the presence of high organic C and high pH, with immobilization of metals and increased soil quality. BC contributed to improved soil structure, increased recalcitrant organic C, and decreased metal mobility, with low stimulation of microbial growth.

  18. Procedure for determining maximum sustainable power generated by microbial fuel cells.

    PubMed

    Menicucci, Joseph; Beyenal, Haluk; Marsili, Enrico; Veluchamy, Raajaraajan Angathevar; Demir, Goksel; Lewandowski, Zbigniew

    2006-02-01

    Power generated by microbial fuel cells is computed as a product of current passing through an external resistor and voltage drop across this resistor. If the applied resistance is very low, then high instantaneous power generated by the cell is measured, which is not sustainable; the cell cannot deliver that much power for long periods of time. Since using small electrical resistors leads to erroneous assessment of the capabilities of microbial fuel cells, a question arises: what resistor should be used in such measurements? To address this question, we have defined the sustainable power as the steady state of power delivery by a microbial fuel cell under a given set of conditions and the maximum sustainable power as the highest sustainable power that a microbial fuel cell can deliver under a given set of conditions. Selecting the external resistance that is associated with the maximum sustainable power in a microbial fuel cell (MFC) is difficult because the operator has limited influence on the main factors that control power generation: the rate of charge transfer at the current-limiting electrode and the potential established across the fuel cell. The internal electrical resistance of microbial fuel cells varies, and it depends on the operational conditions of the fuel cell. We have designed an empirical procedure to predict the maximum sustainable power that can be generated by a microbial fuel cell operated under a given set of conditions. Following the procedure, we change the external resistors incrementally, in steps of 500 omega every 10, 60, or 180 s and measure the anode potential, the cathode potential, and the cell current. Power generated in the microbial fuel cell that we were using was limited by the anodic current. The anodic potential was used to determine the condition where the maximum sustainable power is obtained. The procedure is simple, microbial fuel cells can be characterized within an hour, and the results of the measurements can serve

  19. Effect of temperature on microbial growth rate-mathematical analysis: the Arrhenius and Eyring-Polanyi connections.

    PubMed

    Huang, Lihan; Hwang, Andy; Phillips, John

    2011-10-01

    The objective of this work is to develop a mathematical model for evaluating the effect of temperature on the rate of microbial growth. The new mathematical model is derived by combination and modification of the Arrhenius equation and the Eyring-Polanyi transition theory. The new model, suitable for both suboptimal and the entire growth temperature ranges, was validated using a collection of 23 selected temperature-growth rate curves belonging to 5 groups of microorganisms, including Pseudomonas spp., Listeria monocytogenes, Salmonella spp., Clostridium perfringens, and Escherichia coli, from the published literature. The curve fitting is accomplished by nonlinear regression using the Levenberg-Marquardt algorithm. The resulting estimated growth rate (μ) values are highly correlated to the data collected from the literature (R(2) = 0.985, slope = 1.0, intercept = 0.0). The bias factor (B(f) ) of the new model is very close to 1.0, while the accuracy factor (A(f) ) ranges from 1.0 to 1.22 for most data sets. The new model is compared favorably with the Ratkowsky square root model and the Eyring equation. Even with more parameters, the Akaike information criterion, Bayesian information criterion, and mean square errors of the new model are not statistically different from the square root model and the Eyring equation, suggesting that the model can be used to describe the inherent relationship between temperature and microbial growth rates. The results of this work show that the new growth rate model is suitable for describing the effect of temperature on microbial growth rate. Practical Application:  Temperature is one of the most significant factors affecting the growth of microorganisms in foods. This study attempts to develop and validate a mathematical model to describe the temperature dependence of microbial growth rate. The findings show that the new model is accurate and can be used to describe the effect of temperature on microbial growth rate in foods.

  20. Microbial changes and growth of Listeria monocytogenes during chilled storage of brined shrimp (Pandalus borealis).

    PubMed

    Mejlholm, Ole; Kjeldgaard, Jette; Modberg, Anne; Vest, Mette Bohn; Bøknaes, Niels; Koort, Joanna; Björkroth, Johanna; Dalgaard, Paw

    2008-06-10

    Thirteen storage trials and ten challenge tests were carried out to examine microbial changes, spoilage and the potential growth of Listeria monocytogenes in brined shrimp (Pandalus borealis). Shrimp in brine as well as brined and drained shrimp in modified atmosphere packaging (MAP) were produced and studied. Different recipes were used to study the effect of preserving parameters (organic acids, pH and NaCl) on growth of microorganisms and shelf life at 7-8 degrees C or 12 degrees C. Particularly, brines with different concentrations of (i) benzoic, citric and sorbic acids or (ii) acetic, citric and lactic acids were studied. Furthermore, the effect of adding diacetate to brined shrimp was evaluated. A single batch of cooked and peeled shrimp was used to study both industrially and manually processed brined shrimp with respect to the effect of process hygiene on microbial changes and the shelf life of products. Concentrations of microorganisms on newly produced brined shrimp from an industrial scale processing line were 1.0-2.3 log (CFU g(-1)) higher than comparable concentrations in manually processed samples. This resulted in a substantially shorter shelf life and a more diverse spoilage microflora of the industrially processed brined shrimp. In addition, shelf life of brined shrimp was affected by the types and concentrations of organic acids and by the storage temperature as expected. The effect of MAP was less pronounced. Eighty-two isolates from the spoilage microflora of brined shrimp were identified and they included 53 lactic acid bacteria, 6 coagulase negative Staphylococcus spp., 18 Pseudomonas fluorescens and 5 yeast isolates. After storage at 7 degrees C, P. fluorescens, Enterococcus-like isolates, E. malodoratus, Carnobacterium maltaromaticum, coagulase negative Staphylococcus spp. and Lactobacillus sakei constituted the dominating microflora of shrimp in brines that contained benzoic, citric and sorbic acids as preservatives. L. sakei dominated the

  1. MediaDB: a database of microbial growth conditions in defined media.

    PubMed

    Richards, Matthew A; Cassen, Victor; Heavner, Benjamin D; Ajami, Nassim E; Herrmann, Andrea; Simeonidis, Evangelos; Price, Nathan D

    2014-01-01

    Isolating pure microbial cultures and cultivating them in the laboratory on defined media is used to more fully characterize the metabolism and physiology of organisms. However, identifying an appropriate growth medium for a novel isolate remains a challenging task. Even organisms with sequenced and annotated genomes can be difficult to grow, despite our ability to build genome-scale metabolic networks that connect genomic data with metabolic function. The scientific literature is scattered with information about defined growth media used successfully for cultivating a wide variety of organisms, but to date there exists no centralized repository to inform efforts to cultivate less characterized organisms by bridging the gap between genomic data and compound composition for growth media. Here we present MediaDB, a manually curated database of defined media that have been used for cultivating organisms with sequenced genomes, with an emphasis on organisms with metabolic network models. The database is accessible online, can be queried by keyword searches or downloaded in its entirety, and can generate exportable individual media formulation files. The data assembled in MediaDB facilitate comparative studies of organism growth media, serve as a starting point for formulating novel growth media, and contribute to formulating media for in silico investigation of metabolic networks. MediaDB is freely available for public use at https://mediadb.systemsbiology.net. PMID:25098325

  2. The inhibitory effects of silver nanoparticles, silver ions, and silver chloride colloids on microbial growth.

    PubMed

    Choi, Okkyoung; Deng, Kathy Kanjun; Kim, Nam-Jung; Ross, Louis; Surampalli, Rao Y; Hu, Zhiqiang

    2008-06-01

    Emerging nanomaterials are of great concern to wastewater treatment utilities and the environment. The inhibitory effects of silver nanoparticles (Ag NPs) and other important Ag species on microbial growth were evaluated using extant respirometry and an automatic microtiter fluorescence assay. Using autotrophic nitrifying organisms from a well-controlled continuously operated bioreactor, Ag NPs (average size=14+/-6 nm), Ag(+) ions (AgNO(3)), and AgCl colloids (average size=0.25 microm), all at 1mg/L Ag, inhibited respiration by 86+/-3%, 42+/-7%, and 46+/-4%, respectively. Based on a prolonged microtiter assay, at about 0.5mg/L Ag, the inhibitions on the growth of Escherichia coli PHL628-gfp by Ag NPs, Ag(+) ions, and AgCl colloids were 55+/-8%, 100%, and 66+/-6%, respectively. Cell membrane integrity was not compromised under the treatment of test Ag species by using a LIVE/DEAD Baclight bacterial viability assay. However, electron micrographs demonstrated that Ag NPs attached to the microbial cells, probably causing cell wall pitting. The results suggest that nitrifying bacteria are especially susceptible to inhibition by Ag NPs, and the accumulation of Ag NPs could have detrimental effects on the microorganisms in wastewater treatment.

  3. Microbial diversity determines the invasion of soil by a bacterial pathogen

    PubMed Central

    van Elsas, Jan Dirk; Chiurazzi, Mario; Mallon, Cyrus A.; Elhottovā, Dana; Krištůfek, Václav; Salles, Joana Falcão

    2012-01-01

    Natural ecosystems show variable resistance to invasion by alien species, and this resistance can relate to the species diversity in the system. In soil, microorganisms are key components that determine life support functions, but the functional redundancy in the microbiota of most soils has long been thought to overwhelm microbial diversity–function relationships. We here show an inverse relationship between soil microbial diversity and survival of the invading species Escherichia coli O157:H7, assessed by using the marked derivative strain T. The invader's fate in soil was determined in the presence of (i) differentially constructed culturable bacterial communities, and (ii) microbial communities established using a dilution-to-extinction approach. Both approaches revealed a negative correlation between the diversity of the soil microbiota and survival of the invader. The relationship could be explained by a decrease in the competitive ability of the invader in species-rich vs. species-poor bacterial communities, reflected in the amount of resources used and the rate of their consumption. Soil microbial diversity is a key factor that controls the extent to which bacterial invaders can establish. PMID:22232669

  4. Determining the safety of microbial cultures for consumption by humans and animals.

    PubMed

    Pariza, Michael W; Gillies, Kevin O; Kraak-Ripple, Sarah F; Leyer, Gregory; Smith, Amy B

    2015-10-01

    Fermented foods and feeds have been consumed for millennia, and microorganisms isolated from traditional fermentations have been used as probiotics. There is interest in developing new microbial cultures for these uses, but to date safety evaluation procedures have only been discussed in general terms. We propose a comprehensive approach for determining the safety of microbial cultures that lack an established history of safe use for their intended new applications. Three scenarios are considered: (1) substantially increased exposure to a culture that has an established record of safety in a more limited application; (2) a new strain without a history of safe use that was isolated from a food or feed that has a history of safe use; and (3) a new strain isolated from a non-food or non-feed source. Our safety evaluation process is based on scientific procedures and is in the form of a decision tree composed of 13 questions. Our decision tree for determining the safety of microbial cultures for consumption by humans or animals is modeled on previous decision trees that are used worldwide to evaluate the safety of microbial enzymes for use in human food or animal feed.

  5. Microbial biodiversity in cheese consortia and comparative Listeria growth on surfaces of uncooked pressed cheeses.

    PubMed

    Callon, Cécile; Retureau, Emilie; Didienne, Robert; Montel, Marie-Christine

    2014-03-17

    The study set out to determine how changes in the microbial diversity of a complex antilisterial consortium from the surface of St-Nectaire cheese modify its antilisterial activities. On the basis of the microbial composition of a natural complex consortium named TR15 (Truefood consortium 15), three new consortia of different species and strain compositions were defined: TR15-SC (58 isolates from TR15 collection), TR15-M (pools of isolates from selective counting media) and TR15-BHI (pools of isolates from BHI medium). Their antilisterial activities on the surfaces of uncooked pressed cheese made with pasteurised milk were compared with the activity of complex consortium TR15 and a control cheese inoculated only with starter culture (Streptococcus thermophilus, Lactobacillus delbrueckii). The natural consortium TR15 was the most inhibitory, followed by reconstituted consortium TR15-BHI. The dynamics of the cheese rind microbial flora were monitored by counting on media and by isolate identification using 16S rDNA sequencing and direct 16S rDNA Single Strand Conformation Polymorphism analysis. The combination of these methods showed that rind with natural consortium TR15 had greater microbial diversity and different microbial dynamics than cheese rinds with reconstituted consortia. Cheese rind with the natural consortium showed higher citrate consumption and the highest concentrations of lactic and acetic acids, connected with high levels of lactic acid bacteria such as Carnobacterium maltaromaticum, Vagococcus fluvialis, Enterococcus gilvus, Leuconostoc mesenteroides, Brochothrix thermosphacta and Lactococcus lactis, ripening bacteria such as Arthrobacter nicotianae/arilaitensis, and Gram negative bacteria (Pseudomonas psychrophila and Enterobacter spp.). The highest L. monocytogenes count was on rind with TR15-M and was positively associated with the highest pH value, high succinic and citric acid contents, and the highest levels of Marinilactibacillus

  6. The influence of microbial associations on germination of wheat seeds and growth of seedlings under impact of zinc salts

    NASA Astrophysics Data System (ADS)

    Somova, L. A.; Pechurkin, N. S.

    2009-04-01

    The life support systems (LSS) for long-term missions are to use cycling-recycling systems, including biological recycling. Higher plants are the traditional regenerator of air and producer of food. They should be used in many successive generations of their reproduction in LSS. Studies of influence of microbial associations on germination of wheat seeds and on growth of seedlings under impact of heavy metals are necessary because of migration of heavy metals in LSS. Microbial associations are able to stimulate growth of plants, to protect them from pathogenic organisms and from toxicity of heavy metal salts. The goal of this work was to investigate effect of microbial associations on the germination of wheat seeds and on the growth of seedlings under impact of different concentrations of ZnSO4. The results of investigations showed that:Zinc salt had an adverse effect on germination of wheat seeds, beginning with concentrations of 8 MPC (Maximum Permissible Concentration) and higher.Microbial associations (concentrations -104 to 107 cells/ml) were able to decrease (partly or completely) the adverse effect of ZnSO4 on germination of wheat seeds.Concentrations (104-107 cells/ml) of microbial associations were able to decrease partly the adverse effect of zinc salts (intervals: from 1 to 32 MP?) on the growth and development of wheat plantlets during heterotrophic phase.The root system of plants was more sensitive to the adverse effect of ZnSO4 than shoots of plants.

  7. Development and characterization of a novel immobilized microbial membrane for rapid determination of biochemical oxygen demand load in industrial waste-waters.

    PubMed

    Rastogi, Shikha; Kumar, Anil; Mehra, N K; Makhijani, S D; Manoharan, A; Gangal, V; Kumar, Rita

    2003-01-01

    The rapid determination of waste-water quality of waste-water treatment plants in terms of pollutional strength, i.e. biochemical oxygen demand (BOD) is difficult or even impossible using the chemical determination method. The present study reports the determination of BOD within minutes using microbial BOD sensors, as compared to the 5-day determination using the conventional method. Multiple criteria establish the basis for the development of a BOD biosensor useful for rapid and reliable BOD estimation in industrial waste-waters. Of these, preparation of a suitable novel immobilized microbial membrane used in conjunction with an apt transducer is discussed. As a result, a microbial biosensor based on a formulated, synergistic, pre-tested microbial consortium has been developed for the measurement of BOD load of various industrial waste-waters. The sensor showed maximum response in terms of current difference, when a cell concentration of 2.25 x 10(10) CFU, harvested in their log phase of growth were utilized for microbial membrane construction. The sensor showed a stability of 180 days when the prepared membranes were stored at a temperature of 4 degrees C in 50 mM phosphate buffer of pH 6.8. The reusability of the immobilized membranes was up to 200 cycles without appreciable loss of their response characteristics. A linear relationship between the current change and a glucose-glutamic acid (GAA) concentration up to 60 mg l(-1) was observed (r=0.999). The lower detection limit was 1.0 mg l(-1) BOD. The sensor response was reproducible within +/-5% of the mean in a series of ten samples having 44 mg l(-1) BOD using standard a GGA solution. When used for the BOD estimation of industrial waste-waters, a relatively good agreement was found between the two methods, i.e. 5-day BOD and that measured by the developed microbial sensor. PMID:12445441

  8. Impact of metabolism and growth phase on the hydrogen isotopic composition of microbial fatty acids

    PubMed Central

    Heinzelmann, Sandra M.; Villanueva, Laura; Sinke-Schoen, Danielle; Sinninghe Damsté, Jaap S.; Schouten, Stefan; van der Meer, Marcel T. J.

    2015-01-01

    Microorganisms are involved in all elemental cycles and therefore it is important to study their metabolism in the natural environment. A recent technique to investigate this is the hydrogen isotopic composition of microbial fatty acids, i.e., heterotrophic microorganisms produce fatty acids enriched in deuterium (D) while photoautotrophic and chemoautotrophic microorganisms produce fatty acids depleted in D compared to the water in the culture medium (growth water). However, the impact of factors other than metabolism have not been investigated. Here, we evaluate the impact of growth phase compared to metabolism on the hydrogen isotopic composition of fatty acids of different environmentally relevant microorganisms with heterotrophic, photoautotrophic and chemoautotrophic metabolisms. Fatty acids produced by heterotrophs are enriched in D compared to growth water with εlipid/water between 82 and 359‰ when grown on glucose or acetate, respectively. Photoautotrophs (εlipid/water between −149 and −264‰) and chemoautotrophs (εlipid/water between −217 and −275‰) produce fatty acids depleted in D. Fatty acids become, in general, enriched by between 4 and 46‰ with growth phase which is minor compared to the influence of metabolisms. Therefore, the D/H ratio of fatty acids is a promising tool to investigate community metabolisms in nature. PMID:26005437

  9. Impact of metabolism and growth phase on the hydrogen isotopic composition of microbial fatty acids.

    PubMed

    Heinzelmann, Sandra M; Villanueva, Laura; Sinke-Schoen, Danielle; Sinninghe Damsté, Jaap S; Schouten, Stefan; van der Meer, Marcel T J

    2015-01-01

    Microorganisms are involved in all elemental cycles and therefore it is important to study their metabolism in the natural environment. A recent technique to investigate this is the hydrogen isotopic composition of microbial fatty acids, i.e., heterotrophic microorganisms produce fatty acids enriched in deuterium (D) while photoautotrophic and chemoautotrophic microorganisms produce fatty acids depleted in D compared to the water in the culture medium (growth water). However, the impact of factors other than metabolism have not been investigated. Here, we evaluate the impact of growth phase compared to metabolism on the hydrogen isotopic composition of fatty acids of different environmentally relevant microorganisms with heterotrophic, photoautotrophic and chemoautotrophic metabolisms. Fatty acids produced by heterotrophs are enriched in D compared to growth water with εlipid/water between 82 and 359‰ when grown on glucose or acetate, respectively. Photoautotrophs (εlipid/water between -149 and -264‰) and chemoautotrophs (εlipid/water between -217 and -275‰) produce fatty acids depleted in D. Fatty acids become, in general, enriched by between 4 and 46‰ with growth phase which is minor compared to the influence of metabolisms. Therefore, the D/H ratio of fatty acids is a promising tool to investigate community metabolisms in nature. PMID:26005437

  10. Understanding the performance of sulfate reducing bacteria based packed bed reactor by growth kinetics study and microbial profiling.

    PubMed

    Dev, Subhabrata; Roy, Shantonu; Bhattacharya, Jayanta

    2016-07-15

    A novel marine waste extract (MWE) as alternative nitrogen source was explored for the growth of sulfate reducing bacteria (SRB). Variation of sulfate and nitrogen (MWE) showed that SRB growth follows an uncompetitive inhibition model. The maximum specific growth rates (μmax) of 0.085 and 0.124 h(-1) and inhibition constants (Ki) of 56 and 4.6 g/L were observed under optimized sulfate and MWE concentrations, respectively. The kinetic data shows that MWE improves the microbial growth by 27%. The packed bed bioreactor (PBR) under optimized sulfate and MWE regime showed sulfate removal efficiency of 62-66% and metals removal efficiency of 66-75% on using mine wastewater. The microbial community analysis using DGGE showed dominance of SRB (87-89%). The study indicated the optimum dosing of sulfate and cheap organic nitrogen to promote the growth of SRB over other bacteria.

  11. Understanding the performance of sulfate reducing bacteria based packed bed reactor by growth kinetics study and microbial profiling.

    PubMed

    Dev, Subhabrata; Roy, Shantonu; Bhattacharya, Jayanta

    2016-07-15

    A novel marine waste extract (MWE) as alternative nitrogen source was explored for the growth of sulfate reducing bacteria (SRB). Variation of sulfate and nitrogen (MWE) showed that SRB growth follows an uncompetitive inhibition model. The maximum specific growth rates (μmax) of 0.085 and 0.124 h(-1) and inhibition constants (Ki) of 56 and 4.6 g/L were observed under optimized sulfate and MWE concentrations, respectively. The kinetic data shows that MWE improves the microbial growth by 27%. The packed bed bioreactor (PBR) under optimized sulfate and MWE regime showed sulfate removal efficiency of 62-66% and metals removal efficiency of 66-75% on using mine wastewater. The microbial community analysis using DGGE showed dominance of SRB (87-89%). The study indicated the optimum dosing of sulfate and cheap organic nitrogen to promote the growth of SRB over other bacteria. PMID:27085153

  12. Increased plant productivity and decreased microbial respiratory C loss by plant growth-promoting rhizobacteria under elevated CO2

    PubMed Central

    Nie, Ming; Bell, Colin; Wallenstein, Matthew D.; Pendall, Elise

    2015-01-01

    Increased plant productivity and decreased microbial respiratory C loss can potentially mitigate increasing atmospheric CO2, but we currently lack effective means to achieve these goals. Soil microbes may play critical roles in mediating plant productivity and soil C/N dynamics under future climate scenarios of elevated CO2 (eCO2) through optimizing functioning of the root-soil interface. By using a labeling technique with 13C and 15N, we examined the effects of plant growth-promoting Pseudomonas fluorescens on C and N cycling in the rhizosphere of a common grass species under eCO2. These microbial inoculants were shown to increase plant productivity. Although strong competition for N between the plant and soil microbes was observed, the plant can increase its capacity to store more biomass C per unit of N under P. fluorescens addition. Unlike eCO2 effects, P. fluorescens inoculants did not change mass-specific microbial respiration and accelerate soil decomposition related to N cycling, suggesting these microbial inoculants mitigated positive feedbacks of soil microbial decomposition to eCO2. The potential to mitigate climate change by optimizing soil microbial functioning by plant growth-promoting Pseudomonas fluorescens is a prospect for ecosystem management. PMID:25784647

  13. Increased plant productivity and decreased microbial respiratory C loss by plant growth-promoting rhizobacteria under elevated CO2

    NASA Astrophysics Data System (ADS)

    Nie, Ming; Bell, Colin; Wallenstein, Matthew D.; Pendall, Elise

    2015-03-01

    Increased plant productivity and decreased microbial respiratory C loss can potentially mitigate increasing atmospheric CO2, but we currently lack effective means to achieve these goals. Soil microbes may play critical roles in mediating plant productivity and soil C/N dynamics under future climate scenarios of elevated CO2 (eCO2) through optimizing functioning of the root-soil interface. By using a labeling technique with 13C and 15N, we examined the effects of plant growth-promoting Pseudomonas fluorescens on C and N cycling in the rhizosphere of a common grass species under eCO2. These microbial inoculants were shown to increase plant productivity. Although strong competition for N between the plant and soil microbes was observed, the plant can increase its capacity to store more biomass C per unit of N under P. fluorescens addition. Unlike eCO2 effects, P. fluorescens inoculants did not change mass-specific microbial respiration and accelerate soil decomposition related to N cycling, suggesting these microbial inoculants mitigated positive feedbacks of soil microbial decomposition to eCO2. The potential to mitigate climate change by optimizing soil microbial functioning by plant growth-promoting Pseudomonas fluorescens is a prospect for ecosystem management.

  14. Increased plant productivity and decreased microbial respiratory C loss by plant growth-promoting rhizobacteria under elevated CO₂.

    PubMed

    Nie, Ming; Bell, Colin; Wallenstein, Matthew D; Pendall, Elise

    2015-03-18

    Increased plant productivity and decreased microbial respiratory C loss can potentially mitigate increasing atmospheric CO₂, but we currently lack effective means to achieve these goals. Soil microbes may play critical roles in mediating plant productivity and soil C/N dynamics under future climate scenarios of elevated CO₂ (eCO₂) through optimizing functioning of the root-soil interface. By using a labeling technique with (13)C and (15)N, we examined the effects of plant growth-promoting Pseudomonas fluorescens on C and N cycling in the rhizosphere of a common grass species under eCO₂. These microbial inoculants were shown to increase plant productivity. Although strong competition for N between the plant and soil microbes was observed, the plant can increase its capacity to store more biomass C per unit of N under P. fluorescens addition. Unlike eCO₂ effects, P. fluorescens inoculants did not change mass-specific microbial respiration and accelerate soil decomposition related to N cycling, suggesting these microbial inoculants mitigated positive feedbacks of soil microbial decomposition to eCO₂. The potential to mitigate climate change by optimizing soil microbial functioning by plant growth-promoting Pseudomonas fluorescens is a prospect for ecosystem management.

  15. Elemental Economy: microbial strategies for optimizing growth in the face of nutrient limitation

    PubMed Central

    Merchant, Sabeeha S.; Helmann, John D.

    2014-01-01

    Microorganisms play a dominant role in the biogeochemical cycling of nutrients. They are rightly praised for their facility at fixing both carbon and nitrogen into organic matter, and microbial driven processes have tangibly altered the chemical composition of the biosphere and its surrounding atmosphere. Despite their prodigious capacity for molecular transformations, microorganisms are powerless in the face of the immutability of the elements. Limitations for specific elements, either fleeting or persisting over eons, have left an indelible trace on microbial genomes, physiology, and their very atomic composition. We here review the impact of elemental limitation on microbes, with a focus on selected genetic model systems and representative microbes from the ocean ecosystem. Evolutionary adaptations that enhance growth in the face of persistent or recurrent elemental limitations are evident from genome and proteome analyses. These range from the extreme (such as dispensing with a requirement for a hard to obtain element) to the extremely subtle (changes in protein amino acid sequences that slightly, but significantly, reduce cellular carbon, nitrogen, or sulfur demand). One near universal adaptation is the development of sophisticated acclimation programs by which cells adjust their chemical composition in response to a changing environment. When specific elements become limiting, acclimation typically begins with an increased commitment to acquisition and a concomitant mobilization of stored resources. If elemental limitation persists, the cell implements austerity measures including elemental-sparing and elemental-recycling. Insights into these fundamental cellular properties have emerged from studies at many different levels; including ecology, biological oceanography, biogeochemistry, molecular genetics, genomics, and microbial physiology. Here, we present a synthesis of these diverse studies and attempt to discern some overarching themes. PMID:22633059

  16. Determinate Root Growth and Meristem Maintenance in Angiosperms

    PubMed Central

    Shishkova, S.; Rost, T. L.; Dubrovsky, J. G.

    2008-01-01

    Background The difference between indeterminate and determinate growth in plants consists of the presence or absence of an active meristem in the fully developed organ. Determinate root growth implies that the root apical meristem (RAM) becomes exhausted. As a consequence, all cells in the root tip differentiate. This type of growth is widely found in roots of many angiosperm taxa and might have evolved as a developmental adaptation to water deficit (in desert Cactaceae), or low mineral content in the soil (proteoid roots in various taxa). Scope and Conclusions This review considers the mechanisms of determinate root growth to better understand how the RAM is maintained, how it functions, and the cellular and genetic bases of these processes. The role of the quiescent centre in RAM maintenance and exhaustion will be analysed. During root ageing, the RAM becomes smaller and its organization changes; however, it remains unknown whether every root is truly determinate in the sense that its RAM becomes exhausted before senescence. We define two types of determinate growth: constitutive where determinacy is a natural part of root development; and non-constitutive where determinacy is induced usually by an environmental factor. Determinate root growth is proposed to include two phases: the indeterminate growth phase, when the RAM continuously produces new cells; and the termination growth phase, when cell production gradually decreases and eventually ceases. Finally, new concepts regarding stem cells and a stem cell niche are discussed to help comprehend how the meristem is maintained in a broad taxonomic context. PMID:17954472

  17. Populations of selected microbial and fungal species growing on the surface of rape seeds following treatment with desiccants or plant growth regulators.

    PubMed

    Frac, Magdalena; Jezierska-Tys, Stefania; Tys, Jerzy

    2010-01-01

    The aim of this study was to determine the effects of desiccants and plant growth regulators on selected microbial species affecting rape seeds, with special emphasis on the growth of fungi and identification of the genus and species composition. The experimental material in the study was seeds of winter rape cv. Californium that were collected from the field during combine harvest. The chemical agents applied, both desiccants and growth regulators, generally decreased the populations of bacteria occurring on the surface of rape seeds. The responses of fungi depended upon the type of agent applied and were manifested as either stimulation or inhibition of the growth of the fungal species. The fungi isolated from the surface of rape seeds were characteristic of those found in the field environment (Cladosporium and Penicillium) and typical for those present on the surface of rape seeds (Alternaria).

  18. Changing patterns of soiling and microbial growth on building stone in Oxford, England after implementation of a major traffic scheme.

    PubMed

    Thornbush, M; Viles, H

    2006-08-15

    Surfaces of freshly cut Bath limestone exposed along various roadsides before and after the reduction of traffic in the historical city centre of Oxford, England (following the Oxford Transport Strategy or OTS), presented an opportunity to investigate changes in soiling and fungal growth in relation to changing traffic pollution. Spectrophotometric data using an X-Rite SP68 sphere spectrophotometer provided quantitative information on soiling before and after the OTS. Scanning electron microscopy (SEM) provided a means to view and quantify the microbial inhabitants in detail, using a technique which registered and counted branching beaded structures. Results indicated that at Longwall Street soiling became more pronounced and microbial cover lower, with the reverse occurring at High Street where the greatest improvements in surface lightness were found. Other sites showed less clearcut responses in soiling and microbial growth. Overall, microbial growth was pronounced within hollows on stone surfaces before the OTS, with some signs of spreading of growths away from hollows after the OTS. A complex relationship between air pollution, soiling, and microfloral growths is revealed by the study which needs to be taken into account in soiling management strategies.

  19. Zebrafish and giant danio as models for muscle growth: determinate vs. indeterminate growth as determined by morphometric analysis.

    PubMed

    Biga, P R; Goetz, F W

    2006-11-01

    The zebrafish has become an important genetic model, but their small size makes them impractical for traditional physiological studies. In contrast, the closely related giant danio is larger and can be utilized for physiological studies that can also make use of the extensive zebrafish genomic resources. In addition, the giant danio and zebrafish appear to exhibit different growth types, indicating the potential for developing a comparative muscle growth model system. Therefore, the present study was conducted to compare and characterize the muscle growth pattern of zebrafish and giant danio. Morphometric analyses demonstrated that giant danio exhibit an increased growth rate compared with zebrafish, starting as early as 2 wk posthatch. Total myotome area, mean fiber area, and total fiber number all exhibited positive correlations with larvae length in giant danio but not in zebrafish. Morphometric analysis of giant danio and zebrafish larvae demonstrated faster, more efficient growth in giant danio larvae. Similar to larger teleosts, adult giant danio exhibited increased growth rates in response to growth hormone, suggesting that giant danio exhibit indeterminate growth. In contrast, adult zebrafish do not exhibit mosaic hyperplasia, nor do they respond to growth hormone, suggesting they exhibit determinate growth like mammals. These results demonstrate that giant danio and zebrafish can be utilized as a direct comparative model system for muscle growth studies, with zebrafish serving as a model organism for determinate growth and giant danio for indeterminate growth.

  20. Growth rate determinations from radiocarbon in bamboo corals (genus Keratoisis)

    NASA Astrophysics Data System (ADS)

    Farmer, Jesse R.; Robinson, Laura F.; Hönisch, Bärbel

    2015-11-01

    Radiocarbon (14C) measurements are an important tool for determining growth rates of bamboo corals, a cosmopolitan group of calcitic deep-sea corals. Published growth rate estimates for bamboo corals are highly variable, with potential environmental or ecological drivers of this variability poorly constrained. Here we systematically investigate the application of 14C for growth rate determinations in bamboo corals using 55 14C dates on the calcite and organic fractions of six bamboo corals (identified as Keratoisis sp.) from the western North Atlantic Ocean. Calcite 14C measurements on the distal surface of these corals and five previously published bamboo corals exhibit a strong one-to-one relationship with the 14C of dissolved inorganic carbon (DI14C) in ambient seawater (r2=0.98), confirming the use of Keratoisis sp. calcite 14C as a proxy for seawater 14C activity. Radial growth rates determined from 14C age-depth regressions, 14C plateau tuning and bomb 14C reference chronologies range from 12 to 78 μm y-1, in general agreement with previously published radiometric growth rates. We document potential biases to 14C growth rate determinations resulting from water mass variability, bomb radiocarbon, secondary infilling (ontogeny), and growth rate nonlinearity. Radial growth rates for Keratoisis sp. specimens do not correlate with ambient temperature, suggesting that additional biological and/or environmental factors may influence bamboo coral growth rates.

  1. Marine microbial ecology in the sub-Antarctic Zone: Rates of bacterial and phytoplankton growth and grazing by heterotrophic protists

    NASA Astrophysics Data System (ADS)

    Pearce, Imojen; Davidson, Andrew T.; Thomson, Paul G.; Wright, Simon; van den Enden, Rick

    2011-11-01

    The sub-Antarctic zone (SAZ) of the Southern Ocean is considered one of the largest sinks for atmospheric CO 2 and as such is an important region for climate change research. To determine the importance of micro- and nano-heterotrophs in controlling microbial abundance within this region, we determined microbial standing stocks and rates of herbivory and bacterivory in relation to changes in the water masses south of Tasmania. The SAZ-Sense ('Sensitivity of the sub-Antarctic zone to environmental change') cruise traversed the SAZ during mid-late austral summer and focussed on process stations to the southeast (45°S, 153°E) and southwest (46°S, 140°E) of Tasmania and at the Polar Front (54°S, 147°E). Growth and grazing mortality of phytoplankton and bacteria were estimated by the grazing dilution technique using seawater from 10 m depth at 15 sites along the survey, along with concentrations of heterotrophic nanoflagellates (HNF), microzooplankton, bacteria, cyanobacteria and size fractionated (pico-, nano- and micro-sized) chlorophyll a (Chl a). Rates of herbivory ranged from 0.12 to 1.39 d -1 and were highest in the north-eastern SAZ (NE-SAZ) where concentrations of prey (as indicated by Chl a) and microzooplankton were also highest. Rates of herbivory were correlated with total rates of phytoplankton growth, bacterial growth and concentrations of microzooplankton. On average 82%, 67% and 42% primary production d -1 was consumed by microzooplankton and HNF at process stations in the north-western SAZ (NW-SAZ), NE-SAZ and polar frontal zone (PFZ), respectively. In the NW-SAZ, grazing pressure was highest on the pico-sized Chl a fraction, whereas in the NE-SAZ, grazing pressure was more evenly distributed across all three size fractions of Chl a. Bacterivory removed 77%, 93% and 39% of bacterial production d -1 in the NW-SAZ, NE-SAZ and PFZ, respectively, and rates of bacterivory ranged from 0.12 to 1.03 d -1. Rates of bacterivory were highest in the NE

  2. Well constructions with inhibited microbial growth and methods of antimicrobial treatment in wells

    DOEpatents

    Lee, Brady D.; Dooley, Kirk J.

    2004-11-02

    The invention includes methods of inhibiting microbial growth in a well. A packing material containing a mixture of a first material and an antimicrobial agent is provided to at least partially fill a well bore. One or more access tubes are provided in an annular space around a casing within the well bore. The access tubes have a first terminal opening located at or above a ground surface and have a length that extends from the first terminal opening at least part of the depth of the well bore. The access tubes have a second terminal opening located within the well bore. An antimicrobial material is supplied into the well bore through the first terminal opening of the access tubes. The invention also includes well constructs.

  3. Coupling Microbial Growth with Nanoparticles: A Universal Strategy To Produce Functional Fungal Hyphae Macrospheres.

    PubMed

    Zhu, Wen-Kun; Cong, Huai-Ping; Guan, Qing-Fang; Yao, Wei-Tang; Liang, Hai-Wei; Wang, Wei; Yu, Shu-Hong

    2016-05-25

    Macroscale assembly of nanoscale building blocks is an intriguing way to translate the unique characteristics of individual nanoparticles into macroscopic materials. However, the lack of the efficient universal assembly strategy seriously hinders the possibility of macroscale architectures in practical applications. Herein, we develop a general, environment-friendly, and scalable microbial growth method for the construction of macroscopic composite assemblies with excellent mechanical strength by in situ integrating various types of nanoparticles into fungal hyphae (FH) macrospheres. Notably, the size of the FH-based composite spheres and the loading amount of the nanoparticles with different dimensions can be well tuned by controlling the cultivation time and the dosage of nanoparticles, respectively. Interestingly, bifunctional FH-based core-shell macrospheres can also be achieved by programmed assembling two different kinds of nanoparticles in the cultivation process. The produced multifunctional FH-based composite spheres exhibit wide potential applications in magnetic actuation, photothermal therapy, and contaminant adsorption, etc.

  4. Temperature dependence of metabolic rates for microbial growth, maintenance, and survival

    PubMed Central

    Price, P. Buford; Sowers, Todd

    2004-01-01

    Our work was motivated by discoveries of prokaryotic communities that survive with little nutrient in ice and permafrost, with implications for past or present microbial life in Martian permafrost and Europan ice. We compared the temperature dependence of metabolic rates of microbial communities in permafrost, ice, snow, clouds, oceans, lakes, marine and freshwater sediments, and subsurface aquifer sediments. Metabolic rates per cell fall into three groupings: (i) a rate, μg(T), for growth, measured in the laboratory at in situ temperatures with minimal disturbance of the medium; (ii) a rate, μm(T), sufficient for maintenance of functions but for a nutrient level too low for growth; and (iii) a rate, μs(T), for survival of communities imprisoned in deep glacial ice, subsurface sediment, or ocean sediment, in which they can repair macromolecular damage but are probably largely dormant. The three groups have metabolic rates consistent with a single activation energy of ≈110 kJ and that scale as μg(T):μm(T):μs(T) ≈ 106:103:1. There is no evidence of a minimum temperature for metabolism. The rate at -40°C in ice corresponds to ≈10 turnovers of cellular carbon per billion years. Microbes in ice and permafrost have metabolic rates similar to those in water, soil, and sediment at the same temperature. This finding supports the view that, far below the freezing point, liquid water inside ice and permafrost is available for metabolism. The rate μs(T) for repairing molecular damage by means of DNA-repair enzymes and protein-repair enzymes such as methyltransferase is found to be comparable to the rate of spontaneous molecular damage. PMID:15070769

  5. Temperature dependence of metabolic rates for microbial growth, maintenance, and survival.

    PubMed

    Price, P Buford; Sowers, Todd

    2004-03-30

    Our work was motivated by discoveries of prokaryotic communities that survive with little nutrient in ice and permafrost, with implications for past or present microbial life in Martian permafrost and Europan ice. We compared the temperature dependence of metabolic rates of microbial communities in permafrost, ice, snow, clouds, oceans, lakes, marine and freshwater sediments, and subsurface aquifer sediments. Metabolic rates per cell fall into three groupings: (i) a rate, microg(T), for growth, measured in the laboratory at in situ temperatures with minimal disturbance of the medium; (ii) a rate, microm(T), sufficient for maintenance of functions but for a nutrient level too low for growth; and (iii) a rate, micros(T), for survival of communities imprisoned in deep glacial ice, subsurface sediment, or ocean sediment, in which they can repair macromolecular damage but are probably largely dormant. The three groups have metabolic rates consistent with a single activation energy of approximately 110 kJ and that scale as microg(T):microm(T):micros(T) approximately 10(6):10(3):1. There is no evidence of a minimum temperature for metabolism. The rate at -40 degrees C in ice corresponds to approximately 10 turnovers of cellular carbon per billion years. Microbes in ice and permafrost have metabolic rates similar to those in water, soil, and sediment at the same temperature. This finding supports the view that, far below the freezing point, liquid water inside ice and permafrost is available for metabolism. The rate micros(T) for repairing molecular damage by means of DNA-repair enzymes and protein-repair enzymes such as methyltransferase is found to be comparable to the rate of spontaneous molecular damage.

  6. Microbial growth in dry grain food (Sunsik) beverages prepared with water, milk, soymilk, or honey-water.

    PubMed

    Jung, Jin-Ho; Lee, Sun-Young

    2010-05-01

    This study was conducted to investigate the growth of microorganisms, including pathogenic bacteria such as Cronobacter sakazakii and Bacillus cereus, in Sunsik beverages made of water, milk, soymilk, or honey-water during storage at room temperature. Prepared Sunsik beverages were stored at room temperature and the growth of total aerobic counts, Escherichia coli/coliforms, and yeast and mold were measured. Also, samples inoculated with a cocktail of C. sakazakii or B. cereus spores were stored at room temperature and their growths were determined during storage. Populations of total aerobic counts and coliforms significantly increased with increasing storage time at room temperature, which resulted in higher than 8 log and 7 log after 24 h in all samples except for the honey-water sample, respectively. Levels of total aerobic counts and coliforms were significantly lower in the honey-water sample than in the other samples after 6 and 9 h of storage, respectively. Initial populations of C. sakazakii and B. cereus ranged from 0 to 1 log CFU/mL, respectively, and these populations significantly increased with increasing storage time at room temperature. Therefore, populations of C. sakazakii and B. cereus were approximately 7 to 8 log CFU/mL after 24 h of storage. However, after 12 and 9 h of storage, there were significant differences in levels of C. sakazakii and B. cereus between the honey-water sample and the other samples, respectively. Based on these results, the addition of honey can inhibit microbial growth in Sunsik beverages; however, the best way to avoid pathogen infection would be to consume Sunsik beverages as soon as possible after preparation.

  7. Adenoma-linked barrier defects and microbial products drive IL-23/IL-17-mediated tumour growth

    PubMed Central

    Grivennikov, Sergei I.; Wang, Kepeng; Mucida, Daniel; Stewart, C. Andrew; Schnabl, Bernd; Jauch, Dominik; Taniguchi, Koji; Yu, Guann-Yi; Osterreicher, Christoph H.; Hung, Kenneth E.; Datz, Christian; Feng, Ying; Fearon, Eric R.; Oukka, Mohamed; Tessarollo, Lino; Coppola, Vincenzo; Yarovinsky, Felix; Cheroutre, Hilde; Eckmann, Lars; Trinchieri, Giorgio; Karin, Michael

    2013-01-01

    Approximately 2% of colorectal cancer is linked to pre-existing inflammation known as colitis-associated cancer, but most develops in patients without underlying inflammatory bowel disease. Colorectal cancer often follows a genetic pathway whereby loss of the adenomatous polyposis coli (APC) tumour suppressor and activation of β-catenin are followed by mutations in K-Ras, PIK3CA and TP53, as the tumour emerges and progresses1,2. Curiously, however, ‘inflammatory signature’ genes characteristic of colitis-associated cancer are also upregulated in colorectal cancer3,4. Further, like most solid tumours, colorectal cancer exhibits immune/inflammatory infiltrates5, referred to as ‘tumour elicited inflammation’6. Although infiltrating CD4+ TH1 cells and CD8+ cytotoxic T cells constitute a positive prognostic sign in colorectal cancer7,8, myeloid cells and T-helper interleukin (IL)-17-producing (TH17) cells promote tumorigenesis5,6, and a ‘TH17 expression signature’ in stage I/II colorectal cancer is associated with a drastic decrease in disease-free survival9. Despite its pathogenic importance, the mechanisms responsible for the appearance of tumour-elicited inflammation are poorly understood. Many epithelial cancers develop proximally to microbial communities, which are physically separated from immune cells by an epithelial barrier10. We investigated mechanisms responsible for tumour-elicited inflammation in a mouse model of colorectal tumorigenesis, which, like human colorectal cancer, exhibits upregulation of IL-23 and IL-17. Here we show that IL-23 signalling promotes tumour growth and progression, and development of a tumoural IL-17 response. IL-23 is mainly produced by tumour-associated myeloid cells that are likely to be activated by microbial products, which penetrate the tumours but not adjacent tissue. Both early and late colorectal neoplasms exhibit defective expression of several barrier proteins. We propose that barrier deterioration induced by

  8. Determination of the feasibility of using open path FTIR to monitor levels of 3-methylfuran and 1-octen-3-ol for the purpose of detecting microbial contamination in indoor environments

    SciTech Connect

    Olive, B.

    1996-03-01

    Studies have shown that the presence of microbial growth correlates with health complaints associated with sick building syndrome. Microbial growth may be found in damp places within a building, and may be dispersed to other areas if present in the HVAC system. Certain individuals may be especially sensitive to the presence of these microorganisms, and may experience adverse reactions at extremely low concentrations. Unfortunately, the source of the problem may not be discovered because many times the microbial growth is not visible. However, there are some volatile organic compounds that are given off by certain microorganisms which may be used to determine the presence of microbial contamination. 3-Methylfuran is an excellent indicator of growing fungi. It is produced by a majority of fungi, and can be used as an indicator of ongoing growth. 1-Octen-3-ol is also produced by a number of fungi, and has been used in the past as an indicator of such. These two compounds and many other volatiles given off by microorganisms have been termed microbial volatile organic compounds (MVOCs). Many of these compounds are commonly found in indoor air, and thus, may be present even when there is not microbial contamination.

  9. Evolution of Microbial “Streamer” Growths in an Acidic, Metal-Contaminated Stream Draining an Abandoned Underground Copper Mine

    PubMed Central

    Kay, Catherine M.; Rowe, Owen F.; Rocchetti, Laura; Coupland, Kris; Hallberg, Kevin B.; Johnson, D. Barrie

    2013-01-01

    A nine year study was carried out on the evolution of macroscopic “acid streamer” growths in acidic, metal-rich mine water from the point of construction of a new channel to drain an abandoned underground copper mine. The new channel became rapidly colonized by acidophilic bacteria: two species of autotrophic iron-oxidizers (Acidithiobacillus ferrivorans and “Ferrovum myxofaciens”) and a heterotrophic iron-oxidizer (a novel genus/species with the proposed name “Acidithrix ferrooxidans”). The same bacteria dominated the acid streamer communities for the entire nine year period, with the autotrophic species accounting for ~80% of the micro-organisms in the streamer growths (as determined by terminal restriction enzyme fragment length polymorphism (T-RFLP) analysis). Biodiversity of the acid streamers became somewhat greater in time, and included species of heterotrophic acidophiles that reduce ferric iron (Acidiphilium, Acidobacterium, Acidocella and gammaproteobacterium WJ2) and other autotrophic iron-oxidizers (Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans). The diversity of archaea in the acid streamers was far more limited; relatively few clones were obtained, all of which were very distantly related to known species of euryarchaeotes. Some differences were apparent between the acid streamer community and planktonic-phase bacteria. This study has provided unique insights into the evolution of an extremophilic microbial community, and identified several novel species of acidophilic prokaryotes. PMID:25371339

  10. In situ Determination of Physiological States Under Conditions Characteristic of the Subseafloor Microbial Biosphere

    NASA Astrophysics Data System (ADS)

    Schrenk, M. O.

    2008-12-01

    Studies of water samples from the deep sea have revealed organisms specifically adapted to the low temperatures (~2° C) and elevated pressures (~100 MPa) native to these environments and elucidated genetic and physiological adaptations of life to high pressures. Investigation of the subsurface biosphere, at pressures exceeding those of the deep sea, has pushed the depth limits of microbial ecosystems to at least 1000 meters below the seafloor and 3-4 km into the continental lithosphere. In many of these environments, organisms are confronted with multiple stressors including not only high pressures, but high temperatures and low energy fluxes. Subsurface microorganisms live at a precarious boundary between geologically-supported growth and cell death and remineralization. As a result of these factors the calculated average growth rates of these organisms have challenged our notions of what is biologically possible. A limitation to our study of deep ecosystems has been an inability to accurately characterize microbial physiology under conditions found in subsurface habitats. This paper describes a strategy to distinguish the physiological status of microorganisms indigenous to the deep subseafloor at environmentally relevant temperatures (50 - 200° C) and pressures (30 - 300 MPa). Preliminary results using chemolithoautotrophic bacteria and hyperthermophilic Archaea show that four distinct physiological states (active and growing, active but non-growing, viable but inactive, and dead) can be distinguished in situ using biomolecular probes coupled to geochemical measurements. Further refinements of this approach can be used to expand our understanding of microbial adaptations to high pressure environments, and be linked to both genetic and geochemical studies at high pressure. The data produced by such experiments will be important to deciphering both the extent and the biogeochemical consequences of a deep subsurface biosphere.

  11. BIODEGRADATION DURING CONTAMINANT TRANSPORT IN POROUS MEDIA. 4. IMPACT OF MICROBIAL LAG AND BACTERIAL CELL GROWTH. (R825415)

    EPA Science Inventory

    Abstract

    Miscible-displacement experiments were conducted to examine the impact of microbial lag and bacterial cell growth on the transport of salicylate, a model hydrocarbon compound. The impacts of these processes were examined separately, as well as jointly, to dete...

  12. Artificial Selection for Determinate Growth Habit in Soybean

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Determinacy is an agronomically important trait associated with the domestication in soybean (Glycine max). Most soybean cultivars are classifiable into indeterminate and determinate growth habit, while Glycine soja, the wild progenitor of soybean, is indeterminate. Indeterminate (Dt1) and determina...

  13. Biogeochemistry of Stinking Springs, Utah. Part II: Microbial Diversity and Photo- and Chemo-Autotrophic Growth Rates in a Layered Microbial Mat

    NASA Astrophysics Data System (ADS)

    Monteverde, D.; Metzger, J. G.; Bournod, C.; Kelly, H.; Johnson, H.; Sessions, A. L.; Osburn, M.; Shapiro, R. S.; Rideout, J.; Johnston, D. T.; Stevenson, B.; Stamps, B. W.; Vuono, D.; Hanselmann, K.; Spear, J. R.

    2013-12-01

    Layered microbial mats have garnered attention for their high phylogenetic diversity and exploitation of geochemical gradients often on the mm scale. However, despite their novelty and implications for early life diversification, little is known about layered microbial mat growth rates or the interdependence of the microbial communities within the system. Stinking Springs, a warm, sulfidic, saline spring northeast of the Great Salt Lake, serves as our test-site to investigate some of these questions. Stinking Springs undergoes downstream changes in pH (6.59-8.14), sulfide (527μM - below detection), sulfate (13-600μM), TCO2 (7.77-3.71mM), and temperature (40-21°C) along its ~150m flow path. The first 10m of discharge is channelized, beyond that, the spring supports a 10 to 40mm-thick layered microbial mat covering ~40% of the total spring runoff area. The mat was divided into four texturally-distinct layers which were each analyzed for 16S rRNA, lipid abundance, and bicarbonate and acetate uptake rates in addition to standard microscopy analyses. 16S rRNA analyses confirmed high taxa diversity within each layer, which varied significantly in taxa makeup such that no single phylum dominated the abundance (>33%) in more than one mat layer. The taxonomic diversity tended to increase with mat depth, a similar finding to other studies on layered microbial mats. A mat sampling transect across 16 meters showed that layer taxonomic diversity was conserved horizontally for all four mat layers, which implies mat depth has a larger control on diversity than physical or chemical parameters. Microscopy indicated the presence of diatoms in all layers which was confirmed by lipid abundance of sterols and long-branch fatty acid methyl esters. Incubation experiments were conducted in light and dark conditions over 24 hours with separate 13C-tagged bicarbonate and acetate additions. Heterotrophic growth rates (acetate uptake; 0.03-0.65%/day) were higher than autotrophic growth

  14. An evaluation of microbial growth and corrosion of 316L SS in glycol/seawater mixtures

    NASA Technical Reports Server (NTRS)

    Lee, Jason S.; Ray, Richard I.; Lowe, Kristine L.; Jones-Meehan, Joanne; Little, Brenda J.

    2003-01-01

    Glycol/seawater mixtures containing > 50% glycol inhibit corrosion of 316L stainless steel and do not support bacterial growth. The results indicate bacteria are able to use low concentrations of glycol (10%) as a growth medium, but bacterial growth decreased with increasing glycol concentration. Pitting potential, determined by anodic polarization, was used to evaluate susceptibility of 316L SS to corrosion in seawater-contaminated glycol. Mixture containing a minimum concentration of 50% propylene glycol-based coolant inhibited pitting corrosion. A slightly higher minimum concentration (55%) was needed for corrosion protection in ethylene glycol mixtures.

  15. Microbial colonization and growth on metal sulfides and other mineral surfaces

    NASA Technical Reports Server (NTRS)

    Caldwell, D.; Sundquist, A. R.; Lawrence, J.; Doyle, A. P.

    1985-01-01

    To determine whether a bacterial film forms on sulfur minerals in situ, various sulfur containing and other minerals were incubated in Penitencia Creek. The rate of cell growth and attachment within the surface microenvironment of mineral surfaces was also determined. To determine whether surfaces enriched with soluble sulfur substrates (cysteine, glutathione, thioglycolate, sulfite, and thiosulfate) increased the rate of growth or attachment of natural communities, membrane enrichments were incubated. These rates were determined as described by Caldwell et al. (1981, 1983). The growth of Pseudomonas fluorescens, a heterotrophic sulfur oxidizer, was studied in batch cell suspensions and in continuous culture. In batch culture the cells were oxygen limited (growth rate 0.33 per hour under oxygen limitations and 0.52 per hour when vigorously aerated). Growth within the film was glucose limited. Several behavioral phenomena were observed for cells growing within the hydrodynamic boundary layer. Despite a flow of 10 cm per second in the environment, the bacteria were able to move freely in both directions within the hydrodynamic boundary layer.

  16. Feedbacks between flow, sediment motion and microbial growth on sand bars initiate and shape elongated stromatolite mounds

    NASA Astrophysics Data System (ADS)

    Mariotti, G.; Perron, J. T.; Bosak, T.

    2014-07-01

    Elongated stromatolites are often used as indicators of current direction and shoreline orientation, especially in paleoenvironmental reconstructions. However, mechanisms that create shore-parallel, m-scale elongated stromatolite mounds in carbonate sand are not well understood. We propose that this geometry is initiated by microbial growth on the parts of sand bars that experience low wave-induced bed shear stresses. We test this idea by growing microbial mats on carbonate sand bars in a laboratory wave tank. Cyanobacterial mats grow on the bar runnels, where sediment motion is negligible, but are absent from the bar ridges, where the waves generate migrating ripples. When microbially-promoted lithification reinforces and preserves this initial pattern, elongated stromatolites should initiate in the runnels of sand bars, with long wavelengths (5-100 m) and small width-to-wavelength ratios (∼0.3). These dimensions are consistent with modern shore-parallel stromatolites in Hamelin Pool, Western Australia, and with patterns of microbial colonization in other sandy sediments. This model of elongated stromatolite mounds can inform paleoenvironmental reconstructions by clarifying and quantifying feedbacks among waves, sediment transport and microbial growth.

  17. Real-time optical monitoring of microbial growth using optimal combination of light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kobayashi, Ken-ichi; Yamada, Takeshi; Hiraishi, Akira; Nakauchi, Shigeki

    2012-12-01

    We developed a real-time optical monitoring system consisting of a monochrome complementary metal-oxide semiconductor (CMOS) camera and two light-emitting diodes (LEDs) with a constant temperature incubator for the rapid detection of microbial growth on solid media. As a target organism, we used Alicyclobacillus acidocaldarius, which is an acidophilic thermophilic endospore-forming bacterium able to survive in pasteurization processes and grow in acidic drink products such as apple juice. This bacterium was cultured on agar medium with a redox dye applied to improve detection sensitivity. On the basis of spectroscopic properties of the colony, medium, and LEDs, an optimal combination of two LED illuminations was selected to maximize the contrast between the colony and medium areas. We measured A. acidocaldarius and Escherichia coli at two different dilution levels using these two LEDs. From the results of time-course changes in the number of detected pixels in the detection images, a similar growth rate was estimated amongst the same species of microbes, regardless of the dilution level. This system has the ability to detect a colony of approximately 26 μm in diameter in a detection image, and it can be interpreted that the size corresponds to less than 20 μm diameter in visual inspection.

  18. Growing media constituents determine the microbial nitrogen conversions in organic growing media for horticulture.

    PubMed

    Grunert, Oliver; Reheul, Dirk; Van Labeke, Marie-Christine; Perneel, Maaike; Hernandez-Sanabria, Emma; Vlaeminck, Siegfried E; Boon, Nico

    2016-05-01

    Vegetables and fruits are an important part of a healthy food diet, however, the eco-sustainability of the production of these can still be significantly improved. European farmers and consumers spend an estimated €15.5 billion per year on inorganic fertilizers and the production of N-fertilizers results in a high carbon footprint. We investigated if fertilizer type and medium constituents determine microbial nitrogen conversions in organic growing media and can be used as a next step towards a more sustainable horticulture. We demonstrated that growing media constituents showed differences in urea hydrolysis, ammonia and nitrite oxidation and in carbon dioxide respiration rate. Interestingly, mixing of the growing media constituents resulted in a stimulation of the function of the microorganisms. The use of organic fertilizer resulted in an increase in amoA gene copy number by factor 100 compared to inorganic fertilizers. Our results support our hypothesis that the activity of the functional microbial community with respect to nitrogen turnover in an organic growing medium can be improved by selecting and mixing the appropriate growing media components with each other. These findings contribute to the understanding of the functional microbial community in growing media and its potential role towards a more responsible horticulture. PMID:27005434

  19. Determinants of the microbial community structure of eutrophic, hyporheic river sediments polluted with chlorinated aliphatic hydrocarbons.

    PubMed

    Hamonts, Kelly; Ryngaert, Annemie; Smidt, Hauke; Springael, Dirk; Dejonghe, Winnie

    2014-03-01

    Chlorinated aliphatic hydrocarbons (CAHs) often discharge into rivers as contaminated groundwater baseflow. As biotransformation of CAHs in the impacted river sediments might be an effective remediation strategy, we investigated the determinants of the microbial community structure of eutrophic, CAH-polluted sediments of the Zenne River. Based on PCR-DGGE analysis, a high diversity of Bacteria, sulfate-reducing bacteria, Geobacteraceae, methanogenic archaea, and CAH-respiring Dehalococcoides was found. Depth in the riverbed, organic carbon content, CAH content and texture of the sediment, pore water temperature and conductivity, and concentrations of toluene and methane significantly contributed to the variance in the microbial community structure. On a meter scale, CAH concentrations alone explained only 6% of the variance in the Dehalococcoides and sulfate-reducing communities. On a cm-scale, however, CAHs explained 14.5-35% of the variation in DGGE profiles of Geobacteraceae, methanogens, sulfate-reducing bacteria, and Bacteria, while organic carbon content explained 2-14%. Neither the presence of the CAH reductive dehalogenase genes tceA, bvcA, and vcrA, nor the community structure of the targeted groups significantly differed between riverbed locations showing either no attenuation or reductive dechlorination, indicating that the microbial community composition was not a limiting factor for biotransformation in the Zenne sediments.

  20. Stabilising metal(loid)s in soil with iron and aluminium-based products: microbial, biochemical and plant growth impact.

    PubMed

    Garau, Giovanni; Silvetti, Margherita; Castaldi, Paola; Mele, Elena; Deiana, Pietrino; Deiana, Salvatore

    2014-06-15

    Four iron and aluminium-based products, including red mud (RM), hematite (Fe2O3), an iron-rich water treatment residual (Fe-WTR) and amorphous Al hydroxide (Al-OH), were evaluated for their effectiveness at stabilising As and heavy metals (i.e. Cd, Cu, Pb, Zn) in a circumneutral contaminated soil [As (2105 mg kg(-1)), Cd (18 mg kg(-1)), Cu (264 mg kg(-1)), Pb (710 mg kg(-1)), Zn (522 mg kg(-1))]. Treatment impacts on soil microbial and biochemical features (i.e. microbial biomass-C, microbial counts, 16S rRNA PCR-TTGE of culturable bacteria, dehydrogenase, urease and β-glucosidase activity, Biolog derived parameters-AWCD and richness) as well as bean (Phaseolus vulgaris) and wheat (Triticum vulgare) growth were also assessed. After 6 months equilibration, all the amendments (application rate 3% w/w) but RM reduced labile As while only Al-OH reduced the concentration of water-soluble heavy metals. Despite the highest bioavailability of contaminants, most of the soil microbial and biochemical features monitored (i.e. microbial biomass-C, total bacterial counts, dehydrogenase activity and AWCD) were significantly higher in the RM-soil. Bean germination was completely inhibited in RM-soil while wheat growth was similar to that of the control. The Al-OH treatment was best overall, promoting microbial abundance, diversity and activity while increasing bean and wheat growth and reducing As accumulated in plant shoots. Results suggest that Al-OH is a suitable candidate for field evaluations while the use of RM in the remediation of circumneutral or subalkaline contaminated soils should be reconsidered. PMID:24685456

  1. Dietary Nisin Modulates the Gastrointestinal Microbial Ecology and Enhances Growth Performance of the Broiler Chickens

    PubMed Central

    Józefiak, Damian; Kierończyk, Bartosz; Juśkiewicz, Jerzy; Zduńczyk, Zenon; Rawski, Mateusz; Długosz, Jakub; Sip, Anna; Højberg, Ole

    2013-01-01

    Due to antimicrobial properties, nisin is one of the most commonly used and investigated bacteriocins for food preservation. Surprisingly, nisin has had limited use in animal feed as well as there are only few reports on its influence on microbial ecology of the gastrointestinal tract (GIT). The present study therefore aimed at investigating effects of dietary nisin on broiler chicken GIT microbial ecology and performance in comparison to salinomycin, the widely used ionophore coccidiostat. In total, 720 one-day-old male Ross 308 chicks were randomly distributed to six experimental groups. The positive control (PC) diet was supplemented with salinomycin (60 mg/kg). The nisin (NI) diets were supplemented with increasing levels (100, 300, 900 and 2700 IU nisin/g, respectively) of the bacteriocin. The negative control (NC) diet contained no additives. At slaughter (35 days of age), activity of specific bacterial enzymes (α- and β-glucosidases, α-galactosidases and β-glucuronidase) in crop, ileum and caeca were significantly higher (P<0.05) in the NC group, and nisin supplementation decreased the enzyme activities to levels observed for the PC group. A similar inhibitory influence on bacterial activity was reflected in the levels of short-chain fatty acids (SCFA) and putrefactive SCFA (PSCFA) in digesta from crop and ileum; no effect was observed in caeca. Counts of Bacteroides and Enterobacteriacae in ileum digesta were significantly (P<0.001) decreased by nisin and salinomycin, but no effects were observed on the counts of Clostridium perfringens, Lactobacillus/Enterococcus and total bacteria. Like salinomycin, nisin supplementation improved broiler growth performance in a dose-dependent manner; compared to the NC group, the body weight gain of the NI900 and NI2700 groups was improved by 4.7 and 8.7%, respectively. Our findings suggest that dietary nisin exerts a mode of action similar to salinomycin and could be considered as a dietary supplement for broiler

  2. Dietary nisin modulates the gastrointestinal microbial ecology and enhances growth performance of the broiler chickens.

    PubMed

    Józefiak, Damian; Kierończyk, Bartosz; Juśkiewicz, Jerzy; Zduńczyk, Zenon; Rawski, Mateusz; Długosz, Jakub; Sip, Anna; Højberg, Ole

    2013-01-01

    Due to antimicrobial properties, nisin is one of the most commonly used and investigated bacteriocins for food preservation. Surprisingly, nisin has had limited use in animal feed as well as there are only few reports on its influence on microbial ecology of the gastrointestinal tract (GIT). The present study therefore aimed at investigating effects of dietary nisin on broiler chicken GIT microbial ecology and performance in comparison to salinomycin, the widely used ionophore coccidiostat. In total, 720 one-day-old male Ross 308 chicks were randomly distributed to six experimental groups. The positive control (PC) diet was supplemented with salinomycin (60 mg/kg). The nisin (NI) diets were supplemented with increasing levels (100, 300, 900 and 2700 IU nisin/g, respectively) of the bacteriocin. The negative control (NC) diet contained no additives. At slaughter (35 days of age), activity of specific bacterial enzymes (α- and β-glucosidases, α-galactosidases and β-glucuronidase) in crop, ileum and caeca were significantly higher (P<0.05) in the NC group, and nisin supplementation decreased the enzyme activities to levels observed for the PC group. A similar inhibitory influence on bacterial activity was reflected in the levels of short-chain fatty acids (SCFA) and putrefactive SCFA (PSCFA) in digesta from crop and ileum; no effect was observed in caeca. Counts of Bacteroides and Enterobacteriacae in ileum digesta were significantly (P<0.001) decreased by nisin and salinomycin, but no effects were observed on the counts of Clostridium perfringens, Lactobacillus/Enterococcus and total bacteria. Like salinomycin, nisin supplementation improved broiler growth performance in a dose-dependent manner; compared to the NC group, the body weight gain of the NI₉₀₀ and NI₂₇₀₀ groups was improved by 4.7 and 8.7%, respectively. Our findings suggest that dietary nisin exerts a mode of action similar to salinomycin and could be considered as a dietary supplement

  3. [Influence of Mirabilis jalapa Linn. Growth on the Microbial Community and Petroleum Hydrocarbon Degradation in Petroleum Contaminated Saline-alkali Soil].

    PubMed

    Jiao, Hai-hua; Cui, Bing-jian; Wu, Shang-hua; Bai, Zhi-hui; Huang, Zhan-bin

    2015-09-01

    In order to explore the effect of Mirabilis jalapa Linn. growth on the structure characteristics of the microbial community and the degradation of petroleum hydrocarbon (TPH) in the petroleum-contaminated saline-alkali soil, Microbial biomass and species in the rhizosphere soils of Mirabilis jalapa Linn. in the contaminated saline soil were studied with the technology of phospholipid fatty acids (PLFAs) analysis. The results showed that comparing to CK soils without Mirabilis jalapa Linn., the ratio of PLFAs species varied were 71. 4%, 69. 2% and 33. 3% in the spring, summer and autumn season, respectively. In addition, there was distinct difference of the biomasses of the microbial community between the CK and rhizosphere soils and among the difference seasons of growth of Mirabilis jalapa Linn.. Compare to CK soil, the degradation rates of total petroleum hydrocarbon (TPH) was increased by 47. 6%, 28. 3%, and 18. 9% in spring, summer, and autumn rhizosphere soils, respectively. Correlation analysis was used to determine the correlation between TPH degradation and the soil microbial community. 77. 8% of the total soil microbial PLFAs species showed positive correlation to the TPH degradation (the correlation coefficient r > 0), among which, 55. 6% of PLFAs species showed high positive correlation(the correlation coefficient was r≥0. 8). In addition, the relative content of SAT and MONO had high correlation with TPH degradation in the CK sample soils, the corelation coefficient were 0. 92 and 0. 60 respectively; However, the percent of positive correlation was 42. 1% in the rhizosphere soils with 21. 1% of them had high positive correlation. The relative content of TBSAT, MONO and CYCLO had moderate or low correlation in rhizosphere soils, and the correlation coefficient were 0. 56, 0. 50, and 0. 07 respectively. Our study showed that the growth of mirabilis Mirabilis jalapa Linn. had a higher influence on the species and biomass of microbial community in the

  4. [Influence of Mirabilis jalapa Linn. Growth on the Microbial Community and Petroleum Hydrocarbon Degradation in Petroleum Contaminated Saline-alkali Soil].

    PubMed

    Jiao, Hai-hua; Cui, Bing-jian; Wu, Shang-hua; Bai, Zhi-hui; Huang, Zhan-bin

    2015-09-01

    In order to explore the effect of Mirabilis jalapa Linn. growth on the structure characteristics of the microbial community and the degradation of petroleum hydrocarbon (TPH) in the petroleum-contaminated saline-alkali soil, Microbial biomass and species in the rhizosphere soils of Mirabilis jalapa Linn. in the contaminated saline soil were studied with the technology of phospholipid fatty acids (PLFAs) analysis. The results showed that comparing to CK soils without Mirabilis jalapa Linn., the ratio of PLFAs species varied were 71. 4%, 69. 2% and 33. 3% in the spring, summer and autumn season, respectively. In addition, there was distinct difference of the biomasses of the microbial community between the CK and rhizosphere soils and among the difference seasons of growth of Mirabilis jalapa Linn.. Compare to CK soil, the degradation rates of total petroleum hydrocarbon (TPH) was increased by 47. 6%, 28. 3%, and 18. 9% in spring, summer, and autumn rhizosphere soils, respectively. Correlation analysis was used to determine the correlation between TPH degradation and the soil microbial community. 77. 8% of the total soil microbial PLFAs species showed positive correlation to the TPH degradation (the correlation coefficient r > 0), among which, 55. 6% of PLFAs species showed high positive correlation(the correlation coefficient was r≥0. 8). In addition, the relative content of SAT and MONO had high correlation with TPH degradation in the CK sample soils, the corelation coefficient were 0. 92 and 0. 60 respectively; However, the percent of positive correlation was 42. 1% in the rhizosphere soils with 21. 1% of them had high positive correlation. The relative content of TBSAT, MONO and CYCLO had moderate or low correlation in rhizosphere soils, and the correlation coefficient were 0. 56, 0. 50, and 0. 07 respectively. Our study showed that the growth of mirabilis Mirabilis jalapa Linn. had a higher influence on the species and biomass of microbial community in the

  5. Influence of microbial growth in the redox potential of fermented cucumbers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Commonly, pH measurements are used during the production of fermented cucumbers to indirectly monitor growth of lactic acid bacteria (LAB) and acid production. Redox potential (Eh) measurements, which are determined by the flux of electrons in a system, could serve as a more accurate tool to monitor...

  6. Main factors controlling microbial community structure, growth and activity after reclamation of a tailing pond with aided phytostabilization

    NASA Astrophysics Data System (ADS)

    Zornoza, Raúl; Acosta, José A.; Martínez-Martínez, Silvia; Faz, Ángel; Bååth, Erland

    2015-04-01

    Reclamation on bare tailing ponds has the potential to represent soil genesis in Technosols favoring the understanding of the changes of microbial communities and function. In this study we used phytostabilization aided with calcium carbonate and pig slurry/manure to reclaim an acidic bare tailing pond with the aim of investigating the effect of amending and different species on microbial community structure and function. We sampled after two years of amending and planting: unamended tailing soil (UTS), non-rhizospheric amended tailing soil (ATS), rhizospheric soil from four species, and non-rhizospheric native forest soil (NS), which acted as reference. The application of amendments increased pH up to neutrality, organic carbon (Corg), C/N and aggregate stability, while decreased salinity and heavy metals availability. No effect of rhizosphere was observed on physicochemical properties, metals immobilization and microbial community structure and function. To account for confounding effects due to soil organic matter, microbial properties were expressed per Corg. The high increments in pH and Corg have been the main factors driving changes in microbial community structure and function. Bacterial biomass was higher in UTS, without significant differences among the rest of soils. Fungal biomass followed the trend UTS < ATS = rhizospheric soils < NS. Bacterial growth increased and fungal growth decreased with increasing pH, despite the high availability of metals at low pH. Enzyme activities were lower in UTS, being β-glucosidase and β-glucosaminidase activities highly correlated with bacterial growth. Microbial activities were not correlated with the exchangeable fraction of heavy metals, indicating that microbial function is not strongly affected by these metals, likely due to the efficiency of the reclamation procedure to reduce metals toxicity. Changes in microbial community composition were largely explained by changes in pH, heavy metals availability and Corg

  7. Effects of 2-hydroxy-4-(methylthio) butanoic acid (HMB) on microbial growth in continuous culture.

    PubMed

    Noftsger, S M; St-Pierre, N R; Karnati, S K R; Firkins, J L

    2003-08-01

    2-Hydroxy-4-(methylthio) butanoic acid (HMB) positively affects milk composition and yield, potentially through ruminal actions. Four continuous culture fermenters were used to determine the optimal concentration of HMB for digestibility of organic matter (OM), neutral detergent fiber (NDF), acid detergent fiber (ADF), and hemicellulose and synthesis of microbial N. A highly degradable mix of hay and grain was used as a basal diet to simulate a typical lactation diet. Three concentrations of HMB (0, 0.055, and 0.110%) and one concentration of dl-Met (0.097%) were infused into the fermenters according to a 4 x 4 Latin square design. Digesta samples were collected during the last 3 d of each of the four 10-d experimental periods. Digestibility of OM, hemicellulose, and NDF was largely insensitive to treatment. Digestibility of ADF showed a quadratic effect to supplementation of HMB, with 0.055% having lower digestibility than 0 or 0.110%. Total production of VFA was not influenced by HMB supplementation, but differences in concentration and production of individual VFA were seen. Isobutyrate increased linearly with increasing HMB supplementation. Propionate concentration decreased linearly with increased HMB supplementation, but propionate production showed a quadratic trend (P = 0.13). A higher concentration of acetate was detected for dl-Met compared with the highest HMB concentration. There were trends (P < 0.15) for dl-Met to decrease the production of isobutyrate and to lower the concentration of butyrate when compared with HMB. Microbial efficiency was not different among treatments. The proportion of bacterial N produced from NH3-N decreased linearly with increasing HMB, and bacteria receiving dl-Met synthesized more N from NH3-N than those receiving HMB. These data suggest that supplementation of HMB may have a sparing effect on branched chain volatile fatty acids because the fatty acids are not needed to provide carbon for synthesis of valine, isoleucine and

  8. Microbial phytase in finisher diets of White Pekin ducks: effects on growth performance, plasma phosphorus concentration, and leg bone characteristics.

    PubMed

    Orban, J I; Adeola, O; Stroshine, R

    1999-03-01

    Two experiments (Exp.) were conducted to determine the growth response of White Pekin ducks to inclusion of microbial phytase in finisher diet. In Exp. 1, 1-d-old male ducks (240 total) were reared in litter-floor pens and fed regular starter diet until 3 wk of age. At 3 wk of age, ducks were randomly divided into six groups of 10 ducks each and each group was fed one of four diets. Three finisher diets containing 16% CP and 0.18% available phosphorus (AP) without supplemental P were formulated with microbial phytase (Natuphos) added at 0, 750, or 1,500 phytase units/kg of diet. The fourth diet was a control finisher diet that was supplemented with dicalcium phosphate (DCP) to supply dietary AP of 0.41%. Group BW and feed intake were measured weekly to assess growth response. At 6 wk of age, leg bones (tibia, femur, metatarsus) from five randomly selected ducks were removed and analyzed for bone characteristics. In Exp. 2, a total of 120 ducks reared as in Exp. 1 were randomly divided into six groups of five ducks each and fed one of four diets. A basal finisher diet was formulated to contain 16% CP and 0.18% AP. Monosodium phosphate was added to the basal diet to give dietary AP levels of 0.18, 0.27, and 0.36%. The fourth diet was the basal diet supplemented with microbial phytase (750 phytase units/kg of diet). Ducks were fed these diets from 3 to 6 wk of age. At the end of the study, ducks were bled by cardiac puncture and blood plasma was analyzed for P concentration. Leg bones from all ducks were removed and analyzed for bone characteristics as in Exp. 1. Feed intake increased linearly with increased level of dietary phytase, whereas the weight gain response was quadratic only during the last week of Exp. 1. In Exp. 2, there was a quadratic response for weight gain due to dietary AP. Weight gain due to phytase (750 units) was not different from ducks fed diets at 0 or 0.18% AP. Plasma P concentration increased linearly as dietary AP increased. Plasma P levels

  9. [Determination of Azospirillum Brasilense Cells With Bacteriophages via Electrooptical Analysis of Microbial Suspensions].

    PubMed

    Gulii, O I; Karavayeva, O A; Pavlii, S A; Sokolov, O I; Bunin, V D; Ignatov, O V

    2015-01-01

    The dependence-of changes in the electrooptical properties of Azospirillum brasilense cell suspension Sp7 during interaction with bacteriophage ΦAb-Sp7 on the number and time of interactions was studied. Incubation of cells with bacteriophage significantly changed the electrooptical signal within one minute. The selective effect of bacteriophage ΦAb on 18 strains of bacteria of the genus Azospirillum was studied: A. amazonense Ami4, A. brasilense Sp7, Cd, Sp107, Sp245, Jm6B2, Brl4, KR77, S17, S27, SR55, SR75, A. halopraeferans Au4, A. irakense KBC1, K A3, A. lipoferum Sp59b, SR65 and RG20a. We determined the limit of reliable determination of microbial cells infected with bacteriophage: - 10(4) cells/mL. The presence of foreign cell cultures of E. coli B-878 and E. coli XL-1 did not complicate the detection of A brasilense Sp7 cells with the use of bacteriophage ΦAb-Sp7. The results demonstrated that bacteriophage (ΦAb-Sp7 can be used for the detection of Azospirillum microbial cells via t electrooptical analysis of cell suspensions.

  10. Deep-water microbialites of the Mesoproterozoic Dismal Lakes Group: microbial growth, lithification, and implications for coniform stromatolites.

    PubMed

    Bartley, J K; Kah, L C; Frank, T D; Lyons, T W

    2015-01-01

    Offshore facies of the Mesoproterozoic Sulky Formation, Dismal Lakes Group, arctic Canada, preserve microbialites with unusual morphology. These microbialites grew in water depths greater than several tens of meters and correlate with high-relief conical stromatolites of the more proximal September Lake reef complex. The gross morphology of these microbial facies consists of ridge-like vertical supports draped by concave-upward, subhorizontal elements, resulting in tent-shaped cuspate microbialites with substantial primary void space. Morphological and petrographic analyses suggest a model wherein penecontemporaneous upward growth of ridge elements and development of subhorizontal draping elements initially resulted in a buoyantly supported, unlithified microbial form. Lithification began via precipitation within organic elements during microbialite growth. Mineralization either stabilized or facilitated collapse of initially neutrally buoyant microbialite forms. Microbial structures and breccias were then further stabilized by precipitation of marine herringbone cement. During late-stage diagenesis, remaining void space was occluded by ferroan dolomite cement. Cuspate microbialites are most similar to those found in offshore facies of Neoarchean carbonate platforms and to unlithified, buoyantly supported microbial mats in modern ice-covered Antarctic lakes. We suggest that such unusual microbialite morphologies are a product of the interaction between motile and non-motile communities under nutrient-limiting conditions, followed by early lithification, which served to preserve the resultant microbial form. The presence of marine herringbone cement, commonly associated with high dissolved inorganic carbon (DIC), low O2 conditions, also suggests growth in association with reducing environments at or near the seafloor or in conjunction with a geochemical interface. Predominance of coniform stromatolite forms in the Proterozoic--across a variety of depositional

  11. Deep-water microbialites of the Mesoproterozoic Dismal Lakes Group: microbial growth, lithification, and implications for coniform stromatolites.

    PubMed

    Bartley, J K; Kah, L C; Frank, T D; Lyons, T W

    2015-01-01

    Offshore facies of the Mesoproterozoic Sulky Formation, Dismal Lakes Group, arctic Canada, preserve microbialites with unusual morphology. These microbialites grew in water depths greater than several tens of meters and correlate with high-relief conical stromatolites of the more proximal September Lake reef complex. The gross morphology of these microbial facies consists of ridge-like vertical supports draped by concave-upward, subhorizontal elements, resulting in tent-shaped cuspate microbialites with substantial primary void space. Morphological and petrographic analyses suggest a model wherein penecontemporaneous upward growth of ridge elements and development of subhorizontal draping elements initially resulted in a buoyantly supported, unlithified microbial form. Lithification began via precipitation within organic elements during microbialite growth. Mineralization either stabilized or facilitated collapse of initially neutrally buoyant microbialite forms. Microbial structures and breccias were then further stabilized by precipitation of marine herringbone cement. During late-stage diagenesis, remaining void space was occluded by ferroan dolomite cement. Cuspate microbialites are most similar to those found in offshore facies of Neoarchean carbonate platforms and to unlithified, buoyantly supported microbial mats in modern ice-covered Antarctic lakes. We suggest that such unusual microbialite morphologies are a product of the interaction between motile and non-motile communities under nutrient-limiting conditions, followed by early lithification, which served to preserve the resultant microbial form. The presence of marine herringbone cement, commonly associated with high dissolved inorganic carbon (DIC), low O2 conditions, also suggests growth in association with reducing environments at or near the seafloor or in conjunction with a geochemical interface. Predominance of coniform stromatolite forms in the Proterozoic--across a variety of depositional

  12. A Lipid-Accumulating Alga Maintains Growth in Outdoor, Alkaliphilic Raceway Pond with Mixed Microbial Communities

    PubMed Central

    Bell, Tisza A. S.; Prithiviraj, Bharath; Wahlen, Brad D.; Fields, Matthew W.; Peyton, Brent M.

    2016-01-01

    Algal biofuels and valuable co-products are being produced in both open and closed cultivation systems. Growing algae in open pond systems may be a more economical alternative, but this approach allows environmental microorganisms to colonize the pond and potentially infect or outcompete the algal “crop.” In this study, we monitored the microbial community of an outdoor, open raceway pond inoculated with a high lipid-producing alkaliphilic alga, Chlorella vulgaris BA050. The strain C. vulgaris BA050 was previously isolated from Soap Lake, Washington, a system characterized by a high pH (∼9.8). An outdoor raceway pond (200 L) was inoculated with C. vulgaris and monitored for 10 days and then the culture was transferred to a 2,000 L raceway pond and cultivated for an additional 6 days. Community DNA samples were collected over the 16-day period in conjunction with water chemistry analyses and cell counts. Universal primers for the SSU rRNA gene sequences for Eukarya, Bacteria, and Archaea were used for barcoded pyrosequence determination. The environmental parameters that most closely correlated with C. vulgaris abundance were pH and phosphate. Community analyses indicated that the pond system remained dominated by the Chlorella population (93% of eukaryotic sequences), but was also colonized by other microorganisms. Bacterial sequence diversity increased over time while archaeal sequence diversity declined over the same time period. Using SparCC co-occurrence network analysis, a positive correlation was observed between C. vulgaris and Pseudomonas sp. throughout the experiment, which may suggest a symbiotic relationship between the two organisms. The putative relationship coupled with high pH may have contributed to the success of C. vulgaris. The characterization of the microbial community dynamics of an alkaliphilic open pond system provides significant insight into open pond systems that could be used to control photoautotrophic biomass productivity in an

  13. A Lipid-Accumulating Alga Maintains Growth in Outdoor, Alkaliphilic Raceway Pond with Mixed Microbial Communities.

    PubMed

    Bell, Tisza A S; Prithiviraj, Bharath; Wahlen, Brad D; Fields, Matthew W; Peyton, Brent M

    2015-01-01

    Algal biofuels and valuable co-products are being produced in both open and closed cultivation systems. Growing algae in open pond systems may be a more economical alternative, but this approach allows environmental microorganisms to colonize the pond and potentially infect or outcompete the algal "crop." In this study, we monitored the microbial community of an outdoor, open raceway pond inoculated with a high lipid-producing alkaliphilic alga, Chlorella vulgaris BA050. The strain C. vulgaris BA050 was previously isolated from Soap Lake, Washington, a system characterized by a high pH (∼9.8). An outdoor raceway pond (200 L) was inoculated with C. vulgaris and monitored for 10 days and then the culture was transferred to a 2,000 L raceway pond and cultivated for an additional 6 days. Community DNA samples were collected over the 16-day period in conjunction with water chemistry analyses and cell counts. Universal primers for the SSU rRNA gene sequences for Eukarya, Bacteria, and Archaea were used for barcoded pyrosequence determination. The environmental parameters that most closely correlated with C. vulgaris abundance were pH and phosphate. Community analyses indicated that the pond system remained dominated by the Chlorella population (93% of eukaryotic sequences), but was also colonized by other microorganisms. Bacterial sequence diversity increased over time while archaeal sequence diversity declined over the same time period. Using SparCC co-occurrence network analysis, a positive correlation was observed between C. vulgaris and Pseudomonas sp. throughout the experiment, which may suggest a symbiotic relationship between the two organisms. The putative relationship coupled with high pH may have contributed to the success of C. vulgaris. The characterization of the microbial community dynamics of an alkaliphilic open pond system provides significant insight into open pond systems that could be used to control photoautotrophic biomass productivity in an open

  14. A lipid-accumulating alga maintains growth in outdoor, alkaliphilic raceway pond with mixed microbial communities

    DOE PAGES

    Bell, Tisza A.S.; Prithiviraj, Bharath; Wahlen, Brad D.; Fields, Matthew W.; Peyton, Brent M.

    2016-01-07

    Algal biofuels and valuable co-products are being produced in both open and closed cultivation systems. Growing algae in open pond systems may be a more economical alternative, but this approach allows environmental microorganisms to colonize the pond and potentially infect or outcompete the algal “crop.” In this study, we monitored the microbial community of an outdoor, open raceway pond inoculated with a high lipid-producing alkaliphilic alga, Chlorella vulgaris BA050. The strain C. vulgaris BA050 was previously isolated from Soap Lake, Washington, a system characterized by a high pH (~9.8). An outdoor raceway pond (200 L) was inoculated with C. vulgarismore » and monitored for 10 days and then the culture was transferred to a 2,000 L raceway pond and cultivated for an additional 6 days. Community DNA samples were collected over the 16-day period in conjunction with water chemistry analyses and cell counts. Universal primers for the SSU rRNA gene sequences for Eukarya, Bacteria, and Archaea were used for barcoded pyrosequence determination. The environmental parameters that most closely correlated with C. vulgaris abundance were pH and phosphate. Community analyses indicated that the pond system remained dominated by the Chlorella population (93% of eukaryotic sequences), but was also colonized by other microorganisms. Bacterial sequence diversity increased over time while archaeal sequence diversity declined over the same time period. Using SparCC co-occurrence network analysis, a positive correlation was observed between C. vulgaris and Pseudomonas sp. throughout the experiment, which may suggest a symbiotic relationship between the two organisms. The putative relationship coupled with high pH may have contributed to the success of C. vulgaris. As a result, the characterization of the microbial community dynamics of an alkaliphilic open pond system provides significant insight into open pond systems that could be used to control photoautotrophic biomass

  15. By passing microbial resistance: xylitol controls microorganisms growth by means of its anti-adherence property.

    PubMed

    Ferreira, Aline S; Silva-Paes-Leme, Annelisa F; Raposo, Nádia R B; da Silva, Sílvio S

    2015-01-01

    Xylitol is an important polyalcohol suitable for use in odontological, medical and pharmaceutical products and as an additive in food. The first studies on the efficacy of xylitol in the control and treatment of infections started in the late 1970s and it is still applied for this purpose, with safety and very little contribution to resistance. Xylitol seems to act against microorganisms exerting an anti-adherence effect. Some research studies have demonstrated its action against Gram-positive and Gram-negative bacteria and yeasts. However, a clear explanation of how xylitol is effective has not been completely established yet. Some evidence shows that xylitol acts on gene expression, down-regulating the ones which are involved in the microorganisms' virulence, such as capsule formation. Another possible clarification is that xylitol blocks lectin-like receptors. The most important aspect is that, over time, xylitol bypasses microbial resistance and succeeds in controlling infection, either alone or combined with another compound. In this review, the effect of xylitol in inhibiting the growth of a different microorganism is described, focusing on studies in which such an anti-adherent property was highlighted. This is the first mini-review to describe xylitol as an anti-adherent compound and take into consideration how it exerts such action.

  16. Evaluation of americium-241 toxicity influence on the microbial growth of organic wastes

    SciTech Connect

    Takehiro Marumo, Julio; Padua Ferreira, Rafael Vicente de; Keiko Isiki, Vera Lucia; Miyamoto, Hissae; Sayuri Takara, Aline; Kazumi Sakata, Solange; Bellini, Maria Helena; Cardoso Pedroso de Lima, Luis Filipe

    2007-07-01

    Available in abstract form only. Full text of publication follows: Since the licenses for using radioactive sources in radioactive lightning rods were lifted by the Brazilian national nuclear authority, in 1989, the radioactive devices have been replaced by Franklin type and collected as radioactive waste. However, only 20 percent of the estimated total number of installed rods was delivered to Brazilian Nuclear Commission. This situation causes concern, due to, first, the possibility of the rods being disposed as domestic waste, and second, the americium, the most commonly employed radionuclide, is classified as a high-toxicity element. In the present study, Am-241 migration experiments were performed by a lysimeter system, in order to evaluate the risk of contamination caused by radioactive lightning rods disposed as a common solid waste. Besides the risk evaluation, it is important to know the mechanism of the Am-241 release or retention in waste as well as its influence in the waste decomposition processes. Many factors are involved, but microorganisms present in the waste play an important role in its degradation, which control the physical and chemical processes. The objective of this work was to evaluate the Am-241 influence on the microbial population by counting number of cells in lysimeters leachate. Preliminary results suggest that americium may influence significantly the bacteria growth in organic waste, evidenced by culture under aerobiosis and an-aerobiosis and the antimicrobial resistance test. (authors)

  17. Population growth rate and its determinants: an overview.

    PubMed Central

    Sibly, Richard M; Hone, Jim

    2002-01-01

    We argue that population growth rate is the key unifying variable linking the various facets of population ecology. The importance of population growth rate lies partly in its central role in forecasting future population trends; indeed if the form of density dependence were constant and known, then the future population dynamics could to some degree be predicted. We argue that population growth rate is also central to our understanding of environmental stress: environmental stressors should be defined as factors which when first applied to a population reduce population growth rate. The joint action of such stressors determines an organism's ecological niche, which should be defined as the set of environmental conditions where population growth rate is greater than zero (where population growth rate = r = log(e)(N(t+1)/N(t))). While environmental stressors have negative effects on population growth rate, the same is true of population density, the case of negative linear effects corresponding to the well-known logistic equation. Following Sinclair, we recognize population regulation as occurring when population growth rate is negatively density dependent. Surprisingly, given its fundamental importance in population ecology, only 25 studies were discovered in the literature in which population growth rate has been plotted against population density. In 12 of these the effects of density were linear; in all but two of the remainder the relationship was concave viewed from above. Alternative approaches to establishing the determinants of population growth rate are reviewed, paying special attention to the demographic and mechanistic approaches. The effects of population density on population growth rate may act through their effects on food availability and associated effects on somatic growth, fecundity and survival, according to a 'numerical response', the evidence for which is briefly reviewed. Alternatively, there may be effects on population growth rate of

  18. Microbial enrichment of a novel growing substrate and its effect on plant growth.

    PubMed

    Trifonova, R; Postma, J; Schilder, M T; van Elsas, J D

    2009-10-01

    The quality of torrefied grass fibers (TGF) as a new potting soil ingredient was tested in a greenhouse experiment. TGF was colonized with previously selected microorganisms. Four colonization treatments were compared: (1) no inoculants, (2) the fungus Coniochaeta ligniaria F/TGF15 alone, (3) the fungus followed by inoculation with two selected bacteria, and (4) the fungus with seven selected bacteria. Cultivation-based and DNA-based methods, i.e., PCR-DGGE and BOX-PCR, were applied to assess the bacterial and fungal communities established in the TGF. Although colonization was not performed under sterile conditions, all inoculated strains were recovered from TGF up to 26 days incubation. Stable fungal and bacterial populations of 10(8) and 10(9) CFU/g TGF, respectively, were reached. As a side effect of the torrefaction process that aimed at the chemical stabilization of grass fibers, potentially phytotoxic compounds were generated. These phytotoxic compounds were cold-extracted from the fibers and analyzed by gas chromatography mass spectrometry. Four of 15 target compounds that had previously been found in the extract of TGF were encountered, namely phenol, 2-methoxyphenol, benzopyran-2-one, and tetrahydro-5,6,7,7a-benzofuranone. The concentration of these compounds decreased significantly during incubation. The colonized TGF was mixed with peat (P) in a range of 100%:0%, 50%:50%, 20%:80%, and 0%:100% TGF/P (w/w), respectively, to assess suitability for plant growth. Germination of tomato seeds was assessed three times, i.e., with inoculated TGF that had been incubated for 12, 21, and 26 days. In these tests, 90-100% of the seeds germinated in 50%:50% and 20%:80% TGF/P, whereas on average only 50% of the seeds germinated in pure TGF. Germination was not improved by the microbial inoculants. However, plant fresh weight as well as leaf area of 28-day-old tomato plants were significantly increased in all treatments where C. ligniaria F/TGF15 was inoculated compared

  19. DETERMINATION OF MICROBIAL COMMUNITY STRUCTURE IN UNTREATED WASTEWATER FROM DIFFERENT GEOGRAPHIC LOCALES

    EPA Science Inventory

    Microbial sewage communities consist of a combination of human faecal microorganisms and urban infrastructure-derived microbes originating from infiltration of rainwater and stormwater inputs. Together these different sources of microbial diversity form a unique population struc...

  20. Evaluation of nitrogenous substrates such as peptones from fish:a new method based on Gompertz modeling of microbial growth.

    PubMed

    Dufossé, L; De La Broise, D; Guerard, F

    2001-01-01

    Fish peptones from tuna, cod, salmon, and unspecified fish were compared with a casein one by using a new method based on Gompertz modeling of microbial growth. Cumulative results obtained from six species of bacteria, yeasts, and fungi showed that, in most cases, these fish peptones are very effective. Nevertheless, this study raised some questions about the standardization of fish raw material, the enzymatic hydrolysis of fish proteins, and the composition of the culture medium used for testing the peptones.

  1. The effect of salt reduction on sensory quality and microbial growth in hotdog sausages, bacon, ham and salami.

    PubMed

    Aaslyng, Margit Dall; Vestergaard, Christian; Koch, Anette Granly

    2014-01-01

    Sodium chloride (NaCl) is a multi-functional ingredient used to inhibit microbial growth and to ensure good texture and taste in processed meat. This study showed how moderately (22-25%) and greatly (43-50%) reduction of NaCl affected yield, sensory quality and microbial growth in hotdog sausages, bacon, cooked cured ham and salami. In greatly reduced products, the yield was reduced by 8% in sausages and 6% in ham, whereas the yield in bacon and salami remained unaffected. The microbial growth was generally not affected by reducing the content of NaCl to 2.0% in sausages, 2.3% in bacon, 1.7% in ham and 6.3% in salami (aqueous phase). Salt taste, juiciness and texture were the sensory parameters most affected by the NaCl reduction. In sausages and ham, reduction from 2.2% to 1.7% and from 2.3% to 1.3% (w/w), respectively, did not alter the sensory properties. In contrast, the sensory properties of bacon and salami were significantly affected already after a moderately reduction.

  2. Effect of zinc on growth performance, gut morphometry, and cecal microbial community in broilers challenged with Salmonella enterica serovar typhimurium.

    PubMed

    Shao, Yuxin; Lei, Zhao; Yuan, Jianmin; Yang, Ying; Guo, Yuming; Zhang, Bingkun

    2014-12-01

    To evaluate the effects of supplemental zinc on growth performance, gut morphometry, and the cecal microbial community in broilers challenged with Salmonella typhimurium, 180, 1-day-old male Cobb 500 broiler chicks were randomly assigned to 3 treatments with ten replicates for a 42 day experiment. The 3 treatments were: unchallenged, S. typhimurium-challenged, and S. typhimurium-challenged with 120 mg/kg of zinc supplementation in the diet. Salmonella infection caused a reduction in body-weight gain and feed intake, disrupted the intestinal structure by decreasing the villus-height/crypt-depth ratio of the ileum and increasing the apoptotic index of ileal epithelial cells. Moreover, the cecal microbial community was altered by Salmonella infection, as demonstrated by a reduced number of Lactobacillus and total bacteria. Dietary zinc supplementation improved growth performance by increasing the body-weight gain and feed intake in the challenged broilers. In addition, zinc repaired intestinal injury by reducing the apoptotic index of ileal epithelial cells, enhancing villus height and the villus-height/crypt-depth ratio of the ileum, and the proliferation index of ileal epithelial cells. Finally, zinc regulated the cecal microbial community by increasing the number of total bacteria and beneficial Lactobacillus bacteria, and reducing the number of Salmonella. The results indicated that dietary zinc supplementation improved growth performance, intestinal morphology, and intestinal microbiota in S. typhimurium-challenged broilers. PMID:25467118

  3. An Overview on Novel Microbial Determination Methods in Pharmaceutical and Food Quality Control

    PubMed Central

    Nemati, Mahboob; Hamidi, Aliasghar; Maleki Dizaj, Solmaz; Javaherzadeh, Vahid; Lotfipour, Farzaneh

    2016-01-01

    Traditional microbiological methods tend to be labor-intensive and time-consuming. Rapid and novel methods in microbiological tests provide more sensitive, precise and reproducible results compared with conventional methods. In microbiology, the most rapid testing methods belong to the field of biotechnology such as PCR, ELISA, ATP bioluminescence and etc. Nevertheless impedance microbiology, biosensors and analytical procedures to determine microbial constituents are of significance. The present review article was conducted using internet databases and related scientific literatures and articles that provide information on developments in the rapid methods in microbiology. The main focus is on the application of rapid methods in microbial quality control of pharmaceutical products. Reviewed literature showed that rapid methods and automation in microbiology is an advanced area for studying and applying of improved methods in the early detection, and characterization of microorganisms and their products in food, pharmaceutical and cosmetic industrials as well as environmental monitoring and clinical applications. It can be concluded that rapid methods and automation in microbiology should continue as potent and efficient technologies to develop the novel tests to be performed in the future because of the ever-increasing concerns about the safety of food and pharmaceutical products. However the main issues to be considered are the scale up of developed methods and the regulatory requirements. PMID:27766214

  4. Study to determine the aquatic biological effects on the Solid Rocket Booster (SRB). [technique for monitoring marine microbial fouling

    NASA Technical Reports Server (NTRS)

    Colwell, R. R.; Zachary, A.

    1979-01-01

    The surface of the reusable solid rocket boosters (SRB), which are jettisoned from the Shuttle Orbiter to parachute in the sea, are studied for colonization by marine life. Techniques for monitoring the marine microbial fouling of SRB materials are presented. An assessment of the nature and degree of the biofouling expected on the SRB materials in the recovery zone is reported. A determination of the degree and the effects of seasonal variation occurring on microbial fouling in the retrieval zone waters is made. The susceptibility of the SRB parachute recovery system to microbial fouling and biodeterioration is investigated. The development of scanning electron microscopy and epifluorescence microscopic observation techniques for rapid assessment of microbial fouling is discussed.

  5. Effect of diet and absence of protozoa on the rumen microbial community and on the representativeness of bacterial fractions used in the determination of microbial protein synthesis.

    PubMed

    Belanche, A; de la Fuente, G; Pinloche, E; Newbold, C J; Balcells, J

    2012-11-01

    Accurate estimates of microbial synthesis in the rumen are vital to optimize ruminant nutrition. Liquid- (LAB) and solid-associated bacterial fractions (SAB) harvested from the rumen are generally considered as microbial references when microbial yield is calculated; however, factors that determine their composition are not completely understood. The aim of this study was to evaluate the effect of diet and absence or presence of rumen protozoa on the rumen microbial community. It was hypothesized that these treatments could modify the composition and representativeness of LAB and SAB. Twenty twin lambs (Ovis aries) were used; one-half of the twins were kept protozoa-free, and each respective twin sibling was faunated. At 6 mo of age, 5 animals from each group were randomly allocated to the experimental diets consisting of either alfalfa hay as the sole diet, or 50:50 mixed with ground barley grain. After 15 d of adaptation to the diet, animals were euthanized, rumen and abomasum contents were sampled, and LAB and SAB isolated. The presence of protozoa buffered the effect of diet on the rumen bacterial population. Faunated animals fed alfalfa hay had a greater abundance of F. succinogenes, anaerobic fungi and methanogens, as well as an enhanced rumen bacterial diversity. Cellulolytic bacteria were more abundant in SAB, whereas the abomasal abundance of most of the microorganisms studied was closer to those values observed in LAB. Rumen and abomasal samples showed similar bacterial DNA concentrations, but the fungal and protozoal DNA concentration in the abomasum was only 69% and 13% of that observed in the rumen, respectively, suggesting fungal and protozoal sequestration in the rumen or possible preferential degradation of fungal and protozoal DNA in the abomasum, or both. In conclusion, absence of protozoa and type of diet extensively modified the chemical composition of LAB and SAB as a consequence of changes in the microbial composition of these fractions.

  6. Intrauterine growth restriction: effects of physiological fetal growth determinants on diagnosis.

    PubMed

    Haram, Kjell; Søfteland, Eirik; Bukowski, Radek

    2013-01-01

    The growth of the fetus, which is strongly associated with the outcome of pregnancy, reflects interplay of several physiological and pathological factors. The assessment of fetal growth is based on comparison of birthweight (BW) or estimated fetal weight (EFW) to standards which define reference ranges at a spectrum of gestational ages. Most birthweight standards do not take into account effects of physiological determinants of fetal growth. Additionally, gestational age in many standards is based on the menstrual history and is often inaccurate. Fetal growth norms should be based on an early ultrasound estimate of gestational age. Customized standards, which have included only ultrasound-dated pregnancies, seem to be superior to population-based birthweight norms in predicting perinatal mortality and morbidity. Adjustment for individual variation in customized growth curves reduces false-positive diagnosis of IUGR and may lead to a very significant reduction in intervention for suspected IUGR. Customized growth potential identifies better the risk for adverse outcome than the currently used national standards, but customized charts may fail in detecting growth-restricted stillbirth. An individual's birthweight is the sum of physiological and pathological influences operating during pregnancy. Growth potential norms are a better discriminator of aberrations of fetal growth than population, ultrasound, and customized norms.

  7. Continuous determination of biochemical oxygen demand using microbial fuel cell type biosensor.

    PubMed

    Chang, In Seop; Jang, Jae Kyung; Gil, Geun Cheol; Kim, Mia; Kim, Hyung Joo; Cho, Byung Won; Kim, Byung Hong

    2004-01-15

    A mediator-less microbial fuel cell (MFC) was used as a biochemical oxygen demand (BOD) sensor in an amperometric mode for real-time wastewater monitoring. At a hydraulic retention time of 1.05 h, BOD values of up to 100 mg/l were measured based on a linear relationship, while higher BOD values were measured using a lower feeding rate. About 60 min was required to reach a new steady-state current after the MFCs had been fed with different strength artificial wastewaters (Aws). The current generated from the MFCs fed with AW with a BOD of 100 mg/l was compared to determine the repeatability, and the difference was less than 10%. When the MFC was starved, the original current value was regained with a varying recovery time depending on the length of the starvation. During starvation, the MFC generated a background level current, probably due to an endogenous metabolism.

  8. Mechanical signatures of microbial biofilms in micropillar-embedded growth chambers.

    PubMed

    Chew, S C; Kundukad, B; Teh, W K; Doyle, P; Yang, L; Rice, S A; Kjelleberg, S

    2016-06-21

    Biofilms are surface-attached communities of microorganisms embedded in an extracellular matrix and are essential for the cycling of organic matter in natural and engineered environments. They are also the leading cause of many infections, for example, those associated with chronic wounds and implanted medical devices. The extracellular matrix is a key biofilm component that determines its architecture and defines its physical properties. Herein, we used growth chambers embedded with micropillars to study the net mechanical forces (differential pressure) exerted during biofilm formation in situ. Pressure from the biofilm is transferred to the micropillars via the extracellular matrix, and reduction of major matrix components decreases the magnitude of micropillar deflections. The spatial arrangement of micropillar deflections caused by pressure differences in the different biofilm strains may potentially be used as mechanical signatures for biofilm characterization. Hence, we submit that micropillar-embedded growth chambers provide insights into the mechanical properties and dynamics of the biofilm and its matrix. PMID:27191395

  9. Microbial growth fluctuating in response to solar-terrestrial activity variations.

    PubMed

    Voychuk, S I; Gromozova, E N

    2012-01-01

    Populations of microorganisms display fluctuations in the variable physiological and biochemical properties during cultivation under constant laboratory conditions. A series of explanations were proposed for this phenomenon, and different factors were studied as possible regulators. It was found that such fluctuations possess cosmic rhythms, but no factor(s) were proposed that could sufficiently explain and predict the magnitude of changes that happened on a daily basis in the long-term experiments. In this study we investigated specific growth rate fluctuations of Saccharomyces cerevisiae yeasts that were marked daily during cultivation under constant conditions. The effects of different solar and terrestrial factors were then analysed. The significant correlation indices were found for growth rate fluctuations against solar wind speed and the number of flares M on the Sun. These two factors determined the cyclic nature of the growth rate fluctuations, and thus its general course of increase or decrease. The effects of several other factors (Flares C number, planetary A index variation, and changes in the atmospheric factors such as temperature and humidity) and their two-way interactions were significant in producing an equation to describe the magnitude of changes of the yeast's growth parameters. The R2 of the equation achieved 91% and adjusted R2 was 78%. It is obvious that temperature and humidity are the factors that cannot directly influence the yeast populations under laboratory conditions and thus we suppose that they only reflect modifications of the really important factor(s) that take place in the Earth's atmosphere. We have concluded that different solar and terrestrial factors are responsible for the fluctuations in the daily kinetic parameters of the yeast growth.

  10. Microbial growth fluctuating in response to solar-terrestrial activity variations.

    PubMed

    Voychuk, S I; Gromozova, E N

    2012-01-01

    Populations of microorganisms display fluctuations in the variable physiological and biochemical properties during cultivation under constant laboratory conditions. A series of explanations were proposed for this phenomenon, and different factors were studied as possible regulators. It was found that such fluctuations possess cosmic rhythms, but no factor(s) were proposed that could sufficiently explain and predict the magnitude of changes that happened on a daily basis in the long-term experiments. In this study we investigated specific growth rate fluctuations of Saccharomyces cerevisiae yeasts that were marked daily during cultivation under constant conditions. The effects of different solar and terrestrial factors were then analysed. The significant correlation indices were found for growth rate fluctuations against solar wind speed and the number of flares M on the Sun. These two factors determined the cyclic nature of the growth rate fluctuations, and thus its general course of increase or decrease. The effects of several other factors (Flares C number, planetary A index variation, and changes in the atmospheric factors such as temperature and humidity) and their two-way interactions were significant in producing an equation to describe the magnitude of changes of the yeast's growth parameters. The R2 of the equation achieved 91% and adjusted R2 was 78%. It is obvious that temperature and humidity are the factors that cannot directly influence the yeast populations under laboratory conditions and thus we suppose that they only reflect modifications of the really important factor(s) that take place in the Earth's atmosphere. We have concluded that different solar and terrestrial factors are responsible for the fluctuations in the daily kinetic parameters of the yeast growth. PMID:22830199

  11. Mapping and determinism of soil microbial community distribution across an agricultural landscape

    PubMed Central

    Constancias, Florentin; Terrat, Sébastien; Saby, Nicolas P A; Horrigue, Walid; Villerd, Jean; Guillemin, Jean-Philippe; Biju-Duval, Luc; Nowak, Virginie; Dequiedt, Samuel; Ranjard, Lionel; Chemidlin Prévost-Bouré, Nicolas

    2015-01-01

    Despite the relevance of landscape, regarding the spatial patterning of microbial communities and the relative influence of environmental parameters versus human activities, few investigations have been conducted at this scale. Here, we used a systematic grid to characterize the distribution of soil microbial communities at 278 sites across a monitored agricultural landscape of 13 km². Molecular microbial biomass was estimated by soil DNA recovery and bacterial diversity by 16S rRNA gene pyrosequencing. Geostatistics provided the first maps of microbial community at this scale and revealed a heterogeneous but spatially structured distribution of microbial biomass and diversity with patches of several hundreds of meters. Variance partitioning revealed that both microbial abundance and bacterial diversity distribution were highly dependent of soil properties and land use (total variance explained ranged between 55% and 78%). Microbial biomass and bacterial richness distributions were mainly explained by soil pH and texture whereas bacterial evenness distribution was mainly related to land management. Bacterial diversity (richness, evenness, and Shannon index) was positively influenced by cropping intensity and especially by soil tillage, resulting in spots of low microbial diversity in soils under forest management. Spatial descriptors also explained a small but significant portion of the microbial distribution suggesting that landscape configuration also shapes microbial biomass and bacterial diversity. PMID:25833770

  12. Probiotics: determinants of survival and growth in the gut.

    PubMed

    Bezkorovainy, A

    2001-02-01

    Bifidobacteria and lactobacilli are purportedly beneficial to human health and are called probiotics. Their survival during passage through the human gut, when administered in fermented milk products, has been investigated intensely in recent years. Well-controlled, small-scale studies on diarrhea in both adults and infants have shown that probiotics are beneficial and that they survive in sufficient numbers to affect gut microbial metabolism. Survival rates have been estimated at 20-40% for selected strains, the main obstacles to survival being gastric acidity and the action of bile salts. Although it is believed that the maximum probiotic effect can be achieved if the organisms adhere to intestinal mucosal cells, there is no evidence that exogenously administered probiotics do adhere to the mucosal cells. Instead, they seem to pass into the feces without having adhered or multiplied. Thus, to obtain a continuous exogenous probiotic effect, the probiotic culture must be ingested continually. Certain exogenously administered substances enhance the action of both exogenous and endogenous probiotics. Human milk contains many substances that stimulate the growth of bifidobacteria in vitro and also in the small intestine of infants; however, it is unlikely that they function in the colon. However, lactulose and certain fructose-containing compounds, called prebiotics, are not digested in the small intestine but pass into the cecum unchanged, where they are selectively utilized by probiotics. Beneficial effects may thus accrue from exogenously administered probiotics, often administered with prebiotics, or by endogenous bifidobacteria and lactobacilli, whose metabolic activity and growth may also be enhanced by the administration of prebiotics.

  13. Comparison of Tunable Diode Laser Absorption Spectroscopy and Isothermal Micro-calorimetry for Non-invasive Detection of Microbial Growth in Media Fills

    PubMed Central

    Brueckner, David; Roesti, David; Zuber, Ulrich Georg; Schmidt, Rainer; Kraehenbuehl, Stefan; Bonkat, Gernot; Braissant, Olivier

    2016-01-01

    Two methods were investigated for non-invasive microbial growth-detection in intact glass vials as possible techniques for automated inspection of media-filled units. Tunable diode laser absorption spectroscopy (TDLAS) was used to determine microbially induced changes in O2 and CO2 concentrations within the vial headspaces. Isothermal microcalorimetry (IMC) allowed the detection of metabolic heat production. Bacillus subtilis and Streptococcus salivarius were chosen as test organisms. Parameters as robustness, sensitivity, comparability and time to detection (TtD) were evaluated to assess method adequacy. Both methods robustly detected growth of the tested microorganisms within less than 76 hours using an initial inoculum of <10CFU. TDLA turned out to be less sensitive than TDLA and IMC, as some false negative results were observed. Compared to the visual media-fill examination of spiked samples, the investigated techniques were slightly slower regarding TtD. Although IMC showed shorter TtD than TDLAS the latter is proposed for automating the media-fill inspection, as larger throughput can be achieved. For routine use either TDLA or a combination of TDLA and TDLA should be considered. IMC may be helpful for replacing the sterility assessment of commercial drug products before release. PMID:27282661

  14. Effects of feeding corn silage inoculated with microbial additives on the ruminal fermentation, microbial protein yield, and growth performance of lambs.

    PubMed

    Basso, F C; Adesogan, A T; Lara, E C; Rabelo, C H S; Berchielli, T T; Teixeira, I A M A; Siqueira, G R; Reis, R A

    2014-12-01

    This study aimed to examine the effects of feeding corn silage inoculated without or with either Lactobacillus buchneri (LB) alone or a combination of LB and Lactobacillus plantarum (LBLP) on the apparent digestibility, ruminal fermentation, microbial protein synthesis, and growth performance of lambs. Thirty Santa Inês×Dorper crossbred intact males lambs weighing 20.4±3.8 kg were blocked by weight into 10 groups. Lambs in each group were randomly assigned to 1 of the following 3 dietary treatments: untreated (Control), LB, and LBLP silage. Lambs were fed experimental diets for 61 d. The apparent digestibility was indirectly estimated from indigestible NDF measured on d 57 to 59. Spot urine samples were collected from all animals on d 59 to estimate microbial protein synthesis. Lambs were slaughtered for carcass evaluation on d 61 when they weighed 32.4±5.2 kg. Six additional ruminally cannulated Santa Inês×Dorper crossbred wethers weighing 40.5±1.8 kg were used to examine dietary effects on ruminal fermentation. Average daily gain was increased when lambs were fed LBLP silage (P<0.05) but not LB silage. The LBLP silage had the highest (P<0.05) lactic acid concentration and both inoculated silages had greater acetic acid concentrations than the Control silage (P<0.05). Inoculation of corn silage increased intakes of DM, OM, CP, NDF, total carbohydrate (CHO), and GE by the lambs but decreased digestibility of DM, OM, CP, total and nonstructural carbohydrates, and concentration of GE and ME. (P<0.05). Nevertheless, lambs fed inoculated silages had greater microbial N supply than those on the Control treatment (P<0.05). The acetate to propionate ratio was lower in ruminal fluid of wethers in LBLP treatment than LB and Control treatment (P<0.05) and ruminal pH tended to be greater in LB lambs than in LBLP and Control wethers (P<0.10). Finally, the inoculation with both bacteria combined enhanced the silage fermentation. The intakes of DM, OM, CP, NDF, and GE

  15. Validation of a predictive model coupling gas transfer and microbial growth in fresh food packed under modified atmosphere.

    PubMed

    Guillard, V; Couvert, O; Stahl, V; Hanin, A; Denis, C; Huchet, V; Chaix, E; Loriot, C; Vincelot, T; Thuault, D

    2016-09-01

    Predicting microbial safety of fresh products in modified atmosphere packaging implies to take into account the dynamic of O2, CO2 and N2 exchanges in the system and its effect on microbial growth. In this paper a mechanistic model coupling gas transfer and predictive microbiology was validated using dedicated challenge-tests performed on poultry meat, fresh salmon and processed cheese, inoculated with either Listeria monocytogenes or Pseudomonas fluorescens and packed in commercially used packaging materials (tray + lid films). The model succeeded in predicting the relative variation of O2, CO2 and N2 partial pressure in headspace and the growth of the studied microorganisms without any parameter identification. This work highlighted that the respiration of the targeted microorganism itself and/or that of the naturally present microflora could not be neglected in most of the cases, and could, in the particular case of aerobic microbes contribute to limit the growth by removing all residual O2 in the package. This work also confirmed the low sensitivity of L. monocytogenes toward CO2 while that of P. fluorescens permitted to efficiently prevent its growth by choosing the right combination of packaging gas permeability value and initial % of CO2 initially flushed in the pack. PMID:27217358

  16. Formation of distinct soluble microbial products by activated sludge: kinetic analysis and quantitative determination.

    PubMed

    Ni, Bing-Jie; Fang, Fang; Xie, Wen-Ming; Xu, Juan; Yu, Han-Qing

    2012-02-01

    Soluble microbial products (SMP) released by microorganisms in bioreactors are classified into two distinct groups according to their different chemical and degradation kinetics: utilization-associated products (UAP) and biomass-associated products (BAP). SMP are responsible for effluent chemical oxygen demand or for membrane fouling of membrane bioreactor. Here an effective and convenient approach, other than the complicated chemical methods or complex models, is developed to quantify the formation of UAP and BAP together with their kinetics in activated sludge process. In this approach, an integrated substrate utilization equation is developed and used to determine UAP and their production kinetics. On the basis of total SMP measurements, BAP formation is determined with an integrated BAP formation equation. The fraction of substrate electrons diverted to UAP, and the content of BAP derived from biomass can then be calculated. Dynamic quantification data are obtained for UAP and BAP separately and conveniently. The obtained kinetic parameters are found to be reasonable as they are generally bounded and comparable to the literature values. The validity of this approach is confirmed by independent SMP production tests in six different activated sludge systems, which demonstrates its applicability in a wide range of engineered system regarding SMP production. This work provides a widely applied approach to determine the formation of UAP and BAP conveniently, which may offer engineers with basis to optimize bioreactor operation to avoid a high effluent soluble organics from SMP or SMP-based membrane fouling in membrane bioreactors. PMID:22185635

  17. Spring thaw ionic pulses boost nutrient availability and microbial growth in entombed Antarctic Dry Valley cryoconite holes.

    PubMed

    Telling, Jon; Anesio, Alexandre M; Tranter, Martyn; Fountain, Andrew G; Nylen, Thomas; Hawkings, Jon; Singh, Virendra B; Kaur, Preeti; Musilova, Michaela; Wadham, Jemma L

    2014-01-01

    The seasonal melting of ice entombed cryoconite holes on McMurdo Dry Valley glaciers provides oases for life in the harsh environmental conditions of the polar desert where surface air temperatures only occasionally exceed 0°C during the Austral summer. Here we follow temporal changes in cryoconite hole biogeochemistry on Canada Glacier from fully frozen conditions through the initial stages of spring thaw toward fully melted holes. The cryoconite holes had a mean isolation age from the glacial drainage system of 3.4 years, with an increasing mass of aqueous nutrients (dissolved organic carbon, total nitrogen, total phosphorus) with longer isolation age. During the initial melt there was a mean nine times enrichment in dissolved chloride relative to mean concentrations of the initial frozen holes indicative of an ionic pulse, with similar mean nine times enrichments in nitrite, ammonium, and dissolved organic matter. Nitrate was enriched twelve times and dissolved organic nitrogen six times, suggesting net nitrification, while lower enrichments for dissolved organic phosphorus and phosphate were consistent with net microbial phosphorus uptake. Rates of bacterial production were significantly elevated during the ionic pulse, likely due to the increased nutrient availability. There was no concomitant increase in photosynthesis rates, with a net depletion of dissolved inorganic carbon suggesting inorganic carbon limitation. Potential nitrogen fixation was detected in fully melted holes where it could be an important source of nitrogen to support microbial growth, but not during the ionic pulse where nitrogen availability was higher. This study demonstrates that ionic pulses significantly alter the timing and magnitude of microbial activity within entombed cryoconite holes, and adds credence to hypotheses that ionic enrichments during freeze-thaw can elevate rates of microbial growth and activity in other icy habitats, such as ice veins and subglacial regelation zones

  18. Spring thaw ionic pulses boost nutrient availability and microbial growth in entombed Antarctic Dry Valley cryoconite holes

    PubMed Central

    Telling, Jon; Anesio, Alexandre M.; Tranter, Martyn; Fountain, Andrew G.; Nylen, Thomas; Hawkings, Jon; Singh, Virendra B.; Kaur, Preeti; Musilova, Michaela; Wadham, Jemma L.

    2014-01-01

    The seasonal melting of ice entombed cryoconite holes on McMurdo Dry Valley glaciers provides oases for life in the harsh environmental conditions of the polar desert where surface air temperatures only occasionally exceed 0°C during the Austral summer. Here we follow temporal changes in cryoconite hole biogeochemistry on Canada Glacier from fully frozen conditions through the initial stages of spring thaw toward fully melted holes. The cryoconite holes had a mean isolation age from the glacial drainage system of 3.4 years, with an increasing mass of aqueous nutrients (dissolved organic carbon, total nitrogen, total phosphorus) with longer isolation age. During the initial melt there was a mean nine times enrichment in dissolved chloride relative to mean concentrations of the initial frozen holes indicative of an ionic pulse, with similar mean nine times enrichments in nitrite, ammonium, and dissolved organic matter. Nitrate was enriched twelve times and dissolved organic nitrogen six times, suggesting net nitrification, while lower enrichments for dissolved organic phosphorus and phosphate were consistent with net microbial phosphorus uptake. Rates of bacterial production were significantly elevated during the ionic pulse, likely due to the increased nutrient availability. There was no concomitant increase in photosynthesis rates, with a net depletion of dissolved inorganic carbon suggesting inorganic carbon limitation. Potential nitrogen fixation was detected in fully melted holes where it could be an important source of nitrogen to support microbial growth, but not during the ionic pulse where nitrogen availability was higher. This study demonstrates that ionic pulses significantly alter the timing and magnitude of microbial activity within entombed cryoconite holes, and adds credence to hypotheses that ionic enrichments during freeze-thaw can elevate rates of microbial growth and activity in other icy habitats, such as ice veins and subglacial regelation zones

  19. PAIRED-CITY STUDY TO DETERMINE THE CONTRIBUTION OF SOURCE WATER TYPE TO THE ENDEMIC LEVEL OF MICROBIAL DISEASE

    EPA Science Inventory

    Paired-City Study to Determine the Contribution of Source Water Type to the Endemic Level of Microbial Disease

    F Frost PhD, T Kunde MPH, L Harter PhD, T Muller MS, GF Craun PE MPH, RL Calderon MPH PhD

    ABSTRACT

    Context: The effectiveness of current drinking...

  20. Microbial growth and sensory quality of dried potato slices irradiated by electrons

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Jin; Song, Hyeon-Jeong; Song, Kyung-Bin

    2011-06-01

    Electron beam irradiation was applied to secure the microbial safety of dried purple sweet potato. After purple sweet potato slices had been dehydrated with 20% (w/w) maltodextrin solution, the samples were irradiated at doses 2, 4, 6, 8, and 10 kGy and then stored at 20 °C for 60 days. Microbiological data indicated that the populations of total aerobic bacteria and of yeast and molds significantly decreased with increase in irradiation dosage. Specifically, microbial load was reduced by about three log cycles at 6 kGy compared to those of the control. Based on the color measurement of the potato slices, electron beam irradiation treatment did not affect the color quality. Sensory evaluation results also showed that electron beam irradiation did not affect overall sensory scores during storage. These results suggest that electron beam irradiation could be useful for improving microbial safety without impairing the quality of the potato slices during storage.

  1. Effects of Monotypic and Binary Mixtures of Metal Oxide Nanoparticles on Microbial Growth in Sandy Soil Collected from Artificial Recharge Sites

    PubMed Central

    Ko, Kyung-Seok; Ha, Kyoochul; Kong, In Chul

    2015-01-01

    The potential effects of monotypic and binary metal oxide nanoparticles (NPs, ZnO, NiO, Co3O4 and TiO2) on microbial growth were evaluated in sandy soil collected from artificial recharge sites. Microbial growth was assessed based on adenosine triphosphate (ATP) content, dehydrogenase activity (DHA), and viable cell counts (VCC). Microbial growth based on ATP content and VCC showed considerable differences depending on NP type and concentration, whereas DHA did not significantly change. In general, ZnO NPs showed the strongest effect on microbial growth in all measurements, showing an EC50 value of 10.9 mg/L for ATP content. The ranking (EC50) of NPs based on their effect on microbial growth assessed by ATP content and VCC was ZnO > Co3O4 > NiO > TiO2. Upon exposure to binary NP mixtures, synergistic and additive modes of action were observed for ATP content and VCC, respectively. The ranges of observed (P(O)) and expected (P(E)) activity were 83%–92% and 78%–82% of the control (p-value 0.0010) based on ATP content and 78%–95% and 72%–94% of the control (p-value 0.8813) based on VCC under the tested conditions, respectively. The results indicate that the effects of NP mixtures on microbial growth in the sandy soil matrix were as great, or greater, than those of single NPs. Therefore, understanding the effects of single NPs and NP mixtures is essential for proper ecological risk assessment. Additionally, these findings demonstrate that the evaluation of NP effects may be profoundly influenced by the method of microbial growth measurement. PMID:26610489

  2. Effects of Monotypic and Binary Mixtures of Metal Oxide Nanoparticles on Microbial Growth in Sandy Soil Collected from Artificial Recharge Sites.

    PubMed

    Ko, Kyung-Seok; Ha, Kyoochul; Kong, In Chul

    2015-01-01

    The potential effects of monotypic and binary metal oxide nanoparticles (NPs, ZnO, NiO, Co₃O₄ and TiO₂) on microbial growth were evaluated in sandy soil collected from artificial recharge sites. Microbial growth was assessed based on adenosine triphosphate (ATP) content, dehydrogenase activity (DHA), and viable cell counts (VCC). Microbial growth based on ATP content and VCC showed considerable differences depending on NP type and concentration, whereas DHA did not significantly change. In general, ZnO NPs showed the strongest effect on microbial growth in all measurements, showing an EC50 value of 10.9 mg/L for ATP content. The ranking (EC50) of NPs based on their effect on microbial growth assessed by ATP content and VCC was ZnO > Co₃O₄ > NiO > TiO₂. Upon exposure to binary NP mixtures, synergistic and additive modes of action were observed for ATP content and VCC, respectively. The ranges of observed (P(O)) and expected (P(E)) activity were 83%-92% and 78%-82% of the control (p-value 0.0010) based on ATP content and 78%-95% and 72%-94% of the control (p-value 0.8813) based on VCC under the tested conditions, respectively. The results indicate that the effects of NP mixtures on microbial growth in the sandy soil matrix were as great, or greater, than those of single NPs. Therefore, understanding the effects of single NPs and NP mixtures is essential for proper ecological risk assessment. Additionally, these findings demonstrate that the evaluation of NP effects may be profoundly influenced by the method of microbial growth measurement. PMID:26610489

  3. Environmental Filtering of Microbial Communities in Agricultural Soil Shifts with Crop Growth.

    PubMed

    Hargreaves, Sarah K; Williams, Ryan J; Hofmockel, Kirsten S

    2015-01-01

    Plant and soil properties cooperatively structure soil microbial communities, with implications for ecosystem functioning. However, the extent to which each factor contributes to community structuring is not fully understood. To quantify the influence of plants and soil properties on microbial diversity and composition in an agricultural context, we conducted an experiment within a corn-based annual cropping system and a perennial switchgrass cropping system across three topographic positions. We sequenced barcoded 16S ribosomal RNA genes from whole soil three times throughout a single growing season and across two years in July. To target the belowground effects of plants, we also sampled rhizosphere soil in July. We hypothesized that microbial community α-diversity and composition (β-diversity) would be more sensitive to cropping system effects (annual vs. perennial inputs) than edaphic differences among topographic positions, with greater differences occurring in the rhizosphere compared to whole soil. We found that microbial community composition consistently varied with topographic position, and cropping system and the rhizosphere influenced α-diversity. In July, cropping system and rhizosphere structured a small but specific group of microbes implying a subset of microbial taxa, rather than broad shifts in community composition, may explain previously observed differences in resource cycling between treatments. Using rank abundance analysis, we detected enrichment of Saprospirales and Actinomycetales, including cellulose and chitin degraders, in the rhizosphere soil and enrichment of Nitrospirales, Syntrophobacterales, and MND1 in the whole soil. Overall, these findings support environmental filtering for the soil microbial community first by soil and second by the rhizosphere. Across cropping systems, plants selected for a general rhizosphere community with evidence for plant-specific effects related to time of sampling.

  4. Determining microbial products and identifying molecular targets in the human microbiome

    PubMed Central

    Joice, Regina; Yasuda, Koji; Shafquat, Afrah; Morgan, Xochitl C.; Huttenhower, Curtis

    2014-01-01

    Human-associated microbes are the source of many bioactive microbial products (proteins and metabolites) that play key functions both in human host pathways and in microbe-microbe interactions. Culture-independent studies now provide an accelerated means of exploring novel bioactives in the human microbiome; however, intriguingly, a substantial fraction of the microbial metagenome cannot be mapped to annotated genes or isolate genomes and is thus of unknown function. Meta'omic approaches, including metagenomic sequencing, metatranscriptomics, metabolomics, and integration of multiple assay types, represent an opportunity to efficiently explore this large pool of potential therapeutics. In combination with appropriate follow-up validation, high-throughput culture-independent assays can be combined with computational approaches to identify and characterize novel and biologically interesting microbial products. Here, we briefly review the state of microbial product identification and characterization and discuss possible next steps to catalog and leverage the large uncharted fraction of the microbial metagenome. PMID:25440055

  5. An Apple Fruit Fermentation (AFF) Treatment Improves the Composition of the Rhizosphere Microbial Community and Growth of Strawberry (Fragaria × ananassa Duch ‘Benihoppe’) Seedlings

    PubMed Central

    Bu, Yufen; Shao, Wei; Huang, Weijing; Ji, Qianlong; Yao, Yuncong

    2016-01-01

    Plant growth can be promoted by the application of apple fruit fermentation (AFF), despite unclear of the underlying mechanisms, the effects involved in AFF on rhizosphere microorganisms have been hypothesized. We investigated the consequences of applying AFF alone or in combination with Bacillus licheniformis to strawberry tissue culture seedlings in vitro, the analyses of Denaturing Gradient Gel Electrophoresis (DGGE) and 16S rDNA were performed to determine AFF effects on rhizosphere. Moreover, the growth index and antioxidant enzyme activities were determined 30 days after treatments. We identified five dominant bacteria in AFF: Coprinus atramentarius, Bacillus megaterium, Bacillus licheniformis, Weissella and B. subtilis. The greatest number of bacterial species were observed in the rhizosphere of control matrix (water treated), and the lowest diversity appeared in the rhizosphere soil treated with 108 cfu/mL B. licheniformis alone. Combining AFF plus B. licheniformis in one treatment resulted in the largest leaf area, plant height, root length, plant weight, and the markedly higher activities of antioxidant enzymes. We conclude that a combination of AFF plus B. licheniformis treatment to matrix can increase antioxidant enzymes activities in strawberry seedlings, optimize the status of rhizosphere microbial, and promote plant growth. PMID:27755580

  6. Effect of reduced barometric pressure on water availability related to microbial growth.

    PubMed

    Hawrylewicz, E J; Hagen, C; Tolkacz, V; Ehrlich, R

    1967-01-01

    Data obtained from Mariner IV indicate that the barometric pressure on Mars is considerably lower than previously estimated. Current estimates from Mariner IV indicate a range from 4 to 7 mb and by near infrared spectroscopy 33-56 mb. Inasmuch as the pressure has a marked influence on availability of water, this should affect the existence of Martian life. At the maximum temperatures recorded on Mars, namely 25 degrees C, a barometric pressure of 30 mb is required for the retention of free water. The lower pressure, 4 mb, would suggest that the moisture is present as a vapor above the freezing point and consequently it is not available for utilizing by living cells. The lower estimates of barometric pressure also inversely affect the carbon dioxide concentration in the Martian atmosphere. Our previous studies have demonstrated that spores of Bacillus cereus survive, germinate and grow in a simulated Martian environment (2.4% CO2, 98 mb) supplemented with moisture. The studies described in this paper were designed to determine the effect of low barometric pressures (10 to 98 mb Hg) and high concentrations of carbon dioxide (37 to 100%) in the simulated Martian environment on survival and growth of B cereus. The organism was inoculated into a felsite-limonite soil at 8% moisture level. The temperature cycles used were 8 hr at -65 degrees C and 16 hr at 25 degrees C, or 20 hr at -65 degrees C and 4 hr at 25 degrees C. The data suggest that the organism after achieving maximum growth in the simulated Martian environment (2.4% CO2, 98 mb) immediately enters into the growth phase upon reinoculation into fresh soil. These data reflect upon the possibility of contamination through air movements. Based upon currently available Martian environmental data, the probability of contamination of Mars by terrestrial micro-organisms will be discussed.

  7. Biofilm feeding: Microbial colonization of food promotes the growth of a detritivorous arthropod

    PubMed Central

    Horváthová, Terézia; Babik, Wiesław; Bauchinger, Ulf

    2016-01-01

    Abstract Feeding on plant material is common among animals, but how different animals overcome the dietary deficiencies imposed by this feeding strategy is not well understood. Microorganisms are generally considered to play a vital role in the nutritional ecology of plant feeding animals. Commonly microbes living inside animal bodies are considered more important, but recent studies suggest external microbes significantly shape plant-feeding strategies in invertebrates. Here we investigate how external microbes that typically form biofilm on primary plant material affect growth rates in a terrestrial isopod species Porcellio scaber. We experimentally manipulated the amount of biofilm on three different primary diet sources and quantified growth and survival of individuals that fed on food with either a small or large amount of biofilm. In addition, we tested how dietary manipulation shapes the composition of bacterial communities in the gut. The presence of visible biofilm significantly affected the growth of isopods: individuals that fed on the primary diet source with a large amount of biofilm gained more mass than individuals feeding on a diet with marginal biofilm. Diet also significantly affected the bacterial gut community. The primary diet source mainly determined the taxonomic composition of the bacterial community in the isopod gut, whereas the amount of biofilm affected the relative abundance of bacterial taxa. Our study suggests that terrestrial isopods may cope with low-quality plant matter by feeding on biofilm, with decomposition of plant material by organisms outside of the feeding organism (here a terrestrial isopod) probably playing a major role. Future investigations may be directed towards the primary diet source, plant matter, and the secondary diet source, biofilm, and should assess if both components are indeed uptaken in detritivorous species. PMID:27110187

  8. Physical determinants of vascular network remodeling during tumor growth.

    PubMed

    Welter, M; Rieger, H

    2010-10-01

    The process in which a growing tumor transforms a hierarchically organized arterio-venous blood vessel network into a tumor specific vasculature is analyzed with a theoretical model. The physical determinants of this remodeling involve the morphological and hydrodynamic properties of the initial network, generation of new vessels (sprouting angiogenesis), vessel dilation (circumferential growth), vessel regression, tumor cell proliferation and death, and the interdependence of these processes via spatio-temporal changes of blood flow parameters, oxygen/nutrient supply and growth factor concentration fields. The emerging tumor vasculature is non-hierarchical, compartmentalized into well-characterized zones, displays a complex geometry with necrotic zones and "hot spots" of increased vascular density and blood flow of varying size, and transports drug injections efficiently. Implications for current theoretical views on tumor-induced angiogenesis are discussed.

  9. [Accelerated determination of microbial sensitivity to antibiotics and chemotherapeutic preparations by serial dilutions using the peroxidase test].

    PubMed

    Fel'dman, Iu M; Leĭbman, E T

    1980-02-01

    A rapid method for determination of microbial sensitivity to antibiotics and chemotherapeutic drugs with the use of the peroxidase test is described. The procedure takes 6 hours. Peroxidase is determined by a change in the color of the methyl-para-amino phenol sulfate solution added to the broth culture in 6 hours (simultaneously with hydrogen peroxide). The peroxidase test provides detection of the microbe multiplication even when no turbidity is observed.

  10. Metagenomic Profiling of Microbial Composition and Antibiotic Resistance Determinants in Puget Sound

    PubMed Central

    Port, Jesse A.; Wallace, James C.; Griffith, William C.; Faustman, Elaine M.

    2012-01-01

    Human-health relevant impacts on marine ecosystems are increasing on both spatial and temporal scales. Traditional indicators for environmental health monitoring and microbial risk assessment have relied primarily on single species analyses and have provided only limited spatial and temporal information. More high-throughput, broad-scale approaches to evaluate these impacts are therefore needed to provide a platform for informing public health. This study uses shotgun metagenomics to survey the taxonomic composition and antibiotic resistance determinant content of surface water bacterial communities in the Puget Sound estuary. Metagenomic DNA was collected at six sites in Puget Sound in addition to one wastewater treatment plant (WWTP) that discharges into the Sound and pyrosequenced. A total of ∼550 Mbp (1.4 million reads) were obtained, 22 Mbp of which could be assembled into contigs. While the taxonomic and resistance determinant profiles across the open Sound samples were similar, unique signatures were identified when comparing these profiles across the open Sound, a nearshore marina and WWTP effluent. The open Sound was dominated by α-Proteobacteria (in particular Rhodobacterales sp.), γ-Proteobacteria and Bacteroidetes while the marina and effluent had increased abundances of Actinobacteria, β-Proteobacteria and Firmicutes. There was a significant increase in the antibiotic resistance gene signal from the open Sound to marina to WWTP effluent, suggestive of a potential link to human impacts. Mobile genetic elements associated with environmental and pathogenic bacteria were also differentially abundant across the samples. This study is the first comparative metagenomic survey of Puget Sound and provides baseline data for further assessments of community composition and antibiotic resistance determinants in the environment using next generation sequencing technologies. In addition, these genomic signals of potential human impact can be used to guide

  11. Characterization of microbial growth on processing equipment by electrochemical impedance spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Microbial activity that leads to the formation of biofilms on process equipment can accelerate corrosion, reduce heat transfer rates, and generally decrease process efficiencies. Additional concerns arise in the food and pharma industries where product quality and safety are a high priority. Followi...

  12. A novel nutritional predictor links microbial fastidiousness with lowered ubiquity, growth rate, and cooperativeness.

    PubMed

    Zarecki, Raphy; Oberhardt, Matthew A; Reshef, Leah; Gophna, Uri; Ruppin, Eytan

    2014-07-01

    Understanding microbial nutritional requirements is a key challenge in microbiology. Here we leverage the recent availability of thousands of automatically generated genome-scale metabolic models to develop a predictor of microbial minimal medium requirements, which we apply to thousands of species to study the relationship between their nutritional requirements and their ecological and genomic traits. We first show that nutritional requirements are more similar among species that co-habit many ecological niches. We then reveal three fundamental characteristics of microbial fastidiousness (i.e., complex and specific nutritional requirements): (1) more fastidious microorganisms tend to be more ecologically limited; (2) fastidiousness is positively associated with smaller genomes and smaller metabolic networks; and (3) more fastidious species grow more slowly and have less ability to cooperate with other species than more metabolically versatile organisms. These associations reflect the adaptation of fastidious microorganisms to unique niches with few cohabitating species. They also explain how non-fastidious species inhabit many ecological niches with high abundance rates. Taken together, these results advance our understanding microbial nutrition on a large scale, by presenting new nutrition-related associations that govern the distribution of microorganisms in nature. PMID:25033033

  13. The human gut microbial ecology associated with overweight and obesity determines ellagic acid metabolism.

    PubMed

    Selma, María V; Romo-Vaquero, María; García-Villalba, Rocío; González-Sarrías, Antonio; Tomás-Barberán, Francisco A; Espín, Juan C

    2016-04-01

    We recently identified three metabotypes (0, A and B) that depend on the metabolic profile of urolithins produced from polyphenol ellagic acid (EA). The gut microbiota and Gordonibacter spp. recently were identified as species able to produce urolithins. A higher percentage of metabotype B was found in patients with metabolic syndrome or colorectal cancer in comparison with healthy individuals. The aim of the present study was to analyse differences in EA metabolism between healthy overweight-obese and normoweight individuals and evaluate the role of gut microbial composition including Gordonibacter. Although the three metabotypes were confirmed in both groups, metabotype B prevailed in overweight-obese (31%) versus normoweight (20%) individuals while metabotype A was higher in normoweight (70%) than the overweight-obese group (57%). This suggests that weight gain favours the growth of bacteria capable of producing urolithin B and/or isourolithin A with respect to urolithin A-producing bacteria. Gordonibacter spp. levels were not significantly different between normoweight and overweight-obese groups but higher Gordonibacter levels were found in metabotype A individuals than in those with metabotype B. Other bacterial species have been reported to show a much closer relationship to obesity and dysbiosis than Gordonibacter. However, Gordonibacter levels are negatively correlated with metabotype B, which prevails in metabolic syndrome and colorectal cancer. This is the first report that links overweight and obesity with an alteration in the catabolism of EA, and where the correlation of Gordonibacter to this alteration is shown. Future investigation of Gordonibacter and urolithin metabotypes as potential biomarkers or therapeutic targets of obesity-related diseases is warranted.

  14. Identifying microbial fitness determinants by Insertion Sequencing (INSeq) using genome-wide transposon mutant libraries

    PubMed Central

    Goodman, Andrew L.; Wu, Meng; Gordon, Jeffrey I.

    2012-01-01

    Insertion Sequencing (INSeq) is a method for determining the insertion site and relative abundance of large numbers of transposon mutants in a mixed population of isogenic mutants of a sequenced microbial species. INSeq is based on a modified mariner transposon containing MmeI sites at its ends, allowing cleavage at chromosomal sites 16–17bp from the inserted transposon. Genomic regions adjacent to the transposons are amplified by linear PCR with a biotinylated primer. Products are bound to magnetic beads, digested with MmeI, and barcoded with sample-specific linkers appended to each restriction fragment. After limited PCR amplification, fragments are sequenced using a high-throughput instrument. The sequence of each read can be used to map the location of a transposon in the genome. Read count measures the relative abundance of that mutant in the population. Solid-phase library preparation makes this protocol rapid (18h), easy to scale-up, amenable to automation, and useful for a variety of samples. A protocol for characterizing libraries of transposon mutant strains clonally arrayed in multi-well format is provided. PMID:22094732

  15. Method for determining the temporal response of microbial phosphate transport affinity.

    PubMed Central

    Molot, L A; Brown, E J

    1986-01-01

    Nutrient transport affinities of nutrient-starved microbial populations were measured as initial slopes of plots of limiting-nutrient transport rates versus extracellular limiting-nutrient concentrations. A method was devised for the determination of soluble reactive phosphate (Pi) affinity in Pi-limited continuous culture (aT), which was then used as an indicator of the effects of light/dark cycle (LD) perturbations on the temporal Pi transport abilities of three species of freshwater algae. Cell division was asynchronous for the green alga Selenastrum capricornutum grown in continuous cultures exposed to LD cycles. An apparent rhythm in aT for Pi was greatly affected by the population size parameter. Cell division was phased for the green alga Scenedesmus quadricauda grown in LD continuous culture. A rhythm in aT for Pi was not greatly affected by the biomass parameter. Cell division was also phased in LD continuous culture for the blue-green alga (cyanobacterium) Synechococcus Nägeli, but rhythms in other parameters could not be detected. Synechococcus Nägeli was an extremely efficient Pi transporter at low Pi concentrations in LD continuous culture, and so aT could not be calculated. The results demonstrate that aT is well suited to describing the temporal response of Pi transport in LD-perturbed, Pi-limited continuous culture. PMID:3083772

  16. Soil biochemical properties and microbial resilience in agroforestry systems: effects on wheat growth under controlled drought and flooding conditions.

    PubMed

    Rivest, David; Lorente, Miren; Olivier, Alain; Messier, Christian

    2013-10-01

    Agroforestry is increasingly viewed as an effective means of maintaining or even increasing crop and tree productivity under climate change while promoting other ecosystem functions and services. This study focused on soil biochemical properties and resilience following disturbance within agroforestry and conventional agricultural systems and aimed to determine whether soil differences in terms of these biochemical properties and resilience would subsequently affect crop productivity under extreme soil water conditions. Two research sites that had been established on agricultural land were selected for this study. The first site included an 18-year-old windbreak, while the second site consisted in an 8-year-old tree-based intercropping system. In each site, soil samples were used for the determination of soil nutrient availability, microbial dynamics and microbial resilience to different wetting-drying perturbations and for a greenhouse pot experiment with wheat. Drying and flooding were selected as water stress treatments and compared to a control. These treatments were initiated at the beginning of the wheat anthesis period and maintained over 10 days. Trees contributed to increase soil nutrient pools, as evidenced by the higher extractable-P (both sites), and the higher total N and mineralizable N (tree-based intercropping site) found in the agroforestry compared to the conventional agricultural system. Metabolic quotient (qCO2) was lower in the agroforestry than in the conventional agricultural system, suggesting higher microbial substrate use efficiency in agroforestry systems. Microbial resilience was higher in the agroforestry soils compared to soils from the conventional agricultural system (windbreak site only). At the windbreak site, wheat growing in soils from agroforestry system exhibited higher aboveground biomass and number of grains per spike than in conventional agricultural system soils in the three water stress treatments. At the tree

  17. Soil biochemical properties and microbial resilience in agroforestry systems: effects on wheat growth under controlled drought and flooding conditions.

    PubMed

    Rivest, David; Lorente, Miren; Olivier, Alain; Messier, Christian

    2013-10-01

    Agroforestry is increasingly viewed as an effective means of maintaining or even increasing crop and tree productivity under climate change while promoting other ecosystem functions and services. This study focused on soil biochemical properties and resilience following disturbance within agroforestry and conventional agricultural systems and aimed to determine whether soil differences in terms of these biochemical properties and resilience would subsequently affect crop productivity under extreme soil water conditions. Two research sites that had been established on agricultural land were selected for this study. The first site included an 18-year-old windbreak, while the second site consisted in an 8-year-old tree-based intercropping system. In each site, soil samples were used for the determination of soil nutrient availability, microbial dynamics and microbial resilience to different wetting-drying perturbations and for a greenhouse pot experiment with wheat. Drying and flooding were selected as water stress treatments and compared to a control. These treatments were initiated at the beginning of the wheat anthesis period and maintained over 10 days. Trees contributed to increase soil nutrient pools, as evidenced by the higher extractable-P (both sites), and the higher total N and mineralizable N (tree-based intercropping site) found in the agroforestry compared to the conventional agricultural system. Metabolic quotient (qCO2) was lower in the agroforestry than in the conventional agricultural system, suggesting higher microbial substrate use efficiency in agroforestry systems. Microbial resilience was higher in the agroforestry soils compared to soils from the conventional agricultural system (windbreak site only). At the windbreak site, wheat growing in soils from agroforestry system exhibited higher aboveground biomass and number of grains per spike than in conventional agricultural system soils in the three water stress treatments. At the tree

  18. Dynamics of Microbial Communities on Marine Snow Aggregates: Colonization, Growth, Detachment, and Grazing Mortality of Attached Bacteria

    PubMed Central

    Kiørboe, Thomas; Tang, Kam; Grossart, Hans-Peter; Ploug, Helle

    2003-01-01

    We studied the dynamics of microbial communities attached to model aggregates (4-mm-diameter agar spheres) and the component processes of colonization, detachment, growth, and grazing mortality. Agar spheres incubated in raw seawater were rapidly colonized by bacteria, followed by flagellates and ciliates. Colonization can be described as a diffusion process, and encounter volume rates were estimated at about 0.01 and 0.1 cm3 h−1 for bacteria and flagellates, respectively. After initial colonization, the abundances of flagellates and ciliates remained approximately constant at 103 to 104 and ∼102 cells sphere−1, respectively, whereas bacterial populations increased at a declining rate to >107 cells sphere−1. Attached microorganisms initially detached at high specific rates of ∼10−2 min−1, but the bacteria gradually became irreversibly attached to the spheres. Bacterial growth (0 to 2 day−1) was density dependent and declined hyperbolically when cell density exceeded a threshold. Bacterivorous flagellates grazed on the sphere surface at an average saturated rate of 15 bacteria flagellate−1 h−1. At low bacterial densities, the flagellate surface clearance rate was ∼5 × 10−7 cm2 min−1, but it declined hyperbolically with increasing bacterial density. Using the experimentally estimated process rates and integrating the component processes in a simple model reproduces the main features of the observed microbial population dynamics. Differences between observed and predicted population dynamics suggest, however, that other factors, e.g., antagonistic interactions between bacteria, are of importance in shaping marine snow microbial communities. PMID:12788697

  19. Effects of Agaricus lilaceps fairy rings on soil aggregation and microbial community structure in relation to growth stimulation of western wheatgrass (Pascopyrum smithii) in Eastern Montana rangeland.

    PubMed

    Caesar-Tonthat, The Can; Espeland, Erin; Caesar, Anthony J; Sainju, Upendra M; Lartey, Robert T; Gaskin, John F

    2013-07-01

    Stimulation of plant productivity caused by Agaricus fairy rings has been reported, but little is known about the effects of these fungi on soil aggregation and the microbial community structure, particularly the communities that can bind soil particles. We studied three concentric zones of Agaricus lilaceps fairy rings in Eastern Montana that stimulate western wheatgrass (Pascopyrum smithii): outside the ring (OUT), inside the ring (IN), and stimulated zone adjacent to the fungal fruiting bodies (SZ) to determine (1) soil aggregate proportion and stability, (2) the microbial community composition and the N-acetyl-β-D-glucosaminidase activity associated with bulk soil at 0-15 cm depth, (3) the predominant culturable bacterial communities that can bind to soil adhering to wheatgrass roots, and (4) the stimulation of wheatgrass production. In bulk soil, macroaggregates (4.75-2.00 and 2.00-0.25 mm) and aggregate stability increased in SZ compared to IN and OUT. The high ratio of fungal to bacteria (fatty acid methyl ester) and N-acetyl-β-D-glucosaminidase activity in SZ compared to IN and OUT suggest high fungal biomass. A soil sedimentation assay performed on the predominant isolates from root-adhering soil indicated more soil-binding bacteria in SZ than IN and OUT; Pseudomonas fluorescens and Stenotrophomonas maltophilia isolates predominated in SZ, whereas Bacillus spp. isolates predominated in IN and OUT. This study suggests that growth stimulation of wheatgrass in A. lilaceps fairy rings may be attributed to the activity of the fungus by enhancing soil aggregation of bulk soil at 0-15 cm depth and influencing the amount and functionality of specific predominant microbial communities in the wheatgrass root-adhering soil.

  20. Effects of Agaricus lilaceps fairy rings on soil aggregation and microbial community structure in relation to growth stimulation of western wheatgrass (Pascopyrum smithii) in Eastern Montana rangeland.

    PubMed

    Caesar-Tonthat, The Can; Espeland, Erin; Caesar, Anthony J; Sainju, Upendra M; Lartey, Robert T; Gaskin, John F

    2013-07-01

    Stimulation of plant productivity caused by Agaricus fairy rings has been reported, but little is known about the effects of these fungi on soil aggregation and the microbial community structure, particularly the communities that can bind soil particles. We studied three concentric zones of Agaricus lilaceps fairy rings in Eastern Montana that stimulate western wheatgrass (Pascopyrum smithii): outside the ring (OUT), inside the ring (IN), and stimulated zone adjacent to the fungal fruiting bodies (SZ) to determine (1) soil aggregate proportion and stability, (2) the microbial community composition and the N-acetyl-β-D-glucosaminidase activity associated with bulk soil at 0-15 cm depth, (3) the predominant culturable bacterial communities that can bind to soil adhering to wheatgrass roots, and (4) the stimulation of wheatgrass production. In bulk soil, macroaggregates (4.75-2.00 and 2.00-0.25 mm) and aggregate stability increased in SZ compared to IN and OUT. The high ratio of fungal to bacteria (fatty acid methyl ester) and N-acetyl-β-D-glucosaminidase activity in SZ compared to IN and OUT suggest high fungal biomass. A soil sedimentation assay performed on the predominant isolates from root-adhering soil indicated more soil-binding bacteria in SZ than IN and OUT; Pseudomonas fluorescens and Stenotrophomonas maltophilia isolates predominated in SZ, whereas Bacillus spp. isolates predominated in IN and OUT. This study suggests that growth stimulation of wheatgrass in A. lilaceps fairy rings may be attributed to the activity of the fungus by enhancing soil aggregation of bulk soil at 0-15 cm depth and influencing the amount and functionality of specific predominant microbial communities in the wheatgrass root-adhering soil. PMID:23455430

  1. Microbial maximal specific growth rate as a square-root function of biomass yield and two kinetic parameters.

    PubMed

    Wong, Wilson W; Liao, James C

    2009-11-01

    Understanding how growth rates changes under different perturbations is fundamental to many aspect of microbial physiology. In this work, we experimentally showed that maximal specific growth rate is a square-root function of the biomass yield, the substrate turnover number, and the maximum synthesis rate of the substrate transporter under that condition. We used Escherichia coli cultures in lactose minimal medium as a model system by introducing genetic modifications, in vitro evolution, and ethanol stress to the cell. Deletion of crr affected all three parameters in different directions while deletion of ptsG decreased only the biomass yield. Ethanol stress negatively impacted all three parameters, while anaerobicity decreased biomass yield and transporter synthesis rate. In addition, laboratory evolution increased the growth rate in lactose mostly through enhancing the expression rate of the lac operon. Despite all these changes, the growth rate of the perturbed strain was successfully related to the three parameters by the square-root equation. Thus, this square-root relationship provides insight into how growth rate is altered by different physiological parameters. PMID:19712746

  2. Range expansions transition from pulled to pushed waves as growth becomes more cooperative in an experimental microbial population

    PubMed Central

    Yurtsev, Eugene Anatoly; Korolev, Kirill S.; Gore, Jeff

    2016-01-01

    Range expansions are becoming more frequent due to environmental changes and rare long-distance dispersal, often facilitated by anthropogenic activities. Simple models in theoretical ecology explain many emergent properties of range expansions, such as a constant expansion velocity, in terms of organism-level properties such as growth and dispersal rates. Testing these quantitative predictions in natural populations is difficult because of large environmental variability. Here, we used a controlled microbial model system to study range expansions of populations with and without intraspecific cooperativity. For noncooperative growth, the expansion dynamics were dominated by population growth at the low-density front, which pulled the expansion forward. We found these expansions to be in close quantitative agreement with the classical theory of pulled waves by Fisher [Fisher RA (1937) Ann Eugen 7(4):355–369] and Skellam [Skellam JG (1951) Biometrika 38(1-2):196–218], suitably adapted to our experimental system. However, as cooperativity increased, the expansions transitioned to being pushed, that is, controlled by growth and dispersal in the bulk as well as in the front. Given the prevalence of cooperative growth in nature, understanding the effects of cooperativity is essential to managing invading species and understanding their evolution. PMID:27185918

  3. Efficacy of sodium hypochlorite and acidified sodium chlorite in preventing browning and microbial growth on fresh-cut produce.

    PubMed

    Sun, Shih Hui; Kim, Su Jin; Kwak, Soo Jin; Yoon, Ki Sun

    2012-09-01

    The use of suitable sanitizers can increase the quality of fresh-cut produce and reduce the risk of foodborne illnesses. The objective of this study was to compare the washing effects of 100 mg/L sodium hypochlorite (SH) and 500 mg/L acidified sodium chlorite (ASC) on the prevention of enzymatic browning and the growth of microbial populations, including aerobic plate counts, E. coli, and coliforms, throughout storage at 4°C and 10°C. Fresh-cut zucchini, cucumbers, green bell peppers, and root vegetables such as potatoes, sweet potatoes, carrots, and radishes were used. Compared to SH washing, ASC washing significantly (p<0.05) reduced microbial contamination on the fresh-cut produce and prevented browning of fresh-cut potatoes and sweet potatoes during storage. More effective inhibition of aerobic plate counts and coliforms growth was observed on fresh-cut produce treated with ASC during storage at 10°C. Polyphenol oxidase (PPO) activity of fresh-cut potatoes and sweet potatoes was more effectively inhibited after washing with ASC. The use of 500 mg/L ASC can provide effective antimicrobial and anti-browning treatments of fresh-cut produce, including processed root vegetables. PMID:24471086

  4. Development of a fast and reliable method for the assessment of microbial colonization and growth on textiles by DNA quantification.

    PubMed

    Teufel, Linda; Schuster, K Christian; Merschak, Petra; Bechtold, Thomas; Redl, Bernhard

    2008-01-01

    There is a lack of relevant methods to assess the colonization of textiles by skin bacteria because present methods are mainly culture-based procedures. Therefore, the goal of this study was to develop a fast and sensitive culture-independent procedure for the quantification of microbial colonization and growth on textiles. We have established a suitable protocol to use DNA quantification as a reliable method for in vitroand in vivoinvestigations of textiles. For DNA extraction, a two-step procedure comprising treatment of the textile with a solution containing Triton X-100 and lysozyme for 1 h and a successive treatment by SDS and proteinase K for 2 h turned out to be most efficient. DNA extracted from textiles and fabrics was than quantified with the highly sensitive PicoGreen fluorescent dye. In vitrochallenge tests demonstrated a strong correlation between numbers of bacteria on textiles and amount of DNA extracted from textiles. Therefore, this method was used to compare different materials after in vivotrials for assessment of their susceptibility for microbial colonization and growth.

  5. Efficacy of Sodium Hypochlorite and Acidified Sodium Chlorite in Preventing Browning and Microbial Growth on Fresh-Cut Produce

    PubMed Central

    Sun, Shih Hui; Kim, Su Jin; Kwak, Soo Jin; Yoon, Ki Sun

    2012-01-01

    The use of suitable sanitizers can increase the quality of fresh-cut produce and reduce the risk of foodborne illnesses. The objective of this study was to compare the washing effects of 100 mg/L sodium hypochlorite (SH) and 500 mg/L acidified sodium chlorite (ASC) on the prevention of enzymatic browning and the growth of microbial populations, including aerobic plate counts, E. coli, and coliforms, throughout storage at 4°C and 10°C. Fresh-cut zucchini, cucumbers, green bell peppers, and root vegetables such as potatoes, sweet potatoes, carrots, and radishes were used. Compared to SH washing, ASC washing significantly (p<0.05) reduced microbial contamination on the fresh-cut produce and prevented browning of fresh-cut potatoes and sweet potatoes during storage. More effective inhibition of aerobic plate counts and coliforms growth was observed on fresh-cut produce treated with ASC during storage at 10°C. Polyphenol oxidase (PPO) activity of fresh-cut potatoes and sweet potatoes was more effectively inhibited after washing with ASC. The use of 500 mg/L ASC can provide effective antimicrobial and anti-browning treatments of fresh-cut produce, including processed root vegetables. PMID:24471086

  6. Efficacy of sodium hypochlorite and acidified sodium chlorite in preventing browning and microbial growth on fresh-cut produce.

    PubMed

    Sun, Shih Hui; Kim, Su Jin; Kwak, Soo Jin; Yoon, Ki Sun

    2012-09-01

    The use of suitable sanitizers can increase the quality of fresh-cut produce and reduce the risk of foodborne illnesses. The objective of this study was to compare the washing effects of 100 mg/L sodium hypochlorite (SH) and 500 mg/L acidified sodium chlorite (ASC) on the prevention of enzymatic browning and the growth of microbial populations, including aerobic plate counts, E. coli, and coliforms, throughout storage at 4°C and 10°C. Fresh-cut zucchini, cucumbers, green bell peppers, and root vegetables such as potatoes, sweet potatoes, carrots, and radishes were used. Compared to SH washing, ASC washing significantly (p<0.05) reduced microbial contamination on the fresh-cut produce and prevented browning of fresh-cut potatoes and sweet potatoes during storage. More effective inhibition of aerobic plate counts and coliforms growth was observed on fresh-cut produce treated with ASC during storage at 10°C. Polyphenol oxidase (PPO) activity of fresh-cut potatoes and sweet potatoes was more effectively inhibited after washing with ASC. The use of 500 mg/L ASC can provide effective antimicrobial and anti-browning treatments of fresh-cut produce, including processed root vegetables.

  7. Dimensionless parameters to summarize the influence of microbial growth and inhibition on the bioremediation of groundwater contaminants.

    PubMed

    Mohamed, M; Hatfield, K

    2011-09-01

    Monod expressions are preferred over zero- and first-order decay expressions in modeling contaminants biotransformation in groundwater because they better represent complex conditions. However, the wide-range of values reported for Monod parameters suggests each case-study is unique. Such uniqueness restricts the usefulness of modeling, complicates an interpretation of natural attenuation and limits the utility of a bioattenuation assessment to a small number of similar cases. In this paper, four Monod-based dimensionless parameters are developed that summarize the effects of microbial growth and inhibition on groundwater contaminants. The four parameters represent the normalized effective microbial growth rate (η), the normalized critical contaminant/substrate concentration (S*), the critical contaminant/substrate inhibition factor (N), and the bioremediation efficacy (η*). These parameters enable contaminated site managers to assess natural attenuation or augmented bioremediation at multiple sites and then draw comparisons between disparate remediation activities, sites and target contaminants. Simulations results are presented that reveal the sensitivity of these dimensionless parameters to Monod parameters and varying electron donor/acceptor loads. These simulations also show the efficacy of attenuation (η*) varying over space and time. Results suggest electron donor/acceptor amendments maintained at relative concentrations S* between 0.5 and 1.5 produce the highest remediation efficiencies. Implementation of the developed parameters in a case study proves their usefulness.

  8. LIPID ANALYSIS TO DETERMINE THE EFFECT OF A SOURCE REMEDIAL TECHNOLOGY IN MICROBIAL ECOLOGY

    EPA Science Inventory

    Microbial community structures and related changes in the subsurface environment were investigated following in situ chemical oxidation (ISCO) treatment at Launch Complex 34, Cape Canaveral Air Station, Florida. The site has dense non-aqueous phase (DNAPL) concentrations of TCE ...

  9. Effect of a Bacillus-based direct-fed microbial feed supplement on growth performance and pen cleaning characteristics of growing-finishing pigs.

    PubMed

    Davis, M E; Parrott, T; Brown, D C; de Rodas, B Z; Johnson, Z B; Maxwell, C V; Rehberger, T

    2008-06-01

    A direct-fed microbial (DFM) based on a combination of Bacillus organisms specifically selected to increase the manure decomposition process was evaluated to determine its efficacy for improving growth performance and manure dissolution time. Three experiments involving 336 crossbred barrows and gilts were conducted to determine the effect of the Bacillus-based direct-fed microbial on growth performance and pen cleaning time. In each experiment, 2 dietary treatments (0 and 0.05% DFM) were fed during the growing-finishing period throughout the experiment, such that the DFM provided 1.47 x 10(8) cfu of Bacillus organisms per gram of supplement. Data from the 3 experiments were combined for analysis, such that there were 28 pens representing each of the 2 treatments. Pigs were weighed and feed intake was determined at the initiation and termination of each phase (starter, grower, and finisher). At the end of Exp. 1 and 3, pen cleaning time was determined by measuring the time required for each pen to be scraped and washed with a high-pressure sprayer. Additionally, 2 solid manure mat samples weighing approximately 4 g each were collected from solid manure buildup in each pen (16 pens/treatment), and the time required to completely disperse each manure mat sample was determined. Gain:feed improved (P < 0.05) in pigs fed Bacillus compared with the control diet during the finisher phase and throughout the combined growing-finishing period. The time required to dissolve the manure mat was reduced (P < 0.01) in samples collected from pens containing pigs fed Bacillus compared with samples from control pens. An additional evaluation was conducted in a commercial swine production facility using statistical process control analysis. Statistical process control analysis determined that supplementation with Bacillus increased the expected mean for ADG and decreased the expected mean for death loss percentage. Supplementation with a DFM composed of specifically selected Bacillus

  10. The influence of microbial associations on germination of wheat seeds and on the growth of seedlings under impact of Zink salts

    NASA Astrophysics Data System (ADS)

    Somova, L. A.; Pechurkin, N. S.; Mikheeva, G. A.

    The life support systems LSS for long-term missions are to use cycling-recycling systems including biological recycling Higher plants are the traditional regenerator of air and producer of food They should be used in many successive generations of their reproduction in LSS Development and studies of influence of microbial associations on germination of wheat seeds and on growth of seedlings under impact of heavy metals has good prospects and necessity because of migration of heavy metals in LSS Microbial associations are able to stimulate plants growth to protect them from pathogenic organisms and from toxicity of heavy metals salts The goal of this work was to investigate microbial associations action on the germination of wheat seeds and on the growth of seedlings under impact of different concentrations of ZnSO 4 The results of investigations showed 1 Zink salt had negative action on germination of wheat seeds beginning with concentrations - 8 MPC Maximum Permissible Concentration and higher 2 Microbial associations concentrations -10 4 -- 10 6 cells ml were able to decrease partly or completely the negative action of ZnSO 4 on germination of wheat seeds 3 Concentrations 10 4 -- 10 5 cells ml of microbial associations were able to decrease the negative action of Zink salts intervals from 2 to 32 MPA on the growth and development of wheat plantlets during heterotrophic phase 4 Root system of plants was more sensible to the negative action of ZnSO 4 than shoots of plants

  11. Effects of heavy metals contained in soil irrigated with a mixture of sewage sludge and effluent for thirty years on soil microbial biomass and plant growth

    NASA Astrophysics Data System (ADS)

    Katanda, Y.; Mushonga, C.; Banganayi, F.; Nyamangara, J.

    The use of sewage effluent as a source of nutrients and water in peri-urban crop production is widespread in developing countries. A study was conducted in 2005 at Crowborough and Firle farms (near Harare) to assess effect of Cd on microbial biomass and activity, effect of sewage sludge and effluent on soybean (Glycine max L (Merr)) nodulation, and uptake of Zn and Cu by lettuce ( Lactuca sativa L.), mustard rape ( Brassica juncea L.), covo ( Brassica napus) and star grass ( Cynodon nlemfuensis). The soil that was used had been irrigated with sewage sludge and effluent for 30 years. Soil collected from Crowborough farm was enriched with Cd to different concentrations (0.4-5 mg Cd kg -1 soil) using Cd(NO 3) 2 and microbial biomass C and N (chloroform-incubation extraction) and respiration rates (CO 2 evolution) determined. A similar experiment to determine the effect of repeated addition of small amounts of Cd to soil over time on the same parameters was conducted. Three vegetables and star grass were grown in a pot experiment and harvested at six weeks after transplanting for the determination of above ground dry matter yield, and Zn and Cu, uptake. In another pot experiment, two soybean varieties, Magoye and Solitaire, were harvested after eight weeks and nodule number and effectiveness, and above ground dry matter yield were then determined. Cd significantly decreased biomass C (68%) and N (73%). Microbial respiration also significantly decreased. It was concluded that long-term application of sewage sludge and effluent to soil has negative effects on soil micro organisms, including Rhizobia. These micro organisms are essential for N-fixation. The damage to Rhizobia, caused diminished nodulation of soybean. Mustard rape and lettuce can accumulate Zn and Cu beyond toxic limits without apparent reduction in growth thereby posing a serious concern to the food chain. The consumption of mustard rape and lettuce grown on soil amended with sewage sludge and effluent at

  12. Microbial stratification in low pH oxic and suboxic macroscopic growths along an acid mine drainage.

    PubMed

    Méndez-García, Celia; Mesa, Victoria; Sprenger, Richard R; Richter, Michael; Diez, María Suárez; Solano, Jennifer; Bargiela, Rafael; Golyshina, Olga V; Manteca, Ángel; Ramos, Juan Luis; Gallego, José R; Llorente, Irene; Martins dos Santos, Vitor A P; Jensen, Ole N; Peláez, Ana I; Sánchez, Jesús; Ferrer, Manuel

    2014-06-01

    Macroscopic growths at geographically separated acid mine drainages (AMDs) exhibit distinct populations. Yet, local heterogeneities are poorly understood. To gain novel mechanistic insights into this, we used OMICs tools to profile microbial populations coexisting in a single pyrite gallery AMD (pH ∼2) in three distinct compartments: two from a stratified streamer (uppermost oxic and lowermost anoxic sediment-attached strata) and one from a submerged anoxic non-stratified mat biofilm. The communities colonising pyrite and those in the mature formations appear to be populated by the greatest diversity of bacteria and archaea (including 'ARMAN' (archaeal Richmond Mine acidophilic nano-organisms)-related), as compared with the known AMD, with ∼44.9% unclassified sequences. We propose that the thick polymeric matrix may provide a safety shield against the prevailing extreme condition and also a massive carbon source, enabling non-typical acidophiles to develop more easily. Only 1 of 39 species were shared, suggesting a high metabolic heterogeneity in local microenvironments, defined by the O2 concentration, spatial location and biofilm architecture. The suboxic mats, compositionally most similar to each other, are more diverse and active for S, CO2, CH4, fatty acid and lipopolysaccharide metabolism. The oxic stratum of the streamer, displaying a higher diversity of the so-called 'ARMAN'-related Euryarchaeota, shows a higher expression level of proteins involved in signal transduction, cell growth and N, H2, Fe, aromatic amino acids, sphingolipid and peptidoglycan metabolism. Our study is the first to highlight profound taxonomic and functional shifts in single AMD formations, as well as new microbial species and the importance of H2 in acidic suboxic macroscopic growths. PMID:24430486

  13. Microbial stratification in low pH oxic and suboxic macroscopic growths along an acid mine drainage

    PubMed Central

    Méndez-García, Celia; Mesa, Victoria; Sprenger, Richard R; Richter, Michael; Diez, María Suárez; Solano, Jennifer; Bargiela, Rafael; Golyshina, Olga V; Manteca, Ángel; Ramos, Juan Luis; Gallego, José R; Llorente, Irene; Martins dos Santos, Vitor AP; Jensen, Ole N; Peláez, Ana I; Sánchez, Jesús; Ferrer, Manuel

    2014-01-01

    Macroscopic growths at geographically separated acid mine drainages (AMDs) exhibit distinct populations. Yet, local heterogeneities are poorly understood. To gain novel mechanistic insights into this, we used OMICs tools to profile microbial populations coexisting in a single pyrite gallery AMD (pH ∼2) in three distinct compartments: two from a stratified streamer (uppermost oxic and lowermost anoxic sediment-attached strata) and one from a submerged anoxic non-stratified mat biofilm. The communities colonising pyrite and those in the mature formations appear to be populated by the greatest diversity of bacteria and archaea (including ‘ARMAN' (archaeal Richmond Mine acidophilic nano-organisms)-related), as compared with the known AMD, with ∼44.9% unclassified sequences. We propose that the thick polymeric matrix may provide a safety shield against the prevailing extreme condition and also a massive carbon source, enabling non-typical acidophiles to develop more easily. Only 1 of 39 species were shared, suggesting a high metabolic heterogeneity in local microenvironments, defined by the O2 concentration, spatial location and biofilm architecture. The suboxic mats, compositionally most similar to each other, are more diverse and active for S, CO2, CH4, fatty acid and lipopolysaccharide metabolism. The oxic stratum of the streamer, displaying a higher diversity of the so-called ‘ARMAN'-related Euryarchaeota, shows a higher expression level of proteins involved in signal transduction, cell growth and N, H2, Fe, aromatic amino acids, sphingolipid and peptidoglycan metabolism. Our study is the first to highlight profound taxonomic and functional shifts in single AMD formations, as well as new microbial species and the importance of H2 in acidic suboxic macroscopic growths. PMID:24430486

  14. Microbial community in the soil determines the forest recovery post-exposure to gamma irradiation.

    PubMed

    Shah, Vishal; Shah, Shreya; Mackey, Herman; Kambhampati, Murty; Collins, Daniel; Dowd, Scot E; Colichio, Robert; McDonnell, Kevin T; Green, Timothy

    2013-10-15

    Exposure of an ecosystem to ionizing radiation remains a possibility either due to accidents involving nuclear fuel rods or contamination with high-level radioactive wastes. While the short and long-term effect of ionizing radiation on higher eukaryotes has been well documented, we do not have an understanding on the recovery of the microbial community post radiation. Here we report that at a site within Brookhaven National Laboratory that was radiated from 1961 to 1978 with γ rays (Gamma Forest), the ecosystem has not yet fully recovered from the effects of radiation. The current vegetation type in the Gamma Forest varies as one goes away from the source of ionizing radiation, with the region closest to the source having no vegetation. The microbial tag-encoded FLX amplicon pyrosequencing analysis of the soil from different regions suggests that the current microbial community structure is identical in all the Zones. When soil samples from each vegetation zone of the Gamma Forest were radiated with 1.8 kGy γ radiation and survival microbial community analyzed, clear difference in the microbial communities were observed. It is evident based on the experimental data that the colonization of soil with Nitrosomonadaceae is critical for the higher plants in pine barrens to reestablish and grow after the area had been exposed to ionizing radiation. PMID:24063597

  15. Microbial community in the soil determines the forest recovery post-exposure to gamma irradiation.

    PubMed

    Shah, Vishal; Shah, Shreya; Mackey, Herman; Kambhampati, Murty; Collins, Daniel; Dowd, Scot E; Colichio, Robert; McDonnell, Kevin T; Green, Timothy

    2013-10-15

    Exposure of an ecosystem to ionizing radiation remains a possibility either due to accidents involving nuclear fuel rods or contamination with high-level radioactive wastes. While the short and long-term effect of ionizing radiation on higher eukaryotes has been well documented, we do not have an understanding on the recovery of the microbial community post radiation. Here we report that at a site within Brookhaven National Laboratory that was radiated from 1961 to 1978 with γ rays (Gamma Forest), the ecosystem has not yet fully recovered from the effects of radiation. The current vegetation type in the Gamma Forest varies as one goes away from the source of ionizing radiation, with the region closest to the source having no vegetation. The microbial tag-encoded FLX amplicon pyrosequencing analysis of the soil from different regions suggests that the current microbial community structure is identical in all the Zones. When soil samples from each vegetation zone of the Gamma Forest were radiated with 1.8 kGy γ radiation and survival microbial community analyzed, clear difference in the microbial communities were observed. It is evident based on the experimental data that the colonization of soil with Nitrosomonadaceae is critical for the higher plants in pine barrens to reestablish and grow after the area had been exposed to ionizing radiation.

  16. Determinants of femoral geometry and structure during adolescent growth.

    PubMed

    van der Meulen, M C; Ashford, M W; Kiratli, B J; Bachrach, L K; Carter, D R

    1996-01-01

    Our goal was to understand developmental determinants of femoral structure during growth and sexual maturation by relating femoral measurements to gender and developmental factors (age, pubertal stage, height, and body mass). The bone mineral content of the femur was measured by dual energy x-ray absorptiometry in 101 healthy Caucasian adolescents and young adults, 9-26 years of age. After some simplifying assumptions had been made, cross-sectional geometric properties of the femoral midshaft were estimated. Two geometry-based structural indicators, the section modulus and whole bone strength index, were calculated to assess the structural characteristics of the femur. Femoral strength, as described by these structural indicators, increased dramatically from childhood through young adulthood. Regressions were performed between these femoral measurements and the developmental factors. Our data show that of age, pubertal stage, body mass, and height, body mass is the strongest predictor of femoral cross-sectional properties, and the correlation of body mass with femoral cross-sectional structure is independent of gender. A model including all four developmental factors and gender did not substantially increase the accuracy of predictions compared with the model with body mass alone. In light of previous research, we hypothesize that body mass is an indicator of in vivo loading and that this in vivo loading influences the cross-sectional growth of the long bones.

  17. Advances in determining abdominal aortic aneurysm size and growth.

    PubMed

    Kontopodis, Nikolaos; Lioudaki, Stella; Pantidis, Dimitrios; Papadopoulos, George; Georgakarakos, Efstratios; Ioannou, Christos V

    2016-02-28

    Abdominal aortic aneurysm is a common pathology in the aging population of the developed world which carries a significant mortality in excess of 80% in case of rupture. Aneurysmal disease probably represents the only surgical condition in which size is such a critical determinant of the need for intervention and therefore the ability to accurately and reproducibly record aneurysm size and growth over time is of outmost importance. In the same time that imaging techniques may be limited by intra- and inter-observer variability and there may be inconsistencies due to different modalities [ultrasound, computed tomography (CT)], rapid technologic advancement have taken aortic imaging to the next level. Digital imaging, multi-detector scanners, thin slice CT and most- importantly the ability to perform 3-dimensional reconstruction and image post-processing have currently become widely available rendering most of the imaging modalities used in the past out of date. The aim of the current article is to report on various imaging methods and current state of the art techniques used to record aneurysm size and growth. Moreover we aim to emphasize on the future research directions and report on techniques which probably will be widely used and incorporated in clinical practice in the near future. PMID:26981224

  18. Advances in determining abdominal aortic aneurysm size and growth

    PubMed Central

    Kontopodis, Nikolaos; Lioudaki, Stella; Pantidis, Dimitrios; Papadopoulos, George; Georgakarakos, Efstratios; Ioannou, Christos V

    2016-01-01

    Abdominal aortic aneurysm is a common pathology in the aging population of the developed world which carries a significant mortality in excess of 80% in case of rupture. Aneurysmal disease probably represents the only surgical condition in which size is such a critical determinant of the need for intervention and therefore the ability to accurately and reproducibly record aneurysm size and growth over time is of outmost importance. In the same time that imaging techniques may be limited by intra- and inter-observer variability and there may be inconsistencies due to different modalities [ultrasound, computed tomography (CT)], rapid technologic advancement have taken aortic imaging to the next level. Digital imaging, multi-detector scanners, thin slice CT and most- importantly the ability to perform 3-dimensional reconstruction and image post-processing have currently become widely available rendering most of the imaging modalities used in the past out of date. The aim of the current article is to report on various imaging methods and current state of the art techniques used to record aneurysm size and growth. Moreover we aim to emphasize on the future research directions and report on techniques which probably will be widely used and incorporated in clinical practice in the near future. PMID:26981224

  19. Metabolism of dinosaurs as determined from their growth.

    PubMed

    Lee, Scott A

    2015-09-01

    A model based on cellular properties is used to analyze the mass growth curves of 20 dinosaurs. This analysis yields the first measurement of the average cellular metabolism of dinosaurs. The organismal metabolism is also determined. The cellular metabolism of dinosaurs is found to decrease with mass at a slower rate than is observed in extant animals. The organismal metabolism increases with the mass of the dinosaur. These results come from both the Saurischia and Ornithischia branches of Dinosauria, suggesting that the observed metabolic features were common to all dinosaurs. The results from dinosaurs are compared to data from extant placental and marsupial mammals, a monotreme, and altricial and precocial birds, reptiles, and fish. Dinosaurs had cellular and organismal metabolisms in the range observed in extant mesotherms.

  20. Metabolism of dinosaurs as determined from their growth

    NASA Astrophysics Data System (ADS)

    Lee, Scott A.

    2015-09-01

    A model based on cellular properties is used to analyze the mass growth curves of 20 dinosaurs. This analysis yields the first measurement of the average cellular metabolism of dinosaurs. The organismal metabolism is also determined. The cellular metabolism of dinosaurs is found to decrease with mass at a slower rate than is observed in extant animals. The organismal metabolism increases with the mass of the dinosaur. These results come from both the Saurischia and Ornithischia branches of Dinosauria, suggesting that the observed metabolic features were common to all dinosaurs. The results from dinosaurs are compared to data from extant placental and marsupial mammals, a monotreme, and altricial and precocial birds, reptiles, and fish. Dinosaurs had cellular and organismal metabolisms in the range observed in extant mesotherms.

  1. Integrated Field, Laboratory, and Modeling Studies to Determine the Effects of Linked Microbial and Physical Spatial Heterogeneity on Engineered Vadose Zone Bioremediation

    SciTech Connect

    Brockman, Fred J.; Selker, John S.; Rockhold, Mark L.

    2004-10-31

    Executive Summary - While numerous techniques exist for remediation of contaminant plumes in groundwater or near the soil surface, remediation methods in the deep vadose zone are less established due to complex transport dynamics and sparse microbial populations. There is a lack of knowledge on how physical and hydrologic features of the vadose zone control microbial growth and colonization in response to nutrient delivery during bioremediation. Yet pollution in the vadose zone poses a serious threat to the groundwater resources lying deeper in the sediment. While the contaminants may be slowly degraded by native microbial communities, microbial degradation rates rarely keep pace with the spread of the pollutant. It is crucial to increase indigenous microbial degradation in the vadose zone to combat groundwater contamination...

  2. Integrated Field, Laboratory, and Modeling Studies to Determine the Effects of Linked Microbial and Physical Spatial Heterogeneity on Engineered Vadose Zone Bioremediation

    SciTech Connect

    Fred Brokman; John Selker; Mark Rockhold

    2004-01-26

    While numerous techniques exist for remediation of contaminant plumes in groundwater or near the soil surface, remediation methods in the deep vadose zone are less established due to complex transport dynamics and sparse microbial populations. There is a lack of knowledge on how physical and hydrologic features of the vadose zone control microbial growth and colonization in response to nutrient delivery during bioremediation. Yet pollution in the vadose zone poses a serious threat to the groundwater resources lying deeper in the sediment. While the contaminants may be slowly degraded by native microbial communities, microbial degradation rates rarely keep pace with the spread of the pollutant. It is crucial to increase indigenous microbial degradation in the vadose zone to combat groundwater contamination.

  3. Artificial selection for determinate growth habit in soybean

    PubMed Central

    Tian, Zhixi; Wang, Xiaobo; Lee, Rian; Li, Yinghui; Specht, James E.; Nelson, Randall L.; McClean, Phillip E.; Qiu, Lijuan; Ma, Jianxin

    2010-01-01

    Determinacy is an agronomically important trait associated with the domestication in soybean (Glycine max). Most soybean cultivars are classifiable into indeterminate and determinate growth habit, whereas Glycine soja, the wild progenitor of soybean, is indeterminate. Indeterminate (Dt1/Dt1) and determinate (dt1/dt1) genotypes, when mated, produce progeny that segregate in a monogenic pattern. Here, we show evidence that Dt1 is a homolog (designated as GmTfl1) of Arabidopsis terminal flower 1 (TFL1), a regulatory gene encoding a signaling protein of shoot meristems. The transition from indeterminate to determinate phenotypes in soybean is associated with independent human selections of four distinct single-nucleotide substitutions in the GmTfl1 gene, each of which led to a single amino acid change. Genetic diversity of a minicore collection of Chinese soybean landraces assessed by simple sequence repeat (SSR) markers and allelic variation at the GmTfl1 locus suggest that human selection for determinacy took place at early stages of landrace radiation. The GmTfl1 allele introduced into a determinate-type (tfl1/tfl1) Arabidopsis mutants fully restored the wild-type (TFL1/TFL1) phenotype, but the Gmtfl1 allele in tfl1/tfl1 mutants did not result in apparent phenotypic change. These observations indicate that GmTfl1 complements the functions of TFL1 in Arabidopsis. However, the GmTfl1 homeolog, despite its more recent divergence from GmTfl1 than from Arabidopsis TFL1, appears to be sub- or neo-functionalized, as revealed by the differential expression of the two genes at multiple plant developmental stages and by allelic analysis at both loci. PMID:20421496

  4. Dietary microbial phytase exerts mixed effects on the gut health of tilapia: a possible reason for the null effect on growth promotion.

    PubMed

    Hu, Jun; Ran, Chao; He, Suxu; Cao, Yanan; Yao, Bin; Ye, Yuantu; Zhang, Xuezhen; Zhou, Zhigang

    2016-06-01

    The present study evaluated the effects of dietary microbial phytase on the growth and gut health of hybrid tilapia (Oreochromis niloticus ♀×Oreochromis aureus ♂), focusing on the effect on intestinal histology, adhesive microbiota and expression of immune-related cytokine genes. Tilapia were fed either control diet or diet supplemented with microbial phytase (1000 U/kg). Each diet was randomly assigned to four groups of fish reared in cages (3×3×2 m). After 12 weeks of feeding, weight gain and feed conversion ratio of tilapia were not significantly improved by dietary microbial phytase supplementation. However, significantly higher level of P content in the scales, tighter and more regular intestinal mucosa folds were observed in the microbial phytase group and the microvilli density was significantly increased. The adhesive gut bacterial communities were strikingly altered by microbial phytase supplementation (0·41microbial phytase, as indicated by the up-regulated intestinal expressions of the cytokine genes (tnf-α and tgf-β) and hsp70. In addition, the gut microvilli height was significantly decreased in the phytase group. These results indicate that dietary microbial phytase may exert mixed effects on hybrid tilapia, and can guide our future selection of phytases as aquafeed additives - that is, eliminating those that can stimulate intestinal inflammation. PMID:27080419

  5. GC-based detection of aldononitrile acetate derivatized glucosamine and muramic acid for microbial residue determination in soil.

    PubMed

    Liang, Chao; Read, Harry W; Balser, Teri C

    2012-05-19

    Quantitative approaches to characterizing microorganisms are crucial for a broader understanding of the microbial status and function within ecosystems. Current strategies for microbial analysis include both traditional laboratory culture-dependent techniques and those based on direct extraction and determination of certain biomarkers. Few among the diversity of microbial species inhabiting soil can be cultured, so culture-dependent methods introduce significant biases, a limitation absent in biomarker analysis. The glucosamine, mannosamine, galactosamine and muramic acid have been well served as measures of both the living and dead microbial mass, of these the glucosamine (most abundant) and muramic acid (uniquely from bacterial cell) are most important constituents in the soil systems. However, the lack of knowledge on the analysis restricts the wide popularization among scientific peers. Among all existing analytical methods, derivatization to aldononitrile acetates followed by GC-based analysis has emerged as a good option with respect to optimally balancing precision, sensitivity, simplicity, good chromatographic separation, and stability upon sample storage. Here, we present a detailed protocol for a reliable and relatively simple analysis of glucosamine and muramic acid from soil after their conversion to aldononitrile acetates. The protocol mainly comprises four steps: acid digestion, sample purification, derivatization and GC determination. The step-by-step procedure is modified according to former publications. In addition, we present a strategy to structurally validate the molecular ion of the derivative and its ion fragments formed upon electron ionization. We applied GC-EI-MS-SIM, LC-ESI-TOF-MS and isotopically labeled reagents to determine the molecular weight of aldononitrile acetate derivatized glucosamine and muramic acid; we used the mass shift of isotope-labeled derivatives in the ion spectrum to investigate ion fragments of each derivatives. In

  6. TatC-dependent translocation of pyoverdine is responsible for the microbial growth suppression.

    PubMed

    Lee, Yeji; Kim, Yong-Jae; Lee, Jung-Hoon; Yu, Hyung Eun; Lee, Kiho; Jin, Shouguang; Ha, Un-Hwan

    2016-02-01

    Infections are often not caused by a colonization of Pseudomonas aeruginosa alone but by a consortium of other bacteria. Little is known about the impact of P. aeruginosa on the growth of other bacteria upon coinfection. Here, cell-ree culture supernatants obtained from P. aeruginosa suppressed the growth of a number of bacterial strains such as Corynebacterium glutamicum, Bacillus subtilis, Staphylococcus aureus, and Agrobacterium tumefaciens, but had little effect on the growth of Escherichia coli and Salmonella Typhimurium. The growth suppression effect was obvious when P. aeruginosa was cultivated in M9 minimal media, and the suppression was not due to pyocyanin, a well-known antimicrobial toxin secreted by P. aeruginosa. By performing transposon mutagenesis, PA5070 encoding TatC was identified, and the culture supernatant of its mutant did not suppress the growth. HPLC analysis of supernatants showed that pyoverdine was a secondary metabolite present in culture supernatants of the wild-type strain, but not in those of the PA5070 mutant. Supplementation of FeCl2 as a source of iron compromised the growth suppression effect of supernatants and also recovered biofilm formation of S. aureus, indicating that pyoverdine-mediated iron acquisition is responsible for the growth suppression. Thus, this study provides the action of TatC-dependent pyoverdine translocation for the growth suppression of other bacteria, and it might aid understanding of the impact of P. aeruginosa in the complex community of bacterial species upon coinfection. PMID:26832668

  7. Dissipation and effects of tricyclazole on soil microbial communities and rice growth as affected by amendment with alperujo compost.

    PubMed

    García-Jaramillo, M; Redondo-Gómez, S; Barcia-Piedras, J M; Aguilar, M; Jurado, V; Hermosín, M C; Cox, L

    2016-04-15

    The presence of pesticides in surface and groundwater has grown considerably in the last decades as a consequence of the intensive farming activity. Several studies have shown the benefits of using organic amendments to prevent losses of pesticides from runoff or leaching. A particular soil from the Guadalquivir valley was placed in open air ponds and amended at 1 or 2% (w/w) with alperujo compost (AC), a byproduct from the olive oil industry. Tricyclazole dissipation, rice growth and microbial diversity were monitored along an entire rice growing season. An increase in the net photosynthetic rate of Oryza sativa plants grown in the ponds with AC was observed. These plants produced between 1100 and 1300kgha(-1) more rice than plants from the unamended ponds. No significant differences were observed in tricyclazole dissipation, monitored for a month in soil, surface and drainage water, between the amended and unamended ponds. The structure and diversity of bacteria and fungi communities were also studied by the use of the polymerase chain reaction denaturing gel electrophoresis (PCR-DGGE) from DNA extracted directly from soil samples. The banding pattern was similar for all treatments, although the density of bands varied throughout the time. Apparently, tricyclazole did not affect the structure and diversity of bacteria and fungi communities, and this was attributed to its low bioavailability. Rice cultivation under paddy field conditions may be more efficient under the effects of this compost, due to its positive effects on soil properties, rice yield, and soil microbial diversity.

  8. Effects of electron beam irradiation on the microbial growth and quality of beef jerky during storage

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Jin; Chun, Ho-Hyun; Song, Hyeon-Jeong; Song, Kyung-Bin

    2010-11-01

    Electron beam irradiation was applied to improve the microbial safety of beef jerky during storage. Beef jerky samples were irradiated at doses of 1, 3, 5, and 10 kGy and stored at 20 °C for 60 d. Microbiological data indicated that the populations of total aerobic bacteria significantly decreased with increasing irradiation dosage. In particular, the populations of total aerobic bacteria were significantly decreased by 1.76 log CFU/g at 10 kJ/m 2, compared to the control. Color measurements showed reduced Hunter L and a values of beef jerky for all the treatments during storage, and the Hunter L, a, and b values of beef jerky were not significantly different among the treatments. Sensory evaluation results also showed that electron beam irradiation did not affect sensory scores in overall during storage. Therefore, the results suggest that electron beam irradiation could be useful in improving the microbial safety without impairing the quality of beef jerky during storage.

  9. Analytical determination of the microbial utilization and transformation of humic acids extracted from municipal refuse.

    PubMed

    Filip, Z; Berthelin, J

    2001-11-01

    Humic substances are usually the refractory part of natural organic matter, and in a landfill they can retain inorganic and organic micropollutants. This study has investigated analytically whether humic acids (HA) extracted by use of alkali from either fresh municipal refuse or from refuse disposed of in a landfill for up to 12 months can resist microbial degradation under aerobic conditions. When added as a supplementary nutrient source, up to 63.6% of HA was utilized and this percentage was enhanced to a mean value of 88.5% when different HA preparations were used as the sole source of carbon. In cultures of a soil microbial community containing the same preparations as sole sources of nitrogen, HA was usually completely utilized. The remaining HA re-isolated from some microbial cultures were highly depleted in carbon and, simultaneously, the nitrogen content was enhanced. The FTIR spectra were indicative of strong participation of aliphatic structural units in the refuse-related HA preparations. Because of the microbial activity, different carbonaceous substances were primarily removed from the HA structure, and an increase in nitrogenous molecular groups became apparent. The structural transformations brought about by soil microorganisms "in vitro" corresponded to those occurring naturally in HA obtained from refuse aged for 12 months in a landfill.

  10. Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition

    NASA Astrophysics Data System (ADS)

    Ou, Shiqi; Zhao, Yi; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

    2016-10-01

    This work describes experiments and computational simulations to analyze single-chamber, air-cathode microbial fuel cell (MFC) performance and cathodic limitations in terms of current generation, power output, mass transport, biomass competition, and biofilm growth. Steady-state and transient cathode models were developed and experimentally validated. Two cathode gas mixtures were used to explore oxygen transport in the cathode: the MFCs exposed to a helium-oxygen mixture (heliox) produced higher current and power output than the group of MFCs exposed to air or a nitrogen-oxygen mixture (nitrox), indicating a dependence on gas-phase transport in the cathode. Multi-substance transport, biological reactions, and electrochemical reactions in a multi-layer and multi-biomass cathode biofilm were also simulated in a transient model. The transient model described biofilm growth over 15 days while providing insight into mass transport and cathodic dissolved species concentration profiles during biofilm growth. Simulation results predict that the dissolved oxygen content and diffusion in the cathode are key parameters affecting the power output of the air-cathode MFC system, with greater oxygen content in the cathode resulting in increased power output and fully-matured biomass.

  11. Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition

    DOE PAGES

    Ou, Shiqi; Zhao, Yi; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

    2016-08-15

    This work describes experiments and computational simulations to analyze single-chamber, air-cathode microbial fuel cell (MFC) performance and cathodic limitations in terms of current generation, power output, mass transport, biomass competition, and biofilm growth. Steady-state and transient cathode models were developed and experimentally validated. Two cathode gas mixtures were used to explore oxygen transport in the cathode: the MFCs exposed to a helium-oxygen mixture (heliox) produced higher current and power output than the group of MFCs exposed to air or a nitrogen-oxygen mixture (nitrox), indicating a dependence on gas-phase transport in the cathode. Multi-substance transport, biological reactions, and electrochemical reactions inmore » a multi-layer and multi-biomass cathode biofilm were also simulated in a transient model. The transient model described biofilm growth over 15 days while providing insight into mass transport and cathodic dissolved species concentration profiles during biofilm growth. Lastly, simulation results predict that the dissolved oxygen content and diffusion in the cathode are key parameters affecting the power output of the air-cathode MFC system, with greater oxygen content in the cathode resulting in increased power output and fully-matured biomass.« less

  12. Influence of pulsed magnetic field on soybean (Glycine max L.) seed germination, seedling growth and soil microbial population.

    PubMed

    Radhakrishnan, Ramalingam; Kumari, Bollipo Dyana Ranjitha

    2013-08-01

    The effects of pulsed magnetic field (PMF) treatment of soybean (Glycine max L. cv CO3) seeds were investigated on rate of seed germination, seedling growth, physico-chemical properties of seed leachates and soil microbial population under laboratory conditions. Seeds were exposed to PMF of 1500 nT at 0.1, 1.0 10.0 and 100.0 Hz for 5 h per day for 20 days, induced by enclosure coil systems. Non-treated seeds were considered as controls. All PMF treatments significantly increased the rate of seed germination, while 10 and 100 Hz PMFs showed the most effective response. The 1.0 and 10 Hz PMFs remarkably improved the fresh weight of shoots and roots, leaf area and plant height from seedlings from magnetically-exposed seeds compared to the control, while 10 Hz PMF increased the total soluble sugar, total protein and phenol contents. The leaf chlorophyll a, b and total chlorophyll were higher in PMF (10 and 100 Hz) pretreated plants, as compared to other treatments. In addition, activities of alpha-amylase, acid phosphatase, alkaline phosphatase, nitrate reductase, peroxidase and polyphenoloxidase were increased, while beta-amylase and protease activities were declined in PMF (10 Hz)-exposed soybean plants. Similarly, the capacity of absorbance of water by seeds and electrical conductivity of seed leachates were significantly enhanced by 10 Hz PMF exposure, whereas PMF (10 Hz) pretreated plants did not affect the microbial population in rhizosphere soil. The results suggested the potential of 10 Hz PMF treatment to enhance the germination and seedling growth of soybean.

  13. Effects of mild heat treatment on microbial growth and product quality of packaged fresh-cut table grapes.

    PubMed

    Kou, L; Luo, Y; Wu, D; Liu, X

    2007-10-01

    The changes in packaged fresh-cut grape quality and microbial growth as affected by mild heat treatments and the retention of grape cap stems during 5 degrees C storage were evaluated. Each individual grape was either manually pulled off (stemless) from the stems, or cut (cut stem) to allow for a 1- to 2-mm cap stem remaining on the berry. The samples were sanitized in 100 mg/L chlorine solution for 1 min, followed by a mild heat treatment in a water bath (45 degrees C, 8 min) or an oven (55 degrees C, 5 min). After cooling, the berries were packaged in rigid trays sealed with a gas permeable film and stored at 5 degrees C. Product quality and decay rate were evaluated periodically during storage. The results indicate that in the package headspace for hot water treatment of stemless grapes, partial pressures of O(2) declined significantly (P < 0.05) less and C(2)H(4) increased significantly (P < 0.001) less than for the control and hot air treatment. Stem removal and heat treatment had significant (P < 0.05) effects on the decay rate of grapes during storage. Hot water treatment maintained a significantly lower decay rate than the control and hot air treatment throughout the entire storage. Color and texture were not significantly (P > 0.05) affected by either heat treatment or stem removal. Grapes that retained the cap stems and received hot water treatment had the lowest decay rate and lowest microbial growth with the absence of any negative impact on grape color, texture, and flavor.

  14. Influence of pulsed magnetic field on soybean (Glycine max L.) seed germination, seedling growth and soil microbial population.

    PubMed

    Radhakrishnan, Ramalingam; Kumari, Bollipo Dyana Ranjitha

    2013-08-01

    The effects of pulsed magnetic field (PMF) treatment of soybean (Glycine max L. cv CO3) seeds were investigated on rate of seed germination, seedling growth, physico-chemical properties of seed leachates and soil microbial population under laboratory conditions. Seeds were exposed to PMF of 1500 nT at 0.1, 1.0 10.0 and 100.0 Hz for 5 h per day for 20 days, induced by enclosure coil systems. Non-treated seeds were considered as controls. All PMF treatments significantly increased the rate of seed germination, while 10 and 100 Hz PMFs showed the most effective response. The 1.0 and 10 Hz PMFs remarkably improved the fresh weight of shoots and roots, leaf area and plant height from seedlings from magnetically-exposed seeds compared to the control, while 10 Hz PMF increased the total soluble sugar, total protein and phenol contents. The leaf chlorophyll a, b and total chlorophyll were higher in PMF (10 and 100 Hz) pretreated plants, as compared to other treatments. In addition, activities of alpha-amylase, acid phosphatase, alkaline phosphatase, nitrate reductase, peroxidase and polyphenoloxidase were increased, while beta-amylase and protease activities were declined in PMF (10 Hz)-exposed soybean plants. Similarly, the capacity of absorbance of water by seeds and electrical conductivity of seed leachates were significantly enhanced by 10 Hz PMF exposure, whereas PMF (10 Hz) pretreated plants did not affect the microbial population in rhizosphere soil. The results suggested the potential of 10 Hz PMF treatment to enhance the germination and seedling growth of soybean. PMID:24772951

  15. Effects of mild heat treatment on microbial growth and product quality of packaged fresh-cut table grapes.

    PubMed

    Kou, L; Luo, Y; Wu, D; Liu, X

    2007-10-01

    The changes in packaged fresh-cut grape quality and microbial growth as affected by mild heat treatments and the retention of grape cap stems during 5 degrees C storage were evaluated. Each individual grape was either manually pulled off (stemless) from the stems, or cut (cut stem) to allow for a 1- to 2-mm cap stem remaining on the berry. The samples were sanitized in 100 mg/L chlorine solution for 1 min, followed by a mild heat treatment in a water bath (45 degrees C, 8 min) or an oven (55 degrees C, 5 min). After cooling, the berries were packaged in rigid trays sealed with a gas permeable film and stored at 5 degrees C. Product quality and decay rate were evaluated periodically during storage. The results indicate that in the package headspace for hot water treatment of stemless grapes, partial pressures of O(2) declined significantly (P < 0.05) less and C(2)H(4) increased significantly (P < 0.001) less than for the control and hot air treatment. Stem removal and heat treatment had significant (P < 0.05) effects on the decay rate of grapes during storage. Hot water treatment maintained a significantly lower decay rate than the control and hot air treatment throughout the entire storage. Color and texture were not significantly (P > 0.05) affected by either heat treatment or stem removal. Grapes that retained the cap stems and received hot water treatment had the lowest decay rate and lowest microbial growth with the absence of any negative impact on grape color, texture, and flavor. PMID:17995622

  16. Effect of high oxygen modified atmosphere packaging on microbial growth and sensorial qualities of fresh-cut produce.

    PubMed

    Jacxsens, L; Devlieghere, F; Van der Steen, C; Debevere, J

    2001-12-30

    The application of High Oxygen Atmospheres (HOA) (i.e. > 70% O2) for packaging ready-to-eat vegetables was evaluated as an alternative technique for low O2 Equilibrium Modified Atmosphere (EMA) packaging (3% O2-5% CO2-balance N2) for respiring products. Comparative experiments between both techniques were performed in-vitro and in-vivo. Typical spoilage causing microorganisms (Pseudomonas fluorescens, Candida lambica), the moulds Botrytis cinerea, Aspergillus flavus and the opportunistic psychrotrophic human pathogenic microorganism associated with refrigerated minimally processed vegetables. Aeromonas caviae (HG4), showed a retarded growth during the conducted in-vitro studies at 4 degrees C in 70%, 80% and 95% O2 as examples of HOA compared to the in-vitro experiments in 5% O2 (as example of EMA packaging) and the effect was more pronounced in 95% O2. The effect of the high O2-concentrations on the human pathogen Listeria monocytogenes resulted in an extended lag phase (95% O2). The plant pathogen Erwinia carotovora was increasingly stimulated by increasing high O2-concentrations. During a storage experiment of three types of ready-to-eat vegetables (mushroom slices, grated celeriac and shredded chicory endive), which are sensitive to enzymatic browning and microbial spoilage, the effect of EMA and HOA (95% O2-5% N2) on their quality and shelf life was compared. High O2 atmospheres were found to be particularly effective in inhibiting enzymatic browning of the tested vegetables. Also, the microbial quality was better as a reduction in yeast growth was observed. The HOA can be applied as an alternative for low O2 modified atmospheres for some specific types of ready-to-eat vegetables, sensitive to enzymatic browning and spoilage by yeasts.

  17. Effects of Resveratrol and Essential Oils on Growth Performance, Immunity, Digestibility and Fecal Microbial Shedding in Challenged Piglets

    PubMed Central

    Ahmed, S. T.; Hossain, M. E.; Kim, G. M.; Hwang, J. A.; Ji, H.; Yang, C. J.

    2013-01-01

    A study was conducted to evaluate the effects of resveratrol and essential oils from medicinal plants on the growth performance, immunity, digestibility, and fecal microbial shedding of weaned piglets. A total of 48 weaned piglets (8 kg initial weight, 28-d-old) were randomly allotted to four dietary treatments with 3 replications of 4 piglets each. The dietary treatments were NC (negative control; basal diet), PC (positive control; basal diet+0.002% apramycin), T1 (basal diet+0.2% resveratrol), and T2 (basal diet+0.0125% essential oil blend). All piglets were orally challenged with 5 ml culture fluid containing 2.3×108 cfu/ml of Escherichia coli KCTC 2571 and 5.9×108 cfu/ml Salmonella enterica serover Typhimurium. The PC group (p<0.05) showed the highest average daily gain (ADG) and average daily feed intake (ADFI) throughout the experimental period, although feed conversion ratio (FCR) was improved in the T1 group (p>0.05). Serum IgG level was increased in the T1 group, whereas TNF-α levels was reduced in the supplemented groups compared to control (p<0.05). The PC diet improved the dry matter (DM) digestibility, whereas PC and T2 diets improved nitrogen (N) digestibility compared to NC and T1 diets (p<0.05). Fecal Salmonella and E. coli counts were reduced in all treatment groups compared to control (p<0.05). Fecal Lactobacillus spp. count was increased in the T2 group compared to others (p<0.05). Dietary treatments had no significant effect on fecal Bacillus spp. count throughout the entire experimental period. Based on these results, resveratrol showed strong potential as antibiotic alternatives for reversing the adverse effects of weaning stress on growth performance, immunity and microbial environment in E. coli and Salmonella-challenged piglets. PMID:25049839

  18. Microbial Growth and Air Pollutants in the Corrosion of Carbonate Rocks: Results from Laboratory and Outdoor Experimental Tests

    NASA Astrophysics Data System (ADS)

    Moroni, B.; Poli, G.; Pitzurra, L.

    2003-04-01

    Microorganisms and atmospheric pollution are primary causes of deterioration of materials exposed to open air. Due to the variety of chemical-mineralogical compositions and textures, stone represents a variegated substrate that interacts with environmental fluids and particulate, and is a selective environment for biological proliferation. Carbonate rocks, in particular, are highly exposed to environmental decay and extremely susceptible to acid attack caused by atmospheric pollutants and metabolic acid production. The aim of this work is to study the combined effect of microbial contamination and atmospheric pollutants in the weathering of carbonate rocks by means of laboratory and outdoor exposure tests. Laboratory experiments performed on carbonate rocks allowed evaluation of the influence of the gas mixture in the chemical modifications of the lithic substrate, and formulation of a kinetic model of sulphation. The obtained results suggest that nucleation alternates with growth as leading processes in the development of sulphation. In particular, nucleation of the reaction products is the leading process in the initial period of sulphation, which is characterized by a marked slowdown of the reaction progress, whereas growth of the products is the leading process in the subsequent period of resumption of sulphation. In situ experiments performed by exposing limestone specimens at two air monitoring stations in Perugia with different degrees of urban air pollution showed high levels of fungal colonization at early times and the presence of weathering products (i.e. gypsum) in the longer term. Results point to a combined effect of microbial colonization and atmospheric pollutants in promoting the weathering of stone through acid attack within the film of water present on the surface of the exposed material, and through the oxidation of metal sulphide particulate pollutant to sulphate. Laboratory tests assaying the extent of fungal colonization and/or chemical

  19. Microbial toxicity of methyl tert-butyl ether (MTBE) determined with fluorescent and luminescent bioassays.

    PubMed

    Roslev, Peter; Lentz, Trine; Hesselsoe, Martin

    2015-02-01

    The inhibitory effects of the fuel additive methyl tert-butyl ether (MTBE) and potential degradation products tert-butanol (TBA) and formaldehyde was examined using mixed microbial biomass, and six strains of bioluminescent bacteria and yeast. The purpose was to assess microbial toxicity with quantitative bioluminescent and fluorescent endpoints, and to identify sensitive proxies suitable for monitoring MTBE contamination. Bioluminescent Aliivibrio fischeri DSM 7151 (formerly Vibrio fischeri) appeared highly sensitive to MTBE exposure, and was a superior test organisms compared to lux-tagged Escherichia coli DH5α, Pseudomonas fluorescens DF57-40E7 and Saccharomyces cerevisiae BLYR. EC10 and EC50 for acute MTBE toxicity in A. fischeri were 1.1 and 10.9 mg L(-1), respectively. Long term (24h) MTBE exposure resulted in EC10 values of 0.01 mg L(-1). TBA was significantly less toxic with EC10 and EC50 for acute and chronic toxicity >1000 mg L(-1). Inhibition of bioluminescence was generally a more sensitive endpoint for MTBE toxicity than measuring intracellular ATP levels and heterotrophic CO2 assimilation. A weak estrogenic response was detected for MTBE at concentrations ⩾ 3.7 g L(-1) using an estrogen inducible bioluminescent yeast strain (S. cerevisiae BLYES). Microbial hydrolytic enzyme activity in groundwater was affected by MTBE with EC10 values of 0.5-787 mg L(-1), and EC50 values of 59-3073 for alkaline phosphatase, arylsulfatase, beta-1,4-glucanase, N-acetyl-beta-d-glucosaminidase, and leucine-aminopeptidase. Microbial alkaline phosphatase and beta-1,4-glucanase activity were most sensitive to MTBE exposure with EC50 ⩽ 64.8 mg L(-1). The study suggests that bioassays with luminescent A. fischeri, and fluorescent assays targeting hydrolytic enzyme activity are good candidates for monitoring microbial MTBE toxicity in contaminated water.

  20. Development of a predictive model for the growth kinetics of aerobic microbial population on pomegranate marinated chicken breast fillets under isothermal and dynamic temperature conditions.

    PubMed

    Lytou, Anastasia; Panagou, Efstathios Z; Nychas, George-John E

    2016-05-01

    The aim of this study was the development of a model to describe the growth kinetics of aerobic microbial population of chicken breast fillets marinated in pomegranate juice under isothermal and dynamic temperature conditions. Moreover, the effect of pomegranate juice on the extension of the shelf life of the product was investigated. Samples (10 g) of chicken breast fillets were immersed in marinades containing pomegranate juice for 3 h at 4 °C following storage under aerobic conditions at 4, 10, and 15 °C for 10 days. Total Viable Counts (TVC), Pseudomonas spp and lactic acid bacteria (LAB) were enumerated, in parallel with sensory assessment (odor and overall appearance) of marinated and non-marinated samples. The Baranyi model was fitted to the growth data of TVC to calculate the maximum specific growth rate (μmax) that was further modeled as a function of temperature using a square root-type model. The validation of the model was conducted under dynamic temperature conditions based on two fluctuating temperature scenarios with periodic changes from 6 to 13 °C. The shelf life was determined both mathematically and with sensory assessment and its temperature dependence was modeled by an Arrhenius type equation. Results showed that the μmax of TVC of marinated samples was significantly lower compared to control samples regardless temperature, while under dynamic temperature conditions the model satisfactorily predicted the growth of TVC in both control and marinated samples. The shelf-life of marinated samples was significantly extended compared to the control (5 days extension at 4 °C). The calculated activation energies (Ea), 82 and 52 kJ/mol for control and marinated samples, respectively, indicated higher temperature dependence of the shelf life of control samples compared to marinated ones. The present results indicated that pomegranate juice could be used as an alternative ingredient in marinades to prolong the shelf life of chicken.

  1. Foliar application of microbial and plant based biostimulants increases growth and potassium uptake in almond (Prunus dulcis [Mill.] D. A. Webb)

    PubMed Central

    Saa, Sebastian; Olivos-Del Rio, Andres; Castro, Sebastian; Brown, Patrick H.

    2015-01-01

    The use of biostimulants has become a common practice in agriculture. However, there is little peer-reviewed research on this topic. In this study we tested, under controlled and replicated conditions, the effect of one biostimulant derived from seaweed extraction (Bio-1) and another biostimulant derived from microbial fermentation (Bio-2). This experiment utilized 2-years-old almond plants over two growing seasons in a randomized complete design with a full 2 × 4 factorial structure with two soil potassium treatments (125 μg g-1 of K vs. 5 μg g-1) and four foliar treatments (No spray, Foliar-K, Bio-1, Bio-2). Rubidium was utilized as a surrogate for short-term potassium uptake and plant growth, nutrient concentration, and final plant biomass were evaluated. There was a substantial positive effect of both biostimulant treatments on total shoot leaf area, and significant increases in shoot length and biomass under adequate soil potassium supply with a positive effect of Bio-1 only under low K supply. Rubidium uptake was increased by Bio-1 application an effect that was greater under the low soil K treatment. Though significant beneficial effects of the biostimulants used on plant growth were observed, it is not possible to determine the mode of action of these materials. The results presented here illustrate the promise and complexity of research involving biostimulants. PMID:25755660

  2. Foliar application of microbial and plant based biostimulants increases growth and potassium uptake in almond (Prunus dulcis [Mill.] D. A. Webb).

    PubMed

    Saa, Sebastian; Olivos-Del Rio, Andres; Castro, Sebastian; Brown, Patrick H

    2015-01-01

    The use of biostimulants has become a common practice in agriculture. However, there is little peer-reviewed research on this topic. In this study we tested, under controlled and replicated conditions, the effect of one biostimulant derived from seaweed extraction (Bio-1) and another biostimulant derived from microbial fermentation (Bio-2). This experiment utilized 2-years-old almond plants over two growing seasons in a randomized complete design with a full 2 × 4 factorial structure with two soil potassium treatments (125 μg g(-1) of K vs. 5 μg g(-1)) and four foliar treatments (No spray, Foliar-K, Bio-1, Bio-2). Rubidium was utilized as a surrogate for short-term potassium uptake and plant growth, nutrient concentration, and final plant biomass were evaluated. There was a substantial positive effect of both biostimulant treatments on total shoot leaf area, and significant increases in shoot length and biomass under adequate soil potassium supply with a positive effect of Bio-1 only under low K supply. Rubidium uptake was increased by Bio-1 application an effect that was greater under the low soil K treatment. Though significant beneficial effects of the biostimulants used on plant growth were observed, it is not possible to determine the mode of action of these materials. The results presented here illustrate the promise and complexity of research involving biostimulants. PMID:25755660

  3. Foliar application of microbial and plant based biostimulants increases growth and potassium uptake in almond (Prunus dulcis [Mill.] D. A. Webb).

    PubMed

    Saa, Sebastian; Olivos-Del Rio, Andres; Castro, Sebastian; Brown, Patrick H

    2015-01-01

    The use of biostimulants has become a common practice in agriculture. However, there is little peer-reviewed research on this topic. In this study we tested, under controlled and replicated conditions, the effect of one biostimulant derived from seaweed extraction (Bio-1) and another biostimulant derived from microbial fermentation (Bio-2). This experiment utilized 2-years-old almond plants over two growing seasons in a randomized complete design with a full 2 × 4 factorial structure with two soil potassium treatments (125 μg g(-1) of K vs. 5 μg g(-1)) and four foliar treatments (No spray, Foliar-K, Bio-1, Bio-2). Rubidium was utilized as a surrogate for short-term potassium uptake and plant growth, nutrient concentration, and final plant biomass were evaluated. There was a substantial positive effect of both biostimulant treatments on total shoot leaf area, and significant increases in shoot length and biomass under adequate soil potassium supply with a positive effect of Bio-1 only under low K supply. Rubidium uptake was increased by Bio-1 application an effect that was greater under the low soil K treatment. Though significant beneficial effects of the biostimulants used on plant growth were observed, it is not possible to determine the mode of action of these materials. The results presented here illustrate the promise and complexity of research involving biostimulants.

  4. Microbial Growth Inferred from Nutrient Depletion in Deepwater Horizon Submerged Oil/Gas Plumes

    NASA Astrophysics Data System (ADS)

    Shiller, A. M.; Joung, D.

    2012-12-01

    The Deepwater Horizon accident resulted in a substantial uncontrolled hydrocarbon release to the northern Gulf of Mexico, much of which was entrained in deep submerged plumes. While bio-degradation of the hydrocarbons has been inferred from microbial biomass and genetics, the amount of conversion of oil and gas carbon to biomass remains uncertain. Here we examine correlated depletions of nitrate, phosphate, and oxygen in the submerged plumes during May 2010. Combining these correlations with published estimates of overall oxygen consumption, we estimate that the substantial portion of hydrocarbons in these plumes was initially converted to biomass. This contrasts with nutrient-limited surface waters where other work has suggested respiration to carbon dioxide to be the dominant fate of the hydrocarbons.

  5. Prediction of competitive microbial growth in mixed culture at dynamic temperature patterns.

    PubMed

    Fujikawa, Hiroshi; Sakha, Mohammad Z

    2014-01-01

    A novel competition model developed with the new logistic model and the Lotka-Volterra model successfully predicted the growth of bacteria in mixed culture using the mesophiles Staphylococcus aureus, Escherichia coli, and Salmonella at a constant temperature in our previous studies. In this study, we further studied the prediction of the growth of those bacteria in mixed culture at dynamic temperatures with various initial populations with the competition model. First, we studied the growth kinetics of the species in a monoculture at various constant temperatures ranging from 16℃ to 32℃. With the analyzed data in the monoculture, we then examined the prediction of bacterial growth in mixed culture with two and three species. The growth of the bacteria in the mixed culture at dynamic temperatures was successfully predicted with the model. The residuals between the observed and predicted populations at the data points were <0.5 log at most points, being 83.3% and 84.2% for the two-species mixture and the three-species mixture, respectively. The present study showed that the model could be applied to the competitive growth in mixed culture at dynamic temperature patterns. PMID:25252643

  6. Better to light a candle than curse the darkness: illuminating spatial localization and temporal dynamics of rapid microbial growth in the rhizosphere.

    PubMed

    Herron, Patrick M; Gage, Daniel J; Arango Pinedo, Catalina; Haider, Zane K; Cardon, Zoe G

    2013-01-01

    The rhizosphere is a hotbed of microbial activity in ecosystems, fueled by carbon compounds from plant roots. Basic questions about the location and dynamics of plant-spurred microbial growth in the rhizosphere are difficult to answer with standard, destructive soil assays mixing a multitude of microbe-scale microenvironments in a single, often sieved, sample. Soil microbial biosensors designed with the luxCDABE reporter genes fused to a promoter of interest enable continuous imaging of the microbial perception of (and response to) environmental conditions in soil. We used the common soil bacterium Pseudomonas putida KT2440 as host to plasmid pZKH2 containing a fusion between the strong constitutive promoter nptII and luxCDABE (coding for light-emitting proteins) from Vibrio fischeri. Experiments in liquid media demonstrated that high light production by KT2440/pZKH2 was associated with rapid microbial growth supported by high carbon availability. We applied the biosensors in microcosms filled with non-sterile soil in which corn (Zea mays L.), black poplar (Populus nigra L.), or tomato (Solanum lycopersicum L.) was growing. We detected minimal light production from microbiosensors in the bulk soil, but biosensors reported continuously from around roots for as long as six days. For corn, peaks of luminescence were detected 1-4 and 20-35 mm along the root axis behind growing root tips, with the location of maximum light production moving farther back from the tip as root growth rate increased. For poplar, luminescence around mature roots increased and decreased on a coordinated diel rhythm, but was not bright near root tips. For tomato, luminescence was dynamic, but did not exhibit a diel rhythm, appearing in acropetal waves along roots. KT2440/pZKH2 revealed that root tips are not always the only, or even the dominant, hotspots for rhizosphere microbial growth, and carbon availability is highly variable in space and time around roots. PMID:24032034

  7. Better to light a candle than curse the darkness: illuminating spatial localization and temporal dynamics of rapid microbial growth in the rhizosphere

    PubMed Central

    Herron, Patrick M.; Gage, Daniel J.; Arango Pinedo, Catalina; Haider, Zane K.; Cardon, Zoe G.

    2013-01-01

    The rhizosphere is a hotbed of microbial activity in ecosystems, fueled by carbon compounds from plant roots. Basic questions about the location and dynamics of plant-spurred microbial growth in the rhizosphere are difficult to answer with standard, destructive soil assays mixing a multitude of microbe-scale microenvironments in a single, often sieved, sample. Soil microbial biosensors designed with the luxCDABE reporter genes fused to a promoter of interest enable continuous imaging of the microbial perception of (and response to) environmental conditions in soil. We used the common soil bacterium Pseudomonas putida KT2440 as host to plasmid pZKH2 containing a fusion between the strong constitutive promoter nptII and luxCDABE (coding for light-emitting proteins) from Vibrio fischeri. Experiments in liquid media demonstrated that high light production by KT2440/pZKH2 was associated with rapid microbial growth supported by high carbon availability. We applied the biosensors in microcosms filled with non-sterile soil in which corn (Zea mays L.), black poplar (Populus nigra L.), or tomato (Solanum lycopersicum L.) was growing. We detected minimal light production from microbiosensors in the bulk soil, but biosensors reported continuously from around roots for as long as six days. For corn, peaks of luminescence were detected 1–4 and 20–35 mm along the root axis behind growing root tips, with the location of maximum light production moving farther back from the tip as root growth rate increased. For poplar, luminescence around mature roots increased and decreased on a coordinated diel rhythm, but was not bright near root tips. For tomato, luminescence was dynamic, but did not exhibit a diel rhythm, appearing in acropetal waves along roots. KT2440/pZKH2 revealed that root tips are not always the only, or even the dominant, hotspots for rhizosphere microbial growth, and carbon availability is highly variable in space and time around roots. PMID:24032034

  8. A new mechanistic growth model for simultaneous determination of lag phase duration and exponential growth rate and a new Belehdradek-type model for evaluating the effect of temperature on growth rate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new mechanistic growth model was developed to describe microbial growth under isothermal conditions. The new mathematical model was derived from the basic observation of bacterial growth that may include lag, exponential, and stationary phases. With this model, the lag phase duration and exponen...

  9. Effect of gamma irradiation and storage time on microbial growth and physicochemical characteristics of pumpkin (Cucurbita Moschata Duchesne ex Poiret) puree.

    PubMed

    Gliemmo, María F; Latorre, María E; Narvaiz, Patricia; Campos, Carmen A; Gerschenson, Lía N

    2014-01-01

    The effect of gamma irradiation (0-2 kGy) and storage time (0-28 days) on microbial growth and physicochemical characteristics of a packed pumpkin puree was studied. For that purpose, a factorial design was applied. The puree contained potassium sorbate, glucose and vanillin was stored at 25°C . Gamma irradiation diminished and storage time increased microbial growth. A synergistic effect between both variables on microbial growth was observed. Storage time decreased pH and color of purees. Sorbate content decreased with storage time and gamma irradiation. Mathematical models of microbial growth generated by the factorial design allowed estimating that a puree absorbing 1.63 kGy would have a shelf-life of 4 days. In order to improve this time, some changes in the applied hurdles were assayed. These included a thermal treatment before irradiation, a reduction of irradiation dose to 0.75 kGy and a decrease in storage temperature at 20°C . As a result, the shelf-life of purees increased to 28 days. PMID:23733817

  10. Effect of gamma irradiation and storage time on microbial growth and physicochemical characteristics of pumpkin (Cucurbita Moschata Duchesne ex Poiret) puree.

    PubMed

    Gliemmo, María F; Latorre, María E; Narvaiz, Patricia; Campos, Carmen A; Gerschenson, Lía N

    2014-01-01

    The effect of gamma irradiation (0-2 kGy) and storage time (0-28 days) on microbial growth and physicochemical characteristics of a packed pumpkin puree was studied. For that purpose, a factorial design was applied. The puree contained potassium sorbate, glucose and vanillin was stored at 25°C . Gamma irradiation diminished and storage time increased microbial growth. A synergistic effect between both variables on microbial growth was observed. Storage time decreased pH and color of purees. Sorbate content decreased with storage time and gamma irradiation. Mathematical models of microbial growth generated by the factorial design allowed estimating that a puree absorbing 1.63 kGy would have a shelf-life of 4 days. In order to improve this time, some changes in the applied hurdles were assayed. These included a thermal treatment before irradiation, a reduction of irradiation dose to 0.75 kGy and a decrease in storage temperature at 20°C . As a result, the shelf-life of purees increased to 28 days.

  11. [Determination of sugars, organic acids and alcohols in microbial consortium fermentation broth from cellulose using high performance liquid chromatography].

    PubMed

    Jiang, Yan; Fan, Guifang; Du, Ran; Li, Peipei; Jiang, Li

    2015-08-01

    A high performance liquid chromatographic method was established for the determination of metabolites (sugars, organic acids and alcohols) in microbial consortium fermentation broth from cellulose. Sulfate was first added in the samples to precipitate calcium ions in microbial consortium culture medium and lower the pH of the solution to avoid the dissociation of organic acids, then the filtrates were effectively separated using high performance liquid chromatography. Cellobiose, glucose, ethanol, butanol, glycerol, acetic acid and butyric acid were quantitatively analyzed. The detection limits were in the range of 0.10-2.00 mg/L. The linear correlation coefficients were greater than 0.999 6 in the range of 0.020 to 1.000 g/L. The recoveries were in the range of 85.41%-115.60% with the relative standard deviations of 0.22% -4.62% (n = 6). This method is accurate for the quantitative analysis of the alcohols, organic acids and saccharides in microbial consortium fermentation broth from cellulose.

  12. Mapping high-growth phenotypes in the flux space of microbial metabolism

    PubMed Central

    Güell, Oriol; Massucci, Francesco Alessandro; Font-Clos, Francesc; Sagués, Francesc; Serrano, M. Ángeles

    2015-01-01

    Experimental and empirical observations on cell metabolism cannot be understood as a whole without their integration into a consistent systematic framework. However, the characterization of metabolic flux phenotypes is typically reduced to the study of a single optimal state, such as maximum biomass yield that is by far the most common assumption. Here, we confront optimal growth solutions to the whole set of feasible flux phenotypes (FFPs), which provides a benchmark to assess the likelihood of optimal and high-growth states and their agreement with experimental results. In addition, FFP maps are able to uncover metabolic behaviours, such as aerobic fermentation accompanying exponential growth on sugars at nutrient excess conditions, that are unreachable using standard models based on optimality principles. The information content of the full FFP space provides us with a map to explore and evaluate metabolic behaviour and capabilities, and so it opens new avenues for biotechnological and biomedical applications. PMID:26289659

  13. Improved annotation of antibiotic resistance determinants reveals microbial resistomes cluster by ecology.

    PubMed

    Gibson, Molly K; Forsberg, Kevin J; Dantas, Gautam

    2015-01-01

    Antibiotic resistance is a dire clinical problem with important ecological dimensions. While antibiotic resistance in human pathogens continues to rise at alarming rates, the impact of environmental resistance on human health is still unclear. To investigate the relationship between human-associated and environmental resistomes, we analyzed functional metagenomic selections for resistance against 18 clinically relevant antibiotics from soil and human gut microbiota as well as a set of multidrug-resistant cultured soil isolates. These analyses were enabled by Resfams, a new curated database of protein families and associated highly precise and accurate profile hidden Markov models, confirmed for antibiotic resistance function and organized by ontology. We demonstrate that the antibiotic resistance functions that give rise to the resistance profiles observed in environmental and human-associated microbial communities significantly differ between ecologies. Antibiotic resistance functions that most discriminate between ecologies provide resistance to β-lactams and tetracyclines, two of the most widely used classes of antibiotics in the clinic and agriculture. We also analyzed the antibiotic resistance gene composition of over 6000 sequenced microbial genomes, revealing significant enrichment of resistance functions by both ecology and phylogeny. Together, our results indicate that environmental and human-associated microbial communities harbor distinct resistance genes, suggesting that antibiotic resistance functions are largely constrained by ecology.

  14. Methods to determine the growth domain in a multidimensional environmental space.

    PubMed

    Le Marc, Yvan; Pin, Carmen; Baranyi, József

    2005-04-15

    Data from a database on microbial responses to the food environment (ComBase, see www.combase.cc) were used to study the boundary of growth several pathogens (Aeromonas hydrophila, Escherichia coli, Listeria monocytogenes, Yersinia enterocolitica). Two methods were used to evaluate the growth/no growth interface. The first one is an application of the Minimum Convex Polyhedron (MCP) introduced by Baranyi et al. [Baranyi, J., Ross, T., McMeekin, T., Roberts, T.A., 1996. The effect of parameterisation on the performance of empirical models used in Predictive Microbiology. Food Microbiol. 13, 83-91.]. The second method applies logistic regression to define the boundary of growth. The combination of these two different techniques can be a useful tool to handle the problem of extrapolation of predictive models at the growth limits.

  15. Genetic determinants of prepubertal and pubertal growth and development.

    PubMed

    Thomis, Martine A; Towne, Bradford

    2006-12-01

    This article surveys the current general understanding of genetic influences on within- and between-population variation in growth and development in the context of establishing an International Growth Standard for Preadolescent and Adolescent Children. Traditional genetic epidemiologic analysis methods are reviewed, and evidence from family studies for genetic effects on different measures of growth and development is then presented. Findings from linkage and association studies seeking to identify specific genomic locations and allelic variants of genes influencing variation in growth and maturation are then summarized. Special mention is made of the need to study the interactions between genes and environments. At present, specific genes and polymorphisms contributing to variation in growth and maturation are only beginning to be identified. Larger genetic epidemiologic studies are needed in different parts of the world to better explore population differences in gene frequencies and gene-environment interactions. As advances continue to be made in molecular and statistical genetic methods, the genetic architecture of complex processes, including those of growth and development, will become better elucidated. For now, it can only be concluded that although the fundamental genetic underpinnings of the growth and development of children worldwide are likely to be essentially the same, there are also likely to be differences between populations in the frequencies of allelic gene variants that influence growth and maturation and in the nature of gene-environment interactions. This does not necessarily preclude an international growth reference, but it does have important implications for the form that such a reference might ultimately take.

  16. Beyond Agar: Gel Substrates with Improved Optical Clarity and Drug Efficiency and Reduced Autofluorescence for Microbial Growth Experiments.

    PubMed

    Jaeger, Philipp A; McElfresh, Cameron; Wong, Lily R; Ideker, Trey

    2015-08-15

    Agar, a seaweed extract, has been the standard support matrix for microbial experiments for over a century. Recent developments in high-throughput genetic screens have created a need to reevaluate the suitability of agar for use as colony support, as modern robotic printing systems now routinely spot thousands of colonies within the area of a single microtiter plate. Identifying optimal biophysical, biochemical, and biological properties of the gel support matrix in these extreme experimental conditions is instrumental to achieving the best possible reproducibility and sensitivity. Here we systematically evaluate a range of gelling agents by using the yeast Saccharomyces cerevisiae as a model microbe. We find that carrageenan and Phytagel have superior optical clarity and reduced autofluorescence, crucial for high-resolution imaging and fluorescent reporter screens. Nutrient choice and use of refined Noble agar or pure agarose reduce the effective dose of numerous selective drugs by >50%, potentially enabling large cost savings in genetic screens. Using thousands of mutant yeast strains to compare colony growth between substrates, we found no evidence of significant growth or nutrient biases between gel substrates, indicating that researchers could freely pick and choose the optimal gel for their respective application and experimental condition.

  17. High throughput nanostructure-initiator mass spectrometry screening of microbial growth conditions for maximal β-glucosidase production

    PubMed Central

    Cheng, Xiaoliang; Hiras, Jennifer; Deng, Kai; Bowen, Benjamin; Simmons, Blake A.; Adams, Paul D.; Singer, Steven W.; Northen, Trent R.

    2013-01-01

    Production of biofuels via enzymatic hydrolysis of complex plant polysaccharides is a subject of intense global interest. Microbial communities are known to express a wide range of enzymes necessary for the saccharification of lignocellulosic feedstocks and serve as a powerful reservoir for enzyme discovery. However, the growth temperature and conditions that yield high cellulase activity vary widely, and the throughput to identify optimal conditions has been limited by the slow handling and conventional analysis. A rapid method that uses small volumes of isolate culture to resolve specific enzyme activity is needed. In this work, a high throughput nanostructure-initiator mass spectrometry (NIMS)-based approach was developed for screening a thermophilic cellulolytic actinomycete, Thermobispora bispora, for β-glucosidase production under various growth conditions. Media that produced high β-glucosidase activity were found to be I/S + glucose or microcrystalline cellulose (MCC), Medium 84 + rolled oats, and M9TE + MCC at 45°C. Supernatants of cell cultures grown in M9TE + 1% MCC cleaved 2.5 times more substrate at 45°C than at all other temperatures. While T. bispora is reported to grow optimally at 60°C in Medium 84 + rolled oats and M9TE + 1% MCC, approximately 40% more conversion was observed at 45°C. This high throughput NIMS approach may provide an important tool in discovery and characterization of enzymes from environmental microbes for industrial and biofuel applications. PMID:24367356

  18. Kinetics of microbial growth and biodegradation of methanol and toluene in biofilters and an analysis of the energetic indicators.

    PubMed

    Avalos Ramirez, Antonio; Bénard, Sandrine; Giroir-Fendler, Anne; Jones, J Peter; Heitz, Michèle

    2008-11-25

    The kinetics of microbial growth and the biodegradation of methanol and toluene in (a) biofilters (BFs), and (b) biotrickling filters (BTFs), packed with inert materials, has been studied and analyzed. The specific growth rate, mu, for the treatment of methanol was 0.037h(-1) for a wide range of operating conditions. In the BF, mu was found to be a function of the methanol and toluene concentrations in the biofilm. In the BF used for treating methanol, mu was found to be affected by (1) the nitrogen concentration present in the nutrient solution, and (2) the kind of packing material employed. The kinetics of the methanol and toluene biodegradations were also analyzed using "mixed order" models. A Michaelis-Menten model type provided a good fit for the elimination capacity (EC) of the BTF treating methanol, while a Haldane model type provided a good fit to the EC of the BF treating methanol and toluene. The carbon dioxide production rate was related to the packed bed temperature and the content of the volatile solids within the biofilm. For the BF, the ratio of temperature/carbon dioxide production rate (PCO(2)) was 0.024 degrees C per unit of PCO(2), and for the BTF it was 0.15 degrees C per unit of PCO(2). PMID:18778740

  19. Beyond Agar: Gel Substrates with Improved Optical Clarity and Drug Efficiency and Reduced Autofluorescence for Microbial Growth Experiments

    PubMed Central

    Jaeger, Philipp A.; McElfresh, Cameron; Wong, Lily R.

    2015-01-01

    Agar, a seaweed extract, has been the standard support matrix for microbial experiments for over a century. Recent developments in high-throughput genetic screens have created a need to reevaluate the suitability of agar for use as colony support, as modern robotic printing systems now routinely spot thousands of colonies within the area of a single microtiter plate. Identifying optimal biophysical, biochemical, and biological properties of the gel support matrix in these extreme experimental conditions is instrumental to achieving the best possible reproducibility and sensitivity. Here we systematically evaluate a range of gelling agents by using the yeast Saccharomyces cerevisiae as a model microbe. We find that carrageenan and Phytagel have superior optical clarity and reduced autofluorescence, crucial for high-resolution imaging and fluorescent reporter screens. Nutrient choice and use of refined Noble agar or pure agarose reduce the effective dose of numerous selective drugs by >50%, potentially enabling large cost savings in genetic screens. Using thousands of mutant yeast strains to compare colony growth between substrates, we found no evidence of significant growth or nutrient biases between gel substrates, indicating that researchers could freely pick and choose the optimal gel for their respective application and experimental condition. PMID:26070672

  20. Statistical support for the ATL program. [microbial growth in zero gravity

    NASA Technical Reports Server (NTRS)

    Hinkelmann, K.; Myers, R. H.

    1976-01-01

    Statistical experimental designs are presented for various numbers of organisms and agar solutions pertinent to the experiment, ""colony growth in zero gravity''. Missions lasting 7 and 30 days are considered. For the designs listed, the statistical analysis of the observations obtained on the space shuttle are outlined.

  1. The mechanism of ethanol treatment on inhibiting lettuce enzymatic browning and microbial growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tissue browning of fresh-cut lettuce greatly affects its quality and consumers’ appreciation. This study investigated the effects of ethanol treatment on enzymatic browning and natural microflora growth of lettuce stem discs. After treated with 20% ethanol for 2 min and then drained by a spinner, le...

  2. Single-cell genomics reveal metabolic strategies for microbial growth and survival in an oligotrophic aquifer

    SciTech Connect

    Wilkins, Michael J.; Kennedy, David W.; Castelle, Cindy; Field, Erin; Stepanauskas, Ramunas; Fredrickson, Jim K.; Konopka, Allan

    2014-02-09

    Bacteria from the genus Pedobacter are a major component of microbial assemblages at Hanford Site and have been shown to significantly change in abundance in response to the subsurface intrusion of Columbia River water. Here we employed single cell genomics techniques to shed light on the physiological niche of these microorganisms. Analysis of four Pedobacter single amplified genomes (SAGs) from Hanford Site sediments revealed a chemoheterotrophic lifestyle, with the potential to exist under both aerobic and microaerophilic conditions via expression of both aa3­-type and cbb3-type cytochrome c oxidases. These SAGs encoded a wide-range of both intra-and extra­-cellular carbohydrate-active enzymes, potentially enabling the degradation of recalcitrant substrates such as xylan and chitin, and the utilization of more labile sugars such as mannose and fucose. Coupled to these enzymes, a diversity of transporters and sugar-binding molecules were involved in the uptake of carbon from the extracellular local environment. The SAGs were enriched in TonB-dependent receptors (TBDRs), which play a key role in uptake of substrates resulting from degradation of recalcitrant carbon. CRISPR-Cas mechanisms for resisting viral infections were identified in all SAGs. These data demonstrate the potential mechanisms utilized for persistence by heterotrophic microorganisms in a carbon-limited aquifer, and hint at potential linkages between observed Pedobacter abundance shifts within the 300 Area subsurface and biogeochemical shifts associated with Columbia River water intrusion.

  3. Capsule type of Streptococcus pneumoniae determines growth phenotype.

    PubMed

    Hathaway, Lucy J; Brugger, Silvio D; Morand, Brigitte; Bangert, Mathieu; Rotzetter, Jeannine U; Hauser, Christoph; Graber, Werner A; Gore, Suzanna; Kadioglu, Aras; Mühlemann, Kathrin

    2012-01-01

    The polysaccharide capsule of Streptococcus pneumoniae defines over ninety serotypes, which differ in their carriage prevalence and invasiveness for poorly understood reasons. Recently, an inverse correlation between carriage prevalence and oligosaccharide structure of a given capsule has been described. Our previous work suggested a link between serotype and growth in vitro. Here we investigate whether capsule production interferes with growth in vitro and whether this predicts carriage prevalence in vivo. Eighty-one capsule switch mutants were constructed representing nine different serotypes, five of low (4, 7F, 14, 15, 18C) and four of high carriage prevalence (6B, 9V, 19F, 23F). Growth (length of lag phase, maximum optical density) of wildtype strains, nontypeable mutants and capsule switch mutants was studied in nutrient-restricted Lacks medium (MLM) and in rich undefined brain heart infusion broth supplemented with 5% foetal calf serum (BHI+FCS). In MLM growth phenotype depended on, and was transferred with, capsule operon type. Colonization efficiency of mouse nasopharynx also depended on, and was transferred with, capsule operon type. Capsule production interfered with growth, which correlated inversely with serotype-specific carriage prevalence. Serotypes with better growth and higher carriage prevalence produced thicker capsules (by electron microscopy, FITC-dextran exclusion assays and HPLC) than serotypes with delayed growth and low carriage prevalence. However, expression of cpsA, the first capsule gene, (by quantitative RT-PCR) correlated inversely with capsule thickness. Energy spent for capsule production (incorporation of H3-glucose) relative to amount of capsule produced was higher for serotypes with low carriage prevalence. Experiments in BHI+FCS showed overall better bacterial growth and more capsule production than growth in MLM and differences between serotypes were no longer apparent. Production of polysaccharide capsule in S. pneumoniae

  4. Models and Determinants of Vocabulary Growth from Kindergarten to Adulthood

    ERIC Educational Resources Information Center

    Beitchman, Joseph H.; Jiang, Hedy; Koyama, Emiko; Johnson, Carla J.; Escobar, Michael; Atkinson, Leslie; Brownlie, E. B.; Vida, Ron

    2008-01-01

    Background: Increasing evidence suggests that childhood language problems persist into early adulthood. Nevertheless, little is known about how individual and environmental characteristics influence the language growth of individuals identified with speech/language problems. Method: Individual growth curve models were utilised to examine how…

  5. Determining the Kinetic Parameters Characteristic of Microalgal Growth.

    ERIC Educational Resources Information Center

    Martinez Sancho, Maria Eugenie; And Others

    1991-01-01

    An activity in which students obtain a growth curve for algae, identify the exponential and linear growth phases, and calculate the parameters which characterize both phases is described. The procedure, a list of required materials, experimental conditions, analytical technique, and a discussion of the interpretations of individual results are…

  6. Utility of Ochrobactrum anthropi YC152 in a Microbial Fuel Cell as an Early Warning Device for Hexavalent Chromium Determination

    PubMed Central

    Wang, Guey-Horng; Cheng, Chiu-Yu; Liu, Man-Hai; Chen, Tzu-Yu; Hsieh, Min-Chi; Chung, Ying-Chien

    2016-01-01

    Fast hexavalent chromium (Cr(VI)) determination is important for environmental risk and health-related considerations. We used a microbial fuel cell-based biosensor inoculated with a facultatively anaerobic, Cr(VI)-reducing, and exoelectrogenic Ochrobactrum anthropi YC152 to determine the Cr(VI) concentration in water. The results indicated that O. anthropi YC152 exhibited high adaptability to pH, temperature, salinity, and water quality under anaerobic conditions. The stable performance of the microbial fuel cell (MFC)-based biosensor indicated its potential as a reliable biosensor system. The MFC voltage decreased as the Cr(VI) concentration in the MFC increased. Two satisfactory linear relationships were observed between the Cr(VI) concentration and voltage output for various Cr(VI) concentration ranges (0.0125–0.3 mg/L and 0.3–5 mg/L). The MFC biosensor is a simple device that can accurately measure Cr(VI) concentrations in drinking water, groundwater, and electroplating wastewater in 45 min with low deviations (<10%). The use of the biosensor can help in preventing the violation of effluent regulations and the maximum allowable concentration of Cr(VI) in water. Thus, the developed MFC biosensor has potential as an early warning detection device for Cr(VI) determination even if O. anthropi YC152 is a possible opportunistic pathogen. PMID:27537887

  7. Utility of Ochrobactrum anthropi YC152 in a Microbial Fuel Cell as an Early Warning Device for Hexavalent Chromium Determination.

    PubMed

    Wang, Guey-Horng; Cheng, Chiu-Yu; Liu, Man-Hai; Chen, Tzu-Yu; Hsieh, Min-Chi; Chung, Ying-Chien

    2016-01-01

    Fast hexavalent chromium (Cr(VI)) determination is important for environmental risk and health-related considerations. We used a microbial fuel cell-based biosensor inoculated with a facultatively anaerobic, Cr(VI)-reducing, and exoelectrogenic Ochrobactrum anthropi YC152 to determine the Cr(VI) concentration in water. The results indicated that O. anthropi YC152 exhibited high adaptability to pH, temperature, salinity, and water quality under anaerobic conditions. The stable performance of the microbial fuel cell (MFC)-based biosensor indicated its potential as a reliable biosensor system. The MFC voltage decreased as the Cr(VI) concentration in the MFC increased. Two satisfactory linear relationships were observed between the Cr(VI) concentration and voltage output for various Cr(VI) concentration ranges (0.0125-0.3 mg/L and 0.3-5 mg/L). The MFC biosensor is a simple device that can accurately measure Cr(VI) concentrations in drinking water, groundwater, and electroplating wastewater in 45 min with low deviations (<10%). The use of the biosensor can help in preventing the violation of effluent regulations and the maximum allowable concentration of Cr(VI) in water. Thus, the developed MFC biosensor has potential as an early warning detection device for Cr(VI) determination even if O. anthropi YC152 is a possible opportunistic pathogen. PMID:27537887

  8. Utility of Ochrobactrum anthropi YC152 in a Microbial Fuel Cell as an Early Warning Device for Hexavalent Chromium Determination.

    PubMed

    Wang, Guey-Horng; Cheng, Chiu-Yu; Liu, Man-Hai; Chen, Tzu-Yu; Hsieh, Min-Chi; Chung, Ying-Chien

    2016-01-01

    Fast hexavalent chromium (Cr(VI)) determination is important for environmental risk and health-related considerations. We used a microbial fuel cell-based biosensor inoculated with a facultatively anaerobic, Cr(VI)-reducing, and exoelectrogenic Ochrobactrum anthropi YC152 to determine the Cr(VI) concentration in water. The results indicated that O. anthropi YC152 exhibited high adaptability to pH, temperature, salinity, and water quality under anaerobic conditions. The stable performance of the microbial fuel cell (MFC)-based biosensor indicated its potential as a reliable biosensor system. The MFC voltage decreased as the Cr(VI) concentration in the MFC increased. Two satisfactory linear relationships were observed between the Cr(VI) concentration and voltage output for various Cr(VI) concentration ranges (0.0125-0.3 mg/L and 0.3-5 mg/L). The MFC biosensor is a simple device that can accurately measure Cr(VI) concentrations in drinking water, groundwater, and electroplating wastewater in 45 min with low deviations (<10%). The use of the biosensor can help in preventing the violation of effluent regulations and the maximum allowable concentration of Cr(VI) in water. Thus, the developed MFC biosensor has potential as an early warning detection device for Cr(VI) determination even if O. anthropi YC152 is a possible opportunistic pathogen.

  9. Inhibition of vitamin B12-dependent microbial growth by nitrous oxide

    SciTech Connect

    Alston, T.A. )

    1991-01-01

    In methionine-free media, nitrous oxide inhibits the growth of an auxotrophic strain of Escherichia coli lacking a cobalamin-independent pathway for the de novo synthesis of methionine. Prototrophic E. coli is similarly inhibited by nitrous oxide if the cobalamin-independent pathway is selectively depressed by sulfanilamide. Nitrous oxide thus effectively inactivates cobalamin-dependent 5-methyltetrahydrofolate-homocysteine methyltransferase in intact bacteria.

  10. Automatic on-line analyser of microbial growth using simultaneous measurements of impedance and turbidity.

    PubMed

    Madrid, R E; Felice, C J; Valentinuzzi, M E

    1999-11-01

    An apparatus for the measurement of bacterial growth is described. The instrument applies alternate adequate sequential currents of two different frequencies through a pair of electrodes immersed in a cultured medium. It monitors, detects and quantifies the growth of micro-organisms based on the measurement of the impedance across the two electrodes and, simultaneously, it measures the variation in the medium turbidity. The medium conductivity and the interface electrode impedance changes can be extracted from the measured impedance. The variations in turbidity can be calibrated in absorbance or optical density units. Moreover, all these parameters are also proportional to bacterial proliferation. The computer-controlled apparatus processes and displays the parameters on a monitor showing bulk resistance, electrode impedance and turbidity changes as time course events. The equipment can detect aerobic or anaerobic micro-organisms and permits the operator simultaneously to assess impedance and turbidity, or it can produce each parameter as a separate event. Time growth curves of different micro-organisms are presented in the results.

  11. Effects of chestnut tannins and coconut oil on growth performance, methane emission, ruminal fermentation, and microbial populations in sheep.

    PubMed

    Liu, H; Vaddella, V; Zhou, D

    2011-12-01

    This study was conducted to evaluate the effects of chestnut tannins (CT) and coconut oil (CO) on growth performance, methane (CH₄) emission, ruminal fermentation, and microbial populations in sheep. A total of 48 Rideau Arcott sheep (average body weight 31.5±1.97 kg, 16 wk old) were randomly assigned into 6 treatment groups in a 3 × 2 factorial design, with CT and CO as the main effects (8 sheep per group). The treatments were control diet (CTR), 10 or 30 g of CT/kg of diet (CT10 and CT30), 25 g of CO/kg of concentrate (CO25), and 10 or 30 g of CT/kg of diet+25 g of CO/kg of concentrate (CT10CO25 and CT30CO25). After the feeding trial (60 d), all sheep were moved to respiratory chambers to measure CH₄ emission. After CH₄ emission measurements, all sheep were slaughtered to obtain rumen fluid samples. Results showed that the addition of CT, CO, and CT+CO had no significant effects on growth performance of sheep but reduced CH₄ emission. Addition of CT reduced the NH₃-N concentration in rumen fluid in CT30. Addition of CO decreased the concentration of total volatile fatty acids in rumen fluid. No significant differences were observed in pH and molar proportion of volatile fatty acids among treatments. Addition of CT, CO, and CT+CO significantly decreased methanogen and protozoa populations. Moreover, CO decreased counts of Fibrobacter succinogenes. No significant differences were observed in populations of fungi, Ruminococcus flavefaciens, or Ruminococcus albus among treatments. In conclusion, supplementation of CT and CO seemed to be a feasible means of decreasing emissions of CH₄ from sheep by reduction of methanogen and protozoa populations with no negative effect on growth performance.

  12. Microbial background flora in small-scale cheese production facilities does not inhibit growth and surface attachment of Listeria monocytogenes.

    PubMed

    Schirmer, B C T; Heir, E; Møretrø, T; Skaar, I; Langsrud, S

    2013-10-01

    The background microbiota of 5 Norwegian small-scale cheese production sites was examined and the effect of the isolated strains on the growth and survival of Listeria monocytogenes was investigated. Samples were taken from the air, food contact surfaces (storage surfaces, cheese molds, and brine) and noncontact surfaces (floor, drains, and doors) and all isolates were identified by sequencing and morphology (mold). A total of 1,314 isolates were identified and found to belong to 55 bacterial genera, 1 species of yeast, and 6 species of mold. Lactococcus spp. (all of which were Lactococcus lactis), Staphylococcus spp., Microbacterium spp., and Psychrobacter sp. were isolated from all 5 sites and Rhodococcus spp. and Chryseobacterium spp. from 4 sites. Thirty-two genera were only found in 1 out of 5 facilities each. Great variations were observed in the microbial background flora both between the 5 producers, and also within the various production sites. The greatest diversity of bacteria was found in drains and on rubber seals of doors. The flora on cheese storage shelves and in salt brines was less varied. A total of 62 bacterial isolates and 1 yeast isolate were tested for antilisterial activity in an overlay assay and a spot-on-lawn assay, but none showed significant inhibitory effects. Listeria monocytogenes was also co-cultured on ceramic tiles with bacteria dominating in the cheese production plants: Lactococcus lactis, Pseudomonas putida, Staphylococcus equorum, Rhodococcus spp., or Psychrobacter spp. None of the tested isolates altered the survival of L. monocytogenes on ceramic tiles. The conclusion of the study was that no common background flora exists in cheese production environments. None of the tested isolates inhibited the growth of L. monocytogenes. Hence, this study does not support the hypothesis that the natural background flora in cheese production environments inhibits the growth or survival of L. monocytogenes.

  13. Use of dissolved H2 concentrations to determine distribution of microbially catalyzed redox reactions in anoxic groundwater

    USGS Publications Warehouse

    Lovley, D.R.; Chapelle, F.H.; Woodward, J.C.

    1994-01-01

    The potential for using concentrations of dissolved H2 to determine the distribution of redox processes in anoxic groundwaters was evaluated. In pristine aquifers in which standard geochemical measurements indicated that Fe-(III) reduction, sulfate reduction, or methanogenesis was the terminal electron accepting process (TEAP), the H2 concentrations were similar to the H2 concentrations that have previously been reported for aquatic sediments with the same TEAPs. In two aquifers contaminated with petroleum products, it was impossible with standard geochemical analyses to determine which TEAPs predominated in specific locations. However, the TEAPs predicted from measurements of dissolved H2 were the same as those determined directly through measurements of microbial processes in incubated aquifer material. These results suggest that H2 concentrations may be a useful tool for analyzing the redox chemistry of nonequilibrium groundwaters.

  14. Microbial determinants of biochemical individuality and their impact on toxicology and pharmacology

    PubMed Central

    Patterson, Andrew D.; Turnbaugh, Peter J.

    2014-01-01

    SUMMARY Humans exhibit remarkable inter-individual variations in the concentration of small molecules found throughout the body, due in part to concurrent variations in each person’s associated microbial communities. Recent studies have begun to uncover how microbes interface with their host during exposure to drugs, dietary compounds, and environmental toxicants, with broader implications regarding the causes and consequences of biochemical individuality. Progress in this area will likely be an essential component of personalized medicine and might be accelerated through the implementation of experimental designs and theoretical principles honed through decades of work in the fields of toxicology and pharmacology. PMID:25156450

  15. Determination of some in vitro growth requirements of Bacteroides nodosus.

    PubMed

    Skerman, T M

    1975-03-01

    Physical and nutritional factors required for growth of Bacteroides nodosus isolates from ovine foot-rot lesions were examined. Simplified anaerobic culture techniques were devised utilizing a fully soluble, autoclavable, liquid medium (TAS) which contained proteose-peptone, yeast and meat extracts and certain other essential compounds required to promote prompt and serially transferrable growth of cultures from small inocula. The latter included Trypticase, arginine, a reducing agent (most suitably thioglycollic acid) and CO2; serine and Mg2+ markedly increased growth yields. Trypticase could not be replaced by a commercial preparation of acid-hydrolysed casein; other forms of hydrolysed protein gave delayed and inconsistent growth. Maximum growth of cultures required concentrations of 0-02 to 0-35 M-arginine, which could not be replaced by glutamic acid, citrulline or ornithine. Exogenous carbohydrate compounds were not required. The temperature range for optimum growth of cultures was 37 to 39 degrees C, and anaerobic culture conditions were essential for growth and the production of B. nodosus organisms of normal morphology. Solidified TAS media for the isolation and maintenance of B. nodosus cultures were also devised. PMID:1133574

  16. Determination of some in vitro growth requirements of Bacteroides nodosus.

    PubMed

    Skerman, T M

    1975-03-01

    Physical and nutritional factors required for growth of Bacteroides nodosus isolates from ovine foot-rot lesions were examined. Simplified anaerobic culture techniques were devised utilizing a fully soluble, autoclavable, liquid medium (TAS) which contained proteose-peptone, yeast and meat extracts and certain other essential compounds required to promote prompt and serially transferrable growth of cultures from small inocula. The latter included Trypticase, arginine, a reducing agent (most suitably thioglycollic acid) and CO2; serine and Mg2+ markedly increased growth yields. Trypticase could not be replaced by a commercial preparation of acid-hydrolysed casein; other forms of hydrolysed protein gave delayed and inconsistent growth. Maximum growth of cultures required concentrations of 0-02 to 0-35 M-arginine, which could not be replaced by glutamic acid, citrulline or ornithine. Exogenous carbohydrate compounds were not required. The temperature range for optimum growth of cultures was 37 to 39 degrees C, and anaerobic culture conditions were essential for growth and the production of B. nodosus organisms of normal morphology. Solidified TAS media for the isolation and maintenance of B. nodosus cultures were also devised.

  17. Test method for the determination of crack-growth rates and crack growth resistance under cyclic loading

    SciTech Connect

    Yarema, S.Ya.

    1995-05-01

    This article describes the test method for the determination of crack growth rates and crack growth resistance under cyclic loading conditions. The text of the article is limited to two appendices with the following subjects: (1) general requirements for specimens for testing with a constant cycle of the stress intensity factor, and (2) descriptions of the loading fixtures.

  18. Impact of flue gas desulfurization-calcium sulfite and gypsum on soil microbial activity and wheat growth

    SciTech Connect

    Lee, Y.B.; Bigham, J.M.; Dick, W.A.; Kim, P.J.

    2008-08-15

    We conducted greenhouse tests to evaluate the effects of FGD-CaSO{sub 3} applied at rates of 0, 2.2, 4.4, and 8.8 Mg ha(-1) on wheat growth, soil enzyme activities, and the chemical properties of two soils with differing pH (4.0 vs. 6.2). A gypsum treatment applied at the rate of 2.2 Mg ha{sup -1} was used as a positive control. Exchangeable Ca{sup 2+} and water-extractable Ca{sup 2+} and SO{sub 4}{sup 2-} increased significantly with increasing FGD-CaSO{sub 3} application. SO{sub 4}{sup 2-} increased in both soils, indicating rapid oxidation of SO{sub 3}{sup 2-} to SO{sub 4}{sup 2-} when neither water nor oxygen was limiting. No changes in soil pH were measured. Applications of 2.2, 4.4, or 8.8 Mg CaSO{sub 3} ha{sup -1} to the pH 6.2 soil produced no effect on wheat growth or the uptake of N, P, Ca{sup 2+}, and Mg{sup 2+}. The uptake of SO{sub 4}{sup 2-} -S increased, whereas K uptake decreased. No significant differences in the activities of urease, {beta}-glucosidase, alkaline phosphatase, or arylsulfatase were observed relative to a control. In the acid soil, an application of 2.2 Mg ha{sup -1} FGD-CaSO{sub 3} increased wheat root growth and dry matter yield compared with an untreated control. The uptake of N, P, Ca{sup 2+}, and K{sup +} also increased presumably because of enhanced root development resulting from decreases in exchangeable Al{sup 3+} and increases in soluble Ca{sup 2+}. Wheat growth and alkaline phosphatase and arylsulfatase activities were significantly inhibited by addition of 8.8 Mg ha{sup -1} of FGD-CaSO{sub 3} compared with the untreated control or the same soil receiving 2.2 Mg ha{sup -1} gypsum. We conclude that surface applications of FGD-CaSO{sub 3} may be as effective as gypsum for inhibiting soil crusting, improving water infiltration, and promoting the movement of Ca{sup 2+} into acid subsoils. Moreover, application rates of equal to or less than 4.4 Mg ha-1 should have no negative impact on soil microbial activities or plant growth.

  19. Determination of sterilization effectiveness by measuring bacterial growth in a biological indicator through firefly luciferase determination of ATP.

    PubMed

    Webster, J J; Walker, B G; Ford, S R; Leach, F R

    1988-01-01

    A bioluminescence procedure for measurement of microbial ATP allows a rapid determination of the effectiveness of autoclave sterilization. This determination is achieved faster than detection of acid production in a biological indicator via a pH indicator. Bacterial outgrowth from spores on test strips of the biological indicator was detected by measurement of ATP using the firefly luciferase reaction. A measureable increase in ATP was found after 5 hours of incubation of a biological indicator that had been treated under sterilizing conditions that produced 75% sterility of the biological indicator as measured by acid production. This is a marked improvement over the 24-48 hours of incubation currently required. PMID:3213598

  20. Modeling the microbial growth and temperature profile in a fixed-bed bioreactor.

    PubMed

    da Silveira, Christian L; Mazutti, Marcio A; Salau, Nina P G

    2014-10-01

    Aiming to scale up and apply control and optimization strategies, currently is required the development of accurate plant models to forecast the process nonlinear dynamics. In this work, a mathematical model to predict the growth of the Kluyveromyces marxianus and temperature profile in a fixed-bed bioreactor for solid-state fermentation using sugarcane bagasse as substrate was built up. A parameter estimation technique was performed to fit the mathematical model to the experimental data. The estimated parameters and the model fitness were evaluated with statistical analyses. The results have shown the estimated parameters significance, with 95 % confidence intervals, and the good quality of process model to reproduce the experimental data.

  1. Inhibition of microbial growth by ajoene, a sulfur-containing compound derived from garlic.

    PubMed

    Naganawa, R; Iwata, N; Ishikawa, K; Fukuda, H; Fujino, T; Suzuki, A

    1996-11-01

    Ajoene, a garlic-derived sulfur-containing compound that prevents platelet aggregation, exhibited broad-spectrum antimicrobial activity. Growth of gram-positive bacteria, such as Bacillus cereus, Bacillus subtilis, Mycobacterium smegmatis, and Streptomyces griseus, was inhibited at 5 micrograms of ajoene per ml. Staphylococcus aureus and Lactobacillus plantarum also were inhibited below 20 micrograms of ajoene per ml. For gram-negative bacteria, such as Escherichia coli, Klebsiella pneumoniae, and Xanthomonas maltophilia, MICs were between 100 and 160 micrograms/ml. Ajoene also inhibited yeast growth at concentrations below 20 micrograms/ml. The microbicidal effect of ajoene on growing cells was observed at slightly higher concentrations than the corresponding MICs. B. cereus and Saccharomyces cerevisiae were killed at 30 micrograms of ajoene per ml after 24 h of cultivation when cultivation was started at 10(5) cells per ml. However, the minimal microbicidal concentrations for resting cells were at 10 to 100 times higher concentrations than the corresponding MICs. The disulfide bond in ajoene appears to be necessary for the antimicrobial activity of ajoene, since reduction by cysteine, which reacts with disulfide bonds, abolished its antimicrobial activity.

  2. Bacteria with Phosphate Solubilizing Capacity Alter Mycorrhizal Fungal Growth Both Inside and Outside the Root and in the Presence of Native Microbial Communities.

    PubMed

    Ordoñez, Yuli Marcela; Fernandez, Belen Rocio; Lara, Lidia Susana; Rodriguez, Alia; Uribe-Vélez, Daniel; Sanders, Ian R

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing Pseudomonas bacteria (PSB) could potentially interact synergistically because PSB solubilize phosphate into a form that AMF can absorb and transport to the plant. However, very little is known about the interactions between these two groups of microorganisms and how they influence the growth of each other. We tested whether different strains of bacteria, that have the capacity to solubilize phosphate, are able to grow along AMF hyphae and differentially influence the growth of AMF both outside the roots of carrot in in vitro conditions and inside the roots of potato in the presence of a microbial community. We found strong effects of AMF on the growth of the different bacterial strains. Different bacterial strains also had very strong effects on the growth of AMF extraradical hyphae outside the roots of carrot and on colonization of potato roots by AMF. The differential effects on colonization occurred in the presence of a microbial community. Our results show that these two important groups of rhizosphere microorganisms indeed interact with each other. Such interactions could potentially lead to synergistic effects between the two groups but this could depend on whether the bacteria truly solubilize phosphate in the rhizosphere in the presence of microbial communities. PMID:27253975

  3. Bacteria with Phosphate Solubilizing Capacity Alter Mycorrhizal Fungal Growth Both Inside and Outside the Root and in the Presence of Native Microbial Communities.

    PubMed

    Ordoñez, Yuli Marcela; Fernandez, Belen Rocio; Lara, Lidia Susana; Rodriguez, Alia; Uribe-Vélez, Daniel; Sanders, Ian R

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing Pseudomonas bacteria (PSB) could potentially interact synergistically because PSB solubilize phosphate into a form that AMF can absorb and transport to the plant. However, very little is known about the interactions between these two groups of microorganisms and how they influence the growth of each other. We tested whether different strains of bacteria, that have the capacity to solubilize phosphate, are able to grow along AMF hyphae and differentially influence the growth of AMF both outside the roots of carrot in in vitro conditions and inside the roots of potato in the presence of a microbial community. We found strong effects of AMF on the growth of the different bacterial strains. Different bacterial strains also had very strong effects on the growth of AMF extraradical hyphae outside the roots of carrot and on colonization of potato roots by AMF. The differential effects on colonization occurred in the presence of a microbial community. Our results show that these two important groups of rhizosphere microorganisms indeed interact with each other. Such interactions could potentially lead to synergistic effects between the two groups but this could depend on whether the bacteria truly solubilize phosphate in the rhizosphere in the presence of microbial communities.

  4. Bacteria with Phosphate Solubilizing Capacity Alter Mycorrhizal Fungal Growth Both Inside and Outside the Root and in the Presence of Native Microbial Communities

    PubMed Central

    Lara, Lidia Susana; Rodriguez, Alia; Uribe-Vélez, Daniel; Sanders, Ian R.

    2016-01-01

    Arbuscular mycorrhizal fungi (AMF) and phosphate solubilizing Pseudomonas bacteria (PSB) could potentially interact synergistically because PSB solubilize phosphate into a form that AMF can absorb and transport to the plant. However, very little is known about the interactions between these two groups of microorganisms and how they influence the growth of each other. We tested whether different strains of bacteria, that have the capacity to solubilize phosphate, are able to grow along AMF hyphae and differentially influence the growth of AMF both outside the roots of carrot in in vitro conditions and inside the roots of potato in the presence of a microbial community. We found strong effects of AMF on the growth of the different bacterial strains. Different bacterial strains also had very strong effects on the growth of AMF extraradical hyphae outside the roots of carrot and on colonization of potato roots by AMF. The differential effects on colonization occurred in the presence of a microbial community. Our results show that these two important groups of rhizosphere microorganisms indeed interact with each other. Such interactions could potentially lead to synergistic effects between the two groups but this could depend on whether the bacteria truly solubilize phosphate in the rhizosphere in the presence of microbial communities. PMID:27253975

  5. Fighting fish (Betta splendens) bubble nests do not inhibit microbial growth.

    PubMed

    Brown, Alexandria C; Clotfelter, Ethan D

    2012-12-01

    Some organisms produce antimicrobial substances in nesting foam to favorably manipulate the environment to which their developing offspring are exposed. We tested if fighting fish Betta splendens foamy nest material, which is comprised of bubbles produced in the oral cavity of nesting males, has antimicrobial properties against a pathogenic bacteria (Edwardsiella tarda), a nonpathogenic bacteria (Escherichia coli), or a pathogenic oomycete (Saprolegnia parasitica). We also tested if exposure to nest material increases larval survival by performing in vitro fertilizations and individually incubating eggs in bubble nest extract or tank water (control). Our results show no evidence of antimicrobial properties of bubble nests. On the contrary, bubble nests provided favorable microenvironments for the growth of Saprolegnia parasitica. Our results confirm earlier work citing the importance of male nest attendance, and suggest that the mechanism responsible for decreased survival in the absence of attending males is pathogenic microbes.

  6. Fighting fish (Betta splendens) bubble nests do not inhibit microbial growth.

    PubMed

    Brown, Alexandria C; Clotfelter, Ethan D

    2012-12-01

    Some organisms produce antimicrobial substances in nesting foam to favorably manipulate the environment to which their developing offspring are exposed. We tested if fighting fish Betta splendens foamy nest material, which is comprised of bubbles produced in the oral cavity of nesting males, has antimicrobial properties against a pathogenic bacteria (Edwardsiella tarda), a nonpathogenic bacteria (Escherichia coli), or a pathogenic oomycete (Saprolegnia parasitica). We also tested if exposure to nest material increases larval survival by performing in vitro fertilizations and individually incubating eggs in bubble nest extract or tank water (control). Our results show no evidence of antimicrobial properties of bubble nests. On the contrary, bubble nests provided favorable microenvironments for the growth of Saprolegnia parasitica. Our results confirm earlier work citing the importance of male nest attendance, and suggest that the mechanism responsible for decreased survival in the absence of attending males is pathogenic microbes. PMID:22753365

  7. Determinations of microbial loads associated with microscopic-size particles of Kennedy Space Center soil.

    PubMed

    Ruschmeyer, O R; Pflug, I J

    1977-01-01

    Plate counts for six fractions, of micrometer-size, of Kennedy Space Center soil provided estimates of aerobic, mesophilic, heterotrophic, microbial loads on single soil particles. Analyses included unheated particles, particles subjected to wet heat at 80 degrees C for 20 min, and particles subjected to dry heat at 110 degrees C for 1 hr. Unheated particles yielded mean counts ranging from 6 colonies per particle for the smallest (44-53 micrometers) soil fraction to approximately 55 colonies per particle for the largest size (105-125 micrometers) soil fraction tested. Mean counts for heat-resistant forms ranged from 2 colonies per particle for the smaller particles to 12-15 colonies for the largest particles analyzed.

  8. Evolution of species interactions determines microbial community productivity in new environments.

    PubMed

    Fiegna, Francesca; Moreno-Letelier, Alejandra; Bell, Thomas; Barraclough, Timothy G

    2015-05-01

    Diversity generally increases ecosystem productivity over short timescales. Over longer timescales, both ecological and evolutionary responses to new environments could alter productivity and diversity-productivity relationships. In turn, diversity might affect how component species adapt to new conditions. We tested these ideas by culturing artificial microbial communities containing between 1 and 12 species in three different environments for ∼60 generations. The relationship between community yields and diversity became steeper over time in one environment. This occurred despite a general tendency for the separate yields of isolates of constituent species to be lower at the end if they had evolved in a more diverse community. Statistical comparisons of community and species yields showed that species interactions had evolved to be less negative over time, especially in more diverse communities. Diversity and evolution therefore interacted to enhance community productivity in a new environment. PMID:25387206

  9. Evolution of species interactions determines microbial community productivity in new environments

    PubMed Central

    Fiegna, Francesca; Moreno-Letelier, Alejandra; Bell, Thomas; Barraclough, Timothy G

    2015-01-01

    Diversity generally increases ecosystem productivity over short timescales. Over longer timescales, both ecological and evolutionary responses to new environments could alter productivity and diversity–productivity relationships. In turn, diversity might affect how component species adapt to new conditions. We tested these ideas by culturing artificial microbial communities containing between 1 and 12 species in three different environments for ∼60 generations. The relationship between community yields and diversity became steeper over time in one environment. This occurred despite a general tendency for the separate yields of isolates of constituent species to be lower at the end if they had evolved in a more diverse community. Statistical comparisons of community and species yields showed that species interactions had evolved to be less negative over time, especially in more diverse communities. Diversity and evolution therefore interacted to enhance community productivity in a new environment. PMID:25387206

  10. Determination of vitamins, minerals, and microbial loads of fortified nonalcoholic beverage (kunun zaki) produced from millet.

    PubMed

    Olaoye, Olusegun A; Ubbor, Stella C; Uduma, Ebere A

    2016-01-01

    The objective of this study was to evaluate the possibility of fortifying kunun zaki with tigernut milk extract due to nutritional deficiency of the former. Kunun zaki and tigernut milk extract (TME) were produced using traditional methods, with little modification. They were mixed in respective percentages of 90:10 (KN10), 80:20 (KN20), and 70:30 (KN30) while whole kunun zaki without addition of tigernut milk extract (KN00) served as control. The resulting kunun zaki samples were analyzed for proximate composition, vitamins, minerals, microbial loads, and sensory evaluation. Results showed improvement in thiamine and riboflavin contents of the fortified samples over the unfortified counterparts, with the KN30 sample having highest values of 1.05 and 0.56 mg/kg thiamine and riboflavin, respectively. Minerals were higher in the samples containing TME than their KN00 counterparts; the KN30 sample had highest values of 23.5, 8.8, 148.9, 63.7, 6.7, and 18.6 mg/100 mL for respective Na, Ca, K, Mg, P, and Fe while lowest values were recorded for the KN00 sample. Microbial analysis indicated that total viable bacteria and yeast and molds were in the range 2.2-2.6 and 2.1-2.7 log CFU/g, respectively, while there was no detection of coliforms and Staphylococcus in the samples. The sensory evaluation of the kunun zaki samples indicated that higher mean scores were recorded for samples containing TME than those without it in most of the attributes tested. The KN30 sample was most preferred, having highest mean scores of 7.2, 7.8, 6.9, and 7.4 in the attributes of appearance, flavor, taste, and acceptability, respectively. The study concluded that inclusion of tigernut extract in kunun zaki resulted in improved nutritional and sensory qualities. PMID:26788315

  11. The gompertz function can coherently describe microbial mineralization of growth-sustaining pesticides.

    PubMed

    Johnsen, Anders R; Binning, Philip J; Aamand, Jens; Badawi, Nora; Rosenbom, Annette E

    2013-08-01

    Mineralization of (14)C-labeled tracers is a common way of studying the environmental fate of xenobiotics, but it can be difficult to extract relevant kinetic parameters from such experiments since complex kinetic functions or several kinetic functions may be needed to adequately describe large data sets. In this study, we suggest using a two-parameter, sigmoid Gompertz function for parametrizing mineralization curves. The function was applied to a data set of 252 normalized mineralization curves that represented the potential for degradation of the herbicide MCPA in three horizons of an agricultural soil. The Gompertz function fitted most of the normalized curves, and trends in the data set could be visualized by a scatter plot of the two Gompertz parameters (rate constant and time delay). For agricultural topsoil, we also tested the effect of the MCPA concentration on the mineralization kinetics. Reduced initial concentrations lead to shortened lag-phases, probably due to reduced need for bacterial growth. The effect of substrate concentration could be predicted by simply changing the time delay of the Gompertz curves. This delay could to some extent also simulate concentration effects for 2,4-D mineralization in agricultural soil and aquifer sediment and 2,6-dichlorobenzamide mineralization in single-species, mineral medium.

  12. Complexation of copper(II) with chitosan nanogels: toward control of microbial growth.

    PubMed

    Brunel, Fabrice; El Gueddari, Nour Eddine; Moerschbacher, Bruno M

    2013-02-15

    Pure chitosan nanogels were produced, used to adsorb copper(II), and their antimicrobial activities were assessed. The complexation of copper(II) with chitosan solutions and dispersions was studied using UV-vis spectrometry. The adsorption capacity of chitosan nanogels was comparable to that of chitosan solutions, but copper(II)-loaded nanogels were more stable (i.e. no flocculation was observed while chitosan solutions showed macroscopic gelation at high copper concentration) and were easier to handle (i.e. no increase in viscosity). Adsorption isotherms of copper(II) onto chitosan were established and the impact of the pH on copper(II) release was investigated. The formation of a copper(II)-chitosan complex strongly depended on pH. Hence, release of copper(II) can be triggered by a decrease in pH (i.e. the protonation of chitosan amino groups). Furthermore, chitosan nanohydrogels were shown to be a suitable substrate for chitosan hydrolytic enzymes. Finally, a strong synergistic effect between chitosan and copper in inhibiting Fusarium graminearum growth was observed. The suitability of these copper(II)-chitosan colloids as a new generation of copper-based bio-pesticides, i.e. as a bio-compatible, bio-active and pH-sensitive delivery system, is discussed.

  13. Microbial growth at hyperaccelerations up to 403,627 × g

    PubMed Central

    Deguchi, Shigeru; Shimoshige, Hirokazu; Tsudome, Mikiko; Mukai, Sada-atsu; Corkery, Robert W.; Ito, Susumu; Horikoshi, Koki

    2011-01-01

    It is well known that prokaryotic life can withstand extremes of temperature, pH, pressure, and radiation. Little is known about the proliferation of prokaryotic life under conditions of hyperacceleration attributable to extreme gravity, however. We found that living organisms can be surprisingly proliferative during hyperacceleration. In tests reported here, a variety of microorganisms, including Gram-negative Escherichia coli, Paracoccus denitrificans, and Shewanella amazonensis; Gram-positive Lactobacillus delbrueckii; and eukaryotic Saccharomyces cerevisiae, were cultured while being subjected to hyperaccelerative conditions. We observed and quantified robust cellular growth in these cultures across a wide range of hyperacceleration values. Most notably, the organisms P. denitrificans and E. coli were able to proliferate even at 403,627 × g. Analysis shows that the small size of prokaryotic cells is essential for their proliferation under conditions of hyperacceleration. Our results indicate that microorganisms cannot only survive during hyperacceleration but can display such robust proliferative behavior that the habitability of extraterrestrial environments must not be limited by gravity. PMID:21518884

  14. One-pot enzymatic conversion of carbon dioxide and utilization for improved microbial growth.

    PubMed

    Hong, Sung-Gil; Jeon, Hancheol; Kim, Han Sol; Jun, Seung-Hyun; Jin, EonSeon; Kim, Jungbae

    2015-04-01

    We developed a process for one-pot CO2 conversion and utilization based on simple conversion of CO2 to bicarbonate at ambient temperature with no energy input, by using the cross-linking-based composites of carboxylated polyaniline nanofibers (cPANFs) and carbonic anhydrase. Carbonic anhydrase was immobilized on cPANFs via the approach of magnetically separable enzyme precipitate coatings (Mag-EPC), which consists of covalent enzyme attachment, enzyme precipitation, and cross-linking with amine-functionalized magnetic nanoparticles. Mag-EPC showed a half-life of 236 days under shaking, even resistance to 70% ethanol sterilization, and recyclability via facile magnetic separation. For one-pot CO2 conversion and utilization, Mag-EPC was used to accelerate the growth of microalga by supplying bicarbonate from CO2, representing 1.8-fold increase of cell concentration when compared to the control sample. After two repeated uses via simple magnetic separation, the cell concentration with Mag-EPC was maintained as high as the first cycle. This one-pot CO2 conversion and utilization is an alternative as well as complementary process to adsorption-based CO2 capture and storage as an environmentally friendly approach, demanding no energy input based on the effective action of the stabilized enzyme system.

  15. Effect of probiotic bacteria on microbial host defense, growth, and immune function in human immunodeficiency virus type-1 infection.

    PubMed

    Cunningham-Rundles, Susanna; Ahrné, Siv; Johann-Liang, Rosemary; Abuav, Rachel; Dunn-Navarra, Ann-Margaret; Grassey, Claudia; Bengmark, Stig; Cervia, Joseph S

    2011-12-01

    The hypothesis that probiotic administration protects the gut surface and could delay progression of Human Immunodeficiency Virus type1 (HIV-1) infection to the Acquired Immunodeficiency Syndrome (AIDS) was proposed in 1995. Over the last five years, new studies have clarified the significance of HIV-1 infection of the gut associated lymphoid tissue (GALT) for subsequent alterations in the microflora and breakdown of the gut mucosal barrier leading to pathogenesis and development of AIDS. Current studies show that loss of gut CD4+ Th17 cells, which differentiate in response to normal microflora, occurs early in HIV-1 disease. Microbial translocation and suppression of the T regulatory (Treg) cell response is associated with chronic immune activation and inflammation. Combinations of probiotic bacteria which upregulate Treg activation have shown promise in suppressing pro inflammatory immune response in models of autoimmunity including inflammatory bowel disease and provide a rationale for use of probiotics in HIV-1/AIDS. Disturbance of the microbiota early in HIV-1 infection leads to greater dominance of potential pathogens, reducing levels of bifidobacteria and lactobacillus species and increasing mucosal inflammation. The interaction of chronic or recurrent infections, and immune activation contributes to nutritional deficiencies that have lasting consequences especially in the HIV-1 infected child. While effective anti-retroviral therapy (ART) has enhanced survival, wasting is still an independent predictor of survival and a major presenting symptom. Congenital exposure to HIV-1 is a risk factor for growth delay in both infected and non-infected infants. Nutritional intervention after 6 months of age appears to be largely ineffective. A meta analysis of randomized, controlled clinical trials of infant formulae supplemented with Bifidobacterium lactis showed that weight gain was significantly greater in infants who received B. lactis compared to formula alone

  16. Effect of Probiotic Bacteria on Microbial Host Defense, Growth, and Immune Function in Human Immunodeficiency Virus Type-1 Infection

    PubMed Central

    Cunningham-Rundles, Susanna; Ahrné, Siv; Johann-Liang, Rosemary; Abuav, Rachel; Dunn-Navarra, Ann-Margaret; Grassey, Claudia; Bengmark, Stig; Cervia, Joseph S.

    2011-01-01

    The hypothesis that probiotic administration protects the gut surface and could delay progression of Human Immunodeficiency Virus type1 (HIV-1) infection to the Acquired Immunodeficiency Syndrome (AIDS) was proposed in 1995. Over the last five years, new studies have clarified the significance of HIV-1 infection of the gut associated lymphoid tissue (GALT) for subsequent alterations in the microflora and breakdown of the gut mucosal barrier leading to pathogenesis and development of AIDS. Current studies show that loss of gut CD4+ Th17 cells, which differentiate in response to normal microflora, occurs early in HIV-1 disease. Microbial translocation and suppression of the T regulatory (Treg) cell response is associated with chronic immune activation and inflammation. Combinations of probiotic bacteria which upregulate Treg activation have shown promise in suppressing pro inflammatory immune response in models of autoimmunity including inflammatory bowel disease and provide a rationale for use of probiotics in HIV-1/AIDS. Disturbance of the microbiota early in HIV-1 infection leads to greater dominance of potential pathogens, reducing levels of bifidobacteria and lactobacillus species and increasing mucosal inflammation. The interaction of chronic or recurrent infections, and immune activation contributes to nutritional deficiencies that have lasting consequences especially in the HIV-1 infected child. While effective anti-retroviral therapy (ART) has enhanced survival, wasting is still an independent predictor of survival and a major presenting symptom. Congenital exposure to HIV-1 is a risk factor for growth delay in both infected and non-infected infants. Nutritional intervention after 6 months of age appears to be largely ineffective. A meta analysis of randomized, controlled clinical trials of infant formulae supplemented with Bifidobacterium lactis showed that weight gain was significantly greater in infants who received B. lactis compared to formula alone

  17. Growth of ectomycorrhizal mycelia and composition of soil microbial communities in oak forest soils along a nitrogen deposition gradient.

    PubMed

    Nilsson, Lars Ola; Bååth, Erland; Falkengren-Grerup, Ursula; Wallander, Håkan

    2007-08-01

    Deciduous forests may respond differently from coniferous forests to the anthropogenic deposition of nitrogen (N). Since fungi, especially ectomycorrhizal (EM) fungi, are known to be negatively affected by N deposition, the effects of N deposition on the soil microbial community, total fungal biomass and mycelial growth of EM fungi were studied in oak-dominated deciduous forests along a nitrogen deposition gradient in southern Sweden. In-growth mesh bags were used to estimate the production of mycelia by EM fungi in 19 oak stands in the N deposition gradient, and the results were compared with nitrate leaching data obtained previously. Soil samples from 154 oak forest sites were analysed regarding the content of phospholipid fatty acids (PLFAs). Thirty PLFAs associated with microbes were analysed and the PLFA 18:2omega6,9 was used as an indicator to estimate the total fungal biomass. Higher N deposition (20 kg N ha(-1)y(-1) compared with 10 kg N ha(-1)y(-1)) tended to reduce EM mycelial growth. The total soil fungal biomass was not affected by N deposition or soil pH, while the PLFA 16:1omega5, a biomarker for arbuscular mycorrhizal (AM) fungi, was negatively affected by N deposition, but also positively correlated to soil pH. Other PLFAs positively affected by soil pH were, e.g., i14:0, a15:0, 16:1omega9, a17:0 and 18:1omega7, while some were negatively affected by pH, such as i15:0, 16:1omega7t, 10Me17:0 and cy19:0. In addition, N deposition had an effect on the PLFAs 16:1omega7c and 16:1omega9 (negatively) and cy19:0 (positively). The production of EM mycelia is probably more sensitive to N deposition than total fungal biomass according to the fungal biomarker PLFA 18:2omega6,9. Low amounts of EM mycelia covaried with increased nitrate leaching, suggesting that EM mycelia possibly play an important role in forest soil N retention at increased N input.

  18. Fetal growth in muskoxen determined by transabdominal ultrasonography.

    PubMed

    Pharr, J W; Rowell, J E; Flood, P F

    1994-07-01

    A 5 MHz commercial sector scanner was used to monitor 13 muskox pregnancies and establish normal fetal growth curves. Examinations were carried out between 40 and 197 days of gestation and pregnancy could be detected throughout the period. Early pregnancies were found by scanning lateral to the udder but as pregnancy progressed the fetus was found closer to the dam's umbilicus. Measurements of cranial and abdominal diameters taken at about two week intervals in seven uncomplicated pregnancies in four cows were used to construct fetal growth curves. These can be reliably used in the reproductive management of muskoxen. In addition a series of regressions based on measurements of the fetuses of muskoxen killed in the Arctic are provided. These allow cranial and abdominal diameters to be related to fetal weight and crown-rump length. PMID:7954117

  19. Inhibitory effects of Lactobacillus fermentum on microbial growth and biofilm formation.

    PubMed

    Rybalchenko, Oxana V; Bondarenko, Viktor M; Orlova, Olga G; Markov, Alexander G; Amasheh, S

    2015-10-01

    Beneficial effects of Lactobacilli have been reported, and lactic bacteria are employed for conservation of foods. Therefore, the effects of a Lactobacillus fermentum strain were analyzed regarding inhibitory effects on staphylococci, Candida albicans and enterotoxigenic enterobacteria by transmission electron microscopy (TEM). TEM of bacterial biofilms was performed using cocultures of bacteriocin-producing L. fermentum 97 with different enterotoxigenic strains: Staphylococcus epidermidis expressing the ica gene responsible for biofilm formation, Staphylococcus aureus producing enterotoxin type A, Citrobacter freundii, Enterobacter cloaceae, Klebsiella oxytoca, Proteus mirabilis producing thermolabile and thermostable enterotoxins determined by elt or est genes, and Candida albicans. L. fermentum 97 changed morphological features and suppressed biofilm formation of staphylococci, enterotoxigenic enterobacteria and Candida albicans; a marked transition to resting states, a degradation of the cell walls and cytoplasm, and a disruption of mature bacterial biofilms were observed, the latter indicating efficiency even in the phase of higher cell density.

  20. Automated inference procedure for the determination of cell growth parameters.

    PubMed

    Harris, Edouard A; Koh, Eun Jee; Moffat, Jason; McMillen, David R

    2016-01-01

    The growth rate and carrying capacity of a cell population are key to the characterization of the population's viability and to the quantification of its responses to perturbations such as drug treatments. Accurate estimation of these parameters necessitates careful analysis. Here, we present a rigorous mathematical approach for the robust analysis of cell count data, in which all the experimental stages of the cell counting process are investigated in detail with the machinery of Bayesian probability theory. We advance a flexible theoretical framework that permits accurate estimates of the growth parameters of cell populations and of the logical correlations between them. Moreover, our approach naturally produces an objective metric of avoidable experimental error, which may be tracked over time in a laboratory to detect instrumentation failures or lapses in protocol. We apply our method to the analysis of cell count data in the context of a logistic growth model by means of a user-friendly computer program that automates this analysis, and present some samples of its output. Finally, we note that a traditional least squares fit can provide misleading estimates of parameter values, because it ignores available information with regard to the way in which the data have actually been collected. PMID:26871096

  1. Automated inference procedure for the determination of cell growth parameters

    NASA Astrophysics Data System (ADS)

    Harris, Edouard A.; Koh, Eun Jee; Moffat, Jason; McMillen, David R.

    2016-01-01

    The growth rate and carrying capacity of a cell population are key to the characterization of the population's viability and to the quantification of its responses to perturbations such as drug treatments. Accurate estimation of these parameters necessitates careful analysis. Here, we present a rigorous mathematical approach for the robust analysis of cell count data, in which all the experimental stages of the cell counting process are investigated in detail with the machinery of Bayesian probability theory. We advance a flexible theoretical framework that permits accurate estimates of the growth parameters of cell populations and of the logical correlations between them. Moreover, our approach naturally produces an objective metric of avoidable experimental error, which may be tracked over time in a laboratory to detect instrumentation failures or lapses in protocol. We apply our method to the analysis of cell count data in the context of a logistic growth model by means of a user-friendly computer program that automates this analysis, and present some samples of its output. Finally, we note that a traditional least squares fit can provide misleading estimates of parameter values, because it ignores available information with regard to the way in which the data have actually been collected.

  2. Parenting Styles: A Key Factor to Self Determination and Personal Growth of Adults

    ERIC Educational Resources Information Center

    Aslam, Manika Arbab; Sultan, Sarwat

    2014-01-01

    The study was conducted to explore the impact of parenting styles of adolescents on their self-determination and personal growth. The data was collected from 300 adults evenly divided by gender, aged 23-38 years. To measure the parenting styles, level of self-determination and personal growth, the Caregivers Practices Report, Self Determination…

  3. Pore-scale simulation of microbial growth using a genome-scale metabolic model: Implications for Darcy-scale reactive transport

    SciTech Connect

    Tartakovsky, Guzel D.; Tartakovsky, Alexandre M.; Scheibe, Timothy D.; Fang, Yilin; Mahadevan, Radhakrishnan; Lovley, Derek R.

    2013-09-07

    Recent advances in microbiology have enabled the quantitative simulation of microbial metabolism and growth based on genome-scale characterization of metabolic pathways and fluxes. We have incorporated a genome-scale metabolic model of the iron-reducing bacteria Geobacter sulfurreducens into a pore-scale simulation of microbial growth based on coupling of iron reduction to oxidation of a soluble electron donor (acetate). In our model, fluid flow and solute transport is governed by a combination of the Navier-Stokes and advection-diffusion-reaction equations. Microbial growth occurs only on the surface of soil grains where solid-phase mineral iron oxides are available. Mass fluxes of chemical species associated with microbial growth are described by the genome-scale microbial model, implemented using a constraint-based metabolic model, and provide the Robin-type boundary condition for the advection-diffusion equation at soil grain surfaces. Conventional models of microbially-mediated subsurface reactions use a lumped reaction model that does not consider individual microbial reaction pathways, and describe reactions rates using empirically-derived rate formulations such as the Monod-type kinetics. We have used our pore-scale model to explore the relationship between genome-scale metabolic models and Monod-type formulations, and to assess the manifestation of pore-scale variability (microenvironments) in terms of apparent Darcy-scale microbial reaction rates. The genome-scale model predicted lower biomass yield, and different stoichiometry for iron consumption, in comparisonto prior Monod formulations based on energetics considerations. We were able to fit an equivalent Monod model, by modifying the reaction stoichiometry and biomass yield coefficient, that could effectively match results of the genome-scale simulation of microbial behaviors under excess nutrient conditions, but predictions of the fitted Monod model deviated from those of the genome-scale model under

  4. Pore-scale simulation of microbial growth using a genome-scale metabolic model: Implications for Darcy-scale reactive transport

    NASA Astrophysics Data System (ADS)

    Tartakovsky, G. D.; Tartakovsky, A. M.; Scheibe, T. D.; Fang, Y.; Mahadevan, R.; Lovley, D. R.

    2013-09-01

    Recent advances in microbiology have enabled the quantitative simulation of microbial metabolism and growth based on genome-scale characterization of metabolic pathways and fluxes. We have incorporated a genome-scale metabolic model of the iron-reducing bacteria Geobacter sulfurreducens into a pore-scale simulation of microbial growth based on coupling of iron reduction to oxidation of a soluble electron donor (acetate). In our model, fluid flow and solute transport is governed by a combination of the Navier-Stokes and advection-diffusion-reaction equations. Microbial growth occurs only on the surface of soil grains where solid-phase mineral iron oxides are available. Mass fluxes of chemical species associated with microbial growth are described by the genome-scale microbial model, implemented using a constraint-based metabolic model, and provide the Robin-type boundary condition for the advection-diffusion equation at soil grain surfaces. Conventional models of microbially-mediated subsurface reactions use a lumped reaction model that does not consider individual microbial reaction pathways, and describe reactions rates using empirically-derived rate formulations such as the Monod-type kinetics. We have used our pore-scale model to explore the relationship between genome-scale metabolic models and Monod-type formulations, and to assess the manifestation of pore-scale variability (microenvironments) in terms of apparent Darcy-scale microbial reaction rates. The genome-scale model predicted lower biomass yield, and different stoichiometry for iron consumption, in comparison to prior Monod formulations based on energetics considerations. We were able to fit an equivalent Monod model, by modifying the reaction stoichiometry and biomass yield coefficient, that could effectively match results of the genome-scale simulation of microbial behaviors under excess nutrient conditions, but predictions of the fitted Monod model deviated from those of the genome-scale model

  5. Pore-scale simulation of microbial growth using a genome-scale metabolic model: Implications for Darcy-scale reactive transport

    NASA Astrophysics Data System (ADS)

    Scheibe, T. D.; Tartakovsky, G.; Tartakovsky, A. M.; Fang, Y.; Mahadevan, R.; Lovley, D. R.

    2012-12-01

    Recent advances in microbiology have enabled the quantitative simulation of microbial metabolism and growth based on genome-scale characterization of metabolic pathways and fluxes. We have incorporated a genome-scale metabolic model of the iron-reducing bacteria Geobacter sulfurreducens into a pore-scale simulation of microbial growth based on coupling of iron reduction to oxidation of a soluble electron donor (acetate). In our model, fluid flow and solute transport is governed by a combination of the Navier-Stokes and advection-diffusion-reaction equations. Microbial growth occurs only on the surface of soil grains where solid-phase mineral iron oxides are available. Mass fluxes of chemical species associated with microbial growth are described by the genome-scale microbial model, implemented using a constraint-based metabolic model, and provide the Robin-type boundary condition for the advection-diffusion equation at soil grain surfaces. Conventional models of microbially-mediated subsurface reactions use a lumped reaction model that does not consider individual microbial reaction pathways, and describe reactions rates using empirically-derived rate formulations such as the Monod-type kinetics. We have used our pore-scale model to explore the relationship between genome-scale metabolic models and Monod-type formulations, and to assess the manifestation of pore-scale variability (microenvironments) in terms of apparent Darcy-scale microbial reaction rates. The genome-scale model predicted lower biomass yield, and different stoichiometry for iron consumption, in comparison to prior Monod formulations based on energetics considerations. We were able to fit an equivalent Monod model, by modifying the reaction stoichiometry and biomass yield coefficient, that could effectively match results of the genome-scale simulation of microbial behaviors under excess nutrient conditions, but predictions of the fitted Monod model deviated from those of the genome-scale model

  6. [Composition of the oil-slime microbial community determined by analysis of the 16S rRNA gene].

    PubMed

    Grigor'eva, T V; Laĭkov, A V; Rizvanov, A A; Il'inskaia, O N; Naumova, R P

    2013-01-01

    Analysis of the 16S rRNA genes of the cultured microorganisms of industrial oil-slime revealed predominance (-85-90%) of the Gammaproteobacteria in the community of aerobic heterotrophs and specific oil-slime degraders. Relation of the isolated strains with members of the genera Pseudomonas, Stenotrophomonas, and Enterobacter was established. Analysis of the same gene in the total DNA from the oil-slime revealed greater microbial diversity (-20 operative taxonomic units determined by T-RFLP) than in the cultured part of the community, which included -12 different colony types. Three major restriction fragments were found, with their total area -50%. These results demonstrated the low morphological and phylogenetic diversity of the oil-slime bacterial community.

  7. Inhibition of bacterial growth in sweet cheese whey by carbon dioxide as determined by culture-independent community profiling.

    PubMed

    Lo, Raquel; Xue, Tian; Weeks, Mike; Turner, Mark S; Bansal, Nidhi

    2016-01-18

    Whey is a valuable co-product from cheese making that serves as a raw material for a wide range of products. Its rich nutritional content lends itself to rapid spoilage, thus it typically needs to be pasteurised and refrigerated promptly. Despite the extensive literature on milk spoilage bacteria, little is known about the spoilage bacteria of whey. The utility of carbon dioxide (CO2) to extend the shelf-life of raw milk and cottage cheese has been well established, but its application in whey preservation has not yet been explored. This study aims to characterise the microbial populations of fresh and spoiled sweet whey by culture-independent community profiling using 454 pyrosequencing of 16S rRNA gene amplicons and to determine whether carbonation is effective in inhibiting bacterial growth in sweet whey. The microbiota of raw Cheddar and Mozzarella whey was dominated by cheese starter bacteria. After pasteurisation, two out of the three samples studied became dominated by diverse environmental bacteria from various phyla, with Proteobacteria being the most dominant. Diverse microbial profiles were maintained until spoilage occurred, when the entire population was dominated by just one or two genera. Whey spoilage bacteria were found to be similar to those of milk. Pasteurised Cheddar and Mozzarella whey was spoiled by Bacillus sp. or Pseudomonas sp., and raw Mozzarella whey was spoiled by Pseudomonas sp., Serratia sp., and other members of the Enterobacteriaceae family. CO2 was effective in inhibiting bacterial growth of pasteurised Cheddar and Mozzarella whey stored at 15°C and raw Mozzarella whey stored at 4°C. The spoilage bacteria of the carbonated samples were similar to those of the non-carbonated controls.

  8. Inhibition of bacterial growth in sweet cheese whey by carbon dioxide as determined by culture-independent community profiling.

    PubMed

    Lo, Raquel; Xue, Tian; Weeks, Mike; Turner, Mark S; Bansal, Nidhi

    2016-01-18

    Whey is a valuable co-product from cheese making that serves as a raw material for a wide range of products. Its rich nutritional content lends itself to rapid spoilage, thus it typically needs to be pasteurised and refrigerated promptly. Despite the extensive literature on milk spoilage bacteria, little is known about the spoilage bacteria of whey. The utility of carbon dioxide (CO2) to extend the shelf-life of raw milk and cottage cheese has been well established, but its application in whey preservation has not yet been explored. This study aims to characterise the microbial populations of fresh and spoiled sweet whey by culture-independent community profiling using 454 pyrosequencing of 16S rRNA gene amplicons and to determine whether carbonation is effective in inhibiting bacterial growth in sweet whey. The microbiota of raw Cheddar and Mozzarella whey was dominated by cheese starter bacteria. After pasteurisation, two out of the three samples studied became dominated by diverse environmental bacteria from various phyla, with Proteobacteria being the most dominant. Diverse microbial profiles were maintained until spoilage occurred, when the entire population was dominated by just one or two genera. Whey spoilage bacteria were found to be similar to those of milk. Pasteurised Cheddar and Mozzarella whey was spoiled by Bacillus sp. or Pseudomonas sp., and raw Mozzarella whey was spoiled by Pseudomonas sp., Serratia sp., and other members of the Enterobacteriaceae family. CO2 was effective in inhibiting bacterial growth of pasteurised Cheddar and Mozzarella whey stored at 15°C and raw Mozzarella whey stored at 4°C. The spoilage bacteria of the carbonated samples were similar to those of the non-carbonated controls. PMID:26476573

  9. Microbial perchlorate reduction: A precise laboratory determination of the chlorine isotope fractionation and its possible biochemical basis

    NASA Astrophysics Data System (ADS)

    Ader, Magali; Chaudhuri, Swades; Coates, John D.; Coleman, Max

    2008-05-01

    Perchlorate-reducing bacteria fractionate chlorine stable isotopes giving a powerful approach to monitor the extent of microbial consumption of perchlorate in contaminated sites undergoing remediation or natural perchlorate containing sites. This study reports the full experimental data and methodology used to re-evaluate the chlorine isotope fractionation of perchlorate reduction in duplicate culture experiments of Azospira suillum strain PS at 37 °C (Δ 37Cl Cl --ClO 4-) previously reported, without a supporting data set by Coleman et al. [Coleman, M.L., Ader, M., Chaudhuri, S., Coates, J.D., 2003. Microbial Isotopic Fractionation of Perchlorate Chlorine. Appl. Environ. Microbiol. 69, 4997-5000] in a reconnaissance study, with the goal of increasing the accuracy and precision of the isotopic fractionation determination. The method fully described here for the first time, allows the determination of a higher precision Δ 37Cl Cl --ClO 4- value, either from accumulated chloride content and isotopic composition or from the residual perchlorate content and isotopic composition. The result sets agree perfectly, within error, giving average Δ 37Cl Cl --ClO 4- = - 14.94 ± 0.15‰. Complementary use of chloride and perchlorate data allowed the identification and rejection of poor quality data by applying mass and isotopic balance checks. This precise Δ 37Cl Cl --ClO 4- value can serve as a reference point for comparison with future in situ or microcosm studies but we also note its similarity to the theoretical equilibrium isotopic fractionation between a hypothetical chlorine species of redox state + 6 and perchlorate at 37 °C and suggest that the first electron transfer during perchlorate reduction may occur at isotopic equilibrium between an enzyme-bound chlorine and perchlorate.

  10. [Effects of bio-mulching on rhizosphere soil microbial population, enzyme activity and tree growth in poplar plantation].

    PubMed

    Liu, Jiu-Jun; Fang, Sheng-Zuo; Xie, Bao-Dong; Hao, Juan-Juan

    2008-06-01

    Coriaria nepalensis, Pteridium aquilinum var. latiuscukum, Imperata cylindrical var. major, and Quercus fabric were used as mulching materials to study their effects on the rhizosphere soil microbial population and enzyme activity and the tree growth in poplar plantation. The results showed that after mulching with test materials, the populations of both bacteria and fungi in rhizosphere soil were more than those of the control. Of the mulching materials, I. cylindrical and Q. fabric had the best effect, with the numbers of bacteria and fungi being 23.56 and 1.43 times higher than the control, respectively. The bacterial and fungal populations in rhizosphere soil increased with increasing mulching amount. When the mulching amount was 7.5 kg m(-2), the numbers of bacteria and fungi in rhizosphere soil were 0.5 and 5.14 times higher than the control, respectively. Under bio-mulching, the bacterial and fungal populations in rhizosphere soil had a similar annual variation trend, which was accorded with the annual fluctuation of soil temperature and got to the maximum in July and the minimum in December. The urease and phosphatase activities in rhizosphere soil also increased with increasing mulching amount. As for the effects of different mulching materials on the enzyme activities, they were in the order of C. nepalensis > P. aquilinum > I. cylindrical > Q. fabric. The annual variation of urease and phosphatase activities in rhizosphere soil was similar to that of bacterial and fungal populations, being the highest in July and the lowest in December. Bio-mulching promoted the tree height, DBH, and biomass of poplar trees significantly.

  11. Growth determinations for unattached bacteria in a contaminated aquifer.

    USGS Publications Warehouse

    Harvey, R.W.; George, L.H.

    1987-01-01

    Growth rates of unattached bacteria in groundwater contaminated with treated sewage and collected at various distances from the source of contamination were estimated by using frequency of dividing cells and tritiated-thymidine uptake and compared with growth rates obtained with unsupplemented, closed-bottle incubations. Estimates of bacterial generation times [(In 2)/mu] along a 3-km-long transect in oxygen-depleted (0.1 to 0.7 mg of dissolved oxygen liter-1) groundwater ranged from 16 h at 0.26 km downgradient from an on-land, treated-sewage outfall to 139 h at 1.6 km and correlated with bacterial abundance (r2 = 0.88 at P less than 0.001). Partitioning of assimilated thymidine into nucleic acid generally decreased with distance from the contaminant source, and one population in heavily contaminated groundwater assimilated little thymidine during a 20-h incubation. Several assumptions commonly made when frequency of dividing cells and tritiated-thymidine uptake are used were not applicable to the groundwater samples.

  12. Growth determinations for unattached bacteria in a contaminated aquifer.

    PubMed

    Harvey, R W; George, L H

    1987-12-01

    Growth rates of unattached bacteria in groundwater contaminated with treated sewage and collected at various distances from the source of contamination were estimated by using frequency of dividing cells and tritiated-thymidine uptake and compared with growth rates obtained with unsupplemented, closed-bottle incubations. Estimates of bacterial generation times [(In 2)/mu] along a 3-km-long transect in oxygen-depleted (0.1 to 0.7 mg of dissolved oxygen liter-1) groundwater ranged from 16 h at 0.26 km downgradient from an on-land, treated-sewage outfall to 139 h at 1.6 km and correlated with bacterial abundance (r2 = 0.88 at P less than 0.001). Partitioning of assimilated thymidine into nucleic acid generally decreased with distance from the contaminant source, and one population in heavily contaminated groundwater assimilated little thymidine during a 20-h incubation. Several assumptions commonly made when frequency of dividing cells and tritiated-thymidine uptake are used were not applicable to the groundwater samples.

  13. Influence of superdoses of a novel microbial phytase on growth performance, tibia ash, and gizzard phytate and inositol in young broilers.

    PubMed

    Walk, C L; Santos, T T; Bedford, M R

    2014-05-01

    An experiment was conducted to evaluate the influence of a novel microbial phytase on performance, tibia ash, and the content of phytate, phytate esters, and inositol in the gizzard of young broilers. Male Cobb 500 broilers (n = 1,680) were fed 1 of 7 experimental diets: positive control (PC) formulated to meet or exceed nutrient recommendations; PC plus dicalcium phosphate (PC+DCP) formulated to provide Ca and P at 0.10% above the PC; PC plus 500 U/kg of microbial phytase (PC+500); negative control (NC) with Ca and P reduced from the PC by 0.16% and 0.15%, respectively; and the NC plus phytase at 500 (NC+500), 1,000 (NC+1,000), or 1,500 (NC+1,500) U/kg. Diets were fed in crumbled form to 20 birds/pen and 12 replicate pens/diet from d 0 to 21. On d 21, 4 birds/pen were euthanized for collection of right tibias and gizzard digesta for determination of tibia ash and gizzard phytate. In general, broilers fed the NC diet had reduced (P ≤ 0.05) feed intake and BW gain compared with broilers fed diets supplemented with phytase, but not different than the PC or PC+DCP. Phytase supplementation in the NC diet improved (P ≤ 0.05) BW gain comparable with or above that of the PC. Feed conversion ratio was improved in broilers fed the NC+1,000 or NC+1,500 compared with broilers fed all other diets. Tibia ash was reduced (P ≤ 0.05) in broilers fed the NC compared with broilers fed all other diets, and phytase supplementation improved tibia ash comparable with the PC. Phytase supplementation reduced (P ≤ 0.05) phytate (inositol hexa-phosphate) concentration in the gizzard. Inositol concentration in the gizzard was higher (P ≤ 0.05) in birds fed NC+1,000 or NC+1,500 compared with all other diets and this was correlated with growth performance (P ≤ 0.05) rather than tibia ash (P > 0.05). Improvements in feed conversion ratio associated with superdoses of phytase may be attributed to phytate destruction and the provision of inositol.

  14. Growth performance and gastrointestinal microbial ecology responses of piglets receiving Saccharomyces cerevisiae fermentation products after an oral challenge with Escherichia coli (K88).

    PubMed

    Kiarie, E; Bhandari, S; Scott, M; Krause, D O; Nyachoti, C M

    2011-04-01

    The effects of Saccharomyces cerevisiae fermentation products (YFP) on growth performance and gastrointestinal (GIT) microbial ecology in 90 weanling pigs orally challenged with Escherichia coli K88(+) (ETEC) were investigated. The YFP were an original YFP product (XPC) and a water-suspendable yeast fermentation prototype (WSYFP) from a commercial company. Treatments consisted of a negative control (NC, no in-feed or in-water additive), carbadox (AB, 55 mg of carbadox/kg of feed), XPC (in feed, 0.2%), and WSYFP (in water, 0.5, 1, or 2 g/pig per day), and each was allotted to 5 pens (3 pigs/pen). The diets met the 1998 NRC specifications. Pigs were acclimated to treatments for a 7-d period before an ETEC challenge. On d 8, blood was collected from pigs to determine the baseline packed cell volume (PCV) measurement, and pigs were orally challenged with ETEC. At various time points postchallenge, blood samples were taken, performance measures and fecal consistency scores were recorded, and gut digesta and tissue samples were taken to evaluate GIT morphology, microbial ecology, and metabolites. Preplanned contrasts were used for comparison. Pigs receiving YFP had greater ADFI than NC pigs on d 3 (424 vs. 378 g/d; P = 0.01) and d 7 (506 vs. 458 g/d; P = 0.03) postchallenge. This effect of YFP on ADFI was similar to that of AB on d 3, but pigs receiving AB ate more (576 vs. 506 g/d; P = 0.03) at d 7 than pigs receiving YFP. Pigs exhibited reduced (P < 0.001) PCV upon ETEC challenge; however, pigs receiving additives sustained a greater (P < 0.05) PCV at 72 h compared with the NC group. Compared with the NC pigs, pigs receiving YFP showed a smaller (P < 0.05) number of ileal mucosa adherent ETEC and prevalence of the order Enterobacteriales in the ileal digesta, which corresponded to less (5.09 vs. 6.97 mg/dL; P = 0.03) colonic ammonia on d 7 postchallenge. Most of the indices for ileal digesta bacterial richness and diversity were greater (P < 0.01) for YFP pigs compared

  15. Effectiveness of hydrothermal-calcium chloride treatment and chitosan on quality retention and microbial growth during storage of fresh-cut papaya.

    PubMed

    Ayón-Reyna, Lidia E; Tamayo-Limón, Ransés; Cárdenas-Torres, Feliznando; López-López, Martha E; López-Angulo, Gabriela; López-Moreno, Héctor S; López-Cervántes, Jaime; López-Valenzuela, José A; Vega-García, Misael O

    2015-03-01

    Rapid degradation of fresh-cut papaya limits its marketability. Hydrothermal treatments in combination with a calcium dip, applied to whole fruit before slicing, and also the application of chitosan as a coating film, have been found to have very good results in maintaining the quality of fresh-cut fruits. Based on these considerations, the aim of this study was to evaluate the effect of hydrothermal treatment (HT; 49 °C, 25 min) containing calcium chloride (Ca; 1%, w/v) followed by dipping in chitosan (Chit; 1%, w/v, 3 min) on the physical, chemical, and microbial qualities of papaya slices stored at 5 °C for 10 d. Pulp color, firmness, ascorbic acid, total phenolics, β-carotene, and lycopene were evaluated every 2 d while the microbial quality (mesophilics, psychrophilics, molds, and yeasts) was evaluated every 5 d. Fruit treated with HT-Ca and HT-Ca + Chit showed better color and firmness retention than Control and Chit. Papaya slices treated with HT-Ca + Chit had higher nutritional content and lower microbial growth at the end of storage. The application of the HT-Ca + Chit could be used to reduce deterioration processes, maintaining physical, chemical, and microbial qualities and increasing the shelf life of fresh-cut papaya stored at 5 °C.

  16. Effects of dietary supplementation of modified zinc oxide on growth performance, nutrient digestibility, blood profiles, fecal microbial shedding and fecal score in weanling pigs.

    PubMed

    Cho, Jin Ho; Upadhaya, Santi Devi; Kim, In Ho

    2015-06-01

    One hundred and forty piglets ((Landrace × Yorkshire) × Duroc, 21 day of age) with an initial weight of 6.50 ± 0.71 kg, were randomly allotted into four treatments to determine the effects of a modified form of zinc oxide (ZnO) on growth performance, nutrient digestibility, blood profiles, fecal microbial shedding and fecal score in weanling pigs. Dietary treatments were: (i) NC, negative control, basal diet containing zinc (Zn) from the premix; (ii) PC, positive control, basal diet containing Zn-free premix + 3000 ppm ZnO; (iii) H1, basal diet containing Zn-free premix + 3000 ppm ZnO (phase 1, days 1 to 14)/200 ppm modified ZnO (phase 2, days 15 to 42); (iv) H2, basal diet containing Zn-free premix + 300 ppm modified ZnO (phase 1)/200 ppm modified ZnO (phase 2). During days 1 to 14, average daily gains (ADG) were higher (P = 0.04) in PC, H1 and H2 groups than that in NC group. Overall, H1 treatment increased the ADG compared with NC (P = 0.05). On day 14, the alkaline phosphatase and plasma Zn concentration were increased (P = 0.01 and 0.04, respectively) in PC, H1 and H2 treatments compared with NC treatment. On days 14 and 42, the fecal Lactobacillus counts in NC group were lowest (P = 0.01, P = 0.04 respectively) among treatments. All supplemented groups showed lower (P = 0.03) fecal score than NC treatment on days 21 and 28. In conclusion, dietary supplementation with modified ZnO increased growth rates and reduced fecal scores in weanling pig. Modified ZnO could be used as a substitute to ZnO as a growth promoter and reduce Zn excretion to the environment because of the lower dosage. [Correction added on 3 February 2015, after first online publication: the initial weight of '6.50 ± 1.11 kg' has been replaced with '6.50 ± 0.71 kg' in the abstract.].

  17. Isolate-specific effects of ultraviolet radiation on photosynthesis, growth and mycosporine-like amino acids in the microbial mat-forming cyanobacterium Microcoleus chthonoplastes.

    PubMed

    Pattanaik, Bagmi; Roleda, Michael Y; Schumann, Rhena; Karsten, Ulf

    2008-03-01

    Microcoleus chthonoplastes constitutes one of the dominant microorganisms in intertidal microbial mat communities. In the laboratory, the effects of repeated daily exposure to ultraviolet radiation (16:8 light:dark cycle) was investigated in unicyanobacterial cultures isolated from three different localities (Baltic Sea = WW6; North Sea = STO and Brittany = BRE). Photosynthesis and growth were measured in time series (12-15 days) while UV-absorbing mycosporine-like amino acids (MAAs) and cellular integrity were determined after 12 and 3 days exposure to three radiation treatments [PAR (22 mumol photon m(-2) s(-1)) = P; PAR + UV-A (8 W m(-2)) = PA; PAR + UV-A + UV-B (0.4 W m(-2)) = PAB]. Isolate-specific responses to UVR were observed. The proximate response to radiation stress after 1-day treatment showed that isolate WW6 was the most sensitive to UVR. However, repeated exposure to radiation stress indicated that photosynthetic efficiency (F (v)/F (m)) of WW6 acclimated to UVR. Conversely, although photosynthesis in STO exhibited lower reduction in F (v)/F (m) during the first day, the values declined over time. The BRE isolate was the most tolerant to radiation stress with the lowest reduction in F (v)/F (m )sustained over time. While photosynthetic efficiencies of different isolates were able to acclimate to UVR, growth did not. The discrepancy seems to be due to the higher cell density used for photosynthesis compared to the growth measurement. Apparently, the cell density used for photosynthesis was not high enough to offer self-shading protection because cellular damage was also observed in those filaments under UVR. Most likely, the UVR acclimation of photosynthesis reflects predominantly the performance of the surviving cells within the filaments. Different strategies were observed in MAAs synthesis. Total MAAs content in WW6 was not significantly different between all the radiation treatments. In contrast, the additional fluence of UV-A and UV

  18. Use of 13C-Labeled Substrates to Determine Relative Methane Production Rates in Hypersaline Microbial Communities

    NASA Astrophysics Data System (ADS)

    Kelley, C. A.; Bebout, B.; Chanton, J.

    2015-12-01

    Rates and pathways of methane production were determined from photosynthetic soft microbial mats and gypsum-encrusted endoevaporites collected in hypersaline environments from California, Mexico and Chile, as well as an organic-rich mud from a pond in the El Tatio volcanic fields, Chile. Samples (mud, homogenized soft mats and endoevaporites) were incubated anaerobically with deoxygenated site water, and the increase in methane concentration through time in the headspaces of the incubation vials was used to determine methane production rates. To ascertain the substrates used by the methanogens, 13C-labeled methylamines, methanol, dimethylsulfide, acetate or bicarbonate were added to the incubations (one substrate per vial) and the stable isotopic composition of the resulting methane was measured. The vials amended with 13C-labeled methylamines produced the most 13C-enriched methane, generally followed by the 13C-labeled methanol-amended vials. The stable isotope data and the methane production rates were used to determine first order rate constants for each of the substrates at each of the sites. Estimates of individual substrate use revealed that the methylamines produced 55 to 92% of the methane generated, while methanol was responsible for another 8 to 40%.

  19. Determining the Diversity and Species Abundance Patterns in Arctic Soils using Rational Methods for Exploring Microbial Diversity

    NASA Astrophysics Data System (ADS)

    Ovreas, L.; Quince, C.; Sloan, W.; Lanzen, A.; Davenport, R.; Green, J.; Coulson, S.; Curtis, T.

    2012-12-01

    Arctic microbial soil communities are intrinsically interesting and poorly characterised. We have inferred the diversity and species abundance distribution of 6 Arctic soils: new and mature soil at the foot of a receding glacier, Arctic Semi Desert, the foot of bird cliffs and soil underlying Arctic Tundra Heath: all near Ny-Ålesund, Spitsbergen. Diversity, distribution and sample sizes were estimated using the rational method of Quince et al., (Isme Journal 2 2008:997-1006) to determine the most plausible underlying species abundance distribution. A log-normal species abundance curve was found to give a slightly better fit than an inverse Gaussian curve if, and only if, sequencing error was removed. The median estimates of diversity of operational taxonomic units (at the 3% level) were 3600-5600 (lognormal assumed) and 2825-4100 (inverse Gaussian assumed). The nature and origins of species abundance distributions are poorly understood but may yet be grasped by observing and analysing such distributions in the microbial world. The sample size required to observe the distribution (by sequencing 90% of the taxa) varied between ~ 106 and ~105 for the lognormal and inverse Gaussian respectively. We infer that between 5 and 50 GB of sequencing would be required to capture 90% or the metagenome. Though a principle components analysis clearly divided the sites into three groups there was a high (20-45%) degree of overlap in between locations irrespective of geographical proximity. Interestingly, the nearest relatives of the most abundant taxa at a number of most sites were of alpine or polar origin. Samples plotted on first two principal components together with arbitrary discriminatory OTUs

  20. Aggregate Size and Architecture Determine Microbial Activity Balance for One-Stage Partial Nitritation and Anammox ▿

    PubMed Central

    Vlaeminck, Siegfried E.; Terada, Akihiko; Smets, Barth F.; De Clippeleir, Haydée; Schaubroeck, Thomas; Bolca, Selin; Demeestere, Lien; Mast, Jan; Boon, Nico; Carballa, Marta; Verstraete, Willy

    2010-01-01

    Aerobic ammonium-oxidizing bacteria (AerAOB) and anoxic ammonium-oxidizing bacteria (AnAOB) cooperate in partial nitritation/anammox systems to remove ammonium from wastewater. In this process, large granular microbial aggregates enhance the performance, but little is known about granulation so far. In this study, three suspended-growth oxygen-limited autotrophic nitrification-denitrification (OLAND) reactors with different inoculation and operation (mixing and aeration) conditions, designated reactors A, B, and C, were used. The test objectives were (i) to quantify the AerAOB and AnAOB abundance and the activity balance for the different aggregate sizes and (ii) to relate aggregate morphology, size distribution, and architecture putatively to the inoculation and operation of the three reactors. A nitrite accumulation rate ratio (NARR) was defined as the net aerobic nitrite production rate divided by the anoxic nitrite consumption rate. The smallest reactor A, B, and C aggregates were nitrite sources (NARR, >1.7). Large reactor A and C aggregates were granules capable of autonomous nitrogen removal (NARR, 0.6 to 1.1) with internal AnAOB zones surrounded by an AerAOB rim. Around 50% of the autotrophic space in these granules consisted of AerAOB- and AnAOB-specific extracellular polymeric substances. Large reactor B aggregates were thin film-like nitrite sinks (NARR, <0.5) in which AnAOB were not shielded by an AerAOB layer. Voids and channels occupied 13 to 17% of the anoxic zone of AnAOB-rich aggregates (reactors B and C). The hypothesized granulation pathways include granule replication by division and budding and are driven by growth and/or decay based on species-specific physiology and by hydrodynamic shear and mixing. PMID:19948857

  1. Our unique microbial identity.

    PubMed

    Gilbert, Jack A

    2015-05-14

    A recent article examines the extent of individual variation in microbial identities and how this might determine disease susceptibility, therapeutic responses and recovery from clinical interventions.

  2. Substrate Topography Determines Neuronal Polarization and Growth In Vitro

    PubMed Central

    Micholt, Liesbeth; Gärtner, Annette; Prodanov, Dimiter; Braeken, Dries; Dotti, Carlos G.; Bartic, Carmen

    2013-01-01

    The establishment of neuronal connectivity depends on the correct initial polarization of the young neurons. In vivo, developing neurons sense a multitude of inputs and a great number of molecules are described that affect their outgrowth. In vitro, many studies have shown the possibility to influence neuronal morphology and growth by biophysical, i.e. topographic, signaling. In this work we have taken this approach one step further and investigated the impact of substrate topography in the very early differentiation stages of developing neurons, i.e. when the cell is still at the round stage and when the first neurite is forming. For this purpose we fabricated micron sized pillar structures with highly reproducible feature sizes, and analyzed neurons on the interface of flat and topographic surfaces. We found that topographic signaling was able to attract the polarization markers of mouse embryonic neurons -N-cadherin, Golgi-centrosome complex and the first bud were oriented towards topographic stimuli. Consecutively, the axon was also preferentially extending along the pillars. These events seemed to occur regardless of pillar dimensions in the range we examined. However, we found differences in neurite length that depended on pillar dimensions. This study is one of the first to describe in detail the very early response of hippocampal neurons to topographic stimuli. PMID:23785482

  3. Metabolic Plasticity as a Determinant of Tumor Growth and Metastasis.

    PubMed

    Lehuédé, Camille; Dupuy, Fanny; Rabinovitch, Rebecca; Jones, Russell G; Siegel, Peter M

    2016-09-15

    Cancer cells must adapt their metabolism to meet the energetic and biosynthetic demands that accompany rapid growth of the primary tumor and colonization of distinct metastatic sites. Different stages of the metastatic cascade can also present distinct metabolic challenges to disseminating cancer cells. However, little is known regarding how changes in cellular metabolism, both within the cancer cell and the metastatic microenvironment, alter the ability of tumor cells to colonize and grow in distinct secondary sites. This review examines the concept of metabolic heterogeneity within the primary tumor, and how cancer cells are metabolically coupled with other cancer cells that comprise the tumor and cells within the tumor stroma. We examine how metabolic strategies, which are engaged by cancer cells in the primary site, change during the metastatic process. Finally, we discuss the metabolic adaptations that occur as cancer cells colonize foreign metastatic microenvironments and how cancer cells influence the metabolism of stromal cells at sites of metastasis. Through a discussion of these topics, it is clear that plasticity in tumor metabolic programs, which allows cancer cells to adapt and grow in hostile microenvironments, is emerging as an important variable that may change clinical approaches to managing metastatic disease. Cancer Res; 76(18); 5201-8. ©2016 AACR. PMID:27587539

  4. Metabolic Plasticity as a Determinant of Tumor Growth and Metastasis.

    PubMed

    Lehuédé, Camille; Dupuy, Fanny; Rabinovitch, Rebecca; Jones, Russell G; Siegel, Peter M

    2016-09-15

    Cancer cells must adapt their metabolism to meet the energetic and biosynthetic demands that accompany rapid growth of the primary tumor and colonization of distinct metastatic sites. Different stages of the metastatic cascade can also present distinct metabolic challenges to disseminating cancer cells. However, little is known regarding how changes in cellular metabolism, both within the cancer cell and the metastatic microenvironment, alter the ability of tumor cells to colonize and grow in distinct secondary sites. This review examines the concept of metabolic heterogeneity within the primary tumor, and how cancer cells are metabolically coupled with other cancer cells that comprise the tumor and cells within the tumor stroma. We examine how metabolic strategies, which are engaged by cancer cells in the primary site, change during the metastatic process. Finally, we discuss the metabolic adaptations that occur as cancer cells colonize foreign metastatic microenvironments and how cancer cells influence the metabolism of stromal cells at sites of metastasis. Through a discussion of these topics, it is clear that plasticity in tumor metabolic programs, which allows cancer cells to adapt and grow in hostile microenvironments, is emerging as an important variable that may change clinical approaches to managing metastatic disease. Cancer Res; 76(18); 5201-8. ©2016 AACR.

  5. Growth conditions determine different melatonin levels in Lupinus albus L.

    PubMed

    Arnao, Marino B; Hernández-Ruiz, Josefa

    2013-09-01

    Melatonin, an indoleamine, which has recently been assigned several roles in plant physiology as a growth promoter, as rooting agent, and as antioxidant in senescence delay and cytoprotection, seems to have a relevant function in plant stress situations. The presence of melatonin increases the resistance of lupin plant tissues (Lupinus albus L.) against natural or artificially induced adverse situations. In this work, we studied the response of lupin plants in controlled stress situations (drought-, anaerobic-, pH-, and cold stress and using ZnSO4 , NaCl, and H2 O2 as chemical stressors) and measured the changes in endogenous melatonin levels in lupin plants. Also, the effect of abscisic acid, ethylene, and natural environmental conditions were evaluated. In general, nearly all stressful factors caused an increase in melatonin in the investigated organs. The chemical stress provoked by ZnSO4 or NaCl caused the most pronounced changes in the endogenous level of melatonin, followed by cold and drought stressors. In some cases, the level of melatonin increased 12-fold with respect to the levels in control plants, indicating that melatonin biosynthesis is upregulated in common stress situations, in which it may serve as a signal molecule and/or as a direct antistress agent due to its well-known antioxidative properties.

  6. Determination of charge transfer resistance and capacitance of microbial fuel cell through a transient response analysis of cell voltage.

    PubMed

    Ha, Phuc Thi; Moon, Hyunsoo; Kim, Byung Hong; Ng, How Yong; Chang, In Seop

    2010-03-15

    An alternative method for determining the charge transfer resistance and double-layer capacitance of microbial fuel cells (MFCs), easily implemented without a potentiostat, was developed. A dynamic model with two parameters, the charge transfer resistance and double-layer capacitance of electrodes, was derived from a linear differential equation to depict the current generation with respect to activation overvoltage. This model was then used to fit the transient cell voltage response to the current step change during the continuous operation of a flat-plate type MFC fed with acetate. Variations of the charge transfer resistance and the capacitance value with respect to the MFC design conditions (biocatalyst existence and electrode area) and operating parameters (acetate concentration and buffer strength in the catholyte) were then determined to elucidate the validity of the proposed method. This model was able to describe the dynamic behavior of the MFC during current change in the activation loss region; having an R(2) value of over 0.99 in most tests. Variations of the charge transfer resistance value (thousands of Omega) according to the change of the design factors and operational factors were well-correlated with the corresponding MFC performances. However, though the capacitance values (approximately 0.02 F) reflected the expected trend according to the electrode area change and catalyst property, they did not show significant variation with changes in either the acetate concentration or buffer strength.

  7. Experimental determination of magnesium isotope fractionation during higher plant growth

    NASA Astrophysics Data System (ADS)

    Bolou-Bi, Emile B.; Poszwa, Anne; Leyval, Corinne; Vigier, Nathalie

    2010-05-01

    Two higher plant species (rye grass and clover) were cultivated under laboratory conditions on two substrates (solution, phlogopite) in order to constrain the corresponding Mg isotope fractionations during plant growth and Mg uptake. We show that bulk plants are systematically enriched in heavy isotopes relative to their nutrient source. The Δ 26Mg plant-source range from 0.72‰ to 0.26‰ for rye grass and from 1.05‰ to 0.41‰ for clover. Plants grown on phlogopite display Mg isotope signatures (relative to the Mg source) ˜0.3‰ lower than hydroponic plants. For a given substrate, rye grass display lower δ 26Mg (by ˜0.3‰) relative to clover. Magnesium desorbed from rye grass roots display a δ 26Mg greater than the nutrient solution. Adsorption experiments on dead and living rye grass roots also indicate a significant enrichment in heavy isotopes of the Mg adsorbed on the root surface. Our results indicate that the key processes responsible for heavy isotope enrichment in plants are located at the root level. Both species also exhibit an enrichment in light isotopes from roots to shoots (Δ 26Mg leaf-root = -0.65‰ and -0.34‰ for rye grass and clover grown on phlogopite respectively, and Δ 26Mg leaf-root of -0.06‰ and -0.22‰ for the same species grown hydroponically). This heavy isotope depletion in leaves can be explained by biological processes that affect leaves and roots differently: (1) organo-Mg complex (including chlorophyll) formation, and (2) Mg transport within plant. For both species, a positive correlation between δ 26Mg and K/Mg was observed among the various organs. This correlation is consistent with the link between K and Mg internal cycles, as well as with formation of organo-magnesium compounds associated with enrichment in heavy isotopes. Considering our results together with the published range for δ 26Mg of natural plants and rivers, we estimate that a significant change in continental vegetation would induce a change of

  8. Soil moisture and land use are major determinants of soil microbial community composition and biomass at a regional scale in northeastern China

    NASA Astrophysics Data System (ADS)

    Ma, L.; Guo, C.; Lü, X.; Yuan, S.; Wang, R.

    2015-04-01

    Global environmental factors impact soil microbial communities and further affect organic matter decomposition, nutrient cycling and vegetation dynamic. However, little is known about the relative contributions of climate factors, soil properties, vegetation types, land management practices and spatial structure (which serves as a proxy for underlying effects of temperature and precipitation for spatial variation) on soil microbial community composition and biomass at large spatial scales. Here, we compared soil microbial communities using phospholipid fatty acid method across 7 land use types from 23 locations at a regional scale in northeastern China (850 × 50 km). The results showed that soil moisture and land use changes were most closely related to microbial community composition and biomass at the regional scale, while soil total C content and climate effects were weaker but still significant. Factors such as spatial structure, soil texture, nutrient availability and vegetation types were not important. Higher contributions of gram-positive bacteria were found in wetter soils, whereas higher contributions of gram-negative bacteria and fungi were observed in drier soils. The contributions of gram-negative bacteria and fungi were lower in heavily disturbed soils than historically disturbed and undisturbed soils. The lowest microbial biomass appeared in the wettest and driest soils. In conclusion, dominant climate and soil properties were not the most important drivers governing microbial community composition and biomass because of inclusion of irrigated and managed practices, and thus soil moisture and land use appear to be primary determinants of microbial community composition and biomass at the regional scale in northeastern China.

  9. [Halophilous microbial groups in saline lake of Qinghai and the growth characteristics and anti-microbial and anti-tumor activities of F16].

    PubMed

    Ye, Yanfang; Yan, Xiaojun; Huang, Xiaochun; Chen, Ye; Chen, Haimin; Zhu, Shihua

    2006-10-01

    A total of forty-five halophilous microorganisms were isolated from the sediment of saline lake in Qinghai Province, among which, filamentous fungus F16 showed the highest activity of anti-microorganism and anti-tumor. The ethyl acetate extract of F16 culture filtrate showed a strong cytotoxicity, and could inhibit the growth of four kinds of bacteria, especially Escherichia coli. When the concentration of the crude extract was 50 microg x ml(-1), the inhibition rate to liver cancer cell BEL7402 reached 76. 91%. The optimal temperature for F16 growth was 15 degrees C , and the increase of salt concentration in media would inhibit its growth. When the concentration of salt surpassed 15% , F16 could not survive. F16 grew well when the pH value ranged from 5 to 9.

  10. Microbial field pilot study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Coates, J.D.; Chisholm, J.L.

    1993-05-01

    A multi-well microbially enhanced oil recovery field pilot has been performed in the Southeast Vassar Vertz Sand Unit in Payne County, Oklahoma. The primary emphasis of the experiment was preferential plugging of high permeability zones for the purpose of improving waterflood sweep efficiency. Studies were performed to determine reservoir chemistry, ecology, and indigenous bacteria populations. Growth experiments were used to select a nutrient system compatible with the reservoir that encouraged growth of a group of indigenous nitrate-using bacteria and inhibit growth of sulfate-reducing bacteria. A specific field pilot area behind an active line drive waterflood was selected. Surface facilities were designed and installed. Injection protocols of bulk nutrient materials were prepared to facilitate uniform distribution of nutrients within the pilot area. By the end of December, 1991, 82.5 tons (75.0 tonnes) of nutrients had been injected in the field. A tracer test identified significant heterogeneity in the SEVVSU and made it necessary to monitor additional production wells in the field. The tracer tests and changes in production behavior indicate the additional production wells monitored during the field trial were also affected. Eighty two and one half barrels (13.1 m[sup 3]) of tertiary oil have been recovered. Microbial activity has increased CO[sub 2] content as indicated by increased alkalinity. A temporary rise in sulfide concentration was experienced. These indicate an active microbial community was generated in the field by the nutrient injection. Pilot area interwell pressure interference test results showed that significant permeability reduction occurred. The interwell permeabilities in the pilot area between the injector and the three pilot production wells were made more uniform which indicates a successful preferential plugging enhanced oil recovery project.

  11. In vitro study on the effect of doxycycline on the microbial activity of soil determined by redox-potential measuring system.

    PubMed

    Szakmár, Katalin; Reichart, Olivér; Szatmári, István; Erdősi, Orsolya; Szili, Zsuzsanna; László, Noémi; Székely Körmöczy, Péter; Laczay, Péter

    2014-09-01

    The potential effect of doxycycline on the microbial activity was investigated in three types of soil. Soil samples were spiked with doxycycline, incubated at 25°C and tested at 0, 2, 4 and 6 days after treatment. The microbiological activity of the soil was characterized by the viable count determined by plate pouring and by the time necessary to reach a defined rate of the redox-potential decrease termed as time to detection (TTD).The viable count of the samples was not changed during the storage. The TTD values, however exhibited a significant increase in the 0.2-1.6 mg/kg doxycycline concentration range compared to the untreated samples indicating concentration-dependent inhibitory effect on microbial activity. The potency of the effect was different in the 3 soil types. To describe the combined effect of the doxycycline concentration and time on the biological activity of one type of soil a mathematical model was constructed and applied.The change of microbial metabolic rate could be measured also without (detectable) change of microbial count when the traditional microbiological methods are not applicable. The applied new redox potential measurement-based method is a simple and useful procedure for the examination of microbial activity of soil and its potential inhibition by antibiotics.

  12. Comparison effects of dietary iron dextran and bacterial-iron supplementation on growth performance, fecal microbial flora, and blood profiles in sows and their litters.

    PubMed

    Zhao, Pinyao; Upadhaya, Santi Devi; Li, Jian; Kim, Inho

    2015-11-01

    This study was conducted to compare effects of dietary administration of iron dextran and bacterial-iron on growth performance, fecal microbial flora, and blood profiles in sows and their litters. A total of 20 multiparous sows (Landrace × Yorkshire) were randomly allotted into two treatments: (i) ID (basal diet, piglets were injected with iron dextran); (ii) BR (basal diet + bacterial-iron; bacterial-iron was given to sows, piglets were not injected with iron dextran). There were five replicates per treatment with two sows per replicate. No differences were observed on sow and piglet growth performance, fecal microbial flora as well as sow blood profiles between ID and BR treatments. In piglets, blood iron, red blood cell and hemoglobin concentrations in ID treatment were higher (P < 0.05) on days 12 and 24. Furthermore, concentration of white blood cells in BR treatment was lower (P < 0.05) on day 12. However, the percentage of lymphocytes on day 12 was increased (P < 0.05) in BR treatment. In conclusion, effect of iron dextran and bacterial-iron has no difference on growth performance in lactating sows and piglets, but iron dextran injection has higher blood iron, white blood cell, red blood cell and hemoglobin concentrations in piglets.

  13. Diverse and divergent protein post-translational modifications in two growth stages of a natural microbial community

    SciTech Connect

    Li, Zhou; Wang, Yingfeng; Yao, Qiuming; Justice, Nicholas B.; Ahn, Tae-Hyuk; Xu, Dong; Hettich, Robert {Bob} L; Banfield, Jillian F.; Pan, Chongle

    2014-01-01

    Detailed characterization of posttranslational modifications (PTMs) of proteins in microbial communities remains a significant challenge. Here we directly identify and quantify a broad range of PTMs (hydroxylation, methylation, citrullination, acetylation, phosphorylation, methylthiolation, S-nitrosylation and nitration) in a natural microbial community from an acid mine drainage site. Approximately 29% of the identified proteins of the dominant Leptospirillum group II bacteria are modified, and 43% of modified proteins carry multiple PTM types. Most PTM events, except S-nitrosylations, have low fractional occupancy. Notably, PTM events are detected on Cas proteins involved in antiviral defense, an aspect of Cas biochemistry not considered previously. Further, Cas PTM profiles from Leptospirillum group II differ in early versus mature biofilms. PTM patterns are divergent on orthologues of two closely related, but ecologically differentiated, Leptospirillum group II bacteria. Our results highlight the prevalence and dynamics of PTMs of proteins, with potential significance for ecological adaptation and microbial evolution.

  14. Representation of Dormant and Active Microbial Dynamics for Ecosystem Modeling

    SciTech Connect

    Wang, Gangsheng; Mayes, Melanie; Gu, Lianhong; Schadt, Christopher Warren

    2014-01-01

    Dormancy is an essential strategy for microorganisms to cope with environmental stress. However, global ecosystem models typically ignore microbial dormancy, resulting in notable model uncertainties. To facilitate the consideration of dormancy in these large-scale models, we propose a new microbial physiology component that works for a wide range of substrate availabilities. This new model is based on microbial physiological states and the major parameters are the maximum specific growth and maintenance rates of active microbes and the ratio of dormant to active maintenance rates. A major improvement of our model over extant models is that it can explain the low active microbial fractions commonly observed in undisturbed soils. Our new model shows that the exponentially-increasing respiration from substrate-induced respiration experiments can only be used to determine the maximum specific growth rate and initial active microbial biomass, while the respiration data representing both exponentially-increasing and non-exponentially-increasing phases can robustly determine a range of key parameters including the initial total live biomass, initial active fraction, the maximum specific growth and maintenance rates, and the half-saturation constant. Our new model can be incorporated into existing ecosystem models to account for dormancy in microbially-driven processes and to provide improved estimates of microbial activities.

  15. Fecal microbial diversity in pre-weaned dairy calves as described by pyrosequencing of metagenomic 16S rDNA. Associations of Faecalibacterium species with health and growth.

    PubMed

    Oikonomou, Georgios; Teixeira, Andre Gustavo Vieira; Foditsch, Carla; Bicalho, Marcela Lucas; Machado, Vinicius Silva; Bicalho, Rodrigo Carvalho

    2013-01-01

    In this study, we use barcoded pyrosequencing of the 16S rRNA gene to characterize the fecal microbiota of neonatal calves and identify possible relationships of certain microbiota profiles with health and weight gain. Fecal samples were obtained weekly from 61 calves from birth until weaning (seventh week of the calves' life). Firmicutes was the most prevalent phylum, with a prevalence ranging from 63.84% to 81.90%, followed by Bacteroidetes (8.36% to 23.93%), Proteobacteria (3.72% to 9.75%), Fusobacteria (0.76% to 5.67%), and Actinobacteria (1.02% to 2.35%). Chao1 index gradually increased from the first to the seventh postnatal week. Chao1 index was lower during the third, fourth, and fifth week of life in calves that suffered from pneumonia and were treated with antibiotics. Diarrhea incidence during the first four weeks of the calves' life was also associated with a reduction of microbial diversity during the third week of life. Increased fecal microbial diversity after the second week of life was associated with higher weight gain. Using discriminant analysis we were able to show differences in the microbiota profiles between different weeks of life, between high and low weight gain groups of calves, and between calves affected and not affected with diarrhea during the first four weeks life. The prevalence of Faecalibacterium spp. in the first week of life was associated with weight gain and the incidence of diarrhea, with higher prevalence being associated with higher weight gain and less diarrhea. Representative sequences from Faecalibacterium spp. were closely affiliated to Faecalibacterium prausnitzii. Results presented here provide new information regarding the intestinal microbiota of neonatal calves and its association with health and growth. Fecal microbial diversity was associated with calf age, disease status and growth rates. Results suggesting a possible beneficial effect of Faecalibacterium spp. on health and growth are promising.

  16. Carbon and hydrogen isotope fractionation by microbial methane oxidation: Improved determination

    SciTech Connect

    Mahieu, Koenraad . E-mail: Koenraad.Mahieu@Ugent.be; Visscher, Alex De; Vanrolleghem, Peter A.; Cleemput, Oswald Van

    2006-07-01

    Isotope fractionation is a promising tool for quantifying methane oxidation in landfill cover soils. For good quantification an accurate determination of the isotope fractionation factor ({alpha}) of methane oxidation based on independent batch experiments with soil samples from the landfill cover is required. Most studies so far used data analysis methods based on approximations of the Rayleigh model to determine {alpha}. In this study, the two most common approximations were tested, the simplified Rayleigh approach and the Coleman method. To do this, the original model of Rayleigh was described in measurable variables, methane concentration and isotopic abundances, and fitted to batch oxidation data by means of a weighted non-linear errors-in-variables regression technique. The results of this technique were used as a benchmark to which the results of the two conventional approximations were compared. Three types of batch data were used: simulated data, data obtained from the literature, and data obtained from new batch experiments conducted in our laboratory. The Coleman approximation was shown to be acceptable but not recommended for carbon fractionation (error on {alpha} - 1 up to 5%) and unacceptable for hydrogen fractionation (error up to 20%). The difference between the simplified Rayleigh approach and the exact Rayleigh model is much smaller for both carbon and hydrogen fractionation (error on {alpha} - 1 < 0.05%). There is also a small difference when errors in both variables (methane concentration and isotope abundance) are accounted for instead of assuming an error-free independent variable. By means of theoretical calculations general criteria, not limited to methane, {sup 13}C, or D, were developed for the validity of the simplified Rayleigh approach when using labelled compounds.

  17. Metagenome-Wide Association of Microbial Determinants of Host Phenotype in Drosophila melanogaster

    PubMed Central

    Newell, Peter D.; Douglas, Angela E.

    2014-01-01

    ABSTRACT Animal-associated bacteria (microbiota) affect host behaviors and physiological traits. To identify bacterial genetic determinants of microbiota-responsive host traits, we employed a metagenome-wide association (MGWA) approach in two steps. First, we measured two microbiota-responsive host traits, development time and triglyceride (TAG) content, in Drosophila melanogaster flies monoassociated with each of 41 bacterial strains. The effects of monoassociation on host traits were not confined to particular taxonomic groups. Second, we clustered protein-coding sequences of the bacteria by sequence similarity de novo and statistically associated the magnitude of the host trait with the bacterial gene contents. The animals had been monoassociated with genome-sequenced bacteria, so the metagenome content was unambiguous. This analysis showed significant effects of pyrroloquinoline quinone biosynthesis genes on development time, confirming the results of a published transposon mutagenesis screen, thereby validating the MGWA; it also identified multiple genes predicted to affect host TAG content, including extracellular glucose oxidation pathway components. To test the validity of the statistical associations, we expressed candidate genes in a strain that lacks them. Monoassociation with bacteria that ectopically expressed a predicted oxidoreductase or gluconate dehydrogenase conferred reduced Drosophila TAG contents relative to the TAG contents in empty vector controls. Consistent with the prediction that glucose oxidation pathway gene expression increased bacterial glucose utilization, the glucose content of the host diet was reduced when flies were exposed to these strains. Our findings indicate that microbiota affect host nutritional status through modulation of nutrient acquisition. Together, these findings demonstrate the utility of MGWA for identifying bacterial determinants of host traits and provide mechanistic insight into how gut microbiota modulate the

  18. Temperature dependence of protein solubility-determination, application to crystallization, and growth kinetics studies

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz

    1993-01-01

    A scintillation method was developed for determinations of the temperature dependence of the solubility, and of nucleation induction times of proteins, in 50-100 mu(l) volumes of solution. Solubility data for lysozyme and horse serum albumin were obtained for various combinations of pH and precipitant concentrations. These data and the nucleation induction information were used for dynamic crystallization control, that is, for the controlled separation of nucleation and growth stages. Individual lysozyme and horse serum albumin crystals were grown in 15-20 mu(l) solution volumes contained in x-ray capillaries. The morphology and kinetics of the growth and dissolution of lysozyme in aqueous solutions with 2.5 percent NaCl and at pH = 4.5 was studied in situ with a depth resolution of 300 A (4 unit cells) by high resolution optical microscopy and digital image processing. The bulk super- or under saturation, sigma, of the solution inside a closed growth cell was controlled by temperature. The growth habit was bound by (110) and (101) faces that grew through layer spreading, although with different growth rate dependencies on supersaturation/temperature. At sigma less than 10 (obtained at higher temperatures) growth was purely kinetic ally controlled, with impurity effects (macrostep formation and kinetic hindrance) becoming significant for sigma less than 2. At sigma greater than 10 (lower temperatures), anisotropies in the interfacial kinetics were more pronounced, with interfacial kinetics and bulk transport becoming equally important to the growth morphology. Growth rates were growth history dependent. The formation of striations (layers of irregularly incorporated solution) was unambiguously correlated with growth temperature variations. Etching exposed dislocations and various high-index faces whose growth morphologies were studied during return to the steady state growth form. Growth steps were observed to originate from two-dimensional nuclei or from outcrops

  19. Growth rates of atmospheric molecular clusters determined from cluster appearance times and collision-evaporation fluxes

    NASA Astrophysics Data System (ADS)

    Kontkanen, Jenni; Olenius, Tinja; Lehtipalo, Katrianne; Vehkamäki, Hanna; Kulmala, Markku

    2015-04-01

    The probability of freshly formed particles to survive to climatically relevant sizes is determined by the competition between the coagulation loss rate and the particle growth rate. Therefore, various methods have been developed to deduce the growth rates from measured particle size distributions. Recently, the growth rates of sub-3nm clusters have been determined based on the appearance times of different cluster sizes. However, it is not clear to what extent these growth rates are consistent with the growth rates corresponding to molecular fluxes between clusters. In this work, we simulated the time evolution of a population of sub-3 nm molecular clusters and compared the growth rates determined (1) from the cluster appearance times and (2) from the collision-evaporation fluxes between different cluster sizes. We performed a number of simulations by varying the ambient conditions and the properties of the model substance. In the first simulation set, the Gibbs free energy of the formation of the clusters was assumed to have a single maximum and no minima, corresponding to a monotonically increasing stability as a function of cluster size. The saturation vapor pressure was selected so that the growth proceeded solely via monomer additions. The growth rates were determined separately for each cluster. However, to see the effect of finite size resolution, we also performed simulations where the clusters were grouped into size bins, for which we determined the growth rates. In the second simulation set, the saturation vapor pressure was lowered so that the collisions of small clusters significantly contributed to the growth. As the growth rate of a single cluster is ambiguous in this case, the growth rates were determined only for different size bins. We performed simulations using a similar free energy profile as in other simulations but we also used a free energy profile containing a local minimum, corresponding to small stable clusters. Our simulations show that

  20. Indirect microbial detection

    NASA Technical Reports Server (NTRS)

    Wilkins, J. R. (Inventor)

    1981-01-01

    The growth of microorganisms in a sample is detected and monitored by culturing microorganisms in a growth medium and detecting a change in potential between two electrodes, separated from the microbial growth by a barrier which is permeable to charged paticles but microorganism impermeable.

  1. Determination of unique microbial volatile organic compounds produced by five Aspergillus species commonly found in problem buildings.

    PubMed

    Gao, Pengfei; Korley, Frederick; Martin, Jennifer; Chen, Bean T

    2002-01-01

    This study identified unique microbial volatile organic compounds (UMVOCs) produced by five Aspergillus species (A. fumigatus, A. versicolor, A. sydowi, A. flavus, and A. niger) cultivated on malt extract agar and gypsum board. The hypothesis was that UMVOCs can be used to predict the presence of Aspergillus species. During the cultivation humidified air was continually supplied and evenly distributed through each of the culture flasks. Volatile metabolites were collected using Tenax TA tubes on Days 8, 16, and 30 after inoculation. The volatile metabolites were determined by gas chromatography/mass spectroscopy after thermal desorption. Nine compounds recognized as UMVOCs--3-methyl-1-butanol; 2-methyl-1-propanol; terpineol; 2-heptanone; 1-octen-3-ol; dimethyl disulfide; 2-hexanone; 3-octanone; and 2-pentylfuran--were found on the cultures in detectable amounts. The first two compounds were detected at the highest frequency when combining both media. The first four compounds were found to be the dominant UMVOCs on gypsum board, which could be used as chemical markers of the common Aspergillus species grown indoors.

  2. Determinants in 3Dpol modulate the rate of growth of hepatitis A virus.

    PubMed

    Konduru, Krishnamurthy; Kaplan, Gerardo G

    2010-08-01

    Hepatitis A virus (HAV), an atypical member of the Picornaviridae, grows poorly in cell culture. To define determinants of HAV growth, we introduced a blasticidin (Bsd) resistance gene into the virus genome and selected variants that grew at high concentrations of Bsd. The mutants grew fast and had increased rates of RNA replication and translation but did not produce significantly higher virus yields. Nucleotide sequence analysis and reverse genetic studies revealed that a T6069G change resulting in a F42L amino acid substitution in the viral polymerase (3D(pol)) was required for growth at high Bsd concentrations whereas a silent C7027T mutation enhanced the growth rate. Here, we identified a novel determinant(s) in 3D(pol) that controls the kinetics of HAV growth. PMID:20534860

  3. Dietary marker effects on fecal microbial ecology, fecal VFA, nutrient digestibility coefficients, and growth performance in finishing pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Use of indigestible markers such as Cr2O3, Fe2O3, and TiO2 are commonly used in animal studies to evaluate rate of passage and nutrient digestibility. Yet nothing is known relative to their potential impact on fecal microbial ecology and subsequent VFA generation. Two experiments utilizing a total o...

  4. Comparison of signaling interactions determining annual and perennial plant growth in response to low temperature

    PubMed Central

    Wingler, Astrid

    2015-01-01

    Low temperature inhibits plant growth despite the fact that considerable rates of photosynthetic activity can be maintained. Instead of lower rates of photosynthesis, active inhibition of cell division and expansion is primarily responsible for reduced growth. This results in sink limitation and enables plants to accumulate carbohydrates that act as compatible solutes or are stored throughout the winter to enable re-growth in spring. Regulation of growth in response to temperature therefore requires coordination with carbon metabolism, e.g., via the signaling metabolite trehalose-6-phosphate. The phytohormones gibberellin (GA) and jasmonate (JA) play an important role in regulating growth in response to temperature. Growth restriction at low temperature is mainly mediated by DELLA proteins, whose degradation is promoted by GA. For annual plants, it has been shown that the GA/DELLA pathway interacts with JA signaling and C-repeat binding factor dependent cold acclimation, but these interactions have not been explored in detail for perennials. Growth regulation in response to seasonal factors is, however, particularly important in perennials, especially at high latitudes. In autumn, growth cessation in trees is caused by shortening of the daylength in interaction with phytohormone signaling. In perennial grasses seasonal differences in the sensitivity to GA may enable enhanced growth in spring. This review provides an overview of the signaling interactions that determine plant growth at low temperature and highlights gaps in our knowledge, especially concerning the seasonality of signaling responses in perennial plants. PMID:25628637

  5. Impact of short-term storage temperature on determination of microbial community composition and abundance in aerated forest soil and anoxic pond sediment samples.

    PubMed

    Brandt, Franziska B; Breidenbach, Björn; Brenzinger, Kristof; Conrad, Ralf

    2014-12-01

    Sampling strategy is important for unbiased analysis of the characteristics of microbial communities in the environment. During field work it is not always possible to analyze fresh samples immediately or store them frozen. Therefore, the effect of short-term storage temperature was investigated on the abundance and composition of bacterial, archaeal and denitrifying communities in environmental samples from two different sampling sites. Oxic forest soil and anoxic pond sediment were investigated by measuring microbial abundance (DNA) and transcriptional activity (RNA). Prior to investigating the effect of storage temperature, samples were immediately analyzed, in order to represent the original situation in the habitat. The effect of storage temperature was then determined after 11 days at different low temperatures (room temperature, 4 °C, −22 °C and −80 °C). Community profiling using terminal restriction fragment length polymorphism (T-RFLP) showed no significant differences between the immediately analyzed reference sample and the samples stored at different incubation temperatures, both for DNA and RNA extracts. The abundance of microbial communities was determined using quantitative PCR and it also revealed a stable community size at all temperatures tested. By contrast, incubation at an elevated temperature (37 °C) resulted in changed bacterial community composition. In conclusion, short-term storage, even at room temperature, did not affect microbial community composition, abundance and transcriptional activity in aerated forest soil and anoxic pond sediment.

  6. Characterization of oxygen transfer in miniature and lab-scale bubble column bioreactors and comparison of microbial growth performance based on constant k(L)a.

    PubMed

    Doig, Steven D; Ortiz-Ochoa, Kenny; Ward, John M; Baganz, Frank

    2005-01-01

    This work describes the engineering characterization of miniature (2 mL) and laboratory-scale (100 mL) bubble column bioreactors useful for the cultivation of microbial cells. These bioreactors were constructed of glass and used a range of sintered glass gas diffusers with differently sized pores to disperse humidified air within the liquid biomedium. The effect of the pressure of this supplied air on the breakthrough point for gas diffusers with different pore sizes was examined and could be predicted using the Laplace-Young equation. The influence of the superficial gas velocity (u(g)) on the volumetric mass transfer coefficient (k(L)a) was determined, and values of up to 0.09 s(-1) were observed in this work. Two modeling approaches were considered in order to predict and provide comparison criteria. The first related the volumetric power consumption (P/V) to the k(L)a and a good correlation was obtained for differently sized reactors with a given pore size, but this correlation was not satisfactory for bubble columns with different gas diffusers. Values for P/V ranged from about 10 to 400 W.m(-3). Second, a model was developed predicting bubble size (d(b)), bubble rising velocity (u(b)), gas hold-up (phi), liquid side mass transfer coefficient (k(L)), and thus the k(L)a using established theory and empirical correlations. Good agreement was found with our experimental data at different scales and pore sizes. Values for d(b) varied from 0.1 to 0.6 mm, and k(L) values between 1.7 and 9.8 x 10(-4) m.s(-1) were determined. Several E. coli cultivations were performed in the miniature bubble column at low and high k(L)a values, and the results were compared to those from a conventional stirred tank operated under identical k(L)a values. Results from the two systems were similar in terms of biomass growth rate and carbon source utilization.

  7. Relative contributions of mercury bioavailability and microbial growth rate on net methylmercury production by anaerobic mixed cultures.

    PubMed

    Kucharzyk, Katarzyna H; Deshusses, Marc A; Porter, Kaitlyn A; Hsu-Kim, Heileen

    2015-09-01

    Monomethylmercury (MeHg) is produced in many aquatic environments by anaerobic microorganisms that take up and methylate inorganic forms of Hg(II). Net methylation of Hg(II) appears to be correlated with factors that affect the activity of the anaerobic microbial community and factors that increase the bioavailability of Hg(II) to these organisms. However, the relative importance of one versus the other is difficult to elucidate even though this information can greatly assist remediation efforts and risk assessments. Here, we investigated the effects of Hg speciation (dissolved Hg and nanoparticulate HgS) and microbial activity on the net production of MeHg using two mixed microbial cultures that were enriched from marine sediments under sulfate reducing conditions. The cultures were amended with dissolved Hg (added as a dissolved nitrate salt) and nanoparticulate HgS, and grown under different carbon substrate concentrations. The results indicated that net mercury methylation was the highest for cultures incubated in the greatest carbon substrate concentration (60 mM) compared to incubations with less carbon (0.6 and 6 mM), regardless of the form of mercury amended. Net MeHg production in cultures exposed to HgS nanoparticles was significantly slower than in cultures exposed to dissolved Hg; however, the difference diminished with slower growing cultures with low carbon addition (0.6 mM). The net Hg methylation rate was found to correlate with sulfate reduction rate in cultures exposed to dissolved Hg, while methylation rate was roughly constant for cultures exposed to nanoparticulate HgS. These results indicated a potential threshold of microbial productivity: below this point net MeHg production was limited by microbial activity, regardless of Hg bioavailability. Above this threshold of productivity, Hg speciation became a contributing factor towards net MeHg production. PMID:26211614

  8. Relative contributions of mercury bioavailability and microbial growth rate on net methylmercury production by anaerobic mixed cultures.

    PubMed

    Kucharzyk, Katarzyna H; Deshusses, Marc A; Porter, Kaitlyn A; Hsu-Kim, Heileen

    2015-09-01

    Monomethylmercury (MeHg) is produced in many aquatic environments by anaerobic microorganisms that take up and methylate inorganic forms of Hg(II). Net methylation of Hg(II) appears to be correlated with factors that affect the activity of the anaerobic microbial community and factors that increase the bioavailability of Hg(II) to these organisms. However, the relative importance of one versus the other is difficult to elucidate even though this information can greatly assist remediation efforts and risk assessments. Here, we investigated the effects of Hg speciation (dissolved Hg and nanoparticulate HgS) and microbial activity on the net production of MeHg using two mixed microbial cultures that were enriched from marine sediments under sulfate reducing conditions. The cultures were amended with dissolved Hg (added as a dissolved nitrate salt) and nanoparticulate HgS, and grown under different carbon substrate concentrations. The results indicated that net mercury methylation was the highest for cultures incubated in the greatest carbon substrate concentration (60 mM) compared to incubations with less carbon (0.6 and 6 mM), regardless of the form of mercury amended. Net MeHg production in cultures exposed to HgS nanoparticles was significantly slower than in cultures exposed to dissolved Hg; however, the difference diminished with slower growing cultures with low carbon addition (0.6 mM). The net Hg methylation rate was found to correlate with sulfate reduction rate in cultures exposed to dissolved Hg, while methylation rate was roughly constant for cultures exposed to nanoparticulate HgS. These results indicated a potential threshold of microbial productivity: below this point net MeHg production was limited by microbial activity, regardless of Hg bioavailability. Above this threshold of productivity, Hg speciation became a contributing factor towards net MeHg production.

  9. Relative contributions of mercury bioavailability and microbial growth rate on net methylmercury production by anaerobic mixed cultures†

    PubMed Central

    Kucharzyk, Katarzyna H.; Deshusses, Marc A.; Porter, Kaitlyn A.; Hsu-Kim, Heileen

    2016-01-01

    Monomethylmercury (MeHg) is produced in many aquatic environments by anaerobic microorganisms that take up and methylate inorganic forms of Hg(II). Net methylation of Hg(II) appears to be correlated with factors that affect the activity of the anaerobic microbial community and factors that increase the bioavailability of Hg(II) to these organisms. However, the relative importance of one versus the other is difficult to elucidate even though this information can greatly assist remediation efforts and risk assessments. Here, we investigated the effects of Hg speciation (dissolved Hg and nanoparticulate HgS) and microbial activity on the net production of MeHg using two mixed microbial cultures that were enriched from marine sediments under sulfate reducing conditions. The cultures were amended with dissolved Hg (added as a dissolved nitrate salt) and nanoparticulate HgS, and grown under different carbon substrate concentrations. The results indicated that net mercury methylation was the highest for cultures incubated in the greatest carbon substrate concentration (60 mM) compared to incubations with less carbon (0.6 and 6 mM), regardless of the form of mercury amended. Net MeHg production in cultures exposed to HgS nanoparticles was significantly slower than in cultures exposed to dissolved Hg; however, the difference diminished with slower growing cultures with low carbon addition (0.6 mM). The net Hg methylation rate was found to correlate with sulfate reduction rate in cultures exposed to dissolved Hg, while methylation rate was roughly constant for cultures exposed to nanoparticulate HgS. These results indicated a potential threshold of microbial productivity: below this point net MeHg production was limited by microbial activity, regardless of Hg bioavailability. Above this threshold of productivity, Hg speciation became a contributing factor towards net MeHg production. PMID:26211614

  10. Oxygen availability is a major factor in determining the composition of microbial communities involved in methane oxidation

    PubMed Central

    Hernandez, Maria E.; Beck, David A.C.; Lidstrom, Mary E.

    2015-01-01

    We have previously observed that methane supplied to lake sediment microbial communities as a substrate not only causes a response by bona fide methanotrophic bacteria, but also by non-methane-oxidizing bacteria, especially by members of the family Methylophilaceae. This result suggested that methane oxidation in this environment likely involves communities composed of different functional guilds, rather than a single type of microbe. To obtain further support for this concept and to obtain further insights into the factors that may define such partnerships, we carried out microcosm incubations with sediment samples from Lake Washington at five different oxygen tensions, while methane was supplied at the same concentration in each. Community composition was determined through 16S rRNA gene amplicon sequencing after 10 and 16 weeks of incubation. We demonstrate that, in support of our prior observations, the methane-consuming communities were represented by two major types: the methanotrophs of the family Methylococcaceae and by non-methanotrophic methylotrophs of the family Methylophilaceae. However, different species persisted under different oxygen tensions. At high initial oxygen tensions (150 to 225 µM) the major players were, respectively, species of the genera Methylosarcina and Methylophilus, while at low initial oxygen tensions (15 to 75 µM) the major players were Methylobacter and Methylotenera. These data suggest that oxygen availability is at least one major factor determining specific partnerships in methane oxidation. The data also suggest that speciation within Methylococcaceae and Methylophilaceae may be driven by niche adaptation tailored toward specific placements within the oxygen gradient. PMID:25755930

  11. Microbial profiles at baseline and not the use of antibiotics determine the clinical outcome of the treatment of chronic periodontitis

    PubMed Central

    Bizzarro, S.; Laine, M. L.; Buijs, M. J.; Brandt, B. W.; Crielaard, W.; Loos, B. G.; Zaura, E.

    2016-01-01

    Antibiotics are often used in the treatment of chronic periodontitis, which is a major cause of tooth loss. However, evidence in favour of a microbial indication for the prescription of antibiotics is lacking, which may increase the risk of the possible indiscriminate use of antibiotics, and consequent, microbial resistance. Here, using an open-ended technique, we report the changes in the subgingival microbiome up to one year post-treatment of patients treated with basic periodontal therapy with or without antibiotics. Antibiotics resulted in a greater influence on the microbiome 3 months after therapy, but this difference disappeared at 6 months. Greater microbial diversity, specific taxa and certain microbial co-occurrences at baseline and not the use of antibiotics predicted better clinical treatment outcomes. Our results demonstrate the predictive value of specific subgingival bacterial profiles for the decision to prescribe antibiotics in the treatment of periodontitis, but they also indicate the need for alternative therapies based on ecological approaches. PMID:26830979

  12. Linking microbial carbon utilization with microbially-derived soil organic matter

    NASA Astrophysics Data System (ADS)

    Kallenbach, Cynthia M.; Grandy, A. Stuart

    2014-05-01

    Soil microbial communities are fundamental to plant C turnover, as all C inputs eventually pass through the microbial biomass. In turn, there is increasing evidence that this biomass accumulates as a significant portion of stable soil organic matter (SOM) via physiochemical interactions with the soil matrix. However, when exploring SOM dynamics, these two processes are often regarded as discrete from one another, despite potentially important linkages between microbial C utilization and the fate of that biomass C as SOM. Specifically, if stable SOM is largely comprised of microbial products, we need to better understand the soil C inputs that influence microbial biomass production and microbial C allocation. Microbial physiology, such as microbial growth efficiency (MGE), growth rate and turnover have direct influences on microbial biomass production and are highly sensitive to resource quality. Therefore, the importance of resource quality on SOM accumulation may not necessarily be a function of resistance to decay but the degree to which it optimizes microbial biomass production. To examine the relationship between microbial C utilization and microbial contributions to SOM, an ongoing 15-mo incubation experiment was set up using artificial, initially C- and microbial-free soils. Soil microcosms were constructed by mixing sand with either kaolinite or montmorillonite clays followed with a natural soil microbial inoculum. For both soil mineral treatments, weekly additions of glucose, cellobiose, or syringol are carried out, with an additional treatment of plant leachate to serve as a reference. This simplified system allows us to determine 1) if, in absence of plant-derived C, chemically complex SOM similar to natural soils can accumulate through the production of microbial residues and 2) how differences in C utilization of simple substrates, varying in energy yields, influence the quantity and chemistry of newly formed SOM. Over the course of the incubation, MGE

  13. Impact of microbial growth inhibition and proteolytic activity on the stability of a new formulation containing a phytate-degrading enzyme obtained from mushroom.

    PubMed

    Spier, Michele R; Siepmann, Francieli B; Staack, Larissa; Souza, Priscila Z; Kumar, Vikas; Medeiros, Adriane B P; Soccol, Carlos R

    2016-10-01

    The development of stable enzymes is a key issue in both the food and feed industries. Consequently, the aim of the current study is to evaluate the impact of various additives (sodium chloride, sodium citrate, mannitol, methylparaben, polyethylene glycol 3350, ethylenediaminetetraacetic acid disodium salt, and a serine protease inhibitor) on the stability of a mushroom phytase produced by solid-state cultivation and recovery. Also observed was the effect of the additives on microbial growth inhibition by monitoring both the change in optical density over 30 days of storage and proteolytic activity. Initially, eight experimental formulations were prepared along with a control. After screening, a 3(2) factorial design was applied to define suitable concentrations of the selected additives. Among the eight formulations tested, the formulation containing NaCl, PEG 3350, and methylparaben retained all of the initial phytase activity after 50 days of storage, with no detected interference from protease activity. Sodium citrate, a metal chelation agent, presented the unusual effect of reducing protease activity in the formulations. Although all formulations presented better phytase stability when compared to the control, NaCl and PEG were both able to prolong the stability of the enzyme activity and also to inhibit microbial growth during storage, making them favorable for application as food and feed additives.

  14. Ab initio determination of the instability growth rate of warm dense beryllium-deuterium interface

    SciTech Connect

    Wang, Cong; Zhang, Ping; Li, Zi; Li, DaFang

    2015-10-15

    Accurate knowledge about the interfacial unstable growth is of great importance in inertial confinement fusion. During implosions, the deuterium-tritium capsule is driven by laser beams or X-rays to access the strongly coupled and partially degenerated warm dense matter regime. At this stage, the effects of dissipative processes, such as diffusion and viscosity, have significant impact on the instability growth rates. Here, we present ab initio molecular dynamics simulations to determine the equations of state and the transport coefficients. Several models are used to estimate the reduction in the growth rate dispersion curves of Rayleigh-Taylor and Richtmyer-Meshkov instabilities with considering the presence of these dissipative effects. We show that these instability growth rates are effectively reduced when considering diffusion. The findings provide significant insights into the microscopic mechanism of the instability growth at the ablator-fuel interface and will refine the models used in the laser-driven hydrodynamic instability experiments.

  15. Growth of complex systems can be related to the properties of their underlying determinants

    PubMed Central

    Savageau, Michael A.

    1979-01-01

    Growth—increase in size, number, or amount—in many cases appears to follow simple empirical laws. Such laws have been noted in a wide variety of fields for many years. Until now these laws have never been related to the underlying determinants of these systems. By starting with fundamental properties of the component mechanisms in such systems, one can derive a basic growth equation for which the well-known laws of growth are special cases. PMID:16592715

  16. Universality of human microbial dynamics

    NASA Astrophysics Data System (ADS)

    Bashan, Amir; Gibson, Travis E.; Friedman, Jonathan; Carey, Vincent J.; Weiss, Scott T.; Hohmann, Elizabeth L.; Liu, Yang-Yu

    2016-06-01

    Human-associated microbial communities have a crucial role in determining our health and well-being, and this has led to the continuing development of microbiome-based therapies such as faecal microbiota transplantation. These microbial communities are very complex, dynamic and highly personalized ecosystems, exhibiting a high degree of inter-individual variability in both species assemblages and abundance profiles. It is not known whether the underlying ecological dynamics of these communities, which can be parameterized by growth rates, and intra- and inter-species interactions in population dynamics models, are largely host-independent (that is, universal) or host-specific. If the inter-individual variability reflects host-specific dynamics due to differences in host lifestyle, physiology or genetics, then generic microbiome manipulations may have unintended consequences, rendering them ineffective or even detrimental. Alternatively, microbial ecosystems of different subjects may exhibit universal dynamics, with the inter-individual variability mainly originating from differences in the sets of colonizing species. Here we develop a new computational method to characterize human microbial dynamics. By applying this method to cross-sectional data from two large-scale metagenomic studies—the Human Microbiome Project and the Student Microbiome Project—we show that gut and mouth microbiomes display pronounced universal dynamics, whereas communities associated with certain skin sites are probably shaped by differences in the host environment. Notably, the universality of gut microbial dynamics is not observed in subjects with recurrent Clostridium difficile infection but is observed in the same set of subjects after faecal microbiota transplantation. These results fundamentally improve our understanding of the processes that shape human microbial ecosystems, and pave the way to designing general microbiome-based therapies.

  17. Universality of human microbial dynamics.

    PubMed

    Bashan, Amir; Gibson, Travis E; Friedman, Jonathan; Carey, Vincent J; Weiss, Scott T; Hohmann, Elizabeth L; Liu, Yang-Yu

    2016-06-01

    Human-associated microbial communities have a crucial role in determining our health and well-being, and this has led to the continuing development of microbiome-based therapies such as faecal microbiota transplantation. These microbial communities are very complex, dynamic and highly personalized ecosystems, exhibiting a high degree of inter-individual variability in both species assemblages and abundance profiles. It is not known whether the underlying ecological dynamics of these communities, which can be parameterized by growth rates, and intra- and inter-species interactions in population dynamics models, are largely host-independent (that is, universal) or host-specific. If the inter-individual variability reflects host-specific dynamics due to differences in host lifestyle, physiology or genetics, then generic microbiome manipulations may have unintended consequences, rendering them ineffective or even detrimental. Alternatively, microbial ecosystems of different subjects may exhibit universal dynamics, with the inter-individual variability mainly originating from differences in the sets of colonizing species. Here we develop a new computational method to characterize human microbial dynamics. By applying this method to cross-sectional data from two large-scale metagenomic studies--the Human Microbiome Project and the Student Microbiome Project--we show that gut and mouth microbiomes display pronounced universal dynamics, whereas communities associated with certain skin sites are probably shaped by differences in the host environment. Notably, the universality of gut microbial dynamics is not observed in subjects with recurrent Clostridium difficile infection but is observed in the same set of subjects after faecal microbiota transplantation. These results fundamentally improve our understanding of the processes that shape human microbial ecosystems, and pave the way to designing general microbiome-based therapies. PMID:27279224

  18. Fluorometric Determination of Adenosine Nucleotide Derivatives as Measures of the Microfouling, Detrital, and Sedimentary Microbial Biomass and Physiological Status

    PubMed Central

    Davis, William M.; White, David C.

    1980-01-01

    Adenosine, adenine, cyclic adenosine monophosphate (AMP), AMP, nicotinamide adenine dinucleotide, adenosine diphosphate, and adenosine triphosphate (ATP) were recovered quantitatively from aqueous portions of lipid extracts of microfouling, detrital, and sedimentary microbial communities. These could be detected quantitatively in the picomolar range by forming their 1-N6-etheno derivatives and analyzing by high-pressure liquid chromatography with fluorescence detection. Lipid extraction and subsequent analysis allowed the simultaneous measurement of the microbial community structure, total microbial biomass with the quantitative recovery of the adenine-containing cellular components, which were protected from enzymatic destruction. This extraction and fluorescent derivatization method showed equivalency with the luciferin-luciferase method for bacterial ATP measurements. Quick-freezing samples in the field with dry ice-acetone preserved the ATP and energy charge (a ratio of adenosine nucleotides) for analysis at remote laboratories. The metabolic lability of ATP in estuarine detrital and microfouling communities, as well as bacterial monocultures of constant biomass, showed ATP to be a precarious measure of biomass under some conditions. Combinations of adenosine and adenine nucleotides gave better correlations with microbial biomass measured as extractable lipid phosphate in the detrital and microfouling microbial communities than did ATP alone. Stresses such as anoxia or filtration are reflected in the rapid accumulation of intracellular adenosine and the excretion of adenosine and AMP into the surrounding milieu. Increases in AMP and adenosine may prove to be more sensitive indicators of metabolic status than the energy charge. PMID:16345633

  19. The 13C/12C fractionation by microbial cells immobilized on a solid-phase carrier during the growth on glucose

    NASA Astrophysics Data System (ADS)

    Zyakun, Anatoly; Kochetkov, Vladimir

    2010-05-01

    Problem. In microbiological ecology, the level of basal СО2 respiration and the potential of microbial activity defined as substrate-induced respiration (SIR) are used as criteria of the metabolic state of soil microbiota. The peculiar feature of glucose metabolism in soil is its utilization by microbial cells immobilized on soil particles as a solid-phase carrier. The efficiency of substrate utilization and СО2 production in such cases depend on the rate of microorganisms' growth and colonization of the solid-phase carrier surface, where the substrate is located. The products of microbial metabolism are supposed to inherit the substrate isotope composition correct to the isotopic effects accompanying substrate utilization and metabolic transformations. However, all experiments in carbon isotope fractionation during microbial utilization of glucose as a substrate have been carried out with microorganisms growing in liquid media. Objective: Study of the kinetics of glucose utilization as a test substrate during the growth of soil microorganisms immobilized on a solid-phase carrier and ascertainment of peculiarities of the formation of carbon isotope composition of produced metabolic СО2. The objects of research were Pseudomonas aureofaciens BS1393(pBS216) (culture A) and Rhodococcus sp. 3-30 (culture B) as representatives of pseudomonades and rhodococci, which occur in the soils of different genesis and are of defining value in development and implementation of biotechnological schemes for degradation of toxic organic pollutants in the environment. Results and discussion. The cultures under study had different rates of growth on glucose. Specific rates of СО2 production during the growth of cultures A and B on glucose were 0.34 (± 0.05) and 0.078 (± 0.01) μg С-СО2 h-1, respectively. The lag periods of culture (A and B) growth were about 4.3 and 26 h, respectively. Comparison of the lag periods of these representatives of pseudomonades and rhodococci

  20. Microbial activity balance in size fractionated suspended growth biomass from full-scale sidestream combined nitritation-anammox reactors.

    PubMed

    Shi, Yijing; Wells, George; Morgenroth, Eberhard

    2016-10-01

    The purpose of this study was to determine the abundance, distribution and activity of aerobic ammonia-oxidizing bacteria (AOB) and anammox in size fractionated aggregates from full-scale suspended growth combined nitritation-anammox sidestream reactors. Plants with or without a cyclone device were also studied to assess a purported enrichment of anammox granules. Specific aerobic ammonium oxidation rates (p=0.01) and specific oxygen uptake rates (p=0.02) were significantly greater in flocs than in granules. AOB abundance measured using quantitative FISH was significantly higher in flocs than in granules (p=0.01). Conversely, anammox abundance was significantly greater in granules (p=0.03). The average ratio of anammox/AOB in systems employing hydrocyclone separation devices was 2.4, significantly higher (p=0.02) than the average ratio (0.5) in a system without a hydrocyclone. Our results demonstrate substantial functional and population-level segregation between floccular and granular fractions, and provide a key corroboration that cyclone separation devices can increase anammox levels in such systems.

  1. Microbial activity balance in size fractionated suspended growth biomass from full-scale sidestream combined nitritation-anammox reactors.

    PubMed

    Shi, Yijing; Wells, George; Morgenroth, Eberhard

    2016-10-01

    The purpose of this study was to determine the abundance, distribution and activity of aerobic ammonia-oxidizing bacteria (AOB) and anammox in size fractionated aggregates from full-scale suspended growth combined nitritation-anammox sidestream reactors. Plants with or without a cyclone device were also studied to assess a purported enrichment of anammox granules. Specific aerobic ammonium oxidation rates (p=0.01) and specific oxygen uptake rates (p=0.02) were significantly greater in flocs than in granules. AOB abundance measured using quantitative FISH was significantly higher in flocs than in granules (p=0.01). Conversely, anammox abundance was significantly greater in granules (p=0.03). The average ratio of anammox/AOB in systems employing hydrocyclone separation devices was 2.4, significantly higher (p=0.02) than the average ratio (0.5) in a system without a hydrocyclone. Our results demonstrate substantial functional and population-level segregation between floccular and granular fractions, and provide a key corroboration that cyclone separation devices can increase anammox levels in such systems. PMID:27347796

  2. Combined effect of natural essential oils, modified atmosphere packaging, and gamma radiation on the microbial growth on ground beef.

    PubMed

    Turgis, M; Han, J; Borsa, J; Lacroix, M

    2008-06-01

    Selected Chinese cinnamon, Spanish oregano, and mustard essential oils (EOs) were used in combination with irradiation to evaluate their ability to eliminate pathogenic bacteria and extend the shelf life of medium-fat-content ground beef (23% fat). Shelf life was defined as the time when the total bacterial count reached 10(7) CFU/g. The shelf life of ground beef was determined for 28 days at 4 degrees C after treatment with EOs. The concentrations of EOs were predetermined such that sensory properties of cooked meat were maintained: 0.025% Spanish oregano, 0.025% Chinese cinnamon, and 0.075% mustard. Ground beef samples containing EOs were then packaged under air or a modified atmosphere and irradiated at 1.5 kGy. Ground beef samples (10 g) were taken during the storage period for enumeration of total mesophilic aerobic bacteria, Escherichia coli, Salmonella, total coliforms, lactic acid bacteria, and Pseudomonas. Mustard EO was the most efficient for reducing the total mesophilic aerobic bacteria and eliminating pathogenic bacteria. Irradiation alone completely inhibited the growth of total mesophilic aerobic and pathogenic bacteria. The combination of irradiation and EOs was better for reducing lactic acid bacteria (mustard and cinnamon EOs) and Pseudomonas (oregano and mustard EOs). The best combined treatment for extending the shelf life of ground beef for up to 28 days was EO plus irradiation (1.5 kGy) and modified atmosphere packaging. PMID:18592752

  3. Establishing equivalence for microbial-growth-inhibitory effects ("iso-hurdle rules") by analyzing disparate listeria monocytogenes data with a gamma-type predictive model.

    PubMed

    Pujol, Laure; Kan-King-Yu, Denis; Le Marc, Yvan; Johnston, Moira D; Rama-Heuzard, Florence; Guillou, Sandrine; McClure, Peter; Membré, Jeanne-Marie

    2012-02-01

    Preservative factors act as hurdles against microorganisms by inhibiting their growth; these are essential control measures for particular food-borne pathogens. Different combinations of hurdles can be quantified and compared to each other in terms of their inhibitory effect ("iso-hurdle"). We present here a methodology for establishing microbial iso-hurdle rules in three steps: (i) developing a predictive model based on existing but disparate data sets, (ii) building an experimental design focused on the iso-hurdles using the model output, and (iii) validating the model and the iso-hurdle rules with new data. The methodology is illustrated with Listeria monocytogenes. Existing data from industry, a public database, and the literature were collected and analyzed, after which a total of 650 growth rates were retained. A gamma-type model was developed for the factors temperature, pH, a(w), and acetic, lactic, and sorbic acids. Three iso-hurdle rules were assessed (40 logcount curves generated): salt replacement by addition of organic acids, sorbic acid replacement by addition of acetic and lactic acid, and sorbic acid replacement by addition of lactic/acetic acid and salt. For the three rules, the growth rates were equivalent in the whole experimental domain (γ from 0.1 to 0.5). The lag times were also equivalent in the case of mild inhibitory conditions (γ ≥ 0.2), while they were longer in the presence of salt than acids under stress conditions (γ < 0.2). This methodology allows an assessment of the equivalence of inhibitory effects without intensive data generation; it could be applied to develop milder formulations which guarantee microbial safety and stability.

  4. Removal of pharmaceuticals from synthetic wastewater in an aerobic granular sludge membrane bioreactor and determination of the bioreactor microbial diversity.

    PubMed

    Wang, Xiao-Chun; Shen, Ji-Min; Chen, Zhong-Lin; Zhao, Xia; Xu, Hao

    2016-09-01

    Five types of pharmaceuticals and personal care products (PPCPs) substances were selected as pollutants in this study. The effects of the removal of these pollutants and the microbial succession process in a granular sludge membrane bioreactor (GMBR) were investigated. Results showed that wastewater containing PPCPs influenced the performance of granular sludge. The removal of the five PPCPs from the GMBR had different effects. The removal rates of prednisolone, norfloxacin and naproxen reached 98.5, 87.8 and 84 %, respectively. The degradation effect in the GMBR system was relatively lower for sulphamethoxazole and ibuprofen, with removal efficiency rates of 79.8 and 63.3 %, respectively. Furthermore, the microbial community structure and diversity variation of the GMBR were analysed via high-throughput sequencing technology. The results indicated the structural and functional succession of the microbial community based on the GMBR process. The results indicate the key features of bacteria with an important role in drug degradation. PMID:27234140

  5. Microbial shelf life determination of vacuum-packaged fresh beef treated with polylactic acid, lactic acid, and nisin solutions.

    PubMed

    Ariyapitipun, T; Mustapha, A; Clarke, A D

    1999-08-01

    The effectiveness of polylactic acid, lactic acid, nisin, and combinations of the acids and nisin on extending the shelf-life of raw beef was determined. Fresh beef pieces (5 by 5 by 2.5 cm) were dipped in a solution of 2% low molecular weight polylactic acid (LMW-PLA), 2% lactic acid (LA), 200 IU of nisin per ml, or the combinations of nisin in either 2% LMW-PLA or 2% LA. The samples were then drip-dried, vacuum-packaged, and stored at 4 degrees C for up to 56 days. The beef surface pH values and numbers of psychrotrophic aerobic bacteria, psychrotrophic and mesophilic Enterobacteriaceae, Pseudomonas, and Lactobacillus were determined weekly for 56 days. The average surface pH values of the beef samples treated with 2% LMW-PLA or the combination of 200 IU of nisin per ml and 2% LMW-PLA were significantly reduced to 5.19 and 5.17, respectively, at day 0 (P < or = 0.05), while those decontaminated with 2% LA or 200 IU of nisin per ml in 2% LA solution were significantly decreased from 5.62 to 4.98 and 4.96, respectively. The 2% LMW-PLA, 2% LA, or the combinations of each acid and nisin showed immediate inhibitory effects on psychrotrophic aerobic bacteria (1.94, 2.36, 2.59, and 1.76 log reduction, respectively), psychrotrophic Enterobacteriaceae (1.37, 1.86, 1.77, and 1.35 log reduction, respectively), mesophilic Enterobacteriaceae (1.00, 1.00, 0.82, and 0.68 log reduction, respectively), and Pseudomonas (1.77, 1.57, 1.76, and 1.41 log reduction, respectively) on fresh beef (P < or = 0.05). The reduction was evident up to 56 days as seen by the numbers of Enterobacteriaceae and Pseudomonas (P < or = 0.05). Because there was no interaction between treatments and storage times, the data in each period were combined and presented as effect of treatments on overall microbial counts of fresh beef. It was found that 2% LMW-PLA, 2% LA, and the combinations of each acid and nisin significantly lowered the population of the above organisms compared with the untreated control

  6. Microbial Communities of Pavilion Lake Microbialites

    NASA Astrophysics Data System (ADS)

    Russell, J. A.; Biddle, J.; Pointing, S.; Cardman, Z.; Brady, A. L.; Slater, G. F.; Lim, D. S.

    2011-12-01

    Fossilized remnants of microbial mat growth, called stromatolites, are found in the rock record and are thought to be some of the earliest evidence for life on Earth. On the modern Earth, living versions of these stromatolites, called microbialites, are found in few environments across the globe. Pavilion Lake in British Columbia was found to host these microbialites, even though conditions are not extreme in the lake and grazers exist amongst the microbial growths. The Pavilion Lake Research Project, funded by NASA, the CSA and others, has developed the lake into an analog research site for the exploration of extraplanetary bodies since 2004. Pavilion Lake began to be explored for microbial ecology in 2007 to attempt to determine how the microbial communities change over time, location and depth to build these microbialite structures. DNA extracted from microbialites at two different locations and 3 depths at each location were analyzed by T-RFLP patterns. Significant differences were seen in the total communities from each location. Additional samples were taken in the summer and budding seasons, and significant differences were seen by season. A survey performed on just the cyanobacterial populations show less differences between taxa between sites, but significant differences with depth above and below the chemocline and between mineralized and non-mineralized mats. Differences were also examined between purple and green nodules, which are thought to be the growth forms of the microbialites. Detailed sequence analysis shows that Pavilion Lake microorganisms are similar, yet different, from microbial communities seen in other microbialite systems. In 2011, the research project moved to Kelly Lake, a lake nearby Pavilion Lake, that also contain microbialite structures. Similar morphologies were seen in Kelly Lake with an approximate 20 ft. offset in the typical depths where morphologies were seen. Continued analysis of Kelly Lake microbialites will be performed

  7. Towards Determining the Upper Temperature Limits to Life on Earth: An In-situ Sulfide-Microbial Incubator

    NASA Astrophysics Data System (ADS)

    Kelley, D.; Baross, J.; Delaney, J.; Girguis, P.; Schrenk, M.

    2004-12-01

    Determining the maximum conditions under which life thrives, survives, and expires is critical to understanding how and where life might have evolved on our planet and for investigation of life in extraterrestrial environments. Submarine black smoker systems are optimal sites to study such questions because thermal gradients are extreme and accessible within the chimney walls under high-pressure conditions. Intact cells containing DNA and ribosomes have been observed even within the most extreme environments of sulfide structure walls bounded by 300\\deg C fluids. Membrane lipids from archaea have been detected in sulfide flanges and chimneys where temperatures are believed to be 200-300\\deg C. However, a balanced inquiry into the limits of life must focus on characterization of the actual conditions in a given system that favor reactions necessary to initiate and/or sustain life. At present, in-situ instrumentation of sulfide deposits is the only effective way to gain direct access to these natural high-temperature environments for documentation and experimentation. With this goal in mind, three prototype microbial incubators were developed with funding from the NSF, University of Washington, and the W.M. Keck Foundation. The incubators were deployed in 2003 in the walls of active black smoker chimneys in the Mothra Hydrothermal Field, Endeavour Segment of the Juan de Fuca Ridge. All instruments were successfully recovered in 2004, and one was redeployed for a short time-series experiment. Each 53-cm-long titanium assembly houses 27 temperature sensors that record temperatures from 0 to 500\\deg C within three discrete incubation chambers. Data are logged in a separate housing and inductively coupled links provide access to the data loggers without removal of the instruments. During the initial deployment, data were collected from 189 to 245 days, with up to ˜478° K temperature measurements completed for an individual instrument. Temperatures within the chimney

  8. Determination of ATP-activity as a useful tool for monitoring microbial load in aqueous humidifier samples.

    PubMed

    Liebers, Verena; Bachmann, Dieter; Franke, Gabriele; Freundt, Susanne; Stubel, Heike; Düser, Maria; Kendzia, Benjamin; Böckler, Margret; Brüning, Thomas; Raulf, Monika

    2015-03-01

    Air humidifier water tanks are potential sources of microbial contaminants. Aerosolization of these contaminants is associated with the development of airway and lung diseases; therefore, implementation of preventive strategies including monitoring of the microbial contamination is recommended. So far, culture-based methods that include measuring colony forming units (CFU) are widely used to monitor microbial load. However, these methods are time consuming and have considerable drawbacks. As a result, alternative methods are needed which provide not only clear and accurate results concerning microbial load in water samples, but are also rapid and easy to use in the field. This paper reports on a rapid test for ATP quantification as an alternative method for microbial monitoring, including its implementation, validation and application in the field. For this purpose, 186 water samples were characterized with different methods, which included ATP analysis, culture-based methods, endotoxin activity (common and rapid test), pyrogenic activity and number of particles. Half of the samples was measured directly in the field and the other half one day later in the laboratory. The results of both tests are highly correlated. Furthermore, to check how representative the result from one sample of a water source is, a second sample of the same water tank were collected and measured. Bioluminescence results of the undiluted samples covered a range between 20 and 25,000 relative light units (RLU) and correlated with the results obtained using the other methods. The highest correlation was found between bioluminescence and endotoxin activity (rs=0.79) as well as pyrogenic activity (rs=0.75). Overall, the results of this study indicate that ATP measurement using bioluminescence is a suitable tool to obtain rapid, reproducible and sensitive information on the microbial load of water samples, and is suitable to use in the field. However, to use ATP measurement as an indicator of

  9. Determining Rates of Change and Evaluating Group-Level Resiliency Differences in Hyporheic Microbial Communities in Response to Fluvial Heavy-Metal Deposition

    PubMed Central

    Feris, Kevin P.; Ramsey, Philip W.; Rillig, Matthias; Moore, Johnnie N.; Gannon, James E.; Holben, William E.

    2004-01-01

    Prior field studies by our group have demonstrated a relationship between fluvial deposition of heavy metals and hyporheic-zone microbial community structure. Here, we determined the rates of change in hyporheic microbial communities in response to heavy-metal contamination and assessed group-level differences in resiliency in response to heavy metals. A controlled laboratory study was performed using 20 flowthrough river mesocosms and a repeated-measurement factorial design. A single hyporheic microbial community was exposed to five different levels of an environmentally relevant metal treatment (0, 4, 8, 16, and 30% sterilized contaminated sediments). Community-level responses were monitored at 1, 2, 4, 8, and 12 weeks via denaturing gradient gel electrophoresis and quantitative PCR using group-specific primer sets for indigenous populations most closely related to the α-, β-, and γ-proteobacteria. There was a consistent, strong curvilinear relationship between community composition and heavy-metal contamination (R2 = 0.83; P < 0.001), which was evident after only 7 days of metal exposure (i.e., short-term response). The abundance of each phylogenetic group was negatively affected by the heavy-metal treatments; however, each group recovered from the metal treatments to a different extent and at a unique rate during the course of the experiment. The structure of hyporheic microbial communities responded rapidly and at contamination levels an order of magnitude lower than those shown to elicit a response in aquatic macroinvertebrate assemblages. These studies indicate that hyporheic microbial communities are a sensitive and useful indicator of heavy-metal contamination in streams. PMID:15294812

  10. Integrating microbial traits into ecosystem models

    NASA Astrophysics Data System (ADS)

    Allison, S. D.

    2012-12-01

    Diverse bacterial and fungal communities control the decomposition of complex organic material, thereby driving important ecosystem functions such as CO2 production and nutrient regeneration. Predicting these functions is challenging because microbial communities and the chemical substrates they metabolize are complex. To address this challenge, I developed a theoretical model of microbial decomposition based on microbial traits involved in substrate degradation, uptake, and growth. The model represents a large number of microbial taxa, each of which possesses a set of trait values drawn at random from empirically-based distributions. The model also includes a large number of chemical substrates that can be degraded by microbial extracellular enzymes and taken up by membrane transporters. Microbes with different trait values for enzyme production and uptake capacity compete for chemical substrates and vary in abundance during model runs. I used the model to predict rates of plant litter decomposition and determine which traits were associated with high microbial abundance under different environmental conditions. The model predicted that optimal traits depend on the level of enzyme production in the whole community, which determines resource availability and decomposition rates. There is also evidence for facilitation and competition among microbial taxa that co-occur on decomposing litter, suggesting that microbial interactions may play a role in determining ecosystem function. These interactions vary with community investment in extracellular enzyme production and the magnitude of tradeoffs affecting biochemical traits such as enzyme kinetic parameters. The model accounted for 69% of the variation in decomposition rates and up to 26% of the variation in enzyme activities in an empirical dataset with 15 types of Hawaiian plant litter. By explicitly representing microbial diversity, trait-based models can predict ecosystem processes based on functional trait

  11. Endosomal receptor kinetics determine the stability of intracellular growth factor signalling complexes

    PubMed Central

    Tzafriri, A. Rami; Edelman, Elazer R.

    2006-01-01

    There is an emerging paradigm that growth factor signalling continues in the endosome and that cell response to a growth factor is defined by the integration of cell surface and endosomal events. As activated receptors in the endosome are exposed to a different set of binding partners, they probably elicit differential signals compared with when they are at the cell surface. As such, complete appreciation of growth factor signalling requires understanding of growth factor–receptor binding and trafficking kinetics both at the cell surface and in endosomes. Growth factor binding to surface receptors is well characterized, and endosomal binding is assumed to follow surface kinetics if one accounts for changes in pH. Yet, specific binding kinetics within the endosome has not been examined in detail. To parse the factors governing the binding state of endosomal receptors we analysed a whole-cell mathematical model of epidermal growth factor receptor trafficking and binding. We discovered that the stability of growth factor–receptor complexes within endosomes is governed by three primary independent factors: the endosomal dissociation constant, total endosomal volume and the number of endosomal receptors. These factors were combined into a single dimensionless parameter that determines the endosomal binding state of the growth factor–receptor complex and can distinguish different growth factors from each other and different cell states. Our findings indicate that growth factor binding within endosomal compartments cannot be appreciated solely on the basis of the pH-dependence of the dissociation constant and that the concentration of receptors in the endosomal compartment must also be considered. PMID:17117924

  12. The importance of growth kinetic analysis in determining bacterial susceptibility against antibiotics and silver nanoparticles.

    PubMed

    Theophel, Karsten; Schacht, Veronika J; Schlüter, Michael; Schnell, Sylvia; Stingu, Catalina-Suzana; Schaumann, Reiner; Bunge, Michael

    2014-01-01

    Routine antibiotics susceptibility testing still relies on standardized cultivation-based analyses, including measurement of inhibition zones in conventional agar diffusion tests and endpoint turbidity-based measurements. Here, we demonstrate that common off-line monitoring and endpoint determination after 18-24 h could be insufficient for reliable growth-dependent evaluation of antibiotic susceptibility. Different minimal inhibitory concentrations were obtained in 20- and 48 h microdilution plate tests using an Enterococcus faecium clinical isolate (strain UKI-MB07) as a model organism. Hence, we used an on-line kinetic assay for simultaneous cultivation and time-resolved growth analysis in a 96-well format instead of off-line susceptibility testing. Growth of the Enterococcus test organism was delayed up to 30 h in the presence of 0.25 μg mL(-1) of vancomycin and 8 μg mL(-1) of fosfomycin, after which pronounced growth was observed. Despite the delayed onset of growth, treatment with fosfomycin, daptomycin, fusidic acid, cefoxitin, or gentamicin resulted in higher maximum growth rates and/or higher final optical density values compared with antibiotic-free controls, indicating that growth stimulation and hormetic effects may occur with extended exposure to sublethal antibiotic concentrations. Whereas neither maximum growth rate nor final cell density correlated with antibiotic concentration, the lag phase duration for some antibiotics was a more meaningful indicator of dose-dependent growth inhibition. Our results also reveal that non-temporal growth profiles are only of limited value for cultivation-based antimicrobial silver nanoparticle susceptibility testing. The exposure to Ag(0) nanoparticles led to plasma membrane damage in a concentration-dependent manner and induced oxidative stress in Enterococcus faecium UKI-MB07, as shown by intracellular ROS accumulation. PMID:25426104

  13. The importance of growth kinetic analysis in determining bacterial susceptibility against antibiotics and silver nanoparticles

    PubMed Central

    Theophel, Karsten; Schacht, Veronika J.; Schlüter, Michael; Schnell, Sylvia; Stingu, Catalina-Suzana; Schaumann, Reiner; Bunge, Michael

    2014-01-01

    Routine antibiotics susceptibility testing still relies on standardized cultivation-based analyses, including measurement of inhibition zones in conventional agar diffusion tests and endpoint turbidity-based measurements. Here, we demonstrate that common off-line monitoring and endpoint determination after 18–24 h could be insufficient for reliable growth-dependent evaluation of antibiotic susceptibility. Different minimal inhibitory concentrations were obtained in 20- and 48 h microdilution plate tests using an Enterococcus faecium clinical isolate (strain UKI-MB07) as a model organism. Hence, we used an on-line kinetic assay for simultaneous cultivation and time-resolved growth analysis in a 96-well format instead of off-line susceptibility testing. Growth of the Enterococcus test organism was delayed up to 30 h in the presence of 0.25 μg mL-1 of vancomycin and 8 μg mL-1 of fosfomycin, after which pronounced growth was observed. Despite the delayed onset of growth, treatment with fosfomycin, daptomycin, fusidic acid, cefoxitin, or gentamicin resulted in higher maximum growth rates and/or higher final optical density values compared with antibiotic-free controls, indicating that growth stimulation and hormetic effects may occur with extended exposure to sublethal antibiotic concentrations. Whereas neither maximum growth rate nor final cell density correlated with antibiotic concentration, the lag phase duration for some antibiotics was a more meaningful indicator of dose-dependent growth inhibition. Our results also reveal that non-temporal growth profiles are only of limited value for cultivation-based antimicrobial silver nanoparticle susceptibility testing. The exposure to Ag(0) nanoparticles led to plasma membrane damage in a concentration-dependent manner and induced oxidative stress in Enterococcus faecium UKI-MB07, as shown by intracellular ROS accumulation. PMID:25426104

  14. Vegetation structure determination using LIDAR data and the forest growth parameters

    NASA Astrophysics Data System (ADS)

    Rybansky, M.; Brenova, M.; Cermak, J.; van Genderen, J.; Sivertun, Å.

    2016-06-01

    The goal of this paper is to identify the main vegetation factors in the terrain, which are important for the analysis of forest structure. Such an analysis is important for forestry, rescue operations management during crises situations and disasters such as fires, storms, earthquakes and military analysis (transportation, cover, concealment, etc.). For the forest structure determination, both LIDAR and the forest growth prediction analysis were used. As main results, the vegetation height, tree spacing and stem diameters were determined

  15. Food, sanitation, and the socioeconomic determinants of child growth in Colombia.

    PubMed Central

    Koopman, J S; Jajardo, L; Bertrand, W

    1981-01-01

    To describe the causes of growth failure in a developing country, we studied family food availability, anthropometric measurements of preschool children, and family and neighborhood socioeconomic conditions in a stratified random sample of Cali, Colombia families. The influences on preschool child growth of food availability, neighborhood socioeconomic conditions, and family socioeconomic conditions were separated statistically. Neither food availability nor other family factors were related directly to growth, but neighborhood factors did have a strong relationship to growth. Children decreased progressively from 97.5 percent of expected weight in the top one-sixth of neighborhoods we studied to 89 per cent in the botton one-sixth. Food availability, although not related to growth, was strongly related to family factors. The top one-sixth of families had 115 percent of FAO (Food and Agricultural Organization) protein allowances, while the bottom one-sixth had only 75 per cent. These finding are inconsistent with food availability or family factors being the prinicipal causes of growth retardation. They are consistent with neighborhood determined factors, possibly enteric infections, being the principal cause of growth retardation in preschool children in Cali. PMID:7258428

  16. Radiographically determined growth kinetics of primary lung tumors in the dog

    SciTech Connect

    Perry, R.E. . Coll. of Veterinary Medicine Pacific Northwest Lab., Richland, WA ); Weller, R.E.; Buschbom, R.L.; Dagle, G.E.; Park, J.F. )

    1989-10-01

    Tumor growth rate patterns especially tumor doubling time (TDT), have been extensively evaluated in man. Studies involving the determination of TDT in humans are limited, however, by the number of cases, time consistent radiographic tumor measurements, and inability to perform experimental procedures. In animals similar constraints do not exist. Lifespan animal models lend themselves well to tumor growth pattern analysis. Experimental studies have been designed to evaluate both the biological effects and growth patterns of induced and spontaneous tumors. The purpose of this study was to calculate the tumor volume doubling times (TCDT) for radiation-induced and spontaneous primary pulmonary neoplasms in dogs to see if differences existed due to etiology, sex or histologic cell type, and to determine if the time of tumor onset could be extrapolated from the TVDT. 3 refs.

  17. Indirect microbial detection

    NASA Technical Reports Server (NTRS)

    Wilkins, J. R.

    1980-01-01

    Indirect method for detection of microbial growth utilizes flow of charged particles across barrier that physically separated growing cells from electrodes and measures resulting difference in potential between two platinum electrodes. Technique allows simplified noncontact monitoring of all growth in highly infectious cultures or in critical biochemical studies.

  18. Planetary Resources and Astroecology. Planetary Microcosm Models of Asteroid and Meteorite Interiors: Electrolyte Solutions and Microbial Growth- Implications for Space Populations and Panspermia

    NASA Astrophysics Data System (ADS)

    Mautner, Michael N.

    2002-03-01

    Planetary microcosms were constructed using extracts from meteorites that simulate solutions in the pores of carbonaceous chondrites. The microcosms were found to support the growth of complex algal and microbial populations. Such astroecology experiments demonstrate how a diverse ecosystem could exist in fluids within asteroids, and in meteorites that land on aqueous planets. The microcosm solutions were obtained by extracting nutrient electrolytes under natural conditions from powders of the Allende (CV3) and Murchison (CM2) meteorites at low (0.02 g/ml) and high (10.0 g/ml) solid/solution ratios. The latter solutions contain >3 mol/L electrolytes and about 10 g/L organics, that simulate natural fluids in asteroids during aqueous alteration and in the pores of meteorites, which can help prebiotic synthesis and the survival of early microorganisms. These solutions and wet solids were in fact found to support complex self-sustaining microbial communities with populations of 4 × 105 algae and 6 × 106 bacteria and fungi for long periods (>8 months). The results show that planetary microcosms based on meteorites can: assay the fertilities of planetary materials; identify space bioresources; target astrobiology exploration; and model past and future space-based ecosystems. The results show that bioresources in the carbonaceous asteroids can sustain a biomass of 1018 kg, comprising 1032 microorganisms and a human population of 1014. The results also suggest that protoplanetary nebulae can support and disperse microorganisms and can be therefore effective environments for natural and directed panspermia.

  19. Study of azo dye decolorization and determination of cathode microorganism profile in air-cathode microbial fuel cells.

    PubMed

    Kumru, Mert; Eren, Hilal; Catal, Tunc; Bermek, Hakan; Akarsubaşi, Alper Tunga

    2012-09-01

    Five textile azo dyes, as part of an artificial mixture, were treated in single-chamber air-cathode microbial fuel cells while simultaneously utilizing acetate for electricity production. Remazol Black, Remazol Brilliant Blue, Remazol Turquoise Blue, Reactive Yellow and Reactive Red at concentrations of 40 or 80 mg L(-1) were decolorized to a similar extent, at averages of 78, 95, 53, 93 and 74%, respectively, in 24 hours. During the process of decolorization, electricity generation from acetate oxidation continued. Power densities obtained in the presence of textile dyes ranged from 347 to 521 mW m(-2) at the current density range of 0.071 - 0.086 mA cm(-2). Microbial community analyses of cathode biofilm exhibited dynamic changes in abundant species following dye decolorization. Upon the addition of the first dye, a major change (63%) in microbial diversity was observed; however, subsequent addition of other dyes did not affect the community profile significantly. Actinobacteria, Aquamicrobium, Mesorhizobium, Ochrobactrum, Thauera, Paracoccus, Achromobacter and Chelatacoccus affiliated phylotypes were the major phylotypes detected. Our results demonstrate that microbial fuel cells could be a promising alternative for treatment of textile wastewaters and an active bacterial community can rapidly be established for simultaneous azo dye decolorization and sustainable electricity generation.

  20. Soil microbial community composition does not predominantly determine the variance of heterotrophic soil respiration across four subtropical forests.

    PubMed

    Wei, Hui; Xiao, Guoliang; Guenet, Bertrand; Janssens, Ivan A; Shen, Weijun

    2015-01-19

    To explore the importance of soil microbial community composition on explaining the difference in heterotrophic soil respiration (R(h)) across forests, a field investigation was conducted on Rh and soil physiochemical and microbial properties in four subtropical forests in southern China. We observed that Rh differed significantly among forests, being 2.48 ± 0.23, 2.31 ± 0.21, 1.83 ± 0.08 and 1.56 ± 0.15 μmol m(-2) s(-1) in the climax evergreen broadleaf forest (BF), the mixed conifer and broadleaf forest (CF), the conifer plantation (CP), and the native broadleaved species plantation (BP), respectively. Both linear mixed effect model and variance decomposition analysis indicated that soil microbial community composition derived from phospholipid fatty acids (PLFAs) was not the first-order explanatory variable for the R(h) variance across the forests, with the explanatory power being 15.7%. Contrastingly, vegetational attributes such as root biomass (22.6%) and soil substrate availability (18.6%) were more important for explaining the observed R(h) variance. Our results therefore suggest that vegetation attributes and soil carbon pool size, rather than soil microbial community composition, should be preferentially considered to understand the spatial R(h) variance across the subtropical forests in southern China.

  1. Study of azo dye decolorization and determination of cathode microorganism profile in air-cathode microbial fuel cells.

    PubMed

    Kumru, Mert; Eren, Hilal; Catal, Tunc; Bermek, Hakan; Akarsubaşi, Alper Tunga

    2012-09-01

    Five textile azo dyes, as part of an artificial mixture, were treated in single-chamber air-cathode microbial fuel cells while simultaneously utilizing acetate for electricity production. Remazol Black, Remazol Brilliant Blue, Remazol Turquoise Blue, Reactive Yellow and Reactive Red at concentrations of 40 or 80 mg L(-1) were decolorized to a similar extent, at averages of 78, 95, 53, 93 and 74%, respectively, in 24 hours. During the process of decolorization, electricity generation from acetate oxidation continued. Power densities obtained in the presence of textile dyes ranged from 347 to 521 mW m(-2) at the current density range of 0.071 - 0.086 mA cm(-2). Microbial community analyses of cathode biofilm exhibited dynamic changes in abundant species following dye decolorization. Upon the addition of the first dye, a major change (63%) in microbial diversity was observed; however, subsequent addition of other dyes did not affect the community profile significantly. Actinobacteria, Aquamicrobium, Mesorhizobium, Ochrobactrum, Thauera, Paracoccus, Achromobacter and Chelatacoccus affiliated phylotypes were the major phylotypes detected. Our results demonstrate that microbial fuel cells could be a promising alternative for treatment of textile wastewaters and an active bacterial community can rapidly be established for simultaneous azo dye decolorization and sustainable electricity generation. PMID:23240212

  2. 76 FR 6840 - Determinations Under the African Growth and Opportunity Act

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-08

    ... applicable visa requirements. See Visa Requirements Under the African Growth and Opportunity Act, 66 FR 7837...) has determined that the Republic of Liberia has adopted an effective visa system and related... countries,'' provided that these countries: (1) Have adopted an effective visa system and related...

  3. Parental Interaction As A Determining Factor in Social Growth of the Individual in the Family.

    ERIC Educational Resources Information Center

    Markowitz, Max; Kadis, Asya L.

    Parental interaction is a prime determining factor in an individual's growth. Complementary relationships of the mother and father within the family: i.e., the bringing together of both the mothering attitude and the expectation of "growing up", contribute to the individual's maturation. Many analysts, realizing the importance of triadic…

  4. Microbial Source Tracking: Current and Future Molecular Tools in Microbial Water Quality Forensics

    EPA Science Inventory

    Current regulations in the United States stipulate that the microbial quality of waters used for consumption and recreational activities should be determined regularly by measuring microbial indicators of fecal pollution. Hence, the microbial risk associated with these waters is...

  5. Gastric LTi cells promote lymphoid follicle formation but are limited by IRAK-M and do not alter microbial growth.

    PubMed

    Shiu, J; Piazuelo, M B; Ding, H; Czinn, S J; Drakes, M L; Banerjee, A; Basappa, N; Kobayashi, K S; Fricke, W F; Blanchard, T G

    2015-09-01

    Lymphoid tissue inducer (LTi) cells are activated by accessory cell IL-23, and promote lymphoid tissue genesis and antibacterial peptide production by the mucosal epithelium. We investigated the role of LTi cells in the gastric mucosa in the context of microbial infection. Mice deficient in IRAK-M, a negative regulator of TLR signaling, were investigated for increased LTi cell activity, and antibody mediated LTi cell depletion was used to analyze LTi cell dependent antimicrobial activity. H. pylori infected IRAK-M deficient mice developed increased gastric IL-17 and lymphoid follicles compared to wild type mice. LTi cells were present in naive and infected mice, with increased numbers in IRAK-M deficient mice by two weeks. Helicobacter and Candida infection of LTi cell depleted rag1(-/-) mice demonstrated LTi-dependent increases in calprotectin but not RegIII proteins. However, pathogen and commensal microbiota populations remained unchanged in the presence or absence of LTi cell function. These data demonstrate LTi cells are present in the stomach and promote lymphoid follicle formation in response to infection, but are limited by IRAK-M expression. Additionally, LTi cell mediated antimicrobial peptide production at the gastric epithelium is less efficacious at protecting against microbial pathogens than has been reported for other tissues.

  6. Timescales of growth response of microbial mats to environmental change in an ice-covered antarctic lake.

    PubMed

    Hawes, Ian; Sumner, Dawn Y; Andersen, Dale T; Jungblut, Anne D; Mackey, Tyler J

    2013-01-25

    Lake Vanda is a perennially ice-covered, closed-basin lake in the McMurdo Dry Valleys, Antarctica. Laminated photosynthetic microbial mats cover the floor of the lake from below the ice cover to >40 m depth. In recent decades, the water level of Lake Vanda has been rising, creating a "natural experiment" on development of mat communities on newly flooded substrates and the response of deeper mats to declining irradiance. Mats in recently flooded depths accumulate one lamina (~0.3 mm) per year and accrue ~0.18 µg chlorophyll-a cm-2 y-1. As they increase in thickness, vertical zonation becomes evident, with the upper 2-4 laminae forming an orange-brown zone, rich in myxoxanthophyll and dominated by intertwined Leptolyngbya trichomes. Below this, up to six phycobilin-rich green/pink-pigmented laminae form a subsurface zone, inhabited by Leptolyngbya, Oscillatoria and Phormidium morphotypes. Laminae continued to increase in thickness for several years after burial, and PAM fluorometry indicated photosynthetic potential in all pigmented laminae. At depths that have been submerged for >40 years, mats showed similar internal zonation and formed complex pinnacle structures that were only beginning to appear in shallower mats. Chlorophyll-a did not change over time and these mats appear to represent resource-limited "climax" communities. Acclimation of microbial mats to changing environmental conditions is a slow process, and our data show how legacy effects of past change persist into the modern community structure.

  7. Timescales of growth response of microbial mats to environmental change in an ice-covered antarctic lake.

    PubMed

    Hawes, Ian; Sumner, Dawn Y; Andersen, Dale T; Jungblut, Anne D; Mackey, Tyler J

    2013-01-01

    Lake Vanda is a perennially ice-covered, closed-basin lake in the McMurdo Dry Valleys, Antarctica. Laminated photosynthetic microbial mats cover the floor of the lake from below the ice cover to >40 m depth. In recent decades, the water level of Lake Vanda has been rising, creating a "natural experiment" on development of mat communities on newly flooded substrates and the response of deeper mats to declining irradiance. Mats in recently flooded depths accumulate one lamina (~0.3 mm) per year and accrue ~0.18 µg chlorophyll-a cm-2 y-1. As they increase in thickness, vertical zonation becomes evident, with the upper 2-4 laminae forming an orange-brown zone, rich in myxoxanthophyll and dominated by intertwined Leptolyngbya trichomes. Below this, up to six phycobilin-rich green/pink-pigmented laminae form a subsurface zone, inhabited by Leptolyngbya, Oscillatoria and Phormidium morphotypes. Laminae continued to increase in thickness for several years after burial, and PAM fluorometry indicated photosynthetic potential in all pigmented laminae. At depths that have been submerged for >40 years, mats showed similar internal zonation and formed complex pinnacle structures that were only beginning to appear in shallower mats. Chlorophyll-a did not change over time and these mats appear to represent resource-limited "climax" communities. Acclimation of microbial mats to changing environmental conditions is a slow process, and our data show how legacy effects of past change persist into the modern community structure. PMID:24832656

  8. Effect of dietary replacement of alfalfa with urea-treated almond hulls on intake, growth, digestibility, microbial nitrogen, nitrogen retention, ruminal fermentation, and blood parameters in fattening lambs.

    PubMed

    Rad, M Imani; Rouzbehan, Y; Rezaei, J

    2016-01-01

    The objective of this study was to assess the effect of dietary replacement of alfalfa with urea-treated almond hulls (UAH) on DM and nutrients intakes, growth performance, diet digestibility, microbial N supply (MNS), N retention, rumen fermentation parameters, and blood metabolites in fattening male Shall lambs (29.9 ± 1.9 kg initial BW). Three diets, with equal ME and CP concentrations and a forage-to-concentrate ratio of 40 to 60, were formulated in which alfalfa was replaced by different levels (0, 200, or 400 g/kg of diet DM) of UAH. Experimental diets were randomly assigned to the 3 groups ( = 8/group) in a completely randomized design for a 74-d period (14 d for adaptation and 60 d for data collection). Diets were offered as a total mixed ration to ensure 10% orts. Dry matter and nutrients intakes, animal growth, diet digestibility, MNS, N retention, rumen fermentation parameters, and plasma metabolites were determined. The dietary substitution of UAH for alfalfa had no effects on DMI (linear, = 0.96; quadratic, = 0.86), ADG (linear, = 0.35; quadratic, = 0.19), and G:F (linear, = 0.66; quadratic, = 0.13). In vivo digestibility coefficients of DM (linear, = 0.82; quadratic, = 0.42), OM (linear, = 0.73; quadratic, = 0.95), CP (linear, = 0.24; quadratic, = 0.66), and ash-free NDF (linear, = 0.69; quadratic, = 0.74) were not affected by the dietary treatment. Feeding lambs on diets containing UAH instead of alfalfa had no effects on MNS (linear, = 0.63; quadratic, = 0.68) and N retention (linear, = 0.44; quadratic, = 0.17). Rumen pH (linear, = 0.26; quadratic, = 0.071), ammonia N (linear, = 0.39; quadratic, = 0.13), and VFA (linear, = 0.091; quadratic, = 0.86) concentrations, acetic acid-to-propionic acid ratio (linear, = 0.93; quadratic, = 0.62), and protozoa population (linear, = 0.62; quadratic, = 0.22) were not influenced by the experimental diets. Substituting alfalfa with UAH had no effects on the plasma concentrations of glucose (linear, = 0

  9. Quercetin dietary supplementation of fattening lambs at 0.2% rate reduces discolouration and microbial growth in meat during refrigerated storage.

    PubMed

    Andrés, S; Tejido, M L; Bodas, R; Morán, L; Prieto, N; Blanco, C; Giráldez, F J

    2013-02-01

    Thirty-two Merino lambs fed barley straw and a concentrate formulated either with palm oil (CTRL group) plus quercetin (QCT group) or flaxseed (FS group) plus quercetin (FS-QCT group) were used to assess the effects of this flavonoid on meat quality attributes. The animals were slaughtered after being fed for at least 5 weeks with the experimental diets. Chemical composition of longissimus thoracis (LT) muscle was not different among treatments. The longissimus lumborum (LL) samples of QCT and FS-QCT groups revealed lower discolouration (hue angle) when compared to the CTRL and FS lambs (P<0.05), whereas extract release volume (ERV) and microbiological data jointly suggest that flaxseed and quercetin may reduce the growth of microbial populations responsible for meat spoilage in quadriceps femoris (QF).

  10. Discarded oranges and brewer's spent grains as promoting ingredients for microbial growth by submerged and solid state fermentation of agro-industrial waste mixtures.

    PubMed

    Aggelopoulos, Theodoros; Bekatorou, Argyro; Pandey, Ashok; Kanellaki, Maria; Koutinas, Athanasios A

    2013-08-01

    The exploitation of various agro-industrial wastes for microbial cell mass production of Kluyveromyces marxianus, kefir, and Saccharomyces cerevisiae is reported in the present investigation. Specifically, the promotional effect of whole orange pulp on cell growth in mixtures consisting of cheese whey, molasses, and potato pulp in submerged fermentation processes was examined. A 2- to 3-fold increase of cell mass was observed in the presence of orange pulp. Likewise, the promotional effect of brewer's spent grains on cell growth in solid state fermentation of mixtures of whey, molasses, potato pulp, malt spent rootlets, and orange pulp was examined. The cell mass was increased by 3-fold for K. marxianus and 2-fold for S. cerevisiae in the presence of these substrates, proving their suitability for single-cell protein production without the need for extra nutrients. Cell growth kinetics were also studied by measurements of cell counts at various time intervals at different concentrations of added orange pulp. The protein content of the fermented substrates was increased substantially, indicating potential use of mixed agro-industrial wastes of negligible cost, as protein-enriched livestock feed, achieving at the same time creation of added value and waste minimization. PMID:23780341

  11. Test Standard Developed for Determining the Slow Crack Growth of Advanced Ceramics at Ambient Temperature

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Salem, Jonathan A.

    1998-01-01

    The service life of structural ceramic components is often limited by the process of slow crack growth. Therefore, it is important to develop an appropriate testing methodology for accurately determining the slow crack growth design parameters necessary for component life prediction. In addition, an appropriate test methodology can be used to determine the influences of component processing variables and composition on the slow crack growth and strength behavior of newly developed materials, thus allowing the component process to be tailored and optimized to specific needs. At the NASA Lewis Research Center, work to develop a standard test method to determine the slow crack growth parameters of advanced ceramics was initiated by the authors in early 1994 in the C 28 (Advanced Ceramics) committee of the American Society for Testing and Materials (ASTM). After about 2 years of required balloting, the draft written by the authors was approved and established as a new ASTM test standard: ASTM C 1368-97, Standard Test Method for Determination of Slow Crack Growth Parameters of Advanced Ceramics by Constant Stress-Rate Flexural Testing at Ambient Temperature. Briefly, the test method uses constant stress-rate testing to determine strengths as a function of stress rate at ambient temperature. Strengths are measured in a routine manner at four or more stress rates by applying constant displacement or loading rates. The slow crack growth parameters required for design are then estimated from a relationship between strength and stress rate. This new standard will be published in the Annual Book of ASTM Standards, Vol. 15.01, in 1998. Currently, a companion draft ASTM standard for determination of the slow crack growth parameters of advanced ceramics at elevated temperatures is being prepared by the authors and will be presented to the committee by the middle of 1998. Consequently, Lewis will maintain an active leadership role in advanced ceramics standardization within ASTM

  12. Recreating Microbial Ecosystems of the Late Archean

    NASA Astrophysics Data System (ADS)

    Juarez Rivera, M.; Sumner, D. Y.

    2016-05-01

    Microbialites are important deposits for studying early microbial life. Cuspate and plumose microbialites of the Gamohaan Formation provide evidence for multiple microbial communities that grew contemporaneously with different growth rates.

  13. Net Assimilation Rate Determines the Growth Rates of 14 Species of Subtropical Forest Trees

    PubMed Central

    Li, Xuefei; Schmid, Bernhard; Wang, Fei; Paine, C. E. Timothy

    2016-01-01

    Growth rates are of fundamental importance for plants, as individual size affects myriad ecological processes. We determined the factors that generate variation in RGR among 14 species of trees and shrubs that are abundant in subtropical Chinese forests. We grew seedlings for two years at four light levels in a shade-house experiment. We monitored the growth of every juvenile plant every two weeks. After one and two years, we destructively harvested individuals and measured their functional traits and gas-exchange rates. After calculating individual biomass trajectories, we estimated relative growth rates using nonlinear growth functions. We decomposed the variance in log(RGR) to evaluate the relationships of RGR with its components: specific leaf area (SLA), net assimilation rate (NAR) and leaf mass ratio (LMR). We found that variation in NAR was the primary determinant of variation in RGR at all light levels, whereas SLA and LMR made smaller contributions. Furthermore, NAR was strongly and positively associated with area-based photosynthetic rate and leaf nitrogen content. Photosynthetic rate and leaf nitrogen concentration can, therefore, be good predictors of growth in woody species. PMID:26953884

  14. Net Assimilation Rate Determines the Growth Rates of 14 Species of Subtropical Forest Trees.

    PubMed

    Li, Xuefei; Schmid, Bernhard; Wang, Fei; Paine, C E Timothy

    2016-01-01

    Growth rates are of fundamental importance for plants, as individual size affects myriad ecological processes. We determined the factors that generate variation in RGR among 14 species of trees and shrubs that are abundant in subtropical Chinese forests. We grew seedlings for two years at four light levels in a shade-house experiment. We monitored the growth of every juvenile plant every two weeks. After one and two years, we destructively harvested individuals and measured their functional traits and gas-exchange rates. After calculating individual biomass trajectories, we estimated relative growth rates using nonlinear growth functions. We decomposed the variance in log(RGR) to evaluate the relationships of RGR with its components: specific leaf area (SLA), net assimilation rate (NAR) and leaf mass ratio (LMR). We found that variation in NAR was the primary determinant of variation in RGR at all light levels, whereas SLA and LMR made smaller contributions. Furthermore, NAR was strongly and positively associated with area-based photosynthetic rate and leaf nitrogen content. Photosynthetic rate and leaf nitrogen concentration can, therefore, be good predictors of growth in woody species.

  15. Net Assimilation Rate Determines the Growth Rates of 14 Species of Subtropical Forest Trees.

    PubMed

    Li, Xuefei; Schmid, Bernhard; Wang, Fei; Paine, C E Timothy

    2016-01-01

    Growth rates are of fundamental importance for plants, as individual size affects myriad ecological processes. We determined the factors that generate variation in RGR among 14 species of trees and shrubs that are abundant in subtropical Chinese forests. We grew seedlings for two years at four light levels in a shade-house experiment. We monitored the growth of every juvenile plant every two weeks. After one and two years, we destructively harvested individuals and measured their functional traits and gas-exchange rates. After calculating indiv