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1

Curved microchannels and bacterial streamers  

NASA Astrophysics Data System (ADS)

Bacterial biofilms are commonly identified as microbial communities attached to a surface and encased in a self-secreted extracellular matrix. Due to their increased resistance to antimicrobial agents, biofilms have an enormous impact on health and medicine (e.g., wound healing, implant-associated infections, disease transmission). On the other hand, they constitute a major component of the stream ecosystem by increasing transport of nutrients and retention of suspended particles. In this talk, we present an experimental study of bacterial biofilm development in a microfluidic device. In particular, we show the formation of filamentous structures, or streamers, in curved channels and how these suspended biofilms are linked to the underlying hydrodynamics.

Rusconi, Roberto; Lecuyer, Sigolene; Guglielmini, Laura; Stone, Howard

2010-03-01

2

Bacterial streamers in curved microchannels  

NASA Astrophysics Data System (ADS)

Biofilms, generally identified as microbial communities embedded in a self-produced matrix of extracellular polymeric substances, are involved in a wide variety of health-related problems ranging from implant-associated infections to disease transmissions and dental plaque. The usual picture of these bacterial films is that they grow and develop on surfaces. However, suspended biofilm structures, or streamers, have been found in natural environments (e.g., rivers, acid mines, hydrothermal hot springs) and are always suggested to stem from a turbulent flow. We report the formation of bacterial streamers in curved microfluidic channels. By using confocal laser microscopy we are able to directly image and characterize the spatial and temporal evolution of these filamentous structures. Such streamers, which always connect the inner corners of opposite sides of the channel, are always located in the middle plane. Numerical simulations of the flow provide evidences for an underlying hydrodynamic mechanism behind the formation of the streamers.

Rusconi, Roberto; Lecuyer, Sigolene; Guglielmini, Laura; Stone, Howard

2009-11-01

3

[Determination of thermograms of bacterial growth].  

PubMed

The fundamental growth thermograms of bacteria have been determined by using the microcalorimetric method. These perfect thermogram curves reflect the changes of bacterial growth patterns (including the lag phase of growth, log growth, stationary phase and the decline phase of growth). In our experiments, highly characteristic and reproducible growth patterns are observed under the same condition, therefore one can use these thermograms as "finger print" to discriminate bacteria. On the other hand, there thermogram curves contain ample information, which are very significant for the studies on microorganism metabolism, bio-thermokinetic and clinical fields. PMID:2800546

Xie, C L; Tang, H K; Song, Z H; Qu, S S; Liao, Y T; Liu, H S

1989-04-01

4

Thermokinetic Research Method for Bacterial Growth in Conduction Calorimeter  

Microsoft Academic Search

This paper presents the basic equations of thermokinetics and the thermoanalytical curve equation for bacterial growth in\\u000a conduction calorimeter on the basis of the basic theory of thermokinetics. The bacterial growths in the log phase for Vibro metschnikovii and Bacillus subtilis at different temperatures were calorimetrically investigated. The rate constant of bacterial growth, the cooling constant\\u000a of the thermokinetic system,

Z.-D. Nan; Y. Xiang; S.-Q. Cheng; X.-C. Zeng; H.-L. Zhang

2000-01-01

5

Electromagnetism of Bacterial Growth  

NASA Astrophysics Data System (ADS)

There has been increasing concern from the public about personal health due to the significant rise in the daily use of electrical devices such as cell phones, radios, computers, GPS, video games and television. All of these devices create electromagnetic (EM) fields, which are simply magnetic and electric fields surrounding the appliances that simultaneously affect the human bio-system. Although these can affect the human system, obstacles can easily shield or weaken the electrical fields; however, magnetic fields cannot be weakened and can pass through walls, human bodies and most other objects. The present study was conducted to examine the possible effects of bacteria when exposed to magnetic fields. The results indicate that a strong causal relationship is not clear, since different magnetic fields affect the bacteria differently, with some causing an increase in bacterial cells, and others causing a decrease in the same cells. This phenomenon has yet to be explained, but the current study attempts to offer a mathematical explanation for this occurrence. The researchers added cultures to the magnetic fields to examine any effects to ion transportation. Researchers discovered ions such as potassium and sodium are affected by the magnetic field. A formula is presented in the analysis section to explain this effect.

Ainiwaer, Ailiyasi

2011-10-01

6

Arabidopsis growth curves Antibody effect on fibrinogen to fibrin conversion  

E-print Network

�40 Typical growth trajectory for one plant zero up to day t0 35 (plant-specific) reaches full height aroundArabidopsis growth curves Antibody effect on fibrinogen to fibrin conversion Growth curve modelsCullagh, Mei Wang Growth curve models #12;Arabidopsis growth curves Antibody effect on fibrinogen to fibrin

McCullagh, Peter

7

Growth Curves for Girls with Turner Syndrome  

PubMed Central

The objective of this study was to review the growth curves for Turner syndrome, evaluate the methodological and statistical quality, and suggest potential growth curves for clinical practice guidelines. The search was carried out in the databases Medline and Embase. Of 1006 references identified, 15 were included. Studies constructed curves for weight, height, weight/height, body mass index, head circumference, height velocity, leg length, and sitting height. The sample ranged between 47 and 1,565 (total?=?6,273) girls aged 0 to 24?y, born between 1950 and 2006. The number of measures ranged from 580 to 9,011 (total?=?28,915). Most studies showed strengths such as sample size, exclusion of the use of growth hormone and androgen, and analysis of confounding variables. However, the growth curves were restricted to height, lack of information about selection bias, limited distributional properties, and smoothing aspects. In conclusion, we observe the need to construct an international growth reference for girls with Turner syndrome, in order to provide support for clinical practice guidelines. PMID:24949463

Bertapelli, Fabio; Barros-Filho, Antonio de Azevedo; Antonio, Maria Angela Reis de Goes Monteiro; Barbeta, Camila Justino de Oliveira; de Lemos-Marini, Sofia Helena Valente

2014-01-01

8

Stochasticity in Colonial Growth Dynamics of Individual Bacterial Cells  

PubMed Central

Conventional bacterial growth studies rely on large bacterial populations without considering the individual cells. Individual cells, however, can exhibit marked behavioral heterogeneity. Here, we present experimental observations on the colonial growth of 220 individual cells of Salmonella enterica serotype Typhimurium using time-lapse microscopy videos. We found a highly heterogeneous behavior. Some cells did not grow, showing filamentation or lysis before division. Cells that were able to grow and form microcolonies showed highly diverse growth dynamics. The quality of the videos allowed for counting the cells over time and estimating the kinetic parameters lag time (?) and maximum specific growth rate (?max) for each microcolony originating from a single cell. To interpret the observations, the variability of the kinetic parameters was characterized using appropriate probability distributions and introduced to a stochastic model that allows for taking into account heterogeneity using Monte Carlo simulation. The model provides stochastic growth curves demonstrating that growth of single cells or small microbial populations is a pool of events each one of which has its own probability to occur. Simulations of the model illustrated how the apparent variability in population growth gradually decreases with increasing initial population size (N0). For bacterial populations with N0 of >100 cells, the variability is almost eliminated and the system seems to behave deterministically, even though the underlying law is stochastic. We also used the model to demonstrate the effect of the presence and extent of a nongrowing population fraction on the stochastic growth of bacterial populations. PMID:23354712

Lianou, Alexandra

2013-01-01

9

Bacterial Growth H. L. Smith  

E-print Network

as many bacterial cells on our skin and in our large intestine as cells in our own body. We are nothing for insulin into bacteria and let them produce it in large industrial fermenters. So it is important

Smith, Hal

10

Curved tails in polymerization-based bacterial motility  

NASA Astrophysics Data System (ADS)

The curved actin ``comet-tail'' of the bacterium Listeria monocytogenes is a visually striking signature of actin polymerization-based motility. Similar actin tails are associated with Shigella flexneri, spotted-fever Rickettsiae, the Vaccinia virus, and vesicles and microspheres in related in vitro systems. We show that the torque required to produce the curvature in the tail can arise from randomly placed actin filaments pushing the bacterium or particle. We find that the curvature magnitude determines the number of actively pushing filaments, independent of viscosity and of the molecular details of force generation. The variation of the curvature with time can be used to infer the dynamics of actin filaments at the bacterial surface.

Rutenberg, Andrew D.; Grant, Martin

2001-08-01

11

Growth curve analysis of Rambouillet ewes  

E-print Network

). Specific age~eight models for analyzing growth curves exist (Gompertz [Winsor, 1932]; Brody, 1945; von Bertslanffy, 1957; Richards, 1959; logistic [Nelder, 1961]). Their specific attributes and limitations have been thoroughly reviewed (Seebeck, 1968... be expressed as: I d I t2 tl A dt A t2 tl The change in size over time ~ which is absolute growth rate (AGR) dv dt can be estimated by, yt AGR =~ dt t2 ? tl When y refers to the body weight and t to the age in days, AGR is often called average daily...

Mathenge, James Mwai

2012-06-07

12

Phospholipid metabolism during bacterial growth  

Microsoft Academic Search

Haemophiius parainjuenzae incorporates glycerol and phosphate into the membrane phospholipids without lag during logarithmic growth. In phosphatidyl glycerol (PG), the phosphate and unacylatcd glycerol moieties turn over and incorporate radioactivity much more rapidly than does the diacylated glycerol. At least half the radioactivity is lost from the phosphate and unacylated glycerol in about 1 doubling. The total fatty acids turn

DAVID C. WHITE; ANNE N. TUCKER

13

Coulter counter determination of bacterial growth and cellular size change following ??Co gamma irradiation  

E-print Network

. D. Neff Bacterial growth curves and cellular volume distributions were determined for Serratia marcescens 933, Serratia marcescens WF, and Escherichia coli E63 using a Model ZBI Coulter Counter, an electronic particle counter and size analyzer... WF during growth 17 18 Figure 7. Cellular volume distribution curves of Figure 8. Escherichia coli E63 during growth Change of mean cellular volumes with time of 19 Serratia marcescens 933, Serratia marcescens WF, Figure 9. and Escherichia...

Gaston, Gary W

2012-06-07

14

Survival curves of heated bacterial spores:1 Effect of environmental factors on Weibull parameters2  

E-print Network

1 Survival curves of heated bacterial spores:1 Effect of environmental factors on Weibull heat13 resistance for non-log linear survival curves. One simple model derived from the Weibull14 calculation.39 However in many cases the survival curves of heated bacteria do not present a log linear40

Brest, Université de

15

Bacterial contact-dependent growth inhibition (CDI)  

PubMed Central

Bacteria cooperate to form multicellular communities and compete against one another for environmental resources. Here, we review recent advances in our understanding of bacterial competition mediated by contact-dependent growth inhibition (CDI) systems. Different CDI+ bacteria deploy a variety of toxins to inhibit neighboring cells and protect themselves from autoinhibition by producing specific immunity proteins. The genes encoding CDI toxinimmunity pairs appear to be exchanged between cdi loci and are often associated with other toxin-delivery systems in diverse bacteria. CDI also appears to facilitate cooperative behavior between kin, suggesting that these systems may have other roles beyond competition. PMID:23473845

Ruhe, Zachary C.; Low, David A.; Hayes, Christopher S.

2013-01-01

16

1 Arabidopsis growth curves 1.1 Data description  

E-print Network

1 Arabidopsis growth curves 1.1 Data description The file PlantGrowth.dat contains the heights appeared by day 41. By day 65 or earlier, the growth was complete; for each plant, the height recorded 69 distinct growth trajectories for 70 plants. The illusion is caused in part by heights being

McCullagh, Peter

17

Bacterial Ammonia Causes Significant Plant Growth Inhibition  

PubMed Central

Many and complex plant-bacteria inter-relationships are found in the rhizosphere, since plants release a variety of photosynthetic exudates from their roots and rhizobacteria produce multifaceted specialized compounds including rich mixtures of volatiles, e.g., the bouquet of Serratia odorifera 4Rx13 is composed of up to 100 volatile organic and inorganic compounds. Here we show that when growing on peptone-rich nutrient medium S. odorifera 4Rx13 and six other rhizobacteria emit high levels of ammonia, which during co-cultivation in compartmented Petri dishes caused alkalization of the neighboring plant medium and subsequently reduced the growth of A. thaliana. It is argued that in nature high-protein resource degradations (carcasses, whey, manure and compost) are also accompanied by bacterial ammonia emission which alters the pH of the rhizosphere and thereby influences organismal diversity and plant-microbe interactions. Consequently, bacterial ammonia emission may be more relevant for plant colonization and growth development than previously thought. PMID:23691060

Weise, Teresa; Kai, Marco; Piechulla, Birgit

2013-01-01

18

Coupled effects of chemotaxis and growth on traveling bacterial waves.  

PubMed

Traveling bacterial waves are capable of improving contaminant remediation in the subsurface. It is fairly well understood how bacterial chemotaxis and growth separately affect the formation and propagation of such waves. However, their interaction is not well understood. We therefore perform a modeling study to investigate the coupled effects of chemotaxis and growth on bacterial migration, and examine their effects on contaminant remediation. We study the waves by using different initial electron acceptor concentrations for different bacteria and substrate systems. Three types of traveling waves can occur: a chemotactic wave due to the biased movement of chemotactic bacteria resulting from metabolism-generated substrate concentration gradients; a growth/decay/motility wave due to a dynamic equilibrium between bacterial growth, decay and random motility; and an integrated wave due to the interaction between bacterial chemotaxis and growth. Chemotaxis hardly enhances the bacterial propagation if it is too weak to form a chemotactic wave or its wave speed is less than half of the growth/decay/motility wave speed. However, chemotaxis significantly accelerates bacterial propagation once its wave speed exceeds the growth/decay/motility wave speed. When convection occurs, it speeds up the growth/decay/motility wave but slows down or even eliminates the chemotactic wave due to the dispersion. Bacterial survival proves particularly important for bacterial propagation. Therefore we develop a conceptual model to estimate the speed of growth/decay/motility waves. PMID:24984293

Yan, Zhifeng; Bouwer, Edward J; Hilpert, Markus

2014-08-01

19

Coupled effects of chemotaxis and growth on traveling bacterial waves  

NASA Astrophysics Data System (ADS)

Traveling bacterial waves are capable of improving contaminant remediation in the subsurface. It is fairly well understood how bacterial chemotaxis and growth separately affect the formation and propagation of such waves. However, their interaction is not well understood. We therefore perform a modeling study to investigate the coupled effects of chemotaxis and growth on bacterial migration, and examine their effects on contaminant remediation. We study the waves by using different initial electron acceptor concentrations for different bacteria and substrate systems. Three types of traveling waves can occur: a chemotactic wave due to the biased movement of chemotactic bacteria resulting from metabolism-generated substrate concentration gradients; a growth/decay/motility wave due to a dynamic equilibrium between bacterial growth, decay and random motility; and an integrated wave due to the interaction between bacterial chemotaxis and growth. Chemotaxis hardly enhances the bacterial propagation if it is too weak to form a chemotactic wave or its wave speed is less than half of the growth/decay/motility wave speed. However, chemotaxis significantly accelerates bacterial propagation once its wave speed exceeds the growth/decay/motility wave speed. When convection occurs, it speeds up the growth/decay/motility wave but slows down or even eliminates the chemotactic wave due to the dispersion. Bacterial survival proves particularly important for bacterial propagation. Therefore we develop a conceptual model to estimate the speed of growth/decay/motility waves.

Yan, Zhifeng; Bouwer, Edward J.; Hilpert, Markus

2014-08-01

20

BACTERIAL GROWTH EFFICIENCY ON NATURAL DISSOLVED ORGANIC MATTER  

EPA Science Inventory

Bacterial growth efficiency was examined in batch cultures and continuous flow cultures. atural assemblages of pelagic bacteria were inoculated into particle free water and growth efficiencies determined from measurements of produced particulate organic carbon (POC) and utilized ...

21

Individual growth curve models for assessing evidence based referral criteria in growth monitoring  

Microsoft Academic Search

SUMMARY The goal of this study is to assess whether a growth curve model approach will lead to a more precise detection of Turner sydnrome (TS) than conventional referral criteria for growth monitoring. The Jenss- Bayley growth curve model was used to describe the process of growth over time. A new screening rule is dened on the parameters of this

P. van Dommelen; S. van Buuren; G. R. J. Zandwijken; P. H. Verkerk

2005-01-01

22

Latent Growth Curve Analyses of the Development of Height.  

ERIC Educational Resources Information Center

Describes some applications of latent growth curve models in the context of structural equation modeling using data from P. Trickett and F. Putnam (1993) on the physical height of abused (n=77) and nonabused (n=75) adolescent girls. Presents power calculations for the ability of the different models to discern the growth of the abuse sample from

Ghisletta, Paolo; McArdle, John J.

2001-01-01

23

Twelve Frequently Asked Questions About Growth Curve Modeling  

Microsoft Academic Search

Longitudinal data analysis has long played a significant role in empirical research within the developmental sciences. The past decade has given rise to a host of new and exciting analytic methods for studying between-person differences in within-person change. These methods are broadly organized under the term growth curve models. The historical lines of development leading to current growth models span

Patrick J. Curran; Khawla Obeidat; Diane Losardo

2010-01-01

24

Visualization of Growth Curve Data from Phenotype MicroarrayExperiments  

SciTech Connect

Phenotype microarrays provide a technology to simultaneouslysurvey the response of an organism to nearly 2,000 substrates, includingcarbon, nitrogen and potassium sources; varying pH; varying saltconcentrations; and antibiotics. In order to more quickly and easily viewand compare the large number of growth curves produced by phenotypemicroarray experiments, we have developed software to produce and displaycolor images, each of which corresponds to a set of 96 growth curves.Using color images to represent growth curves data has proven to be avaluable way to assess experiment quality, compare replicates, facilitatecomparison of the responses of different organisms, and identifysignificant phenotypes. The color images are linked to traditional plotsof growth versus time, as well as to information about the experiment,organism, and substrate. In order to share and view information and dataproject-wide, all information, plots, and data are accessible using onlya Web browser.

Jacobsen, Janet S.; Joyner, Dominique C.; Borglin, Sharon E.; Hazen, Terry C.; Arkin, Adam P.; Bethel, E. Wes

2007-04-19

25

Study of release speeds and bacteria inhibiting capabilities of drug delivery membranes fabricated via electrospinning by observing bacteria growth curves  

Microsoft Academic Search

The study found that biodegradable drug delivery membranes that were fabricated from Poly(a-L-alanine) (PLLA) and chlorhexidine\\u000a (CHX)-gluconate via electrospinning could steadily and continuously inhibit the growth of bacteria. Bacterial growth curves\\u000a were used to evaluate on a real-time basis the relationship between drug delivery speeds of the membranes and growth rates\\u000a of bacteria in different phases. The results showed that

Yao Nan Lin; Kai Ming Chang; Shiang Cheng Jeng; Ping Yu Lin; Ray Quen Hsu

2011-01-01

26

Using bacterial cell growth to template catalytic asymmetry.  

PubMed

We report an approach to position gold nanoparticle catalysts for metal reduction asymmetrically on a biological template (E. coli) by exploiting the polarity of the bacterial cell envelope undergoing growth and division. PMID:20544084

Kaehr, Bryan; Brinker, C Jeffrey

2010-08-01

27

Genomic growth curves of an outbred pig population.  

PubMed

In the current post-genomic era, the genetic basis of pig growth can be understood by assessing SNP marker effects and genomic breeding values (GEBV) based on estimates of these growth curve parameters as phenotypes. Although various statistical methods, such as random regression (RR-BLUP) and Bayesian LASSO (BL), have been applied to genomic selection (GS), none of these has yet been used in a growth curve approach. In this work, we compared the accuracies of RR-BLUP and BL using empirical weight-age data from an outbred F2 (Brazilian Piau X commercial) population. The phenotypes were determined by parameter estimates using a nonlinear logistic regression model and the halothane gene was considered as a marker for evaluating the assumptions of the GS methods in relation to the genetic variation explained by each locus. BL yielded more accurate values for all of the phenotypes evaluated and was used to estimate SNP effects and GEBV vectors. The latter allowed the construction of genomic growth curves, which showed substantial genetic discrimination among animals in the final growth phase. The SNP effect estimates allowed identification of the most relevant markers for each phenotype, the positions of which were coincident with reported QTL regions for growth traits. PMID:24385855

Silva, Fabyano Fonseca E; de Resende, Marcos Deon V; Rocha, Gilson Silvrio; Duarte, Darlene Ana S; Lopes, Paulo Svio; Brustolini, Otvio J B; Thus, Sander; Viana, Jos Marcelo S; Guimares, Simone E F

2013-12-01

28

Latent Growth Curves within Developmental Structural Equation Models.  

ERIC Educational Resources Information Center

Uses structural equation modeling to combine traditional ideas from repeated-measures ANOVA with some traditional ideas from longitudinal factor analysis. The model describes a latent growth curve model that permits the estimation of parameters representing individual and group dynamics. (Author/RH)

McArdle, J. J.; Epstein, David

1987-01-01

29

Twelve Frequently Asked Questions about Growth Curve Modeling  

ERIC Educational Resources Information Center

Longitudinal data analysis has long played a significant role in empirical research within the developmental sciences. The past decade has given rise to a host of new and exciting analytic methods for studying between-person differences in within-person change. These methods are broadly organized under the term "growth curve models." The

Curran, Patrick J.; Obeidat, Khawla; Losardo, Diane

2010-01-01

30

The Multigroup Multilevel Categorical Latent Growth Curve Models  

ERIC Educational Resources Information Center

Longitudinal data describe developmental patterns and enable predictions of individual changes beyond sampled time points. Major methodological issues in longitudinal data include modeling random effects, subject effects, growth curve parameters, and autoregressive residuals. This study embedded the longitudinal model within a multigroup

Hung, Lai-Fa

2010-01-01

31

Sensitivity of Fit Indices to Misspecification in Growth Curve Models  

ERIC Educational Resources Information Center

This study investigated the sensitivity of fit indices to model misspecification in within-individual covariance structure, between-individual covariance structure, and marginal mean structure in growth curve models. Five commonly used fit indices were examined, including the likelihood ratio test statistic, root mean square error of

Wu, Wei; West, Stephen G.

2010-01-01

32

Catecholamines and in vitro growth of pathogenic bacteria: enhancement of growth varies greatly among bacterial species  

NASA Technical Reports Server (NTRS)

The purpose of this study was to examine the effects of catecholamines on in vitro growth of a range of bacterial species, including anaerobes. Bacteria tested included: Porphyromonas gingivalis, Bacteriodes fragilis, Shigella boydii, Shigella sonnie, Enterobacter Sp, and Salmonella choleraesuis. The results of the current study indicated that supplementation of bacterial cultures in minimal medium with norepinephrine or epinephrine did not result in increased growth of bacteria. Positive controls involving treatment of Escherichia coli with catecholamines did result in increased growth of that bacterial species. The results of the present study extend previous observations that showed differential capability of catecholamines to enhance bacterial growth in vitro.

Belay, Tesfaye; Aviles, Hernan; Vance, Monique; Fountain, Kimberly; Sonnenfeld, Gerald

2003-01-01

33

Curves of growth for van der Waals broadened spectral lines  

NASA Technical Reports Server (NTRS)

Curves of growth are evaluated for a spectral line broadened by the van der Waals interactions during collisions. The growth of the equivalent widths of such lines is shown to be dependent on the product of the perturber density and the 6/10 power of the van der Waals potential coefficient. When the parameter is small, the widths grow as the 1/2 power of the optical depth as they do for the Voigt profile: but when the parameter is large, they grow as 2/3 power and, hence, faster than the Voigt profile. An approximate analytical expression for the computed growth characteristics is given.

Park, C.

1980-01-01

34

Twelve Frequently Asked Questions About Growth Curve Modeling  

PubMed Central

Longitudinal data analysis has long played a significant role in empirical research within the developmental sciences. The past decade has given rise to a host of new and exciting analytic methods for studying between-person differences in within-person change. These methods are broadly organized under the term growth curve models. The historical lines of development leading to current growth models span multiple disciplines within both the social and statistical sciences, and this in turn makes it challenging for developmental researchers to gain a broader understanding of the current state of this literature. To help address this challenge, the authors pose 12 questions that frequently arise in growth curve modeling, particularly in applications within developmental psychology. They provide concise and nontechnical responses to each question and make specific recommendations for further readings. PMID:21743795

Curran, Patrick J.; Obeidat, Khawla; Losardo, Diane

2011-01-01

35

Net growth delay: a novel parameter derived from tumor growth curves  

SciTech Connect

Growth delay does not only reflect the effect of treatment on the tumor parenchymal cells but also on the stroma. Due to tumor bed effect, the extent of growth delay determined from tumor growth curves is highly dependent on the end volume chosen. It was aimed to minimize the influence of the tumor bed effect on the growth delay calculated by choosing a smaller size and essentially an earlier time for regrowth. Net growth delay is a novel parameter derived from the tumor growth curves, allowing a better comparison of the results with colony assay and tumor control data.

Beck-Bornholdt, H.P.; Wuerschmidt, F.V.; Vogler, H.

1987-05-01

36

Application of LASCA technique for monitoring of bacterial colonies growth  

NASA Astrophysics Data System (ADS)

Methods of s-LASCA and t-LASCA have been adopted to problem of monitoring growth of colonies of bacteria E. coli culture B6. Set-up of LASCA-microscope is developed. Results of experimental investigations of influence of speckled biospeckles on results of monitoring of growth of bacterial colonies have been obtained.

Ulianova, Onega; Rebeza, Olga; Rebeza, Nadezhda; Ulyanov, Sergey

2013-02-01

37

Can we estimate bacterial growth rates from ribosomal RNA content?  

SciTech Connect

Several studies have demonstrated a strong relationship between the quantity of RNA in bacterial cells and their growth rate under laboratory conditions. It may be possible to use this relationship to provide information on the activity of natural bacterial communities, and in particular on growth rate. However, if this approach is to provide reliably interpretable information, the relationship between RNA content and growth rate must be well-understood. In particular, a requisite of such applications is that the relationship must be universal among bacteria, or alternately that the relationship can be determined and measured for specific bacterial taxa. The RNA-growth rate relationship has not been used to evaluate bacterial growth in field studies, although RNA content has been measured in single cells and in bulk extracts of field samples taken from coastal environments. These measurements have been treated as probable indicators of bacterial activity, but have not yet been interpreted as estimators of growth rate. The primary obstacle to such interpretations is a lack of information on biological and environmental factors that affect the RNA-growth rate relationship. In this paper, the available data on the RNA-growth rate relationship in bacteria will be reviewed, including hypotheses regarding the regulation of RNA synthesis and degradation as a function of growth rate and environmental factors; i.e. the basic mechanisms for maintaining RNA content in proportion to growth rate. An assessment of the published laboratory and field data, the current status of this research area, and some of the remaining questions will be presented.

Kemp, P.F.

1995-12-31

38

Biological Consequences and Advantages of Asymmetric Bacterial Growth  

PubMed Central

Asymmetries in cell growth and division occur in eukaryotes and prokaryotes alike. Even seemingly simple and morphologically symmetric cell division processes belie inherent underlying asymmetries in the composition of the resulting daughter cells. We consider the types of asymmetry that arise in various bacterial cell growth and division processes, which include both conditionally activated mechanisms and constitutive, hardwired aspects of bacterial life histories. Although asymmetry disposes some cells to the deleterious effects of aging, it may also benefit populations by efficiently purging accumulated damage and rejuvenating newborn cells. Asymmetries may also generate phenotypic variation required for successful exploitation of variable environments, even when extrinsic changes outpace the capacity of cells to sense and respond to challenges. We propose specific experimental approaches to further develop our understanding of the prevalence and the ultimate importance of asymmetric bacterial growth. PMID:23808335

Kysela, David T.; Brown, Pamela J.B.; Huang, Kerwyn Casey; Brun, Yves V.

2014-01-01

39

Measuring bacterial growth by refractive index tapered fiber optic biosensor  

Microsoft Academic Search

A single-mode tapered fiber optic biosensor was utilized for real-time monitoring of the Escherichia coli (E. coli K-12) growth in an aqueous medium. The applied fiber tapers were fabricated using heat-pulling method with waist diameter and length of 67?m and 3mm, respectively. The bacteria were immobilized on the tapered surface using Poly-l-Lysine. By providing the proper condition, bacterial population growth

Mohammad Ismail Zibaii; Alireza Kazemi; Hamid Latifi; Mahmoud Karimi Azar; Seyed Masoud Hosseini; Mohammad Hossein Ghezelaiagh

2010-01-01

40

Spatiotemporal growth of faceted and curved single crystals  

PubMed

The spatiotemporal growth of single crystals in a crystalline polymer has been investigated theoretically based on a nonconserved time dependent Ginzburg-Landau equation (known as TDGL model A). In the description of the total free energy, a double-well local free energy density signifying metastability of crystal ordering is combined with a nonlocal free energy term representing an interface gradient. The resulting nonlinear reaction diffusion equation after renormalization possesses a solitary wave property. Two-dimensional numerical calculations were performed to elucidate the faceted single crystal growth including square, rectangular, diamond-shaped, and curved single crystals. A three-dimensional simulation was also undertaken for the emergence of diamond-shaped single crystals in polyethylene. Of particular importance is that the model field parameters can be linked directly to the material parameters of polyethylene single crystals. Simulation with various elements of the interface gradient coefficient tensor captures various topologies of polymer single crystals. PMID:11088211

Kyu; Mehta; Chiu

2000-04-01

41

Study of release speeds and bacteria inhibiting capabilities of drug delivery membranes fabricated via electrospinning by observing bacteria growth curves.  

PubMed

The study found that biodegradable drug delivery membranes that were fabricated from Poly(a-L-alanine) (PLLA) and chlorhexidine (CHX)-gluconate via electrospinning could steadily and continuously inhibit the growth of bacteria. Bacterial growth curves were used to evaluate on a real-time basis the relationship between drug delivery speeds of the membranes and growth rates of bacteria in different phases. The results showed that PLLA/CHX (50:50 in terms of volume) drug delivery membranes could do what drug delivery systems can normally do. SEM morphology observations, FTIR, and Raman spectra analyses were conducted on the drug delivery membranes. This is the first study that confirms that biodegradable CHX delivery membranes fabricated via electrospinning are a rate-preprogrammed drug delivery system by comparing the growth curves of competent cell and plasmid inserted competent cell, bacteria that are of the same strain but grow at different speeds due to the insertion. PMID:21287237

Lin, Yao Nan; Chang, Kai Ming; Jeng, Shiang Cheng; Lin, Ping Yu; Hsu, Ray Quen

2011-03-01

42

Parent involvement and science achievement: A latent growth curve analysis  

NASA Astrophysics Data System (ADS)

This study examined science achievement growth across elementary and middle school and parent school involvement using the Early Childhood Longitudinal Study - Kindergarten Class of 1998--1999 (ECLS-K). The ECLS-K is a nationally representative kindergarten cohort of students from public and private schools who attended full-day or half-day kindergarten class in 1998--1999. The present study's sample (N = 8,070) was based on students that had a sampling weight available from the public-use data file. Students were assessed in science achievement at third, fifth, and eighth grades and parents of the students were surveyed at the same time points. Analyses using latent growth curve modeling with time invariant and varying covariates in an SEM framework revealed a positive relationship between science achievement and parent involvement at eighth grade. Furthermore, there were gender and racial/ethnic differences in parents' school involvement as a predictor of science achievement. Findings indicated that students with lower initial science achievement scores had a faster rate of growth across time. The achievement gap between low and high achievers in earth, space and life sciences lessened from elementary to middle school. Parents' involvement with school usually tapers off after elementary school, but due to parent school involvement being a significant predictor of eighth grade science achievement, later school involvement may need to be supported and better implemented in secondary schooling.

Johnson, Ursula Yvette

43

Reducing atelectasis attenuates bacterial growth and translocation in experimental pneumonia  

Microsoft Academic Search

Abstract Besides being one of the mechanisms responsible for ventilator-induced lung injury, atelectasis also seems to aggravate the course of experimental pneumonia. In this study, we examined,the effect of reducing the degree of atelectasis by natural modified surfactant and\\/or open lung ventilation, on bacterial growth and translocation in a piglet model of group B streptococcal pneumonia. After creating surfactant-deficiency by

Kaam van A. H. L. C; Robert A. Lachmann; Egbert Herting; Anne De Jaegere; F. Iwaarden; L. Arnold Noorduyn; Joke H. Kok; Jack J. Haitsma; Burkhard Lachmann

2004-01-01

44

Microcoupon Assay Of Adhesion And Growth Of Bacterial Films  

NASA Technical Reports Server (NTRS)

Microbiological assay technique facilitates determination of some characteristics of sessile bacteria like those that attach to and coat interior walls of water-purification systems. Biofilms cause sickness and interfere with purification process. Technique enables direct measurement of rate of attachment of bacterial cells, their metabolism, and effects of chemicals on them. Used to quantify effects of both bactericides and growth-stimulating agents and in place of older standard plate-count and tube-dilution techniques.

Pierson, Duane L.; Koenig, David W.

1994-01-01

45

Beyond growth: novel functions for bacterial cell wall hydrolases  

PubMed Central

The peptidoglycan cell wall maintains turgor pressure and cell shape of most bacteria. Cell wall hydrolases are essential, along with synthases, for growth and daughter cell separation. Recent work in diverse organisms has uncovered new cell wall hydrolases that act autonomously or on neighboring cells to modulate invasion of prey cells, cell shape, innate immune detection, intercellular communication, and competitor lysis. The hydrolases involved in these processes catalyze the cleavage of bonds throughout the sugar and peptide moities of peptidoglycan. Phenotypes associated with these diverse hydrolases reveal new functions of the bacterial cell wall beyond growth and division. PMID:22944244

Wyckoff, Timna J.; Taylor, Jennifer A.; Salama, Nina R.

2012-01-01

46

Surface Growth of a Motile Bacterial Population Resembles Growth in a Chemostat  

E-print Network

, and we observe these parameters in populations of Escherichia coli swimming in galactose soft agar plates;observe a population of Escherichia coli that grows and performs chemotaxis through soft agar plates10Surface Growth of a Motile Bacterial Population Resembles Growth in a Chemostat Daniel A. Koster

47

Limitation of Bacterial Growth by Dissolved Organic Matter and Iron in the Southern Ocean  

Microsoft Academic Search

Bacterial abundance, mean cell volume, and (3H)thymidine and (3H)leucine incorporation were measured during 4- to 5-day incubations. Bacterial biomass, production, and rates of growth all responded to organic enrichments in three of the four experiments. These results indicate that bacterial growth was constrained primarily by the availability of dissolved organic matter. Bacterial growth in the subtropical front, subantarctic zone, and

MATTHEW J. CHURCH; DAVID A. HUTCHINS; HUGH W. DUCKLOW

2000-01-01

48

Bacterial Growth Phase Influences Methylmercury Production by the Sulfate-Reducing Bacterium  

E-print Network

Bacterial Growth Phase Influences Methylmercury Production by the Sulfate-Reducing Bacterium on bacterial MMHg production in natural systems. #12;Bacterial Growth Phase Influences Methylmercury Production­fumarate media. This NOM did not affect MMHg production even under very low Hg:SRNOM ratios, where Hg binding

49

Slow protein fluctuations explain the emergence of growth phenotypes and persistence in clonal bacterial populations  

E-print Network

One of the most challenging problems in microbiology is to understand how a small fraction of microbes that resists killing by antibiotics can emerge in a population of genetically identical cells, the phenomenon known as persistence or drug tolerance. Its characteristic signature is the biphasic kill curve, whereby microbes exposed to a bactericidal agent are initially killed very rapidly but then much more slowly. Here we relate this problem to the more general problem of understanding the emergence of distinct growth phenotypes in clonal populations. We address the problem mathematically by adopting the framework of the phenomenon of so-called weak ergodicity breaking, well known in dynamical physical systems, which we extend to the biological context. We show analytically and by direct stochastic simulations that distinct growth phenotypes can emerge as a consequence of slow-down of stochastic fluctuations in the expression of a gene controlling growth rate. In the regime of fast gene transcription, the system is ergodic, the growth rate distribution is unimodal, and accounts for one phenotype only. In contrast, at slow transcription and fast translation, weakly non-ergodic components emerge, the population distribution of growth rates becomes bimodal, and two distinct growth phenotypes are identified. When coupled to the well-established growth rate dependence of antibiotic killing, this model describes the observed fast and slow killing phases, and reproduces much of the phenomenology of bacterial persistence. The model has major implications for efforts to develop control strategies for persistent infections.

Andrea Rocco; Andrzej M. Kierzek; Johnjoe McFadden

2013-10-31

50

Modeling bacterial population growth from stochastic single-cell dynamics.  

PubMed

A few bacterial cells may be sufficient to produce a food-borne illness outbreak, provided that they are capable of adapting and proliferating on a food matrix. This is why any quantitative health risk assessment policy must incorporate methods to accurately predict the growth of bacterial populations from a small number of pathogens. In this aim, mathematical models have become a powerful tool. Unfortunately, at low cell concentrations, standard deterministic models fail to predict the fate of the population, essentially because the heterogeneity between individuals becomes relevant. In this work, a stochastic differential equation (SDE) model is proposed to describe variability within single-cell growth and division and to simulate population growth from a given initial number of individuals. We provide evidence of the model ability to explain the observed distributions of times to division, including the lag time produced by the adaptation to the environment, by comparing model predictions with experiments from the literature for Escherichia coli, Listeria innocua, and Salmonella enterica. The model is shown to accurately predict experimental growth population dynamics for both small and large microbial populations. The use of stochastic models for the estimation of parameters to successfully fit experimental data is a particularly challenging problem. For instance, if Monte Carlo methods are employed to model the required distributions of times to division, the parameter estimation problem can become numerically intractable. We overcame this limitation by converting the stochastic description to a partial differential equation (backward Kolmogorov) instead, which relates to the distribution of division times. Contrary to previous stochastic formulations based on random parameters, the present model is capable of explaining the variability observed in populations that result from the growth of a small number of initial cells as well as the lack of it compared to populations initiated by a larger number of individuals, where the random effects become negligible. PMID:24928885

Alonso, Antonio A; Molina, Ignacio; Theodoropoulos, Constantinos

2014-09-01

51

Experimental investigation on the role of bacterial growth and bacterial transport in MEOR processes  

SciTech Connect

In order to define the dynamics of Microbial Enhanced Oil Recovery (MEOR) process bench-scale MEOR using Bacillus subtilis was undertaken. The relationship between bacterial transport in the oil containing porous media, growth rate and the efficiency of oil recovery was investigated. Work using Pseudomonas fluorescens and clostridium acetobutylicum is in progress (no data). Heavy crude (API gravity 17/sup 0/) was used in these studies in which Continuous Flooding Process and the combination Huff-and-Puff and Nutrient Flooding Processes were compared. B. subtilis provided greater than 40% oil recovery after secondary flooding. Growth is satisfactory provided adequate nutrient and oxygen supply. Liquid phase metabolites (polysaccharides, lipids) and gaseous phase metabolites (CO/sub 2/, etc.) improve recovery. The Huff-and-Puff, etc. combination process is the most efficient based on nutrient consumption.

Jang, L.K.; Yen, T.F.

1983-03-01

52

Dislocation-mediated growth of bacterial cell walls  

PubMed Central

Recent experiments have illuminated a remarkable growth mechanism of rod-shaped bacteria: proteins associated with cell wall extension move at constant velocity in circles oriented approximately along the cell circumference [Garner EC, et al., (2011) Science 333:222225], [Domnguez-Escobar J, et al. (2011) Science 333:225228], [van Teeffelen S, et al. (2011) PNAS 108:1582215827]. We view these as dislocations in the partially ordered peptidoglycan structure, activated by glycan strand extension machinery, and study theoretically the dynamics of these interacting defects on the surface of a cylinder. Generation and motion of these interacting defects lead to surprising effects arising from the cylindrical geometry, with important implications for growth. We also discuss how long range elastic interactions and turgor pressure affect the dynamics of the fraction of actively moving dislocations in the bacterial cell wall. PMID:22660931

Amir, Ariel; Nelson, David R.

2012-01-01

53

Dislocation-mediated growth of bacterial cell walls  

E-print Network

Recent experiments have illuminated a remarkable growth mechanism of rod-shaped bacteria: proteins associated with cell wall extension move at constant velocity in circles oriented approximately along the cell circumference (Garner et al., Science (2011), Dominguez-Escobar et al. Science (2011), van Teeffelen et al. PNAS (2011). We view these as dislocations in the partially ordered peptidoglycan structure, activated by glycan strand extension machinery, and study theoretically the dynamics of these interacting defects on the surface of a cylinder. Generation and motion of these interacting defects lead to surprising effects arising from the cylindrical geometry, with important implications for growth. We also discuss how long range elastic interactions and turgor pressure affect the dynamics of the fraction of actively moving dislocations in the bacterial cell wall.

Ariel Amir; David R. Nelson

2012-05-07

54

Gradient microfluidics enables rapid bacterial growth inhibition testing.  

PubMed

Bacterial growth inhibition tests have become a standard measure of the adverse effects of inhibitors for a wide range of applications, such as toxicity testing in the medical and environmental sciences. However, conventional well-plate formats for these tests are laborious and provide limited information (often being restricted to an end-point assay). In this study, we have developed a microfluidic system that enables fast quantification of the effect of an inhibitor on bacteria growth and survival, within a single experiment. This format offers a unique combination of advantages, including long-term continuous flow culture, generation of concentration gradients, and single cell morphology tracking. Using Escherichia coli and the inhibitor amoxicillin as one model system, we show excellent agreement between an on-chip single cell-based assay and conventional methods to obtain quantitative measures of antibiotic inhibition (for example, minimum inhibition concentration). Furthermore, we show that our methods can provide additional information, over and above that of the standard well-plate assay, including kinetic information on growth inhibition and measurements of bacterial morphological dynamics over a wide range of inhibitor concentrations. Finally, using a second model system, we show that this chip-based systems does not require the bacteria to be labeled and is well suited for the study of naturally occurring species. We illustrate this using Nitrosomonas europaea, an environmentally important bacteria, and show that the chip system can lead to a significant reduction in the period required for growth and inhibition measurements (<4 days, compared to weeks in a culture flask). PMID:24548044

Li, Bing; Qiu, Yong; Glidle, Andrew; McIlvenna, David; Luo, Qian; Cooper, Jon; Shi, Han-Chang; Yin, Huabing

2014-03-18

55

Lactic acid bacterial extract as a biogenic mineral growth modifier  

NASA Astrophysics Data System (ADS)

The formation of minerals and mechanisms by which bacteria could control their formation in natural habitats is now of current interest for material scientists to have an insight of the mechanism of in vivo mineralization, as well as to seek industrial and technological applications. Crystalline uniform structures of calcium and barium minerals formed micron-sized building blocks when synthesized in the presence of an organic matrix consisting of secreted protein extracts from three different lactic acid bacteria (LAB) viz.: Lactobacillus plantarum MTCC 1325, Lactobacillus acidophilus NRRL B4495 and Pediococcus acidilactici CFR K7. LABs are not known to form organic matrix in biological materialization processes. The influence of these bacterial extracts on the crystallization behavior was investigated in details to test the basic coordination behavior of the acidic protein. In this report, varied architecture of the mineral crystals obtained in presence of high molecular weight protein extracts of three different LAB strains has been discussed. The role of native form of high molecular weight bacterial protein extracts in the generation of nucleation centers for crystal growth was clearly established. A model for the formation of organic matrix-cation complex and the subsequent events leading to crystal growth is proposed.

Borah, Ballav M.; Singh, Atul K.; Ramesh, Aiyagari; Das, Gopal

2009-04-01

56

Using Design-Based Latent Growth Curve Modeling with Cluster-Level Predictor to Address Dependency  

ERIC Educational Resources Information Center

The authors compared the effects of using the true Multilevel Latent Growth Curve Model (MLGCM) with single-level regular and design-based Latent Growth Curve Models (LGCM) with or without the higher-level predictor on various criterion variables for multilevel longitudinal data. They found that random effect estimates were biased when the

Wu, Jiun-Yu; Kwok, Oi-Man; Willson, Victor L.

2014-01-01

57

The Effects of Autocorrelation on the Curve-of-Factors Growth Model  

ERIC Educational Resources Information Center

This simulation study examined the performance of the curve-of-factors model (COFM) when autocorrelation and growth processes were present in the first-level factor structure. In addition to the standard curve-of factors growth model, 2 new models were examined: one COFM that included a first-order autoregressive autocorrelation parameter, and a

Murphy, Daniel L.; Beretvas, S. Natasha; Pituch, Keenan A.

2011-01-01

58

Modeling Pacing Behavior and Test Speededness Using Latent Growth Curve Models  

ERIC Educational Resources Information Center

This research explores the usefulness of latent growth curve modeling in the study of pacing behavior and test speededness. Examinee response times from a high-stakes, computerized examination, collected before and after the examination was subjected to a timing change, were analyzed using a series of latent growth curve models to detect

Kahraman, Nilufer; Cuddy, Monica M.; Clauser, Brian E.

2013-01-01

59

Latent growth curve modeling as an integrative approach to the analysis of change  

Microsoft Academic Search

Latent Growth Curve Models (LGCM) are discussed as a general data-analytic approach to the analysis of change. Conventional, but popular, methods of analyzing change over time, such as the paired t-test, repeated measures ANOVA, or MANOVA, have a tradition, which is quite different from the more recently developed latent growth curve models. While the former originated from the idea of

MANUEL C. VOELKLE

2007-01-01

60

Engineered cerium oxide nanoparticles: Effects on bacterial growth and viability  

SciTech Connect

Interest in engineered nanostructures has risen in recent years due to their use in energy conservation strategies and biomedicine. To ensure prudent development and use of nanomaterials, the fate and effects of such engineered structures on the environment should be understood. Interactions of nanomaterials with environmental microorganisms are inevitable, but the general consequences of such interactions remain unclear. Further, standardized methods for assessing such interactions are lacking. Therefore, we have initiated a multianalytical approach to understand the interactions of synthesized nanoparticles with bacterial systems. These efforts are focused initially on cerium oxide nanoparticles and model bacteria in order to evaluate characterization procedures and the possible fate of such materials in the environment. In this study the effects of cerium oxide nanoparticles on the growth and viability of Gram-negative Escherichia coli and Shewanella oneidensis, a metal-reducing bacteria, and Gram-positive Bacillus subtilis were examined relative to particle size, growth media, pH, and dosage. A hydrothermal based synthesis procedure was used to prepare cerium oxide nanoparticles of defined sizes in order to eliminate complications originating from the use of organic solvents and surfactants. Bactericidal effects were determined by minimum inhibitory concentration, colony forming units, disc diffusion tests and Live/Dead assays. In growth inhibition experiments involving E. coli and B. subtilis, a clear strain and size-dependent inhibition was observed. S. oneidensis appeared to be unaffected by the cerium oxide nanoparticles. Transmission electron microscopy along with microarray-based transcriptional profiling have been used to understand the response mechanism of the bacteria. The use of multiple analytical approaches adds confidence to toxicity assessments while the use of different bacterial systems highlights the potential wide-ranging effects of nanomaterial interactions in the environment.

Pelletier, Dale A [ORNL; Suresh, Anil K [ORNL; Holton, Gregory A [ORNL; McKeown, Catherine K [ORNL; Wang, Wei [ORNL; Gu, Baohua [ORNL; Mortensen, Ninell P [ORNL; Allison, David P [ORNL; Joy, David Charles [ORNL; Allison, Martin R [ORNL; Brown, Steven D [ORNL; Phelps, Tommy Joe [ORNL; Doktycz, Mitchel John [ORNL

2010-01-01

61

Effect of a metal alloy fuel catalyst on bacterial growth.  

PubMed

Many microorganisms have been demonstrated to utilize petroleum fuel products to fulfill their nutritional requirement for carbon. As a result, the ability of these microbes to degrade fuel has both a deleterious affect as well as beneficial applications. This study focused on the undesired ability of bacteria to grow on fuel and the potential for some metal alloys to inhibit this biodegradation. The objective of this study was to review the pattern of growth of two reference strains of petroleum-degrading bacteria, Pseudomonas oleovorans and Rhodococcus rhodocrous, in a specific hydrocarbon environment in the presence of a commercially available alloy. The alloy formulated and supplied by Advanced Power Systems International Inc. (APSI) is sold for fuel reformulation and other purposes. The components of the alloy used in the study were antimony, tin, lead, and mercury formulated as pellets. Surface characterization also showed the presence of tin oxide and lead amalgam phases. Hydrocarbon used for the study was primarily 87-octane gasoline. The growth of the bacteria in the water and mineral-supplemented gasoline mixture over 6-8 weeks was monitored by the viable plate count method. While an initial increase in bacteria occurred in the first week, overall bacterial growth was found to be suppressed in the presence of the alloy. Results also indicate that the alloy surface characteristics that convey the catalytic activity may also contribute to the observed antibacterial activity. PMID:16262333

Ghosh, Ruma; Koerting, Claudia; Suib, Steven L; Best, Michael H; Berlin, Alvin J

2005-11-01

62

Effects of Low-Level Deuterium Enrichment on Bacterial Growth  

PubMed Central

Using very precise (0.05%) measurements of the growth parameters for bacteria E. coli grown on minimal media, we aimed to determine the lowest deuterium concentration at which the adverse effects that are prominent at higher enrichments start to become noticeable. Such a threshold was found at 0.5% D, a surprisingly high value, while the ultralow deuterium concentrations (?0.25% D) showed signs of the opposite trend. Bacterial adaptation for 400 generations in isotopically different environment confirmed preference for ultralow (?0.25% D) enrichment. This effect appears to be similar to those described in sporadic but multiple earlier reports. Possible explanations include hormesis and isotopic resonance phenomena, with the latter explanation being favored. PMID:25033078

Xie, Xueshu; Zubarev, Roman A.

2014-01-01

63

Effects of low-level deuterium enrichment on bacterial growth.  

PubMed

Using very precise (0.05%) measurements of the growth parameters for bacteria E. coli grown on minimal media, we aimed to determine the lowest deuterium concentration at which the adverse effects that are prominent at higher enrichments start to become noticeable. Such a threshold was found at 0.5% D, a surprisingly high value, while the ultralow deuterium concentrations (?0.25% D) showed signs of the opposite trend. Bacterial adaptation for 400 generations in isotopically different environment confirmed preference for ultralow (?0.25% D) enrichment. This effect appears to be similar to those described in sporadic but multiple earlier reports. Possible explanations include hormesis and isotopic resonance phenomena, with the latter explanation being favored. PMID:25033078

Xie, Xueshu; Zubarev, Roman A

2014-01-01

64

A Multilevel Latent Growth Curve Approach to Predicting Student Proficiency  

ERIC Educational Resources Information Center

Value-added models and growth-based accountability aim to evaluate school's performance based on student growth in learning. The current focus is on linking the results from value-added models to the ones from growth-based accountability systems including Adequate Yearly Progress decisions mandated by No Child Left Behind. We present a new

Choi, Kilchan; Goldschmidt, Pete

2012-01-01

65

Bacterial Growth Phase Influences Methylmercury Production by the Sulfate-Reducing Bacterium Desulfovibrio desulfuricans ND132  

SciTech Connect

The effect of bacterial growth phase is an aspect of mercury (Hg) methylation that previous studies have not investigated in detail. Here we consider the effect of growth phase (mid-log, late-log and late stationary phase) on Hg methylation by the known methylator Desulfovibrio desulfuricans ND132. We tested the addition of Hg alone (chloride-complex), Hg with Suwannee River natural organic matter (SRNOM) (unequilibrated), and Hg equilibrated with SRNOM on monomethylmercury (MMHg) production by ND132 over a growth curve in pyruvate-fumarate media. This NOM did not affect MMHg production even under very low Hg:SRNOM ratios, where Hg binding is predicted to be dominated by high energy sites. Adding Hg or Hg-NOM to growing cultures 24h before sampling (late addition) resulted in {approx}2x greater net fraction of Hg methylated than for comparably aged cultures exposed to Hg from the initial culture inoculation (early addition). Mid- and late-log phase cultures produced similar amounts of MMHg, but late stationary phase cultures (both under early and late Hg addition conditions) produced up to {approx}3x more MMHg, indicating the potential importance of growth phase in studies of MMHg production.

Biswas, Abir [ORNL; Brooks, Scott C [ORNL; Miller, Carrie L [ORNL; Mosher, Jennifer J [ORNL; Yin, Xiangping Lisa [ORNL; Drake, Meghan M [ORNL

2011-01-01

66

Bacterial Growth Phase Influences Methylmercury Production by the Sulfate-Reducing Bacterium Desulfovibrio desulfuricans ND132  

SciTech Connect

The effect of bacterial growth phase is an aspect of mercury (Hg) methylation that previous studies have not investigated in detail. Here we consider the effect of growth phase (mid-log, late-log and late stationary phase) on Hg methylation by the known methylator Desulfovibrio desulfuricans ND132. We tested the addition of Hg alone (chloride-complex), Hg with Suwannee River natural organic matter (SRNOM) (unequilibrated), and Hg equilibrated with SRNOM on monomethylmercury (MMHg) production by ND132 over a growth curve in pyruvate fumarate media. This NOM did not affect MMHg production even under very low Hg: SRNOM ratios, where Hg binding is predicted to be dominated by high energy sites. Adding Hg or Hg NOM to growing cultures 24 h before sampling (late addition) resulted in ~2 greater net fraction of Hg methylated than for comparably aged cultures exposed to Hg from the initial culture inoculation (early addition). Mid-and late-log phase cultures produced similar amounts of MMHg, but late stationary phase cultures (both under early and late Hg addition conditions) produced up to ~3 more MMHg, indicating the potential importance of growth phase in studies of MMHg production.

Biswas, Abir [ORNL; Brooks, Scott C [ORNL; Miller, Carrie L [ORNL; Mosher, Jennifer J [ORNL; Yin, Xiangping Lisa [ORNL; Drake, Meghan M [ORNL

2011-01-01

67

Effects of grain growth on the interstellar polarization curve  

NASA Astrophysics Data System (ADS)

We apply the time evolution of grain size distributions through accretion and coagulation found in our previous work to the modelling of the wavelength dependence of interstellar linear polarization. We focus in particular on the parameters of the Serkowski curve K and ?max , characterizing the width and maximum wavelength of this curve, respectively. We use aligned silicate and non-aligned carbonaceous spheroidal particles with different aspect ratios a/b. The imperfect alignment of grains with sizes larger than a cut-off size rV, cut is considered. We find that the evolutionary effects on the polarization curve are negligible in the original model with commonly used material parameters (hydrogen number density nH = 103 cm-3, gas temperature Tgas = 10 K and sticking probability for accretion Sacc = 0.3). Therefore, we apply the tuned model, where the coagulation threshold of silicate is removed. In this model, ?max displaces to longer wavelengths and the polarization curve becomes wider (K reduces) on time-scales (30-50)(nH/103cm-3)-1 Myr. The tuned models at T ? 30 (n_H/10^3 cm^{-3})^{-1} Myr and different values of the parameters rV, cut can also explain the observed trend between K and ?max . It is significant that the evolutionary effect appears in the perpendicular direction to the effect of rV, cut on the K - ?max diagram. Very narrow polarization curves can be reproduced if we change the type of particles (prolate/oblate) and/or vary a/b.

Voshchinnikov, Nikolai V.; Hirashita, Hiroyuki

2014-11-01

68

An Approach of Estimating Individual Growth Curves for Young Thoroughbred Horses Based on Their Birthdays  

PubMed Central

ABSTRACT We propose an approach of estimating individual growth curves based on the birthday information of Japanese Thoroughbred horses, with considerations of the seasonal compensatory growth that is a typical characteristic of seasonal breeding animals. The compensatory growth patterns appear during only the winter and spring seasons in the life of growing horses, and the meeting point between winter and spring depends on the birthday of each horse. We previously developed new growth curve equations for Japanese Thoroughbreds adjusting for compensatory growth. Based on the equations, a parameter denoting the birthday information was added for the modeling of the individual growth curves for each horse by shifting the meeting points in the compensatory growth periods. A total of 5,594 and 5,680 body weight and age measurements of Thoroughbred colts and fillies, respectively, and 3,770 withers height and age measurements of both sexes were used in the analyses. The results of predicted error difference and Akaike Information Criterion showed that the individual growth curves using birthday information better fit to the body weight and withers height data than not using them. The individual growth curve for each horse would be a useful tool for the feeding managements of young Japanese Thoroughbreds in compensatory growth periods. PMID:25013356

ONODA, Tomoaki; YAMAMOTO, Ryuta; SAWAMURA, Kyohei; MURASE, Harutaka; NAMBO, Yasuo; INOUE, Yoshinobu; MATSUI, Akira; MIYAKE, Takeshi; HIRAI, Nobuhiro

2014-01-01

69

Effects of grain growth on the interstellar polarization curve  

E-print Network

We apply the time evolution of grain size distributions by accretion and coagulation found in our previous work to the modelling of the wavelength dependence of interstellar linear polarization. We especially focus on the parameters of the Serkowski curve $K$ and $\\lambda_{\\max}$ characterizing the width and the maximum wavelength of this curve, respectively. We use aligned silicate and non-aligned carbonaceous spheroidal particles with different aspect ratios $a/b$. The imperfect alignment of grains with sizes larger than a cut-off size $r_{V,\\rm cut}$ is considered. We find that the evolutionary effects on the polarization curve are negligible in the original model with commonly used material parameters (hydrogen number density $n_\\mathrm{H}=10^3$ cm$^{-3}$, gas temperature $T_\\mathrm{gas}=10$~K, and the sticking probability for accretion $S_\\mathrm{acc}=0.3$). Therefore, we apply the tuned model where the coagulation threshold of silicate is removed. In this model, $\\lambda_{\\max}$ displaces to the longer ...

Voshchinnikov, Nikolai V

2014-01-01

70

Predicting Marine Phytoplankton Maximum Growth Rates from Temperature: Improving on the Eppley Curve Using Quantile Regression  

Microsoft Academic Search

The Eppley curve describes an exponential function that defines the maximum attainable daily growth rate of marine phytoplankton as a function of temperature. The curve was originally fitted by eye as the upper envelope of a data set, and despite its wide use, the reliability of this function has not been statistically tested. Our analysis of the data using quantile

Jan E. Bissinger; David J. S. Montagnes; Jonathan Sharples; David Atkinson

2008-01-01

71

Predictions of J-R Curves with Large Crack Growth from Small Specimen Data.  

National Technical Information Service (NTIS)

The report examines the practice of extrapolating small-specimen J-resistance curves for use in predictive analyses of large crack growth in nuclear pipes prior to instability. The study involved a combined experimental and analytical effort. The experime...

V. Papaspyropoulos, C. Marschall, M. Landow

1986-01-01

72

Understanding the Scalability of Bayesian Network Inference Using Clique Tree Growth Curves  

NASA Technical Reports Server (NTRS)

One of the main approaches to performing computation in Bayesian networks (BNs) is clique tree clustering and propagation. The clique tree approach consists of propagation in a clique tree compiled from a Bayesian network, and while it was introduced in the 1980s, there is still a lack of understanding of how clique tree computation time depends on variations in BN size and structure. In this article, we improve this understanding by developing an approach to characterizing clique tree growth as a function of parameters that can be computed in polynomial time from BNs, specifically: (i) the ratio of the number of a BN s non-root nodes to the number of root nodes, and (ii) the expected number of moral edges in their moral graphs. Analytically, we partition the set of cliques in a clique tree into different sets, and introduce a growth curve for the total size of each set. For the special case of bipartite BNs, there are two sets and two growth curves, a mixed clique growth curve and a root clique growth curve. In experiments, where random bipartite BNs generated using the BPART algorithm are studied, we systematically increase the out-degree of the root nodes in bipartite Bayesian networks, by increasing the number of leaf nodes. Surprisingly, root clique growth is well-approximated by Gompertz growth curves, an S-shaped family of curves that has previously been used to describe growth processes in biology, medicine, and neuroscience. We believe that this research improves the understanding of the scaling behavior of clique tree clustering for a certain class of Bayesian networks; presents an aid for trade-off studies of clique tree clustering using growth curves; and ultimately provides a foundation for benchmarking and developing improved BN inference and machine learning algorithms.

Mengshoel, Ole J.

2010-01-01

73

Fructose-enhanced reduction of bacterial growth on nanorough surfaces  

PubMed Central

Patients on mechanical ventilators for extended periods of time often face the risk of developing ventilator-associated pneumonia. During the ventilation process, patients incapable of breathing are intubated with polyvinyl chloride (PVC) endotracheal tubes (ETTs). PVC ETTs provide surfaces where bacteria can attach and proliferate from the contaminated oropharyngeal space to the sterile bronchoalveolar area. To overcome this problem, ETTs can be coated with antimicrobial agents. However, such coatings may easily delaminate during use. Recently, it has been shown that changes in material topography at the nanometer level can provide antibacterial properties. In addition, some metabolites, such as fructose, have been found to increase the efficiency of antibiotics used to treat Staphylococcus aureus (S. aureus) infections. In this study, we combined the antibacterial effect of nanorough ETT topographies with sugar metabolites to decrease bacterial growth and biofilm formation on ETTs. We present for the first time that the presence of fructose on the nanorough surfaces decreases the number of planktonic S. aureus bacteria in the solution and biofilm formation on the surface after 24 hours. We thus envision that this method has the potential to impact the future of surface engineering of biomaterials leading to more successful clinical outcomes in terms of longer ETT lifetimes, minimized infections, and decreased antibiotic usage; all of which can decrease the presence of antibiotic resistant bacteria in the clinical setting. PMID:22334783

Durmus, Naside Gozde; Taylor, Erik N; Inci, Fatih; Kummer, Kim M; Tarquinio, Keiko M; Webster, Thomas J

2012-01-01

74

Bacterial growth on chitosan-coated polypropylene textile.  

PubMed

Biofouling is a problem common in all systems where microorganisms and aqueous environment meet. Prevention of biofouling is therefore important in many industrial processes. The aim of this study was to develop a method to evaluate the ability of material coating to inhibit biofilm formation. Chitosan-coated polypropylene nonwoven textile was prepared using dielectric barrier discharge plasma activation. Resistance of the textile to biofouling was then tested. First, the textile was submerged into a growth medium inoculated with green fluorescein protein labelled Pseudomonas aeruginosa. After overnight incubation at 33C, the textile was observed using confocal laser scanning microscopy for bacterial enumeration and biofilm structure characterisation. In the second stage, the textile was used as a filter medium for prefiltered river water, and the pressure development on the in-flow side was measured to quantify the overall level of biofouling. In both cases, nontreated textile samples were used as a control. The results indicate that the chitosan coating exhibits antibacterial properties. The developed method is applicable for the evaluation of the ability to inhibit biofilm formation. PMID:23724330

Erben, D; Hola, V; Jaros, J; Rahel, J

2012-01-01

75

Bacterial Growth on Chitosan-Coated Polypropylene Textile  

PubMed Central

Biofouling is a problem common in all systems where microorganisms and aqueous environment meet. Prevention of biofouling is therefore important in many industrial processes. The aim of this study was to develop a method to evaluate the ability of material coating to inhibit biofilm formation. Chitosan-coated polypropylene nonwoven textile was prepared using dielectric barrier discharge plasma activation. Resistance of the textile to biofouling was then tested. First, the textile was submerged into a growth medium inoculated with green fluorescein protein labelled Pseudomonas aeruginosa. After overnight incubation at 33C, the textile was observed using confocal laser scanning microscopy for bacterial enumeration and biofilm structure characterisation. In the second stage, the textile was used as a filter medium for prefiltered river water, and the pressure development on the in-flow side was measured to quantify the overall level of biofouling. In both cases, nontreated textile samples were used as a control. The results indicate that the chitosan coating exhibits antibacterial properties. The developed method is applicable for the evaluation of the ability to inhibit biofilm formation. PMID:23724330

Erben, D.; Hola, V.; Jaros, J.; Rahel, J.

2012-01-01

76

Parent Involvement and Science Achievement: A Cross-Classified Multilevel Latent Growth Curve Analysis  

ERIC Educational Resources Information Center

The authors examined science achievement growth at Grades 3, 5, and 8 and parent school involvement at the same time points using the Early Childhood Longitudinal Study-Kindergarten Class of 1998-1999. Data were analyzed using cross-classified multilevel latent growth curve modeling with time invariant and varying covariates. School-based

Johnson, Ursula Y.; Hull, Darrell M.

2014-01-01

77

Including Time-Invariant Covariates in the Latent Growth Curve Model  

ERIC Educational Resources Information Center

Within the latent growth curve model, time-invariant covariates are generally modeled on the subject level, thereby estimating the effect of the covariate on the latent growth parameters. Incorporating the time-invariant covariate in this manner may have some advantages regarding the interpretation of the effect but may also be incorrect in

Stoel, Reinoud D.; van den Wittenboer, Godfried; Hox, Joop

2004-01-01

78

Exploring Gains in Reading and Mathematics Achievement among Regular and Exceptional Students Using Growth Curve Modeling  

ERIC Educational Resources Information Center

Using four-wave longitudinal reading and mathematics data (4th to 7th grades) from a large urban school district, growth curve modeling was used as a tool for examining three research questions: Are achievement gaps closing in reading and mathematics? What are the associations between prior-achievement and growth across the reading and mathematics

Shin, Tacksoo; Davison, Mark L.; Long, Jeffrey D.; Chan, Chi-Keung; Heistad, David

2013-01-01

79

Heterotrophic Bacterial Growth Efficiency and Community Structure at Different Natural Organic Carbon Concentrations  

PubMed Central

Batch cultures of aquatic bacteria and dissolved organic matter were used to examine the impact of carbon source concentration on bacterial growth, biomass, growth efficiency, and community composition. An aged concentrate of dissolved organic matter from a humic lake was diluted with organic compound-free artificial lake water to obtain concentrations of dissolved organic carbon (DOC) ranging from 0.04 to 2.53 mM. The bacterial biomass produced in the cultures increased linearly with the DOC concentration, indicating that bacterial biomass production was limited by the supply of carbon. The bacterial growth rate in the exponential growth phase exhibited a hyperbolic response to the DOC concentration, suggesting that the maximum growth rate was constrained by the substrate concentration at low DOC concentrations. Likewise, the bacterial growth efficiency calculated from the production of biomass and CO2 increased asymptotically from 0.4 to 10.4% with increasing DOC concentration. The compositions of the microbial communities that emerged in the cultures were assessed by separation of PCR-amplified 16S rRNA fragments by denaturing gradient gel electrophoresis. Nonmetric multidimensional scaling of the gel profiles showed that there was a gradual change in the community composition along the DOC gradient; members of the ? subclass of the class Proteobacteria and members of the Cytophaga-Flavobacterium group were well represented at all concentrations, whereas members of the ? subclass of the Proteobacteria were found exclusively at the lowest carbon concentration. The shift in community composition along the DOC gradient was similar to the patterns of growth efficiency and growth rate. The results suggest that the bacterial growth efficiencies, the rates of bacterial growth, and the compositions of bacterial communities are not constrained by substrate concentrations in most natural waters, with the possible exception of the most oligotrophic environments. PMID:12839735

Eiler, Alexander; Langenheder, Silke; Bertilsson, Stefan; Tranvik, Lars J.

2003-01-01

80

The Papain Inhibitor (SPI) of Streptomyces mobaraensis Inhibits Bacterial Cysteine Proteases and Is an Antagonist of Bacterial Growth  

PubMed Central

A novel papain inhibitory protein (SPI) from Streptomyces mobaraensis was studied to measure its inhibitory effect on bacterial cysteine protease activity (Staphylococcus aureus SspB) and culture supernatants (Porphyromonas gingivalis, Bacillus anthracis). Further, growth of Bacillus anthracis, Staphylococcus aureus, Pseudomonas aeruginosa, and Vibrio cholerae was completely inhibited by 10 ?M SPI. At this concentration of SPI, no cytotoxicity was observed. We conclude that SPI inhibits bacterial virulence factors and has the potential to become a novel therapeutic treatment against a range of unrelated pathogenic bacteria. PMID:23587952

Zindel, Stephan; Kaman, Wendy E.; Frols, Sabrina; Pfeifer, Felicitas; Peters, Anna; Hays, John P.

2013-01-01

81

Growth curve analysis of tumourigenesis using cellular level cancer model.  

PubMed

It is known that carcinogenesis by low-dose radiation will start from DNA damage by ionising radiation. After the long time period, these very small effects will appear on a cellular scale by accumulation of various intracellular biological responses and finally grow to the tumour with clonal expansion of cancer cell. Thus, the biological radiation effects are phenomena with a very wide scale from DNA damage (10(-9) m, 10(-6) s) to the tumour (10(-3) m, 10(5) s); so the risk estimation of low-dose radiation is difficult to study by the experiments. To overcome these difficult situations at low-dose radiation effects' problems, it is good to study the process of carcinogenesis using a biologically based mathematical model. This study's cellular-scale mathematical model of tumourigenesis and some results of the statistical calculations about the tumour growth as presented in the work. PMID:21156785

Ouchi, N B

2011-02-01

82

Body temperatures in dinosaurs: what can growth curves tell us?  

PubMed

To estimate the body temperature (BT) of seven dinosaurs Gillooly, Alleen, and Charnov (2006) used an equation that predicts BT from the body mass and maximum growth rate (MGR) with the latter preserved in ontogenetic growth trajectories (BT-equation). The results of these authors evidence inertial homeothermy in Dinosauria and suggest that, due to overheating, the maximum body size in Dinosauria was ultimately limited by BT. In this paper, I revisit this hypothesis of Gillooly, Alleen, and Charnov (2006). I first studied whether BTs derived from the BT-equation of today's crocodiles, birds and mammals are consistent with core temperatures of animals. Second, I applied the BT-equation to a larger number of dinosaurs than Gillooly, Alleen, and Charnov (2006) did. In particular, I estimated BT of Archaeopteryx (from two MGRs), ornithischians (two), theropods (three), prosauropods (three), and sauropods (nine). For extant species, the BT value estimated from the BT-equation was a poor estimate of an animal's core temperature. For birds, BT was always strongly overestimated and for crocodiles underestimated; for mammals the accuracy of BT was moderate. I argue that taxon-specific differences in the scaling of MGR (intercept and exponent of the regression line, log-log-transformed) and in the parameterization of the Arrhenius model both used in the BT-equation as well as ecological and evolutionary adaptations of species cause these inaccuracies. Irrespective of the found inaccuracy of BTs estimated from the BT-equation and contrary to the results of Gillooly, Alleen, and Charnov (2006) I found no increase in BT with increasing body mass across all dinosaurs (Sauropodomorpha, Sauropoda) studied. This observation questions that, due to overheating, the maximum size in Dinosauria was ultimately limited by BT. However, the general high inaccuracy of dinosaurian BTs derived from the BT-equation makes a reliable test of whether body size in dinosaurs was ultimately limited by overheating impossible. PMID:24204568

Griebeler, Eva Maria

2013-01-01

83

Body Temperatures in Dinosaurs: What Can Growth Curves Tell Us?  

PubMed Central

To estimate the body temperature (BT) of seven dinosaurs Gillooly, Alleen, and Charnov (2006) used an equation that predicts BT from the body mass and maximum growth rate (MGR) with the latter preserved in ontogenetic growth trajectories (BT-equation). The results of these authors evidence inertial homeothermy in Dinosauria and suggest that, due to overheating, the maximum body size in Dinosauria was ultimately limited by BT. In this paper, I revisit this hypothesis of Gillooly, Alleen, and Charnov (2006). I first studied whether BTs derived from the BT-equation of todays crocodiles, birds and mammals are consistent with core temperatures of animals. Second, I applied the BT-equation to a larger number of dinosaurs than Gillooly, Alleen, and Charnov (2006) did. In particular, I estimated BT of Archaeopteryx (from two MGRs), ornithischians (two), theropods (three), prosauropods (three), and sauropods (nine). For extant species, the BT value estimated from the BT-equation was a poor estimate of an animals core temperature. For birds, BT was always strongly overestimated and for crocodiles underestimated; for mammals the accuracy of BT was moderate. I argue that taxon-specific differences in the scaling of MGR (intercept and exponent of the regression line, log-log-transformed) and in the parameterization of the Arrhenius model both used in the BT-equation as well as ecological and evolutionary adaptations of species cause these inaccuracies. Irrespective of the found inaccuracy of BTs estimated from the BT-equation and contrary to the results of Gillooly, Alleen, and Charnov (2006) I found no increase in BT with increasing body mass across all dinosaurs (Sauropodomorpha, Sauropoda) studied. This observation questions that, due to overheating, the maximum size in Dinosauria was ultimately limited by BT. However, the general high inaccuracy of dinosaurian BTs derived from the BT-equation makes a reliable test of whether body size in dinosaurs was ultimately limited by overheating impossible. PMID:24204568

Griebeler, Eva Maria

2013-01-01

84

Bacterial Activity and Bacterioplankton Diversity in the Eutrophic River WarnowDirect Measurement of Bacterial Growth Efficiency and Its Effect on Carbon Utilization  

Microsoft Academic Search

The influence of bacterial activity and diversity on bacterial growth efficiency was investigated in a flatland river. Eutrophic\\u000a River Warnow drains predominantly agricultural land and is heavily loaded with nutrients, dissolved and particulate organic\\u000a matter (DOM and POM), especially humic substances. Although the water column bacterial community consists of many inactive\\u000a or damaged cells, bacterioplankton sustained a high bacterial secondary

Mareike Warkentin; Heike M. Freese; Rhena Schumann

2011-01-01

85

Effect of Vibration on Bacterial Growth and Antibiotic Resistance  

NASA Technical Reports Server (NTRS)

The purpose of this research grant was to provide a fundamental, systematic investigation of the effects of oscillatory acceleration on bacterial proliferation and their responses to antibiotics in a liquid medium.

Juergensmeyer, Elizabeth A.; Juergensmeyer, Margaret A.

2004-01-01

86

PEROXOTITANATE- AND MONOSODIUM METAL-TITANATE COMPOUNDS AS INHIBITORS OF BACTERIAL GROWTH  

SciTech Connect

Sodium titanates are ion-exchange materials that effectively bind a variety of metal ions over a wide pH range. Sodium titanates alone have no known adverse biological effects but metal-exchanged titanates (or metal titanates) can deliver metal ions to mammalian cells to alter cell processes in vitro. In this work, we test a hypothesis that metal-titanate compounds inhibit bacterial growth; demonstration of this principle is one prerequisite to developing metal-based, titanate-delivered antibacterial agents. Focusing initially on oral diseases, we exposed five species of oral bacteria to titanates for 24 h, with or without loading of Au(III), Pd(II), Pt(II), and Pt(IV), and measuring bacterial growth in planktonic assays through increases in optical density. In each experiment, bacterial growth was compared with control cultures of titanates or bacteria alone. We observed no suppression of bacterial growth by the sodium titanates alone, but significant (p < 0.05, two-sided t-tests) suppression was observed with metal-titanate compounds, particularly Au(III)-titanates, but with other metal titanates as well. Growth inhibition ranged from 15 to 100% depending on the metal ion and bacterial species involved. Furthermore, in specific cases, the titanates inhibited bacterial growth 5- to 375-fold versus metal ions alone, suggesting that titanates enhanced metal-bacteria interactions. This work supports further development of metal titanates as a novel class of antibacterials.

Hobbs, D.

2011-01-19

87

The combination of different carbon sources enhances bacterial growth efficiency in aquatic ecosystems.  

PubMed

The dissolved organic carbon (DOC) pool is composed of several organic carbon compounds from different carbon sources. Each of these sources may support different bacterial growth rates, but few studies have specifically analyzed the effects of the combination of different carbon sources on bacterial metabolism. In this study, we evaluated the response of several metabolic parameters, including bacterial biomass production (BP), bacterial respiration (BR), bacterial growth efficiency (BGE), and bacterial community structure, on the presence of three DOC sources alone and in combination. We hypothesized that the mixture of different DOC sources would increase the efficiency of carbon use by bacteria (BGE). We established a full-factorial substitutive design (seven treatments) in which the effects of the number and identity of DOC sources on bacterial metabolism were evaluated. We calculated the expected metabolic rates of the combined DOC treatments based on the single-DOC treatments and observed a positive interaction on BP, a negative interaction on BR, and, consequently, a positive interaction on BGE for the combinations. The bacterial community composition appeared to have a minor impact on differences in bacterial metabolism among the treatments. Our data indicate that mixtures of DOC sources result in a more efficient biological use of carbon. This study provides strong evidence that the mixture of different DOC sources is a key factor affecting the role of bacteria in the carbon flux of aquatic ecosystems. PMID:23963223

Fonte, Ellen S; Amado, Andr M; Meirelles-Pereira, Frederico; Esteves, Francisco A; Rosado, Alexandre S; Farjalla, Vinicius F

2013-11-01

88

Fast and accurate generation of the curve of growth for the Voigt lineshape  

NASA Astrophysics Data System (ADS)

A set of relatively simple analytical expressions is given for the rapid computation of the curve growth of a spectral line over the whole range of damping-constant or mixing-parameter values. The computed equivalent width of a pure Gaussian (Doppler broadened) or pure Lorentz (naturally plus collisionally broadened) line-shape is accurate within 1 percent while, for the mixed Voigt lineshape, it is generally accurate within 1 percent, with a maximum of about 5 percent in some narrow regions of the curve of growth.

Vardavas, Ilias M.

1993-02-01

89

Changes in the Bacterial Community of Soybean Rhizospheres during Growth in the Field  

PubMed Central

Highly diverse communities of bacteria inhabiting soybean rhizospheres play pivotal roles in plant growth and crop production; however, little is known about the changes that occur in these communities during growth. We used both culture-dependent physiological profiling and culture independent DNA-based approaches to characterize the bacterial communities of the soybean rhizosphere during growth in the field. The physiological properties of the bacterial communities were analyzed by a community-level substrate utilization assay with BioLog Eco plates, and the composition of the communities was assessed by gene pyrosequencing. Higher metabolic capabilities were found in rhizosphere soil than in bulk soil during all stages of the BioLog assay. Pyrosequencing analysis revealed that differences between the bacterial communities of rhizosphere and bulk soils at the phylum level; i.e., Proteobacteria were increased, while Acidobacteria and Firmicutes were decreased in rhizosphere soil during growth. Analysis of operational taxonomic units showed that the bacterial communities of the rhizosphere changed significantly during growth, with a higher abundance of potential plant growth promoting rhizobacteria, including Bacillus, Bradyrhizobium, and Rhizobium, in a stage-specific manner. These findings demonstrated that rhizosphere bacterial communities were changed during soybean growth in the field. PMID:24955843

Sugiyama, Akifumi; Ueda, Yoshikatsu; Zushi, Takahiro; Takase, Hisabumi; Yazaki, Kazufumi

2014-01-01

90

Changes in the bacterial community of soybean rhizospheres during growth in the field.  

PubMed

Highly diverse communities of bacteria inhabiting soybean rhizospheres play pivotal roles in plant growth and crop production; however, little is known about the changes that occur in these communities during growth. We used both culture-dependent physiological profiling and culture independent DNA-based approaches to characterize the bacterial communities of the soybean rhizosphere during growth in the field. The physiological properties of the bacterial communities were analyzed by a community-level substrate utilization assay with BioLog Eco plates, and the composition of the communities was assessed by gene pyrosequencing. Higher metabolic capabilities were found in rhizosphere soil than in bulk soil during all stages of the BioLog assay. Pyrosequencing analysis revealed that differences between the bacterial communities of rhizosphere and bulk soils at the phylum level; i.e., Proteobacteria were increased, while Acidobacteria and Firmicutes were decreased in rhizosphere soil during growth. Analysis of operational taxonomic units showed that the bacterial communities of the rhizosphere changed significantly during growth, with a higher abundance of potential plant growth promoting rhizobacteria, including Bacillus, Bradyrhizobium, and Rhizobium, in a stage-specific manner. These findings demonstrated that rhizosphere bacterial communities were changed during soybean growth in the field. PMID:24955843

Sugiyama, Akifumi; Ueda, Yoshikatsu; Zushi, Takahiro; Takase, Hisabumi; Yazaki, Kazufumi

2014-01-01

91

Cooperative Bacterial Growth Dynamics Predict the Evolution of Antibiotic Resistance  

Microsoft Academic Search

Since the discovery of penicillin, antibiotics have been our primary weapon against bacterial infections. Unfortunately, bacteria can gain resistance to penicillin by acquiring the gene that encodes beta-lactamase, which inactivates the antibiotic. However, mutations in this gene are necessary to degrade the modern antibiotic cefotaxime. Understanding the conditions that favor the spread of these mutations is a challenge. Here we

Tatiana Artemova; Ylaine Gerardin; Sophia Hsin-Jung Li; Jeff Gore

2011-01-01

92

Growth of Thiobacillus ferrooxidans: a Novel Experimental Design for Batch Growth and Bacterial Leaching Studies.  

PubMed

The concentrations of ferrous and ferric ions change dramatically during the course of the batch experiments usually performed to study the kinetics of the bacterial oxidation of ferrous ions and sulfide minerals. This change in concentration of the iron species during the course of the experiment often makes it difficult to interpret the results of these experiments, as is evidenced by the lack of consensus concerning the mechanism of bacterial leaching. If the concentrations of ferrous and ferric ions were constant throughout the course of the batch experiment, then the role of the bacteria could be easily established, because the rate of the chemical leaching should be the same at a given redox potential in the presence and in the absence of bacteria. In this paper we report an experiment designed to obtain kinetic data under these conditions. The redox potential is used as a measure of the concentrations of ferrous and ferric ions, and the redox potential of the leaching solution is controlled throughout the experiment by electrolysis. The effects of ferrous, ferric, and arsenite ions on the rate of growth of Thiobacillus ferrooxidans on ferrous ions in this redox-controlled reactor are presented. In addition, the growth of this bacterium on ferrous ions in batch culture was also determined, and it is shown that the parameters obtained from the batch culture and the redox-controlled batch culture are the same. An analysis of the results from the batch culture indicates that the initial number of bacteria that are adapted to the solution depends on the concentrations of ferrous and arsenite ions. PMID:16535639

Harvey, P I; Crundwell, F K

1997-07-01

93

The Performance of Multilevel Growth Curve Models under an Autoregressive Moving Average Process  

ERIC Educational Resources Information Center

The authors examined the robustness of multilevel linear growth curve modeling to misspecification of an autoregressive moving average process. As previous research has shown (J. Ferron, R. Dailey, & Q. Yi, 2002; O. Kwok, S. G. West, & S. B. Green, 2007; S. Sivo, X. Fan, & L. Witta, 2005), estimates of the fixed effects were unbiased, and Type I

Murphy, Daniel L.; Pituch, Keenan A.

2009-01-01

94

Sample Sizes for Two-Group Second-Order Latent Growth Curve Models  

ERIC Educational Resources Information Center

Second-order latent growth curve models (S. C. Duncan & Duncan, 1996; McArdle, 1988) can be used to study group differences in change in latent constructs. We give exact formulas for the covariance matrix of the parameter estimates and an algebraic expression for the estimation of slope differences. Formulas for calculations of the required sample

Wanstrom, Linda

2009-01-01

95

Heterogeneous nucleation and crystal growth on curved surfaces observed by real-space imaging.  

PubMed

We present a real-space imaging study of homogeneous and heterogeneous crystal nucleation and growth in colloidal suspensions of slightly charged and polydisperse particles. Heterogeneous crystallization is observed close to curved surfaces with radii of curvature, R, in the range from 4 to 40 particle diameters, d. Close to a curved surface, we find crystal nucleation and growth to be suppressed for R approximately < 10d. For R approximately > 15d, fast crystal growth is observed similar to that on a flat wall (R = ?). We use the purely topological method of shortest path rings to determine the orientation of the crystal on the length scale of the nearest neighbor distance. Crystal nuclei forming close to a curved surface are oriented analogous to crystal growth on a flat wall with hexagonal planes parallel to the wall. While the smallest nuclei appear to be unaffected by the surface, larger nuclei are found to be suppressed for radii of curvature R approximately < 10d. The critical nucleus size in the vicinity of a curved surface is found to be about the same as for homogeneous nucleation. PMID:23963437

Ziese, F; Maret, G; Gasser, U

2013-09-18

96

A Latent Growth Curve Analysis of Reading Achievement for an At-Risk Population  

ERIC Educational Resources Information Center

The development of reading skills from age seven until age 19 was investigated for children who were referred for special education preschool intervention using latent growth curve analysis (n=206). Approximately one-third of the study sample did not require special education services after preschool, providing a natural comparison group. Reading

Beecher, Constance C.

2011-01-01

97

Aptitude-Treatment Interaction Effects on Explicit Rule Learning: A Latent Growth Curve Analysis  

ERIC Educational Resources Information Center

Finding the match between individuals and educational treatments is the aim of both educators and the aptitude-treatment interaction research paradigm. Using the latent growth curve analysis, the present study investigates the interaction between the type of explicit instructional approaches (deductive vs. explicit-inductive) and the level of

Hwu, Fenfang; Pan, Wei; Sun, Shuyan

2014-01-01

98

INFLUENTIAL OBSERVATION IDENTIFICATION IN THE GROWTH CURVE MODEL WITH RAO'S SIMPLE COVARIANCE STRUCTURE  

Microsoft Academic Search

In this paper we discuss the identification of influential observations in a growth curve model with Rao's simple covariance structure. Based on the generalized Cook-type distance and the volume of a confidence ellipsoid, a variety of influence measures are proposed in terms of the case-deletion technique. Also, the influence of observations on a linear combination of regression coefficients is considered.

Jian-Xin Pan

2002-01-01

99

Investigation of Mediational Processes Using Parallel Process Latent Growth Curve Modeling.  

ERIC Educational Resources Information Center

Investigated a method to evaluate mediational processes using latent growth curve modeling and tested it with empirical data from a longitudinal steroid use prevention program focusing on 1,506 high school football players over 4 years. Findings suggest the usefulness of the approach. (SLD)

Cheong, JeeWon; MacKinnon, David P.; Khoo, Siek Toon

2003-01-01

100

Bacterial volatiles promote growth in Arabidopsis Choong-Min Ryu*, Mohamed A. Farag  

E-print Network

Bacterial volatiles promote growth in Arabidopsis Choong-Min Ryu*, Mohamed A. Farag , Chia-Hui Hu of agricultural species for the purposes of growth enhance- ment, including increased seed emergence, plant weight when seeds were coated with PGPR before planting (1), and plant weight of tuber-treated potatoes

Paré, Paul W.

101

Alcohol, intestinal bacterial growth, intestinal permeability to endotoxin, and medical consequences: Summary of a symposium  

Microsoft Academic Search

This report is a summary of the symposium on Alcohol, Intestinal Bacterial Growth, Intestinal Permeability to Endotoxin, and Medical Consequences, organized by National Institute on Alcohol Abuse and Alcoholism, Office of Dietary Supplements, and National Institute of Diabetes and Digestive and Kidney Diseases of National Institutes of Health in Rockville, Maryland, October 11, 2006. Alcohol exposure can promote the growth

Vishnudutt Purohit; J. Christian Bode; Christiane Bode; David A. Brenner; Mashkoor A. Choudhry; Frank Hamilton; Y. James Kang; Ali Keshavarzian; Radhakrishna Rao; R. Balfour Sartor; Christine Swanson; Jerrold R. Turner

2008-01-01

102

Comparison of temperature effects on soil respiration and bacterial and fungal growth rates  

Microsoft Academic Search

Temperature is an important factor regulating microbial activity and shaping the soil microbial community. Little is known, however, on how temperature affects the most important groups of the soil microorganisms, the bacteria and the fungi, in situ. We have therefore measured the instantaneous total activity (respiration rate), bacterial activity (growth rate as thymidine incorporation rate) and fungal activity (growth rate

Janna Pietikinen; Marie Pettersson; Erland Bth

2005-01-01

103

Differentiation of bacterial colonies and temporal growth patterns using hyperspectral imaging  

NASA Astrophysics Data System (ADS)

Detection and identification of bacteria are important for health and safety. Hyperspectral imaging offers the potential to capture unique spectral patterns and spatial information from bacteria which can then be used to detect and differentiate bacterial species. Here, hyperspectral imaging has been used to characterize different bacterial colonies and investigate their growth over time. Six bacterial species (Pseudomonas fluorescens, Escherichia coli, Serratia marcescens, Salmonella enterica, Staphylococcus aureus, Enterobacter aerogenes) were grown on tryptic soy agar plates. Hyperspectral data were acquired immediately after, 24 hours after, and 96 hours after incubation. Spectral signatures from bacterial colonies demonstrated repeatable measurements for five out of six species. Spatial variations as well as changes in spectral signatures were observed across temporal measurements within and among species at multiple wavelengths due to strengthening or weakening reflectance signals from growing bacterial colonies based on their pigmentation. Between-class differences and within-class similarities were the most prominent in hyperspectral data collected 96 hours after incubation.

Mehrbeoglu, Mehrube; Buck, Gregory W.; Livingston, Daniel W.

2014-09-01

104

Blue light (470nm) effectively inhibits bacterial and fungal growth.  

PubMed

Blue light (470nm) LED antimicrobial properties were studied alone against bacteria and with or without the food grade photosensitizer, erythrosine (ERY) against filamentous fungi. Leuconostoc mesenteroides (LM), Bacillus atrophaeus (BA) or Pseudomonas aeruginosa (PA) aliquots were exposed on nutrient agar plates to Array 1 (AR1, 02mWcm(-2) ) or Array 2 (AR2, 80mWcm(-2) ), which emitted impure or pure blue light (0-300Jcm(-2) ), respectively. Inoculated control (room light only) plates were incubated (48h) and colonies enumerated. The antifungal properties of blue light combined with ERY (114 and 228?moll(-1) ) on Penicillium digitatum (PD) and Fusarium graminearum (FG) conidia were determined. Conidial controls consisted of: no light, room light-treated conidia and ERY plus room light. Light-treated (ERY+blue light) conidial samples were exposed only to AR2 (0-100Jcm(-2) ), aliquots spread on potato dextrose agar plates, incubated (48h, 30C) and colonies counted. Blue light alone significantly reduced bacterial and FG viability. Combined with ERY, it significantly reduced PD viability. Blue light is lethal to bacteria and filamentous fungi although effectiveness is dependent on light purity, energy levels and microbial genus. SIGNIFICANCE AND IMPACT OF THE STUDY: Light from two arrays of different blue LEDs significantly reduced bacterial (Leuconostoc mesenteroides, Bacillus atrophaeus and Pseudomonas aeruginosa) viabilities. Significant in vitro viability loss was observed for the filamentous fungi, Penicillium digitatum and Fusarium graminearum when exposed to pure blue light only plus a photosensitizer. F.graminearum viability was significantly reduced by blue light alone. Results suggest that (i) the amount of significant loss in bacterial viability observed for blue light that is pure or with traces of other wavelengths is genus dependent and (ii) depending on fungal genera, pure blue light is fungicidal with or without a photosensitizer. PMID:23009190

De Lucca, A J; Carter-Wientjes, C; Williams, K A; Bhatnagar, D

2012-09-25

105

Modality of bacterial growth presents unique targets: how do we treat biofilm-mediated infections?  

PubMed Central

Summary of recent advances It is well accepted that bacterial pathogens growing in a biofilm are recalcitrant to the action of most antibiotics and are resistant to the innate immune system. New treatment modalities are greatly warranted to effectively eradicate these infections. However, bacteria growing in a biofilm are metabolically unique in comparison to bacteria grown in a planktonic state. Unfortunately, most antibiotics have been developed to inhibit growth of bacteria growing in a planktonic mode of growth. This review focuses on the metabolism and physiology of biofilm growth with special emphasis on the staphylococci. Future treatment options should include targeting unique metabolic niches found within bacterial biofilms in addition to enzymes or compounds that inhibit biofilm accumulation molecules and/or interact with quorum sensing and intercellular bacterial communication. PMID:20884280

Fey, Paul D.

2010-01-01

106

Growth Curve Models for the Analysis of Phenotype Arrays for a Systems Biology Overview of Yersinia pestis  

SciTech Connect

The Phenotype MicroArray technology of Biolog, Inc. (Hayward, CA) measures the respiration of cells as a function of time in thousands of microwells simultaneously, and thus provides a high-throughput means of studying cellular phenotypes. The microwells contain compounds involved in a number of biochemical pathways, as well as chemicals that test the sensitivity of cells against antibiotics and stress. While the PM experimental workflow is completely automated, statistical methods to analyze and interpret the data are lagging behind. To take full advantage of the technology, it is essential to develop efficient analytical methods to quantify the information in the complex datasets resulting from PM experiments. We propose the use of statistical growth-curve models to rigorously quantify observed differences in PM experiments, in the context of the growth and metabolism of Yersinia pestis cells grown under different physiological conditions. The information from PM experiments complement genomic and proteomic results and can be used to identify gene function and in drug development. Successful coupling of phenomics results with genomics and proteomics will lead to an unprecedented ability to characterize bacterial function at a systems biology level.

Fodor, I K; Holtz-Morris, A E; McCutchen-Maloney, S L

2005-09-08

107

Morphology, Growth, and Size Limit of Bacterial Cells  

PubMed Central

Bacterial cells utilize a living peptidoglycan network (PG) to separate the cell interior from the surroundings. The shape of the cell is controlled by PG synthesis and cytoskeletal proteins that form bundles and filaments underneath the cell wall. The PG layer also resists turgor pressure and protects the cell from osmotic shock. We argue that mechanical influences alter the chemical equilibrium of the reversible PG assembly and determine the cell shape and cell size. Using a mechanochemical approach, we show that the cell shape can be regarded as a steady state of a growing network under the influence of turgor pressure and mechanical stress. Using simple elastic models, we predict the size of common spherical and rodlike bacteria. The influence of cytoskeletal bundles such as crescentin and MreB are discussed within the context of our model. PMID:20867742

Jiang, Hongyuan; Sun, Sean X.

2010-01-01

108

Temperature effects on recovery time of bacterial growth after rewetting dry soil.  

PubMed

The effect of temperature on the recovery of bacterial growth after rewetting dry soil was measured in a soil that responded with bacterial growth increasing immediately upon rewetting in a linear fashion (type (i) response sensu Meisner et al. (Soil Biol Biochem 66: 188-192, 2013)). The soil was air-dried for 4days and then rewetted at different temperatures. Bacterial growth over time was then estimated using the leucine incorporation method. At 25C, the recovery of bacterial growth to levels of a wet control soil was rapid, within 6h, while at 15C, recovery time increased to around 60h, becoming more than a week at 5C. The temperature dependency of the recovery time was well modeled by a square root function. Thus, temperature will not only directly affect growth rates but also affect length of transition periods, like resuscitation after a drying event. The temperature during the rewetting event thus has to be taken into consideration when analyzing the microbial response dynamics. PMID:24952818

Maienza, Anita; Bth, Erland

2014-11-01

109

A free dendritic growth model accommodating curved phase boundaries and high Peclet number conditions  

SciTech Connect

A steady-state free dendrite growth model accommodating nonlocal equilibrium tip conditions and curved liquidus and solidus has been developed. The developed model assumes a dendrite tip of a paraboloid of revolution and is applicable to dendrite growth in dilute binary alloys for all values of P{sub c}, and reduces to the BCT model for linear liquidus and solidus. The marginal stability criterion of Trivedi and Kurz is shown to apply even in the presence of kinetic undercooling and curved phase boundaries when used with an appropriate concentration-dependent liquidus slope. The model is applied to Sn-Pb alloys to predict the tip velocity, tip radius, solute trapping, and four components of undercooling in the quasi-solutal, solutal-to-thermal transition and quasi-thermal regions.

DiVenuti, A.G. [Tufts Univ., Medford, MA (United States). Dept. of Mechanical Engineering; Ando, T. [Northeastern Univ., Boston, MA (United States). Dept. of Mechanical, Industrial and Mfg. Engineering

1998-12-01

110

Supplemental oxygen attenuates the increase in wound bacterial growth during simulated aeromedical evacuation in goats  

PubMed Central

Background Bacterial growth in soft tissue and open fractures is a known risk factor for tissue loss and complications in contaminated musculoskeletal wounds. Current care for battlefield casualties with soft tissue and musculoskeletal wounds includes tactical and strategic aeromedical evacuation (AE). This exposes patients to a hypobaric, hypoxic environment. In the present study, we sought to determine whether exposure to AE alters bacterial growth in contaminated complex musculoskeletal wounds and whether supplemental oxygen had any effect on wound infections during simulated AE. Methods A caprine model of a contaminated complex musculoskeletal wound was employed. Complex musculoskeletal wounds were created and inoculated with bioluminescent Pseudomonas aeruginosa. Goats were divided into three experimental groups: ground control, simulated aeromedical evacuation (AE), and simulated AE with supplemental oxygen (AE+O2). Simulated AE was induced in a hypobaric chamber pressurized to 8800 feet for 7 hours. Bacterial luminescence was measured using a photon counting camera at three timepoints: preflight (20 hours post surgery), postflight (7 hours from preflight and 27 hours post-surgery), and necropsy (24 hours from preflight and 44 hours post surgery). Results There was a significant increase in bacterial growth in the AE group compared to the ground control group measured postflight and at necropsy. Simulated AE induced hypoxia with oxygen saturation less than 93%. Supplemental oxygen corrected the hypoxia and significantly reduced bacterial growth in wounds at necropsy. Conclusions Hypoxia induced during simulated AE enhances bacterial growth in complex musculoskeletal wounds which can be prevented with the application of supplemental oxygen to the host. PMID:22743376

Earnest, Ryan E.; Sonnier, Dennis I.; Makley, Amy T.; Campion, Eric M.; Wenke, Joseph C.; Bailey, Stephanie R.; Dorlac, Warren C.; Lentsch, Alex B.; Pritts, Timothy A.

2012-01-01

111

Individual Growth Curves of Frequency of Sexual Intercourse Among Urban, Adolescent, African American Youth  

Microsoft Academic Search

In the current study we examined individual growth curves of frequency of sexual intercourse among a sample of urban, low-income, African American youth at increased risk for subsequent HIV\\/AIDS exposure. Three waves of longitudinal data from the Collaborative HIV-Prevention AdolescentMental Health (CHAMP) project were utilized. Participant ages ranged from 9 to 12 years (M = 11 years) at the first

Christian Delucia; Roberta L. Paikoff; Grayson N. Holmbeck

2007-01-01

112

Choice of Bacterial Growth Medium Alters the Transcriptome and Phenotype of Salmonella enterica Serovar Typhimurium  

PubMed Central

The type of bacterial culture medium is an important consideration during design of any experimental protocol. The aim of this study was to understand the impact of medium choice on bacterial gene expression and physiology by comparing the transcriptome of Salmonella enterica SL1344 after growth in the widely used LB broth or the rationally designed MOPS minimal medium. Transcriptomics showed that after growth in MOPS minimal media, compared to LB, there was increased expression of 42 genes involved in amino acid synthesis and 23 genes coding for ABC transporters. Seven flagellar genes had decreased expression after growth in MOPS minimal medium and this correlated with a decreased motility. In both MOPS minimal medium and MEM expression of genes from SPI-2 was increased and the adhesion of S. Typhimurium to intestinal epithelial cells was higher compared to the levels after growth in LB. However, SL1344 invasion was not significantly altered by growth in either MOPs minimal media or MEM. Expression of SPI-2 was also measured using chromosomal GFP reporter fusions followed by flow cytometry which showed, for the first time, that the reduction in SPI-2 transcript after growth in different media related to a reduction in the proportion of the bacterial population expressing SPI-2. These data highlight the profound differences in the global transcriptome after in vitro growth in different media and show that choice of medium should be considered carefully during experimental design, particularly when virulence related phenotypes are being measured. PMID:23704954

Blair, Jessica M. A.; Richmond, Grace E.; Bailey, Andrew M.; Ivens, Al; Piddock, Laura J. V.

2013-01-01

113

Differential growth responses of soil bacterial taxa to carbon substrates of varying chemical recalcitrance  

SciTech Connect

Soils are immensely diverse microbial habitats with thousands of co-existing bacterial, archaeal, and fungal species. Across broad spatial scales, factors such as pH and soil moisture appear to determine the diversity and structure of soil bacterial communities. Within any one site however, bacterial taxon diversity is high and factors maintaining this diversity are poorly resolved. Candidate factors include organic substrate availability and chemical recalcitrance, and given that they appear to structure bacterial communities at the phylum level, we examine whether these factors might structure bacterial communities at finer levels of taxonomic resolution. Analyzing 16S rRNA gene composition of nucleotide analog-labeled DNA by PhyloChip microarrays, we compare relative growth rates on organic substrates of increasing chemical recalcitrance of >2,200 bacterial taxa across 43 divisions/phyla. Taxa that increase in relative abundance with labile organic substrates (i.e., glycine, sucrose) are numerous (>500), phylogenetically clustered, and occur predominantly in two phyla (Proteobacteria and Actinobacteria) including orders Actinomycetales, Enterobacteriales, Burkholderiales, Rhodocyclales, Alteromonadales, and Pseudomonadales. Taxa increasing in relative abundance with more chemically recalcitrant substrates (i.e., cellulose, lignin, or tannin-protein) are fewer (168) but more phylogenetically dispersed, occurring across eight phyla and including Clostridiales, Sphingomonadalaes, Desulfovibrionales. Just over 6% of detected taxa, including many Burkholderiales increase in relative abundance with both labile and chemically recalcitrant substrates. Estimates of median rRNA copy number per genome of responding taxa demonstrate that these patterns are broadly consistent with bacterial growth strategies. Taken together, these data suggest that changes in availability of intrinsically labile substrates may result in predictable shifts in soil bacterial composition.

Goldfarb, K.C.; Karaoz, U.; Hanson, C.A.; Santee, C.A.; Bradford, M.A.; Treseder, K.K.; Wallenstein, M.D.; Brodie, E.L.

2011-04-18

114

BIOASSAY PROCEDURE FOR PREDICTING COLIFORM BACTERIAL GROWTH IN DRINKING WATER  

EPA Science Inventory

Water quality degradation due to the growth of microorganisms Is an area of concern for many water utilities. urrently the nutrient status of drinking water is difficult to measure and can only be defined in relative terms. o date, the procedures developed for determining the amo...

115

BIOASSAY PROCEDURES FOR PREDICTING COLIFORM BACTERIAL GROWTH IN DRINKING WATER  

EPA Science Inventory

Water quality degradation due to the growth of microorganisms is an area of concern for many water utilities. o date, the procedures developed or determining the amount of biodegradable material present in potable water have utilized heterotrophic non-coliform bacteria as bioassa...

116

Heterotrophic Bacterial Growth Efficiency and Community Structure at Different Natural Organic Carbon Concentrations  

Microsoft Academic Search

Batch cultures of aquatic bacteria and dissolved organic matter were used to examine the impact of carbon source concentration on bacterial growth, biomass, growth efficiency, and community composition. An aged concentrate of dissolved organic matter from a humic lake was diluted with organic compound-free artificial lake water to obtain concentrations of dissolved organic carbon (DOC) ranging from 0.04 to 2.53

Alexander Eiler; Silke Langenheder; Stefan Bertilsson; Lars J. Tranvik

2003-01-01

117

Effects of nitric oxide and nitrogen dioxide on bacterial growth  

NASA Technical Reports Server (NTRS)

While it is generally thought that the bactericidal effects of NO and NO2 derive from their reaction with water to form nitrous and nitric acids (Shank et al., 1962), this appears to be true only at high concentrations. The data presented here suggest that at low NO and NO2 concentrations, acids are not present in high enough concentrations to act as toxic agents. Reference is made to a study by Grant et al. (1979), which found that exposing acid forest soil to 1 ppm of NO2 did not cause the soil pH to drop. The results presented here show that at low concentrations of NO and NO2, the NO is bacteriostatic for some organisms and not for others, whereas NO2 may protect some bacteria from the inhibitory effects of NO. Since it has been shown that bacteria can divide while airborne (Dimmick et al., 1979), the present results suggest that NO at the low concentrations found in the atmosphere can select for resistant bacteria in the air and affect the viable airborne bacterial population.

Mancinelli, R. L.; Mckay, C. P.

1983-01-01

118

Tetracycline Resistance Gene Maintenance under Varying Bacterial Growth Rate, Substrate and Oxygen Availability, and Tetracycline  

E-print Network

at lower levels, with ratios of resistance to 16S rDNA genes decreasing by about 2- fold). A higher rateTetracycline Resistance Gene Maintenance under Varying Bacterial Growth Rate, Substrate and Oxygen. J. Alvarez*, GSI Environmental Inc., 2211 Norfolk, Suite 1000, Houston, Texas 77098, United States

Alvarez, Pedro J.

119

Divergent effects of desferrioxamine on bacterial growth and characteristics.  

PubMed

Desferrioxamines (DF's) are siderophores produced by some groups of bacteria. Previously, we discovered that DFE, produced by Streptomyces griseus, induced divergent developmental phenotypes in various Streptomyces isolates. In this study, we isolated bacteria whose phenotype was affected by the presence of 0.1 mM DFB from soil samples, and studied their phylogenetic position via 16 S rRNA gene-based analysis. Isolates belonging to Microbacterium grew only in the presence of DFB in the medium. DFB promoted growth of some isolates, while significantly inhibiting that of other divergent bacteria. Different groups of isolates were affected, not because of growth-related changes, but because of changes in the colony morphology based on possible stimulation of motility. An isolate affiliated with Janthinobacterium was stimulated for violacein production as well as for pilus formation. The wide and divergent effects of DFB suggest that availability of siderophores significantly affect the structure of microbial community. PMID:23232933

Eto, Daisei; Watanabe, Kenta; Saeki, Hisafumi; Oinuma, Ken-ichi; Otani, Ko-ichi; Nobukuni, Megumi; Shiratori-Takano, Hatsumi; Takano, Hideaki; Beppu, Teruhiko; Ueda, Kenji

2013-04-01

120

Longitudinal growth curves of brain function underlying inhibitory control through adolescence.  

PubMed

Neuroimaging studies suggest that developmental improvements in inhibitory control are primarily supported by changes in prefrontal executive function. However, studies are contradictory with respect to how activation in prefrontal regions changes with age, and they have yet to analyze longitudinal data using growth curve modeling, which allows characterization of dynamic processes of developmental change, individual differences in growth trajectories, and variables that predict any interindividual variability in trajectories. In this study, we present growth curves modeled from longitudinal fMRI data collected over 302 visits (across ages 9 to 26 years) from 123 human participants. Brain regions within circuits known to support motor response control, executive control, and error processing (i.e., aspects of inhibitory control) were investigated. Findings revealed distinct developmental trajectories for regions within each circuit and indicated that a hierarchical pattern of maturation of brain activation supports the gradual emergence of adult-like inhibitory control. Mean growth curves of activation in motor response control regions revealed no changes with age, although interindividual variability decreased with development, indicating equifinality with maturity. Activation in certain executive control regions decreased with age until adolescence, and variability was stable across development. Error-processing activation in the dorsal anterior cingulate cortex showed continued increases into adulthood and no significant interindividual variability across development, and was uniquely associated with task performance. These findings provide evidence that continued maturation of error-processing abilities supports the protracted development of inhibitory control over adolescence, while motor response control regions provide early-maturing foundational capacities and suggest that some executive control regions may buttress immature networks as error processing continues to mature. PMID:24227721

Ordaz, Sarah J; Foran, William; Velanova, Katerina; Luna, Beatriz

2013-11-13

121

Bacterial growth in a simulated Martian subsurface environment  

NASA Astrophysics Data System (ADS)

The ability of microorganisms to grow under Martian conditions has implications in both the search for life and habitability of Mars as well as the potential contamination of Mars by landing spacecraft. Factors that inhibit the growth of organisms on Mars include UV radiation, low pressure and temperature, CO2 atmosphere, lack of liquid water, and extreme desiccation. Yet a possible biozone capable of supporting microbial life on Mars exists in the shallow subsurface where there is protection from harsh UV rays. In addition, the presence of widespread subsurface ice, confirmed by the Phoenix Lander, offers a water source as the ice sublimates through the upper soil. Here we will determine the ability of the organism Halomonas desiderata strain SP1 to grow in the simulated Martian subsurface environment. Halomonas was chosen as the bacteria of interest due to its tolerance to extreme environments, including carrying salt concentrations and pH. Experiments were carried out in the Mars Simulation Chamber, where temperatures, pressures, and atmospheric composition can be closely monitored to simulate Martian conditions. A series of stress experiments were conducted to observe Halomonas's ability to withstand exposure to a Mars analog soil, freezing temperatures, anoxic conditions, and low pressures. We have determined that Halomonas is able to survive exposures to low temperatures, pressures, and anoxic conditions. We will report on the survival and growth of Halomonas in the simulated Martian permafrost under low (6-10 mbar) atmospheric pressures.

Kronyak, R. E.; Pavlov, A.; House, C. H.

2013-12-01

122

Bacterial exopolysaccharide and biofilm formation stimulate chickpea growth and soil aggregation under salt stress  

PubMed Central

To compensate for stress imposed by salinity, biofilm formation and exopolysaccharide production are significant strategies of salt tolerant bacteria to assist metabolism. We hypothesized that two previously isolated salt-tolerant strains Halomonas variabilis (HT1) and Planococcus rifietoensis (RT4) have an ability to improve plant growth, These strains can form biofilm and accumulate exopolysacharides at increasing salt stress. These results showed that bacteria might be involved in developing microbial communities under salt stress and helpful in colonizing of bacterial strains to plant roots and soil particles. Eventually, it can add to the plant growth and soil structure. We investigated the comparative effect of exopolysacharide and biofilm formation in two bacterial strains Halomonas variabilis (HT1) and Planococcus rifietoensis (RT4) in response to varying salt stress. We found that biofilm formation and exopolysaccharide accumulation increased at higher salinity. To check the effect of bacterial inoculation on the plant (Cicer arietinum Var. CM-98) growth and soil aggregation, pot experiment was conducted by growing seedlings under salt stress. Inoculation of both strains increased plant growth at elevated salt stress. Weight of soil aggregates attached with roots and present in soil were added at higher salt concentrations compared to untreated controls. Soil aggregation was higher at plant roots under salinity. These results suggest the feasibility of using above strains in improving plant growth and soil fertility under salinity. PMID:24031943

Qurashi, Aisha Waheed; Sabri, Anjum Nasim

2012-01-01

123

Culturable bacterial endophytes isolated from Mangrove tree (Rhizophora apiculata Blume) enhance seedling growth in Rice  

PubMed Central

Background: Endophytic bacteria do have several potential applications in medicine and in other various sectors of biotechnology including agriculture. Bacterial endophytes need to be explored for their potential applications in agricultural biotechnology. One of the potential applications of bacterial endophytes in agricultural is to enhance the growth of the agricultural crops. Hence, this study was undertaken to explore the plant growth promoting potential application of bacterial endophytes. Objective: The objective of this study was to examine the effect of endophytic bacteria from mangrove tree (Rhizophora apiculata Blume) for their efficacy in promoting seedling growth in rice. Materials and Methods: Eight endophytic bacterial isolates (EBIs) isolated from twig and petiole tissues of the mangrove were identified based on their 16S ribosomal ribonucleic acid (rRNA) gene sequence homology. Separately, surface sterilized paddy seeds were treated with cell-free broth and cell suspension of the EBIs. Rice seedlings were analyzed by various bioassays and data was recorded. Results: The gene sequences of the isolates were closely related to two genera namely, Bacillus and Pantoea. Inoculation of EBIs from R. apiculata with rice seeds resulted in accelerated root and shoot growth with significant increase in chlorophyll content. Among the isolates, Pantoea ananatis (1MSE1) and Bacillus amyloliquefaciens (3MPE1) had shown predominance of activity. Endophytic invasion was recognized by the non-host by rapid accumulation of reactive oxygen species (ROS) and was counteracted by the production of hydrogen peroxide (H2O2) and lipid peroxide. The results demonstrated that EBIs from mangrove tree can increase the fitness of the rice seedlings under controlled conditions. Conclusion: These research findings could be useful to enhance the seedling growth and could serve as foundation in further research on enhancing the growth of the rice crop using endophytic bacteria. PMID:25097431

Deivanai, Subramanian; Bindusara, Amitraghata Santhanam; Prabhakaran, Guruswamy; Bhore, Subhash Janardhan

2014-01-01

124

Growth Yields in Bacterial Denitrification and Nitrate Ammonification?  

PubMed Central

Denitrification and nitrate ammonification are considered the highest-energy-yielding respiration systems in anoxic environments after oxygen has been consumed. The corresponding free energy changes are 7 and 35% lower than that of aerobic respiration, respectively. Growth yield determinations with pure cultures of Paracoccus denitrificans and Pseudomonas stutzeri revealed that far less energy is converted via ATP into cell mass than expected from the above calculations. Denitrification with formate or hydrogen as electron donor yielded about 2.4 to 3.0 g dry matter per mol formate or hydrogen and 15 to 18 g dry matter per mol acetate. Similar yields with acetate were obtained with Pseudomonas stutzeri. Wolinella succinogenes and Sulfurospirillum deleyianum, which reduce nitrate to ammonia, both exhibited similar yield values with formate or H2 plus nitrate. The results indicate that ATP synthesis in denitrification is far lower than expected from the free energy changes and even lower than in nitrate ammonification. The results are discussed against the background of our present understanding of electron flow in denitrification and with respect to the importance of denitrification and nitrate ammonification in the environment. PMID:17209072

Strohm, Tobin O.; Griffin, Ben; Zumft, Walter G.; Schink, Bernhard

2007-01-01

125

Social complementation and growth advantages promote socially defective bacterial isolates.  

PubMed

Social interactions among diverse individuals that encounter one another in nature have often been studied among animals but rarely among microbes. For example, the evolutionary forces that determine natural frequencies of bacteria that express cooperative behaviours at low levels remain poorly understood. Natural isolates of the soil bacterium Myxococcus xanthus sampled from the same fruiting body often vary in social phenotypes, such as group swarming and multicellular development. Here, we tested whether genotypes highly proficient at swarming or development might promote the persistence of less socially proficient genotypes from the same fruiting body. Fast-swarming strains complemented slower isolates, allowing the latter to keep pace with faster strains in mixed groups. During development, one low-sporulating strain was antagonized by high sporulators, whereas others with severe developmental defects had those defects partially complemented by high-sporulating strains. Despite declining in frequency overall during competition experiments spanning multiple cycles of development, developmentally defective strains exhibited advantages during the growth phases of competitions. These results suggest that microbes with low-sociality phenotypes often benefit from interacting with more socially proficient strains. Such complementation may combine with advantages at other traits to increase equilibrium frequencies of low-sociality genotypes in natural populations. PMID:24573856

Kraemer, Susanne A; Velicer, Gregory J

2014-04-22

126

Predicting growth and curve progression in the individual patient with adolescent idiopathic scoliosis: design of a prospective longitudinal cohort study  

Microsoft Academic Search

BACKGROUND: Scoliosis is present in 3-5% of the children in the adolescent age group, with a higher incidence in females. Treatment of adolescent idiopathic scoliosis is mainly dependent on the progression of the scoliotic curve. There is a close relationship between curve progression and rapid (spinal) growth of the patient during puberty. However, until present time no conclusive method was

Iris Busscher; Frits Hein Wapstra; Albert G Veldhuizen

2010-01-01

127

Diamagnetic levitation enhances growth of liquid bacterial cultures by increasing oxygen availability  

PubMed Central

Diamagnetic levitation is a technique that uses a strong, spatially varying magnetic field to reproduce aspects of weightlessness, on the Earth. We used a superconducting magnet to levitate growing bacterial cultures for up to 18 h, to determine the effect of diamagnetic levitation on all phases of the bacterial growth cycle. We find that diamagnetic levitation increases the rate of population growth in a liquid culture and reduces the sedimentation rate of the cells. Further experiments and microarray gene analysis show that the increase in growth rate is owing to enhanced oxygen availability. We also demonstrate that the magnetic field that levitates the cells also induces convective stirring in the liquid. We present a simple theoretical model, showing how the paramagnetic force on dissolved oxygen can cause convection during the aerobic phases of bacterial growth. We propose that this convection enhances oxygen availability by transporting oxygen around the liquid culture. Since this process results from the strong magnetic field, it is not present in other weightless environments, e.g. in Earth orbit. Hence, these results are of significance and timely to researchers considering the use of diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena. PMID:20667843

Dijkstra, Camelia E.; Larkin, Oliver J.; Anthony, Paul; Davey, Michael R.; Eaves, Laurence; Rees, Catherine E. D.; Hill, Richard J. A.

2011-01-01

128

Chemical Interference with Iron Transport Systems to Suppress Bacterial Growth of Streptococcus pneumoniae  

PubMed Central

Iron is an essential nutrient for the growth of most bacteria. To obtain iron, bacteria have developed specific iron-transport systems located on the membrane surface to uptake iron and iron complexes such as ferrichrome. Interference with the iron-acquisition systems should be therefore an efficient strategy to suppress bacterial growth and infection. Based on the chemical similarity of iron and ruthenium, we used a Ru(II) complex R-825 to compete with ferrichrome for the ferrichrome-transport pathway in Streptococcus pneumoniae. R-825 inhibited the bacterial growth of S. pneumoniae and stimulated the expression of PiuA, the iron-binding protein in the ferrichrome-uptake system on the cell surface. R-825 treatment decreased the cellular content of iron, accompanying with the increase of Ru(II) level in the bacterium. When the piuA gene (SPD_0915) was deleted in the bacterium, the mutant strain became resistant to R-825 treatment, with decreased content of Ru(II). Addition of ferrichrome can rescue the bacterial growth that was suppressed by R-825. Fluorescence spectral quenching showed that R-825 can bind with PiuA in a similar pattern to the ferrichrome-PiuA interaction in vitro. These observations demonstrated that Ru(II) complex R-825 can compete with ferrichrome for the ferrichrome-transport system to enter S. pneumoniae, reduce the cellular iron supply, and thus suppress the bacterial growth. This finding suggests a novel antimicrobial approach by interfering with iron-uptake pathways, which is different from the mechanisms used by current antibiotics. PMID:25170896

Zhang, Liang; Li, Nan; Han, Junlong; Zhang, Jing; Sun, Xuesong; He, Qing-Yu

2014-01-01

129

Bacterial Population in Intestines of the Black Tiger Shrimp (Penaeus monodon) under Different Growth Stages  

PubMed Central

Intestinal bacterial communities in aquaculture have been drawn to attention due to potential benefit to their hosts. To identify core intestinal bacteria in the black tiger shrimp (Penaeus monodon), bacterial populations of disease-free shrimp were characterized from intestines of four developmental stages (15-day-old post larvae (PL15), 1- (J1), 2- (J2), and 3-month-old (J3) juveniles) using pyrosequencing, real-time PCR and denaturing gradient gel electrophoresis (DGGE) approaches. A total of 25,121 pyrosequencing reads (reading length?=?44224 bases) were obtained, which were categorized by barcode for PL15 (7,045 sequences), J1 (3,055 sequences), J2 (13,130 sequences) and J3 (1,890 sequences). Bacteria in the phyla Bacteroides, Firmicutes and Proteobacteria were found in intestines at all four growth stages. There were 88, 14, 27, and 20 bacterial genera associated with the intestinal tract of PL15, J1, J2 and J3, respectively. Pyrosequencing analysis revealed that Proteobacteria (class Gammaproteobacteria) was a dominant bacteria group with a relative abundance of 89% for PL15 and 99% for J1, J2 and J3. Real-time PCR assay also confirmed that Gammaproteobacteria had the highest relative abundance in intestines from all growth stages. Intestinal bacterial communities from the three juvenile stages were more similar to each other than that of the PL shrimp based on PCA analyses of pyrosequencing results and their DGGE profiles. This study provides descriptive bacterial communities associated to the black tiger shrimp intestines during these growth development stages in rearing facilities. PMID:23577162

Rungrassamee, Wanilada; Klanchui, Amornpan; Chaiyapechara, Sage; Maibunkaew, Sawarot; Tangphatsornruang, Sithichoke; Jiravanichpaisal, Pikul; Karoonuthaisiri, Nitsara

2013-01-01

130

Determining Cloud Parameters with the Curve-Of-Growth: Application Eta Car  

NASA Technical Reports Server (NTRS)

We have investigated the NUV part of the Eta Car spectrum, using data with high spatial and high spectral resolving power obtained with the HST/STIS under the Treasury Program. The NUV spectrum of Eta Car Shows a great contribution of absorption features from neutral and singly ionized elements along the line-of-sight. A large number of velocity systems have been observed. The two most prominent, with Doppler shifts corresponding to -146 and -513 km/s respectively, are shown to be useful for investigations of the gaseous environments responsible for the absorption. The -146 and the -513 km/s velocity systems display different characteristics regarding the ionization state and spectral line width, which suggest that they originate at different distances from the central object. We have investigated the absorption structures before the spectroscopic minimum, occurring during the summer of 2003, with a standard curve-of-growth. We have independently derived the column density and the b-value for the Fe II (-146 km/s) and Ti II (-513 km/s) velocity systems. The excitation temperature has been determined for the -146 km/s velocity system using the photo-ionization code \\textsc(cloudy). The -146 km/s velocity structure shows noticeable variation over the spectroscopic minimum. The sudden appearance and disappearance of Ti II and V II are astonishing. We have made an attempt to analyze these variations with the curve-of-growth method and will present preliminary results.

Vieira, G. L.; Gull, T. R.; Bruhweiler, F.; Nielsen, K. E.; Verner, E. M.

2004-01-01

131

Chlorhexidine Digluconate Effects on Planktonic Growth and Biofilm Formation in Some Field Isolates of Animal Bacterial Pathogens  

PubMed Central

Background: To study chlorhexidine digluconate disinfectant effects on planktonic growth and biofilm formation in some bacterial field isolates from animals. Objectives: The current study investigated chlorhexidine digluconate effects on planktonic growth and biofilm formation in some field isolates of veterinary bacterial pathogens. Materials and Methods: Forty clinical isolates of Escherichia coli, Salmonella serotypes, Staphylococcus. aureus and Streptococcus agalactiae (10 isolates for each) were examined for chlorhexidine digluconate effects on biofilm formation and planktonic growth using microtiter plates. In all of the examined strains in the presence of chlorhexidine digluconate, biofilm development and planktonic growth were affected at the same concentrations of the disinfectant. Results: Chlorhexidine digluconate inhibited the planktonic growth of different bacterial species at sub-MICs. But they were able to induce biofilm development of the E. coli, Salmonella spp., S. aureus and Str. agalactiae strains. Conclusions: Bacterial resistance against chlorhexidine is increasing. Sub-MIC doses of chlorhexidine digluconate can stimulate the formation of biofilm strains. PMID:24872940

Ebrahimi, Azizollah; Hemati, Majid; Habibian Dehkordi, Saeed; Bahadoran, Shahab; Khoshnood, Sheida; Khubani, Shahin; Dokht Faraj, Mahdi; Hakimi Alni, Reza

2014-01-01

132

Differential susceptibility of pumpkins to bacterial wilt related to plant growth stage and cultivar  

Microsoft Academic Search

Fifteen jack-o'-lantern and three processing-pie pumpkin (Cucurbita pepo L.) cultivars were tested in the greenhouse and field for their susceptibility at different growth stages to Erwinia tracheiphila, the causal agent of bacterial wilt. The bacterium is vectored by cucumber beetles (Acalymma vittatum (F) and Diabrotica undecimpunctata howardi Barber). Each variety was artificially inoculated with E. tracheiphila in the greenhouse at

Gerald E. Brust

1997-01-01

133

Effect of plant growth promoting rhizobacteria on bacterial canker of tomato  

Microsoft Academic Search

Use of plant growth promoting rhizobacteria in managing bacterial canker disease of tomato was studied in the present work. Tomato seeds were treated with PGPR strains viz., Bacillus pumilus INR7, Bacillus pumilus SE34, Bacillus pumilus T4, Bacillus subtilis GBO3, Bacillus amyloliquefaciens IN937a and Brevibacillus brevis IPC11 were subjected for seed germination and seedling vigor. Among the PGPR strains tested, only

N Girish; S Umesha

2005-01-01

134

Effect of Human Milk Fortifiers on Bacterial Growth in Human Milk  

Microsoft Academic Search

BACKGROUND:As a component in human milk fortifiers (HMF), iron may equilibrate with human milk for as long as 24 hours, bind important bacteriostatic proteins, and potentially affect the host defense properties of human milk.OBJECTIVE:We compared bacterial growth in human milk prepared with each of two HMF differing in their content of iron.STUDY DESIGN:Samples of human milk obtained from mothers of

Myla S Santiago; Champa N Codipilly; Debra C Potak; Richard J Schanler

2005-01-01

135

Evaluation of toxic effects of several carboxylic acids on bacterial growth by toxicodynamic modelling  

PubMed Central

Background Effects of organic acids on microbial fermentation are commonly tested in investigations about metabolic behaviour of bacteria. However, they typically provide only descriptive information without modelling the influence of acid concentrations on bacterial kinetics. Results We developed and applied a mathematical model (secondary model) to capture the toxicological effects of those chemicals on kinetic parameters that define the growth of bacteria in batch cultures. Thus, dose-response kinetics were performed with different bacteria (Leuconostoc mesenteroides, Carnobacterium pisicola, Escherichia coli, Bacillus subtilis and Listonella anguillarum) exposed at increasing concentrations of individual carboxylic acids (formic, acetic, propionic, butyric and lactic). In all bioassays the acids affected the maximum bacterial load (Xm) and the maximum growth rate (vm) but only in specific cases the lag phase (?) was modified. Significance of the parameters was always high and in all fermentations the toxicodynamic equation was statistically consistent and had good predictability. The differences between D and L-lactic acid effects were significant for the growth of E. coli, L. mesenteroides and C. piscicola. In addition, a global parameter (EC50,?) was used to compare toxic effects and provided a realistic characterization of antimicrobial agents using a single value. Conclusions The effect of several organic acids on the growth of different bacteria was accurately studied and perfectly characterized by a bivariate equation which combines the basis of dose-response theory with microbial growth kinetics (secondary model). The toxicity of carboxylic acids was lower with the increase of the molecular weight of these chemicals. PMID:22118421

2011-01-01

136

Mycobacterial Growth and Bacterial Contamination in the Mycobacteria Growth Indicator Tube and BACTEC 460 Culture Systems  

Microsoft Academic Search

The BACTEC 460 system currently provides the most rapid detection of mycobacterial growth, but the system is radiometric and requires needles to inoculate specimens through the bottle's septum. The Myco- bacteria Growth Indicator Tube (MGIT) system has a liquid medium, like the BACTEC system, and does not require needles when inoculating specimens. We compared mycobacterial growth from 510 specimens in

DENNIS B. CORNFIELD; KATHLEEN GLEASON BEAVIS; JULIE A. GREENE; MARYANN BOJAK; JAMES BONDI

1997-01-01

137

Essays on the predictability of oil shocks and yield curves for real-time output growth  

NASA Astrophysics Data System (ADS)

This dissertation is a collection of three essays that revisits the long-standing puzzle of the apparently disproportionate effect of oil prices in the economy by examining output growth predictability with real-time data. Each study of the predictive content of oil shocks is from a different perspective by using newly developed real-time datasets, which allows for replicating the economic environment faced by policymakers in real time. The first study extends the conventional set of models of output growth determination by investigating predictability of models that incorporate various functional forms of oil prices and real-time data. The results are supportive of the relationship of GDP and oil in the context of Granger causality with real-time data. In the second essay, I use oil shocks to predict the economy is changing direction earlier than would be predicted by solely using initial GDP releases. The model provides compelling evidence of negative GDP growth predictability in response to oil price shocks, which could shorten the "recognition lag" for successful implementation of discretionary counter-cyclical policies. In the third essay, I evaluate short-horizon output growth predictability using real-time data for different sample periods. I find strong evidence of predictability at the one-quarter and four-quarter horizon for the United States. The major result of the paper is that we reject the null hypothesis of no predictability against an alternative hypothesis of predictability with oil shocks that include yield curves in the forecasting regression. This relationship suggests the combination of monetary policy and oil shocks are important for subsequent GDP growth.

Carlton, Amelie B.

138

The inhibition of bacterial growth by hypochlorous acid. Possible role in the bactericidal activity of phagocytes.  

PubMed Central

The 'respiratory burst' of phagocytes such as neutrophils generates superoxide which forms H2O2 by dismutation. H2O2 and Cl- ions serve as substrates for the enzyme myeloperoxidase to generate hypochlorous acid (HOCl). HOCl is thought to play an important role in bacterial killing, but its mechanism of action is not well characterized. Furthermore, although many studies in vitro have shown HOCl to be a damaging oxidant with little or no specificity (particularly at high concentrations), bacteria which have been ingested by phagocytes appear to experience a rapid and selective inhibition of cell division. Bacterial membrane disruption, protein degradation, and inhibition of protein synthesis, do not seem to occur in the early phases of phagocyte action. We have now found that low concentrations of HOCl exert a rapid and selective inhibition of bacterial growth and cell division, which can be blocked by taurine or amino acids. Only 20 microM-HOCl was required for 50% inhibition of bacterial growth (5 x 10(8) Escherichia coli/ml), and 50 microM-HOCl completely inhibited cell division (colony formation). These effects were apparent within 5 min of HOCl exposure, and were not reversed by extensive washings. DNA synthesis (incorporation of [3H]-thymidine) was significantly affected by even a 1 min exposure to 50 microM-HOCl, and decreased by as much as 96% after 5 min. In contrast, bacterial membrane disruption and extensive protein degradation/fragmentation (release of acid-soluble counts from [3H]leucine-labelled cells) were not observed at concentrations below 5 mM-HOCl. Protein synthesis (incorporation of [3H]leucine) was only inhibited by 10-30% following 5 min exposure to 50 microM-HOCl, although longer exposure produced more marked reductions (80% after 30 min). Neutrophils deficient in myeloperoxidase cannot convert H2O2 to HOCl, yet can kill bacteria. We have found that H2O2 is only 6% as effective as HOCl in inhibiting E. coli growth and cell division (0.34 mM-H2O2 required for 50% inhibition of colony formation), and taurine or amino acids do not block this effect. Our results are consistent with a rapid and selective inhibition of bacterial cell division by HOCl in phagocytes. H2O2 may substitute for HOCl in myeloperoxidase deficiency, but by a different mechanism and at a greater metabolic cost. PMID:2848494

McKenna, S M; Davies, K J

1988-01-01

139

Measuring the stiffness of bacterial cells from growth rates in hydrogels of tunable elasticity  

PubMed Central

Summary Although bacterial cells are known to experience large forces from osmotic pressure differences and their local microenvironment, quantitative measurements of the mechanical properties of growing bacterial cells have been limited. We provide an experimental approach and theoretical framework for measuring the mechanical properties of live bacteria. We encapsulated bacteria in agarose with a user-defined stiffness, measured the growth rate of individual cells, and fit data to a thin-shell mechanical model to extract the effective longitudinal Young's modulus of the cell envelope of Escherichia coli (50150 MPa), Bacillus subtilis (100200 MPa), and Pseudomonas aeruginosa (100200 MPa). Our data provide estimates of cell wall stiffness similar to values obtained via the more labor-intensive technique of atomic force microscopy. To address physiological perturbations that produce changes in cellular mechanical properties, we tested the effect of A22-induced MreB depolymerization on the stiffness of E. coli. The effective longitudinal Young's modulus was not significantly affected by A22 treatment at short time scales, supporting a model in which the interactions between MreB and the cell wall persist on the same time scale as growth. Our technique therefore enables the rapid determination of how changes in genotype and biochemistry affect the mechanical properties of the bacterial envelope. PMID:22548341

Tuson, Hannah H.; Auer, George K.; Renner, Lars D.; Hasebe, Mariko; Tropini, Carolina; Salick, Max; Crone, Wendy C.; Gopinathan, Ajay; Huang, Kerwyn Casey; Weibel, Douglas B.

2012-01-01

140

Control of bacterial biofilm growth on surfaces by nanostructural mechanics and geometry  

NASA Astrophysics Data System (ADS)

Surface-associated communities of bacteria, called biofilms, pervade natural and anthropogenic environments. Mature biofilms are resistant to a wide range of antimicrobial treatments and therefore pose persistent pathogenic threats. The use of surface chemistry to inhibit biofilm growth has been found to only transiently affect initial attachment. In this work, we investigate the tunable effects of physical surface properties, including high-aspect-ratio (HAR) surface nanostructure arrays recently reported to induce long-range spontaneous spatial patterning of bacteria on the surface. The functional parameters and length scale regimes that control such artificial patterning for the rod-shaped pathogenic species Pseudomonas aeruginosa are elucidated through a combinatorial approach. We further report a crossover regime of biofilm growth on a HAR nanostructured surface versus the nanostructure effective stiffness. When the 'softness' of the hair-like nanoarray is increased beyond a threshold value, biofilm growth is inhibited as compared to a flat control surface. This result is consistent with the mechanoselective adhesion of bacteria to surfaces. Therefore by combining nanoarray-induced bacterial patterning and modulating the effective stiffness of the nanoarraythus mimicking an extremely compliant flat surfacebacterial mechanoselective adhesion can be exploited to control and inhibit biofilm growth.

Epstein, A. K.; Hochbaum, A. I.; Kim, Philseok; Aizenberg, J.

2011-12-01

141

Characteristics of bacterial and fungal growth in plastic bottled beverages under a consuming condition model.  

PubMed

Microbial contamination in unfinished beverages can occur when drinking directly from the bottle. Various microorganisms, including foodborne pathogens, are able to grow in these beverages at room temperature or in a refrigerator. In this study, we elucidated the characteristics of microorganism growth in bottled beverages under consuming condition models. Furthermore, we provide insight into the safety of partially consumed bottled beverages with respect to food hygiene. We inoculated microorganisms, including foodborne pathogens, into various plastic bottled beverages and analysed the dynamic growth of microorganisms as well as bacterial toxin production in the beverages. Eight bottled beverage types were tested in this study, namely green tea, apple juice drink, tomato juice, carbonated drink, sport drink, coffee with milk, isotonic water and mineral water, and in these beverages several microorganism types were used: nine bacteria including three toxin producers, three yeasts, and five moulds. Following inoculation, the bottles were incubated at 35C for 48 h for bacteria, 25C for 48 h for yeasts, and 25C for 28 days for moulds. During the incubation period, the number of bacteria and yeasts and visible changes in mould-growth were determined over time. Our results indicated that combinations of the beverage types and microorganism species correlated with the degree of growth. Regarding factors that affect the growth and toxin-productivity of microorganisms in beverages, it is speculated that the pH, static/shaking culture, temperature, additives, or ingredients, such as carbon dioxide or organic matter (especially of plant origin), may be important for microorganism growth in beverages. Our results suggest that various types of unfinished beverages have microorganism growth and can include food borne pathogens and bacterial toxins. Therefore, our results indicate that in terms of food hygiene it is necessary to consume beverages immediately after opening the bottle. PMID:24679089

Watanabe, Maiko; Ohnishi, Takahiro; Araki, Emiko; Kanda, Takashi; Tomita, Atsuko; Ozawa, Kazuhiro; Goto, Keiichi; Sugiyama, Kanji; Konuma, Hirotaka; Hara-Kudo, Yukiko

2014-01-01

142

Scaling laws governing stochastic growth and division of single bacterial cells  

E-print Network

Uncovering the quantitative laws that govern the growth and division of single cells remains a major challenge. Using a unique combination of technologies that yields unprecedented statistical precision, we find that the sizes of individual Caulobacter crescentus cells increase exponentially in time. We also establish that they divide upon reaching a critical multiple ($\\approx$1.8) of their initial sizes, rather than an absolute size. We show that when the temperature is varied, the growth and division timescales scale proportionally with each other over the physiological temperature range. Strikingly, the cell-size and division-time distributions can both be rescaled by their mean values such that the condition-specific distributions collapse to universal curves. We account for these observations with a minimal stochastic model that is based on an autocatalytic cycle. It predicts the scalings, as well as specific functional forms for the universal curves. Our experimental and theoretical analysis reveals a ...

Iyer-Biswas, Srividya; Henry, Jonathan T; Lo, Klevin; Burov, Stanislav; Lin, Yihan; Crooks, Gavin E; Crosson, Sean; Dinner, Aaron R; Scherer, Norbert F

2014-01-01

143

Individual growth detection of bacterial species in an in vitro oral polymicrobial biofilm model.  

PubMed

Most in vitro studies on the antibacterial effects of antiseptics have used planktonic bacteria in monocultures. However, this study design does not reflect the in vivo situation in oral cavities harboring different bacterial species that live in symbiotic relationships in biofilms. The aim of this study was to establish a simple in vitro polymicrobial model consisting of only three bacterial strains of different phases of oral biofilm formation to simulate in vivo oral conditions. Therefore, we studied the biofilm formation of Actinomyces naeslundii (An), Fusobacterium nucleatum (Fn), and Enterococcus faecalis (Ef) on 96-well tissue culture plates under static anaerobic conditions using artificial saliva according to the method established by Pratten et al. that was supplemented with 1gl(-1) sucrose. Growth was separately determined for each bacterial strain after incubation periods of up to 72h by means of quantitative real-time polymerase chain reaction and live/dead staining. Presence of an extracellular polymeric substance (EPS) was visualized by Concanavalin A staining. Increasing incubation times of up to 72h showed adhesion and propagation of the bacterial strains with artificial saliva formulation. An and Ef had significantly higher growth rates than Fn. Live/dead staining showed a median of 49.9% (range 46.0-53.0%) of living bacteria after 72h of incubation, and 3D fluorescence microscopy showed a three-dimensional structure containing EPS. An in vitro oral polymicrobial biofilm model was established to better simulate oral conditions and had the advantage of providing the well-controlled experimental conditions of in vitro testing. PMID:25119373

Tabenski, L; Maisch, T; Santarelli, F; Hiller, K-A; Schmalz, G

2014-11-01

144

Continuous monitoring of bacterial biofilm growth using uncoated Thickness-Shear Mode resonators  

NASA Astrophysics Data System (ADS)

Quartz Crystal Microbalances (QCM) were used to nondestructively monitor in real time the microbial growth of the bacteria Staphylococcus epidermidis (S. epidermidis) in a liquid broth. QCM, sometimes referred to as Thickness-Shear Mode (TSM) resonators, are highly sensitive sensors not only able to measure very small mass, but also non-gravimetric contributions of viscoelastic media. These devices can be used as biosensors for bacterial detection and are employed in many applications including their use in the food industry, water and environment monitoring, pharmaceutical sciences and clinical diagnosis. In this work, three strains of S. epidermidis (which differ in the ability to produce biofilm) have been continuously monitored using an array of piezoelectric TSM resonators, at 37 C in a selective culturing media. Microbial growth was followed by measuring the changes in the crystal resonant frequency and bandwidth at several harmonics. It was shown that microbial growth can be monitored in real time using multichannel and multiparametric QCM sensors.

Castro, P.; Resa, P.; Durn, C.; Maestre, J. R.; Mateo, M.; Elvira, L.

2012-12-01

145

Btcd, a mouse protein that binds to curved DNA, can substitute in Escherichia coli for H-NS, a bacterial nucleoid protein.  

PubMed Central

In an Escherichia coli mutant devoid of H-NS, a bacterial nucleoid protein, mouse protein Btcd was able to substitute for H-NS in two tested functions. It restored cell motility and repression of the expression of the bgl operon. Btcd1, a mutant Btcd protein deleted of its zinc finger and thus having reduced DNA binding, failed to substitute for H-NS. Mouse protein Btcd was shown to repress the bgl operon at the level of transcription initiation and to bind preferentially to a curved DNA fragment encompassing the bgl promoter. These effects of Btcd on bacterial gene transcription can be accounted for by the binding of Btcd or H-NS to a curved DNA sequence near a promoter. A few mammalian proteins have been shown to substitute for their Escherichia prototypes involved in DNA and RNA transactions. The efficiency of Btcd protein in substituting for H-NS in Escherichia suggests its possible involvement in regulating gene expression in mouse cells. Images PMID:8670903

Timchenko, T; Bailone, A; Devoret, R

1996-01-01

146

Conditional quantile regression models of melanoma tumor growth curves for assessing treatment effect in small sample studies.  

PubMed

Tumor growth curves provide a simple way to understand how tumors change over time. The traditional approach to fitting such curves to empirical data has been to estimate conditional mean regression functions, which describe the average effect of covariates on growth. However, this method ignores the possibility that tumor growth dynamics are different for different quantiles of the possible distribution of growth patterns. Furthermore, typical individual preclinical cancer drug study designs have very small sample sizes and can have lower power to detect a statistically significant difference in tumor volume between treatment groups. In our work, we begin to address these issues by combining several independent small sample studies of an experimental cancer treatment with differing study designs to construct quantile tumor growth curves. For modeling, we use a Penalized Fixed Effects Quantile Regression with added study effects to control for study differences. We demonstrate this approach using data from a series of small sample studies that investigated the effect of a naturally derived biological peptide, P28, on tumor volumes in mice grafted with human melanoma cells. We find a statistically significant quantile treatment effect on tumor volume trajectories and baseline values. In particular, the experimental treatment and a corresponding conventional chemotherapy had different effects on tumor growth by quantile. The conventional treatment, Dacarbazine (DTIC), tended to inhibit growth for smaller quantiles, while the experimental treatment P28 produced slower rates of growth in the upper quantiles, especially in the 95th quantile. Copyright 2014 John Wiley & Sons, Ltd. PMID:25231497

Revzin, Ella; Majumdar, Dibyen; Bassett, Gilbert W

2014-12-20

147

A new model for the spectral induced polarization signature of bacterial growth in porous media  

NASA Astrophysics Data System (ADS)

Recent biogeophysics studies demonstrated the sensitivity of complex conductivity to bacterial growth and microbial mediated mineral transformations in porous media. Frequency-domain induced polarization is a minimally invasive manner to measure the complex conductivity of a material over a broad range of frequencies. The real component of complex conductivity is associated with electromigration of the charge carriers, and the imaginary component represents reversible energy storage of charge carriers at polarization length scales. Quantitative relationship between frequency-domain induced polarization responses and bacterial growth and decay in porous media is analyzed in this study using a new developed model. We focus on the direct contribution of bacteria themselves to the complex conductivity in porous media in the absence of biomineralization. At low frequencies, the induced polarization of bacteria (?-polarization) is related to the properties of the electrical double layer surrounding the membrane surface of bacteria. Surface conductivity and ?-polarization are due to the Stern layer of the counterions occurring in a brush of polymers coating the surface of the bacteria, and can be related to the cation exchange capacity of the bacteria. From the modeling results, at low frequencies (< 10 Hz), the mobility of the counterions (K+) in the Stern layer of bacteria is found to be extremely small (4.710-10 m2s-1 V-1 at 25C), and is close to the mobility of the same counterions along the surface of clay minerals (Na+, 1.510-10 m2s-1 V-1 at 25C). This result is in agreement with experimental observations and it indicates a very low relaxation frequency for the ?-polarization of the bacteria cells (typically around 0.1 to 5 Hertz). By coupling this new model with reactive transport modeling in which the evolution of bacterial populations are usually described by Monod kinetics, we show that the changes in imaginary conductivity with time can be used to determine bacterial growth kinetics parameters such as the growth and endogenous decay coefficient.

Zhang, C.; Revil, A.; Atekwana, E. A.; Jardani, A.; Smith, S.

2012-12-01

148

Scaling laws governing stochastic growth and division of single bacterial cells.  

PubMed

Uncovering the quantitative laws that govern the growth and division of single cells remains a major challenge. Using a unique combination of technologies that yields unprecedented statistical precision, we find that the sizes of individual Caulobacter crescentus cells increase exponentially in time. We also establish that they divide upon reaching a critical multiple (?1.8) of their initial sizes, rather than an absolute size. We show that when the temperature is varied, the growth and division timescales scale proportionally with each other over the physiological temperature range. Strikingly, the cell-size and division-time distributions can both be rescaled by their mean values such that the condition-specific distributions collapse to universal curves. We account for these observations with a minimal stochastic model that is based on an autocatalytic cycle. It predicts the scalings, as well as specific functional forms for the universal curves. Our experimental and theoretical analysis reveals a simple physical principle governing these complex biological processes: a single temperature-dependent scale of cellular time governs the stochastic dynamics of growth and division in balanced growth conditions. PMID:25349411

Iyer-Biswas, Srividya; Wright, Charles S; Henry, Jonathan T; Lo, Klevin; Burov, Stanislav; Lin, Yihan; Crooks, Gavin E; Crosson, Sean; Dinner, Aaron R; Scherer, Norbert F

2014-11-11

149

A New Method to Compare Statistical Tree Growth Curves: The PL-GMANOVA Model and Its Application with Dendrochronological Data  

PubMed Central

Growth curves are monotonically increasing functions that measure repeatedly the same subjects over time. The classical growth curve model in the statistical literature is the Generalized Multivariate Analysis of Variance (GMANOVA) model. In order to model the tree trunk radius (r) over time (t) of trees on different sites, GMANOVA is combined here with the adapted PL regression model Q?=?AT+E, where for and for , A?=? initial relative growth to be estimated, , and E is an error term for each tree and time point. Furthermore, Ei[br] ?=?, , with TPR being the turning point radius in a sigmoid curve, and at is an estimated calibrating time-radius point. Advantages of the approach are that growth rates can be compared among growth curves with different turning point radiuses and different starting points, hidden outliers are easily detectable, the method is statistically robust, and heteroscedasticity of the residuals among time points is allowed. The model was implemented with dendrochronological data of 235 Pinus montezumae trees on ten Mexican volcano sites to calculate comparison intervals for the estimated initial relative growth . One site (at the Popocatpetl volcano) stood out, with being 3.9 times the value of the site with the slowest-growing trees. Calculating variance components for the initial relative growth, 34% of the growth variation was found among sites, 31% among trees, and 35% over time. Without the Popocatpetl site, the numbers changed to 7%, 42%, and 51%. Further explanation of differences in growth would need to focus on factors that vary within sites and over time. PMID:25402427

Ricker, Martin; Pea Ramrez, Vctor M.; von Rosen, Dietrich

2014-01-01

150

Asynchrony in the growth and motility responses to environmental changes by individual bacterial cells  

SciTech Connect

Knowing how individual cells respond to environmental changes helps one understand phenotypic diversity in a bacterial cell population, so we simultaneously monitored the growth and motility of isolated motile Escherichia coli cells over several generations by using a method called on-chip single-cell cultivation. Starved cells quickly stopped growing but remained motile for several hours before gradually becoming immotile. When nutrients were restored the cells soon resumed their growth and proliferation but remained immotile for up to six generations. A flagella visualization assay suggested that deflagellation underlies the observed loss of motility. This set of results demonstrates that single-cell transgenerational study under well-characterized environmental conditions can provide information that will help us understand distinct functions within individual cells.

Umehara, Senkei [Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo (Japan); Hattori, Akihiro [Department of Biomedical Information, Division of Biosystems, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (Japan); Inoue, Ippei [Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo (Japan); Yasuda, Kenji [Department of Biomedical Information, Division of Biosystems, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University (Japan)]. E-mail: yasuda.bmi@tmd.ac.jp

2007-05-04

151

Effect of humic substance photodegradation on bacterial growth and respiration in lake water  

USGS Publications Warehouse

This study addresses how humic substance (HS) chemical composition and photoreactivity affect bacterial growth, respiration, and growth efficiency (BGE) in lake water. Aqueous solutions of HSs from diverse aquatic environments representing different dissolved organic matter sources (autochthonous and allochthonous) were exposed to artificial solar UV radiation. These solutions were added to lake water passed through a 0.7-??m-pore-size filter (containing grazer-free lake bacteria) followed by dark incubation for 5, 43, and 65 h. For the 5-h incubation, several irradiated HSs inhibited bacterial carbon production (BCP) and this inhibition was highly correlated with H 2O2 photoproduction. The H2O2 decayed in the dark, and after 43 h, nearly all irradiated HSs enhanced BCP (average 39% increase relative to nonirradiated controls, standard error = 7.5%, n = 16). UV exposure of HSs also increased bacterial respiration (by ???18%, standard error = 5%, n = 4), but less than BCP, resulting in an average increase in BGE of 32% (standard error = 10%, n = 4). Photoenhancement of BCP did not correlate to HS bulk properties (i.e., elemental and chemical composition). However, when the photoenhancement of BCP was normalized to absorbance, several trends with HS origin and extraction method emerged. Absorbance-normalized hydrophilic acid and humic acid samples showed greater enhancement of BCP than hydrophobic acid and fulvic acid samples. Furthermore, absorbance-normalized autochthonous samples showed ???10-fold greater enhancement of BCP than allochthonous-dominated samples, indicating that the former are more efficient photoproducers of biological substrates. Copyright ?? 2005, American Society for Microbiology. All Rights Reserved.

Anesio, A. M.; Graneli, W.; Aiken, G. R.; Kieber, D. J.; Mopper, K.

2005-01-01

152

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

NASA Astrophysics Data System (ADS)

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.

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

2001-08-01

153

Bacterial diversity in five Icelandic geothermal waters: temperature and sinter growth rate effects.  

PubMed

The microbial ecology associated with siliceous sinters was studied in five geochemically diverse Icelandic geothermal systems. Bacterial 16S rRNA clone libraries were constructed from water-saturated precipitates from each site resulting in a total of 342 bacterial clone sequences and 43 species level phylotypes. In near-neutral, saline (2.6-4.7% salinity) geothermal waters where sinter growth varied between 10 and ~300 kg year(-1) m(-2), 16S rRNA gene analyses revealed very low (no OTUs could be detected) to medium (9 OTUs) microbial activity. The most dominant phylotypes found in these waters belong to marine genera of the Proteobacteria. In contrast, in alkaline (pH = 9-10), meteoric geothermal waters with temperature = 66-96C and <1-20 kg year(-1)m(-2) sinter growth, extensive biofilms (a total of 34 OTUs) were observed within the waters and these were dominated by members of the class Aquificae (mostly related to Thermocrinis), Deinococci (Thermus species) as well as Proteobacteria. The observed phylogenetic diversity (i.e., number and composition of detected OTUs) is argued to be related to the physico-chemical regime prevalent in the studied geothermal waters; alkaliphilic thermophilic microbial communities with phylotypes related to heterotrophic and autotrophic microorganisms developed in alkaline high temperature waters, whereas halophilic mesophilic communities dominated coastal geothermal waters. PMID:21607550

Tobler, Dominique J; Benning, Liane G

2011-07-01

154

Growth performance and carcase quality in broiler chickens fed on bacterial protein grown on natural gas.  

PubMed

1. The effects of increasing concentrations (0, 40, 80 or 120 g/kg) of bacterial protein meal (BPM) and bacterial protein autolysate (BPA) grown on natural gas on growth performance and carcase quality in broiler chickens were examined. 2. Adding BPM to diets reduced feed intake and improved gain: feed from 0 to 21 d and overall to 35 d, but did not significantly affect weight gain compared to the soybean meal based control diet. 3. Increasing concentrations of BPA significantly reduced growth rate, feed intake, gain: feed, carcase weight and dressing percentage, but significantly increased carcase dry matter, fat and energy content. 4. Adding BPM to diets had no effect on viscosity of diets and jejunal digesta, and minor effects on litter quality, whereas BPA increased the viscosity of diets and jejunal digesta, improved litter quality at 21 d, but decreased litter quality at 32 d. 5. To conclude, broiler chickens performed better on a BPM product with intact proteins than on an autolysate with ruptured cell walls and a high content of free amino acids and low molecular-weight peptides. PMID:21058073

verland, M; Schyen, H F; Skrede, A

2010-10-01

155

[In vitro study over statins effects on cellular growth curves and its reversibility with mevalonate].  

PubMed

HMG-CoA-Reductase inhibitors, also known as statins, are currently the most powerful cholesterol-lowering drugs available on the market. Clinical trials and experimental evidence suggest that statins have heavy anti-atherosclerotic effects. These are in part consequence of lipid lowering but also result from pleiotropic actions of the drugs. These so-called pleiotropic properties affect various aspects of cell function, inflammation, coagulation, and vasomotor activity. These effects are mediated either indirectly through LDL-c reduction or via a direct effect on cellular functions. Although many of the pleiotropic properties of statins may be a class effect, some may be unique to certain agents and account for differences in their pharmacological activity. So, although statins typically have similar effects on LDL-c levels, differences in chemical structure and pharmacokinetic profile can lead to variations in pleiotropic effects. In this paper we analize the in vitro effects of different statins over different cell lines from cells implicated in atherosclerotic process: endothelial cells, fibroblasts, and vascular muscular cells. In relation with our results we can proof that the effects of different dosis of different statins provides singular effects over growth curves of different cellular lines, a despite of a class-dependent effects. So, pleiotropic effects and its reversibility with mevalonate are different according with the molecule and the dosis. PMID:24126321

Millan Nez-Corts, Jess; Alvarez Rodriguez, Ysmael; Alvarez Novs, Granada; Recarte Garcia-Andrade, Carlos; Alvarez-Sala Walther, Luis

2014-01-01

156

Factors influencing community health centers' efficiency: a latent growth curve modeling approach.  

PubMed

The objective of study is to examine factors affecting the variation in technical and cost efficiency of community health centers (CHCs). A panel study design was formulated to examine the relationships among the contextual, organizational structural, and performance variables. Data Envelopment Analysis (DEA) of technical efficiency and latent growth curve modeling of multi-wave technical and cost efficiency were performed. Regardless of the efficiency measures, CHC efficiency was influenced more by contextual factors than organizational structural factors. The study confirms the independent and additive influences of contextual and organizational predictors on efficiency. The change in CHC technical efficiency positively affects the change in CHC cost efficiency. The practical implication of this finding is that healthcare managers can simultaneously optimize both technical and cost efficiency through appropriate use of inputs to generate optimal outputs. An innovative solution is to employ decision support software to prepare an expert system to assist poorly performing CHCs to achieve better cost efficiency through optimizing technical efficiency. PMID:17918690

Marathe, Shriram; Wan, Thomas T H; Zhang, Jackie; Sherin, Kevin

2007-10-01

157

Modeling Latent Growth Curves With Incomplete Data Using Different Types of Structural Equation Modeling and Multilevel Software  

ERIC Educational Resources Information Center

This article offers different examples of how to fit latent growth curve (LGC) models to longitudinal data using a variety of different software programs (i.e., LISREL, Mx, Mplus, AMOS, SAS). The article shows how the same model can be fitted using both structural equation modeling and multilevel software, with nearly identical results, even in

Ferrer, Emilio; Hamagami, Fumiaki; McArdle, John J.

2004-01-01

158

Differential School Effects among Low, Middle, and High Social Class Composition Schools: A Multiple Group, Multilevel Latent Growth Curve Analysis  

ERIC Educational Resources Information Center

This study uses large-scale survey data and a multiple group, multilevel latent growth curve model to examine differential school effects between low, middle, and high social class composition public schools. The results show that the effects of school inputs and school practices on learning differ across the 3 subpopulations. Moreover, student

Palardy, Gregory J.

2008-01-01

159

Effects of Dissolved Organic Matter Photoproducts and Mineral Nutrient Supply on Bacterial Growth in Mediterranean Inland Waters  

Microsoft Academic Search

Sunlight reacts with dissolved organic matter (DOM) modifying its availability as bacterial substrate. We assessed the impact\\u000a of DOM photoproducts and mineral nutrient supply on bacterial growth in seven inland waters from the South of Spain, where\\u000a DOM is characterized by low chromophoric content and long residence time. Factorial experiments were performed with presence\\u000a vs absence of DOM photoproducts and

Eva Ortega-Retuerta; Elvira Pulido-Villena; Isabel Reche

2007-01-01

160

Seasonal Dynamics of Bacterial Colonization of Cotton Fiber and Effects of Moisture on Growth of Bacteria within the Cotton Boll  

PubMed Central

A highly replicated 3-year field study was conducted to determine the seasonal patterns of bacterial colonization of cotton fiber from the time of dehiscence of the bolls (the point at which the bolls just begin to open) through harvest and commercial ginning. Bacterial numbers on fiber samples from 16 plots were determined by dilution pour plating with tryptic soy agar containing cycloheximide, and numbers of gram-negative bacteria were determined by plating on tryptic soy agar containing vancomycin and cycloheximide. Populations of bacteria varied from year to year, but in all three seasons the pattern of colonization was generally a pattern consisting of a rapid increase following opening of the bolls and a more or less stable number thereafter throughout the growing season. Gram-negative bacteria accounted for 50% or more of the recoverable bacterial population. We hypothesized that the luxuriant bacterial flora developed as a result of the availability of sufficient free water in the bolls to allow bacterial proliferation with the carbon sources remaining after fiber maturation. Therefore, laboratory experiments were conducted to determine the threshold moisture level allowing growth of bacteria on fiber in the bolls. Bacterial proliferation occurred when as little as 2% moisture was added to air-dried fiber. Using simulated bolls, we demonstrated bacterial growth resulting from dew formation on fiber held in controlled-humidity chambers. PMID:16348921

Zuberer, D. A.; Kenerley, C. M.

1993-01-01

161

The effect of different growth regimes on the endophytic bacterial communities of the fern, Dicksonia sellowiana hook (Dicksoniaceae)  

PubMed Central

Endophytic bacteria associated with the fern Dicksonia sellowiana were investigated. The bacterial communities from the surface-sterilized pinnae and rachis segments of the plants from the Brazilian Atlantic Rainforest that grew in native field conditions were compared with the bacterial communities from plants grown in greenhouses and plants that were initially grown in greenhouses and then transferred to the forest. From 540 pinnae and 540 rachis segments, 163 (30.2%) and 346 (64.2%) were colonized by bacteria, respectively. The main bacterial genera and species that were isolated included Bacillus spp. ( B. cereus, B. megaterium, B. pumilus and B. subtilis ) , Paenibacillus sp. , Amphibacillus sp. , Gracilibacillus sp. , Micrococcus sp. and Stenotrophomonas spp. ( S. maltophilia and S. nitroreducens ). B. pumilus was the most frequently isolated bacterial species . Amphibacillus and Gracilibacillus were reported as endophytes for the first time. Other commonly found bacterial genera were not observed in D. sellowiana , which may reflect preferences of specific bacterial communities inside this fern or detection limitations due to the isolation procedures. Plants that were grown in greenhouses and plants that were reintroduced into the forest displayed more bacterial genera and species diversity than native field plants, suggesting that reintroduction shifts the bacterial diversity. Endophytic bacteria that displayed antagonistic properties against different microorganisms were detected, but no obvious correlation was found between their frequencies with plant tissues or with plants from different growth regimes. This paper reports the first isolation of endophytic bacteria from a fern. PMID:24031575

de Arajo Barros, Irene; Luiz Arajo, Welington; Lcio Azevedo, Joo

2010-01-01

162

Bacterial growth in the cold: Evidence for an enhanced substrate requirement  

SciTech Connect

Growth responses and biovolume changes for four facultatively psychrophilic bacterial isolates from Conception Bay, Newfoundland, and the Arctic Ocean were examined at temperatures from {minus}1.5 to 35C, with substrate concentrations of 0.15, 1.5, and 1,500 mg of proteose peptone-yeast extract per liter. For two cultures, growth in 0.1, 1.0, and 1,000 mg of proline per liter was also examined. At 10 to 15C and above, growth rates showed no marked effect of substrate concentration, while at {minus}1.5 and 0C, there was an increasing requirement for organic nutrients, with generation times in low-nutrient media that were two to three times longer than in high-nutrient media. Biovolume showed a clear dependence on substrate concentration and quality; the largest cells were in the highest-nutrient media. Biovolume was also affected by temperature; the largest cells were found at the lowest temperatures. These data have implications for both food web structure and carbon flow in cold waters and for the effects of global climate change, since the change in growth rate is most dramatic at the lowest temperatures.

Wiebe, W.J.; Sheldon, W.M. Jr.; Pomeroy, L.R. (Univ. of Georgia, Athens (United States))

1992-01-01

163

Bacterial endophyte Sphingomonas sp. LK11 produces gibberellins and IAA and promotes tomato plant growth.  

PubMed

Plant growth promoting endophytic bacteria have been identified as potential growth regulators of crops. Endophytic bacterium, Sphingomonas sp. LK11, was isolated from the leaves of Tephrosia apollinea. The pure culture of Sphingomonas sp. LK11 was subjected to advance chromatographic and spectroscopic techniques to extract and isolate gibberellins (GAs). Deuterated standards of [17, 17-(2)H2]-GA4, [17, 17-(2)H2]-GA9 and [17, 17-(2)H2]-GA20 were used to quantify the bacterial GAs. The analysis of the culture broth of Sphingomonas sp. LK11 revealed the existence of physiologically active gibberellins (GA4: 2.97 0.11 ng/ml) and inactive GA9 (0.98 0.15 ng/ml) and GA20 (2.41 0.23). The endophyte also produced indole acetic acid (11.23 0.93 ?M/ml). Tomato plants inoculated with endophytic Sphingomonas sp. LK11 showed significantly increased growth attributes (shoot length, chlorophyll contents, shoot, and root dry weights) compared to the control. This indicated that such phyto-hormones-producing strains could help in increasing crop growth. PMID:24994010

Khan, Abdul Latif; Waqas, Muhammad; Kang, Sang-Mo; Al-Harrasi, Ahmed; Hussain, Javid; Al-Rawahi, Ahmed; Al-Khiziri, Salima; Ullah, Ihsan; Ali, Liaqat; Jung, Hee-Young; Lee, In-Jung

2014-08-01

164

Assessment of bacterial growth and total organic carbon removal on granular activated carbon contactors.  

PubMed Central

The overall growth rate of bacteria on granular activated carbon (GAC) contactors at the Philadelphia Torresdale Water Treatment Pilot Plant facility was found to decrease until steady state was reached. The growth rate was found to fluctuate between 6.94 X 10(-3) and 8.68 X 10(-4) doublings per h. The microbiological removal of total organic carbon (TOC) was calculated by considering the GAC contactors as semiclosed continuous culture systems and using growth yield factors determined in laboratory experiments. After ozonation, the average TOC entering the contactors was 1,488 micrograms/liter, and the average effluent TOC was 497 micrograms/liter. Microbiological TOC removal was found to average 240 micrograms/liter on GAC contactors, which was not significantly different from microbiological TOC (220 micrograms/liter) removal across a parallel sand contactor where no adsorption took place. Thus, GAC did not appear to enhance biological TOC removal. Bacterial growth and maintenance was responsible for approximately 24% of the TOC removal on GAC under the conditions of this study. PMID:6639023

Bancroft, K; Maloney, S W; McElhaney, J; Suffet, I H; Pipes, W O

1983-01-01

165

A simple interpretation of the growth of scientific/technological research impact leading to hype-type evolution curves  

E-print Network

The empirical and theoretical justification of Gartner hype curves is a very relevant open question in the field of Technological Life Cycle analysis. The scope of the present paper is to introduce a simple model describing the growth of scientific/technological research impact, in the specific case where science is the main source of a new idea driving a technological development, leading to hype-type evolution curves. The main idea of the model is that, in a first stage, the growth of the scientific interest of a new specific field (as can be measured by publication numbers) basically follows the classical logistic growth curve. At a second stage, starting at a later trigger time, the technological development based on that scientific idea (as can be measured by patent deposits) can be described as the integral (in a mathematical sense) of the first curve, since technology is based on the overall accumulated scientific knowledge. The model is tested through a bibliometric analysis of the publication and pat...

Campani, Marco

2014-01-01

166

Effects of Gypsophila saponins on bacterial growth kinetics and on selection of subterranean clover rhizosphere bacteria.  

PubMed

Plant secondary metabolites, such as saponins, have a considerable impact in agriculture because of their allelopathic effects. They also affect the growth of soil microorganisms, especially fungi. We investigated the influence of saponins on rhizosphere bacteria in vitro and in soil conditions. The effects of gypsophila saponins on the growth kinetics of rhizosphere bacteria were studied by monitoring the absorbance of the cultures in microtiter plates. Gypsophila saponins (1%) increased the lag phase of bacterial growth. The impact of gypsophila saponins on subterranean clover rhizosphere was also investigated in a pot experiment. The addition of gypsophila saponins did not modify clover biomass but significantly increased (twofold with 1% saponins) the weight of adhering soil. The number of culturable heterotrophic bacteria of the clover rhizosphere was not affected by the addition of gypsophila saponins. Nevertheless, the phenotypical characterization of the dominant Gram-negative strains of the clover rhizosphere, using the Biolog system, showed qualitative and quantitative differences induced by 1% saponins. With the addition of saponins, the populations of Chryseomonas spp. and Acinetobacter spp., the two dominant culturable genera of control clover, were no longer detectable or were significantly decreased, while that of Aquaspirillum dispar increased and Aquaspirillum spp. became the major genus. Aquaspirillum dispar and Aquaspirillum spp. were also the dominant rhizosphere bacteria of Gypsophila paniculata, which greatly accumulates these saponins in its roots. These results suggest that saponins may control rhizosphere bacteria in soil through rhizodeposition mechanisms. PMID:14569290

Fons, F; Amellal, N; Leyval, C; Saint-Martin, N; Henry, M

2003-06-01

167

A role for Bacteroides fragilis neuraminidase in bacterial growth in two model systems.  

PubMed Central

Two Bacteroides fragilis neuraminidase-deficient mutants were used to study the role of neuraminidase activity in growth of B. fragilis in tissue culture monolayers (CHO cells) and in the in vivo rat granuloma pouch. The nanH structural gene for neuraminidase was cloned from B. fragilis TM4000 and was used to create two isogenic strains with chromosomal disruptions at the nanH gene. B. fragilis VRC404 contains an insertion flanked by disrupted copies of the nanH gene, and B. fragilis VRC426 contains a deletion of a significant portion of nanH coding sequences. The insertion mutant VRC404 is capable of reverting to nanH+. It grew as well as the wild type in CHO monolayers. However, between 48 and 72 h after infection, the bacterial population was enriched with nanH+ bacterial cells (10 to 20%). In the rat pouch 48 h after infection, more than 90% of the population sampled had become nanH+. The deletion mutant VRC426 showed a severe growth defect in the rat pouch model. In addition, VRC426 was efficiently outgrown by the wild type in competition experiments, even when the mutant was present at 10 times the number of wild-type cells at the time of infection. A common characteristic of both model systems is a drastic decrease in the free glucose concentration 16 to 24 h postinfection. We suggest that neuraminidase activity may be required for B. fragilis to grow to maximal levels in the tissue culture and rat pouch systems by making other carbon sources available after glucose levels are reduced. Images PMID:8406832

Godoy, V G; Dallas, M M; Russo, T A; Malamy, M H

1993-01-01

168

Television Viewing and Adolescents Judgment of Sexual Request Scripts: A Latent Growth Curve Analysis in Early and Middle Adolescence  

Microsoft Academic Search

A longitudinal study was conducted to explore the relationship between television viewing and beliefs about expressing sexual\\u000a desire in dating situations. In three consecutive years, a panel of early adolescents (N?=?883) and a panel of middle adolescents (N?=?651) rated the effectiveness of a sexual approach and a romantic approach. Latent growth curve analyses indicate that between\\u000a the ages of 12

Steven Eggermont

2006-01-01

169

Influence of untreated and bacterial-treated Yamuna water on the plant growth of Zea mays L  

Microsoft Academic Search

In present study an attempt has been made to study the pollution level of river Yamuna at Agra, by analyzing the physico-chemical parameters of untreated and bacterial-treated water and its effect on the growth of maize plant. Among different concentrations (25, 50, 75 and 100%) of treated water, the 100% concentration of treated water sample showed good effect on the

Pragati Saini; Ajay Kumar; J. N. Shrivastava

170

Biocontrol of Fusarium graminearum growth and deoxynivalenol production in wheat kernels with bacterial antagonists.  

PubMed

Fusarium graminearum is the main causal pathogen affecting small-grain cereals, and it produces deoxynivalenol, a kind of mycotoxin, which displays a wide range of toxic effects in human and animals. Bacterial strains isolated from peanut shells were investigated for their activities against F. graminearum by dual-culture plate and tip-culture assays. Among them, twenty strains exhibited potent inhibition to the growth of F. graminearum, and the inhibition rates ranged from 41.41% to 54.55% in dual-culture plate assay and 92.70% to 100% in tip-culture assay. Furthermore, eighteen strains reduced the production of deoxynivalenol by 16.69% to 90.30% in the wheat kernels assay. Finally, the strains with the strongest inhibitory activity were identified by morphological, physiological, biochemical methods and also 16S rDNA and gyrA gene analysis as Bacillus amyloliquefaciens. The current study highlights the potential application of antagonistic microorganisms and their metabolites in the prevention of fungal growth and mycotoxin production in wheat kernels. As a biological strategy, it might avoid safety problems and nutrition loss which always caused by physical and chemical strategies. PMID:24441510

Shi, Cuijuan; Yan, Peisheng; Li, Jiafei; Wu, Hanqi; Li, Qianwei; Guan, Shanshan

2014-01-01

171

Effective inhibition of bacterial respiration and growth by CuO microspheres composed of thin nanosheets.  

PubMed

This study describes the synthesis, characterization and biocidal potential of copper oxide micro-spheres composed of thin sheets (CuOMSs-Ths). Microscopic observations of synthesized CuOMSs-Ths revealed the clusters of thin sheets arranged in small flower like micro-spheres. Diameter of each micro-sphere was determined in the range of 2-3 ?m, whereas the size of each sheet was ? 80 nm. These micro-flowers like nanostructures were synthesized using copper nitrate hexahydrate and sodium hydroxide via solution process. The CuOMSs-Ths exhibited a broad-spectrum anti-bacterial activity involving significant growth inhibition of Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Micrococcus luteus. The IC50 values of these engineered NPs against E. coli, P. aeruginosa, S. aureus and M. luteus were determined to be 195, 200, 131 and 184 ?g/ml, respectively. Also, the respiration of Gram+ ve organisms (M. luteus and S. aureus) was inhibited significantly (p value < 0.005) at relatively lower concentrations of 12.5 and 50 ?g/ml, respectively, as compared to the Gram- ve bacteria (E. coli and P. aeruginosa), where the growth inhibition occurred at a much greater concentration of 100 ?g/ml. The results explicitly demonstrated anti-microbial activity of CuOMSs-Ths with a higher level of toxicity against the Gram+ ve vis-a-vis Gram- ve bacteria. PMID:23816782

Wahab, Rizwan; Khan, Shams Tabrez; Dwivedi, Sourabh; Ahamed, Maqusood; Musarrat, Javed; Al-Khedhairy, Abdulaziz A

2013-11-01

172

Adaptation of an automatic bacterial colony counter for measuring lung tumor growth in mice.  

PubMed

Adaptation of an automatic bacterial colony counter proved to be an efficient procedure for detecting and quantitating tumor growth in mouse lungs prepared by the Wexler method of India ink insufflation. After correlation of the size discriminator settings on the automatic counter with the Wexler visual scale, the amount of tumor growth in the lungs of 52 mice was determined by eye and independently by the automatic counter. There was no statistical difference between the two procedures. When the mouse lungs were grouped according to the number of tumors computed by eye, there was no statistical difference between the two counting procedures in any of the groups. The standard deviation was independent of the number of tumors in the lungs. This caused the precision of the automatic counter to be poor in lungs with few tumors because the error was a greater percentage of the total. In lungs with a large number of tumors, which were difficult to count by eye, close agreement between the two methods of counting was demonstrated. PMID:326389

Filardi, M J; Lininger, L; McKneally, M F

1977-08-01

173

Production of fungal and bacterial growth modulating secondary metabolites is widespread among mycorrhiza-associated streptomycetes  

PubMed Central

Background Studies on mycorrhiza associated bacteria suggest that bacterial-fungal interactions play important roles during mycorrhiza formation and affect plant health. We surveyed Streptomyces Actinobacteria, known as antibiotic producers and antagonists of fungi, from Norway spruce mycorrhizas with predominantly Piloderma species as the fungal partner. Results Fifteen Streptomyces isolates exhibited substantial variation in inhibition of tested mycorrhizal and plant pathogenic fungi (Amanita muscaria, Fusarium oxysporum, Hebeloma cylindrosporum, Heterobasidion abietinum, Heterobasidion annosum, Laccaria bicolor, Piloderma croceum). The growth of the mycorrhiza-forming fungus Laccaria bicolor was stimulated by some of the streptomycetes, and Piloderma croceum was only moderately affected. Bacteria responded to the streptomycetes differently than the fungi. For instance the strain Streptomyces sp. AcM11, which inhibited most tested fungi, was less inhibitory to bacteria than other tested streptomycetes. The determined patterns of Streptomyces-microbe interactions were associated with distinct patterns of secondary metabolite production. Notably, potentially novel metabolites were produced by strains that were less antagonistic to fungi. Most of the identified metabolites were antibiotics (e.g. cycloheximide, actiphenol) and siderophores (e.g. ferulic acid, desferroxiamines). Plant disease resistance was activated by a single streptomycete strain only. Conclusions Mycorrhiza associated streptomycetes appear to have an important role in inhibiting the growth of fungi and bacteria. Additionally, our study indicates that the Streptomyces strains, which are not general antagonists of fungi, may produce still un-described metabolites. PMID:22852578

2012-01-01

174

Acetate Availability and Utilization Supports the Growth of Mutant Sub-Populations on Aging Bacterial Colonies  

PubMed Central

When bacterial colonies age most cells enter a stationary phase, but sub-populations of mutant bacteria can continue to grow and accumulate. These sub-populations include bacteria with mutations in rpoB (RNA polymerase ?-subunit) or rpoS (RNA polymerase stress-response sigma factor). Here we have identified acetate as a nutrient present in the aging colonies that is utilized by these mutant subpopulations to support their continued growth. Proteome analysis of aging colonies showed that several proteins involved in acetate conversion and utilization were upregulated during aging. Acetate is known to be excreted during the exponential growth phase but can be imported later during the transition to stationary phase and converted to acetyl-CoA. Acetyl-CoA is used in multiple processes, including feeding into the TCA cycle, generating ATP via the glyoxylate shunt, as a source of acetyl groups for protein modification, and to support fatty acid biosynthesis. We showed that deletion of acs (encodes acetyl-CoA synthetase; converts acetate into acetyl-CoA) significantly reduced the accumulation of rpoB and rpoS mutant subpopulations on aging colonies. Measurement of radioactive acetate uptake showed that the rate of conversion decreased in aging wild-type colonies, was maintained at a constant level in the rpoB mutant, and significantly increased in the aging rpoS mutant. Finally, we showed that the growth of subpopulations on aging colonies was greatly enhanced if the aging colony itself was unable to utilize acetate, leaving more acetate available for mutant subpopulations to use. Accordingly, the data show that the accumulation of subpopulations of rpoB and rpoS mutants on aging colonies is supported by the availability in the aging colony of acetate, and by the ability of the subpopulation cells to convert the acetate to acetyl-CoA. PMID:25275605

Bergman, Jessica M.; Wrande, Marie; Hughes, Diarmaid

2014-01-01

175

Acetate availability and utilization supports the growth of mutant sub-populations on aging bacterial colonies.  

PubMed

When bacterial colonies age most cells enter a stationary phase, but sub-populations of mutant bacteria can continue to grow and accumulate. These sub-populations include bacteria with mutations in rpoB (RNA polymerase ?-subunit) or rpoS (RNA polymerase stress-response sigma factor). Here we have identified acetate as a nutrient present in the aging colonies that is utilized by these mutant subpopulations to support their continued growth. Proteome analysis of aging colonies showed that several proteins involved in acetate conversion and utilization were upregulated during aging. Acetate is known to be excreted during the exponential growth phase but can be imported later during the transition to stationary phase and converted to acetyl-CoA. Acetyl-CoA is used in multiple processes, including feeding into the TCA cycle, generating ATP via the glyoxylate shunt, as a source of acetyl groups for protein modification, and to support fatty acid biosynthesis. We showed that deletion of acs (encodes acetyl-CoA synthetase; converts acetate into acetyl-CoA) significantly reduced the accumulation of rpoB and rpoS mutant subpopulations on aging colonies. Measurement of radioactive acetate uptake showed that the rate of conversion decreased in aging wild-type colonies, was maintained at a constant level in the rpoB mutant, and significantly increased in the aging rpoS mutant. Finally, we showed that the growth of subpopulations on aging colonies was greatly enhanced if the aging colony itself was unable to utilize acetate, leaving more acetate available for mutant subpopulations to use. Accordingly, the data show that the accumulation of subpopulations of rpoB and rpoS mutants on aging colonies is supported by the availability in the aging colony of acetate, and by the ability of the subpopulation cells to convert the acetate to acetyl-CoA. PMID:25275605

Bergman, Jessica M; Wrande, Marie; Hughes, Diarmaid

2014-01-01

176

Radiative Heat Transfer in Curved Specular Surfaces in Czochralski Crystal Growth Furnace  

Microsoft Academic Search

A numerical investigation of radiative heat transfer constructed by curved surfaces with specular and diffuse reflection components is carried out. The ray tracing method is adopted for the calculation of view factors, in which a new ray emission model is proposed. The second-degree radiation ring elements are introduced, which are of engineering importance and numerical efficiency. The accuracy of the

Zhixiong Guo; Shigenao Maruyama; Takao Tsukada

1997-01-01

177

Bacterial O-Methylation of Chloroguaiacols: Effect of Substrate Concentration, Cell Density, and Growth Conditions  

PubMed Central

O-methylation of chloroguaiacols has been examined in a number of gram-positive and gram-negative bacteria to elucidate the effects of substrate concentration, growth conditions, and cell density. Substrate concentrations between 0.1 and 20.0 mg liter?1 were used, and it was found that (i) yields of the O-methylated products were significantly higher at the lowest concentrations and (ii) rates of O-methylation were not linear functions of concentration. With 3,4,5-trichloroguaiacol, the nature of the metabolites also changed with concentration. During growth with a range of substrates, O-methylation of chloroguaiacols also took place. With vanillate, however, de-O-methylation occurred: the chlorocatechol formed from 4,5,6-trichloroguaiacol was successively O-methylated to 3,4,5-trichloroguaiacol and 3,4,5-trichloroveratrole, whereas that produced from 4,5-dichloroguaiacol was degraded without O-methylation. Effective O-methylation in nonproliferating suspensions occurred at cell densities as low as 105 cells ml?1, although both the yields and the rates were lower than in more dense cultures. By using disk assays, it was shown that, compared with their precursors, all of the O-methylated metabolites were virtually nontoxic to the strains examined. It is therefore proposed that O-methylation functions as a detoxification mechanism for cells exposed to chloroguaiacols and chlorophenols. In detail, significant differences were observed in the response of gram-positive and gram-negative cell strains to chloroguaiacols. It is concluded that bacterial O-methylation is to be expected in the natural environment subjected to discharge of chloroguaiacols. PMID:16346715

Allard, Ann-Sofie; Remberger, Mikael; Neilson, Alasdair H.

1985-01-01

178

Energy utilisation and growth performance of chicken fed diets containing graded levels of supplementary bacterial phytase.  

PubMed

A total of 364 female Ross 308 chicks (1 d old) were used in the present study conducted in floor pens to investigate the effects of graded levels of supplementary bacterial phytase on dietary energy utilisation and growth performance. For this purpose, four maize-soyabean-based diets were offered to the birds from 0 to 21 d of age. These included a suboptimal P negative control (NC, 3.0 g/kg non-phytate P), NC+250 phytase units (FTU)/kg feed, NC+500 FTU and NC+2500 FTU. The effect of phytase activity on bird growth performance was best described as a linear relationship between increasing dose and increased feed intake (P< 0.001), but was quadratic for body-weight gain (P= 0.002) and feed efficiency (P= 0.023). There was no significant response (P>0.05) of dietary apparent metabolisable energy (AME) to supplementary phytase. The birds fed phytase increased their retention of total carcass energy in a linear fashion (P= 0.009) with increased phytase dose. The efficiency of dietary AME used for overall carcass energy retention also improved (P= 0.007) in a linear manner with increased dietary phytase activity. Dietary net energy for production (NEp) increased (P= 0.047) with an increase in phytase dose following a linear pattern, as an increase of 100 FTU increased dietary net energy by 15.4 J (estimated within the range of doses used in the present experiment). Dietary NEp was more highly correlated with performance criteria than dietary AME, and it seems to be a more sensitive way to evaluate broiler response to phytase supplementation. PMID:22716908

Pirgozliev, V; Bedford, M R

2013-01-28

179

A growth model for primary cancer (II). New rules, progress curves and morphology transitions  

Microsoft Academic Search

In the present paper we extend the analysis of another model recently proposed to simulate the growth of carcinoma in situ, which includes cell proliferation, motility and death, as well as chemotactic interactions among cells. The tumour patterns generated by two distinct growth rules are characterised by its gyration radius, surface roughness, total number of cancer cells, and number of

S. C. Ferreira Jr; M. L Martins; M. J Vilela

1999-01-01

180

Two bacterial strains isolated from a Zn-polluted soil enhance plant growth and mycorrhizal efficiency under Zn-toxicity.  

PubMed

In this study we investigated the interactions among plant, rhizosphere microorganisms and Zn pollution. We tested the influence of two bacterial strains isolated from a Zn-polluted soil on plant growth and on the symbiotic efficiency of native arbuscular mycorrhizal fungi (AMF) under Zn toxicity. The two bacterial strains exhibited Zn tolerance when cultivated under increasing Zn levels in the medium. However, strain B-I showed a higher Zn tolerance than strain B-II at the two highest Zn levels in the medium (75 and 100 mg l(-1) Zn). Molecular identification placed the strain B-I within the genus Brevibacillus. Our results showed that bacterial strain B-I consistently enhanced plant growth, N and P accumulation, as well as nodule number and mycorrhizal infection which demonstrated its plant-growth promoting (PGP) activity. This strain B-I has been shown to produce IAA (3.95 microg ml) and to accumulate 5.6% of Zn from the growing medium. The enhanced growth and nutrition of plants dually inoculated with the AMF and bacterium B-I was observed at three Zn levels assayed. This effect can be related to the stimulation of symbiotic structures (nodules and AMF colonization) and a decreased Zn concentration in plant tissues. The amount of Zn acquired per root weight unit was reduced by each one of these bacterial strains or AMF and particularly by the mixed bacterium-AMF inocula. These mechanisms explain the alleviation of Zn toxicity by selected microorganisms and indicate that metal-adapted bacteria and AMF play a key role enhancing plant growth under soil Zn contamination. PMID:16098559

Vivas, A; Bir, B; Ruz-Lozano, J M; Barea, J M; Azcn, R

2006-03-01

181

Hierarchical growth of curved organic nanowires upon evaporation induced self-assembly.  

PubMed

Self-assembly of a TTF derivative capable of forming self-assembled monolayers at the surface of graphite displays hierarchical growth of multilayers and concentric nanorings upon evaporation of the solvent as observed by AFM. PMID:25027031

Li, Bing; Puigmart-Luis, Jiosep; Jonas, Alain M; Amabilino, David B; De Feyter, Steven

2014-11-11

182

Culturability of Mycobacterium tuberculosis cells isolated from murine macrophages: a bacterial growth factor promotes recovery  

Microsoft Academic Search

Very little is known about the culturability and viability of mycobacteria following their phagocytosis by macrophages. We therefore studied populations of the avirulent Academia strain of Mycobacterium tuberculosis isolated from murine peritoneal macrophage lysates several days post-infection in vivo. The resulting bacterial suspensions contained a range of morphological types including rods, ovoid forms and coccoid forms. Bacterial viability measured using

Sergey Biketov; Galina V. Mukamolova; Vasiliy Potapov; Evgeniy Gilenkov; Galina Vostroknutova; Douglas B. Kell; Michael Young; Arseny S. Kaprelyants

2000-01-01

183

Expression of the bacterial gdhA gene encoding a NADPH glutamate dehydrogenase in tobacco affects plant growth and development  

Microsoft Academic Search

We investigated the effects of genetic modification of nitrogen metabolism via the bacterial glutamate dehydrogenase (GDH)\\u000a on plant growth and metabolism. The gdhA gene from Escherichia coli encoding a NADPH-GDH was expressed in tobacco plants under the control of the 35 S promoter. The specific activity of GDH\\u000a in gdhA plants was 8-fold of that in E. coli. Damage caused

Rafiqa Ameziane; Karen Bernhard; David Lightfoot

2000-01-01

184

Root exudation and rhizoplane bacterial abundance of barley ( Hordeum vulgare L.) in relation to nitrogen fertilization and root growth  

Microsoft Academic Search

The abundance of bacteria in the rhizoplane of barley varieties was investigated at different soil nitrogen levels. Increased\\u000a amendments of nitrogen resulted in higher bacterial numbers in the rhizoplane of barley seedlings of different varieties.\\u000a A negative correlation was found between nitrogen level in the soil and the growth rate of the seedling roots. The effect\\u000a of nitrogen on the

E. Liljeroth; E. Bth; I. Mathiasson; T. Lundborg

1990-01-01

185

Stimulated bacterioplankton growth and selection for certain bacterial taxa in the vicinity of the ctenophore Mnemiopsis leidyi  

PubMed Central

Episodic blooms of voracious gelatinous zooplankton, such as the ctenophore Mnemiopsis leidyi, affect pools of inorganic nutrients and dissolved organic carbon by intensive grazing activities and mucus release. This will potentially influence bacterioplankton activity and community composition, at least at local scales; however, available studies on this are scarce. In the present study we examined effects of M. leidyi on bacterioplankton growth and composition in incubation experiments. Moreover, we examined community composition of bacteria associated with the surface and gut of M. leidyi. High release of ammonium and high bacterial growth was observed in the treatments with M. leidyi relative to controls. Deep 454 pyrosequencing of 16 S rRNA genes showed specific bacterial communities in treatments with M. leidyi as well as specific communities associated with M. leidyi tissue and gut. In particular, members of Flavobacteriaceae were associated with M. leidyi. Our study shows that M. leidyi influences bacterioplankton activity and community composition in the vicinity of the jellyfish. In particular during temporary aggregations of jellyfish, these local zones of high bacterial growth may contribute significantly to the spatial heterogeneity of bacterioplankton activity and community composition in the sea. PMID:22912629

Dinasquet, Julie; Granhag, Lena; Riemann, Lasse

2012-01-01

186

Common Components of Industrial Metal-Working Fluids as Sources of Carbon for Bacterial Growth  

PubMed Central

Water-based metal-working fluids used in large-scale industrial operations consist of many components, but in the most commonly used formulations only three classes of components are present in high enough concentrations that they could, in principle, provide enough carbon to support the high bacterial densities (109 CFU/ml) often observed in contaminated factory fluids. These components are petroleum oil (1 to 5%), petroleum sulfonates (0.1 to 0.5%), and fatty acids (less than 0.1%, mainly linoleic and oleic acids supplied as tall oils). We isolated pure strains of predominating bacteria from contaminated reservoirs of two metal-working systems and randomly selected 12 strains which we tested in liquid culture for growth with each of the metal-working fluid components as the sole source of carbon. Of the 12 strains, 7 reached high density (109 CFU/ml from an initial inoculum of less than 2 103) in 24 h, and 1 strain did the same in 48 h with 0.05% oleic or linoleic acid as the carbon source. These same strains also grew on 1% naphthenic petroleum oil but required up to 72 h to reach densities near 108 CFU/ml. One strain grew slightly and the others not at all on the petroleum sulfonates. The four remaining strains did not grow on any of the components, even though they were among the predominating bacteria in the contaminated system. Of the seven strains that grew best on the fatty acids and on the naphthenic petroleum oil, five were tentatively identified as Acinetobacter species and two were identified as Pseudomonas species. Four of the bacteria that did not grow were tentatively identified as species of Pseudomonas, and one could not be identified. PMID:16347072

Foxall-VanAken, S.; Brown, J. A.; Young, W.; Salmeen, I.; McClure, T.; Napier, S.; Olsen, R. H.

1986-01-01

187

Bacterial growth at the high concentrations of magnesium sulfate found in martian soils.  

PubMed

The martian surface environment exhibits extremes of salinity, temperature, desiccation, and radiation that would make it difficult for terrestrial microbes to survive. Recent evidence suggests that martian soils contain high concentrations of MgSO? minerals. Through warming of the soils, meltwater derived from subterranean ice-rich regolith may exist for an extended period of time and thus allow the propagation of terrestrial microbes and create significant bioburden at the near surface of Mars. The current report demonstrates that halotolerant bacteria from the Great Salt Plains (GSP) of Oklahoma are capable of growing at high concentrations of MgSO? in the form of 2 M solutions of epsomite. The epsotolerance of isolates in the GSP bacterial collection was determined, with 35% growing at 2 M MgSO?. There was a complex physiological response to mixtures of MgSO? and NaCl coupled with other environmental stressors. Growth also was measured at 1 M concentrations of other magnesium and sulfate salts. The complex responses may be partially explained by the pattern of chaotropicity observed for high-salt solutions as measured by agar gelation temperature. Select isolates could grow at the high salt concentrations and low temperatures found on Mars. Survival during repetitive freeze-thaw or drying-rewetting cycles was used as other measures of potential success on the martian surface. Our results indicate that terrestrial microbes might survive under the high-salt, low-temperature, anaerobic conditions on Mars and present significant potential for forward contamination. Stringent planetary protection requirements are needed for future life-detection missions to Mars. PMID:22248384

Crisler, J D; Newville, T M; Chen, F; Clark, B C; Schneegurt, M A

2012-02-01

188

Bacterial Growth at the High Concentrations of Magnesium Sulfate Found in Martian Soils  

PubMed Central

Abstract The martian surface environment exhibits extremes of salinity, temperature, desiccation, and radiation that would make it difficult for terrestrial microbes to survive. Recent evidence suggests that martian soils contain high concentrations of MgSO4 minerals. Through warming of the soils, meltwater derived from subterranean ice-rich regolith may exist for an extended period of time and thus allow the propagation of terrestrial microbes and create significant bioburden at the near surface of Mars. The current report demonstrates that halotolerant bacteria from the Great Salt Plains (GSP) of Oklahoma are capable of growing at high concentrations of MgSO4 in the form of 2 M solutions of epsomite. The epsotolerance of isolates in the GSP bacterial collection was determined, with 35% growing at 2 M MgSO4. There was a complex physiological response to mixtures of MgSO4 and NaCl coupled with other environmental stressors. Growth also was measured at 1 M concentrations of other magnesium and sulfate salts. The complex responses may be partially explained by the pattern of chaotropicity observed for high-salt solutions as measured by agar gelation temperature. Select isolates could grow at the high salt concentrations and low temperatures found on Mars. Survival during repetitive freeze-thaw or drying-rewetting cycles was used as other measures of potential success on the martian surface. Our results indicate that terrestrial microbes might survive under the high-salt, low-temperature, anaerobic conditions on Mars and present significant potential for forward contamination. Stringent planetary protection requirements are needed for future life-detection missions to Mars. Key Words: AnalogueMarsPlanetary protectionSaltsLife in extreme environments. Astrobiology 12, 98106. PMID:22248384

Crisler, J.D.; Newville, T.M.; Chen, F.; Clark, B.C.

2012-01-01

189

Effects of High Hydrostatic Pressure on Bacterial Growth on Human Ossicles Explanted from Cholesteatoma Patients  

PubMed Central

Background High hydrostatic pressure (HHP) treatment can eliminate cholesteatoma cells from explanted human ossicles prior to re-insertion. We analyzed the effects of HHP treatment on the microbial flora on ossicles and on the planktonic and biofilm states of selected isolates. Methodology Twenty-six ossicles were explanted from cholesteatoma patients. Five ossicles were directly analyzed for microbial growth without further treatment. Fifteen ossicles were cut into two pieces. One piece was exposed to HHP of 350 MPa for 10 minutes. Both the treated and untreated (control) pieces were then assessed semi-quantitatively. Three ossicles were cut into two pieces and exposed to identical pressure conditions with or without the addition of one of two different combinations of antibiotics to the medium. Differential effects of 10-minute in vitro exposure of planktonic and biofilm bacteria to pressures of 100 MPa, 250 MPa, 400 MPa and 540 MPa in isotonic and hypotonic media were analyzed using two patient isolates of Staphylococcus epidermidis and Neisseria subflava. Bacterial cell inactivation and biofilm destruction were assessed by colony counting and electron microscopy. Principal Findings A variety of microorganisms were isolated from the ossicles. Irrespective of the medium, HHP treatment at 350 MPa for 10 minutes led to satisfying but incomplete inactivation especially of Gram-negative bacteria. The addition of antibiotics increased the efficacy of elimination. A comparison of HHP treatment of planktonic and biofilm cells showed that the effects of HPP were reduced by about one decadic logarithmic unit when HPP was applied to biofilms. High hydrostatic pressure conditions that are suitable to inactivate cholesteatoma cells fail to completely sterilize ossicles even if antibiotics are added. As a result of the reduced microbial load and the viability loss of surviving bacteria, however, there is a lower risk of re-infection after re-insertion. PMID:22291908

Ostwald, Jurgen; Lindner, Tobias; Zautner, Andreas Erich; Arndt, Kathleen; Pau, Hans Wilhelm; Podbielski, Andreas

2012-01-01

190

Biodegradation of soil-applied pesticides by selected strains of plant growth-promoting rhizobacteria (PGPR) and their effects on bacterial growth  

Microsoft Academic Search

A laboratory study was conducted to investigate the influence of four PGPR strains on the degradation of five soil applied\\u000a pesticides and their effects on bacterial growth. Interactions of Bacillus subtilis GB03, Bacillus subtilis FZB24, Bacillus amyloliquefaciens IN937a and Bacillus pumilus SE34 with two concentrations of acibenzolar-S-methyl, metribuzin, napropamide, propamocarb hydrochloride and thiamethoxam in liquid culture and soil microcosm were

Charalampos K. Myresiotis; Zisis Vryzas; Euphemia Papadopoulou-Mourkidou

191

Structural equation modeling of latent growth curves of weight gain among treated tuberculosis patients.  

PubMed

Tuberculosis still remains a major public health problem even though it is treatable and curable. Weight gain measurement during anti tuberculosis (TB) treatment period is an important component to assess the progress of TB patients. In this study, Latent Growth Models (LGMs) were implemented in a longitudinal design to predict the change in weight of TB patients who were given three different regimens under randomized controlled clinical trial for anti-TB treatment. Linear and Quadratic LGMs were fitted using Mplus software. The age, sex and treatment response of the TB patients were used as time invariant independent variables of the growth trajectories. The quadratic trend was found to be better in explaining the changes in weight without grouping than the quadratic model for three group comparisons. A significant increase in the change of weight over time was identified while a significant quadratic effect indicated that weights were sustained over time. The growth rate was similar in both the groups. The treatment response had significant association with the growth rate of weight scores of the patients. PMID:24618577

Vasantha, Mahalingam; Venkatesan, Perumal

2014-01-01

192

Individual Differences in the Onset of Tense Marking: A Growth-Curve Analysis  

ERIC Educational Resources Information Center

The purpose of this study was to explore individual differences in children's tense onset growth trajectories and to determine whether any within- or between-child predictors could account for these differences. Twenty-two children with expressive vocabulary abilities in the low-average to below-average range participated. Sixteen children were at

Hadley, Pamela A.; Holt, Janet K.

2006-01-01

193

Quantitative Genetic Analysis of Latent Growth Curve Models of Cognitive Abilities in Adulthood  

ERIC Educational Resources Information Center

Though many cognitive abilities exhibit marked decline over the adult years, individual differences in rates of change have been observed. In the current study, biometrical latent growth models were used to examine sources of variability for ability level (intercept) and change (linear and quadratic effects) for verbal, fluid, memory, and

Reynolds, Chandra A.; Finkel, Deborah; McArdle, John J.; Gatz, Margaret; Berg, Stig; Pedersen, Nancy L.

2005-01-01

194

Level and Change of Bullying Behavior during High School: A Multilevel Growth Curve Analysis  

ERIC Educational Resources Information Center

The development of bullying behavior was examined across three years in a sample of 515 adolescents (46% females) from 41 classrooms. At time 1, the students were in grades 9 and 10 (mean age = 14.5 years; SD = 0.54). Results of a multilevel growth model showed that both baseline level and change of bullying varied significantly across individuals

Nocentini, Annalaura; Menesini, Ersilia; Salmivalli, Christina

2013-01-01

195

CURVED WALLS: GRAIN GROWTH, SETTLING, AND COMPOSITION PATTERNS IN T TAURI DISK DUST SUBLIMATION FRONTS  

SciTech Connect

The dust sublimation walls of disks around T Tauri stars represent a directly observable cross-section through the disk atmosphere and midplane. Their emission properties can probe the grain size distribution and composition of the innermost regions of the disk, where terrestrial planets form. Here we calculate the inner dust sublimation wall properties for four classical T Tauri stars with a narrow range of spectral types and inclination angles and a wide range of mass accretion rates to determine the extent to which the walls are radially curved. Best fits to the near- and mid-IR excesses are found for curved, two-layer walls in which the lower layer contains larger, hotter, amorphous pyroxene grains with Mg/(Mg+Fe) = 0.6 and the upper layer contains submicron, cooler, mixed amorphous olivine and forsterite grains. As the mass accretion rates decrease from 10{sup 8} to 10{sup 10} M{sub ?} yr{sup 1}, the maximum grain size in the lower layer decreases from ?3 to 0.5 ?m. We attribute this to a decrease in fragmentation and turbulent support for micron-sized grains with decreasing viscous heating. The atmosphere of these disks is depleted of dust with dust-gas mass ratios 1 10{sup 4} of the interstellar medium (ISM) value, while the midplane is enhanced to eight times the ISM value. For all accretion rates, the wall contributes at least half of the flux in the optically thin 10 ?m silicate feature. Finally, we find evidence for an iron gradient in the disk, suggestive of that found in our solar system.

McClure, M. K.; Calvet, N.; Hartmann, L.; Ingleby, L. [Department of Astronomy, The University of Michigan, 500 Church Street, 830 Dennison Building., Ann Arbor, MI 48109 (United States); D'Alessio, P. [Centro de Radioastronoma y Astrofsica, Universidad Nacional Autnoma de Mxico, 58089 Morelia, Michoacn (Mexico); Espaillat, C. [Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Sargent, B. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Watson, D. M. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Hernndez, J., E-mail: melisma@umich.edu, E-mail: ncalvet@umich.edu, E-mail: lhartm@umich.edu, E-mail: lingleby@umich.edu, E-mail: p.dalessio@astrosmo.unam.mx, E-mail: cespaillat@cfa.harvard.edu, E-mail: baspci@rit.edu, E-mail: dmw@pas.rochester.edu, E-mail: hernandj@cida.ve [Centro de Investigaciones de Astronoma (CIDA), Mrida 5101-A (Venezuela, Bolivarian Republic of)

2013-10-01

196

A Latent Growth Curve Analysis of Early and Increasing Peer Victimization as Predictors of Mental Health Across Elementary School  

PubMed Central

Peer victimization has been implicated as a traumatic stressor that compromises childrens long-term mental health, yet a dearth of prospective research specifically demonstrates lasting effects of early victimization. This research examined whether early (2nd grade) victimization and increasing (2nd 5th grade) victimization independently predicted depressive symptoms and aggressive behavior (overt and relational) in 5th grade. Participants included 433 children (238 girls, 195 boys). Children reported on peer victimization and depressive symptoms; teachers reported on peer victimization and aggressive behavior. Latent growth curve analysis revealed that both early and increasing victimization made unique contributions to subsequent depressive symptoms and aggressive behavior. Relational aggression was particularly likely to follow victimization in girls. PMID:21229448

Rudolph, Karen D.; Troop-Gordon, Wendy; Hessel, Elenda T.; Schmidt, Jennifer D.

2011-01-01

197

Bacterial growth state distinguished by single-cell protein profiling: Does chlorination kill coliforms in municipal effluent?  

SciTech Connect

Municipal effluent is the largest reservoir of human enteric bacteria. Its public health significance, however, depends upon the physiological status of the wastewater bacterial community. A novel immunofluorescence assay was developed and used to examine the bacterial growth state during wastewater disinfection. Quantitative levels of three highly conserved cytosolic proteins (DnaK, Dps, and Fis) were determined by using enterobacterium-specific antibody fluorochrome-coupled probes. Enterobacterial Fis homologs were abundant in growing cells and nearly undetectable in stationary-phase cells. In contrast, enterobacterial Dps homologs were abundant in stationary-phase cells but virtually undetectable in growing cells. The range of variation in the abundance of both proteins was at least 100-fold as determined by Western blotting and immunofluorescence analysis. Enterobacterial DnaK homologs were nearly invariant with growth state, enabling their use as permeabilization controls. The cellular growth states of individual enterobacteria in wastewater samples were determined by measurement of Fis, Dps, and DnaK abundance (protein profiling). Intermediate levels of Fis and Dps were evident and occurred in response to physiological transitions. The results indicate that chlorination failed to kill coliforms but rather elicited nutrient starvation and a reversible nonculturable state. These studies suggest that the current standard procedures for wastewater analysis which rely on detection of culturable cells likely underestimate fecal coliform content.

Rockabrand, D.; Austin, T.; Kaiser, R.; Blum, P.

1999-09-01

198

Evaluation of the electrical potential drop technique in the determination of crack growth resistance-curves of Carbon\\/Carbon composites and carbon bonded refractories  

Microsoft Academic Search

Electrical potential drop (EPD) and compliance techniques are compared as techniques for crack length measurement in determining the crack growth resistance-curve (R-curve) of two Carbon\\/Carbon (C\\/C) composites and two carbon-bonded oxide-graphite refractories. The two C\\/C composites differ in the strength of the fibre\\/matrix interaction, resulting from the use of untreated and surface treated carbon fibres. The refractories differ in the

A. Antonarulrajah; V. P. S. Ramos; S. B. Fazluddin; B. Rand

2005-01-01

199

Predicting Response to Intensive Multimodal Inpatient Treatment: A Comparison of Single and Multiple Class Latent Growth Curve Modeling Approaches  

PubMed Central

In a modest body of research, personality functioning assessed via performance-based instruments has been found to validly predict treatment outcome and, to some extent, differential response to treatment. However, state-of-the-science longitudinal and mixture modeling techniques, which are common in many areas of clinical psychology, have rarely been used. In this article, we compare multilevel growth curve modeling (MLM) and latent class growth modeling (LCGM) approaches with the same dataset to illustrate the different research questions that can be addressed by each method. Global Assessment of Functioning (GAF) scores collected at six points during the course of a long-term multimodal inpatient treatment of 58 severely and persistently mentally ill adults were used to model the trajectory of treatment outcome. Pretreatment personality functioning and other markers of psychiatric severity were examined as covariates in each modeling approach. The results of both modeling approaches generally indicated that more psychologically impaired clients responded less favorably to treatment. The LCGM approach revealed two unique trajectories of improvement (a persistently low group and a higher starting, improving group). Personality functioning and baseline psychiatric variables significantly predicted group membership and the rate of change within the groups. A side-by-side examination of these two methods was found to be useful in predicting differential treatment response with personality functioning variables. PMID:24066712

Smith, Justin D.; Van Ryzin, Mark J.; Fowler, J. Christopher; Handler, Leonard

2013-01-01

200

Evaluation of free-stall mattress bedding treatments to reduce mastitis bacterial growth  

SciTech Connect

Bacterial counts were compared in free-stall mattresses and teat ends exposed to 5 treatments in a factorial study design on 1 dairy farm. Mattresses in five 30-cow groups were subjected to 1 of 5 bedding treatments every other day: 0.5 kg of hydrated limestone, 120 mL of commercial acidic conditioner, 1 kg of coal fly ash, 1 kg of kiln-dried wood shavings, and control (no bedding). Counts of coliforms, Klebsiella spp., Escherichia coli, and Streptococcus spp. were lowest on mattresses bedded with lime. Mattresses bedded with the commercial acidic conditioner had the next lowest counts for coliforms, Klebsiella spp., and Streptococcus spp. Wood shavings and the no-bedding control had the highest counts for coliform and Klebsiella spp. Compared with wood shavings or control, fly ash reduced the counts of coliforms, whereas for the other 3 bacterial groups, the reduction was not always significant. Streptococcus spp. counts were greatest in the control group and did not differ among the shavings and fly ash groups. Teat swab results indicated that hydrated lime was the only bedding treatment that significantly decreased the counts of both coliforms and Klebsiella spp. There were no differences in Streptococcus spp. numbers on the teats between any of the bedding treatments. Bacterial populations grew steadily on mattresses and were generally higher at 36 to 48 h than at 12 to 24 h, whereas bacterial populations on teats grew rapidly by 12 h and then remained constant. Hydrated lime was the only treatment that significantly reduced bacterial counts on both mattresses and teat ends, but it caused some skin irritation.

Kristula, M.A.; Dou, Z.; Toth, J.D.; Smith, B.I.; Harvey, N.; Sabo, M. [University of Penn, Kennett Square, PA (United States)

2008-05-15

201

Native Bacterial Endophytes Promote Host Growth in a Species-Specific Manner; Phytohormone Manipulations Do Not Result in Common Growth Responses  

PubMed Central

Background All plants in nature harbor a diverse community of endophytic bacteria which can positively affect host plant growth. Changes in plant growth frequently reflect alterations in phytohormone homoeostasis by plant-growth-promoting (PGP) rhizobacteria which can decrease ethylene (ET) levels enzymatically by 1-aminocyclopropane-1-carboxylate (ACC) deaminase or produce indole acetic acid (IAA). Whether these common PGP mechanisms work similarly for different plant species has not been rigorously tested. Methodology/ Principal Findings We isolated bacterial endophytes from field-grown Solanum nigrum; characterized PGP traits (ACC deaminase activity, IAA production, phosphate solubilization and seedling colonization); and determined their effects on their host, S. nigrum, as well as on another Solanaceous native plant, Nicotiana attenuata. In S. nigrum, a majority of isolates that promoted root growth were associated with ACC deaminase activity and IAA production. However, in N. attenuata, IAA but not ACC deaminase activity was associated with root growth. Inoculating N. attenuata and S. nigrum with known PGP bacteria from a culture collection (DSMZ) reinforced the conclusion that the PGP effects are not highly conserved. Conclusions/ Significance We conclude that natural endophytic bacteria with PGP traits do not have general and predictable effects on the growth and fitness of all host plants, although the underlying mechanisms are conserved. PMID:18628963

Long, Hoang Hoa; Schmidt, Dominik D.; Baldwin, Ian T.

2008-01-01

202

CONSEQUENCES OF PROTIST-STIMULATED BACTERIAL PRODUCTION FOR ESTIMATING PROTIST GROWTH EFFICIENCIES  

EPA Science Inventory

The trophic link between bacteria and bacterivorous protists is a complex interaction that involves feedback of inorganic nutrients and growth substrates that are immediately available for prey growth. These interactions were examined in the laboratory and in incubations of conce...

203

Illustration of year-to-year variation in wheat spectral profile crop growth curves. [Kansas, Oklahoma, North Dakota and South Dakota  

NASA Technical Reports Server (NTRS)

Data previously compiled on the year to year variability of spectral profile crop growth parameters for spring and winter wheat in Kansas, Oklahoma, and the Dakotas were used with a profile model to develop graphs illustrating spectral profile crop growth curves for a number of years and a number of spring and winter wheat segments. These curves show the apparent variability in spectral profiles for wheat from one year to another within the same segment and from one segment to another within the same year.

Gonzalez, P.; Jones, C. (principal investigators)

1980-01-01

204

Anthocyanin Incorporated Dental Copolymer: Bacterial Growth Inhibition, Mechanical Properties, and Compound Release Rates and Stability by 1H NMR  

PubMed Central

Objective. To evaluate bacterial growth inhibition, mechanical properties, and compound release rate and stability of copolymers incorporated with anthocyanin (ACY; Vaccinium macrocarpon). Methods. Resin samples were prepared (Bis-GMA/TEGDMA at 70/30?mol%) and incorporated with 2 w/w% of either ACY or chlorhexidine (CHX), except for the control group. Samples were individually immersed in a bacterial culture (Streptococcus mutans) for 24?h. Cell viability (n = 3) was assessed by counting the number of colony forming units on replica agar plates. Flexural strength (FS) and elastic modulus (E) were tested on a universal testing machine (n = 8). Compound release and chemical stability were evaluated by UV spectrophotometry and 1H NMR (n = 3). Data were analyzed by one-way ANOVA and Tukey's test (? = 0.05). Results. Both compounds inhibited S. mutans growth, with CHX being most effective (P < 0.05). Control resin had the lowest FS and E values, followed by ACY and CHX, with statistical difference between control and CHX groups for both mechanical properties (P < 0.05). The 24?h compound release rates were ACY: 1.33??g/mL and CHX: 1.92??g/mL. 1H NMR spectra suggests that both compounds remained stable after being released in water. Conclusion. The present findings indicate that anthocyanins might be used as a natural antibacterial agent in resin based materials. PMID:24693287

Hrynash, Halyna; Pilly, Vinay Kumar; Mankovskaia, Alexandra; Xiong, Yaoyang; Nogueira Filho, Getulio; Bresciani, Eduardo; Levesque, Celine Marie

2014-01-01

205

Anthocyanin incorporated dental copolymer: bacterial growth inhibition, mechanical properties, and compound release rates and stability by (1)h NMR.  

PubMed

Objective. To evaluate bacterial growth inhibition, mechanical properties, and compound release rate and stability of copolymers incorporated with anthocyanin (ACY; Vaccinium macrocarpon). Methods. Resin samples were prepared (Bis-GMA/TEGDMA at 70/30?mol%) and incorporated with 2 w/w% of either ACY or chlorhexidine (CHX), except for the control group. Samples were individually immersed in a bacterial culture (Streptococcus mutans) for 24?h. Cell viability (n = 3) was assessed by counting the number of colony forming units on replica agar plates. Flexural strength (FS) and elastic modulus (E) were tested on a universal testing machine (n = 8). Compound release and chemical stability were evaluated by UV spectrophotometry and (1)H NMR (n = 3). Data were analyzed by one-way ANOVA and Tukey's test ( ? = 0.05). Results. Both compounds inhibited S. mutans growth, with CHX being most effective (P < 0.05). Control resin had the lowest FS and E values, followed by ACY and CHX, with statistical difference between control and CHX groups for both mechanical properties (P < 0.05). The 24?h compound release rates were ACY: 1.33??g/mL and CHX: 1.92??g/mL. (1)H NMR spectra suggests that both compounds remained stable after being released in water. Conclusion. The present findings indicate that anthocyanins might be used as a natural antibacterial agent in resin based materials. PMID:24693287

Hrynash, Halyna; Pilly, Vinay Kumar; Mankovskaia, Alexandra; Xiong, Yaoyang; Nogueira Filho, Getulio; Bresciani, Eduardo; Lvesque, Cline Marie; Prakki, Anuradha

2014-01-01

206

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

NASA Astrophysics Data System (ADS)

Marine microbes (<200 ?m) 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 80E. Concentrations of heterotrophic nanoflagellates (HNF) (2 to 20 ?m), microzooplankton (20 to 200 ?m), 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 community. Cluster groups differentiated between low Chl a (0.3 ?g l -1) open ocean Antarctic Circumpolar Current (ACC) communities; and high Chl a (2.4 ?g l -1) ice-associated coastal blooms at various stages between bloom formation and senescence. This partitioning of cluster groups can be used to determine spatial and temporal patterns of carbon transfer by the microbial loop within the BROKE-West survey area.

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

2010-05-01

207

Effect of silver-doped phosphate-based glasses on bacterial biofilm growth.  

PubMed

Silver-containing phosphate-based glasses were found to reduce the growth of Pseudomonas aeruginosa and Staphylococcus aureus biofilms, which are leading causes of nosocomial infections. The rates of glass degradation (1.27 to 1.41 microg.mm(-2).h(-1)) and the corresponding silver release were found to account for the variation in biofilm growth inhibitory effect. PMID:18567679

Valappil, Sabeel P; Knowles, Jonathan C; Wilson, Michael

2008-08-01

208

Effects of gypsophila saponins on bacterial growth kinetics and on selection of subterranean clover rhizosphere bacteria  

Microsoft Academic Search

Plant secondary metabolites, such as saponins, have a considerable impact in agriculture because of their allelopathic effects. They also affect the growth of soil microorganisms, especially fungi. We investigated the influence of saponins on rhizosphere bacteria in vitro and in soil conditions. The effects of gypsophila saponins on the growth kinetics of rhizosphere bacteria were studied by monitoring the absorbance

F. Fons; N. Amellal; C. Leyval; N. Saint-Martin; M. Henry

2003-01-01

209

Bacterial Manganese Reduction and Growth with Manganese Oxide as the Sole Electron Acceptor  

Microsoft Academic Search

Microbes that couple growth to the reduction of manganese could play an important role in the biogeochemistry of certain anaerobic environments. Such a bacterium, Alteromonas putrefaciens MR-1, couples its growth to the reduction of manganese oxides only under anaerobic conditions. The characteristics of this reduction are consistent with a biological, and not an indirect chemical, reduction of manganese, which suggest

Charles R. Myers; Kenneth H. Nealson

1988-01-01

210

Analyzing latent state-trait and multiple-indicator latent growth curve models as multilevel structural equation models.  

PubMed

Latent state-trait (LST) and latent growth curve (LGC) models are frequently used in the analysis of longitudinal data. Although it is well-known that standard single-indicator LGC models can be analyzed within either the structural equation modeling (SEM) or multilevel (ML; hierarchical linear modeling) frameworks, few researchers realize that LST and multivariate LGC models, which use multiple indicators at each time point, can also be specified as ML models. In the present paper, we demonstrate that using the ML-SEM rather than the SL-SEM framework to estimate the parameters of these models can be practical when the study involves (1) a large number of time points, (2) individually-varying times of observation, (3) unequally spaced time intervals, and/or (4) incomplete data. Despite the practical advantages of the ML-SEM approach under these circumstances, there are also some limitations that researchers should consider. We present an application to an ecological momentary assessment study (N = 158 youths with an average of 23.49 observations of positive mood per person) using the software Mplus (Muthn and Muthn, 1998-2012) and discuss advantages and disadvantages of using the ML-SEM approach to estimate the parameters of LST and multiple-indicator LGC models. PMID:24416023

Geiser, Christian; Bishop, Jacob; Lockhart, Ginger; Shiffman, Saul; Grenard, Jerry L

2013-01-01

211

12-step Affiliation and Attendance following Treatment for Comorbid Substance Dependence and Depression: A Latent Growth Curve Mediation Model  

PubMed Central

Among substance-dependent individuals comorbid major depressive disorder (MDD) is associated with greater severity and poorer treatment outcomes, but little research has examined mediators of post-treatment substance use outcomes within this population. Using latent growth curve models we tested relationships between individual rates of change in 12-step involvement and substance use, utilizing post-treatment follow-up data from a trial of group Twelve-Step Facilitation (TSF) and Integrated Cognitive-Behavioral Therapy (ICBT) for veterans with substance dependence and MDD. While TSF patients were higher on 12-step affiliation and meeting attendance at end-of-treatment as compared to ICBT, they also experienced significantly greater reductions in these variables during the year following treatment, ending at similar levels as ICBT. Veterans in TSF also had significantly greater increases in drinking frequency during follow-up, and this group difference was mediated by their greater reductions in 12-step affiliation and meeting attendance. Patients with comorbid depression appear to have difficulty sustaining high levels of 12-step involvement after the conclusion of formal 12-step interventions, which predicts poorer drinking outcomes over time. Modifications to TSF and other formal 12-step protocols or continued therapeutic contact may be necessary to sustain 12-step involvement and reduced drinking for patients with substance dependence and MDD. PMID:23327503

Worley, Matthew J.; Tate, Susan R.; McQuaid, John R.; Granholm, Eric L.; Brown, Sandra A.

2012-01-01

212

Analyzing latent state-trait and multiple-indicator latent growth curve models as multilevel structural equation models  

PubMed Central

Latent state-trait (LST) and latent growth curve (LGC) models are frequently used in the analysis of longitudinal data. Although it is well-known that standard single-indicator LGC models can be analyzed within either the structural equation modeling (SEM) or multilevel (ML; hierarchical linear modeling) frameworks, few researchers realize that LST and multivariate LGC models, which use multiple indicators at each time point, can also be specified as ML models. In the present paper, we demonstrate that using the ML-SEM rather than the SL-SEM framework to estimate the parameters of these models can be practical when the study involves (1) a large number of time points, (2) individually-varying times of observation, (3) unequally spaced time intervals, and/or (4) incomplete data. Despite the practical advantages of the ML-SEM approach under these circumstances, there are also some limitations that researchers should consider. We present an application to an ecological momentary assessment study (N = 158 youths with an average of 23.49 observations of positive mood per person) using the software Mplus (Muthn and Muthn, 19982012) and discuss advantages and disadvantages of using the ML-SEM approach to estimate the parameters of LST and multiple-indicator LGC models. PMID:24416023

Geiser, Christian; Bishop, Jacob; Lockhart, Ginger; Shiffman, Saul; Grenard, Jerry L.

2013-01-01

213

Development of skin conductance orienting, habituation, and reorienting from ages 3 to 8 years: a longitudinal latent growth curve analysis.  

PubMed

Little is known about the development of the skin conductance orienting response (SCOR) in childhood. This longitudinal study examines the effects of age on initial SCOR, habituation, and reorienting. Skin conductance responses to nonsignal auditory stimuli were recorded from 200 male and female children at five different time points (ages 3, 4, 5, 6, and 8 years). Longitudinal latent growth curve analyses were used to determine the trajectory of each SCOR measure during this period. Results indicated that (a) initial SCOR is present at age 3, increases thereafter to peak at age 6, and then levels off, (b) habituation is absent at age 3, but becomes apparent at age 4 years and increases thereafter with increasing age, (c) SC reorienting is absent from ages 3 to 8, and (d) boys and girls do not exhibit different developmental trajectories. Results suggest that from age 3 to 8 years, the transition from the functionally immature to mature neural network underlying orienting and habituation is a continuous process and may be related to children's cognitive development during this period. PMID:17666032

Gao, Yu; Raine, Adrian; Dawson, Michael E; Venables, Peter H; Mednick, Sarnoff A

2007-11-01

214

Latent Growth Curve Analysis of Fear during a Speech Task before and after Treatment for Social Phobia  

PubMed Central

Models of social phobia highlight the importance of anticipatory anxiety in the experience of fear during a social situation. Anticipatory anxiety has been shown to be highly correlated with performance anxiety for a variety of social situations. A few studies show that average ratings of anxiety during the anticipation and performance phases of a social situation decline following treatment. Evidence also suggests that the point of confrontation with the feared stimulus is the peak level of fear. No study to date has evaluated the pattern of anxious responding across the anticipation, confrontation, and performance phases before and after treatment, which is the focus of the current study. Socially phobic individuals (N=51) completed a behavioral avoidance task before and after two types of manualized cognitive behavioral therapy, and gave ratings of fear during the anticipation and performance phases. Results from latent growth curve analysis were the same for the two treatments and suggest that before treatment, anxiety sharply increased during the anticipation phase, was highly elevated at the confrontation, and, to a gradually increased during the performance phase. After treatment, anxiety increased during the anticipation phase, although at a much slower rate than at pretreatment, peaking at confrontation, and declined at the performance phase. The findings suggest that anticipatory experiences are critical to the experience of fear for public speaking and should be incorporated into exposures. PMID:21907972

Price, Matthew; Anderson, Page L.

2011-01-01

215

Noninvasive Quantitative Measurement of Bacterial Growth in Porous Media under Unsaturated-Flow Conditions  

PubMed Central

Glucose-dependent growth of the luxCDABE reporter bacterium Pseudomonas fluorescens HK44 was monitored noninvasively in quartz sand under unsaturated-flow conditions within a 45- by 56- by 1-cm two-dimensional light transmission chamber. The spatial and temporal development of growth were mapped daily over 7 days by quantifying salicylate-induced bioluminescence. A nonlinear model relating the rate of increase in light emission after salicylate exposure to microbial density successfully predicted growth over 4 orders of magnitude (r2 = 0.95). Total model-predicted growth agreed with growth calculated from the mass balance of the system by using previously established growth parameters of HK44 (predicted, 1.2 1012 cells; calculated, 1.7 1012 cells). Colonization expanded in all directions from the inoculation region, including upward migration against the liquid flow. Both the daily rate of expansion of the colonized zone and the population density of the first day's growth in each newly colonized region remained relatively constant throughout the experiment. Nonetheless, substantial growth continued to occur on subsequent days in the older regions of the colonized zone. The proportion of daily potential growth that remained within the chamber declined progressively between days 2 and 7 (from 97 to 13%). A densely populated, anoxic region developed in the interior of the colonized zone even though the sand was unsaturated and fresh growth medium continued to flow through the colonized zone. These data illustrate the potential of a light transmission chamber, bioluminescent bacteria, and sensitive digital camera technology to noninvasively study real-time hydrology-microbiology interactions associated with unsaturated flow in porous media. PMID:12089048

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

2002-01-01

216

The importance of growth kinetic analysis in determining bacterial susceptibility against antibiotics and silver nanoparticles  

PubMed Central

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 1824 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 ?g mL-1 of vancomycin and 8 ?g 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.

Theophel, Karsten; Schacht, Veronika J.; Schlter, Michael; Schnell, Sylvia; Stingu, Catalina-Suzana; Schaumann, Reiner; Bunge, Michael

2014-01-01

217

Noninvasive Quantitative Measurement of Bacterial Growth in Porous Media Under Unsaturated-Flow Conditions  

SciTech Connect

Glucose-dependent growth of the luxCDABE reporter bacterium Pseudomonas fluorescens HK44 was monitored noninvasively in quartz sand under unsaturated-flow conditions within a 45- by 56- by 1-cm two-dimensional light transmission chamber. The spatial and temporal development of growth were mapped daily over 7 days by quantifying salicylate-induced bioluminescence. A nonlinear model relating the rate of increase in light emission after salicylate exposure to microbial density successfully predicted growth over 4 orders of magnitude (r{sup 2}=0.95). Total model-predicted growth agreed with growth calculated from the mass balance of the system by using previously determined growth parameters of HK44 (predicted, 1.2 x 10{sup 12} cells; calculated, 1.7 x 10{sup 12} cells). Colonization expanded in all directions from the inoculation region, including upward migration against the liquid flow. Both the daily rate of expansion of the colonized zone and the population density of the first day's growth in each newly colonized region remained relatively constant throughout the experiment. Nonetheless, substantial growth continued to occur on subsequent days in the older regions of the colonized zone. The proportion of daily potential growth that remained within the chamber declined progressively between days 2 and 7 (from 97 to 13%). A densely populated, anoxic region developed in the interior of the colonized zone even though the sand was unsaturated and fresh growth medium continued to flow through the colonized zone. These data illustrate the potential of a light transmission chamber, bioluminescent bacteria, and sensitive digital camera technology to noninvasively study real-time hydrology-microbiology interactions associated with unsaturated flow in porous media.

Yarwood, Rocky (Oregon State University) [Oregon State University; Rockhold, Mark L.(BATTELLE (PACIFIC NW LAB)) [BATTELLE (PACIFIC NW LAB); Niemet, Mike (Oregon State University) [Oregon State University; Selker, John S.(VISITORS) [VISITORS; Bottomley, Peter J.(Oregon State University) [Oregon State University

2002-07-01

218

A possible mechanism of action of plant growth-promoting rhizobacteria (PGPR) strain Bacillus pumilus WP8 via regulation of soil bacterial community structure.  

PubMed

According to the traditional view, establishment and maintenance of critical population densities in the rhizosphere was the premise of PGPR to exert growth-promoting effects. In light of the facts that soil bacterial community structures can be changed by some PGPR strains including Bacillus pumilus WP8, we hypothesize that regulation of soil bacterial community structure is one of the plant growth-promoting mechanisms of B. pumilus WP8, rather than depending on high-density cells in soil. In this study, denaturing gradient gel electrophoresis (PCR-DGGE) was performed to evaluate the relationship between changes in soil bacterial community structure and growth-promoting effect on the seedling growth of fava beans (Vicia faba L.) during three successive cultivations. We found that B. pumilus WP8 lacks capacity to reproduce in large enough numbers to survive in bulk soil more than 40 days, yet the bacterial community structures were gradually influenced by inoculation of WP8, especially on dominant populations. Despite WP8 being short-lived, it confers the ability of steadily promoting fava bean seedling growth on soil during the whole growing period for at least 90 days. Pseudomonas chlororaphis RA6, another tested PGPR strain, exists in large numbers for at least 60 days but less than 90 days, whilst giving rise to slight influence on bacterial community structure. In addition, along with the extinction of RA6 cells in bulk soils, the effect of growth promotion disappeared simultaneously. Furthermore, the increment of soil catalase activity from WP8 treatment implied the ability to stimulate soil microbial activity, which may be the reason why the dominant population changed and increased as time passed. Our study suggests that regulation of treated soil bacterial community structure may be another possible action mechanism. PMID:24005176

Kang, Yijun; Shen, Min; Wang, Huanli; Zhao, Qingxin

2013-01-01

219

Effects of Pore-Scale Heterogeneity and Transverse Mixing on Bacterial Growth in Porous Media  

SciTech Connect

Microbial degradation of contaminants in the subsurface requires the availability of nutrients; this is impacted by porous media heterogeneity and the degree of transverse mixing. Two types of microfluidic pore structures etched into silicon wafers (i.e., micromodels), i) a homogeneous distribution of cylindrical posts and ii) aggregates of large and small cylindrical posts, were used to evaluate the impact of heterogeneity on growth of a pure culture (Delftia acidovorans) that degrades (R)-2-(2,4-dichlorophenoxy)propionate (R-2,4-DP). Following inoculation, dissolved O2 and R-2,4-DP were introduced as two parallel streams that mixed transverse to the direction of flow. In the homogeneous micromodel, biomass growth was uniform in pore bodies along the center mixing line, while in the aggregate micromodel, preferential growth occurred between aggregates and slower less dense growth occurred throughout aggregates along the center mixing line. The homogeneous micromodel had more rapid growth overall (2X), and more R-2,4-DP degradation (9.5%) than the aggregate pore structure (5.7%). Simulation results from a pore-scale reactive transport model indicate mass transfer limitations within aggregates along the center mixing line decreased overall reaction; hence, slower biomass growth rates relative to the homogeneous micromodel are expected. Results from this study contribute to a better understanding of the coupling between mass transfer, reaction rates, and biomass growth in complex porous media, and suggest successful implementation and analysis of bioremediation systems requires knowledge of subsurface heterogeneity.

Zhang, Changyong; Kang, Qinjun; Wang, Xing; Zilles, Julie L.; Muller, Roland H.; Werth, Charles J.

2010-04-13

220

Effects of space flight and mixing on bacterial growth in low volume cultures.  

PubMed

Previous investigations have shown that liquid suspension bacterial cultures grow to higher cell concentrations in spaceflight than on Earth. None of these studies included ground-control experiments designed to evaluate the fluid effects potentially responsible for the reported increases. Therefore, the emphasis of this research was to both confirm differences in final cell concentration between 1g and microgravity cultures, and to examine the effects of mixing as a partial explanation for this difference. Flight experiments were performed in the Fluid Processing Apparatus (FPA), aboard Space Shuttle Missions STS-63 and STS-69, with simultaneous 1g static and agitated controls. Additional static 1g, agitated, and clino-rotated controls were performed in 9-ml culture tubes. This research revealed that both E. coli and B. subtilis samples cultured in space flight grew to higher final cell densities (120-345% increase) than simultaneous static 1g controls. The final cell concentration of E. coli cells cultured under agitation was 43% higher than in static 1g cultures and was 102% higher with clino-rotation. However, for B. subtilis cultures grown while being agitated on a shaker or clino-rotated, the final cell concentrations were nearly identical to those of the simultaneous static 1g controls. Therefore, these data suggest that the unique fluid quiescence in the microgravity environment (lack of sedimentation, creating unique transfer of nutrients and waste products), was responsible for the enhanced bacterial proliferation reported in this and other studies. PMID:11543425

Kacena, M A; Manfredi, B; Todd, P

1999-01-01

221

Effects of space flight and mixing on bacterial growth in low volume cultures  

NASA Technical Reports Server (NTRS)

Previous investigations have shown that liquid suspension bacterial cultures grow to higher cell concentrations in spaceflight than on Earth. None of these studies included ground-control experiments designed to evaluate the fluid effects potentially responsible for the reported increases. Therefore, the emphasis of this research was to both confirm differences in final cell concentration between 1g and microgravity cultures, and to examine the effects of mixing as a partial explanation for this difference. Flight experiments were performed in the Fluid Processing Apparatus (FPA), aboard Space Shuttle Missions STS-63 and STS-69, with simultaneous 1g static and agitated controls. Additional static 1g, agitated, and clino-rotated controls were performed in 9-ml culture tubes. This research revealed that both E. coli and B. subtilis samples cultured in space flight grew to higher final cell densities (120-345% increase) than simultaneous static 1g controls. The final cell concentration of E. coli cells cultured under agitation was 43% higher than in static 1g cultures and was 102% higher with clino-rotation. However, for B. subtilis cultures grown while being agitated on a shaker or clino-rotated, the final cell concentrations were nearly identical to those of the simultaneous static 1g controls. Therefore, these data suggest that the unique fluid quiescence in the microgravity environment (lack of sedimentation, creating unique transfer of nutrients and waste products), was responsible for the enhanced bacterial proliferation reported in this and other studies.

Kacena, M. A.; Manfredi, B.; Todd, P.

1999-01-01

222

Macrophage arginase-1 controls bacterial growth and pathology in hypoxic tuberculosis granulomas  

PubMed Central

Lung granulomas develop upon Mycobacterium tuberculosis (Mtb) infection as a hallmark of human tuberculosis (TB). They are structured aggregates consisting mainly of Mtb-infected and -uninfected macrophages and Mtb-specific T cells. The production of NO by granuloma macrophages expressing nitric oxide synthase-2 (NOS2) via l-arginine and oxygen is a key protective mechanism against mycobacteria. Despite this protection, TB granulomas are often hypoxic, and bacterial killing via NOS2 in these conditions is likely suboptimal. Arginase-1 (Arg1) also metabolizes l-arginine but does not require oxygen as a substrate and has been shown to regulate NOS2 via substrate competition. However, in other infectious diseases in which granulomas occur, such as leishmaniasis and schistosomiasis, Arg1 plays additional roles such as T-cell regulation and tissue repair that are independent of NOS2 suppression. To address whether Arg1 could perform similar functions in hypoxic regions of TB granulomas, we used a TB murine granuloma model in which NOS2 is absent. Abrogation of Arg1 expression in macrophages in this setting resulted in exacerbated lung granuloma pathology and bacterial burden. Arg1 expression in hypoxic granuloma regions correlated with decreased T-cell proliferation, suggesting that Arg1 regulation of T-cell immunity is involved in disease control. Our data argue that Arg1 plays a central role in the control of TB when NOS2 is rendered ineffective by hypoxia. PMID:25201986

Duque-Correa, Maria A.; Kuhl, Anja A.; Rodriguez, Paulo C.; Zedler, Ulrike; Schommer-Leitner, Sandra; Rao, Martin; Weiner, January; Hurwitz, Robert; Qualls, Joseph E.; Kosmiadi, George A.; Murray, Peter J.; Kaufmann, Stefan H. E.; Reece, Stephen T.

2014-01-01

223

Antibacterial Nitroacridine, Nitroakridin 3582: Effects on Bacterial Growth and Macromolecular Biosynthesis In Vivo  

PubMed Central

The antibacterial drug Nitroakridin 3582 inhibited the growth of selected grampositive bacteria more strongly than it inhibited the growth of gram-negative bacilli. Nitroakridin at concentrations of the order of 5 10?5m induced lysis of Bacillus licheniformis and Micrococcus lysodeikticus. At concentrations less than 10?4m, Nitroakridin 3582 reduced the exponential growth rate of Escherichia coli C-2; at 10?4m the drug was bacteriostatic, and, at concentrations greater than 10?4m, it was bactericidal. Prolonged bacteriostasis resulted in the formation of long filaments by E. coli, Serratia marcescens, Shigella sonnei, and Proteus mirabilis. The reversible effects of Nitroakridin 3582 on the growth of E. coli correlated with partial inhibitions of deoxyribonucleic acid biosynthesis; ribonucleic acid and protein syntheses were inhibited less strongly. Nitroakridin 3582 at concentrations greater than 2 10?4m, which block deoxyribonucleic acid biosynthesis, produced an accelerated bactericidal action. Images PMID:4941562

Wolfe, Alan D.; Cook, Thomas M.; Hahn, Fred E.

1971-01-01

224

PRODUCTION OF PLANT GROWTH PROMOTING SUBSTANCES IN BACTERIAL ISOLATES FROM THE SEAGRASS RHIZOSPHERE  

EPA Science Inventory

Plants and rhizosphere bacteria have evolved chemical signals that enable their mutual growth. These relationships have been well investigated with agriculturally important plants, but not in seagrasses, which are important to the stability of estuaries. Seagrasses are rooted in ...

225

Heterologous expression of a bacterial haemoglobin improves the growth properties of recombinant Escherichia coli  

Microsoft Academic Search

Rational design of novel as well as improved cellular biocatalysts by genetic manipulation of cellular metabolism has recently attracted considerable interest. A wide range of bacteria have been genetically modified by integrating new enzymatic functions into their metabolic network1-7. A central problem in the aerobic growth of any cell culture is the maintenance of dissolved oxygen (DO) concentrations above growth-limiting

Chaitan Khosla; James E. Bailey

1988-01-01

226

Plankton metabolism and bacterial growth efficiency in offshore waters along a latitudinal transect between the UK and Svalbard  

NASA Astrophysics Data System (ADS)

Euphotic zone gross primary production, community respiration and net community production were determined from in vitro changes of dissolved oxygen, and from in vivo INT reduction capacity fractionated into two size classes, in offshore waters along a latitudinal transect crossing the North, Norwegian and Greenland Seas between the UK and Svalbard. Rates of gross primary production were higher and more variable than community respiration, so net autotrophy prevailed in the euphotic zone with an average net community production of 16464 mmol O2 m-2 d-1. Respiration seemed to be mainly attributed to large eukaryotic cells (>0.8 ?m) with smaller cells, mainly bacteria, accounting for a mean of 25% (range 5-48%) of community respiration. Estimates of bacterial growth efficiency were very variable (range 7-69%) due to uncoupling between bacterial respiration and production. Larger cells tended to contribute more towards total respiration in communities with high gross primary production and low community respiration, while bacteria contributed more towards total respiration in communities with lower gross primary production, typical of microbial-dominated systems. This suggests that community respiration is related to the size structure of the plankton community.

Garca-Martn, E. E.; McNeill, S.; Serret, P.; Leakey, R. J. G.

2014-10-01

227

Viral effects on bacterial respiration, production and growth efficiency: Consistent trends in the Southern Ocean and the Mediterranean Sea  

NASA Astrophysics Data System (ADS)

To investigate the potential effects of viruses on bacterial respiration (BR), production (BP) and growth efficiency (BGE), experiments were performed using natural microbial communities from the coastal Mediterranean Sea, from a typical high-nutrient low-chlorophyll (HNLC) region in the Southern Ocean and from a naturally iron (Fe)-fertilized algal bloom above the Kerguelen Plateau (Southern Ocean). Seawater was sequentially filtered and concentrated to produce a bacterial concentrate, a viral concentrate and a virus-free ultrafiltrate. The combination of all three fractions served as treatments with active viruses. Heating or microwaving was used to inactivate viruses for the control treatments. Despite the differences in the initial trophic state and community composition of the study sites, consistent trends were found. In the presence of active viruses, BR was stimulated (up to 113%), whereas BP and BGE were reduced (up to 51%). Our results suggest that viruses enhance the role of bacteria as oxidizers of organic matter, hence as producers of CO 2, and remineralizers of CO 2, N, P and Fe. In the context of Fe-fertilization, this has important implications for the final fate of organic carbon in marine systems.

Bonilla-Findji, Osana; Malits, Andrea; Lefvre, Dominique; Rochelle-Newall, Emma; Leme, Rodolphe; Weinbauer, Markus G.; Gattuso, Jean-Pierre

2008-03-01

228

Effect of autochthonous bacteriocin-producing Lactococcus lactis on bacterial population dynamics and growth of halotolerant bacteria in Brazilian charqui.  

PubMed

Charqui is a fermented, salted and sun-dried meat product, widely consumed in Brazil and exported to several countries. Growth of microorganisms in this product is unlikely due to reduced Aw, but halophilic and halotolerant bacteria may grow and cause spoilage. Charqui is a good source of lactic acid bacteria able to produce antimicrobial bacteriocins. In this study, an autochthonous bacteriocinogenic strain (Lactococcus lactis subsp. lactis 69), isolated from charqui, was added to the meat used for charqui manufacture and evaluated for its capability to prevent the growth of spoilage bacteria during storage up to 45 days. The influence of L.lactis 69 on the bacterial diversity during the manufacturing of the product was also studied, using denaturing gradient gel electrophoresis (DGGE). L.lactis 69 did not affect the counts and diversity of lactic acid bacteria during manufacturing and storage, but influenced negatively the populations of halotolerant microorganisms, reducing the spoilage potential. The majority of tested virulence genes was absent, evidencing the safety and potential technological application of this strain as an additional hurdle to inhibit undesirable microbial growth in this and similar fermented meat products. PMID:25084676

Biscola, Vanessa; Abriouel, Hikmate; Todorov, Svetoslav Dimitrov; Capuano, Verena Sant'Anna Cabral; Glvez, Antonio; Franco, Bernadette Dora Gombossy de Melo

2014-12-01

229

Effects of Porous Media Heterogeneity and Transverse Mixing on Bacterial Growth  

NASA Astrophysics Data System (ADS)

Microbial degradation of contaminants in the subsurface depends to a large extent on the availability of nutrients, which is impacted by porous media heterogeneity and the degree of transverse mixing. The growth of a pure culture (Delftia acidovorans strain R39bR) that degrades (R)-2-(2,4-dichlorophenoxy)propionate (R-2,4-DP) was evaluated in two types of microfluidic pore structures etched into silicon wafers (i.e., micromodels): i) a homogeneous distribution of cylindrical posts, and ii) aggregates of large and small cylindrical posts. Each micromodel was inoculated with suspended cells of R39bR for 5-8 days. Next, aqueous phase O2 and R-2,4-DP were introduced as two separate and parallel streams that mixed transverse to the direction of flow along the centerline of each pore structure. In the homogeneous micromodel, biomass growth was observed as a narrow line along the centerline; in the aggregate micromodel, preferential microbial growth was observed in the inter-aggregate pore spaces. Image analysis indicates the initial rate (i.e., over first 30 days) of microbial growth is greater in the homogeneous micromodel than the aggregate micromodel. Effluent samples were collected and results showed higher R-2,4-DP degradation in the homogeneous pore structure than in the aggregate pore structure. A pore scale reactive transport model was used to simulate flow and substrates distribution in the two different pore structures. Simulation results indicate that biomass growth in intra-aggregate pore structures is limited by diffusion, and preferential growth occurs in inter-aggregate pores due to the high mass flux of nutrients in these spaces. Results from this study contribute to a better understanding of biomass growth in complex porous media systems and will help designing more effective bioremediation systems.

Werth, C. J.; Zhang, C.; Zilles, J.; Mueller, R.; Kang, Q.

2009-12-01

230

Bacterial manganese reduction and growth with manganese oxide as the sole electron acceptor  

NASA Technical Reports Server (NTRS)

Microbes that couple growth to the reduction of manganese could play an important role in the biogeochemistry of certain anaerobic environments. Such a bacterium, Alteromonas putrefaciens MR-1, couples its growth to the reduction of manganese oxides only under anaerobic conditions. The characteristics of this reduction are consistent with a biological, and not an indirect chemical, reduction of manganese, which suggest that this bacterium uses manganic oxide as a terminal electron acceptor. It can also utilize a large number of other compounds as terminal electron acceptors; this versatility could provide a distinct advantage in environments where electron-acceptor concentrations may vary.

Myers, Charles R.; Nealson, Kenneth H.

1988-01-01

231

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

NASA Astrophysics Data System (ADS)

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 (45S, 153E) and southwest (46S, 140E) of Tasmania and at the Polar Front (54S, 147E). 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-SAZ where concentrations of bacteria were significantly higher than elsewhere in the region and bacterivory was correlated with bacterial growth rates and rates of cyanobacterivory. Cluster analysis of the concentrations of marine microbes and their rates of growth and grazing mortality identified 5 groups of sampling sites that differed in community structure. Analysis distinguished between high nutrient, low Chl a (HNLC) communities in the NW-SAZ that were iron-limited; iron-limited low Chl a PFZ communities; and iron-replete NE-SAZ communities where high rates of remineralisation correlated with higher concentrations of Chl a. Our findings show that much of the carbon sequestered by photosynthesis in the SAZ during summer is reprocessed via the microbial loop rather than contributing to vertical flux, particularly to the southeast of Tasmania. This suggests strong seasonality in carbon export in the region and that future climate-driven changes in oceanography may reduce carbon export from the region in summer.

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

2011-11-01

232

Evaluation of a creosote-based medium for the growth and preparation of a PAH-degrading bacterial community for bioaugmentation  

Microsoft Academic Search

Creosote was evaluated as an inexpensive carbon source for growing inocula of a polycyclic aromatic hydrocarbon (PAH)-degrading\\u000a bacterial community (community five). Creosote was a poor growth substrate when provided as sole carbon source in a basal\\u000a salts solution (BSM). Alternatively, peptone, yeast extract or glucose in BSM supported high growth rates, but community five\\u000a could not subsequently degrade pyrene. A

A L Juhasz; M L Britz; G A Stanley

2000-01-01

233

Bacterial adhesion and growth reduction by novel rubber-derived oligomers  

PubMed Central

In the medical field, attached bacteria can cause infections associated with catheters, incisions, burns, and medical implants especially in immunocompromised patients. The problem is exacerbated by the fact that attached bacteria are ~1000 times more resistant to antibiotics than planktonic cells. The rapid spread of antibiotic resistance in these and other organisms has led to a significant need to find new methods for preventing bacterial attachment. The goal of this research was to evaluate the effectiveness of novel polymer coatings to prevent the attachment of three medically relevant bacteria. Tests were conducted with Pseudomonas aeruginosa, Staphylococcus epidermidis, and Staphylococcus aureus for oligomers derived from modifications of natural rubber (cis 1,4-polyisoprene). The different oligomers were: PP04, with no quaternary ammonium (QA); MV067, one QA; PP06, three QA groups. In almost all experiments, cell attachment was inhibited to various extents as long as the oligomers were used. PP06 was the most effective as it decreased the planktonic cell numbers by at least 50% for all bacteria. Differences between species sensitivity were also observed. P. aeruginosa was the most resistant bacteria tested, S. aureus, the most sensitive. Further experiments are required to understand the full extent and mode of the antimicrobial properties of these surfaces. PMID:23921230

Badawy, Hope T.; Pasetto, Pamela; Mouget, Jean-Luc; Pilard, Jean-Francois; Cutright, Teresa J.

2013-01-01

234

Bacterial adhesion and growth reduction by novel rubber-derived oligomers.  

PubMed

In the medical field, attached bacteria can cause infections associated with catheters, incisions, burns, and medical implants especially in immunocompromised patients. The problem is exacerbated by the fact that attached bacteria are ?1000 times more resistant to antibiotics than planktonic cells. The rapid spread of antibiotic resistance in these and other organisms has led to a significant need to find new methods for preventing bacterial attachment. The goal of this research was to evaluate the effectiveness of novel polymer coatings to prevent the attachment of three medically relevant bacteria. Tests were conducted with Pseudomonas aeruginosa, Staphylococcus epidermidis, and Staphylococcus aureus for oligomers derived from modifications of natural rubber (cis 1,4-polyisoprene). The different oligomers were: PP04, with no quaternary ammonium (QA); MV067, one QA; PP06, three QA groups. In almost all experiments, cell attachment was inhibited to various extents as long as the oligomers were used. PP06 was the most effective as it decreased the planktonic cell numbers by at least 50% for all bacteria. Differences between species sensitivity were also observed. P. aeruginosa was the most resistant bacteria tested, S. aureus, the most sensitive. Further experiments are required to understand the full extent and mode of the antimicrobial properties of these surfaces. PMID:23921230

Badawy, Hope T; Pasetto, Pamela; Mouget, Jean-Luc; Pilard, Jean-Franois; Cutright, Teresa J; Milsted, Amy

2013-09-01

235

Biological evaluation of hyperforin and its hydrogenated analogue on bacterial growth and biofilm production.  

PubMed

Bacterial biofilms are organized communities of microorganisms, embedded in a self-produced matrix, growing on a biotic surface and resistant to many antimicrobial agents when associated with a medical device. These biofilms require the development of new strategies for the prevention and treatment of infectious disease, including the potential use of natural products. One interesting natural product example is Hypericum, a plant genus that contains species known to have antimicrobial properties. The major constituent of Hypericum perforatum is an unstable compound named hyperforin (1); for this reason it was not believed to play a significant role in the pharmacological effects. In this investigation a hydrogenated hyperforin analogue (2) was tested on several ATCC and clinical isolate strains, in their planktonic and biofilm form (Staphylococcus aureus, MRSA, and Enterococcus faecalis). Compound 2 was effective against planktonic and biofilm cultures, probably due to higher stability, showing the percentage of cells killed in the range from 45% to 52%. These results are noteworthy from the point of view of future development of these polyprenylated phloroglucinols as potential antibiotics. PMID:23981190

Schiavone, Brigida Immacolata Pia; Rosato, Antonio; Marilena, Muraglia; Gibbons, Simon; Bombardelli, Ezio; Verotta, Luisella; Franchini, Carlo; Corbo, Filomena

2013-09-27

236

Influence of bacterial strains isolated from lead-polluted soil and their interactions with arbuscular mycorrhizae on the growth of Trifolium pratense L. under lead toxicity.  

PubMed

We isolated two bacterial strains from an experimentally lead (Pb)-polluted soil in Hungary, 10 years after soil contamination. These strains represented the two most abundant cultivable bacterial groups in such soil, and we tested their influence on Trifolium pratense L. growth and on the functioning of native mycorrhizal fungi under Pb toxicity in a second Pb-spiked soil. Our results showed that bacterial strain A enhanced plant growth, nitrogen and phosphorus accumulations, nodule formation, and mycorrhizal infection, demonstrating its plant-growth-promoting activity. In addition, strain A decreased the amount of Pb absorbed by plants, when expressed on a root weight basis, because of increased root biomass due to the production of indoleacetic acid. The positive effect of strain A was not only evident after a single inoculation but also in dual inoculation with arbuscular mycorrhizal fungi. Strain A also exhibited higher tolerance than strain B when cultivated under increasing Pb levels in the spiked soil. Molecular identification unambiguously placed strain A within the genus Brevibacillus. We showed that it is important to select the most tolerant and efficient bacterial strain for co-inoculation with arbuscular mycorrhizal fungi to promote effective symbiosis and thus stimulate plant growth under adverse environmental conditions, such as heavy-metal contamination. PMID:14663492

Vivas, A; Azcn, R; Bir, B; Barea, J M; Ruiz-Lozano, J M

2003-10-01

237

Bacterial growth and motility in sub-micron constrictions Jaan Mannik, Rosalie Driessen, Peter Galajda, Juan E. Keymer, and Cees Dekker1  

E-print Network

establish how Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria can grow, move treatment and purification. Whereas microbiology text- books consider output from 0.2- m pore size filters). In these experiments, confinement affected bacterial growth in the di- rection of its elongation. The experiments

Dekker, Cees

238

Evolution of cooperation in microbial biofilms - A stochastic model for the growth and survival of bacterial mats  

NASA Astrophysics Data System (ADS)

Cooperative behavior is essential for microbial biofilms. The structure and composition of a biofilm change over time and thereby influence the evolution of cooperation within the system. In turn, the level of cooperation affects the growth dynamics of the biofilm. Here, we investigate this coupling for an experimentally well-defined situation in which mutants of the Pseudomonas fluorescens strain form a mat at the liquid-air interface by the production of an extra-cellular matrix [1]. We model the occurrence of cooperation in this bacterial population by taking into account the formation of the mat. The presence of cooperators enhances the growth of the mat, but at the same time cheaters can infiltrate the population and put the viability of the mat at risk. We find that the survival time of the mat crucially depends on its initial dynamics which is subject to demographic fluctuations [2]. More generally, our work provides conceptual insights into the requirements and mechanisms for the evolution of cooperation.[1] P. Rainey et al., Nature 425, 72 (2003).[2] A. Melbinger et al., PRL 105, 178101 (2010).

Knebel, Johannes; Cremer, Jonas; Melbinger, Anna; Frey, Erwin

2012-02-01

239

Control of bacterial biofilm growth on surfaces by nanostructural mechanics and geometry  

Microsoft Academic Search

Surface-associated communities of bacteria, called biofilms, pervade natural and anthropogenic environments. Mature biofilms are resistant to a wide range of antimicrobial treatments and therefore pose persistent pathogenic threats. The use of surface chemistry to inhibit biofilm growth has been found to only transiently affect initial attachment. In this work, we investigate the tunable effects of physical surface properties, including high-aspect-ratio

A K Epstein; A I Hochbaum; Philseok Kim; J Aizenberg

2011-01-01

240

Determination of In Situ Bacterial Growth Rates in Aquifers and Aquifer Sediments  

Microsoft Academic Search

Laboratory and field-scale studies with stained cells were performed to monitor cell growth in groundwater systems. During cell division, the fluorescence intensity of the protein stain 5-(and 6-)-carboxyfluorescein diacetate succinimidyl ester (CFDA\\/SE) for each cell is halved, and the intensity can be tracked with a flow cytometer. Two strains of bacteria, Comamonas sp. strain DA001 and Acidovorax sp. strain OY-107,

Brian J. Mailloux; Mark E. Fuller

2003-01-01

241

Structure, Growth, and Decomposition of Laminated Algal-Bacterial Mats in Alkaline Hot Springs  

PubMed Central

Laminated mats of unique character in siliceous alkaline hot springs of Yellowstone Park are formed predominantly by two organisms, a unicellular blue-green alga, Synechococcus lividus, and a filamentous, gliding, photosynthetic bacterium, Chloroflexus aurantiacus. The mats can be divided approximately into two major zones: an upper, aerobic zone in which sufficient light penetrates for net photosynthesis, and a lower, anaerobic zone, where photosynthesis does not occur and decomposition is the dominant process. Growth of the mat was followed by marking the mat surface with silicon carbide particles. The motile Chloroflexus migrates vertically at night, due to positive aerotaxis, responding to reduced O2 levels induced by dark respiration. The growth rates of mats were estimated at about 50 ?m/day. Observations of a single mat at Octopus Spring showed that despite the rapid growth rate, the thickness of the mat remained essentially constant, and silicon carbide layers placed on the surface gradually moved to the bottom of the mat, showing that decomposition was taking place. There was a rapid initial rate of decomposition, with an apparent half-time of about 1 month, followed by a slower period of decomposition with a half-time of about 12 months. Within a year, complete decomposition of a mat of about 2-cm thickness can occur. Also, the region in which decomposition occurs is strictly anaerobic, showing that complete decomposition of organic matter from these organisms can occur in the absence of O2. Images PMID:16345254

Doemel, W. N.; Brock, Thomas D.

1977-01-01

242

Heterologous expression of a bacterial haemoglobin improves the growth properties of recombinant Escherichia coli.  

PubMed

Rational design of novel as well as improved cellular biocatalysts by genetic manipulation of cellular metabolism has recently attracted considerable interest. A wide range of bacteria have been genetically modified by integrating new enzymatic functions into their metabolic network. A central problem in the aerobic growth of any cell culture is the maintenance of dissolved oxygen (DO) concentrations above growth-limiting levels especially in high cell-density fermentations which are usually of a fed-batch type. The optimal rate of nutrient addition (and consequently the productivity) is ultimately limited by the rate at which cells can aerobically catabolize the carbon source without generating growth-inhibitory metabolites such as lactate and acetate. All approaches thus far have concentrated on improving the oxygen mass transfer rates by manipulating various environmental parameters. We have isolated the gene for a haemoglobin-like molecule, expressed by the aerobic bacterium Vitreoscilla in poorly-oxygenated environments, and expressed it in Escherichia coli. The recombinant cells contain enhanced haem as well as active haemoglobin, and they grow faster and to considerably greater cell densities than comparable plasmid-containing cells which do not express haemoglobin. This haemoglobin increases the rate of oxygen use, especially when dissolved oxygen is less than 5% of air saturation. PMID:3277067

Khosla, C; Bailey, J E

1988-02-18

243

Light-response curves of Potamogeton pectinatus L. as a function of plant age and irradiance level during growth  

Microsoft Academic Search

\\u000a Macrophytes usually play a dominant role in a shallow aquatic ecosystem. Thus, among others, knowledge of plant photosynthesis\\u000a in relation to light conditions and plant age is important to understand the functioning of this system. The relation between\\u000a the rate of net photosynthesis P and light intensity I, the P-I curve or light-response curve, can be described with numerical\\u000a equations

M. J. M. Hootsmans; J. E. Vermaat

1994-01-01

244

Molecular characterization of RNA and protein synthesis during a one-step growth curve of bovine viral diarrhoea virus in ovine (SFT-R) cells  

Microsoft Academic Search

The aim of this study was to determine the kinetics of noncytopathic bovine viral diarrhoea virus (BVDV) multiplication and synthesis of BVDV specific RNA and proteins in ovine cells (SFT-R) during a one-step growth curve. The virus titre and RNA level were determined by focus-forming assay and real time RT-PCR. The RNA synthesis was detected by Northern blot while synthesis

N. Mishra; B. S. Mathapati; K. Rajukumar; R. K. Nema; S. P. Behera; S. C. Dubey

2010-01-01

245

Systems level analysis of protein synthesis patterns associated with bacterial growth and metabolic transitions.  

PubMed

Gene expression databases, acquired by proteomics and transcriptomics, describe physiological and developmental programs at the systems level. Here we analyze proteosynthetic profiles in a bacterium undergoing defined metabolic changes. Streptomyces coelicolor cultured in a defined liquid medium displays four distinct patterns of gene expression associated with growth on glutamate, diauxic transition, and growth on maltose and ammonia that terminates by starvation for nitrogen and entry into stationary phase. Principal component and fuzzy cluster analyses of the proteome database of 935 protein spot profiles revealed principal kinetic patterns. Online linkage of the proteome database (SWICZ) to a protein-function database (KEGG) revealed limited correlations between expression profiles and metabolic pathway activities. Proteins belonging to principal metabolic pathways defined characteristic kinetic profiles correlated with the physiological state of the culture. These analyses supported the concept that metabolic flux was regulated not by individual enzymes but rather by groups of enzymes whose synthesis responded to changes in nutritional conditions. Higher-level regulation is reflected by the distribution of all kinetic profiles into only nine groups. The observation that enzymes representing principal metabolic pathways displayed their own distinctive average kinetic profiles suggested that expression of a "high-flux backbone" may dominate regulation of metabolic flux. PMID:16400688

Vohradsky, Jiri; Thompson, Charles J

2006-02-01

246

Arabidopsis growth and defense are modulated by bacterial quorum sensing molecules  

PubMed Central

N-acyl-homoserine lactones (AHLs) play an important role in the communication within the rhizosphere; they serve as a chemical base for interactions within and between different species of Gram-negative bacteria. Not only bacteria, also plants perceive and react to AHLs with diverse responses. Here we describe a negative correlation between the length of AHLs lipid chains and the observed growth promotion in Arabidopsis thaliana. Moreover, we speculate on a positive correlation between the reinforcement of defense mechanisms and the length of the lipid moieties. Observation presented here may be of great importance for understanding of the complex interplay between plants and their environment, as well as for agronomic applications. PMID:22307043

Schenk, Sebastian T.; Stein, Elke; Kogel, Karl-Heinz; Schikora, Adam

2012-01-01

247

New protein hydrolysates from collagen wastes used as peptone for bacterial growth.  

PubMed

A simple and low-cost procedure was developed for the effective processing of native calf skin and blood wastes to produce protein hydrolysates. The method includes extraction of high-molecular-weight protein from the raw material, followed by enzymatic hydrolysis of the extracted residue. The enzymatic hydrolysis was performed by inexpensive commercial subtilisin DY, produced by Bacillus subtilis strain DY possessing high specific activity. The contents of protein, nitrogen, ash, and amino acids of the obtained hydrolysates were determined and compared with those of the commonly used commercial casein hydrolysate (Fluka Biochemica, Switzerland). The newly obtained calf skin hydrolysate, called Eladin, was found to be suitable as a low-cost alternative peptone in growth media of different microorganisms, such as Escherichia coli, Pseudomonas aeruginosa, Salmonella dublin, and Staphylococcus aureus. The method allows utilization of waste materials by converting them into valuable protein products that could find widespread application in microbiologic practice. PMID:17171464

Vasileva-Tonkova, E; Nustorova, M; Gushterova, A

2007-01-01

248

Iodine from bacterial iodide oxidization by Roseovarius spp. inhibits the growth of other bacteria.  

PubMed

Microbial activities in brine, seawater, or estuarine mud are involved in iodine cycle. To investigate the effects of the microbiologically induced iodine on other bacteria in the environment, a total of 13 bacteria that potentially participated in the iodide-oxidizing process were isolated from water or biofilm at a location containing 131 ?g ml(-1) iodide. Three distinct strains were further identified as Roseovarius spp. based on 16 S rRNA gene sequences after being distinguished by restriction fragment length polymorphism analysis. Morphological characteristics of these three Roseovarius spp. varied considerably across and within strains. Iodine production increased with Roseovarius spp. growth when cultured in Marine Broth with 200 ?g ml(-1) iodide (I(-)). When 10(6) CFU/ml Escherichia coli, Pseudomonas aeruginosa, and Bacillus pumilus were exposed to various concentrations of molecular iodine (I(2)), the minimum inhibitory concentrations (MICs) were 0.5, 1.0, and 1.0 ?g ml(-1), respectively. However, fivefold increases in the MICs for Roseovarius spp. were obtained. In co-cultured Roseovarius sp. IOB-7 and E. coli in Marine Broth containing iodide (I(-)), the molecular iodine concentration was estimated to be 0.76 ?g ml(-1) after 24 h and less than 50 % of E. coli was viable compared to that co-cultured without iodide. The growth inhibition of E. coli was also observed in co-cultures with the two other Roseovarius spp. strains when the molecular iodine concentration was assumed to be 0.52 ?g ml(-1). PMID:22526798

Zhao, Dan; Lim, Choon-Ping; Miyanaga, Kazuhiko; Tanji, Yasunori

2013-03-01

249

CdTe-TiO2 nanocomposite: an impeder of bacterial growth and biofilm  

NASA Astrophysics Data System (ADS)

The resurgence of infectious diseases and associated issues related to antibiotic resistance has raised enormous challenges which may possibly be confronted primarily by nanotechnology routes. One key need of critical significance in this context is the development of an agent capable of inhibiting quorum sensing mediated biofilm formation in pathogenic organisms. In this work we examine the possible use of a nanocomposite, CdTe-TiO2, as an impeder of growth and biofilm. In the presence of CdTe-TiO2, scanning electron microscopy (SEM) analysis shows exposed cells without the surrounding matrix. Confocal laser scanning microscopy shows spatially distributed fluorescence, a typical indication of an impeded biofilm, as opposed to the control which shows matrix-covered cells and continuous fluorescence, typical of biofilm formation. Quantitatively, the inhibition of biofilm was 57%. CdTe-TiO2 also exhibits good antibacterial properties against Gram positive and Gram negative organisms by virtue of the generation of reactive oxygen species inside the cells, reflected by a ruptured appearance in the SEM analysis.

Gholap, Haribhau; Patil, Rajendra; Yadav, Prasad; Banpurkar, Arun; Ogale, Satishchandra; Gade, Wasudeo

2013-05-01

250

Metschnikowia Strains Isolated from Botrytized Grapes Antagonize Fungal and Bacterial Growth by Iron Depletion?  

PubMed Central

Noble-rotted grapes are colonized by complex microbial populations. I isolated pigment-producing Metschnikowia strains from noble-rotted grapes that had antagonistic activity against filamentous fungi, yeasts, and bacteria. A red-maroon pigment was formed from a diffusible colorless precursor released by the cells into the medium. The conversion of the precursor required iron and could occur both in the cells (red colonies) and in the medium (red halos around colonies). The intensity of pigmentation was correlated with the intensity of the antimicrobial activity. Mutants that did not form pigment also lacked antifungal activity. Within the pigmented halos, conidia of the sensitive fungi did not germinate, and their hyphae did not grow and frequently lysed at the tips. Supplementation of the medium with iron reduced the size of the halos and the inhibition zones, while it increased the pigment accumulation by the colonies. The iron-binding agent tropolone had a similar effect, so I hypothesize that pigmented Metschnikowia isolates inhibit the growth of the sensitive microorganisms by pigment formation, which depletes the free iron in the medium. As the pigment is a large nondiffusible complex produced in the presence of both low and high concentrations of ferric ions, the proposed mechanism is different from the mechanisms operating in microbes that release siderophores into the environment for iron acquisition. PMID:17021223

Sipiczki, Matthias

2006-01-01

251

Spectrumeffect relationships between ultra performance liquid chromatography fingerprints and anti-bacterial activities of Rhizoma coptidis  

Microsoft Academic Search

The fingerprints of Rhizoma coptidis from various sources were established by ultra performance liquid chromatography (UPLC) and the anti-bacterial activities of R. coptidis on Escherichia coli (E. coli) growth was studied by microcalarimetry. The UPLC fingerprints were evaluated using similarity analysis (SA) and hierarchical clustering analysis (HCA). Some quantitative parameters obtained from the thermo-genic curves of E. coli growth affected

Wei-Jun Kong; Yan-Ling Zhao; Xiao-He Xiao; Jia-Bo Wang; Han-Bing Li; Zu-Lun Li; Cheng Jin; Yi Liu

2009-01-01

252

Multilevel Growth Curve Analyses of Treatment Effects of a Web-Based Intervention for Stress Reduction: Randomized Controlled Trial  

PubMed Central

Background Stress is commonly experienced by many people and it is a contributing factor to many mental and physical health conditions, However, few efforts have been made to develop and test the effects of interventions for stress. Objective The aim of this study was to examine the effects of a Web-based stress-reduction intervention on stress, investigate mindfulness and procrastination as potential mediators of any treatment effects, and test whether the intervention is equally effective for females as males, all ages, and all levels of education. Methods We employed a randomized controlled trial in this study. Participants were recruited online via Facebook and randomly assigned to either the stress intervention or a control condition. The Web-based stress intervention was fully automated and consisted of 13 sessions over 1 month. The controls were informed that they would get access to the intervention after the final data collection. Data were collected at baseline and at 1, 2, and 6 months after intervention onset by means of online questionnaires. Outcomes were stress, mindfulness, and procrastination, which were all measured at every measurement occasion. Results A total of 259 participants were included and were allocated to either the stress intervention (n=126) or the control condition (n=133). Participants in the intervention and control group were comparable at baseline; however, results revealed that participants in the stress intervention followed a statistically different (ie, cubic) developmental trajectory in stress levels over time compared to the controls. A growth curve analysis showed that participants in the stress intervention (unstandardized beta coefficient [B]=3.45, P=.008) recovered more quickly compared to the control group (B=0.81, P=.34) from baseline to 1 month. Although participants in the stress intervention did show increases in stress levels during the study period (B=2.23, P=.008), long-term stress levels did decrease again toward study end at 6 months (B=0.28, P=.009). Stress levels in the control group, however, remained largely unchanged after 1 month (B=0.29, P=.61) and toward 6 months (B=0.03, P=.67). Mediation analyses showed nonlinear (ie, cubic) specific indirect effects of mindfulness and a linear specific indirect effect of procrastination on stress. In simple terms, the intervention increased mindfulness and decreased procrastination, which was related to lower stress levels. Finally, the effect of the stress intervention was independent of participants gender, age, or education. Conclusions The results from this randomized controlled trial suggest that a Web-based intervention can reduce levels of stress in a normal population and that both mindfulness and procrastination may be important components included in future eHealth interventions for stress. Trial Registration International Standard Randomized Controlled Trial Number (ISRCTN): 25619675; http://controlled-trials.com/ISRCTN25619675 (Archived by Webcite at http://www.webcitation.org/6FxB1gOKY) PMID:23607962

Raeder, Sabine; Kraft, Pal; Bj?rkli, Cato Alexander

2013-01-01

253

Fungal and bacterial growth responses to N fertilization and pH in the 150-year 'Park Grass' UK grassland experiment.  

PubMed

The effects of nitrogen (N) fertilization (0-150 kg N ha? year? since 1865) and pH (3.3-7.4) on fungal and bacterial growth, biomass and phospholipid fatty acid (PLFA) composition were investigated in grassland soils from the 'Park Grass Experiment', Rothamsted Research, UK. Bacterial growth decreased and fungal growth increased with lower pH, resulting in a 50-fold increase in the relative importance of fungi between pH 7.4 and 3.3. The PLFA-based fungal:bacterial biomass ratio was unchanged between pH 4.5 and 7.4, and decreased only below pH 4.5. Respiration and substrate-induced respiration biomass both decreased three- to fourfold with lower pH, but biomass concentrations estimated using PLFAs were unaffected by pH. N fertilization did not affect bacterial growth and marginally affected fungal growth while PLFA biomass marker concentrations were all reduced by higher N additions. Respiration decreased with higher N application, suggesting a reduced quality of the soil organic carbon. The PLFA composition was strongly affected by both pH and N. A comparison with a pH gradient in arable soil allowed us to generalize the pH effect between systems. There are 30-50-fold increases in the relative importance of fungi between high (7.4-8.3) and low (3.3-4.5) pH with concomitant reductions of respiration by 30-70%. PMID:21223326

Rousk, Johannes; Brookes, Philip C; Bth, Erland

2011-04-01

254

Genetic variances, heritabilities and maternal effects on body weight, breast meat yield, meat quality traits and the shape of the growth curve in turkey birds  

PubMed Central

Background Turkey is an important agricultural species and is largely used as a meat bird. In 2004, turkey represented 6.5% of the world poultry meat production. The world-wide turkey population has rapidly grown due to increased commercial farming. Due to the high demand for turkey meat from both consumers and industry global turkey stocks increased from 100 million in 1970 to over 276 million in 2004. This rapidly increasing importance of turkeys was a reason to design this study for the estimation of genetic parameters that control body weight, body composition, meat quality traits and parameters that shape the growth curve in turkey birds. Results The average heritability estimate for body weight traits was 0.38, except for early weights that were strongly affected by maternal effects. This study showed that body weight traits, upper asymptote (a growth curve trait), percent breast meat and redness of meat had high heritability whereas heritabilities of breast length, breast width, percent drip loss, ultimate pH, lightness and yellowness of meat were medium to low. We found high positive genetic and phenotypic correlations between body weight, upper asymptote, most breast meat yield traits and percent drip loss but percent drip loss was found strongly negatively correlated with ultimate pH. Percent breast meat, however, showed genetic correlations close to zero with body weight traits and upper asymptote. Conclusion The results of this analysis and the growth curve from the studied population of turkey birds suggest that the turkey birds could be selected for breeding between 60 and 80 days of age in order to improve overall production and the production of desirable cuts of meat. The continuous selection of birds within this age range could promote high growth rates but specific attention to meat quality would be needed to avoid a negative impact on the quality of meat. PMID:21266032

2011-01-01

255

Fluorescent assay based on resazurin for detection of activity of disinfectants against bacterial biofilm  

Microsoft Academic Search

A new, quick method, using the resazurin dye test as a bacterial respiration indicator, has been developed to assay the antibacterial\\u000a activity of various substances used as disinfectants against bacterial biofilm growth on clinical devices. Resazurin was used\\u000a to measure the presence of active biofilm bacteria, after adding disinfectant, in relation to a standard curve generated from\\u000a inocula in suspension

Alberto Mariscal; Rosa M. Lopez-Gigosos; Manuel Carnero-Varo; Joaquin Fernandez-Crehuet

2009-01-01

256

Effects of Bacillus amyloliquefaciens FZB42 on Lettuce Growth and Health under Pathogen Pressure and Its Impact on the Rhizosphere Bacterial Community  

PubMed Central

The soil-borne pathogen Rhizoctonia solani is responsible for crop losses on a wide range of important crops worldwide. The lack of effective control strategies and the increasing demand for organically grown food has stimulated research on biological control. The aim of the present study was to evaluate the rhizosphere competence of the commercially available inoculant Bacillus amyloliquefaciens FZB42 on lettuce growth and health together with its impact on the indigenous rhizosphere bacterial community in field and pot experiments. Results of both experiments demonstrated that FZB42 is able to effectively colonize the rhizosphere (7.45 to 6.61 Log 10 CFU g?1 root dry mass) within the growth period of lettuce in the field. The disease severity (DS) of bottom rot on lettuce was significantly reduced from severe symptoms with DS category 5 to slight symptom expression with DS category 3 on average through treatment of young plants with FZB42 before and after planting. The 16S rRNA gene based fingerprinting method terminal restriction fragment length polymorphism (T-RFLP) showed that the treatment with FZB42 did not have a major impact on the indigenous rhizosphere bacterial community. However, the bacterial community showed a clear temporal shift. The results also indicated that the pathogen R. solani AG1-IB affects the rhizosphere microbial community after inoculation. Thus, we revealed that the inoculant FZB42 could establish itself successfully in the rhizosphere without showing any durable effect on the rhizosphere bacterial community. PMID:23935892

Randler, Manuela; Schmid, Michael; Junge, Helmut; Borriss, Rainer; Hartmann, Anton; Grosch, Rita

2013-01-01

257

RELATIONS BETWEEN BACTERIAL NITROGEN METABOLISM AND GROWTH EFFICIENCY IN AN ESTUARINE AND AN OPEN-WATER ECOSYSTEM  

EPA Science Inventory

Bacterial uptake or release of dissolved nitrogen compounds (amino nitrogen, urea, ammonium and nitrate) were examined in 0.8 |m filtered water from an estuary (Santa Rosa Sound [SRS], northwestern Florida) and an open-water location in the Gulf of Mexico [GM]. The bacterial nutr...

258

Paclobutrazol and plant-growth promoting bacterial endophyte Pantoea sp. enhance copper tolerance of guinea grass ( Panicum maximum ) in hydroponic culture  

Microsoft Academic Search

As most gramineous plants, guinea grass (Panicum maximum) comprise cellulosic biomass, which may be used as a feedstock for bioenergy. In order to develop such potential energy plants\\u000a on copper-polluted lands, the hydroponic experiments with Cu, Paclobutrazol (PP333, a kind of antigibberellin) and plant growth-promoting\\u000a bacterial endophyte (PGPB) treatments were carried out in a greenhouse. The seedlings of two cultivars

Wei HuoChun-hua; Chun-hua Zhuang; Ya Cao; Meng Pu; Hui Yao; Lai-qing Lou; Qing-sheng Cai

259

Growth of inoculated white-rot fungi and their interactions with the bacterial community in soil contaminated with polycyclic aromatic hydrocarbons, as measured by phospholipid fatty acids  

Microsoft Academic Search

The objective of this study was to examine the possibility of measuring the growth of three white-rot fungi in soil contaminated with polycyclic aromatic hydrocarbons (PAHs), by estimating the soil levels of the phospholipid fatty acid (PLFA) 18:2?6,9. The effect of the fungi on the PAH concentration and on the indigenous bacterial population in the soil was monitored. As shown

B. E Andersson; L Welinder; P. A Olsson; S Olsson; T Henrysson

2000-01-01

260

Stimulation of Plant Growth and Drought Tolerance by Native Microorganisms (AM Fungi and Bacteria) from Dry Environments: Mechanisms Related to Bacterial Effectiveness  

Microsoft Academic Search

In this study we tested whether rhizosphere microorganisms can increase drought tolerance to plants growing under water-limitation\\u000a conditions. Three indigenous bacterial strains isolated from droughted soil and identified as Pseudomonas putida, Pseudomonas sp., and Bacillus megaterium were able to stimulate plant growth under dry conditions. When the bacteria were grown in axenic culture at increasing osmotic\\u000a stress caused by polyethylene

Adriana Marulanda; Jos-Miguel Barea; Rosario Azcn

2009-01-01

261

Curved Mirrors  

NSDL National Science Digital Library

This inquiry activity will be used before discussing curved mirrors in class. Students will discover how curved mirrors act and how the size and the orientation of the image are related to the distance from the mirror. Ray diagrams for curved mirrors are

Horton, Michael

2009-05-30

262

Fructose transport-deficient Staphylococcus aureus reveals important role of epithelial glucose transporters in limiting sugar-driven bacterial growth in airway surface liquid.  

PubMed

Hyperglycaemia as a result of diabetes mellitus or acute illness is associated with increased susceptibility to respiratory infection with Staphylococcus aureus. Hyperglycaemia increases the concentration of glucose in airway surface liquid (ASL) and promotes the growth of S. aureus in vitro and in vivo. Whether elevation of other sugars in the blood, such as fructose, also results in increased concentrations in ASL is unknown and whether sugars in ASL are directly utilised by S. aureus for growth has not been investigated. We obtained mutant S. aureus JE2 strains with transposon disrupted sugar transport genes. NE768(fruA) exhibited restricted growth in 10mM fructose. In H441 airway epithelial-bacterial co-culture, elevation of basolateral sugar concentration (5-20mM) increased the apical growth of JE2. However, sugar-induced growth of NE768(fruA) was significantly less when basolateral fructose rather than glucose was elevated. This is the first experimental evidence to show that S. aureus directly utilises sugars present in the ASL for growth. Interestingly, JE2 growth was promoted less by glucose than fructose. Net transepithelial flux of D-glucose was lower than D-fructose. However, uptake of D-glucose was higher than D-fructose across both apical and basolateral membranes consistent with the presence of GLUT1/10 in the airway epithelium. Therefore, we propose that the preferential uptake of glucose (compared to fructose) limits its accumulation in ASL. Pre-treatment with metformin increased transepithelial resistance and reduced the sugar-dependent growth of S. aureus. Thus, epithelial paracellular permeability and glucose transport mechanisms are vital to maintain low glucose concentration in ASL and limit bacterial nutrient sources as a defence against infection. PMID:24810961

Garnett, James P; Braun, Daniela; McCarthy, Alex J; Farrant, Matthew R; Baker, Emma H; Lindsay, Jodi A; Baines, Deborah L

2014-12-01

263

Parametric Curves parametric curves (Splines)  

E-print Network

curves (Splines) · polygonal meshes #12;2 Roller coaster · Next programming assignment involves creating a 3D roller coaster animation · We must model the 3D curve describing the roller coaster, but how

Treuille, Adrien

264

A new logistic model for Escherichia coli growth at constant and dynamic temperatures  

Microsoft Academic Search

A new logistic model for bacterial growth was developed in this study. The model, which is based on the logistic model, contains an additional term for expression of the very low rate of growth during a lag phase, in its differential equation. The model successfully described sigmoidal growth curves of Escherichia coli at various initial cell concentrations and constant temperatures.

Hiroshi Fujikawa; Akemi Kai; Satoshi Morozumi

2004-01-01

265

Unifying temperature effects on the growth rate of bacteria and the stability of globular proteins  

Microsoft Academic Search

The specific growth rate constant for bacterial growth does not obey the Arrhenius-type kinetics displayed by simple chemical reactions. Instead, for bacteria, steep convex curves are observed on an Arrhenius plot at the low- and high-temperature ends of the biokinetic range, with a region towards the middle of the growth range loosely approximating linearity. This central region has been considered

David A. Ratkowsky; June Olley; Tom Ross

2005-01-01

266

Bacterial growth and wound infection following saphenous vein harvesting in cardiac surgery: a randomized controlled trial of the impact of microbial skin sealant.  

PubMed

The aim of the present study was to compare microbial skin sealant versus bare skin on the leg regarding intraoperative bacterial presence in the surgical wound and time to recolonization of the adjacent skin at the saphenous vein harvesting site. A second aim was to evaluate the incidence of leg wound infection 2months after surgery. In this randomized controlled trial, 140 patients undergoing coronary artery bypass grafting (CABG) between May 2010 and October 2011 were enrolled. Bacterial samples were taken preoperatively and intraoperatively at multiple time points and locations. OF the patients, 125 (92.6%) were followed up 2months postoperatively regarding wound infection. Intraoperative bacterial growth did not differ between the bare skin (n?=?68) and the microbial skin sealant group (n?=?67) at any time point. At 2months postoperatively, 7/61 patients (11.5%) in the skin sealant versus 14/64 (21.9%) in the bare skin group (p?=?0.120) had been treated with antibiotics for a verified or suspected surgical site infection (SSI) at the harvest site. We found almost no intraoperative bacterial presence on the skin or in the subcutaneous tissue, irrespective of microbial skin sealant use. In contrast, we observed a relatively high incidence of late wound infection, indicating that wound contamination occurred postoperatively. Further research is necessary to determine whether the use of microbial skin sealant reduces the incidence of leg wound infection at the saphenous vein harvest site. PMID:24907853

Falk-Brynhildsen, K; Sderquist, B; Friberg, O; Nilsson, U

2014-11-01

267

[Speed of information processing and fluid intelligence in advanced age. A secondary analysis of data of the Bonn Longitudinal Study of Aging based on "latent growth curve models"].  

PubMed

According to the "speed"-hypothesis of cognitive development, the slowing of information processing in old age is at the core of negative age differences in psychometric intelligence. The present study investigates the "speed"-hypothesis for fluid intelligence at the individual level using Latent Growth Curve Methodology. Data on 4 measurement points come from the Bonn Longitudinal Study of aging (N = 127, mean age 67.2, 53% women). Based on principal factor analysis, markers of mental speed were the WAIS Digit Symbol Test and a simple psychomotor task. As indicators of fluid intelligence the WAIS Object Assembly and Block Design were used. After separately fitting Latent Growth Curve Models for the trajectory of mental speed and fluid intelligence, a combined model showed no statistically significant improvement of fit for freeing the covariance between the two slope-factors. Interpreting this result, contrary to the "speed"-hypothesis the intraindividual change of fluid intelligence does not relate to the according change of mental speed. PMID:9610501

Zimprich, D

1998-04-01

268

Comparison of the bacterial community and characterization of plant growth-promoting rhizobacteria from different genotypes of Chrysopogon zizanioides (L.) Roberty (vetiver) rhizospheres.  

PubMed

Molecular approaches [PCR-denaturing gradient gel electrophoresis (DGGE)] were used to determine whether three different vetiver (Chrysopogon zizanioides) genotypes, commercially used in Brazil and considered economically important over the world, select specific bacterial populations to coexist in their rhizospheres. DGGE profiles revealed that the predominant rhizospheric bacterial community hardly varies regarding the vetiver genotype. Moreover, using traditional cultivation methods, bacterial strains were isolated from the different rhizospheres. Colonies presenting different morphologies (83) were selected for determining their potential for plant growth promotion. More than half of the strains tested (57.8%) were amplified by PCR using nifH-based primers, specific for the enzyme nitrogenase reductase. The production of siderophores was observed in 88% of the strains, while the production of antimicrobial substances was detected in only 14.5% of the isolates when Micrococcus sp. was used as the indicator strain. Production of indole-3-acetic acid and the solubilization of phosphate were observed in 55.4% and 59% of the isolates, respectively. In total, 44 strains (53%) presented at least three characteristics of plant growth promotion and were submitted to amplified ribosomal DNA restriction analysis. Twenty-four genetic groups were formed at 100% similarity and one representative of each group was selected for their identification by partial 16S rRNA gene sequencing. They were affiliated with the genera Acinetobacter, Comamonas, Chryseobacterium, Klebsiella, Enterobacter, Pantoea, Dyella, Burkholderia, or Pseudomonas. These strains can be considered of great importance as possible biofertilizers in vetiver. PMID:19763409

Monteiro, Juliana Mendes; Voll, Renata Estebanez; Coelho, Marcia Reed Rodrigues; Alviano, Celuta Sales; Blank, Arie Fitzgerald; Seldin, Lucy

2009-08-01

269

Aging, Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions  

PubMed Central

Information on aging, maturation, and growth is important for understanding life histories of organisms. In extinct dinosaurs, such information can be derived from the histological growth record preserved in the mid-shaft cortex of long bones. Here, we construct growth models to estimate ages at death, ages at sexual maturity, ages at which individuals were fully-grown, and maximum growth rates from the growth record preserved in long bones of six sauropod dinosaur individuals (one indeterminate mamenchisaurid, two Apatosaurus sp., two indeterminate diplodocids, and one Camarasaurus sp.) and one basal sauropodomorph dinosaur individual (Plateosaurus engelhardti). Using these estimates, we establish allometries between body mass and each of these traits and compare these to extant taxa. Growth models considered for each dinosaur individual were the von Bertalanffy model, the Gompertz model, and the logistic model (LGM), all of which have inherently fixed inflection points, and the Chapman-Richards model in which the point is not fixed. We use the arithmetic mean of the age at the inflection point and of the age at which 90% of asymptotic mass is reached to assess respectively the age at sexual maturity or the age at onset of reproduction, because unambiguous indicators of maturity in Sauropodomorpha are lacking. According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample. Allometries established are consistent with literature data on other Sauropodomorpha. All Sauropodomorpha reached full size within a time span similar to scaled-up modern mammalian megaherbivores and had similar maximum growth rates to scaled-up modern megaherbivores and ratites, but growth rates of Sauropodomorpha were lower than of an average mammal. Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores. Sauropodomorpha were older at maturation than scaled-up ratites and average mammals, but younger than scaled-up megaherbivores. PMID:23840575

Griebeler, Eva Maria; Klein, Nicole; Sander, P. Martin

2013-01-01

270

The effect of micro-architectural structure of cabbage substratum and or background bacterial flora on the growth of Listeria monocytogenes.  

PubMed

The effect of micro-architectural structure of cabbage (Brassica oleracea var. capitata L.) substratum and or background bacterial flora on the growth of Listeria monocytogenes as a function of incubation temperature was investigated. A cocktail mixture of Pseudomonas fluorescens, Pantoea agglomerans and Lactobacillus plantarum was constituted to a population density of approximately 5 log CFU/ml in order to pseudo-simulate background bacterial flora of fresh-cut cabbage. This mixture was co-inoculated with L. monocytogenes (approximately 3 log CFU/ml) on fresh-cut cabbage or in autoclaved cabbage juice followed by incubation at different temperatures (4-30 degrees C). Data on growth of L. monocytogenes were fitted to the primary growth model of Baranyi in order to generate the growth kinetic parameters of the pathogen. During storage, microbial ecology was dominated by P. fluorescens and L. plantarum at refrigeration and abuse temperature, respectively. At all temperatures investigated, lag duration (lambda, h), maximum specific growth rate (micro(max), h(-1)) and maximum population density (MPD, log CFU/ml) of L. monocytogenes were only affected by medium micro-architectural structure, except at 4 degrees C where it had no effect on the micro(max) of the pathogen. Comparison of observed values of micro(max) with those obtained from the Pathogen Modelling Program (PMP), showed that PMP overestimated the growth rate of L. monocytogenes on fresh-cut cabbage and in cabbage juice, respectively. Temperature dependency of micro(max) of L. monocytogenes, according to the models of Ratkowsky and Arrhenius, showed linearity for temperature range of 4-15 degrees C, discontinuities and linearity again for temperature range of 20-30 degrees C. The results of this experiment have shown that the constituted background bacterial flora had no effect on the growth of L. monocytogenes and that micro-architectural structure of the vegetable was the primary factor that limited the applicability of PMP model for predicting the growth of L. monocytogenes on fresh-cut cabbage. A major limitation of this study however is that nutrient profile of the autoclaved cabbage juice may be different from that of the raw juice thus compromising realistic comparison of the behaviour of L. monocytogenes as affected by micro-architectural structure. PMID:17910986

Ongeng, Duncan; Ryckeboer, Jaak; Vermeulen, An; Devlieghere, Frank

2007-11-01

271

Overcoming the anaerobic hurdle in phenotypic microarrays: Generation and visualization of growth curve data for Desulfovibrio vulgaris Hildenborough  

Microsoft Academic Search

Growing anaerobic microorganisms in phenotypic microarrays (PM) and 96-well microtiter plates is an emerging technology that allows high throughput survey of the growth and physiology and\\/or phenotype of cultivable microorganisms. For non-model bacteria, a method for phenotypic analysis is invaluable, not only to serve as a starting point for further evaluation, but also to provide a broad understanding of the

Sharon Borglin; Dominique Joyner; Janet Jacobsen; Aindrila Mukhopadhyay; Terry C. Hazen

2009-01-01

272

Design fire curves for tunnels  

Microsoft Academic Search

Various ways exist to represent a design fire curve for tunnels. These can include different fire growth rates or combinations of fire growth rates with constant levels of heat release rate (HRR) coupled to a decay period. This means that the curve has to be represented with different mathematical expressions for different time periods. A more convenient way is to

Haukur Ingason

2009-01-01

273

Interspecific prediction of photosynthetic light response curves using specific leaf mass and leaf nitrogen content: effects of differences in soil fertility and growth irradiance  

PubMed Central

Background and Aims Previous work has shown that the entire photosynthetic light response curve, based on both Mitscherlich and MichaelisMenten functions, could be predicted in an interspecific context through allometric relations linking the parameters of these functions to two static leaf traits: leaf nitrogen (N) content and leaf mass per area (LMA). This paper describes to what extent these allometric relations are robust to changes in soil fertility and the growth irradiance of the plants. Methods Plants of 25 herbaceous species were grown under controlled conditions in factorial combinations of low/high soil fertility and low/high growth irradiance. Net photosynthetic rates per unit dry mass were measured at light intensities ranging from 0 to 700 mol m?2 s?1 photosynthetically active radiation (PAR). Key Results The differing growth environments induced large changes in N, LMA and in each of the parameter estimates of the Mitscherlich and MichaelisMenten functions. However, the differing growth environments induced only small (although significant) changes in the allometric relationships linking N and LMA to the parameters of the two functions. As a result, 88 % (Mitcherlich) and 89 % (MichaelisMenten) of the observed net photosynthetic rates over the full range of light intensities (0700 mol m?2 s?1 PAR) and across all four growth environments could be predicted using only N and LMA using the same allometric relations. Conclusions These results suggest the possibility of predicting net photosynthetic rates in nature across species over the full range of light intensities using readily available data. PMID:22442344

Lachapelle, Pierre-Philippe; Shipley, Bill

2012-01-01

274

Mechanisms of biocontrol and plant growth-promoting activity in soil bacterial species of Bacillus and Pseudomonas: a review  

Microsoft Academic Search

Plant pathogens are responsible for many crop plant diseases, resulting in economic losses. The use of bacterial agents is an excellent option to fight against plant pathogens and an excellent alternative to the use of chemicals, which are offensive to the environment and to human health. Two of the most common biocontrol agents are members of the Bacillus and Pseudomonas

Gustavo Santoyo; Ma del Carmen Orozco-Mosqueda; M. Govindappa

2012-01-01

275

Two DHH Subfamily 1 Proteins in Streptococcus pneumoniae Possess Cyclic Di-AMP Phosphodiesterase Activity and Affect Bacterial Growth and Virulence  

PubMed Central

Cyclic di-AMP (c-di-AMP) and cyclic di-GMP (c-di-GMP) are signaling molecules that play important roles in bacterial biology and pathogenesis. However, these nucleotides have not been explored in Streptococcus pneumoniae, an important bacterial pathogen. In this study, we characterized the c-di-AMP-associated genes of S. pneumoniae. The results showed that SPD_1392 (DacA) is a diadenylate cyclase that converts ATP to c-di-AMP. Both SPD_2032 (Pde1) and SPD_1153 (Pde2), which belong to the DHH subfamily 1 proteins, displayed c-di-AMP phosphodiesterase activity. Pde1 cleaved c-di-AMP into phosphoadenylyl adenosine (pApA), whereas Pde2 directly hydrolyzed c-di-AMP into AMP. Additionally, Pde2, but not Pde1, degraded pApA into AMP. Our results also demonstrated that both Pde1 and Pde2 played roles in bacterial growth, resistance to UV treatment, and virulence in a mouse pneumonia model. These results indicate that c-di-AMP homeostasis is essential for pneumococcal biology and disease. PMID:24013631

Bai, Yinlan; Yang, Jun; Eisele, Leslie E.; Underwood, Adam J.; Koestler, Benjamin J.; Waters, Christopher M.; Metzger, Dennis W.

2013-01-01

276

Bdellovibrio and Like Organisms Enhanced Growth and Survival of Penaeus monodon and Altered Bacterial Community Structures in Its Rearing Water.  

PubMed

In this study, a 96-h laboratory reduction test was conducted with strain BDHSH06 (GenBank accession no. EF011103) as the test strain for Bdellovibrio and like organisms (BALOs) and 20 susceptible marine bacterial strains forming microcosms as the targets. The results showed that BDHSH06 reduced the levels of approximately 50% of prey bacterial strains within 96 h in the seawater microcosms. An 85-day black tiger shrimp (Penaeus monodon) rearing experiment was performed. The shrimp survival rate, body length, and weight in the test tanks were 48.1% 1.2%, 99.8 10.0 mm, and 6.36 1.50 g, respectively, which were values significantly (P < 0.05) higher than those for the control, viz., 31.0% 2.1%, 86.0 11.1 mm, and 4.21 1.56 g, respectively. With the addition of BDHSH06, total bacterial and Vibrio numbers were significantly reduced (P < 0.05) by 1.3 to 4.5 log CFU ml(-1) and CFU g(-1) in both water and shrimp intestines, respectively, compared to those in the control. The effect of BDHSH06 on bacterial community structures in the rearing water was also examined using PCR amplification of the 16S rRNA gene and denaturing gradient gel electrophoresis (DGGE). The DGGE profiles of rearing water samples from the control and test tanks revealed that the amounts of 44% of the bacterial species were reduced when BDHSH06 was added to the rearing water over the 85-day rearing period, and among these, approximately 57.1% were nonculturable. The results of this study demonstrated that BDHSH06 can be used as a biocontrol/probiotic agent in P. monodon culture. PMID:25107962

Li, Huanhuan; Chen, Cheng; Sun, Qiuping; Liu, Renliang; Cai, Junpeng

2014-10-15

277

Overcoming the anaerobic hurdle in phenotypic microarrays: Generation andvisualization of growth curve data for Desulfovibrio vulgaris Hildenborough  

SciTech Connect

Growing anaerobic microorganisms in phenotypic microarrays (PM) and 96-well microtiter plates is an emerging technology that allows high throughput survey of the growth and physiology and/or phenotype of cultivable microorganisms. For non-model bacteria, a method for phenotypic analysis is invaluable, not only to serve as a starting point for further evaluation, but also to provide a broad understanding of the physiology of an uncharacterized wild-type organism or the physiology/phenotype of a newly created mutant of that organism. Given recent advances in genetic characterization and targeted mutations to elucidate genetic networks and metabolic pathways, high-throughput methods for determining phenotypic differences are essential. Here we outline challenges presented in studying the physiology and phenotype of a sulfate reducing anaerobic delta proteobacterium, Desulfovibrio vulgaris Hildenborough. Modifications of the commercially available OmniLog(TM) system (Hayward, CA) for experimental setup, and configuration, as well as considerations in PM data analysis are presented. Also highlighted here is data viewing software that enables users to view and compare multiple PM data sets. The PM method promises to be a valuable strategy in our systems biology approach to D. vulgaris studies and is readily applicable to other anaerobic and aerobic bacteria.

Borglin, Sharon E; Joyner, Dominique; Jacobsen, Janet; Mukhopadhyay, Aindrila; Hazen, Terry C.

2008-10-04

278

Soil Bacterial Diversity Responses to Root Colonization by an Ectomycorrhizal Fungus are not Root-Growth-Dependent  

E-print Network

and fertilizer applications significantly improved the plant growth after 4-month culture in the disinfested soil. In the nondisinfested cultural substrate, these positive effects on plant growth were maintained. The total soil roots have an important influence on plant nutrition, growth promo- tion, and disease interactions

Thioulouse, Jean

279

Colloidal and dissolved organic matter in lake water: Carbohydrate and amino acid composition, and ability to support bacterial growth  

Microsoft Academic Search

Bacterial utilization of dissolved organic matter (DOM) was studied in water from a humic and a clearwater oligotrophic lake. Indigenous bacteria were inoculated into either 0.2 m natural filtered lake water, or lake water enriched fivefold with colloidal DOM >100 kD but below 0.2 m. Consumption of DOM was followed from changes in concentrations of total dissolved organic carbon (DOC),

Lars J. Tranvik; Niels O. G. Jrgensen

1995-01-01

280

Development and validation of a combined temperature, water activity, pH model for bacterial growth rate of Lactobacillus curvatus  

Microsoft Academic Search

A model was established to predict growth rate as a function of temperature, pH and water activity. The model is based on two, earlier developed models, one for growth rate as a function of temperature and water activity and the other for growth rate as a function of temperature and pH. Based on the assumption that combinatory effects between pH

T. Wijtzes; F. M. Rombouts; M. L. T. Kant-Muermans; K. van t Riet; M. H. Zwietering

2001-01-01

281

Expression of the bacterial type III effector DspA/E in Saccharomyces cerevisiae down-regulates the sphingolipid biosynthetic pathway leading to growth arrest.  

PubMed

Erwinia amylovora, the bacterium responsible for fire blight, relies on a type III secretion system and a single injected effector, DspA/E, to induce disease in host plants. DspA/E belongs to the widespread AvrE family of type III effectors that suppress plant defense responses and promote bacterial growth following infection. Ectopic expression of DspA/E in plant or in Saccharomyces cerevisiae is toxic, indicating that DspA/E likely targets a cellular process conserved between yeast and plant. To unravel the mode of action of DspA/E, we screened the Euroscarf S. cerevisiae library for mutants resistant to DspA/E-induced growth arrest. The most resistant mutants (?sur4, ?fen1, ?ipt1, ?skn1, ?csg1, ?csg2, ?orm1, and ?orm2) were impaired in the sphingolipid biosynthetic pathway. Exogenously supplied sphingolipid precursors such as the long chain bases (LCBs) phytosphingosine and dihydrosphingosine also suppressed the DspA/E-induced yeast growth defect. Expression of DspA/E in yeast down-regulated LCB biosynthesis and induced a rapid decrease in LCB levels, indicating that serine palmitoyltransferase (SPT), the first and rate-limiting enzyme of the sphingolipid biosynthetic pathway, was repressed. SPT down-regulation was mediated by dephosphorylation and activation of Orm proteins that negatively regulate SPT. A ?cdc55 mutation affecting Cdc55-PP2A protein phosphatase activity prevented Orm dephosphorylation and suppressed DspA/E-induced growth arrest. PMID:24828506

Siamer, Sabrina; Guillas, Isabelle; Shimobayashi, Mitsugu; Kunz, Caroline; Hall, Michael N; Barny, Marie-Anne

2014-06-27

282

A family of protein growth curves with extension to other chemical body components together with application to animal nutrition and improvement.  

PubMed

Theory that successfully explains the magnitude and range of estimates of protein retention (PR) efficiency from the cost of turnover of existing protein indicates that conventional curves for growth description are inappropriate for protein growth. A solution to this problem is found in the consideration that the rate-limiting steps for protein synthesis (PS) and breakdown are likely to be associated with the diffusion of metabolites in and between cells. The algebraic scaling of nuclear and cellular diffusion capacity with tissue or total body protein leads to a parameterization of the primal differential equation for PR (kg/day) based on two terms representing PS and breakdown, viz.where c is an arbitrary constant, Q is the proportion of nuclei active in cell growth or division in a tissue or the whole body, ? is the limit mass for protein (P, kg) in a tissue or the whole body, the power X + Z represents the rate-limiting steps in protein breakdown and Y is the power of the relationship between cell volume and the amount of tissue protein. For the whole body, the contribution of the different tissues should be weighted in proportion to their PS rates with, on average, Y = 1/2. The constant 4/9 arises from the scaling of the specific diffusion rate of DNA activator precursors from nuclear dimensions and from the relationship between nuclear and cell volume. Experimental evidence on protein breakdown rate as well as protein and body mass points of inflection indicates that the range of theoretically possible numerical values of the rate-limiting powers X + Z = (i + 3)/9 for i = 1, 2, ,12 seems adequate for the description of the range of observed whole body protein and body mass growth patterns for mammals. Q = 1 represents maximal protein retention, and for 0 < Q < 1, experimental evidence exists in support of a theoretical relationship between Q and food ingestion. The conclusion follows that some knowledge of the protein limit mass (?) and of the point of inflection (related to X + Z) is the main requirement for the application of the theory for description and prediction in animal nutrition and breeding. PMID:22445411

Roux, C Z

2011-03-01

283

Bradford Curves.  

ERIC Educational Resources Information Center

Discussion of informetric distributions shows that generalized Leimkuhler functions give proper fits to a large variety of Bradford curves, including those exhibiting a Groos droop or a rising tail. The Kolmogorov-Smirnov test is used to test goodness of fit, and least-square fits are compared with Egghe's method. (Contains 53 references.) (LRW)

Rousseau, Ronald

1994-01-01

284

Curved Knives  

Microsoft Academic Search

IT may interest your correspondent, Dr. Otis T. Mason, to know that the curved ``drawing-knife'' described by him has representatives in Western (British) India. The Kolis (fishing races) of the Bombay coast wore lately, and some still wear, knives made by local blacksmiths, of which the blade, 2 to 3 inches long, was shaped and edged like that of an

W. F. Sinclair

1897-01-01

285

Sources and composition of organic matter for bacterial growth in a large European river floodplain system (Danube, Austria).  

PubMed

Dissolved and particulate organic matter (DOM and POM) distribution, lignin phenol signatures, bulk elemental compositions, fluorescence indices and microbial plankton (algae, bacteria, viruses) in a temperate river floodplain system were monitored from January to November 2003. We aimed to elucidate the sources and compositions of allochthonous and autochthonous organic matter (OM) in the main channel and a representative backwater in relation to the hydrological regime. Additionally, bacterial secondary production was measured to evaluate the impact of organic carbon source on heterotrophic prokaryotic productivity. OM properties in the backwater tended to diverge from those in the main channel during phases without surface water connectivity; this was likely enhanced due to the exceptionally low river discharge in 2003. The terrestrial OM in this river floodplain system was largely derived from angiosperm leaves and grasses, as indicated by the lignin phenol composition. The lignin signatures exhibited significant seasonal changes, comparable to the seasonality of plankton-derived material. Microbially-derived material contributed significantly to POM and DOM, especially during periods of low discharge. High rates of bacterial secondary production (up to 135 ?g C L(-1) d(-1)) followed algal blooms and suggested that autochthonous OM significantly supported heterotrophic microbial productivity. PMID:21151814

Besemer, Katharina; Luef, Birgit; Preiner, Stefan; Eichberger, Birgit; Agis, Martin; Peduzzi, Peter

2009-03-01

286

Sources and composition of organic matter for bacterial growth in a large European river floodplain system (Danube, Austria)  

PubMed Central

Dissolved and particulate organic matter (DOM and POM) distribution, lignin phenol signatures, bulk elemental compositions, fluorescence indices and microbial plankton (algae, bacteria, viruses) in a temperate river floodplain system were monitored from January to November 2003. We aimed to elucidate the sources and compositions of allochthonous and autochthonous organic matter (OM) in the main channel and a representative backwater in relation to the hydrological regime. Additionally, bacterial secondary production was measured to evaluate the impact of organic carbon source on heterotrophic prokaryotic productivity. OM properties in the backwater tended to diverge from those in the main channel during phases without surface water connectivity; this was likely enhanced due to the exceptionally low river discharge in 2003. The terrestrial OM in this river floodplain system was largely derived from angiosperm leaves and grasses, as indicated by the lignin phenol composition. The lignin signatures exhibited significant seasonal changes, comparable to the seasonality of plankton-derived material. Microbially-derived material contributed significantly to POM and DOM, especially during periods of low discharge. High rates of bacterial secondary production (up to 135 ?g C L?1 d?1) followed algal blooms and suggested that autochthonous OM significantly supported heterotrophic microbial productivity. PMID:21151814

Besemer, Katharina; Luef, Birgit; Preiner, Stefan; Eichberger, Birgit; Agis, Martin; Peduzzi, Peter

2010-01-01

287

Bacterial Vaginosis  

MedlinePLUS

... vaginosis can increase your chance of getting an STD. What is bacterial vaginosis? Bacterial vaginosis (BV) is ... contributes to BV. BV is not considered an STD, but having BV can increase your chances of ...

288

Survey of naturally and conventionally cured commercial frankfurters, ham, and bacon for physio-chemical characteristics that affect bacterial growth.  

PubMed

Natural and organic food regulations preclude the use of sodium nitrite/nitrate and other antimicrobials for processed meat products. Consequently, processors have begun to use natural nitrate/nitrite sources, such as celery juice/powder, sea salt, and turbinado sugar, to manufacture natural and organic products with cured meat characteristics but without sodium nitrite. The objective of this study was to compare physio-chemical characteristics that affect Clostridium perfringens and Listeria monocytogenes growth in naturally cured and traditionally cured commercial frankfurters, hams, and bacon. Correlations of specific product characteristics to pathogen growth varied between products and pathogens, though water activity, salt concentration, and product composition (moisture, protein and fat) were common intrinsic factors correlated to pathogen growth across products. Other frequently correlated traits were related to curing reactions such as % cured pigment. Residual nitrite and nitrate were significantly correlated to C. perfringens growth but only for the ham products. PMID:22857852

Sullivan, Gary A; Jackson-Davis, Armitra L; Schrader, Kohl D; Xi, Yuan; Kulchaiyawat, Charlwit; Sebranek, Joseph G; Dickson, James S

2012-12-01

289

40 CFR 798.5500 - Differential growth inhibition of repair proficient and repair deficient bacteria: Bacterial DNA...  

Code of Federal Regulations, 2012 CFR

...i) Tests performed on solid medium (diffusion tests). (ii) Tests performed in...of zones of growth inhibition in the diffusion test, it is most important that the... (e) Test performance (1) Diffusion assay (i) Disc diffusion...

2012-07-01

290

40 CFR 798.5500 - Differential growth inhibition of repair proficient and repair deficient bacteria: Bacterial DNA...  

...i) Tests performed on solid medium (diffusion tests). (ii) Tests performed in...of zones of growth inhibition in the diffusion test, it is most important that the... (e) Test performance (1) Diffusion assay (i) Disc diffusion...

2014-07-01

291

40 CFR 798.5500 - Differential growth inhibition of repair proficient and repair deficient bacteria: Bacterial DNA...  

Code of Federal Regulations, 2013 CFR

...i) Tests performed on solid medium (diffusion tests). (ii) Tests performed in...of zones of growth inhibition in the diffusion test, it is most important that the... (e) Test performance (1) Diffusion assay (i) Disc diffusion...

2013-07-01

292

Marine Heterotrophic Bacteria in Continuous Culture, the Bacterial Carbon Growth Efficiency, and Mineralization at Excess Substrate and Different Temperatures  

Microsoft Academic Search

To model the physiological potential of marine heterotrophic bacteria, their role in the food web, and in the biogeochemical\\u000a carbon cycle, we need to know their growth efficiency response within a matrix of different temperatures and degrees of organic\\u000a substrate limitation. In this work, we present one part of this matrix, the carbon growth efficiencies of marine bacteria\\u000a under different

Alejandrina Jimnez-Mercado; Ramn Cajal-Medrano; Helmut Maske

2007-01-01

293

Using multilevel growth curve modeling to examine emotional modulation of temporal summation of pain (TS-pain) and the nociceptive flexion reflex (TS-NFR).  

PubMed

Emotion can modulate pain and spinal nociception, and correlational data suggest that cognitive-emotional processes can facilitate wind-up-like phenomena (ie, temporal summation of pain). However, there have been no experimental studies that manipulated emotion to determine whether within-subject changes in emotion influence temporal summation of pain (TS-pain) and the nociceptive flexion reflex (TS-NFR, a physiological measure of spinal nociception). The present study presented a series of emotionally charged pictures (mutilation, neutral, erotic) during which electric stimuli at 2 Hz were delivered to the sural nerve to evoke TS-pain and TS-NFR. Participants (n=46 healthy; 32 female) were asked to rate their emotional reactions to pictures as a manipulation check. Pain outcomes were analyzed using statistically powerful multilevel growth curve models. Results indicated that emotional state was effectively manipulated. Further, emotion modulated the overall level of pain and NFR; pain and NFR were highest during mutilation and lowest during erotic pictures. Although pain and NFR both summated in response to the 2-Hz stimulation series, the magnitude of pain summation (TS-pain) and NFR summation (TS-NFR) was not modulated by picture-viewing. These results imply that, at least in healthy humans, within-subject changes in emotions do not promote central sensitization via amplification of temporal summation. However, future studies are needed to determine whether these findings generalize to clinical populations (eg, chronic pain). PMID:22920754

Rhudy, Jamie L; Martin, Satin L; Terry, Ellen L; Delventura, Jennifer L; Kerr, Kara L; Palit, Shreela

2012-11-01

294

Patterns and sources of adult personality development: growth curve analyses of the NEO PI-R scales in a longitudinal twin study.  

PubMed

The present study examined the patterns and sources of 10-year stability and change of adult personality assessed by the 5 domains and 30 facets of the Revised NEO Personality Inventory. Phenotypic and biometric analyses were performed on data from 126 identical and 61 fraternal twins from the Bielefeld Longitudinal Study of Adult Twins (BiLSAT). Consistent with previous research, LGM analyses revealed significant mean-level changes in domains and facets suggesting maturation of personality. There were also substantial individual differences in the change trajectories of both domain and facet scales. Correlations between age and trait changes were modest and there were no significant associations between change and gender. Biometric extensions of growth curve models showed that 10-year stability and change of personality were influenced by both genetic as well as environmental factors. Regarding the etiology of change, the analyses uncovered a more complex picture than originally stated, as findings suggest noticeable differences between traits with respect to the magnitude of genetic and environmental effects. PMID:19586245

Bleidorn, Wiebke; Kandler, Christian; Riemann, Rainer; Spinath, Frank M; Angleitner, Alois

2009-07-01

295

Bacterial conjunctivitis  

PubMed Central

Clinical question What is the best treatment for bacterial conjunctivitis? Results Topical antibiotics expedite recovery from bacterial conjunctivitis. The choice of antibiotic usually does not affect outcome. Implementation Recognition of key distinguishing features of bacterial conjunctivitis Pitfalls that can be recognized in the history and physical examinationChoice of antibioticWhen to refer for specialist treatment. PMID:21188158

Hutnik, Cindy; Mohammad-Shahi, Mohammad H

2010-01-01

296

Stimulated bacterial growth under elevated p?CO2: results from an off-shore mesocosm study.  

PubMed

Marine bacteria are the main consumers of freshly produced organic matter. Many enzymatic processes involved in the bacterial digestion of organic compounds were shown to be pH sensitive in previous studies. Due to the continuous rise in atmospheric CO2 concentration, seawater pH is presently decreasing at a rate unprecedented during the last 300 million years but the consequences for microbial physiology, organic matter cycling and marine biogeochemistry are still unresolved. We studied the effects of elevated seawater pCO2 on a natural plankton community during a large-scale mesocosm study in a Norwegian fjord. Nine Kiel Off-Shore Mesocosms for Future Ocean Simulations (KOSMOS) were adjusted to different pCO2 levels ranging initially from ca. 280 to 3000 atm and sampled every second day for 34 days. The first phytoplankton bloom developed around day 5. On day 14, inorganic nutrients were added to the enclosed, nutrient-poor waters to stimulate a second phytoplankton bloom, which occurred around day 20. Our results indicate that marine bacteria benefit directly and indirectly from decreasing seawater pH. During the first phytoplankton bloom, 5-10% more transparent exopolymer particles were formed in the high pCO2 mesocosms. Simultaneously, the efficiency of the protein-degrading enzyme leucine aminopeptidase increased with decreasing pH resulting in up to three times higher values in the highest pCO2/lowest pH mesocosm compared to the controls. In general, total and cell-specific aminopeptidase activities were elevated under low pH conditions. The combination of enhanced enzymatic hydrolysis of organic matter and increased availability of gel particles as substrate supported up to 28% higher bacterial abundance in the high pCO2 treatments. We conclude that ocean acidification has the potential to stimulate the bacterial community and facilitate the microbial recycling of freshly produced organic matter, thus strengthening the role of the microbial loop in the surface ocean. PMID:24941307

Endres, Sonja; Galgani, Luisa; Riebesell, Ulf; Schulz, Kai-Georg; Engel, Anja

2014-01-01

297

The metabolism of neonicotinoid insecticide thiamethoxam by soil enrichment cultures, and the bacterial diversity and plant growth-promoting properties of the cultured isolates.  

PubMed

A soil enrichment culture (SEC) rapidly degraded 96% of 200 mg L(-1) neonicotinoid insecticide thiamethoxam (TMX) in MSM broth within 30 d; therefore, its metabolic pathway of TMX, bacterial diversity and plant growth-promoting rhizobacteria (PGPR) activities of the cultured isolates were studied. The SEC transformed TMX via the nitro reduction pathway to form nitrso, urea metabolites and via cleavage of the oxadiazine cycle to form a new metabolite, hydroxyl CLO-tri. In addition, 16S rRNA gene-denaturing gradient gel electrophoresis analysis revealed that uncultured rhizobacteria are predominant in the SEC broth and that 77.8% of the identified bacteria belonged to uncultured bacteria. A total of 31 cultured bacterial strains including six genera (Achromobacter, Agromyces, Ensifer, Mesorhizobium, Microbacterium and Pseudoxanthomonas) were isolated from the SEC broth. The 12 strains of Ensifer adhaerens have the ability to degrade TMX. All six selected bacteria showed PGPR activities. E. adhaerens TMX-23 and Agromyces mediolanus TMX-25 produced indole-3-acetic acid, whereas E. adhaerens TMX-23 and Mesorhizobium alhagi TMX-36 are N2-fixing bacteria. The six-isolated microbes were tolerant to 200 mg L(-1) TMX, and the growth of E. adhaerens was significantly enhanced by TMX, whereas that of Achromobacter sp. TMX-5 and Microbacterium sp.TMX-6 were enhanced slightly. The present study will help to explain the fate of TMX in the environment and its microbial degradation mechanism, as well as to facilitate future investigations of the mechanism through which TMX enhances plant vigor. PMID:24762175

Zhou, Guang-Can; Wang, Ying; Ma, Yuan; Zhai, Shan; Zhou, Ling-Yan; Dai, Yi-Jun; Yuan, Sheng

2014-06-01

298

Fungal biodegradation of dibutyl phthalate and toxicity of its breakdown products on the basis of fungal and bacterial growth.  

PubMed

Phthalates are esters of phthalic acid that give flexibility to polyvinyl chloride. Diverse studies have reported that these compounds might be carcinogenic, mutagenic and/or teratogenic. Radial growth rate, biomass, hyphal thickness of Neurospora sitophyla, Trichoderma harzianum and Aspergillus niger, grown in two different concentrations of dibutyl phthalate (DBP) (500 and 1,000mg/l) in agar and in submerged fermentation were studied. The inhibitory concentration (IC50) and the constant of biodegradation of dibutyl phthalate in Escherichia coli cultures were used to evaluate toxicity. The radial growth rate and thickness of the hypha were positively correlated with the concentration of phthalate. The pH of the cultures decreased as the fermentation proceeded. It is shown that these fungi are able to degrade DBP to non-toxic compounds and that these can be used as sole carbon and energy sources by this bacterium. It is demonstrated that the biodegradation of the DBP is directly correlated with the IC50. This is the first study that reports a method to determine the biodegradation of DBP on the basis of the IC50 and fungal growth, and the effect of this phthalate on the growth and thickness of hyphae of filamentous fungi in agar and in submerged fermentation. PMID:25063688

Ahuactzin-Prez, M; Torres, J L; Rodrguez-Pastrana, B R; Soriano-Santos, J; Daz-Godnez, G; Daz, R; Tlecuitl-Beristain, S; Snchez, C

2014-11-01

299

Journal of Theoretical Biology 244 (2007) 326348 Bacterial gene regulation in diauxic and non-diauxic growth  

E-print Network

exponential growth phase because the synthesis of the peripheral enzymes for lactose is somehow abolished in the presence of glucose. These enzymes include lactose permease (which catalyses the transport of lactose into the cell), b-galactosidase (which hydrolyses the intracellular lactose into products that feed

Pilyugin, Sergei S.

300

SUBVERSION OF HOST DEFENSE MECHANISMS BY MALIGNANT TUMORS: AN ESTABLISHED TUMOR AS A PRIVILEGED SITE FOR BACTERIAL GROWTH  

Microsoft Academic Search

There is ample evidence to support the proposal that most, if not all, tumors possess tumor-specific antigens and are immunogenic to varying degrees. This proposal rests on two main lines of evidence. First, that a state of specific immunity to growth of a tumor cell challenge can be generated in a host pre-exposed to various immunizing regimens with tumor cells

GEORGE L. SPITALNY; ROBERT J. NORTH

301

The Francisella pathogenicity island protein IglA localizes to the bacterial cytoplasm and is needed for intracellular growth  

PubMed Central

Background Francisella tularensis is a gram negative, facultative intracellular bacterium that is the etiological agent of tularemia. F. novicida is closely related to F. tularensis but has low virulence for humans while being highly virulent in mice. IglA is a 21 kDa protein encoded by a gene that is part of an iglABCD operon located on the Francisella pathogenicity island (FPI). Results Bioinformatics analysis of the FPI suggests that IglA and IglB are components of a newly described type VI secretion system. In this study, we showed that IglA regulation is controlled by the global regulators MglA and MglB. During intracellular growth IglA production reaches a maximum at about 10 hours post infection. Biochemical fractionation showed that IglA is a soluble cytoplasmic protein and immunoprecipitation experiments demonstrate that it interacts with the downstream-encoded IglB. When the iglB gene was disrupted IglA could not be detected in cell extracts of F. novicida, although IglC could be detected. We further demonstrated that IglA is needed for intracellular growth of F. novicida. A non-polar iglA deletion mutant was defective for growth in mouse macrophage-like cells, and in cis complementation largely restored the wild type macrophage growth phenotype. Conclusion The results of this study demonstrate that IglA and IglB are interacting cytoplasmic proteins that are required for intramacrophage growth. The significance of the interaction may be to secrete effector molecules that affect host cell processes. PMID:17233889

de Bruin, Olle M; Ludu, Jagjit S; Nano, Francis E

2007-01-01

302

Bacterial Inhibition by Electrical Stimulation  

PubMed Central

Significance: Much evidence shows that electrical stimulation (ES) promotes the wound healing process. The inhibitory effect of ES on bacterial growth has been proposed as a mechanism to explain the useful effects of ES on wound healing. Bacterial burden has been associated with chronic wounds. The extensive use of antibiotics can lead to the spread of multiple drug resistant bacteria. Whether biophysical energies, such as ES, can be used as a treatment modality against pathogenic microorganisms remains an open question. Recent Advances: The research literature provides evidence for useful effects of ES in terms of inhibition of bacterial growth. The type of ES, its polarity, and the intensity of the current play a major role in establishment of antibacterial effects. Both direct current (DC) and high voltage pulse current are more effective at inhibiting bacterial growth than are other types of ES. The exact mechanism underlying the antibacterial effects of ES is not clear. Critical Issues: Available evidence indicates that microampere DC (?ADC) is better than other ES types for inhibition of bacterial growth. The results of most studies also support the application of cathodal current for bacterial growth inhibition. The current intensity of ES would appear to be tolerable by humans if used clinically for treatment of infected wounds. Future Directions: The cathodal ?ADC appears to be more effective for inhibition of microorganism growth. Further research, especially in vivo, is necessary to clarify the inhibitory effects of ES on wound bacterial infections. PMID:24761349

Asadi, Mohammad Reza; Torkaman, Giti

2014-01-01

303

Reduction of Bacterial Speck ( Pseudomonas syringae pv. tomato ) of Tomato by Combined Treatments of Plant Growth-promoting Bacterium, Azospirillum brasilense , Streptomycin Sulfate, and Chemo-thermal Seed Treatment  

Microsoft Academic Search

Inoculation of tomato seeds with the plant growth-promoting bacterium Azospirillum brasilense, or spraying tomato foliage with A. brasilense, streptomycin sulfate, or commercial copper bactericides, separately, before or after inoculation with Pseudomonas syringae pv. tomato, the casual agent of bacterial speck of tomato, had no lasting effect on disease severity or on plant height and dry weight. Seed inoculation with A.

Yoav Bashan; Luz E. de-Bashan

2002-01-01

304

Changes in teachers' involvement versus rejection and links with academic motivation during the first year of secondary education: a multilevel growth curve analysis.  

PubMed

Research consistently shows that the learning environment plays an important role for early adolescents' learning and outcomes and suggests that good teacher-student relationships can serve as a protective factor for maintaining young adolescents' interest and active engagement in learning. However, less is known about the dynamic nature of teacher-student relationships and how they link with academic motivation development. Furthermore, little is known about the nature and the effects of teacher-student relationships in a cross-national context. The present study investigated changes in two components of teacher-student relationships (teachers' involvement vs. rejection) and examined links with students' academic motivation during the first grade of secondary school. Ten Dutch and ten Indonesian teachers (65% female) from 24 classes were videoed 12 times across the school year, and four videos for each class were selected randomly and coded on teachers' involvement versus rejection. A total of 713 students (52% girls) completed four-wave measures of their academic motivation after each video observation. Multilevel growth curve modeling revealed that the teacher's involvement changed in a curvilinear way and decreased across the first year of secondary education, while changes in the teacher's rejection did not follow a linear time function. Academic motivation changed in an undesirable way: controlled motivation increased, while autonomous motivation decreased over time. Teachers' involvement had a unique contribution in preventing high levels of controlled motivation in both countries. Findings suggest that teacher-student relationships (teachers' involvement) play an essential role in early adolescents' motivation regardless of the nations and should be a priority for schools. PMID:23381778

Maulana, Ridwan; Opdenakker, Marie-Christine; Stroet, Kim; Bosker, Roel

2013-09-01

305

Predictive Equations to Assess the Effect of Lactic Acid and Temperature on Bacterial Growth in a Model Meat System  

Microsoft Academic Search

Meat microflora is mainly composed of Acinetobacter, Moraxella, Brochothrix termosphacta, Lactobacillus, Pseudomonas and Enterobacteriaceae family genera, such as Klebsiella sp. and E. coli. In natural conditions meat pH can range from about 6.0 (being close to the optimum level for most pathogenic and alteration-causing\\u000a bacteria) to values close to 5.5, at which microbial growth rate decreases significantly. Combining low pH

F. Coll Crdenas; L. Giannuzzi; N. E. Zaritzky

306

Direct exchange of vitamin B12 is demonstrated by modelling the growth dynamics of algal-bacterial cocultures.  

PubMed

The growth dynamics of populations of interacting species in the aquatic environment is of great importance, both for understanding natural ecosystems and in efforts to cultivate these organisms for industrial purposes. Here we consider a simple two-species system wherein the bacterium Mesorhizobium loti supplies vitamin B12 (cobalamin) to the freshwater green alga Lobomonas rostrata, which requires this organic micronutrient for growth. In return, the bacterium receives photosynthate from the alga. Mathematical models are developed that describe minimally the interdependence between the two organisms, and that fit the experimental observations of the consortium. These models enable us to distinguish between different mechanisms of nutrient exchange between the organisms, and provide strong evidence that, rather than undergoing simple lysis and release of nutrients into the medium, M. loti regulates the levels of cobalamin it produces, resulting in a true mutualism with L. rostrata. Over half of all microalgae are dependent on an exogenous source of cobalamin for growth, and this vitamin is synthesised only by bacteria; it is very likely that similar symbiotic interactions underpin algal productivity more generally. PMID:24522262

Grant, Matthew A A; Kazamia, Elena; Cicuta, Pietro; Smith, Alison G

2014-07-01

307

Comparative study of wild and transformed salt tolerant bacterial strains on Triticum aestivum growth under salt stress  

PubMed Central

Eleven salt tolerant bacteria isolated from different sources (soil, plants) and their transformed strains were used to study their influence on Triticum aestivum var. Inqlab-91 growth under salt (100 mM NaCl) stress. Salt stress caused reduction in germination (19.4%), seedling growth (46%) and fresh weight (39%) in non-inoculated plants. In general, both wild and transformed strains stimulated germination, seedling growth and fresh weight in salt free and salt stressed conditions. At 100 mM NaCl, Staphylococcus xylosus ST-1 caused 25% increments in seedling length over respective control. Soluble protein content significantly enhanced (49%) under salt stress as compared to salt free control. At 100 mM NaCl parental strain PT-5 resulted about 32% enhancement in protein content over respective control treatment. Salt stress induced the promotion of auxin content in seedlings. Overall, Bacillus subtilis HAa2 and transformed E. coli -SP-7-T, caused 33% and 30% increases in auxin content, respectively, were recorded under salt stress in comparison to control. PMID:24031574

Afrasayab, Shazia; Faisal, Muhammad; Hasnain, Shahida

2010-01-01

308

Bacterial Overgrowth  

Microsoft Academic Search

\\u000a The human gastrointestinal tract typically contains 300500 bacterial species. Most bacterial species are acquired during\\u000a the birth process and although some changes to the flora may occur during later stages of life, the composition of the intestinal\\u000a microflora remains relatively constant. Small bowel bacterial overgrowth (SBBO) is defined as an excessive increase in the\\u000a number of bacteria in the upper

Rosemary J. Young; Jon A. Vanderhoof

309

Diversity and characterization of culturable bacterial endophytes from Zea mays and their potential as plant growth-promoting agents in metal-degraded soils.  

PubMed

In this study, we evaluated the phylogenetic diversity of culturable bacterial endophytes of Zea mays plants growing in an agricultural soil contaminated with Zn and Cd. Endophytic bacterial counts were determined in roots and shoots, and isolates were grouped by random amplified polymorphic DNA and identified by 16S ribosomal RNA (rRNA) gene sequencing. Endophytes were further characterized for the production of plant growth-promoting (PGP) substances, such as NH3, siderophores, indol-3-acetic acid (IAA), hydrogen cyanide and extracellular enzymes, and for the capacity to solubilize phosphate. The endophytes producing higher amounts of IAA were screened for their tolerance to Zn and Cd and used as bioinoculants for maize seedlings grown in the Zn/Cd-contaminated soil. The counts of endophytes varied between plant tissues, being higher in roots (6.48 log10 g(-1) fresh weight) when compared to shoots (5.77 log10 g(-1) fresh weight). Phylogenetic analysis showed that endophytes belong to three major groups: ?-Proteobacteria (31%), ?-Proteobacteria (26%) and Actinobacteria (26%). Pseudomonas, Agrobacterium, Variovorax and Curtobacterium were among the most represented genera. Endophytes were well-adapted to high Zn/Cd concentrations (up to 300mg Cd l(-1) and 1,000mg Zn l(-1)) and showed ability to produce several PGP traits. Strains Ochrobactrum haematophilum ZR 3-5, Acidovorax oryzae ZS 1-7, Frigoribacterium faeni ZS 3-5 and Pantoea allii ZS 3-6 increased root elongation and biomass of maize seedlings grown in soil contaminated with Cd and Zn. The endophytes isolated in this study have potential to be used in bioremediation/phytoremediation strategies. PMID:25053283

Pereira, S I A; Castro, P M L

2014-12-01

310

Adaptive acid tolerance response of Vibrio parahaemolyticus as affected by acid adaptation conditions, growth phase, and bacterial strains.  

PubMed

Vibrio parahaemolyticus strain 690 was isolated from gastroenteritis patients. Its thermal and ethanol stress responses have been reported in our previous studies. In this study, we further investigated the effects of various acid adaptation conditions including pH (5.0-6.0) and time (30-90?min) on the acid tolerance in different growth phases of V. parahaemolyticus 690. Additionally, the adaptive acid tolerance among different V. parahaemolyticus strains was compared. Results indicated that the acid tolerance of V. parahaemolyticus 690 was significantly increased after acid adaptation at pH 5.5 and 6.0 for 30-90?min. Among the various acid adaptation conditions examined, V. parahaemolyticus 690 acid-adapted at pH 5.5 for 90?min exhibited the highest acid tolerance. The acid adaptation also influenced the acid tolerance of V. parahaemolyticus 690 in different growth phases with late-exponential phase demonstrating the greatest acid tolerance response (ATR) than other phases. Additionally, the results also showed that the induction of adaptive ATR varied with different strains of V. parahaemolyticus. An increase in acid tolerance of V. parahaemolyticus was observed after prior acid adaptation in five strains (556, 690, BCRC 13023, BCRC 13025, and BCRC 12864), but not in strains 405 and BCRC 12863. PMID:22827515

Chiang, Ming-Lun; Chou, Cheng-Chun; Chen, Hsi-Chia; Tseng, Yu-Ting; Chen, Ming-Ju

2012-08-01

311

Bacterial amyloids.  

PubMed

Many bacteria can assemble functional amyloid fibers on their cell surface. The majority of bacterial amyloids contribute to biofilm or other community behaviors where cells interact with a surface or with another cell. Bacterial amyloids, like all functional amyloids, share structural and biochemical properties with disease-associated eukaryotic amyloids. The general ability of amyloids to bind amyloid-specific dyes, such as Congo red, and their resistance to denaturation have provided useful tools for scoring and quantifying bacterial amyloid formation. Here, we present basic approaches to study bacterial amyloids by focusing on the well-studied curli amyloid fibers expressed by Enterobacteriaceae. These methods exploit the specific tinctorial and biophysical properties of amyloids. The methods described here are straightforward and can be easily applied by any modern molecular biology lab for the study of other bacterial amyloids. PMID:22528099

Zhou, Yizhou; Blanco, Luz P; Smith, Daniel R; Chapman, Matthew R

2012-01-01

312

High-pressure-temperature gradient instrument: use for determining the temperature and pressure limits of bacterial growth.  

PubMed Central

A pressurized temperature gradient instrument allowed a synoptic determination of the effects of temperature and pressure on the reproduction of bacteria. The instrument consisted of eight pressure vessels housed parallel to each other in an insulated aluminum block in which a linear temperature gradient was supported. For a given experiment, eight pressures between 1 and 1,100 bars were chosen; the linear temperature gradient was established over an interval within -20 to 100 degrees C. Pure cultures and natural populations were studied in liquid or solid medium either in short (ca. 2-cm) culture tubes or in long (76.2-cm) glass capillaries. In the case of a pure culture, experiments with the pressurized temperature gradient instrument determined values of temperature and pressure that bounded its growth. Feasibility experiments with mixed populations of bacteria from water samples from a shallow depth of the sea showed that the instrument may be useful in identifying the extent to which a natural population is adapted to the temperatures and pressures at the locale of origin of the sample. Additional conceived uses of the instrument included synoptic determinations of cell functions other than reproduction and of biochemical activities. Images PMID:6391378

Yayanos, A A; van Boxtel, R; Dietz, A S

1984-01-01

313

Physics of Bacterial Morphogenesis  

PubMed Central

Summary: Bacterial cells utilize three-dimensional (3D) protein assemblies to perform important cellular functions such as growth, division, chemoreception, and motility. These assemblies are composed of mechanoproteins that can mechanically deform and exert force. Sometimes, small-nucleotide hydrolysis is coupled to mechanical deformations. In this review, we describe the general principle for an understanding of the coupling of mechanics with chemistry in mechanochemical systems. We apply this principle to understand bacterial cell shape and morphogenesis and how mechanical forces can influence peptidoglycan cell wall growth. We review a model that can potentially reconcile the growth dynamics of the cell wall with the role of cytoskeletal proteins such as MreB and crescentin. We also review the application of mechanochemical principles to understand the assembly and constriction of the FtsZ ring. A number of potential mechanisms are proposed, and important questions are discussed. PMID:22126993

Sun, Sean X.; Jiang, Hongyuan

2011-01-01

314

Protective effect of Growth Hormone-Releasing Hormone agonist in bacterial toxin-induced pulmonary barrier dysfunction  

PubMed Central

Rationale: Antibiotic treatment of patients infected with G? or G+ bacteria promotes release of the toxins lipopolysaccharide (LPS) and pneumolysin (PLY) in their lungs. Growth Hormone-releasing Hormone (GHRH) agonist JI-34 protects human lung microvascular endothelial cells (HL-MVEC), expressing splice variant 1 (SV-1) of the receptor, from PLY-induced barrier dysfunction. We investigated whether JI-34 also blunts LPS-induced hyperpermeability. Since GHRH receptor (GHRH-R) signaling can potentially stimulate both cAMP-dependent barrier-protective pathways as well as barrier-disruptive protein kinase C pathways, we studied their interaction in GHRH agonist-treated HL-MVEC, in the presence of PLY, by means of siRNA-mediated protein kinase A (PKA) depletion. Methods: Barrier function measurements were done in HL-MVEC monolayers using Electrical Cell substrate Impedance Sensing (ECIS) and VE-cadherin expression by Western blotting. Capillary leak was assessed by Evans Blue dye (EBD) incorporation. Cytokine generation in broncho-alveolar lavage fluid (BALF) was measured by multiplex analysis. PKA and PKC-? activity were assessed by Western blotting. Results: GHRH agonist JI-34 significantly blunts LPS-induced barrier dysfunction, at least in part by preserving VE-cadherin expression, while not affecting inflammation. In addition to activating PKA, GHRH agonist also increases PKC-? activity in PLY-treated HL-MVEC. Treatment with PLY significantly decreases resistance in control siRNA-treated HL-MVEC, but does so even more in PKA-depleted monolayers. Pretreatment with GHRH agonist blunts PLY-induced permeability in control siRNA-treated HL-MVEC, but fails to improve barrier function in PKA-depleted PLY-treated monolayers. Conclusions: GHRH signaling in HL-MVEC protects from both LPS and PLY-mediated endothelial barrier dysfunction and concurrently induces a barrier-protective PKA-mediated and a barrier-disruptive PKC-?-induced pathway in the presence of PLY, the former of which dominates the latter. PMID:25076911

Czikora, Istvan; Sridhar, Supriya; Gorshkov, Boris; Alieva, Irina B.; Kasa, Anita; Gonzales, Joyce; Potapenko, Olena; Umapathy, Nagavedi S.; Pillich, Helena; Rick, Ferenc G.; Block, Norman L.; Verin, Alexander D.; Chakraborty, Trinad; Matthay, Michael A.; Schally, Andrew V.; Lucas, Rudolf

2014-01-01

315

Bacterial Vaginosis  

MedlinePLUS

... Field Search Button Advanced Search NIAID Home Health & Research Topics Labs & Scientific Resources Funding About NIAID News & Events NIAID > Health & Research Topics > Bacterial Vaginosis Skip Website Tools Website Tools Print ...

316

Curves and Their Properties.  

ERIC Educational Resources Information Center

This volume, a reprinting of a classic first published in 1952, presents detailed discussions of 26 curves or families of curves, and 17 analytic systems of curves. For each curve the author provides a historical note, a sketch or sketches, a description of the curve, a discussion of pertinent facts, and a bibliography. Depending upon the curve,

Yates, Robert C.

317

Silver nanoparticles synthesized by pulsed laser ablation: as a potent antibacterial agent for human enteropathogenic gram-positive and gram-negative bacterial strains.  

PubMed

Present investigation deals with the study, to quantify the antibacterial property of silver nanoparticles (SNPs), synthesized by pulsed laser ablation (PLA) in aqueous media, on some human enteropathogenic gram-positive and gram-negative bacterial strains. Antibacterial property was studied by measuring the zone of inhibition using agar cup double-diffusion method, minimum inhibitory concentration by serial dilution method, and growth curve for 24h. The results clearly show the potency of antibacterial property of PLA-synthesized SNPs and suggest that it can be used as an effective growth inhibitor against various pathogenic bacterial strains in various medical devices and antibacterial control systems. PMID:24801405

Pandey, Jitendra Kumar; Swarnkar, R K; Soumya, K K; Dwivedi, Priyanka; Singh, Manish Kumar; Sundaram, Shanthy; Gopal, R

2014-10-01

318

Quotient curves of the GK curve  

E-print Network

For every $q=l^3$ with $l$ a prime power greater than 2, the GK curve $X$ is an $F_{q^2}$-maximal curve that is not $F_{q^2}$-covered by any $F_{q^2}$-maximal Deligne-Lusztig curve. Interestingly, $X$ has a very large $F_{q^2}$-automorphism group with respect to its genus. In this paper we compute the genera of a large variety of curves that are Galois-covered by the GK curve, thus providing several new values in the spectrum of genera of $F_{q^2}$-maximal curves.

Giulietti, Stefania Fanali; Massimo

2009-01-01

319

Do maggots have an influence on bacterial growth? A study on the susceptibility of strains of six different bacterial species to maggots of Lucilia sericata and their excretions\\/secretions  

Microsoft Academic Search

PurposeThe maggots of Lucilia sericata are successfully used as a treatment for infected wounds. Many articles are published about possible direct antibacterial properties of maggots and their excretions\\/secretions (ES), but with different results. The present study reinvestigates the susceptibility of six bacterial strains to maggots and their ES.

G. Cazander; K. E. B. van Veen; A. T. Bernards; G. N. Jukema

2009-01-01

320

Antibacterial Compounds of Canadian Honeys Target Bacterial Cell Wall Inducing Phenotype Changes, Growth Inhibition and Cell Lysis That Resemble Action of ?-Lactam Antibiotics  

PubMed Central

Honeys show a desirable broad spectrum activity against Gram-positive and negative bacteria making antibacterial activity an intrinsic property of honey and a desirable source for new drug development. The cellular targets and underlying mechanism of action of honey antibacterial compounds remain largely unknown. To facilitate the target discovery, we employed a method of phenotypic profiling by directly comparing morphological changes in Escherichia coli induced by honeys to that of ampicillin, the cell wall-active ?-lactam of known mechanism of action. Firstly, we demonstrated the purity of tested honeys from potential ?-lactam contaminations using quantitative LC-ESI-MS. Exposure of log-phase E. coli to honey or ampicillin resulted in time- and concentration-dependent changes in bacterial cell shape with the appearance of filamentous phenotypes at sub-inhibitory concentrations and spheroplasts at the MBC. Cell wall destruction by both agents, clearly visible on microscopic micrographs, was accompanied by increased permeability of the lipopolysaccharide outer membrane as indicated by fluorescence-activated cell sorting (FACS). More than 90% E. coli exposed to honey or ampicillin became permeable to propidium iodide. Consistently with the FACS results, both honey-treated and ampicillin-treated E. coli cells released lipopolysaccharide endotoxins at comparable levels, which were significantly higher than controls (p<0.0001). E. coli cells transformed with the ampicillin-resistance gene (?lactamase) remained sensitive to honey, displayed the same level of cytotoxicity, cell shape changes and endotoxin release as ampicillin-sensitive cells. As expected, ?lactamase protected the host cell from antibacterial action of ampicillin. Thus, both honey and ampicillin induced similar structural changes to the cell wall and LPS and that this ability underlies antibacterial activities of both agents. Since the cell wall is critical for cell growth and survival, honey active compounds would be highly applicable for therapeutic purposes while differences in the mode of action between honey and ampicillin may provide clinical advantage in eradicating ?-lactam-resistant pathogens. PMID:25191847

Brudzynski, Katrina; Sjaarda, Calvin

2014-01-01

321

Studying the Relationship between Children's Self-Control and Academic Achievement: An Application of Second-Order Growth Curve Model Analysis.  

ERIC Educational Resources Information Center

The functional relationships between developmental change in children's self-control and academic achievement were examined using longitudinal family data. Multivariate latent growth models (LGM) were specified to determine whether the rate of growth in academic achievement changes as a function of developmental change in self-control. Data came

Kim, Sooyeon; Murry, Velma McBride; Brody, Gene H.

322

Standard Mastery Curves and Skew Curves.  

ERIC Educational Resources Information Center

The objective of the study is to convince educational researchers of the necessity for "standard mastery curves" for the graphical representation of scores on summative tests for a group of students. Attention is drawn to the study of theoretical and empirical skew curves in education and biology. Use of standard mastery curves and study of skew

Warries, Egbert

323

Bacterial glycoproteomics.  

PubMed

Glycosylated proteins are ubiquitous components of eukaryote cellular surfaces, where the glycan moieties are implicated in a wide range of cell-cell recognition events. Once thought to be restricted to eukaryotes, glycosylation is now being increasingly reported in prokaryotes. Many of these discoveries have grown from advances in analytical technologies and genome sequencing. This review highlights the capabilities of high-sensitivity mass spectrometry for carbohydrate structure determination of bacterial glycoproteins and the emergence of glycoproteomic strategies that have evolved from proteomics and genomics for the functional analysis of bacterial glycosylation. PMID:16735721

Hitchen, Paul G; Dell, Anne

2006-06-01

324

Interactive aesthetic curve segments  

Microsoft Academic Search

To meet highly aesthetic requirements in in- dustrial design and styling, we propose a new category of aesthetic curve segments. To achieve these aesthetic requirements, we use curves whose logarithmic curvature histograms(LCH) are represented by straight lines. We call such curves aesthetic curves. We identify the overall shapes of aesthetic curves depending on the slope of LCH ?, by imposing

Norimasa Yoshida; Takafumi Saito

2006-01-01

325

Bacterial Mining  

Microsoft Academic Search

Bacterial mining (biomining) represents the use of microorganisms to leach out metals from ores or mine tailings (wastes), followed by the subsequent recovery of metals of interest from the leaching solution. This leaching of metals from ores is a natural process, which can be considerably accelerated by inducing and\\/or supporting the microbial activity of certain species with the ability to

I. G. Petrisor; I. Lazar; T. F. Yen

2007-01-01

326

Curves of constant width  

Microsoft Academic Search

Curves of constant width have the same breadth regardless of how they are rotated. Highly noncircular curves with this property may be constructed geometrically. Such curves make good rollers, manhole covers, and allow one to drill nearly square holes.

James A. Flaten

1999-01-01

327

Curves of constant width  

NASA Astrophysics Data System (ADS)

Curves of constant width have the same breadth regardless of how they are rotated. Highly noncircular curves with this property may be constructed geometrically. Such curves make good rollers, manhole covers, and allow one to drill nearly square holes.

Flaten, James A.

1999-10-01

328

Features of membrane receptors in bacterial multiplication process and necessary conditions for phage infection of bacteria.  

PubMed

According to the obtained experimental results, the thermal shock (from 37 to 53C) not only stops the multiplication process of Escherichia coli bacteria, but also causes bacterial titer to decrease gradually. After this period lasting up to 1hour, the bacterial cells continue to grow. A similar type of response was observed when bacteria were subjected to acid shock. Increasing acidity of media leads to decrease of bacterial growth process, and finally, their titer curve sharply falls over time. Also, interesting results were obtained about necessary conditions for infecting the bacteria by phages. Particularly, DNA injection from phages into bacterial cells requires most of corresponding bacterial membrane receptors to be occupied by phages. We suppose that this occurs due to autocrine phenomenon when the signaling molecules block the DNA ejection from phage particles. This effect lasts until a certain number of phage particles are attached to the membrane. After that, DNA injection from phage head into the cytoplasm takes place and the process of bacterial infection begins. The real number of phages in a stock is by several orders higher than the number of plaque-forming units in a given stock, which is determined by a classical double-layer agar method. PMID:25096899

Mdzinarashvili, Tamaz; Papukashvili, Irina; Shengelia, Nino; Khvedelidze, Mariam

2014-12-01

329

ORIGINAL ARTICLE Colorimetric / fluorescent bacterial sensing by agarose-  

E-print Network

interest owing to the recurring incidents of bacterial con- taminations in foods and water, the anthrax and fluorescence transformations in response to bacterial growth. The sensing constructs comprise glass

Jelinek, Raz

330

Parent and Child Personality Traits and Childrens Externalizing Problem Behavior From Age 4 to 9 Years: A Cohort Sequential Latent Growth Curve Analysis  

Microsoft Academic Search

Cohort-sequential latent growth modeling was used to analyze longitudinal data for childrens externalizing behavior from four overlapping age cohorts (4, 5, 6, and 7 years at first assessment) measured at three annual time points. The data included mother and father ratings on the Child Behavior Checklist and the Five- Factor Personality Inventory and teacher ratings on the Hierarchical Personality Inventory

P. Prinzie; Patrick Onghena; Walter Hellinckx

2005-01-01

331

A Latent Growth Curve Modeling Approach Using an Accelerated Longitudinal Design: The Ontogeny of Boys' and Girls' Talent Perceptions and Intrinsic Values through Adolescence  

ERIC Educational Resources Information Center

This article presents latent growth modeling, a particular application of multilevel modeling, to examine the development of adolescents' math- and English-related talent perceptions and intrinsic values which are emphasized by Expectancy-Value theory as important precursors to a range of achievement-related outcomes. The longitudinal

Watt, Helen M. G.

2008-01-01

332

Development of Morphological Awareness and Vocabulary Knowledge in Spanish-Speaking Language Minority Learners: A Parallel Process Latent Growth Curve Model  

ERIC Educational Resources Information Center

Despite acknowledgement of the limited English vocabularies demonstrated by many language minority (LM) learners, few studies have identified skills that relate to variation in vocabulary growth in this population. This study investigated the concurrent development of morphological awareness (i.e., students' understanding of complex words as

Kieffer, Michael J.; Lesaux, Nonie K.

2012-01-01

333

A Cohort-Sequential Multivariate Latent Growth Curve Analysis of Normative CBCL Aggressive and Delinquent Problem Behavior: Associations with Harsh Discipline and Gender  

ERIC Educational Resources Information Center

The aim of this study was to examine the normative developmental trajectories of aggressive and delinquent behavior in young children. Cohort-sequential univariate latent growth modeling (LGM) analyses were employed to conceptualize and analyze intraindividual changes in children's aggressive and delinquent behavior and interindividual differences

Prinzie, P.; Onghena, P.; Hellinckx, W.

2006-01-01

334

Parent and Child Personality Traits and Children's Externalizing Problem Behavior from Age 4 to 9 Years: A Cohort-Sequential Latent Growth Curve Analysis  

ERIC Educational Resources Information Center

Cohort-sequential latent growth modeling was used to analyze longitudinal data for children's externalizing behavior from four overlapping age cohorts (4, 5, 6, and 7 years at first assessment) measured at three annual time points. The data included mother and father ratings on the Child Behavior Checklist and the Five-Factor Personality Inventory

Prinzie, P.; Onghena, P.; Hellinckx, W.

2005-01-01

335

Is there an animal welfare Kuznets curve?  

Microsoft Academic Search

The concept of a Kuznets curve has been applied to income inequality and to the environment. The Kuznets curve takes an inverted U-shape, with income or GDP on the X-axis and environmental degradation or inequality on the Y-axis. It is hypothesized here that an animal welfare Kuznets curve may exist, with harm to animals initially rising with economic growth followed

Joshua Frank

2008-01-01

336

National Curve Bank  

NSDL National Science Digital Library

The National Curve Bank displays representations of two- and three-dimensional curves. Geometrical, algebraic, and historical aspects of curves are included. Educators and students have access to animations, interactions, java applets, Mathematica code, and more. Users may submit curves. Materials are reveiwed and selected by faculty at Cal State Los Angeles.

2009-03-01

337

Characterizations of Special Curves  

E-print Network

In this study, the new characterizations of special curves are investigated without using the curvatures of these special curves: general helices, slant helices, Bertrand curves, Mannheim curves. The curvatures are given by the help of the norms of the derivatives of Frenet vectors.

Yayli, Yusuf

2012-01-01

338

Modeling Microbial Growth  

NSDL National Science Digital Library

Is bacterial growth always exponential? Do bacteria with the fastest rate of growth always have the largest populations? Biota models offer extended opportunities to observe population growth over time. What are the factors that affect growth? Explore continuous, chaotic, and cyclic growth models. * examine the dynamics of growth for populations of virtual bacteria with differing growth rates and carrying capacities

Ethel D. Stanley (Beloit College;Biology)

2006-05-20

339

Understanding curved detonation waves  

SciTech Connect

A wave curve is the set of final states to which an initial state may be connected by a traveling wave. In gas dynamics, for example, the wave curve consists of the shock Hugoniot curve for compressive waves and the rarefaction curve for expansive waves. In this paper, we discuss the wave curve for an undriven planar detonation and for general planar detonations. We then extend the wave curve concept to detonations in converging and diverging geometry. We also discuss the application of these wave curves to the numerical computation of detonation problems.

Bukiet, B.G. [New Jersey Inst. of Tech., Newark, NJ (United States). Dept. of Mathematics; Menikoff, R. [Los Alamos National Lab., NM (United States)

1992-10-01

340

Understanding curved detonation waves  

SciTech Connect

A wave curve is the set of final states to which an initial state may be connected by a traveling wave. In gas dynamics, for example, the wave curve consists of the shock Hugoniot curve for compressive waves and the rarefaction curve for expansive waves. In this paper, we discuss the wave curve for an undriven planar detonation and for general planar detonations. We then extend the wave curve concept to detonations in converging and diverging geometry. We also discuss the application of these wave curves to the numerical computation of detonation problems.

Bukiet, B.G. (New Jersey Inst. of Tech., Newark, NJ (United States). Dept. of Mathematics); Menikoff, R. (Los Alamos National Lab., NM (United States))

1992-01-01

341

A latent growth curve modeling approach using an accelerated longitudinal design: the ontogeny of boys' and girls' talent perceptions and intrinsic values through adolescence  

Microsoft Academic Search

This article presents latent growth modeling, a particular application of multilevel modeling, to examine the development of adolescents' math- and English-related talent perceptions and intrinsic values which are emphasized by Expectancy-Value theory as important precursors to a range of achievement-related outcomes. The longitudinal cohort-sequential study included participants in 3 overlapping cohorts, together spanning Grades 7 to 11 (N=1,323). In this

Helen M. G. Watt

2008-01-01

342

Equine platelets inhibit E. coli growth and can be activated by bacterial lipopolysaccharide and lipoteichoic acid although superoxide anion production does not occur and platelet activation is not associated with enhanced production by neutrophils.  

PubMed

Activated platelets can contribute to host defense through release of products with bactericidal actions such as antimicrobial peptides and reactive oxygen species (ROS), as well as by forming heterotypic aggregates with neutrophils and enhancing their antimicrobial properties. Whilst release of vasoactive mediators from equine platelets in response to stimuli including bacterial lipopolysaccharide (LPS) has been documented, neither ROS production, nor the effects of activated platelets on equine neutrophil ROS production, have been reported. This study first sought evidence that activated equine platelets inhibit bacterial growth. Platelet superoxide production in response to stimuli including Escherichia coli-derived LPS and lipoteichoic acid (LTA) from Staphylococcus aureus was then determined. The ability of LPS and LTA to up-regulate platelet P-selectin expression and induce platelet-neutrophil aggregate formation was investigated and the effect of co-incubating activated platelets with neutrophils on superoxide production measured. Growth of E. coli was inhibited in a time-dependent manner, and to a similar extent, by addition of platelet rich plasma (PRP) or platelet poor plasma (PPP) obtained by centrifugation of PRP. Activation of platelets in PRP by addition of thrombin led to a significant increase in the inhibitory action between 0.5 and 2h. Although phorbol myristate acetate (PMA) caused superoxide production by equine platelets in a protein kinase C-dependent manner, thrombin, platelet activating factor (PAF), LPS, LTA and formyl-methionyl-leucyl phenylalanine (FMLP) were without effect. LPS and LTA did induce platelet activation, measured as an increase in P-selectin expression (% positive cells: 173 (un-stimulated); 636 (1?g/ml LPS); 646 (1?g/ml LTA); n=5) but not platelet superoxide production or heterotypic aggregate formation. Co-incubation of activated platelets with neutrophils did not increase neutrophil superoxide production. This study has demonstrated for the first time that when activated, equine platelets, like those of other species, are capable of releasing ROS that could assist in bacterial killing. However, the findings suggest that neither superoxide production by platelets nor enhancement of production by neutrophils is likely to play a significant role. Nevertheless, as has been reported in man, equine PPP and PRP did inhibit E. coli growth in vitro, and addition of thrombin significantly increased the inhibitory effect of PRP. This suggests that products released from activated platelets could contribute to antimicrobial activity in the horse. The factors in equine plasma and released by activated platelets that are responsible for inhibiting bacterial growth have yet to be determined. PMID:23332730

Aktan, I; Dunkel, B; Cunningham, F M

2013-04-15

343

Standardized centile curves and reference intervals of serum insulin-like growth factor-I (IGF-I) levels in a normal Japanese population using the LMS method.  

PubMed

Measurements of insulin-like growth factor-I (IGF-I) are useful not only for diagnosis and management of patients with growth hormone (GH)-related disorders but also for assessing nutritional status. We reported population-based references of serum IGF-I in 1996. However, they did not properly reflect data in the transition period from puberty to maturity. The aim of the present study was to re-establish a set of normative data for IGF-I for the Japanese population. The study included 1,685 healthy Japanese subjects (845 males, 840 females) from 0 to 83 years old. Subjects suffering from diseases that could affect IGF-I levels were excluded. Obese or extremely thin adult subjects were also excluded. IGF-I concentrations were determined by commercially available immunoradiometric assays. The reference intervals were calculated using the LMS method. Median IGF-I levels reached 310 ng/mL in males at the age of 14 years and 349 ng/mL in females at the age of 13 years, falling to 124 ng/mL and 103 ng/mL, respectively, by the age of 70 years. The mean pretreatment IGF-1 SD scores in patients with severe GH deficiency (GHD) obtained from the database of the Foundation for Growth Science and from clinical studies for adult GHD were -2.11.6 and -4.92.5, respectively. The present study established age- and gender-specific normative IGF-I data for the Japanese population and showed the utility of these references for screening patients with severe GHD. PMID:22673406

Isojima, Tsuyoshi; Shimatsu, Akira; Yokoya, Susumu; Chihara, Kazuo; Tanaka, Toshiaki; Hizuka, Naomi; Teramoto, Akira; Tatsumi, Ke-ita; Tachibana, Katsuhiko; Katsumata, Noriyuki; Horikawa, Reiko

2012-09-30

344

Growth  

NSDL National Science Digital Library

Introduction to models of economic growth with a great deal of focus on the Solow Growth Model both its theory and testing it with data. Also contains a discussion of the effects of the Greenspan Put. From a macroeconomics course at the the Massachusetts Institute of Technology.

Technology, Massachusetts I.

345

Principal curves revisited  

Microsoft Academic Search

A principal curve (Hastie and Stuetzle, 1989) is a smooth curve passing through the middle of a distribution or data cloud, and is a generalization of linear principal components. We give an alternative definition of a principal curve, based on a mixture model. Estimation is carried out through an EM algorithm. Some comparisons are made to the Hastie-Stuetzle definition.

Robert Tibshirani

1992-01-01

346

Over-expression of bacterial gamma-glutamylcysteine synthetase (GSH1) in plastids affects photosynthesis, growth and sulphur metabolism in poplar (Populus tremula x Populus alba) dependent on the resulting gamma-glutamylcysteine and glutathione levels.  

PubMed

We compared three transgenic poplar lines over-expressing the bacterial gamma-glutamylcysteine synthetase (GSH1) targeted to plastids. Lines Lggs6 and Lggs12 have two copies, while line Lggs20 has three copies of the transgene. The three lines differ in their expression levels of the transgene and in the accumulation of gamma-glutamylcysteine (gamma-EC) and glutathione (GSH) in leaves, roots and phloem exudates. The lowest transgene expression level was observed in line Lggs6 which showed an increased growth, an enhanced rate of photosynthesis and a decreased excitation pressure (1-qP). The latter typically represents a lower reduction state of the plastoquinone pool, and thereby facilitates electron flow along the electron transport chain. Line Lggs12 showed the highest transgene expression level, highest gamma-EC accumulation in leaves and highest GSH enrichment in phloem exudates and roots. This line also exhibited a reduced growth, and after a prolonged growth of 4.5 months, symptoms of leaf injury. Decreased maximum quantum yield (F(v)/F(m)) indicated down-regulation of photosystem II reaction centre (PSII RC), which correlates with decreased PSII RC protein D1 (PsbA) and diminished light-harvesting complex (Lhcb1). Potential effects of changes in chloroplastic and cytosolic GSH contents on photosynthesis, growth and the whole-plant sulphur nutrition are discussed for each line. PMID:20199621

Herschbach, Cornelia; Rizzini, Luca; Mult, Susanne; Hartmann, Tanja; Busch, Florian; Peuke, Andreas D; Kopriva, Stanislav; Ensminger, Ingo

2010-07-01

347

[Regulatory functions of bacterial exometabolites].  

PubMed

This review deals with the issue of growth autoregulation and survival in bacterial cultures under starvation conditions. Based on our results and on published data, the conclusion has been drawn that low-molecular products of metabolism (carboxylic acids, amino acids, and other metabolites) perform regulatory functions. The same compounds also control the ecological relationship between microorganisms at the interspecific level, and affect their antagonistic activity. It is suggested that complexes of bacterial metabolites can be used for controlling the composition of various microbiocenosis, including those of humans. PMID:17025173

Vakhitov, T Ia; Petrov, L N

2006-01-01

348

Predicting Individual Bacterium Cell Growth Behavior from Population Information We explore the kinetics of bacterial cells to predict the dependency of growth and division rates on cell length and  

E-print Network

length and age. Our model is applied to the analysis of two bacterial populations, a wild-type strain of Bacillus subtilis, and a minicell-producing strain that carries the divID B1 mutation. The results show of cell age. 1 Introduction Bacteria only have a single, circular double-stranded DNA molecule, and hence

Watkins, Joseph C.

349

Breakpoint chlorination curves of greywater.  

PubMed

A study on chlorination of raw greywater with hypochlorite is reported in this paper. Samples were chlorinated in a variety of conditions, and residual chlorine (Cl2) was measured spectrophotometrically. For each sample, the chlorination curve (chlorine residuals versus chlorine dose) was obtained. Curves showed the typical hump-and-dip profile attributable to the formation and destruction of chloramines. It was observed that, after reactions with strong reductants and chloramines-forming compounds, the remaining organic matter exerted a certain demand of chlorine. The evolution of chlorination curves with addition of ammonia and dodecylbencene sulfonate sodium salt and with dilution of the greywater sample were studied. In addition, chlorination curves at several contact times have been obtained, resulting in slower chlorine decay in the hump zone than in the dip zone. In addition, the decay of coliforms in chlorinated samples was also investigated. It was found that, for a chlorination dosage corresponding to the maximum of the hump zone (average 8.9 mg Cl2/ L), samples were negative in coliforms after 10 to 30 minutes of contact time. After-growth was not observed within 3 days after chlorination. Implications in chlorination treatments of raw greywater can be derived from these results. PMID:17824528

March, J G; Gual, M

2007-08-01

350

Bacterial vaginosis.  

PubMed Central

Bacterial vaginosis (BV) is the most common of the vaginitides affecting women of reproductive age. It appears to be due to an alteration in the vaginal ecology by which Lactobacillus spp., the predominant organisms in the healthy vagina, are replaced by a mixed flora including Prevotella bivia, Prevotella disiens, Porphyromonas spp., Mobiluncus spp., and Peptostreptococcus spp. All of these organisms except Mobiluncus spp. are also members of the endogenous vaginal flora. While evidence from treatment trials does not support the notion that BV is sexually transmitted, recent studies have shown an increased risk associated with multiple sexual partners. It has also been suggested that the pathogenesis of BV may be similar to that of urinary tract infections, with the rectum serving as a reservoir for some BV-associated flora. The organisms associated with BV have also been recognized as agents of female upper genital tract infection, including pelvic inflammatory disease, and the syndrome BV has been associated with adverse outcome of pregnancy, including premature rupture of membranes, chorioamnionitis, and fetal loss; postpartum endometritis; cuff cellulitis; and urinary tract infections. The mechanisms by which the BV-associated flora causes the signs of BV are not well understood, but a role for H2O2-producing Lactobacillus spp. in protecting against colonization by catalase-negative anaerobic bacteria has been recognized. These and other aspects of BV are reviewed. PMID:1747864

Spiegel, C A

1991-01-01

351

Inhibitory effects on bacterial growth and beta-ketoacyl-ACP reductase by different species of maple leaf extracts and tannic acid.  

PubMed

It is important to develop new antibiotics aimed at novel targets. The investigation found that the leaf extracts from five maples (Acer platanoides, Acer campestre, Acer rubrum, Acer saccharum and Acer truncatum Bunge collected in Denmark, Canada and China) and their component tannic acid displayed antibacterial ability against 24 standard bacteria strains with the minimum inhibitory concentration of 0.3-8.0 mg/mL. Unlike the standard antibiotic levofloxacin (LFX), these samples inhibited Gram-positive bacteria more effectively than they inhibited Gram-negative bacteria. These samples effectively inhibited two antidrug bacterial strains. The results show that these samples inhibit bacteria by a different mechanism from LFX. These samples potently inhibited b-ketoacyl-ACP reductase (FabG), which is an important enzyme in bacterial fatty acid synthesis. Tannic acid showed the strongest inhibition on FabG with a half inhibition concentration of 0.78 microM (0.81 microg/mL). Furthermore, tannic acid and two maple leaf extracts showed time-dependent irreversible inhibition of FabG. These three samples also exhibited better inhibition on bacteria. It is suggested that FabG is the antibacteria target of maple leaf extracts and tannic acid, and both reversible and irreversible inhibitions of FabG are important for the antibacterial effect. PMID:19444866

Wu, Dan; Wu, Xiao-Dong; You, Xue-Fu; Ma, Xiao-Feng; Tian, Wei-Xi

2010-01-01

352

Sculpting the Bacterial Cell  

PubMed Central

Prokaryotes come in a wide variety of shapes, determined largely by natural selection, physical constraints, and patterns of cell growth and division. Because of their relative simplicity, bacterial cells are excellent models for how genes and proteins can directly determine morphology. Recent advances in cytological methods for bacteria have shown that distinct cytoskeletal filaments composed of actin and tubulin homologs are important for guiding growth patterns of the cell wall in bacteria, and that the glycan strands that constitute the wall are generally perpendicular to the direction of growth. This cytoskeleton-directed cell wall patterning is strikingly reminiscent of how plant cell wall growth is regulated by microtubules. In rod-shaped bacilli, helical cables of actin-like MreB protein stretch along the cell length and orchestrate elongation of the cell wall, whereas the tubulin-like FtsZ protein directs formation of the division septum and the resulting cell poles. The overlap and interplay between these two systems and the peptidoglycan-synthesizing enzymes they recruit are the major driving forces of cylindrical shapes. Round cocci, on the other hand, have lost their MreBcables and instead mustgrowmainly via their division septum, giving them their characteristic round or ovoid shapes. Other bacteria that lack MreB homologs or even cell walls usedistinct cytoskeletal systemsto maintain their distinct shapes. Here I review what is known about the mechanisms that determine the shape of prokaryotic cells. PMID:19906583

Margolin, William

2014-01-01

353

Virus Progeny of Murine Cytomegalovirus Bacterial Artificial Chromosome pSM3fr Show Reduced Growth in Salivary Glands due to a Fixed Mutation of MCK-2 ?  

PubMed Central

Murine cytomegalovirus (MCMV) Smith strain has been cloned as a bacterial artificial chromosome (BAC) named pSM3fr and used for analysis of virus gene functions in vitro and in vivo. When sequencing the complete BAC genome, we identified a frameshift mutation within the open reading frame (ORF) encoding MCMV chemokine homologue MCK-2. This mutation would result in a truncated MCK-2 protein. When mice were infected with pSM3fr-derived virus, we observed reduced virus production in salivary glands, which could be reverted by repair of the frameshift mutation. When looking for the source of the mutation, we consistently found that virus stocks of cell culture-passaged MCMV Smith strain are mixtures of viruses with or without the MCK-2 mutation. We conclude that the MCK-2 mutation in the pSM3fr BAC is the result of clonal selection during the BAC cloning procedure. PMID:21813614

Jordan, Stefan; Krause, Johannes; Prager, Adrian; Mitrovic, Maja; Jonjic, Stipan; Koszinowski, Ulrich H.; Adler, Barbara

2011-01-01

354

Growth  

NASA Astrophysics Data System (ADS)

This chapter is devoted to the growth of ZnO. It starts with various techniques to grow bulk samples and presents in some detail the growth of epitaxial layers by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and pulsed laser deposition (PLD). The last section is devoted to the growth of nanorods. Some properties of the resulting samples are also presented. If a comparison between GaN and ZnO is made, very often the huge variety of different growth techniques available to fabricate ZnO is said to be an advantage of this material system. Indeed, growth techniques range from low cost wet chemical growth at almost room temperature to high quality MOCVD growth at temperatures above 1, 000?C. In most cases, there is a very strong tendency of c-axis oriented growth, with a much higher growth rate in c-direction as compared to other crystal directions. This often leads to columnar structures, even at relatively low temperatures. However, it is, in general, not straight forward to fabricate smooth ZnO thin films with flat surfaces. Another advantage of a potential ZnO technology is said to be the possibility to grow thin films homoepitaxially on ZnO substrates. ZnO substrates are mostly fabricated by vapor phase transport (VPT) or hydrothermal growth. These techniques are enabling high volume manufacturing at reasonable cost, at least in principle. The availability of homoepitaxial substrates should be beneficial to the development of ZnO technology and devices and is in contrast to the situation of GaN. However, even though a number of companies are developing ZnO substrates, only recently good quality substrates have been demonstrated. However, these substrates are not yet widely available. Still, the situation concerning ZnO substrates seems to be far from low-cost, high-volume production. The fabrication of dense, single crystal thin films is, in general, surprisingly difficult, even when ZnO is grown on a ZnO substrate. However, molecular beam epitaxy (MBE) delivers high quality ZnMgO-ZnO quantum well structures. Other thin film techniques such as PLD or MOCVD are also widely used. The main problem at present is to consistently achieve reliable p-type doping. For this topic, see also Chap. 5. In the past years, there have been numerous publications on p-type doping of ZnO, as well as ZnO p-n junctions and light emitting diodes (LEDs). However, a lot of these reports are in one way or the other inconsistent or at least incomplete. It is quite clear from optical data that once a reliable hole injection can be achieved, high brightness ZnO LEDs should be possible. In contrast to that expectation, none of the LEDs reported so far shows efficient light emission, as would be expected from a reasonable quality ZnO-based LED. See also Chap. 13. As a matter of fact, there seems to be no generally accepted and reliable technique for p-type doping available at present. The reason for this is the unfavorable position of the band structure of ZnO relative to the vacuum level, with a very low lying valence band. See also Fig. 5.1. This makes the incorporation of electrically active acceptors difficult. Another difficulty is the huge defect density in ZnO. There are many indications that defects play a major role in transport and doping. In order to solve the doping problem, it is generally accepted that the quality of the ZnO material grown by the various techniques needs to be improved. Therefore, the optimization of ZnO epitaxy is thought to play a key role in the further development of this material system. Besides being used as an active material in optoelectronic devices, ZnO plays a major role as transparent contact material in thin film solar cells. Polycrystalline, heavily n-type doped ZnO is used for this, combining a high electrical conductivity with a good optical transparency. In this case, ZnO thin films are fabricated by large area growth techniques such as sputtering. For this and other applications, see also Chap. 13.

Waag, Andreas

355

The Curved Cube  

NSDL National Science Digital Library

Take a solid cube with rods attached at diagonally opposite vertices. Hold the rods horizontally and rapidly spin the cube. (See Figure 1.) You should see a curved outline formed by the spinning cube. The objective of this demos is to discover how the straight edges of the cube become curved. The demo is physically based, but can be simulated within various software packages.

Hill, David R.

2003-02-24

356

Anodic Polarization Curves Revisited  

ERIC Educational Resources Information Center

An experiment published in this "Journal" has been revisited and it is found that the curve pattern of the anodic polarization curve for iron repeats itself successively when the potential scan is repeated. It is surprising that this observation has not been reported previously in the literature because it immediately brings into

Liu, Yue; Drew, Michael G. B.; Liu, Ying; Liu, Lin

2013-01-01

357

Dynamics of bacterial gene regulation  

NASA Astrophysics Data System (ADS)

The phenomenon of diauxic growth is a classical problem of bacterial gene regulation. The most well studied example of this phenomenon is the glucose-lactose diauxie, which occurs because the expression of the lac operon is strongly repressed in the presence of glucose. This repression is often explained by appealing to molecular mechanisms such as cAMP activation and inducer exclusion. I will begin by analyzing data showing that these molecular mechanisms cannot explain the strong lac repression because they exert a relatively weak effect. I will then present a minimal model accounting only for enzyme induction and dilution, which yields strong repression despite the absence of catabolite repression and inducer exclusion. The model also explains the growth patterns observed in batch and continuous cultures of various bacterial strains and substrate mixtures. The talk will conclude with a discussion of the experimental evidence regarding positive feedback, the key component of the minimal model.

Narang, Atul

2009-03-01

358

Low-intensity electromagnetic irradiation of 70.6 and 73 GHz frequencies enhances the effects of disulfide bonds reducer on Escherichia coli growth and affects the bacterial surface oxidation-reduction state  

SciTech Connect

Highlights: {yields} Low intensity 70.6 and 73 GHz electromagnetic irradiation (EMI) strongly suppressed Escherichia coli growth at 73 GHz and pH 7.3. {yields} Reducer DL-dithiothreitol had bactericidal effect and disturbed the SH-groups number. {yields} EMI enhanced E. coli sensitivity toward dithiothreitol. {yields} EMI decreased the SH-groups number of membrane disturbed by ATP and N,N'-dicyclohexycarbodiimide. {yields} The changed membrane oxidation-reduction state could be the primary mechanisms in EMI effects. -- Abstract: Low-intensity electromagnetic irradiation (EMI) of 70.6 and 73 GHz frequencies (flux capacity - 0.06 mW cm{sup -2}) had bactericidal effects on Escherichia coli. This EMI (1 h) exposure suppressed the growth of E. coli K-12({lambda}). The pH value (6.0-8.0) did not significantly affect the growth. The lag-phase duration was prolonged, and the growth specific rate was inhibited, and these effects were more noticeable after 73 GHz irradiation. These effects were enhanced by the addition of DL-dithiothreitol (DTT), a strong reducer of disulfide bonds in surface membrane proteins, which in its turn also has bactericidal effect. Further, the number of accessible SH-groups in membrane vesicles was markedly decreased by EMI that was augmented by N,N'-dicyclohexycarbodiimide and DTT. These results indicate a change in the oxidation-reduction state of bacterial cell membrane proteins that could be the primary membranous mechanism in the bactericidal effects of low-intensity EMI of the 70.6 and 73 GHz frequencies.

Torgomyan, Heghine [Department of Biophysics of Biology Faculty, Yerevan State University, Yerevan 0025 (Armenia)] [Department of Biophysics of Biology Faculty, Yerevan State University, Yerevan 0025 (Armenia); Trchounian, Armen, E-mail: Trchounian@ysu.am [Department of Biophysics of Biology Faculty, Yerevan State University, Yerevan 0025 (Armenia)] [Department of Biophysics of Biology Faculty, Yerevan State University, Yerevan 0025 (Armenia)

2011-10-14

359

1-alkyl-(N,N-dimethylamino)pyridinium bromides: inhibitory effect on virulence factors of Candida albicans and on the growth of bacterial pathogens.  

PubMed

A homologous series of 1-alkyl-(N,N-dimethylamino)pyridinium bromides, termed compounds 1-11, was synthesized and studied for antibacterial and antifungal activity. Of these, compound 8, containing a ten-carbon alkyl chain, showed maximum inhibition against all the tested bacterial strains. The highest antibacterial activity using a disc diffusion method was recorded against Mycobacterium smegmatis [zone of inhibition (ZOI): 45.750.25 mm], followed by Escherichia coli, Proteus mirabilis, Vibrio cholerae, Staphylococcus aureus and Salmonella typhi. In addition to antibacterial activity, compounds 3-11 displayed good inhibitory action against the human opportunistic yeast pathogens Cryptococcus neoformans and various Candida spp. The maximum ZOI was observed against Cryptococcus neoformans (51.50.5 mm) using compound 8, with ZOIs of 23.50.5, 32.00.0, 27.750.25 and 41.50.5 mm against Candida albicans, Candida glabrata, Candida tropicalis and Candida krusei, respectively. Furthermore, compound 8 caused inhibition of the candidal yeast-hyphae transition at a concentration of 0.29 M and also inhibited the secretion of extracellular hydrolytic enzyme such as secreted aspartyl proteinase at subinhibitory concentrations. Compound 8 showed very little haemolytic activity at a concentration of 0.58 M (1.3150.75?%), with its highest haemolytic activity (47.8062.32?%) observed at a concentration of 2.9 M. PMID:23118472

Sundararaman, Muthuraman; Rajesh Kumar, Radhakrishnan; Venkatesan, Perumal; Ilangovan, Andivelu

2013-02-01

360

Regulation of Cell Growth during Serum Starvation and Bacterial Survival in Macrophages by the Bifunctional Enzyme SpoT in Helicobacter pylori  

Microsoft Academic Search

In Helicobacter pylori the stringent response is mediated solely by spoT. The spoT gene is known to encode (p)ppGpp synthetase activity and is required for H. pylori survival in the stationary phase. However, neither the hydrolase activity of the H. pylori SpoT protein nor the role of SpoT in the regulation of growth during serum starvation and intracellular survival of

Yan Ning Zhou; William G. Coleman; Z. Yang; Y. Yang; N. Hodgson; F. Chen; D. J. Jin

2008-01-01

361

Plastome-encoded bacterial ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) supports photosynthesis and growth in tobacco.  

PubMed

The efficiency with which crop plants use their resources of light, water, and fertilizer nitrogen could be enhanced by replacing their CO(2)-fixing enzyme, d-ribulose-1,5-bisphosphate carboxylase-oxygenase (RubisCO), with more efficient forms, such as those found in some algae, for example. This important challenge has been frustrated by failure of all previous attempts to substitute a fully functional, foreign RubisCO (efficient or inefficient) into higher plants. This failure could be caused by incompatibility between the plastid-encoded large subunits and the nucleus-encoded small subunits or by inability of the foreign RubisCO subunits to fold or assemble efficiently in the plastid. Mismatch between the regulatory requirements of the foreign RubisCO and conditions in the chloroplast also might render the substituted enzyme inactive but, previously, it has not been possible to test this. To answer the general question of whether a foreign RubisCO can support photosynthesis in a plant, we used plastid transformation to replace RubisCO in tobacco with the simple homodimeric form of the enzyme from the alpha-proteobacterium, Rhodospirillum rubrum, which has no small subunits and no special assembly requirements. The transplastomic plants so obtained are fully autotrophic and reproductive but require CO(2) supplementation, consistent with the kinetic properties of the bacterial RubisCO. This establishes that the activity of a RubisCO from a very different phylogeny can be integrated into chloroplast photosynthetic metabolism without prohibitive problems. PMID:11724961

Whitney, S M; Andrews, T J

2001-12-01

362

Terrestrial Exoplanet Light Curves  

E-print Network

The phase or orbital light curves of extrasolar terrestrial planets in reflected or emitted light will contain information about their atmospheres and surfaces complementary to data obtained by other techniques such as spectrosopy. We show calculated light curves at optical and thermal infrared wavelengths for a variety of Earth-like and Earth-unlike planets. We also show that large satellites of Earth-sized planets are detectable, but may cause aliasing effects if the lightcurve is insufficiently sampled.

Eric Gaidos; Nicholas Moskovitz; Darren M. Williams

2005-11-23

363

Macrophages inhibit human osteosarcoma cell growth after activation with the bacterial cell wall derivative liposomal muramyl tripeptide in combination with interferon-?  

PubMed Central

Background In osteosarcoma, the presence of tumor-infiltrating macrophages positively correlates with patient survival in contrast to the negative effect of tumor-associated macrophages in patients with other tumors. Liposome-encapsulated muramyl tripeptide (L-MTP-PE) has been introduced in the treatment of osteosarcoma patients, which may enhance the potential anti-tumor activity of macrophages. Direct anti-tumor activity of human macrophages against human osteosarcoma cells has not been described so far. Hence, we assessed osteosarcoma cell growth after co-culture with human macrophages. Methods Monocyte-derived M1-like and M2-like macrophages were polarized with LPS?+?IFN-?, L-MTP-PE +/? IFN-? or IL-10 and incubated with osteosarcoma cells. Two days later, viable tumor cell numbers were analyzed. Antibody-dependent effects were investigated using the therapeutic anti-EGFR antibody cetuximab. Results M1-like macrophages inhibited osteosarcoma cell growth when activated with LPS?+?IFN-?. Likewise, stimulation of M1-like macrophages with liposomal muramyl tripeptide (L-MTP-PE) inhibited tumor growth, but only when combined with IFN-?. Addition of the tumor-reactive anti-EGFR antibody cetuximab did not further improve the anti-tumor activity of activated M1-like macrophages. The inhibition was mediated by supernatants of activated M1-like macrophages, containing TNF-? and IL-1?. However, specific blockage of these cytokines, nitric oxide or reactive oxygen species did not inhibit the anti-tumor effect, suggesting the involvement of other soluble factors released upon macrophage activation. While LPS?+?IFN-?activated M2-like macrophages had low anti-tumor activity, IL-10polarized M2-like macrophages were able to reduce osteosarcoma cell growth in the presence of the anti-EGFR cetuximab involving antibody-dependent tumor cell phagocytosis. Conclusion This study demonstrates that human macrophages can be induced to exert direct anti-tumor activity against osteosarcoma cells. Our observation that the induction of macrophage anti-tumor activity by L-MTP-PE required IFN-? may be of relevance for the optimization of L-MTP-PE therapy in osteosarcoma patients. PMID:24612598

2014-01-01

364

Evolution of bacterial genomes  

Microsoft Academic Search

This review examines evolution of bacterial genomes with an emphasis on RNA based life, the transition to functional DNA and small evolving genomes (possibly plasmids) that led to larger, functional bacterial genomes.

J. T. Trevors

1997-01-01

365

Interfacial Properties and Iron Binding to Bacterial Proteins That Promote the Growth of Magnetite Nanocrystals: X-ray Reflectivity and Surface Spectroscopy Studies  

SciTech Connect

Surface sensitive X-ray scattering and spectroscopic studies have been conducted to determine structural properties of Mms6, the protein in Magnetospirillum magneticum AMB-1 that is implicated as promoter of magnetite nanocrystals growth. Surface pressure versus molecular area isotherms indicate Mms6 forms stable monolayers at the aqueous/vapor interface that are strongly affected by ionic conditions of the subphase. Analysis of X-ray reflectivity from the monolayers shows that the protein conformation at the interface depends on surface pressure and on the presence of ions in the solutions, in particular of iron ions and its complexes. X-ray fluorescence at grazing angles of incidence from the same monolayers allows quantitative determination of surface bound ions to the protein showing that ferric iron binds to Mms6 at higher densities compared to other ions such as Fe{sup 2+} or La{sup 3+} under similar buffer conditions.

Wang, Wenjie; Bu, Wei; Wang, Lijun; Palo, Pierre E.; Mallapragada, Surya; Nilsen-Hamilton, Marit; Vaknin, David (Iowa State)

2012-04-30

366

Bacterial responses to periodic micropillar array.  

PubMed

For a basic understanding and potential biomedical applications of surface topographical effects on bacterial responses, this study focuses on not only the bacterial retention but also the bacterial growth, proliferation, and viability that are significant post-retentive behaviors playing critical roles in infections of medical implants. Specifically, periodic micropillar arrays (SiPA ) with nine different feature sizes were fabricated on silicon substrates with photolithography and dry etching methods. The SiPA was cultured with Staphylococcus aureus or Escherichia coli for different periods to investigate the bacterial retention, growth and proliferation behavior on a patterned surface. The experimental results show that a significant reduction of bacterial retention, growth, and proliferation can be achieved when the pillar size is reduced to the submicrometer level. However, micropillars have no obvious influence on the viability of the bacteria within 24 h. On the basis of the bacterial experiment results, it is inferred that the topographical effects may have resulted from bacterial confinement by micropillars, either limiting the attachment area for individual bacterium or trapping a bacterium between pillars. Furthermore, the extended Derjaguin-Landau-Verwey-Overbeek theoretical analysis indicates the effects might have come from the topographic induced surface property changes, mainly hydrophobicity, which is represented by the changes in the interaction free energy of Lifshitz-van der Waals among different periodic micropillar arrays. This study could help to deepen the understanding about the surface topographical effects on bacterial responses and may provide a guidance for the future medical implant surface design to decrease the infection risk by avoiding the surface topography which could attract more bacteria. 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 384-396, 2015. PMID:24719359

Ge, Xiang; Leng, Yang; Lu, Xiong; Ren, Fuzeng; Wang, Kefeng; Ding, Yonghui; Yang, Meng

2015-01-01

367

Universality in Stochastic Exponential Growth  

NASA Astrophysics Data System (ADS)

Recent imaging data for single bacterial cells reveal that their mean sizes grow exponentially in time and that their size distributions collapse to a single curve when rescaled by their means. An analogous result holds for the division-time distributions. A model is needed to delineate the minimal requirements for these scaling behaviors. We formulate a microscopic theory of stochastic exponential growth as a Master Equation that accounts for these observations, in contrast to existing quantitative models of stochastic exponential growth (e.g., the Black-Scholes equation or geometric Brownian motion). Our model, the stochastic Hinshelwood cycle (SHC), is an autocatalytic reaction cycle in which each molecular species catalyzes the production of the next. By finding exact analytical solutions to the SHC and the corresponding first passage time problem, we uncover universal signatures of fluctuations in exponential growth and division. The model makes minimal assumptions, and we describe how more complex reaction networks can reduce to such a cycle. We thus expect similar scalings to be discovered in stochastic processes resulting in exponential growth that appear in diverse contexts such as cosmology, finance, technology, and population growth.

Iyer-Biswas, Srividya; Crooks, Gavin E.; Scherer, Norbert F.; Dinner, Aaron R.

2014-07-01

368

Universality in stochastic exponential growth.  

PubMed

Recent imaging data for single bacterial cells reveal that their mean sizes grow exponentially in time and that their size distributions collapse to a single curve when rescaled by their means. An analogous result holds for the division-time distributions. A model is needed to delineate the minimal requirements for these scaling behaviors. We formulate a microscopic theory of stochastic exponential growth as a Master Equation that accounts for these observations, in contrast to existing quantitative models of stochastic exponential growth (e.g., the Black-Scholes equation or geometric Brownian motion). Our model, the stochastic Hinshelwood cycle (SHC), is an autocatalytic reaction cycle in which each molecular species catalyzes the production of the next. By finding exact analytical solutions to the SHC and the corresponding first passage time problem, we uncover universal signatures of fluctuations in exponential growth and division. The model makes minimal assumptions, and we describe how more complex reaction networks can reduce to such a cycle. We thus expect similar scalings to be discovered in stochastic processes resulting in exponential growth that appear in diverse contexts such as cosmology, finance, technology, and population growth. PMID:25062238

Iyer-Biswas, Srividya; Crooks, Gavin E; Scherer, Norbert F; Dinner, Aaron R

2014-07-11

369

Universality in stochastic exponential growth  

E-print Network

Recent imaging data for single bacterial cells reveal that their mean sizes grow exponentially in time and that their size distributions collapse to a single curve when rescaled by their means. An analogous result holds for the division-time distributions. A model is needed to delineate the minimal requirements for these scaling behaviors. We formulate a microscopic theory of stochastic exponential growth as a Master Equation that accounts for these observations, in contrast to existing quantitative models of stochastic exponential growth (e.g., the Black-Scholes equation or geometric Brownian motion). Our model, the stochastic Hinshelwood cycle (SHC), is an autocatalytic reaction cycle in which each molecular species catalyzes the production of the next. By finding exact analytical solutions to the SHC and the corresponding first passage time problem, we uncover universal signatures of fluctuations in exponential growth and division. The model makes minimal assumptions, and we describe how more complex reaction networks can reduce to such a cycle. We thus expect similar scalings to be discovered in stochastic processes resulting in exponential growth that appear in diverse contexts such as cosmology, finance, technology, and population growth.

Srividya Iyer-Biswas; Gavin E. Crooks; Norbert F. Scherer; Aaron R. Dinner

2014-07-10

370

Dexamethasone modulates expression of genes involved in the innate immune system, growth and stress and increases susceptibility to bacterial disease in Senegalese sole (Solea senegalensis Kaup, 1858).  

PubMed

Cortisol, the main glucocorticoid in fish, undertakes pleiotropic biological effects in response to stressors to maintain homeostasis. It can exert several actions on the immune system, growth and cellular metabolism, establishing a fine-tune regulation stress response and cross-talk interactions with other regulatory pathways. In this study, we investigated a causal relationship between high levels of glucocorticoids and susceptibility to pathogens and modification of gene expression profiles in Senegalese sole. For this purpose, we carried out two experiments using post-metamorphic individuals (21 days after hatching) that were exposed to dexamethasone (DXM), a potent glucocorticoid, in order to mimic cortisol effects. We quantified transcript levels of a wide set of genes involved in innate immune system (g-type lysozyme and hepcidin (hamp1)), HPI axis (crf, crfbp, pomc?, pomc?, gr1 and gr2), HPT axis (tgb), cellular stress defense system (hsp70 and hsp90aa), GH/IGF axis (igf-I and igf-Ir) and the neuropeptide trh. Short-term exposure to 0.1, 1 and 10 ppm DXM provoked a reduction of pomc? transcripts and an increase of crfbp mRNAs in a dose-dependent manner at 48 and 72 h after treatment. Moreover, g-type lysozyme transcript levels decreased significantly at 72 h whereas hamp1 mRNA levels increased at 48 h after exposure. Long-term DXM treatment (10 ppm DXM) affected negatively weight of soles (~20% lower than controls). Moreover, reduced mRNA levels were observed for pomc? after 1 week and igf-I and hamp1 after 2 weeks. In contrast, crfbp and crf increased mRNA levels after 2 weeks. hsp70 exhibited a dual response increasing transcript levels at 1 week after treatment and reducing thereafter. No significant changes in gene expression were observed at any time during this study for tgb, trh, hsp90aa, pomc?, gr1 and gr2. Finally, a challenge experiment using the pathogen Photobacterium damselae subsp piscicida confirmed earlier and higher mortalities in DXM-treated animals. Taken together, these data indicate that a prolonged exposure to DXM increases the susceptibility to pathogens and reduces growth. Moreover, DXM can trigger a wide cellular response modulating the expression of genes involved in the innate immune system, HPI and GH/IGF axes as well as cellular stress defense. These results are highly valuable to evaluate responses associated to aquaculture stressful conditions and discriminate specific glucocorticoid-mediated effects. PMID:22326938

Salas-Leiton, E; Coste, O; Asensio, E; Infante, C; Caavate, J P; Manchado, M

2012-05-01

371

Exploring Area between Curves  

NSDL National Science Digital Library

Calculus texts have problems on finding the Areas between Curves in the chapters on applications of Integration. The NCB suggests finding some of these examples in a text and trying them in Harumi's graph. Experimenting on a computer with the approximation for finding the area using rectangles is fascinating. As the number of rectangles increases, the approximation improves. Therefore, mathematicians define the area A between the two curves as the limit of the sum of the areas of these approximating rectangles where n is the number of rectangles bounded between a and b.

Monroy, Harumi

2006-01-01

372

Bacterial cheating limits antibiotic resistance  

NASA Astrophysics Data System (ADS)

The widespread use of antibiotics has led to the evolution of resistance in bacteria. Bacteria can gain resistance to the antibiotic ampicillin by acquiring a plasmid carrying the gene beta-lactamase, which inactivates the antibiotic. This inactivation may represent a cooperative behavior, as the entire bacterial population benefits from removing the antibiotic. The cooperative nature of this growth suggests that a cheater strain---which does not contribute to breaking down the antibiotic---may be able to take advantage of cells cooperatively inactivating the antibiotic. Here we find experimentally that a ``sensitive'' bacterial strain lacking the plasmid conferring resistance can invade a population of resistant bacteria, even in antibiotic concentrations that should kill the sensitive strain. We observe stable coexistence between the two strains and find that a simple model successfully explains the behavior as a function of antibiotic concentration and cell density. We anticipate that our results will provide insight into the evolutionary origin of phenotypic diversity and cooperative behaviors.

Xiao Chao, Hui; Yurtsev, Eugene; Datta, Manoshi; Artemova, Tanya; Gore, Jeff

2012-02-01

373

Oxygen-Controlled Bacterial Growth in the Sponge Suberites domuncula: toward a Molecular Understanding of the Symbiotic Relationships between Sponge and Bacteria  

PubMed Central

Sponges (phylum Porifera), known to be the richest producers among the metazoans of bioactive secondary metabolites, are assumed to live in a symbiotic relationship with microorganisms, especially bacteria. Until now, the molecular basis of the mutual symbiosis, the exchange of metabolites for the benefit of the other partner, has not been understood. We show with the demosponge Suberites domuncula as a model that the sponge expresses under optimal aeration conditions the enzyme tyrosinase, which synthesizes diphenols from monophenolic compounds. The cDNA isolated was used as a probe to determine the steady-state level of gene expression. The gene expression level parallels the level of specific activity in sponge tissue, indicating that without aeration the tyrosinase level drops drastically; this effect is reversible. The SB2 bacterium isolated from the sponge surface grew well in M9 minimal salt medium supplemented with the dihydroxylated aromatic compound protocatechuate; this carbon source supported growth more than did glucose. From the SB2 bacterium the protocatechuate gene cluster was cloned and sequenced. This cluster comprises all genes coding for enzymes involved in the conversion of protocatechuate to acetyl coenzyme A. Expression is strongly induced if the bacteria are cultivated on M9-protocatechuate medium; the genes pcaQ (encoding the putative transcriptional activator of the pca operon) and pcaDC were used for quantitative PCR analyses. We conclude that metabolites, in this case diphenols, which might be produced by the sponge S. domuncula are utilized by the sponge surface-associated bacterium for energy generation. This rationale will help to further uncover the symbiotic pathways between sponges and their associated nonculturable microorganisms; our approach is flanked by the establishment of an EST (expressed sequence tags) database in our laboratory. PMID:15066829

Muller, Werner E. G.; Grebenjuk, Vladislav A.; Thakur, Narsinh L.; Thakur, Archana N.; Batel, Renato; Krasko, Anatoli; Muller, Isabel M.; Breter, Hans J.

2004-01-01

374

Graphing Polar Curves  

ERIC Educational Resources Information Center

Graphing polar curves typically involves a combination of three traditional techniques, all of which can be time-consuming and tedious. However, an alternative method--graphing the polar function on a rectangular plane--simplifies graphing, increases student understanding of the polar coordinate system, and reinforces graphing techniques learned

Lawes, Jonathan F.

2013-01-01

375

Atlas of fatigue curves  

Microsoft Academic Search

This Atlas was developed to serve engineers who are looking for fatigue data on a particular metal or alloy. Having these curves compiled in a single book will also facilitate the computerization of the involved data. It is pointed out that plans are under way to make the data in this book available in ASCII files for analysis by computer

1986-01-01

376

Characteristic Curves of PEMFC  

NSDL National Science Digital Library

This in-class exercise will allow students hands-on experience working with a proton exchange membrane fuel cell, or PEMFC. The class will examine the characteristic curve of one of these fuel cells and measure the voltage and current output of the cell. Step by step instructions are provided for the experiment. This document may be downloaded in PDF file format.

2012-07-11

377

Econophysics Master curve for  

E-print Network

-curve collapse of the price-impact function suggests that fluctuations from the supply- and-demand equilibrium this separately for buying and selling. The transactions are classified as being initiated by a buyer or seller is the liq- uidity and sign( ) is +1 or 1 for buying and selling, respectively. For all four years

378

Principal curve time warping  

Microsoft Academic Search

Time warping finds use in many fields of time series analysis, and it has been effectively implemented in many different application areas. Rather than focusing on a particular application area we approach the general problem definition, and employ principal curves, a powerful machine learning tool, to improve the noise robustness of existing time warping methods. The increasing noise level is

Umut Ozertem; Deniz Erdogmus

2009-01-01

379

Extinction curves in AGN  

E-print Network

The presence of the dust in the circumnuclear region strongly affects our view of the nucleus itself. The effect is strong in type 2 objects but weaker effect is likely to be present in type 1 objects as well. In these objects a correction to the observed optical/UV spectrum must be done in order to recover the intrinsic spectrum of a nucleus. The approach based on the extinction curve is convenient for that purpose so significant effort has been recently done in order to determine the extinction curve for the circumnuclear material. It seems clear that the circumnuclear dust is different from the average properties of the dust in the Interstellar Medium in our galaxy: the well known 2175 A feature is weak or absent in AGN nuclear dust, and the extinction curve at shorter wavelength does not seem to be rising as steeply. The circumnuclear dust is therefore more similar to SMC dust, or more likely, to the dust in very dense molecular clouds in our Galaxy. However, the exact shape of the extinction curve in the far UV is still a matter of debate, and various effects are difficult to disentangle.

B. Czerny

2006-12-16

380

Crystallization dynamics on curved surfaces.  

PubMed

We study the evolution from a liquid to a crystal phase in two-dimensional curved space. At early times, while crystal seeds grow preferentially in regions of low curvature, the lattice frustration produced in regions with high curvature is rapidly relaxed through isolated defects. Further relaxation involves a mechanism of crystal growth and defect annihilation where regions with high curvature act as sinks for the diffusion of domain walls. The pinning of grain boundaries at regions of low curvature leads to the formation of a metastable structure of defects, characterized by asymptotically slow dynamics of ordering and activation energies dictated by the largest curvatures of the system. These glassylike ordering dynamics may completely inhibit the appearance of the ground-state structures. PMID:23944462

Garca, Nicols A; Register, Richard A; Vega, Daniel A; Gmez, Leopoldo R

2013-07-01

381

Respiration and bacterial carbon dynamics in Arctic sea ice  

Microsoft Academic Search

Bacterial carbon demand, an important component of ecosystem dynamics in polar waters and sea ice, is a function of both bacterial\\u000a production (BP) and respiration (BR). BP has been found to be generally higher in sea ice than underlying waters, but rates\\u000a of BR and bacterial growth efficiency (BGE) are poorly characterized in sea ice. Using melted ice core incubations,

Dan Nguyen; Roxane Maranger

382

Recession, S-curves and Digital Equipment Corporation  

E-print Network

it conformed to this model in the first thirty years but missed out on the disruptive technology of PCs. Their growth can be linked to disruptive technology, the `S-curve' and also to the world's financial `wave to disappear completely. This paper looks at DEC both in relation to the S-curve of technology and how

Paris-Sud XI, Université de

383

Bacterial colonization of functionalized polyurethanes.  

PubMed

A protocol was developed for studying the growth of bacteria upon polyurethanes subsequent to the establishment of an adherent bacterial population. An inocula of approximately 10(5) cfu S. aureus were spread on functionalized polyurethanes which included Pellethane, sulfonated Pellethane, phosphonated Pellethane, quaternized amine polyurethanes, and a zwitterionic phosphonated polyurethane. After 24 h incubation, Pellethane, sulfonated Pellethane, and phosphonated Pellethane showed bacterial growth by at least a factor of 10. In contrast, the zwitterionic phosphonated polyurethane showed a factor of 10 decrease in bacteria after 24 h and the quaternized amine polyurethanes reduced the bacteria to only a few hundred after only 1 h. When treated with bovine serum albumin, Pellethane, sulfonated Pellethane, and phosphonated Pellethane again showed bacterial growth by as much as a factor of 10 over 24 h. The quaternized amine polyurethanes and the zwitterionic phosphonated polyurethane still exhibited bactericidal abilities even when coated with bovine serum albumin, with the zwitterionic material reducing bacteria by more than a factor of 10 over 24 h and the quaternized amine polyurethane reducing the bacteria to only a few hundred after only 1 h. A zone of inhibition study suggested that the bactericidal activity of the zwitterionic phosphonated polyurethane was due to the leaching of cadmium ions. A quaternized amine polyurethane which contained chloride instead of iodide as the counterion to the amine moiety was less bactericidal than the iodide-containing polymer when treated with albumin. Thus, bacteria were able to colonize Pellethane, phosphonated sulfonated Pellethane, and phosphonated Pellethane, but the iodide-containing quaternized amine polyurethane and the zwitterionic polyurethane prevented colonization. PMID:10646944

Flemming, R G; Capelli, C C; Cooper, S L; Proctor, R A

2000-02-01

384

Atlas of fatigue curves  

SciTech Connect

This Atlas was developed to serve engineers who are looking for fatigue data on a particular metal or alloy. Having these curves compiled in a single book will also facilitate the computerization of the involved data. It is pointed out that plans are under way to make the data in this book available in ASCII files for analysis by computer programs. S-N curves which typify effects of major variables are considered along with low-carbon steels, medium-carbon steels, alloy steels, HSLA steels, high-strength alloy steels, heat-resisting steels, stainless steels, maraging steels, cast irons, and heat-resisting alloys. Attention is also given to aluminum alloys, copper alloys, magnesium alloys, molybdenum, tin alloys, titanium and titanium alloys, zirconium, steel castings, closed-die forgings, powder metallurgy parts, composites, effects of surface treatments, and test results for component parts.

Boyer, H.E.

1986-01-01

385

Curve parametrization by moments.  

PubMed

We present a method for deriving a parametric description of a conic section (quadratic curve) in an image from the moments of the image with respect to several specially-constructed kernel functions. In contrast to Hough-transform-type methods, the moment approach requires no large accumulator array. Judicious implementation allows the parameters to be determined using five multiplication operations and six addition operations per pixel. The use of moments renders the calculation robust in the presence of high-frequency noise or texture and resistant to small-scale irregularities in the edge. Our method is generalizable to more complex classes of curves with more parameters as well as to surfaces in higher dimensions. PMID:19029543

Popovici, Irina; Withers, William Douglas

2009-01-01

386

Curve-Skeleton Applications  

Microsoft Academic Search

Curve-skeletons are a 1D subset of the medial surface of a 3D object and are useful for many visualization tasks including virtual navigation, reduced-model formulation, visualization improvement, mesh repair, animation, etc. There are many algorithms in the literature describing extraction methodologies for different applications; however, it is unclear how general and robust they are. In this paper, we provide an

Nicu D. Cornea; Deborah Silver; Patrick Min

2005-01-01

387

Diffusion in Curved Spacetimes  

E-print Network

Using simple kinematical arguments, we derive the Fokker-Planck equation for diffusion processes in curved spacetimes. In the case of Brownian motion, it coincides with Eckart's relativistic heat equation (albeit in a simpler form), and therefore provides a microscopic justification for his phenomenological heat-flux ansatz. Furthermore, we obtain the small-time asymptotic expansion of the mean square displacement of Brownian motion in static spacetimes. Beyond general relativity itself, this result has potential applications in analogue gravitational systems.

Matteo Smerlak

2011-04-17

388

Demonstrating Bacterial Flagella.  

ERIC Educational Resources Information Center

Describes an effective laboratory method for demonstrating bacterial flagella that utilizes the Proteus mirabilis organism and a special harvesting technique. Includes safety considerations for the laboratory exercise. (MDH)

Porter, John R.; And Others

1992-01-01

389

Engineering the perfect (bacterial) cancer therapy  

Microsoft Academic Search

Bacterial therapies possess many unique mechanisms for treating cancer that are unachievable with standard methods. Bacteria can specifically target tumours, actively penetrate tissue, are easily detected and can controllably induce cytotoxicity. Over the past decade, Salmonella, Clostridium and other genera have been shown to control tumour growth and promote survival in animal models. In this Innovation article I propose that

Neil S. Forbes

2010-01-01

390

Molecular genetics of bacterial attachment and biofouling  

Microsoft Academic Search

Microbial adhesion to animate or inert surfaces is potentially mediated by nonspecific physical or specific ligandreceptor interactions. Growth and survival of the microbial community or biofilm then depends on adaptation to a series of changing environmental milieux. Within the realm of cellcell interaction, recent advances suggest that flagella, fimbriae and other protein receptors are essential for bacterial attachment to surfaces.

Helen M Dalton; Paul E March

1998-01-01

391

Antibiotic resistance of bacterial biofilms.  

PubMed

A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and DNA. Bacterial biofilms cause chronic infections because they show increased tolerance to antibiotics and disinfectant chemicals as well as resisting phagocytosis and other components of the body's defence system. The persistence of, for example, staphylococcal infections related to foreign bodies is due to biofilm formation. Likewise, chronic Pseudomonas aeruginosa lung infection in cystic fibrosis patients is caused by biofilm-growing mucoid strains. Characteristically, gradients of nutrients and oxygen exist from the top to the bottom of biofilms and these gradients are associated with decreased bacterial metabolic activity and increased doubling times of the bacterial cells; it is these more or less dormant cells that are responsible for some of the tolerance to antibiotics. Biofilm growth is associated with an increased level of mutations as well as with quorum-sensing-regulated mechanisms. Conventional resistance mechanisms such as chromosomal beta-lactamase, upregulated efflux pumps and mutations in antibiotic target molecules in bacteria also contribute to the survival of biofilms. Biofilms can be prevented by early aggressive antibiotic prophylaxis or therapy and they can be treated by chronic suppressive therapy. A promising strategy may be the use of enzymes that can dissolve the biofilm matrix (e.g. DNase and alginate lyase) as well as quorum-sensing inhibitors that increase biofilm susceptibility to antibiotics. PMID:20149602

Hiby, Niels; Bjarnsholt, Thomas; Givskov, Michael; Molin, Sren; Ciofu, Oana

2010-04-01

392

Planar dimers and Harnack curves  

E-print Network

In this paper we study the connection between dimers and Harnack curves discovered in math-ph/0311005. We prove that every Harnack curve arises as a spectral curve of some dimer model. We also prove that the space of Harnack curve of given degree is homeomorphic to a closed octant and that the areas of the amoeba holes and the distances between the amoeba tentacles give these global coordinates. We characterize Harnack curves of genus zero as spectral curves of isoradial dimers and also as minimizers of the volume under their Ronkin function with given boundary conditions.

Richard Kenyon; Andrei Okounkov

2003-11-05

393

Bacterial cell shape  

Microsoft Academic Search

Bacterial species have long been classified on the basis of their characteristic cell shapes. Despite intensive research, the molecular mechanisms underlying the generation and maintenance of bacterial cell shape remain largely unresolved. The field has recently taken an important step forward with the discovery that eukaryotic cytoskeletal proteins have homologues in bacteria that affect cell shape. Here, we discuss how

Matthew T. Cabeen; Christine Jacobs-Wagner

2005-01-01

394

Modeling the Keeling Curve  

NSDL National Science Digital Library

In this problem set, learners will refer to the tabulated data used to create the Keeling Curve of atmospheric carbon dioxide to create a mathematical function that accounts for both periodic and long-term changes. They will use this function to answer a series of questions, including predictions of atmospheric concentration in the future. A link to the data, which is in an Excel file, as well as the answer key are provided. This is part of Earth Math: A Brief Mathematical Guide to Earth Science and Climate Change.

395

Crystallography on curved surfaces  

PubMed Central

We study static and dynamical properties that distinguish 2D crystals constrained to lie on a curved substrate from their flat-space counterparts. A generic mechanism of dislocation unbinding in the presence of varying Gaussian curvature is presented in the context of a model surface amenable to full analytical treatment. We find that glide diffusion of isolated dislocations is suppressed by a binding potential of purely geometrical origin. Finally, the energetics and biased diffusion dynamics of point defects such as vacancies and interstitials are explained in terms of their geometric potential. PMID:16894160

Vitelli, Vincenzo; Lucks, J. B.; Nelson, D. R.

2006-01-01

396

Lenses on curved surfaces.  

PubMed

This Letter presents a theory that allows graded index lenses to be mapped onto arbitrary rotationally symmetric curved surfaces. Examples of the Luneburg and Maxwell fish-eye lens are given, for numerous surfaces, always resulting in isotropic permittivity requirements. The performance of these lenses is initially illustrated with full-wave simulations utilizing a waveguide structure. A transformation of the refractive index profiles is then performed to design surface-wave lenses, where the dielectric layer is not only isotropic but also homogenous, demonstrating the applicability and ease of fabrication. PMID:24978534

Mitchell-Thomas, R C; Quevedo-Teruel, O; McManus, T M; Horsley, S A R; Hao, Y

2014-06-15

397

Curved cap corrugated sheet  

NASA Technical Reports Server (NTRS)

The report describes a structure for a strong, lightweight corrugated sheet. The sheet is planar or curved and includes a plurality of corrugation segments, each segment being comprised of a generally U-shaped corrugation with a part-cylindrical crown and cap strip, and straight side walls and with secondary corrugations oriented at right angles to said side walls. The cap strip is bonded to the crown and the longitudinal edge of said cap strip extends beyond edge at the intersection between said crown and said side walls. The high strength relative to weight of the structure makes it desirable for use in aircraft or spacecraft.

Davis, R. C.; Bales, T. T.; Royster, D. M.; Jackson, L. R. (inventors)

1984-01-01

398

Curve analysis of the aging orbital aperture.  

PubMed

It was hypothesized that skeletal aging results in curve distortion of the orbital aperture. Data were compiled from a cross-sectional study of the Robert J. Terry human skull collection at the Smithsonian Institution, Washington, D.C. Statistical analyses suggest that postadult differential growth results in progressive distortion of the orbital aperture. These changes may have both cosmetic and functional consequences. PMID:11818864

Pessa, Joel E; Chen, Yuan

2002-02-01

399

Data Plotting and Curve Fitting in MATLAB Curve Fitting  

E-print Network

Data Plotting and Curve Fitting in MATLAB Curve Fitting Get the file pwl.dat from the class web(1)*pwl(:,1)+fit1(2)) If you're getting tired of typing pwl(:,1), etc., create new variables with shorter]') ylabel(`Output Current [mA]') title(`Curve Fitting Exercise') It is very important to always label your

Harrison, Reid R.

400

Effect of Perfluorooctyl Bromide on Bacterial Growth  

Microsoft Academic Search

Background: Perfluorooctyl bromide (PFOB) is administered directly into the lungs of critically ill patients during partial liquid ventilation. This adjunctive therapy facilitates respiratory support in lung-injured patients and potentially interacts with pathogens in patients with pneumonia. The purpose of this study was to determine the interaction of PFOB with Pseudomonas aeruginosa. Methods: The antimicrobial activity of PFOB against P. aeruginosa

Rose Jung; Susan L. Pendland; Steven J. Martin

2003-01-01

401

On planar rational cuspidal curves  

E-print Network

This thesis studies rational curves in the complex projective plane that are homeomorphic to their normalizations. We derive some combinatorial constraints on such curves from a result of Borodzik-Livingston in Heegaard-Floer ...

Liu, Tiankai

2014-01-01

402

Curve walking in crayfish  

PubMed

Curve walking of crayfish Astacus leptodactylus was investigated by exploiting their optomotor response. The animal walked while spatially fixed on a motor-driven treadmill and turning behaviour was induced by an optical stimulus, a pattern consisting of vertical stripes moving in a horizontal direction. In this open-loop situation, the crayfish maintains the same step frequency for the legs on both sides of the body for low and intermediate turning speeds, but increases the step amplitude of the outer legs 2, 3 and 4 by shifting the posterior extreme position (PEP) of these legs in a posterior direction and reduces the step amplitude of inner leg 5 by shifting the PEP of this leg in an anterior direction. Furthermore, the main movement direction of the legs can change relative to the body. This was observed for outer leg 5 and also, at higher turning speeds, for outer leg 2. As coordinating influences between contra- and ipsilateral legs were found directly to influence only the anterior extreme position of the legs, these results indicate that the mechanisms controlling curve walking may be different from those controlling normal leg coordination. PMID:9319377

Cruse; Saavedra

1996-01-01

403

Polymer Crystallization at Curved Liquid-Liquid Interface  

NASA Astrophysics Data System (ADS)

Curved space is incommensurate with typical ordered structures with three-dimensional (3D) translational symmetry. However, upon assembly, soft matter, including colloids, amphiphiles, and block copolymers (BCPs), often forms structures depicting curved surface/interface. Examples include liposomes, colloidosomes, spherical micelles, worm-like micelles, and vesicles (also known as polymersomes). For crystalline BCPs, crystallization oftentimes overwrites curved geometries since the latter is incommensurate with crystalline order. On the other hand, twisted and curved crystals are often observed in crystalline polymers. Various mechanisms have been proposed for these non-flat crystalline morphologies. In this presentation, we will demonstrate that curved liquid/liquid (L/L) interface can guide polymer single crystal growth. The crystal morphology is strongly dependent on the nucleation mechanism. A myriad of controlled curved single crystals can be readily obtained.

Li, Christopher; Wang, Wenda; Qi, Hao; Huang, Ziyin

2013-03-01

404

Normal bacterial flora from vaginas of Criollo Limonero cows.  

PubMed

In order to describe the normal bacterial flora in vaginas of Criollo Limonero cows, 51 healthy multiparous cows, at least 90-day postpartum, were selected. Duplicated swabs (N = 102) were taken from the vaginal fornix of cows to perform aerobic and anaerobic cultures as well as conventional biochemical tests. Out of 102 swabs, bacterial growth was obtained in 55 (53.9%) while the remaining 47 (46.1%) did not exhibited any bacterial growth. Of the 55 bacterial growths, 23 (41.8%) were aerobic whereas 32 (58.1%) were anaerobic. Likewise, 29 (52.72%) of bacterial growths were pure and 26 (47.27%) were mixed. Under both aerobic and anaerobic conditions, Gram positive bacteria were predominant (81.82% and 73.08%, respectively) over Gram negative bacteria (18.18% and 26.92%, respectively). Isolated bacteria were Arcanobacterium pyogenes (22.92%), Staphylococcus aureus (15.63%), Staphylococcus coagulase negative (17.71%), Erysipelothrix rhusiopathiae (6.25%), Bacteroides spp. (13.54%), and Peptostreptococcus spp. (7.29%). In conclusion, normal vaginal bacterial flora of Criollo Limonero cows was predominantly Gram positive and included A. pyogenes, S. aureus, coagulase negative Staphylococcus, E. rhusiopathiae, Bacteroides spp., and Peptostreptococcus spp. In Criollo Limonero cattle, adaptive aspects such as development of humoral and physical mechanisms for defense, and bacterial adaptation to host deserve research attention. PMID:21082249

Zambrano-Nava, Sunny; Boscn-Ocando, Julio; Nava, Jexenia

2011-02-01

405

The role of bacterial biofilms and surface components in plant-bacterial associations.  

PubMed

The role of bacterial surface components in combination with bacterial functional signals in the process of biofilm formation has been increasingly studied in recent years. Plants support a diverse array of bacteria on or in their roots, transport vessels, stems, and leaves. These plant-associated bacteria have important effects on plant health and productivity. Biofilm formation on plants is associated with symbiotic and pathogenic responses, but how plants regulate such associations is unclear. Certain bacteria in biofilm matrices have been found to induce plant growth and to protect plants from phytopathogens (a process termed biocontrol), whereas others are involved in pathogenesis. In this review, we systematically describe the various components and mechanisms involved in bacterial biofilm formation and attachment to plant surfaces and the relationships of these mechanisms to bacterial activity and survival. PMID:23903045

Bogino, Pablo C; Oliva, Mara de las Mercedes; Sorroche, Fernando G; Giordano, Walter

2013-01-01

406

Ironing Out Curves  

NSDL National Science Digital Library

In this activity, students graph second and third order functions, discovering an inverse relationship between squares and square roots and between cubes and cube roots. Students graph these functions on both linear grid (evenly spaced numbers), and a log-log grid (evenly space exponents). Graph lines that curve on linear grids transform into straight lines on the log-log grids, with slopes equal to their exponential powers. This activity is activity E3 in the "Far Out Math" educator's guide. Lessons in the guide include activities in which students measure, compare quantities as orders of magnitude, become familiar with scientific notation, and develop an understanding of exponents and logarithms using examples from NASA's GLAST mission. These are skills needed to understand the very large and very small quantities characteristic of astronomical observations. Note: In 2008, GLAST was renamed Fermi, for the physicist Enrico Fermi.

407

Microfluidics for bacterial chemotaxis  

E-print Network

Bacterial chemotaxis, a remarkable behavioral trait which allows bacteria to sense and respond to chemical gradients in the environment, has implications in a broad range of fields including but not limited to disease ...

Ahmed, Tanvir, Ph. D. Massachusetts Institute of Technology

2011-01-01

408

Bistability and Bacterial Infections  

PubMed Central

Bacterial infections occur when the natural host defenses are overwhelmed by invading bacteria. The main component of the host defense is impaired when neutrophil count or function is too low, putting the host at great risk of developing an acute infection. In people with intact immune systems, neutrophil count increases during bacterial infection. However, there are two important clinical cases in which they remain constant: a) in patients with neutropenic-associated conditions, such as those undergoing chemotherapy at the nadir (the minimum clinically observable neutrophil level); b) in ex vivo examination of the patient's neutrophil bactericidal activity. Here we study bacterial population dynamics under fixed neutrophil levels by mathematical modelling. We show that under reasonable biological assumptions, there are only two possible scenarios: 1) Bacterial behavior is monostable: it always converges to a stable equilibrium of bacterial concentration which only depends, in a gradual manner, on the neutrophil level (and not on the initial bacterial level). We call such a behavior type I dynamics. 2) The bacterial dynamics is bistable for some range of neutrophil levels. We call such a behavior type II dynamics. In the bistable case (type II), one equilibrium corresponds to a healthy state whereas the other corresponds to a fulminant bacterial infection. We demonstrate that published data of in vitro Staphylococcus epidermidis bactericidal experiments are inconsistent with both the type I dynamics and the commonly used linear model and are consistent with type II dynamics. We argue that type II dynamics is a plausible mechanism for the development of a fulminant infection. PMID:20463954

Malka, Roy; Shochat, Eliezer; Rom-Kedar, Vered

2010-01-01

409

Bistability and bacterial infections.  

PubMed

Bacterial infections occur when the natural host defenses are overwhelmed by invading bacteria. The main component of the host defense is impaired when neutrophil count or function is too low, putting the host at great risk of developing an acute infection. In people with intact immune systems, neutrophil count increases during bacterial infection. However, there are two important clinical cases in which they remain constant: a) in patients with neutropenic-associated conditions, such as those undergoing chemotherapy at the nadir (the minimum clinically observable neutrophil level); b) in ex vivo examination of the patient's neutrophil bactericidal activity. Here we study bacterial population dynamics under fixed neutrophil levels by mathematical modelling. We show that under reasonable biological assumptions, there are only two possible scenarios: 1) Bacterial behavior is monostable: it always converges to a stable equilibrium of bacterial concentration which only depends, in a gradual manner, on the neutrophil level (and not on the initial bacterial level). We call such a behavior type I dynamics. 2) The bacterial dynamics is bistable for some range of neutrophil levels. We call such a behavior type II dynamics. In the bistable case (type II), one equilibrium corresponds to a healthy state whereas the other corresponds to a fulminant bacterial infection. We demonstrate that published data of in vitro Staphylococcus epidermidis bactericidal experiments are inconsistent with both the type I dynamics and the commonly used linear model and are consistent with type II dynamics. We argue that type II dynamics is a plausible mechanism for the development of a fulminant infection. PMID:20463954

Malka, Roy; Shochat, Eliezer; Rom-Kedar, Vered

2010-01-01

410

ALMOST-COMPLEX CURVES IN S6 AND SPECTRAL CURVES  

Microsoft Academic Search

There are three types of almost-complex curves in the nearly-Kahler 6- sphere: they are totally geodesic, pseudo-holomorphic or superconformal, the last case being generic. This paper concerns superconformal almost-complex curves. We begin by giving a geometric construction of a particularly natural G2-framing for such curves. This framing can easily be shown to agree with that in (6); the exposition here

EMMA CARBERRY

411

Curve Matching by using B-spline Curves  

Microsoft Academic Search

This paper presents an algorithm for estimating the control points of the B-spline and curve matching which is achieved by using the dissimilarity measure based on the knot associated with the B-spline curves. The B-splines stand as one of the most efficient curve representations and possess very attractive properties such as spatial uniqueness, boundedness and continuity, local shape controllability, and

Tet Toe; Tang Van To

412

Titania single crystals with a curved surface.  

PubMed

Owing to its scientific and technological importance, crystallization as a ubiquitous phenomenon has been widely studied over centuries. Well-developed single crystals are generally enclosed by regular flat facets spontaneously to form polyhedral morphologies because of the well-known self-confinement principle for crystal growth. However, in nature, complex single crystalline calcitic skeleton of biological organisms generally has a curved external surface formed by specific interactions between organic moieties and biocompatible minerals. Here we show a new class of crystal surface of TiO2, which is enclosed by quasi continuous high-index microfacets and thus has a unique truncated biconic morphology. Such single crystals may open a new direction for crystal growth study since, in principle, crystal growth rates of all facets between two normal {101} and {011} crystal surfaces are almost identical. In other words, the facet with continuous Miller index can exist because of the continuous curvature on the crystal surface. PMID:25373513

Yang, Shuang; Yang, Bing Xing; Wu, Long; Li, Yu Hang; Liu, Porun; Zhao, Huijun; Yu, Yan Yan; Gong, Xue Qing; Yang, Hua Gui

2014-01-01

413

Quantification, Distribution, and Possible Source of Bacterial Biofilm in Mouse Automated Watering Systems  

PubMed Central

The use of automated watering systems for providing drinking water to rodents has become commonplace in the research setting. Little is known regarding bacterial biofilm growth within the water piping attached to the racks (manifolds). The purposes of this project were to determine whether the mouse oral flora contributed to the aerobic bacterial component of the rack biofilm, quantify bacterial growth in rack manifolds over 6 mo, assess our rack sanitation practices, and quantify bacterial biofilm development within sections of the manifold. By using standard methods of bacterial identification, the aerobic oral flora of 8 strains and stocks of mice were determined on their arrival at our animal facility. Ten rack manifolds were sampled before, during, and after sanitation and monthly for 6 mo. Manifolds were evaluated for aerobic bacterial growth by culture on R2A and trypticase soy agar, in addition to bacterial ATP quantification by bioluminescence. In addition, 6 racks were sampled at 32 accessible sites for evaluation of biofilm distribution within the watering manifold. The identified aerobic bacteria in the oral flora were inconsistent with the bacteria from the manifold, suggesting that the mice do not contribute to the biofilm bacteria. Bacterial growth in manifolds increased while they were in service, with exponential growth of the biofilm from months 3 to 6 and a significant decrease after sanitization. Bacterial biofilm distribution was not significantly different across location quartiles of the rack manifold, but bacterial levels differed between the shelf pipe and connecting elbow pipes. PMID:18351724

Meier, Thomas R; Maute, Carrie J; Cadillac, Joan M; Lee, Ji Young; Righter, Daniel J; Hugunin, Kelly MS; Deininger, Rolf A; Dysko, Robert C

2008-01-01

414

Structure and Complexity of a Bacterial Transcriptome?  

PubMed Central

Although gene expression has been studied in bacteria for decades, many aspects of the bacterial transcriptome remain poorly understood. Transcript structure, operon linkages, and information on absolute abundance all provide valuable insights into gene function and regulation, but none has ever been determined on a genome-wide scale for any bacterium. Indeed, these aspects of the prokaryotic transcriptome have been explored on a large scale in only a few instances, and consequently little is known about the absolute composition of the mRNA population within a bacterial cell. Here we report the use of a high-throughput sequencing-based approach in assembling the first comprehensive, single-nucleotide resolution view of a bacterial transcriptome. We sampled the Bacillus anthracis transcriptome under a variety of growth conditions and showed that the data provide an accurate and high-resolution map of transcript start sites and operon structure throughout the genome. Further, the sequence data identified previously nonannotated regions with significant transcriptional activity and enhanced the accuracy of existing genome annotations. Finally, our data provide estimates of absolute transcript abundance and suggest that there is significant transcriptional heterogeneity within a clonal, synchronized bacterial population. Overall, our results offer an unprecedented view of gene expression and regulation in a bacterial cell. PMID:19304856

Passalacqua, Karla D.; Varadarajan, Anjana; Ondov, Brian D.; Okou, David T.; Zwick, Michael E.; Bergman, Nicholas H.

2009-01-01

415

The bacterial translation stress response.  

PubMed

Throughout their life, bacteria need to sense and respond to environmental stress. Thus, such stress responses can require dramatic cellular reprogramming, both at the transcriptional as well as the translational level. This review focuses on the protein factors that interact with the bacterial translational apparatus to respond to and cope with different types of environmental stress. For example, the stringent factor RelA interacts with the ribosome to generate ppGpp under nutrient deprivation, whereas a variety of factors have been identified that bind to the ribosome under unfavorable growth conditions to shut-down (RelE, pY, RMF, HPF and EttA) or re-program (MazF, EF4 and BipA) translation. Additional factors have been identified that rescue ribosomes stalled due to stress-induced mRNA truncation (tmRNA, ArfA, ArfB), translation of unfavorable protein sequences (EF-P), heat shock-induced subunit dissociation (Hsp15), or antibiotic inhibition (TetM, FusB). Understanding the mechanism of how the bacterial cell responds to stress will not only provide fundamental insight into translation regulation, but will also be an important step to identifying new targets for the development of novel antimicrobial agents. PMID:25135187

Starosta, Agata L; Lassak, Jrgen; Jung, Kirsten; Wilson, Daniel N

2014-11-01

416

Apoptosis of human intestinal epithelial cells after bacterial invasion.  

PubMed Central

Epithelial cells that line the human intestinal mucosa are the initial site of host invasion by bacterial pathogens. The studies herein define apoptosis as a new category of intestinal epithelial cell response to bacterial infection. Human colon epithelial cells are shown to undergo apoptosis following infection with invasive enteric pathogens, such as Salmonella or enteroinvasive Escherichia coli. In contrast to the rapid onset of apoptosis seen after bacterial infection of mouse monocyte-macrophage cell lines, the commitment of human intestinal epithelial cell lines to undergo apoptosis is delayed for at least 6 h after bacterial infection, requires bacterial entry and replication, and the ensuing phenotypic expression of apoptosis is delayed for 12-18 h after bacterial entry. TNF-alpha and nitric oxide, which are produced as components of the intestinal epithelial cell proinflammatory program in the early period after bacterial invasion, play an important role in the later induction and regulation of the epithelial cell apoptotic program. Apoptosis in response to bacterial infection may function to delete infected and damaged epithelial cells and restore epithelial cell growth regulation and epithelial integrity that are altered during the course of enteric infection. The delay in onset of epithelial cell apoptosis after bacterial infection may be important both to the host and the invading pathogen since it provides sufficient time for epithelial cells to generate signals important for the activation of mucosal inflammation and concurrently allows invading bacteria time to adapt to the intracellular environment before invading deeper mucosal layers. PMID:9819367

Kim, J M; Eckmann, L; Savidge, T C; Lowe, D C; Witthoft, T; Kagnoff, M F

1998-01-01

417

Connecting curves in higher dimensions  

NASA Astrophysics Data System (ADS)

Connecting curves have been shown to organize the rotational structure of strange attractors in three-dimensional dynamical systems. We extend the description of connecting curves and their properties to higher dimensions within a special class of differential dynamical systems. The general properties of connecting curves are derived and selection rules stated. Examples are presented to illustrate these properties for dynamical systems of dimension n = 3, 4, 5.

Byrne, Greg; Gilmore, Robert; Cebral, Juan

2014-05-01

418

Langevin Equation on Fractal Curves  

E-print Network

We analyse a random motion of a particle on a fractal curve, using Langevin approach. This involves defining a new velocity in terms of mass of the fractal curve, as defined in recent work. The geometry of the fractal curve, hence plays an important role in this analysis. A Langevin equation with a particular noise model is thus proposed and solved using techniques of the newly developed $F^\\alpha$-Calculus .

Seema Satin; A. D. Gangal

2014-04-28

419

Mechanical Control of Bacterial Cell Shape  

PubMed Central

In bacteria, cytoskeletal filament bundles such as MreB control the cell morphology and determine whether the cell takes on a spherical or a rod-like shape. Here we use a theoretical model to describe the interplay of cell wall growth, mechanics, and cytoskeletal filaments in shaping the bacterial cell. We predict that growing cells without MreB exhibit an instability that favors rounded cells. MreB can mechanically reinforce the cell wall and prevent the onset of instability. We propose that the overall bacterial shape is determined by a dynamic turnover of cell wall material that is controlled by mechanical stresses in the wall. The model affirms that morphological transformations with and without MreB are reversible, and quantitatively describes the growth of irregular shapes and cells undergoing division. The theory also suggests a unique coupling between mechanics and chemistry that can control organismal shapes in general. PMID:21767484

Jiang, Hongyuan; Si, Fangwei; Margolin, William; Sun, Sean X.

2011-01-01