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1

The Bacterial Growth Curve.  

ERIC Educational Resources Information Center

A procedure that allows students to view an entire bacterial growth curve during a two- to three-hour student laboratory period is described. Observations of the lag phase, logarithmic phase, maximum stationary phase, and phase of decline are possible. A nonpathogenic, marine bacterium is used in the investigation. (KR)

Paulton, Richard J. L.

1991-01-01

2

When is simple good enough: a comparison of the Gompertz, Baranyi, and three-phase linear models for fitting bacterial growth curves  

Microsoft Academic Search

The use of primary mathematical models with curve fitting software is dramatically changing quantitative food microbiology. The two most widely used primary growth models are the Baranyi and Gompertz models. A three-phase linear model was developed to determine how well growth curves could be described using a simpler model. The model divides bacterial growth curves into three phases: the lag

R. L Buchanan; R. C Whiting; W. C Damert

1997-01-01

3

Growth of Bacterial Colonies  

NASA Astrophysics Data System (ADS)

On hard agar gel, there is insufficient surface hydration for bacteria to swim or swarm. Instead, growth occurs in colonies of close-packed cells, which expand purely due to repulsive interactions: individual bacteria push each other out of the way through the force of their growth. In this way, bacterial colonies represent a new type of ``active'' granular matter. In this study, we investigate the physical, biochemical, and genetic elements that determine the static and dynamic aspects of this mode of bacterial growth for E. coli. We characterize the process of colony expansion empirically, and use discrete and continuum models to examine the extent to which our observations can be explained by the growth characteristics of non-communicating cells, coupled together by physical forces, nutrients, and waste products. Our results challenge the commonly accepted modes of bacterial colony growth and provide insight into sources of growth limitation in crowded bacterial communities.

Warren, Mya; Hwa, Terence

2013-03-01

4

Phenotypic signatures arising from unbalanced bacterial growth.  

PubMed

Fluctuations in the growth rate of a bacterial culture during unbalanced growth are generally considered undesirable in quantitative studies of bacterial physiology. Under well-controlled experimental conditions, however, these fluctuations are not random but instead reflect the interplay between intra-cellular networks underlying bacterial growth and the growth environment. Therefore, these fluctuations could be considered quantitative phenotypes of the bacteria under a specific growth condition. Here, we present a method to identify "phenotypic signatures" by time-frequency analysis of unbalanced growth curves measured with high temporal resolution. The signatures are then applied to differentiate amongst different bacterial strains or the same strain under different growth conditions, and to identify the essential architecture of the gene network underlying the observed growth dynamics. Our method has implications for both basic understanding of bacterial physiology and for the classification of bacterial strains. PMID:25101949

Tan, Cheemeng; Smith, Robert Phillip; Tsai, Ming-Chi; Schwartz, Russell; You, Lingchong

2014-08-01

5

Phenotypic Signatures Arising from Unbalanced Bacterial Growth  

PubMed Central

Fluctuations in the growth rate of a bacterial culture during unbalanced growth are generally considered undesirable in quantitative studies of bacterial physiology. Under well-controlled experimental conditions, however, these fluctuations are not random but instead reflect the interplay between intra-cellular networks underlying bacterial growth and the growth environment. Therefore, these fluctuations could be considered quantitative phenotypes of the bacteria under a specific growth condition. Here, we present a method to identify “phenotypic signatures” by time-frequency analysis of unbalanced growth curves measured with high temporal resolution. The signatures are then applied to differentiate amongst different bacterial strains or the same strain under different growth conditions, and to identify the essential architecture of the gene network underlying the observed growth dynamics. Our method has implications for both basic understanding of bacterial physiology and for the classification of bacterial strains. PMID:25101949

Tan, Cheemeng; Smith, Robert Phillip; Tsai, Ming-Chi; Schwartz, Russell; You, Lingchong

2014-01-01

6

Modelling bacterial flagellar growth  

E-print Network

The growth of bacterial flagellar filaments is a self-assembly process where flagellin molecules are transported through the narrow core of the flagellum and are added at the distal end. To model this situation, we generalize a growth process based on the TASEP model by allowing particles to move both forward and backward on the lattice. The bias in the forward and backward jump rates determines the lattice tip speed, which we analyze and also compare to simulations. For positive bias, the system is in a non-equilibrium steady state and exhibits boundary-induced phase transitions. The tip speed is constant. In the no-bias case we find that the length of the lattice grows as $N(t)\\propto\\sqrt{t}$, whereas for negative drift $N(t)\\propto\\ln{t}$. The latter result agrees with experimental data of bacterial flagellar growth.

Schmitt, Maximilian; 10.1209/0295-5075/96/28001

2012-01-01

7

Bacterial cell curvature through mechanical control of cell growth  

E-print Network

Bacterial cell curvature through mechanical control of cell growth Matthew T Cabeen1 , Godefroid growth. The bacterial peptidogly- can cell wall is a covalently closed meshwork of rigid glycan strands, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus

Weibel, Douglas B.

8

Bacterial growth properties at low optical densities  

Microsoft Academic Search

A method for accurate quantification of growth rate and yield of bacterial populations at low densities was developed with\\u000a a modified version of a stepwise linear model for fitting growth curves based on optical density measurements, and adapted\\u000a to measurements at low optical densities in 96-well microtiter plates. The method can be used for rapid and precise estimates\\u000a of growth

Maja Novak; Thomas Pfeiffer; Martin Ackermann; Sebastian Bonhoeffer

2009-01-01

9

Metabolic AssessmentQC Preprocessing Growth curves from PM undergo filtering to  

E-print Network

pipeline to accurately qualify growth of bacterial cells using PM measurements. Using logistic growth curve parameters, quantify the growth level of various bacterial cells. Apply this analysis toward biologicalMetabolic AssessmentQC Preprocessing Growth curves from PM undergo filtering to remove troublesome

10

Bacterial Growth on Allochthonous Carbon in Humic  

E-print Network

Bacterial Growth on Allochthonous Carbon in Humic and Nutrient-enriched Lakes: Results from Whole biomass con- sisted of 43­46% allochthonous C. In Tuesday Lake more than 75% of bacterial growth the relative importance of autochtho- nous and allochthonous C in supporting bacterial production. For 35 days

Pace, Michael L.

11

Bacterial volatiles promote growth in Arabidopsis  

Microsoft Academic Search

Several chemical changes in soil are associated with plant growth-promoting rhizobacteria (PGPR). Some bacterial strains directly regulate plant physiology by mimicking synthesis of plant hormones, whereas others increase mineral and nitrogen availability in the soil as a way to augment growth. Identification of bacterial chemical messengers that trigger growth promotion has been limited in part by the understanding of how

Choong-Min Ryu; Mohamed A. Farag; Chia-Hui Hu; Munagala S. Reddy; Han-Xun Wei; Paul W. Paré; Joseph W. Kloepper

2003-01-01

12

Bacterial volatiles promote growth in Arabidopsis  

PubMed Central

Several chemical changes in soil are associated with plant growth-promoting rhizobacteria (PGPR). Some bacterial strains directly regulate plant physiology by mimicking synthesis of plant hormones, whereas others increase mineral and nitrogen availability in the soil as a way to augment growth. Identification of bacterial chemical messengers that trigger growth promotion has been limited in part by the understanding of how plants respond to external stimuli. With an increasing appreciation of how volatile organic compounds signal plants and serve in plant defense, investigations into the role of volatile components in plant–bacterial systems now can follow. Here, we present chemical and plant-growth data showing that some PGPR release a blend of volatile components that promote growth of Arabidopsis thaliana. In particular, the volatile components 2,3-butanediol and acetoin were released exclusively from two bacterial strains that trigger the greatest level of growth promotion. Furthermore, pharmacological applications of 2,3-butanediol enhanced plant growth whereas bacterial mutants blocked in 2,3-butanediol and acetoin synthesis were devoid in this growth-promotion capacity. The demonstration that PGPR strains release different volatile blends and that plant growth is stimulated by differences in these volatile blends establishes an additional function for volatile organic compounds as signaling molecules mediating plant–microbe interactions. PMID:12684534

Ryu, Choong-Min; Farag, Mohamed A.; Hu, Chia-Hui; Reddy, Munagala S.; Wei, Han-Xun; Paré, Paul W.; Kloepper, Joseph W.

2003-01-01

13

Bacterial Growth H. L. Smith  

E-print Network

. There are 105 cells in a milliliter of seawater, or on a square centimeter of our skin. There are ten times as many bacterial cells on our skin and in our large intestine as cells in our own body. We are nothing case, the shape of the graph of N(t) versus t has the classic "S" shape. However, the logistic equation

Smith, Hal

14

A quantitative measure of nitrifying bacterial growth.  

PubMed

Nitrifying bacteria convert ammonia (NH3) to nitrate (NO3-) in a nitrification reaction. Methods to quantitatively separate the growth rate of these important bacterial populations from that of the dominant heterotrophic bacteria are important to our understanding of the nitrification process. The changing concentration of ammonia is often used as an indirect measure of nitrification but ammonification processes generate ammonia and confound this approach while heterotrophs remove nitrate via denitrification. Molecular probe methods can tell us what proportion of the microbial community is nitrifying bacteria but not their growth rate. The technique proposed here was able to quantify the growth rate of the nitrifying bacterial populations amidst complex ecological processes. The method incubates [methyl-3H] thymidine with water samples in the presence and absence of an inhibitor of nitrification-thiourea. The radioactively labeled DNA in the growing bacteria was extracted. The rate of incorporation of the label into the dividing bacterial DNA was used to determine bacterial growth rate. Total bacterial community growth rates in full-scale and pilot-scale fixed-film nitrifying reactors and an activated sludge reactor were 2.1 x 10(8), 4.1 x 10(8) and 0.4 x 10(8)cell ml(-1)d(-1), respectively; the growth rate of autotrophic-nitrifying bacteria was 0.7 x 10(8), 2.6 x 10(8) and 0.01 x 10(8)cell ml(-1)d(-1), respectively. Autotrophic-nitrifying bacteria contributed 30% and 60% of the total bacterial community growth rate in the nitrifying reactors whereas only 2% was observed in the activated sludge reactor that was not designed to nitrify. The rates of ammonia loss from the nitrifying reactors corresponded to the rate of growth of the nitrifying bacteria. This method has the potential to more often identify factors that enhance or limit nitrifying processes in both engineered and natural aquatic environments. PMID:16603221

Pollard, Peter C

2006-05-01

15

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 Ângela Reis de Góes Monteiro; Barbeta, Camila Justino de Oliveira; de Lemos-Marini, Sofia Helena Valente

2014-01-01

16

Growth curves for girls with Turner syndrome.  

PubMed

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 Ângela Reis de Góes Monteiro; Barbeta, Camila Justino de Oliveira; de Lemos-Marini, Sofia Helena Valente; Guerra-Junior, Gil

2014-01-01

17

Dislocation dynamics and bacterial growth  

NASA Astrophysics Data System (ADS)

Recent experiments have revealed remarkable phenomena in the growth mechanisms of rod-shaped bacteria: proteins associated with the cell wall growth move at constant velocity in circles oriented approximately along the cell circumference (Garner et al., Science 2011, Dom'inguez-Escobar et al., Science 2011, Deng et al., PNAS 2011). We view these dislocations in the partially ordered peptidoglycan structure, and study theoretically the dynamics of these interacting dislocations on the surface of a cylinder. The physics of the nucleation of these dislocations and the resulting dynamics within the model show surprising effects arising from the cylindrical geometry, which are predicted to have important implications on the growth mechanism. We also discuss how long range elastic interactions affect the dynamics of the fraction of active dislocations in the environment.

Amir, Ariel; Nelson, David

2012-02-01

18

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

19

Bacterial contact-dependent growth inhibition.  

PubMed

Bacteria cooperate to form multicellular communities and compete against one another for environmental resources. Here, we review recent advances in the 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 toxin-immunity protein pairs appear to be exchanged between cdi loci and are often associated with other toxin-delivery systems in diverse bacterial species. 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

2013-05-01

20

Modelling and Analysis of Phase Variation in Bacterial Colony Growth  

E-print Network

Modelling and Analysis of Phase Variation in Bacterial Colony Growth Ovidiu P^arvu1 , David Gilbert case study, namely phase variation patterning in bacterial colony growth, forming circular colonies phase variation patterning in bacterial colony growth, forming circular colonies on a flat medium

Gilbert, David

21

Bacterial growth on dissolved organic carbon from a blackwater river  

Microsoft Academic Search

Different nominal molecular weight (nMW) fractions of DOC from a southeastern blackwater river were concentrated by ultrafiltration and added to sieved river water to assess each fraction's ability to stimulate bacterial growth. Bacterial growth was measured using change in bacterial biomass from direct counts and using3H-thymidine incorporated into DNA. Bacterial growth and amount of DOC used was greatest in the

Judy L. Meyer; Richard T. Edwards; Rebecca Risley

1987-01-01

22

Growth factor parametrization in curved space  

SciTech Connect

The growth rate of matter perturbation and the expansion rate of the Universe can be used to distinguish modified gravity and dark energy models in explaining cosmic acceleration. We explore here the inclusion of spatial curvature into the growth factor. We expand previous results using the approximation {omega}{sub m}{sup {gamma}} and then suggest a new form, f{sub a}={omega}{sub m}{sup {gamma}}+({gamma}-4/7){omega}{sub k}, as an approximation for the growth factor when the curvature {omega}{sub k} is not negligible, and where the growth index {gamma} is usually model dependent. The expression recovers the standard results for the curved and flat {lambda}CDM and Dvali-Gabadadze-Porrati models. Using the best fit values of {omega}{sub m0} and {omega}{sub k0} to the expansion/distance measurements from Type Ia SNe, baryon acoustic oscillation, WMAP5, and H(z) data, we fit the growth index parameter to current growth factor data and obtain {gamma}{sub {lambda}}({omega}{sub k}{ne}0)=0.65{sub -0.15}{sup +0.17} and {gamma}{sub DGP}({omega}{sub k}{ne}0)=0.53{sub -0.12}{sup +0.14}. For the {lambda}CDM model, the 1-{sigma} observational bounds are found consistent with theoretical value, unlike the case for the Dvali-Gabadadze-Porrati model. We also find that the current data we used is not enough to put significant constraints when the 3 parameters in f{sub a} are fit simultaneously. Importantly, we find that, in the presence of curvature, the analytical expression proposed for f{sub a} provides a better fit to the growth factor than other forms and should be useful for future high precision missions and studies.

Gong Yungui; Ishak, Mustapha; Wang Anzhong [College of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China) and Kavli Institute for Theoretical Physics China, CAS, Beijing 100190 (China); Department of Physics, University of Texas at Dallas, Richardson, Texas 75083 (United States); CASPER, Physics Department, Baylor University, Waco, Texas 76798 (United States)

2009-07-15

23

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 toxin–immunity 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

24

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

E-print Network

Surface Growth of a Motile Bacterial Population Resembles Growth in a Chemostat Daniel A. Koster, that is similar to bacterial growth in a chemostat predicts that the fraction of the population lagging behind in space in terms of their gene expression and growth.5,7,8 Bacterial colonies on hard surfaces typically

25

Bounds on bacterial cell growth rates  

E-print Network

Recent experiments have shown that rod-like bacteria in nutrient-rich media grow in length at an exponential rate. Here, I point out that it is the elongated shape of these bacteria that allows for this behavior. Further, I show that when a bacterium's growth is limited by some nutrient -- taken in by the cell through a diffusion-to-capture process -- its growth is suppressed: In three-dimensional geometries, the length $L$ is bounded by $\\log L \\lesssim t^{1/2}$, while in two dimensions the length is bounded by a power-law form. Fits of experimental growth curves to these predicted, sub-exponential forms could allow for direct measures of quantities relating to cellular metabolic rates.

Landy, Jonathan

2013-01-01

26

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

27

Menaquinone Analogs Inhibit Growth of Bacterial Pathogens  

PubMed Central

Gram-positive bacteria cause serious human illnesses through combinations of cell surface and secreted virulence factors. We initiated studies with four of these organisms to develop novel topical antibacterial agents that interfere with growth and exotoxin production, focusing on menaquinone analogs. Menadione, 1,4-naphthoquinone, and coenzymes Q1 to Q3 but not menaquinone, phylloquinone, or coenzyme Q10 inhibited the growth and to a greater extent exotoxin production of Staphylococcus aureus, Bacillus anthracis, Streptococcus pyogenes, and Streptococcus agalactiae at concentrations of 10 to 200 ?g/ml. Coenzyme Q1 reduced the ability of S. aureus to cause toxic shock syndrome in a rabbit model, inhibited the growth of four Gram-negative bacteria, and synergized with another antimicrobial agent, glycerol monolaurate, to inhibit S. aureus growth. The staphylococcal two-component system SrrA/B was shown to be an antibacterial target of coenzyme Q1. We hypothesize that menaquinone analogs both induce toxic reactive oxygen species and affect bacterial plasma membranes and biosynthetic machinery to interfere with two-component systems, respiration, and macromolecular synthesis. These compounds represent a novel class of potential topical therapeutic agents. PMID:23959313

Merriman, Joseph A.; Salgado-Pabón, Wilmara; Mueller, Elizabeth A.; Spaulding, Adam R.; Vu, Bao G.; Chuang-Smith, Olivia N.; Kohler, Petra L.; Kirby, John R.

2013-01-01

28

A METHOD FOR GROWTH CURVE COMPARISONS RUSSELL F. KAPPENMAN'  

E-print Network

of assessing growth variation of a species from envi- ronment to environment, area to area, or stratumA METHOD FOR GROWTH CURVE COMPARISONS RUSSELL F. KAPPENMAN' ABSTRACT Suppose one has a sample ofthe growth curves associated with the populations are assumed to be specified but each form contains

29

Genetic Screening for Bacterial Mutants in Liquid Growth Media By Fluorescence-Activated Cell Sorting  

PubMed Central

Many bacterial pathogens have defined in vitro virulence inducing conditions in liquid media which lead to production of virulence factors important during an infection. Identifying mutants that no longer respond to virulence inducing conditions will increase our understanding of bacterial pathogenesis. However, traditional genetic screens require growth on solid media. Bacteria in a single colony are in every phase of the growth curve, which complicates the analysis and make screens for growth phase-specific mutants problematic. Here, we utilize fluorescence-activated cell sorting in conjunction with random transposon mutagenesis to isolate bacteria grown in liquid media that are defective in virulence activation. This method permits analysis of an entire bacterial population in real time and selection of individual bacterial mutants with the desired gene expression profile at any time point after induction. We have used this method to identify Vibrio cholerae mutants defective in virulence induction. PMID:21094189

Abuaita, Basel H.; Withey, Jeffrey H.

2010-01-01

30

Descriptive and Predictive Growth Curves in Energy System Analysis  

Microsoft Academic Search

This study reviews a variety of growth curve models and the theoretical frameworks that lay behind them. In many systems,\\u000a growth patterns are, or must, ultimately be subjected to some form of limitation. A number of curve models have been developed\\u000a to describe and predict such behaviours. Symmetric growth curves have frequently been used for forecasting fossil fuel production,\\u000a but

Mikael Höök; Junchen Li; Noriaki Oba; Simon Snowden

2011-01-01

31

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 ...

32

`Growth of bacterial cultures' 50 years on: towards an uncertainty principle instead of constants in bacterial growth kinetics  

Microsoft Academic Search

Ever since Monod's efforts to study bacterial cultures in quantitative terms, the growth of Escherichia coli on sugars like glucose has appeared an attractive subject for the mathematical description of nutrient conversion into biomass. But instead of simplicity, it is becoming evident that bacterial adaptations affect `constants' such as Ks (growth affinity constant) and are, in turn, a complex function

Thomas Ferenci

1999-01-01

33

BACTERIAL GROWTH EFFICIENCY IN NATURAL AQUATIC SYSTEMS  

Microsoft Academic Search

Heterotrophic bacteria perform two major functions in the transformation of or- ganic matter: They produce new bacterial biomass (bacterial secondary produc- tion (BP)), and they respire organic C to inorganic C (bacterial respiration (BR)). For planktonic bacteria, a great deal has been learned about BP and its regulation during the past several decades but far less has been learned about

Paul A. del Giorgio; Jonathan J. Cole

1998-01-01

34

Regime Switching in the Latent Growth Curve Mixture Model  

ERIC Educational Resources Information Center

A linear latent growth curve mixture model is presented which includes switching between growth curves. Switching is accommodated by means of a Markov transition model. The model is formulated with switching as a highly constrained multivariate mixture model and is fitted using the freely available Mx program. The model is illustrated by analyzing…

Dolan, Conor V.; Schmittmann, Verena D.; Lubke, Gitta H.; Neale, Michael C.

2005-01-01

35

Evaluating Latent Growth Curve Models Using Individual Fit Statistics  

ERIC Educational Resources Information Center

The usefulness of assessing individual fit in latent growth curve models was examined. The study used simulated data based on an unconditional and a conditional latent growth curve model with a linear component and a small quadratic component and a linear model was fit to the data. Then the overall fit of linear and quadratic models to these data…

Coffman, Donna L.; Millsap, Roger E.

2006-01-01

36

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

37

Estimating Bacterial Growth Parameters by Means of Detection Times  

Microsoft Academic Search

We developed a new numerical method to estimate bacterial growth parameters by means of detection times generated by different initial counts. The observed detection times are subjected to a transformation involving the (unknown) maximum specific growth rate and the (known) ratios between the different inoculum sizes and the constant detectable level of counts. We present an analysis of variance (ANOVA)

JOZSEF BARANYI; CARMEN PIN

1999-01-01

38

Growth curve for girls with Turner syndrome  

Microsoft Academic Search

A growth chart for girls with Turner syndrome has been prepared using data from four published series of European patients, and evaluated using retrospective data on the heights of girls with Turner syndrome seen at this hospital. The results indicate that calculation of height standard deviation score from this chart allows a reasonable prediction of adult stature in any patient

A J Lyon; M A Preece; D B Grant

1985-01-01

39

Modeling growth curves to track growing obesity  

Technology Transfer Automated Retrieval System (TEKTRAN)

Our purpose was to examine the relationship between total physical activity (PA) and PA at various intensity levels with insulin resistance at increasing waist circumference and skinfold thickness levels. Being able to describe growth appropriately and succinctly is important in many nutrition and p...

40

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

41

Curved anaerobic bacteria in bacterial (nonspecific) vaginosis and their response to antimicrobial therapy.  

PubMed

Vaginal fluid samples from normal college students, college students with bacterial (nonspecific) vaginosis, and sexually transmitted disease clinic patients with bacterial vaginosis, before and after therapy with metronidazole, ampicillin, or amoxicillin, were evaluated by direct Gram stain and culture for the predominant anaerobic and facultative flora. Curved rods were detected by direct Gram stain of vaginal fluid from 31 (51%) of 61 women with bacterial vaginosis and none of 42 normal student controls (P less than 0.001). Curved, gram-variable to gram-negative organisms were recovered from six of these 31 women, seven other women with bacterial vaginosis, and no controls. All 13 isolates were anaerobic, motile, and oxidase-negative, produced succinic acid as their major metabolic product, and hydrolyzed starch. After treatment with ampicillin or amoxicillin (n = 10) or greater than or equal to 2 g of metronidazole (n = 9), no curved motile rods were detected by Gram stain or culture, although the minimal inhibitory concentration of metronidazole was greater than or equal 8 micrograms/ml for 11 of the 13 isolates tested. PMID:6631073

Spiegel, C A; Eschenbach, D A; Amsel, R; Holmes, K K

1983-11-01

42

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 of bacterial growth phase on monomethyl mercury (MMHg) production by D. desulfuricans ND132. At late on bacterial MMHg production in natural systems. #12;Bacterial Growth Phase Influences Methylmercury Production

43

R-Curve Instability Calculations Of Crack Growth  

NASA Technical Reports Server (NTRS)

Report discusses use of instability method of calculation and R-curve mathematical models to analyze growth of cracks in fracture-mechanics specimens. In case of single material and structure, such analysis sometimes simple enough to be done on pocket calculator. Where microcomputer or larger computer available, comprehensive program includes libraries of driving-force equations for various configurations and R-curve mathematical models for different materials. Author concludes instability method simple and effective and model equations studied all viable in sense at lease one of them should fit almost any applicable set of crack-growth data. Method and models constitute powerful mathematical tools for analysis of fractures.

Orange, Thomas W.

1989-01-01

44

Bayesian Inference and Application of Robust Growth Curve Models Using Student's "t" Distribution  

ERIC Educational Resources Information Center

Despite the widespread popularity of growth curve analysis, few studies have investigated robust growth curve models. In this article, the "t" distribution is applied to model heavy-tailed data and contaminated normal data with outliers for growth curve analysis. The derived robust growth curve models are estimated through Bayesian…

Zhang, Zhiyong; Lai, Keke; Lu, Zhenqiu; Tong, Xin

2013-01-01

45

[Bacterial phagelysates and malignant tumor growth].  

PubMed

Anti-tumor preventive efficacy of E.coli phagelysate has been studied. Investigations were conducted on 2-3 months 48 male mice. Regimen of preventive vaccinations were: single - 0,25 ml phagelysate intraperitoneal injection, 3 days before Ehrlich carcinoma inoculation (1x10(6) tumor cells); 3 times vaccinations (0,25 ml, with 3 day intervals) 3, 6, and 9 days before inoculation of carcinoma; and 10 times (during 10 days, before inoculation of carcinoma). Treatment efficacy was evaluated according to the indices of cancer growth (development of cancer tissue, cancer growth inhibition percent, lifespan and survival percent). Experiments have shown that single and 3 times preventive vaccinations inhibited tumor development and delayed malignant growth, while, 10 times permanent vaccinations had no effects on cancer growth. Cancer growth inhibition percent in single and 3 times vaccinated animals were 58% on the average. Maximal lifespan in control group mice consisted 59 days. By the 125th day of cancer growth, at single vaccination 17% of mice were alive, while in 3 times vaccinated mice the survival percent was 25%. Anti-tumor potential of E.coli pagelysate supposedly could be explained by immunoregulatory properties of the preparation. PMID:24743131

Gambashidze, K; Bejitashvili, N; Azaladze, T; Pkhaladze, M; Azaladze, A

2014-03-01

46

Theoretical Population Biology 69 (2006) 181191 The ideal free distribution and bacterial growth on two substrates  

E-print Network

Theoretical Population Biology 69 (2006) 181­191 The ideal free distribution and bacterial growth population growth rate. For batch bacterial growth, the model predicts that as the concentration is good. For bacterial growth in the chemostat, the model predicts that at low dilution rates bacteria

Krivan, Vlastimil

47

Tracking bacterial growth in liquid media and a new bacterial life model  

Microsoft Academic Search

By increasing viscosity of liquid media above 8.4 centipoise (cp) i.e. 0.084 g· cm-1 · s-1, individual growth and family formation ofEscherichia coli was continuously observed in real-time for up to 6 h. The observations showed primarily unidirectional growth and reproduction\\u000a ofE. coli and suggested more than one reproduction in the observed portion ofE. coli life span. A new bacterial

Shi Liu

1999-01-01

48

Genomic growth curves of an outbred pig population  

PubMed Central

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 Silvério; Duarte, Darlene Ana S.; Lopes, Paulo Sávio; Brustolini, Otávio J.B.; Thus, Sander; Viana, José Marcelo S.; Guimarães, Simone E.F.

2013-01-01

49

Adaptive identification and control algorithms for nonlinear bacterial growth systems  

Microsoft Academic Search

This paper suggests how nonlinear adaptive control of nonlinear bacterial growth systems could be performed. The process is described by a time-varying nonlinear model obtained from material balance equations. Two different control problems are considered: substrate concentration control and production rate control. For each of these cases, an adaptive minimum variance control algorithm is proposed and its effectiveness is shown

D. DOCHAINt; G. BASTIN

1984-01-01

50

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

51

Predicting Change in Postpartum Depression: An Individual Growth Curve Approach.  

ERIC Educational Resources Information Center

Recently, methodologists interested in examining problems associated with measuring change have suggested that developmental researchers should focus upon assessing change at both intra-individual and inter-individual levels. This study used an application of individual growth curve analysis to the problem of maternal postpartum depression.…

Buchanan, Trey

52

A SAS Macro for Estimating and Visualizing Individual Growth Curves  

ERIC Educational Resources Information Center

Longitudinal data analyses can be usefully supplemented by the plotting of individual growth curves. Unfortunately, such graphics can be challenging and tedious to produce. This article presents and demonstrates a SAS macro designed to automate this task. The OLStraj macro graphically depicts ordinary least squares (OLS)-estimated individual…

Carrig, Madeline M.; Wirth, R. J.; Curran, Patrick J.

2004-01-01

53

Analysis of Microtubule Dynamics Using Growth Curve Models  

E-print Network

, providing structural support as well as taking part in many of the cellular processes. A large body of data isoforms of a protein tau on micro- tubule dynamics using growth curve models. The results show of 3-repeat tau protein has a similar effect as a 4-repeat tau protein on microtubule dynamics

Jammalamadaka, S. Rao

54

Diagnostics of Robust Growth Curve Modeling Using Student's "t" Distribution  

ERIC Educational Resources Information Center

Growth curve models with different types of distributions of random effects and of intraindividual measurement errors for robust analysis are compared. After demonstrating the influence of distribution specification on parameter estimation, 3 methods for diagnosing the distributions for both random effects and intraindividual measurement errors…

Tong, Xin; Zhang, Zhiyong

2012-01-01

55

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

56

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

57

Bacterial growth on 1,2-dichloroethane  

Microsoft Academic Search

Summary 1,2-Dichloroethane (5 mM) served as the only carbon and energy source for bacterium DE2, a gramnegative, oxidase-positive, motile rod. The specific growth rate ? of strain DE2 on 1,2-dichloroethane was 0.08 h?1. A NAD-dependent 2-chloroacetaldehyde dehydrogenase activity and a 2-chloroacetate halidohydrolase activity were detected in extracts of cells grown on 1,2-dichloroethane.

G. Stucki; U. Krebser; T. Leisinger

1983-01-01

58

Cooperative Bacterial Growth Dynamics Predict the Evolution of Antibiotic Resistance  

NASA Astrophysics Data System (ADS)

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 show that bacterial growth in beta-lactam antibiotics is cooperative and that the nature of this growth determines the conditions in which resistance evolves. Quantitative analysis of the growth dynamics predicts a peak in selection at very low antibiotic concentrations; competition between strains confirms this prediction. We also find significant selection at higher antibiotic concentrations, close to the minimum inhibitory concentrations of the strains. Our results argue that an understanding of the evolutionary forces that lead to antibiotic resistance requires a quantitative understanding of the evolution of cooperation in bacteria.

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

2011-03-01

59

Bacterial and fungal growth in total parenteral nutrition solutions,.  

PubMed

The most serious complication of prolonged intravenous infusion of hypertonic dextrose and amino acids is infection. Frequently, the etiology is fungal rather than bacterial. Previous authors have suggested that bacterial survival and growth in the solutions is suppressed by (a) high dextrose concentration, (b) high osmolality, or (c) low pH. This paper presents evidence that proposals (a) and (b) are untenable and (c) is only partly responsible. We call attention to the presence of a factor that is antibacterial but not antifungal; namely, a high concentration of glycine. PMID:2102

Failla, M L; Benedict, C D; Weinberg, E D

1975-01-01

60

Bacterial Growth Classification with Support Vector Machines: A Comparative Emad A. El-Sebakhy  

E-print Network

Bacterial Growth Classification with Support Vector Machines: A Comparative Study Emad A. El@ccse.kfupm.edu.sa Abstract In this paper, we propose to use support vector machines for classification of bacterial growth. Keywords: Bacterial growth; Logistic regression; Support Vector Machines; K-nearest neighbors

Faisal, Kanaan Abed

61

Microb Ecol (1989) 18 :29-44 Rapid Bacterial Growth in the Hindgut of a  

E-print Network

Microb Ecol (1989) 18 :29-44 Rapid Bacterial Growth in the Hindgut of a Marine Deposit Feeder Craig slightly greater (66 min) for all ingested bacteria that survive midgut digestion . These bacterial growth that hindgut bacterial growth, though of little immediate impor- tance in the energetics of the animals, may

Jumars, Pete

62

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. Identifica- tion of bacterial chemical messengers that trigger growth pro- motion has been limited in part- nents in plant­bacterial systems now can follow. Here, we present chemical and plant-growth data showing

Paré, Paul W.

63

Morphology, Growth, and Size Limit of Bacterial Cells Hongyuan Jiang1  

E-print Network

Morphology, Growth, and Size Limit of Bacterial Cells Hongyuan Jiang1 and Sean X. Sun1,2 1 a general mechanochemical model of the growing bacterial cell wall, which shows explicitly how growth and shape are coupled together to determine the growth velocity and the bacteria size. The bacterial cell

Sun, Sean

64

Both rate and extent of bacterial growth from 8h onwards ranked  

E-print Network

Both rate and extent of bacterial growth from 8h onwards ranked S>P>M>CW (P growth. Addition of starch promoted a higher bacterial growth than pectin, but the latter enhanced- duced specific fibrolytic enzymatic activ- ity, but total activity was increased by a higher bacterial

Paris-Sud XI, Université de

65

RESEARCH ARTICLE Open Access The last generation of bacterial growth in limiting  

E-print Network

RESEARCH ARTICLE Open Access The last generation of bacterial growth in limiting nutrient Anat Bren , Yuval Hart , Erez Dekel, Daniel Koster and Uri Alon* Abstract Background: Bacterial growth as a function conditions. Here, we address this challenge by means of a robotic assay and measure bacterial growth rate

66

Stimulation of Alexandrium fundyense growth by bacterial assemblages from the Bay of Fundy  

E-print Network

Stimulation of Alexandrium fundyense growth by bacterial assemblages from the Bay of Fundy M on Alexandrium fundyense str. CB301 growth. Methods and Results: Bacterial assemblages were collected from into axenic CB301 cultures. Bacterial assemblages dramatically enhanced CB301 growth. Retrieval and analysis

Rooney-Varga, Juliette N.

67

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

68

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

69

VIRULENCE OF BRUCELLA : BACTERIAL GROWTH AND DECLINE IN MICE M PLOMMET AM PLOMMET  

E-print Network

Short note VIRULENCE OF BRUCELLA : BACTERIAL GROWTH AND DECLINE IN MICE M PLOMMET AM PLOMMET organs, liver, spleen, lungs and lymph nodes occurs followed by bacterial growth or decay. Growth may go evolving in three pha- ses, growth, decrease and plateau, whereas vacci- nal strain 19 differed in three

Boyer, Edmond

70

Morphological instability and dynamics of fronts in bacterial growth models with nonlinear diffusion  

E-print Network

Morphological instability and dynamics of fronts in bacterial growth models with nonlinear the growth of bacterial colonies under different growth conditions has been the focus of attention of several Leiden, The Netherlands Received 26 November 2001; published 28 June 2002 Depending on the growth

van Saarloos, Wim

71

Avian Incubation Inhibits Growth and Diversification of Bacterial Assemblages on Eggs  

E-print Network

Avian Incubation Inhibits Growth and Diversification of Bacterial Assemblages on Eggs Matthew D (2009) Avian Incubation Inhibits Growth and Diversification of Bacterial Assemblages on Eggs. PLoS ONE 4 by limiting microbial growth of pathogenic bacteria on eggshells, while enhancing growth of commensal

Beissinger, Steven R.

72

Gyramides Prevent Bacterial Growth by Inhibiting DNA Gyrase and Altering Chromosome Topology  

E-print Network

Gyramides Prevent Bacterial Growth by Inhibiting DNA Gyrase and Altering Chromosome Topology that the gyramides prevent bacterial growth by a mechanism in which the topological state of chromosomes is altered-century, and the emergence of bacterial resistance has fueled the search for new gyrase inhibitors. In this paper we

Weibel, Douglas B.

73

Bacterial growth laws reflect the evolutionary importance of energy efficiency  

PubMed Central

We are interested in the balance of energy and protein synthesis in bacterial growth. How has evolution optimized this balance? We describe an analytical model that leverages extensive literature data on growth laws to infer the underlying fitness landscape and to draw inferences about what evolution has optimized in Escherichia coli. Is E. coli optimized for growth speed, energy efficiency, or some other property? Experimental data show that at its replication speed limit, E. coli produces about four mass equivalents of nonribosomal proteins for every mass equivalent of ribosomes. This ratio can be explained if the cell’s fitness function is the the energy efficiency of cells under fast growth conditions, indicating a tradeoff between the high energy costs of ribosomes under fast growth and the high energy costs of turning over nonribosomal proteins under slow growth. This model gives insight into some of the complex nonlinear relationships between energy utilization and ribosomal and nonribosomal production as a function of cell growth conditions. PMID:25548180

Maitra, Arijit; Dill, Ken A.

2015-01-01

74

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

75

Influence of Polyelectrolyte Film Stiffness on Bacterial Growth  

PubMed Central

Photo-crosslinkable polyelectrolyte films whose nanomechanical properties can be varied under UV light illumination, were prepared from poly(L-lysine) (PLL) and a hyaluronan derivative modified with photoreactive vinylbenzyl groups (HAVB). The adhesion and the growth of two model bacteria, namely Escherichia coli and Lactococcus lactis, were studied on non-crosslinked and crosslinked films to investigate how the film stiffness influences the bacterial behavior. While the Gram positive L. lactis was shown to grow slowly on both films, independently of their rigidity, the Gram negative E. coli exhibited a more rapid growth on non-crosslinked softer films compared to the stiffer ones. Experiments performed on photo-patterned films showing both soft and stiff regions, confirmed a faster development of E. coli colonies on softer regions. Interestingly, this behavior is opposite to the one reported before for mammalian cells. Therefore, the photo-crosslinked (PLL/HAVB) films are interesting coatings for tissue engineering since they promote the growth of mammalian cells while limiting the bacterial colonization. PMID:23289403

Saha, Naresh; Monge, Claire; Dulong, Virginie; Picart, Catherine; Glinel, Karine

2015-01-01

76

Regulation of Bacterial Growth Rates by Dissolved Organic Carbon and Temperature in the Equatorial Pacific Ocean  

Microsoft Academic Search

The effect of dissolved organic matter (DOM) and temperature on bacterial production was examined in the equatorial Pacific\\u000a Ocean. Addition of glucose, glucose plus ammonium, or free amino acids stimulated bacterial production ([3H]thymidine incorporation), whereas changes in bacterial abundance were either negligible or much less than changes in bacterial\\u000a production. The average bacterial growth rate also greatly increased following DOM

D. L. Kirchman; J. H. Rich

1997-01-01

77

Inhibition of bacterial growth under composite restorations following GLUMA pretreatment.  

PubMed

The purpose of this investigation was to test in five adult monkeys the effects of a glutaraldehyde-containing dentin bonding agent, GLUMA, on bacterial colonization in Class V cavities restored with composite resin. Experimental groups consisted of immediate placement of GLUMA and composite resin as well as placement of GLUMA or Scotchbond (control) in acid-etched cavities that had been left open to the oral environment for 48 hours. Various procedures for pretreatment of the cavities were included. Tissue specimens were prepared for light microscopy for observation of bacterial presence and pulp tissue reactions after eight days and 90 days. Bacteria were not detected in any of the 54 cavities treated with GLUMA regardless of observation period or use of enamel-etching procedure prior to placement of composite resin. When cavities were restored with composite resin without prior GLUMA pretreatment or with Scotchbond, bacteria were present under the majority of restorations at both time intervals. Pulpal inflammation of varying extent and character was seen after eight days in teeth that had been previously infected. At 90 days, pulps showed repair and healing regardless of treatment protocol. Data indicate that GLUMA has a distinct in vivo antibacterial effect that seems to prevent bacterial growth in tooth/restoration interfaces. PMID:2493491

Felton, D; Bergenholtz, G; Cox, C F

1989-03-01

78

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

79

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.

Amir, Ariel

2012-01-01

80

The role of hydrolases in bacterial cell-wall growth.  

PubMed

Although hydrolysis is known to be as important as synthesis in the growth and development of the bacterial cell wall, the coupling between these processes is not well understood. Bond cleavage can generate deleterious pores, but may also be required for the incorporation of new material and for the expansion of the wall, highlighting the importance of mechanical forces in interpreting the consequences of hydrolysis in models of growth. Critically, minimal essential subsets of hydrolases have now been identified in several model organisms, enabling the reduction of genetic complexity. Recent studies in Bacillus subtilis have provided evidence for both the presence and absence of coupling between synthesis and hydrolysis during sporulation and elongation, respectively. In this review, we discuss strategies for dissecting the relationship between synthesis and hydrolysis using time-lapse imaging, biophysical measurements of cell-wall architecture, and computational modeling. PMID:24035761

Lee, Timothy K; Huang, Kerwyn Casey

2013-12-01

81

Scaling laws governing stochastic growth and division of single bacterial cells  

E-print Network

Scaling laws governing stochastic growth and division of single bacterial cells Srividya Iyer | Arrhenius law Quantitative studies of bacterial growth and division initiated the molecular biology that govern the growth and division of single cells remains a major challenge. Using a unique combination

Scherer, Norbert F.

82

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

E-print Network

Tetracycline Resistance Gene Maintenance under Varying Bacterial Growth Rate, Substrate and Oxygen, bacterial growth rate, and medium richness affect the maintenance of plasmid-borne TC resistance (Tet. aeruginosa in the absence of TC, and faster loss was observed in continuous culture at higher growth rates

Alvarez, Pedro J.

83

Bacterial Growth on Surfaces: Automated Image Analysis for Quantification of Growth Rate-Related Parameters  

Microsoft Academic Search

A fast routine method for estimating bacterial cell growth rates by using the metachromatic dye acridine orange is described. The method allows simultaneous estimates of cellular RNA and DNA contents of single cells. Acridine orange staining can be used as a nonspecific supplement to quantitative species-specific hybridizationswithfluorescence-labelledribosomalprobestoestimatethesingle-cellconcentrationofRNA.By automated analysis of digitized images of stained cells, we determined four independent growth

SØREN MØLLER; CLAUS S. KRISTENSEN; LARS K. POULSEN; JENS M. CARSTENSEN; ANDSØREN MOLIN

1995-01-01

84

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

85

Incorporating Student Mobility in Achievement Growth Modeling: A Cross-Classified Multiple Membership Growth Curve Model  

ERIC Educational Resources Information Center

Multiple membership random effects models (MMREMs) have been developed for use in situations where individuals are members of multiple higher level organizational units. Despite their availability and the frequency with which multiple membership structures are encountered, no studies have extended the MMREM approach to hierarchical growth curve…

Grady, Matthew W.; Beretvas, S. Natasha

2010-01-01

86

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

87

Dynamic Laser-Light Scattering Study on Bacterial Growth  

NASA Astrophysics Data System (ADS)

The motility changes in growing bacteria in a culture medium were observed with a dynamic light-scattering technique used to analyse the frequency spectrum of the scattered light intensity. Two typical enterobacteriaceae, E. coil and P. morganii, were examined, and the change in the velocity distribution of the bacteria with time was analysed using the observed spectrum. The distribution pattern was found to change from a Gaussian-type to a Saclay-type with time, and the mean speed of the bacteria had a maximum value at around the turning point of the growth curve.

Miike, Hidetoshi; Hideshima, Masao; Hashimoto, Hajime; Ebina, Yoshio

1984-08-01

88

The Biasing Effects of Unmodeled ARMA Time Series Processes on Latent Growth Curve Model Estimates  

ERIC Educational Resources Information Center

The purpose of this study was to evaluate the robustness of estimated growth curve models when there is stationary autocorrelation among manifest variable errors. The results suggest that when, in practice, growth curve models are fitted to longitudinal data, alternative rival hypotheses to consider would include growth models that also specify…

Sivo, Stephen; Fan, Xitao; Witta, Lea

2005-01-01

89

Silver Nanoparticles Part 2: BDo Silver Nanoparticles Inhibit Bacterial Growth?  

NSDL National Science Digital Library

The NACK Center is an organization committed to supporting two â??year degree programs in micro and nanotechnology. The center offers online educational material for curriculum enhancement in this subject field. One of these resources is a lab documentation focusing on the topic of silver nanoparticles. The lab "may be used with a middle school through high school biology class.â? The lesson includes objectives, sample solution preparations, and sample data and calculations. Overall, the objectives of this lesson are to practice aseptic techniques to inoculate/grow bacteria and describe the impact of silver nanoparticles on bacterial growth. The site requires a free log-in for access to the material.

90

Effects of sevoflurane and\\/or nitrous oxide on bacterial growth in in vitro culture conditions  

Microsoft Academic Search

The aim of this study was to determine the role of sevoflurane and\\/or nitrous oxide on bacterial growth under conditions in\\u000a vitro similar to those of clinical practice. We assessed these effects on Pseudomonas aeruginosa, Acinetobacter lwoffii, and Staphylococcus aureus growth. Bacterial inoculums were prepared from reference strains in nutritive broth. Airtight chambers were filled with bacterial\\u000a suspensions. Each strain

Lale Karabiyik; Hülya Türkan; Tahir Öz???k; Mehmet Ali Saraçli; Tuncer Haznedaro?lu

2007-01-01

91

Accumulation of mutants in ``aging'' bacterial colonies is due to growth under selection,  

E-print Network

Accumulation of mutants in ``aging'' bacterial colonies is due to growth under selection (sent for review April 25, 2008) Several bacterial systems show behavior interpreted as evidence in cell populations that ``age'' on solid medium with little net growth. Mutant accumulation was initially

California at Davis, University of

92

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

93

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

94

Analysis of cholera epidemics with bacterial growth and spatial movement.  

PubMed

In this work, we propose novel epidemic models (named, susceptible-infected-recovered-susceptible-bacteria) for cholera dynamics by incorporating a general formulation of bacteria growth and spatial variation. In the first part, a generalized ordinary differential equation (ODE) model is presented and it is found that bacterial growth contributes to the increase in the basic reproduction number, [Formula: see text]. With the derived basic reproduction number, we analyse the local and global dynamics of the model. Particularly, we give a rigorous proof on the endemic global stability by employing the geometric approach. In the second part, we extend the ODE model to a partial differential equation (PDE) model with the inclusion of diffusion to capture the movement of human hosts and bacteria in a heterogeneous environment. The disease threshold of this PDE model is studied again by using the basic reproduction number. The results on the threshold dynamics of the ODE and PDE models are compared, and verified through numerical simulation. Additionally, our analysis shows that incorporating diffusive spatial spread does not produce a Turing instability when [Formula: see text] associated with the ODE model is less than the unity. PMID:25363286

Wang, Xueying; Wang, Jin

2014-11-01

95

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

96

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

97

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 33°C, 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

98

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

99

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.; Fröls, Sabrina; Pfeifer, Felicitas; Peters, Anna; Hays, John P.

2013-01-01

100

The papain inhibitor (SPI) of Streptomyces mobaraensis inhibits bacterial cysteine proteases and is an antagonist of bacterial growth.  

PubMed

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; Fröls, Sabrina; Pfeifer, Felicitas; Peters, Anna; Hays, John P; Fuchsbauer, Hans-Lothar

2013-07-01

101

Temporal Variation of Bacterial Respiration and Growth Efficiency in Tropical Coastal Waters ?  

PubMed Central

We investigated the temporal variation of bacterial production, respiration, and growth efficiency in the tropical coastal waters of Peninsular Malaysia. We selected five stations including two estuaries and three coastal water stations. The temperature was relatively stable (averaging around 29.5°C), whereas salinity was more variable in the estuaries. We also measured dissolved organic carbon and nitrogen (DOC and DON, respectively) concentrations. DOC generally ranged from 100 to 900 ?M, whereas DON ranged from 0 to 32 ?M. Bacterial respiration ranged from 0.5 to 3.2 ?M O2 h?1, whereas bacterial production ranged from 0.05 to 0.51 ?M C h?1. Bacterial growth efficiency was calculated as bacterial production/(bacterial production + respiration), and ranged from 0.02 to 0.40. Multiple correlation analyses revealed that bacterial production was dependent upon primary production (r2 = 0.169, df = 31, and P < 0.02) whereas bacterial respiration was dependent upon both substrate quality (i.e., DOC/DON ratio) (r2 = 0.137, df = 32, and P = 0.03) and temperature (r2 = 0.113, df = 36, and P = 0.04). Substrate quality was the most important factor (r2 = 0.119, df = 33, and P = 0.04) for the regulation of bacterial growth efficiency. Using bacterial growth efficiency values, the average bacterial carbon demand calculated was from 5.30 to 11.28 ?M C h?1. When the bacterial carbon demand was compared with primary productivity, we found that net heterotrophy was established at only two stations. The ratio of bacterial carbon demand to net primary production correlated significantly with bacterial growth efficiency (r2 = 0.341, df = 35, and P < 0.001). From nonlinear regression analysis, we found that net heterotrophy was established when bacterial growth efficiency was <0.08. Our study showed the extent of net heterotrophy in these waters and illustrated the importance of heterotrophic microbial processes in coastal aquatic food webs. PMID:19820145

Lee, Choon Weng; Bong, Chui Wei; Hii, Yii Siang

2009-01-01

102

Regulation of planktonic bacterial growth rates: The effects of temperature and resources  

Microsoft Academic Search

We examined the potential limitation of bacterial growth by temperature and nutrients in a eutrophic lake. Dilution cultures from winter and summer were incubated at both high (>20°C) and low (4°C) temperatures and enriched with various combinations of organic carbon (C), inorganic nitrogen (N), and inorganic phosphorus (P). Bacterial abundance, 3H-thymidine incorporation, and 3H-leucine incorporation were measured over the growth

M. Felip; M. L. Pace; J. J. Cole

1996-01-01

103

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

E-print Network

COULTER COUNTER DETERMINATION OF BACTERIAL GROWTH AND CELLULAR SIZE CHANGE FOLLOWING Co GAMMA IRRADIATION A Thesis by GARY W. GASTON Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement... for the degree of MASTER OF SCIENCE December 1976 Ma)or Subject: Biophysics COULTER COUNTER DETERMINATION OF BACTERIAL GROWTH AND CELLULAR SIZE CHANGE FOLLOWING Co GAMMA IRRADIATION A Thesis by GARY W. GASTON APPROVED as to style and content by: ead...

Gaston, Gary W

1976-01-01

104

A unique crack growth rate curve method for fatigue life prediction of steel structures  

Microsoft Academic Search

In this paper, a unique crack growth rate curve method, which is based on the equivalent stress intensity factor range (ESIFR) as the driving force, has been proposed and examined with crack growth rate data of base metals and as welded joints of some structural steels under constant amplitude external loading. By expressing the crack growth rate data with ESIFR

Xiaoping Huang; Torgeir Moan; Weicheng Cui

2009-01-01

105

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

106

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

107

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

E-print Network

was that the ectomycorrhizosphere effect on the bacterial community was not root-growth-dependent. The impacts of ecto- mycorrhizal growth were examined on (1) the structure of bacterial community and (2) fluorescent pseudomonadMicrobial Ecology Soil Bacterial Diversity Responses to Root Colonization by an Ectomycorrhizal

Thioulouse, Jean

108

Selecting a Linear Mixed Model for Longitudinal Data: Repeated Measures Analysis of Variance, Covariance Pattern Model, and Growth Curve Approaches  

Microsoft Academic Search

With increasing popularity, growth curve modeling is more and more often considered as the 1st choice for analyzing longitudinal data. Although the growth curve approach is often a good choice, other modeling strategies may more directly answer questions of interest. It is common to see researchers fit growth curve models without considering alterative modeling strategies. In this article we compare

Siwei Liu; Michael J. Rovine; Peter C. M. Molenaar

2012-01-01

109

On the growth-curve method for calibrating stellar photometry with CCDs  

NASA Astrophysics Data System (ADS)

Stellar photometry with CCDs usually relies on the construction of aperture growth curves for its ultimate calibration. In the past this has been a tedious chore requiring a great deal of human intervention, mostly to select data suitable for defining empirical growth curves from data sets containing some corrupt values. A computer program has been written which incorporates a priori knowledge of the typical morphology of stellar profiles and is capable of taking a synoptic overview of all the aperture growth curves from an entire night or observing run. The program is thus enabled to make its own judgments as to the reliability of individual data points and to draw physically reasonable growth curves without human supervision, even for individual frames with insufficient or badly contaminated data. The program runs quickly and independently and produces results not noticeably inferior to those obtained by traditional hand-and-eye methods.

Stetson, Peter B.

1990-08-01

110

Revealing bacterial targets of growth inhibitors encoded by bacteriophage T7.  

PubMed

Today's arsenal of antibiotics is ineffective against some emerging strains of antibiotic-resistant pathogens. Novel inhibitors of bacterial growth therefore need to be found. The target of such bacterial-growth inhibitors must be identified, and one way to achieve this is by locating mutations that suppress their inhibitory effect. Here, we identified five growth inhibitors encoded by T7 bacteriophage. High-throughput sequencing of genomic DNA of resistant bacterial mutants evolving against three of these inhibitors revealed unique mutations in three specific genes. We found that a nonessential host gene, ppiB, is required for growth inhibition by one bacteriophage inhibitor and another nonessential gene, pcnB, is required for growth inhibition by a different inhibitor. Notably, we found a previously unidentified growth inhibitor, gene product (Gp) 0.6, that interacts with the essential cytoskeleton protein MreB and inhibits its function. We further identified mutations in two distinct regions in the mreB gene that overcome this inhibition. Bacterial two-hybrid assay and accumulation of Gp0.6 only in MreB-expressing bacteria confirmed interaction of MreB and Gp0.6. Expression of Gp0.6 resulted in lemon-shaped bacteria followed by cell lysis, as previously reported for MreB inhibitors. The described approach may be extended for the identification of new growth inhibitors and their targets across bacterial species and in higher organisms. PMID:25512533

Molshanski-Mor, Shahar; Yosef, Ido; Kiro, Ruth; Edgar, Rotem; Manor, Miriam; Gershovits, Michael; Laserson, Mia; Pupko, Tal; Qimron, Udi

2014-12-30

111

Empirical growth curve estimation considering multiple seasonal compensatory growths of body weights in Japanese Thoroughbred colts and fillies.  

PubMed

Thoroughbred horses are seasonal mating animals, and their foals are born yearly in spring seasons. In northern regions or countries, the foals generally show a typical seasonal compensatory growth pattern, where their growth rate declines in winter and increases in the next spring. In this study, a new empirical approach is proposed to adjust for this compensatory growth when growth curve equations are estimated, by using BW of Japanese Thoroughbred colts and fillies raised in Hidaka, Hokkaido. Based on the traditional Richards growth curve equation, new growth curve equations were developed and fit to the weight-age data. The foals generally experience 2 major winter seasons before their debut in horseracing. The new equations had sigmoid subfunctions that can empirically adjust the first and second year compensatory growths, combined with the Richards biological parameter responsible for the maturity of animals. The unknown parameters included in the equations were estimated by SAS NLMIXED procedure. The goodness-of-fit was examined by using several indices of goodness-of-fit (i.e., Akaike's information criterion, Bayesian information criterion, -2 log likelihood, and residual sum of squares) for the multiple applications of the subfunctions. The indices indicated the best fit of the new equations including both subfunctions for the first and second compensatory growths to the weight-age data. The shapes of the growth curves were improved during the periods of compensatory growth. The proposed method is one of the useful approaches for adjusting multiple seasonal compensatory growths in growth curve estimations of Thoroughbreds and for the management of young horses during the compensatory periods. PMID:24085406

Onoda, T; Yamamoto, R; Sawamura, K; Inoue, Y; Murase, H; Nambo, Y; Tozaki, T; Matsui, A; Miyake, T; Hirai, N

2013-12-01

112

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

113

Growing Growth curves using PROC MIXED and PROC NLMIXED  

Technology Transfer Automated Retrieval System (TEKTRAN)

Being able to describe growth appropriately and succinctly is important in many contexts, including biology, epidemiology, and statistics. Various approaches are used varying from differential equations, deterministic modeling, and statistical approaches like regression. Often, with epidemiologic da...

114

Growth promotion of Prunus rootstocks by root treatment with specific bacterial strains  

Microsoft Academic Search

A collection of bacterial strains obtained from a wide-range origin was screened for ability to promote growth in two types of Prunus rootstocks in a commercial nursery. Only few strains promoted growth significantly and consistently, and a strong specificity for the rootstock cultivar was observed. Irrigation of plants with Pseudomonas fluorescens EPS282 and Pantoea agglomerans EPS427 significantly increased plant height

A. Bonaterra; L. Ruz; E. Badosa; J. Pinochet; E. Montesinos

2003-01-01

115

Microbial degradation of polycyclic aromatic hydrocarbons: effect of substrate availability on bacterial growth kinetics  

Microsoft Academic Search

It is demonstrated that bacterial growth on crystalline or adsorbed polycyclic aromatic hydrocarbons can result in a linear increase in biomass concentration. A simple mathematical approach is presented, showing that under these circumstances mass transfer from the solid phase to the liquid phase is rate-limiting for growth.

F. Volkering; A. M. Breure; A. Sterkenburg; J. G. van Andel

1992-01-01

116

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

PubMed Central

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.

1997-01-01

117

Monensin inhibits growth of bacterial contaminants from fuel ethanol plants  

Technology Transfer Automated Retrieval System (TEKTRAN)

Contamination of commercial fermentation cultures by lactic acid bacteria (LAB) is a common and costly problem to the fuel ethanol industry. Virginiamycin (VIR) and penicillin (PEN) are frequently used to control bacterial contamination but extensive use of antibiotics may select for strains with d...

118

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

Technology Transfer Automated Retrieval System (TEKTRAN)

The activity of blue light (470nm) alone on (1) bacterial viability, and (2) with a food grade photosensitizer on filamentous fungal viability, was studied. Suspensions of the bacteria Leuconostoc mesenteroides (LM), Bacillus atrophaeus (BA), and Pseudomonas aeruginosa (PA) were prepared and aliquo...

119

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.

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

2014-09-01

120

INFLUENCE OF PHOSPHATE CORROSION CONTROL COMPOUNDS ON BACTERIAL GROWTH  

EPA Science Inventory

The influence of two phosphate corrosion compounds on the growth and survival of coliform and other heterotrophic bacteria was investigated in laboratory, field, and model system studies. Growth of Citrobacter freundii, Enterobacter cloacae, and Klebsiella pneumoniae was not sign...

121

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

ERIC Educational Resources Information Center

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

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

2010-01-01

122

Growth curves of deviant behavior in early adolescence: A multilevel analysis  

Microsoft Academic Search

Multilevel growth curve models provide a means of analyzing individual differences in the growth of deviance, allow a number of theories to be integrated in a single model, and can help to unify research on deviant\\/delinquent\\/criminal careers at different stages of the life cycle. Building on the distinction between “population heterogeneity” and “state dependence” as alternative explanations of persistent individual

Robert A. Johnson; John P. Hoffmann; S. Susan Su; Dean R. Gerstein

1997-01-01

123

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

124

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

125

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

126

Promotion of Plant Growth by Bacterial ACC Deaminase  

Microsoft Academic Search

To date, there has been only limited commercial use of plant growth-promoting bacteria in agriculture, horticulture, and silviculture. However, with recent progress toward understanding the mechanisms that these organisms utilize to facilitate plant growth, the use of plant growth-promoting bacteria is expected to continue to increase worldwide. One of the key mechanisms employed by plant growth-promoting bacteria to facilitate plant

Bernard R. Glick; Biljana Todorovic; Jennifer Czarny; Zhenyu Cheng; Jin Duan; Brendan McConkey

2007-01-01

127

Heritabilities and genetic correlations for estimated growth curve parameters in maritime pine.  

PubMed

Height growth curves and several other characters were measured in five maritime pine (Pinus pinaster Ait) progeny tests aged from 18 to 27 years (about half the rotation age), with sample sizes of 272-1555 trees. These curves were fitted with a reparametrized Lundqvist-Matèrn sigmoidal growth function with global estimation of two of the four parameters. Each curve was characterized by two parameters: : the maximal growth rate (r), approximately proportional to the stem height at age 16 years, and essentially determined by the height increments around age 6 years. the asymptote (A), which is an extrapolation of growth after the measurement age. A is essentially determined by the latter growth period (around age 20 years), and is also related to the shape of the observed curve. The modelling framework appeared to be well suited to the characteristics of the data studied, and the estimation standard errors of the parameters were reasonably low. The heritabilities yielded for the growth curve parameters were high, similar to the heritabilities of cumulative heights. The genetic correlation between r and A was low, pointing to a poor juvenile-mature correlation. Discrepancies from one trial to another in heritabilities and in the correlation pattern were observed, they probably originated from environmental stresses. Maritime pine is actually selected using height and butt angle of lean at age 10 years as criteria. Improvements in the breeding program are suggested. PMID:24178103

Danjon, F

1994-12-01

128

Diffusion-limited growth in bacterial colony formation  

Microsoft Academic Search

Colonies of bacterial species called Bacillus subtilis have been found to grow two-dimensionally and self-similarly on agar plates through diffusion-limited processes in a nutrient concentration field. We obtained a fractal dimension of the colony patterns of D=1.73+\\/-0.02, very close to that of the two-dimensional DLA model, and confirmed the existence of the screening effect of protruding main branches against inner

Mitsugu Matsushita; Hiroshi Fujikawa

1990-01-01

129

Distribution of Bacterial Growth Activity in Flow-Chamber Biofilms  

Microsoft Academic Search

In microbial communities such as those found in biofilms, individual organisms most often display heter- ogeneous behavior with respect to their metabolic activity, growth status, gene expression pattern, etc. In that context, a novel reporter system for monitoring of cellular growth activity has been designed. It comprises a transposon cassette carrying fusions between the growth rate-regulated Escherichia coli rrnBP1 promoter

CLAUS STERNBERG; BJARKE B. CHRISTENSEN; TOVE JOHANSEN; ALEX TOFTGAARD NIELSEN; JENS BO ANDERSEN; MICHAEL GIVSKOV; SØREN MOLIN

1999-01-01

130

Genetic relationships between feed conversion ratio, growth curve and body composition in slow-growing chickens.  

PubMed

1. Relationships between feed conversion ratio, growth curve parameters and carcase composition were investigated on 1061 chickens from a slow-growing line of label-type chickens. The growth curve was modelled with the Gompertz function. Individual feed conversion ratio (FCR) was recorded between 8 and 10 weeks of age and residual feed consumption (RES) was calculated over the same interval. Abdominal fat yield (AFY), breast yield (BRY) and leg yield (LY) were also measured on the birds following slaughter at 75 d of age. 2. The means for FCR and RES were 3.15 and 0.62 g, respectively. Growth curve parameters were 0.141/d for initial specific growth rate (L), 0.031/d for maturation rate (K) and 48.9 d for age at inflexion (TI). Mean values for BRY, LY and AFY were 166, 306 and 40 g/kg, respectively. 3. Heritability of FCR and RES were moderate to high (0.33 and 0.38 to 0.45). Growth curve parameters and LY were moderately heritable (0.22 to 0.34) and BRY and AFY were highly heritable (0.50 and 0.66). Genetic correlations between growth curve parameters and either FCR or RES were low to moderate (-0.31 to 0.51). LY and AFY were highly correlated with FCR (-0.70 and 0.44) and RES (-0.32 and 0.44) but BRY was not (0.00 and -0.35). These results show that indirect selection for feed conversion ratio is possible by using growth curve parameters and abdominal fatness, which do not require rearing the chickens in cages. PMID:16787850

N'Dri, A L; Mignon-Grasteau, S; Sellier, N; Tixier-Boichard, M; Beaumont, C

2006-06-01

131

Growth curve analysis for plasma profiles using smoothing splines  

SciTech Connect

We are developing a profile analysis code for the statistical estimation of the parametric dependencies of the temperature and density profiles in tokamaks. Our code uses advanced statistical techniques to determine the optimal fit, i.e. the fit which minimized the predictive error. For a forty TFTR Ohmic profile dataset, our preliminary results indicate that the profile shape depends almost exclusively on q[sub a][prime] but that the shape dependencies are not Gaussian. We are now comparing various shape models on the TFTR data. In the first six months, we have completed the core modules of the code, including a B-spline package for variable knot locations, a data-based method to determine the optimal smoothing parameters, self-consistent estimation of the bias errors, and adaptive fitting near the plasma edge. Visualization graphics already include three dimensional surface plots, and discharge by discharge plots of the predicted curves with error bars together with the actual measurements values, and plots of the basis functions with errors.

Imre, K.

1993-05-01

132

Growth-rate dependence of a bacterial genetic oscillator dynamics  

E-print Network

Gene networks exhibiting oscillatory dynamics are widespread in biology. The minimal regulatory designs giving rise to oscillations have been implemented synthetically and studied by mathematical modeling. However, most of the available analyses generally neglect the coupling of regulatory circuits with the cellular "chassis" in which the circuits are embedded. For example, the cell macromolecular composition of fast-growing bacteria changes with growth rate. As a consequence, important parameters of gene expression, such as ribosome concentration or cell volume, are growth-rate dependent, ultimately coupling the dynamics of genetic circuits with cell physiology. This work addresses the effects of growth rate on the dynamics of a paradigmatic example of genetic oscillator, the repressilator. Making use of empirical growth-rate dependences of parameters in bacteria, we show that the repressilator dynamics can switch between oscillations and convergence to a fixed point depending on the cellular state of growth...

Osella, Matteo

2012-01-01

133

Development of a restricted state space stochastic differential equation model for bacterial growth in rich media.  

PubMed

In the present study, bacterial growth in a rich media is analysed in a Stochastic Differential Equation (SDE) framework. It is demonstrated that the SDE formulation and smoothened state estimates provide a systematic framework for data driven model improvements, using random walk hidden states. Bacterial growth is limited by the available substrate and the inclusion of diffusion must obey this natural restriction. By inclusion of a modified logistic diffusion term it is possible to introduce a diffusion term flexible enough to capture both the growth phase and the stationary phase, while concentration is restricted to the natural state space (substrate and bacteria non-negative). The case considered is the growth of Salmonella and Enterococcus in a rich media. It is found that a hidden state is necessary to capture the lag phase of growth, and that a flexible logistic diffusion term is needed to capture the random behaviour of the growth model. Further, it is concluded that the Monod effect is not needed to capture the dynamics of bacterial growth in the data presented. PMID:22575551

Møller, Jan Kloppenborg; Bergmann, Kirsten Riber; Christiansen, Lasse Engbo; Madsen, Henrik

2012-07-21

134

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

135

Biofilm vs. planktonic bacterial mode of growth: which do human macrophages prefer?  

PubMed

Although the natural mode of bacterial growth in nature is as biofilm, almost all antimicrobial and immunological tests are routinely developed using planktonic inoculums. Bacterial biofilms protect the microbial community from external damage and promote the persistence of chronic infections. In this study, interactions between human macrophages and bacterial inoculums of planktonic and biofilm modes of growth have been explored using Escherichia coli (E. coli) K12. Human macrophages phagocytize planktonic E. coli more efficiently than bacteria grown in a biofilm. Moreover, they prefer to phagocytize planktonic bacteria. In this context, CD64 expression is involved. Our data indicate that bacteria with "a biofilm background" avoid phagocytosis by naïve macrophages, which could create a favorable environment for chronic infection. Our findings were corroborated in a clinical O25b-ST131 ESBL-producer E. coli isolate, which caused urinary tract infections. PMID:24239884

Hernández-Jiménez, Enrique; Del Campo, Rosa; Toledano, Victor; Vallejo-Cremades, Maria Teresa; Muñoz, Aurora; Largo, Carlota; Arnalich, Francisco; García-Rio, Francisco; Cubillos-Zapata, Carolina; López-Collazo, Eduardo

2013-11-29

136

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

137

Effects of sevoflurane and/or nitrous oxide on bacterial growth in in vitro culture conditions.  

PubMed

The aim of this study was to determine the role of sevoflurane and/or nitrous oxide on bacterial growth under conditions in vitro similar to those of clinical practice. We assessed these effects on Pseudomonas aeruginosa, Acinetobacter lwoffii, and Staphylococcus aureus growth. Bacterial inoculums were prepared from reference strains in nutritive broth. Airtight chambers were filled with bacterial suspensions. Each strain was studied with and without exposure to sevoflurane and/or nitrous oxide at baseline, after 1 and 3 h. Serial dilutions and agar plates were made and the colonies were counted. P. aeruginosa were grown after exposure to the nitrous oxide alone (2.8 x 10(3) colony-forming units/ml; CFU ml(-1)) after 3 h according to the control (P < 0.05). A. lwoffii were grown after exposure to the nitrous oxide and sevoflurane with nitrous oxide (8.7 x 10(3) and 8.0 x 10(3) CFU ml(-1)) (P < 0.05), respectively. There were no changes in S. aureus growth in controls and anesthesia groups. We conclude that the effects of anesthetic agents on bacterial growth may change owing to the type of anesthetic and microorganism. PMID:17680203

Karabiyik, Lale; Türkan, Hülya; Ozi?ik, Tahir; Saraçli, Mehmet Ali; Haznedaro?lu, Tuncer

2007-01-01

138

Modelling bacterial growth in quantitative microbiological risk assessment: is it possible?  

Microsoft Academic Search

Quantitative microbiological risk assessment (QMRA), predictive modelling and HACCP may be used as tools to increase food safety and can be integrated fruitfully for many purposes. However, when QMRA is applied for public health issues like the evaluation of the status of public health, existing predictive models may not be suited to model bacterial growth. In this context, precise quantification

Maarten J. Nauta

2002-01-01

139

Improved bacterial growth test for rapid water toxicity screening  

Microsoft Academic Search

Bacteria have several attributes which make them attractive as test organisms for the rapid screening of chemical pollution in natural waters. They have relatively short life cycles and, therefore, respond rapidly to environmental change. The degree of toxicity of chemicals to bacteria is normally established by measuring viability or growth. A very sensitive test has been described measuring cell multiplication

J. L. Slabbert

1986-01-01

140

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...

141

Optimization of a new mathematical model for bacterial growth  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this research is to optimize a new mathematical equation as a primary model to describe the growth of bacteria under constant temperature conditions. An optimization algorithm was used in combination with a numerical (Runge-Kutta) method to solve the differential form of the new gr...

142

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...

143

EFFECT OF THE GROWTH REGULATOR PACLOBUTRAZOL ON GROWTH OF THE BACTERIAL PATHOGEN XYLELLA FASTIDIOSA  

Technology Transfer Automated Retrieval System (TEKTRAN)

Xyella fastidiosa is a fastidious, xylem-limited, insect transmitted, bacterial plant pathogen that has a wide host range and causes bacterial leaf scorch (BLS) in shade trees. BLS is a chronic disorder characterized by late season leaf scorch and dieback and is common in urban and suburban areas o...

144

Longitudinal Changes in Physical Fitness Performance in Youth: A Multilevel Latent Growth Curve Modeling Approach  

ERIC Educational Resources Information Center

Using a multilevel latent growth curve modeling (LGCM) approach, this study examined longitudinal change in levels of physical fitness performance over time (i.e. four years) in young adolescents aged from 12-13 years. The sample consisted of 6622 students from 138 secondary schools in Singapore. Initial analyses found between-school variation on…

Wang, Chee Keng John; Pyun, Do Young; Liu, Woon Chia; Lim, Boon San Coral; Li, Fuzhong

2013-01-01

145

Evaluating Model Fit for Growth Curve Models: Integration of Fit Indices from SEM and MLM Frameworks  

ERIC Educational Resources Information Center

Evaluating overall model fit for growth curve models involves 3 challenging issues. (a) Three types of longitudinal data with different implications for model fit may be distinguished: balanced on time with complete data, balanced on time with data missing at random, and unbalanced on time. (b) Traditional work on fit from the structural equation…

Wu, Wei; West, Stephen G.; Taylor, Aaron B.

2009-01-01

146

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

147

Career Maturity Growth Curve and Sex-Role Stereotypes of Korean Adolescents  

ERIC Educational Resources Information Center

This longitudinal study investigated the career maturity growth curve of Korean Adolescents from 4th grade to 12th grade. The participants consisted of 3,241 male and 3,029 female students from the Korea Youth Panel Survey, a nationwide longitudinal study of South Korean adolescents. The present study explored the shape of the career maturity…

Yon, Kyu Jin; Choi, Wonseok; Goh, Michael

2013-01-01

148

Economic growth and environmental degradation: The environmental Kuznets curve and sustainable development  

Microsoft Academic Search

In this paper we critically examine the concept of the environmental Kuznets curve (EKC). It proposes that there is an inverted U-shape relation between environmental degradation and income per capita, so that, eventually, growth reduces the environmental impact of economic activity. The concept is dependent on a model of the economy in which there is no feedback from the quality

Edward B. Barbier; Michael S. Common

1996-01-01

149

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

150

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

151

Lubricating bacteria model for the growth of bacterial colonies exposed to ultraviolet radiation  

SciTech Connect

In this paper, we study the morphological transition of bacterial colonies exposed to ultraviolet radiation by modifying the bacteria model proposed by Delprato et al. Our model considers four factors: the lubricant fluid generated by bacterial colonies, a chemotaxis initiated by the ultraviolet radiation, the intensity of the ultraviolet radiation, and the bacteria's two-stage destruction rate with given radiation intensities. Using this modified model, we simulate the ringlike pattern formation of the bacterial colony exposed to uniform ultraviolet radiation. The following is shown. (1) Without the UV radiation the colony forms a disklike pattern and reaches a constant front velocity. (2) After the radiation is switched on, the bacterial population migrates to the edge of the colony and forms a ringlike pattern. As the intensity of the UV radiation is increased the ring forms faster and the outer velocity of the colony decreases. (3) For higher radiation intensities the total population decreases, while for lower intensities the total population increases initially at a small rate and then decreases. (4) After the UV radiation is switched off, the bacterial population grows both outward as well as into the inner region, and the colony's outer front velocity recovers to a constant value. All these results agree well with the experimental observations [Phys. Rev. Lett. 87, 158102 (2001)]. Along with the chemotaxis, we find that lubricant fluid and the two-stage destruction rate are critical to the dynamics of the growth of the bacterial colony when exposed to UV radiation, and these were not previously considered.

Zhang Shengli; Zhang Lei; Liang Run; Zhang Erhu; Liu Yachao; Zhao Shumin [Department of Applied Physics, Xi'an Jiaotong University, Xi'an 710049 (China)

2005-11-01

152

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

153

The Leucine Incorporation Method Estimates Bacterial Growth Equally Well in Both Oxic and Anoxic Lake Waters  

PubMed Central

Bacterial biomass production is often estimated from incorporation of radioactively labeled leucine into protein, in both oxic and anoxic waters and sediments. However, the validity of the method in anoxic environments has so far not been tested. We compared the leucine incorporation of bacterial assemblages growing in oxic and anoxic waters from three lakes differing in nutrient and humic contents. The method was modified to avoid O2 contamination by performing the incubation in syringes. Isotope saturation levels in oxic and anoxic waters were determined, and leucine incorporation rates were compared to microscopically observed bacterial growth. Finally, we evaluated the effects of O2 contamination during incubation with leucine, as well as the potential effects of a headspace in the incubation vessel. Isotope saturation occurred at a leucine concentration of above about 50 nM in both oxic and anoxic waters from all three lakes. Leucine incorporation rates were linearly correlated to observed growth, and there was no significant difference between oxic and anoxic conditions. O2 contamination of anoxic water during 1-h incubations with leucine had no detectable impact on the incorporation rate, while a headspace in the incubation vessel caused leucine incorporation to increase in both anoxic and O2-contaminated samples. The results indicate that the leucine incorporation method relates equally to bacterial growth rates under oxic and anoxic conditions and that incubation should be performed without a headspace. PMID:11425702

Bastviken, David; Tranvik, Lars

2001-01-01

154

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

155

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

156

Simultaneous estimation of multiple quantitative trait loci and growth curve parameters through hierarchical Bayesian modeling.  

PubMed

A novel hierarchical quantitative trait locus (QTL) mapping method using a polynomial growth function and a multiple-QTL model (with no dependence in time) in a multitrait framework is presented. The method considers a population-based sample where individuals have been phenotyped (over time) with respect to some dynamic trait and genotyped at a given set of loci. A specific feature of the proposed approach is that, instead of an average functional curve, each individual has its own functional curve. Moreover, each QTL can modify the dynamic characteristics of the trait value of an individual through its influence on one or more growth curve parameters. Apparent advantages of the approach include: (1) assumption of time-independent QTL and environmental effects, (2) alleviating the necessity for an autoregressive covariance structure for residuals and (3) the flexibility to use variable selection methods. As a by-product of the method, heritabilities and genetic correlations can also be estimated for individual growth curve parameters, which are considered as latent traits. For selecting trait-associated loci in the model, we use a modified version of the well-known Bayesian adaptive shrinkage technique. We illustrate our approach by analysing a sub sample of 500 individuals from the simulated QTLMAS 2009 data set, as well as simulation replicates and a real Scots pine (Pinus sylvestris) data set, using temporal measurements of height as dynamic trait of interest. PMID:21792229

Sillanpää, M J; Pikkuhookana, P; Abrahamsson, S; Knürr, T; Fries, A; Lerceteau, E; Waldmann, P; García-Gil, M R

2012-02-01

157

Spatial Patterning of Newly-Inserted Material during Bacterial Cell Growth  

NASA Astrophysics Data System (ADS)

In the life cycle of a bacterium, rudimentary microscopy demonstrates that cell growth and elongation are essential characteristics of cellular reproduction. The peptidoglycan cell wall is the main load-bearing structure that determines both cell shape and overall size. However, simple imaging of cellular growth gives no indication of the spatial patterning nor mechanism by which material is being incorporated into the pre-existing cell wall. We employ a combination of high-resolution pulse-chase fluorescence microscopy, 3D computational microscopy, and detailed mechanistic simulations to explore how spatial patterning results in uniform growth and maintenance of cell shape. We show that growth is happening in discrete bursts randomly distributed over the cell surface, with a well-defined mean size and average rate. We further use these techniques to explore the effects of division and cell wall disrupting antibiotics, like cephalexin and A22, respectively, on the patterning of cell wall growth in E. coli. Finally, we explore the spatial correlation between presence of the bacterial actin-like cytoskeletal protein, MreB, and local cell wall growth. Together these techniques form a powerful method for exploring the detailed dynamics and involvement of antibiotics and cell wall-associated proteins in bacterial cell growth.[4pt] In collaboration with Kerwyn Huang, Stanford University.

Ursell, Tristan

2012-02-01

158

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

E-print Network

Bacterial growth and motility in sub-micron constrictions Jaan Ma¨nnik, Rosalie Driessen, Peter, bacteria live in micrometer- size confined spaces. Although bacterial growth and motility microfluidics Bacterial growth and movement in confined spaces is ubiq- uitous in nature and plays an important

Dekker, Cees

159

Morphological Instability and Dynamics of Fronts in Bacterial Growth Models with Nonlinear Diffusion  

E-print Network

It has been argued that there is biological and modeling evidence that a non-linear diffusion coefficient of the type D(b) = D_0 b^{k} underlies the formation of a number of growth patterns of bacterial colonies. We study a reaction-diffusion system with a non-linear diffusion coefficient introduced by Ben-Jacob et al. Due to the fact that the bacterial diffusion coefficient vanishes when the bacterial density b -> 0, the standard linear stability analysis for fronts cannot be used. We introduce an extension of the stability analysis which can be applied to such singular fronts, map out the region of stability in the D-k-plane and derive an interfacial approximation in some limits. Our linear stability analysis and sharp interface formulation will also be applicable to other examples of interface formation due to nonlinear diffusion, like in porous media or in the problem of vortex motion in superconductors.

J. Mueller; W. van Saarloos

2002-11-21

160

Bacterial-Feeding Nematode Growth and Preference for Biocontrol Isolates of the Bacterium Burkholderia cepacia  

PubMed Central

The potential of different bacterial-feeding Rhabditida to consume isolates of Burkholderia cepacia with known agricultural biocontrol ability was examined. Caenorhabditis elegans, Diploscapter sp., Oscheius myriophila, Pelodera strongyloides, Pristionchus pacificus, Zeldia punctata, Panagrellus redivivus, and Distolabrellus veechi were tested for growth on and preference for Escherichia coli OP50 or B. cepacia maize soil isolates J82, BcF, M36, Bc2, and PHQM100. Considerable growth and preference variations occurred between nematode taxa on individual bacterial isolates, and between different bacterial isolates on a given nematode. Populations of Diploscapter sp. and P. redivivus were most strongly suppressed. Only Z. punctata and P. pacificus grew well on all isolates, though Z. punctata preferentially accumulated on all isolates and P. pacificus had no preference. Oscheius myriophila preferentially accumulated on growth-supportive Bc2 and M36, and avoided less supportive J82 and PHQM100. Isolates with plant-parasitic nematicidal properties and poor fungicidal properties supported the best growth of three members of the Rhabditidae, C. elegans, O. myriophila, and P. strongyloides. Distolabrellus veechi avoided commercial nematicide M36 more strongly than fungicide J82. PMID:19270990

Carta, Lynn K.

2000-01-01

161

The effects of a low-intensity red laser on bacterial growth, filamentation and plasmid DNA  

NASA Astrophysics Data System (ADS)

Exposure of nonphotosynthesizing microorganisms to light could increase cell division in cultures, a phenomenon denominated as biostimulation. However, data concerning the importance of the genetic characteristics of cells on this effect are as yet scarce. The aim of this work was to evaluate the effects of a low-intensity red laser on the growth, filamentation and plasmids in Escherichia coli cells proficient and deficient in DNA repair. E. coli cultures were exposed to a laser (658 nm, 10 mW, 1 and 8 J cm?2) to study bacterial growth and filamentation. Also, bacterial cultures hosting pBSK plasmids were exposed to the laser to study DNA topological forms from the electrophoretic profile in agarose gels. Data indicate the low-intensity red laser: (i) had no effect on the growth of E. coli wild type and exonuclease III deficient cells; (ii) induced bacterial filamentation, (iii) led to no alteration in the electrophoretic profile of plasmids from exonuclease III deficient cells, but plasmids from wild type cells were altered. A low-intensity red laser at the low fluences used in phototherapy has no effect on growth, but induces filamentation and alters the topological forms of plasmid DNA in E. coli cultures depending on the DNA repair mechanisms.

Roos, C.; Santos, J. N.; Guimarães, O. R.; Geller, M.; Paoli, F.; Fonseca, A. S.

2013-07-01

162

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

163

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

164

Coal Fly Ash Impairs Airway Antimicrobial Peptides and Increases Bacterial Growth  

PubMed Central

Air pollution is a risk factor for respiratory infections, and one of its main components is particulate matter (PM), which is comprised of a number of particles that contain iron, such as coal fly ash (CFA). Since free iron concentrations are extremely low in airway surface liquid (ASL), we hypothesize that CFA impairs antimicrobial peptides (AMP) function and can be a source of iron to bacteria. We tested this hypothesis in vivo by instilling mice with Pseudomonas aeruginosa (PA01) and CFA and determine the percentage of bacterial clearance. In addition, we tested bacterial clearance in cell culture by exposing primary human airway epithelial cells to PA01 and CFA and determining the AMP activity and bacterial growth in vitro. We report that CFA is a bioavailable source of iron for bacteria. We show that CFA interferes with bacterial clearance in vivo and in primary human airway epithelial cultures. Also, we demonstrate that CFA inhibits AMP activity in vitro, which we propose as a mechanism of our cell culture and in vivo results. Furthermore, PA01 uses CFA as an iron source with a direct correlation between CFA iron dissolution and bacterial growth. CFA concentrations used are very relevant to human daily exposures, thus posing a potential public health risk for susceptible subjects. Although CFA provides a source of bioavailable iron for bacteria, not all CFA particles have the same biological effects, and their propensity for iron dissolution is an important factor. CFA impairs lung innate immune mechanisms of bacterial clearance, specifically AMP activity. We expect that identifying the PM mechanisms of respiratory infections will translate into public health policies aimed at controlling, not only concentration of PM exposure, but physicochemical characteristics that will potentially cause respiratory infections in susceptible individuals and populations. PMID:23469047

Borcherding, Jennifer A.; Chen, Haihan; Caraballo, Juan C.; Baltrusaitis, Jonas; Pezzulo, Alejandro A.; Zabner, Joseph; Grassian, Vicki H.; Comellas, Alejandro P.

2013-01-01

165

Coal fly ash impairs airway antimicrobial peptides and increases bacterial growth.  

PubMed

Air pollution is a risk factor for respiratory infections, and one of its main components is particulate matter (PM), which is comprised of a number of particles that contain iron, such as coal fly ash (CFA). Since free iron concentrations are extremely low in airway surface liquid (ASL), we hypothesize that CFA impairs antimicrobial peptides (AMP) function and can be a source of iron to bacteria. We tested this hypothesis in vivo by instilling mice with Pseudomonas aeruginosa (PA01) and CFA and determine the percentage of bacterial clearance. In addition, we tested bacterial clearance in cell culture by exposing primary human airway epithelial cells to PA01 and CFA and determining the AMP activity and bacterial growth in vitro. We report that CFA is a bioavailable source of iron for bacteria. We show that CFA interferes with bacterial clearance in vivo and in primary human airway epithelial cultures. Also, we demonstrate that CFA inhibits AMP activity in vitro, which we propose as a mechanism of our cell culture and in vivo results. Furthermore, PA01 uses CFA as an iron source with a direct correlation between CFA iron dissolution and bacterial growth. CFA concentrations used are very relevant to human daily exposures, thus posing a potential public health risk for susceptible subjects. Although CFA provides a source of bioavailable iron for bacteria, not all CFA particles have the same biological effects, and their propensity for iron dissolution is an important factor. CFA impairs lung innate immune mechanisms of bacterial clearance, specifically AMP activity. We expect that identifying the PM mechanisms of respiratory infections will translate into public health policies aimed at controlling, not only concentration of PM exposure, but physicochemical characteristics that will potentially cause respiratory infections in susceptible individuals and populations. PMID:23469047

Borcherding, Jennifer A; Chen, Haihan; Caraballo, Juan C; Baltrusaitis, Jonas; Pezzulo, Alejandro A; Zabner, Joseph; Grassian, Vicki H; Comellas, Alejandro P

2013-01-01

166

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

NASA Astrophysics Data System (ADS)

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 cells on tumour periphery. Our results indicate that very distinct morphological patterns follow Gompertz growth curves and their gyration radii increase linearly in time and scale, in the asymptotic limit, as a square root of the total number of tumour cells. In contrast, these distinct tumour patterns exhibit different scaling laws for their surfaces. Thus, some biological features of malignant behaviour seem to influence particularly the structure of the tumour border, while its gyration radius and progress curve are described by more robust functions. Finally, for both rules used, morphology transitions as well as a transient behaviour up to the onset of the phase of rapid growth in the Gompertz curves are observed.

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

1999-10-01

167

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?=?442±24 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

168

From snowflake formation to growth of bacterial colonies II: Cooperative formation of complex colonial patterns  

NASA Astrophysics Data System (ADS)

In nature, bacterial colonies must often cope with hostile environmental conditions. To do so they have developed sophisticated cooperative behaviour and intricate communication capabilities, such as direct cell- cell physical interactions via extra-membrane polymers, collective production of extracellular 'wetting' fluid for movement on hard surfaces, longrange chemical signalling such as quorum sensing and chemotactic (bias of movement according to gradient of chemical agent) signalling, collective activation and deactivation of genes and even exchange of genetic material. Utilizing these capabilities, the bacterial colonies develop complex spatio-temporal patterns in response to adverse growth conditions. We present a wealth of beautiful patterns formed during colonial development of various bacterial strains and for different environmental conditions. Invoking ideas from pattern formation in non-living systems and using generic modelling we are able to reveal novel bacterial strategies which account for the salient features of the evolved patterns. Using the models, we demonstrate how bacterial communication leads to colonial self-organization that can only be achieved via cooperative behaviour of the cells. It can be viewed as the action of a singular feedback between the microscopic level (the individual cells) and the macroscopic level (the colony) in the determination of the emerging patterns.

Ben-Jacob, Eshel

1997-03-01

169

Inhibition of selected bacterial growth by three hydrocarbons: mathematical evaluation of toxicity using a toxicodynamic equation.  

PubMed

The individual toxicity of different hydrocarbons (naphthalene, cyclododecane and aniline) on the growth of selected bacteria (Pseudomonas sp., Phaeobacter sp. and Leuconostoc mesenteroides) was studied by means of a toxicodynamic model combination of two sigmoid equations (logistic and Weibull). All the toxicological effects on growth parameters and kinetic properties were characterized and the global toxicity of such chemicals was evaluated. It was observed that two kinetic parameters (maximum growth and maximum growth rate) were in almost all cases influenced by the hydrocarbons studied. Aniline was less toxic than cyclododecane and naphthalene. The presented approach is a reasonable starting point for understanding and modeling complete and real assessment of chemical toxic effects on bacterial growths. The values of EC50,? could be used for a most efficient comparison of the individual toxicity of chemicals. PMID:25048888

Vázquez, José A; Rial, Diego

2014-10-01

170

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

171

Spatial and Temporal Features of the Growth of a Bacterial Species Colonizing the Zebrafish Gut  

PubMed Central

ABSTRACT The vertebrate intestine is home to microbial ecosystems that play key roles in host development and health. Little is known about the spatial and temporal dynamics of these microbial communities, limiting our understanding of fundamental properties, such as their mechanisms of growth, propagation, and persistence. To address this, we inoculated initially germ-free zebrafish larvae with fluorescently labeled strains of an Aeromonas species, representing an abundant genus in the zebrafish gut. Using light sheet fluorescence microscopy to obtain three-dimensional images spanning the gut, we quantified the entire bacterial load, as founding populations grew from tens to tens of thousands of cells over several hours. The data yield the first ever measurements of the growth kinetics of a microbial species inside a live vertebrate intestine and show dynamics that robustly fit a logistic growth model. Intriguingly, bacteria were nonuniformly distributed throughout the gut, and bacterial aggregates showed considerably higher growth rates than did discrete individuals. The form of aggregate growth indicates intrinsically higher division rates for clustered bacteria, rather than surface-mediated agglomeration onto clusters. Thus, the spatial organization of gut bacteria both relative to the host and to each other impacts overall growth kinetics, suggesting that spatial characterizations will be an important input to predictive models of host-associated microbial community assembly. PMID:25516613

Jemielita, Matthew; Taormina, Michael J.; Burns, Adam R.; Hampton, Jennifer S.; Rolig, Annah S.; Guillemin, Karen

2014-01-01

172

GROWTH AND METABOLISM OF INDIVIDUAL BACTERIAL CELLS UTILIZING NANOSIMS  

SciTech Connect

This work involved the use of the Nano-SIMS Instrument at Lawrence Livermore Laboratory, in an effort to utilize this unique tool for experiments in Biology. The work consisted primarily of experiments to measure in real time, C and N fixation in cyanobacteria. The work revealed a number of the difficulties in using the nano-SIMS approach with biological material, but with collaboration from a number of individuals at USC and LLNL, major progress was made. The collaborators from LLNL were from the Chemistry Group (Dr. Peter Weber), and the Biology Group (Dr. Jennifer Pett-Ridge). In addition, there were a number of other scientists involved from LLNL. The USC group consisted of Dr. K.H. Nealson, the PI on the grant, Dr. R. Popa, a postdoctoral fellow and research associate at USC, Professor Douglas Capone, and Juliet Finze, a graduate student in biology. Two major experiments were done, both of which yielded new and exciting data. (1) We studied nitrogen and carbon fixation in Anabaena, demonstrating that fixation ofN occurred rapidly in the heterocysts, and that the fixed N was transported rapidly and completely to the vegetative cells. C fixation occurred in the vegetative cells, with labeled C remaining in these cells in support of their growth and metabolism. This work was accepted in the ISME Journal (Nature Publication), and published last month. (2) We studied nitrogen and carbon fixation in Trichodesmium, a non-heterocystous cyanobacterium that also fixes nitrogen. Interestingly, the nitrogen fixation was confined to regions within the filaments that seem to be identical to the so-called cyanophycaen granules. The fixed N is then transported to other parts of the cyanobacterium, as judged by movement of the heavy N throughout the filaments. On the basis of these very exciting results, we have applied for funding from the NSF to continue the collaboration with LLNL. The results of both studies were presented in the summer of 2007 at the Gordon Research Conference (Applied Environmental Microbiol.).

NEALSON, H. K.

2007-08-03

173

The effect of epidermal growth factor on bacterial translocation in newborn rabbits  

Microsoft Academic Search

Purpose: Epidermal growth factor (EGF), which is present in breast milk, has both trophic and maturational effects on intestinal mucosa. The aim of this study is to deermine the effect of EGF on spontaneous intestinal bacterial translocation (BT) in formula-fed newborn rabbits, who have a high incidence of BT compared with breast-fed newborn rabbits.Methods: Sixty-one rabbit pups were divided into

H Okuyama; M Urao; D Lee; R. A Drongowski; A. G Coran

1998-01-01

174

Volatile hydrocarbon biodegradation by a mixed-bacterial culture during growth on crude oil  

Microsoft Academic Search

  Volatile hydrocarbon biodegradation by a mixed-bacterial culture during growth on Bow River crude oil was investigated using\\u000a solid phase microextraction (SPME). Inoculum treatments were examined in relation to C5–C11 hydrocarbon degradation. Up to 1600 mg\\/l biomass (dry weight) was tested without achieving significant volatile hydrocarbon\\u000a partitioning and affecting analysis. Inoculum age rather than concentration had the most profound impact on

J D Van Hamme; O P Ward

2001-01-01

175

The Effects of Cyanobacterial Exudates on Bacterial Growth and Biodegradation of Organic Contaminants  

Microsoft Academic Search

The pulp and paper industry largely depends on the biodegradation activities of heterotrophic bacteria to remove organic contaminants\\u000a in wastewater prior to discharge. Our recent discovery of extensive cyanobacterial communities in pulp and paper waste treatment\\u000a systems led us to investigate the potential impacts of cyanobacterial exudates on growth and biodegradation efficiency of\\u000a three bacterial heterotrophs. Each of the three

A. E. Kirkwood; C. Nalewajko; R. R. Fulthorpe

2006-01-01

176

Growth promoting effects of corn ( Zea mays) bacterial isolates under greenhouse and field conditions  

Microsoft Academic Search

Fertilizer costs are a major component of corn production. The use of biofertilizers may be one way of reducing production costs. In this study we present isolation and identification of three plant growth promoting bacteria that were identified as Enterobacter cloacae (CR1), Pseudomonas putida (CR7) and Stenotrophomonas maltophilia (CR3). All bacterial strains produced IAA in the presence of 100mgl?1 of

Samina Mehnaz; Tom Kowalik; Bruce Reynolds; George Lazarovits

2010-01-01

177

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

178

A Recursive Regression for High-Dimensional Models, with Application to Growth Curves and Repeated Measures  

Microsoft Academic Search

A fixed-effects formulation of repeated-measures and growth-curve problems usually leads to an unwieldy linear model, so mixed models are widely used for inference that the conditional linear error model could otherwise support with weaker distributional assumptions. Very high-dimensional regressions (not necessarily arising this way) can be fitted by the proposed alternating algorithm, which partitions the design matrix into singly manageable

Ian Abramson

1988-01-01

179

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

...repair proficient and repair deficient bacteria: âBacterial DNA damage or repair tests...repair proficient and repair deficient bacteria: “Bacterial DNA damage or repair tests...growth inhibition of repair deficient bacteria in a set of repair proficient and...

2014-07-01

180

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

Code of Federal Regulations, 2012 CFR

...repair proficient and repair deficient bacteria: âBacterial DNA damage or repair tests...repair proficient and repair deficient bacteria: “Bacterial DNA damage or repair tests...growth inhibition of repair deficient bacteria in a set of repair proficient and...

2012-07-01

181

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

Code of Federal Regulations, 2013 CFR

...repair proficient and repair deficient bacteria: âBacterial DNA damage or repair tests...repair proficient and repair deficient bacteria: “Bacterial DNA damage or repair tests...growth inhibition of repair deficient bacteria in a set of repair proficient and...

2013-07-01

182

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

Code of Federal Regulations, 2011 CFR

...repair proficient and repair deficient bacteria: âBacterial DNA damage or repair tests...repair proficient and repair deficient bacteria: “Bacterial DNA damage or repair tests...growth inhibition of repair deficient bacteria in a set of repair proficient and...

2011-07-01

183

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

Code of Federal Regulations, 2010 CFR

...repair proficient and repair deficient bacteria: âBacterial DNA damage or repair tests...repair proficient and repair deficient bacteria: “Bacterial DNA damage or repair tests...growth inhibition of repair deficient bacteria in a set of repair proficient and...

2010-07-01

184

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

185

Tropical freshwater ecosystems have lower bacterial growth efficiency than temperate ones  

PubMed Central

Current models and observations indicate that bacterial respiration should increase and growth efficiency (BGE) should decrease with increasing temperatures. However, these models and observations are mostly derived from data collected in temperate regions, and the tropics are under-represented. The aim of this work was to compare bacterial metabolism, namely bacterial production (BP) and respiration (BR), bacterial growth efficiency (BGE) and bacterial carbon demand (BCD) between tropical and temperate ecosystems via a literature review and using unpublished data. We hypothesized that (1) tropical ecosystems have higher metabolism than temperate ones and, (2) that BGE is lower in tropical relative to temperate ecosystems. We collected a total of 498 coupled BP and BR observations (Ntotal = 498; Ntemperate = 301; Ntropical = 197), calculated BGE (BP/(BP+BR)) and BCD (BP+BR) for each case and examined patterns using a model II regression analysis and compared each parameter between the two regions using non-parametric Mann–Whitney U test. We observed a significant positive linear regression between BR and BP for the whole dataset, and also for tropical and temperate data separately. We found that BP, BR and BCD were higher in the tropics, but BGE was lower compared to temperate regions. Also, BR rates per BP unit were at least two fold higher in the tropics than in temperate ecosystems. We argue that higher temperature, nutrient limitation, and light exposure all contribute to lower BGE in the tropics, mediated through effects on thermodynamics, substrate stoichiometry, nutrient availability and interactions with photochemically produced compounds. More efforts are needed in this study area in the tropics, but our work indicates that bottom-up (nutrient availability and resource stoichiometry) and top-down (grazer pressure) processes, coupled with thermodynamic constraints, might contribute to the lower BGE in the tropics relative to temperate regions. PMID:23801986

Amado, André M.; Meirelles-Pereira, Frederico; Vidal, Luciana O.; Sarmento, Hugo; Suhett, Albert L.; Farjalla, Vinicius F.; Cotner, James B.; Roland, Fabio

2013-01-01

186

[Effects of growth years of Paeonia lactiflora on bacterial community in rhizosphere soil and paeoniflorin content].  

PubMed

To explore the relationship between microecological environment and Paeonia lactiflora the effects of growth years of P. lactillora on rhizosphere bacterial communities were studied by PCR-DGGE and the paeoniflorin content determined by HPLC. Results showed that the soil pH increased with growing years of P. lactillora. In the fourth year, soil pH and enzyme activity reached the highest level, while organic matter content was the lowest. The bacterial diversity had a positive correlation with growing years varied from 3.38 to 3.61. Sequencing results demonstrated that Gammaproteobacteria, llphaproteobacteria, Actinobacteria, Acidobacte- ria and Firmicutes were predominant bacteria kinds in the soil of P. lactillora. Gammaproteobacteria was only detected in the bulk soil, while llphaproteobacteria, Acidobacteria G1l, Actinobacteria were only in the rhizosphere soil and the bacterial community among different growing years were similar except few species. HLPC results showed that paeoniflorin content was 3.26%, 3.30%, 3.36%, 3.41% separately from one to four-year-old P. lactiflora with an upward trend. The correlation analysis indicated that the paeoniflorin content had a positive correlation with soil pH and bacterial diversity, conversely, had a negative correlation with organic matter con- tent. During the growth years the rhizosphere bacterial diversity increased without changes of predominant bacteria and the paeoniflorin content increased without significant differences while its production increased significantly, which was different from the plants showing replanting diseases. This is in line with the farming practice choosing 4-year-old P. lactllora, but not the 1-3 year old one. In addition, the accumulation of paeoniflorin is closely related to soil pH, organic matter content and bacteria diversity, confirming that the geoherblism of P. lactiflora is closely related with microbial environment in the soil. PMID:25423827

Yuan, Xiao-Feng; Peng, San-Mei; Wang, Bo-Lin; Ding, Zhi-Shan

2014-08-01

187

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

explore the kinetics of bacterial cells to predict the dependency of growth and division rates on cell 0157:H7 (division) (SEM x22,810). 10 #12;Statistics Case Studies: Bacterial Growth Behavior Math 363 x + for minicells. The first integral 11 #12;Statistics Case Studies: Bacterial Growth Behavior

Watkins, Joseph C.

188

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

189

Preventing bacterial growth on implanted device with an interfacial metallic film and penetrating X-rays.  

PubMed

Device-related infections have been a big problem for a long time. This paper describes a new method to inhibit bacterial growth on implanted device with tissue-penetrating X-ray radiation, where a thin m etallic film deposited on the device is used as a radio-sensitizing film for bacterial inhibition. At a given dose of X-ray, the bacterial viability decreases as the thickness of metal film (bismuth) increases. The bacterial viability decreases with X-ray dose increases. At X-ray dose of 2.5 Gy, 98 % of bacteria on 10 nm thick bismuth film are killed; while it is only 25 % of bacteria are killed on the bare petri dish. The same dose of X-ray kills 8 % fibroblast cells that are within a short distance from bismuth film (4 mm). These results suggest that penetrating X-rays can kill bacteria on bismuth thin film deposited on surface of implant device efficiently. PMID:25631261

An, Jincui; Sun, An; Qiao, Yong; Zhang, Peipei; Su, Ming

2015-02-01

190

Bacterial growth: global effects on gene expression, growth feedback and proteome partition.  

PubMed

The function of endogenous as well as synthetic genetic circuits is generically coupled to the physiological state of the cell. For exponentially growing bacteria, a key characteristic of the state of the cell is the growth rate and thus gene expression is often growth-rate dependent. Here we review recent results on growth-rate dependent gene expression. We distinguish different types of growth-rate dependencies by the mechanisms of regulation involved and the presence or absence of an effect of the gene product on growth. The latter can lead to growth feedback, feedback mediated by changes of the global state of the cell. Moreover, we discuss how growth rate dependence can be used as a guide to study the molecular implementation of physiological regulation. PMID:24495512

Klumpp, Stefan; Hwa, Terence

2014-08-01

191

Association of Growth Substrates and Bacterial Genera with Benzo[a]pyrene Mineralization in Contaminated Soil.  

PubMed

Benzo[a]pyrene (BaP) is a carcinogenic polycyclic aromatic hydrocarbon (PAH) that is not known to be a bacterial growth substrate. Organisms capable of cometabolizing BaP in complex field-contaminated systems have not previously been identified. We evaluated BaP mineralization by a bacterial community from a bioreactor treating PAH-contaminated soil during coincubation with or after pre-enrichment on various PAHs as growth substrates. Pyrosequence libraries of 16S rRNA genes were used to identify bacteria that were enriched on the added growth substrate as a means of associating specific organisms with BaP mineralization. Coincubating the bioreactor-treated soil with naphthalene, phenanthrene, or pyrene inhibited BaP mineralization, whereas pre-enriching the soil on the same three PAHs enhanced BaP mineralization. Combined, these results suggest that bacteria in the bioreactor community that are capable of growing on naphthalene, phenanthrene, and/or pyrene can metabolize BaP, with coincubation competitively inhibiting BaP metabolism. Anthracene, fluoranthene, and benz[a]anthracene had little effect on BaP mineralization compared to incubations without an added growth substrate under either coincubation or pre-enrichment conditions. Substantial increases in relative abundance after pre-enrichment with phenanthrene, naphthalene, or pyrene, but not the other PAHs, suggest that members of the genera Cupriavidus and Luteimonas may have been associated with BaP mineralization. PMID:25469077

Jones, Maiysha D; Rodgers-Vieira, Elyse A; Hu, Jing; Aitken, Michael D

2014-12-01

192

Growth enhancement of ETBE-degrading bacterial consortium with various carbon sources.  

PubMed

In this study, we evaluated Ethyl tert-Butyl Ether (ETBE)-degrading consortia growths in the presence of diverse carbon sources (alcohols, alkanes, ether compounds and carbohydrates). In a second step, we studied the consortium ability to maintain its ETBE degradation activity after growing on these carbon sources in presence or in absence of ETBE. The results indicate that the bacterial growth of ETBE-degrading consortia is enhanced three times more with addition of ethanol than with ETBE alone, while maintaining its ability to degrade ETBE. The bacterial yield growth rate was 0.504 d(-1) when growing on ETBE alone, 1.728 d(-1) on both ETBE and ethanol and 2.856 d(-1) on ethanol alone. Both ETBE and ethanol are completely degraded at 8.33 mg L(-1) h(-1) and 18.55 mg L(-1) h(-1) respectively for an initial OD of 0.4. The frequency of ethanol addition, as growth co-substrate, was studied to preserve the ETBE-degrading capacity of the consortium, and to observe the stability of the genetic character of the ether degradation. PMID:15296148

Bekri, M; Pauss, A

2003-01-01

193

[Effects of bamboo charcoal on the growth of Trifolium repens and soil bacterial community structure].  

PubMed

The effects of addition rates (0, 3% and 9%) and particle sizes (0.05, 0.05-1.0 and 1.0-2.0 mm) of bamboo charcoal on the growth of Trifolium repens and soil microbial community structure were investigated. The results showed that bamboo charcoal addition greatly promoted the early growth of T. repens, with the 9% charcoal addition rate being slightly better than the 3% charcoal addition rate. The effects of different particle sizes of bamboo charcoal on the growth of T. repens were not different significantly. Growth promotion declined with time during 120 days after sowing, and disappeared completely after 5 months. DGGE analysis of the bacterial 16S rDNA V3 fragment indicated that bamboo charcoal altered the soil bacterial community structure. The amount and Shannon diversity index of bacteria in the bamboo charcoal addition treatments increased compared with CK. The quantitative analysis showed that the amount of bacteria in the treatment with bamboo charcoal of fine particle (D < 0.05 mm) at the 9% addition rate was significantly higher than in the other treatments. The fine bamboo charcoal had a great effect on soil bacteria amount compared with the charcoal of other sizes at the same addition rate. PMID:25509086

Li, Song-Hao; He, Dong-Hua; Shen, Qiu-Lan; Xu, Qiu-Fang

2014-08-01

194

Effects of Eyjafjallajökull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro  

PubMed Central

Background: On 20 March 2010, the Icelandic volcano Eyjafjallajökull erupted for the first time in 190 years. Despite many epidemiological reports showing effects of volcanic ash on the respiratory system, there are limited data evaluating cellular mechanisms involved in the response to ash. Epidemiological studies have observed an increase in respiratory infections in subjects and populations exposed to volcanic eruptions. Methods: We physicochemically characterized volcanic ash, finding various sizes of particles, as well as the presence of several transition metals, including iron. We examined the effect of Eyjafjallajökull ash on primary rat alveolar epithelial cells and human airway epithelial cells (20–100 µg/cm2), primary rat and human alveolar macrophages (5–20 µg/cm2), and Pseudomonas aeruginosa (PAO1) growth (3 µg/104 bacteria). Results: Volcanic ash had minimal effect on alveolar and airway epithelial cell integrity. In alveolar macrophages, volcanic ash disrupted pathogen-killing and inflammatory responses. In in vitro bacterial growth models, volcanic ash increased bacterial replication and decreased bacterial killing by antimicrobial peptides. Conclusions: These results provide potential biological plausibility for epidemiological data that show an association between air pollution exposure and the development of respiratory infections. These data suggest that volcanic ash exposure, while not seriously compromising lung cell function, may be able to impair innate immunity responses in exposed individuals. PMID:23478268

Baltrusaitis, Jonas; Powers, Linda S.; Borcherding, Jennifer A.; Caraballo, Juan C.; Mudunkotuwa, Imali; Peate, David W.; Walters, Katherine; Thompson, Jay M.; Grassian, Vicki H.; Gudmundsson, Gunnar; Comellas, Alejandro P.

2013-01-01

195

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 35°C for 48 h for bacteria, 25°C for 48 h for yeasts, and 25°C 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

196

Longitudinal Growth Curves of Brain Function Underlying Inhibitory Control through Adolescence  

PubMed Central

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

Foran, William; Velanova, Katerina; Luna, Beatriz

2013-01-01

197

Associated bacterial flora, growth, and toxicity of cultured benthic dinoflagellates Ostreopsis lenticularis and Gambierdiscus toxicus.  

PubMed Central

The growth, toxicity, and associated bacterial flora of 10 clonal cultures of the toxic benthic dinoflagellates Ostreopsis lenticularis and Gambierdiscus toxicus isolated from the coastal waters of southwest Puerto Rico have been examined. Clonal cultures of O. lenticularis grew more rapidly and at broader temperature ranges than those of G. toxicus. All five Ostreopsis clones were toxic, while only one of the five Gambierdiscus clones was poisonous. The degree of toxicity among poisonous clones was highly variable. The number of associated bacterial genera and their frequency of occurrence were quite variable among clones of both dinoflagellate genera. Bacterial isolates represented six genera (Nocardia, Pseudomonas, Vibrio, Aeromonas, Flavobacterium, and Moraxella) in addition to coryneform bacteria. Extracts of dinoflagellate-associated bacteria grown in pure culture were not toxic. Gambierdiscus clones were characterized by the frequent presence of Pseudomonas spp. (four of five clones) and the absence of coryneforms. In O. lenticularis, only one of five clones showed the presence of Pseudomonas spp., and Moraxella sp. was absent altogether. Detailed analyses of toxicity and associated microflora in a selected Ostreopsis clone, repeatedly cultivated (four times) over a period of 160 days, showed that peak cell toxicities developed in the late static and early negative culture growth phases. Peak Ostreopsis cell toxicities in the stationary phase of culture growth were correlated with significant increases in the percent total bacteria directly associated with these cells. Changes in the quantity of bacteria directly associated with microalgal cell surfaces and extracellular matrices during culture growth may be related to variability and degree of toxicity in these laboratory-cultured benthic dinoflagellates. PMID:2705766

Tosteson, T R; Ballantine, D L; Tosteson, C G; Hensley, V; Bardales, A T

1989-01-01

198

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.; Durán, C.; Maestre, J. R.; Mateo, M.; Elvira, L.

2012-12-01

199

Early detection of bacterial growth in blood culture by impedance monitoring with a Bactometer model 32.  

PubMed Central

A Bactometer model 32 was evaluated for use in early detection of bacterial growth. Experiments with simulated cultures showed that 2 ml of broth introduced into the Bactometer module wells could detect 10(2) and 10(6) CFU/ml in 6 h and 2 h respectively. Both Brain Heart Infusion (BHI) and Fastidious Anaerobic broths supported good growth. Detection of nine of 10 organisms inoculated at approximately 10(6) CFU/ml in BHI were detected within 8.5 h. A culture of Bacteroides fragilis failed to grow under these conditions. Of 189 blood cultures, tested by incubation of 2 ml of BHI, 18 were positive by both conventional and Bactometer methods. False-positive or false-negative specimens were not observed using the Bactometer. Use of the Bactometer enables growth detection at least 12 h earlier than culture methods. PMID:6345594

Buckland, A; Kessock-Philip, S; Bascomb, S

1983-01-01

200

Autotrophic growth of bacterial and archaeal ammonia oxidizers in freshwater sediment microcosms incubated at different temperatures.  

PubMed

Both bacteria and archaea potentially contribute to ammonia oxidation, but their roles in freshwater sediments are still poorly understood. Seasonal differences in the relative activities of these groups might exist, since cultivated archaeal ammonia oxidizers have higher temperature optima than their bacterial counterparts. In this study, sediment collected from eutrophic freshwater Lake Taihu (China) was incubated at different temperatures (4°C, 15°C, 25°C, and 37°C) for up to 8 weeks. We examined the active bacterial and archaeal ammonia oxidizers in these sediment microcosms by using combined stable isotope probing (SIP) and molecular community analysis. The results showed that accumulation of nitrate in microcosms correlated negatively with temperature, although ammonium depletion was the same, which might have been related to enhanced activity of other nitrogen transformation processes. Incubation at different temperatures significantly changed the microbial community composition, as revealed by 454 pyrosequencing targeting bacterial 16S rRNA genes. After 8 weeks of incubation, [(13)C]bicarbonate labeling of bacterial amoA genes, which encode the ammonia monooxygenase subunit A, and an observed increase in copy numbers indicated the activity of ammonia-oxidizing bacteria in all microcosms. Nitrosomonas sp. strain Is79A3 and Nitrosomonas communis lineages dominated the heavy fraction of CsCl gradients at low and high temperatures, respectively, indicating a niche differentiation of active bacterial ammonia oxidizers along the temperature gradient. The (13)C labeling of ammonia-oxidizing archaea in microcosms incubated at 4 to 25°C was minor. In contrast, significant (13)C labeling of Nitrososphaera-like archaea and changes in the abundance and composition of archaeal amoA genes were observed at 37°C, implicating autotrophic growth of ammonia-oxidizing archaea under warmer conditions. PMID:23455342

Wu, Yucheng; Ke, Xiubin; Hernández, Marcela; Wang, Baozhan; Dumont, Marc G; Jia, Zhongjun; Conrad, Ralf

2013-05-01

201

Autotrophic Growth of Bacterial and Archaeal Ammonia Oxidizers in Freshwater Sediment Microcosms Incubated at Different Temperatures  

PubMed Central

Both bacteria and archaea potentially contribute to ammonia oxidation, but their roles in freshwater sediments are still poorly understood. Seasonal differences in the relative activities of these groups might exist, since cultivated archaeal ammonia oxidizers have higher temperature optima than their bacterial counterparts. In this study, sediment collected from eutrophic freshwater Lake Taihu (China) was incubated at different temperatures (4°C, 15°C, 25°C, and 37°C) for up to 8 weeks. We examined the active bacterial and archaeal ammonia oxidizers in these sediment microcosms by using combined stable isotope probing (SIP) and molecular community analysis. The results showed that accumulation of nitrate in microcosms correlated negatively with temperature, although ammonium depletion was the same, which might have been related to enhanced activity of other nitrogen transformation processes. Incubation at different temperatures significantly changed the microbial community composition, as revealed by 454 pyrosequencing targeting bacterial 16S rRNA genes. After 8 weeks of incubation, [13C]bicarbonate labeling of bacterial amoA genes, which encode the ammonia monooxygenase subunit A, and an observed increase in copy numbers indicated the activity of ammonia-oxidizing bacteria in all microcosms. Nitrosomonas sp. strain Is79A3 and Nitrosomonas communis lineages dominated the heavy fraction of CsCl gradients at low and high temperatures, respectively, indicating a niche differentiation of active bacterial ammonia oxidizers along the temperature gradient. The 13C labeling of ammonia-oxidizing archaea in microcosms incubated at 4 to 25°C was minor. In contrast, significant 13C labeling of Nitrososphaera-like archaea and changes in the abundance and composition of archaeal amoA genes were observed at 37°C, implicating autotrophic growth of ammonia-oxidizing archaea under warmer conditions. PMID:23455342

Wu, Yucheng; Ke, Xiubin; Hernández, Marcela; Wang, Baozhan; Dumont, Marc G.; Jia, Zhongjun

2013-01-01

202

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 1 g l(-1) sucrose. Growth was separately determined for each bacterial strain after incubation periods of up to 72 h 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 72 h 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 72 h 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

203

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

204

Methodology of factorial design deriving guidelines for simulation of growth curve and production of sugars by Spirulina (Arthrospira) maxima  

Microsoft Academic Search

It is practical, economic and sometimes essential to derive rules or conclusions by performing lesser runs of experiments.\\u000a In this part, a methodology based on 2\\u000a f\\u000a factorial design was brought up to derive guidelines to simulate growth curve and production of sugars by Spirulina (Arthrospira) maxima. The growth curve or accumulation process of sugars was idealized by sets of

Zhen-yuan Nie; Jin-lan Xia; J. M. Levert

2001-01-01

205

Carboxyl-modified single-walled carbon nanotubes negatively affect bacterial growth and denitrification activity  

PubMed Central

Single-walled carbon nanotubes (SWNTs) have been used in a wide range of fields, and the surface modification via carboxyl functionalization can further improve their physicochemical properties. However, whether carboxyl-modified SWNT poses potential risks to microbial denitrification after its release into the environment remains unknown. Here we present the possible effects of carboxyl-modified SWNT on the growth and denitrification activity of Paracoccus denitrificans (a model denitrifying bacterium). It was found that carboxyl-modified SWNT were present both outside and inside the bacteria, and thus induced bacterial growth inhibition at the concentrations of 10 and 50?mg/L. After 24?h of exposure, the final nitrate concentration in the presence of 50?mg/L carboxyl-modified SWNT was 21-fold higher than that in its absence, indicating that nitrate reduction was substantially suppressed by carboxyl-modified SWNT. The transcriptional profiling revealed that carboxyl-modified SWNT led to the transcriptional activation of the genes encoding ribonucleotide reductase in response to DNA damage and also decreased the gene expressions involved in glucose metabolism and energy production, which was an important reason for bacterial growth inhibition. Moreover, carboxyl-modified SWNT caused the significant down-regulation and lower activity of nitrate reductase, which was consistent with the decreased efficiency of nitrate reduction. PMID:25008009

Zheng, Xiong; Su, Yinglong; Chen, Yinguang; Wan, Rui; Li, Mu; Wei, Yuanyuan; Huang, Haining

2014-01-01

206

Comparison of methods for measurement of bacterial growth rates in mixed batch cultures.  

PubMed Central

Eight methods of assessing growth rate constants of bacteria were compared in batch cultures of 3-micrometers-filtered estuarine water from the Skidaway River in Ga. Mixed assemblages of bacteria were grown under four nutrient regimes of added yeast extract ranging from 0 to 100 mg/liter. Linear and exponential growth rate constants were computed from changes in cell densities, biovolumes, and ATP concentrations. Exponential growth rate constants were obtained from the frequency of dividing cells and RNA synthesis as measured by [3H]adenine uptake. Rate constants obtained during lag, exponential, and stationary growth phases depended largely on the method used. Constants calculated from changes in cell densities, frequency of dividing cells, and adenine uptake correlated most closely with each other, whereas constants calculated from changes in ATP concentrations and biovolumes correlated best with each other. Estimates of in situ bacterial productivity and growth vary depending on the method used and the assumptions made regarding the growth state of bacteria. PMID:6179477

Christian, R R; Hanson, R B; Newell, S Y

1982-01-01

207

Direct Observation and Analysis of Bacterial Growth on an Antimicrobial Surface?  

PubMed Central

Cells of Escherichia coli NBRC 3972 and Staphylococcus aureus NBRC 12732 were inoculated onto an agar (1.5%) medium varying in nutrient concentration from full strength of the nutrient broth (NB) to 1/10 NB. Immediately thereafter, the inoculated agar was placed on antimicrobial and nonantimicrobial surfaces in such a way that the microbial cells came into contact with these surfaces. Cell growth was directly observed under a microscope, and the growth rate constant of the cells was measured based on the increase in the area of the colonies formed by the growing cells. On the antimicrobial surface, the growth rate constant decreased at lower nutrient concentrations for both E. coli and S. aureus cells, whereas it showed little change on the nonantimicrobial surface. It was supposed that either the nutrient uptake or the nutrient utilization efficiency was retarded by the antimicrobial surface. At the lowest nutrient concentration examined in the present study, 1/10 NB, the cells could hardly grow on the antimicrobial surface, indicating that the surface would be sufficiently active in preventing bacterial growth under normal usage conditions, such as the wet areas of a kitchen. It was also revealed that the antimicrobial surface could prevent the division of cells either during the growth stage or before the onset of growth. PMID:20562272

Yamada, Hiroyuki; Takahashi, Nobuyuki; Okuda, Shujiro; Tsuchiya, Yuki; Morisaki, Hisao

2010-01-01

208

The Mammalian Neuroendocrine Hormone Norepinephrine Supplies Iron for Bacterial Growth in the Presence of Transferrin or Lactoferrin  

PubMed Central

Norepinephrine stimulates the growth of a range of bacterial species in nutritionally poor SAPI minimal salts medium containing 30% serum. Addition of size-fractionated serum components to SAPI medium indicated that transferrin was required for norepinephrine stimulation of growth of Escherichia coli. Since bacteriostasis by serum is primarily due to the iron-withholding capacity of transferrin, we considered the possibility that norepinephrine can overcome this effect by supplying transferrin-bound iron for growth. Incubation with concentrations of norepinephrine that stimulated bacterial growth in serum-SAPI medium resulted in loss of bound iron from iron-saturated transferrin, as indicated by the appearance of monoferric and apo- isoforms upon electrophoresis in denaturing gels. Norepinephrine also caused the loss of iron from lactoferrin. The pharmacologically inactive metabolite norepinephrine 3-O-sulfate, by contrast, did not result in iron loss from transferrin or lactoferrin and did not stimulate bacterial growth in serum-SAPI medium. Norepinephrine formed stable complexes with transferrin, lactoferrin, and serum albumin. Norepinephrine-transferrin and norepinephrine-lactoferrin complexes, but not norepinephrine-apotransferrin or norepinephrine-albumin complexes, stimulated bacterial growth in serum-SAPI medium in the absence of additional norepinephrine. Norepinephrine-stimulated growth in medium containing 55Fe complexed with transferrin or lactoferrin resulted in uptake of radioactivity by bacterial cells. Moreover, norepinephrine-stimulated growth in medium containing [3H]norepinephrine indicated concomitant uptake of norepinephrine. In each case, addition of excess iron did not affect growth but significantly reduced levels of radioactivity (55Fe or 3H) associated with bacterial cells. A role for catecholamine-mediated iron supply in the pathophysiology of infectious diseases is proposed. PMID:11029429

Freestone, Primrose P. E.; Lyte, Mark; Neal, Christopher P.; Maggs, Anthony F.; Haigh, Richard D.; Williams, Peter H.

2000-01-01

209

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

E-print Network

Journal of Theoretical Biology 244 (2007) 326­348 Bacterial gene regulation in diauxic and non-diauxic growth Atul Naranga,�, Sergei S. Pilyuginb a Department of Chemical Engineering, University of Florida growth-limiting substrates, they exhibit a rich spectrum of substrate consumption patterns including

Pilyugin, Sergei S.

210

Effects of small abalone, Haliotis diversicolor, pedal mucus on bacterial growth, attachment, biofilm formation and community structure  

Microsoft Academic Search

Pedal mucus is important for locomotion, protection and signal transmission in the Gastropoda. It also provides nutrients and a habitat for microbes. In this study, we examined the effects of pedal mucus and the mucus trail of the small abalone, Haliotis diversicolor, on bacterial growth, attachment, biofilm formation and community structure. The results showed that pedal mucus enhanced the growth

Feng Guo; Zhao-bin Huang; Miao-qin Huang; Jing Zhao; Cai-huan Ke

2009-01-01

211

Zinc-Triggered Hydrogelation of Self-assembled Small Molecules to Inhibit Bacterial Growth.  

PubMed

There is a significant need to develop antibacterial materials that could be applied locally and directly to the places surrounded by large amount of bacteria, in order to address the problems of bacterial antibiotic-resistance or irreversible biofilm formation. Hydrogels are thought to be suitable candidates due to their versatile applications in biomedical field. Among them, small molecular hydrogels have been paid lots of attention because they are easy to design and fabricate and often sensitive to external stimuli. Meanwhile, the antibacterial activity of metal ions are attracting more and more attention because resistance to them are not yet found within bacteria. We therefore designed the zinc ion binding peptide of Nap-GFFYGGGHGRGD, who can self-assemble into hydrogels after binds Zn(2+) and inhibit the growth of bacteria due to the excellent antibacterial activity of Zn(2+). Upon the addition of zinc ions, solutions containing Nap-GFFYGGGHGRGD transformed into supramolecular hydrogels composed of network of long nano-fibers. Bacterial tests revealed an antibacterial effect of the zinc triggered hydrogels on E. coli. The studied small molecular hydrogel shows great potential in locally addressing bacterial infections. PMID:25583430

Xu, Chao; Cai, Yanbin; Ren, Chunhua; Gao, Jie; Hao, Jihui

2015-01-01

212

Zinc-Triggered Hydrogelation of Self-assembled Small Molecules to Inhibit Bacterial Growth  

NASA Astrophysics Data System (ADS)

There is a significant need to develop antibacterial materials that could be applied locally and directly to the places surrounded by large amount of bacteria, in order to address the problems of bacterial antibiotic-resistance or irreversible biofilm formation. Hydrogels are thought to be suitable candidates due to their versatile applications in biomedical field. Among them, small molecular hydrogels have been paid lots of attention because they are easy to design and fabricate and often sensitive to external stimuli. Meanwhile, the antibacterial activity of metal ions are attracting more and more attention because resistance to them are not yet found within bacteria. We therefore designed the zinc ion binding peptide of Nap-GFFYGGGHGRGD, who can self-assemble into hydrogels after binds Zn2+ and inhibit the growth of bacteria due to the excellent antibacterial activity of Zn2+. Upon the addition of zinc ions, solutions containing Nap-GFFYGGGHGRGD transformed into supramolecular hydrogels composed of network of long nano-fibers. Bacterial tests revealed an antibacterial effect of the zinc triggered hydrogels on E. coli. The studied small molecular hydrogel shows great potential in locally addressing bacterial infections.

Xu, Chao; Cai, Yanbin; Ren, Chunhua; Gao, Jie; Hao, Jihui

2015-01-01

213

Zinc-Triggered Hydrogelation of Self-assembled Small Molecules to Inhibit Bacterial Growth  

PubMed Central

There is a significant need to develop antibacterial materials that could be applied locally and directly to the places surrounded by large amount of bacteria, in order to address the problems of bacterial antibiotic-resistance or irreversible biofilm formation. Hydrogels are thought to be suitable candidates due to their versatile applications in biomedical field. Among them, small molecular hydrogels have been paid lots of attention because they are easy to design and fabricate and often sensitive to external stimuli. Meanwhile, the antibacterial activity of metal ions are attracting more and more attention because resistance to them are not yet found within bacteria. We therefore designed the zinc ion binding peptide of Nap-GFFYGGGHGRGD, who can self-assemble into hydrogels after binds Zn2+ and inhibit the growth of bacteria due to the excellent antibacterial activity of Zn2+. Upon the addition of zinc ions, solutions containing Nap-GFFYGGGHGRGD transformed into supramolecular hydrogels composed of network of long nano-fibers. Bacterial tests revealed an antibacterial effect of the zinc triggered hydrogels on E. coli. The studied small molecular hydrogel shows great potential in locally addressing bacterial infections. PMID:25583430

Xu, Chao; Cai, Yanbin; Ren, Chunhua; Gao, Jie; Hao, Jihui

2015-01-01

214

Curved-Lattice Epitaxial Growth of InxAl1-xN Nanospirals with Tailored Chirality.  

PubMed

Chirality, tailored by external morphology and internal composition, has been realized by controlled curved-lattice epitaxial growth of InxAl1-xN nanospirals. The curved morphology of the spiral segments is a result of a lateral compositional gradient while maintaining a preferred crystallographic growth direction, implying a lateral gradient in optical properties. Individual nanospirals show an asymmetric core-shell structure with curved basal planes. Mueller matrix spectroscopic ellipsometry shows that the tailored chirality is manifested in the polarization state of light reflected off the nanospirals. PMID:25427233

Hsiao, Ching-Lien; Magnusson, Roger; Palisaitis, Justinas; Sandström, Per; Persson, Per O Å; Valyukh, Sergiy; Hultman, Lars; Järrendahl, Kenneth; Birch, Jens

2015-01-14

215

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

216

Bacterial growth and substrate degradation by BTX-oxidizing culture in response to salt stress.  

PubMed

Interactions between microbial growth and substrate degradation are important in determining the performance of trickle-bed bioreactors (TBB), especially when salt is added to reduce biomass formation in order to alleviate media clogging. This study was aimed at quantifying salinity effects on bacterial growth and substrate degradation, and at acquiring kinetic information in order to improve the design and operation of TBB. Experiment works began by cultivating a mixed culture in a chemostat reactor receiving artificial influent containing a mixture of benzene, toluene, and xylene (BTX), followed by using the enrichment culture to degrade the individual BTX substrates under a particular salinity, which ranged 0-50 g l(-1) in batch mode. Then, the measured concentrations of biomass and residual substrate versus time were analyzed with the microbial kinetics; moreover, the obtained microbial kinetic constants under various salinities were modeled using noncompetitive inhibition kinetics. For the three substrates the observed bacterial yields appeared to be decreased from 0.51-0.74 to 0.20-0.22 mg mg(-1) and the maximum specific rate of substrate utilization, q, declined from 0.25-0.42 to 0.07-0.11 h(-1), as the salinity increased from 0 to 50 NaCl g l(-1). The NaCl acted as noncompetitive inhibitor, where the modeling inhibitions of the coefficients, K ( T(S)), were 22.7-29.7 g l(-1) for substrate degradation and K ( T(mu)), 13.0-19.0 g l(-1), for biomass formation. The calculated ratios for the bacterial maintenance rate, m (S), to q, further indicated that the percentage energy spent on maintenance increased from 19-24 to 86-91% as salinity level increased from 0 to 50 g l(-1). These results revealed that the bacterial growth was more inhibited than substrate degradation by the BTX oxidizers under the tested salinity levels. The findings from this study demonstrate the potential of applying NaCl salt to control excessive biomass formation in biotrickling filters. PMID:16284744

Lee, Chi-Yuan; Lin, Ching-Hsing

2006-01-01

217

Alcohol, Intestinal Bacterial Growth, Intestinal Permeability to Endotoxin, and Medical Consequences  

PubMed Central

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 of Gram negative bacteria in the intestine which may result in accumulation of endotoxin. In addition, alcohol metabolism by Gram negative bacteria and intestinal epithelial cells can result in accumulation of acetaldehyde, which in turn can increase intestinal permeability to endotoxin by increasing tyrosine phosphorylation of tight junction and adherens junction proteins. Alcohol-induced generation of nitric oxide may also contribute to increased permeability to endotoxin by reacting with tubulin, which may cause damage to microtubule cytoskeleton and subsequent disruption of intestinal barrier function. Increased intestinal permeability can lead to increased transfer of endotoxin from the intestine to the liver and general circulation where endotoxin may trigger inflammatory changes in the liver and other organs. Alcohol may also increase intestinal permeability to peptidoglycan which can initiate inflammatory response in liver and other organs. In addition, acute alcohol exposure may potentiate the effect of burn injury on intestinal bacterial growth and permeability. Decreasing the number of Gram negative bacteria in the intestine can result in decreased production of endotoxin as well as acetaldehyde which is expected to decrease intestinal permeability to endotoxin. In addition, intestinal permeability may be preserved by administering epidermal growth factor, L-glutamine, oats supplementation, or zinc thereby preventing the transfer of endotoxin to the general circulation. Thus reducing the number of intestinal Gram negative bacteria and preserving intestinal permeability to endotoxin may attenuate alcoholic liver and other organ injuries. PMID:18504085

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

2008-01-01

218

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

219

Inhibition of Pseudogymnoascus destructans growth from conidia and mycelial extension by bacterially produced volatile organic compounds.  

PubMed

The recently identified causative agent of white-nose syndrome (WNS), Pseudogymnoascus destructans, has been implicated in the mortality of an estimated 5.5 million North American bats since its initial documentation in 2006 (Frick et al. in Science 329:679-682, 2010). In an effort to identify potential biological and chemical control options for WNS, 6 previously described bacterially produced volatile organic compounds (VOCs) were screened for anti-P. destructans activity. The compounds include decanal; 2-ethyl-1-hexanol; nonanal; benzothiazole; benzaldehyde; andN,N-dimethyloctylamine. P. destructans conidia and mycelial plugs were exposed to the VOCs in a closed air space at 15 and 4 °C and then evaluated for growth inhibition. All VOCs inhibited growth from conidia as well as inhibiting radial mycelial extension, with the greatest effect at 4 °C. Studies of the ecology of fungistatic soils and the natural abundance of the fungistatic VOCs present in these environments suggest a synergistic activity of select VOCs may occur. The evaluation of formulations of two or three VOCs at equivalent concentrations was supportive of synergistic activity in several cases. The identification of bacterially produced VOCs with anti-P. destructans activity indicates disease-suppressive and fungistatic soils as a potentially significant reservoir of biological and chemical control options for WNS and provides wildlife management personnel with tools to combat this devastating disease. PMID:24190516

Cornelison, Christopher T; Gabriel, Kyle T; Barlament, Courtney; Crow, Sidney A

2014-02-01

220

Resource availability and competition shape the evolution of survival and growth ability in a bacterial community.  

PubMed

Resource availability is one of the main factors determining the ecological dynamics of populations or species. Fluctuations in resource availability can increase or decrease the intensity of resource competition. Resource availability and competition can also cause evolutionary changes in life-history traits. We studied how community structure and resource fluctuations affect the evolution of fitness related traits using a two-species bacterial model system. Replicated populations of Serratia marcescens (copiotroph) and Novosphingobium capsulatum (oligotroph) were reared alone or together in environments with intergenerational, pulsed resource renewal. The comparison of ancestral and evolved bacterial clones with 1 or 13 weeks history in pulsed resource environment revealed species-specific changes in life-history traits. Co-evolution with S. marcescens caused N. capsulatum clones to grow faster. The evolved S. marcescens clones had higher survival and slower growth rate then their ancestor. The survival increased in all treatments after one week, and thereafter continued to increase only in the S. marcescens monocultures that experienced large resource pulses. Though adaptive radiation is often reported in evolution studies with bacteria, clonal variation increased only in N. capsulatum growth rate. Our results suggest that S. marcescens adapted to the resource renewal cycle whereas N. capsulatum was more affected by the interspecific competition. Our results exemplify species-specific evolutionary response to both competition and environmental variation. PMID:24098791

Pekkonen, Minna; Ketola, Tarmo; Laakso, Jouni T

2013-01-01

221

Resource Availability and Competition Shape the Evolution of Survival and Growth Ability in a Bacterial Community  

PubMed Central

Resource availability is one of the main factors determining the ecological dynamics of populations or species. Fluctuations in resource availability can increase or decrease the intensity of resource competition. Resource availability and competition can also cause evolutionary changes in life-history traits. We studied how community structure and resource fluctuations affect the evolution of fitness related traits using a two-species bacterial model system. Replicated populations of Serratia marcescens (copiotroph) and Novosophingobium capsulatum (oligotroph) were reared alone or together in environments with intergenerational, pulsed resource renewal. The comparison of ancestral and evolved bacterial clones with 1 or 13 weeks history in pulsed resource environment revealed species-specific changes in life-history traits. Co-evolution with S. marcescens caused N. capsulatum clones to grow faster. The evolved S. marcescens clones had higher survival and slower growth rate then their ancestor. The survival increased in all treatments after one week, and thereafter continued to increase only in the S. marcescens monocultures that experienced large resource pulses. Though adaptive radiation is often reported in evolution studies with bacteria, clonal variation increased only in N. capsulatum growth rate. Our results suggest that S. marcescens adapted to the resource renewal cycle whereas N. capsulatum was more affected by the interspecific competition. Our results exemplify species-specific evolutionary response to both competition and environmental variation. PMID:24098791

Pekkonen, Minna; Ketola, Tarmo; Laakso, Jouni T.

2013-01-01

222

Mixed models defined by stochastic differential equations 1 Bayesian analysis of growth curves using mixed models defined by stochastic  

E-print Network

Mixed models defined by stochastic differential equations 1 Bayesian analysis of growth curves using mixed models defined by stochastic differential equations Sophie Donnet1 Ceremade, Universite are classically analyzed by nonlinear mixed models. However, the standard growth functions used in this context

Paris-Sud XI, Université de

223

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

224

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

PubMed

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 Araújo Barros, Irene; Luiz Araújo, Welington; Lúcio Azevedo, João

2010-10-01

225

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 Araújo Barros, Irene; Luiz Araújo, Welington; Lúcio Azevedo, João

2010-01-01

226

Growth curves in short supply: a descriptive study of the availability and utility of growth curve data in adolescents with eating disorders  

PubMed Central

Background Healthy body weight (HBW) determination affects multiple aspects of eating disorder (ED) treatment. For example, it can inform patients and providers as to when return of menses (ROM), an objective determinant of health, can occur. Growth curves (GCs) are sensitive indicators of health in youth and when up to date provide critical information regarding normal and expected trajectories of growth. Although not widely recommended as a first line tool for HBW calculation, a GC guides providers selecting a HBW that is individualized to each patient. The primary aim of this paper was to assess availability and feasibility of utilizing GC data for HBW prediction in adolescents referred for an ED assessment. We also sought to determine how this calculation compared to the standardized HBW calculation that uses mean body mass index (BMI) for age and how each of these numbers compared to the actual weight at ROM. Methods A retrospective chart review was completed on outpatients assessed for EDs between January 2004 and December 2006. A total of 102 patients met inclusion criteria. Demographic information, GC data, HBW predictions, and menstrual history were analyzed. A comparison of predicted HBWs using the aforementioned calculations and weight at ROM was performed using t-test analyses. Results Eighty-one patients (79.4%) had GC data available at assessment although HBW prediction was possible in only 24 patients (23.8%) due to poor GC completion. Of those 24 patients, 9 had ROM data available; no significant difference between our predicted HBW and the weight at ROM was found in these patients. In cases where HBW predictions could be compared using GC data and the BMI method, we found the GC calculation to be overall superior. Conclusions We found overall rates of GC completion to be very low in our patients, which in turn limited the feasibility of relying on a GC for HBW calculation in ED patients. When complete, GCs provide accurate HBWs for most patients with EDs although it is clear that secondary methods of calculation are required given the gaps in data observed using this cohort. PMID:24010557

2013-01-01

227

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.

228

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

PubMed Central

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, both isolated from a shallow aquifer, were utilized in this study. The change in the average generation or the average fluorescence intensity of the CFDA/SE-stained cells could be used to obtain estimates of doubling times. In microcosm experiments, the CFDA/SE-based doubling times were similar to the values calculated by total cell counting and were independent of cell concentration. Intact and repacked sediment core experiments with the same bacteria indicated that changes in groundwater chemistry were just as important as growth rates in determining planktonic cell concentrations. The growth rates within the sediment cores were similar to those calculated in microcosm experiments, and preferential transport of the daughter cells was not observed. The experiments indicated that the growth rates could be determined in systems with cell losses due to other phenomena, such as attachment to sediment or predation. Application of this growth rate estimation method to data from a field-scale bacterial transport experiment indicated that the doubling time was approximately 15 days, which is the first known direct determination of an in situ growth rate for bacteria in an aquifer. PMID:12839747

Mailloux, Brian J.; Fuller, Mark E.

2003-01-01

229

7, 787822, 2010 Increased bacterial  

E-print Network

BGD 7, 787­822, 2010 Increased bacterial growth efficiency with environmental variability M if available. Increased bacterial growth efficiency with environmental variability: results from DOC­822, 2010 Increased bacterial growth efficiency with environmental variability M. Eichinger et al. Title

Poggiale, Jean-Christophe

230

BacSim, a simulator for individual-based modelling of bacterial colony growth.  

PubMed

The generic, quantitative, spatially explicit, individual-based model BacSim was developed to simulate growth and behaviour of bacteria. The potential of this approach is in relating the properties of microscopic entities - cells - to the properties of macroscopic, complex systems such as biofilms. Here, the growth of a single Escherichia coli cell into a colony was studied. The object-oriented program BacSim is an extension of Gecko, an ecosystem dynamics model which uses the Swarm toolkit for multi-agent simulations. The model describes bacterial properties including substrate uptake, metabolism, maintenance, cell division and death at the individual cell level. With the aim of making the model easily applicable to various bacteria under different conditions, the model uses as few as eight readily obtainable parameters which can be randomly varied. For substrate diffusion, a two-dimensional diffusion lattice is used. For growth-rate-dependent cell size variation, a conceptual model of cell division proposed by Donachie was examined. A mechanistic version of the Donachie model led to unbalanced growth at higher growth rates, whereas including a minimum period between subsequent replication initiations ensured balanced growth only if this period was unphysiologically long. Only a descriptive version of the Donachie model predicted cell sizes correctly. For maintenance, the Herbert model (constant specific rate of biomass consumption) and for substrate uptake, the Michaelis-Menten or the Best equations were implemented. The simulator output faithfully reproduced all input parameters. Growth characteristics when maintenance and uptake rates were proportional to either cell mass or surface area are compared. The authors propose a new generic measure of growth synchrony to quantify the loss of synchrony due to random variation of cell parameters or spatial heterogeneity. Variation of the maximal uptake rate completely desynchronizes the simulated culture but variation of the volume-at-division does not. A new measure for spatial heterogeneity is introduced: the standard deviation of substrate concentrations as experienced by the cells. Spatial heterogeneity desynchronizes population growth by subdividing the population into parts synchronously growing at different rates. At a high enough spatial heterogeneity, the population appears to grow completely asynchronously. PMID:9884219

Kreft, J U; Booth, G; Wimpenny, J W

1998-12-01

231

Agarose particle-templated porous bacterial cellulose and its application in cartilage growth in vitro.  

PubMed

Bacterial cellulose (BC) is a biocompatible hydrogel with a three-dimensional (3-D) structure formed by a dense network of cellulose nanofibers. A limitation of using BC for applications in tissue engineering is that the pore size of the material (?0.02-10?m) is smaller than the dimensions of mammalian cells and prevents cells from penetrating into the material and growing into 3-D structures that mimic tissues. This paper describes a new route to porous bacterial cellulose (pBC) scaffolds by cultivating Acetobacter xylinum in the presence of agarose microparticles deposited on the surface of a growing BC pellicle. Monodisperse agarose microparticles with a diameter of 300-500?m were created using a microfluidic technique, layered on growing BC pellicles and incorporated into the polymer as A. xylinum cells moved upward through the growing pellicle. Removing the agarose microparticles by autoclaving produced BC gels containing a continuous, interconnected network of pores with diameters ranging from 300 to 500?m. Human P1 chondrocytes seeded on the scaffolds, replicated, invaded the 3-D porous network and distributed evenly throughout the substrate. Chondrocytes grown on pBC substrates displayed a higher viability compared to growth on the surface of unmodified BC substrates. The approach described in this paper introduces a new method for creating pBC substrates with user-defined control over the physical dimensions of the pore network, and demonstrates the application of these materials for tissue engineering. PMID:25449918

Yin, Na; Stilwell, Matthew D; Santos, Thiago M A; Wang, Huaping; Weibel, Douglas B

2015-01-15

232

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

233

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

234

Hydroxyapatite bioactivated bacterial cellulose promotes osteoblast growth and the formation of bone nodules.  

PubMed

The goal of this study was to investigate the feasibility of bacterial cellulose (BC) scaffold to support osteoblast growth and bone formation. BC was produced by culturing Acetobacter xylinum supplemented with hydroxyapatite (HA) to form BC membranes (without HA) and BC/HA membranes. Membranes were subjected to X-ray photoelectron spectroscopy (XPS) analysis to determine surface element composition. The membranes were further used to evaluate osteoblast growth, alkaline phosphatase activity and bone nodule formation. BC was free of calcium and phosphate. However, XPS analysis revealed the presence of both calcium (10%) and phosphate (10%) at the surface of the BC/HA membrane. Osteoblast culture showed that BC alone was non-toxic and could sustain osteoblast adhesion. Furthermore, osteoblast adhesion and growth were significantly (p ?0.05) increased on BC/HA membranes as compared to BC alone. Both BC and BC/HA membranes improved osteoconductivity, as confirmed by the level of alkaline phosphatase (ALP) activity that increased from 2.5 mM with BC alone to 5.3 mM with BC/HA. BC/HA membranes also showed greater nodule formation and mineralization than the BC membrane alone. This was confirmed by Alizarin red staining (ARS) and energy dispersive X-ray spectroscopy (EDX). This work demonstrates that both BC and BC/HA may be useful in bone tissue engineering. PMID:23174338

Tazi, Neftaha; Zhang, Ze; Messaddeq, Younès; Almeida-Lopes, Luciana; Zanardi, Lisinéia M; Levinson, Dennis; Rouabhia, Mahmoud

2012-01-01

235

Hydroxyapatite bioactivated bacterial cellulose promotes osteoblast growth and the formation of bone nodules  

PubMed Central

The goal of this study was to investigate the feasibility of bacterial cellulose (BC) scaffold to support osteoblast growth and bone formation. BC was produced by culturing Acetobacter xylinum supplemented with hydroxyapatite (HA) to form BC membranes (without HA) and BC/HA membranes. Membranes were subjected to X-ray photoelectron spectroscopy (XPS) analysis to determine surface element composition. The membranes were further used to evaluate osteoblast growth, alkaline phosphatase activity and bone nodule formation. BC was free of calcium and phosphate. However, XPS analysis revealed the presence of both calcium (10%) and phosphate (10%) at the surface of the BC/HA membrane. Osteoblast culture showed that BC alone was non-toxic and could sustain osteoblast adhesion. Furthermore, osteoblast adhesion and growth were significantly (p ?0.05) increased on BC/HA membranes as compared to BC alone. Both BC and BC/HA membranes improved osteoconductivity, as confirmed by the level of alkaline phosphatase (ALP) activity that increased from 2.5 mM with BC alone to 5.3 mM with BC/HA. BC/HA membranes also showed greater nodule formation and mineralization than the BC membrane alone. This was confirmed by Alizarin red staining (ARS) and energy dispersive X-ray spectroscopy (EDX). This work demonstrates that both BC and BC/HA may be useful in bone tissue engineering. PMID:23174338

2012-01-01

236

Effects of Engineered Cerium Oxide Nanoparticles on Bacterial Growth and Viability?†  

PubMed Central

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, due to a lack of standard methods for assessing such interactions. 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. The growth and viability of the Gram-negative species Escherichia coli and Shewanella oneidensis, a metal-reducing bacterium, and the Gram-positive species Bacillus subtilis were examined relative to cerium oxide particle size, growth media, pH, and dosage. A hydrothermal synthesis approach 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 from MIC and CFU measurements, disk diffusion tests, and live/dead assays. For E. coli and B. subtilis, clear strain- and size-dependent inhibition was observed, whereas S. oneidensis appeared to be unaffected by the particles. Transmission electron microscopy along with microarray-based transcriptional profiling was used to understand the response mechanism of the bacteria. 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. PMID:20952651

Pelletier, Dale A.; Suresh, Anil K.; Holton, Gregory A.; McKeown, Catherine K.; Wang, Wei; Gu, Baohua; Mortensen, Ninell P.; Allison, David P.; Joy, David C.; Allison, Martin R.; Brown, Steven D.; Phelps, Tommy J.; Doktycz, Mitchel J.

2010-01-01

237

A new method to compare statistical tree growth curves: the PL-GMANOVA model and its application with dendrochronological data.  

PubMed

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 = A · T+E, where for b ? 0 : Q = Ei[-b · r]-Ei[-b · r1] and for b = 0 : Q ?= Ln[r/r1], A = ?initial relative growth to be estimated, T = t-t1, and E is an error term for each tree and time point. Furthermore, Ei[-b · r] ?= ?(Exp[-b · r]/r)dr, b = -1/TPR, with TPR being the turning point radius in a sigmoid curve, and r1 at t1 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 A. One site (at the Popocatépetl volcano) stood out, with A 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 Popocatépetl 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; Peña Ramírez, Víctor M; von Rosen, Dietrich

2014-01-01

238

Inhibition of Mastitic Bacteria by Bovine Milk Apo-Lactoferrin Evaluated by In Vitro Microassay of Bacterial Growth1  

Microsoft Academic Search

An in vitro microassay was developed to evaluate antimicrobial properties of bovine apo-lactoferrin. The growth of coliform, staphylococcal, and streptococ- cal bacterial strains in a defined synthetic medium was inhibited by bovine apo- lactoferrin (.5 to 30.0 mg\\/ml). Addition of iron-saturated lactoferrin to the synthetic medium did not inhibit growth of test strains. Inhibition by apo-lacto- ferrin was greater for

Brian J. Nonnecke; K. Larry Smith

1984-01-01

239

Effects of inoculation with PGPR Bacillus and Pisolithus tinctorius on Pinus pinea L. growth, bacterial rhizosphere colonization, and mycorrhizal infection  

Microsoft Academic Search

The effect of co-inoculation with Pisolithus tinctorius and a PGPR belonging to the genus Bacillus (Bacillus licheniformis CECT 5106 and Bacillus pumilus CECT 5105) in enhancing growth of Pinus pinea plants and the changes that occurred in rhizosphere microbial communities and the degree of mycorrhization were evaluated.\\u000a Both bacterial strains of Bacillus promote the growth of Pinus pinea seedlings, but

A. Probanza; J. L. Mateos; J. A. Lucas Garcia; B. Ramos; M. R. de Felipe; F. J. Gutierrez Manero

2001-01-01

240

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

EPA Science Inventory

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

241

IN VITRO BACTERIAL GROWTH AND IN VIVO RUMEN MICROBIOTA POPULATIONS ASSOCIATED WITH BLOAT IN STEERS GRAZING WHEAT FORAGE  

Technology Transfer Automated Retrieval System (TEKTRAN)

The role of rumen bacteria in the frothy bloat complex common to cattle grazing winter wheat has not been previously elucidated. A series of in vitro and in vivo experiments were designed to elucidate the effect of fresh wheat forage on the bacterial growth, bio-film complexes, rumen fermentation e...

242

Adherence of Staphylococcus aureus to Endothelial Cells: Influence of Capsular Polysaccharide, Global Regulator agr, and Bacterial Growth Phase  

Microsoft Academic Search

The adherence of Staphylococcus aureus to human endothelial cells (EC) is probably an important step in the pathogenesis of systemic staphylococcal infections. We examined the influence of type 5 capsular polysaccha- ride (CP5) production, the global regulator agr, and the bacterial growth phase on S. aureus adherence to EC. Whereas S. aureus Newman showed maximal adherence to EC in the

PETRA POHLMANN-DIETZE; MARTINA ULRICH; KEVIN B. KISER; GERD DORING; JEAN C. LEE; JEAN-MICHEL FOURNIER; KONRAD BOTZENHART; CHRISTIANE WOLZ

2000-01-01

243

QUANTITATIVE ANALYSIS OF THE GASTROINTESTINAL BACTERIAL COMMUNITY OF BROILER CHICKENS REARED WITH AND WITHOUT ANTIMICROBIAL GROWTH PROMOTANTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aims: To explore the effect of antimicrobial growth promotants (AGP) on the intestinal microflora of broiler chickens, the bacterial community of this environment was quantitatively profiled in birds reared with and without AGPs. Methods and Results: Quantitative, real-time PCR with group-specifi...

244

Development and validation of a liquid chromatography-mass spectrometry assay for polymyxin B in bacterial growth media.  

PubMed

There is increasing interest in the optimization of polymyxin B dosing regimens to treat infections caused by multidrug-resistant Gram-negative bacteria. We aimed to develop and validate a liquid chromatography-single quadrupole mass spectrometry (LC-MS) method to quantify polymyxin B in two growth media commonly used in in vitro pharmacodynamic studies, cation-adjusted Mueller-Hinton and tryptone soya broth. Samples were pre-treated with sodium hydroxide (1.0M) and formic acid in acetonitrile (1:100, v/v) before analysis. The summed peak areas of polymyxin B1 and B2 relative to the summed peak areas of colistin A and B (internal standard) were used to quantify polymyxin B. Quality control samples were prepared and analyzed to assess the intra- and inter-day accuracy and precision. The robustness of the assay in the presence of bacteria and commonly co-administered antibiotics (rifampicin, doripenem, imipenem, cefepime and tigecycline) was also examined. Chromatographic separation was achieved with retention times of approximately 9.7min for polymyxin B2 and 10.4min for polymyxin B1. Calibration curves were linear between 0.103 and 6.60mg/L. Accuracy (% relative error) and precision (% coefficient of variation), pooled for all assay days and matrices (n=84), were -6.85% (8.17%) at 0.248mg/L, 1.73% (6.15%) at 2.48mg/L and 1.54% (5.49%) at 4.95mg/L, and within acceptable ranges at all concentrations examined. Further, the presence of high bacterial concentrations or of commonly co-administered antibiotics in the samples did not affect the assay. The accuracy, precision and cost-efficiency of the assay make it ideally suited to quantifying polymyxin B in samples from in vitro pharmacodynamic models. PMID:24530981

Cheah, Soon-Ee; Bulitta, Jurgen B; Li, Jian; Nation, Roger L

2014-04-01

245

Secreted Pyomelanin of Legionella pneumophila Promotes Bacterial Iron Uptake and Growth under Iron-Limiting Conditions  

PubMed Central

Iron acquisition is critical to the growth and virulence of Legionella pneumophila. Previously, we found that L. pneumophila uses both a ferrisiderophore pathway and ferrous iron transport to obtain iron. We now report that two molecules secreted by L. pneumophila, homogentisic acid (HGA) and its polymerized variant (HGA-melanin, a pyomelanin), are able to directly mediate the reduction of various ferric iron salts. Furthermore, HGA, synthetic HGA-melanin, and HGA-melanin derived from bacterial supernatants enhanced the ability of L. pneumophila and other species of Legionella to take up radiolabeled iron. Enhanced iron uptake was not observed with a ferrous iron transport mutant. Thus, HGA and HGA-melanin mediate ferric iron reduction, with the resulting ferrous iron being available to the bacterium for uptake. Upon further testing of L. pneumophila culture supernatants, we found that significant amounts of ferric and ferrous iron were associated with secreted HGA-melanin. Importantly, a pyomelanin-containing fraction obtained from a wild-type culture supernatant was able to stimulate the growth of iron-starved legionellae. That the corresponding supernatant fraction obtained from a nonpigmented mutant culture did not stimulate growth demonstrated that HGA-melanin is able to both promote iron uptake and enhance growth under iron-limiting conditions. Indicative of a complementary role in iron acquisition, HGA-melanin levels were inversely related to the levels of siderophore activity. Compatible with a role in the ecology and pathogenesis of L. pneumophila, HGA and HGA-melanin were effective at reducing and releasing iron from both insoluble ferric hydroxide and the mammalian iron chelates ferritin and transferrin. PMID:23980114

Zheng, Huaixin; Chatfield, Christa H.; Liles, Mark R.

2013-01-01

246

Bacterial Biofertilizers  

Microsoft Academic Search

Many bacteria and fungi can enhance plant growth. The present review is limited to plant growth promoting rhizobacteria (PGPR). However, it includes endophytic bacteria that show plant growth enhancing activity as well. Also the best studied bacterial mechanisms of plant growth promotion are discussed, with a special emphasis on biological nitrogen fixation and synthesis of phytohormones, including less understood mechanisms

LUIS E. FUENTES-RAMIREZ; Jesus Caballero-Mellado

247

Silver nanoparticle impact on bacterial growth: effect of pH, concentration, and organic matter.  

PubMed

Silver nanoparticles (Ag NPs) are widely used as antibacterial agents. This antibacterial property carries with it a potential environmental risk once these NPs are discharged into the environment. This study investigated the impact on Pseudomonas fluorescens over a 24 h exposure of well characterized Ag NPs at pH values of 6-9, in the presence and absence of Suwannee River humic acids (SRHA). Ag NPs were characterized by size, aggregation, morphology, dissolution, and surface properties under all conditions. Solubility was low (less than 2%) for all Ag NP concentrations (2-2000 ppb) and under all conditions was less than 40 ppb (0.38 microM). SRHA caused a partial disaggregation of Ag NP aggregates by nanoscale film formation, with individual NPs stabilized by charge and entropically driven steric effects. Dissolved Ag reduced bacterial growth entirely at 2000 ppb (19 microM) under all conditions and adversely affected growth at 200 ppb (1.9 microM) under some conditions, indicating some toxicity. The Ag NPs showed similar toxicity at 2000 ppb (19 microM) in the absence of SRHA and at pH 9 only i.e. SRHA mitigated bactericidal action. Solubility and interactions with SRHA indicate that there was a specific nanoparticle effect which could not be explained by the effect of dissolved Ag. PMID:19848135

Fabrega, Julia; Fawcett, Shona R; Renshaw, Joanna C; Lead, Jamie R

2009-10-01

248

Methicillin-resistant Staphylococcus aureus screening by online immunometric monitoring of bacterial growth under selective pressure.  

PubMed

Rapid, high-throughput screening tools are needed to contain the spread of hospital-acquired methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) strains. Most techniques used in current clinical practice still require time-consuming culture for primary isolation of the microbe. We present a new phenotypic assay for MRSA screening. The technique employs a two-photon excited fluorescence (TPX) detection technology with S. aureus-specific antibodies that allows the online monitoring of bacterial growth in a single separation-free process. Different progressions of fluorescence signals are recorded for methicillin-susceptible and -resistant strains when the growth of S. aureus is monitored in the presence of cefoxitin. The performance of the new technique was evaluated with 20 MRSA strains, 6 methicillin-susceptible S. aureus strains, and 7 coagulase-negative staphylococcal strains and two different monoclonal S. aureus-specific antibodies. When either of these antibodies was used, the sensitivity and the specificity of the TPX assay were 100%. All strains were correctly classified within 8 to 12 h, and up to 70 samples were simultaneously analyzed on a single 96-well microtiter plate. As a phenotypic method, the TPX assay is suited for screening purposes. The final definition of methicillin resistance in any S. aureus strain should be based on the presence of the mecA gene. The main benefit afforded by the initial use of the TPX methodology lies in its low cost and applicability to high-throughput analysis. PMID:19752281

Stenholm, Teppo; Hakanen, Antti J; Vaarno, Jonne; Pihlasalo, Sari; Terho, Perttu; Hänninen, Pekka E; Vuopio-Varkila, Jaana; Huovinen, Pentti; Kotilainen, Pirkko

2009-12-01

249

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

250

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

251

Artemisia princeps Pamp. Essential oil and its constituents eucalyptol and ?-terpineol ameliorate bacterial vaginosis and vulvovaginal candidiasis in mice by inhibiting bacterial growth and NF-?B activation.  

PubMed

To investigate the inhibitory effects of Artemisia princeps Pamp. (family Asteraceae) essential oil (APEO) and its main constituents against bacterial vaginosis and vulvovaginal candidiasis, their antimicrobial activities against Gardnerella vaginalis and Candida albicans in vitro and their anti-inflammatory effects against G. vaginalis-induced vaginosis and vulvovaginal candidiasis were examined in mice. APEO and its constituents eucalyptol and ?-terpineol were found to inhibit microbe growths. ?-Terpineol most potently inhibited the growths of G. vaginalis and C. albicans with MIC values of 0.06 and 0.125?% (v/v), respectively. The antimicrobial activity of ?-terpineol was found to be comparable to that of clotrimazole. Intravaginal treatment with APEO, eucalyptol, or ?-terpineol significantly decreased viable G. vaginalis and C. albicans numbers in the vaginal cavity and myeloperoxidase activity in mouse vaginal tissues compared with controls. These agents also inhibited the expressions of proinflammatory cytokines (IL-1 ?, IL-6, TNF- ?), COX-2, iNOS, and the activation of NF- ?B and increased expression of the anti-inflammatory cytokine IL-10. In addition, they inhibited the expressions of proinflammatory cytokines and the activation of NF- ?B in lipopolysaccharide-stimulated peritoneal macrophages, and ?-terpineol most potently inhibited the expressions of proinflammatory cytokines and NF- ?B activation. Based on these findings, APEO and its constituents, particularly ?-terpineol, ameliorate bacterial vaginosis and vulvovaginal candidiasis by inhibiting the growths of vaginal pathogens and the activation of NF- ?B. PMID:21830186

Trinh, Hien-Trung; Lee, In-Ah; Hyun, Yang-Jin; Kim, Dong-Hyun

2011-12-01

252

N-acetyl-L-cysteine affects growth, extracellular polysaccharide production, and bacterial biofilm formation on solid surfaces.  

PubMed

N-Acetyl-L-cysteine (NAC) is used in medical treatment of patients with chronic bronchitis. The positive effects of NAC treatment have primarily been attributed to the mucus-dissolving properties of NAC, as well as its ability to decrease biofilm formation, which reduces bacterial infections. Our results suggest that NAC also may be an interesting candidate for use as an agent to reduce and prevent biofilm formation on stainless steel surfaces in environments typical of paper mill plants. Using 10 different bacterial strains isolated from a paper mill, we found that the mode of action of NAC is chemical, as well as biological, in the case of bacterial adhesion to stainless steel surfaces. The initial adhesion of bacteria is dependent on the wettability of the substratum. NAC was shown to bind to stainless steel, increasing the wettability of the surface. Moreover, NAC decreased bacterial adhesion and even detached bacteria that were adhering to stainless steel surfaces. Growth of various bacteria, as monocultures or in a multispecies community, was inhibited at different concentrations of NAC. We also found that there was no detectable degradation of extracellular polysaccharides (EPS) by NAC, indicating that NAC reduced the production of EPS, in most bacteria tested, even at concentrations at which growth was not affected. Altogether, the presence of NAC changes the texture of the biofilm formed and makes NAC an interesting candidate for use as a general inhibitor of formation of bacterial biofilms on stainless steel surfaces. PMID:12902275

Olofsson, Ann-Cathrin; Hermansson, Malte; Elwing, Hans

2003-08-01

253

Testing a Dynamic Model of Student and School Effectiveness with a Multivariate Multilevel Latent Growth Curve Approach  

ERIC Educational Resources Information Center

This article addresses whether students' achievement motivation changes over time, the relationship between changes in motivation and changes in educational attainment, and the between-school differences in these changes and their interrelationships. Also gender differences were studied. Multivariate multilevel latent growth curve analysis was…

van der Werf, Greetje; Opdenakker, Marie-Christine; Kuyper, Hans

2008-01-01

254

Modeling the growth curve for Spirulina ( Arthrospira ) maxima , a versatile microalga for producing uniformly labelled compounds with stable isotopes  

Microsoft Academic Search

The paper presents a five-phase model to describe batch culture of Spirulina maxima under limitations of light and nutrients nitrogen andsulfur. The general equation for the exponential, linear, decelerating andstationary phases of the growth curve took into account that (i) the specificgrowth rate was proportional to the local light intensity in thephotobioreactor; (ii) light attenuation was due to cell's absorption

J. M. Levert; Jinlan Xia

2001-01-01

255

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

256

Hormone-Dependent Bacterial Growth, Persistence and Biofilm Formation – A Pilot Study Investigating Human Follicular Fluid Collected during IVF Cycles  

PubMed Central

Human follicular fluid, considered sterile, is aspirated as part of an in vitro fertilization (IVF) cycle. However, it is easily contaminated by the trans-vaginal collection route and little information exists in its potential to support the growth of microorganisms. The objectives of this study were to determine whether human follicular fluid can support bacterial growth over time, whether the steroid hormones estradiol and progesterone (present at high levels within follicular fluid) contribute to the in vitro growth of bacterial species, and whether species isolated from follicular fluid form biofilms. We found that bacteria in follicular fluid could persist for at least 28 weeks in vitro and that the steroid hormones stimulated the growth of some bacterial species, specifically Lactobacillus spp., Bifidobacterium spp. Streptococcus spp. and E. coli. Several species, Lactobacillus spp., Propionibacterium spp., and Streptococcus spp., formed biofilms when incubated in native follicular fluids in vitro (18/24, 75%). We conclude that bacteria aspirated along with follicular fluid during IVF cycles demonstrate a persistent pattern of growth. This discovery is important since it can offer a new avenue for investigation in infertile couples. PMID:23226503

Pelzer, Elise S.; Allan, John A.; Theodoropoulos, Christina; Ross, Tara; Beagley, Kenneth W.; Knox, Christine L.

2012-01-01

257

Using trajectories from a bivariate growth curve as predictors in a Cox regression model.  

PubMed

An important research objective in most psychiatric clinical trials of maintenance treatment is to find predictors of recurrence of illness. In those trials, patients are first admitted into an open treatment period also called acute treatment. If they respond to the treatment and are considered to have stable remission from the illness, they enter the second phase of the trial where they are randomized into different arms of the 'maintenance treatments'. Often, more than one response variable is measured longitudinally in the acute treatment phase to monitor treatment responses. Trajectories of these response measures are believed to have predictive ability for recurrences in the maintenance phase of the trial. By using a bivariate growth curve from two such longitudinal measures, we developed a method to use the estimated trajectories of each subject in a Cox regression model to predict recurrence in the maintenance phase. To adjust for the parameter estimation errors, we applied a full likelihood approach based on the conditional expectations of the predictors. Simulation studies indicate that the estimation error corrected estimators for the Cox model parameters are less biased when compared to the naive regression estimators without accounting for these errors. The uniqueness of this method lies in estimating trajectories from bivariate unequally spaced longitudinal response measures. An illustrative example is provided with data from a maintenance treatment trial for major depression in an elderly population. Visual Fortran 90 programs were developed to implement the algorithm. PMID:16612837

Dang, Qianyu; Mazumdar, Sati; Anderson, Stewart J; Houck, Patricia R; Reynolds, Charles F

2007-02-20

258

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

259

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

260

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

261

Lysozyme-triggered epidermal growth factor release from bacterial cellulose membranes controlled by smart nanostructured films.  

PubMed

A novel wound-dressing biodevice, sensitive to lysozyme, an enzyme commonly found at infected skin wounds, was assembled by the layer-by-layer deposition of nanopolymeric chitosan and alginate films onto oxidized bacterial cellulose membranes incorporated with epidermal growth factor (EGF). Distinct EGF release profiles were obtained according to specific stimuli caused by infection. In in vitro conditions simulating noninfected wounds, the EGF rate and burst release effect were reduced by three deposited layers (Mt /M? of 0.25 at 3 h) in a process dependent on the porosity of the compact chitosan-alginate complex. The importance of the organized structure was revealed when an infected wound was simulated by adding lysozyme to the release medium, thus inducing the formation of a loosely polyelectrolyte architecture that caused rapid EGF diffusion (Mt /M? of 0.75 at 30 min). The results indicate that the nanopolymeric layers were capable of slowly releasing EGF as required for normal wound repair and rapidly undergoing architectural transitions that allow the diffusion of massive amounts of drug to enhance the process of re-epithelialization. In summary, the proposed system comprises the roles of both wound dressing and local delivery mechanism to recognize infections and respond with a burst of EGF release. PMID:25308839

Picheth, Guilherme Fadel; Sierakowski, Maria Rita; Woehl, Marco Aurelio; Ono, Lucy; Cofré, Axel Rulf; Vanin, Luana Pasetti; Pontarolo, Roberto; De Freitas, Rilton Alves

2014-12-01

262

Soil bacterial diversity responses to root colonization by an ectomycorrhizal fungus are not root-growth-dependent.  

PubMed

The hypothesis tested in this present study was that the ectomycorrhizosphere effect on the bacterial community was not root-growth-dependent. The impacts of ectomycorrhizal infection (Pisolithus albus COI007) and a chemical fertilization to reproduce the fungal effect on root growth were examined on (1) the structure of bacterial community and (2) fluorescent pseudomonad and actinomycete populations in the mycorrhizosphere of Acacia auriculiformis using both culture-independent and culture-dependent methods. A. auriculiformis plants were grown in disinfested soil in pots with or without addition of the ectomycorrhizal fungus or N/P/K fertilization (to reproduce the fungal effect on root growth) for 4 months and then transferred to 20-L pots filled with nondisinfested sandy soil. The fungal 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 microbiota was significantly different within the treatments as revealed from DNA analysis [denaturing gradient gel electrophoresis (DGGE)]. The structure of fluorescent pseudomonad populations was also affected by fungal and fertilizer applications. In contrast, no qualitative effect was observed for the actinomycete communities within each treatment, but fungal inoculation significantly decreased the number of actinomycetes compared to the fertilizer application treatment. These results show that the mycorrhizosphere effect is not root-growth-dependent but is mainly due to the presence of the ectomycorrhizal fungus and more particularly to the extramatrical mycelium. PMID:16254760

Assigbetse, Komi; Gueye, Mariama; Thioulouse, Jean; Duponnois, Robin

2005-10-01

263

Preweaning growth curves in Brown Swiss and Pirenaica calves with emphasis on individual variability.  

PubMed

A quadratic polynomial model with random regression coefficients was used to describe preweaning growth curves of two beef cattle breeds widely used in the Spanish Pyrenees, according to genotype and season of birth effects. In addition, parameters of individual variability that can be used in a stochastic model were obtained. Data recorded indoors from birth to weaning of 217 Brown Swiss calves (3,509 observations) born either in spring or autumn (BS-S, BS-A) and 101 spring-born Pirenaica calves (PI-S, 967 observations) were analyzed. A quadratic model accurately fitted the preweaning weights (R2 = .99). Use of random regression coefficients improved the weaning weight adjustment; the residual variance of the model with intercept and linear random coefficients (9.61 kg2) was smaller than that of the model without them (130.03 kg2). Brown Swiss-S and PI-S calves had similar birth weight (40.9 +/- .96 vs 39.4 +/- .73 kg), but BS-S calves achieved significantly higher weaning weights at 150 d of age (175.2 +/- 2.45 vs 158.4 +/- 3.17 kg). Preweaning growth patterns were different for each season of birth, but there were no differences in weaning weight at 150 d of age (172.9 +/- 2.01 BS-A vs 175.2 +/- 2.45 BS-S). Standardization of weaning weights using a linear approximation could lead to biases, especially when comparing animals from the two calving seasons. The estimate of variances of random parameters should be done within breed and season of birth in order to take into account heteroscedasticity. The variances for BS-A, BS-S, and PI-S were 39.9, 57.6, and 32.2 kg2 for the intercept, respectively, and .0159, .0141, and .0205 kg2 for the linear coefficient. Covariance between the intercept and the linear coefficient (.34 kg2) was only statistically significant in the case of BS-S. The individual variance of weight at 150 d was 424.7 kg2 and 526.7 kg2 for BS-S and PI-S, respectively, almost 65% of the observed variance of weaning weight. PMID:10834564

Villalba, D; Casasús, I; Sanz, A; Estany, J; Revilla, R

2000-05-01

264

Modeling Trajectory of Depressive Symptoms Among Psychiatric Inpatients: A Latent Growth Curve Approach  

PubMed Central

Objectives Changes in the parameters of inpatient psychiatric care have inspired a sizable literature exploring correlates of prolonged intervention as well as symptom change over varying lengths of hospitalization. However, existing data offer limited insight regarding the nature of symptom change over time. Objectives of this longitudinal research were to (a) model the trajectory of depressive symptoms within an inpatient psychiatric sample, (b) identify characteristics associated with unique patterns of change, and (c) evaluate the magnitude of expected gains using objective clinical benchmarks. Methods Participants included psychiatric inpatients treated between April 2008 and December 2010. Latent growth curve modeling was used to determine the trajectory of Beck Depression Inventory II depressive symptoms in response to treatment. Age, gender, trauma history, prior hospitalization, and DSM-IV diagnoses were examined as potential moderators of recovery. Results Results indicate a nonlinear model of recovery, with symptom reductions greatest following admission and slowing gradually over time. Female gender, probable trauma exposure, prior psychiatric hospitalization, and primary depressive diagnosis were associated with more severe trajectories. Diagnosis of alcohol/substance use, by contrast, was associated with more moderate trajectories. Objective benchmarks occurred relatively consistently across patient groups with clinically significant change occurring between 2–4 weeks post-admission. Conclusion The nonlinear trajectory of recovery observed in these data provides insight regarding the dynamics of inpatient recovery. Across all patient groups, symptom reduction was most dramatic in the initial week of hospitalization. However, notable improvement continued for several weeks post-admission. Results suggest timelines for adequate inpatient care are largely contingent on program-specific goals. PMID:23759452

Clapp, Joshua D.; Grubaugh, Anouk L.; Allen, Jon G.; Mahoney, Jane; Oldham, John M.; Fowler, J. Christopher; Ellis, Tom; Elhai, Jon D.; Frueh, B. Christopher

2014-01-01

265

Spectral variations and a classical curve-of-growth analysis of HDE 226868 (Cyg X-1).  

NASA Astrophysics Data System (ADS)

The authors present an analysis of high resolution (R ˜ 17000) echelle spectra in the wavelength range 3200 to 6800 Å obtained at the Observatorio Astronómico Nacional at San Pedro Mártir, of HDE 226868, the optical component of the Cyg X-1 binary system. Empirical radial velocity vs. excitation (RV vs. E) relations are obtained from the spectra at 7 orbital phases and the slope (A) of these relations is found to vary, having two extrema: -0.30 km s-1eV-1 near phase 0.5 (collapsed object "in front") and -0.22 km s-1eV-1 near phase 0.0. At other phases the value is A = -0.13 km s-1eV-1. This variability in the slope of the RV vs. E relation is in very good agreement with the theoretically predicted anisotropic mass-loss rates resulting from the modified gravitational potential of the system (Friend and Castor, 1982) for the case in which the primary star fills its Roche lobe. Variations at the 25% level in the shapes and strengths of H? and He I photospheric absorption lines are detected. The variability of the absorption line profiles appears to correlate with the H? and the He II 4686 Å emission line variations, suggesting that the absorption lines are contaminated by variable emission components. From a classical curve-of-growth analysis HDE 226868 is found to have Texc = 32100±1600° K, and to be overabundant in He and underabundant in C with respect to the B0 Ia supergiant ? Ori.

Canalizo, G.; Koenigsberger, G.; Peña, D.; Ruiz, E.

1995-04-01

266

Estimation of gestational ages in the common marmoset (Callithrix jacchus) from published prenatal growth curves.  

PubMed

This report compares estimated gestational ages from published cubic spline curves to gestational ages estimated retrospectively from delivery dates in 28 pregnancies from ten common marmosets (Callithrix jacchus). Both CRL- and BPD-based estimates of gestational age were closely correlated with delivery-based gestational age estimates. Of the three ultrasound machines used, the one with 16 shades of gray and a sequential linear array overestimated gestational age during early pregnancy, based on CRL measures. Measures from the other two machines (64 or 264 shades of gray; linear sector and annular array or electronic phase array) were similar and resulted in a correlation of the two estimates of gestational age of 0.94 and a mean difference between the two estimates of 0.16 days with 80% of CRL-based gestational age estimates being within +/- 5 days of the delivery-based estimate. The reliability of BPD-based estimates of gestational age was strongly related to pregnancy outcome. BPD-based estimates underestimated gestational age in poor outcome pregnancies (i.e., those in which infants died within 7 days of birth) but not in good outcome pregnancies. The combined CRL- and BPD-based estimates on poor outcome pregnancies suggest that there was less growth in BPD in late gestation for those pregnancies that resulted in nonviable offspring. For good outcome pregnancies, the correlation between BPD-based and delivery-based estimates of gestational age was 0.871 and the mean difference between the two estimates was -0.06 days with 83.3% of BPD-based estimates falling within +/- 5 days of delivery-based estimates. PMID:9606040

Tardif, S D; Jaquish, C E; Toal, R L; Layne, D G; Power, R A

1998-02-01

267

Diffusion in immobilized-cell agar layers: influence of bacterial growth on the diffusivity of potassium chloride  

Microsoft Academic Search

The diffusitivity of potassium chloride in composite agar slab\\/microporous membrane structures loaded with various amounts of Escherichia coli whole cells was determined using both time-lag and steady-state methods. The diffusion coefficient of KCl decreased linearly with the logarithm of the immobilized-cells content. The effect exerted by bacterial growth inside the immobilization matrices on KCl diffusivity was then investigated. The diffusion

Laurent Mignot; Guy-Alain Junter

1990-01-01

268

High-resolution time series of Pseudomonas aeruginosa gene expression and rhamnolipid secretion through growth curve synchronization  

PubMed Central

Background Online spectrophotometric measurements allow monitoring dynamic biological processes with high-time resolution. Contrastingly, numerous other methods require laborious treatment of samples and can only be carried out offline. Integrating both types of measurement would allow analyzing biological processes more comprehensively. A typical example of this problem is acquiring quantitative data on rhamnolipid secretion by the opportunistic pathogen Pseudomonas aeruginosa. P. aeruginosa cell growth can be measured by optical density (OD600) and gene expression can be measured using reporter fusions with a fluorescent protein, allowing high time resolution monitoring. However, measuring the secreted rhamnolipid biosurfactants requires laborious sample processing, which makes this an offline measurement. Results Here, we propose a method to integrate growth curve data with endpoint measurements of secreted metabolites that is inspired by a model of exponential cell growth. If serial diluting an inoculum gives reproducible time series shifted in time, then time series of endpoint measurements can be reconstructed using calculated time shifts between dilutions. We illustrate the method using measured rhamnolipid secretion by P. aeruginosa as endpoint measurements and we integrate these measurements with high-resolution growth curves measured by OD600 and expression of rhamnolipid synthesis genes monitored using a reporter fusion. Two-fold serial dilution allowed integrating rhamnolipid measurements at a ~0.4 h-1 frequency with high-time resolved data measured at a 6 h-1 frequency. We show how this simple method can be used in combination with mutants lacking specific genes in the rhamnolipid synthesis or quorum sensing regulation to acquire rich dynamic data on P. aeruginosa virulence regulation. Additionally, the linear relation between the ratio of inocula and the time-shift between curves produces high-precision measurements of maximum specific growth rates, which were determined with a precision of ~5.4%. Conclusions Growth curve synchronization allows integration of rich time-resolved data with endpoint measurements to produce time-resolved quantitative measurements. Such data can be valuable to unveil the dynamic regulation of virulence in P. aeruginosa. More generally, growth curve synchronization can be applied to many biological systems thus helping to overcome a key obstacle in dynamic regulation: the scarceness of quantitative time-resolved data. PMID:21682889

2011-01-01

269

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

270

A Model to Explain Plant Growth Promotion Traits: A Multivariate Analysis of 2,211 Bacterial Isolates  

PubMed Central

Plant growth-promoting bacteria can greatly assist sustainable farming by improving plant health and biomass while reducing fertilizer use. The plant-microorganism-environment interaction is an open and complex system, and despite the active research in the area, patterns in root ecology are elusive. Here, we simultaneously analyzed the plant growth-promoting bacteria datasets from seven independent studies that shared a methodology for bioprospection and phenotype screening. The soil richness of the isolate's origin was classified by a Principal Component Analysis. A Categorical Principal Component Analysis was used to classify the soil richness according to isolate's indolic compound production, siderophores production and phosphate solubilization abilities, and bacterial genera composition. Multiple patterns and relationships were found and verified with nonparametric hypothesis testing. Including niche colonization in the analysis, we proposed a model to explain the expression of bacterial plant growth-promoting traits according to the soil nutritional status. Our model shows that plants favor interaction with growth hormone producers under rich nutrient conditions but favor nutrient solubilizers under poor conditions. We also performed several comparisons among the different genera, highlighting interesting ecological interactions and limitations. Our model could be used to direct plant growth-promoting bacteria bioprospection and metagenomic sampling. PMID:25542031

da Costa, Pedro Beschoren; Granada, Camille E.; Ambrosini, Adriana; Moreira, Fernanda; de Souza, Rocheli; dos Passos, João Frederico M.; Arruda, Letícia; Passaglia, Luciane M. P.

2014-01-01

271

A model to explain plant growth promotion traits: a multivariate analysis of 2,211 bacterial isolates.  

PubMed

Plant growth-promoting bacteria can greatly assist sustainable farming by improving plant health and biomass while reducing fertilizer use. The plant-microorganism-environment interaction is an open and complex system, and despite the active research in the area, patterns in root ecology are elusive. Here, we simultaneously analyzed the plant growth-promoting bacteria datasets from seven independent studies that shared a methodology for bioprospection and phenotype screening. The soil richness of the isolate's origin was classified by a Principal Component Analysis. A Categorical Principal Component Analysis was used to classify the soil richness according to isolate's indolic compound production, siderophores production and phosphate solubilization abilities, and bacterial genera composition. Multiple patterns and relationships were found and verified with nonparametric hypothesis testing. Including niche colonization in the analysis, we proposed a model to explain the expression of bacterial plant growth-promoting traits according to the soil nutritional status. Our model shows that plants favor interaction with growth hormone producers under rich nutrient conditions but favor nutrient solubilizers under poor conditions. We also performed several comparisons among the different genera, highlighting interesting ecological interactions and limitations. Our model could be used to direct plant growth-promoting bacteria bioprospection and metagenomic sampling. PMID:25542031

Costa, Pedro Beschoren da; Granada, Camille E; Ambrosini, Adriana; Moreira, Fernanda; de Souza, Rocheli; Dos Passos, João Frederico M; Arruda, Letícia; Passaglia, Luciane M P

2014-01-01

272

Human Capital, Social Support, and Economic Well-being among Rural, Low-income Mothers: A Latent Growth Curve Analysis  

Microsoft Academic Search

The purpose of this study was to better understand human capital and social support in the long-term economic well-being of\\u000a rural, low-income mothers in the US. Three waves of data from a multi-state, longitudinal investigation tracking the well-being\\u000a of rural families, known as “Rural Families Speak,” were used to test two latent growth curve models of economic well-being.\\u000a Results indicated

Leigh Ann Simmons; Bonnie Braun; David W. Wright; Scott R. Miller

2007-01-01

273

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

2012-01-01

274

Effects of Bacillus subtilis KN-42 on Growth Performance, Diarrhea and Faecal Bacterial Flora of Weaned Piglets  

PubMed Central

This research focused on the effects of different doses of Bacillus subtilis KN-42 on the growth performance, diarrhea incidence, faecal bacterial flora, and the relative number of Lactobacillus and Escherichia coli in faeces of weaned piglets to determine whether the strain can serve as a candidate antimicrobial growth promoter. A total of 360 piglets (initial body weight 7.14±0.63 kg) weaned at 26±2 days of age were randomly allotted to 5 treatment groups (4 pens per treatment with 18 pigs per pen) for a 28-day trial. Dietary treatments were basal diet without any antimicrobial (negative control; NC), basal diet supplemented with 120 mg/kg feed of neomycin sulfate (positive control; PC) and basal diet supplemented with 2×109 (L), 4×109 (M) and 20×109 (H) CFU/kg feed of B. subtilis KN-42. During the overall period, average daily gain and feed efficiency of piglets were higher in groups PC, M, and H than those in group NC (p<0.05), and all probiotics and antibiotics groups had a lower diarrhea index than group NC (p<0.05). The 16S rDNA gene-based methods were used to analyze faecal bacterial flora on day 28 of experiment. The result of denaturing gradient gel electrophoresis analysis showed that supplementation of B. subtilis KN-42 to the diet changed the bacterial communities, with a higher bacterial diversity and band number in group M than in the other four groups. Real-time polymerase chain reaction analysis showed that the relative number of Lactobacillus were higher in groups PC and H than in group NC (p<0.05), and the supplemented B. subtilis KN-42 to the diet also reduced the relative number of E. coli (p<0.05). These results suggest that dietary addition of B. subtilis KN-42 can improve the growth performance and gastrointestinal health of piglets. PMID:25083107

Hu, Yuanliang; Dun, Yaohao; Li, Shenao; Zhao, Shumiao; Peng, Nan; Liang, Yunxiang

2014-01-01

275

Lipocalin 2 Imparts Selective Pressure on Bacterial Growth in the Bladder and Is Elevated in Women with Urinary Tract Infection  

PubMed Central

Competition for iron is a critical component of successful bacterial infections, but the underlying in vivo mechanisms are poorly understood. We have previously demonstrated that lipocalin 2 (LCN2) is an innate immunity protein that binds to bacterial siderophores and starves them for iron, thus representing a novel host defense mechanism to infection. In the present study we show that LCN2 is secreted by the urinary tract mucosa and protects against urinary tract infection (UTI). We found that LCN2 was expressed in the bladder, ureters, and kidneys of mice subject to UTI. LCN2 was protective with higher bacterial numbers retrieved from bladders of Lcn2-deficient mice than from wild-type mice infected with the LCN2-sensitive Escherichia coli strain H9049. Uropathogenic E. coli mutants in siderophore receptors for salmochelin, aerobactin, or yersiniabactin displayed reduced fitness in wild-type mice, but not in mice deficient of LCN2, demonstrating that LCN2 imparts a selective pressure on bacterial growth in the bladder. In a human cohort of women with recurrent E. coli UTIs, urine LCN2 levels were associated with UTI episodes and with levels of bacteriuria. The number of siderophore systems was associated with increasing bacteriuria during cystitis. Our data demonstrate that LCN2 is secreted by the urinary tract mucosa in response to uropathogenic E. coli challenge and acts in innate immune defenses as a colonization barrier that pathogens must overcome to establish infection. PMID:25398327

Steigedal, Magnus; Marstad, Anne; Haug, Markus; Damås, Jan K.; Strong, Roland K.; Roberts, Pacita L.; Himpsl, Stephanie D.; Stapleton, Ann; Hooton, Thomas M.; Mobley, Harry L. T.; Hawn, Thomas R.

2014-01-01

276

Lipocalin 2 imparts selective pressure on bacterial growth in the bladder and is elevated in women with urinary tract infection.  

PubMed

Competition for iron is a critical component of successful bacterial infections, but the underlying in vivo mechanisms are poorly understood. We have previously demonstrated that lipocalin 2 (LCN2) is an innate immunity protein that binds to bacterial siderophores and starves them for iron, thus representing a novel host defense mechanism to infection. In the present study we show that LCN2 is secreted by the urinary tract mucosa and protects against urinary tract infection (UTI). We found that LCN2 was expressed in the bladder, ureters, and kidneys of mice subject to UTI. LCN2 was protective with higher bacterial numbers retrieved from bladders of Lcn2-deficient mice than from wild-type mice infected with the LCN2-sensitive Escherichia coli strain H9049. Uropathogenic E. coli mutants in siderophore receptors for salmochelin, aerobactin, or yersiniabactin displayed reduced fitness in wild-type mice, but not in mice deficient of LCN2, demonstrating that LCN2 imparts a selective pressure on bacterial growth in the bladder. In a human cohort of women with recurrent E. coli UTIs, urine LCN2 levels were associated with UTI episodes and with levels of bacteriuria. The number of siderophore systems was associated with increasing bacteriuria during cystitis. Our data demonstrate that LCN2 is secreted by the urinary tract mucosa in response to uropathogenic E. coli challenge and acts in innate immune defenses as a colonization barrier that pathogens must overcome to establish infection. PMID:25398327

Steigedal, Magnus; Marstad, Anne; Haug, Markus; Damås, Jan K; Strong, Roland K; Roberts, Pacita L; Himpsl, Stephanie D; Stapleton, Ann; Hooton, Thomas M; Mobley, Harry L T; Hawn, Thomas R; Flo, Trude H

2014-12-15

277

Root ethylene signalling is involved in Miscanthus sinensis growth promotion by the bacterial endophyte Herbaspirillum frisingense GSF30(T).  

PubMed

The bacterial endophyte Herbaspirillum frisingense GSF30(T) is a colonizer of several grasses grown in temperate climates, including the highly nitrogen-efficient perennial energy grass Miscanthus. Inoculation of Miscanthus sinensis seedlings with H. frisingense promoted root and shoot growth but had only a minor impact on nutrient concentrations. The bacterium affected the root architecture and increased fine-root structures. Although H. frisingense has the genetic requirements to fix nitrogen, only minor changes in nitrogen concentrations were observed. Herbaspirillum agglomerates were identified primarily in the root apoplast but also in the shoots. The short-term (3h) and long-term (3 weeks) transcriptomic responses of the plant to bacterial inoculation revealed that H. frisingense induced rapid changes in plant hormone signalling, most prominent in jasmonate signalling. Ethylene signalling pathways were also affected and persisted after 3 weeks in the root. Growth stimulation of the root by the ethylene precursor 1-aminocyclopropane 1-carboxylic acid was dose dependent and was affected by H. frisingense inoculation. Minor changes in the proteome were identified after 3 weeks. This study suggests that H. frisingense improves plant growth by modulating plant hormone signalling pathways and provides a framework to understand the beneficial effects of diazotrophic plant-growth-promoting bacteria, such as H. frisingense, on the biomass grass Miscanthus. PMID:24043849

Straub, Daniel; Yang, Huaiyu; Liu, Yan; Tsap, Tatsiana; Ludewig, Uwe

2013-11-01

278

Growth models of the continuous bacterial leaching of iron pyrite by Thiobacillus ferrooxidans  

Microsoft Academic Search

In recent years there has been increasing interest in the bacterial leaching of low grade metal ores and the bacterial leaching of pyritic sulfur from coal. The leaching of iron pyrite by Thiobacillus ferrooxidans was studied in a continuous stirred tank reactor at a variety of dilution rates (0.012-0.22 h⁻¹), pyrite surface areas (18-194 m²\\/L), and inlet soluble substrate (Fe\\/sup

Yun Chea Chang; Allan S. Myerson

1982-01-01

279

The Kuznets curve for the environment and economic growth: examining the evidence  

Microsoft Academic Search

Recent research has examined the relationship between certain indicator of environmental quality and income, concluding on the basis of econometric estimation that in some cases an inverted-U relationship, which has been called an environmental Kuznets curve (EKC), exists between these variables. There has been speculation on the implications of this for economic and environmental policy. In this paper I examine

P Ekins

1997-01-01

280

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

PubMed

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. PMID:10473432

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

1999-09-01

281

The Ability of Salmonella to Enter Mammalian Cells is Affected by Bacterial Growth State  

Microsoft Academic Search

We have examined the effect of different growth conditions on the ability of Salmonella to interact with Madin-Darby canine kidney cells. Two growth conditions that affect the expression of Salmonella adherence and invasiveness have been identified. First, bacteria lose their invasiveness in the stationary phase of growth. Second, bacteria growing in oxygen-limited growth conditions are induced for adherence and invasiveness,

Catherine A. Lee; Stanley Falkow

1990-01-01

282

Appropriate Fe (II) Addition Significantly Enhances Anaerobic Ammonium Oxidation (Anammox) Activity through Improving the Bacterial Growth Rate  

PubMed Central

The application of anaerobic ammonium oxidation (Anammox) process is often limited by the slow growth rate of Anammox bacteria. As the essential substrate element that required for culturing Anammox sludge, Fe (II) is expected to affect Anammox bacterial growth. This work systematically studied the effects of Fe (II) addition on Anammox activity based on the kinetic analysis of specific growth rate using data from batch tests with an enriched Anammox sludge at different dosing levels. Results clearly demonstrated that appropriate Fe (II) dosing (i.e., 0.09?mM) significantly enhanced the specific Anammox growth rate up to 0.172?d?1 compared to 0.118?d?1 at regular Fe (II) level (0.03?mM). The relationship between Fe (II) concentration and specific Anammox growth rate was found to be well described by typical substrate inhibition kinetics, which was integrated into currently well-established Anammox model to describe the enhanced Anammox growth with Fe (II) addition. The validity of the integrated Anammox model was verified using long-term experimental data from three independent Anammox reactors with different Fe (II) dosing levels. This Fe (II)-based approach could be potentially implemented to enhance the process rate for possible mainstream application of Anammox technology, in order for an energy autarchic wastewater treatment. PMID:25644239

Liu, Yiwen; Ni, Bing-Jie

2015-01-01

283

Potential Bacillus probiotics enhance bacterial numbers, water quality and growth during early development of white shrimp (Litopenaeus vannamei).  

PubMed

Epidemics of epizootics and occurrence of multiresistant antibiotics of pathogenic bacteria in aquaculture have put forward a development of effective probiotics for the sustainable culture. This study examined the effectiveness of forms of mixed Bacillus probiotics (probiotic A and probiotic B) and mode of probiotic administration on growth, bacterial numbers and water quality during rearing of white shrimp (Litopenaeus vannamei) in two separated experiments: (1) larval stages and (2) postlarval (PL) stages. Forms of Bacillus probiotics and modes of probiotic administration did not affect growth and survival of larval to PL shrimp. The compositions of Bacillus species in probiotic A and probiotic B did not affect growth and survival of larvae. However, postlarvae treated with probiotic B exhibited higher (P<0.05) growth than probiotic A and controls, indicating Bacillus probiotic composition affects the growth of PL shrimp. Total heterotrophic bacteria and Bacillus numbers in larval and PL shrimp or culture water of the treated groups were higher (P<0.05) than in controls. Levels of pH, ammonia and nitrite of the treated shrimp were significantly decreased, compared to the controls. Microencapsulated Bacillus probiotic was effective for rearing of PL L. vannamei. This investigation showed that administration of mixed Bacillus probiotics significantly improved growth and survival of PL shrimp, increased beneficial bacteria in shrimp and culture water and enhanced water quality for the levels of pH, ammonia and nitrite of culture water. PMID:22595137

Nimrat, Subuntith; Suksawat, Sunisa; Boonthai, Traimat; Vuthiphandchai, Verapong

2012-10-12

284

Study on Growth Curves of Longissimus dorsi Muscle Area, Backfat Thickness and Body Conformation for Hanwoo (Korean Native) Cows  

PubMed Central

The objective of this study was to estimate the parameters of Gompertz growth curves with the measurements of body conformation, real-time ultrasound longissimus dorsi muscle area (LMA) and backfat thickness (BFT) in Hanwoo cows. The Hanwoo cows (n = 3,373) were born in 97 Hanwoo commercial farms in the 17 cities or counties of Gyeongbuk province, Korea, between 2000 and 2007. A total of 5,504 ultrasound measurements were collected for the cows at the age of 13 to 165 months in 2007 and 2008. Wither height (HW), rump height (HR), the horizontal distance between the top of the hips (WH), and girth of chest (GC) were also measured. Analysis of variance was conducted to investigate variables affecting LMA and BFT. The effect of farm nested in location was included in the statistical model, as well as the effects of HW, HR, WH, and GC as covariates. All of the effects were significant in the analysis of variance for LMA and BFT (p<0.01), except for the HR effect for LMA. The two ultrasound measures and the four body conformation traits were fitted to a Gompertz growth curve function to estimate parameters. Upper asymptotic weights were estimated as 54.0 cm2, 7.67 mm, 125.6 cm, 126.4 cm, 29.3 cm, and 184.1 cm, for LMA, BFT, HW, HR, WH, and GC, respectively. Results of ultrasound measurements showed that Hanwoo cows had smaller LMA and greater BFT than other western cattle breeds, suggesting that care must be taken to select for thick BFT rather than an increase of only beef yield. More ultrasound records per cow are needed to get accurate estimates of growth curve, which, thus, helps producers select animals with high accuracy. PMID:25178367

Lee, J. H.; Oh, S.-H.; Lee, Y. M.; Kim, Y. S.; Son, H. J.; Jeong, D. J.; Whitley, N. C.; Kim, J. J.

2014-01-01

285

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

286

Plant Growth Promotion Potential Is Equally Represented in Diverse Grapevine Root-Associated Bacterial Communities from Different Biopedoclimatic Environments  

PubMed Central

Plant-associated bacteria provide important services to host plants. Environmental factors such as cultivar type and pedoclimatic conditions contribute to shape their diversity. However, whether these environmental factors may influence the plant growth promoting (PGP) potential of the root-associated bacteria is not widely understood. To address this issue, the diversity and PGP potential of the bacterial assemblage associated with the grapevine root system of different cultivars in three Mediterranean environments along a macrotransect identifying an aridity gradient were assessed by culture-dependent and independent approaches. According to 16S rRNA gene PCR-DGGE, the structure of endosphere and rhizosphere bacterial communities was highly diverse (P = 0.03) and was associated with a cultivar/latitudinal/climatic effect. Despite being diverse, the bacterial communities associated with Egyptian grapevines shared a higher similarity with the Tunisian grapevines than those cultivated in North Italy. A similar distribution, according to the cultivar/latitude/aridity gradients, was observed for the cultivable bacteria. Many isolates (23%) presented in vitro multiple stress resistance capabilities and PGP activities, the most frequent being auxin synthesis (82%), insoluble phosphate solubilisation (61%), and ammonia production (70%). The comparable numbers and types of potential PGP traits among the three different environmental settings indicate a strong functional homeostasis of beneficial bacteria associated with grape root. PMID:23878810

Fusi, Marco; Cherif, Ameur; Abou-Hadid, Ayman; El-Bahairy, Usama; Sorlini, Claudia; Daffonchio, Daniele

2013-01-01

287

Bacterial Skin Infections  

MedlinePLUS

... Disorders Pigment Disorders Blistering Diseases Parasitic Skin Infections Bacterial Skin Infections Fungal Skin Infections Viral Skin Infections Sunlight and Skin Damage Noncancerous Skin Growths Skin Cancers Nail Disorders Topics in Bacterial Skin ...

288

From snowflake formation to growth of bacterial colonies II: Cooperative formation of complex colonial patterns  

Microsoft Academic Search

In nature, bacterial colonies must often cope with hostile environmental conditions. To do so they have developed sophisticated cooperative behaviour and intricate communication capabilities, such as direct cell- cell physical interactions via extra-membrane polymers, collective production of extracellular 'wetting' fluid for movement on hard surfaces, longrange chemical signalling such as quorum sensing and chemotactic (bias of movement according to gradient

Eshel Ben-Jacob

1997-01-01

289

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; Puigmartí-Luis, Jiosep; Jonas, Alain M; Amabilino, David B; De Feyter, Steven

2014-11-11

290

Nonlinear estimation of Monod growth kinetic parameters from a single substrate depletion curve.  

PubMed Central

Monod growth kinetic parameters were estimated by fitting sigmoidal substrate depletion data to the integrated Monod equation, using nonlinear least-squares analysis. When the initial substrate concentration was in the mixed-order region, nonlinear estimation of simulated data sets containing known measurement errors provided accurate estimates of the mu max, Ks, and Y values used to create these data. Nonlinear regression analysis of sigmoidal substrate depletion data was also evaluated for H2-limited batch growth of Desulfovibrio sp. strain G11. The integrated Monod equation can be more convenient for the estimation of growth kinetic parameters, particularly for gaseous substrates, but it must be recognized that the estimates of mu max, Ks, and Y obtained may be influenced by the growth rate history of the inoculum. PMID:6870238

Robinson, J A; Tiedje, J M

1983-01-01

291

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

292

Explanation of an apparent abnormality in fatigue crack growth rate curves in titanium alloys  

SciTech Connect

A surprising phenomenon is investigated where titanium alloys exhibit no threshold fatigue crack growth value if K{sub max} in the K{sub max}-constant testing procedure exceeds a certain value. The crack growth rate increases with decreasing {Delta}K up to final fracture. The phenomenon was found repeatedly for Ti-6Al-2Sn-4Zr-6Mo above K{sub max} = 21 MPa{radical}m (equal to 72% of K{sub IC}), and its causes were investigated. The same crack growth rates as in the K{sub max}-constant test were reproduced by two independent experimental procedures, the so-called ``jump`` test and sustained K cracking experiments along with a calculation. It is demonstrated that the observed phenomenon is not a special crack growth feature or a new phenomenon, but simply caused by time-dependent crack growth, which is known to exist in titanium alloys or steels. Fractographic work revealed that intergranular crack growth along {alpha} and transformed {beta} grain boundaries increases with decreasing {Delta}K and increasing K{sub max} value, accompanied by creep deformation in the transformed {beta} grains. The conditions for time-dependent cracking are believed to be a sufficiently high stress and strain field in the crack tip region, along with hydrogen-assisted cracking.

Lang, M. [Air Force Research Lab., Wright-Patterson AFB, OH (United States). Materials and Manufacturing Directorate] [Air Force Research Lab., Wright-Patterson AFB, OH (United States). Materials and Manufacturing Directorate

1999-09-08

293

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...

294

Effects of Inoculation with PGPR Bacillus and Pisolithus tinctorius on Pinus pinea L. Growth, Bacterial rhizosphere Colonization, and Mycorrhizal Infection.  

PubMed

The effect of co-inoculation with Pisolithus tinctorius and a PGPR belonging to the genus Bacillus (Bacillus licheniformis CECT 5106 and Bacillus pumilus CECT 5105) in enhancing growth of Pinus pinea plants and the changes that occurred in rhizosphere microbial communities and the degree of mycorrhization were evaluated. Both bacterial strains of Bacillus promote the growth of Pinus pinea seedlings, but this biological effect does not imply a synergic effect with mycorrhizal infection. However, the positive response to mycorrhiza in a longer-term experiment it could be expected. The introduction of both inocula causes an alteration in the microbial rhizosphere composition, despite the low levels of inocula that were found at the end of the assay. PMID:12032619

Probanza, A.; Mateos, J.L.; Lucas García, J.A.; Ramos, B.; De Felipe, M.R.; Gutierrez Mañero, F.J.

2001-02-01

295

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; Lévesque, Céline Marie; Prakki, Anuradha

2014-01-01

296

Growth curve analyses of the relationship between early maternal age and children's mathematics and reading performance.  

PubMed

Regarding the methods used to examine the early maternal age-child academic outcomes relationship, the extant literature has tended to examine change using statistical analyses that fail to appreciate that individuals vary in their rates of growth. Of the one study I have been able to find that employs a true growth model to estimate this relationship, the authors only controlled for characteristics of the maternal household after family formation; confounding background factors of mothers that might select them into early childbearing, a possible source of bias, were ignored. The authors' findings nonetheless suggested an inverse relationship between early maternal age, i.e., a first birth between the ages of 13 and 17, and Canadian adolescents' mean math performance at age 10. Early maternal age was not related to the linear slope of age. To elucidate whether the early maternal age-child academic outcomes association, treated in a growth context, is consistent with this finding, the present study built on it using US data and explored children's mathematics and reading trajectories from age 5 on. Its unique contribution is that it further explicitly controlled for maternal background factors and employed a three-level growth model with repeated measures of children nested within their mothers. Though the strength of the relationship varied between mean initial academic performance and mean academic growth, results confirmed that early maternal age was negatively related to children's mathematics and reading achievement, net of post-teen first birth child-specific and maternal household factors. Once maternal background factors were included, there was no statistically significant relationship between early maternal age and either children's mean initial mathematics and reading scores or their mean mathematics and reading growth. PMID:25592941

Torres, D Diego

2015-03-01

297

Self-Esteem and Delinquency Revisited (Again): A Test of Kaplan's Self-Derogation Theory of Delinquency Using Latent Growth Curve Modeling.  

ERIC Educational Resources Information Center

Studied the relationship between self-esteem and delinquency using latent growth curve modeling. Analyses of panel data for 2,213 adolescent boys from the Youth in Transition Study supported Kaplan's self-derogation theory of delinquency (H. Kaplan, 1978) by showing that delinquency was positively associated with growth in self-esteem among…

Mason, W. Alex

2001-01-01

298

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

NASA Astrophysics Data System (ADS)

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 80°E. 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

299

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

300

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

301

Rapid estimation of depositional ages of eolian dune sands using a portable OSL reader and polymineralic coarse grain standardized luminescence growth curves  

NASA Astrophysics Data System (ADS)

Two developments in luminescence dating studies over the last few years have the potential to contribute significantly to the abbreviation of the usually lengthy and laborious dating protocols, at least for reconnaissance exercises. One of these developments has been the introduction of portable optically stimulated luminescence (OSL) readers that can be used to perform measurements in the field. Apart from portability, an additional advantage for some of the portable systems is the ability to make luminescence measurements directly on bulk polymineralic samples, negating the need for lengthy mineral separation procedures. The second development stems from studies which have looked at the use of standardized luminescence growth curves for paleodose estimation. These studies have shown that normalized growth curves constructed using different samples from the same region are generally similar for doses below about 50 Gy and can be used to reliably approximate equivalent doses by simply obtaining a measurement of the normalized natural signal. The use of such standardized growth curves shortens the dating procedure significantly because it eliminates the need for constructing individual growth curves for each sample, which is the practice in regular OSL dating. In this study we merge these two recent developments by using a portable OSL reader developed by the Scottish Universities Environmental Research Centre (SUERC) to prepare standardized growth curves for quartz and feldspar from polymineralic sands from postglacial eolian dunes in Alberta, Canada. To differentiate the signal yielded by the feldspar from that given out by the quartz grains, we stimulate the bulk sample by first using IRSL followed by post-IR blue OSL stimulation. For the growth curve, artificial doses of 5, 20, 15, 25, 30, 40, 50, 70 and 100 Gy are administered on aliquots of the bulk samples using a Cs-137 irradiation source. A test dose of 4 Gy is used for the normalization of all aliquots. The results show that standardized growth curves from different dune fields in Alberta are relatively similar and they display a linear growth pattern when working with doses below 50-60 Gy. A comparison of paleodoses determined on samples from the same stratigraphic levels using both the polymineralic standardized growth curves and regular OSL dating procedures (SAR protocol) indicates that the results are a fairly consistent. Overall, our data suggest that the use of portable OSL measurements in conjunction with standardized growth curves offers a viable tool for rapid estimation of depositional ages of eolian dune sediments.

Munyikwa, K.; Brown, S.

2011-12-01

302

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 Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, 58089 Morelia, Michoacán (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); Hernández, 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 Astronomía (CIDA), Mérida 5101-A (Venezuela, Bolivarian Republic of)

2013-10-01

303

Family Structure and Problem Behavior of Adolescents and Young Adults: A Growth-Curve Study  

Microsoft Academic Search

In the present longitudinal 3-wave study of 1274 adolescents and young adults, aged 12–24 at the 1st wave, it is examined\\u000a whether youngsters from intact versus postdivorce families show long-term differences in internalizing and externalizing problems.\\u000a Furthermore, possible differences in the development of this problem behavior between offspring from intact and postdivorce\\u000a families are examined, i.e., possible differences in growth

Inge VanderValk; Ed Spruijt; Martijn de Goede; Cora Maas; Wim Meeus

2005-01-01

304

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

305

BacSim, a simulator for individual-based modelling of bacterial colony growth  

Microsoft Academic Search

The generic, quantitative, spatially explicit, individual-based model BacSim was developed to simulate growth and behaviour of bacteria. The potential of this approach is in relating the properties of microscopic entities - cells - to the properties of macroscopic, complex systems such as biofilms. Here, the growth of a single Escherichia coli cell into a colony was studied. The object-oriented program

Jan-Ulrich Kreft; Ginger Booth; Julian W. T. Wimpenny

1998-01-01

306

From snowflake formation to growth of bacterial colonies. Diffusive patterning in azoic systems  

Microsoft Academic Search

Many phenomena display the emergence of patterns during diffusive growth, ranging from the growth of snowflake s to the aggregation of a soot particle, from oil recovery by fluid injection to solidification of metals and from the formation of a coral reef to cell differentiation during embryonic development. Is the diversity of patterns found in Nature a result of different

Eshel Ben-Jacob

1993-01-01

307

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

308

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

309

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 18–24 h could be insufficient for reliable growth-dependent evaluation of antibiotic susceptibility. Different minimal inhibitory concentrations were obtained in 20- and 48 h microdilution plate tests using an Enterococcus faecium clinical isolate (strain UKI-MB07) as a model organism. Hence, we used an on-line kinetic assay for simultaneous cultivation and time-resolved growth analysis in a 96-well format instead of off-line susceptibility testing. Growth of the Enterococcus test organism was delayed up to 30 h in the presence of 0.25 ?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. PMID:25426104

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

2014-01-01

310

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

311

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

312

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, María A.; Kühl, 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

313

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 164±64 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.

García-Martín, E. E.; McNeill, S.; Serret, P.; Leakey, R. J. G.

2014-10-01

314

Growth curve analysis for plasma profiles using smoothing splines. Annual progress report, June 1992--June 1993  

SciTech Connect

We are developing a profile analysis code for the statistical estimation of the parametric dependencies of the temperature and density profiles in tokamaks. Our code uses advanced statistical techniques to determine the optimal fit, i.e. the fit which minimized the predictive error. For a forty TFTR Ohmic profile dataset, our preliminary results indicate that the profile shape depends almost exclusively on q{sub a}{prime} but that the shape dependencies are not Gaussian. We are now comparing various shape models on the TFTR data. In the first six months, we have completed the core modules of the code, including a B-spline package for variable knot locations, a data-based method to determine the optimal smoothing parameters, self-consistent estimation of the bias errors, and adaptive fitting near the plasma edge. Visualization graphics already include three dimensional surface plots, and discharge by discharge plots of the predicted curves with error bars together with the actual measurements values, and plots of the basis functions with errors.

Imre, K.

1993-05-01

315

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; Gálvez, Antonio; Franco, Bernadette Dora Gombossy de Melo

2014-12-01

316

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 ...

317

Consideration of probability of bacterial growth for Jovian planets and their satellites  

NASA Technical Reports Server (NTRS)

Environmental parameters affecting growth of bacteria are compared with current atmospheric models for Jupiter and Saturn, and with the available physical data for their satellites. Different zones of relative probability of growth are identified for Jupiter and Saturn. Of the more than two dozen satellites, only the largest (Io, Europa, Ganymede, Callisto, and Titan) are found to be interesting biologically. Titan's atmosphere may produce a substantial greenhouse effect providing increased surface temperatures. Models predicting a dense atmosphere are compatible with microbial growth for a range of pressures at Titan's surface. For Titan's surface the probability of growth would be enhanced if: (1) the surface is entirely or partially liquid; (2) volcanism is present; or (3) access to internal heat sources is significant.

Taylor, D. M.; Berkman, R. M.; Divine, N.

1974-01-01

318

A heterogeneous population model for the analysis of bacterial growth kinetics  

Microsoft Academic Search

A two-compartment, heterogeneous population model (HPM) was derived using the simulation software SB ModelMaker© to describe the growth of Listeria monocytogenes in bacteriological media at 5–35 °C. The model assumed that, at time t = 0, the inoculum was distributed between two distinct compartments, Non-Growing and Growing, and that growth could be described by four parameters: initial total cell population

R. C. McKellar

1997-01-01

319

Growth kinetics of a diesel-degrading bacterial strain from petroleum-contaminated soil.  

PubMed

A diesel-degrading bacterium was isolated from a diesel-contaminated site in Selangor, Malaysia. The isolate was tentatively identified as Acinetobacter sp. strain DRY12 based on partial 16S rDNA molecular phylogeny and Biolog GN microplate panels and Microlog database. Optimum growth occurred from 3 to 5% diesel and the strain was able to tolerate as high as 8% diesel. The optimal pH that supported growth of the bacterium was between pH 7.5 to 8.0. The isolate exhibited optimal growth in between 30 and 35 degrees C. The best nitrogen source was potassium nitrate (between 0.6 and 0.9% (w/v)) followed by ammonium chloride, sodium nitrite and ammonium sulphate in descending order. An almost complete removal of diesel components was seen from the reduction in hydrocarbon peaks observed using Solid Phase Microextraction Gas Chromatography analysis after 10 days of incubation. The best growth kinetic model to fit experimental data was the Haldane model of substrate inhibiting growth with a correlation coefficient value of 0.97. The maximum growth rate- micromax was 0.039 hr(-1) while the saturation constant or half velocity constant Ks and inhibition constant Ki, were 0.387% and 4.46%, respectively. MATH assays showed that 75% of the bacterium was found in the hexadecane phase indicating that the bacterium was hydrophobic. The characteristics of this bacterium make it useful for bioremediation works in the Tropics. PMID:24665769

Dahalan, S F A; Yunus, I; Johari, W L W; Shukor, M Y; Halmi, M I E; Shamaan, N A; Syed, M A

2014-03-01

320

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

321

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 (45°S, 153°E) and southwest (46°S, 140°E) of Tasmania and at the Polar Front (54°S, 147°E). Growth and grazing mortality of phytoplankton and bacteria were estimated by the grazing dilution technique using seawater from 10 m depth at 15 sites along the survey, along with concentrations of heterotrophic nanoflagellates (HNF), microzooplankton, bacteria, cyanobacteria and size fractionated (pico-, nano- and micro-sized) chlorophyll a (Chl a). Rates of herbivory ranged from 0.12 to 1.39 d -1 and were highest in the north-eastern SAZ (NE-SAZ) where concentrations of prey (as indicated by Chl a) and microzooplankton were also highest. Rates of herbivory were correlated with total rates of phytoplankton growth, bacterial growth and concentrations of microzooplankton. On average 82%, 67% and 42% primary production d -1 was consumed by microzooplankton and HNF at process stations in the north-western SAZ (NW-SAZ), NE-SAZ and polar frontal zone (PFZ), respectively. In the NW-SAZ, grazing pressure was highest on the pico-sized Chl a fraction, whereas in the NE-SAZ, grazing pressure was more evenly distributed across all three size fractions of Chl a. Bacterivory removed 77%, 93% and 39% of bacterial production d -1 in the NW-SAZ, NE-SAZ and PFZ, respectively, and rates of bacterivory ranged from 0.12 to 1.03 d -1. Rates of bacterivory were highest in the NE-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

322

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

323

A flow cytometry based oligotrophic pollutant exposure test to detect bacterial growth inhibition and cell injury.  

PubMed

Toxicity of chemical pollutants in aquatic environments is often addressed by assays that inquire reproductive inhibition of test microorganisms, such as algae or bacteria. Those tests, however, assess growth of populations as a whole via macroscopic methods such as culture turbidity or colony-forming units. Here we use flow cytometry to interrogate the fate of individual cells in low-density populations of the bacterium Pseudomonas fluorescens SV3 exposed or not under oligotrophic conditions to a number of common pollutants, some of which derive from oil contamination. Cells were stained at regular time intervals during the exposure assay with fluorescent dyes that detect membrane injury (i.e., live-dead assay). Reduction of population growth rates was observed upon toxicant insult and depended on the type of toxicant. Modeling and cell staining indicate that population growth rate decrease is a combined effect of an increased number of injured cells that may or may not multiply, and live cells dividing at normal growth rates. The oligotrophic assay concept presented here could be a useful complement for existing biomarker assays in compliance with new regulations on chemical effect studies or, more specifically, for judging recovery after exposure to fluctuating toxicant conditions. PMID:21657560

Czechowska, Kamila; van der Meer, Jan Roelof

2011-07-01

324

Consideration of probability of bacterial growth for Jovian planets and their satellites  

NASA Technical Reports Server (NTRS)

Environmental parameters affecting growth of bacteria (e.g., moisture, temperature, pH, and chemical composition) were compared with current atmospheric models for Jupiter and Saturn, and with the available physical data for their satellites. Different zones of relative probability of growth were identified for Jupiter and Saturn, with the highest in pressure regions of 1-10 million N/sq m (10 to 100 atmospheres) and 3-30 million N/sq m (30 to 300 atmospheres), respectively. Of the more than two dozen satellites, only the largest (Io, Europa, Ganymede, Callisto, and Titan) were found to be interesting biologically. Titan's atmosphere may produce a substantial greenhouse effect providing increased surface temperatures. Models predicting a dense atmosphere are compatible with microbial growth for a range of pressures at Titan's surface. For Titan's surface the probability of growth would be enhanced if (1) the surface is entirely or partially liquid (water), (2) volcanism (in an ice-water-steam system) is present, or (3) access to internal heat sources is significant.

Taylor, D. M.; Berkman, R. M.; Divine, N.

1975-01-01

325

Induction of Purple Sulfur Bacterial Growth in Dairy Wastewater Lagoons by Circulation  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aims: To determine if circulation of diary wastewater induces the growth of phototrophic purple sulfur bacteria (PSB). Methods and Results: Two dairy wastewater lagoons that were similar in size, geographic location, number and type of cattle loading the lagoons were chosen. The only obvious diffe...

326

Measurement of bacterial growth rates in subsurface sediments using the incorporation of tritiated thymidine into DNA  

Microsoft Academic Search

Microbial growth rates in subsurface sediment from three sites were measured using incorporation of tritiated thymidine into DNA. Sampling sites included Lula, Oklahoma, Traverse City, Michigan, and Summit Lake, Wisconsin. Application of the thymidine method to subsurface sediments required (1) thymidine concentrations greater than 125 nM, (2) incubation periods of less than 4 hours, (3) addition of SDS and EDTA

Patti M. Thorn; Roy M. Ventullo

1988-01-01

327

Growth curves and survival characteristics of the animals used in the Biomarkers of Aging Program.  

PubMed

The collaborative Interagency Agreement between the National Center for Toxicological Research (NCTR) and the National Institute on Aging (NIA) was aimed at identifying and validating a panel of biomarkers of aging in rodents in order to rapidly test the efficacy and safety of interventions designed to slow aging. Another aim was to provide a basis for developing biomarkers of aging in humans, using the assumption that biomarkers that were useful across different genotypes and species were sensitive to fundamental processes that would extrapolate to humans. Caloric restriction (CR), the only intervention that consistently extends both mean and maximal life span in a variety of species, was used to provide a model with extended life span. C57BI/6NNia, DBA/2JNia, B6D2F1, and B6C3F1 mice and Brown Norway (BN/RijNia), Fischer (F344/NNia) and Fischer x Brown Norway hybrid (F344 x BN F1) rats were bred and maintained on study. NCTR generated data from over 60,000 individually housed animals of the seven different genotypes and both sexes, approximately half ad libitum (AL) fed, the remainder CR. Approximately half the animals were shipped to offsite NIA investigators internationally, with the majority of the remainder maintained at NCTR until they died. The collaboration supplied a choice of healthy, long-lived rodent models to investigators, while allowing for the development of some of the most definitive information on life span, food consumption, and growth characteristics in these genotypes under diverse feeding paradigms. PMID:10619312

Turturro, A; Witt, W W; Lewis, S; Hass, B S; Lipman, R D; Hart, R W

1999-11-01

328

Characterisation of bacterial growth and antimicrobial susceptibility patterns in canine urinary tract infections.  

PubMed

BackgroundBacterial urinary tract infection (UTI) is a common reason for antimicrobial therapy in dogs.A reported increase in multi-drug resistance in canine bacterial pathogens, including resistance to extended-spectrum cephalosporins (ESC) is of concern as antimicrobial resistance complicates therapy in dogs. In addition, it is a possible public health concern.The objectives of this study were to investigate the relative prevalence of pathogens in urine samples from dogs with urinary tract infection sampled at referral hospitals, clinics and mixed veterinary practices and to investigate if this was influenced by sample material or by contamination of the culture. The second objective was to assess the susceptibility patterns to clinically relevant antimicrobials and to investigate if this was influenced by whether the samples originated from smaller clinics or from referral hospitals and to perform active screening for the presence of Enterobacteriaceae resistant to ESC.Results Escherichia coli was the most frequently isolated pathogen (68%) followed by staphylococci (11%). E. coli isolates were found significantly more often in pure culture than in contaminated samples. Staphylococcus pseudintermedius and Staphylococcus aureus isolates were significantly more prevalent in pre-incubated samples compared to samples submitted as non-incubated media.Susceptibility to the majority of the tested first-line antimicrobials was common. Multiresistance was rare, and these isolates were all susceptible to at least one relevant antimicrobial. Isolates in samples from small animal clinics or mixed veterinary practices were less likely to be susceptible compared to isolates originating from referral animal hospitals. ESC-resistant Enterobacteriacae isolates were found in one per cent of the positive cultures. Bacteria with transferable ESC resistance were confirmed in one dog. The gene demonstrated was bla CMY2.ConclusionsChoice of sample material might influence the possibility of detecting Staphylococcus pseudintermedius and Staphylococcus aureus isolates in clinical cases of UTI in dogs. Based on the study results, use of first-line antimicrobials is a rational empirical antimicrobial therapy for the studied dog population. E. coli was the most prevalent pathogen, but prevalence of infection with ESC resistant Enterobacteriaceae including E. coli was low, as such isolates were found in only one per cent of the positive cultures. PMID:25249356

Windahl, Ulrika; Holst, Bodil; Nyman, Ann; Grönlund, Ulrika; Bengtsson, Björn

2014-09-24

329

Effects of elaidic Acid, a predominant industrial trans Fatty Acid, on bacterial growth and cell surface hydrophobicity of lactobacilli.  

PubMed

The consumption of trans fatty acids (TFAs) increases the risk of cardiovascular diseases and coronary heart disease in human, and there are no effective ways to remove TFAs after consumption. The aim of this study was to investigate the effects of elaidic acid on bacterial growth, cell surface hydrophobicity of lactobacilli, and metabolism of elaidic acid by lactobacilli. Lactobacilli were inoculated in MRS broth containing 0, 100, 200, and 500 mg/L of elaidic acid. Viable cell counts of lactobacilli were enumerated, concentrations of elaidic acid were determined, and cell surface hydrophobicity of lactobacilli was measured. The results showed that the growth of lactobacilli was significantly inhibited by 500 mg/L of elaidic acid, however, a cell count of 8.50 log10 CFU/mL was still reached for tested lactobacilli after 24-h incubation. In particular, a reduction of elaidic acid was found for tested lactobacilli after 24-h incubation as compared to its initial concentration of 200 mg/L. However, cell surface hydrophobicity showed no correlations with the metabolism of elaidic acid by lactobacilli. Moreover, elaidic acid was able to influence cell surface hydrophobicity, and the decrease in hydrophobicity was more obvious in Lactobacillus paracasei and Lactobacillus casei compared with that in other tested lactobacilli. This study suggests that elaidic acid could change physiochemical surface properties of lactobacilli and the lactobacilli have the potential to reduce TFAs. PMID:25384717

Wu, Qinglong; Shah, Nagendra P

2014-12-01

330

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-François; Cutright, Teresa J.

2013-01-01

331

Bacterial Abundance Measure bacterial numbers and mass per unit volume.  

E-print Network

.37 1021 l oceans-1 Crude estimate of element fluxes (x: bacterial biomass) · Growth rate: G = xBacterial Abundance Objective · Measure bacterial numbers and mass per unit volume. · Note, we). · Plate (or viable) count (Today). · Direct count. (Thursday). #12;Why do we want to measure bacterial

Vallino, Joseph J.

332

Bacterial Abundance Measure bacterial numbers and mass per unit volume.  

E-print Network

.37 � 1021 l oceans-1 Crude estimate of element fluxes (x: bacterial biomass) · Growth rate: G = µx; µBacterial Abundance Objective · Measure bacterial numbers and mass per unit volume. · Note, we). · Plate (or viable) count (Today). · Direct count. (Thursday). #12;Why do we want to measure bacterial

Vallino, Joseph J.

333

Plant growth promotion by inoculation with selected bacterial strains versus mineral soil supplements.  

PubMed

In the process of remediation of mine sites, the establishment of a vegetation cover is one of the most important tasks. This study tests two different approaches to manipulate soil properties in order to facilitate plant growth. Mine waste from Ingurtosu, Sardinia, Italy rich in silt, clay, and heavy metals like Cd, Cu, and Zn was used in a series of greenhouse experiments. Bacteria with putative beneficial properties for plant growth were isolated from this substrate, propagated and consortia of ten strains were used to inoculate the substrate. Alternatively, sand and volcanic clay were added. On these treated and untreated soils, seeds of Helianthus annuus, of the native Euphorbia pithyusa, and of the grasses Agrostis capillaris, Deschampsia flexuosa and Festuca rubra were germinated, and the growth of the seedlings was monitored. The added bacteria established well under all experimental conditions and reduced the extractability of most metals. In association with H. annuus, E. pithyusa and D. flexuosa bacteria improved microbial activity and functional diversity of the original soil. Their effect on plant growth, however, was ambiguous and usually negative. The addition of sand and volcanic clay, on the other hand, had a positive effect on all plant species except E. pithyusa. Especially the grasses experienced a significant benefit. The effects of a double treatment with both bacteria and sand and volcanic clay were rather negative. It is concluded that the addition of mechanical support has great potential to boost revegetation of mining sites though it is comparatively expensive. The possibilities offered by the inoculation of bacteria, on the other hand, appear rather limited. PMID:23990253

Wernitznig, S; Adlassnig, W; Sprocati, A R; Turnau, K; Neagoe, A; Alisi, C; Sassmann, S; Nicoara, A; Pinto, V; Cremisini, C; Lichtscheidl, I

2014-06-01

334

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

PubMed

A laboratory study was conducted to investigate the influence of four PGPR strains on the degradation of five soil applied 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 studied. The degradation of acibenzolar-S-methyl by all PGPR tested in low and high concentration, was 5.4 and 5.7 times, respectively, faster than that in non-inoculated liquid culture medium. At the end of the 72-h liquid cultured experiments, 8-18, 9-11, 15-36 and 11-22% of metribuzin, napropamide, propamocarb hydrochloride and thiamethoxam, respectively, had disappeared from PGPR inoculated medium. Under the soil microcosm experimental conditions, the half-lives of acibenzolar-S-methyl incubated in the presence of PGPR strains spiked at 1.0 and 10.0 mg kg(-1) were 10.3-16.4 and 9.2-15.9 days, respectively, markedly lower compared with >34.2 days in the control. From the rest pesticides studied degradation of propamocarb hydrochloride and thiamethoxam was enhanced in the presence of B. amyloliquefaciens IN937a and B. pumilus SE34. Acibenzolar-S-methyl, propamocarb hydrochloride and thiamethoxam significantly increased the PGPR growth. However, the stimulatory effect was related to the level of pesticide spiked. PMID:21870159

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

2012-04-01

335

Toxicity of four spill-treating agents on bacterial growth and sea urchin embryogenesis.  

PubMed

The toxicity of spill-treating agents (STAs) is a topic that needs to be assessed prior to their potential application in environmental disasters. The aim of the present work was to study the effects of four commercial STAs (CytoSol, Finasol OSR 51, Agma OSD 569 and OD4000) on the growth of marine (Phaeobacter sp., Pseudomonas sp.) and terrestrial (Leuconostoc mesenteroides) bacteria, and sea urchin (Paracentrotus lividus) embryolarval development. In general, STA did not inhibit significantly the biomass production of the tested marine bacteria. Finasol OSR 51 and OD4000 clearly inhibited the growth of L. mesenteroides and an accurate description of the kinetics was provided by a proposed bivariate equation. For this species, a global parameter (EC50,?) was defined to summarize the set of growth kinetics. Using this parameter Finasol OSR 51 was found to be less toxic (754?L L(-1)) than OD4000 (129?L L(-1)). For the sea urchin embryo assay, the ranking of toxicity as EC50 (?L L(-1)) was Agma OSD 569 (34.0)

Rial, Diego; Murado, Miguel A; Beiras, Ricardo; Vázquez, José A

2014-06-01

336

The Role of Peer Contacts in the Relationship between Parental Knowledge and Adolescents' Externalizing Behaviors: A Latent Growth Curve Modeling Approach  

ERIC Educational Resources Information Center

The purpose of the present study was to examine the direct and indirect effects (through peer contacts) of parental knowledge on adolescents' delinquent and aggressive problem behavior, using latent growth curve modeling. A sample of 457 13- to 14-year old adolescents at first measurement wave (M = 13.27; SD = 0.45 years) filled out questionnaires…

Reitz, Ellen; Prinzie, Peter; Dekovic, Maja; Buist, Kirsten L.

2007-01-01

337

Autoinducer 2: A concentration-dependent signal for mutualistic bacterial biofilm growth  

USGS Publications Warehouse

4,5-dihydroxy-2,3-pentanedione (DPD), a product of the LuxS enzyme in the catabolism of S-ribosylhomocysteine, spontaneously cyclizes to form autoinducer 2 (AI-2). AI-2 is proposed to be a universal signal molecule mediating interspecies communication among bacteria. We show that mutualistic and abundant biofilm growth in flowing saliva of two human oral commensal bacteria, Actinomyces naeslundii T14V and Streptococcus oralis 34, is dependent upon production of AI-2 by S. oralis 34. A luxS mutant of S. oralis 34 was constructed which did not produce AI-2. Unlike wild-type dual-species biofilms, A. naeslundii T14V and an S. oralis 34 luxS mutant did not exhibit mutualism and generated only sparse biofilms which contained a 10-fold lower biomass of each species. Restoration of AI-2 levels by genetic or chemical (synthetic AI-2 in the form of DPD) complementation re-established the mutualistic growth and high biomass characteristic for the wild-type dual-species biofilm. Furthermore, an optimal concentration of DPD was determined, above and below which biofilm formation was suppressed. The optimal concentration was 100-fold lower than the detection limit of the currently accepted AI-2 assay. Thus, AI-2 acts as an interspecies signal and its concentration is critical for mutualism between two species of oral bacteria grown under conditions that are representative of the human oral cavity. ?? 2006 Blackwell Publishing Ltd.

Rickard, A.H.; Palmer, R.J., Jr.; Blehert, D.S.; Campagna, S.R.; Semmelhack, M.F.; Egland, P.G.; Bassler, B.L.; Kolenbrander, P.E.

2006-01-01

338

Pressate from peat dewatering as a substrate for bacterial growth. [Rhizopus arrhizus; Xanthomonas campestris; Aureobasidium  

SciTech Connect

This study considered the possibility of using water expressed during the drying of fuel-grade peat as a substrate for microbial growth. Highly humified peat pressed for 2.5 min at 1.96 MPa produced water with a chemical oxygen demand of 690 mg/liter. Several biological compounds could be produced by using the organic matter inexpressed peat water as a substrate. These included polymers such as chitosan, contained in the cell wall of Rhizopus arrhizus, and two extracellular polysaccharides, xanthan gum and pullulan, produced by Bacillus subtilis grown in the expressed water. Small additions of nutrients to the peat pressate were necessary to obtain substantial yields of products. The addition of peptone, yeast extract, and glucose improved production of the various compounds. Biological treatment improved the quality of the expressed water to the extent that in an industrial process it could be returned to the environment.

Mulligan, C.N.; Cooper, D.G.

1985-07-01

339

Water reservoir maintained by cell growth fuels the spreading of a bacterial swarm  

PubMed Central

Flagellated bacteria can swim across moist surfaces within a thin layer of fluid, a means for surface colonization known as swarming. This fluid spreads with the swarm, but how it does so is unclear. We used micron-sized air bubbles to study the motion of this fluid within swarms of Escherichia coli. The bubbles moved diffusively, with drift. Bubbles starting at the swarm edge drifted inward for the first 5 s and then moved outward. Bubbles starting 30 ?m from the swarm edge moved inward for the first 20 s, wandered around in place for the next 40 s, and then moved outward. Bubbles starting at 200 or 300 ?m from the edge moved outward or wandered around in place, respectively. So the general trend was inward near the outer edge of the swarm and outward farther inside, with flows converging on a region about 100 ?m from the swarm edge. We measured cellular metabolic activities with cells expressing a short-lived GFP and cell densities with cells labeled with a membrane fluorescent dye. The fluorescence plots were similar, with peaks about 80 ?m from the swarm edge and slopes that mimicked the particle drift rates. These plots suggest that net fluid flow is driven by cell growth. Fluid depth is largest in the multilayered region between approximately 30 and 200 ?m from the swarm edge, where fluid agitation is more vigorous. This water reservoir travels with the swarm, fueling its spreading. Intercellular communication is not required; cells need only grow. PMID:22371567

Wu, Yilin; Berg, Howard C.

2012-01-01

340

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

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

2013-01-01

341

Bacterial mortality and the fate of bacterial production  

Microsoft Academic Search

Knowledge of the rates of bacterial mortality, particularly predatory mortality, is important in determining the fate of bacterial\\u000a production. Communities of planktonic bacteria have specific growth rates on the order of 1 d?1, but there is relatively little variation in bacterial abundance, implying that growth and mortality are closely coupled.\\u000a A review of the mechanisms of bacterial mortality suggests that

Michael L. Pace; Mary Flagler Cary Arboretum

1988-01-01

342

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; José-Miguel Barea; Rosario Azcón

2009-01-01

343

Severity of Prenatal Cocaine Exposure and Child Language Functioning Through Age Seven Years: A Longitudinal Latent Growth Curve Analysis  

PubMed Central

The current study estimates the longitudinal effects of severity of prenatal cocaine exposure on language functioning in an urban sample of full-term African-American children (200 cocaine-exposed, 176 noncocaine-exposed) through age 7 years. The Miami Prenatal Cocaine Study sample was enrolled prospectively at birth, with documentation of prenatal drug exposure status through maternal interview and toxicology assays of maternal and infant urine and infant meconium. Language functioning was measured at ages 3 and 5 years using the Clinical Evaluation of Language Fundamentals–Preschool (CELF-P) and at age 7 years using the Core Language Domain of the NEPSY: A Developmental Neuropsychological Assessment. Longitudinal latent growth curve analyses were used to examine two components of language functioning, a more stable aptitude for language performance and a time-varying trajectory of language development, across the three time points and their relationship to varying levels of prenatal cocaine exposure. Severity of prenatal cocaine exposure was characterized using a latent construct combining maternal self-report of cocaine use during pregnancy by trimesters and maternal and infant bioassays, allowing all available information to be taken into account. The association between severity of exposure and language functioning was examined within a model including factors for fetal growth, gestational age, and IQ as intercorrelated response variables and child’s age, gender, and prenatal alcohol, tobacco, and marijuana exposure as covariates. Results indicated that greater severity of prenatal cocaine exposure was associated with greater deficits within the more stable aptitude for language performance (D = ?0.071, 95% CI = ?0.133, ?0.009; p = 0.026). There was no relationship between severity of prenatal cocaine exposure and the time-varying trajectory of language development. The observed cocaine-associated deficit was independent of multiple alternative suspected sources of variation in language performance, including other potential responses to prenatal cocaine exposure, such as child’s intellectual functioning, and other birth and postnatal influences, including language stimulation in the home environment. PMID:15002943

Bandstra, Emmalee S.; Vogel, April L.; Morrow, Connie E.; Xue, Lihua; Anthony, James C.

2009-01-01

344

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

345

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...

346

Influence of topology on bacterial social interaction  

E-print Network

Diffusion. J ­ current of bacteria, ­ bacterial density, c ­ attractant concentration, a ­ growth rate, Db of bacteria, ­ bacterial density, c ­ attractant concentration, a ­ growth rate, Db ­ bacterial diffusionInfluence of topology on bacterial social interaction Emil Yuzbashyan Princeton University #12

Yuzbashyan, Emil

347

Inhibition of Bacterial Growth and Intramniotic Infection in a Guinea Pig Model of Chorioamnionitis Using PAMAM Dendrimers  

PubMed Central

Dendrimers have emerged as topical microbicides to treat vaginal infections. This study explores the in-vitro, in-vivo antimicrobial activity of PAMAM dendrimers, and the associated mechanism. Interestingly, topical cervical application of 500 µg of generation-4 neutral dendrimer (G4-PAMAM-OH) showed potential to treat the Escherichia coli induced ascending uterine infection in guinea pig model of chorioamnionitis. Amniotic fluid collected from different gestational sacs of infected guinea pigs post treatment showed absence of E. coli growth in the cultures plated with it. The cytokine level [tumor necrosis factor (TNF?) and interleukin (IL-6 and IL-1?)] in placenta of the G4-PAMAM-OH treated animals were comparable to those in healthy animals while these were notably high in infected animals. Since, antibacterial activity of amine-terminated PAMAM dendrimers is known, the activity of hydroxyl and carboxylic acid terminated PAMAM dendrimers was compared with it. Though the G4-PAMAM-NH2 shows superior antibacterial activity, it was found to be cytotoxic to human cervical epithelial cell line above 10µg / mL, while the G4-PAMAM-OH was non cytotoxic upto 1mg / mL concentration. Cell integrity, outer (OM) and inner (IM) membrane permeabilization assays showed that G4-PAMAM-OH dendrimer efficiently changed the OM permeability, while G4-PAMAM-NH2 and G3.5-PAMAM-COOH damaged both OM and IM causing the bacterial lysis. The possible antibacterial mechanism are; G4-PAMAM-NH2 acts as polycation binding to the polyanionic lipopolysaccharide in E. coli, the G4-PAMAM-OH forms hydrogen bonds with the hydrophilic O-antigens in E. coli membrane and the G3.5-PAMAM-COOH acts as a polyanion, chelating the divalent ions in outer cell membrane of E. coli. This is the first study which shows that G4-PAMAM-OH dendrimer acts as an antibacterial agent. PMID:20580797

Wang, Bing; Navath, Raghavendra S.; Menjoge, Anupa R.; Balakrishnan, Bindu; Bellair, Robert; Dai, Hui; Romero, Roberto; Kannan, Sujatha; Kannan, Rangaramanujam M.

2010-01-01

348

Optimized polymeric film-based nitric oxide delivery inhibits bacterial growth in a mouse burn wound model.  

PubMed

Nitric oxide (NO) has many biological roles (e.g. antimicrobial agent, promoter of angiogenesis, prevention of platelet activation) that make NO releasing materials desirable for a variety of biomedical applications. Localized NO release can be achieved from biomedical grade polymers doped with diazeniumdiolated dibutylhexanediamine (DBHD/N2O2) and poly(lactic-co-glycolic acid) (PLGA). In this study, the optimization of this chemistry to create film/patches that can be used to decrease microbial infection at wound sites is examined. Two polyurethanes with different water uptakes (Tecoflex SG-80A (6.2±0.7wt.%) and Tecophilic SP-60D-20 (22.5±1.1wt.%)) were doped with 25wt.% DBHD/N2O2 and 10wt.% of PLGA with various hydrolysis rates. Films prepared with the polymer that has the higher water uptake (SP-60D-20) were found to have higher NO release and for a longer duration than the polyurethane with the lower water uptake (SG-80A). The more hydrophilic polymer enhances the hydrolysis rate of the PLGA additive, thereby providing a more acidic environment that increases the rate of NO release from the NO donor. The optimal NO releasing and control SG-80A patches were then applied to scald burn wounds that were infected with Acinetobacter baumannii. The NO released from these patches applied to the wounds is shown to significantly reduce the A. baumannii infection after 24h (?4 log reduction). The NO release patches are also able to reduce the level of transforming growth factor-? in comparison to controls, which can enhance re-epithelialization, decrease scarring and reduce migration of bacteria. The combined DBHD/N2O2 and PLGA-doped polymer patches, which could be replaced periodically throughout the wound healing process, demonstrate the potential to reduce risk of bacterial infection and promote the overall wound healing process. PMID:24980058

Brisbois, Elizabeth J; Bayliss, Jill; Wu, Jianfeng; Major, Terry C; Xi, Chuanwu; Wang, Stewart C; Bartlett, Robert H; Handa, Hitesh; Meyerhoff, Mark E

2014-10-01

349

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

350

Initiation and growth of multiple-site damage in the riveted lap joint of a curved stiffened fuselage panel: An experimental and analytical study  

Microsoft Academic Search

As part of the structural integrity research of the National Aging Aircraft Research Program, a comprehensive study on multiple-site damage (MSD) initiation and growth in a pristine lap-joint fuselage panel has been conducted. The curved stiffened fuselage panel was tested at the Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) facility located at the Federal Aviation Administration William J. Hughes

Abubaker Ali Ahmed

2007-01-01

351

THE EFFECT OF PH ON MAXIMUM BACTERIAL GROWTH RATE AND ITS POSSIBLE ROLE AS A DETERMINANT OF BACTERIAL COMPETITION IN THE RUMEN  

Microsoft Academic Search

SUMMARY Five rumen bacteria were inoculated into media with pH values ranging from 6.7 to 4.7 to determine effects on maximum growth rate. Streptococcus boris, Bacteroides ruminicola, and Selenomanas ruminantium appeared to be more resistant to low pH than either Butyrivib- rio fibrisolvens or Megasphaera elsdenii. S. Boris, B. ruminicola, and S. ruminantium showed gradual decreases in maximum growth rate

J. B. Russell; W. M. Sharp; R. L. Baldwin

352

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 2 months 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 2 months 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 2 months 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; Söderquist, B; Friberg, O; Nilsson, U

2014-11-01

353

A Multiphasic Approach for the Identification of Endophytic Bacterial in Strawberry Fruit and their Potential for Plant Growth Promotion  

Microsoft Academic Search

This study used a multiphasic approach, characterized by the simultaneous use of culture-dependent and culture-independent\\u000a methods, to investigate endophytic bacterial communities in strawberry (Fragaria ananassa) fruit. A total of 92 bacterial endophytes were isolated and initially grouped by their repetitive extragenic palindromic\\u000a (rep)-PCR banding pattern and biochemical features. Phylogenetic analysis of the 16S rRNA gene sequences of 45 representatives\\u000a showed

Gilberto Vinícius de Melo Pereira; Karina Teixeira Magalhães; Emi Rainildes Lorenzetii; Thiago Pereira Souza; Rosane Freitas Schwan

354

Diversity of culturable bacterial populations associated to Tuber borchii ectomycorrhizas and their activity on T. borchii mycelial growth  

Microsoft Academic Search

Isolation and physiological and molecular characterisation of culturable bacterial strains belonging to actinomycetes, pseudomonads and aerobic spore-forming bacteria were carried out on mycorrhizal root tips of Quercus robur var. peduncolata infected by Tuber borchii. Cellular density of the three bacterial groups in ectomycorrhizal root tips was estimated to be 1.3±0.11×106 cfu g?1 dry weight for total heterotrophic bacteria and 1.08±0.6×105

Cristiana Sbrana; Monica Agnolucci; Stefano Bedini; Annamaria Lepera; Annita Toffanin; Manuela Giovannetti; Marco P Nuti

2002-01-01

355

Aerobic biological treatment of low-strength synthetic wastewater in membrane-coupled bioreactors: the structure and function of bacterial enrichment cultures as the net growth rate approaches zero.  

PubMed

The goal of the current research was to determine if the stringent nutrient limitation imposed by membrane-coupled bioreactors (MBRs) could be used to force mixed bacterial communities to exhibit a zero net growth rate over an extended time period. Mechanistically, this zero net growth rate could be achieved when the amount of energy available for growth is balanced by the maintenance requirements of the bacterial community. Bench-scale MBRs were fed synthetic feed medium containing gelatin as the major organic substrate. Biomass concentrations initially increased rapidly, but subsequently declined until an asymptote was reached. Leucine aminopeptidase activities concomitantly increased by at least 10-fold, suggesting that bacterial catabolic activity remained high even while growth rates became negligible. In contrast, alpha-glucosidase and heptanoate esterase activities decreased, indicating that the bacterial community specifically adapted to the carbon source in the feed medium. Bacterial community analysis by denaturing gradient gel electrophoresis of PCR-amplified 16S rRNA gene fragments (PCR-DGGE) suggested that the bacterial community structure completely changed from the beginning to the end of each MBR. Excision and nucleotide sequence analysis of prominent PCR-DGGE bands suggested that many of the dominant populations were similar to novel bacterial strains that were previously uncultivated or recently cultivated during studies specifically targeting these novel populations. This research demonstrates that MBRs have substantial practical applications for biological wastewater treatment; in addition, MBRs are a useful tool to study the ecology of slow-growing bacteria. PMID:16400538

Chen, Ruoyu; LaPara, Timothy M

2006-01-01

356

Bacterial Production Lab State variables and processes  

E-print Network

: Bacterial Growth Rate (gC h-1) Why do we want to measure processes? Objective: Measure bacterial growth rateBacterial Production Lab State variables and processes BDOM Other compounds (e.g., EtOH) CO2 G. Process #12;Growth Equations dt tt txtx 0 20 )()( td Where: td Doubling time of population. x(t) Number

Vallino, Joseph J.

357

Bacterial Production Lab State variables and processes  

E-print Network

B: Bacterial Growth Rate (gC h-1) Why do we want to measure processes? Objective: Measure bacterial growth rateBacterial Production Lab State variables and processes BDOM Other compounds (e.g., EtOH) CO2 r Var. Process #12;Growth Equation td Where: td Doubling time of population. x(t) Number or mass

Vallino, Joseph J.

358

Bacterial Production Lab State variables and processes  

E-print Network

: Bacterial Growth Rate (gC h-1) Why do we want to measure processes? Objective: Measure bacterial growth rateBacterial Production Lab State variables and processes BDOM Other compounds (e.g., EtOH) CO2 G. Process #12;Growth Equations dt tt txtx 0 20 - = )()( td Where: td Doubling time of population. x

Vallino, Joseph J.

359

4, 37993828, 2007 Bacterial production  

E-print Network

limiting bacterial growth was investigated along vertical and longitudinal gradients across the SouthBGD 4, 3799­3828, 2007 Bacterial production limitation in the South Pacific Gyre F. Van Wambeke et forum of Biogeosciences Factors limiting heterotrophic bacterial production in the southern Pacific

Boyer, Edmond

360

Comparative analysis of quantitative trait loci for body weight, growth rate and growth curve parameters from 3 to 72 weeks of age in female chickens of a broiler–layer cross  

PubMed Central

Background Comparisons of quantitative trait loci (QTL) for growth and parameters of growth curves assist in understanding the genetics and ultimately the physiology of growth. Records of body weight at 3, 6, 12, 24, 48 and 72 weeks of age and growth rate between successive age intervals of about 500 F2 female chickens of the Roslin broiler-layer cross were available for analysis. These data were analysed to detect and compare QTL for body weight, growth rate and parameters of the Gompertz growth function. Results Over 50 QTL were identified for body weight at specific ages and most were also detected in the nearest preceding and/or subsequent growth stage. The sum of the significant and suggestive additive effects for bodyweight at specific ages accounted for 23-43% of the phenotypic variation. A single QTL for body weight on chromosome 4 at 48 weeks of age had the largest additive effect (550.4?±?68.0 g, 11.5% of the phenotypic variation) and a QTL at a similar position accounted 14.5% of the phenotypic variation at 12 weeks of age. Age specific QTL for growth rate were detected suggesting that there are specific genes that affect developmental processes during the different stages of growth. Relatively few QTL influencing Gompertz growth curve parameters were detected and overlapped with loci affecting growth rate. Dominance effects were generally not significant but from 12 weeks of age they exceeded the additive effect in a few cases. No evidence for epistatic QTL pairs was found. Conclusions The results confirm the location for body weight and body weight gain during growth that were identified in previous studies and were consistent with QTL for the parameters of the Gompertz growth function. Chromosome 4 explained a relatively large proportion of the observed growth variation across the different ages, and also harboured most of the detected QTL for Gompertz parameters, confirming its importance in controlling growth. Very few QTL were detected for body weight or gain at 48 and 72 weeks of age, probably reflecting the effect of differences in reproduction and random environmental effects. PMID:23496818

2013-01-01

361

Limits to growth, sustainable development and environmental kuznets curves: an examination of the environmental impact of economic development  

Microsoft Academic Search

The nature of the relationship between economic development and the environment has been discussed since the 1960s, yet opinion remains divided. This paper provides a comprehensive analysis of the relationship between economic growth and environmental degradation and begins by reviewing the largely theoretical discussions from the 'limits to growth' debate of the 1970s to the advent of sustainable development in

Matthew A. Cole

1999-01-01

362

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

363

Characterization of tilapia (Oreochromis niloticus) viperin expression, and inhibition of bacterial growth and modulation of immune-related gene expression by electrotransfer of viperin DNA into zebrafish muscle.  

PubMed

Viperin is an anti-viral protein, induced by viral infection. In this study, we examined whether over-expression of viperin in fish muscle could inhibit bacterial growth. We first obtained the cDNA sequence of tilapia viperin, through RT-PCR-mediated cloning and sequencing. The cDNA sequence was similar to those of several fish viperins in GenBank, and it was predicted to encode the conserved domain of radical S-adenosylmethionine superfamily proteins. Phylogenetic analysis revealed that tilapia viperin was most closely related to viperin of Sciaenops ocellatus, Coreoperca kawamebari, and C. whiteheadi. Expression of tilapia viperin was significantly up-regulated in the kidney, liver, spleen, and gills upon challenge with lipopolysaccharide (LPS) and poly(I:C) in a time- and dose-dependent manner. Injection of Vibrio vulnificus (204) and Streptococcus agalactiae (SA47) bacteria into tilapia resulted in significant induction of viperin expression in the whole body, kidney, liver, and spleen. Electrotransfer of a viperin-expressing plasmid into zebrafish muscles decreased bacterial numbers and altered expression of immune-related genes. These data indicate that such altered expression may account for the improvement in bacterial clearance following electroporation of viperin, suggesting that fish viperin has antiviral and antibacterial activities. PMID:23237906

Lee, Shu-Hua; Peng, Kuan-Chieh; Lee, Lin-Han; Pan, Chieh-Yu; Hour, Ai-Ling; Her, Guor Mour; Hui, Cho-Fat; Chen, Jyh-Yih

2013-02-15

364

Ogive Curves  

NSDL National Science Digital Library

This page contains a discussion of ogive curves, logistic regression curves, and architecture. Nice photographs of architectural applications are included. The classic Birthday Problems is included as an example of an ogive curve.

2008-01-01

365

Hierarchical Bayesian analysis to incorporate age uncertainty in growth curve analysis and estimates of age from length: Florida manatee (Trichechus manatus) carcasses  

USGS Publications Warehouse

Age estimation of individuals is often an integral part of species management research, and a number of ageestimation techniques are commonly employed. Often, the error in these techniques is not quantified or accounted for in other analyses, particularly in growth curve models used to describe physiological responses to environment and human impacts. Also, noninvasive, quick, and inexpensive methods to estimate age are needed. This research aims to provide two Bayesian methods to (i) incorporate age uncertainty into an age-length Schnute growth model and (ii) produce a method from the growth model to estimate age from length. The methods are then employed for Florida manatee (Trichechus manatus) carcasses. After quantifying the uncertainty in the aging technique (counts of ear bone growth layers), we fit age-length data to the Schnute growth model separately by sex and season. Independent prior information about population age structure and the results of the Schnute model are then combined to estimate age from length. Results describing the age-length relationship agree with our understanding of manatee biology. The new methods allow us to estimate age, with quantified uncertainty, for 98% of collected carcasses: 36% from ear bones, 62% from length.

Schwarz, L.K.; Runge, M.C.

2009-01-01

366

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

2014-10-01

367

Species-area curves and growth-form spectra for some herb-rich woodlands in western Victoria, Australia  

Microsoft Academic Search

Species-area curves are presented for three woodlands with herbaceous understoreys in western Victoria, Australia. Up to 93 species of vascular plant were recorded from 128 m2, making these woodlands one of the richest terrestrial vegetations recordedfrom temperate Australia. Species richness at this scale is comparable with that recorded from kwongan (sclerophyllous shrubland) in south-western Australia. Up to 45 species were

IAN D. LUNT

1990-01-01

368

Bacterial community compositions of tomato (Lycopersicum esculentum Mill.) seeds and plant growth promoting activity of ACC deaminase producing Bacillus subtilis (HYT-12-1) on tomato seedlings.  

PubMed

Study of endophytic bacteria within plant seeds is very essential and meaningful on account of their heritability and versatility. This study investigated Bacillus bacterial communities within the seeds of four commercial tomato varieties, by 16S rRNA gene PCR-RFLP (restriction fragment length polymorphism). Phylogenetic analysis of 16S rRNA gene sequences indicated that the 22 representative isolates belonged to five species of genus Bacillus and the bacterial compositions showed remarkable differences among tomato varieties. Isolates exhibited multiple plant growth promoting (PGP) traits: 37 % of indole-3-acetic acid production; 37 % of phosphate solubilization; 24 % of siderophores production; 85 % of potential nitrogen fixation and 6 % of 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. Isolate HYT-12-1 was shown to have highest ACC deaminase activity (112.02 nmol ?-ketobutyrate mg?¹ protein h?¹) among the five ACC deamiase producing strains. 16S rRNA gene sequencing indicated that the isolate HYT-12-1 shared the highest sequence similarity (100 %) with B. subtilis. PGP experiments under gnotobiotic and greenhouse conditions revealed the ability of strain HYT-12-1 to enhance the growth of tomato seedlings. This is the first study to describe endophytic Bacillus communities within tomato seeds, and the results suggest that B. subtilis strain HYT-12-1 would have a great potential for industrial application as biofertilizer in the future. PMID:24114316

Xu, Mingshuang; Sheng, Jiping; Chen, Lin; Men, Yejun; Gan, Lin; Guo, Shuntang; Shen, Lin

2014-03-01

369

Evaluation of liquid culture media to support growth of Mobiluncus species  

Microsoft Academic Search

Mobiluncus curtisii and M. mulieris are anaerobic, gram-negative, motile curved rods isolated commonly from the vagina of women with bacterial vaginosis. Hitherto, there has been difficulty in isolating and growing these bacteria and little attention has been paid to growth in liquid media. Reasons for establishing the means of attaining optimal growth in such media include production of antigens for

A. W. TAYLOR-ROBINSONand; D. TAYLOR-ROBINSON

370

N-Acetyl-L-Cysteine Affects Growth, Extracellular Polysaccharide Production, and Bacterial Biofilm Formation on Solid Surfaces  

Microsoft Academic Search

N-Acetyl-L-cysteine (NAC) is used in medical treatment of patients with chronic bronchitis. The positive effects of NAC treatment have primarily been attributed to the mucus-dissolving properties of NAC, as well as its ability to decrease biofilm formation, which reduces bacterial infections. Our results suggest that NAC also may be an interesting candidate for use as an agent to reduce and

Ann-Cathrin Olofsson; Malte Hermansson; Hans Elwing

2003-01-01

371

Indoor-Biofilter Growth and Exposure to Airborne Chemicals Drive Similar Changes in Plant Root Bacterial Communities  

PubMed Central

Due to the long durations spent inside by many humans, indoor air quality has become a growing concern. Biofiltration has emerged as a potential mechanism to clean indoor air of harmful volatile organic compounds (VOCs), which are typically found at concentrations higher indoors than outdoors. Root-associated microbes are thought to drive the functioning of plant-based biofilters, or biowalls, converting VOCs into biomass, energy, and carbon dioxide, but little is known about the root microbial communities of such artificially grown plants, how or whether they differ from those of plants grown in soil, and whether any changes in composition are driven by VOCs. In this study, we investigated how bacterial communities on biofilter plant roots change over time and in response to VOC exposure. Through 16S rRNA amplicon sequencing, we compared root bacterial communities from soil-grown plants with those from two biowalls, while also comparing communities from roots exposed to clean versus VOC-laden air in a laboratory biofiltration system. The results showed differences in bacterial communities between soil-grown and biowall-grown plants and between bacterial communities from plant roots exposed to clean air and those from VOC-exposed plant roots. Both biowall-grown and VOC-exposed roots harbored enriched levels of bacteria from the genus Hyphomicrobium. Given their known capacities to break down aromatic and halogenated compounds, we hypothesize that these bacteria are important VOC degraders. While different strains of Hyphomicrobium proliferated in the two studied biowalls and our lab experiment, strains were shared across plant species, suggesting that a wide range of ornamental houseplants harbor similar microbes of potential use in living biofilters. PMID:24878602

Hu, Yi; Chau, Linh; Pauliushchyk, Margarita; Anastopoulos, Ioannis; Anandan, Shivanthi; Waring, Michael S.

2014-01-01

372

Antibiotic production in relation to bacterial growth and nematode development in Photorhabdus–Heterorhabditis infected Galleria mellonella larvae  

Microsoft Academic Search

The population of Photorhabdus luminescens C9, bacterial symbiont of the entomopathogenic nematode, Heterorhabditis megidis 90, increased rapidly to 1.2–2.6×109 cells g?1 wet Galleria mellonella larvae within 24 h of nematode infection of the larvae, and maintained a relatively constant level (1.2–2.0×1010 cells g?1) through the entire 14-day period of nematode development. The antibiotic, 3,5-dihydroxy-4-isopropylstilbene, was produced by P. luminescens C9

Kaiji Hu; John M Webster

2000-01-01

373

Indoor-biofilter growth and exposure to airborne chemicals drive similar changes in plant root bacterial communities.  

PubMed

Due to the long durations spent inside by many humans, indoor air quality has become a growing concern. Biofiltration has emerged as a potential mechanism to clean indoor air of harmful volatile organic compounds (VOCs), which are typically found at concentrations higher indoors than outdoors. Root-associated microbes are thought to drive the functioning of plant-based biofilters, or biowalls, converting VOCs into biomass, energy, and carbon dioxide, but little is known about the root microbial communities of such artificially grown plants, how or whether they differ from those of plants grown in soil, and whether any changes in composition are driven by VOCs. In this study, we investigated how bacterial communities on biofilter plant roots change over time and in response to VOC exposure. Through 16S rRNA amplicon sequencing, we compared root bacterial communities from soil-grown plants with those from two biowalls, while also comparing communities from roots exposed to clean versus VOC-laden air in a laboratory biofiltration system. The results showed differences in bacterial communities between soil-grown and biowall-grown plants and between bacterial communities from plant roots exposed to clean air and those from VOC-exposed plant roots. Both biowall-grown and VOC-exposed roots harbored enriched levels of bacteria from the genus Hyphomicrobium. Given their known capacities to break down aromatic and halogenated compounds, we hypothesize that these bacteria are important VOC degraders. While different strains of Hyphomicrobium proliferated in the two studied biowalls and our lab experiment, strains were shared across plant species, suggesting that a wide range of ornamental houseplants harbor similar microbes of potential use in living biofilters. PMID:24878602

Russell, Jacob A; Hu, Yi; Chau, Linh; Pauliushchyk, Margarita; Anastopoulos, Ioannis; Anandan, Shivanthi; Waring, Michael S

2014-08-01

374

Molecular hydrogen from water radiolysis as an energy source for bacterial growth in a basin containing irradiating waste.  

PubMed

Although being deionized, filtered and therefore normally deeply oligotrophic, the water from a basin containing irradiating waste presented relatively high bacterial concentrations (ca 10(5) cfu ml(-1)) and biofilm development at its surface and on the walls. This water was characterized by a high concentration of molecular H2 due to water radiolysis, while its electrochemical potential was around +400 mV due the presence of dissolved O2 and active oxygen compounds. This combination of H2 availability and of an oxidant environment is completely original and not described in nature. From surface and wall biofilms, we enumerated the autotrophic populations ( approximately 10(5) bacteria ml(-1)) able to grow in presence of H2 as energy source and CO2 as carbon source, and we isolated the most abundant ones among cultivable bacteria. They efficiently grew on a mineral medium, in the presence of H2, O2 and CO2, the presence of the three gases being indispensable. Two strains were selected and identified using their rrs gene sequence as Ralstonia sp. GGLH002 and Burkholderia sp. GGLH005. In pure culture and using isotope exchange between hydrogen and deuterium, we demonstrated that these strains are able to oxidize hydrogen as energy source, using oxygen as an electron acceptor, and to use carbon dioxide as carbon source. These chemoautotroph hydrogen-oxidizing bacteria probably represent the pioneer bacterial populations in this basin and could be primary producers in the bacterial community. PMID:15522503

Galès, Grégoire; Libert, Marie-Françoise; Sellier, Régine; Cournac, Laurent; Chapon, Virginie; Heulin, Thierry

2004-11-15

375

Bacterial Growth Stimulation with Exogenous Siderophore and Synthetic N-Acyl Homoserine Lactone Autoinducers under Iron-Limited and Low-Nutrient Conditions  

PubMed Central

The growth of marine bacteria under iron-limited conditions was investigated. Neither siderophore production nor bacterial growth was detected for Pelagiobacter sp. strain V0110 when Fe(III) was present in the culture medium at a concentration of <1.0 ?M. However, the growth of V0110 was strongly stimulated by the presence of trace amounts of exogenous siderophore from an alpha proteobacterium, V0902, and 1 nM N-acyl-octanoylhomoserine lactone (C8-HSL), which is known as a quorum-sensing chemical signal. Even though the iron-binding functionality of a hydroxamate siderophore was undetected in the supernatant of V0902, a hydroxamate siderophore was detected in the supernatant of V0110 under the above conditions. These results indicated that hydroxamate siderophore biosynthesis by V0110 began in response to the exogenous siderophore from V0902 when in the presence of C8-HSL; however, C8-HSL production by V0110 and V0902 was not detected. Direct interaction between V0902 and V0110 through siderophore from V0902 was observed in the dialyzing culture. Similar stimulated growth by exogenous siderophore and HSL was also observed in other non-siderophore-producing bacteria isolated from marine sponges and seawater. The requirement of an exogenous siderophore and an HSL for heterologous siderophore production indicated the possibility that cell-cell communication between different species was occurring. PMID:10877770

Guan, Le Luo; Onuki, Hiroyuki; Kamino, Kei

2000-01-01

376

Destruction of bacterial viruses in serum by heat and radiation under conditions that sustain the ability of serum to support growth of cells in suspended culture.  

PubMed Central

Methods for inactivating bacterial viruses in serum were developed through the use of heat and ionizing radiation, and the effects of these treatments on the growth rates of cultured cells were tested. Viruses chosen for this study were the radiation-resistant bacteriphage f2 and heat-resistant phage T4. The viabilities of these phages were reduced more than 2 and 4 orders of magnitude, respectively, by a treatment at 60 degrees C for 30 min followed by 420 krads of ionizing radiation. Simultaneous application of heat and radiation caused a considerably greater reduction in viability of both phages in serum, but also caused a significant decrease in the growth rates of L cells in medium supplemented with serum treated in this manner. Treatment of serum with these same doses but given in the sequential fashion of heat followed by radiation caused little or no change in the growth rates of L cells. Finally, it was found that simultaneous treatment of serum with these doses of heat and radiation had little effect on the growth rates of either HeLa or Chinese hamster cells. PMID:544633

Ward, R L

1979-01-01

377

Effect of feeding tannin degrading bacterial culture (Streptococcus gallolyticus strain TDGB 406) on nutrient utilization, urinary purine derivatives and growth performance of goats fed on Quercus semicarpifolia leaves.  

PubMed

To study the effect of supplementation of tannin degrading bacterial culture (Streptococcus gallolyticus strain TDGB 406) on growth performance, nutrient utilization and urinary purine derivatives of goats fed on oak (Quercus semicarpifolia) leaves. For growth study, eighteen billy goats (4 month old, average body weight 9.50 ± 1.50 kg) were distributed into three groups of six animals each. The animals of group 1 served as control while animals of groups 2 (T1) and 3 (T2) were given (@ 5 ml/kg live weight) autoclaved and live culture of isolate TDGB 406 (10(6) cells/ml) respectively. The animals were fed measured quantity of dry oak leaves as the main roughage source and ad libitum maize hay along with fixed quantity of concentrate mixture. The feeding of live culture of isolate TDGB 406 (probiotic) did not affect dry matter intake and digestibility of nutrients except that of dry matter and crude protein, which was higher in T2 group as compared to control. All the animals were in positive nitrogen balance. There was no significant effect of feeding isolate TDGB 406 on urinary purine derivatives (microbial protein production) in goats. The body weight gain and average live weight gain was significantly higher (p = 0.071) in T2 group as compared to control. Feed conversion efficiency was also better in the goats fed on live culture of TDGB 406 (T2). The feeding of tannin degrading bacterial isolate TDGB 406 as probiotic resulted in improved growth performance and feed conversion ratio in goats fed on oak leaves as one of the main roughage source. PMID:24313948

Kumar, K; Chaudhary, L C; Agarwal, N; Kamra, D N

2014-10-01

378

A Growth Curve Analysis of Literacy Performance among Second-Grade, Spanish-Speaking, English-Language Learners  

ERIC Educational Resources Information Center

The literacy growth of 260 second-grade English learners (ELs) with varying degrees of English language proficiency (e.g., Beginning, Early Intermediate, Intermediate, Early Advanced and Advanced English language proficiency) was assessed with English literacy skill assessments. Dynamic Indicators of Basic Early Literacy Skills measures were…

Gutiierrez, Gabriel; Vanderwood, Mike L.

2013-01-01

379

Modeling Life-Span Growth Curves of Cognition using Longitudinal Data with Multiple Samples and Changing Scales of Measurement  

PubMed Central

This research uses multiple-sample longitudinal data from different test batteries to examine propositions about changes in constructs over the lifespan. The data come from three classic studies on intellectual abilities where, in combination, N=441 persons are repeatedly measures as many as 16 times over 70 years. Cognitive constructs of Vocabulary and Memory were measured using eight different age-appropriate intelligence test batteries, and we explore possible linkage of these scales using Item Response Theory (IRT). We simultaneously estimate the parameters of both IRT and Latent Curve Models (LCM) based on a joint model likelihood approach (i.e., NLMIXED and WINBUGS). Group differences are included in the model to examine potential inter-individual differences in levels and change. The resulting Longitudinal IRT (LIRT) analyses leads to a few new methodological suggestions for dealing with repeated constructs based on changing measurements in developmental studies. PMID:19485625

McArdle, John J.; Grimm, Kevin; Hamagami, Fumiaki; Bowles, Ryan; Meredith, William

2010-01-01

380

Intestinal Epithelial Serum Amyloid A Modulates Bacterial Growth In Vitro and Pro-Inflammatory Responses in Mouse Experimental Colitis  

PubMed Central

Background Serum Amyloid A (SAA) is a major acute phase protein of unknown function. SAA is mostly expressed in the liver, but also in other tissues including the intestinal epithelium. SAA reportedly has anti-bacterial effects, and because inflammatory bowel diseases (IBD) result from a breakdown in homeostatic interactions between intestinal epithelia and bacteria, we hypothesized that SAA is protective during experimental colitis. Methods Intestinal SAA expression was measured in mouse and human samples. Dextran sodium sulfate (DSS) colitis was induced in SAA 1/2 double knockout (DKO) mice and in wildtype controls. Anti-bacterial effects of SAA1/2 were tested in intestinal epithelial cell lines transduced with adenoviral vectors encoding the CE/J SAA isoform or control vectors prior to exposure to live Escherichia coli. Results Significant levels of SAA1/SAA2 RNA and SAA protein were detected by in situ hybridization and immunohistochemistry in mouse colonic epithelium. SAA3 expression was weaker, but similarly distributed. SAA1/2 RNA was present in the ileum and colon of conventional mice and in the colon of germfree mice. Expression of SAA3 was strongly regulated by bacterial lipopolysaccharides in cultured epithelial cell lines, whereas SAA1/2 expression was constitutive and not LPS inducible. Overexpression of SAA1/2 in cultured epithelial cell lines reduced the viability of co-cultured E. coli. This might partially explain the observed increase in susceptibility of DKO mice to DSS colitis. SAA1/2 expression was increased in colon samples obtained from Crohn's Disease patients compared to controls. Conclusions Intestinal epithelial SAA displays bactericidal properties in vitro and could play a protective role in experimental mouse colitis. Altered expression of SAA in intestinal biopsies from Crohn's Disease patients suggests that SAA is involved in the disease process.. PMID:21067563

2010-01-01

381

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 Michaelis–Menten 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 µmol 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 Michaelis–Menten 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 % (Michaelis–Menten) of the observed net photosynthetic rates over the full range of light intensities (0–700 µmol 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

382

ORIGINAL ARTICLE Colorimetric / fluorescent bacterial sensing by agarose-  

E-print Network

and fluorescence transformations in response to bacterial growth. The sensing constructs comprise glassORIGINAL ARTICLE Colorimetric / fluorescent bacterial sensing by agarose- embedded lipid The development of simple and rapid bacterial detection techniques is drawing intense scientific and technological

Jelinek, Raz

383

ORIGINAL ARTICLE Colorimetric / fluorescent bacterial sensing by agarose-  

E-print Network

in response to bacterial growth. The sensing constructs comprise glass-supported LangmuirORIGINAL ARTICLE Colorimetric / fluorescent bacterial sensing by agarose- embedded lipid The development of simple and rapid bacterial detection techniques is drawing intense scientific and technological

Jelinek, Raz

384

SIMPLAS: A Simulation of Bacterial Plasmid Maintenance.  

ERIC Educational Resources Information Center

This article describes a computer simulation of bacterial physiology during growth in a chemostat. The program was designed to help students to appreciate and understand the related effects of parameters which influence plasmid persistence in bacterial populations. (CW)

Dunn, A.; And Others

1988-01-01

385

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

386

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

387

Initiation and growth of multiple-site damage in the riveted lap joint of a curved stiffened fuselage panel: An experimental and analytical study  

NASA Astrophysics Data System (ADS)

As part of the structural integrity research of the National Aging Aircraft Research Program, a comprehensive study on multiple-site damage (MSD) initiation and growth in a pristine lap-joint fuselage panel has been conducted. The curved stiffened fuselage panel was tested at the Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) facility located at the Federal Aviation Administration William J. Hughes Technical Center. A strain survey test was conducted to verify proper load application. The panel was then subjected to a fatigue test with constant-amplitude cyclic loading. The applied loading spectrum included underload marker cycles so that crack growth history could be reconstructed from post-test fractographic examinations. Crack formation and growth were monitored via nondestructive and high-magnification visual inspections. Strain gage measurements recorded during the strain survey tests indicated that the inner surface of the skin along the upper rivet row of the lap joint experienced high tensile stresses due to local bending. During the fatigue loading, cracks were detected by eddy-current inspections at multiple rivet holes along the upper rivet row. Through-thickness cracks were detected visually after about 80% of the fatigue life. Once MSD cracks from two adjacent rivet holes linked up, there was a quick deterioration in the structural integrity of the lap joint. The linkup resulted in a 2.87" (72.9-mm) lead fatigue crack that rapidly propagated across 12 rivet holes and crossed over into the next skin bay, at which stage the fatigue test was terminated. A post-fatigue residual strength test was then conducted by loading the panel quasi-statically up to final failure. The panel failed catastrophically when the crack extended instantaneously across three additional bays. Post-test fractographic examinations of the fracture surfaces in the lap joint of the fuselage panel were conducted to characterize subsurface crack initiation and growth. Results showed evidence of fretting damage and crack initiation at multiple locations near the rivet holes along the faying surface of the skin. The subsurface cracks grew significantly along the faying surface before reaching the outer surface of the skin, forming elliptical crack fronts. A finite element model (FE) of the panel was constructed and geometrically-nonlinear analyses conducted to determine strain distribution under the applied loads. The FE model was validated by comparing the analysis results with the strain gage measurements recorded during the strain survey test. The validated FE model was then used to determine stress-intensity factors at the crack tips. Stress-intensity factor results indicated that crack growth in the lap joint was under mixed-mode; however, the opening-mode stress intensity factor was dominant. The stress-intensity factors computed from the FE analysis were used to conduct cycle-by-cycle integration of fatigue crack growth. In the cycle-by-cycle integration, the NASGRO crack growth model was used with its parameters selected to account for the effects of plasticity-induced crack closure and the test environment on crack growth rate. Fatigue crack growth predictions from cycle-by-cycle computation were in good agreement with the experimental measured crack growth data. The results of the study provide key insights into the natural development and growth of MSD cracks in the pristine lap joint. The data provided by the study represent a valuable source for the evaluation and validation of analytical methodologies used for predicting MSD crack initiation and growth.

Ahmed, Abubaker Ali

388

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

389

Prostatitis - bacterial  

MedlinePLUS

Prostatitis is most often caused by a bacterial infection of the prostate gland. Any bacteria that can cause a urinary tract infection can cause acute bacterial prostatitis. Some sexually transmitted diseases (STDs) ...

390

[Application of bacterial thermo- and phagelysates for suppression of malignant tumor growth in experimental studies: 2 comparative analysis of anticancer efficacy of thermo- and phagelysates of Ps. aeruginosa and E. coli].  

PubMed

In the presented work antitumor effects of thermo- and phagelysates of Ps.aeruginosa and E.coli on Ehrlich carcinoma growth in mice have been studied. The treatment efficacy was evaluated according to the dynamic changes in volume of cancer tissue, cancer growth inhibition percent and calculations using Semi-empirical mathematical model describing cancer volume variations in relation to time passed after carcinoma inoculation. It was shown that at the early stage of cancer growth all tested bacterial preparations significantly inhibit cancer growth. Antitumor treatment effects were better expressed in animal studies using bacterial pagelysates in comparison to that of thermolysates. Comparative analysis of anticancer treatment efficacy of Ps.aeruginosa and E.coli phagelysates have shown that E.coli phagelysates reveal stronger and more prolonged anticancer treatment properties than phagelysates of Ps.aeruginosa. PMID:22859451

Gambashidze, K G; Kalandarishvili, K G; Khorava, P A; Azaladze, T N; Lasareishvili, B G; Dzhaiani, E G; Tediashvili, M I

2012-06-01

391

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

392

Bacterial Sialidase  

NASA Technical Reports Server (NTRS)

Data shows that elevated sialidase in bacterial vaginosis patients correlates to premature births in women. Bacterial sialidase also plays a significant role in the unusual colonization of Pseudomonas aeruginosa in cystic fibrosis patients. Crystals of Salmonella sialidase have been reproduced and are used for studying the inhibitor-enzyme complexes. These inhibitors may also be used to inhibit a trans-sialidase of Trypanosome cruzi, a very similar enzyme to bacterial sialidase, therefore preventing T. cruzi infection, the causitive agent of Chagas' disease. The Center for Macromolecular Crystallography suggests that inhibitors of bacterial sialidases can be used as prophylactic drugs to prevent bacterial infections in these critical cases.

2004-01-01

393

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 1,000 mg/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-Pérez, M; Torres, J L; Rodríguez-Pastrana, B R; Soriano-Santos, J; Díaz-Godínez, G; Díaz, R; Tlecuitl-Beristain, S; Sánchez, C

2014-11-01

394

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

395

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

396

Novel Bacterial and Archaeal Lineages from an In Situ Growth Chamber Deployed at a Mid-Atlantic Ridge Hydrothermal Vent  

Microsoft Academic Search

The phylogenetic diversity was determined for a microbial community obtained from an in situ growth chamber placed on a deep-sea hydrothermal vent on the Mid-Atlantic Ridge (23°22* N, 44°57* W). The chamber was deployed for 5 days, and the temperature within the chamber gradually decreased from 70 to 20°C. Upon retrieval of the chamber, the DNA was extracted and the

ANNA-LOUISE REYSENBACH; KRISTA LONGNECKER; JULIE KIRSHTEIN

2000-01-01

397

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

398

Bacterial Cyanide Oxygenase Is a Suite of Enzymes Catalyzing the Scavenging and Adventitious Utilization of Cyanide as a Nitrogenous Growth Substrate  

PubMed Central

Cyanide oxygenase (CNO) from Pseudomonas fluorescens NCIMB 11764 catalyzes the pterin-dependent oxygenolytic cleavage of cyanide (CN) to formic acid and ammonia. CNO was resolved into four protein components (P1 to P4), each of which along with a source of pterin cofactor was obligately required for CNO activity. Component P1 was characterized as a multimeric 230-kDa flavoprotein exhibiting the properties of a peroxide-forming NADH oxidase (oxidoreductase) (Nox). P2 consisted of a 49.7-kDa homodimer that showed 100% amino acid identity at its N terminus to NADH peroxidase (Npx) from Enterococcus faecalis. Enzyme assays further confirmed the identities of both Nox and Npx enzymes (specific activity, 1 U/mg). P3 was characterized as a large oligomeric protein (?300 kDa) that exhibited cyanide dihydratase (CynD) activity (specific activity, 100 U/mg). Two polypeptides of 38 kDa and 43 kDa were each detected in the isolated enzyme, the former believed to confer catalytic activity based on its similar size to other CynD enzymes. The amino acid sequence of an internal peptide of the 43-kDa protein was 100% identical to bacterial elongation factor Tu, suggesting a role as a possible chaperone in the assembly of CynD or a multienzyme CNO complex. The remaining P4 component consisted of a 28.9-kDa homodimer and was identified as carbonic anhydrase (specific activity, 2,000 U/mg). While the function of participating pterin and the roles of Nox, Npx, CynD, and CA in the CNO-catalyzed scavenging of CN remain to be determined, this is the first report describing the collective involvement of these four enzymes in the metabolic detoxification and utilization of CN as a bacterial nitrogenous growth substrate. PMID:16159773

Fernandez, Ruby F.; Kunz, Daniel A.

2005-01-01

399

A Novel Mouse Model of Soft-Tissue Infection Using Bioluminescence Imaging Allows Noninvasive, Real-Time Monitoring of Bacterial Growth  

PubMed Central

Musculoskeletal infections, including surgical-site and implant-associated infections, often cause progressive inflammation and destroy areas of the soft tissue. Treating infections, especially those caused by multi-antibiotic resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) remains a challenge. Although there are a few animal models that enable the quantitative evaluation of infection in soft tissues, these models are not always reproducible or sustainable. Here, we successfully established a real-time, in vivo, quantitative mouse model of soft-tissue infection in the superficial gluteus muscle (SGM) using bioluminescence imaging. A bioluminescent strain of MRSA was inoculated into the SGM of BALB/c adult male mice, followed by sequential measurement of bacterial photon intensity and serological and histological analyses of the mice. The mean photon intensity in the mice peaked immediately after inoculation and remained stable until day 28. The serum levels of interleukin-6, interleukin-1 and C-reactive protein at 12 hours after inoculation were significantly higher than those prior to inoculation, and the C-reactive protein remained significantly elevated until day 21. Histological analyses showed marked neutrophil infiltration and abscesses containing necrotic and fibrous tissues in the SGM. With this SGM mouse model, we successfully visualized and quantified stable bacterial growth over an extended period of time with bioluminescence imaging, which allowed us to monitor the process of infection without euthanizing the experimental animals. This model is applicable to in vivo evaluations of the long-term efficacy of novel antibiotics or antibacterial implants. PMID:25184249

Yoshioka, Kenji; Ishii, Ken; Kuramoto, Tetsuya; Nagai, Shigenori; Funao, Haruki; Ishihama, Hiroko; Shiono, Yuta; Sasaki, Aya; Aizawa, Mamoru; Okada, Yasunori; Koyasu, Shigeo; Toyama, Yoshiaki; Matsumoto, Morio

2014-01-01

400

A novel mouse model of soft-tissue infection using bioluminescence imaging allows noninvasive, real-time monitoring of bacterial growth.  

PubMed

Musculoskeletal infections, including surgical-site and implant-associated infections, often cause progressive inflammation and destroy areas of the soft tissue. Treating infections, especially those caused by multi-antibiotic resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) remains a challenge. Although there are a few animal models that enable the quantitative evaluation of infection in soft tissues, these models are not always reproducible or sustainable. Here, we successfully established a real-time, in vivo, quantitative mouse model of soft-tissue infection in the superficial gluteus muscle (SGM) using bioluminescence imaging. A bioluminescent strain of MRSA was inoculated into the SGM of BALB/c adult male mice, followed by sequential measurement of bacterial photon intensity and serological and histological analyses of the mice. The mean photon intensity in the mice peaked immediately after inoculation and remained stable until day 28. The serum levels of interleukin-6, interleukin-1 and C-reactive protein at 12 hours after inoculation were significantly higher than those prior to inoculation, and the C-reactive protein remained significantly elevated until day 21. Histological analyses showed marked neutrophil infiltration and abscesses containing necrotic and fibrous tissues in the SGM. With this SGM mouse model, we successfully visualized and quantified stable bacterial growth over an extended period of time with bioluminescence imaging, which allowed us to monitor the process of infection without euthanizing the experimental animals. This model is applicable to in vivo evaluations of the long-term efficacy of novel antibiotics or antibacterial implants. PMID:25184249

Yoshioka, Kenji; Ishii, Ken; Kuramoto, Tetsuya; Nagai, Shigenori; Funao, Haruki; Ishihama, Hiroko; Shiono, Yuta; Sasaki, Aya; Aizawa, Mamoru; Okada, Yasunori; Koyasu, Shigeo; Toyama, Yoshiaki; Matsumoto, Morio

2014-01-01

401

Bacterial Identification by Microcalorimetry  

Microsoft Academic Search

FORREST1 and other workers have shown that interesting data regarding bacterial metabolism can be obtained by microcalorimetry of growing cultures. In our investigations into the use of microcalorimetry as a means of differentiating one microbial species from another, we have obtained characteristic profiles for different members of the family Enterobacteriaceae by observing the heat produced during their growth in liquid

E. A. Boling; G. C. Blanchard

1973-01-01

402

Chemical Modification of Reactive Multilayered Films Fabricated from Poly(2-Alkenyl Azlactone)s: Design of Surfaces that Prevent or Promote Mammalian Cell Adhesion and Bacterial Biofilm Growth  

PubMed Central

We report an approach to the design of reactive polymer films that can be functionalized post-fabrication to either prevent or promote the attachment and growth of cells. Our approach is based on the reactive layer-by-layer assembly of covalently crosslinked thin films using a synthetic polyamine and a polymer containing reactive azlactone functionality. Our results demonstrate (i) that the residual azlactone functionality in these films can be exploited to immobilize amine-functionalized chemical motifs similar to those that promote or prevent cell and protein adhesion when assembled as self-assembled monolayers on gold-coated surfaces, and (ii) that the immobilization of these motifs changes significantly the behaviors and interactions of cells with the surfaces of these polymer films. We demonstrate that films treated with the hydrophobic molecule decylamine support the attachment and growth of mammalian cells in vitro. In contrast, films treated with the hydrophilic carbohydrate D-glucamine prevent cell adhesion and growth almost completely. The results of additional experiments suggest that these large differences in cell behavior can be understood, at least in part, in terms of differences in the abilities of these two different chemical motifs to promote or prevent the adsorption of protein onto film coated surfaces. We demonstrate further that this approach can be used to pattern regions of these reactive films that resist the initial attachment and subsequent invasion of mammalian cells for periods of at least one month in the presence of serum-containing cell culture media. Finally, we report that films that prevent the adhesion and growth of mammalian cells also prevent the initial formation of bacterial biofilms when incubated in the presence of the clinically relevant pathogen Pseudomonas aeruginosa. The results of these studies, collectively, suggest the basis of general approaches to the fabrication and functionalization of thin films that prevent, promote, or pattern cell growth or the formation of biofilms on surfaces of interest in the contexts of both fundamental biological studies and a broad range of other practical applications. PMID:19438231

Buck, Maren E.; Breitbach, Anthony S.; Belgrade, Sonja K.; Blackwell, Helen E.; Lynn, David M.

2009-01-01

403

Leading Edge Bacterial Genomics and Pathogen Evolution  

E-print Network

utilized to identify genes that are es- sential for bacterial growth or pathogenesis. There are two generalLeading Edge Review Bacterial Genomics and Pathogen Evolution David M. Raskin,1 Rekha Seshadri,2.02.002 The availability of hundreds of bacterial genome sequences has altered the study of bacte- rial pathogenesis

Mekalanos, John

404

MINIREVIEWS Bacterial Signaling Ecology and Potential Applications  

E-print Network

of bacterial growth as shown in the fossil record. Consequently, many aquatic or- ganisms have evolvedMINIREVIEWS Bacterial Signaling Ecology and Potential Applications During Aquatic Biofilm], Marshall [8], White [9], and their colleagues conducted a number of pivotal studies on bacterial adhesion

Alvarez, Pedro J.

405

Light Curves  

NSDL National Science Digital Library

This is a game about light curves that will test your ability to figure out things about an asteroid from just a graph of its brightness. Astronomers use telescopes to collect light curves - measurements of the brightness of distant asteroids over time. It is part of the Killer Asteroids Web Site. The site also features a background overview of the differences between asteroids and comets, information on different types of asteroids (rubble piles vs monoliths), a discussion of how at risk Earth really is to an asteroid or comet impact, and background information on light curves.

406

Effects of dietary antibiotic growth promoter and Saccharomyces cerevisiae fermentation product on production, intestinal bacterial community, and nonspecific immunity of hybrid tilapia (Oreochromis niloticus female x Oreochromis aureus male).  

PubMed

To investigate the effects of a dietary antibiotic growth promoter (florfenicol) and a Saccharomyces cerevisiae fermentation product (DVAQUA) on growth, G:F, daily feed intake, intestinal bacterial community, and nonspecific immunity of hybrid tilapia (Oreochromis niloticus ? × Oreochromis aureus ?), a 16-wk feeding trial was conducted in a recirculating aquaculture system. Four feeding regimens were evaluated: control, dietary florenicol (0.02 g/kg; 16 wk), dietary DVAQUA (0.5 g/kg; 16 wk), and sequential use of florenicol (0.02 g/kg; 8 wk), and DVAQUA (0.5 g/kg; 8 wk). Each regimen had 4 replicate tanks (0.5 × 0.5 × 0.5 m) and each tank contained 12 fish (initial BW: 46.88 ± 0.38 g). Dietary florfenicol improved growth (P = 0.089), G:F (P = 0.036), and serum complement component concentrations (P < 0.001) of hybrid tilapia. However, the compound decreased the estimated intestinal bacterial count estimated by rpoB quantitative PCR (P < 0.001) and bacterial diversity (visual band numbers, Shannon diversity index, and Shannon equitability index based on 16S rDNA V3 denaturing gradient gel electrophoresis fingerprints) compared with the control. Although sequential use of florfenicol and DVAQUA improved growth and G:F numerically to a similar extent as dietary florfenicol, and increased intestinal bacterial count to normal quantities, the sequential use of florenicol and DVAQUA decreased intestinal bacterial diversity (visual band numbers, Shannon diversity index, and Shannon equitability index) as well as serum complement component concentrations (P < 0.001) compared with their respective use and the control. These findings might be negatively related to disease control and host defense, and the sequential use of florenicol and DVAQUA should be practiced with caution. Feeding DAVQUA to the fish improved nonspecific immunity and increased intestinal bacterial count and bacterial diversity, but further research, including challenge studies, should be conducted before recommendation of DVAQUA supplementation to hybrid tilapia diets. PMID:20852079

He, S; Zhou, Z; Meng, K; Zhao, H; Yao, B; Ringø, E; Yoon, I

2011-01-01

407

Bacterial proteases: targets for diagnostics and therapy.  

PubMed

Proteases are essential for the proliferation and growth of bacteria, and are also known to contribute to bacterial virulence. This makes them interesting candidates as diagnostic and therapeutic targets for infectious diseases. In this review, the authors discuss the most recent developments and potential applications for bacterial proteases in the diagnosis and treatment of bacterial infections. Current and future bacterial protease targets are described and their limitations outlined. PMID:24535571

Kaman, W E; Hays, J P; Endtz, H P; Bikker, F J

2014-07-01

408

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

409

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 24 h. 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

410

Curves of growth of spectral lines emitted by a laser-induced plasma: influence of the temporal evolution and spatial inhomogeneity of the plasma  

NASA Astrophysics Data System (ADS)

The curves of growth (COG) of five Fe I lines emitted from a laser-induced plasma, generated with Fe-Ni alloys in air at atmospheric pressure, have been investigated. Spectral lines with different energy levels and line widths, emitted with a broad range of optical depths, have been included in the study in order to check the validity of theoretical models proposed for COG generation, based in the radiative transfer within a plasma in local thermodynamic equilibrium. The COGs have been measured at time windows of 4-5 ?s and 15-18 ?s. The Stark widths of the Fe I lines have been obtained, and the line widths have been determined by measuring the plasma electron density at the time windows selected. It is shown that at a time window of 4-5 ?s, the inhomogeneity of the plasma magnitudes has an important influence on the COGs of intense lines. For this time window, a two-region model of the plasma has been used to generate theoretical COGs that describe satisfactorily the experimental curves of all the lines using a single set of plasma parameters. The results reveal the existence of considerable gradients between the inner and the outer plasma regions in the temperature (9400-7800 K) and in the density of Fe atoms (4×10 16-0.02×10 16 cm -3 for a sample with 100% Fe). On the contrary, at the time window 15-18 ?s, at which the plasma has suffered most of its expansion and cooling process, the COGs of all the lines may be described by a single-region model, corresponding to a plasma with uniform temperature (6700 K) and density of Fe atoms (0.06×10 16 cm -3 for a sample with 100% Fe). It is also shown that at initial times, the plasma inhomogeneity has an important effect in the line profiles of intense spectral lines, which are described by using the two-region model of the laser-induced plasma.

Aguilera, J. A.; Bengoechea, J.; Aragón, C.

2003-02-01

411

Staphylococcus epidermidis SrrAB Regulates Bacterial Growth and Biofilm Formation Differently under Oxic and Microaerobic Conditions  

PubMed Central

SrrAB expression in Staphylococcus epidermidis strain 1457 (SE1457) was upregulated during a shift from oxic to microaerobic conditions. An srrA deletion (?srrA) mutant was constructed for studying the regulatory function of SrrAB. The deletion resulted in retarded growth and abolished biofilm formation both in vitro and in vivo and under both oxic and microaerobic conditions. Associated with the reduced biofilm formation, the ?srrA mutant produced much less polysaccharide intercellular adhesion (PIA) and showed decreased initial adherence capacity. Microarray analysis showed that the srrA mutation affected transcription of 230 genes under microaerobic conditions, and 51 genes under oxic conditions. Quantitative real-time PCR confirmed this observation and showed downregulation of genes involved in maintaining the electron transport chain by supporting cytochrome and quinol-oxidase assembly (e.g., qoxB and ctaA) and in anaerobic metabolism (e.g., pflBA and nrdD). In the ?srrA mutant, the expression of the biofilm formation-related gene icaR was upregulated under oxic conditions and downregulated under microaerobic conditions, whereas icaA was downregulated under both conditions. An electrophoretic mobility shift assay further revealed that phosphorylated SrrA bound to the promoter regions of icaR, icaA, qoxB, and pflBA, as well as its own promoter region. These findings demonstrate that in S. epidermidis SrrAB is an autoregulator and regulates biofilm formation in an ica-dependent manner. Under oxic conditions, SrrAB modulates electron transport chain activity by positively regulating qoxBACD transcription. Under microaerobic conditions, it regulates fermentation processes and DNA synthesis by modulating the expression of both the pfl operon and nrdDG. PMID:25404696

Wu, Youcong; Wu, Yang; Zhu, Tao; Han, Haiyan; Liu, Huayong; Xu, Tao; Francois, Patrice; Fischer, Adrien; Bai, Li; Götz, Friedrich

2014-01-01

412

Staphylococcus epidermidis SrrAB Regulates Bacterial Growth and Biofilm Formation Differently under Oxic and Microaerobic Conditions.  

PubMed

SrrAB expression in Staphylococcus epidermidis strain 1457 (SE1457) was upregulated during a shift from oxic to microaerobic conditions. An srrA deletion (?srrA) mutant was constructed for studying the regulatory function of SrrAB. The deletion resulted in retarded growth and abolished biofilm formation both in vitro and in vivo and under both oxic and microaerobic conditions. Associated with the reduced biofilm formation, the ?srrA mutant produced much less polysaccharide intercellular adhesion (PIA) and showed decreased initial adherence capacity. Microarray analysis showed that the srrA mutation affected transcription of 230 genes under microaerobic conditions, and 51 genes under oxic conditions. Quantitative real-time PCR confirmed this observation and showed downregulation of genes involved in maintaining the electron transport chain by supporting cytochrome and quinol-oxidase assembly (e.g., qoxB and ctaA) and in anaerobic metabolism (e.g., pflBA and nrdD). In the ?srrA mutant, the expression of the biofilm formation-related gene icaR was upregulated under oxic conditions and downregulated under microaerobic conditions, whereas icaA was downregulated under both conditions. An electrophoretic mobility shift assay further revealed that phosphorylated SrrA bound to the promoter regions of icaR, icaA, qoxB, and pflBA, as well as its own promoter region. These findings demonstrate that in S. epidermidis SrrAB is an autoregulator and regulates biofilm formation in an ica-dependent manner. Under oxic conditions, SrrAB modulates electron transport chain activity by positively regulating qoxBACD transcription. Under microaerobic conditions, it regulates fermentation processes and DNA synthesis by modulating the expression of both the pfl operon and nrdDG. PMID:25404696

Wu, Youcong; Wu, Yang; Zhu, Tao; Han, Haiyan; Liu, Huayong; Xu, Tao; Francois, Patrice; Fischer, Adrien; Bai, Li; Götz, Friedrich; Qu, Di

2015-02-01

413

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

414

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

415

Systemic Acquired Tolerance to Virulent Bacterial Pathogens in Tomato1  

E-print Network

, ethylene and salicylic acid (SA) mediate symptom development but do not influence bacterial growth but not bacterial growth during subsequent challenge with virulent Xcv. This systemic acquired tolerance (SATSystemic Acquired Tolerance to Virulent Bacterial Pathogens in Tomato1 Anna Block, Eric Schmelz

Klee, Harry J.

416

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

417

Bacterial conjunctivitis  

PubMed Central

Introduction Most cases of conjunctivitis in adults are probably due to viral infection, but children are more likely to develop bacterial conjunctivitis than they are viral forms. The main bacterial pathogens are Haemophilus influenzae and Streptococcus pneumoniae in adults and children, and Moraxella catarrhalis in children. Contact lens wearers may be more likely to develop gram-negative infections. Bacterial keratitis occurs in up to 30 per 100,000 contact lens wearers. Methods and outcomes We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of empirical treatment in adults and children with suspected bacterial conjunctivitis? What are the effects of treatment in adults and children with bacteriologically confirmed bacterial conjunctivitis? What are the effects of treatment in adults and children with clinically confirmed gonococcal conjunctivitis? We searched: Medline, Embase, The Cochrane Library, and other important databases up to July 2009 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 40 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review we present information relating to the effectiveness and safety of the following interventions: ocular decongestants; oral antibiotics; parenteral antibiotics; saline; topical antibiotics; and warm compresses. PMID:21718563

2010-01-01

418

Bacterial conjunctivitis  

PubMed Central

Introduction Most cases of conjunctivitis in adults are probably due to viral infection, but children are more likely to develop bacterial conjunctivitis than they are viral forms. The main bacterial pathogens are Haemophilus influenzae and Streptococcus pneumoniae in adults and children, and Moraxella catarrhalis in children. Contact lens wearers may be more likely to develop gram-negative infections. Bacterial keratitis occurs in up to 30 per 100,000 contact lens wearers. Methods and outcomes We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of empirical treatment in adults and children with suspected bacterial conjunctivitis? What are the effects of treatment in adults and children with bacteriologically confirmed bacterial conjunctivitis? What are the effects of treatment in adults and children with clinically confirmed gonococcal conjunctivitis? We searched: Medline, Embase, The Cochrane Library, and other important databases up to July 2011 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 44 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review we present information relating to the effectiveness and safety of the following interventions: ocular decongestants, oral antibiotics, parenteral antibiotics, saline, topical antibiotics, and warm compresses. PMID:22348418

2012-01-01

419

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 53 °C) not only stops the multiplication process of Escherichia coli bacteria, but also causes bacterial titer to decrease gradually. After this period lasting up to 1 hour, 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

420

Curved Space or Curved Vacuum?  

E-print Network

While the simple picture of a spatially flat, matter plus cosmological constant universe fits current observation of the accelerated expansion, strong consideration has also been given to models with dynamical vacuum energy. We examine the tradeoff of ``curving'' the vacuum but retaining spatial flatness, vs. curving space but retaining the cosmological constant. These different breakdowns in the simple picture could readily be distinguished by combined high accuracy supernovae and cosmic microwave background distance measurements. If we allow the uneasy situation of both breakdowns, the curvature can still be measured to 1%, but at the price of degrading estimation of the equation of state time variation by 60% or more, unless additional information (such as weak lensing data or a tight matter density prior) is included.

Eric V. Linder

2005-08-15

421

Bacterial pathogenomics  

Microsoft Academic Search

Genomes from all of the crucial bacterial pathogens of humans, plants and animals have now been sequenced, as have genomes from many of the important commensal, symbiotic and environmental microorganisms. Analysis of these sequences has revealed the forces that shape pathogen evolution and has brought to light unexpected aspects of pathogen biology. The finding that horizontal gene transfer and genome

Mark J. Pallen; Brendan W. Wren

2007-01-01

422

Bacterial concrete  

Microsoft Academic Search

Cracks in concrete are inevitable and are one of the inherent weaknesses of concrete. Water and other salts seep through these cracks, corrosion initiates, and thus reduces the life of concrete. So there was a need to develop an inherent biomaterial, a self-repairing material which can remediate the cracks and fissures in concrete. Bacterial concrete is a material, which can

Venkataswamy Ramakrishnan; K. P. Ramesh; S. S. Bang

2001-01-01

423

Rapid Antimicrobial Susceptibility Testing with Electrokinetics Enhanced Biosensors for Diagnosis of Acute Bacterial Infections  

E-print Network

of bacterial 16S rRNA. The assay determines the susceptibility of pathogens by detecting bacterial growth under,26 Conventional cul- ture-based analysis, however, requires at least 2­3 days for bacterial growth and could of Acute Bacterial Infections TINGTING LIU,1 YI LU,1 VINCENT GAU,2 JOSEPH C. LIAO,3,4 and PAK KIN WONG 1 1

Wong, Pak Kin

424

Lethal protein produced in response to competition between sibling bacterial colonies  

E-print Network

-regulation of colony growth might not be limited to P. dendritiformis. bacterial competition bacterial growthLethal protein produced in response to competition between sibling bacterial colonies Avraham Be 24, 2009) Sibling Paenibacillus dendritiformis bacterial colonies grown on low-nutrient agar medium

Ariel, Gil

425

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.

426

Electrical spiking in bacterial biofilms.  

PubMed

In nature, biofilms are the most common form of bacterial growth. In biofilms, bacteria display coordinated behaviour to perform specific functions. Here, we investigated electrical signalling as a possible driver in biofilm sociobiology. Using a multi-electrode array system that enables high spatio-temporal resolution, we studied the electrical activity in two biofilm-forming strains and one non-biofilm-forming strain. The action potential rates monitored during biofilm-forming bacterial growth exhibited a one-peak maximum with a long tail, corresponding to the highest biofilm development. This peak was not observed for the non-biofilm-forming strain, demonstrating that the intensity of the electrical activity was not linearly related to the bacterial density, but was instead correlated with biofilm formation. Results obtained indicate that the analysis of the spatio-temporal electrical activity of bacteria during biofilm formation can open a new frontier in the study of the emergence of collective microbial behaviour. PMID:25392401

Masi, Elisa; Ciszak, Marzena; Santopolo, Luisa; Frascella, Arcangela; Giovannetti, Luciana; Marchi, Emmanuela; Viti, Carlo; Mancuso, Stefano

2015-01-01

427

BACTERIAL INDICATORS OF RECREATIONAL WATER QUALITY  

EPA Science Inventory

The selection of bacterial indicators of recreational water quality are considered with respect to suggested ideal characteristics, such as association with pathogens, growth in aquatic environments, resistance to disinfection and ease of enumeration, and through the use of epide...

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