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Sample records for bacterial growth curve

  1. The Bacterial Growth Curve.

    ERIC Educational Resources Information Center

    Paulton, Richard J. L.

    1991-01-01

    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)

  2. Bacterial streamers in curved microchannels

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  3. Phenotypic Signatures Arising from Unbalanced Bacterial Growth

    PubMed Central

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

    2014-01-01

    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

  4. Solubilization and bio-conjugation of quantum dots and bacterial toxicity assays by growth curve and plate count.

    PubMed

    Park, Soonhyang; Chibli, Hicham; Nadeau, Jay

    2012-01-01

    Quantum dots (QDs) are fluorescent semiconductor nanoparticles with size-dependent emission spectra that can be excited by a broad choice of wavelengths. QDs have attracted a lot of interest for imaging, diagnostics, and therapy due to their bright, stable fluorescence. QDs can be conjugated to a variety of bio-active molecules for binding to bacteria and mammalian cells. QDs are also being widely investigated as cytotoxic agents for targeted killing of bacteria. The emergence of multiply-resistant bacterial strains is rapidly becoming a public health crisis, particularly in the case of Gram negative pathogens. Because of the well-known antimicrobial effect of certain nanomaterials, especially Ag, there are hundreds of studies examining the toxicity of nanoparticles to bacteria. Bacterial studies have been performed with other types of semiconductor nanoparticles as well, especially TiO(2), but also ZnO and others including CuO. Some comparisons of bacterial strains have been performed in these studies, usually comparing a Gram negative strain with a Gram positive. With all of these particles, mechanisms of toxicity are attributed to oxidation: either the photogeneration of reactive oxygen species (ROS) by the particles or the direct release of metal ions that can cause oxidative toxicity. Even with these materials, results of different studies vary greatly. In some studies the Gram positive test strain is reportedly more sensitive than the Gram negative; in others it is the opposite. These studies have been well reviewed. In all nanoparticle studies, particle composition, size, surface chemistry, sample aging/breakdown, and wavelength, power, and duration of light exposure can all dramatically affect the results. In addition, synthesis byproducts and solvents must be considered. High-throughput screening techniques are needed to be able to develop effective new nanomedicine agents. CdTe QDs have anti-microbial effects alone or in combination with antibiotics. In a

  5. Growth curves for Laron syndrome.

    PubMed Central

    Laron, Z; Lilos, P; Klinger, B

    1993-01-01

    Growth curves for children with Laron syndrome were constructed on the basis of repeated measurements made throughout infancy, childhood, and puberty in 24 (10 boys, 14 girls) of the 41 patients with this syndrome investigated in our clinic. Growth retardation was already noted at birth, the birth length ranging from 42 to 46 cm in the 12/20 available measurements. The postnatal growth curves deviated sharply from the normal from infancy on. Both sexes showed no clear pubertal spurt. Girls completed their growth between the age of 16-19 years to a final mean (SD) height of 119 (8.5) cm whereas the boys continued growing beyond the age of 20 years, achieving a final height of 124 (8.5) cm. At all ages the upper to lower body segment ratio was more than 2 SD above the normal mean. These growth curves constitute a model not only for primary, hereditary insulin-like growth factor-I (IGF-I) deficiency (Laron syndrome) but also for untreated secondary IGF-I deficiencies such as growth hormone gene deletion and idiopathic congenital isolated growth hormone deficiency. They should also be useful in the follow up of children with Laron syndrome treated with biosynthetic recombinant IGF-I. PMID:8333769

  6. Force-extension curves of bacterial flagella.

    PubMed

    Vogel, R; Stark, H

    2010-11-01

    Bacterial flagella assume different helical shapes during the tumbling phase of a bacterium but also in response to varying environmental conditions. Force-extension measurements by Darnton and Berg explicitly demonstrate a transformation from the coiled to the normal helical state (N.C. Darnton, H.C. Berg, Biophys. J. 92, 2230 (2007)). We here develop an elastic model for the flagellum based on Kirchhoff's theory of an elastic rod that describes such a polymorphic transformation and use resistive force theory to couple the flagellum to the aqueous environment. We present Brownian-dynamics simulations that quantitatively reproduce the force-extension curves and study how the ratio Γ of torsional to bending rigidity and the extensional rate influence the response of the flagellum. An upper bound for Γ is given. Using clamped flagella, we show in an adiabatic approximation that the mean extension, where a local coiled-to-normal transition occurs first, depends on the logarithm of the extensional rate. PMID:21046183

  7. Nonlinear Growth Curves in Developmental Research

    ERIC Educational Resources Information Center

    Grimm, Kevin J.; Ram, Nilam; Hamagami, Fumiaki

    2011-01-01

    Developmentalists are often interested in understanding change processes, and growth models are the most common analytic tool for examining such processes. Nonlinear growth curves are especially valuable to developmentalists because the defining characteristics of the growth process such as initial levels, rates of change during growth spurts, and…

  8. Electromagnetism of Bacterial Growth

    NASA Astrophysics Data System (ADS)

    Ainiwaer, Ailiyasi

    2011-10-01

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

  9. Residual Structures in Latent Growth Curve Modeling

    ERIC Educational Resources Information Center

    Grimm, Kevin J.; Widaman, Keith F.

    2010-01-01

    Several alternatives are available for specifying the residual structure in latent growth curve modeling. Two specifications involve uncorrelated residuals and represent the most commonly used residual structures. The first, building on repeated measures analysis of variance and common specifications in multilevel models, forces residual variances…

  10. Growth curve analyses in selected duck lines.

    PubMed

    Maruyama, K; Vinyard, B; Akbar, M K; Shafer, D J; Turk, C M

    2001-12-01

    1. Growth patterns of male ducks from 4 lines (lines A, B, C and D) selected for market weight were analysed and compared to growth patterns of ducks in the respective line 7 generations earlier. Growth curves were analysed using procedures derived from the Weibull sigmoidal function and the linear-linear relative growth rate model and simple allometry. 2. The ducks were fed ad libitum under 24-h lighting throughout the experiment. At weekly intervals from the time of hatch through 70 d of age, 16 ducks from each line were killed to determine body, carcase, breast-muscle, leg and thigh-muscle, and abdominal fat weights. 3. Line A was the heaviest line, followed by line B, line C and line D. However, body weight, carcase weight and breast-muscle weight at 49 d of age were not significantly different between lines A and B. After 7 generations of selection, the breast-muscle yield was increased to >19% and the abdominal fat percent was reduced to <1.4% in all lines. 4. The Weibull growth curve analysis of body weight showed an increase in the asymptotes during selection, while the age of the inflection point remained constant in all lines (21.3 to 26.0 d). For breast-muscle growth, ducks reached the inflection point 12.8 to 14.3 d later than for body weight. Between line A and line B, asymptotes for body weight, asymptotes for breast-muscle weight and allometric growth coefficients of breast muscle and leg and thigh muscles from 14 to 49 d were not significantly different. 5. The relative growth rate model discriminated body and breast-muscle growth patterns of line A and line B. The initial decline in the relative body growth rate was less and the time to reach the transition was longer in line A than line B. On the other hand, the initial decline in the relative breast-muscle growth rate was greater in line A than line B. PMID:11811908

  11. Curved tails in polymerization-based bacterial motility

    NASA Astrophysics Data System (ADS)

    Rutenberg, Andrew D.; Grant, Martin

    2001-08-01

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

  12. Bacterial volatiles promote growth in Arabidopsis

    PubMed Central

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

    2003-01-01

    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

  13. Technological growth curves. A competition of forecasting models

    SciTech Connect

    Young, P.

    1993-12-01

    In order to determine procedures for appropriate model selection of technological growth curves, numerous time series that were representative of growth behavior were collected and categorized according to data characteristics. Nine different growth curve models were each fitted onto the various data sets in an attempt to determine which growth curve models achieved the best forecasts for differing types of growth data. The analysis of the results gives rise to a new approach for selecting appropriate growth curve models for a given set of data, prior to fitting the models, based on the characteristics of the data sets. 58 refs., 9 tabs.

  14. Enteral nutrient solutions. Limiting bacterial growth.

    PubMed

    Paauw, J D; Fagerman, K E; McCamish, M A; Dean, R E

    1984-06-01

    Bacterial contamination of enteral nutrient solutions ( ENS ) in FFcess of food product standards is known to occur in the hospital setting. The large amounts of bacteria often given with ENS have been shown to create a reservoir for nosocomial infections, and nonpathogenic bacteria have been implicated. Patient tolerance is dependent on immune status and the bacterial load delivered to the gut. The purpose of this study was to evaluate the bacterial growth-sustaining properties of various ENS and to devise methods to limit bacterial growth. Five commercial products were prepared under sterile conditions. After inoculation with approximately 5 X 10(3) organisms/cm3 of Enterobacter cloacae, each solution was hung at room temperature for 24 hours with samples drawn at fixed intervals and plated for bacterial counts. Bacterial growth rates in Ensure, Travasorb , and Vital were markedly higher than those in Precision and Vivonex. Vivonex was noted to contain potassium sorbate (KS) used as a fungistatic agent. Recent studies have identified KS as a broad-spectrum bacteriostatic food preservative that is federally approved for this use. KS (0.03%) was added to Travasorb inoculated with 5 X 10(3) organisms/cm(3) of E. cloacae. The bacterial growth rate was reduced by 75 per cent, and the final count of 2-3 X 10(4) organisms/ml was within the federally regulated limit for milk. This study suggests that initial inoculum, growth rate, and hang time can be altered to provide a significant reduction in final bacterial counts in ENS . PMID:6428286

  15. Bounded Population Growth: A Curve Fitting Lesson.

    ERIC Educational Resources Information Center

    Mathews, John H.

    1992-01-01

    Presents two mathematical methods for fitting the logistic curve to population data supplied by the U.S. Census Bureau utilizing computer algebra software to carry out the computations and plot graphs. (JKK)

  16. Hypothesis Generation in Latent Growth Curve Modeling Using Principal Components

    ERIC Educational Resources Information Center

    Davison, Mark L.

    2008-01-01

    While confirmatory latent growth curve analyses provide procedures for testing hypotheses about latent growth curves underlying data, one must first derive hypotheses to be tested. It is argued that such hypotheses should be generated from a combination of theory and exploratory data analyses. An exploratory components analysis is described and…

  17. Regime Switching in the Latent Growth Curve Mixture Model

    ERIC Educational Resources Information Center

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

    2005-01-01

    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…

  18. Evaluating Latent Growth Curve Models Using Individual Fit Statistics

    ERIC Educational Resources Information Center

    Coffman, Donna L.; Millsap, Roger E.

    2006-01-01

    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…

  19. Bacterial cell curvature through mechanical control of cell growth

    PubMed Central

    Cabeen, Matthew T; Charbon, Godefroid; Vollmer, Waldemar; Born, Petra; Ausmees, Nora; Weibel, Douglas B; Jacobs-Wagner, Christine

    2009-01-01

    The cytoskeleton is a key regulator of cell morphogenesis. Crescentin, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus and localizes to the inner cell curvature. Here, we show that crescentin forms a single filamentous structure that collapses into a helix when detached from the cell membrane, suggesting that it is normally maintained in a stretched configuration. Crescentin causes an elongation rate gradient around the circumference of the sidewall, creating a longitudinal cell length differential and hence curvature. Such curvature can be produced by physical force alone when cells are grown in circular microchambers. Production of crescentin in Escherichia coli is sufficient to generate cell curvature. Our data argue for a model in which physical strain borne by the crescentin structure anisotropically alters the kinetics of cell wall insertion to produce curved growth. Our study suggests that bacteria may use the cytoskeleton for mechanical control of growth to alter morphology. PMID:19279668

  20. 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...

  1. [The measurement of growth curve and generation time of lactobacillus

    PubMed

    Gu, S P; Liu, Z; Song, P Z

    1998-12-01

    OBJECTIVE:The purpose of this test was to understand the growth pattern of lactobacillus for the research of its cariogenicity. METHODS: The growth quantity of lactobacillus which was culture in a constant condition was measured periodically by spectrophotometry and flora counting,and its growth curve and generation time were measured. RESULTS: It was found that the logarithmic phase of lactobacillus was 6-16 hours after it was cultured.And its generatin time was 54 minutes. CONCLUSIN: The growth curve of lactobacillus was in accordance with streptococcus mutan. PMID:15071634

  2. BGFit: management and automated fitting of biological growth curves

    PubMed Central

    2013-01-01

    Background Existing tools to model cell growth curves do not offer a flexible integrative approach to manage large datasets and automatically estimate parameters. Due to the increase of experimental time-series from microbiology and oncology, the need for a software that allows researchers to easily organize experimental data and simultaneously extract relevant parameters in an efficient way is crucial. Results BGFit provides a web-based unified platform, where a rich set of dynamic models can be fitted to experimental time-series data, further allowing to efficiently manage the results in a structured and hierarchical way. The data managing system allows to organize projects, experiments and measurements data and also to define teams with different editing and viewing permission. Several dynamic and algebraic models are already implemented, such as polynomial regression, Gompertz, Baranyi, Logistic and Live Cell Fraction models and the user can add easily new models thus expanding current ones. Conclusions BGFit allows users to easily manage their data and models in an integrated way, even if they are not familiar with databases or existing computational tools for parameter estimation. BGFit is designed with a flexible architecture that focus on extensibility and leverages free software with existing tools and methods, allowing to compare and evaluate different data modeling techniques. The application is described in the context of bacterial and tumor cells growth data fitting, but it is also applicable to any type of two-dimensional data, e.g. physical chemistry and macroeconomic time series, being fully scalable to high number of projects, data and model complexity. PMID:24067087

  3. Modeling error distributions of growth curve models through Bayesian methods.

    PubMed

    Zhang, Zhiyong

    2016-06-01

    Growth curve models are widely used in social and behavioral sciences. However, typical growth curve models often assume that the errors are normally distributed although non-normal data may be even more common than normal data. In order to avoid possible statistical inference problems in blindly assuming normality, a general Bayesian framework is proposed to flexibly model normal and non-normal data through the explicit specification of the error distributions. A simulation study shows when the distribution of the error is correctly specified, one can avoid the loss in the efficiency of standard error estimates. A real example on the analysis of mathematical ability growth data from the Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 is used to show the application of the proposed methods. Instructions and code on how to conduct growth curve analysis with both normal and non-normal error distributions using the the MCMC procedure of SAS are provided. PMID:26019004

  4. Visualization of Growth Curve Data from Phenotype MicroarrayExperiments

    SciTech Connect

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

    2007-04-19

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

  5. Interactions of cosmic rays in the atmosphere: growth curves revisited

    SciTech Connect

    Obermeier, A.; Boyle, P.; Müller, D.; Hörandel, J.

    2013-12-01

    Measurements of cosmic-ray abundances on balloons are affected by interactions in the residual atmosphere above the balloon. Corrections for such interactions are particularly important for observations of rare secondary particles such as boron, antiprotons, and positrons. These corrections either can be calculated if the relevant cross sections in the atmosphere are known or may be empirically determined by extrapolation of the 'growth curves', i.e., the individual particle intensities as functions of atmospheric depth. The growth-curve technique is particularly attractive for long-duration balloon flights where the periodic daily altitude variations permit rather precise determinations of the corresponding particle intensity variations. We determine growth curves for nuclei from boron (Z = 5) to iron (Z = 26) using data from the 2006 Arctic balloon flight of the TRACER detector for cosmic-ray nuclei, and we compare the growth curves with predictions from published cross section values. In general, good agreement is observed. We then study the boron/carbon abundance ratio and derive a simple and energy-independent correction term for this ratio. We emphasize that the growth-curve technique can be developed further to provide highly accurate tests of published interaction cross section values.

  6. R-Curve Instability Calculations Of Crack Growth

    NASA Technical Reports Server (NTRS)

    Orange, Thomas W.

    1989-01-01

    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.

  7. Synergy of fresh and accumulated organic matter to bacterial growth.

    PubMed

    Farjalla, Vinicius F; Marinho, Claudio C; Faria, Bias M; Amado, André M; Esteves, Francisco de A; Bozelli, Reinaldo L; Giroldo, Danilo

    2009-05-01

    The main goal of this research was to evaluate whether the mixture of fresh labile dissolved organic matter (DOM) and accumulated refractory DOM influences bacterial production, respiration, and growth efficiency (BGE) in aquatic ecosystems. Bacterial batch cultures were set up using DOM leached from aquatic macrophytes as the fresh DOM pool and DOM accumulated from a tropical humic lagoon. Two sets of experiments were performed and bacterial growth was followed in cultures composed of each carbon substrate (first experiment) and by carbon substrates combined (second experiment), with and without the addition of nitrogen and phosphorus. In both experiments, bacterial production, respiration, and BGE were always higher in cultures with N and P additions, indicating a consistent inorganic nutrient limitation. Bacterial production, respiration, and BGE were higher in cultures set up with leachate DOM than in cultures set up with humic DOM, indicating that the quality of the organic matter pool influenced the bacterial growth. Bacterial production and respiration were higher in the mixture of substrates (second experiment) than expected by bacterial production and respiration in single substrate cultures (first experiment). We suggest that the differences in the concentration of some compounds between DOM sources, the co-metabolism on carbon compound decomposition, and the higher diversity of molecules possibly support a greater bacterial diversity which might explain the higher bacterial growth observed. Finally, our results indicate that the mixture of fresh labile and accumulated refractory DOM that naturally occurs in aquatic ecosystems could accelerate the bacterial growth and bacterial DOM removal. PMID:18985269

  8. Coupled effects of chemotaxis and growth on traveling bacterial waves

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

  9. Coupled effects of chemotaxis and growth on traveling bacterial waves

    NASA Astrophysics Data System (ADS)

    Yan, Z.; Hilpert, M.; Bouwer, E. J.

    2014-12-01

    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.

  10. Twelve Frequently Asked Questions about Growth Curve Modeling

    ERIC Educational Resources Information Center

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

    2010-01-01

    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…

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

    ERIC Educational Resources Information Center

    Buchanan, Trey

    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.…

  12. The Multigroup Multilevel Categorical Latent Growth Curve Models

    ERIC Educational Resources Information Center

    Hung, Lai-Fa

    2010-01-01

    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…

  13. Mediation Analysis in a Latent Growth Curve Modeling Framework

    ERIC Educational Resources Information Center

    von Soest, Tilmann; Hagtvet, Knut A.

    2011-01-01

    This article presents several longitudinal mediation models in the framework of latent growth curve modeling and provides a detailed account of how such models can be constructed. Logical and statistical challenges that might arise when such analyses are conducted are also discussed. Specifically, we discuss how the initial status (intercept) and…

  14. Developmental Trajectories of Adolescent Popularity: A Growth Curve Modelling Analysis

    ERIC Educational Resources Information Center

    Cillessen, Antonius H. N.; Borch, Casey

    2006-01-01

    Growth curve modelling was used to examine developmental trajectories of sociometric and perceived popularity across eight years in adolescence, and the effects of gender, overt aggression, and relational aggression on these trajectories. Participants were 303 initially popular students (167 girls, 136 boys) for whom sociometric data were…

  15. Sensitivity of Fit Indices to Misspecification in Growth Curve Models

    ERIC Educational Resources Information Center

    Wu, Wei; West, Stephen G.

    2010-01-01

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

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

    ERIC Educational Resources Information Center

    Tong, Xin; Zhang, Zhiyong

    2012-01-01

    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…

  17. Latent Growth Curves within Developmental Structural Equation Models.

    ERIC Educational Resources Information Center

    McArdle, J. J.; Epstein, David

    1987-01-01

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

  18. Analysis of growth curves of fowl. III. Geese.

    PubMed

    Knízetová, H; Hyánek, J; Veselský, A

    1994-07-01

    1. Growth curves of two lines (S,D) and their reciprocal hybrids (in total,. n = 344) were evaluated by the Richards function. Geese were weighed at 7 d intervals to the ninth week, and then at 92, 154, 192 and 217 d of age. Food and water were supplied ad libitum. 2. The accuracy of curve fit measured by the coefficient of determination (R2) for different genetic groups ranged from 0.9840 to 0.9918. The highest percentage deviations between observed and estimated live weights were recorded at hatching (on average 15.1%), while at the others points of curve they were significantly lower (from 0.6 to 6.8%). 3. The geese are characterised by an early maturing rate. The peak of the absolute growth rate (the inflection point of the curve) occurred at 18.7 to 23.5 d of age (t+). The degree of maturity at a slaughter age of 63 d (u63 = y63/A) ranged from 0.69 to 0.76. Fitting the inflection point at the beginning of the linear growth phase significantly affects the maturing rate (k) and the ratio between the inflection (y+) and the asymptotic (A) weights. The values of these correlated parameters were very low (y+/A = 0.233 to 0.294, k = 0.0281 to 0.0373 ln theta/d). 4. The live weights of geese from 28 d of age and the parameters of the Richards function were significantly higher (P < 0.05, P < 0.01) in th sire line (S) than in the dam line (D). A low negative heterosis was observed at all points of the growth curves (-0.01 to -9.7%). The results indicated the effect of sex-linked growth genes. 5. The phenotypic correlations between parameters of the Richards function within genetic groups are discussed. PMID:7953778

  19. Curves of growth for van der Waals broadened spectral lines

    NASA Technical Reports Server (NTRS)

    Park, C.

    1980-01-01

    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.

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

    ERIC Educational Resources Information Center

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

    2013-01-01

    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…

  1. A brief history of bacterial growth physiology

    PubMed Central

    Schaechter, Moselio

    2015-01-01

    Arguably, microbial physiology started when Leeuwenhoek became fascinated by observing a Vorticella beating its cilia, my point being that almost any observation of microbes has a physiological component. With the advent of modern microbiology in the mid-19th century, the field became recognizably distinctive with such discoveries as anaerobiosis, fermentation as a biological phenomenon, and the nutritional requirements of microbes. Soon came the discoveries of Winogradsky and his followers of the chemical changes in the environment that result from microbial activities. Later, during the first half of the 20th century, microbial physiology became the basis for much of the elucidation of central metabolism. Bacterial physiology then became a handmaiden of molecular biology and was greatly influenced by the discovery of cellular regulatory mechanisms. Microbial growth, which had come of age with the early work of Hershey, Monod, and others, was later pursued by studies on a whole cell level by what became known as the “Copenhagen School.” During this time, the exploration of physiological activities became coupled to modern inquiries into the structure of the bacterial cell. Recent years have seen the development of a further phase in microbial physiology, one seeking a deeper quantitative understanding of phenomena on a whole cell level. This pursuit is exemplified by the emergence of systems biology, which is made possible by the development of technologies that permit the gathering of information in huge amounts. As has been true through history, the research into microbial physiology continues to be guided by the development of new methods of analysis. Some of these developments may well afford the possibility of making stunning breakthroughs. PMID:25954250

  2. Analysis of growth curves of fowl. II. Ducks.

    PubMed

    Knízetová, H; Hyánek, J; Kníze, B; Procházková, H

    1991-12-01

    1. Growth curves of nine selected lines and one random-bred control population (in total, n = 1070) were evaluated by the Richards function. The ducks were weighed at 7-d intervals and, after the tenth week, every second week (up to 18 weeks). Food and water were supplied ad libitum. 2. The predicted curves closely fitted the weight data points (R2 = 0.9991-0.9997). 3. The ducks are characterized by early maturity rate. The peak of the absolute growth rate (the inflection point of the curve) occurred at 24.1-27.6 d of age (t+). A higher ratio of the inflection to the asymptotic weights (y+/A = 0.380-0.424) was found in comparison to those from the Gompertz-type function of growth (y+/A = 0.368). 4. In the selected lines the degree of maturity at a slaughter age of 7 weeks (u7 = y7/A) ranged from 0.784 to 0.835 for males and from 0.819 to 0.889 for females. 5. Ducks within the non-selected control line had a significantly lower maturing rate than the selected lines. 6. Sexual dimorphism was recorded for all growth parameters analysed. Females have faster maturation rate than males (higher values of y+/A, u7, k and a shorter auto-acceleration phase of growth). 7. High interline differences were found for body weight (A, y+, y7) and for absolute growth rate (v, v+) and smaller ones for parameters of the maturation rate (y+/A, u7, k and t+). 8. The intragroup phenotype correlation between growth parameters and the use of weight data only up to 7 weeks of age for the estimation of parameters of the Richards function are discussed. PMID:1786569

  3. Logistic growth curve of chickens: heritability of parameters.

    PubMed

    Grossman, M; Bohren, B B

    1985-01-01

    Parameters of the logistic function of growth, fit to individual body weight curves of two randombred control populations of each sex of chickens from hatching to 45 weeks of age, were evaluated. Growth-rate constant and age at the infection point in the curve were estimated by the method of sample quantiles from individual weekly body weights of 225 males and 281 females of the Rhode Island Red (RIR) line, and 164 males and 239 females of the White Leghorn (WL) line. Heritability estimates, based on correlation among full-sibs, of growth rate constant were 0.18 +/- 0.32 in males and 0.29 +/- 0.29 in females of the RIR line, and 0.41 +/- 0.40 in males and 0.46 +/- 0.32 in females of the WL line. Estimates of heritability of age at the inflection point were 0.36 +/- 0.44 in males and 0.42 +/- 0.32 in females of the RIR line, and 0.46 +/- 0.41 in males and 0.50 +/- 0.28 in females of the WL line. Observed variation for each trait probably does not provide evidence for heritable differences. No genetic correlations were evident among growth-rate constant, age at the point of inflection, and initial or maximum weight. According to these results, it does not appear that selection for growth-rate constant or age at the point of inflection will change the shape of the growth curve of these populations genetically. Moreover, correlated genetic change in initial or maximum weight would not be expected. PMID:4086789

  4. Analysis of growth curves of fowl. I. Chickens.

    PubMed

    Knízetová, H; Hyánek, J; Kníze, B; Roubícek, J

    1991-12-01

    1. The Richards function was used to describe the growth curves (n = 989) of 9 broiler lines. Chickens were fed ad libitum and body weight was recorded every second week from hatching to 26 weeks of age. 2. The accuracy of curve fit measured by the coefficient of determination (R2) was better for males than for females (0.9986-0.9995 vs 0.9972-0.9988, respectively). 3. The estimation of the asymptotic final weight (A) for different lines enabled the degree of maturity (ut = yt/A) to be determined at any fixed point of the curve. At the age of 7 weeks this had a value of 0.318-0.369 for cockerels and 0.325-0.377 for pullets and represented the slaughter maturity of individual lines. The ratio of inflection/asymptotic weight (y+/A = 0.370-0.388) indicated that in some cases chicken growth can be described approximately by the Gompertz function (y+/A = 0.368). 4. It was found that the age at the inflection point of curves (t+ 48.2-55.7 d for cockerels and t+ = 47.8-52.8 d for pullets) roughly corresponds to the slaughter age of the chickens. 5. The interline differences in the parameters of maturation rate for weight (y+/A, k, t+, u7) are low in comparison with the differences in body weight (A, y+, y7) and absolute growth rate (v, v+). 6. The intragroup phenotypic correlation among growth parameters and the importance of the mathematical models are discussed. PMID:1786568

  5. Comparative Study of Bacterial Growth in Magnet Fields

    NASA Astrophysics Data System (ADS)

    Smith, Derek; Masood, Samina

    It has been shown that magnetic fields affect bacterial growth. A comparative study of growth rates for gram-positive and gram-negative bacteria with different types of magnetic fields is done. Special focus is placed upon growth within liquid media, and the effect of magnetic fields relative to the chosen growth medium is considered.

  6. Practical application of generic growth theory and the significance of the growth curve parameters.

    PubMed

    Pruitt, K M; DeMuth, R E; Turner, M E

    1979-03-01

    The generic growth curve is developed by plausibility arguments based on simple growth models. Parameters of the generic curve include the maximum size, maximum specific growth rate, and a dimensionless velocity constant which can be related to metabolic efficiency in the case of nutrient-limited growth. Parameter estimates are obtained from estimates of the size and time at the point of inflection, the size and time at any other arbitrarily selected point, and the maximum size. Parameter estimates thus obtained and used as initial estimates in nonlinear least squares analysis often give rapid convergence to a minimum error mean square. [For the growth of Escherichia coli K-12 in liquid medium, the generic curve could be simplified to a form containing only three parameters: the maximum specific growth rate, the maximum size, and the time required to reach maximum size. When the bacteria were inhibited by the addition of increasing amounts of the lactoperoxidase antimicrobial factor, there was no significant change in viable counts or maximum specific growth rate, but the time required to reach maximum growth increased linearly with increasing amounts of added antimicrobial factor.] Analysis of growth in terms of the generic growth curve can be a powerful technique for finding relationships which may not be apparent from qualitative consideration of the data. PMID:378773

  7. Multiscale study of bacterial growth: Experiments and model to understand the impact of gas exchange on global growth

    NASA Astrophysics Data System (ADS)

    Lalanne-Aulet, David; Piacentini, Adalberto; Guillot, Pierre; Marchal, Philippe; Moreau, Gilles; Colin, Annie

    2015-11-01

    Using a millifluidics and macroscale setup, we study quantitatively the impact of gas exchange on bacterial growth. In millifluidic environments, the permeability of the incubator materials allows an unlimited oxygen supply by diffusion. Moreover, the efficiency of diffusion at small scales makes the supply instantaneous in comparison with the cell division time. In hermetic closed vials, the amount of available oxygen is low. The growth curve has the same trend but is quantitatively different from the millifluidic situation. The analysis of all the data allows us to write a quantitative modeling enabling us to capture the entire growth process.

  8. A Bayesian analysis of the effect of selection for growth rate on growth curves in rabbits

    PubMed Central

    Blasco, Agustín; Piles, Miriam; Varona, Luis

    2003-01-01

    Gompertz growth curves were fitted to the data of 137 rabbits from control (C) and selected (S) lines. The animals came from a synthetic rabbit line selected for an increased growth rate. The embryos from generations 3 and 4 were frozen and thawed to be contemporary of rabbits born in generation 10. Group C was the offspring of generations 3 and 4, and group S was the contemporary offspring of generation 10. The animals were weighed individually twice a week during the first four weeks of life, and once a week thereafter, until 20 weeks of age. Subsequently, the males were weighed weekly until 40 weeks of age. The random samples of the posterior distributions of the growth curve parameters were drawn by using Markov Chain Monte Carlo (MCMC) methods. As a consequence of selection, the selected animals were heavier than the C animals throughout the entire growth curve. Adult body weight, estimated as a parameter of the Gompertz curve, was 7% higher in the selected line. The other parameters of the Gompertz curve were scarcely affected by selection. When selected and control growth curves are represented in a metabolic scale, all differences disappear. PMID:12605849

  9. Complementarity among plant growth promoting traits in rhizospheric bacterial communities promotes plant growth

    PubMed Central

    Singh, Mangal; Awasthi, Ashutosh; Soni, Sumit K.; Singh, Rakshapal; Verma, Rajesh K.; Kalra, Alok

    2015-01-01

    An assessment of roles of rhizospheric microbial diversity in plant growth is helpful in understanding plant-microbe interactions. Using random combinations of rhizospheric bacterial species at different richness levels, we analysed the contribution of species richness, compositions, interactions and identity on soil microbial respiration and plant biomass. We showed that bacterial inoculation in plant rhizosphere enhanced microbial respiration and plant biomass with complementary relationships among bacterial species. Plant growth was found to increase linearly with inoculation of rhizospheric bacterial communities with increasing levels of species or plant growth promoting trait diversity. However, inoculation of diverse bacterial communities having single plant growth promoting trait, i.e., nitrogen fixation could not enhance plant growth over inoculation of single bacteria. Our results indicate that bacterial diversity in rhizosphere affect ecosystem functioning through complementary relationship among plant growth promoting traits and may play significant roles in delivering microbial services to plants. PMID:26503744

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  11. Parent involvement and science achievement: A latent growth curve analysis

    NASA Astrophysics Data System (ADS)

    Johnson, Ursula Yvette

    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.

  12. Paenibacillus dendritiformis Bacterial Colony Growth Depends on Surfactant but Not on Bacterial Motion▿ †

    PubMed Central

    Be'er, Avraham; Smith, Rachel S.; Zhang, H. P.; Florin, E.-L.; Payne, Shelley M.; Swinney, Harry L.

    2009-01-01

    Most research on growing bacterial colonies on agar plates has concerned the effect of genetic or morphotype variation. Some studies have indicated that there is a correlation between microscopic bacterial motion and macroscopic colonial expansion, especially for swarming strains, but no measurements have been obtained for a single strain to relate the microscopic scale to the macroscopic scale. We examined here a single strain (Paenibacillus dendritiformis type T; tip splitting) to determine both the macroscopic growth of colonies and the microscopic bacterial motion within the colonies. Our multiscale measurements for a variety of growth conditions revealed that motion on the microscopic scale and colonial growth are largely independent. Instead, the growth of the colony is strongly affected by the availability of a surfactant that reduces surface tension. PMID:19617369

  13. Can we estimate bacterial growth rates from ribosomal RNA content?

    SciTech Connect

    Kemp, P.F.

    1995-12-31

    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.

  14. Effects of time, temperature, and preservative on bacterial growth in enteral nutrient solutions.

    PubMed

    Fagerman, K E; Paauw, J D; McCamish, M A; Dean, R E

    1984-06-01

    Bacterial contamination and the effects of time, temperature, and preservative on bacterial growth in enteral nutrient solutions were studied. Bacteria were counted after 24-hour incubation of five samples of frozen Travasorb STD (Travenol Laboratories) from the pharmacy and five samples freshly reconstituted in the dietary department. Growth in samples of Travasorb STD prepared in the pharmacy was studied after (1) fresh mixing, 24-hour refrigeration, and 12 hours at room temperature, (2) freezing, thawing, and 12 hours at room temperature, and (3) freezing, thawing, 24-hour refrigeration, and 12 hours at room temperature. Duplicate samples of five products [Ensure (Ross Laboratories), Precision LR (Doyle Pharmaceuticals), Travasorb STD, Vital (Ross Laboratories), and Vivonex STD ( Norwich -Eaton)] were inoculated with Enterobacter cloacae, and growth curves for 24 hours were plotted. This challenge study was repeated using Travasorb STD as a control and Travasorb STD with potassium sorbate added. Bacterial contamination following reconstitution was not significantly different between pharmacy and dietary department samples. Growth after 12 hours at room temperature was not significantly different for the three sets of storage conditions. Logarithmic growth occurred only at room temperature. All products supported growth of E. cloacae, but growth was significantly lower in Vivonex STD (which contains potassium sorbate) and Precision LR. Growth was reduced by 70% versus control at 12 hours in Travasorb STD containing 0.036% potassium sorbate and by 90% with 0.2% potassium sorbate. Microbial growth in enteral nutrient solutions was dependent on the initial inoculum and the storage time at room temperature. Addition of potassium sorbate to these solutions may greatly reduce bacterial growth. PMID:6430069

  15. Economic growth and energy regulation in the environmental Kuznets curve.

    PubMed

    Lorente, Daniel Balsalobre; Álvarez-Herranz, Agustín

    2016-08-01

    This study establishes the existence of a pattern of behavior, between economic growth and environmental degradation, consistent with the environmental Kuznets curve (EKC) hypothesis for 17 Organization for Economic Cooperation and Development (OECD) countries between 1990 and 2012. Based on this EKC pattern, it shows that energy regulation measures help reduce per capita greenhouse gas (GHG) emissions. To validate this hypothesis, we also add the explanatory variables: renewable energy promotion, energy innovation processes, and the suppression effect of income level on the contribution of renewable energy sources to total energy consumption. It aims to be a tool for decision-making regarding energy policy. This paper provides a two-stage econometric analysis of instrumental variables with the aim of correcting the existence of endogeneity in the variable GDP per capita, verifying that the instrumental variables used in this research are appropriate for our aim. To this end, it first makes a methodological contribution before incorporating additional variables associated with environmental air pollution into the EKC hypothesis and showing how they positively affect the explanation of the correction in the GHG emission levels. This study concludes that air pollution will not disappear on its own as economic growth increases. Therefore, it is necessary to promote energy regulation measures to reduce environmental pollution. PMID:27164892

  16. Biological Consequences and Advantages of Asymmetric Bacterial Growth

    PubMed Central

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

    2014-01-01

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

  17. Integrated kinetic and probabilistic modeling of the growth potential of bacterial populations.

    PubMed

    George, S M; Métris, A; Baranyi, J

    2015-05-01

    When bacteria are exposed to osmotic stress, some cells recover and grow, while others die or are unculturable. This leads to a viable count growth curve where the cell number decreases before the onset of the exponential growth phase. From such curves, it is impossible to estimate what proportion of the initial cells generates the growth because it leads to an ill-conditioned numerical problem. Here, we applied a combination of experimental and statistical methods, based on optical density measurements, to infer both the probability of growth and the maximum specific growth rate of the culture. We quantified the growth potential of a bacterial population as a quantity composed from the probability of growth and the "suitability" of the growing subpopulation to the new environment. We found that, for all three laboratory media studied, the probability of growth decreased while the "work to be done" by the growing subpopulation (defined as the negative logarithm of their suitability parameter) increased with NaCl concentration. The results suggest that the effect of medium on the probability of growth could be described by a simple shift parameter, a differential NaCl concentration that can be accounted for by the change in the medium composition. Finally, we highlighted the need for further understanding of the effect of the osmoprotectant glycine betaine on metabolism. PMID:25747002

  18. Quantification of antibiotic drug potency by a two-compartment radioassay of bacterial growth

    SciTech Connect

    Boonkitticharoen, V.; Ehrhardt, J.C.; Kirchner, P.T. )

    1990-06-01

    The two-compartment radioassay for microbial kinetics based on continuous measurement of the {sup 14}CO{sub 2} released by bacterial metabolism of 14C-labeled substrate offers a valuable approach to testing the potency of antimicrobial drugs. By using a previously validated radioassay with gram-positive and gram-negative bacteria, a group of protein synthesis inhibitors was evaluated for their effect on microbial growth kinetics. All tested drugs induced changes in both the slopes and intercepts of the growth curves. An exponential growth model was applied to quantify the drug effect on the processes of bacterial {sup 14}CO{sub 2} liberation and cell generation. The response was measured in terms of a generation rate constant. A linear dependence of the generation rate constant on the dose of spectinomycin was observed with Escherichia coli. Sigmoidal-shaped curves were found in the assays of chloramphenicol and tetracycline. The implications of dose-response curves are discussed on the basis of the receptor site concept for drug action. The assay sensitivities for chloramphenicol and tetracycline were similar to those obtained by the cell counting method, but the sensitivity of the radioassay was at least 10 times greater for spectinomycin.

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

    ERIC Educational Resources Information Center

    Sivo, Stephen; Fan, Xitao; Witta, Lea

    2005-01-01

    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…

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

    PubMed

    Liu, S

    1999-12-01

    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 of Escherichia coli was continuously observed in real-time for up to 6 h. The observations showed primarily unidirectional growth and reproduction of E. coli and suggested more than one reproduction in the observed portion of E. coli life span. A new bacterial life model is proposed: each bacterium has a stable cell polarity that ultimately transforms into two bacteria of different generations; the life cycle of a bacterium can contain more than one reproduction cycle; and the age of a bacterium should be defined by its experienced chronological time. This new bacterial life model differs from the dominant concepts of bacterial life but complies with all basic life principles based on direct observation of macroorganisms. PMID:18726488

  1. Impact of medications on bacterial growth in syringes.

    PubMed

    Kerenyi, M; Borza, Z; Csontos, C; Ittzes, B; Batai, I

    2011-11-01

    Syringes used to administer intravenous medications in an intensive care unit were cultured, and the isolates were compared with those from positive blood cultures from the same patients. The overall contamination rate was 16%, and syringes used for drugs such as insulin, which support bacterial growth, had higher contamination rates. All syringes should be changed routinely after 6h. PMID:21864939

  2. Kinetics of bacterial growth on chlorinated aliphatic compounds

    SciTech Connect

    Wijngaard, A.J. van den; Wind, R.E.; Janssen, D.B. )

    1993-07-01

    Halogenated aliphatic compounds are frequent constituents of industrial waste gases. Because of the environmental and biological toxic effects of these compounds, there is a growing interest in technologies for their removal. Biological waste gas purification is an option if specialized bacterial strains that use halogenated aliphatics as sole carbon and energy sources can be used. Elimination efficiency of the compounds depends not only on the process technology but on the degradation properties of the bacterial strains. Important aspects of bacterial growth are the Monod half-saturation constant and the maximum growth rate. In this study the kinetic properties of the organisms (Ancylobacter aquaticus AD20 and AD25, Xanthobacter autotrophicus GJ10, Pseudomonas sp. strain AD1) weree measured during growth in continuous cultures and wer compared with the kinetic properties of the first catabolic enzyme involved in the degradation of the growth substrate. The results indicate that the growth of the strains examined followed Monod kinetics. Stains AD20 and GJ10 showed growth rates on DCE somewhat higher than predicted from the amount of haloalkane dehalogenase present in the cells, while strain AD25 was much lower. 33 refs., 3 figs., 4 tabs.

  3. Evolution of bacterial and fungal growth media

    PubMed Central

    Basu, Srijoni; Bose, Chandra; Ojha, Nupur; Das, Nabajit; Das, Jagaree; Pal, Mrinmoy; Khurana, Sukant

    2015-01-01

    Microbial media has undergone several changes since its inception but some key challenges remain. In recent years, there has been exploration of several alternative nutrient sources, both to cater to the specificity in requirement of growth of “fussy microorganisms” and also to reduce costs for large-scale fermentation that is required for biotechnology. Our mini-review explores these developments and also points at lacunas in the present areas of exploration, such as a lack of concerted effort in pH and osmolarity regulation. We hope that our commentary provides direction for future research in microbial media. PMID:26124557

  4. Relationship between model bacterial peptidoglycan network structures and AFM force-distance curves

    NASA Astrophysics Data System (ADS)

    Brown, Aidan; Wickham, Robert; Touhami, Ahmed; Dutcher, John

    2010-03-01

    Recent atomic force microscopy (AFM) measurements have involved pulling on Gram-negative bacterial sacculi with the AFM tip as a means of distinguishing between different proposed structures of the peptidoglycan network. The goal of the present study is to provide the theoretical connection between a given network structure and its response to the pulling force. We model the glycan strands as hinged rods, and the peptide cross-links as wormlike chains. Using Monte Carlo simulation to equilibrate the three-dimensional network, subject to a fixed AFM tip-to-substrate distance, we can compute the force exerted by the network on the AFM tip. The effects of adhesion of the sacculi to the substrate and enzymatic action on the network are included. We have modeled both the layered and the scaffold model for the peptidoglycan network structure. We have compared our theoretical force-distance curves for each network structure with experimental curves to determine which structure provides the best agreement with experiment.

  5. Cooperative Bacterial Growth Dynamics Predict the Evolution of Antibiotic Resistance

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    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.

  6. Crack growth measured on flat and curved surfaces at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Orange, T. W.; Sullivan, T. L.

    1967-01-01

    Multiple element continuity gage measures plane stress crack growth plus surface crack growth under plane strain conditions. The gage measures flat and curved surfaces and operates at cryogenic temperatures.

  7. Effect of DSS on Bacterial Growth in Gastrointestinal Tract.

    PubMed

    Hlinková, J; Svobodová, H; Brachtlová, T; Gardlík, R

    2016-01-01

    Inflammatory bowel disease is an idiopathic autoimmune disorder that is mainly divided into ulcerative colitis and Crohn's disease. Probiotics are known for their beneficial effect and used as a treatment option in different gastrointestinal problems. The aim of our study was to find suitable bacterial vectors for gene therapy of inflammatory bowel disease. Salmonella enterica serovar Typhimurium SL7207 and Escherichia coli Nissle 1917 were investigated as potential vectors. Our results show that the growth of Escherichia coli Nissle 1917 was inhibited in the majority of samples collected from dextran sodium sulphate-treated animals compared with control growth in phosphate-buffered saline. The growth of Salmonella enterica serovar Typhimurium SL7207 in all investigated samples was enhanced or unaffected in comparison with phosphate-buffered saline; however, it did not reach the growth rates of Escherichia coli Nissle 1917. Dextran sodium sulphate treatment had a stimulating effect on the growth of both strains in homogenates of distant small intestine and proximal colon samples. The gastrointestinal tract contents and tissue homogenates did not inhibit growth of Salmonella enterica serovar Typhimurium SL7207 in comparison with the negative control, and provided more suitable environment for growth compared to Escherichia coli Nissle 1917. We therefore conclude that Salmonella enterica serovar Typhimurium SL7207 is a more suitable candidate for a potential bacterial vector, even though it has no known probiotic properties. PMID:27085009

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

    ERIC Educational Resources Information Center

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

    2014-01-01

    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…

  9. Modeling Pacing Behavior and Test Speededness Using Latent Growth Curve Models

    ERIC Educational Resources Information Center

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

    2013-01-01

    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…

  10. Growth Curve Models for Zero-Inflated Count Data: An Application to Smoking Behavior

    ERIC Educational Resources Information Center

    Liu, Hui; Powers, Daniel A.

    2007-01-01

    This article applies growth curve models to longitudinal count data characterized by an excess of zero counts. We discuss a zero-inflated Poisson regression model for longitudinal data in which the impact of covariates on the initial counts and the rate of change in counts over time is the focus of inference. Basic growth curve models using a…

  11. Evaluating the Power of Latent Growth Curve Models to Detect Individual Differences in Change

    ERIC Educational Resources Information Center

    Hertzog, Christopher; von Oertzen, Timo; Ghisletta, Paolo; Lindenberger, Ulman

    2008-01-01

    We evaluated the statistical power of single-indicator latent growth curve models to detect individual differences in change (variances of latent slopes) as a function of sample size, number of longitudinal measurement occasions, and growth curve reliability. We recommend the 2 degree-of-freedom generalized test assessing loss of fit when both…

  12. The Role of Coding Time in Estimating and Interpreting Growth Curve Models.

    ERIC Educational Resources Information Center

    Biesanz, Jeremy C.; Deeb-Sossa, Natalia; Papadakis, Alison A.; Bollen, Kenneth A.; Curran, Patrick J.

    2004-01-01

    The coding of time in growth curve models has important implications for the interpretation of the resulting model that are sometimes not transparent. The authors develop a general framework that includes predictors of growth curve components to illustrate how parameter estimates and their standard errors are exactly determined as a function of…

  13. ULTRASOUND INCREASES THE RATE OF BACTERIAL CELL GROWTH

    PubMed Central

    Pitt, William G.; Ross, S. Aaron

    2006-01-01

    Ultrasound was employed to increase the growth rate of bacterial cells attached to surfaces. Staphylococcus epidermidis, Pseudomonas aeruginosa and Escherichia coli cells adhered to and grew on a polyethylene surface in the presence of ultrasound. It was found that low frequency ultrasound (70 kHz) of low acoustic intensity (<2 W/cm2) increased the growth rate of the cells compared to growth without ultrasound. However, at high intensity levels, cells were partially removed from the surface. Ultrasound also enhanced planktonic growth of S. epidermidis and other planktonic bacteria. It is hypothesized that ultrasound increases the rate of transport of oxygen and nutrients to the cells and increases the rate of transport of waste products away from the cells, thus enhancing their growth. PMID:12790676

  14. Individual based simulations of bacterial growth on agar plates

    NASA Astrophysics Data System (ADS)

    Ginovart, M.; López, D.; Valls, J.; Silbert, M.

    2002-03-01

    The individual based simulator, INDividual DIScrete SIMulations (INDISIM) has been used to study the behaviour of the growth of bacterial colonies on a finite dish. The simulations reproduce the qualitative trends of pattern formation that appear during the growth of Bacillus subtilis on an agar plate under different initial conditions of nutrient peptone concentration, the amount of agar on the plate, and the temperature. The simulations are carried out by imposing closed boundary conditions on a square lattice divided into square spatial cells. The simulator studies the temporal evolution of the bacterial population possible by setting rules of behaviour for each bacterium, such as its uptake, metabolism and reproduction, as well as rules for the medium in which the bacterial cells grow, such as concentration of nutrient particles and their diffusion. The determining factors that characterize the structure of the bacterial colony patterns in the presents simulations, are the initial concentrations of nutrient particles, that mimic the amount of peptone in the experiments, and the set of values for the microscopic diffusion parameter related, in the experiments, to the amount of the agar medium.

  15. Effect of surgical hand scrub time on subsequent bacterial growth.

    PubMed

    Wheelock, S M; Lookinland, S

    1997-06-01

    In this experimental study, the researchers evaluated the effect of surgical hand scrub time on subsequent bacterial growth and assessed the effectiveness of the glove juice technique in a clinical setting. In a randomized crossover design, 25 perioperative staff members scrubbed for two or three minutes in the first trial and vice versa in the second trial, after which the wore sterile surgical gloves for one hour under clinical conditions. The researchers then sampled the subjects' nondominant hands for bacterial growth, cultured aliquots from the sampling solution, and counted microorganisms. Scrubbing for three minutes produced lower mean log bacterial counts than scrubbing for two minutes. Although the mean bacterial count differed significantly (P = .02) between the two-minute and three-minute surgical hand scrub times, it fell below 0.5 log, which is the threshold for practical and clinical significance. This finding suggests that a two-minute surgical hand scrub is clinically as effective as a three-minute surgical had scrub. The glove juice technique demonstrated sensitivity and reliability in enumerating bacteria on the hands of perioperative staff members in a clinical setting. PMID:9187454

  16. Microcoupon Assay Of Adhesion And Growth Of Bacterial Films

    NASA Technical Reports Server (NTRS)

    Pierson, Duane L.; Koenig, David W.

    1994-01-01

    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.

  17. A Multilevel Latent Growth Curve Approach to Predicting Student Proficiency

    ERIC Educational Resources Information Center

    Choi, Kilchan; Goldschmidt, Pete

    2012-01-01

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

  18. Leuconostoc mesenteroides growth kinetics with application to bacterial profile modification

    SciTech Connect

    Lappan, R.E.; Fogler, H.S. . Dept. of Chemical Engineering)

    1994-04-15

    Bacterial profile modification (BPM) is being developed as an oil recovery technique that uses bacteria to selectively plug oil depleted zones within a reservoir to divert displacing fluids into oil-rich zones. Leuconostoc mesenteroides, which produces dextran when supplied with sucrose, is a bacterium that is technically feasible for use in profile modification. However, the technique requires controlled bacterial growth to produce selective plugging. A kinetic model for the production of cells and polysaccharides has been developed for L. mesenteroides bacteria. This model, based on data from batch growth experiments, predicts saccharide utilization, cell generation, and dextran production. The underlying mechanism is the extracellular breakdown of sucrose into glucose and fructose and the subsequent production of polysaccharide. The monosaccharides are then available for growth. Accompanying sucrose consumption is the utilization of yeast extract. The cell requires a complex media that is provided by yeast extract as a source of vitamins and amino acids. Varying the concentration ratio of yeast extract to sucrose in the growth media provides a means of controlling the amount of polymer produced per cell. Consequently, in situ bacteria growth can be controlled by the manipulation of nutrient media composition, thereby providing the ability to create an overall strategy for the use of L. mesenteroides bacteria for profile modification.

  19. Effects of grain growth on the interstellar polarization curve

    NASA Astrophysics Data System (ADS)

    Voshchinnikov, Nikolai V.; Hirashita, Hiroyuki

    2014-11-01

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

  20. Mycobacterium massiliense Induces Macrophage Extracellular Traps with Facilitating Bacterial Growth

    PubMed Central

    Yoon, Yina; Na, Yirang; Kim, Bum-Joon; Seok, Seung Hyeok

    2016-01-01

    Human neutrophils have been known to release neutrophil extracellular traps (NETs), antimicrobial DNA structures capable of capturing and killing microbes. Recently, a similar phenomenon has been reported in macrophages infected with various pathogens. However, a role for macrophages extracellular traps (METs) in host defense responses against Mycobacterium massiliense (M. mass) has yet to be described. In this study, we show that M. mass, a rapid growing mycobacterium (RGM), also induces the release of METs from PMA-differentiated THP-1 cells. Intriguingly, this process is not dependent on NADPH oxidase activity, which regulates NET formation. Instead, M. mass-induced MET formation partially depends on calcium influx and requires phagocytosis of high bacterial load. The METs consist of a DNA backbone embedded with microbicidal proteins such as histone, MPO and elastase. Released METs entrap M. mass and prevent their dissemination, but do not have bactericidal activity. Instead, they result in enhanced bacterial growth. In this regard, METs were considered to provide interaction of M. mass with cells and an environment for bacterial aggregation, which may facilitate mycobacterial survival and growth. In conclusion, our results demonstrate METs as an innate defense response against M. mass infection, and suggest that extracellular traps play a multifaceted role in the interplay between host and bacteria. PMID:27191593

  1. Bacterial growth laws reflect the evolutionary importance of energy efficiency

    PubMed Central

    Maitra, Arijit; Dill, Ken A.

    2015-01-01

    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

  2. On growth and flow: bacterial biofilms in porous media

    NASA Astrophysics Data System (ADS)

    Durham, William; Leombruni, Alberto; Tranzer, Olivier; Stocker, Roman

    2011-11-01

    Bacterial biofilms often occur in porous media, where they play pivotal roles in medicine, industry and the environment. Though flow is ubiquitous in porous media, its effects on biofilm growth have been largely ignored. Using patterned microfluidic devices that simulate unconsolidated soil, we find that the structure of Escherichia coli biofilms undergoes a self-organization mediated by the interaction of growth and flow. Intriguingly, we find that biofilm productivity peaks at intermediate flow rates, when the biofilm is irrigated by a minimum number of preferential flow channels. At larger and smaller flow rates, fluid flows more uniformly through the matrix, but productivity drops due to removal by shear and reduced nutrient transport, respectively. These dynamics are correctly predicted by a simple network model. The observed tradeoff between growth and flow may have important consequences on biofilm-mediated processes such as biochemical cycling, antibiotic resistance and water filtration.

  3. 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...

  4. Bacterial growth, detachment and cell size control on polyethylene terephthalate surfaces

    PubMed Central

    Wang, Liyun; Fan, Daming; Chen, Wei; Terentjev, Eugene M.

    2015-01-01

    In medicine and food industry, bacterial colonisation on surfaces is a common cause of infections and severe illnesses. However, the detailed quantitative information about the dynamics and the mechanisms involved in bacterial proliferation on solid substrates is still lacking. In this study we investigated the adhesion and detachment, the individual growth and colonisation, and the cell size control of Escherichia coli (E. coli) MG1655 on polyethylene terephthalate (PET) surfaces. The results show that the bacterial growth curve on PET exhibits the distinct lag and log phases, but the generation time is more than twice longer than in bulk medium. Single cells in the lag phase are more likely to detach than clustered ones in the log phase; clustered bacteria in micro-colonies have stronger adhesive bonds with surfaces and their neighbours with the progressing colonisation. We show that the cell size is under the density-dependent pathway control: when the adherent cells are at low density, the culture medium is responsible for coordinating cell division and cell size; when the clustered cells are at high population density, we demonstrate that the effect of quorum sensing causes the cell size decrease as the cell density on surfaces increases. PMID:26464114

  5. A new growth curve model for biological growth: some inferential studies on the growth of Cirrhinus mrigala.

    PubMed

    Bhowmick, Amiya Ranjan; Bhattacharya, Sabyasachi

    2014-08-01

    Growth of living organisms is a fundamental biological process. It depicts the physiological development of the species related to the environment. Mathematical development of growth curve models has a long history since its birth. We propose a mathematical model to describe the evolution of relative growth rate as a function of time based on a real life experiment on a major Indian Carp Cirrhinus mrigala. We establish that the proposed model is able to describe the fish growth dynamics more accurately for our experimental data than some existing models e.g. logistic, Gompertz, exponential. Approximate expressions of the points of inflection and the time of achieving the maximum relative growth rate are derived. We study, in detail, the existence of a nonlinear least squares estimator of the model parameters and their consistency properties. Test-statistics is developed to study the equality of points of inflection and equality of the amount of time necessary to achieve the maximum relative growth rate for a species at two different locations. Using the theory of variance stabilizing transformations, we propose a new test statistic to test the effect of the decay parameter for the proposed growth law. The testing procedure is found to be more sensitive in comparison with the test based on nonlinear least squares estimates. Our proposed model provides a general framework to model growth in other disciplines as well. PMID:24933474

  6. A Rhizocarpon geographicum growth curve for the Cascade Range of Washington and northern Oregon, usa

    NASA Astrophysics Data System (ADS)

    O'Neal, Michael A.; Schoenenberger, Katherine R.

    2003-09-01

    Lichen thallus measurements from 22 surfaces of known age on Mount Baker, Mount Hood, and Mount Rainier are used to construct a regional Rhizocarpon geographicum growth curve for the Cascade Range of Washington and northern Oregon. Growth rates determined by measuring the largest thallus diameters on the same surfaces at Mount Rainier in 1976 and 2002 are used for comparison with lichenometric data from Mount Baker and Mount Hood. Similar lichen thallus diameter vs age relationships identified in the data from the three mountains suggest the presence of uniform growth rates over the 400-km range. A regional growth curve developed during our study shows three growth phases of successively slower growth: a rapid phase from 8 to 20 yr, a linear phase from 20 to 145 yr, and a slow phase of unknown duration beyond ca. 145 yr. Uncertainty in lichen growth rates beyond 145 yr limits projection of the curve beyond that age; however, the age range of the constrained growth curve covers an important period of recent climate variability. When applied in appropriate settings, our growth curve can be used to determine numeric ages to ±10 yr for surfaces between 20 and 145 years old in areas where other techniques are not applicable or do not provide unique or well-constrained ages.

  7. Slow Protein Fluctuations Explain the Emergence of Growth Phenotypes and Persistence in Clonal Bacterial Populations

    PubMed Central

    Rocco, Andrea; Kierzek, Andrzej M.; McFadden, Johnjoe

    2013-01-01

    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. PMID:23382887

  8. Bacterial Spring Constant in Log-Phase Growth

    NASA Astrophysics Data System (ADS)

    Jain, Deepti; Nanda, H.; Nath, R.; Chitnis, D. S.; Ganesan, V.

    2011-07-01

    Atomic Force Microscopy is a powerful tool in studying bacterial systems too. The turgor pressure studies on well known systems like E-coli and Staphylococcus revealed a fascinating fact that the numbers are in tens of atmosphere depending upon the microbial activity. Hence there is no way that one can destroy them by physical means. This is due to the robust nature of the cell wall. Understanding the cell wall structure requires an estimate of spring constant of the cell wall membrane and its variation upon activity. Here we present an experimental estimate of the spring constant of the cell wall (˜10-2 N/m) using force curve measurements on bacteria using an AFM tip. This has a bearing on measuring turgor pressure of bacterium.

  9. Parent Involvement and Science Achievement: A Latent Growth Curve Analysis

    ERIC Educational Resources Information Center

    Johnson, Ursula Yvette

    2011-01-01

    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…

  10. Lubricating bacteria model for branching growth of bacterial colonies

    NASA Astrophysics Data System (ADS)

    Kozlovsky, Yonathan; Cohen, Inon; Golding, Ido; Ben-Jacob, Eshel

    1999-06-01

    Various bacterial strains (e.g., strains belonging to the genera Bacillus, Paenibacillus, Serratia, and Salmonella) exhibit colonial branching patterns during growth on poor semisolid substrates. These patterns reflect the bacterial cooperative self-organization. A central part of the cooperation is the collective formation of a lubricant on top of the agar which enables the bacteria to swim. Hence it provides the colony means to advance towards the food. One method of modeling the colonial development is via coupled reaction-diffusion equations which describe the time evolution of the bacterial density and the concentrations of the relevant chemical fields. This idea has been pursued by a number of groups. Here we present an additional model which specifically includes an evolution equation for the lubricant excreted by the bacteria. We show that when the diffusion of the fluid is governed by a nonlinear diffusion coefficient, branching patterns evolve. We study the effect of the rates of emission and decomposition of the lubricant fluid on the observed patterns. The results are compared with experimental observations. We also include fields of chemotactic agents and food chemotaxis and conclude that these features are needed in order to explain the observations.

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

    NASA Technical Reports Server (NTRS)

    Mengshoel, Ole J.

    2010-01-01

    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.

  12. Effect of bacterial growth stage on resistance to chlorine disinfection.

    PubMed

    Cherchi, C; Gu, A Z

    2011-01-01

    The mechanisms and factors that affect microbial resistance to chlorine disinfection have not been fully elucidated. In this study, we investigated the impact of the cell growth stage on chlorine disinfection efficiency. Specifically, we evaluated the impact of the growth stage on chlorination resistance by comparing the inactivation efficiencies of two indicator bacterial strains (Escherichia coli K12 and Escherichia coli O157:H7) obtained from various growth phases, using Chick-Watson kinetic parameters. For both E. coli strains (K12 and O157:H7), the inactivation rate constants are the lowest at stationary phase (0.19 and 0.32) compared to those at initial lag (0.54 and 0.76) and exponential growth phase (0.63 and 0.69), respectively. These results suggested that the abundance of resistant subpopulations increases at stressed stationary conditions and E. coli cells obtained from the stationary growth phase exhibited more resistance and lower inactivation efficiency compared to those from the lag and exponential phases. This implies that microbes in wastewater treatment process with varying solids retention times (SRTs, which indicate growth rates) may show different extents of chlorine resistance. Comparison of the coefficient of dilution (n) values in both E. coli strains for the various growth phases suggest that cells seem to be more sensitive to disinfectant concentration at the stationary-lag phase than that at the exponential stage. Comparing the two E. coli strains, higher inactivation rates were observed for the pathogenic O157:H7 than for K12 at different stages of growth. The strain-to-strain variability in survivability to chlorine exposure has to be considered when selecting indicator microorganisms for water quality monitoring. PMID:22053451

  13. Oral iron acutely elevates bacterial growth in human serum

    PubMed Central

    Cross, James H.; Bradbury, Richard S.; Fulford, Anthony J.; Jallow, Amadou T.; Wegmüller, Rita; Prentice, Andrew M.; Cerami, Carla

    2015-01-01

    Iron deficiency is the most common nutrient deficiency worldwide and routine supplementation is standard policy for pregnant mothers and children in most low-income countries. However, iron lies at the center of host-pathogen competition for nutritional resources and recent trials of iron administration in African and Asian children have resulted in significant excesses of serious adverse events including hospitalizations and deaths. Increased rates of malaria, respiratory infections, severe diarrhea and febrile illnesses of unknown origin have all been reported, but the mechanisms are unclear. We here investigated the ex vivo growth characteristics of exemplar sentinel bacteria in adult sera collected before and 4 h after oral supplementation with 2 mg/kg iron as ferrous sulfate. Escherichia coli, Yersinia enterocolitica and Salmonella enterica serovar Typhimurium (all gram-negative bacteria) and Staphylococcus epidermidis (gram-positive) showed markedly elevated growth in serum collected after iron supplementation. Growth rates were very strongly correlated with transferrin saturation (p < 0.0001 in all cases). Growth of Staphylococcus aureus, which preferentially scavenges heme iron, was unaffected. These data suggest that even modest oral supplements with highly soluble (non-physiological) iron, as typically used in low-income settings, could promote bacteremia by accelerating early phase bacterial growth prior to the induction of immune defenses. PMID:26593732

  14. Lactic acid bacterial extract as a biogenic mineral growth modifier

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  15. [Osmoregulation--an important parameter of bacterial growth].

    PubMed

    Sochocka, Marta; Boratyński, Janusz

    2011-01-01

    Environmental conditions such as temperature, pH, radiation and osmotic pressure are important factors limiting the growth and multiplication of bacteria. Regular structure and metabolism of bacterial cells are maintained through a stable arrangement of the water-electrolyte system, regulated by osmosis. The rapid changes caused by osmotic shock (dehydration, rehydration) might lead to modifications of the phospholipid structure of the cell membrane and even cell death. Advances disturbing the osmosis, which are a natural part of living cells, may appear for example in colloid systems. The biological identification of the osmotic pressure is connected with an increase or decrease in the environmental osmotic strength of microorganisms' habitat. Cells exposed to osmotic stress, such as an increase in osmotic pressure, initiate mechanisms of active coping with the adverse consequences of its effects. Osmoregulatory processes are designed to maintain cell turgor, hence ensuring proper conditions for bacterial growth. Osmoregulation, which consists of maintaining fluid and electrolyte balance of cells, raising concerns accumulation of specific compatible solutes (osmolytes). Osmolytes are small, soluble organic molecules with a positive influence on membrane stabilization and proteins, without disrupting cellular functions. Storage of compatible solutes takes place by synthesis or by downregulation from the medium by means of special transport systems, activated by mechanical stimuli. Knowledge of the impact of osmotic pressure on microbial cells and the regulation of its activity led to the appropriate use of bacteria in various branches of the biotechnology industry. PMID:22173436

  16. Growth curve analysis for plasma profiles using smoothing splines

    SciTech Connect

    Imre, K.

    1993-05-01

    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.

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

    ERIC Educational Resources Information Center

    Johnson, Ursula Y.; Hull, Darrell M.

    2014-01-01

    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…

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

    ERIC Educational Resources Information Center

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

    2013-01-01

    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…

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

    ERIC Educational Resources Information Center

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

    2010-01-01

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

  20. Development of Oral Reading Fluency in Children with Speech or Language Impairments: A Growth Curve Analysis

    ERIC Educational Resources Information Center

    Puranik, Cynthia S.; Petscher, Yaacov; Al Otaiba, Stephanie; Catts, Hugh W.; Lonigan, Christopher J.

    2008-01-01

    This longitudinal study used piece-wise growth curve analyses to examine growth patterns in oral reading fluency for 1,991 students with speech impairments (SI) or language impairments (LI) from first through third grade. The main finding of this study was that a diagnosis of SI or LI can have a detrimental and persistent effect on early reading…

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

    PubMed Central

    Griebeler, Eva Maria

    2013-01-01

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

  2. Engineered cerium oxide nanoparticles: Effects on bacterial growth and viability

    SciTech Connect

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

    2010-01-01

    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

  3. Effect of a metal alloy fuel catalyst on bacterial growth.

    PubMed

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

    2005-11-01

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

  4. Bacterial actin and tubulin homologs in cell growth and division.

    PubMed

    Busiek, Kimberly K; Margolin, William

    2015-03-16

    In contrast to the elaborate cytoskeletal machines harbored by eukaryotic cells, such as mitotic spindles, cytoskeletal structures detectable by typical negative stain electron microscopy are generally absent from bacterial cells. As a result, for decades it was thought that bacteria lacked cytoskeletal machines. Revolutions in genomics and fluorescence microscopy have confirmed the existence not only of smaller-scale cytoskeletal structures in bacteria, but also of widespread functional homologs of eukaryotic cytoskeletal proteins. The presence of actin, tubulin, and intermediate filament homologs in these relatively simple cells suggests that primitive cytoskeletons first arose in bacteria. In bacteria such as Escherichia coli, homologs of tubulin and actin directly interact with each other and are crucial for coordinating cell growth and division. The function and direct interactions between these proteins will be the focus of this review. PMID:25784047

  5. Effects of Low-Level Deuterium Enrichment on Bacterial Growth

    PubMed Central

    Xie, Xueshu; Zubarev, Roman A.

    2014-01-01

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

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

    SciTech Connect

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

    2011-01-01

    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.

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

    SciTech Connect

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

    2011-01-01

    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.

  8. Bacterial locomotion, adsorption and growth over chemically patterned surfaces

    NASA Astrophysics Data System (ADS)

    Jalali, Maryam; Molaei, Mehdi; Sheng, Jian

    2013-11-01

    Complex dynamic interactions between bacteria and chemically patched interface that mimics the heterogeneous energy landscape of a real-life interfacial environment are studied in the paper. We explore effects of these spatially varying chemical patches on bacterial locomotion, adsorption, biofilm formation and the film growth rate. Using micro-fabrication and soft-lithography, we have fabricated PDMS microfluidic channels with a solid substrate covered by micro-scale chemical patches. Arrays of 2D geometries of characteristic scales varying from 10 to 50 μm are transferred onto a glass substrate by soft-lithography. The substrate is functionalized to generate alternating hydrophobic and hydrophilic regions and bonded with the channel. The 3D swimming characteristics near these surfaces, such as swimming velocity, linear and angular dispersions, are measured in-situ using 3D digital holographic microscopy. The observations are used to examine the mechanisms involved in adsorption and desorption of swimming bacteria onto the substrate. Long-term experiments are conducted to quantify the growth rate and structures of colony. A correlation between various length scales of the substrate and bacteria motility are observed.

  9. Investigation of growth processes in bacterial colonies by the LASCA technique

    NASA Astrophysics Data System (ADS)

    Ulianova, O. V.; Rebeza, O. S.; Ulyanov, S. S.

    2016-01-01

    The method of analysis of the temporal and spatial contrasts of speckle fields formed during the coherent scattering of radiation in bacterial colonies has been adapted to monitor the growth and structure of bacterial colonies by the example of E. coli. A noticeable change in the spatial structures of colonies during their growth has been demonstrated.

  10. Growth curve analysis of placental and fetal growth influenced by adjacent fetal sex status under crowded uterine conditions in pigs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Intrauterine position and sex of adjacent fetuses in litter bearing species have been implicated in physiological and behavioral differences in males and females. Our objective was to establish growth curves for fetal and placental weight gain as influenced by sex status of flanking fetuses under cr...

  11. Infant Gaze Following and Pointing Predict Accelerated Vocabulary Growth through Two Years of Age: A Longitudinal, Growth Curve Modeling Study

    ERIC Educational Resources Information Center

    Brooks, Rechele; Meltzoff, Andrew N.

    2008-01-01

    We found that infant gaze following and pointing predicts subsequent language development. At ages 0 ; 10 or 0 ; 11, infants saw an adult turn to look at an object in an experimental setting. Productive vocabulary was assessed longitudinally through two years of age. Growth curve modeling showed that infants who gaze followed and looked longer at…

  12. Identifying Longitudinal Growth Trajectories of Learning Domains in Problem-Based Learning: A Latent Growth Curve Modeling Approach Using SEM

    ERIC Educational Resources Information Center

    Wimmers, Paul F.; Lee, Ming

    2015-01-01

    To determine the direction and extent to which medical student scores (as observed by small-group tutors) on four problem-based-learning-related domains change over nine consecutive blocks during a two-year period (Domains: Problem Solving/Use of Information/Group Process/Professionalism). Latent growth curve modeling is used to analyze…

  13. Examining the Earnings Trajectories of Community College Students Using a Piecewise Growth Curve Modeling Approach

    ERIC Educational Resources Information Center

    Jaggars, Shanna Smith; Xu, Di

    2016-01-01

    Policymakers have become increasingly concerned with measuring--and holding colleges accountable for--students' labor market outcomes. In this article we introduce a piecewise growth curve approach to analyzing community college students' labor market outcomes, and we discuss how this approach differs from two popular econometric approaches:…

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

    ERIC Educational Resources Information Center

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

    2013-01-01

    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…

  15. The Dynamics of Self-Esteem: A Growth-Curve Analysis.

    ERIC Educational Resources Information Center

    Baldwin, Scott A.; Hoffmann, John P.

    2002-01-01

    Using 7 years of sequential data from the Family Health Study for 762 subjects aged 11 to 16 years in year 1, estimated a hierarchical growth curve model that emphasized the effects of age, life events, gender, and family cohesion on self-esteem. Results show a curvilinear relationship between age and self-esteem, suggesting that self-esteem is a…

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

    ERIC Educational Resources Information Center

    Murphy, Daniel L.; Pituch, Keenan A.

    2009-01-01

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

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

    ERIC Educational Resources Information Center

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

    2013-01-01

    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…

  18. Accuracy of Estimates and Statistical Power for Testing Meditation in Latent Growth Curve Modeling

    ERIC Educational Resources Information Center

    Cheong, JeeWon

    2011-01-01

    The latent growth curve modeling (LGCM) approach has been increasingly utilized to investigate longitudinal mediation. However, little is known about the accuracy of the estimates and statistical power when mediation is evaluated in the LGCM framework. A simulation study was conducted to address these issues under various conditions including…

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

    ERIC Educational Resources Information Center

    Beecher, Constance C.

    2011-01-01

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

  20. Transcriptome analysis of genetic mechanism of growth curve inflection point using a pig model.

    PubMed

    Shen, Linyuan; Zhang, Shunhua; Zhu, Li

    2015-12-01

    Animal growth curves play an important role for animal breeders to optimize feeding and management strategies (De Lange et al., 2001 [1]; Brossard et al., 2009 [2]; Strathe et al., 2010 [3]). However, the genetic mechanism of the phenotypic difference between the inflection point and noninflection points of the growth curve remains unclear. Here, we report the differentially expressed gene pattern in pig longissimus dorsi among three typical time points of the growth curve, inflection point (IP), before inflection point (BIP) and after inflection point (AIP). The whole genome RNA-seq data was deposited at GenBank under the accession number PRJNA2284587. The RNA-seq libraries generated 117 million reads of 5.89 gigabases in length. Totals of 21,331, 20,996 and 20,139 expressed transcripts were identified in IP, UIP and AIP, respectively. Furthermore, we identified 757 differentially expressed genes (DEGs) between IP and UIP, and 271 DEGs between AIP and IP. Function enrichment analysis of DEGs found that the highly expressed genes in IP were mainly enriched in energy metabolism, global transcriptional activity and bone development intensity. This study contributes to reveal the genetic mechanism of growth curve inflection point. PMID:26697358

  1. Ignoring Individual Differences in Times of Assessment in Growth Curve Modeling

    ERIC Educational Resources Information Center

    Coulombe, Patrick; Selig, James P.; Delaney, Harold D.

    2016-01-01

    Researchers often collect longitudinal data to model change over time in a phenomenon of interest. Inevitably, there will be some variation across individuals in specific time intervals between assessments. In this simulation study of growth curve modeling, we investigate how ignoring individual differences in time points when modeling change over…

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

    ERIC Educational Resources Information Center

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

    2003-01-01

    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)

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

    ERIC Educational Resources Information Center

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

    2009-01-01

    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…

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

    ERIC Educational Resources Information Center

    Hwu, Fenfang; Pan, Wei; Sun, Shuyan

    2014-01-01

    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…

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

    ERIC Educational Resources Information Center

    Wanstrom, Linda

    2009-01-01

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

  6. Mode of physical activity and self-efficacy in older adults: a latent growth curve analysis.

    PubMed

    McAuley, E; Katula, J; Mihalko, S L; Blissmer, B; Duncan, T E; Pena, M; Dunn, E

    1999-09-01

    A randomized controlled trial examined the effect of two physical activity modes on changes in self-efficacy over the course of a 12-month period in older, formerly sedentary adults (N = 174, M age = 65.5 years). Participants were randomized into either an aerobic activity group or a stretching and toning group. Structural equation modeling was employed to conduct multiple sample latent growth curve analyses of individual growth in exercise and physical self-efficacy over time. Results revealed a curvilinear growth pattern for both types of efficacy with increases occurring over the first 6 months followed by declines at the 6-month follow-up. There was a significant treatment by mean level growth interaction for exercise efficacy with both groups increasing over time, but the aerobic group evidenced a twofold increase in growth over the stretching group. Structural analyses indicated that frequency of exercise participation was a significant predictor of overall growth in efficacy, and improvements in fitness were only related to exercise efficacy growth in the stretching group. Findings are discussed in terms of social cognitive theory and further application of latent growth curve modeling to studies of physical activity effects in older adults. PMID:10542821

  7. Bacterial Growth on Chitosan-Coated Polypropylene Textile

    PubMed Central

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

    2012-01-01

    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

  8. Bacterial growth on chitosan-coated polypropylene textile.

    PubMed

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

    2012-01-01

    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

  9. Re-Evaluating Sexual Violence Prevention Through Bystander Education: A Latent Growth Curve Approach.

    PubMed

    Shaw, Jessica; Janulis, Patrick

    2016-10-01

    Recently, there has been a call for more advanced analytic techniques in violence against women research, particularly in community interventions that use longitudinal designs. The current study re-evaluates experimental evaluation data from a sexual violence bystander intervention program. Using an exploratory latent growth curve approach, we were able to model the longitudinal growth trajectories of individual participants over the course of the entire study. Although the results largely confirm the original evaluation findings, the latent growth curve approach better fits the demands of "messy" data (e.g., missing data, varying number of time points per participant, and unequal time spacing within and between participants) that are frequently obtained during a community-based intervention. The benefits of modern statistical techniques to practitioners and researchers in the field of sexual violence prevention, and violence against women more generally, are further discussed. PMID:25888503

  10. Multilevel models for repeated measures research designs in psychophysiology: an introduction to growth curve modeling.

    PubMed

    Kristjansson, Sean D; Kircher, John C; Webb, Andrea K

    2007-09-01

    Psychophysiologists often use repeated measures analysis of variance (RMANOVA) and multivariate analysis of variance (MANOVA) to analyze data collected in repeated measures research designs. ANOVA and MANOVA are nomothetic approaches that focus on group means. Newer multilevel modeling techniques are more informative than ANOVA because they characterize both group-level (nomothetic) and individual-level (idiographic) effects, yielding a more complete understanding of the phenomena under study. This article was written as an introduction to growth curve modeling for applied researchers. A growth model is defined that can be used in place of RMANOVAs and MANOVAs for single-group and mixed repeated measures designs. The model is expanded to test and control for the effects of baseline levels of physiological activity on stimulus-specific responses. Practical, conceptual, and statistical advantages of growth curve modeling are discussed. PMID:17596179

  11. Using growth curves to forecast regional resource recovery: approaches, analytics and consistency tests.

    PubMed

    Sorrell, Steve; Speirs, Jamie

    2014-01-13

    There is growing concern about the depletion of hydrocarbon resources and the risk of near-term peaks in production. These concerns hinge upon contested estimates of the recoverable resources of different regions and the associated forecasts of regional production. Beginning with Hubbert, an influential group of analysts have used growth curves both to estimate recoverable resources and to forecast future production. Despite widespread use, these 'curve-fitting' techniques remain a focus of misunderstanding and dispute. The aim of this paper is to classify and explain these techniques and to identify both their relative suitability in different circumstances and the expected level of confidence in their results. The paper develops a mathematical framework that maps curve-fitting techniques onto the available data for conventional oil and highlights the critical importance of the so-called 'reserve growth'. It then summarizes the historical origins, contemporary application and strengths and weaknesses of each group of curve-fitting techniques and uses illustrative data from a number of oil-producing regions to explore the extent to which these techniques provide consistent estimates of recoverable resources. The paper argues that the applicability of curve-fitting techniques is more limited than adherents claim, the confidence bounds on the results are wider than commonly assumed and the techniques have a tendency to underestimate recoverable resources. PMID:24298074

  12. Growth curves for Turkish Girls with Turner Syndrome: Results of the Turkish Turner Syndrome Study Group

    PubMed Central

    Darendeliler, Feyza; Yeşilkaya, Ediz; Bereket, Abdullah; Baş, Firdevs; Bundak, Rüveyde; Sarı, Erkan; Küçükemre Aydın, Banu; Darcan, Şükran; Dündar, Bumin; Büyükinan, Muammer; Kara, Cengiz; Mazıcıoğlu, Mümtaz M.; Adal, Erdal; Akıncı, Ayşehan; Atabek, Mehmet Emre; Demirel, Fatma; Çelik, Nurullah; Özkan, Behzat; Özhan, Bayram; Orbak, Zerrin; Ersoy, Betül; Doğan, Murat; Ataş, Ali; Turan, Serap; Gökşen, Damla; Tarım, Ömer; Yüksel, Bilgin; Ercan, Oya; Hatun, Şükrü; Şimşek, Enver; Ökten, Ayşenur; Abacı, Ayhan; Döneray, Hakan; Özbek, Mehmet Nuri; Keskin, Mehmet; Önal, Hasan; Akyürek, Nesibe; Bulan, Kezban; Tepe, Derya; Emeksiz, Hamdi Cihan; Demir, Korcan; Kızılay, Deniz; Topaloğlu, Ali Kemal; Eren, Erdal; Özen, Samim; Demirbilek, Hüseyin; Abalı, Saygın; Akın, Leyla; Eklioğlu, Beray Selver; Kaba, Sultan; Anık, Ahmet; Baş, Serpil; Ünüvar, Tolga; Sağlam, Halil; Bolu, Semih; Özgen, Tolga; Doğan, Durmuş; Çakır, Esra Deniz; Şen, Yaşar; Andıran, Nesibe; Çizmecioğlu, Filiz; Evliyaoğlu, Olcay; Karagüzel, Gülay; Pirgon, Özgür; Çatlı, Gönül; Can, Hatice Dilek; Gürbüz, Fatih; Binay, Çiğdem; Baş, Veysel Nijat; Sağlam, Celal; Gül, Davut; Polat, Adem; Açıkel, Cengizhan; Cinaz, Peyami

    2015-01-01

    Objective: Children with Turner syndrome (TS) have a specific growth pattern that is quite different from that of healthy children. Many countries have population-specific growth charts for TS. Considering national and ethnic differences, we undertook this multicenter collaborative study to construct growth charts and reference values for height, weight and body mass index (BMI) from 3 years of age to adulthood for spontaneous growth of Turkish girls with TS. Methods: Cross-sectional height and weight data of 842 patients with TS, younger than 18 years of age and before starting any therapy, were evaluated. Results: The data were processed to calculate the 3rd, 10th, 25th, 50th, 75th, 90th and 97th percentile values for defined ages and to construct growth curves for height-for-age, weight-for-age and BMI-for-age of girls with TS. The growth pattern of TS girls in this series resembled the growth pattern of TS girls in other reports, but there were differences in height between our series and the others. Conclusion: This study provides disease-specific growth charts for Turkish girls with TS. These disease-specific national growth charts will serve to improve the evaluation of growth and its management with growth-promoting therapeutic agents in TS patients. PMID:26831551

  13. Nanoparticle-Templated Formation and Growth Mechanism of Curved Protein Polymer Fibrils.

    PubMed

    Pham, Thao T H; Rombouts, Wolf H; Fokkink, Remco; Stuart, Marc C A; Cohen Stuart, Martien A; Kleijn, J Mieke

    2016-07-11

    We investigated the growth of biosynthetic protein polymers with templated curvature on pluronic nanospheres. The protein has a central silk-like block containing glutamic residues (S(E)) and collagen-like end-blocks (C). The S(E) blocks stack into filaments when their charge is removed (pH <5). Indeed, at low pH curved and circular fibers are formed at the surface of the nanospheres, which keep their shape after removal of the pluronics. The data reveal the mechanism of the templated fibril-growth: The growth of protein assemblies is nucleated in solution; small protein fibrils adsorb on the nanospheres, presumably due to hydrogen bond formation between the silk-like blocks and the pluronic PEO blocks. The surface of the pluronic particles templates further growth. At relatively low protein/pluronic weight ratios, only a fraction of the nanospheres bears protein fibers, pointing to a limiting amount of nuclei in solution. Because the nanospheres capture fibrils at an early stage of growth, they can be used to separate growth and nucleation rates in protein fibril formation. Moreover, the nanoparticle-templated growth of stable curved fibers opens ways to build proteinaceous nanocapsules from designed protein polymers. PMID:27250876

  14. Effect of flow and active mixing on bacterial growth in a colon-like geometry

    NASA Astrophysics Data System (ADS)

    Cremer, Jonas; Segota, Igor; Arnoldini, Markus; Groisman, Alex; Hwa, Terence

    The large intestine harbors bacteria from hundreds of species, with bacterial densities reaching up to 1012 cells per gram. Many different factors influence bacterial growth dynamics and thus bacterial density and microbiota composition. One dominant force is flow which can in principle lead to a washout of bacteria from the proximal colon. Active mixing by Contractions of the colonic wall together with bacterial growth might counteract such flow-forces and allow high bacterial densities to occur. As a step towards understanding bacterial growth in the presence of mixing and flow, we constructed an in-vitro setup where controlled wall-deformations of a channel emulate Contractions. We investigate growth along the channel under a steady nutrient inflow. In the limits of no or very frequent Contractions, the device behaves like a plug-flow reactor and a chemostat respectively. Depending on mixing and flow, we observe varying spatial gradients in bacterial density along the channel. Active mixing by deformations of the channel wall is shown to be crucial in maintaining a steady-state bacterial population in the presence of flow. The growth-dynamics is quantitatively captured by a simple mathematical model, with the effect of mixing described by an effective diffusion term.

  15. Polymer film deposition on agar using a dielectric barrier discharge jet and its bacterial growth inhibition

    NASA Astrophysics Data System (ADS)

    Tsai, T.-C.; Cho, J.; Mcintyre, K.; Jo, Y.-K.; Staack, D.

    2012-08-01

    Polymer film deposition on agar in ambient air was achieved using the helium dielectric barrier discharge jet (DBD jet) fed with polymer precursors, and the bacterial growth inhibition due to the deposited film was observed. The DBD jet with precursor addition was more efficient at sterilization than a helium-only DBD jet. On the areas where polymer films cover the agar the bacterial growth was significantly inhibited. The inhibition efficacy showed dependence on the film thickness. The DBD jet without precursor also created a modified agar layer, which may slow the growth of some bacterial strains.

  16. Divergent selection for shape of growth curve in Japanese quail. 4. Carcase composition and thyroid hormones.

    PubMed

    Hyánková, L; Novotná, B; Darras, V M

    2008-03-01

    1. Changes in the relative weights of carcase, abdominal fat, breast and leg muscles, and plasma thyroid hormone concentrations occurring during the first 6 weeks of postnatal growth were analysed in males of HG and LG lines divergently selected for high and low relative body weight (BW) gain between 11 and 28 d of age, respectively, and constant adult BW. 2. The second week of postnatal life was a critical age at which the HG males exhibited a relatively faster growth in comparison to their LG counterparts and permanently exceeded LG males in the percentage by weight of carcase, breast and leg muscle. A higher production of muscle tissues was associated with lower accumulation of abdominal fat before sexual maturity. 3. In general, the plasma T(3) level of HG quail exceeded that of LG quail. Nevertheless, significant differences were found only at 14, 21 and 28 d of age, that is, in the period during which the highest inter-line differences in relative growth rate were noted. Also the T(3)/T(4) ratio followed a similar trend while plasma T(4) level showed no clear and consistent inter-line differences. 4. The results suggest that the selection for the shape of the growth curve, like the selection for body fat, modifies the carcase quality owing to shortening/prolongation of the acceleration growth phase. Individuals with a short acceleration phase of the growth curve are characterised by low carcase quality during the fattening period. PMID:18409082

  17. A probabilistic neural network approach for modeling and classification of bacterial growth/no-growth data.

    PubMed

    Hajmeer, M; Basheer, I

    2002-10-01

    In this paper, we propose to use probabilistic neural networks (PNNs) for classification of bacterial growth/no-growth data and modeling the probability of growth. The PNN approach combines both Bayes theorem of conditional probability and Parzen's method for estimating the probability density functions of the random variables. Unlike other neural network training paradigms, PNNs are characterized by high training speed and their ability to produce confidence levels for their classification decision. As a practical application of the proposed approach, PNNs were investigated for their ability in classification of growth/no-growth state of a pathogenic Escherichia coli R31 in response to temperature and water activity. A comparison with the most frequently used traditional statistical method based on logistic regression and multilayer feedforward artificial neural network (MFANN) trained by error backpropagation was also carried out. The PNN-based models were found to outperform linear and nonlinear logistic regression and MFANN in both the classification accuracy and ease by which PNN-based models are developed. PMID:12133614

  18. Estimation of the growth curve and heritability of the growth rate for giant panda (Ailuropoda melanoleuca) cubs.

    PubMed

    Che, T D; Wang, C D; Jin, L; Wei, M; Wu, K; Zhang, Y H; Zhang, H M; Li, D S

    2015-01-01

    Giant panda cubs have a low survival rate during the newborn and early growth stages. However, the growth and developmental parameters of giant panda cubs during the early lactation stage (from birth to 6 months) are not well known. We examined the growth and development of giant panda cubs by the Chapman growth curve model and estimated the heritability of the maximum growth rate at the early lactation stage. We found that 83 giant panda cubs reached their maximum growth rate at approximately 75-120 days after birth. The body weight of cubs at 75 days was 4285.99 g. Furthermore, we estimated that the heritability of the maximum growth rate was moderate (h(2) = 0.38). Our study describes the growth and development of giant panda cubs at the early lactation stage and provides valuable growth benchmarks. We anticipate that our results will be a starting point for more detailed research on increasing the survival rate of giant panda cubs. Feeding programs for giant panda cubs need further improvement. PMID:25867378

  19. A Case Study of a Computer Assisted Learning Unit, "The Growth Curve of Microorganisms": Development, Implementation, and Evaluation.

    ERIC Educational Resources Information Center

    Huppert, Jehuda; Lazarovitz, Reuven

    This three-part paper describes the development of a software program called "The Growth Curve of Microorganisms" for a tenth-grade biology class. Designed to improve students' cognitive skills, the program enables them to investigate, through computer simulations, the impact upon the growth curve of a population of three variables: temperature,…

  20. Prediction of stable crack growth and instability using the V sub R-curve method

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.

    1985-01-01

    A methodology is presented for predicting stable crack growth and instability of cracked structural components from results of laboratory tests on metallic materials under plane-stress conditions. The methodology is based on the displacement V sub R at the tip of a stably tearing crack. Basically, the V sub R-curve method is a resistance curve approach, such as K sub R and J sub R, except that the 'crack drive' is written in terms of crack-tip displacement instead of K or J. The relationship between crack-tip-opening displacement, crack length, specimen type, and tensile properties is derived from the Dugdale model for the cracked structure of interest. This report describes the laboratory test procedure and calculations used to obtain the V sub R resistance curve from fracture tests of compact or of middle-crack tension (formally center-crack) specimens. The analysis procedure used to predict stable crack growth and instability of any through-the-thickness crack configuration made of the same material and thickness, and tested under the same environmental conditions, is presented. The various limitations of the present V sub R curve method are given. Four example calculations and predictions are shown.

  1. Theoretical quasar emission-line profiles. I - Curve-of-growth effects on observed profiles

    NASA Technical Reports Server (NTRS)

    Hubbard, E. N.; Puetter, R. C.

    1983-01-01

    Radiative transfer effects are examined in an investigation of the kinematics of quasar and Seyfert emission-line regions with pancake cloud geometries. Consideration is given only to the effects of limb brightening with the aspect angle of pancake clouds, assuming that all lines lie on a single portion of the curve of growth. This effect is coupled with several simple but plausible ensemble geometries and dynamics, and a number of theoretical emission-line profiles have been generated. It is shown that these profiles differ substantially depending on both the ensemble geometry and the portion of the curve of growth considered; for a given ensemble geometry, optically thick line profiles are different from optically thick profiles. It is shown that, for radiatively driven clouds, ensembles of clouds which have maximum velocities approaching the terminal velocity of the acceleration mechanism never produce acceptable profiles unless the cloud luminosity is a strongly decreasing function of radius.

  2. Evaluation of fatigue-crack growth rates by polynomial curve fitting. [Ti alloy plate

    NASA Technical Reports Server (NTRS)

    Davies, K. B.; Feddersen, C. E.

    1973-01-01

    Fundamental characterization of the constant-amplitude fatigue crack propagation is achieved by an analysis of the rate of change of crack length with change in number of applied loading cycles, defining the rate values such that they are consistent with the basic assumption of smoothness and continuity in the fatigue crack growth process. The technique used to satisfy the analytical conditions and minimize the effects of local material anomalies and experimental errors is that of fitting a smooth curve to the entire set of basic data by least square regression. This yields a well-behaved function relating the number of cycles to the crack length. By taking the first derivative of the function, the crack growth rate is obtained for each point. The class of curve fitting functions used in the analysis is the polynomial of degree n.

  3. A GROWTH CURVE MODEL OF LEARNING ACQUISITION AMONG COGNITIVELY NORMAL OLDER ADULTS

    PubMed Central

    Jones, Richard N.; Rosenberg, Adrienne L.; Morris, John N.; Allaire, Jason C.; McCoy, Karin J. M.; Marsiske, Michael; Kleinman, Ken P.; Rebok, George W.; Malloy, Paul F.

    2010-01-01

    The objective of this study was to model recall and learning on the Auditory Verbal Learning Test using latent growth curve techniques. Participants were older adults recruited for the ACTIVE cognitive intervention pilot. A series of nested models revealed that an approximately logarithmic growth curve model provided optimal fit to the data. Although recall and learning factors were statistically uncorrelated, a fitted multivariate model suggested that initial recall was significantly associated with demographic characteristics but unrelated to health factors and cognitive abilities. Individual differences in learning were related to race/ethnicity, speed of processing, verbal knowledge, and global cognitive function level. These results suggest that failing to recognize initial recall and learning as distinct constructs clouds the interpretation of supraspan memory tasks. PMID:16036723

  4. Effect of lag time distribution on the lag phase of bacterial growth - a Monte Carlo analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study is to use Monte Carlo simulation to evaluate the effect of lag time distribution of individual bacterial cells incubated under isothermal conditions on the development of lag phase. The growth of bacterial cells of the same initial concentration and mean lag phase durati...

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

    PubMed Central

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

    2013-01-01

    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 μM 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

  6. [[sup 3]H] Thymidine incorporation to estimate growth rates of anaerobic bacterial strains

    SciTech Connect

    Winding, A. )

    1992-08-01

    The incorporation of [[sup 3]H] thymidine by axenic cultures of anaerobic bacteria was investigated as a means to measure growth. The three fermentative strains and one of the methanogenic strains tested incorporated [[sup 3]H] thymidine during growth. It is concluded that the [[sup 3]H] thymidine incorporation method underestimates bacterial growth in anaerobic environments.

  7. Research note: Influence of body weight selection on the growth curve of turkeys.

    PubMed

    Anthony, N B; Emmerson, D A; Nestor, K E

    1991-01-01

    The growth curve of a population of turkeys selected for increased 16 wk BW (Line F) and a randombred control population (RBC2) was determined. It was concluded that the Gompertz equation best described the growth pattern of Lines F and RBC2 regardless of sex. Line F had higher BW at hatching, BW and slope at point of inflection (POI), and asymptotic BW than Line RBC2. Age at POI and asymptote were achieved later for Line RBC2 than for Line F. Male turkeys had higher BW and age at POI and BW and age at asymptote than females. Slope at POI was greater for females than for males. PMID:2017414

  8. Effect of Vibration on Bacterial Growth and Antibiotic Resistance

    NASA Technical Reports Server (NTRS)

    Juergensmeyer, Elizabeth A.; Juergensmeyer, Margaret A.

    2004-01-01

    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.

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

    SciTech Connect

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

    2005-09-08

    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.

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

    NASA Astrophysics Data System (ADS)

    Lambert, Guillaume; Kussell, Edo

    2013-03-01

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

  11. Divergent selection for shape of growth curve in Japanese quail. 1. Responses in growth parameters and food conversion.

    PubMed

    Hyánková, L; Knízetová, H; Dĕdková, L; Hort, J

    2001-12-01

    1. HG and LG quail lines selected for high and low relative weight gain between 11 and 28 d of age (RG11-28), respectively, and an unselected C line were compared. Mature body weight of both selected lines was held at that of the C line. Progeny of generation 6 were used for analysis. 2. Divergent selection for RG11-28 brought about opposite changes in the growth rates shortly after hatching. 3. Parameters of the Richards function were used to describe the growth curve. The largest differences between HG and LG lines occurred in age (t+) and body weight (y+) at the inflection point of the growth curve (on average for both sexes 28% and 20%, respectively). For HG quail, the parameter t+ was 5 d later than that for LG quail (18.6 vs 14.1 d for males and 20.6 vs 15.6 d for females, respectively), and consequently the parameter y+ was greater (90.3 vs 84.0 g for males and 104.5 vs 96.1 g for females, respectively). The shape of the growth curve expressed by the y+/A ratio was substantialy different for HG and LG quail (44.8% vs 39.6% for males and 43.5% vs 36.8% for females, respectively). 4. The food/gain ratios for the fattening period (3 to 35 d of age) were 3.21, 3.47 and 3.34 for the HG, LG and C lines, respectively. The HG quail started to utilise food more efficiently than the LG quail as early as 10 to 14 d, that is, at the age when their relative growth rate first became greater. 5. The relative deviations of the HG and LG lines from the C line are discussed. PMID:11811909

  12. Saguaro (Carnegiea gigantea, Cactaceae) age-height relationships and growth: the development of a general growth curve.

    PubMed

    Drezner, Taly Dawn

    2003-06-01

    Because the growth rate of saguaros varies across different environments, past studies on saguaro population structure required extensive data collection (often over many decades) followed by site-specific analysis to estimate age at the sampled locale. However, when height-growth data from different populations are compared, the overall shape of the growth curves is similar. In this study, a formula was developed to establish saguaro age-height relationships (using stepwise regression) that can be applied to any saguaro population and only requires a site-specific factor to adjust the curve to the local growth rate. This adjustment factor can be established more efficiently and requires less data than the full analyses required for previous studies. Saguaro National Park East (SNP-E) was used as the baseline factor, set to 1.0. Results yielded a factor of 0.743 for SNP West. When the formula was applied to 10-yr interval data from Organ Pipe Cactus National Monument (OPCNM) in Arizona, USA, this location had a factor of 0.617 (relative to SNP-E). With this formula and relatively little field sampling, the age of any individual saguaro (whether the individual was sampled or not) in any population can be estimated. PMID:21659186

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

    SciTech Connect

    Hobbs, D.

    2011-01-19

    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.

  14. Control of bacterial adhesion and growth on honeycomb-like patterned surfaces.

    PubMed

    Yang, Meng; Ding, Yonghui; Ge, Xiang; Leng, Yang

    2015-11-01

    It is a great challenge to construct a persistent bacteria-resistant surface even though it has been demonstrated that several surface features might be used to control bacterial behavior, including surface topography. In this study, we develop micro-scale honeycomb-like patterns of different sizes (0.5-10 μm) as well as a flat area as the control on a single platform to evaluate the bacterial adhesion and growth. Bacteria strains, Escherichia coli and Staphylococcus aureus with two distinct shapes (rod and sphere) are cultured on the platforms, with the patterned surface-up and surface-down in the culture medium. The results demonstrate that the 1 μm patterns remarkably reduce bacterial adhesion and growth while suppressing bacterial colonization when compared to the flat surface. The selective adhesion of the bacterial cells on the patterns reveals that the bacterial adhesion is cooperatively mediated by maximizing the cell-substrate contact area and minimizing the cell deformation, from a thermodynamic point of view. Moreover, study of bacterial behaviors on the surface-up vs. surface-down samples shows that gravity does not apparently affect the spatial distribution of the adherent cells although it indeed facilitates bacterial adhesion. Furthermore, the experimental results suggest that two major factors, i.e. the availability of energetically favorable adhesion sites and the physical confinements, contribute to the anti-bacterial nature of the honeycomb-like patterns. PMID:26302067

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

    PubMed

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

    2013-11-01

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

  16. Growth curve by Gompertz nonlinear regression model in female and males in tambaqui (Colossoma macropomum).

    PubMed

    De Mello, Fernanda; Oliveira, Carlos A L; Ribeiro, Ricardo P; Resende, Emiko K; Povh, Jayme A; Fornari, Darci C; Barreto, Rogério V; McManus, Concepta; Streit, Danilo

    2015-01-01

    Was evaluated the pattern of growth among females and males of tambaqui by Gompertz nonlinear regression model. Five traits of economic importance were measured on 145 animals during the three years, totaling 981 morphometric data analyzed. Different curves were adjusted between males and females for body weight, height and head length and only one curve was adjusted to the width and body length. The asymptotic weight (a) and relative growth rate to maturity (k) were different between sexes in animals with ± 5 kg; slaughter weight practiced by a specific niche market, very profitable. However, there was no difference between males and females up to ± 2 kg; slaughter weight established to supply the bigger consumer market. Females showed weight greater than males (± 280 g), which are more suitable for fish farming purposes defined for the niche market to larger animals. In general, males had lower maximum growth rate (8.66 g / day) than females (9.34 g / day), however, reached faster than females, 476 and 486 days growth rate, respectively. The height and length body are the traits that contributed most to the weight at 516 days (P <0.001). PMID:26628036

  17. Multi-Trait GWAS and New Candidate Genes Annotation for Growth Curve Parameters in Brahman Cattle.

    PubMed

    Crispim, Aline Camporez; Kelly, Matthew John; Guimarães, Simone Eliza Facioni; Fonseca e Silva, Fabyano; Fortes, Marina Rufino Salinas; Wenceslau, Raphael Rocha; Moore, Stephen

    2015-01-01

    Understanding the genetic architecture of beef cattle growth cannot be limited simply to the genome-wide association study (GWAS) for body weight at any specific ages, but should be extended to a more general purpose by considering the whole growth trajectory over time using a growth curve approach. For such an approach, the parameters that are used to describe growth curves were treated as phenotypes under a GWAS model. Data from 1,255 Brahman cattle that were weighed at birth, 6, 12, 15, 18, and 24 months of age were analyzed. Parameter estimates, such as mature weight (A) and maturity rate (K) from nonlinear models are utilized as substitutes for the original body weights for the GWAS analysis. We chose the best nonlinear model to describe the weight-age data, and the estimated parameters were used as phenotypes in a multi-trait GWAS. Our aims were to identify and characterize associated SNP markers to indicate SNP-derived candidate genes and annotate their function as related to growth processes in beef cattle. The Brody model presented the best goodness of fit, and the heritability values for the parameter estimates for mature weight (A) and maturity rate (K) were 0.23 and 0.32, respectively, proving that these traits can be a feasible alternative when the objective is to change the shape of growth curves within genetic improvement programs. The genetic correlation between A and K was -0.84, indicating that animals with lower mature body weights reached that weight at younger ages. One hundred and sixty seven (167) and two hundred and sixty two (262) significant SNPs were associated with A and K, respectively. The annotated genes closest to the most significant SNPs for A had direct biological functions related to muscle development (RAB28), myogenic induction (BTG1), fetal growth (IL2), and body weights (APEX2); K genes were functionally associated with body weight, body height, average daily gain (TMEM18), and skeletal muscle development (SMN1). Candidate

  18. Multi-Trait GWAS and New Candidate Genes Annotation for Growth Curve Parameters in Brahman Cattle

    PubMed Central

    Crispim, Aline Camporez; Kelly, Matthew John; Guimarães, Simone Eliza Facioni; e Silva, Fabyano Fonseca; Fortes, Marina Rufino Salinas; Wenceslau, Raphael Rocha; Moore, Stephen

    2015-01-01

    Understanding the genetic architecture of beef cattle growth cannot be limited simply to the genome-wide association study (GWAS) for body weight at any specific ages, but should be extended to a more general purpose by considering the whole growth trajectory over time using a growth curve approach. For such an approach, the parameters that are used to describe growth curves were treated as phenotypes under a GWAS model. Data from 1,255 Brahman cattle that were weighed at birth, 6, 12, 15, 18, and 24 months of age were analyzed. Parameter estimates, such as mature weight (A) and maturity rate (K) from nonlinear models are utilized as substitutes for the original body weights for the GWAS analysis. We chose the best nonlinear model to describe the weight-age data, and the estimated parameters were used as phenotypes in a multi-trait GWAS. Our aims were to identify and characterize associated SNP markers to indicate SNP-derived candidate genes and annotate their function as related to growth processes in beef cattle. The Brody model presented the best goodness of fit, and the heritability values for the parameter estimates for mature weight (A) and maturity rate (K) were 0.23 and 0.32, respectively, proving that these traits can be a feasible alternative when the objective is to change the shape of growth curves within genetic improvement programs. The genetic correlation between A and K was -0.84, indicating that animals with lower mature body weights reached that weight at younger ages. One hundred and sixty seven (167) and two hundred and sixty two (262) significant SNPs were associated with A and K, respectively. The annotated genes closest to the most significant SNPs for A had direct biological functions related to muscle development (RAB28), myogenic induction (BTG1), fetal growth (IL2), and body weights (APEX2); K genes were functionally associated with body weight, body height, average daily gain (TMEM18), and skeletal muscle development (SMN1). Candidate

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

    ERIC Educational Resources Information Center

    Grady, Matthew W.; Beretvas, S. Natasha

    2010-01-01

    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…

  20. Genetic parameters of traits associated with the growth curve in Segureña sheep.

    PubMed

    Lupi, T M; León, J M; Nogales, S; Barba, C; Delgado, J V

    2016-05-01

    This paper studies the genetic importance of growth curve parameters and their relevance as selection criteria in breeding programmes of Segureño sheep. Logistic and Verhulst growth functions were chosen for their best fit to BW/age in this breed; the first showed the best general fit and the second the best individual fit. Live weights of 41 330 individuals from the historical archives of the National Association of Segureña Sheep Breeders were used in the analysis. The progeny of 1464 rams and 27 048 ewes were used to study the genetic and phenotypic parameters of growth curve parameters and derived traits. Reproductive management in the population consists in controlled natural mating inside every herd, with a minimum of 15% of the females fertilized by artificial insemination with fresh semen; with the purpose being the herd genetic connections, all herd genealogies are screened with DNA markers. Estimates of growth curve parameters from birth to 80 days were obtained for each individual and each function by the non-linear regression procedure using IBM SPSS statistics (version 21) with the Levenberg-Marquart estimation method. (Co)variance components and genetic parameters were estimated by using the REML/Animal model methodology. The heritability of mature weight was estimated as 0.41±0.042 and 0.38±0.021 with the logistic and Verhulst models, respectively, and the heritability of other parameters ranged from 0.41 to 0.62 and 0.37 to 0.61, with the models, respectively. A negative genetic correlation between mature weight and rate of maturing was found. PMID:26696444

  1. Genetic parameter estimates of growth curve and reproduction traits in Japanese quail.

    PubMed

    Narinc, Dogan; Karaman, Emre; Aksoy, Tulin; Firat, Mehmet Ziya

    2014-01-01

    The goal of selection studies in broilers is to obtain genetically superior chicks in terms of major economic traits, which are mainly growth rate, meat yield, and feed conversion ratio. Multiple selection schedules for growth and reproduction are used in selection programs within commercial broiler dam lines. Modern genetic improvement methods have not been applied in experimental quail lines. The current research was conducted to estimate heritabilities and genetic correlations for growth and reproduction traits in a Japanese quail flock. The Gompertz equation was used to determine growth curve parameters. The Gibbs sampling under a multi-trait animal model was applied to estimate the heritabilities and genetic correlations for these traits. A total of 948 quail were used with complete pedigree information to estimate the genetic parameters. Heritability estimates of BW, absolute and relative growth rates at 5 wk of age (AGR and RGR), β0 and β2 parameters, and age at point of inflection (IPT) of Gompertz growth curve, total egg number (EN) from the day of first lay to 24 wk of age were moderate to high, with values ranging from 0.25 to 0.40. A low heritability (0.07) for fertility (FR) and a strong genetic correlation (0.83) between FR and EN were estimated in our study. Body weight exhibited negative genetic correlation with EN, FR, RGR, and IPT. This genetic antagonism among the mentioned traits may be overcome using modern poultry breeding methods such as selection using multi-trait best linear unbiased prediction and crossbreeding. PMID:24570419

  2. The effect of pH and storage on copper speciation and bacterial growth in complex growth media.

    PubMed

    Hasman, Henrik; Bjerrum, Morten J; Christiansen, Lasse E; Bruun Hansen, Hans Christian; Aarestrup, Frank M

    2009-07-01

    In this paper we examine how the bacterial growth is influenced by the availability of copper ions in complex Mueller Hinton growth media. The data shows that the free copper concentration is seven to eight orders of magnitude lower the total copper concentration and that there seems to be a better correlation between the free copper concentration and bacterial growth, than for the total copper concentration and growth. Furthermore, it is shown that the initial pH influences the amount of free copper ions in the media and that this has a direct effect on the ability of bacterial cultures to grow. However, there still remains an effect of pH on bacterial growth which cannot be attributed to the influence of the Cu(2+) concentration alone. The study also shows that the sterilization treatment can have some effect on the availability of copper ions in the media over time. Freshly autoclaved and sterile filtered media contain the same level of free copper ions and perform equally well in the biological assay. However, storage in the refrigerator influences the free copper contents in media, which have been autoclaved, but not in media, which were sterile filtered. Therefore, the latter method is to be recommended, when working with bacterial copper testing. PMID:19341771

  3. Development of luminescent pH sensor films for monitoring bacterial growth through tissue

    PubMed Central

    Wang, Fenglin; Raval, Yash; Chen, Hongyu; Tzeng, Tzuen-Rong J.; DesJardins, John D.

    2014-01-01

    Although implanted medical devices (IMDs) offer many benefits, they are susceptible to bacterial colonization and infections. Such infections are difficult to treat because bacteria could form biofilms on the implant surface, which reduce antibiotics penetration and generate local dormant regions with low pH and low oxygen. In addition, these infections are hard to detect early because biofilms are often localized on the surface. Herein, an optical sensor film is developed to detect local acidosis on an implanted surface. The film contains both upconverting particles (UCPs) that serve as a light source and a pH indicator that alters the luminescence spectrum. When irradiated with 980 nm light, the UCPs produce deeply penetrating red light emission, while generating negligible autofluorescence in the tissue. The basic form of the pH indicator absorbs more of upconversion luminescence at 661 nm than at 671 nm and consequently the spectral ratio indicates pH. Implanting this pH sensor film beneath 6-7 mm of porcine tissue does not substantially affect the calibration curve because the peaks are closely spaced. Furthermore, growth of Staphylococcus epidermidis on the sensor surface causes a local pH decrease that can be detected non-invasively through the tissue. PMID:23832869

  4. 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...

  5. 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...

  6. 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...

  7. Effects of Au/Fe and Fe nanoparticles on Serratia bacterial growth and production of biosurfactant.

    PubMed

    Liu, Jia; Vipulanandan, Cumaraswamy

    2013-10-01

    The overall objective of this study was to compare the effects of Au/Fe and Fe nanoparticles on the growth and performance of Serratia Jl0300. The nanoparticle effect was quantified not only by the bacterial growth on agar plate after 1 hour interaction with the nanoparticles, but also by its production of a biosurfactant from used vegetable oil. The nanoparticles were prepared using the foam method. The concentrations of the nanoparticles used for the bacterial interaction study were varied from 1 mg/L to 1 g/L. The test results showed that the effect of nanoparticles on the bacterial growth and biosurfactant production varied with nanoparticle type, concentrations, and interaction time with the bacteria. Au/Fe nanoparticles didn't show toxicity to Serratia after short time (1 h) exposure, while during 8 days fermentation Au/Fe nanoparticles inhibited the growth of Serratia as well as the biosurfactant production when the concentration of the nanoparticles was higher than 10mg/L. Fe nanoparticles showed inhibition effects to bacterial growth both after short time and long time interaction with Serratia, as well as to biosurfactant production when its concentration was higher than 100 mg/L. Based on the trends observed in this study, analytical models have been developed to predict the bacterial growth and biosurfactant production with varying concentrations of nanoparticles. PMID:23910295

  8. Using growth curve analysis to examine challenges in instrumentation in longitudinal measurement in home visiting.

    PubMed

    Goltz, Heather Honoré; Mena, Kristin Cotter; Swank, Paul R

    2014-01-01

    Home visitation programs aim to decrease child maltreatment, yet limited longitudinal data exists concerning their screening and assessment instruments. "At risk" families (N = 2,054) were screened using the Family Stress Checklist and referred to Healthy Families Indiana. The Home Observation Measurement of the Environment Scale (HOME) and Community Life Skills Scale (CLS) were administered at multiple intervals. Growth curve analyses indicate families with lower HOME and CLS scores received more home visits and visits between assessments. However, these instruments may have "ceiling effects" and may be unsuitable for longitudinal assessment and program evaluation. Programmatic changes were made based on evaluation results. PMID:24405137

  9. Diffusion-limited growth in bacterial colony formation

    NASA Astrophysics Data System (ADS)

    Matsushita, Mitsugu; Fujikawa, Hiroshi

    1990-09-01

    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 ones in a colony, the repulsion between two neighboring colonies and the tendency to grow toward nutrient. These effects are all characteristic of the pattern formation in a Laplacian field. This finding implies the importance of physical properties of the environment for the morphology of bacterial colonies in general.

  10. Logistic growth curve of chickens: a comparison of techniques to estimate parameters.

    PubMed

    Grossman, M; Bohren, B B; Anderson, V L

    1985-01-01

    Parameters of a mathematical function of growth, fit to the body weight curve of two randombred control populations of each sex of chickens from hatching through 45 weeks of age, were estimated. The logistic function was chosen from among growth formulae that express rate of gain as a function of weight at a given time and gain to be made. Two logistic parameters, growth-rate constant and age at the point of inflection, were estimated by the methods of sample quantiles and nonlinear regression from weekly mean body weights of 225 males and 281 females of the Rhode Island Red (RIR) line, and 164 males and 239 females of the White Leghorn (WL) line. Males had a larger growth-rate constant than females of the same line. The RIR line had a larger rate constant than the WL line, for each sex. Age at the point of inflection was similar for males and females in the RIR line, but smaller for males than females in the WL line. Sample quantiles yielded larger, less precise estimates of the growth-rate constant than nonlinear regression. Estimates of age at the point of inflection were usually smaller using sample quantiles. PMID:4056375

  11. Differentiation of bacterial colonies and temporal growth patterns using hyperspectral imaging

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

  12. Description of the growth curve for Angus pasture-fed cows under extensive systems.

    PubMed

    Goldberg, V; Ravagnolo, O

    2015-09-01

    Growth curves are useful for describing the sigmoid shape of an animal's weight pattern over time. The purpose of the present study was to describe, for the first time, a complete growth curve for pasture-fed Angus cows in Uruguay and to analyze the major fixed effects that affect the estimation of mature cow weight (CW). A total of 22,743 records from 5,284 cows belonging to 73 herds were used in the statistical analysis. Five nonlinear models (Brody, Gompertz, Von Bertalanffy, logistic, and Richards) and a 3-knot cubic spline function were fitted to model weight change across age. Body weights were recorded at birth, weaning, and 18 mo and as an adult (at 2.3-3.6, 3.6-4.6, 4.6 to 5.6, 5.6 to 6.6, and 6.6 to 8.1 yr). After preliminary analyses, the fixed effects included in the model to estimate CW were BCS, herd, year and month of measurement, and age of dam. The herd and BCS were the major significant sources of variation. The Richards model had the lowest values for Akaike information criterion, Bayesian information criterion, and -2 log likelihood, with the asymptotic weight being 542 kg. The spline function was the model that fitted the data most closely to the observed weights followed by the Richards function. The Richards model gave better predictions of weights from birth to maturity than the other 4 nonlinear models, because these functions were shown to over- or underestimate weights at different ages in this beef cattle data set. The predicted curve showed that cows reach mature CW after 5 yr of age, which is the age commonly assumed as adult weight in beef cattle. Results form this analysis allowed the estimation of CW and rate of maturing and to take knowledge of the shape of growth curve for Angus females in Uruguay under extensive conditions, helping breeders to take selection decisions. In this way, breeders can optimize the management and efficiency for each production system. PMID:26440328

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  14. Scattering in the atmosphere of Venus. I - Line profiles and curves of growth for isotropic scattering

    NASA Technical Reports Server (NTRS)

    Young, L. D. G.; Kattawar, G. W.

    1976-01-01

    Line profiles and curves of growth were computed for both reflected and transmitted radiation for typical lines in CO2 bands (in the photographic infrared) which occur in the spectrum of Venus. In the model, the pressure variation with altitude was considered, and the base of the cloud deck was set at the 2 bar level. The temperature was held constant at 250 K, and a Voigt profile was used for the line shape. It was also assumed that the scale height of the cloud particles was equal to the scale height of the gas. The calculations were made for four values of the scattering optical thickness (0.1, 1.0, and 100) using a continuum single-scattering albedo of 0.9975 (which gives a Bond albedo of 0.896 for a scattering optical thickness of 100, the value observed for Venus at these wavelengths). Curves of growth are also presented for reflected radiation which has been averaged over the visible disk for three values of the Venus phase angle (0, 86, and 166 deg).

  15. Inhibition of bacterial growth by iron oxide nanoparticles with and without attached drug: Have we conquered the antibiotic resistance problem?

    NASA Astrophysics Data System (ADS)

    Armijo, Leisha M.; Jain, Priyanka; Malagodi, Angelina; Fornelli, F. Zuly; Hayat, Allison; Rivera, Antonio C.; French, Michael; Smyth, Hugh D. C.; Osiński, Marek

    2015-03-01

    Pseudomonas aeruginosa is among the top three leading causative opportunistic human pathogens, possessing one of the largest bacterial genomes and an exceptionally large proportion of regulatory genes therein. It has been known for more than a decade that the size and complexity of the P. aeruginosa genome is responsible for the adaptability and resilience of the bacteria to include its ability to resist many disinfectants and antibiotics. We have investigated the susceptibility of P. aeruginosa bacterial biofilms to iron oxide (magnetite) nanoparticles (NPs) with and without attached drug (tobramycin). We also characterized the susceptibility of zero-valent iron NPs, which are known to inactivate microbes. The particles, having an average diameter of 16 nm were capped with natural alginate, thus doubling the hydrodynamic size. Nanoparticle-drug conjugates were produced via cross-linking drug and alginate functional groups. Drug conjugates were investigated in the interest of determining dosage, during these dosage-curve experiments, NPs unbound to drug were tested in cultures as a negative control. Surprisingly, we found that the iron oxide NPs inhibited bacterial growth, and thus, biofilm formation without the addition of antibiotic drug. The inhibitory dosages of iron oxide NPs were investigated and the minimum inhibitory concentrations are presented. These findings suggest that NP-drug conjugates may overcome the antibiotic drug resistance common in P. aeruginosa infections.

  16. Mode of growth of bacterial pathogens in chronic polymicrobial human osteomyelitis.

    PubMed Central

    Marrie, T J; Costerton, J W

    1985-01-01

    Direct examination of material from two cases of persistent (2 and 60 years) osteomyelitis by morphological and culture techniques showed that the pathogens comprised several bacterial species whose cells grew predominantly in discrete exopolysaccharide-enclosed microcolonies made up of a single bacterial morphotype. Bacterial microcolonies were seen between tissue elements in infected connective tissue, and the microcolonies adherent to bone surfaces coalesced to form extensive biofilms that occluded the surfaces of dead bone in sequestrae. Decalcification techniques were required to examine the interior of infected bone, but recognizable remnants were associated with very large amounts of fibrous, ruthenium red-stained material. All bacterial growth in these persistent infections occurred within an intercellular matrix, and some elements of this matrix, which was fibrous in transmission electron microscopy and amorphous in scanning electron microscopy, were associated with the surfaces of bacterial cells in a manner that suggested their production by these organisms. All of the implications of this microcolony mode of bacterial growth in osteomyelitis, and in other chronic bacterial diseases, have yet to be determined. Images PMID:4066923

  17. Analyzing Exercise Behaviors during the College Years: Results from Latent Growth Curve Analysis

    PubMed Central

    Wittman, Werner

    2016-01-01

    The objective of this study is to analyze changes in the predictors of physical activity behavior among college students. The Theory of Planned Behavior served as its theoretical framework. Methods: Among an initial sample of 417 college students, 195 participants completed a validated questionnaire measuring attitudes, subjective norms, perceived control, intentions and self-reported physical activity, at the beginning and end of each of 3 college semesters. Latent growth curve modeling analyses were conducted to examine the relationships between the trajectories of changes in PA, intentions, attitudes, subjective norms, and perceived control. Results: Good fit indices supported the validity of the proposed longitudinal model (CFI > .97, RMSEA < .05). Changes in perceived control (γ = 0.57) were significantly linked with changes in intentions (p < .05). Perceived control (γ = 0.28) and intention growth (γ = 0.36) predicted behavior changes (p < .05). No gender differences were observed on attitudes, subjective norms and perceived control (p > .10). However, girls tend to have higher growth parameters on intentions and physical activity (p < .05). In summary, intentions and physical activity has significantly increased over 3 college semesters (growth parameters significant at p < .05). Conclusions: This study demonstrated that attitudes and perceived control are key determinants regarding the intentions of being active. On a longer term perspective, future physical activity interventions should focus on the enhancement of students’ perceived control. Such educational context should help in promoting the adoption of an active lifestyle during college. PMID:27124179

  18. Growth curve changes associated with long-term selection for body weight in Japanese quail.

    PubMed

    Marks, H L

    1978-06-01

    Four quail lines were utilized to investigate growth patterns in quail. Three of these lines (P, T and S) had previously undergone long-term selection for high 4-week body weight, while line C was maintained as a nonselected control. Quail progeny from generation 37 and 38 breeders were fed diets containing 28% and 20% protein. Within each trial, the diet/line treatments were replicated 3 times with 12 quail per subclass. Body weight measurements suggested that the growth of all lines was best approximated by the logistic growth curve model. When fed a 28% protein diet the age at maximum growth (point of inflection) of selected lines was 4 to 6 days earlier than the corresponding age of controls. Similar rates of gain after 4 weeks of age between selected and control lines suggested that mechanisms influenced by selection for 4-week body weight in quail operate only during the period prior to the age at selection with little or no residual effect. PMID:680578

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

    PubMed Central

    2013-01-01

    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

  20. Shaping the Growth Behaviour of Biofilms Initiated from Bacterial Aggregates.

    PubMed

    Melaugh, Gavin; Hutchison, Jaime; Kragh, Kasper Nørskov; Irie, Yasuhiko; Roberts, Aled; Bjarnsholt, Thomas; Diggle, Stephen P; Gordon, Vernita D; Allen, Rosalind J

    2016-01-01

    Bacterial biofilms are usually assumed to originate from individual cells deposited on a surface. However, many biofilm-forming bacteria tend to aggregate in the planktonic phase so that it is possible that many natural and infectious biofilms originate wholly or partially from pre-formed cell aggregates. Here, we use agent-based computer simulations to investigate the role of pre-formed aggregates in biofilm development. Focusing on the initial shape the aggregate forms on the surface, we find that the degree of spreading of an aggregate on a surface can play an important role in determining its eventual fate during biofilm development. Specifically, initially spread aggregates perform better when competition with surrounding unaggregated bacterial cells is low, while initially rounded aggregates perform better when competition with surrounding unaggregated cells is high. These contrasting outcomes are governed by a trade-off between aggregate surface area and height. Our results provide new insight into biofilm formation and development, and reveal new factors that may be at play in the social evolution of biofilm communities. PMID:26934187

  1. Shaping the Growth Behaviour of Biofilms Initiated from Bacterial Aggregates

    PubMed Central

    Melaugh, Gavin; Hutchison, Jaime; Kragh, Kasper Nørskov; Irie, Yasuhiko; Roberts, Aled; Bjarnsholt, Thomas; Diggle, Stephen P.; Gordon, Vernita D.; Allen, Rosalind J.

    2016-01-01

    Bacterial biofilms are usually assumed to originate from individual cells deposited on a surface. However, many biofilm-forming bacteria tend to aggregate in the planktonic phase so that it is possible that many natural and infectious biofilms originate wholly or partially from pre-formed cell aggregates. Here, we use agent-based computer simulations to investigate the role of pre-formed aggregates in biofilm development. Focusing on the initial shape the aggregate forms on the surface, we find that the degree of spreading of an aggregate on a surface can play an important role in determining its eventual fate during biofilm development. Specifically, initially spread aggregates perform better when competition with surrounding unaggregated bacterial cells is low, while initially rounded aggregates perform better when competition with surrounding unaggregated cells is high. These contrasting outcomes are governed by a trade-off between aggregate surface area and height. Our results provide new insight into biofilm formation and development, and reveal new factors that may be at play in the social evolution of biofilm communities. PMID:26934187

  2. Bacterial growth on a superhydrophobic surface containing silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Heinonen, S.; Nikkanen, J.-P.; Laakso, J.; Raulio, M.; Priha, O.; Levänen, E.

    2013-12-01

    The antibacterial effect of silver can be exploited in the food and beverage industry and medicinal applications to reduce biofouling of surfaces. Very small amount of silver ions are enough to destructively affect the metabolism of bacteria. Moreover, superhydrophobic properties could reduce bacterial adhesion to the surface. In this study we fabricated superhydrophobic surfaces that contained nanosized silver particles. The superhydrophobic surfaces were manufactured onto stainless steel as combination of ceramic nanotopography and hydrophobication by fluorosilane. Silver nanoparticles were precipitated onto the surface by a chemical method. The dissolution of silver from the surface was tested in an aqueous environment under pH values of 1, 3, 5, 7, 9, 11 and 13. The pH value was adjusted with nitric acid and ammonia. It was found that dissolution rate of silver increased as the pH of the solution altered from the pH of de-ionized water to lower and higher pH values but dissolution occurred also in de-ionized water. The antimicrobial potential of this coating was investigated using bacterial strains isolated from the brewery equipment surfaces. The results showed that the number of bacteria adhering onto steel surface was significantly reduced (88%) on the superhydrophobic silver containing coating.

  3. Bacterial Growth on Distant Naphthalene Diffusing through Water, Air, and Water-Saturated and Nonsaturated Porous Media

    PubMed Central

    Harms, H.

    1996-01-01

    The influence of substrate diffusion on bacterial growth was investigated. Crystalline naphthalene was supplied as the substrate at various distances in the range of centimeters from naphthalene-degrading organisms separated from the substrate by agar-solidified mineral medium. Within 2 weeks, the cells grew to final numbers which were negatively correlated with the distance from the substrate. A mathematical model that combined (i) Monod growth kinetics extended by a term for culture maintenance and (ii) substrate diffusion could explain the observed growth curves. The model could also predict growth on naphthalene that was separated from the bacteria by air. In addition, the bacteria were grown on distant naphthalene that had to diffuse to the cells through water-saturated and unsaturated porous media. The growth of the bacteria could be used to calculate the effective diffusivity of naphthalene in the three-phase system. Diffusion of naphthalene in the pore space containing 80% air was roughly 1 order of magnitude faster than in medium containing only 20% air because of the high Henry's law coefficient of naphthalene. It is proposed that the effective diffusivities of the substrates and the spatial distribution of substrates and bacteria are the main determinants of final cell numbers and, consequently, final degradation rates. PMID:16535349

  4. Growth studies on Mycobacterium BCG: establishment of growth curves and measurement of the oxygen tension of the growth medium.

    PubMed

    Moore, D F; James, A M

    1982-01-01

    Mycobacterium BCG grew exponentially in shallow, static volumes of culture medium for approximately 10 days; the oxygen tension of the medium at all stages of growth was 100% saturation. Higher yields were obtained from Dubos than from glycerol-free medium. In static cultures, the oxygen tension of the culture and consequently the growth rate of BCG was dependent on the depth of the medium; active growth ceased at an oxygen tension of less than 40% saturation. BCG grew actively in a cell sediment, while cells growing in suspension made a negligible contribution to the yield. PMID:6757673

  5. Growth-rate-dependent dynamics of a bacterial genetic oscillator

    NASA Astrophysics Data System (ADS)

    Osella, Matteo; Lagomarsino, Marco Cosentino

    2013-01-01

    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 intracellular 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 dependencies 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, and thus on the nutrients it is fed. The physical support of the circuit (type of plasmid or gene positions on the chromosome) also plays an important role in determining the oscillation stability and the growth-rate dependence of period and amplitude. This analysis has potential application in the field of synthetic biology, and suggests that the coupling between endogenous genetic oscillators and cell physiology can have substantial consequences for their functionality.

  6. Moral Disengagement, Anticipated Social Outcomes and Adolescents' Alcohol Use: Parallel Latent Growth Curve Analyses.

    PubMed

    Quinn, Catherine A; Bussey, Kay

    2015-10-01

    Moral disengagement is a social cognitive process that has been extensively applied to transgressive behaviors, including delinquency, aggression and illicit substance use. However, there has been limited research on moral disengagement as it relates to underage drinking. The current study aimed to examine moral disengagement contextualized to underage drinking and its longitudinal relationship to alcohol use. Moreover, the social context in which adolescent alcohol use typically occurs was also considered, with a specific emphasis on the social sanctions, or social outcomes, that adolescents anticipate receiving from friends for their alcohol use. Adolescents were assessed across three time-points, 8 months apart. The longitudinal sample consisted of 382 (46% female) underage drinkers (12-16 years at T1). Parallel latent growth curve analysis was used to examine the bi-directional influence of initial moral disengagement, anticipated social outcomes, and alcohol use on subsequent growth in moral disengagement, anticipated social outcomes and alcohol use. The interrelation of initial scores and growth curves was also assessed. The findings revealed that, in the binary parallel analyses, initial moral disengagement and anticipated social outcomes both significantly predicted changes in alcohol use across time. Moreover, initial anticipated social outcomes predicted changes in moral disengagement. These findings were not consistently found when all three process analyses were included in a single model. The results emphasize the impact of social context on moral disengagement and suggest that by targeting adolescents' propensity to justify or excuse their drinking, as well as the social outcomes adolescents anticipate for being drunk, it may be possible to reduce their underage drinking. PMID:26318080

  7. Theoretical and Experimental Study of Bacterial Colony Growth in 3D

    NASA Astrophysics Data System (ADS)

    Shao, Xinxian; Mugler, Andrew; Nemenman, Ilya

    2014-03-01

    Bacterial cells growing in liquid culture have been well studied and modeled. However, in nature, bacteria often grow as biofilms or colonies in physically structured habitats. A comprehensive model for population growth in such conditions has not yet been developed. Based on the well-established theory for bacterial growth in liquid culture, we develop a model for colony growth in 3D in which a homogeneous colony of cells locally consume a diffusing nutrient. We predict that colony growth is initially exponential, as in liquid culture, but quickly slows to sub-exponential after nutrient is locally depleted. This prediction is consistent with our experiments performed with E. coli in soft agar. Our model provides a baseline to which studies of complex growth process, such as such as spatially and phenotypically heterogeneous colonies, must be compared.

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

    NASA Astrophysics Data System (ADS)

    Carlton, Amelie B.

    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.

  9. 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...

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

    PubMed Central

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

    2012-01-01

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

  11. Volatile Emissions from Mycobacterium avium subsp. paratuberculosis Mirror Bacterial Growth and Enable Distinction of Different Strains

    PubMed Central

    Trefz, Phillip; Koehler, Heike; Klepik, Klaus; Moebius, Petra; Reinhold, Petra; Schubert, Jochen K.; Miekisch, Wolfram

    2013-01-01

    Control of paratuberculosis in livestock is hampered by the low sensitivity of established direct and indirect diagnostic methods. Like other bacteria, Mycobacterium avium subsp. paratuberculosis (MAP) emits volatile organic compounds (VOCs). Differences of VOC patterns in breath and feces of infected and not infected animals were described in first pilot experiments but detailed information on potential marker substances is missing. This study was intended to look for characteristic volatile substances in the headspace of cultures of different MAP strains and to find out how the emission of VOCs was affected by density of bacterial growth. One laboratory adapted and four field strains, three of MAP C-type and one MAP S-type were cultivated on Herrold’s egg yolk medium in dilutions of 10-0, 10-2, 10-4 and 10-6. Volatile substances were pre-concentrated from the headspace over the MAP cultures by means of Solid Phase Micro Extraction (SPME), thermally desorbed from the SPME fibers and separated and identified by means of GC-MS. Out of the large number of compounds found in the headspace over MAP cultures, 34 volatile marker substances could be identified as potential biomarkers for growth and metabolic activity. All five MAP strains could clearly be distinguished from blank culture media by means of emission patterns based on these 34 substances. In addition, patterns of volatiles emitted by the reference strain were significantly different from the field strains. Headspace concentrations of 2-ethylfuran, 2-methylfuran, 3-methylfuran, 2-pentylfuran, ethyl acetate, 1-methyl-1-H-pyrrole and dimethyldisulfide varied with density of bacterial growth. Analysis of VOCs emitted from mycobacterial cultures can be used to identify bacterial growth and, in addition, to differentiate between different bacterial strains. VOC emission patterns may be used to approximate bacterial growth density. In a perspective volatile marker substances could be used to diagnose MAP

  12. Accuracy of Estimates and Statistical Power for Testing Meditation in Latent Growth Curve Modeling

    PubMed Central

    Cheong, JeeWon

    2016-01-01

    The latent growth curve modeling (LGCM) approach has been increasingly utilized to investigate longitudinal mediation. However, little is known about the accuracy of the estimates and statistical power when mediation is evaluated in the LGCM framework. A simulation study was conducted to address these issues under various conditions including sample size, effect size of mediated effect, number of measurement occasions, and R2 of measured variables. In general, the results showed that relatively large samples were needed to accurately estimate the mediated effects and to have adequate statistical power, when testing mediation in the LGCM framework. Guidelines for designing studies to examine longitudinal mediation and ways to improve the accuracy of the estimates and statistical power were discussed.

  13. Radiative heat transfer in curved specular surfaces in Czochralski crystal growth furnace

    SciTech Connect

    Guo, Z.; Maruyama, Shigenao; Tsukada, Takao

    1997-11-07

    A numerical investigation of radiative heat transfer constructed by curved surfaces with specular and diffuse reflection components is carried out. The ray tracing method is adopted for the calculation of view factors, in which a new ray emission model is proposed. The second-degree radiation ring elements are introduced, which are of engineering importance and numerical efficiency. The accuracy of the method is analyzed and verified using a simple configuration. The present computation using the proposed ray emission model is in good agreement with the analytical solution. As a numerical example and engineering application, the effects of the specular reflection and the meniscus of the melt surface in Czochralski (CZ) crystal growth are investigated. A marked temperature decrease in the melt surface is found by introducing specular reflection and the meniscus. The combined effects of the specular reflection and the meniscus should be considered in precision heat transfer control of a CZ apparatus.

  14. Tidally Induced Changes in Bacterial Growth and Viability in the Macrotidal Han River Estuary, Yellow Sea

    NASA Astrophysics Data System (ADS)

    Hyun, J.-H.; Choi, J. K.; Chung, K. H.; Yang, E.-J.; Kim, M.-K.

    1999-02-01

    The Han River estuary in the Yellow Sea is a macrotidal (tidal range of 3·5 m at neap tide and 8·0 m at spring tide) eutrophic environment. Changes in bacterial growth and viability at different NaCl concentrations as well as other physico-chemical environmental parameters were investigated at different tidal levels in order to elucidate the major environmental factors controlling the bacterial community. Bacterial growth rates (μ) varied with tidal state; maximum (μ=0·159 h -1) at high tide, and minimum (μ=0·069 h -1) at low tide. Although bacteria play a substantial role in ammonia removal and regeneration, growth was not controlled by the fluctuations of nutrient concentrations in the high nutrient estuary. The low viable cell number recorded with the increased NaCl concentration indicated that the salinity changes with tidal state was a major environmental factor controlling the viability of the freshwater bacterial populations. Portions of freshwater bacterial CFU (colony forming units) during low tide accounted for approximately 30% of the total CFU, and decreased down to 10% during high tide. Overall, the results indicate that the microbial communities in the macrotidal Han River estuary can be divided into two distinct groups according to the variations in salinity and freshwater runoff: (1) autochthonous halotolerant estuarine populations which are nourished by the high nutrient runoff; and (2) allochthonous halophobic freshwater populations which are adversely affected by salinity increase.

  15. Determining cloud parameters with the Curve-of-Growth: Application Eta Car

    NASA Astrophysics Data System (ADS)

    Vieira, G. L.; Gull, T. R.; Bruhweiler, F.; Nielsen, K. E.; Verner, E. M.; Eta Car HST Treasury Team

    2003-12-01

    We have investigated the NUV part of the Eta Car spectrum, using data with high spatial and high spectral resolving power obtained with the HST/STIS under the Treasury Program (K. Davidson P.I.). The NUV spectrum of Eta Car shows a great contribution of absorption features from neutral and singly ionized elements along the line-of-sight. A large number of velocity systems have been observed. The two most prominent, with Doppler shifts corresponding to -146 and -513 km/s respectively, are shown to be useful for investigations of the gaseous environments responsible for the absorption. The -146 and the -513 km/s velocity systems display different characteristics regarding the ionization state and spectral line width, which suggest that they originate at different distances from the central object. We have investigated the absorption structures before the spectroscopic minimum, occurring during the summer of 2003, with a standard curve-of-growth. We have independently derived the column density and the b-value for the Fe II (-146 km/s) and Ti II (-513 km/s) velocity systems. The excitation temperature has been determined for the -146 km/s velocity system using the photo-ionization code \\textsc{cloudy} (Ferland 1996, Ferland et al. 2000). The -146 km/s velocity structure shows noticeable variation over the spectroscopic minimum. The sudden appearance and disappearance of Ti II and V II are astonishing. We have made an attempt to analyze these variations with the curve-of-growth method and will present preliminary results.

  16. Estimation of median growth curves for children up two years old based on biresponse local linear estimator

    NASA Astrophysics Data System (ADS)

    Chamidah, Nur; Rifada, Marisa

    2016-03-01

    There is significant of the coeficient correlation between weight and height of the children. Therefore, the simultaneous model estimation is better than partial single response approach. In this study we investigate the pattern of sex difference in growth curve of children from birth up to two years of age in Surabaya, Indonesia based on biresponse model. The data was collected in a longitudinal representative sample of the Surabaya population of healthy children that consists of two response variables i.e. weight (kg) and height (cm). While a predictor variable is age (month). Based on generalized cross validation criterion, the modeling result based on biresponse model by using local linear estimator for boy and girl growth curve gives optimal bandwidth i.e 1.41 and 1.56 and the determination coefficient (R2) i.e. 99.99% and 99.98%,.respectively. Both boy and girl curves satisfy the goodness of fit criterion i.e..the determination coefficient tends to one. Also, there is difference pattern of growth curve between boy and girl. The boy median growth curves is higher than those of girl curve.

  17. 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...

  18. Effects of nitric oxide and nitrogen dioxide on bacterial growth

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    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.

  19. Divergent effects of desferrioxamine on bacterial growth and characteristics.

    PubMed

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

    2013-04-01

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

  20. Rapid detection of bacterial growth in blood samples by a continuous-monitoring electrical impedance apparatus.

    PubMed Central

    Specter, S; Throm, R; Strauss, R; Friedman, H

    1977-01-01

    A growth detection method utilizing an automated apparatus capable of rapidly detecting bacterial growth by measuring changes of electrical impedance in bacteriological medium was utilized with "mock" blood cultures containing various gram-negative and gram-positive bacteria. Measurement of changes of electrical impedance was found to ba as accurate and comparable for time of growth detection as the radiometric method for detection of the same bacteria using mock blood cultures. In a limited clinical trial the use of the electrical impedance apparatus detected in 1 positive specimen from 40 clinical blood specimens as rapidly as by radiometric measurement. Both methods were considerably faster for detecting bacterial growth as compared with conventional culture methods. The selected species of gram-positive and -negative organisms tested were all detected by the electrical impedance method, including aerobes and anerobes. However, addition of 5% CO2 to the incubation atmosphere enhanced detection of gram-positive organisms. PMID:336642

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

    SciTech Connect

    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

    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.

  2. Stimulation of Lipase Production During Bacterial Growth on Alkanes

    PubMed Central

    Breuil, Colette; Shindler, D. B.; Sijher, J. S.; Kushner, D. J.

    1978-01-01

    Acinetobacter lwoffi strain O16, a facultative psychrophile, can grow on crude oil, hexadecane, octadecane, and most alkanes when tested at 20 but not at 30°C. Growth occurred on a few alkanes at 30°C but after a longer lag than at 20°C. Cells grown on alkanes as sole carbon sources had high levels of cell-bound lipase. In contrast, previous work has shown that those grown on complex medium produced cell-free lipase and those grown on defined medium without alkanes produced little or no lipase. Low concentrations of the detergent Triton X-100 caused the liberation of most of the lipase activity of alkane-grown cells and increased total lipase activity. When ethanol and hexadecane were both present in a mineral medium, diauxic growth occurred; until the ethanol was completely used up, hexadecane was not utilized, and the lipase activity was very low. When growth on hexadecane began, lipase activity increased, reaching a level 50- to 100-fold higher than that of cells growing on ethanol. A similar pattern of lipase formation and hexadecane utilization was observed with Pseudomonas aeruginosa. Whenever A. lwoffi and other bacteria degraded alkanes they exhibited substantial lipase activity. Not all bacteria that produced lipase, however, could attack alkanes. Bacteria that could not produce lipase did not attack alkanes. The results suggest that a correlation may exist between lipase formation and alkane utilization. PMID:627533

  3. Cell Wall Nonlinear Elasticity and Growth Dynamics: How Do Bacterial Cells Regulate Pressure and Growth?

    NASA Astrophysics Data System (ADS)

    Deng, Yi

    In my thesis, I study intact and bulging Escherichia coli cells using atomic force microscopy to separate the contributions of the cell wall and turgor pressure to the overall cell stiffness. I find strong evidence of power--law stress--stiffening in the E. coli cell wall, with an exponent of 1.22±0.12, such that the wall is significantly stiffer in intact cells (E = 23±8 MPa and 49±20 MPa in the axial and circumferential directions) than in unpressurized sacculi. These measurements also indicate that the turgor pressure in living cells E. coli is 29±3 kPa. The nonlinearity in cell elasticity serves as a plausible mechanism to balance the mechanical protection and tension measurement sensitivity of the cell envelope. I also study the growth dynamics of the Bacillus subtilis cell wall to help understand the mechanism of the spatiotemporal order of inserting new cell wall material. High density fluorescent markers are used to label the entire cell surface to capture the morphological changes of the cell surface at sub-cellular to diffraction-limited spatial resolution and sub-minute temporal resolution. This approach reveals that rod-shaped chaining B. subtilis cells grow and twist in a highly heterogeneous fashion both spatially and temporally. Regions of high growth and twisting activity have a typical length scale of 5 μm, and last for 10-40 minutes. Motivated by the quantification of the cell wall growth dynamics, two microscopy and image analysis techniques are developed and applied to broader applications beyond resolving bacterial growth. To resolve densely distributed quantum dots, we present a fast and efficient image analysis algorithm, namely Spatial Covariance Reconstruction (SCORE) microscopy that takes into account the blinking statistics of the fluorescence emitters. We achieve sub-diffraction lateral resolution of 100 nm from 5 to 7 seconds of imaging, which is at least an order of magnitude faster than single-particle localization based methods

  4. Trajectories of Change in Obesity among Tehranian Families: Multilevel Latent Growth Curve Modeling

    PubMed Central

    Akbarzadeh, Mahdi; Mahjub, Hossein; Soltanian, Ali Reza; Daneshpour, Maryam; Morris, Nathan

    2016-01-01

    Objectives. To evaluate the trajectories of change in obesity within and between Tehranian families, who participated in the Tehran Lipid and Glucose Study (TLGS). Methods. This study is a family-based longitudinal design, in four waves. A total of 14761 individuals, within 3980 families, were selected. Three anthropometric measurements, body mass index (BMI), waist circumference (WC), and a body shape index (ABSI), were recorded. Multilevel latent growth curve modeling (MLGCM) approach was used for evaluating the change trajectories in obesity within and between the families. Results. The mean age of the subjects in the present study was 33.28 ± 19.01 (range 3–89 years) and 50.1% were male. Obesity was significantly increased (P < 0.001). Individuals with more fat become obese slower, whereas families with more fat become obese faster (P < 0.001). The initial value and growth rate of WC and ABSI were greater in men than in women, while this result is contrary to BMI (P < 0.001). Conclusions. Our findings demonstrated that there is an alarming increase in the obesity trend in Tehranian families. The important role of the family in the prevention of obesity is highlighted, underlining the need for public health programs, as family centered educations to lifestyle modification, which can address this emerging crisis. PMID:27042349

  5. Bacterial growth in a simulated Martian subsurface environment

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  6. Dynamic Metabolic Modeling of Denitrifying Bacterial Growth: The Cybernetic Approach

    SciTech Connect

    Song, Hyun-Seob; Liu, Chongxuan

    2015-06-29

    Denitrification is a multistage reduction process converting nitrate ultimately to nitrogen gas, carried out mostly by facultative bacteria. Modeling of the denitrification process is challenging due to the complex metabolic regulation that modulates sequential formation and consumption of a series of nitrogen oxide intermediates, which serve as the final electron acceptors for denitrifying bacteria. In this work, we examined the effectiveness and accuracy of the cybernetic modeling framework in simulating the growth dynamics of denitrifying bacteria in comparison with kinetic models. In four different case studies using the literature data, we successfully simulated diauxic and triauxic growth patterns observed in anoxic and aerobic conditions, only by tuning two or three parameters. In order to understand the regulatory structure of the cybernetic model, we systematically analyzed the effect of cybernetic control variables on simulation accuracy. The results showed that the consideration of both enzyme synthesis and activity control through u- and v-variables is necessary and relevant and that uvariables are of greater importance in comparison to v-variables. In contrast, simple kinetic models were unable to accurately capture dynamic metabolic shifts across alternative electron acceptors, unless an inhibition term was additionally incorporated. Therefore, the denitrification process represents a reasonable example highlighting the criticality of considering dynamic regulation for successful metabolic modeling.

  7. Growth Curves of Preschool Children in the Northeast of Iran: A Population Based Study Using Quantile Regression Approach

    PubMed Central

    Payande, Abolfazl; Tabesh, Hamed; Shakeri, Mohammad Taghi; Saki, Azadeh; Safarian, Mohammad

    2013-01-01

    Introduction: Growth charts are widely used to assess children’s growth status and can provide a trajectory of growth during early important months of life. The objectives of this study are going to construct growth charts and normal values of weight-for-age for children aged 0 to 5 years using a powerful and applicable methodology. The results compare with the World Health Organization (WHO) references and semi-parametric LMS method of Cole and Green. Methods: A total of 70737 apparently healthy boys and girls aged 0 to 5 years were recruited in July 2004 for 20 days from those attending community clinics for routine health checks as a part of a national survey. Anthropometric measurements were done by trained health staff using WHO methodology. The nonparametric quantile regression method obtained by local constant kernel estimation of conditional quantiles curves using for estimation of curves and normal values. Results: The weight-for-age growth curves for boys and girls aged from 0 to 5 years were derived utilizing a population of children living in the northeast of Iran. The results were similar to the ones obtained by the semi-parametric LMS method in the same data. Among all age groups from 0 to 5 years, the median values of children’s weight living in the northeast of Iran were lower than the corresponding values in WHO reference data. The weight curves of boys were higher than those of girls in all age groups. Conclusion: The differences between growth patterns of children living in the northeast of Iran versus international ones necessitate using local and regional growth charts. International normal values may not properly recognize the populations at risk for growth problems in Iranian children. Quantile regression (QR) as a flexible method which doesn’t require restricted assumptions, proposed for estimation reference curves and normal values. PMID:23618470

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

    SciTech Connect

    Zhang Shengli; Zhang Lei; Liang Run; Zhang Erhu; Liu Yachao; Zhao Shumin

    2005-11-01

    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.

  9. Primordial soup was edible: abiotically produced Miller-Urey mixture supports bacterial growth

    PubMed Central

    Xie, Xueshu; Backman, Daniel; Lebedev, Albert T.; Artaev, Viatcheslav B.; Jiang, Liying; Ilag, Leopold L.; Zubarev, Roman A.

    2015-01-01

    Sixty years after the seminal Miller-Urey experiment that abiotically produced a mixture of racemized amino acids, we provide a definite proof that this primordial soup, when properly cooked, was edible for primitive organisms. Direct admixture of even small amounts of Miller-Urey mixture strongly inhibits E. coli bacteria growth due to the toxicity of abundant components, such as cyanides. However, these toxic compounds are both volatile and extremely reactive, while bacteria are highly capable of adaptation. Consequently, after bacterial adaptation to a mixture of the two most abundant abiotic amino acids, glycine and racemized alanine, dried and reconstituted MU soup was found to support bacterial growth and even accelerate it compared to a simple mixture of the two amino acids. Therefore, primordial Miller-Urey soup was perfectly suitable as a growth media for early life forms. PMID:26412575

  10. Primordial soup was edible: abiotically produced Miller-Urey mixture supports bacterial growth.

    PubMed

    Xie, Xueshu; Backman, Daniel; Lebedev, Albert T; Artaev, Viatcheslav B; Jiang, Liying; Ilag, Leopold L; Zubarev, Roman A

    2015-01-01

    Sixty years after the seminal Miller-Urey experiment that abiotically produced a mixture of racemized amino acids, we provide a definite proof that this primordial soup, when properly cooked, was edible for primitive organisms. Direct admixture of even small amounts of Miller-Urey mixture strongly inhibits E. coli bacteria growth due to the toxicity of abundant components, such as cyanides. However, these toxic compounds are both volatile and extremely reactive, while bacteria are highly capable of adaptation. Consequently, after bacterial adaptation to a mixture of the two most abundant abiotic amino acids, glycine and racemized alanine, dried and reconstituted MU soup was found to support bacterial growth and even accelerate it compared to a simple mixture of the two amino acids. Therefore, primordial Miller-Urey soup was perfectly suitable as a growth media for early life forms. PMID:26412575

  11. Quantitative spectral light scattering polarimetry for monitoring fractal growth pattern of Bacillus thuringiensis bacterial colonies

    NASA Astrophysics Data System (ADS)

    Banerjee, Paromita; Soni, Jalpa; Ghosh, Nirmalya; Sengupta, Tapas K.

    2013-02-01

    It is of considerable current interest to develop various methods which help to understand and quantify the cellular association in growing bacterial colonies and is also important in terms of detection and identification of a bacterial species. A novel approach is used here to probe the morphological structural changes occurring during the growth of the bacterial colony of Bacillus thuringiensis under different environmental conditions (in normal nutrient agar, in presence of glucose - acting as additional nutrient and additional 3mM arsenate as additional toxic material). This approach combines the quantitative Mueller matrix polarimetry to extract intrinsic polarization properties and inverse analysis of the polarization preserving part of the light scattering spectra to determine the fractal parameter H (Hurst exponent) using Born approximation. Interesting differences are observed in the intrinsic polarization parameters and also in the Hurst exponent, which is a measurement of the fractality of a pattern formed by bacteria while growing as a colony. These findings are further confirmed with optical microscopic studies of the same sample and the results indicate a very strong and distinct dependence on the environmental conditions during growth, which can be exploited to quantify different bacterial species and their growth patterns.

  12. REVERSAL OF d-CYCLOSERINE INHIBITION OF BACTERIAL GROWTH BY ALANINE

    PubMed Central

    Zygmunt, Walter A.

    1962-01-01

    Zygmunt, Walter A. (Mead Johnson & Co., Evansville, Ind.). Reversal of d-cycloserine inhibition of bacterial growth by alanine. J. Bacteriol. 84:154–156. 1962.—Reversal of the antibacterial activity of d-4-amino-3-isoxazolidone by alanine in bacterial cultures actively growing on chemically defined media was compared in cultures requiring exogenous alanine and those capable of its synthesis. dl-Alanine was the most effective reversal agent in Pediococcus cerevisiae, an alanine-requiring organism, and d-alanine was effective in Escherichia coli and Staphylococcus aureus, organisms synthesizing alanine. With all three cultures, l-alanine was the least effective reversal agent. PMID:16561951

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

    PubMed Central

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

    2014-01-01

    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

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

    PubMed

    Ricker, Martin; Peña Ramírez, Víctor M; von Rosen, Dietrich

    2014-01-01

    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

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

    PubMed Central

    Ricker, Martin; Peña Ramírez, Víctor M.; von Rosen, Dietrich

    2014-01-01

    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 and for , A =  initial relative growth to be estimated, , and E is an error term for each tree and time point. Furthermore, Ei[–b·r]  = , , with TPR being the turning point radius in a sigmoid curve, and at is an estimated calibrating time-radius point. Advantages of the approach are that growth rates can be compared among growth curves with different turning point radiuses and different starting points, hidden outliers are easily detectable, the method is statistically robust, and heteroscedasticity of the residuals among time points is allowed. The model was implemented with dendrochronological data of 235 Pinus montezumae trees on ten Mexican volcano sites to calculate comparison intervals for the estimated initial relative growth . One site (at the Popocatépetl volcano) stood out, with being 3.9 times the value of the site with the slowest-growing trees. Calculating variance components for the initial relative growth, 34% of the growth variation was found among sites, 31% among trees, and 35% over time. Without the 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

  16. Spatial Patterning of Newly-Inserted Material during Bacterial Cell Growth

    NASA Astrophysics Data System (ADS)

    Ursell, Tristan

    2012-02-01

    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.

  17. GROWTH AND METABOLISM OF INDIVIDUAL BACTERIAL CELLS UTILIZING NANOSIMS

    SciTech Connect

    NEALSON, H. K.

    2007-08-03

    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

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

    PubMed

    Millan Núñez-Cortés, Jesús; Alvarez Rodriguez, Ysmael; Alvarez Novés, Granada; Recarte Garcia-Andrade, Carlos; Alvarez-Sala Walther, Luis

    2014-01-01

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

  19. Determinants of rate of change in functional disability: An application of latent growth curve modeling.

    PubMed

    Chen, Ya-Mei; Chen, Duan-Rung; Chiang, Tung-Liang; Tu, Yu-Kang; Yu, Hsiao-Wei

    2016-01-01

    Our aim was to identify disablement factors, including predisposing, intra-individual, and extra-individual factors, which predict the rate of change in general functional disability (GFD) in older adults. This study utilized the Taiwan Longitudinal Study on Aging Survey in 1996-2007 (N=3,186). Multiple-indicator latent growth curve modeling was used to examine how 12 disablement factors predicted the rate of change in GFD. GFD trajectories were modeled using Nagi's functional limitations, activities of daily living, and instrumental activities of daily living. Greater age (B=.025), female gender (B=.114), and greater numbers of comorbidities (B=.038) were associated with faster increase in GFD. Education (B=-.005) and participation in physically active leisure time activities (B=-.031) were associated with slower increase in GFD. Our findings add to the understanding of how disablement factors contribute to the rate of change in GFD. Predisposing factors played the main role. However, the factors we found to be associated with the rate of change in GFD in older adults were slightly different from the factors reported in the literature. Decreasing the number of comorbidities and increasing the level of physically active leisure time activity should be considered priorities for preventing disability as people age. PMID:26952373

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

    PubMed

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

    2011-03-01

    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

  1. Effects of Benzalkonium Chloride on Planktonic Growth and Biofilm Formation by Animal Bacterial Pathogens

    PubMed Central

    Ebrahimi, Azizollah; Hemati, Majid; Shabanpour, Ziba; Habibian Dehkordi, Saeed; Bahadoran, Shahab; Lotfalian, Sharareh; Khubani, Shahin

    2015-01-01

    Background: Resistance toward quaternary ammonium compounds (QACs) is widespread among a diverse range of microorganisms and is facilitated by several mechanisms such as biofilm formation. Objectives: In this study, the effects of benzalkonium chloride on planktonic growth and biofilm formation by some field isolates of animal bacterial pathogens were investigated. Materials and Methods: Forty clinical isolates of Escherichia coli, Salmonella serotypes, Staphylococcus aureus and Streptococcus agalactiae (10 isolates of each) were examined for effects of benzalkonium chloride on biofilm formation and planktonic growth using microtiter plates. For all the examined strains in the presence of benzalkonium chloride, biofilm development and planktonic growth were affected at the same concentrations of disinfectant. Results: The means of strains growth increase after the minimal inhibitory concentration (MIC) were significant in all the bacteria (except for E. coli in 1/32 and S. agalactiae in of 1/8 MIC). Biofilm formation increased with decrease of antiseptics concentration; a significant increase was found in all the samples. The most turbidity related to S. aureus and the least to Salmonella. Conclusions: Bacterial resistance against quaternary ammonium compounds is increasing which can increase the bacterial biofilm formation. PMID:25793094

  2. Monitoring bacterial growth using tunable resistive pulse sensing with a pore-based technique.

    PubMed

    Yu, Allen C S; Loo, Jacky F C; Yu, Samuel; Kong, S K; Chan, Ting-Fung

    2014-01-01

    A novel bacterial growth monitoring method using a tunable resistive pulse sensor (TRPS) system is introduced in this study for accurate and sensitive measurement of cell size and cell concentration simultaneously. Two model bacterial strains, Bacillus subtilis str.168 (BSU168) and Escherichia coli str.DH5α (DH5α), were chosen for benchmarking the growth-monitoring performance of the system. Results showed that the technique of TRPS is sensitive and accurate relative to widely used methods, with a lower detection limit of cell concentration measurement of 5 × 10⁵ cells/ml; at the same time, the mean coefficient of variation from TRPS was within 2 %. The growth of BSU168 and DH5α in liquid cultures was studied by TRPS, optical density (OD), and colony plating. Compared to OD measurement, TRPS-measured concentration correlates better with colony plating (R = 0.85 vs. R = 0.72), which is often regarded as the gold standard of cell concentration determination. General agreement was also observed by comparing TRPS-derived cell volume measurements and those determined from microscopy. We have demonstrated that TRPS is a reliable method for bacterial growth monitoring, where the study of both cell volume and cell concentration are needed to provide further details about the physical aspects of cell dynamics in real time. PMID:24287933

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    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.

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

    PubMed Central

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

    2014-01-01

    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

  5. Growth curves of carcass traits obtained by ultrasonography in three lines of Nellore cattle selected for body weight.

    PubMed

    Coutinho, C C; Mercadante, M E Z; Jorge, A M; Paz, C C P; El Faro, L; Monteiro, F M

    2015-01-01

    The effect of selection for postweaning weight was evaluated within the growth curve parameters for both growth and carcass traits. Records of 2404 Nellore animals from three selection lines were analyzed: two selection lines for high postweaning weight, selection (NeS) and traditional (NeT); and a control line (NeC) in which animals were selected for postweaning weight close to the average. Body weight (BW), hip height (HH), rib eye area (REA), back fat thickness (BFT), and rump fat thickness (RFT) were measured and records collected from animals 8 to 20 (males) and 11 to 26 (females) months of age. The parameters A (asymptotic value) and k (growth rate) were estimated using the nonlinear model procedure of the Statistical Analysis System program, which included fixed effect of line (NeS, NeT, and NeC) in the model, with the objective to evaluate differences in the estimated parameters between lines. Selected animals (NeS and NeT) showed higher growth rates than control line animals (NeC) for all traits. Line effect on curves parameters was significant (P < 0.001) for BW, HH, and REA in males, and for BFT and RFT in females. Selection for postweaning weight was effective in altering growth curves, resulting in animals with higher growth potential. PMID:26535722

  6. Enhancing the Psychological Well-Being of Elderly Individuals through Tai Chi Exercise: A Latent Growth Curve Analysis.

    ERIC Educational Resources Information Center

    Li, Fuzhong; Duncan, Terry E.; Duncan, Susan C.; McAuley, Edward; Chaumeton, Nigel R.; Harmer, Peter

    2001-01-01

    Examined whether a Tai Chi exercise program enhanced the psychological well-being of 98 elderly individuals. Analyzed repeated measures data about participants using latent growth curve analysis. Results indicate the beneficial effects of participation in the Tai Chi program. Discusses implications related to the exercise-psychological health…

  7. The Influence of Input on Connective Acquisition: A Growth Curve Analysis of English "Because" and German "Weil"

    ERIC Educational Resources Information Center

    van Veen, Rosie; Evers-Vermeul, Jacqueline; Sanders, Ted; van den Bergh, Huub

    2013-01-01

    The current study used growth curve analysis to study the role of input during the acquisition of the English causal connective "because" and its German counterpart "weil." The corpora of five German and five English children and their adult caretakers (age range 0;10-4;3) were analyzed for the amount as well as for the type of…

  8. Self-Esteem Trajectories among Ethnic Minority Adolescents: A Growth Curve Analysis of the Patterns and Predictors of Change

    ERIC Educational Resources Information Center

    Greene, Melissa L.; Way, Niobe

    2005-01-01

    The current study presents a growth curve analysis of self-esteem among Black, Latino, and Asian American high school students. A series of hierarchical linear models were used to examine patterns and predictors of change in self-esteem over time. Results revealed an average increase in self-esteem with age. Although boys and girls experienced…

  9. Exploring the Different Trajectories of Analytical Thinking Ability Factors: An Application of the Second-Order Growth Curve Factor Model

    ERIC Educational Resources Information Center

    Saengprom, Narumon; Erawan, Waraporn; Damrongpanit, Suntonrapot; Sakulku, Jaruwan

    2015-01-01

    The purposes of this study were 1) Compare analytical thinking ability by testing the same sets of students 5 times 2) Develop and verify whether analytical thinking ability of students corresponds to second-order growth curve factors model. Samples were 1,093 eighth-grade students. The results revealed that 1) Analytical thinking ability scores…

  10. Examining the Earnings Trajectories of Community College Students Using a Piecewise Growth Curve Modeling Approach. A CAPSEE Working Paper

    ERIC Educational Resources Information Center

    Jaggars, Shanna Smith; Xu, Di

    2015-01-01

    Policymakers have become increasingly concerned with measuring--and holding colleges accountable for--students' labor market outcomes. In this paper we introduce a piecewise growth curve approach to analyzing community college students' labor market outcomes, and we discuss how this approach differs from Mincerian and fixed-effects approaches. Our…

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

    ERIC Educational Resources Information Center

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

    2004-01-01

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

  12. Impact of Witnessing Violence on Growth Curves for Problem Behaviors among Early Adolescents in Urban and Rural Settings

    ERIC Educational Resources Information Center

    Farrell, Albert D.; Sullivan, Terri N.

    2004-01-01

    Two studies used latent growth-curve analysis to examine the relation between witnessing violence and changes in problem behaviors (drug use, aggression, and delinquency) and attitudes during early adolescence. In Study 1, six waves of data covering 6th to 8th grades were collected from 731 students in urban schools serving mostly African-American…

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

    PubMed Central

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

    2014-01-01

    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

  14. Illumination of growth, division and secretion by metabolic labeling of the bacterial cell surface

    PubMed Central

    Siegrist, M. Sloan; Swarts, Benjamin M.; Fox, Douglas M.; Lim, Shion An; Bertozzi, Carolyn R.

    2015-01-01

    The cell surface is the essential interface between a bacterium and its surroundings. Composed primarily of molecules that are not directly genetically encoded, this highly dynamic structure accommodates the basic cellular processes of growth and division as well as the transport of molecules between the cytoplasm and the extracellular milieu. In this review, we describe aspects of bacterial growth, division and secretion that have recently been uncovered by metabolic labeling of the cell envelope. Metabolite derivatives can be used to label a variety of macromolecules, from proteins to non-genetically-encoded glycans and lipids. The embedded metabolite enables precise tracking in time and space, and the versatility of newer chemoselective detection methods offers the ability to execute multiple experiments concurrently. In addition to reviewing the discoveries enabled by metabolic labeling of the bacterial cell envelope, we also discuss the potential of these techniques for translational applications. Finally, we offer some guidelines for implementing this emerging technology. PMID:25725012

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

    PubMed Central

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

    2014-01-01

    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

  16. In-depth characterization of wastewater bacterial community in response to algal growth using pyrosequencing.

    PubMed

    Lee, Jangho; Lee, Juyoun; Lee, Tae Kwon; Woo, Sung-Geun; Baek, Gyu Seok; Park, Joonhong

    2013-10-28

    Microalgae have been regarded as a natural resource for sustainable materials and fuels, as well as for removal of nutrients and micropollutants from wastewater, and their interaction with bacteria in wastewater is a critical factor to consider because of the microbial diversity and complexity in a variety of wastewater conditions. Despite their importance, very little is known about the ecological interactions between algae and bacteria in a wastewater environment. In this study, we characterized the wastewater bacterial community in response to the growth of a Selenastrum gracile UTEX 325 population in a real municipal wastewater environment. The Roche 454 GS-FLX Titanium pyrosequencing technique was used for indepth analysis of amplicons of 16S rRNA genes from different conditions in each reactor, with and without the algal population. The algal growth reduced the bacterial diversity and affected the bacterial community structure in the wastewater. The following in-depth analysis of the deep-sequenced amplicons showed that the algal growth selectively stimulated Sphingobacteria class members, especially the Sediminibacterium genus population, in the municipal wastewater environment. PMID:23867704

  17. Bacterial sensing underlies artificial sweetener-induced growth of gut Lactobacillus.

    PubMed

    Daly, Kristian; Darby, Alistair C; Hall, Neil; Wilkinson, Mark C; Pongchaikul, Pisut; Bravo, David; Shirazi-Beechey, Soraya P

    2016-07-01

    Disruption in stable establishment of commensal gut microbiota by early weaning is an important factor in susceptibility of young animals to enteric disorders. The artificial sweetener SUCRAM [consisting of neohesperidin dihydrochalcone (NHDC) and saccharin] included in piglets' feed reduces incidence of enteric disease. Pyrosequencing of pig caecal 16S rRNA gene amplicons identified 25 major families encompassing seven bacterial classes with Bacteroidia, Clostridia and Bacilli dominating the microbiota. There were significant shifts in microbial composition in pigs maintained on a diet containing SUCRAM, establishing SUCRAM as a major influence driving bacterial community dynamics. The most notable change was a significant increase of Lactobacillaceae population abundance, almost entirely due to a single phylotype, designated Lactobacillus 4228. The sweetener-induced increase in Lactobacillaceae was observed in two different breeds of pigs signifying a general effect. We isolated Lactobacillus 4228, sequenced its genome and found it to be related to Lactobacillus amylovorus. In vitro analyses of Lactobacillus 4228 growth characteristics showed that presence of NHDC significantly reduces the lag phase of growth and enhances expression of specific sugar transporters, independently of NHDC metabolism. This study suggests that sensing of NHDC by a bacterial plasma membrane receptor underlies sweetener-induced growth of a health promoting gut bacterium. PMID:26058469

  18. Two bacterial entophytes eliciting both plant growth promotion and plant defense on pepper (Capsicum annuum L.).

    PubMed

    Kang, Seung Hoon; Cho, Hyun-Soo; Cheong, Hoon; Ryu, Choong-Min; Kim, Jihyun F; Park, Seung-Hwan

    2007-01-01

    Plant growth-promoting rhizobacteria (PGPR) have the potential to be used as microbial inoculants to reduce disease incidence and severity and to increase crop yield. Some of the PGPR have been reported to be able to enter plant tissues and establish endophytic populations. Here, we demonstrated an approach to screen bacterial endophytes that have the capacity to promote the growth of pepper seedlings and protect pepper plants against a bacterial pathogen. Initially, out of 150 bacterial isolates collected from healthy stems of peppers cultivated in the Chungcheong and Gyeongsang provinces of Korea, 23 putative endophytic isolates that were considered to be predominating and representative of each pepper sample were selected. By phenotypic characterization and partial 16S rDNA sequence analysis, the isolates were identified as species of Ochrobacterium, Pantoea, Pseudomonas, Sphingomonas, Janthinobacterium, Ralstonia, Arthrobacter, Clavibacter, Sporosarcina, Acidovorax, and Brevundimonas. Among them, two isolates, PS4 and PS27, were selected because they showed consistent colonizing capacity in pepper stems at the levels of 10(6)-10(7) CFU/g tissue, and were found to be most closely related to Pseudomonas rhodesiae and Pantoea ananatis, respectively, by additional analyses of their entire 16S rDNA sequences. Drenching application of the two strains on the pepper seedlings promoted significant growth of peppers, enhancing their root fresh weight by 73.9% and 41.5%, respectively. The two strains also elicited induced systemic resistance of plants against Xanthomonas axonopodis pv. vesicatoria. PMID:18051359

  19. Stability of Cigarette Consumption Over Time Among Continuing Smokers: A Latent Growth Curve Analysis

    PubMed Central

    Borland, Ron; Thrasher, James F.; Thompson, Mary E.

    2012-01-01

    Objectives: This paper examined the stability over time of daily cigarette consumption of continuing smokers and explored factors that might account for the patterns of change in consumption using a latent growth curve (LGC) analytic approach. Methods: Data come from the first 5 waves of the International Tobacco Control Four-Country Survey, conducted in Canada, the United States, the United Kingdom, and Australia where a cohort of over 2,000 smokers from each country were recruited and followed up annually with replenishment. Results: Raw data revealed that continuing smokers showed a marked steep decline in cigarettes per day during the first 2 waves followed by a gentler linear decline in consumption over the remaining waves of the study period. This pattern of change in cigarette consumption was best modelled using a piecewise linear LGC model. Baseline consumption level was highest in Australia and lowest in the United Kingdom, although the rate of decline was similar across the 4 countries. Being older than 55 years and having made at least 1 quit attempt were related to greater rate of decline in consumption. Conclusions: Continuing smokers who are unwilling or unable to quit smoking can and do attempt to reduce their daily cigarette consumption over time. Factors such as making a quit attempt even if unsuccessful and experiencing smoking bans at work and at homes can contribute to reduced smoking among this group, which suggests that interventions focusing in on these factors, along with providing cessation help, may greatly improve their chances of quitting smoking altogether. PMID:22311963

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

    PubMed Central

    2011-01-01

    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 (λ) 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,τ) 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

  1. Bacterial growth rates are influenced by cellular characteristics of individual species when immersed in electromagnetic fields.

    PubMed

    Tessaro, Lucas W E; Murugan, Nirosha J; Persinger, Michael A

    2015-03-01

    Previous studies have shown that exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) have negative effects on the rate of growth of bacteria. In the present study, two Gram-positive and two Gram-negative species were exposed to six magnetic field conditions in broth cultures. Three variations of the 'Thomas' pulsed frequency-modulated pattern; a strong-static "puck" magnet upwards of 5000G in intensity; a pair of these magnets rotating opposite one another at ∼30rpm; and finally a strong dynamic magnetic field generator termed the 'Resonator' with an average intensity of 250μT were used. Growth rate was discerned by optical density (OD) measurements every hour at 600nm. ELF-EMF conditions significantly affected the rates of growth of the bacterial cultures, while the two static magnetic field conditions were not statistically significant. Most interestingly, the 'Resonator' dynamic magnetic field increased the rates of growth of three species (Staphylococcus epidermidis, Staphylococcus aureus, and Escherichia coli), while slowing the growth of one (Serratia marcescens). We suggest that these effects are due to individual biophysical characteristics of the bacterial species. PMID:25721476

  2. Flotillin-1 (Reggie-2) Contributes to Chlamydia pneumoniae Growth and Is Associated with Bacterial Inclusion

    PubMed Central

    Korhonen, Juha T.; Puolakkainen, Mirja; Häivälä, Reetta; Penttilä, Tuula; Haveri, Anu; Markkula, Eveliina

    2012-01-01

    Chlamydiae are obligate intracellular pathogens replicating only inside the eukaryotic host. Here, we studied the effect of human flotillin-1 protein on Chlamydia pneumoniae growth in human line (HL) and A549 epithelial cell lines. RNA interference was applied to disrupt flotillin-1-mediated endocytosis. Host-associated bacteria were detected by quantitative PCR, and C. pneumoniae growth was evaluated by inclusion counts. C. pneumoniae attachment to host cells was unaffected, but bacterial intracellular growth was attenuated in the flotillin-1-silenced cells. By using confocal microscopy, we detected flotillin-1 colocalized with the inclusion membrane protein A (IncA) in the C. pneumoniae inclusion membranes. In addition, flotillin-1 was associated with IncA in detergent-resistant membrane microdomains (DRMs) in biochemical fractioning. These results suggest that flotillin-1 localizes to the C. pneumoniae inclusion membrane and plays an important role for intracellular growth of C. pneumoniae. PMID:22215737

  3. Inhibitory Effects of Synthetic Peptides Containing Bovine Lactoferrin C-lobe Sequence on Bacterial Growth

    PubMed Central

    Kim, Woan-Sub; Ohashi, Midori; Shimazaki, Kei-ichi

    2016-01-01

    Lactoferrin is a glycoprotein with various biological effects, with antibacterial activity being one of the first effects reported. This glycoprotein suppresses bacterial growth through bacteriostatic or bactericidal action. It also stimulates the growth of certain kinds of bacteria such as lactic acid bacteria and bifidobacteria. In this study, Asn-Leu-Asn-Arg was selected and chemically synthesized based on the partial sequences of bovine lactoferrin tryptic fragments. Synthetic Asn-Leu-Asn-Arg suppressed the growth of Pseudomonas fluorescens, P. syringae and Escherichia coli. P. fluorescens is a major psychrotrophic bacteria found in raw and pasteurized milk, which decreases milk quality. P. syringae is a harmful infectious bacterium that damages plants. However, synthetic Asn-Leu-Asn-Arg did not inhibit the growth of Lactobacillus acidophilus. It is expected that this synthetic peptide would be the first peptide sequence from the bovine lactoferrin C-lobe that shows antibacterial activity. PMID:27621684

  4. Inhibitory Effects of Synthetic Peptides Containing Bovine Lactoferrin C-lobe Sequence on Bacterial Growth.

    PubMed

    Kim, Woan-Sub; Ohashi, Midori; Shimazaki, Kei-Ichi

    2016-01-01

    Lactoferrin is a glycoprotein with various biological effects, with antibacterial activity being one of the first effects reported. This glycoprotein suppresses bacterial growth through bacteriostatic or bactericidal action. It also stimulates the growth of certain kinds of bacteria such as lactic acid bacteria and bifidobacteria. In this study, Asn-Leu-Asn-Arg was selected and chemically synthesized based on the partial sequences of bovine lactoferrin tryptic fragments. Synthetic Asn-Leu-Asn-Arg suppressed the growth of Pseudomonas fluorescens, P. syringae and Escherichia coli. P. fluorescens is a major psychrotrophic bacteria found in raw and pasteurized milk, which decreases milk quality. P. syringae is a harmful infectious bacterium that damages plants. However, synthetic Asn-Leu-Asn-Arg did not inhibit the growth of Lactobacillus acidophilus. It is expected that this synthetic peptide would be the first peptide sequence from the bovine lactoferrin C-lobe that shows antibacterial activity. PMID:27621684

  5. Tropical freshwater ecosystems have lower bacterial growth efficiency than temperate ones

    PubMed Central

    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

    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

  6. Application of Direct Current Potential Drop for the J-integral vs. Crack Growth Resistance Curve Characterization

    SciTech Connect

    Chen, Xiang; Nanstad, Randy K; Sokolov, Mikhail A

    2014-01-01

    The direct current potential drop (DCPD) technique has been applied to derive the J-integral vs. crack growth resistance curve (J-R curve) for fracture toughness characterization of structural materials. The test matrix covered three materials including type 316LN stainless steels, Ni-based alloy 617, and one ferritic-martensitic steel, three specimen configurations including standard compact, single edge bending, and disk-shaped compact specimens, and temperatures ranging from 20 C to 650 C. When compared with baseline J-R curves derived from the ASTM normalization method, the original J-R curves from the DCPD technique yielded much smaller Jq values due to the influence of crack blunting, plastic deformation, etc. on potential drop. To counter these effects, a new procedure for adjusting DCPD J-R curves was proposed. After applying the new adjustment procedure, the average difference in Jq between the DCPD technique and the normalization method was only 5.2% and the difference in tearing modulus was 7.4%. The promising result demonstrates the applicability of the DCPD technique for the J-R curve characterization especially in extreme environments, such as elevated temperatures, where the conventional elastic unloading compliance method faces considerable challenges.

  7. Effects of viral enrichment on bacterial production, respiration and growth efficiency

    NASA Astrophysics Data System (ADS)

    Bonilla-Findji, O.; Rochelle-Newall, E.; Weinbauer, M. G.; Gattuso, J.-P.

    2003-04-01

    Viruses are the most common biological agents in the sea. They can influence many ecological processes such as nutrient and carbon cycling, particle size distribution, algal bloom control, species diversity and gene transfer. As they are mainly bacteriophages they not only influence bacterial abundances but also potentially, the bacterial respiration and production, as has been suggested in by Fuhrman’s model in 1992 and a few recent experimental studies. Through their lytic action viruses can influence biogeochemical cycles and so affect the functioning of the whole marine ecosystem. In order to explore this hypothesis and provide some quantitative data we: (1) studied the effects of viruses on bacterial respiration (BR), production (BP) and growth efficiency (BGE) and (2) investigated whether these effects change over time. A viral enrichment experiment was performed in April and May 2002, where the bacterial community isolated from the Bay of Villefranche was exposed to three treatments: Vo (no viral addition), Vm (enrichment of 1-1.5 fold inactivated viruses) and V+ (enrichment of 1-1.5 fold active viruses). No virally induced effects on bacterial metabolism were observed in April but in May after 24 h of incubation, BR was stimulated by ca. 39% in V+ compared to Vo and by 20% relative to Vm. In the presence of active viruses, BP was repressed by ca. 40% compared to Vo and BGE was reduced by 48%. In May, viruses increased the total bacterial carbon demand (17% in V+ compared to Vo, and by 11% relative to Vm). Our results suggest that viruses seem to induce a shift in the specific role of bacterioplankton by reducing the carbon flow to the higher trophic levels and by stimulating the DOM ‡ bacteria ‡ CO2, N, P, Fe pathway.

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

    PubMed Central

    Timchenko, T; Bailone, A; Devoret, R

    1996-01-01

    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

  9. Rainbow trout resistance to bacterial cold-water disease is moderately heritable and is not adversely correlated with growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to estimate the heritabilities for and genetic correlations among resistance to bacterial cold-water disease and growth traits in a population of rainbow trout. Bacterial cold-water disease, a chronic disease of rainbow trout, is caused by Flavobacterium psychrophilu...

  10. Wheat and Rice Growth Stages and Fertilization Regimes Alter Soil Bacterial Community Structure, But Not Diversity

    PubMed Central

    Wang, Jichen; Xue, Chao; Song, Yang; Wang, Lei; Huang, Qiwei; Shen, Qirong

    2016-01-01

    Maintaining soil fertility and the microbial communities that determine fertility is critical to sustainable agricultural strategies, and the use of different organic fertilizer (OF) regimes represents an important practice in attempts to preserve soil quality. However, little is known about the dynamic response of bacterial communities to fertilization regimes across crop growth stages. In this study, we examined microbial community structure and diversity across eight representative growth stages of wheat-rice rotation under four different fertilization treatments: no nitrogen fertilizer (NNF), chemical fertilizer (CF), organic–inorganic mixed fertilizer (OIMF), and OF. Quantitative PCR (QPCR) and high-throughput sequencing of bacterial 16S rRNA gene fragments revealed that growth stage as the best predictor of bacterial community abundance and structure. Additionally, bacterial community compositions differed between wheat and rice rotations. Relative to soils under wheat rotation, soils under rice rotation contained higher relative abundances (RA) of anaerobic and mesophilic microbes and lower RA of aerophilic microbes. With respect to fertilization regime, NNF plots had a higher abundance of nitrogen–fixing Cyanobacteria. OIMF had a lower abundance of ammonia-oxidizing Thaumarchaeota compared with CF. Application of chemical fertilizers (CF and OIMF treatments) significantly increased the abundance of some generally oligotrophic bacteria such those belonging to the Acidobacteria, while more copiotrophic of the phylum Proteobacteria increased with OF application. A high correlation coefficient was found when comparing RA of Acidobacteria based upon QPCR vs. sequence analysis, yet poor correlations were found for the α- and β- Proteobacteria, highlighting the caution required when interpreting these molecular data. In total, crop, fertilization scheme and plant developmental stage all influenced soil microbial community structure, but not total levels of