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1

The Bacterial Growth Curve and the History of Species  

Microsoft Academic Search

WHEN a nutrient solution is inoculated with a species of micro-organism, in pure culture, the curve obtained by plotting the population against the time is characteristic and conforms to a general type of growth curve; an initial period of slow increase in numbers being followed by a rapid rise in population which, in turn, is superseded by a decline. An

A. Steven Corbet

1933-01-01

2

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

Microsoft Academic Search

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

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

1997-01-01

3

Bacterial Growth  

NSDL National Science Digital Library

Dr. Brett Finlay shows how bacteria can grow rapidly to incredible numbers, and also explains what limits this explosive growth. This resource would be great preparation material for a classroom discussion or video presentation for both the students and the teacher. This visual helps further broaden the knowledge of students in both the upper high school and college undergraduate on bacterial growth. The lecture is featured on the DVD 2000 and Beyond: Confronting the Microbe Menace, available free from HHMI. The video is 54 seconds long and available on WMV (10MB) and MOV (8MB). All Infection Disease videos can be found at http://www.hhmi.org/biointeractive/disease/video.html .

Howard Hughes Medical Institute (;)

2007-03-27

4

Curved microchannels and bacterial streamers  

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

5

Analyzing population growth curves  

Microsoft Academic Search

Assessing animal population growth curves is an essential feature of field studies in ecology and wildlife management. We used five models to assess population growth rates with a number of sets of population growth rate data. A 'generalized' logistic curve provides a better model than do four other popular models. Use of difference equations for fitting was checked by a

L. L. Eberhardt; J. M. Breiwick; D. P. Demaster

2008-01-01

6

Classification Using Growth Curves  

Microsoft Academic Search

Classification using the growth curve model is analyzed according to whether the covariance matrix structure is known to be compound symmetric. A new classification procedure appropriate for classification in the case of models with means that follow a Potthoff and Roy [Potthoff, R. F., Roy, S. N. (1964). A generalized multivariate analysis of variance model useful especially for growth curve

Graciela B. Mentz; Anant M. Kshirsagar

2005-01-01

7

Electric fields induce curved growth of Enterobacter cloacae, Escherichia coli, and Bacillus subtilis cells: implications for mechanisms of galvanotropism and bacterial growth.  

PubMed Central

Directional growth in response to electric fields (galvanotropism) is known for eukaryotic cells as diverse as fibroblasts, neurons, algae, and fungal hyphae. The mechanism is not understood, but all proposals invoke actin either directly or indirectly. We applied electric fields to bacteria (which are inherently free of actin) to determine whether actin was essential for galvanotropism. Field-treated (but not control) Enterobacter cloacae and Escherichia coli cells curved rapidly toward the anode. The response was both field strength and pH dependent. The direction of curvature was reversed upon reversal of field polarity. The directional growth was not due to passive bending of the cells or to field-induced gradients of tropic substances in the medium. Field-treated Bacillus subtilis cells also curved, but the threshold was much higher than for E. cloacae or E. coli. Since the curved morphology must reflect spatial differences in the rates of cell wall synthesis and degradation, we looked for regions of active wall growth. Experiments in which the cells were decorated with latex beads revealed that the anode-facing ends of cells grew faster than the cathode-facing ends of the same cells. Inhibitors of cell wall synthesis caused spheroplasts to form on the convex regions of field-treated cells, suggesting that the initial curvature resulted from enhanced growth of cathode-facing regions. Our results indicate that an electric field modulates wall growth spatially and that the mechanism may involve differential stimulation of wall growth in both anode- and cathode-facing regions. Electric fields may therefore serve as valuable tools for studies of bacterial wall growth. Use of specific E. coli mutants may allow dissection of the galvanotropic mechanism at the molecular level. Images

Rajnicek, A M; McCaig, C D; Gow, N A

1994-01-01

8

Bacterial streamers in curved microchannels  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

9

HUMAN GROWTH CURVE.  

PubMed

The human growth curve shows two (and only two) outstanding periods of accelerated growth-the circumnatal and the adolescent. The circumnatal growth cycle attains great velocity, which reaches a maximum at the time of birth. The curve of this cycle is best fitted by a theoretical skew curve of Pearson's Type I. It has a theoretical range of 44 months and a standard deviation of 5.17 months. The modal velocity is 10.2 kilos per year. The adolescent growth cycle has less maximum velocity and greater range in time than the circumnatal cycle. The best fitting theoretical curve is a normal frequency curve ranging over about 10 years with a standard deviation of about 21 months and a modal velocity of 4.5 kilos per year. The two great growth accelerations are superimposed on a residual curve of growth which measures a substratum of growth out of which the accelerations arise. This probably extends from conception to 55 years, on the average. It is characterized by low velocity, averaging about 2 kilos per year from 2 to 12 years. It is interpreted as due to many growth operations coincident or closely blending in time. Our curve shows no third marked period of acceleration at between the 3rd and 6th years. The total growth in weight of the body is the sum of the weight of its constituent organs. In some cases these keep pace with the growth of the body as a whole; great accelerations of body growth are due to great accelerations in growth of the constituent organs. In other cases one of the organs of the body (like the thymus gland) may undergo a change in weight that is not in harmony with that of the body as a whole. The development of the weight in man is the resultant of many more or less elementary growth processes. These result in two special episodes of growth and numerous smaller, blending, growth operations. Hypotheses are suggested as to the basis of the special growth accelerations. PMID:19872316

Davenport, C B

1926-11-20

10

Growth curves for preterm infants  

Microsoft Academic Search

The commonly used growth curves for preterm infants are four decades old and may not be suitable for the current population. Uncertainty exists regarding the most suitable curves for monitoring the growth of preterm infants. While intrauterine growth rate appears to be the ideal growth that needs to be attained by the preterm infants, it may not be feasible given

Shripada C. Rao; Jeffrey Tompkins

2007-01-01

11

Fitting and using growth curves  

Microsoft Academic Search

A technique is presented for fitting and analyzing growth patterns using Gompertz, power, and exponential curves. Data collection involves measuring growth rate as a function of size. This is useful because growth rates at many different sizes can be measured at the same time, which removes the effect of environmental change from the observed growth pattern. Using size instead of

Karl W. Kaufmann

1981-01-01

12

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

PubMed

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 previous study, we showed that coupling of antibiotics to CdTe can increase toxicity to bacteria but decrease toxicity to mammalian cells, due to decreased production of reactive oxygen species from the conjugates. Although it is unlikely that cadmium-containing compounds will be approved for use in humans, such preparations could be used for disinfection of surfaces or sterilization of water. In this protocol, we give a straightforward approach to solubilizing CdTe QDs with mercaptopropionic acid (MPA). The QDs are ready to use within an hour. We then demonstrate coupling to an antimicrobial agent. The second part of the protocol demonstrates a 96-well bacterial inhibition assay using the conjugated and unconjugated QDs. The optical density is read over many hours, permitting the effects of QD addition and light exposure to be evaluated immediately as well as after a recovery period. We also illustrate a colony count for quantifying bacterial survival. PMID:22824953

Park, Soonhyang; Chibli, Hicham; Nadeau, Jay

2012-07-11

13

Modelling bacterial flagellar growth  

NASA Astrophysics Data System (ADS)

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

Schmitt, M.; Stark, H.

2011-10-01

14

Growth curves for Laron syndrome.  

PubMed Central

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.

Laron, Z; Lilos, P; Klinger, B

1993-01-01

15

A random effect multiplicative heteroscedastic model for bacterial growth  

Microsoft Academic Search

Background: Predictive microbiology develops mathematical models that can predict the growth rate of a microorganism population under a set of environmental conditions. Many primary growth models have been proposed. However, when primary models are applied to bacterial growth curves, the biological variability is reduced to a single curve defined by some kinetic parameters (lag time and growth rate), and sometimes

Ricardo Cao; Mario Francisco-Fernández; Emiliano J. Quinto

2010-01-01

16

Structured latent growth curves for twin data  

Microsoft Academic Search

We describe methods to fit structured latent growth curves to data from MZ and DZ twins. The well-known Gompertz, logistic and exponential curves may be written as a function of three components - asymptote, initial value, and rate of change. These components are allowed to vary and covary within individuals in a structured latent growth model. Such models are highly

Michael C Neale; John J McArdle

2000-01-01

17

Key curve analysis of crack-growth-resistance curves  

Microsoft Academic Search

A previously suggested relation among load, displacement, and remaining-ligament for stable crack growth was validated by examining literature data on three-point-bend and compact specimens. The resulting key curves were found to consist of one or more power-law segments, with the major portion of growth generally confined to one of the segments. The J-integral was then expressed in terms of the

I.-H. Lin

1982-01-01

18

Growth rate models: emphasizing growth rate analysis through growth curve modeling  

Microsoft Academic Search

To emphasize growth rate analysis, we develop a general method to reparametrize growth curve models to analyze rates of growth for a variety of growth trajectories, such as quadratic and exponential growth. The resulting growth rate models are shown to be related to rotations of growth curves. Estimated conveniently through growth curve modeling techniques, growth rate models have advantages above

Zhiyong Zhang; John J. McArdle; John R. Nesselroade

2011-01-01

19

Growth rate models: emphasizing growth rate analysis through growth curve modeling  

Microsoft Academic Search

To emphasize growth rate analysis, we develop a general method to reparametrize growth curve models to analyze rates of growth for a variety of growth trajectories, such as quadratic and exponential growth. The resulting growth rate models are shown to be related to rotations of growth curves. Estimated conveniently through growth curve modeling techniques, growth rate models have advantages above

Zhiyong Zhang; John J. McArdle; John R. Nesselroade

2012-01-01

20

Fundal Height Growth Curve for Thai Women  

PubMed Central

Objectives. To develop fundal height (FH) growth curve from normal singleton pregnancy based on last menstrual period (LMP) and/or ultrasound dating for women in the northern part of Thailand. Methods. A retrospective time-series study was conducted at four hospitals in the upper northern part of Thailand between January 2009 and March 2011. FH from 20 to 40 weeks was measured in centimeters. The FH growth curve was presented as smoothed function of the 10th, 50th, and 90th percentiles, which were derived from a regression model fitted by a multilevel model for continuous data. Results. FH growth curve was derived from 7,523 measurements of 1,038 women. Gestational age was calculated from LMP in 648 women and ultrasound in 390 women. The FH increased from 19.1?cm at 20 weeks to 35.4?cm at 40 weeks. The maximum increase of 1.0?cm/wk was observed between 20 and 32 weeks, declining to 0.7?cm/wk between 33 and 36 weeks and 0.3?cm/wk between 37 and 40 weeks. A quadratic regression equation was FH (cm) = ?19.7882 + 2.438157?GA?(wk) ? 0.0262178 GA2 (wk) (R-squared?=?0.85). Conclusions. A demographically specific FH growth curve may be an appropriate tool for monitoring and screening abnormal intrauterine growth.

Deeluea, Jirawan; Sirichotiyakul, Supatra; Weerakiet, Sawaek; Buntha, Renu; Tawichasri, Chamaiporn

2013-01-01

21

A Method for Growth Curve Comparisons.  

National Technical Information Service (NTIS)

Suppose one has a sample of pairs of age and length measurements from each of two or more populations of fish. The mathematical forms of the growth curves associated with the populations are assumed to be specified but each form contains at least one unkn...

R. F. Kappenman

1981-01-01

22

Can telomere shortening explain sigmoidal growth curves?  

Microsoft Academic Search

A general branching process model is proposed to describe the shortening of telomeres in eukaryotic chromosomes. The model is flexible and incorporates many special cases to be found in the literature. In particular, we show how telomere shortening can give rise to sigmoidal growth curves, an idea first expressed by Portugal et al. [A computational model for telomere-dependent cell-replicative aging,

Peter Olofsson

2010-01-01

23

Nonparametric Regression Analysis of Growth Curves  

Microsoft Academic Search

In recent years, nonparametric curve estimates have been extensively explored in theoretical work. There has, however, been a certain lack of convincing applications, in particular involving comparisons with parametric techniques. The present investigation deals with the analysis of human height growth, where longitudinal measurements were collected for a sample of boys and a sample of girls. Evidence is presented that

Theo Gasser; Hans-Georg Muller; Walter Kohler; Luciano Molinari; Andrea Prader

1984-01-01

24

Growth Assessment in Clinical Practice: Whose Growth Curve?  

Microsoft Academic Search

Differences in growth curves can influence the diagnosis of under- and overnutrition, and the interpretation of adequate growth\\u000a following nutrition intervention. This effect is notable when comparing the World Health Organization (WHO) 2006 Growth Standard\\u000a and the Centers for Disease Control and Prevention (CDC) 2000 Growth Reference for infants and children to 59 months of age.\\u000a Important differences relate to conceptual

Howard G. Parsons; Michael A. George; Sheila M. Innis

2011-01-01

25

Bacterial growth with chlorinated methanes.  

PubMed

Chlorinated methanes are important industrial chemicals and significant environmental pollutants. While the highly chlorinated methanes, trichloromethane and tetrachloromethane, are not productively metabolized by bacteria, chloromethane and dichloromethane are used by both aerobic and anaerobic methylotrophic bacteria as carbon and energy sources. Some of the dehalogenation reactions involved in the utilization of the latter two compounds have been elucidated. In a strictly anaerobic acetogenic bacterium growing with chloromethane, an inducible enzyme forming methyltetrahydrofolate and chloride from chloromethane and tetrahydrofolate catalyzes dehalogenation of the growth substrate. A different mechanism for the nucleophilic displacement of chloride is observed in aerobic methylotrophic bacteria utilizing dichloromethane as the sole carbon and energy source. These organisms possess the enzyme dichloromethane dehalogenase which, in a glutathione-dependent reaction, converts dichloromethane to inorganic chloride and formaldehyde, a central metabolite of methylotrophic growth. Sequence comparisons have shown that bacterial dichloromethane dehalogenases belong to the glutathione S-transferase enzyme family, and within this family to class Theta. The dehalogenation reactions underlying aerobic utilization of chloromethane by a pure culture and anaerobic growth with dichloromethane by an acetogenic mixed culture are not known. It appears that they are based on mechanisms other than nucleophilic attack by tetrahydrofolate or glutathione. PMID:8565906

Leisinger, T; Braus-Stromeyer, S A

1995-06-01

26

Bacterial growth with chlorinated methanes.  

PubMed Central

Chlorinated methanes are important industrial chemicals and significant environmental pollutants. While the highly chlorinated methanes, trichloromethane and tetrachloromethane, are not productively metabolized by bacteria, chloromethane and dichloromethane are used by both aerobic and anaerobic methylotrophic bacteria as carbon and energy sources. Some of the dehalogenation reactions involved in the utilization of the latter two compounds have been elucidated. In a strictly anaerobic acetogenic bacterium growing with chloromethane, an inducible enzyme forming methyltetrahydrofolate and chloride from chloromethane and tetrahydrofolate catalyzes dehalogenation of the growth substrate. A different mechanism for the nucleophilic displacement of chloride is observed in aerobic methylotrophic bacteria utilizing dichloromethane as the sole carbon and energy source. These organisms possess the enzyme dichloromethane dehalogenase which, in a glutathione-dependent reaction, converts dichloromethane to inorganic chloride and formaldehyde, a central metabolite of methylotrophic growth. Sequence comparisons have shown that bacterial dichloromethane dehalogenases belong to the glutathione S-transferase enzyme family, and within this family to class Theta. The dehalogenation reactions underlying aerobic utilization of chloromethane by a pure culture and anaerobic growth with dichloromethane by an acetogenic mixed culture are not known. It appears that they are based on mechanisms other than nucleophilic attack by tetrahydrofolate or glutathione.

Leisinger, T; Braus-Stromeyer, S A

1995-01-01

27

Growth assessment in clinical practice: whose growth curve?  

PubMed

Differences in growth curves can influence the diagnosis of under- and overnutrition, and the interpretation of adequate growth following nutrition intervention. This effect is notable when comparing the World Health Organization (WHO) 2006 Growth Standard and the Centers for Disease Control and Prevention (CDC) 2000 Growth Reference for infants and children to 59 months of age. Important differences relate to conceptual approaches for generating growth standards to describe what population growth should be, compared to a reference of what growth is. WHO included only term infants exclusively or predominantly breast-fed beyond 4 months, and data for infants and children indicative of excess adiposity and growth failure were removed. Thus, fewer children are diagnosed with poor weight gain, and more with excess adiposity, using the WHO Growth Standard than when using the CDC Growth Reference. Adequate growth is based on proportional height and weight gains that track along growth curve trajectories. Use of the WHO curves should assist in prevention of inappropriate intervention or overfeeding in young children. PMID:21445575

Parsons, Howard G; George, Michael A; Innis, Sheila M

2011-06-01

28

Curved tails in polymerization-based bacterial motility  

NASA Astrophysics Data System (ADS)

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

Rutenberg, Andrew D.; Grant, Martin

2001-08-01

29

Periodic growth of bacterial colonies  

NASA Astrophysics Data System (ADS)

The formation of concentric ring colonies by bacterial species Bacillus subtilis and Proteus mirabilis has been investigated experimentally, focusing our attention on the dependence of local cell density upon the bacterial motility. It has been confirmed that these concentric ring colonies reflect the periodic change of the bacterial motility between motile cell state and immotile cell state. We conclude that this periodic change is macroscopically determined neither by biological factors (i.e., biological clock) nor by chemical factors (chemotaxis as inhibitor). And our experimental results strongly suggest that the essential factor for the change of the bacterial motility during concentric ring formation is the local cell density.

Yamazaki, Yoshihiro; Ikeda, Takemasa; Shimada, Hirotoshi; Hiramatsu, Fumiko; Kobayashi, Naoki; Wakita, Jun-Ichi; Itoh, Hiroto; Kurosu, Sayuri; Nakatsuchi, Michio; Matsuyama, Tohey; Matsushita, Mitsugu

2005-06-01

30

Stochasticity in Colonial Growth Dynamics of Individual Bacterial Cells  

PubMed Central

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

Lianou, Alexandra

2013-01-01

31

Human Fetal Weight and Placental Weight Growth Curves  

Microsoft Academic Search

A mathematical analysis of human fetal and placental growth curves was made on data collected prospectively from a population at sea level. Both the fetal and placental growth curves can best be described by a form of the logistic equation inhibited growth model. The fetal growth rate reaches its maximum approximately 4 weeks after the placental growth rate has reached

Duane R. Bonds; Bwalya Mwape; Savitri Kumar; Steven G. Gabbe

1984-01-01

32

Growth factor parametrization in curved space  

SciTech Connect

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

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

2009-07-15

33

Growth strategy of heterotrophic bacterial population along successional sequence on spoil of brown coal colliery substrate  

Microsoft Academic Search

The bacterial population of brown coal colliery spoil (Sokolov coal mining district, Czechia) was characterized by measuring\\u000a viable bacterial biomass, the culturable to total cell ratio (C:T), colony-forming curve (CFC) analysis and species and\\/or\\u000a biotype diversity. Bacterial representatives that differed in colony-forming growth (fast and\\/or slow growers) were used for\\u000a growth-strategy investigation of heterotrophic bacteria. Spoil substrates from the surface

V. Krišt?fek; D. Elhottová; A. Chro?áková; I. Dostálková; T. Picek; J. Kal?ík

2005-01-01

34

A method for turbidimetric measurement of bacterial growth in liquid cultures and agar plug diffusion cultures, using standard test tubes  

Microsoft Academic Search

A method has been developed for turbidimetric measurement of bacterial growth in standard inexpensive test tubes with closures in-place. Liquid cultures and agar plug diffusion cultures can be assayed using an unmodified spectrophotometer. Growth curves of replicate cultures grown in test tubes, are reproducible with respect to similarity of curve shape, onset of logarithmic growth phase, and maximum growth.

K. J. Brown

1980-01-01

35

Comparison of Models for Estimating Individual Growth Curves.  

ERIC Educational Resources Information Center

|Growth curve models are a useful tool for developmentalists because they can estimate an attribute's developmental function by providing a mathematical description of growth on an attribute over time. However, selection of a growth curve model appropriate for estimating individual developmental functions is problematic. The ideal model is the one…

Burchinal, Margaret R.

36

A statistical method for comparing viral growth curves  

Microsoft Academic Search

Viral replication is often analyzed by growth curves, in which viral multiplication in the presence of host cells is measured as a function of time. Comparing growth curves is one of the most sensitive ways of comparing viral growth under different conditions or for comparing replication of different viral mutants. However, such experiments are rarely analyzed in a statistically rigorous

Gary P. Wang; Frederic D. Bushman

2006-01-01

37

Comparison of Models for Estimating Individual Growth Curves.  

ERIC Educational Resources Information Center

Growth curve models are a useful tool for developmentalists because they can estimate an attribute's developmental function by providing a mathematical description of growth on an attribute over time. However, selection of a growth curve model appropriate for estimating individual developmental functions is problematic. The ideal model is the one…

Burchinal, Margaret R.

38

Descriptive and Predictive Growth Curves in Energy System Analysis  

Microsoft Academic Search

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

Mikael Höök; Junchen Li; Noriaki Oba; Simon Snowden

2011-01-01

39

Stochastic simulation of growth curves of Acidithiobacillus ferrooxidans  

Microsoft Academic Search

To reveal the low growth rate of Acidithiobacillus ferrooxidans, a stochastic growth model was proposed to analyze growth curves of these bacteria in a batch culture. An algorithm was applied\\u000a to simulate the bacteria population during lag and exponential phase. The results show that the model moderately fits the\\u000a experimental data. Further, the mean growth constant (K) of growth curves

Yu Yang; Hong Peng; Guan-zhou Qiu; Jian-she Liu; Yue-hua Hu

2006-01-01

40

Dislocation dynamics and bacterial growth  

NASA Astrophysics Data System (ADS)

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

Amir, Ariel; Nelson, David

2012-02-01

41

Growth Curves and Takeover Time in Distributed Evolutionary Algorithms  

Microsoft Academic Search

This paper presents a study of difierent models for the growth curves and takeover time in a distributed EA (dEA). The calculation of the takeover time and the dynamical growth curves is a common analy- tical approach to measure the selection pressure of an EA. This work is a flrst step to mathematically unify and describe the roles of the

Enrique Alba; Gabriel Luque

2004-01-01

42

Regime switching in the latent growth curve mixture model  

Microsoft Academic Search

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 data from the National Longitudinal Survey of

Conor V. Dolan; Verena D. Schmittmann; M. C. Neale; G. H. Lubke

2005-01-01

43

Applications of Individual Growth Curve Modeling for Pediatric Psychology Research  

Microsoft Academic Search

Objective To provide a brief, nontechnical introduction to individual growth curve modeling for the analysis of longitudinal data. Several applications of individual growth curve modeling for pediatric psychology research are discussed. Methods To illustrate these applications, we analyze data from an ongoing pediatric psychology study of the possible impact of spina bifida on child and family development (N = 135).

Christian DeLucia; Steven C. Pitts

2006-01-01

44

Regime Switching in the Latent Growth Curve Mixture Model  

ERIC Educational Resources Information Center

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

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

2005-01-01

45

Does noise reduction matter for curve fitting in growth curve models?  

PubMed

In this paper, we discuss the efficiency of noise reduction for curve fitting in nonlinear growth curve models. We use singular spectrum analysis as a nonlinear-nonparametric denoising method. A set of longitudinal measurements is used in considering the performance of the method. We also use artificially generated data sets with and without noise for the purpose of validation of the results obtained in this study. The results show that noise reduction is important for curve fitting in growth curve models and also, that the singular spectrum analysis technique can be used as a powerful tool for noise reduction in longitudinal measurements. PMID:19573946

Hassani, Hossein; Zokaei, Mohammad; von Rosen, Dietrich; Amiri, Saeid; Ghodsi, Mansoureh

2009-07-01

46

On crack-growth resistance curve fitting for ceramics  

Microsoft Academic Search

KR-curves of crack growth resistance were studied for a particulate ceramic-metal composite in the system lanthanium chromite–chromium in the temperature range 20 to 1100°C. It is shown that the KR-curves can be described satisfactory by an exponential function. With the use of this function, the similarity of the crack-growth resistance curves for the specimens tested at different temperatures can be

Sergei M. Barinov

2000-01-01

47

Bounded Population Growth: A Curve Fitting Lesson.  

ERIC Educational Resources Information Center

|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)|

Mathews, John H.

1992-01-01

48

SITAR--a useful instrument for growth curve analysis  

PubMed Central

Background Growth curve analysis is a statistical issue in life course epidemiology. Height in puberty involves a growth spurt, the timing and intensity of which varies between individuals. Such data can be summarized with individual Preece–Baines (PB) curves, and their five parameters then related to earlier exposures or later outcomes. But it involves fitting many curves. Methods We present an alternative SuperImposition by Translation And Rotation (SITAR) model, a shape invariant model with a single fitted curve. Curves for individuals are matched to the mean curve by shifting their curve up–down (representing differences in mean size) and left–right (for differences in growth tempo), and the age scale is also shrunk or stretched to indicate how fast time passes in the individual (i.e. velocity). These three parameters per individual are estimated as random effects while fitting the curve. The outcome is a mean curve plus triplets of parameters per individual (size, tempo and velocity) that summarize the individual growth patterns. The data are heights for Christ’s Hospital School (CHS) boys aged 9–19 years (N?=?3245, n?=?129?508), and girls with Turner syndrome (TS) aged 9–18 years from the UK Turner Study (N?=?105, n?=?1321). Results The SITAR model explained 99% of the variance in both datasets [residual standard deviation (RSD) 6–7?mm], matching the fit of individually-fitted PB curves. In CHS, growth tempo was associated with insulin-like growth factor-1 measured 50 years later (P?=?0.01, N?=?1009). For the girls with TS randomized to receive oxandrolone from 9 years, velocity was substantially increased compared with placebo (P?=?10?8). Conclusions The SITAR growth curve model is a useful epidemiological instrument for the analysis of height in puberty.

Cole, Tim J; Donaldson, Malcolm D C; Ben-Shlomo, Yoav

2010-01-01

49

Growth rate control of adherent bacterial populations.  

PubMed Central

We report a novel in vitro method which, through application of appropriate nutrient limitations, enables growth rate control of adherent bacterial populations. Exponentially growing cells are collected by pressure filtration onto cellulose acetate membranes. Following inversion into the bases of modified fermentors, membranes and bacteria are perfused with fresh medium. Newly formed and loosely attached cells are eluted with spent medium. Steady-state conditions (dependent upon the medium flow rate) at which the adherent bacterial biomass is constant and proportional to the limiting nutrient concentrations are rapidly achieved, and within limits, the growth rate is proportional to the medium flow rate. Scanning electron microscopic studies showed that such populations consist of individual cells embedded within an extracellular polymer matrix. Images

Gilbert, P; Allison, D G; Evans, D J; Handley, P S; Brown, M R

1989-01-01

50

Developmental Growth Curves of Preschool Children with Vision Impairments.  

ERIC Educational Resources Information Center

Used growth curve analysis to describe the development of 186 preschoolers with vision impairments. Found that mental retardation and developmental delay were associated with lower developmental ages and slower growth rates. Visual function of 20/800 or worse was associated with lower developmental ages and slower growth rates in personal-social…

Hatton, Deborah D.; Bailey, Donald B., Jr.; Burchinal, Margaret R.; Ferrell, Kay Alicyn

1997-01-01

51

New Intrauterine Growth Curves Based on United States Data  

Microsoft Academic Search

OBJECTIVE: The objective of this study was to create and validate new intrauterine weight, length, and head circumference growth curves using a contemporary, large, racially diverse US sample and compare with the Lubchenco curves. METHODS: Data on 391 681 infants (Pediatrix Medical Group) aged 22 to 42 weeks at birth from 248 hospitals within 33 US states (1998 - 2006)

Irene E. Olsen; Sue A. Groveman; M. Louise Lawson; Reese H. Clark; Babette S. Zemel

2010-01-01

52

Bacterial growth on dissolved organic carbon from a blackwater river  

Microsoft Academic Search

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

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

1987-01-01

53

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

Microsoft Academic Search

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

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

2005-01-01

54

A SAS Macro for Estimating and Visualizing Individual Growth Curves  

Microsoft Academic Search

Longitudinal data analyses can be usefully supplemented by the plotting of individ- ual growth curves. Unfortunately, such graphics can be challenging and tedious to produce. This article presents and demonstrates a SAS macro designed to automate this task. The OLStraj macro graphically depicts ordinary least squares (OLS)-esti- mated individual trajectories, describes interindividual variability in OLS-estimated growth parameters, and identifies possible

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

2004-01-01

55

Genetic architecture of growth curve parameters in chickens  

Microsoft Academic Search

Genetic improvement in growth of poultry has traditionally proceeded via selection for body weight at a fixed age. Due to increased maintenance costs and reproductive problems of adult broiler breeders, the potential for genetic manipulation of the growth curve has been receiving increased interest. Research of both male and female progeny of a three-way diallel cross was used to investigate

G. F. Barbato

1991-01-01

56

Comparative study of the growth curves of B. Subtilis, K. Pneumoniae, C. Xerosis, and E. Coli bacteria using nanometric silicon particles as a bacteriological sensor  

Microsoft Academic Search

In this research nanometric particles from luminescent porous silicon film were synthesized. This particles were later inoculated in bacterial strains of B. subtilis (BSi) and K. pneumoniae (KSi). A comparison of the behavior of their growth curve and the ones reported for C. xerosis (XSi) and E. coli (ESi) in presence of silicon nanoparticles is presented. The growth curve of

Lilyanna Perez; Marjorie Flores; Javier Avalos; L. San Miguel; O. Resto; L. F. Fonseca

2003-01-01

57

Bacterial Ammonia Causes Significant Plant Growth Inhibition  

PubMed Central

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

Weise, Teresa; Kai, Marco; Piechulla, Birgit

2013-01-01

58

Analysis of growth curves of fowl. II. Ducks  

Microsoft Academic Search

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 (R = 0.9991–0.9997).3. The

H. Knížetová; J. Hyánek; B. Kníže; H. Procházková

1991-01-01

59

Menaquinone analogs inhibit growth of bacterial pathogens.  

PubMed

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

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

2013-08-19

60

Mediation Analysis in a Latent Growth Curve Modeling Framework  

ERIC Educational Resources Information Center

|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…

von Soest, Tilmann; Hagtvet, Knut A.

2011-01-01

61

Sensitivity of Fit Indices to Misspecification in Growth Curve Models  

ERIC Educational Resources Information Center

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

Wu, Wei; West, Stephen G.

2010-01-01

62

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

ERIC Educational Resources Information Center

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

Tong, Xin; Zhang, Zhiyong

2012-01-01

63

Shortening of telomeres, sigmoidal growth curves, and general branching processes  

Microsoft Academic Search

A general branching process model is proposed to describe the shortening of telomeres in eukariotic chromosomes. The model is flexible and incorporates many special cases to be found in the literature. In particular, we show how telomere shortening can give rise to sigmoidal growth curves, an idea first expressed by Portugal et al. (2008). We also demonstrate how other types

Peter Olofsson

2009-01-01

64

Why do rotifer populations present a typical sigmoid growth curve?  

Microsoft Academic Search

To determine the underlying processes to population growth in the rotifer Brachionus plicatilis, we conducted an experiment using 1.5 ml cultures for 70 days. All individuals were transferred daily to culture media containing algae, and the number of individuals, clutch sizes and number of deaths were counted. The population dynamics showed a typical sigmoid curve. The population density increased exponentially

Tatsuki Yoshinaga; Atsushi Hagiwara; Katsumi Tsukamoto

2001-01-01

65

Mediation Analysis in a Latent Growth Curve Modeling Framework  

ERIC Educational Resources Information Center

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…

von Soest, Tilmann; Hagtvet, Knut A.

2011-01-01

66

Bayesian Analysis of Longitudinal Data Using Growth Curve Models  

ERIC Educational Resources Information Center

Bayesian methods for analyzing longitudinal data in social and behavioral research are recommended for their ability to incorporate prior information in estimating simple and complex models. We first summarize the basics of Bayesian methods before presenting an empirical example in which we fit a latent basis growth curve model to achievement data…

Zhang, Zhiyong; Hamagami, Fumiaki; Wang, Lijuan Lijuan; Nesselroade, John R.; Grimm, Kevin J.

2007-01-01

67

Sensitivity of Fit Indices to Misspecification in Growth Curve Models  

ERIC Educational Resources Information Center

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

Wu, Wei; West, Stephen G.

2010-01-01

68

BACTERIAL GROWTH EFFICIENCY ON NATURAL DISSOLVED ORGANIC MATTER  

EPA Science Inventory

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

69

Bacterial Growth Efficiency on Natural Dissolved Organic Matter.  

National Technical Information Service (NTIS)

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

N. Kroer

1993-01-01

70

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

Microsoft Academic Search

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 modeling (GCM). This study introduces a cross-classified multiple membership growth curve model (CCMM-GCM)

Matthew W. Grady; S. Natasha Beretvas

2010-01-01

71

Sensitivity of Fit Indices to Misspecification in Growth Curve Models  

Microsoft Academic Search

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 approximation, standardized root mean square residual, comparative fit index, and Tucker-Lewis Index. The fit indices were

Wei Wu; Stephen G. West

2010-01-01

72

[Comparison of stature growth curves in children and adolescents].  

PubMed

Growth charts of height in Chinese children and adolescents (excluding Taiwan and Hong Kong) in the 1980s and 1990s were fitted to JPA2 model to study their growth and developmental characteristics and their future trend and to compare them with the criteria for growth in the developed countries and areas. Results showed that fitted growth curves were comparable. The difference in body height of children in cities during puberty period was the most significant during the 1980s. Body height of boys and girls aged over seven to maturity period in Beijing during the 1990s was higher than that in Hong Kong and Japan, and reached basically the criteria set by the National Center for Health Statistics (NCHS), United States, but body height of adults was still three to four centimeters lower than that in criteria set by NCHS. Body height in adolescents in Beijing was kept in stable as compared with that in the 1980s. PMID:9812579

Xu, Y; Liang, S; Liu, D

1997-07-01

73

Effect of bacterial satellites on Chlamydomonas reinhardtii growth in an algo-bacterial community  

Microsoft Academic Search

The growth characteristics of an algo-bacterial community (Chlamydomonas reinhardtii and bacterial satellites) were studied, as well as the mechanism and patterns of bacterial effect on algae. Four strains\\u000a of predominant bacteria were isolated and partially characterized. They were assigned to the following taxa: Rhodococcus terrea, Micrococcus roseus, and Bacillus spp. A pure culture of the alga under study was obtained

Yu. A. Nikolaev; V. K. Plakunov; N. A. Voronina; N. V. Nemtseva; A. O. Plotnikov; O. A. Gogoleva; M. E. Murav’eva; G. V. Ovechkina

2008-01-01

74

Growth Response of Soda Lake Bacterial Communities to Simulated Rainfall  

Microsoft Academic Search

Moderately saline soda lakes harbor extremely abundant and fast growing bacterial communities. An interesting phenomenon of\\u000a an explosive bacterial growth in shallow soda lakes in Eastern Austria after dilution with rainwater, concomitantly with a\\u000a significant decrease in temperature was observed in a former study. In the present study, we tried to identify the factors\\u000a being responsible for this enhanced bacterial

M. Krammer; B. Velimirov; U. Fischer; A. H. Farnleitner; A. Herzig; A. K. T. Kirschner

2008-01-01

75

Super-diffusive Bacterial Growth in Highly Advective Random Environments  

NASA Astrophysics Data System (ADS)

Bacterial growth may be modeled using a reaction-diffusion equation with Fisher-like growth terms. This includes a growth term proportional to the bacterial concentration in addition to a non-linear term to prevent unbounded growth. An additional random growth term may be added to simulate the spatial fluctuation of nutrients in the environment. Recent calculations for such a model with only linear terms has predicted that in the highly advective regime bacterial growth is super-diffusive in directions orthogonal to the convection velocity(D. R. Nelson and N. M. Shnerb, Phys. Rev. E 58), 1383 (1998).. We test these predictions via numerical simulations of the corresponding growth equation in two dimensions. The full non-linear equation is also numerically simulated and compared with the linear case.

Carpenter, John H.; Dahmen, Karin A.; Nelson, David R.

2003-03-01

76

Influence of bacterial type and density on population growth of bacterial-feeding nematodes  

Microsoft Academic Search

The contribution of bacterial-feeding nematodes to litter decomposition and nutrient mineralization depends, in part, on the abundance of particular nematode species. Population dynamics will be constrained by edaphic factors, food availability and food quality. We report the population growth rates for six nematode species as affected by different bacterial isolates and by changes in food supply. Populations of Caenorhabditis elegans

R. C. Venette; H. Ferris

1998-01-01

77

Thermal constraints to population growth of bacterial-feeding nematodes  

Microsoft Academic Search

Bacterial-feeding nematodes are important participants in decomposition pathways and nutrient cycles in soils. The contribution of each species to component processes depends upon the physiology of individuals and the dynamics of populations. Having determined the effects of temperature on metabolic rates of several species of bacterial-feeding nematodes, we now present the effects of temperature on population growth rates and relate

R. C. Venette; H. Ferris

1997-01-01

78

Leuconostoc mesenteroides growth kinetics with application to bacterial profile modification  

Microsoft Academic Search

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

Raymond E. Lappan; H. Scott Fogler

1994-01-01

79

Estimating the parameters of the Baranyi model for bacterial growth  

Microsoft Academic Search

The identifiability properties of the Baranyi model for bacterial growth were investigated, both structurally and applied to real-life data. Using the Taylor-series approach, it was formally proven that the model is structurally identifiable, i.e. it is now ascertained that it is certainly possible to give unique values to all parameters of the model, provided the bacterial growth data are of

K. Grijspeerdt; P. Vanrolleghem

1999-01-01

80

Bacterial Growth Without Net Protein Synthesis.  

National Technical Information Service (NTIS)

The report discusses postesponential growth and the so-called stationary growth phase of bacteria. Exponential growth can cease for different reasons, one of which is depletion of an essential nutrient from the medium. Depletion of different nutrients res...

G. Toennies

1970-01-01

81

Curved faces in polymer crystals with asymmetrically spreading growth patches  

NASA Astrophysics Data System (ADS)

Polymer crystals often have curved faces. Understanding such morphology is of major interest since it allows distinction between fundamentally different theories of polymer crystallization. E.g. Sadler's ``roughness-pinning'' theory assumes that the curvature is a result of roughening transition on lateral faces. It has since been shown by Mansfield that the curvature can be explained quantitatively, essentially within the Lauritzen-Hoffman nucleation theory. However, the step propagation rates v implied in their treatment are substantially lower than predicted by the LH theory. The retardation appears to be due to the ``self-poisoning'' or ``pinning'' effect of incorrect chain attachment, effectively demonstrated by the extreme cases of growth rate minima in long-chain monodisperse n-alkanes. Recently crystals of poly(vinylidene fluoride) and alkanes C162H326 and C198H398 have been found with habits that can be best described as bounded by curved 110 faces. The interesting feature is the asymmetry of the curvature: while the faces are curved at one end, they are straight at the other. We carried out mathematical analysis of the curvature, generalizing the Mansfield model. We suggest that such asymmetric curvature arises from the propagation rates to the left, vl, and to the right, vr, being different because of the lack of mirror bisecting planes such as (110). By solving appropriate equations with moving boundaries, we obtained the shape of the growth front y(x,t). Calculated crystal habits gave excellent fits to the observed growth shapes of a-axis lenticular crystals of long alkanes and PVDF, as well as of single crystals of PEO. This explains some hitherto poorly understood morphologies and, in principle, allows independent measurements of step initiation and propagation rates in all polymers.

Ungar, Goran

2006-03-01

82

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

Microsoft Academic Search

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

Agustín Blasco; Miriam Piles; Luis Varona

2003-01-01

83

Pantothenate and Coenzyme a in Bacterial Growth.  

National Technical Information Service (NTIS)

The effect of environmental pantothenate levels on the growth of Streptococcus faecalis 9790 was studied in terms of growth rate, depletion phenomena, cellular coenzyme A (CoA) content, and differential rates of wall and membrane synthesis. Low concentrat...

G. Toennies D. N. Das F. Feng

1966-01-01

84

[Effect of bacterial satellites on Chlamydomonas reinhardtii growth in an algo-bacterial community].  

PubMed

The growth characteristics of an algo-bacterial community (Chlamydomonas reinhardtii and bacterial satellites) were studied, as well as the mechanism and patterns of bacterial effect on algae. Four strains of predominant bacteria were isolated and partially characterized. They were assigned to the following taxa: Rhodococcus terrea, Micrococcus roseus, and Bacillus spp. A pure culture of the alga under study was obtained by plating serial dilutions on agarized media with ampicillin. Within the algo-bacterial association, the alga had a higher growth rate (0.76 day(-1)) and yield (60 microg chlorophyll/ml culture) than in pure cultures (0.4 day(-1) and 10 microg chlorophyll/ml culture, respectively). The viability of the algal cells within the association was retained longer than in pure culture. Among the isolated bacterial satellites, strains B1 and Y1, assigned to the species Rhodococcus terrae, had the highest stimulatory effect on algal growth. The culture liquid of bacteria incubated under the conditions not permitting growth stimulated algal growth; the culture liquid of actively growing bacteria had an opposite effect. PMID:18365726

Nikolaev, Iu A; Plakunov, V K; Voronina, N A; Nemtseva, N V; Plotnikov, A O; Gogoleva, O A; Murav'eva, M E; Ovechkina, G V

85

Parent involvement and science achievement: A latent growth curve analysis  

NASA Astrophysics Data System (ADS)

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

Johnson, Ursula Yvette

86

Bacterial and fungal growth in total parenteral nutrition solutions  

Microsoft Academic Search

The most serious complication of prolonged intravenous infusion of hypertonic dextrose and amino acids is infection. Frequently,\\u000a the etiology is fungal rather than bacterial. Previous authors have suggested that bacterial survival and growth in the solutions\\u000a is suppressed by (a) high dextrose concentration, (b) high osmolality, or (c) low pH. This paper presents evidence that proposals\\u000a (a) and (b) are

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

1975-01-01

87

SELECTION FOR ANNUAL GROWTH CURVES IN NICOTZANA TABACUM L.I  

Microsoft Academic Search

The cumulative growth of a plant is the result of interrelated processes, and response to selection for changes in the annual growth curve requires many physiological adjustments. Selection to modify the entire annual growth curve may therefore not be as effective as linear models may predict. Periodic growth of a population of Nicotiana tabacum L. was estimated to have herit-

G. NAMKOONG; D. F. MATZINGER

88

The curve of growth for stars in the effective temperature range 4000–8500 K  

Microsoft Academic Search

A comparison of different curves of growth derived from available model atmospheres has been done. We found that, in the effective temperature range (4000–8500 K), the differences between models with the same (Teff, logg) from different authors, do not affect the shape of the curve of growth. Moreoyer, the shifts needed to superpose the curves, for different elements, differ only

M. Villada; L. Rossi

1987-01-01

89

Discrepancy between growth of Coccidioides immitis in bacterial blood culture media and a radiometric growth index  

SciTech Connect

Spherules of Coccidioides immitis grew readily after inoculation in vented trypticase soy broth, biphasic brain heart infusion media, and aerobic tryptic soy broth bottles used in a radiometric system (BACTEC). However, visible growth was not accompanied by a significant radiometric growth index. Growth of C. immitis can be visually detected in routine bacterial blood culture media while the radiometric growth index remains negative.

Ampel, N.M.; Wieden, M.A.

1988-01-01

90

Growth curves: how to best measure growth of the preterm infant.  

PubMed

Birth weight is one of the most important anthropometric measures in the evaluation of an infant. For the full-term infant, birth weight is compared with reference or standard growth curves that are constructed by plotting weight, length, and head circumference against postnatal age. Following a similar approach for preterm infants is less effective for a variety of reasons. Birth weight and other anthropometric measures used to evaluate an infant at birth are influenced by various maternal characteristics, the intrauterine milieu, and duration of gestation. Second, the causes of premature birth and their impact on birth weight are largely unknown. Third, gestational age is difficult to determine with full certainty. One approach that has been used to circumvent these issues is to use intrauterine growth reference curves. However, these curves do not really reflect "normal" growth because they were constructed using cross-sectional data from infants born prematurely and, as such, do not reflect the normal condition. Thus, there is a need to develop normative growth curves derived from "healthy" preterm infants that can be applied to neonates born prematurely. These should be updated periodically to reflect secular trends in maternal body weight, height, and overall health. PMID:23445844

Bhatia, Jatinder

2013-03-01

91

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

ERIC Educational Resources Information Center

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

Grady, Matthew W.; Beretvas, S. Natasha

2010-01-01

92

A Parallel Study on Bacterial Growth and Inactivation  

Microsoft Academic Search

Pure stochastic birth process models are used to establish the connection between the traditional food microbiology concept of bacterial lag period, before the exponential growth, and the distribution of the lag times of individual cells. In a parallel way, similar study is carried out on the connection between the “shoulder” period, before the exponential decay, and the distribution of the

JOD ZSEF BARANYI; CARMEN PIN

2001-01-01

93

Determination of Compounds Inhibiting Bacterial Growth in Sterilized Medical Devices  

Microsoft Academic Search

Summary Medical devices must be sterilized before shipping. During sterilization the quality of the medical device must be maintained. Polysulfone (PS) and polycarbonate (PC) are often used as materials for medical devices. It has been observed that compounds inhibiting bacterial growth are produced when PS or PC are sterilized by autoclaving or by use of ozone gas, especially when ozone

H. Shintani; E. Suzuki; M. Sakurai

2003-01-01

94

Comparative study of the growth curves of B. Subtilis, K. Pneumoniae, C. Xerosis, and E. Coli bacteria using nanometric silicon particles as a bacteriological sensor  

NASA Astrophysics Data System (ADS)

In this research nanometric particles from luminescent porous silicon film were synthesized. This particles were later inoculated in bacterial strains of B. subtilis (BSi) and K. pneumoniae (KSi). A comparison of the behavior of their growth curve and the ones reported for C. xerosis (XSi) and E. coli (ESi) in presence of silicon nanoparticles is presented. The growth curve of BSi, as well as the KSi, present changes compared to their standard curves. The BSi growth curve grows below the standard curve after teh fifth hor, while in the KSi this happens after the eighth hour. Based on our preliminary findings we can sepculate that at this point in time a critical population is present, and this may give rise to the possible incorporation of the silicon particles by the bacteria, or a possible pleomorphism inhibits reproduction. The stationary region, in both case, takes place sooner than in the standard curve. No significant oscillations are observed in any case, which differs from the XSi curve, were oscillations of intervals of almost 1 hour were reported. In addition, these curves have a different behavior when compared to the ESi growth curve, in which no significant differences between the standard and teh particle containing sample were reported.

Perez, Lilyanna; Flores, Marjorie; Avalos, Javier; San Miguel, L.; Resto, O.; Fonseca, L. F.

2003-04-01

95

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

Microsoft Academic Search

Growth curve data consist of repeated measurements of a continuous growth process over time in a population of individuals. These data are classically analyzed by nonlinear mixed models. However, the standard growth functions used in this context prescribe monotone increasing growth and can fail to model unexpected changes in growth rates. We propose to model these variations using stochastic differential

Jean-Louis Foulley; Adeline Samson; Sophie Donnet

2010-01-01

96

Association between different growth curve definitions of overweight and obesity and cardiometabolic risk in children  

PubMed Central

Background: Overweight and obesity in young people are assessed by comparing body mass index (BMI) with a reference population. However, two widely used reference standards, the Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) growth curves, have different definitions of overweight and obesity, thus affecting estimates of prevalence. We compared the associations between overweight and obesity as defined by each of these curves and the presence of cardiometabolic risk factors. Methods: We obtained data from a population-representative study involving 2466 boys and girls aged 9, 13 and 16 years in Quebec, Canada. We calculated BMI percentiles using the CDC and WHO growth curves and compared their abilities to detect unfavourable levels of fasting lipids, glucose and insulin, and systolic and diastolic blood pressure using receiver operating characteristic curves, sensitivity, specificity and kappa coefficients. Results: The z scores for BMI using the WHO growth curves were higher than those using the CDC growth curves (0.35–0.43 v. 0.12–0.28, p < 0.001 for all comparisons). The WHO and CDC growth curves generated virtually identical receiver operating characteristic curves for individual or combined cardiometabolic risk factors. The definitions of overweight and obesity had low sensitivities but adequate specificities for cardiometabolic risk. Obesity as defined by the WHO or CDC growth curves discriminated cardiometabolic risk similarly, but overweight as defined by the WHO curves had marginally higher sensitivities (by 0.6%–8.6%) and lower specificities (by 2.6%–4.2%) than the CDC curves. Interpretation: The WHO growth curves show no significant discriminatory advantage over the CDC growth curves in detecting cardiometabolic abnormalities in children aged 9–16 years.

Kakinami, Lisa; Henderson, Melanie; Delvin, Edgard E.; Levy, Emile; O'Loughlin, Jennifer; Lambert, Marie; Paradis, Gilles

2012-01-01

97

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

ERIC Educational Resources Information Center

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…

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

2004-01-01

98

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

ERIC Educational Resources Information Center

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

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

2011-01-01

99

A Growth Curve Model of Learning Acquisition among Cognitively Normal Older Adults  

Microsoft Academic Search

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,

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

2005-01-01

100

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

ERIC Educational Resources Information Center

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

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

2011-01-01

101

Crack growth resistance curve and size effect in the fracture of cement paste  

Microsoft Academic Search

A general theory is presented for the fracture of cementitious materials. It is shown that crack growth resistance curves can be constructed for cement pastes using fracture data available in the literature. The crack growth resistance curves are used to explain the specimen size and crack length dependence of fracture toughness in cement pastes.

Brian Cotterell; Yiu-Wing Mai

1987-01-01

102

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

ERIC Educational Resources Information Center

|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…

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

2008-01-01

103

Automated spatial and temporal image analysis of bacterial cell growth  

Microsoft Academic Search

The state-of-the-art technology using o w-chamber microscopy imaging enables us to gain insight into the arcana of bacterial cell growth. How- ever, a large number of high resolution develop- mental image data sets are produced that need to be properly processed and analyzed. The math- ematical challenge lies in the automated image analysis, extraction of cell size proles and de-

Moe Razaz; J ozsef Baranyi

104

Modeling bacterial growth patterns in the presence of antibiotic  

Microsoft Academic Search

With recent growth in systems biology research there has been a significant increase in complex systems modeling research relating to biological systems. Multi-drug resistant (MDR) organisms are a threat not only as hospital-acquired infections, but also now as community-acquired infections. Multilocus sequence typing (MLST) can genetically characterize clones of several bacterial pathogens, allowing the tracking of hypervirulent\\/ antibiotic resistant lineages

Ray Walshe

2006-01-01

105

Two-stage method of estimation for general linear growth curve models.  

PubMed

We extend the linear random-effects growth curve model (REGCM) (Laird and Ware, 1982, Biometrics 38, 963-974) to study the effects of population covariates on one or more characteristics of the growth curve when the characteristics are expressed as linear combinations of the growth curve parameters. This definition includes the actual growth curve parameters (the usual model) or any subset of these parameters. Such an analysis would be cumbersome using standard growth curve methods because it would require reparameterization of the original growth curve. We implement a two-stage method of estimation based on the two-stage growth curve model used to describe the response. The resulting generalized least squares (GLS) estimator for the population parameters is consistent, asymptotically efficient, and multivariate normal when the number of individuals is large. It is also robust to model misspecification in terms of bias and efficiency of the parameter estimates compared to maximum likelihood with the usual REGCM. We apply the method to a study of factors affecting the growth rate of salmonellae in a cubic growth model, a characteristic that cannot be analyzed easily using standard techniques. PMID:9192460

Stukel, T A; Demidenko, E

1997-06-01

106

Fitting growth curves to retrospective size-at-age data  

Microsoft Academic Search

The bones and scales of fish are a rich source of information, for they encode in their microstructure the fish’s age and growth history. The growth history in the hard part is used to estimate the somatic growth history of an individual. This, in turn, is used to estimate the growth of the population. Although straightforward in concept, the estimation

Cynthia M Jones

2000-01-01

107

Phenotypic and genetic variability of estimated growth curve parameters in mice  

Microsoft Academic Search

Data from 1,919 outbred ICR mice were used to examine the potential usefulness of growth curve parameters as selection criteria for altering the relationship between body weight and age. A logistic growth function was used to model growth through 12 weeks of age. Estimates of asymptotic weight (A), maximum growth rate (r) and age at point of inflection (t*) were

S. D. Kachman; R. L. Baker; D. Gianola

1988-01-01

108

Leuconostoc mesenteroides growth kinetics with application to bacterial profile modification  

SciTech Connect

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.

Lappan, R.E.; Fogler, H.S. (Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Chemical Engineering)

1994-04-15

109

Development of normalized curves for the international growth reference: historical and technical considerations?3  

Microsoft Academic Search

ABSTRACF The World Health Organization recommended in 1978 that the National Center for Health Statistics\\/Centers for Disease Control growth reference curves be used as an inter- national growth reference. To permit the expression ofgrowth in terms of standard deviations, CDC developed growth curves from the observed data that approximate normal distributions. Because of significant skewness, standard deviations for weight-for-age and

Michael J Dibley; James B Goldsby; Norman W Staehling; Frederick L Trowbridge

110

A Multilevel Latent Growth Curve Approach to Predicting Student Proficiency  

ERIC Educational Resources Information Center

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

Choi, Kilchan; Goldschmidt, Pete

2012-01-01

111

Investigations on standardized growth curve (SGC) procedure for optical dating of heated quartz  

Microsoft Academic Search

When an equivalent dose value (D\\u000a \\u000a e\\u000a ) is estimated by using a conventional OSL-SAR method, it is necessary to make growth curves of all the aliquots used for\\u000a D\\u000a \\u000a e\\u000a estimation. However, the technique using standardized growth curve (SGC) has an advantage in that, once a standardized growth\\u000a curve is defined, an equivalent dose value can be quickly obtained

D. G. Hong; J. H. Choi

2008-01-01

112

Ecological inference on bacterial succession using curve-based community fingerprint data analysis, demonstrated with rhizoremediation experiment.  

PubMed

Nucleic acid-based community fingerprinting methods are valuable tools in microbial ecology, as they offer rapid and robust means to compare large series of replicates and references. To avoid the time-consuming and potentially subjective procedures of peak-based examination, we assessed the possibility to apply direct curve-based data analysis on community fingerprints produced with bacterial length heterogeneity PCR (LH-PCR). The dataset comprised 180 profiles from a 21-week rhizoremediation greenhouse experiment with three treatments and 10 sampling times. Curve-based analysis quantified the progressive effect of the plant (Galega orientalis) and the reversible effect of the contaminant (fuel oil) on bacterial succession. The major observed community shifts were assigned to changes in plant biomass and contamination level by canonical correlation analysis. A novel method to extract relative abundance data from the fingerprint curves for Shannon diversity index revealed contamination to reversibly decrease community complexity. By cloning and sequencing the fragment lengths, recognized to change in time in the averaged LH-PCR profiles, we identified Aquabacterium (Betaproteobacteria) as the putative r-strategic fuel oil degrader, and K-strategic Alphaproteobacteria growing in abundance later in succession. Curve-based community fingerprint analysis can be used for rapid data prescreening or as a robust alternative for the more heavily parameterized peak-based analysis. PMID:22066474

Mikkonen, Anu; Lappi, Kaisa; Wallenius, Kaisa; Lindström, Kristina; Suominen, Leena

2011-09-12

113

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

Microsoft Academic Search

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

TALY DAWN DREZNER

2003-01-01

114

Investigation of Mediational Processes Using Parallel Process Latent Growth Curve Modeling  

Microsoft Academic Search

This study investigated a method to evaluate mediational processes using latent growth curve modeling. The mediator and the outcome measured across multiple time points were viewed as 2 separate parallel processes. The mediational process was defined as the independent variable influencing the growth of the mediator, which, in turn, af- fected the growth of the outcome. To illustrate modeling procedures,

JeeWon Cheong; David P. MacKinnon; Siek Toon Khoo

2003-01-01

115

Growth curves in untreated Ullrich-Turner syndrome: French reference standards 1-22 years  

Microsoft Academic Search

In this retrospective study spanning 22 years, 167 untreated females with Ullrich-Turner syndrome were identified and their case records followed throughout their growth period. Information on total and segmental height and weight was retrieved from the case records and used to plot growth curves. Centiles from birth to adulthood were calculated which showed that the normal pubertal growth spurt was

M. Sempé; C. Hansson Bondallaz; C. Limoni

1996-01-01

116

Bacterial Spring Constant in Log-Phase Growth  

NASA Astrophysics Data System (ADS)

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.

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

2011-07-01

117

A new mathematical model for chemotactic bacterial colony growth.  

PubMed

A new continuum model for the growth of a single species biofilm is proposed. The geometry of the biofilm is described by the interface between the biomass and the surrounding liquid. Nutrient transport is given by the solution of a semi-linear Poisson equation. In this model we study the morphology of a chemotactic bacterial colony, which grows in the direction of increasing nutrient concentration. Numerical simulations using the level set method and finite difference schemes are presented. The results show rich heterogeneous morphology. PMID:15303740

Alpkvist, E; Overgaard, N Chr; Gustafsson, S; Heyden, A

2004-01-01

118

Economic development and population growth: an inverted-U shaped curve?  

Microsoft Academic Search

There has been a large debate on the relations between demography and economic development. Our paper discusses the possibility that there exists an inverted-U curve, similar in shape to Kuznets’s curve, between the growth rate of population and the growth rate of the per-capita GDP. The cross-country empirical analysis, carried out on over 90 countries in the period 1980-2010, seems

Valli Vittorio; Saccone Donatella

2011-01-01

119

A mixed model for investigating a population of asymptotic growth curves using restricted B -splines  

Microsoft Academic Search

We introduce a new method for modeling a population of growth curves with B-splines, adapting the usual regression spline basis to ensure a horizontal upper asymptote in all fitted curves. The new\\u000a method is easily implemented in standard statistical software. We motivate and illustrate our method using data on the growth\\u000a of Brown Kiwi (Apteryx mantelli) in the North Island

Geoffrey Jones; Joyce Leung; Hugh Robertson

2009-01-01

120

How Stable is the Forecasting Performance of the Yield Curve for Output Growth?  

Microsoft Academic Search

We provide an extensive evaluation of the predictive performance of the US yield curve for US gross domestic product growth by using new tests for forecast breakdown, in addition to a variety of in-sample and out-of-sample evaluation procedures. Empirical research over the past decades has uncovered a strong predictive relationship between the yield curve and output growth, whose stability has

Raffaella Giacomini; Barbara Rossi

2006-01-01

121

How Stable is the Forecasting Performance of the Yield Curve for Outpot Growth?  

Microsoft Academic Search

We provide an extensive evaluation of the predictive performance of the U.S. yield curve for U.S. GDP growth by using a new test for forecast breakdown as well as a variety of in-sample and out-of-sample testing procedures. Empirical research over the past decades uncovered a strong predictive relationship between the yield curve and output growth. However, the parameter estimates that

Barbara Rossi; Raffaella Giacomini

2005-01-01

122

Growth characteristics of three bacterial isolates from an arctic soil.  

PubMed

Three bacterial isolates, a Pseudomonas sp., a Bacillus sp., and an Arthrobacter sp., commonly isolated from a hummocky sedge-moss meadow at Devon Island, N.W.T., Canada, were selected for further taxonomic characterization and for a study of the effects of temperature and limiting carbon source on growth. Pseudomonas M216 resembled P. putida and Bacillus M153, B. carotarum. Arthrobacter M51 had growth-factor requirements which were more complex than those of any named species of that genus. The temperature ranges of growth indicated that Pseudomonas M216 and Arthrobacter M51 were psychrotrophic while Bacillus M153 was mesophilic. Growth in batch culture at limiting glucose concentrations enabled the calculation of Ks and Y values for each isolate. These were similar to those obtained for other organisms and Pseudomonas M216 and Bacillus M153 showed a high affinity for glucose. The nutritional versatility of Arthrobacter M51 and its ability to grow at low temperatures and the high growth rates and affinity of Pseudomonas M216 for low substrate concentrations may account for their competitive abilities in the natural environment, while the inability of Bacillus M153 to grow at low temperatures may limit its activity in tundra soils. PMID:688099

Nelson, L M; Parkinson, D

1978-08-01

123

Dislocation-mediated growth of bacterial cell walls  

PubMed Central

Recent experiments have illuminated a remarkable growth mechanism of rod-shaped bacteria: proteins associated with cell wall extension move at constant velocity in circles oriented approximately along the cell circumference [Garner EC, et al., (2011) Science 333:222–225], [Domínguez-Escobar J, et al. (2011) Science 333:225–228], [van Teeffelen S, et al. (2011) PNAS 108:15822–15827]. We view these as dislocations in the partially ordered peptidoglycan structure, activated by glycan strand extension machinery, and study theoretically the dynamics of these interacting defects on the surface of a cylinder. Generation and motion of these interacting defects lead to surprising effects arising from the cylindrical geometry, with important implications for growth. We also discuss how long range elastic interactions and turgor pressure affect the dynamics of the fraction of actively moving dislocations in the bacterial cell wall.

Amir, Ariel; Nelson, David R.

2012-01-01

124

[The development of bacterial growth stimulants from plants].  

PubMed

Dried bacterial growth stimulators in the form of water extracts of wild marjoram were developed; they produced a stimulating effect on Escherichia coli and Streptococcus pyogenes Dick 1 and had no influence on the growth of Corynebacterium xerosis 1911. The study aimed at finding out the active principle of the stimulator prepared from marjoram extract revealed that under experimental conditions marjoram extract could be divided into 3 fractions of these: fraction 1 contained terpenic hydrocarbons, fraction 2 contained vitamins and vitamin-like substances, fraction 3 contained phenols, flavonoids, phenolcarbonic and fatty acids. Fraction 3 at a concentration of 0.0001% produced the best effect. The stimulating effect of extracts obtained from lime and aspen leaves, haw berries was demonstrated. PMID:9532679

Adlova, G P; Denisova, S V; Ilidzhev, A K; Smirnova, G A; Ratnikova, T N; Arep'eva, A A; Mel'nikova, V A

125

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

Microsoft Academic Search

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

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

1995-01-01

126

Medium-dependent control of the bacterial growth rate.  

PubMed

By combining results from previous studies of nutritional up-shifts we here re-investigate how bacteria adapt to different nutritional environments by adjusting their macromolecular composition for optimal growth. We demonstrate that, in contrast to a commonly held view the macromolecular composition of bacteria does not depend on the growth rate as an independent variable, but on three factors: (i) the genetic background (i.e. the strain used), (ii) the physiological history of the bacteria used for inoculation of a given growth medium, and (iii) the kind of nutrients in the growth medium. These factors determine the ribosome concentration and the average rate of protein synthesis per ribosome, and thus the growth rate. Immediately after a nutritional up-shift, the average number of ribosomes in the bacterial population increases exponentially with time at a rate which eventually is attained as the final post-shift growth rate of all cell components. After a nutritional up-shift from one minimal medium to another minimal medium of higher nutritional quality, ribosome and RNA polymerase syntheses are co-regulated and immediately increase by the same factor equal to the increase in the final growth rate. However, after an up-shift from a minimal medium to a medium containing all 20 amino acids, RNA polymerase and ribosome syntheses are no longer coregulated; a smaller rate of synthesis of RNA polymerase is compensated by a gradual increase in the fraction of free RNA polymerase, possibly due to a gradual saturation of mRNA promoters. We have also analyzed data from a recent publication, in which it was concluded that the macromolecular composition in terms of RNA/protein and RNA/DNA ratios is solely determined by the effector molecule ppGpp. Our analysis indicates that this is true only in special cases and that, in general, medium adaptation also depends on factors other than ppGpp. PMID:23228516

Ehrenberg, Måns; Bremer, Hans; Dennis, Patrick P

2012-12-07

127

Maternal adaptation to pediatric neurosurgical diagnosis: A growth curve analysis  

Microsoft Academic Search

Objective: To describe trajectories of change in maternal adaptation to chronic pediatric neurosurgical diagnosis and to identify variables predicting the level and rate of adaptation.Methods: One hundred and thirty seven mothers of children diagnosed with neurosurgical illness participated. Mothers reported socio-demographic variables, neuroticism, optimism, spouse support, mental health, and personal growth. The coordinating nurse assessed illness variables. Data were collected

Sigal Tifferet; Yoel Elizur; Shlomi Constantini; Orna Friedman; Orly Manor

2010-01-01

128

What does the yield curve tell us about GDP growth?  

Microsoft Academic Search

A lot, including a few things you may not expect. Previous studies find that the term spread forecasts GDP but these regressions are unconstrained and do not model regressor endogeneity. We build a dynamic model for GDP growth and yields that completely characterizes expectations of GDP. The model does not permit arbitrage. Contrary to previous findings, we predict that the

Andrew Ang; Monika Piazzesi; Min Wei

2006-01-01

129

Growth Kinetics of Bacterial Pili from Pairwise Pilin Association Rates  

PubMed Central

Bacterial pilogenesis is a remarkable example of biological non-templated self-assembly where a small number of different building blocks are arranged in a specific order resulting in a macroscopic hair-like fiber containing up to thousands copies of protein subunits. A number of advanced experimental techniques have been used to understand pilus growth. While details such as the conformation of the protein building blocks before and after the elementary polymerization step have enhanced our understanding of this mechanism, such information does not explain the high efficiency of this growth process. In this study, we focused on the growth of the Escherichia coli P-pilus, which is formed by the assembly of six subunits, structurally similar incomplete Ig-like domains. These subunits undergo polymerization through fold complementation by the donation of a ?-sheet strand in a specific conserved order. All pairwise rates of association of the individual subunits with the corresponding ?-sheet donor strand peptides have been previously determined through non-covalent mass-spectrometry. Here we use computational simulations to determine donor-strand exchange rates and subunit concentrations necessary to warrant the growth of pili showing similar lengths and subunit orders to those observed in vivo. Our findings confirm that additional factors must be involved in the modulation of the donor-strand exchange rate and/or pilin subunit concentration at the usher must be important for the precise ordering and rapid polymerization rates observed in vivo.

Monteiro, Diana C. F.; Kamdoum, Wilfride V. Petnga; Paci, Emanuele

2013-01-01

130

Changes in urine composition after trauma facilitate bacterial growth  

PubMed Central

Background Critically ill patients including trauma patients are at high risk of urinary tract infection (UTI). The composition of urine in trauma patients may be modified due to inflammation, systemic stress, rhabdomyolysis, life support treatment and/or urinary catheter insertion. Methods Prospective, single-centre, observational study conducted in patients with severe trauma and without a history of UTIs or recent antibiotic treatment. The 24-hour urine samples were collected on the first and the fifth days and the growth of Escherichia coli in urine from patients and healthy volunteers was compared. Biochemical and hormonal modifications in urine that could potentially influence bacterial growth were explored. Results Growth of E. coli in urine from trauma patients was significantly higher on days 1 and 5 than in urine of healthy volunteers. Several significant modifications of urine composition could explain these findings. On days 1 and 5, trauma patients had an increase in glycosuria, in urine iron concentration, and in the concentrations of several amino acids compared to healthy volunteers. On day 1, the urinary osmotic pressure was significantly lower than for healthy volunteers. Conclusion We showed that urine of trauma patients facilitated growth of E. coli when compared to urine from healthy volunteers. This effect was present in the first 24 hours and until at least the fifth day after trauma. This phenomenon may be involved in the pathophysiology of UTIs in trauma patients. Further studies are required to define the exact causes of such modifications.

2012-01-01

131

Growth curve analysis for plasma profiles using smoothing splines  

SciTech Connect

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

Imre, K.

1993-05-01

132

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

ERIC Educational Resources Information Center

|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…

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

2008-01-01

133

Including Time-Invariant Covariates in the Latent Growth Curve Model  

ERIC Educational Resources Information Center

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

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

2004-01-01

134

Genetic and phenotypic aspects of the growth curve characteristics in Mehraban Iranian fat-tailed sheep  

Microsoft Academic Search

Brody's growth function was fitted to body weight–age data from 1281 Mehraban Iranian fat-tailed lambs (432 males, 849 females and 18 sires), progeny of 18 rams and 660 ewes, to study the genetic and phenotypic aspects of growth curve parameters and derived traits. Estimates of mature weight, rate of maturing and weight from birth to 48 months were obtained by

S. Saeid Bathaei; Pascal L. Leroy

1998-01-01

135

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

ERIC Educational Resources Information Center

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

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

2010-01-01

136

Comparison of Fetal and Neonatal Growth Curves in Detecting Growth Restriction  

PubMed Central

Objective To evaluate the outcome of intrauterine growth restriction (IUGR) infants with abnormal pulsatility index of the umbilical artery according to the neonatal birth weight/gestational age standards and the intrauterine growth charts. Methods We analyzed 53 pregnancies with severe IUGR classified as Group 2 (22 IUGR: abnormal pulsatility index and normal fetal heart rate) and Group 3 (31 IUGR: abnormal pulsatility index and fetal heart rate). Neonatal birth weight/gestational age distribution, body size measurements, maternal characteristics and obstetric outcome, and neonatal major and minor morbidity and mortality were compared with those obtained in 79 singleton pregnancies with normal fetal growth and pulsatility index, matched for gestational age [appropriate for gestational age (AGA) group]. Differences were analyzed with the ?2 test and the Student’s t test. Differences between means corrected for gestational age in the different groups were assessed by analysis of covariance test. A P value <0.05 was considered significant. Results At delivery, utilizing the neonatal standards, 25/53 (47%) IUGR showed a birthweight above the 10th percentile (IUGRAGA) whereas in 28, birthweight was below the 10th percentile (IUGRSGA). All body size measurements were significantly higher in AGA than in IUGRAGA and IUGRSGA. Forty-nine out of 79 (62%) AGA and 49/53 (92%) IUGR were admitted in the neonatal intensive care unit (p<0.001). One out of 79 (1%) AGA and 6/53 (11%) IUGR newborns died within 28 days (p<0.02). Major and minor morbidity was not different. Conclusion This study shows that neonatal outcome is similar in IUGR of the same clinical severity, whether or not they could be defined AGA or SGA according to the neonatal standards. Neonatal curves are misleading in detecting low birthweight infants and should be utilized only when obstetrical data are unavailable.

Marconi, Anna Maria; Ronzoni, Stefania; Bozzetti, Patrizia; Vailati, Simona; Morabito, Alberto; Battaglia, Frederick C

2009-01-01

137

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

SciTech Connect

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

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

2011-01-01

138

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

SciTech Connect

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

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

2011-01-01

139

Crack-growth resistance-curve behavior in silicon carbide: Small versus long cracks  

Microsoft Academic Search

Crack-growth resistance-curve (R-curve) behavior for small (<400 μm) surface cracks and long (>3 mm) through-thickness cracks is examined in two silicon carbide (SiC) ceramics that have sharply contrasting fracture properties. The first, an in-situ toughened material designated ABC-SiC fails by intergranular fracture, whereas the second, a commercial SiC (Hexoloy SA), fails by transgranular cleavage. In the former microstructure, hot pressing

C. J. Gilbert; J. J. Cao; L. C. De Jonghe; R. O. Ritchie

1997-01-01

140

Energetics of bacterial growth: balance of anabolic and catabolic reactions.  

PubMed Central

Biomass formation represents one of the most basic aspects of bacterial metabolism. While there is an abundance of information concerning individual reactions that result in cell duplication, there has been surprisingly little information on the bioenergetics of growth. For many years, it was assumed that biomass production (anabolism) was proportional to the amount of ATP which could be derived from energy-yielding pathways (catabolism), but later work showed that the ATP yield (YATP) was not necessarily a constant. Continuous-culture experiments indicated that bacteria utilized ATP for metabolic reactions that were not directly related to growth (maintenance functions). Mathematical derivations showed that maintenance energy appeared to be a growth rate-independent function of the cell mass and time. Later work, however, showed that maintenance energy alone could not account for all the variations in yield. Because only some of the discrepancy could be explained by the secretion of metabolites (overflow metabolism) or the diversion of catabolism to metabolic pathways which produced less ATP, it appeared that energy-excess cultures had mechanisms of spilling energy. Bacteria have the potential to spill excess ATP in futile enzyme cycles, but there has been little proof that such cycles are significant. Recent work indicated that bacteria can also use futile cycles of potassium, ammonia, and protons through the cell membrane to dissipate ATP either directly or indirectly. The utility of energy spilling in bacteria has been a curiosity. The deprivation of energy from potential competitors is at best a teleological explanation that cannot be easily supported by standard theories of natural selection. The priming of intracellular intermediates for future growth or protection of cells from potentially toxic end products (e.g., methylglyoxal) seems a more plausible explanation.

Russell, J B; Cook, G M

1995-01-01

141

Randomly curved runs interrupted by tumbling: A model for bacterial motion  

NASA Astrophysics Data System (ADS)

Small bacteria are strongly buffeted by Brownian forces that make completely straight runs impossible. A model for bacterial motion is formulated in which the effects of fluctuational forces and torques on the run phase are taken into account by using coupled Langevin equations. An integrated description of the motion, including runs and tumbles, is then obtained by the use of convolution and Laplace transforms. The properties of the velocity-velocity correlation function, of the mean displacement, and of the two relevant diffusion coefficients are examined in terms of the bacterial sizes and of the magnitude of the propelling forces. For bacteria smaller than E. coli, the integrated diffusion coefficient crosses over from a jump-dominated to a rotational-diffusion-dominated form.

Condat, C. A.; Jäckle, J.; Menchón, S. A.

2005-08-01

142

Study of environmental and antimicrobial agents impact on features of bacterial growth.  

PubMed

Continuous, real-time observation of bacterial growth has a great advantage for studying the mechanisms of interactions of various compounds with the bacterial cell membrane. With the use of physical methods, which are specific for assessment of continuous changes in turbidity over time, we have shown that bacterial growth was affected by not only on types of antibiotics and phages, but also by their concentration in media. Low concentration of antibiotics and bacteriophages in media has no effect on the bacterial growth process. Our research has shown that if bacterial cell membrane is not completely saturated with antibiotics membrane sensitive sites (MSS), or bacteriophages free unbounded receptors are remained, bacterial growth continues unimpeded. PMID:23385891

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

2013-07-01

143

Accuracy of abundance determinations by weighting functions method of curves of growth  

NASA Astrophysics Data System (ADS)

The curve of growth abundance determinations is studied using the method of weighting functions. The magnitude of the error of abundance determination caused by changes in effective temperatures and gravitational accelerations in the range of their mean accuracy is examined for 15 stars in a wide range of spectral types. The analysis proceeds by adapting the curve of growth method for atomic iron, with values of oscillator strengths given by Kurucz and Peytremann (1975). Using abundances obtained from FE I lines, errors of abundances resulting from using Fe II lines from the same stars are evaluated. The results show that the accuracy of abundance determination is sometimes very small even for the most accurate method of curve of growth analysis, and that the value of the accuracy is related to the spectral type of the stars under investigation.

Wiszniewski, A.; Bojanowski, T.

1983-04-01

144

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

Microsoft Academic Search

Aims: To evaluate the influence of marine bacterial assemblages from the Bay of Fundy on Alexandrium fundyense str. CB301 growth. Methods and Results: Bacterial assemblages were collected from the Bay of Fundy during an Alexandrium spp. bloom, serially diluted to extinction and inoculated into axenic CB301 cultures. Bacterial assemblages dramatically enhanced CB301 growth. Retrieval and analysis of 16S rDNA fragments

M. Ferrier; J. L. Martin; J. N. Rooney-Varga

2002-01-01

145

Kinetics of Bacterial Growth on Chlorinated Aliphatic Compounds  

PubMed Central

With the pure bacterial cultures Ancylobacter aquaticus AD20 and AD25, Xanthobacter autotrophicus GJ10, and Pseudomonas sp. strain AD1, Monod kinetics was observed during growth in chemostat cultures on 1,2-dichloroethane (AD20, AD25, and GJ10), 2-chloroethanol (AD20 and GJ10), and 1,3-dichloro-2-propanol (AD1). Both the Michaelis-Menten constants (Km) of the first catabolic (dehalogenating) enzyme and the Monod half-saturation constants (Ks) followed the order 2-chloroethanol, 1,3-dichloro-2-propanol, epichlorohydrin, and 1,2-dichloroethane. The Ks values of strains GJ10, AD20, and AD25 for 1,2-dichloroethane were 260, 222, and 24 ?M, respectively. The low Ks value of strain AD25 was correlated with a higher haloalkane dehalogenase content of this bacterium. The growth rates of strains AD20 and GJ10 in continuous cultures on 1,2-dichloroethane were higher than the rates predicted from the kinetics of the haloalkane dehalogenase and the concentration of the enzyme in the cells. The results indicate that the efficiency of chlorinated compound removal is indeed influenced by the kinetic properties and cellular content of the first catabolic enzyme. The cell envelope did not seem to act as a barrier for permeation of 1,2-dichloroethane.

van den Wijngaard, Arjan J.; Wind, Richele D.; Janssen, Dick B.

1993-01-01

146

Evaluation of crack-Growth resistance curve for a particulate ceramic–Metal composite  

Microsoft Academic Search

A technique is described to evaluate the crack growth resistance behaviour in brittle ceramic-base materials. In this method, the crack increment measurements during the stable crack propagation process are not required. The crack growth resistance curves are studied for a particulate ceramic–metal composite in the system lanthanium chromite–chromium. Experiments were performed with standard fracture mechanics single-edge notched beam specimens in

S. M. Barinov; V. Ja. Shevchenko

1998-01-01

147

Grain growth behavior of tungsten heavy alloys based on the master sintering curve concept  

Microsoft Academic Search

Time and temperature relationships for grain growth by Ostwald ripening are transformed into the master sintering curve (MSC)\\u000a form. The resulting MSC equations are used to analyze grain size data obtained from W-Ni-Fe heavy alloys that were quenched\\u000a from sintering temperatures ranging from 1200 °C to 1500 °C. Activation energies for grain growth during both solid-state\\u000a and liquid-phase sintering are

S. J. Park; J. M. Martin; J. F. Guo; John L. Johnson; Randall M. German

2006-01-01

148

Growth Curves for Macrobrachium rosenbergii in Semi-Intensive Culture in Brazil  

Microsoft Academic Search

Four 0.02-ha earthen ponds at the UNESP Aquaculture Center, Jaboticabal, S5o Paulo, Brazil, were stocked with newly metamorphosed Mac- robrachium rosenbergii post-larvae at 1.5 animals\\/m2. After 8 mo, prawn density at harvest ranged from 0.3\\/ mz to 0.8\\/m2. Growth curves were determined for each population using von Bertalanffy growth functions. Asymptotic maximum length and asymptotic maxi- mum weight increased as

Célia M. S. Sampaio; Wagner C. Valenti

1996-01-01

149

In-situ measurement of rocking curves during lysozyme crystal growth.  

PubMed

The rocking curve of protein crystals contains a lot of useful information concerning crystal quality, most of which is lost owing to the superimposition of spurious features appearing in these fragile materials after growth, during handling and mounting. To minimize such data spoiling, an experimental setup to perform in situ X-ray diffraction experiments during crystal growth has been designed. The setup, which includes video observation to allow the correlation of crystal shape, size and growth rate with X-ray data, has been used to assess the mosaicity of tetragonal lysozyme crystals during crystal growth. The full width at half maximum (FWHM) of diffraction peaks collected from these crystals changes during the growth process as a (directly proportional) response to the growth rates and the different development of different domain blocks. These changes in the domain distribution and FWHM with time involve a 'zonation' of the crystals, which show very different rocking curves in different parts of their volume. The rocking curves recorded in situ from growing crystals are easier to understand than those from crystals that have suffered even minor handling. PMID:10089461

Otálora, F; Gavira, J A; Capelle, B; García-Ruiz, J M

1999-03-01

150

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

ERIC Educational Resources Information Center

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

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

2003-01-01

151

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

Microsoft Academic Search

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

Edward B. Barbier; Michael S. Common

1996-01-01

152

Growth Curves, Measurement and Three-Dimensional Reconstruction in the Histopathology of Temporal Bones  

Microsoft Academic Search

The paper consists of three parts, in which the opportunities for measurement in histopathology of the temporal bone are shown. Measurement of size and distance (1D measurement) is used for determining the growth curves during the fetal period. Measurement of area (2D measurement) shows a difference in volume of mesenchymal tissue in the middle ear cavity between the groups with

Viktor Chrobok; Milan Meloun; Eva Šimáková; Karel Antoš

2003-01-01

153

Testing a developmental–ecological model of student engagement: a multilevel latent growth curve analysis  

Microsoft Academic Search

US schools fail to engage a significant proportion of adolescent students. Although student engagement is significantly related to academic achievement, there is a dearth of longitudinal research simultaneously examining the impact of personal and contextual factors on student engagement at both individual and school levels. Using a nationally?representative sample, multilevel growth curve analyses found significant factors related to adolescents’ student

Sukkyung You; Jill Sharkey

2009-01-01

154

Fluorescence induction curves registered from individual microalgae cenobiums in the process of population growth  

Microsoft Academic Search

Registration of chlorophyll fluorescence induction curves (IC) from individual microalgae cenobiums was performed during Scenedesmus quadricauda culture growth. Emphasis was placed on the analysis of patterns of the slow phase of IC, since these slow fluorescence transitions reflect complex interactions between primary and secondary photosynthetic processes. A classification was performed of the ICs obtained according to the patterns of their

Galina Riznichenko; Galina Lebedeva; Sergei Pogosyan; Marina Sivchenko; Andrei Rubin

1996-01-01

155

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

ERIC Educational Resources Information Center

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

Beecher, Constance C.

2011-01-01

156

Standardised growth curves for optical dating of sediment using multiple-grain aliquots  

Microsoft Academic Search

The single aliquot regenerative dose (SAR) protocol offers the opportunity of exploring, relatively simply, the existence of a ‘universal’ growth curve for use in dating using optically stimulated luminescence (OSL). A test dose is used in the SAR procedure to monitor and correct for sensitivity change occurring either over the burial period, or as a result of thermal pretreatments during

H. M. Roberts; G. A. T. Duller

2004-01-01

157

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

ERIC Educational Resources Information Center

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

Wanstrom, Linda

2009-01-01

158

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

ERIC Educational Resources Information Center

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

Murphy, Daniel L.; Pituch, Keenan A.

2009-01-01

159

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

NASA Astrophysics Data System (ADS)

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

Ziese, F.; Maret, G.; Gasser, U.

2013-09-01

160

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

PubMed

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

Ziese, F; Maret, G; Gasser, U

2013-09-18

161

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

Microsoft Academic Search

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 size are presented, illustrated, and discussed.

Linda Wänström

2009-01-01

162

Latent Growth Curve Analyses of Peer and Parent Influences on Smoking Progression Among Early Adolescents  

Microsoft Academic Search

Social influences on smoking uptake were examined in latent growth curve analyses of data from 1,320 youths assessed 5 times during 6th to 9th grade. Initial smoking stage predicted increases in number of friends who smoked, indicating selection; however, initial number of friends who smoked did not predict smoking stage progression, indicating no significant effect of socialization. Associations over time

Bruce Simons-Morton; Rusan Chen; Lorien Abroms; Denise L. Haynie

2004-01-01

163

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

ERIC Educational Resources Information Center

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

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

2003-01-01

164

Worm plot: a simple diagnostic device for modelling growth reference curves  

Microsoft Academic Search

SUMMARY The worm plot visualizes di6erences between two distributions, conditional on the values of a covariate. Though the worm plot is a general diagnostic tool for the analysis of residuals, this paper focuses on an application in constructing growth reference curves, where the covariate of interest is age. The LMS model of Cole and Green is used to construct reference

Stef van Buuren; Miranda Fredriks

2001-01-01

165

On the Power of Multivariate Latent Growth Curve Models to Detect Correlated Change  

ERIC Educational Resources Information Center

|We evaluated the statistical power of single-indicator latent growth curve models (LGCMs) to detect correlated change between two variables (covariance of slopes) as a function of sample size, number of longitudinal measurement occasions, and reliability (measurement error variance). Power approximations following the method of Satorra and Saris…

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

2006-01-01

166

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

ERIC Educational Resources Information Center

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…

Baldwin, Scott A.; Hoffmann, John P.

2002-01-01

167

Bacterial Growth on Chitosan-Coated Polypropylene Textile  

PubMed Central

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

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

2012-01-01

168

Glucose-sensitive holographic sensors for monitoring bacterial growth.  

PubMed

A glucose sensor comprising a reflection hologram incorporated into a thin, acrylamide hydrogel film bearing the cis-diol binding ligand, 3-acrylamidophenylboronic acid (3-APB), is described. The diffraction wavelength (color) of the hologram changes as the polymer swells upon binding cis-diols. The effect of various concentrations of glucose, a variety of mono- and disaccharides, and the alpha-hydroxy acid, lactate, on the holographic response was investigated. The sensor displayed reversible changes in diffraction wavelength as a function of cis-diol concentration, with the sensitivity of the system being dependent on the cis-diol tested. The effect of varying 3-APB concentration in the hydrogel on the holographic response to glucose was investigated, and maximum sensitivity was observed at a functional monomer concentration of 20 mol %. The potential for using this holographic sensor to detect real-time changes in bacterial cell metabolism was demonstrated by monitoring the germination and subsequent vegetative growth of Bacillus subtilis spores. PMID:15456294

Lee, Mei-Ching; Kabilan, Satyamoorthy; Hussain, Abid; Yang, Xiaoping; Blyth, Jeff; Lowe, Christopher R

2004-10-01

169

Use of Turbidimetric Growth Curves for Early Determination of Antifungal Drug Resistance of Filamentous Fungi  

PubMed Central

A previously described microbroth kinetic system (J. Meletiadis, J. F. Meis, J. W. Mouton, and P. E. Verweij, J. Clin. Microbiol. 39:478-484, 2001) based on continuous monitoring of changes in the optical density of fungal growth was used to describe turbidimetric growth curves of different filamentous fungi in the presence of increasing concentrations of antifungal drugs. Therefore, 24 clinical mold isolates, including Rhizopus oryzae, Aspergillus fumigatus, Aspergillus flavus, and Scedosporium prolificans, were tested against itraconazole, terbinafine, and amphotericin B according to NCCLS guidelines. Among various parameters of the growth curves, the duration of the lag phase was strongly affected by the presence of antifungal drugs. Exposure to increasing drug concentrations resulted in prolonged lag phases of the turbidimetric growth curves. The lag phases of the growth curves at drug concentrations which resulted in more than 50% growth (for itraconazole and terbinafine) and more than 75% growth (for amphotericin B) after 24 h of incubation for R. oryzae, 48 h for Aspergillus spp., and 72 h for S. prolificans were 4 h longer than the lag phases of the growth curves at the corresponding drug-free growth controls which varied from 4.4 h for R. oryzae, 6.5 h for A. flavus, 7.9 h for A. fumigatus, and 11.6 h for S. prolificans. The duration of the lag phases showed small experimental and interstrain variability, with differences of less than 2 h in most of the cases. Using this system, itraconazole and terbinafine resistance (presence of >50% growth) as well as amphotericin B resistance (presence of >75% growth) was determined within incubation periods of 5.0 to 7.7 h for R. oryzae (for amphotericin B resistance incubation for up to 12 h was required), 8.8 to 11.4 h for A. fumigatus, 6.7 to 8.5 h for A. flavus, and 13 to 15.6 h for S. prolificans while awaiting formal MIC determination by the NCCLS reference method.

Meletiadis, Joseph; te Dorsthorst, Debbie T. A.; Verweij, Paul E.

2003-01-01

170

Demonstration and Partial Characterization of a Bacterial Growth Enhancer in sera  

Microsoft Academic Search

During our research into the pathogenesis of Vibrio parahaemolyticus, we noticed that the concentration of serum added to the tissue culture medium (Dulbecco’s modified Eagle’s medium: DMEM)\\u000a greatly affected its growth. Using gel filtration column chromatography, we clearly demonstrated that serum contains not only\\u000a a bacterial growth inhibitor (BGI) but also a bacterial growth enhancer (BGE) for Vibrio parahaemolyticus. Our

Kanna Okayama; Takeshi Honda; Shigeaki Matsuda; Tadashi Saito; Masaya Kawase

2011-01-01

171

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

NASA Astrophysics Data System (ADS)

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.

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

2012-08-01

172

Effects of nitric oxide and nitrogen dioxide on bacterial growth.  

PubMed

The effects of low concentrations of nitric oxide (NO) and nitrogen dioxide (NO2) on actively dividing cultures of Staphylococcus aureus, Micrococcus luteus, Micrococcus roseus, Serratia marcescens, Bacillus subtilis, Bacillus circulans, Bacillus megaterium, and Bacillus cereus were studied. Fresh cultures of each organism were incubated for 24 h at 25 degrees C on both nutrient agar and mineral salts glucose agar plates under atmospheres containing various low concentrations of NO in air (0 to 1.9 ppm [0 to 2.0 micrograms/g of air]), NO2 in air (0 to 5.5 ppm [0 to 8.8 micrograms/g of air]), or NO and NO2 in air. Bacteria grown under air only were used as controls. After incubation, the colonies that developed on the plates were counted. None of the bacteria tested was affected by NO or NO2 at the indicated concentrations while growing on nutrient agar. Serratia marcescens, B. circulans, B. subtilis, B. megaterium, and B. cereus grown on mineral salts glucose agar were not significantly affected by NO or NO2. Low concentrations (0 to 1.9 ppm) of NO were bacteriostatic to log-phase cultures of M. roseus, M. luteus, and Staphylococcus aureus grown on mineral salts glucose agar. Bacteriostatic activity over a 24-h interval was maximal at an initial NO concentration of 1 ppm. Appreciable amounts of NO2 were produced in 24 h at initial NO concentrations greater than 1 ppm. These results suggest that NO2 may reduce the bacteriostatic activity of NO. Low concentrations (0 to 5.5 ppm) of NO2 in air did not affect any of the bacteria tested. At these low concentrations, NO affected bacterial growth, although NO2, NO2-, and NO3- did not. In addition, it was determined that the bacteriostatic activity observed in this study was not due to an increase in the acidity of the medium. PMID:6351744

Mancinelli, R L; McKay, C P

1983-07-01

173

Effects of nitric oxide and nitrogen dioxide on bacterial growth.  

PubMed Central

The effects of low concentrations of nitric oxide (NO) and nitrogen dioxide (NO2) on actively dividing cultures of Staphylococcus aureus, Micrococcus luteus, Micrococcus roseus, Serratia marcescens, Bacillus subtilis, Bacillus circulans, Bacillus megaterium, and Bacillus cereus were studied. Fresh cultures of each organism were incubated for 24 h at 25 degrees C on both nutrient agar and mineral salts glucose agar plates under atmospheres containing various low concentrations of NO in air (0 to 1.9 ppm [0 to 2.0 micrograms/g of air]), NO2 in air (0 to 5.5 ppm [0 to 8.8 micrograms/g of air]), or NO and NO2 in air. Bacteria grown under air only were used as controls. After incubation, the colonies that developed on the plates were counted. None of the bacteria tested was affected by NO or NO2 at the indicated concentrations while growing on nutrient agar. Serratia marcescens, B. circulans, B. subtilis, B. megaterium, and B. cereus grown on mineral salts glucose agar were not significantly affected by NO or NO2. Low concentrations (0 to 1.9 ppm) of NO were bacteriostatic to log-phase cultures of M. roseus, M. luteus, and Staphylococcus aureus grown on mineral salts glucose agar. Bacteriostatic activity over a 24-h interval was maximal at an initial NO concentration of 1 ppm. Appreciable amounts of NO2 were produced in 24 h at initial NO concentrations greater than 1 ppm. These results suggest that NO2 may reduce the bacteriostatic activity of NO. Low concentrations (0 to 5.5 ppm) of NO2 in air did not affect any of the bacteria tested. At these low concentrations, NO affected bacterial growth, although NO2, NO2-, and NO3- did not. In addition, it was determined that the bacteriostatic activity observed in this study was not due to an increase in the acidity of the medium.

Mancinelli, R L; McKay, C P

1983-01-01

174

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

PubMed

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

Zindel, Stephan; Kaman, Wendy E; Fröls, Sabrina; Pfeifer, Felicitas; Peters, Anna; Hays, John P; Fuchsbauer, Hans-Lothar

2013-04-15

175

The effect of temperature and algal biomass on bacterial production and specific growth rate in freshwater and marine habitats  

Microsoft Academic Search

We analyzed heterotrophic, pelagic bacterial production and specific growth rate data from 57 studies conducted in fresh,\\u000a marine and estuarine\\/coastal waters. Strong positive relationships were identified between 1) bacterial production and bacterial\\u000a abundance and 2) bacterial production and algal biomass. The relationship between bacterial production and bacterial abundance\\u000a was improved by also considering water temperature. The analysis of covariance model

Paul A. White; Jacob Kalff; Joseph B. Rasmussen; Josep M. Gasol

1991-01-01

176

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

PubMed Central

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

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

2009-01-01

177

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

ERIC Educational Resources Information Center

|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,…

Huppert, Jehuda; Lazarovitz, Reuven

178

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

ERIC Educational Resources Information Center

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,…

Huppert, Jehuda; Lazarovitz, Reuven

179

Modelling individual growth and competition in plant populations: growth curves of Chenopodium album at two densities  

Microsoft Academic Search

Summary 1 We modelled the growth in estimated biomass of individuals in experimental popu- lations of Chenopodium album grown at two densities and measured sequentially nine times over 128 days. Competition is modelled by coupling individual growth equations and, within the population, the growth rate of a plant at any point in time is a function of its size to

Christian Damgaard; Jacob Weiner; Hisae Nagashima

2002-01-01

180

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

Microsoft Academic Search

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

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

1996-01-01

181

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

PubMed Central

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.

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

182

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

Microsoft Academic Search

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

Mareike Warkentin; Heike M. Freese; Rhena Schumann

2011-01-01

183

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

SciTech Connect

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

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

2005-09-08

184

Genetic Analysis of a Selection Experiment on the Growth Curve of Chickens  

Microsoft Academic Search

A selection experiment on the shape of the growth curve was performed on meat-type chickens through combined selection on juvenile and adult BW. Line X?+ was selected for low BW at 8 wk (BW8) and high BW at 36 wk (BW36). Line X+? was selected for high BW8 and low BW36. Line X++ was selected for high BW8 and BW36,

S. Mignon-Grasteau; C. Beaumont; F. H. Ricard

185

Subcritical interlaminar crack growth in fibre composites exhibiting a rising R -curve  

Microsoft Academic Search

Subcritical crack growth behaviour has been evaluated in composite laminates based on uniaxial carbon fibres in poly(ether-ether ketone) matrices. Double cantilever beam (DCB) specimens have been employed to give mode I loading and it is first shown that the materials exhibit a risingR-curve, i.e. the value of the interlaminar fracture energy,GIC, increases as the crack propagates through the specimens. Secondly,

A. Okada; I. N. Dyson; A. J. Kinloch

1995-01-01

186

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

SciTech Connect

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

Hobbs, D.

2011-01-19

187

Single nucleotide polymorphism detection in aldehyde dehydrogenase 2 (ALDH2) gene using bacterial magnetic particles based on dissociation curve analysis.  

PubMed

Single nucleotide polymorphism (SNP) detection for aldehyde dehydrogenase 2 (ALDH2) gene based on DNA thermal dissociation curve analysis was successfully demonstrated using an automated system with bacterial magnetic particles (BMPs) by developing a new method for avoiding light scattering caused by nanometer-size particles when using commercially available fluorescent dyes such as FITC, Cy3, and Cy5 as labeling chromophores. Biotin-labeled PCR products in ALDH2, two allele-specific probes (Cy3-labeled detection probe for ALDH2*1 and Cy5-labeled detection probe for ALDH2*2), streptavidin-immobilized BMPs (SA-BMPs) were simultaneously mixed. The mixture was denatured at 70 degrees C for 3 min, cooled slowly to 25 degrees C, and incubated for 10 min, allowing the DNA duplex to form between Cy3- or Cy5-labeled detection probes and biotin-labeled PCR products on SA-BMPs. Then duplex DNA-BMP complex was heated to 58 degrees C, a temperature determined by dissociation curve analysis and a dissociated single-base mismatched detection probe was removed at the same temperature under precise control. Furthermore, fluorescence signal from the detection probe was liberated into the supernatant from completely matched duplex DNA-BMP complex by heating to 80 degrees C and measured. In the homozygote target DNA (ALDH2*1/*1 and ALDH2*2/*2), the fluorescence signals from single-base mismatched were decreased to background level, indicating that mismatched hybridization was efficiently removed by the washing process. In the heterozygote target DNA (ALDH2*1/*2), each fluorescence signals was at a similar level. Therefore, three genotypes of SNP in ALDH2 gene were detected using the automated detection system with BMPs. PMID:15329927

Maruyama, Kohei; Takeyama, Haruko; Nemoto, Etsuo; Tanaka, Tsuyoshi; Yoda, Kiyoshi; Matsunaga, Tadashi

2004-09-20

188

Growth Curves for Graptemys, with a Comparison to Other Emydid Turtles  

Microsoft Academic Search

ABSTRACT.—Von Bertalanffy growth-curve parameters,were calculated from plastral annuli of specimens,of Graptemys ouachitensis and G. pseudogeographica kohnii captured,in western Kentucky, and museum specimens of G. ernsti from Alabama and G. caglei (males only) from Texas. Males had estimated,values of k (intrinsic rate of growth,toward,asymptotic,plastron length, PLA) ranging from 0.264 to 0.498. Values of k for females of three species (range 0.110?0.182)

PETER V. LINDEMAN

1999-01-01

189

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

PubMed

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

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

2013-08-22

190

Grain growth behavior of tungsten heavy alloys based on the master sintering curve concept  

NASA Astrophysics Data System (ADS)

Time and temperature relationships for grain growth by Ostwald ripening are transformed into the master sintering curve (MSC) form. The resulting MSC equations are used to analyze grain size data obtained from W-Ni-Fe heavy alloys that were quenched from sintering temperatures ranging from 1200 °C to 1500 °C. Activation energies for grain growth during both solid-state and liquid-phase sintering are calculated and compared to experimental values for diffusion. The MSC equations are further modified to include the effect of the solid volume fraction on the grain growth constant. A sensitivity analysis of material properties and process variables shows that the grain growth rate constant is most affected by changes in the sintering temperature and activation energy.

Park, S. J.; Martin, J. M.; Guo, J. F.; Johnson, John L.; German, Randall M.

2006-11-01

191

Bacterial production and growth efficiencies: Direct measurements on riverine aggregates  

Microsoft Academic Search

Heterotrophic bacteria transform organic matter by respiration and production of new biomass. Because there are only a limited number of studies on the respiration of bacteria attached to particulate organic matter, their role in the carbon cycle of aquatic systems is not well known. In this study, we combine radiotracer with microsensor techniques to measure bacterial production and respiration rates

Hans-Peter Grossart; Helle Ploug

2000-01-01

192

On Evidence Supporting a Deterministic Process of Bacterial Growth  

Microsoft Academic Search

SUMMARY Recent evidence supporting a proposed model (Koch & Schaechter, 1962) for the control of bacterial cell division is reviewed. Calculations from the published work of others are presented which show that the standard deviation of length of time between a cell division and Nth cell division does not increase, at least up to N = 9. This finding implies

A. L. Koch

1966-01-01

193

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

PubMed Central

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

Harvey, P. I.; Crundwell, F. K.

1997-01-01

194

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

PubMed

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

Harvey, P I; Crundwell, F K

1997-07-01

195

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...

196

Influence of Phosphate Corrosion Control Compounds on Bacterial Growth.  

National Technical Information Service (NTIS)

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 Klebsiell...

W. D. Rosenzweig

1987-01-01

197

Promotion of Plant Growth by Bacterial ACC Deaminase  

Microsoft Academic Search

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

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

2007-01-01

198

Bacterial gene regulation in diauxic and non-diauxic growth  

Microsoft Academic Search

When bacteria are grown in a batch culture containing a mixture of two growth-limiting substrates, they exhibit a rich spectrum of substrate consumption patterns including diauxic growth, simultaneous consumption, and bistable growth. In previous work, we showed that a minimal model accounting only for enzyme induction and dilution captures all the substrate consumption patterns [Narang, A., 1998a. The dynamical analogy

Atul Narang; Sergei S. Pilyugin

2007-01-01

199

Bacterial gene regulation in diauxic and nondiauxic growth  

Microsoft Academic Search

When bacteria are grown on a mixture of two growth-limiting substrates, they exhibit a rich spectrum of substrate consumption patterns including diauxic growth, simultaneous consumption, and bistable growth. In previous work, we showed that a minimal model accounting only for enzyme induction and dilution captures all the substrate consumption patterns. Here, we construct the bifurcation diagram of the minimal model.

Atul Narang; Sergei S. Pilyugin

2006-01-01

200

Isolation and characterization of new plant growth-promoting bacterial endophytes  

Microsoft Academic Search

Those bacterial endophytes that also provide some benefit to plants may be considered to be plant growth-promoting bacteria (PGPB) and can facilitate plant growth by a number of different mechanisms. In the work that is reported here, soil samples from several locales around the world were used as a starting point for the isolation of new endophytes. Subsequently, those newly

Shimaila Rashid; Trevor C. Charles; Bernard R. Glick

201

Linear-Arrhenius models for bacterial growth and death and vitamin denaturations  

Microsoft Academic Search

Summary The development of the quantitative, linear-Arrhenius model of Davey for predicting bacterial growth and death (inactivation) is reviewed. The applicability of the model to published data from independent researchers for both the growth phase and lag phase, involving combined environmental factors (T, aw) is illustrated. Also illustrated is its applicability to thermal inactivation kinetics and vitamin denaturation (with combinedT,

K. R. Davey

1993-01-01

202

Mode I intra-laminar crack growth in composites — modelling of R-curves from measured bridging laws  

Microsoft Academic Search

In this paper R-curves for mode I crack growth in composites are modelled based on measured bridging laws. It is shown that simulated and measured R-curves are in good agreement. Simulations show that variations in the measured bridging law parameters can explain the scatter in overall R-curves. Finite element procedures for treating a generalised nonlinear law for intra-laminar fibre bridging

T. K. Jacobsen; B. F. Sørensen

2001-01-01

203

Parameters of bacterial killing and regrowth kinetics and antimicrobial effect examined in terms of area under the concentration-time curve relationships: action of ciprofloxacin against Escherichia coli in an in vitro dynamic model.  

PubMed Central

Although many parameters have been described to quantitate the killing and regrowth of bacteria, substantial shortcomings are inherent in most of them, such as low sensitivity to pharmacokinetic determinants of the antimicrobial effect, an inability to predict a total effect, insufficient robustness, and uncertain interrelations between the parameters that prevent an ultimate determination of the effect. To examine different parameters, the kinetics of killing and regrowth of Escherichia coli (MIC, 0.013 microg/ml) were studied in vitro by simulating a series of ciprofloxacin monoexponential pharmacokinetic profiles. Initial ciprofloxacin concentrations varied from 0.02 to 19.2 microg/ml, whereas the half-life of 4 h was the same in all experiments. The following parameters were calculated and estimated: the time to reduce the initial inoculum (N0) 10-, 100-, and 1,000-fold (T90%, T99%, and T99.9%, respectively), the rate constant of bacterial elimination (k(elb)), the nadir level (Nmin) in the viable count (N)-versus-time (t) curve, the time to reach Nmin (t(min)), the numbers of bacteria that survived (Ntau) by the end of the observation period (tau), the area under the bacterial killing and regrowth curve (log N(A)-t curve) from the zero point (time zero) to tau (AUBC), the area above this curve (AAC), the area between the control growth curve (log N(C)-t curve) and the bacterial killing and regrowth curve (log N(A)-t curve) from the zero point to tau (ABBC) or to the time point when log N(A) reaches the maximal values observed in the log N(C)-t curve (I(E); intensity of the effect), and the time shift between the control growth and regrowth curves (T(E); duration of the effect). Being highly sensitive to the AUC, I(E), and T(E) showed the most regular AUC relationships: the effect expressed by I(E) or T(E) increased systematically when the AUC or initial concentration of ciprofloxacin rose. Other parameters, especially T90%, T99%, T99.9%, t(min), and log N0 - log Nmin = delta log Nmin, related to the AUC less regularly and were poorly sensitive to the AUC. T(E) proved to be the best predictor and t(min) proved to be the worst predictor of the total antimicrobial effect reflected by I(E). Distinct feedback relationships between the effect determination and the experimental design were demonstrated. It was shown that unjustified shortening of the observation period, i.e., cutting off the log N(A)-t curves, may lead to the degeneration of the AUC-response relationships, as expressed by log N0 - log Ntau = delta log Ntau, AUBC, AAC, or ABBC, to a point where it gives rise to the false idea of an AUC- or concentration-independent effect. Thus, use of I(E) and T(E) provides the most unbiased, robust, and comprehensive means of determining the antimicrobial effect.

Firsov, A A; Vostrov, S N; Shevchenko, A A; Cornaglia, G

1997-01-01

204

Inside the root microbiome: Bacterial root endophytes and plant growth promotion.  

PubMed

Bacterial root endophytes reside in a vast number of plant species as part of their root microbiome, with some being shown to positively influence plant growth. Endophyte community structure (species diversity: richness and relative abundances) within the plant is dynamic and is influenced by abiotic and biotic factors such as soil conditions, biogeography, plant species, microbe-microbe interactions and plant-microbe interactions, both at local and larger scales. Plant-growth-promoting bacterial endophytes (PGPBEs) have been identified, but the predictive success at positively influencing plant growth in field conditions has been limited. Concurrent to the development of modern molecular techniques, the goal of predicting an organism's ability to promote plant growth can perhaps be realized by more thorough examination of endophyte community dynamics. This paper reviews the drivers of endophyte community structure relating to plant growth promotion, the mechanisms of plant growth promotion, and the current and future use of molecular techniques to study these communities. PMID:23935113

Gaiero, Jonathan R; McCall, Crystal A; Thompson, Karen A; Day, Nicola J; Best, Anna S; Dunfield, Kari E

2013-08-08

205

Demonstration and partial characterization of a bacterial growth enhancer in sera.  

PubMed

During our research into the pathogenesis of Vibrio parahaemolyticus, we noticed that the concentration of serum added to the tissue culture medium (Dulbecco's modified Eagle's medium: DMEM) greatly affected its growth. Using gel filtration column chromatography, we clearly demonstrated that serum contains not only a bacterial growth inhibitor (BGI) but also a bacterial growth enhancer (BGE) for Vibrio parahaemolyticus. Our data indicate that the BGI is transferrin, whereas the BGE seems to be an undescribed small molecule (molecular weight of 1,000-3,000 Da) and is associated with magnesium and molybdenum ions. BGE activity was not decreased by heat treatment (at 60 or 100°C for 30 min) and affected the growth rate of a wide range of Gram-negative and Gram-positive bacteria. The addition of EDTA into DMEM lowered the growth rate, whereas the addition of BGE restored the growth activity. This study suggests that sera contain a previously undescribed small BGE molecule. PMID:20514485

Okayama, Kanna; Honda, Takeshi; Matsuda, Shigeaki; Saito, Tadashi; Kawase, Masaya

2010-06-01

206

Growth curves of anthropometric indices in a general population of French children and comparison with reference data  

Microsoft Academic Search

Background:The description of growth patterns of the different anthropometric measurements mainly used in epidemiological studies is useful to better understand the development of obesity in children and its consequences.Objective:Our aim was to establish growth curves of anthropometric indices in a general population of French children born during the 1980s and to compare them with the French reference curves based on

B Heude; A Kettaneh; B de Lauzon Guillain; A Lommez; J-M Borys; P Ducimetière; M-A Charles

2006-01-01

207

Distribution of Bacterial Growth Activity in Flow-Chamber Biofilms  

PubMed Central

In microbial communities such as those found in biofilms, individual organisms most often display heterogeneous behavior with respect to their metabolic activity, growth status, gene expression pattern, etc. In that context, a novel reporter system for monitoring of cellular growth activity has been designed. It comprises a transposon cassette carrying fusions between the growth rate-regulated Escherichia coli rrnBP1 promoter and different variant gfp genes. It is shown that the P1 promoter is regulated in the same way in E. coli and Pseudomonas putida, making it useful for monitoring of growth activity in organisms outside the group of enteric bacteria. Construction of fusions to genes encoding unstable Gfp proteins opened up the possibility of the monitoring of rates of rRNA synthesis and, in this way, allowing on-line determination of the distribution of growth activity in a complex community. With the use of these reporter tools, it is demonstrated that individual cells of a toluene-degrading P. putida strain growing in a benzyl alcohol-supplemented biofilm have different levels of growth activity which develop as the biofilm gets older. Cells that eventually grow very slowly or not at all may be stimulated to restart growth if provided with a more easily metabolizable carbon source. Thus, the dynamics of biofilm growth activity has been tracked to the level of individual cells, cell clusters, and microcolonies.

Sternberg, Claus; Christensen, Bjarke B.; Johansen, Tove; Toftgaard Nielsen, Alex; Andersen, Jens Bo; Givskov, Michael; Molin, S?ren

1999-01-01

208

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

PubMed Central

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

Fey, Paul D.

2010-01-01

209

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

PubMed

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. PMID:23410378

Osella, Matteo; Lagomarsino, Marco Cosentino

2013-01-30

210

Growth-rate-dependent dynamics of a bacterial genetic oscillator  

NASA Astrophysics Data System (ADS)

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.

Osella, Matteo; Lagomarsino, Marco Cosentino

2013-01-01

211

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

PubMed

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 infections in animals and to identify different bacterial strains and origins. PMID:24116177

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

2013-10-08

212

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

PubMed Central

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 infections in animals and to identify different bacterial strains and origins.

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

2013-01-01

213

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

PubMed Central

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

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

2013-01-01

214

Effects of selenium coating of orthopaedic implant surfaces on bacterial adherence and osteoblastic cell growth.  

PubMed

The aim of this study was to evaluate whether coating titanium discs with selenium in the form of sodium selenite decreased bacterial adhesion of Staphylococcus aureus and Staph. epidermidis and impeded osteoblastic cell growth. In order to evaluate bacterial adhesion, sterile titanium discs were coated with increasing concentrations of selenium and incubated with bacterial solutions of Staph. aureus (ATCC 29213) and Staph. epidermidis (DSM 3269) and stained with Safranin-O. The effect of selenium on osteoblastic cell growth was also observed. The adherence of MG-63 cells on the coated discs was detected by staining with Safranin-O. The proportion of covered area was calculated with imaging software. The tested Staph. aureus strain showed a significantly reduced attachment on titanium discs with 0.5% (p = 0.011) and 0.2% (p = 0.02) selenium coating. Our test strain from Staph. epidermidis showed a highly significant reduction in bacterial adherence on discs coated with 0.5% (p = 0.0099) and 0.2% (p = 0.002) selenium solution. There was no inhibitory effect of the selenium coating on the osteoblastic cell growth. Selenium coating is a promising method to reduce bacterial attachment on prosthetic material. PMID:23632681

Holinka, J; Pilz, M; Kubista, B; Presterl, E; Windhager, R

2013-05-01

215

VON BERTALANFFY GROWTH CURVES FOR STRIPED MARLIN, TETRAPTURUS AUDAX, AND BLUE MARLIN, MAKAZRA NZGRZCANS, IN THE CENTRAL NORTH PACIFIC OCEAN  

Microsoft Academic Search

The growth of striped marlin, Tetrapturus audaz, and blue marlin, Makaira nigricans, was described by fitting von Bertalanffy growth curves (an assumed age model and a length-increment model) to the progression of age-groups, by quarters, through the Hawaiian longline fishery from 1960 to 1970. For striped marlin, the sexes grew at about the same rate and had similar predicted asymptotic

ROBERT A. SKILLMAN; MARIAN Y. Y. YONG

216

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...

217

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

SciTech Connect

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

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

2011-04-18

218

Effect of temperature on the dose–response curves for auxin-induced elongation growth in maize coleoptile segments  

Microsoft Academic Search

The dose–response curves for IAA-induced growth in maize coleoptile segments were studied as a function of time and temperature.\\u000a In addition, the kinetics of growth rate responses at some auxin concentrations and temperatures was also compared. It was\\u000a found that the dose–response curves for IAA-induced elongation growth were, independently of time and temperature, bell-shaped\\u000a with an optimal concentration at 10?5 M

Ma?gorzata Polak; Zbigniew Tukaj; Waldemar Karcz

2011-01-01

219

Evaluation of bacterial growth with occlusive dressing use on excoriated skin in the premature infant.  

PubMed

This study evaluated the effects of an occlusive (OpSite Flexigrid) dressing on bacterial growth over excoriated and the surrounding intact skin of eight premature infants. Cultures were obtained before placement and four days after dressing placement. An analysis of variance demonstrated significant increases in coagulase-negative Staphylococcus and overall total skin. No significant differences in bacterial growth occurred between intact skin underneath the dressing and that on the opposite side of the body post-dressing placement. Significant increases were found in bacterial concentrations for both intact and excoriated skin post-dressing placement. Small sample size and no between-subject design hinder generalization to the neonatal population. PMID:9087009

Strickland, M E

1997-03-01

220

Development of oral reading fluency in children with speech or language impairments: A growth curve analysis  

PubMed Central

This longitudinal study used piece-wise growth curve analyses to examine growth patterns in oral reading fluency for students diagnosed with speech (SI) or language impairments (LI) from first through third grade (N = 1,991). The main finding of this study was that a diagnosis of SI or LI can have a detrimental effect on early reading skills and these problems can be persistent. The results indicate differences between subgroups in growth trajectories that were evident in first grade. These differences were associated with a students’ speech or language status. A large proportion of students with SI or LI did not meet grade-level reading fluency benchmarks. Overall students with SI showed better performance than students with LI. Reading fluency performance was negatively related to the persistence of the SI or LI; the lowest performing students were those originally identified with SI or LI whose diagnosis changed to a learning disability. The results underscore the need to identify, monitor, and address reading fluency difficulties early among students with SI or LI.

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

2012-01-01

221

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

Microsoft Academic Search

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

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

2003-01-01

222

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

Microsoft Academic Search

Growth responses and biovolume changes for four facultatively psychrophilic bacterial isolates from Conception Bay, Newfoundland, and the Arctic Ocean were examined at temperatures from -1.5 to 35C, with substrate concentrations of 0.15, 1.5, and 1,500 mg of proteose peptone-yeast extract per liter. For two cultures, growth in 0.1, 1.0, and 1,000 mg of proline per liter was also examined. At

W. J. Wiebe; W. M. Jr. Sheldon; L. R. Pomeroy

1992-01-01

223

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

Microsoft Academic Search

Interactions between microbial growth and substrate degradation are important in determining the performance of trickle-bed\\u000a bioreactors (TBB), especially when salt is added to reduce biomass formation in order to alleviate media clogging. This study\\u000a was aimed at quantifying salinity effects on bacterial growth and substrate degradation, and at acquiring kinetic information\\u000a in order to improve the design and operation of

Chi-Yuan Lee; Ching-Hsing Lin

2006-01-01

224

Semielectronic turbidimeter for automated monitoring of bacterial growth in test tubes.  

PubMed Central

An automated turbidimeter for measuring bacterial growth in ordinary test tubes is described. The device records and prints adsorbance, expressed as Klett units, of 60 cultures every 15 min. Provision is made for either aerobic or anaerobic incubation. The device is adaptable to modification, depending upon local requirements and availability of computation facilities. Images

Marcelis, J H; Versteeg, H; Beck, H J; Vinke, D

1980-01-01

225

Alveolar Macrophages that Phagocytose Apoptotic Neutrophils Produce Hepatocyte Growth Factor during Bacterial Pneumonia in Mice  

Microsoft Academic Search

Hepatocyte growth factor (HGF) is postulated to play an im- portant role in the repair of pulmonary epithelium in acute lung injury. To evaluate the role of HGF in bacterial pneumo- nia, the kinetics of HGF production and the cellular sources of HGF have been examined in the lungs of mice that had been intratracheally challenged with Pseudomonas aeruginosa .

Kounosuke Morimoto; Hideaki Amano; Fuminari Sonoda; Motoo Baba; Masachika Senba; Hiroyuki Yoshimine; Hidefumi Yamamoto; Tsuyoshi Ii; Kazunori Oishi; Tsuyoshi Nagatake

2001-01-01

226

Divergent effects of desferrioxamine on bacterial growth and characteristics.  

PubMed

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

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

2012-12-12

227

Metabolism, cell growth and the bacterial cell cycle  

PubMed Central

Adaptation to fluctuations in nutrient availability is a fact of life for single-celled organisms in the ‘wild’. A decade ago our understanding of how bacteria adjust cell cycle parameters to accommodate changes in nutrient availability stemmed almost entirely from elegant physiological studies completed in the 1960s. In this Opinion article we summarize recent groundbreaking work in this area and discuss potential mechanisms by which nutrient availability and metabolic status are coordinated with cell growth, chromosome replication and cell division.

Wang, Jue D.; Levin, Petra A.

2010-01-01

228

Modeling of Bacterial Growth with Shifts in Temperature  

PubMed Central

The temperature of chilled foods is an important variable for the shelf life of a product in a production and distribution chain. To predict the number of organisms as a function of temperature and time, it is essential to model the growth as a function of temperature. The temperature is often not constant in various stages of distribution. The objective of this research was to determine the effect of shifts in temperature. The suitability and usefulness of several models to describe the growth of Lactobacillus plantarum with fluctuating temperatures was evaluated. It can be assumed that temperature shifts within the lag phase can be handled by adding relative parts of the lag time to be completed and that temperature shifts within the exponential phase result in no lag phase. With these assumptions, the kinetic behavior of temperature shift experiments was reasonably well predicted, and this hypothesis was accepted statistically in 73% of the cases. Only shifts of temperature around the minimum temperature for growth showed very large deviations from the model prediction. The best results were obtained with the assumption that a temperature shift (within the lag phase as well as within the exponential phase) results in an additional lag phase. This hypothesis was accepted statistically in 93% of the cases. The length of the additional lag phase is one-fourth of the lag time normally found at the temperature after the shift.

Zwietering, M. H.; de Wit, J. C.; Cuppers, H. G. A. M.; van 't Riet, K.

1994-01-01

229

Influence of Hydrological Pulse on Bacterial Growth and DOC Uptake in a ClearWater Amazonian Lake  

Microsoft Academic Search

This study was conducted to evaluate: (1) the bacterial growth and the dissolved organic carbon (DOC) uptake in an Amazonian lake (Lake Batata) at high-water and low-water periods of the flood pulse; (2) the influence of nitrogen and phosphorus (NP) additions on bacterial growth and DOC uptake in Lake Batata at two flood pulse periods; and (3) the bioavailability of

Vinicius F. Farjalla; Debora A. Azevedo; Francisco A. Esteves; Reinaldo L. Bozelli; Fabio Roland; Alex Enrich-Prast

2006-01-01

230

A Markovian Growth Dynamics on Rooted Binary Trees Evolving According to the Gompertz Curve  

NASA Astrophysics Data System (ADS)

Inspired by biological dynamics, we consider a growth Markov process taking values on the space of rooted binary trees, similar to the Aldous-Shields (Probab. Theory Relat. Fields 79(4):509-542, 1988) model. Fix n?1 and ?>0. We start at time 0 with the tree composed of a root only. At any time, each node with no descendants, independently from the other nodes, produces two successors at rate ?( n- k)/ n, where k is the distance from the node to the root. Denote by Z n ( t) the number of nodes with no descendants at time t and let T n = ? -1 nln( n/ln4)+(ln2)/(2 ?). We prove that 2- n Z n ( T n + n?), ???, converges to the Gompertz curve exp(-(ln2) e - ?? ). We also prove a central limit theorem for the martingale associated to Z n ( t).

Landim, C.; Portugal, R. D.; Svaiter, B. F.

2012-08-01

231

Comparison of non-linear growth models to describe the growth curve in West African Dwarf sheep.  

PubMed

The objectives of this study were to compare the goodness of fit of four non-linear growth models, i.e. Brody, Gompertz, Logistic and Von Bertalanffy, in West African Dwarf (WAD) sheep. A total of 5274 monthly weight records from birth up to 180 days of age from 889 lambs, collected during 2001 to 2004 in Betecoucou breeding farm in Benin were used. In the preliminary analysis, the General Linear Model Procedure of the Statistical Analysis Systems Institute was applied to the dataset to identify the significant effects of the sex of lamb (male and female), type of birth (single and twin), season of birth (rainy season and dry season), parity of dam (1, 2 and 3) and year of birth (2001, 2002, 2003 and 2004) on the observed birth weight and monthly weight up to 6 months of age. The models parameters (A, B and k), coefficient of determination (R2), mean square error (MSE) were calculated using language of technical computing package Matlab®, 2006. The mean values of A, B and k were substituted into each model to calculate the corresponding Akaike's Information Criterion (AIC). Among the four growth functions, the Brody model has been selected for its accuracy of fit according to the higher R2, lower MSE and AIC. Finally, the parameters A, B and k were adjusted in Matlab®, 2006 for the sex of lamb, year of birth, season of birth, birth type and the parity of ewe, providing a specific slope of the Brody growth curve. The results of this study suggest that Brody model can be useful for WAD sheep breeding in Betecoucou farm conditions through growth monitoring. PMID:22443700

Gbangboche, A B; Glele-Kakai, R; Salifou, S; Albuquerque, L G; Leroy, P L

2008-07-01

232

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

SciTech Connect

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

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

2005-11-01

233

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

PubMed Central

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

Qurashi, Aisha Waheed; Sabri, Anjum Nasim

2012-01-01

234

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

PubMed

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

Qurashi, Aisha Waheed; Sabri, Anjum Nasim

2012-06-01

235

[Influence of granulated bacterial preparation complex action on the growth and yield of barley].  

PubMed

The influence of granulated bacterial preparation of complex action on the growth and yield of barley (H. distichum L.) has been studied. The treatment of barley seeds by this preparation has been established to have a very significant effect on the mass of 1000 grains, grain natural weight and to increase the yield of plants, but to different degree. Consequently, the interaction of certain barley varieties with bacteria-components of the preparation is rather specific. It has been displayed that the treatment of grains of different barley varieties by the bacterial preparation takes a very significant influence on the function of microbial associations in the rhizosphere. PMID:22830193

Skorokhod, I O; Tserkovniak, L S; Kurdysh, I K; Plotnikov, V V; Gyl'chuk, V G; Korni?chuk, O V

236

Kinetics of chitinase production. II. Relationship between bacterial growth, chitin hydrolysis and enzyme synthesis.  

PubMed

A comprehensive model for chitinase production during growth of Serratia marcescens QMB 1466 on chitin was developed taking into account the rate of chitin hydrolysis in order to estimate the rate of bacterial growth. In relating growth with enzyme synthesis the total enzyme concentration was used as the sum of the enzyme present in the bulk of the fermentation broth and the enzyme adsorbed on the chitin particles. The equations constituting the proposed model were fitted to the experimental results from both continuous and batch fermentation to obtain parameters describing substrate yield, metabolic maintenance, and enzyme yields. PMID:18553735

Young, M E; Bell, R L; Carroad, P A

1985-06-01

237

Growth Yields in Bacterial Denitrification and Nitrate Ammonification?  

PubMed Central

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

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

2007-01-01

238

Biofilm growth alters regulation of conjugation by a bacterial pheromone  

PubMed Central

Conjugation is an important mode of horizontal gene transfer in bacteria, enhancing the spread of antibiotic resistance. In clinical settings, biofilms are likely locations for antibiotic resistance transfer events involving nosocomial pathogens such as Enterococcus faecalis. Here we demonstrate that growth in biofilms alters the induction of conjugation by a sex pheromone in E. faecalis. Mathematical modeling suggested that a higher plasmid copy number in biofilm cells would enhance a switch-like behavior in the pheromone response of donor cells with a delayed, but increased response to the mating signal. Alterations in plasmid copy number, and a bimodal response to induction of conjugation in populations of plasmid-containing donor cells were both observed in biofilms, consistent with the predictions of the model. The pheromone system may have evolved such that donor cells in biofilms are only induced to transfer when they are in extremely close proximity to potential recipients in the biofilm community. These results may have important implications for development of chemotherapeutic agents to block resistance transfer and treat biofilm-related clinical infections.

Cook, Laura; Barnes, Aaron; Dunny, Gary; Chatterjee, Anushree; Hu, Wei-Shou; Yarwood, Jeremy

2011-01-01

239

Pressate from Peat Dewatering as a Substrate for Bacterial Growth  

PubMed Central

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

Mulligan, Catherine N.; Cooper, David G.

1985-01-01

240

Spatial Patterning of Newly-Inserted Material during Bacterial Cell Growth  

NASA Astrophysics Data System (ADS)

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

Ursell, Tristan

2012-02-01

241

Effect of growth curve and sampling regime on instantaneous-growth, removal-summation, and Hynes\\/Hamilton estimates of aquatic insect production: a computerr simulation  

Microsoft Academic Search

Hypothetical populations of aquatic insects were periodically sampled, using a computer model, to estimate production by the instantaneous-growth, removal-summation, and Hynes\\/Hamilton methods. These estimates were compared with the production values calculated from the daily growth of all individuals in the populations. The removal-summation method yielded the most accurate estimates for a variety of growth curves and sampling regimes and appeared

R. M. Cushman; H. H. Jr. Shugart; S. G. Hildebrand; J. W. Elwood

1978-01-01

242

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

PubMed

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

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

2010-07-28

243

Coal Fly Ash Impairs Airway Antimicrobial Peptides and Increases Bacterial Growth  

PubMed Central

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

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

2013-01-01

244

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

PubMed

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

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

2013-02-28

245

Bacterial population in intestines of the black tiger shrimp (Penaeus monodon) under different growth stages.  

PubMed

Intestinal bacterial communities in aquaculture have been drawn to attention due to potential benefit to their hosts. To identify core intestinal bacteria in the black tiger shrimp (Penaeus monodon), bacterial populations of disease-free shrimp were characterized from intestines of four developmental stages (15-day-old post larvae (PL15), 1- (J1), 2- (J2), and 3-month-old (J3) juveniles) using pyrosequencing, real-time PCR and denaturing gradient gel electrophoresis (DGGE) approaches. A total of 25,121 pyrosequencing reads (reading length?=?442±24 bases) were obtained, which were categorized by barcode for PL15 (7,045 sequences), J1 (3,055 sequences), J2 (13,130 sequences) and J3 (1,890 sequences). Bacteria in the phyla Bacteroides, Firmicutes and Proteobacteria were found in intestines at all four growth stages. There were 88, 14, 27, and 20 bacterial genera associated with the intestinal tract of PL15, J1, J2 and J3, respectively. Pyrosequencing analysis revealed that Proteobacteria (class Gammaproteobacteria) was a dominant bacteria group with a relative abundance of 89% for PL15 and 99% for J1, J2 and J3. Real-time PCR assay also confirmed that Gammaproteobacteria had the highest relative abundance in intestines from all growth stages. Intestinal bacterial communities from the three juvenile stages were more similar to each other than that of the PL shrimp based on PCA analyses of pyrosequencing results and their DGGE profiles. This study provides descriptive bacterial communities associated to the black tiger shrimp intestines during these growth development stages in rearing facilities. PMID:23577162

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

2013-04-05

246

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

NASA Astrophysics Data System (ADS)

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

Ben-Jacob, Eshel

1997-03-01

247

Rapid Determination of Bacterial Abundance, Biovolume, Morphology, and Growth by Neural Network-Based Image Analysis  

PubMed Central

Annual bacterial plankton dynamics at several depths and locations in the Baltic Sea were studied by image analysis. Individual bacteria were classified by using an artificial neural network which also effectively identified nonbacterial objects. Cell counts and frequencies of dividing cells were determined, and the data obtained agreed well with visual observations and previously published values. Cell volumes were measured accurately by comparison with bead standards. The survey included 690 images from a total of 138 samples. Each image contained approximately 200 bacteria. The images were analyzed automatically at a rate of 100 images per h. Bacterial abundance exhibited coherent patterns with time and depth, and there were distinct subsurface peaks in the summer months. Four distinct morphological classes were resolved by the image analyzer, and the dynamics of each could be visualized. The bacterial growth rates estimated from frequencies of dividing cells were different from the bacterial growth rates estimated by the thymidine incorporation method. With minor modifications, the image analysis technique described here can be used to analyze other planktonic classes.

Blackburn, Nicholas; Hagstrom, ?ke; Wikner, Johan; Cuadros-Hansson, Rocio; Bj?rnsen, Peter Koefoed

1998-01-01

248

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

PubMed Central

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

Timchenko, T; Bailone, A; Devoret, R

1996-01-01

249

Bayesian analysis for nonlinear regression model under skewed errors, with application in growth curves.  

PubMed

We have considered a Bayesian approach for the nonlinear regression model by replacing the normal distribution on the error term by some skewed distributions, which account for both skewness and heavy tails or skewness alone. The type of data considered in this paper concerns repeated measurements taken in time on a set of individuals. Such multiple observations on the same individual generally produce serially correlated outcomes. Thus, additionally, our model does allow for a correlation between observations made from the same individual. We have illustrated the procedure using a data set to study the growth curves of a clinic measurement of a group of pregnant women from an obstetrics clinic in Santiago, Chile. Parameter estimation and prediction were carried out using appropriate posterior simulation schemes based in Markov Chain Monte Carlo methods. Besides the deviance information criterion (DIC) and the conditional predictive ordinate (CPO), we suggest the use of proper scoring rules based on the posterior predictive distribution for comparing models. For our data set, all these criteria chose the skew-t model as the best model for the errors. These DIC and CPO criteria are also validated, for the model proposed here, through a simulation study. As a conclusion of this study, the DIC criterion is not trustful for this kind of complex model. PMID:19629998

De la Cruz, Rolando; Branco, Márcia D

2009-08-01

250

Growth Curve and Distribution of Rous Sarcoma Virus (Bryan) in Japanese Quail 1  

PubMed Central

On primary infection with the Bryan strain of Rous sarcoma virus (RSV), the growth curve of the virus in the brain of Japanese quail was similar to that observed in chicks and turkey poults. Infectious virus disappeared from the brain after inoculation. After an eclipse period during which no virus was detectable, infectious virus began to appear at 2 days and reached maximal titers in the brain samples at 7 days after inoculation. When Japanese quail were infected intracerebrally with RSV, relatively high titers of virus were recovered from brain tissue but not from liver, lung, kidney, or blood of moribund birds. Only tumors produced in the wing web of quail infected subcutaneously yielded high titers of virus. Other tissues yielded no virus, even though wing web tumors appeared as early as in chicks similarly infected. RSV could be propagated in the wing web of quail for at least 14 passages without any loss of infectivity. On the other hand, serial passage in quail brain resulted in a progressive loss of infectivity until virus was completely lost.

Pienta, Roman J.; Groupe, Vincent

1967-01-01

251

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

PubMed

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

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

2007-10-01

252

Single-cell analysis of bacterial growth, cell size, and community structure in the Delaware estuary  

Microsoft Academic Search

The abundance and size of thymidine and leucine-assimilating bacteria were examined using a combination of microautoradiography and fluorescence in situ hybridization (micro-FISH) to explore the relationship between community structure and bacterial growth in the Delaware estuary. Community structure varied along the salinity gradient; ?-proteobacteria and Cytophaga-like bacte- ria dominated in freshwater parts of the estuary and ?-proteobacteria were the most

Matthew T. Cottrell; David L. Kirchman

2004-01-01

253

Bacterial diversity, community structure and potential growth rates along an estuarine salinity gradient.  

PubMed

Very little is known about growth rates of individual bacterial taxa and how they respond to environmental flux. Here, we characterized bacterial community diversity, structure and the relative abundance of 16S rRNA and 16S rRNA genes (rDNA) using pyrosequencing along the salinity gradient in the Delaware Bay. Indices of diversity, evenness, structure and growth rates of the surface bacterial community significantly varied along the transect, reflecting active mixing between the freshwater and marine ends of the estuary. There was no positive correlation between relative abundances of 16S rRNA and rDNA for the entire bacterial community, suggesting that abundance of bacteria does not necessarily reflect potential growth rate or activity. However, for almost half of the individual taxa, 16S rRNA positively correlated with rDNA, suggesting that activity did follow abundance in these cases. The positive relationship between 16S rRNA and rDNA was less in the whole water community than for free-living taxa, indicating that the two communities differed in activity. The 16S rRNA:rDNA ratios of some typically marine taxa reflected differences in light, nutrient concentrations and other environmental factors along the estuarine gradient. The ratios of individual freshwater taxa declined as salinity increased, whereas the 16S rRNA:rDNA ratios of only some typical marine bacteria increased as salinity increased. These data suggest that physical and other bottom-up factors differentially affect growth rates, but not necessarily abundance of individual taxa in this highly variable environment. PMID:22895159

Campbell, Barbara J; Kirchman, David L

2012-08-16

254

Standard Curves of Cerebral Doppler Flow Velocity Waveforms and Predictive Values for Intrauterine Growth Retardation and Fetal Acidosis  

Microsoft Academic Search

Cerebral Doppler measurements seem to be a future method to evaluate the degree of fetal hypoxemia. The aim of this study was (1) to elaborate standard curves for the different cerebral vessels in our own population, and (2) to describe the predictive value of Doppler measurements for intrauterine growth retardation (IUGR) and fetal acidosis. We recorded cerebral flow velocity waveforms

R. Favre; R. Schönenberger; I. Nisand; U. Lorenz

1991-01-01

255

Fuzzy Clusterwise Growth Curve Models via Generalized Estimating Equations: An Application to the Antisocial Behavior of Children  

ERIC Educational Resources Information Center

|The growth curve model has been a useful tool for the analysis of repeated measures data. However, it is designed for an aggregate-sample analysis based on the assumption that the entire sample of respondents are from a single homogenous population. Thus, this method may not be suitable when heterogeneous subgroups exist in the population with…

Hwang, Heungsun; Takane, Yoshio; DeSarbo, Wayne S.

2007-01-01

256

The Effect of Covariance Structure on Variance Estimation in Balanced Growth-Curve Models with Random Parameters  

Microsoft Academic Search

Intuition suggests that altering the covariance structure of a parametric model for repeated-measures data alters the variances of the model's estimated mean parameters. The purpose of this article is to sharpen such intuition for a family of growth-curve models with differing numbers of random effects for the individual sampling units and with a fixed structure on the mean. For every

Nicholas Lange; Nan M. Laird

1989-01-01

257

Fuzzy Clusterwise Growth Curve Models via Generalized Estimating Equations: An Application to the Antisocial Behavior of Children  

Microsoft Academic Search

The growth curve model has been a useful tool for the analysis of repeated measures data. However, it is designed for an aggregate-sample analysis based on the assumption that the entire sample of respondents are from a single homogenous population. Thus, this method may not be suitable when heterogeneous subgroups exist in the population with qualitatively distinct patterns of trajectories.

Heungsun Hwang; Yoshio Takane; Wayne S. DeSarbo

2007-01-01

258

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

ERIC Educational Resources Information Center

|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…

Farrell, Albert D.; Sullivan, Terri N.

2004-01-01

259

Transformation Yielding, Plasticity and Crack-Growth-Resistance (R-Curve) Behavior of CeO2-TZP.  

National Technical Information Service (NTIS)

Transformation yield and plasticity, transformation zone sizes at crack tips and rising crack-growth-resistance (R-curve) behaviours were studied in a commercial-grade ceria partially stabilized zirconia polycrystalline material (CeO2-TZP). The yield stre...

C. S. Yu D. K. Shetty

1990-01-01

260

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

ERIC Educational Resources Information Center

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

Palardy, Gregory J.

2008-01-01

261

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

PubMed

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

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

2013-10-28

262

Frequency of Dividing Cells, a New Approach to the Determination of Bacterial Growth Rates in Aquatic Environments  

PubMed Central

Frequency of dividing cells is suggested to be an indirect measure of the mean growth rate of an aquatic bacterial community. Seasonal changes in frequency of dividing cells were found which covariated with the bacterial uptake of 14C-labeled phytoplankton exudates. Batch and continuous culture growth experiments, using brackish water bacteria in pure and mixed enrichment cultures, were performed to establish a relationship between frequency of dividing cells and growth rate. An improved technique for bacterial direct counts, using fluorescent staining and epifluorescence microscopy, is presented. Based on a 6-month survey in a coastal area of the Baltic Sea, the bacterial production in the photic zone is estimated. Compared to the total primary production in the area, the bacterial population during this period utilized approximately 25% of the amount of carbon originally fixed by the primary producers.

Hagstrom, A.; Larsson, U.; Horstedt, P.; Normark, S.

1979-01-01

263

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

Microsoft Academic Search

The concentrations of ferrous and ferric ions change dramatically during the course of the batch experiments usually performed to study the kinetics of the bacterial oxidation of ferrous ions and sulfide minerals. This change in concentration of the iron species during the course of the experiment often makes it difficult to interpret the results of these experiments, as is evidenced

P. I. HARVEY; F. K. CRUNDWELL

1997-01-01

264

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

Microsoft Academic Search

Municipal effluent is the largest reservoir of human enteric bacteria. Its public health significance, however, depends upon the physiological status of the wastewater bacterial community. A novel immunofluorescence assay was developed and used to examine the bacterial growth state during wastewater disinfection. Quantitative levels of three highly conserved cytosolic proteins (DnaK, Dps, and Fis) were determined by using enterobacterium-specific antibody

DAVID ROCKABRAND; TERESA AUSTIN; ROBYN KAISER; PAUL BLUM

1999-01-01

265

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

Microsoft Academic Search

In this study we investigated the interactions among plant, rhizosphere microorganisms and Zn pollution. We tested the influence of two bacterial strains isolated from a Zn-polluted soil on plant growth and on the symbiotic efficiency of native arbuscular mycorrhizal fungi (AMF) under Zn toxicity. The two bacterial strains exhibited Zn tolerance when cultivated under increasing Zn levels in the medium.

A. Vivas; B. Biró; J. M. Ruíz-Lozano; J. M. Barea; R. Azcón

2006-01-01

266

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...

267

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

Code of Federal Regulations, 2010 CFR

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

2009-07-01

268

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

269

Nitrogen and Phosphorus Co-Limitation of Bacterial Productivity and Growth in the Oligotrophic Subtropical North Atlantic  

Microsoft Academic Search

Bacterial productivity and biomass are thought to be limited by dissolved organic carbon (DOC) in much of the world's oceans. However, the mixed layer of oligotrophic oceans is often depleted in dissolved inorganic nitrogen and phosphate, raising the possibility that macronutrients may also limit heterotrophic bacterial growth. We used nutrient bioassay experiments to determine whether inorganic nutrients (N, P, Fe)

M. M. Mills; C. M. Moore; R. Langlois; A. Milne; E. Achterberg; K. Nachtigall; K. Lochte; R. J. Geider; J. La Roche

2008-01-01

270

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

NASA Astrophysics Data System (ADS)

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.

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

2003-04-01

271

Birth, growth and death as structuring operators in bacterial population dynamics.  

PubMed

A new model is presented that describes microbial population dynamics that emerge from complex interactions among birth, growth and death as oriented, discrete events. Specifically, birth and death act as structuring operators for individual organisms within the population, which become synchronised as age clusters (called cell generations that are structured in age classes) that are born at the same time and die in concert; a pattern very consistent with recent experimental data that show bacterial group death correlates with temporal population dynamics in chemostats operating at carrying capacity. Although the model only assumes "natural death" (i.e., no death from predation or antimicrobial exposure), it indicates that short-term non-linear dynamic behaviour can exist in a bacterial population growing under longer term pseudo-steady-state conditions (a confined dynamic equilibrium). After summarizing traditional assumptions about bacterial aging, simulations of batch, continuous-flow, and bioreactors with recycle are used to show how population dynamics vary as function of hydraulic retention time, microbial kinetics, substrate level, and other factors that cause differential changes in the distribution of living and dead cells within the system. In summary, we show that population structures induced by birth and death (as discrete and delayed events) intrinsically create a non-linear dynamic system, implying that a true steady state can never exist in growing bacterial populations. This conclusion is discussed within the context of process stability in biotechnology. PMID:20097208

Lavric, Vasile; Graham, David W

2010-01-25

272

Analysis of bacterial growth by UV/Vis spectroscopy and laser reflectometry  

NASA Astrophysics Data System (ADS)

This work presents a preliminary study on an experimental analysis of the lactobacillus bacterial growth in liquid medium with and without the presence of silver nanoparticles. The study aims to quantify the bactericidal effect of nanoparticles. Quantification of bacterial growth at different times was analyzed by spectroscopy UV/visible and laser reflectometry near the critical angle. From these two techniques the best results were obtained by spectroscopy, showing that as the concentration of silver nanoparticles increases, it inhibits the growth of bacteria, it only grows 63% of the population. Regarding Laser Reflectometry, the variation of reflectance near the critical angle is measured in real time. The observed results at short times are reasonable, since they indicate a gradual growth of the bacteria and the stabilization stage of the population. But at long time, the observed results show abrupt changes caused by temperature effects. The bacteria were isolated from samples taken from commercial yougurth, and cultured in MRS broth at pH 6.5, and controlled with citric acid and constant temperature of 32 °C. Separately, silver nanoparticles were synthesized at 3 °C from aqueous solutions of 1.0 mM silver nitrate and chemically reduced with sodium borohydride to 2.0 mM, with magnetic stirring.

Peña-Gomar, Mary Carmen; Viramontes-Gamboa, Gonzalo; Peña-Gomar, Grethel; Ortiz Gutiérrez, Mauricio; Hernández Ramírez, Mariano

273

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

PubMed

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

Bekri, M; Pauss, A

2003-01-01

274

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

275

Inhibition of Bacterial Growth and Biofilm Production by Constituents from Hypericum spp  

PubMed Central

Biofilm embedded bacterial pathogens such as Staphylococcus spp., Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii are difficult to eradicate and are major sources of bacterial infections. New drugs are needed to combat these pathogens. Hypericum is a plant genus that contains species known to have antimicrobial properties. However, the specific constituents responsible for the antimicrobial properties are not entirely known, nor have most compounds been tested as inhibitors of biofilm development. The investigation presented here tested seven secondary metabolites isolated from the species Hypericum densiflorum, Hypericumellipticum, Hypericum prolificum and Hypericum punctatum as inhibitors of bacterial growth and biofilm production. Assays were conducted against Staphylococcus epidermidis, Staphylococcusaureus, clinical methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Escherichia coli, and Acinetobacter baumannii. Five of the seven compounds demonstrated growth inhibition against the Gram-positive bacteria with minimum inhibitory concentrations (MIC) ranging from 1.95 ?g/mL to 7.81 ?g/mL. Four of the secondary metabolites inhibited biofilm production by certain Gram-positive strains at sub-MIC concentrations.

Sarkisian, S.A.; Janssen, M.J.; Matta, H.; Henry, G.E.; LaPlante, K.L.; Rowley, D.C.

2011-01-01

276

Intestinal bacterial community and growth performance of chickens fed diets containing antibiotics.  

PubMed

This study was conducted to relate the performance of broiler chickens fed diets containing growth-promoting antibiotics to changes in the intestinal microbiota. The technique of denaturing gradient gel electrophoresis (DGGE) of amplicons of the region V3 of 16S rDNA was used to characterize the microbiota. Two experiments were conducted, one with broilers raised in battery cages and the other with broilers raised in floor pens. Antibiotics improved the performance of the chickens raised in floor pens only. Avilamycin, bacitracin methylene disalicylate, and enramycin induced changes in the composition of the intestinal bacterial community of the birds in both experiments. The number of bacterial genotypes found in the intestinal tract of chickens was not reduced by the antibiotics supplemented in either environment. However, the changes in the composition of the intestinal bacterial community induced by antibiotics may be related to improvement in growth performance. This was indicated by the suppression of 6 amplicons and the presence of 4 amplicons exclusive to the treatment that had the best performance in the floor pen experiment. PMID:16615359

Pedroso, A A; Menten, J F M; Lambais, M R; Racanicci, A M C; Longo, F A; Sorbara, J O B

2006-04-01

277

Estimating the equivalent dose of late Pleistocene fine silt quartz from the Lower Mississippi Valley using a standardized OSL growth curve  

Microsoft Academic Search

The establishment of a standardized growth curve is desired for optical dating as it facilitates the dating procedures. Here, we analyzed the dose responses of 16 fine silt quartz samples from the Lower Mississippi Valley in order to identify common properties that would allow establishing a standardized OSL growth curve (SGC). The analysis confirms the dependence of the standardized dose

Zhixiong Shen; Barbara Mauz

2011-01-01

278

Intrauterine growth curves of twins: effects of socioeconomic level Curvas de crescimento intra-uterino de gêmeos: efeitos do nível socioeconômico  

Microsoft Academic Search

Objective: To study the influence of different socioeconomic level on intrauterine growth curves of singletons and twins. Methods: Data referring to the birth weight and gestational age of singletons and twins were obtained from neonatal records from three different hospitals so called A, B and C, from lower to higher socioeconomic level, in the 90s. Intrauterine growth curves were constructed

Conceição Aparecida; Gloria Maria dal Colletto; Silvia Terezinha Rielli

2005-01-01

279

The temporal factor of change in stressor-strain relationships: a growth curve model on a longitudinal study in East Germany  

Microsoft Academic Search

Several theoretical models describing how stressor-strain relationships unfold in time (e.g., M. Frese & D. Zapf, 1988) were tested with a longitudinal study, with 6 measurement waves, using multivariate latent growth curve models. The latent growth curve model made it possible to decompose trait and state components of strains and to show that both trait and state components are affected

GJA Garst; Michael Frese; Peter C. M. Molenaar

2000-01-01

280

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

281

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

PubMed Central

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

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

2013-01-01

282

Structure of a Bacterial Dynamin-like Protein Lipid Tube Provides a Mechanism For Assembly and Membrane Curving  

PubMed Central

Summary Proteins of the dynamin superfamily mediate membrane fission, fusion, and restructuring events by polymerizing upon lipid bilayers and forcing regions of high curvature. In this work, we show the electron cryomicroscopy reconstruction of a bacterial dynamin-like protein (BDLP) helical filament decorating a lipid tube at ?11 Å resolution. We fitted the BDLP crystal structure and produced a molecular model for the entire filament. The BDLP GTPase domain dimerizes and forms the tube surface, the GTPase effector domain (GED) mediates self-assembly, and the paddle region contacts the lipids and promotes curvature. Association of BDLP with GMPPNP and lipid induces radical, large-scale conformational changes affecting polymerization. Nucleotide hydrolysis seems therefore to be coupled to polymer disassembly and dissociation from lipid, rather than membrane restructuring. Observed structural similarities with rat dynamin 1 suggest that our results have broad implication for other dynamin family members.

Low, Harry H.; Sachse, Carsten; Amos, Linda A.; Lowe, Jan

2009-01-01

283

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

PubMed Central

Laboratory and field-scale studies with stained cells were performed to monitor cell growth in groundwater systems. During cell division, the fluorescence intensity of the protein stain 5-(and 6-)-carboxyfluorescein diacetate succinimidyl ester (CFDA/SE) for each cell is halved, and the intensity can be tracked with a flow cytometer. Two strains of bacteria, Comamonas sp. strain DA001 and Acidovorax sp. strain OY-107, both isolated from a shallow aquifer, were utilized in this study. The change in the average generation or the average fluorescence intensity of the CFDA/SE-stained cells could be used to obtain estimates of doubling times. In microcosm experiments, the CFDA/SE-based doubling times were similar to the values calculated by total cell counting and were independent of cell concentration. Intact and repacked sediment core experiments with the same bacteria indicated that changes in groundwater chemistry were just as important as growth rates in determining planktonic cell concentrations. The growth rates within the sediment cores were similar to those calculated in microcosm experiments, and preferential transport of the daughter cells was not observed. The experiments indicated that the growth rates could be determined in systems with cell losses due to other phenomena, such as attachment to sediment or predation. Application of this growth rate estimation method to data from a field-scale bacterial transport experiment indicated that the doubling time was approximately 15 days, which is the first known direct determination of an in situ growth rate for bacteria in an aquifer.

Mailloux, Brian J.; Fuller, Mark E.

2003-01-01

284

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

Microsoft Academic Search

Among substance-dependent individuals comorbid major depressive disorder (MDD) is associated with greater severity and poorer treatment outcomes, but little research has examined mediators of post-treatment substance use outcomes within this population. Using latent growth curve models we tested relationships between individual rates of change in 12-step involvement and substance use, utilizing post-treatment follow-up data from a trial of group Twelve-Step

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

2013-01-01

285

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

Microsoft Academic Search

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

Steven Eggermont

2006-01-01

286

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

Microsoft Academic Search

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

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

2007-01-01

287

Transformation yielding, plasticity and crack-growth-resistance (R-curve) behaviour of CeO 2 -TZP  

Microsoft Academic Search

Transformation yield and plasticity, transformation zone sizes at crack tips and rising crack-growth-resistance (R-curve) behaviours were studied in a commercial-grade ceria partially stabilized zirconia polycrystalline material (CeO2-TZP). The yield stresses measured in three-point bending decreased from 390 to 176 MPa when the sintering temperature was varied from 1425 to 1525° C. The corresponding total plastic strain to fracture increased with

Cheng-Sheng Yu; D. K. Shetty

1990-01-01

288

Master Sintering Curve for Densification Derived from a Constitutive Equation with Consideration of Grain Growth: Application to Tungsten Heavy Alloys  

NASA Astrophysics Data System (ADS)

A new formulation of the master sintering curve (MSC) is developed to include the effects of grain growth on densification during both solid state and liquid phase sintering. Densification is described by a continuum mechanics model in which the grain size appears as a material parameter. The grain size is calculated along a given heating schedule using a grain growth law, rather than assuming its dependence on the density. The final equation contains two apparent activation energies, one for densification kinetics and another for grain growth kinetics. This equation is used to analyze densification and grain size data for W-Ni-Fe heavy alloys with W contents ranging from 83 to 93 wt pct during both solid state and liquid phase sintering. The calculated apparent activation energies are compared with previous values and are used to analyze transport mechanisms for densification and grain growth.

Park, S. J.; Chung, S. H.; Martín, J. M.; Johnson, John L.; German, Randall M.

2008-12-01

289

Estimation of long-term bacterial respiration and growth efficiency in Lake Kinneret.  

PubMed

Semi-annual averaged values of photosynthetic carbon fixation (PCF), community respiration (CR), bacterial productivity (BP) and zooplankton carbon biomass, measured biweekly or monthly, were used to obtain long-term estimates of bacterial respiration (BR) and bacterial growth efficiency (BGE) in Lake Kinneret from 2001 through 2007. We posited that CR=BR+phytoplankton respiration (PR)+zooplankton respiration (ZR). Based on the results of independent experimental series, PR was estimated as 0.3 x gross primary production (GPP) and GPP as 1.5 x PCF. ZR was determined by multiplying zooplankton carbon biomass, measured biweekly, with published respiration rates for major zooplankton groups. From these data, we calculated BR and consequently BGE, determined as BP/(BR+BP). Over the entire study period, BR averaged 49 (+/-10)% of CR and was consistently higher during the first half of the year. Semi-annual averaged BGE ranged from 26% to 53%, mean 39 (+/-9)%. Similar values of BGE were obtained if we did not use the measured values for ZR, but estimated BR+ZR from CR-PR and then assumed that BR ranged from two to three times ZR. The approach outlined in this paper can be useful for determining BGE in aquatic systems where long-term data sets of PCF, CR and BP are available. PMID:20041950

Berman, Tom; Yacobi, Yosef Z; Parparov, Arkadi; Gal, Gideon

2009-11-27

290

Effects of Bacterial Prey Species and Their Concentration on Growth of the Amoebae Acanthamoeba castellanii and Hartmannella vermiformis?  

PubMed Central

Two amoebae were presented with six bacterial prey at a range of concentrations, and the growth parameters of the amoebae were deduced. All but one bacterium (Synechococcus) resulted in a positive growth response, but the gram-positive bacterium Staphylococcus aureus proved to be difficult to digest and the heavily pigmented bacterium Klebsiella ozaenae induced unusual amoebic behavior prior to ingestion.

Pickup, Zoe L.; Pickup, Roger; Parry, Jacqueline D.

2007-01-01

291

Effects of bacterial prey species and their concentration on growth of the amoebae Acanthamoeba castellanii and Hartmannella vermiformis.  

PubMed

Two amoebae were presented with six bacterial prey at a range of concentrations, and the growth parameters of the amoebae were deduced. All but one bacterium (Synechococcus) resulted in a positive growth response, but the gram-positive bacterium Staphylococcus aureus proved to be difficult to digest and the heavily pigmented bacterium Klebsiella ozaenae induced unusual amoebic behavior prior to ingestion. PMID:17293529

Pickup, Zoë L; Pickup, Roger; Parry, Jacqueline D

2007-02-09

292

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

Microsoft Academic Search

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

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

2009-01-01

293

Bacterial-growth inhibiting properties of multilayers formed with modified polyvinylamine.  

PubMed

New methods are needed to fight antibiotic-resistant bacteria. One alternative that has been proposed is non-leaching, permanently antibacterial surfaces. In this study, we test multilayers formed with antibacterial cationic polyvinylamine (PVAm) and polyacrylic acid (PAA) in a growth-inhibition assay. Both hydrophobically modified and native PVAm were investigated. Multilayers did reduce the bacterial growth, as compared to single layers. However, the sampling time in the assay was critical, as the treated surface area is a capacity-limiting factor. After 2h incubation, a maximal growth inhibition of more than 99% was achieved with multilayers. In contrast, after 8h we observed a maximal growth-inhibition of 40%. At longer incubation times, the surface becomes saturated, which explains the observed time-dependent effectiveness. The polymers giving multilayers with the strongest growth-inhibiting properties were native PVAm and PVAm modified with C(8), which also were the polymers with highest charge density. We therefore conclude that this effect is mainly an electrostatically driven process. Viability staining using a fluorescent stain showed a high viability rate of the adhered bacteria. The multilayers are therefore more bacteriostatic than antibacterial. PMID:21802911

Illergård, Josefin; Wågberg, Lars; Ek, Monica

2011-07-08

294

Theoretical and Computational Investigation of Flagellin Translocation and Bacterial Flagellum Growth  

PubMed Central

The bacterial flagellum is a self-assembling filament, which bacteria use for swimming. It is built from tens of thousands of flagellin monomers in a self-assembly process that involves translocation of the monomers through the flagellar interior, a channel, to the growing tip. Flagellum monomers are pumped into the filament at the base, move unfolded along the channel and then bind to the tip of the filament, thereby extending the growing flagellum. The flagellin translocation process, due to the flagellum maximum length of 20 ?m, is an extreme example of protein transport through channels. Here, we derive a model for flagellin transport through the long confining channel, testing the key assumptions of the model through molecular dynamics simulations that also furnish system parameters needed for quantitative description. Together, mathematical model and molecular dynamics simulations explain why the growth rate of flagellar filaments decays exponentially with filament length and why flagellum growth ceases at a certain maximum length.

Tanner, David E.; Ma, Wen; Chen, Zhongzhou; Schulten, Klaus

2011-01-01

295

Application of a Microcomputer-Based System to Control and Monitor Bacterial Growth  

PubMed Central

A modular microcomputer-based system was developed to control and monitor various modes of bacterial growth. The control system was composed of an Apple II Plus microcomputer with 64-kilobyte random-access memory; a Cyborg ISAAC model 91A multichannel analog-to-digital and digital-to-analog converter; paired MRR-1 pH, pO2, and foam control units; and in-house-designed relay, servo control, and turbidimetry systems. To demonstrate the flexibility of the system, we grew bacteria under various computer-controlled and monitored modes of growth, including batch, turbidostat, and chemostat systems. The Apple-ISAAC system was programmed in Labsoft BASIC (extended Applesoft) with an average control program using ca. 6 to 8 kilobytes of memory and up to 30 kilobytes for datum arrays. This modular microcomputer-based control system was easily coupled to laboratory scale fermentors for a variety of fermentations.

Titus, Jeffrey A.; Luli, Gregory W.; Dekleva, Michael L.; Strohl, William R.

1984-01-01

296

Application of a microcomputer-based system to control and monitor bacterial growth.  

PubMed

A modular microcomputer-based system was developed to control and monitor various modes of bacterial growth. The control system was composed of an Apple II Plus microcomputer with 64-kilobyte random-access memory; a Cyborg ISAAC model 91A multichannel analog-to-digital and digital-to-analog converter; paired MRR-1 pH, pO(2), and foam control units; and in-house-designed relay, servo control, and turbidimetry systems. To demonstrate the flexibility of the system, we grew bacteria under various computer-controlled and monitored modes of growth, including batch, turbidostat, and chemostat systems. The Apple-ISAAC system was programmed in Labsoft BASIC (extended Applesoft) with an average control program using ca. 6 to 8 kilobytes of memory and up to 30 kilobytes for datum arrays. This modular microcomputer-based control system was easily coupled to laboratory scale fermentors for a variety of fermentations. PMID:16346462

Titus, J A; Luli, G W; Dekleva, M L; Strohl, W R

1984-02-01

297

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

PubMed

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

Øverland, M; Schøyen, H F; Skrede, A

2010-10-01

298

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

PubMed

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

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

2013-09-30

299

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

PubMed Central

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

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

2013-01-01

300

Economic growth and atmospheric pollution in Spain: discussing the environmental Kuznets curve hypothesis  

Microsoft Academic Search

The environmental Kuznets curve (EKC) hypothesis posits an inverted U relationship between environmental pressure and per capita income. Recent research has examined this hypothesis for different pollutants in different countries. Despite certain empirical evidence showing that some specific environmental pressures have diminished in developed countries, the hypothesis could not be generalized to the global relationship between economy and environment at

Jordi Roca; Emilio Padilla; Mariona Farré; Vittorio Galletto

2001-01-01

301

A Growth Curve Model with Fractional Polynomials for Analysing Incomplete Time-Course Data in Microarray Gene Expression Studies  

PubMed Central

Identifying the various gene expression response patterns is a challenging issue in expression microarray time-course experiments. Due to heterogeneity in the regulatory reaction among thousands of genes tested, it is impossible to manually characterize a parametric form for each of the time-course pattern in a gene by gene manner. We introduce a growth curve model with fractional polynomials to automatically capture the various time-dependent expression patterns and meanwhile efficiently handle missing values due to incomplete observations. For each gene, our procedure compares the performances among fractional polynomial models with power terms from a set of fixed values that offer a wide range of curve shapes and suggests a best fitting model. After a limited simulation study, the model has been applied to our human in vivo irritated epidermis data with missing observations to investigate time-dependent transcriptional responses to a chemical irritant. Our method was able to identify the various nonlinear time-course expression trajectories. The integration of growth curves with fractional polynomials provides a flexible way to model different time-course patterns together with model selection and significant gene identification strategies that can be applied in microarray-based time-course gene expression experiments with missing observations.

Tan, Qihua; Thomassen, Mads; Hjelmborg, Jacob v. B.; Clemmensen, Anders; Andersen, Klaus Ejner; Petersen, Thomas K.; McGue, Matthew; Christensen, Kaare; Kruse, Torben A.

2011-01-01

302

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

PubMed Central

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

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

1993-01-01

303

The Tzs protein and exogenous cytokinin affect virulence gene expression and bacterial growth of Agrobacterium tumefaciens.  

PubMed

The soil phytopathogen Agrobacterium tumefaciens causes crown gall disease in a wide range of plant species. The neoplastic growth at the infection sites is caused by transferring, integrating, and expressing transfer DNA (T-DNA) from A. tumefaciens into plant cells. A trans-zeatin synthesizing (tzs) gene is located in the nopaline-type tumor-inducing plasmid and causes trans-zeatin production in A. tumefaciens. Similar to known virulence (Vir) proteins that are induced by the vir gene inducer acetosyringone (AS) at acidic pH 5.5, Tzs protein is highly induced by AS under this growth condition but also constitutively expressed and moderately upregulated by AS at neutral pH 7.0. We found that the promoter activities and protein levels of several AS-induced vir genes increased in the tzs deletion mutant, a mutant with decreased tumorigenesis and transient transformation efficiencies, in Arabidopsis roots. During AS induction and infection of Arabidopsis roots, the tzs deletion mutant conferred impaired growth, which could be rescued by genetic complementation and supplementing exogenous cytokinin. Exogenous cytokinin also repressed vir promoter activities and Vir protein accumulation in both the wild-type and tzs mutant bacteria with AS induction. Thus, the tzs gene or its product, cytokinin, may be involved in regulating AS-induced vir gene expression and, therefore, affect bacterial growth and virulence during A. tumefaciens infection. PMID:23593941

Hwang, Hau-Hsuan; Yang, Fong-Jhih; Cheng, Tun-Fang; Chen, Yi-Chun; Lee, Ying-Ling; Tsai, Yun-Long; Lai, Erh-Min

2013-09-01

304

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

PubMed Central

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

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

1983-01-01

305

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

PubMed

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

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

1983-09-01

306

Validating the weight gain of preterm infants between the reference growth curve of the fetus and the term infant  

PubMed Central

Background Current fetal-infant growth references have an obvious growth disjuncture around 40 week gestation overlapping where the fetal and infant growth references are combined. Graphical smoothening of the disjuncture to connect the matching percentile curves has never been validated. This study was designed to compare weight gain patterns of contemporary preterm infants with a fetal-infant growth reference (derived from a meta-analysis) to validate the previous smoothening assumptions and inform the revision of the Fenton chart. Methods Growth and descriptive data of preterm infants (23 to 31 weeks) from birth through 10 weeks post term age were collected in three cities in Canada and the USA between 2001 and 2010 (n?=?977). Preterm infants were grouped by gestational age into 23–25, 26–28, and 29–31 weeks. Comparisons were made between the weight data of the preterm cohort and the fetal-infant growth reference. Results Median weight gain curves of the three preterm gestational age groups were almost identical and remained between the 3rd and the 50th percentiles of the fetal-infant-growth-reference from birth through 10 weeks post term. The growth velocity of the preterm infants decreased in a pattern similar to the decreased velocity of the fetus and term infant estimates, from a high of 17–18 g/kg/day between 31–34 weeks to rates of 4–5 g/kg/day by 50 weeks in each gestational age group. The greatest discrepancy in weight gain velocity between the preterm infants and the fetal estimate was between 37 and 40 weeks; preterm infants grew more rapidly than the fetus. The infants in this study regained their birthweight earlier compared to those in the 1999 National Institute of Child Health and Human Development report. Conclusion The weight gain velocity of preterm infants through the period of growth data disjuncture between 37 and 50 weeks gestation is consistent with and thus validates the smoothening assumptions made between preterm and post-term growth references.

2013-01-01

307

Body mass index trajectories and predictors among 3rd to 12th graders using growth curve mixture modeling the Child and Adolescent Trial for Cardiovascular Health (CATCH) study  

Microsoft Academic Search

This dissertation examined body mass index (BMI) growth trajectories and the effects of gender, ethnicity, dietary intake, and physical activity (PA) on BMI growth trajectories among 3rd to 12th graders (9-18 years of age). Growth curve model analysis was performed using data from The Child and Adolescent Trial for Cardiovascular Health (CATCH) study. The study population included 2909 students who

Hao T Duong

2009-01-01

308

Microbial Growth Curves: What the Models Tell Us and What They Cannot  

Microsoft Academic Search

Most of the models of microbial growth in food are Empirical algebraic, of which the Gompertz model is the most notable, Rate equations, mostly variants of the Verhulst's logistic model, or Population Dynamics models, which can be deterministic and continuous or stochastic and discrete. The models of the first two kinds only address net growth and hence cannot account for

Micha Peleg; Maria G. Corradini

2011-01-01

309

Contrasting soil pH effects on fungal and bacterial growth suggest functional redundancy in carbon mineralization.  

PubMed

The influence of pH on the relative importance of the two principal decomposer groups in soil, fungi and bacteria, was investigated along a continuous soil pH gradient at Hoosfield acid strip at Rothamsted Research in the United Kingdom. This experimental location provides a uniform pH gradient, ranging from pH 8.3 to 4.0, within 180 m in a silty loam soil on which barley has been continuously grown for more than 100 years. We estimated the importance of fungi and bacteria directly by measuring acetate incorporation into ergosterol to measure fungal growth and leucine and thymidine incorporation to measure bacterial growth. The growth-based measurements revealed a fivefold decrease in bacterial growth and a fivefold increase in fungal growth with lower pH. This resulted in an approximately 30-fold increase in fungal importance, as indicated by the fungal growth/bacterial growth ratio, from pH 8.3 to pH 4.5. In contrast, corresponding effects on biomass markers for fungi (ergosterol and phospholipid fatty acid [PLFA] 18:2omega6,9) and bacteria (bacterial PLFAs) showed only a two- to threefold difference in fungal importance in the same pH interval. The shift in fungal and bacterial importance along the pH gradient decreased the total carbon mineralization, measured as basal respiration, by only about one-third, possibly suggesting functional redundancy. Below pH 4.5 there was universal inhibition of all microbial variables, probably derived from increased inhibitory effects due to release of free aluminum or decreasing plant productivity. To investigate decomposer group importance, growth measurements provided significantly increased sensitivity compared with biomass-based measurements. PMID:19151179

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

2009-01-16

310

Methods for Intense Aeration, Growth, Storage, and Replication of Bacterial Strains in Microtiter Plates  

PubMed Central

Miniaturized growth systems for heterogeneous culture collections are not only attractive in reducing demands for incubation space and medium but also in making the parallel handling of large numbers of strains more practicable. We report here on the optimization of oxygen transfer rates in deep-well microtiter plates and the development of a replication system allowing the simultaneous and reproducible sampling of 96 frozen glycerol stock cultures while the remaining culture volume remains frozen. Oxygen transfer rates were derived from growth curves of Pseudomonas putida and from rates of oxygen disappearance due to the cobalt-catalyzed oxidation of sulfite. Maximum oxygen transfer rates (38 mmol liter?1 h?1, corresponding to a mass transfer coefficient of 188 h?1) were measured during orbital shaking at 300 rpm at a shaking diameter of 5 cm and a culture volume of 0.5 ml. A shaking diameter of 2.5 cm resulted in threefold-lower values. These high oxygen transfer rates allowed P. putida to reach a cell density of approximately 9 g (dry weight) liter?1 during growth on a glucose mineral medium at culture volumes of up to 1 ml. The growth-and-replication system was evaluated for a culture collection consisting of aerobic strains, mainly from the genera Pseudomonas, Rhodococcus, and Alcaligenes, using mineral media and rich media. Cross-contamination and excessive evaporation during vigorous aeration were adequately prevented by the use of a sandwich cover of spongy silicone and cotton wool on top of the microtiter plates.

Duetz, Wouter A.; Ruedi, Lorenz; Hermann, Robert; O'Connor, Kevin; Buchs, Jochen; Witholt, Bernard

2000-01-01

311

Bacterial Growth as a Practical Indicator of Extensive Biodegradability of Organic Compounds  

PubMed Central

The proportionality of growth, as indicated by turbidity of cultures of Pseudomonas C12B, to the initial concentration of sodium dodecyl sulfate, dodecanol, or a mixture of C10-C20 secondary alcohol sulfates, each provided as sole carbon source in basal mineral salts medium, was demonstrated. Subsequently, the direct correlation of culture turbidity as a growth indicator and degradation of sodium dodecyl sulfate and the C10-C20 compounds was established. Degradation of these detergents was measured by the rise in surface tension and the decrease in methylene blue values, respectively. Turbidimetry was found to be a poor indicator of degradation of dodecanol in the early hours of culture, however, and did not correlate over a significant range with degradation of substrate. Viable cell counts did parallel dodecanol degradation as measured by gas-liquid chromatography. The use of bacterial growth as a reliable, quantitative, and easily measured parameter indicating biodegradability was suggested for those organic compounds which can be shown to serve as a carbon source for a bacterium.

Prochazka, G. J.; Payne, W. J.

1965-01-01

312

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

PubMed Central

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

2012-01-01

313

Integrated biological control of bacterial speck and spot of tomato under field conditions using foliar biological control agents and plant growth-promoting rhizobacteria  

Microsoft Academic Search

Integration of foliar bacterial biological control agents and plant growth promoting rhizobacteria (PGPR) was investigated to determine whether biological control of bacterial speck of tomato, caused by Pseudomonas syringae pv. tomato, and bacterial spot of tomato, caused by Xanthomonas campestris pv. vesicatoria and Xanthomonas vesicatoria, could be improved. Three foliar biological control agents and two selected PGPR strains were employed

P. Ji; H. L. Campbell; J. W. Kloepper; J. B. Jones; T. V. Suslow; M. Wilson

2006-01-01

314

Integrated biological control of bacterial speck and spot of tomato under Weld conditions using foliar biological control agents and plant growth-promoting rhizobacteria  

Microsoft Academic Search

Integration of foliar bacterial biological control agents and plant growth promoting rhizobacteria (PGPR) was investigated to deter- mine whether biological control of bacterial speck of tomato, caused by Pseudomonas syringae pv. tomato, and bacterial spot of tomato, caused by Xanthomonas campestris pv. vesicatoria and Xanthomonas vesicatoria, could be improved. Three foliar biological control agents and two selected PGPR strains were

P. Ji; H. L. Campbell; J. W. Kloepper; J. B. Jones; T. V. Suslow; M. Wilson

2006-01-01

315

Influences of altitude on growth curves in Tibetan chicken and its hybrid  

Microsoft Academic Search

Tibetan chicken is a precious resource in Qinghai-Tibet Plateau, China. In order to study its growth rhythm and heterosis\\u000a of its hybrid, three groups comprising Tibetan chicken (T), Dwarf Recessive White (D) and Tibetan × Dwarf Recessive White\\u000a (TD) were reared under the same management conditions at low and high altitudes. Body weight and shank length were measured,\\u000a and growth

Hao Zhang; Changxin Wu; Yangzom Chamba; Yao Ling; Suling Ji

2008-01-01

316

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

SciTech Connect

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

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

1999-09-08

317

SNP detection in transforming growth factor-beta1 gene using bacterial magnetic particles.  

PubMed

A single nucleotide polymorphism (SNP) within the transforming growth factor-beta1 (TGF-beta1) gene was detected by hybridization-based method using bacterial magnetic particles (BMPs). TGF-beta1 is commonly associated with a single base change resulting in a Leu(10)-->Pro (T(869)-->C) polymorphism and is a genetic marker for susceptibility to osteoporosis. Short (9 bases) and specific probes were designed to detect SNP in TGF-beta1. Detection probes were immobilized on BMPs using cross-linking reagents. TGF-beta1 PCR products (139 bp) were labeled with the fluorescent dye coumarin and hybridized with detection probes on BMPs. Complementary hybridized targets gave over four times higher fluorescent intensities, compared with one base mismatched hybridizations. The SNP genotype was successfully discriminated using this technique. PMID:12706579

Ota, Hiroyuki; Takeyama, Haruko; Nakayama, Hideki; Katoh, Takahiko; Matsunaga, Tadashi

2003-05-01

318

Effect of Bacterial Memory Dependent Growth by Using Fractional Derivatives Reaction-Diffusion Chemotactic Model  

NASA Astrophysics Data System (ADS)

In this paper, numerical solutions of a reaction-diffusion chemotactic model of fractional orders for bacterial growth will be present. A new solution is constructed in power series. The fractional derivatives are described in the Caputo sense. We compare the experimental result obtained with those obtained by simulation of the chemotactic model without fractional derivatives. The results show that the solution continuously depends on the time-fractional derivative. The resulting solutions spread faster than the classical solutions and may exhibit asymmetry, depending on the fractional derivative used. We present results of numerical simulations to illustrate the method, and investigate properties of numerical solutions. The Adomian's decomposition method (ADM) is used to find the approximate solution of fractional `reaction-diffusion chemotactic model. Numerical results show that the approach is easy to implement and accurate when applied to partial differential equations of fractional order.

Rida, S. Z.; El-Sayed, A. M. A.; Arafa, A. A. M.

2010-08-01

319

Dynamics of growth and succession of bacterial and fungal communities during composting of feather waste.  

PubMed

Succession of communities of different bacteria and fungi, mainly proteolytic and keratinolytic ones, was observed during composting of chicken feathers with pine bark (FB) and with pine bark/rye straw (FBS). The succession was dominated by fungal than bacterial communities. Bacteria, including Actinomycetes, grew intensively during the first 2-4 weeks of composting and included mainly proteolytic, rarely cellulolytic, populations; afterwards, bacteria were gradually replaced by fungi. Meso- and thermophilic ubiquitous fungi, including cellulolytic ones, appeared among fungal representatives as the first, while keratinolytic strains were detected in the compost biomass at the 6th week of the process. The development of strains within the second fungal group was significantly more intensive than that of cellulolytic populations. The intensity of growth of particular ecological-physiological communities was found to be dependent on chemical content and C/N ratio of biomass and was the strongest in C/N=25 composts. PMID:19819132

Korni??owicz-Kowalska, Teresa; Bohacz, Justyna

2009-10-09

320

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

PubMed Central

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

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

2010-01-01

321

Unusual Spherulite Radial Growth Rate Kinetics of Poly(ethylene adipate): Observation of a Double Maximum in Growth Rate Curve  

NASA Astrophysics Data System (ADS)

Poly(ethylene adipate) (PEA) is an aliphatic polyester often blended in small amounts with aromatic polyesters in order to impart some of its biodegradability to the resultant blend. Hot-stage polarized-light microscopy and differential scanning calorimetry have been used to investigate the isothermal melt-crystallization kinetics and thermal behaviour of PEA. The unusual spherulite radial growth rate dependence on isothermal crystallization temperature exhibits two maxima. A change in spherulite morphology from banded to non-banded spherulites is associated with the phase behaviour anomaly. The results are interpreted in terms of traditional Hoffmann-Lauritzen growth kinetics.

Singfield, Kathy; Rowe, Ashley

2009-03-01

322

Using Reactive Transport Modeling to Understand Changes in Electrical Conductivity Associated with Bacterial Growth and Respiration  

NASA Astrophysics Data System (ADS)

Previous research has linked measured changes in the bulk electrical conductivity (?b) of water-saturated sediments to the respiration and growth of anaerobic bacteria. If the mechanism causing this signal is understood and characterized it could be used to identify and monitor zones of bacterial activity in the subsurface. The 1-D reactive transport model PHREEQC was used to understand ?b signals by modeling chemical gradients within two column reactors and corresponding changes in effluent chemistry. The flow-through column reactors were packed with Fe(III)-bearing sediment from Oyster, VA and inoculated with an environmental consortia of microorganisms. Influent in the first reactor was amended with 1mM Na-acetate to encourage the growth of iron-reducing bacteria. Influent in the second reactor was amended with 0.1mM Na-Acetate and 2mM NaNO3 to encourage the growth of nitrate-reducing bacteria. While effluent concentrations of acetate, Fe(II), NO3-, NO2-, and NH4+ remained at steady state, we measured a 3-fold increase (0.055 S/m - 0.2 S/m) in ?b in the iron-reducing column and a 10-fold increase in ?b (0.07 S/m - 0.8 S/m) in the nitrate-reducing column over 198 days. The ionic strength in both reactors remained constant through time indicating that the measured increases in ?b were not caused by changing effluent concentrations. PHREEQC successfully matched the measured changes in effluent concentrations for both columns when the reaction database was modified in the following manner. For the iron-reducing column, kinetic expressions governing the rate of iron reduction, the rate of bacterial growth, and the production of methane were added to the reaction database. Additionally, surface adsorption and cation exchange reactions were added so that the model was consistent with measured effluent chemistry. For the nitrate-reducing column, kinetic expressions governing nitrate reduction and bacterial growth were added to the reaction database. Additionally, immobile porosity was added along with adsorption and cation exchange reactions. Although the model revealed the existence of chemical and biological gradients within the columns that were not discernable as changes in effluent concentrations, none of the chemical reactions or gradients could explain the measured ?b increases in either column. This result is not consistent with chemical gradients within the column reactor causing the measured changes in ?b. To test the alternate hypothesis that microbial biofilms are electrically conductive, we used the output from PHREEQC to calculate the amount of biomass produced within the column reactors. If biofilm causes the ?b changes, our model is consistent with an electrical conductivity for biomass in the iron-reducing column between 2.75 and 220 S/m. The model is also consistent with an electrical conductivity for biomass in the nitrate-reducing column between 350 and 35,000 S/m. These estimates of biomass electrical conductivity are poorly constrained but represent a first step towards understanding the electrical properties associated with respiring biofilms.

Regberg, A. B.; Singha, K.; Picardal, F.; Brantley, S. L.

2011-12-01

323

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

PubMed

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

Zheng, Huaixin; Chatfield, Christa H; Liles, Mark R; Cianciotto, Nicholas P

2013-08-26

324

Growth conditions influence UVB sensitivity and oxidative damage in an estuarine bacterial isolate.  

PubMed

The dose-dependent variation of oxidative cellular damage imposed by UVB exposure in a representative estuarine bacterial strain, Pseudomonas sp. NT5I1.2B, was studied at different growth phases (mid-exponential, late-exponential, and stationary), growth temperatures (15 °C and 25 °C) and growth media (nutrient-rich Tryptic Soy Broth [TSB] and nutrient-poor M9). Survival and markers of oxidative damage (lipid peroxidation, protein carbonylation, DNA strand breakage, and DNA-protein cross-links) were monitored during exposure to increasing UVB doses (0-60 kJ m(-2)). Oxidative damage did not follow a clear linear dose-dependent pattern, particularly at high UVB doses (>10 kJ m(-2)), suggesting a dynamic interaction between damage induction and repair during irradiation and/or saturation of oxidative damage. Survival of stationary phase cells generally exceeded that of exponential phase cells by up to 33.5 times; the latter displayed enhanced levels of DNA-protein cross-links (up to 15.6-fold) and protein carbonylation (up to 6.0-fold). Survival of mid-exponential phase cells was generally higher at 15 °C than at 25 °C (up to 6.6-fold), which was accompanied by lower levels of DNA strand breaks (up to 4000-fold), suggesting a temperature effect on reactive oxygen species (ROS) generation and/or ROS interaction with cellular targets. Survival under medium-high UVB doses (>10 kJ m(-2)) was generally higher (up to 5.4-fold) in cells grown in TSB than in M9. These results highlight the influence of growth conditions preceding irradiation on the extent of oxidative damage induced by UVB exposure in bacteria. PMID:23493991

Santos, Ana L; Gomes, Newton C M; Henriques, Isabel; Almeida, Adelaide; Correia, António; Cunha, Angela

2013-03-15

325

Examination of Bacterial Characteristics of Anaerobic Membrane Bioreactors in Three Pilot-Scale Plants for Treating Low-Strength Wastewater by Application of the Colony-Forming-Curve Analysis Method  

PubMed Central

Characteristic sludge ecosystems arising in anaerobic membrane bioreactors of three pilot-scale plants treating low-strength (less than 1 g of biological oxygen demand per liter) sewage or soybean-processing wastewater were examined by analysis of the colony-forming-curves (CFC) obtained by counting colonies at suitable intervals. The wastewaters, containing high amounts of suspended solids (SS) (SS/chemical oxygen demand ratio, 0.51 to 0.80), were treated by using two types of bioreactors: (i) a hydrolyzation reactor for solubilization and acidification of SS in wastewater and (ii) a methane fermentation reactor for producing methane. The colony counts for the two sewage treatment plants continued to increase even after 3 weeks of incubation, whereas those for soybean-processing wastewater reached an approximately constant level within 3 weeks of incubation. The CFCs were analyzed by correlating the rate of colony appearance on roll tubes with the physiological types of bacteria present in the bioreactors. It was found that there were large numbers of slow-colony-forming anaerobic bacteria within the bioreactors and that the viable populations consisted of a few groups with different growth rates. It is considered that the slow-growing colonies appearing after 10 days of incubation were the dominant microflora in the sewage treated by hydrolyzation reactors. In particular, highly concentrated sludge (30.0 g of mixed-liquor volatile SS per liter) retained by the membrane separation module contained a large number of such bacteria. Slow-growing colonies of these bacteria could be counted by using a sludge extract medium prepared from only the supernatant of autoclaved sludge. In addition, the highest colony counts were almost always obtained with the sludge extract medium, meaning that most of the anaerobic bacteria in these sludges have complex nutrient requirements for growth. This report also indicates the usefulness of application of the CFC analysis method to the study of bacterial populations of anaerobic treatment systems.

Kataoka, Naoaki; Tokiwa, Yutaka; Tanaka, Yasuo; Fujiki, Kiichi; Taroda, Hiroyuki; Takeda, Kiyoshi

1992-01-01

326

Curved Walls: Grain Growth, Settling, and Composition Patterns in T Tauri Disk Dust Sublimation Fronts  

NASA Astrophysics Data System (ADS)

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

McClure, M. K.; D'Alessio, P.; Calvet, N.; Espaillat, C.; Hartmann, L.; Sargent, B.; Watson, D. M.; Ingleby, L.; Hernández, J.

2013-10-01

327

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

Microsoft Academic Search

A novel hierarchical quantitative trait locus (QTL) mapping method using a polynomial growth function and a multiple-QTL model (with no dependence in time) in a multitrait framework is presented. The method considers a population-based sample where individuals have been phenotyped (over time) with respect to some dynamic trait and genotyped at a given set of loci. A specific feature of

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

2012-01-01

328

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

ERIC Educational Resources Information Center

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

Hadley, Pamela A.; Holt, Janet K.

2006-01-01

329

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

ERIC Educational Resources Information Center

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

Nocentini, Annalaura; Menesini, Ersilia; Salmivalli, Christina

2013-01-01

330

Individual Latent Growth Curves in the Development of Marijuana Use from Childhood to Young Adulthood  

Microsoft Academic Search

The present study was designed to examine the relationship between unconventionality and marijuana use over time. The sample for this paper consisted of 532 male and female participants interviewed during early adolescence, late adolescence, their early twenties, and their late twenties. Latent growth modeling was used. The findings indicated that (1) the influence of initial unconventionality (T2) on initial marijuana

Judith S. Brook; Martin Whiteman; Stephen J. Finch; Neo K. Morojele; Patricia Cohen

2000-01-01

331

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

Microsoft Academic Search

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

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

2001-01-01

332

Effect of the bacterial growth rate on replication control of plasmid pBR322 in Escherichia coli  

Microsoft Academic Search

The concentration of plasmid pBR322, of its replication inhibitor, RNAI, and preprimer, RNAII, were observed in E. coli as functions of the bacterial growth rate. At growth rates between 0.6 and 2.5 doubling\\/h, the copy number (number of plasmids per genome equivalent of chromosomal DNA) decreased from 32 to 15, the number of plasmids per cell increased fro, 39 to

S. Lin-Chao; H. Bremer

1986-01-01

333

Estimating the Growth Rate of a Bacterial Species in a Complex Mixture by Hybridization of Genomic DNA  

Microsoft Academic Search

Advances in molecular techniques have enabled new approaches to identifying bacteria. However, once identified, there is no\\u000a quantitative information on the in situ growth rate of the species, mainly because the technology has not been available. The quantitative incorporation of [methyl-3H]thymidine into dividing bacteria is coupled with a molecular (hybridization) method, to determine the growth rate of bacterial\\u000a species in

P. C. Pollard

1998-01-01

334

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

Microsoft Academic Search

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

Brian J. Nonnecke; K. Larry Smith

1984-01-01

335

Convexity of the Photosynthetic Light-Response Curve in Relation to Intensity and Direction of Light during Growth.  

PubMed Central

Photosynthesis in the intermediate light range is most efficient when the convexity of the photosynthetic light-response curve is high. Factors determining the convexity were examined for intact leaves using Salix sp. and for a plant cell culture using the green microalga Coccomyxa sp. It was found that the leaf had lower convexity than diluted plant cells because the light gradient through the leaf was not fully matched by a corresponding gradient in photosynthetic capacity. The degree to which the leaf gradients were matched was quantified by measuring photosynthesis at both leaf surfaces using modulated fluorescence. Two principal growth conditions were identified as those causing mismatch of leaf gradients and lowering of the convexity relative to cells. The first was growth under low light, where leaves did not develop any noteworthy gradient in photosynthetic capacity. This led to decreased convexity, particularly in old leaves with high chlorophyll content and, hence, steep light gradients. Second and less conspicuous was growth under high light conditions when light was given bilaterally rather than unilaterally, which yielded leaves of high photosynthetic capacity at both surfaces. Two situations were also identified that caused the convexity to decrease at the chloroplast level: (a) increased light during growth, for both leaves and cells, and (b) increased CO2 concentration during measurement of high-light-grown leaves. These changes of the intrinsic convexity were interpreted to indicate that the convexity declines with increased capacity of ribulose-1,5-bisphosphate carboxylase/oxygenase relative to the capacity of electron transport.

Ogren, E.

1993-01-01

336

Convexity of the Photosynthetic Light-Response Curve in Relation to Intensity and Direction of Light during Growth.  

PubMed

Photosynthesis in the intermediate light range is most efficient when the convexity of the photosynthetic light-response curve is high. Factors determining the convexity were examined for intact leaves using Salix sp. and for a plant cell culture using the green microalga Coccomyxa sp. It was found that the leaf had lower convexity than diluted plant cells because the light gradient through the leaf was not fully matched by a corresponding gradient in photosynthetic capacity. The degree to which the leaf gradients were matched was quantified by measuring photosynthesis at both leaf surfaces using modulated fluorescence. Two principal growth conditions were identified as those causing mismatch of leaf gradients and lowering of the convexity relative to cells. The first was growth under low light, where leaves did not develop any noteworthy gradient in photosynthetic capacity. This led to decreased convexity, particularly in old leaves with high chlorophyll content and, hence, steep light gradients. Second and less conspicuous was growth under high light conditions when light was given bilaterally rather than unilaterally, which yielded leaves of high photosynthetic capacity at both surfaces. Two situations were also identified that caused the convexity to decrease at the chloroplast level: (a) increased light during growth, for both leaves and cells, and (b) increased CO2 concentration during measurement of high-light-grown leaves. These changes of the intrinsic convexity were interpreted to indicate that the convexity declines with increased capacity of ribulose-1,5-bisphosphate carboxylase/oxygenase relative to the capacity of electron transport. PMID:12231754

Ogren, E.

1993-03-01

337

Effects of maize inoculation with Fusarium verticillioides and with two bacterial biocontrol agents on seedlings growth and antioxidative enzymatic activities  

Microsoft Academic Search

Maize (Zea mays L.) is a staple food for the majority of the world's population and different diseases may affect its emergence, growth and development. Fusarium verticillioides (Sacc.) Nirenberg (Teleomorph: Gibberella moniliformis Wineland) is the most commonly reported fungal species infecting this crop. The present work analyzes the bioprotective role of two bacterial agents, Bacillus amyloliquefaciens and Microbacterium oleovorans, against

Paola Pereira; Sabrina G. Ibáñez; Elizabeth Agostini; Miriam Etcheverry

2011-01-01

338

Effects of plant genotype and growth stage on the structure of bacterial communities associated with potato (Solanum tuberosum L.).  

PubMed

The effects of genotype, plant growth and experimental factors (soil and year) on potato-associated bacterial communities were studied. Cultivars Achirana Inta, Désirée, Merkur and transgenic Désirée line DL12 (containing T4 lysozyme gene) were assessed in two field experiments. Cross-comparisons between both experiments were made using Désirée plants. Culture-dependent and -independent approaches were used to demonstrate effects on total bacterial, actinobacterial and Pseudomonas communities in bulk and rhizosphere soils and endospheres. PCR-denaturing gradient gel electrophoresis fingerprints prepared with group-specific primers were analyzed using multivariate analyses and revealed that bacterial communities in Achirana Inta plants differed most from those of Désirée and Merkur. No significant effects were found between Désirée and DL12 lines. Plant growth stage strongly affected different plant-associated communities in both experiments. To investigate the effect of plant-associated communities on plant health, 800 isolates from rhizospheres and endospheres at the flowering stage were tested for suppression of Ralstonia solanacearum biovar 2 and/or Rhizoctonia solani AG3. A group of isolates closely resembling Lysobacter sp. dominated in young plants. Its prevalence was affected by plant growth stage and experiment rather than by plant genotype. It was concluded that plant growth stage overwhelmed any effect of plant genotype on the bacterial communities associated with potato. PMID:18355298

van Overbeek, Leo; van Elsas, Jan Dirk

2008-03-18

339

Growth and specific P-uptake rates of bacterial and phytoplanktonic communities in the Southeast Pacific (BIOSOPE cruise)  

Microsoft Academic Search

Predicting heterotrophic bacteria and phytoplankton growth rates (mu) is of great scientific interest. Many methods have been developed in order to assess bacterial or phytoplankton mu. One widely used method is to estimate mu from data obtained on biomass or cell abundance and rates of biomass or cell production. According to Kirchman (2002), the most appropriate approach for estimating mu

S. Duhamel; T. Moutin; F. van Wambeke; B. van Mooy; P. Rimmelin; P. Raimbault; H. Claustre

2007-01-01

340

The effect of zinc on microbial growth and bacterial killing by cefazolin in a Staphylococcus aureus abscess milieu.  

PubMed

Microbial growth and antimicrobial bacterial killing are both diminished in abscesses. It was postulated that zinc depletion in abscesses, perhaps secondary to a neutrophil protein resembling calprotectin, may be partly responsible for these effects. In a rabbit tissue-cage abscess model, pooled abscess supernatant concentration of zinc was < 1.53 microM. The addition of 41.7 microM zinc had no effect on Staphylococcus aureus growth or the bacterial killing effect of cefazolin in serum. In abscess fluid supernatants, bacterial growth without antibiotic and bacterial killing by cefazolin were both enhanced by the addition of zinc. Fractionation of the abscess fluid with ultrafiltration membranes showed that these effects could be reproduced with the fraction between 30 and 50 kDa. These findings suggest that a protein in abscess fluid supernatants that resembles the neutrophil protein calprotectin may, through its zinc binding effects, inhibit microbial growth within an abscess but also inhibit the activity of bactericidal antibiotics. PMID:8376834

Bamberger, D M; Herndon, B L; Suvarna, P R

1993-10-01

341

Bacterial pH-optima for growth track soil pH, but are higher than expected at low pH  

Microsoft Academic Search

One of the most influential factors determining the growth and composition of soil bacterial communities is pH. However, soil pH is often correlated with many other factors, including nutrient availability and plant community, and causality among factors is not easily determined. If soil pH is directly influencing the bacterial community, this must lead to a bacterial community growth optimised for

David Fernández-Calviño; Johannes Rousk; Philip C. Brookes; Erland Bååth

2011-01-01

342

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

PubMed Central

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

2012-01-01

343

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

NASA Astrophysics Data System (ADS)

The complex conductivity of porous materials and colloidal suspensions comprises two components: an in-phase conductivity associated with electromigration of the charge carriers and a quadrature conductivity associated with the reversible storage of the charges at some polarization length scales. We developed a quantitative model to investigate the frequency domain induced polarization response of suspensions of bacteria and bacteria growth in porous media. Induced polarization of bacteria (? polarization) is related to the properties of the electrical double layer of the bacteria. Surface conductivity and ? polarization are due to the Stern layer of counterions occurring in a brush of polymers coating the surface of the bacteria. These phenomena can be related to their cation exchange capacity. The mobility of the counterions in this Stern layer is found to be very small (4.7 × 10-10 m2 s-1 V-1 at 25°C). This implies a very low relaxation frequency for the ?polarization of the bacteria cells (typically around 0.1-5 Hz), in agreement with experimental observations. This new model can be coupled to reactive transport modeling codes in which the evolution of bacterial populations are usually described by Monod kinetics. We show that the growth rate and endogenous decay coefficients of bacteria in a porous sand can be inferred nonintrusively from time-lapse frequency domain induced polarization data.

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

2012-09-01

344

A new predictive dynamic model describing the effect of the ambient temperature and the convective heat transfer coefficient on bacterial growth  

Microsoft Academic Search

In this study, predictive microbiology and food engineering were combined in order to develop a new analytical model predicting the bacterial growth under dynamic temperature conditions. The proposed model associates a simplified primary bacterial growth model without lag, the secondary Ratkowsky “square root” model and a simplified two-parameter heat transfer model regarding an infinite slab. The model takes into consideration

H. Ben Yaghlene; I. Leguerinel; M. Hamdi; P. Mafart

2009-01-01

345

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

Microsoft Academic Search

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

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

2005-01-01

346

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

PubMed

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

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

2011-08-09

347

Bacterial Biofertilizers  

Microsoft Academic Search

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

LUIS E. FUENTES-RAMIREZ; Jesus Caballero-Mellado

348

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

SciTech Connect

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

Imre, K.

1993-05-01

349

Growth and collapse of cavitation bubbles near a curved rigid boundary  

NASA Astrophysics Data System (ADS)

Laser-induced cavitation bubbles near a curved rigid boundary are observed experimentally using high-speed photography. An image theory is applied to obtain information on global bubble motion while a boundary integral method is employed to gain a more detailed understanding of the behaviour of a liquid jet that threads a collapsing bubble, creating a toroidal bubble. Comparisons between the theory and experiment show that when a comparable sized bubble is located near a rigid boundary the bubble motion is significantly influenced by the surface curvature of the boundary, which is characterized by a parameter [zeta], giving convex walls for [zeta] < 1, concave walls for [zeta] > 1 and a flat wall when [zeta] = 1. If a boundary is slightly concave, the most pronounced migration occurs at the first bubble collapse. The velocity of a liquid jet impacting on the far side of the bubble surface tends to increase with decreasing parameter [zeta]. In the case of a convex boundary, the jet velocity is larger than that generated in the flat boundary case. Although the situation considered here is restricted to axisymmetric motion without mean flow, this result suggests that higher pressures can occur when cavitation bubbles collapse near a non-flat boundary. Bubble separation, including the pinch-off phenomenon, is observed in the final stage of the collapse of a bubble, with the oblate shape at its maximum volume attached to the surface of a convex boundary, followed by bubble splitting which is responsible for further bubble proliferation.

Tomita, Y.; Robinson, P. B.; Tong, R. P.; Blake, J. R.

2002-09-01

350

Nitrifying bacterial growth inhibition in the presence of algae and cyanobacteria.  

PubMed

Nitrifying bacteria, cyanobacteria, and algae are important microorganisms in open pond wastewater treatment systems. Nitrification involving the sequential oxidation of ammonia to nitrite and nitrate, mainly due to autotrophic nitrifying bacteria, is essential to biological nitrogen removal in wastewater and global nitrogen cycling. A continuous flow autotrophic bioreactor was initially designed for nitrifying bacterial growth only. In the presence of cyanobacteria and algae, we monitored both the microbial activity by measuring specific oxygen production rate (SOPR) for microalgae and cyanobacteria and specific oxygen uptake rate (SOUR) for nitrifying bacteria. The growth of cyanobacteria and algae inhibited the maximum nitrification rate by a factor of 4 although the ammonium nitrogen fed to the reactor was almost completely removed. Terminal restriction fragment length polymorphism (T-RFLP) analysis indicated that the community structures of nitrifying bacteria remained unchanged, containing the dominant Nitrosospira, Nitrospira, and Nitrobacter species. PCR amplification coupled with cloning and sequencing analysis resulted in identifying Chlorella emersonii and an uncultured cyanobacterium as the dominant species in the autotrophic bioreactor. Notwithstanding their fast growth rate and their toxicity to nitrifiers, microalgae and cyanobacteria were more easily lost in effluent than nitrifying bacteria because of their poor settling characteristics. The microorganisms were able to grow together in the bioreactor with constant individual biomass fractions because of the uncoupled solids retention times for algae/cyanobacteria and nitrifiers. The results indicate that compared to conventional wastewater treatment systems, longer solids retention times (e.g., by a factor of 4) should be considered in phototrophic bioreactors for complete nitrification and nitrogen removal. PMID:20632370

Choi, Okkyoung; Das, Atreyee; Yu, Chang-Ping; Hu, Zhiqiang

2010-12-15

351

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

PubMed

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

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

2003-08-01

352

Contrasting short-term antibiotic effects on respiration and bacterial growth compromises the validity of the selective respiratory inhibition technique to distinguish fungi and bacteria.  

PubMed

The selective inhibition (SI) technique has been widely used to resolve fungal and bacterial biomass. By studying bacterial growth (leucine/thymidine incorporation) and respiration simultaneously, this study demonstrates that the inhibitors the SI technique is based on do not efficiently or specifically resolve fungal and bacterial contributions to respiration. At concentrations that completely inhibited bacterial growth, the bactericide streptomycin had no influence on the SI technique's respiration measurement, and complete inhibition of bacterial growth using oxytetracycline resulted in marginal respiration reductions. The fungicides captan and benomyl severely inhibited non-target bacterial growth. Cycloheximide did not reduce bacterial growth at moderate concentrations, but the cycloheximide respiration reduction was no higher in a soil with more fungal biomass, casting doubt on its ability to discriminate fungal respiration contribution. Conclusions regarding bacteria and fungi based on the SI technique using these inhibitors are thus compromised. The inhibition of glucose-activated respiration by the bactericide bronopol appeared to correlate with bacterial growth inhibition, however. Bronopol, combined with growth-based techniques, could aid development of a new framework to resolve decomposer ecology in soil. PMID:18797957

Rousk, Johannes; Demoling, Louise Aldén; Bååth, Erland

2008-09-17

353

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

NASA Astrophysics Data System (ADS)

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

Munyikwa, K.; Brown, S.

2011-12-01

354

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

PubMed Central

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

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

2012-01-01

355

Estimation of chicken microbial load using the growth curve parameters of chicken microflora.  

PubMed

Chicken microbial loads, estimated through absorbance increase of culture medium inoculated with the contaminant microflora of the carcasses, were compared with total plate counts and psychrotrophic counts obtained on the same carcasses using the pour plate method after 0, 48, 96, and 144 hr stored chicken at 4 to 5 C. For estimating microbial loads on the carcasses, the mathematical relation 1n AO = 1nA1 - R - Kt was used, which was developed by combining the growth and R equations (described in Materials and Methods) and using growth data at 28 C. The values obtained by this method, when compared with those of plating, give correlation coefficients of .94, .91, .88, and .64 for total plate counts after 0, 48, 96, and 144 hr of storage and .94, .83, .82, and .86 for psychrotrophics counts after 0, 48, 96, and 144 hr of cold storage. The method proposed in the present work permits the estimation of psychrotrophics and total counts in no more than 11 hr, which is very promising for industrial applications. PMID:3960817

Ibarra, J J; Yokoya, F

1986-01-01

356

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

PubMed Central

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

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

2011-01-01

357

Level and change of bullying behavior during high school: a multilevel growth curve analysis.  

PubMed

The development of bullying behavior was examined across three years in a sample of 515 adolescents (46% females) from 41 classrooms. At time 1, the students were in grades 9 and 10 (mean age=14.5 years; SD=.54). Results of a multilevel growth model showed that both baseline level and change of bullying varied significantly across individuals as well as across classrooms. At the individual level, gender, aggression and competition for social dominance were related with baseline level of bullying. Competition for social dominance and class change were additionally associated with increases in bullying over time. At the classroom level, pro-bullying behaviors were associated with higher baseline level of bullying, whereas anti-bullying behaviors with decreases in bullying over time. Finally, a cross-level interaction underlined that the link between aggression and bullying was moderated by the pro-bullying behaviors within each class. Results are discussed according to the child by environment perspective. PMID:23523327

Nocentini, Annalaura; Menesini, Ersilia; Salmivalli, Christina

2013-03-22

358

Population based growth curve analysis: a comparison between models based on ordinary or stochastic differential equations implemented in a nonlinear mixed effect framework  

Microsoft Academic Search

\\u000a Growth curve analysis is frequently carried out in the study of growth of farm animals because measurements are taken repeatedly\\u000a over time on the same individual within groups of animals. Growth functions like the Gompertz, Richards and Lopez, which are\\u000a based on ordinary differential equations (ODE), can be used to model the functional relationship between size or mass and\\u000a age.

A. B. Strathe; A. Danfœr; B. Nielsen; S. Klim; H. Sørensen

359

Mood and Motor Trajectories in Parkinson's Disease: Multivariate Latent Growth Curve Modeling  

PubMed Central

Objective Apathy is a common feature of Parkinson's disease (PD) that can manifest independently of depression, but little is known about its natural progression in medically-managed patients. The present study sought to characterize and compare trajectories of apathy, depression, and motor symptoms in PD over 18 months. Method Data from a sample of 186 PD patients (mean disease duration of 8.2 years) followed by the University of Florida Movement Disorders Center were obtained from a clinical research database. Scores on the Unified Parkinson's Disease Rating Scale (motor portion), Apathy Scale, and Beck Depression Inventory at three time-points (baseline, 6 months, 18 months) were analyzed in a structural equation modeling framework. Results A multivariate growth model controlling for age, sex, education, and disease duration identified linear worsening of both apathy (slope estimate = 0.73; p <.001) and motor symptoms (slope estimate = 1.51; p <.001), and quadratic changes in depression (slope estimate = 1.18; p = .07). All symptoms were positively correlated. Higher education was associated with lower apathy, depression, and motor severity. Advanced age was associated with greater motor and apathy severity. Female sex and longer disease duration were associated with attenuated motor worsening. Antidepressant use was associated only with depression scores. Conclusions These longitudinal results support the differentiation of apathy and depression in PD. Like motor progression, apathy progression may be linked at least partially to dopaminergic neurodegeneration. Empirically-supported treatments for apathy in PD are needed.

Zahodne, Laura B.; Marsiske, Michael; Okun, Michael S.; Rodriguez, Ramon L.; Malaty, Irene; Bowers, Dawn

2011-01-01

360

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

Microsoft Academic Search

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

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

2005-01-01

361

Bacterial Succession in Glacial Forefield Soils Characterized by Community Structure, Activity and Opportunistic Growth Dynamics  

Microsoft Academic Search

The succession of bacterial communities inhabiting the forefield of the Dammaglacier (Switzerland) was investigated in soils ranging in successional age from 0 to 100 years since deglaciation. Overall activity per bacterial cell was estimated by the amount of fluorescein diacetate (FDA) hydrolyzed per DAPI-stained cell, and an index of \\

W. V. Sigler; S. Crivii; J. Zeyer

2002-01-01

362

Organic carbon and mineral nutrient limitation of oxygen consumption, bacterial growth and efficiency in the Norwegian Sea  

Microsoft Academic Search

To evaluate the role of bacteria in the transformation of organic matter in subarctic waters, we investigated the effect of\\u000a mineral nutrients (ammonia and phosphate) and organic carbon (glucose) enrichment on heterotrophic bacterial processes and\\u000a community structure. Eight experiments were done in the Norwegian Sea during May and June 2008. The growth-limiting factor\\u000a (carbon or mineral nutrient) for heterotrophic bacteria

L. Antonio Cuevas; Jorun K. Egge; T. Frede Thingstad; Birte Töpper

2011-01-01

363

Analysis of bacterial communities in rhizosphere soil of healthy and diseased cotton ( Gossypium sp.) at different plant growth stages  

Microsoft Academic Search

Bacterial communities in rhizosphere soil of healthy and diseased cotton (infected by the pathogenic fungus Verticillium dahliae Kleb.) were examined at different plant growth stages using T-RFLP and 16S rDNA clone library. At flowering and bolling,\\u000a soil samples from the rhizosphere of healthy cotton had the highest richness, whereas the highest evenness was found in the\\u000a rhizosphere of diseased cotton

Yan Zhang; Bing-Hai Du; Zhi-gang Jin; Zheng-hua Li; Hong-ning Song; Yan-Qin Ding

2011-01-01

364

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

PubMed Central

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

Dinasquet, Julie; Granhag, Lena; Riemann, Lasse

2012-01-01

365

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

Microsoft Academic Search

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

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

366

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

PubMed Central

Abstract The martian surface environment exhibits extremes of salinity, temperature, desiccation, and radiation that would make it difficult for terrestrial microbes to survive. Recent evidence suggests that martian soils contain high concentrations of MgSO4 minerals. Through warming of the soils, meltwater derived from subterranean ice-rich regolith may exist for an extended period of time and thus allow the propagation of terrestrial microbes and create significant bioburden at the near surface of Mars. The current report demonstrates that halotolerant bacteria from the Great Salt Plains (GSP) of Oklahoma are capable of growing at high concentrations of MgSO4 in the form of 2 M solutions of epsomite. The epsotolerance of isolates in the GSP bacterial collection was determined, with 35% growing at 2 M MgSO4. There was a complex physiological response to mixtures of MgSO4 and NaCl coupled with other environmental stressors. Growth also was measured at 1 M concentrations of other magnesium and sulfate salts. The complex responses may be partially explained by the pattern of chaotropicity observed for high-salt solutions as measured by agar gelation temperature. Select isolates could grow at the high salt concentrations and low temperatures found on Mars. Survival during repetitive freeze-thaw or drying-rewetting cycles was used as other measures of potential success on the martian surface. Our results indicate that terrestrial microbes might survive under the high-salt, low-temperature, anaerobic conditions on Mars and present significant potential for forward contamination. Stringent planetary protection requirements are needed for future life-detection missions to Mars. Key Words: Analogue—Mars—Planetary protection—Salts—Life in extreme environments. Astrobiology 12, 98–106.

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

2012-01-01

367

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

PubMed

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

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

2012-01-16

368

Intrauterine growth curve in a low-income population in the outskirts of the city of São Paulo Curva de crescimento intra-uterino em uma população de baixa renda da periferia da cidade de São Paulo  

Microsoft Academic Search

Objective: To design an intrauterine growth curve of an Institution that serves the needy population of the city of Sao Paulo and compare it to the intrauterine growth curves of the city of Denver and of the State of California which are considered classic in the literature, and to verify whether the small-for-gestational-age infants classified by the different intrauterine growth

Julie Schlesinger; Patricia Vega dos Santos; José Ricardo Dias Bertagnon

369

Influence of the interval between time points on individual fetal growth curve standards derived from Rossavik models and two ultrasound scans before 26 weeks, menstrual age.  

PubMed

We studied the influence of the interval between the two scans used before 26 weeks' menstrual age to generate individual fetal growth curve standards utilizing the Rossavik growth model: P = c(t) kappa + s(t) (model specification functions previously reported). Intervals of 3 weeks to 12 weeks were suitable for predicting the growth of the abdominal and head circumferences and femur diaphysis length in individual fetuses. However, large systematic and random errors were found with intervals less than 5 weeks for three-dimensional parameters such as the head and abdominal cubes and estimated fetal weight. In addition, the data suggest that the systematic errors for these latter parameters may increase with intervals of 10 weeks or more. Overall, optimal individual fetal growth curve standards were best generated from two scans before 26 weeks' menstrual age separated by 5 weeks to 9 weeks. PMID:2497142

Simon, N V; Deter, R L; Levisky, J S; Stefos, T; Shearer, D M

1989-05-01

370

Adherence to Pediatric Asthma Treatment in Economically Disadvantaged African-American Children and Adolescents: An Application of Growth Curve Analysis  

PubMed Central

Objectives?The primary aims of the study were to: (a) describe the trajectories of adherence to daily inhaled corticosteroid (ICS) medication for a year in economically disadvantaged, African-American youth with asthma based on growth curve modeling; and (b) test the relationship of treatment adherence to symptom control, quick-relief medication, and healthcare utilization.?Methods?This prospective study measured adherence to daily ICS treatment using electronic monitoring in 92 children and adolescents with moderate to severe asthma for 9–12 months and assessed clinical outcomes, including asthma-related symptoms, quick-relief medication, and healthcare utilization.?Results?Youth showed a decrement in treatment adherence to less than half of prescribed corticosteroid treatment over the course of the study, which related to increased healthcare utilization (p < .04), but not to asthma symptoms or albuterol use.?Conclusion?Economically disadvantaged youth with asthma demonstrate high rates of chronic nonadherence that warrant identification and intervention to reduce asthma-related healthcare utilization.

Drotar, Dennis; McNally, Kelly; Schluchter, Mark; Riekert, Kristin; Vavrek, Pamela; Schmidt, Amy; Redline, Susan; Kercsmar, Carolyn

2010-01-01

371

Association of single nucleotide polymorphisms in the leptin gene with body weight and backfat growth curve parameters for beef cattle1  

Microsoft Academic Search

Previous research has identified differ- ences in carcass characteristics across SNP in the bo- vine leptin gene at slaughter, but before feedlot opera- tors implement selection and sorting strategies, more information is needed to determine how carcass charac- teristics change over time. The objective of this study was to investigate the effect of 2 leptin SNP on growth curve parameters

J. L. Lusk

372

Intrauterine growth curve for newborns of the city of São Paulo, Brazil Curva de crescimento intra-uterino para recém-nascidos no município de São Paulo  

Microsoft Academic Search

Objective: To construct an intrauterine growth curve for a population of a large city based on existing data. Methods: Based on the Live Newborn Registry from 2004, for the city of São Paulo, birth weight distribution according to gestational age was analyzed. Twin births as well as newborns with congenital malformation or those lacking the information on birth weight or

José Ricardo Dias Bertagnon; Cínthia Leci Rodrigues; Jane D'Eston Armand; Conceição Aparecida de Mattos

2008-01-01

373

A Latent Growth Curve Analysis of Late-Life Sensory and Cognitive Function Over 8 Years: Evidence for Specific and Common Factors Underlying Change  

Microsoft Academic Search

Correlations among rates of change in sensory and cognitive functioning in adulthood were evaluated. Measures of Vision, Hearing, Memory, Speed and Verbal ability were obtained in 1992, 1994, and 2000 in the Australian Longitudinal Study of Aging (N = 2,087 at baseline). Data from 1,823 participants who undertook at least 1 clinical assessment were analyzed using latent growth curve models.

Kaarin J. Anstey; Scott M. Hofer; Mary A. Luszcz

2003-01-01

374

Curva de crescimento intra-uterino para recém-nascidos no município de São Paulo Intrauterine growth curve for newborns of the city of São Paulo, Brazil  

Microsoft Academic Search

Objective: To construct an intrauterine growth curve for a population of a large city based on existing data. Methods: Based on the Live Newborn Registry from 2004, for the city of São Paulo, birth weight distribution according to gestational age was analyzed. Twin births as well as newborns with congenital malformation or those lacking the information on birth weight or

José Ricardo Dias Bertagnon; Cínthia Leci Rodrigues; Jane D'Eston Armand; Conceição Aparecida de Mattos Segre

375

A Latent Growth Curve Analysis of the Structure of Aggression, Drug Use, and Delinquent Behaviors and their Interrelations over Time in Urban and Rural Adolescents  

ERIC Educational Resources Information Center

|Latent growth curve analysis was used to examine the structure and interrelations among aggression, drug use, and delinquent behavior during early adolescence. Five waves of data were collected from 667 students at three urban middle schools serving a predominantly African American population, and from a more ethnically diverse sample of 950…

Farrell, Albert D.; Sullivan, Terri N.; Esposito, Layla E.; Meyer, Aleta L.; Valois, Robert F.

2005-01-01

376

The potential drop method for monitoring crack growth in real components subjected to combined fatigue and creep conditions: application of FE techniques for deriving calibration curves  

Microsoft Academic Search

The potential drop technique is a robust method to provide continuous in situ crack growth monitoring of real power-plant components. For a correct assessment of the crack depth, accurate calibration curves for the geometry at hand are required. The problem entails determining the electrical potential field in a body usually characterised by a complicated geometry as a function of the

L Gandossi; S. A Summers; N. G Taylor; R. C Hurst; B. J Hulm; J. D Parker

2001-01-01

377

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

Microsoft Academic Search

The curves of growth (COG) of five Fe I lines emitted from a laser-induced plasma, generated with Fe–Ni alloys in air at atmospheric pressure, have been investigated. Spectral lines with different energy levels and line widths, emitted with a broad range of optical depths, have been included in the study in order to check the validity of theoretical models proposed

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

2003-01-01

378

Growth curves of crossbred cows sired by Hereford, Angus, Belgian Blue, Brahman, Boran, and Tuli bulls, and the fraction of mature weight and height at puberty  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this study was to evaluate the growth curves of females to determine if mature size and relative rates of maturing amongst breeds differed. Body weight and hip height data were fit to the nonlinear function: BW = f(t) = A – Bek(age) where A is an estimate of mature BW and k determi...

379

Root ethylene signalling is involved in Miscanthus sinensis growth promotion by the bacterial endophyte Herbaspirillum frisingense GSF30T  

PubMed Central

The bacterial endophyte Herbaspirillum frisingense GSF30T is a colonizer of several grasses grown in temperate climates, including the highly nitrogen-efficient perennial energy grass Miscanthus. Inoculation of Miscanthus sinensis seedlings with H. frisingense promoted root and shoot growth but had only a minor impact on nutrient concentrations. The bacterium affected the root architecture and increased fine-root structures. Although H. frisingense has the genetic requirements to fix nitrogen, only minor changes in nitrogen concentrations were observed. Herbaspirillum agglomerates were identified primarily in the root apoplast but also in the shoots. The short-term (3h) and long-term (3 weeks) transcriptomic responses of the plant to bacterial inoculation revealed that H. frisingense induced rapid changes in plant hormone signalling, most prominent in jasmonate signalling. Ethylene signalling pathways were also affected and persisted after 3 weeks in the root. Growth stimulation of the root by the ethylene precursor 1-aminocyclopropane 1-carboxylic acid was dose dependent and was affected by H. frisingense inoculation. Minor changes in the proteome were identified after 3 weeks. This study suggests that H. frisingense improves plant growth by modulating plant hormone signalling pathways and provides a framework to understand the beneficial effects of diazotrophic plant-growth-promoting bacteria, such as H. frisingense, on the biomass grass Miscanthus.

Ludewig, Uwe

2013-01-01

380

Growth of Acanthamoeba castellanii and Hartmannella vermiformis on live, heat-killed and DTAF-stained bacterial prey.  

PubMed

The growth responses of two species of amoeba were evaluated in the presence of live, heat-killed and heat-killed/5-(4,6-dichlorotriazin-2-yl) aminofluorescein (DTAF)-stained cells of Escherichia coli, Pseudomonas aeruginosa, Klebsiella aerogenes, Klebsiella ozaenae and Staphylococcus aureus. The specific growth rates of both species were significantly higher with live bacterial prey, the only exception being Hartmannella vermiformis feeding on S. aureus, for which growth rates were equivalent on all prey states. There was no significant difference between growth rates, yield or ingestion rates of amoebae feeding on heat-killed or heat-killed/stained bacterial cells, suggesting that it was the heat-killing process that influenced the amoeba-bacteria interaction. Pretreatment of prey cells had a greater influence on amoebic processing of Gram-negative bacteria compared with the Gram-positive bacterium, which appeared to be as a result of the former cells being more difficult to digest and/or losing their ability to deter amoebic ingestion. These antipredatory mechanisms included microcolony formation in P. aeruginosa, toxin production in K. ozaenae, and the presence of an intact capsule in K. aerogenes. E. coli and S. aureus did not appear to possess an antipredator mechanism, although intact cells of the S. aureus were observed in faecal pellets, suggesting that any antipredatory mechanism was occurring at the digestion stage. PMID:17596189

Pickup, Zoë L; Pickup, Roger; Parry, Jacqueline D

2007-06-27

381

Root ethylene signalling is involved in Miscanthus sinensis growth promotion by the bacterial endophyte Herbaspirillum frisingense GSF30T.  

PubMed

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

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

2013-09-16

382

Effects of Eyjafjallaj?kull Volcanic Ash on Innate Immune System Responses and Bacterial Growth in Vitro  

PubMed Central

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

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

2013-01-01

383

Myeloid differentiation factor 88-dependent signalling controls bacterial growth during colonization and systemic pneumococcal disease in mice.  

PubMed

The Toll-like receptors (TLRs) and the myeloid differentiation factor 88 (MyD88) are key players in the activation of the innate immune defence during microbial infections. Using different murine infection models, we show that MyD88-dependent signalling is crucial for the activation of the innate immune defence against Streptococcus pneumoniae. Our data demonstrate that both local and systemic inflammatory response to S. pneumoniae depends on the presence of MyD88 to clear bacterial colonization of the upper respiratory tract and to prevent pulmonary and systemic infection in mice. Finally, we described a strong correlation between enhanced bacterial growth in the bloodstream of MyD88-deficient mice and the inability to lower the serum iron concentration in response to infection. PMID:16207247

Albiger, Barbara; Sandgren, Andreas; Katsuragi, Hiroaki; Meyer-Hoffert, Ulf; Beiter, Katharina; Wartha, Florian; Hornef, Mathias; Normark, Staffan; Normark, Birgitta Henriques

2005-11-01

384

Growth promotion and colonization of switchgrass (Panicum virgatum) cv. Alamo by bacterial endophyte Burkholderia phytofirmans strain PsJN  

PubMed Central

Background Switchgrass is one of the most promising bioenergy crop candidates for the US. It gives relatively high biomass yield and can grow on marginal lands. However, its yields vary from year to year and from location to location. Thus it is imperative to develop a low input and sustainable switchgrass feedstock production system. One of the most feasible ways to increase biomass yields is to harness benefits of microbial endophytes. Results We demonstrate that one of the most studied plant growth promoting bacterial endophytes, Burkholderia phytofirmans strain PsJN, is able to colonize and significantly promote growth of switchgrass cv. Alamo under in vitro, growth chamber, and greenhouse conditions. In several in vitro experiments, the average fresh weight of PsJN-inoculated plants was approximately 50% higher than non-inoculated plants. When one-month-old seedlings were grown in a growth chamber for 30 days, the PsJN-inoculated Alamo plants had significantly higher shoot and root biomass compared to controls. Biomass yield (dry weight) averaged from five experiments was 54.1% higher in the inoculated treatment compared to non-inoculated control. Similar results were obtained in greenhouse experiments with transplants grown in 4-gallon pots for two months. The inoculated plants exhibited more early tillers and persistent growth vigor with 48.6% higher biomass than controls. We also found that PsJN could significantly promote growth of switchgrass cv. Alamo under sub-optimal conditions. However, PsJN-mediated growth promotion in switchgrass is genotype specific. Conclusions Our results show B. phytofirmans strain PsJN significantly promotes growth of switchgrass cv. Alamo under different conditions, especially in the early growth stages leading to enhanced production of tillers. This phenomenon may benefit switchgrass establishment in the first year. Moreover, PsJN significantly stimulated growth of switchgrass cv. Alamo under sub-optimal conditions, indicating that the use of the beneficial bacterial endophytes may boost switchgrass growth on marginal lands and significantly contribute to the development of a low input and sustainable feedstock production system.

2012-01-01

385

Bacterial Growth Kinetics under a Novel Flexible Methacrylate Dressing Serving as a Drug Delivery Vehicle for Antiseptics.  

PubMed

A flexible methacrylate powder dressing (Altrazeal®) transforms into a wound contour conforming matrix once in contact with wound exudate. We hypothesised that it may also serve as a drug delivery vehicle for antiseptics. The antimicrobial efficacy and influence on bacterial growth kinetics in combination with three antiseptics was investigated in an in vitro porcine wound model. Standardized in vitro wounds were contaminated with Staphylococcus aureus (MRSA; ATCC 33591) and divided into six groups: no dressing (negative control), methacrylate dressing alone, and combinations with application of 0.02% Polyhexamethylene Biguanide (PHMB), 0.4% PHMB, 0.1% PHMB + 0.1% betaine, 7.7 mg/mL Povidone-iodine (PVP-iodine), and 0.1% Octenidine-dihydrochloride (OCT) + 2% phenoxyethanol. Bacterial load per gram tissue was measured over five days. The highest reduction was observed with PVP-iodine at 24 h to log10 1.43 cfu/g, followed by OCT at 48 h to log10 2.41 cfu/g. Whilst 0.02% PHMB resulted in a stable bacterial load over 120 h to log10 4.00 cfu/g over 120 h, 0.1% PHMB + 0.1% betaine inhibited growth during the first 48 h, with slightly increasing bacterial numbers up to log10 5.38 cfu/g at 120 h. These results indicate that this flexible methacrylate dressing can be loaded with various antiseptics serving as drug delivery system. Depending on the selected combination, an individually shaped and controlled antibacterial effect may be achieved using the same type of wound dressing. PMID:23698780

Forstner, Christina; Leitgeb, Johannes; Schuster, Rupert; Dosch, Verena; Kramer, Axel; Cutting, Keith F; Leaper, David J; Assadian, Ojan

2013-05-21

386

Bacterial Growth Kinetics under a Novel Flexible Methacrylate Dressing Serving as a Drug Delivery Vehicle for Antiseptics  

PubMed Central

A flexible methacrylate powder dressing (Altrazeal®) transforms into a wound contour conforming matrix once in contact with wound exudate. We hypothesised that it may also serve as a drug delivery vehicle for antiseptics. The antimicrobial efficacy and influence on bacterial growth kinetics in combination with three antiseptics was investigated in an in vitro porcine wound model. Standardized in vitro wounds were contaminated with Staphylococcus aureus (MRSA; ATCC 33591) and divided into six groups: no dressing (negative control), methacrylate dressing alone, and combinations with application of 0.02% Polyhexamethylene Biguanide (PHMB), 0.4% PHMB, 0.1% PHMB + 0.1% betaine, 7.7 mg/mL Povidone-iodine (PVP-iodine), and 0.1% Octenidine-dihydrochloride (OCT) + 2% phenoxyethanol. Bacterial load per gram tissue was measured over five days. The highest reduction was observed with PVP-iodine at 24 h to log10 1.43 cfu/g, followed by OCT at 48 h to log10 2.41 cfu/g. Whilst 0.02% PHMB resulted in a stable bacterial load over 120 h to log10 4.00 cfu/g over 120 h, 0.1% PHMB + 0.1% betaine inhibited growth during the first 48 h, with slightly increasing bacterial numbers up to log10 5.38 cfu/g at 120 h. These results indicate that this flexible methacrylate dressing can be loaded with various antiseptics serving as drug delivery system. Depending on the selected combination, an individually shaped and controlled antibacterial effect may be achieved using the same type of wound dressing.

Forstner, Christina; Leitgeb, Johannes; Schuster, Rupert; Dosch, Verena; Kramer, Axel; Cutting, Keith F.; Leaper, David J.; Assadian, Ojan

2013-01-01

387

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

Microsoft Academic Search

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

Catherine A. Lee; Stanley Falkow

1990-01-01

388

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

SciTech Connect

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

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

1999-09-01

389

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

PubMed Central

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

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

2009-01-01

390

Microbial Biogeography along an Estuarine Salinity Gradient: Combined Influences of Bacterial Growth and Residence Time  

PubMed Central

Shifts in bacterioplankton community composition along the salinity gradient of the Parker River estuary and Plum Island Sound, in northeastern Massachusetts, were related to residence time and bacterial community doubling time in spring, summer, and fall seasons. Bacterial community composition was characterized with denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA. Average community doubling time was calculated from bacterial production ([14C]leucine incorporation) and bacterial abundance (direct counts). Freshwater and marine populations advected into the estuary represented a large fraction of the bacterioplankton community in all seasons. However, a unique estuarine community formed at intermediate salinities in summer and fall, when average doubling time was much shorter than water residence time, but not in spring, when doubling time was similar to residence time. Sequencing of DNA in DGGE bands demonstrated that most bands represented single phylotypes and that matching bands from different samples represented identical phylotypes. Most river and coastal ocean bacterioplankton were members of common freshwater and marine phylogenetic clusters within the phyla Proteobacteria, Bacteroidetes, and Actinobacteria. Estuarine bacterioplankton also belonged to these phyla but were related to clones and isolates from several different environments, including marine water columns, freshwater sediments, and soil.

Crump, Byron C.; Hopkinson, Charles S.; Sogin, Mitchell L.; Hobbie, John E.

2004-01-01

391

Mobilization of Rock Phosphate Phosphorus through Bacterial Inoculants to Enhance Growth and Yield of Wetland Rice  

Microsoft Academic Search

Pot and field studies were undertaken to assess the substitutability of triple superphosphate (TSP) by a phosphorus (P) fertilizer mixture (PFM) comprising TSP, rock phosphate (RP), and P-solubilizing bacterial inoculants for wetland rice. Six single and two dual inoculants were formulated with Enterobactor gegovie and five Bacillus species and tested in pot and field experiments. Soil-available P and tissue P

R. M. C. P. Rajapaksha; D. Herath; A. P. Senanayake; M. G. T. L. Senevirathne

2011-01-01

392

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

SciTech Connect

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

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

2008-05-15

393

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

PubMed

Bacterial counts were compared in free-stall mattresses and teat ends exposed to 5 treatments in a factorial study design on 1 dairy farm. Mattresses in five 30-cow groups were subjected to 1 of 5 bedding treatments every other day: 0.5 kg of hydrated limestone, 120 mL of commercial acidic conditioner, 1 kg of coal fly ash, 1 kg of kiln-dried wood shavings, and control (no bedding). Counts of coliforms, Klebsiella spp., Escherichia coli, and Streptococcus spp. were lowest on mattresses bedded with lime. Mattresses bedded with the commercial acidic conditioner had the next lowest counts for coliforms, Klebsiella spp., and Streptococcus spp. Wood shavings and the no-bedding control had the highest counts for coliform and Klebsiella spp. Compared with wood shavings or control, fly ash reduced the counts of coliforms, whereas for the other 3 bacterial groups, the reduction was not always significant. Streptococcus spp. counts were greatest in the control group and did not differ among the shavings and fly ash groups. Teat swab results indicated that hydrated lime was the only bedding treatment that significantly decreased the counts of both coliforms and Klebsiella spp. There were no differences in Streptococcus spp. numbers on the teats between any of the bedding treatments. Bacterial populations grew steadily on mattresses and were generally higher at 36 to 48 h than at 12 to 24 h, whereas bacterial populations on teats grew rapidly by 12 h and then remained constant. Hydrated lime was the only treatment that significantly reduced bacterial counts on both mattresses and teat ends, but it caused some skin irritation. PMID:18420619

Kristula, M A; Dou, Z; Toth, J D; Smith, B I; Harvey, N; Sabo, M

2008-05-01

394

Specimen geometry and extended-crack-growth effects on J/sub I/-R curve characteristics for HY-130 and ASTM A533B steels  

SciTech Connect

An evaluation of the ductile fracture toughness and J/sub I/-R curve properties of HY-130 and ASTM A533B-HSST-03 steels in response to systematic variations of thickness and crack length in the side grooved compact specimen geometry was carried out. A series of 2T compact specimens were produced to varying thicknesses, and with various fatigue crack lengths. Elastic compliance J/sub I/-R curve test were performed, and analyses of J/sub Ic/, the slope of the J/sub I/-R curve, the accuracy of the Ernst-Paris-Landes approximation for J/sub I/, and an assessment of the criterion for J-controlled crack growth were carried out. Results showed that J/sub Ic/ of both steels was geometry independent when validity criteria were met. Both steels displayed a clear dependence of the slope of the J/sub I/-R curve as related to thickness/ligament ratio and degree of crack extension. A limiting thickness/ligament ratio of 1 is necessary to ensure a conservative J/sub I/-R-curve slope over the full range of crack growth. The Ernst-Paris-Landes expression was shown to accurately describe J/sub I/ to crack extension values of 0.4b/sub 0/ for HY-130 steel. Limited evidence suggests that a minimum value of ..omega.. to guarantee J-controlled crack growth with compact specimens in HY-130 steel is 2. 20 figures, 7 tables.

Davis, D.A.; Vassilaros, M.G.; Gudas, J.P.

1983-05-01

395

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

Microsoft Academic Search

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

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

1994-01-01

396

Frequency curves  

USGS Publications Warehouse

This manual describes graphical and mathematical procedures for preparing frequency curves from samples of hydrologic data. It also discusses the theory of frequency curves, compares advantages of graphical and mathematical fitting, suggests methods of describing graphically defined frequency curves analytically, and emphasizes the correct interpretations of a frequency curve.

Riggs, H. C.

1968-01-01

397

Impact of Genome Reduction on Bacterial Metabolism and Its Regulation  

Microsoft Academic Search

To understand basic principles of bacterial metabolism organization and regulation, but also the impact of genome size, we systematically studied one of the smallest bacteria, Mycoplasma pneumoniae. A manually curated metabolic network of 189 reactions catalyzed by 129 enzymes allowed the design of a defined, minimal medium with 19 essential nutrients. More than 1300 growth curves were recorded in the

Eva Yus; Tobias Maier; Konstantinos Michalodimitrakis; Vera van Noort; Takuji Yamada; Wei-Hua Chen; Judith A. H. Wodke; Marc Güell; Sira Martínez; Ronan Bourgeois; Sebastian Kühner; Emanuele Raineri; Ivica Letunic; Olga V. Kalinina; Michaela Rode; Richard Herrmann; Ricardo Gutiérrez-Gallego; Robert B. Russell; Anne-Claude Gavin; Peer Bork; Luis Serrano

2009-01-01

398

Crack growth resistance ( R-curve) behaviour and thermo-physical properties of Al 2O 3 particle-reinforced AlN\\/Al matrix composites  

Microsoft Academic Search

Crack growth resistance behaviour and thermo-physical properties of Al2O3 particle-reinforced AlN\\/Al matrix composites have been studied as a function of AlN volume fraction as well as Al2O3 particle size. The fracture toughness of the composites decreased with increase in vol% AlN and decrease in Al2O3 particle size. All the composites exhibited R-curve behaviour which has been attributed to crack bridging

Srinivasa Rao Boddapati; Jürgen Rödel; Vikram Jayaram

2007-01-01

399

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

Microsoft Academic Search

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

Abubaker Ali Ahmed

2007-01-01

400

A Growth Curve Analysis of the Joint Influences of Parenting Affect, Child Characteristics and Deviant Peers on Adolescent Illicit Drug Use  

Microsoft Academic Search

This study purports that parental rejection and warmth are critical to the development of adolescent drug use, and investigates\\u000a a model that also considers children's vulnerability and deviant peer affiliations. It tests mediation through the proximal\\u000a risk factor of deviant peers. Poisson growth curve modeling was used to examine participants from the Canadian National Longitudinal\\u000a Survey of Children and Youth

Paulo Pires; Jennifer M. Jenkins

2007-01-01

401

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

Microsoft Academic Search

The purpose of the present study was to examine the direct and indirect effects (through peer contacts) of parental knowledge\\u000a on adolescents’ delinquent and aggressive problem behavior, using latent growth curve modeling. A sample of 457 13- to 14-year\\u000a old adolescents at first measurement wave (M=13.27; SD=0.45 years) filled out questionnaires about their parents, peers, and problem behavior three times

Ellen Reitz; Peter Prinzie; Maja Dekovi?; Kirsten L. Buist

2007-01-01

402

Dynamics of growth and succession of bacterial and fungal communities during composting of feather waste  

Microsoft Academic Search

Succession of communities of different bacteria and fungi, mainly proteolytic and keratinolytic ones, was observed during composting of chicken feathers with pine bark (FB) and with pine bark\\/rye straw (FBS). The succession was dominated by fungal than bacterial communities. Bacteria, including Actinomycetes, grew intensively during the first 2–4weeks of composting and included mainly proteolytic, rarely cellulolytic, populations; afterwards, bacteria were

Teresa Korni??owicz-Kowalska; Justyna Bohacz

2010-01-01

403

Group A Streptococcus transcriptome dynamics during growth in human blood reveals bacterial adaptive and survival strategies.  

PubMed

The molecular basis for bacterial responses to host signals during natural infections is poorly understood. The gram-positive bacterial pathogen group A Streptococcus (GAS) causes human mucosal, skin, and life-threatening systemic infections. During the transition from a throat or skin infection to an invasive infection, GAS must adapt to changing environments and host factors. To better understand how GAS adapts, we used transcript profiling and functional analysis to investigate the transcriptome of a wild-type serotype M1 GAS strain in human blood. Global changes in GAS gene expression occur rapidly in response to human blood exposure. Increased transcription was observed for many genes that likely enhance bacterial survival, including those encoding superantigens and host-evasion proteins regulated by a multiple gene activator called Mga. GAS also coordinately expressed genes involved in proteolysis, transport, and catabolism of oligopeptides to obtain amino acids in this protein-rich host environment. Comparison of the transcriptome of the wild-type strain to that of an isogenic deletion mutant (DeltacovR) mutated in the two-component regulatory system designated CovR-CovS reinforced the hypothesis that CovR-CovS has an important role linking key biosynthetic, catabolic, and virulence functions during transcriptome restructuring. Taken together, the data provide crucial insights into strategies used by pathogenic bacteria for thwarting host defenses and surviving in human blood. PMID:15681829

Graham, Morag R; Virtaneva, Kimmo; Porcella, Stephen F; Barry, William T; Gowen, Brian B; Johnson, Claire R; Wright, Fred A; Musser, James M

2005-02-01

404

PHYSICAL GROWTH AND BIOMASS CHARACTERIZATION OF BACTERIAL CELLS EXPOSED TO Cd(II), Cr(VI), Cu(II), Ni(II), AND Pb(II)  

Microsoft Academic Search

This paper describes the growth characterization of consortium culture (CC) comprising an acclimatized mixed bacterial culture in aqueous solution containing heavy metal ions, namely Cd(II), Cr(VI), Cu(II), Ni(II), and Pb(II). Microscopy and biochemical tests performed revealed that consortium culture (CC), an environmental mixed bacterial culture to predominantly consist of six Gram negative (Pseudomonas sp, Serratia sp, Flavobacterium sp, Chryseomonas sp,

Bandar Baru Nilai

2009-01-01

405

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

406

Avian Incubation Inhibits Growth and Diversification of Bacterial Assemblages on Eggs  

Microsoft Academic Search

Microbial infection is a critical source of mortality for early life stages of oviparous vertebrates, but parental defenses against infection are less well known. Avian incubation has been hypothesized to reduce the risk of trans-shell infection by limiting microbial growth of pathogenic bacteria on eggshells, while enhancing growth of commensal or beneficial bacteria that inhibit or competitively exclude pathogens. We

Matthew D. Shawkey; Mary K. Firestone; Eoin L. Brodie; Steven R. Beissinger; Ryan L. Earley

2009-01-01

407

The Role of Enhanced Heterotrophic Bacterial Growth on Iron Oxidation by Acidithiobacillus ferrooxidans  

Microsoft Academic Search

Addition of organic carbon substrate (glucose) profoundly affected the growth of cultures of acidophilic bacteria typical of acid mine drainage (AMD) sites: the iron-oxidizing autotrophic bacteria, Acidithiobacillus ferrooxidans , and a common heterotrophic strain, Acidiphilium acidophilum . Growth of A. ferrooxidans on soluble ferrous iron media was significantly inhibited in the presence of 1,000 mg\\/L glucose, regardless of the initial

Eric A. Marchand; Joann Silverstein

2003-01-01

408

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

Microsoft Academic Search

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

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

1998-01-01

409

A multiphasic approach for the identification of endophytic bacterial in strawberry fruit and their potential for plant growth promotion.  

PubMed

This study used a multiphasic approach, characterized by the simultaneous use of culture-dependent and culture-independent methods, to investigate endophytic bacterial communities in strawberry (Fragaria ananassa) fruit. A total of 92 bacterial endophytes were isolated and initially grouped by their repetitive extragenic palindromic (rep)-PCR banding pattern and biochemical features. Phylogenetic analysis of the 16S rRNA gene sequences of 45 representatives showed that the isolates belonged to the species Bacillus subtilis (eight isolates), Bacillus sp. (seven isolates), Enterobacter sp. (seven isolates), Enterobacter ludwigii (six isolates), Lactobacillus plantarum (six isolates), Pseudomonas sp. (five isolates), Pantoea punctata (three isolates), and Curtobacterium citreum (three isolates). Nucleic acids were extracted from the strawberry fruit and subjected to 16S rRNA gene directed polymerase chain reaction denaturing gradient gel electrophoresis (16S rRNA PCR-DGGE). The species B. subtilis, Enterobacter sp., and Pseudomonas sp. were detected both by isolation and DGGE. The DGGE fingerprints of total bacterial DNA did not exhibit bands corresponding to several of the representative species isolated in the extinction dilution (L. plantarum, C. citreum, and P. punctata). In contrast, bands in the DGGE profile that were identified as relatives of Arthrobacter sp. and one uncultivable Erythrobacter sp. were not recovered by cultivation techniques. After isolation, the nitrogen fixation ability and the in vitro production of indole-3-acetic acid (IAA) equivalents and siderophores were evaluated. A high percentage of isolates were found to possess the ability to produce siderophores and IAA equivalents; however, only a few isolates belonging to the genera Pseudomonas and Enterobacter showed the ability to fix nitrogen. Plant growth promotion was evaluated under greenhouse conditions and revealed the ability of the Bacillus strains to enhance the number of leaves, shoot length, root dry weight, and shoot dry weight. The activity of the bacterial isolate identified as B. subtilis NA-108 exerted the greatest influence on strawberry growth and showed a 42.8% increase in number of leaves, 15.26% for high shoot, 43.5% increase in root dry weight, and a 77% increase in shoot dry weight when compared with untreated controls. PMID:21837472

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

2011-08-12

410

Assessment of bacterial and fungal growth on natural substrates: consequences for preserving caves with prehistoric paintings.  

PubMed

The most representative bacterium (Pseudonocardia sp.) and fungus (Fusarium sp.) from the microbial communities of a cave containing paleolithic paintings were isolated and their growth on natural substrates assessed. Growth was tested at the in situ and optimal, laboratory growth temperature. Development was analyzed with and without supplemented nutrients (glucose, ammonium, phosphate, peptone). Results showed that the assayed bacterium on natural substrate was able to develop best at in situ temperature and the addition of organic nutrients and/or phosphate enhanced its growth. The growth of the assayed fungus, however, was limited by low temperature and the availability of ammonium. These results confirm a differential behavior of microorganisms between the laboratory and the natural environments and could explain previous invasion of fungi reported for some caves with prehistoric paintings. PMID:19536596

Stomeo, Francesca; Portillo, Maria C; Gonzalez, Juan M

2009-06-18

411

Mathematical models and simulations of bacterial growth and chemotaxis in a diffusion gradient chamber.  

PubMed

The diffusion gradient chamber (DGC) is a novel device developed to study the response of chemotactic bacteria to combinations of nutrients and attractants [7]. Its purpose is to characterize genetic variants that occur in many biological experiments. In this paper, a mathematical model which describes the spatial distribution of a bacterial population within the DGC is developed. Mathematical analysis of the model concerning positivity and boundedness of the solutions are given. An ADI (Alternating Direction Implicit) method is constructed for finding numerical solutions of the model and carrying out computer simulations. The numerical results of the model successfully reproduced the patterns that were observed in the experiments using the DGC. PMID:11261315

Chiu, C; Hoppensteadt, F C

2001-02-01

412

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

PubMed

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

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

2013-01-01

413

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

PubMed Central

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

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

2013-01-01

414

Convexity of the Photosynthetic Light-Response Curve in Relation to lntensity and Direction of Light during Growth  

Microsoft Academic Search

Photosynthesis in the intermediate light range is most efficient when the convexity of the photosynthetic light-response curve is high. Factors determining the convexity were examined for intact leaves using Salix sp. and for a plant cell culture using the green microalga Coccomyra sp. It was found that the leaf had lower convexity than diluted plant cells because the light gradient

Erling Ogren

1993-01-01

415

Measuring bacterial growth by tapered fiber and changes in evanescent field.  

PubMed

Single mode continuous tapered fibers were fabricated with waist diameters of 6-8 microm and of 11 mm waist lengths. The tapered surface was coated with poly-l-lysine and Escherichia coli (E. coli) (JM 101) expressing green fluorescent protein was immobilized. Growth of this culture at 22 and 32 degrees C was monitored by 480 nm light transmission through the tapered fiber. Change in transmission is a measure of change in absorption of the evanescent field. The transmission decreased exponentially with cell growth on the tapered surface. Growth rate was determined and compared favorably with cells grown on the same medium in multiwell plates. Significance of the results is that a tapered fiber sensor can be used effectively for rapid assessment to determine the presence of bacteria by growth. PMID:15913977

Maraldo, David; Shankar, P Mohana; Mutharasan, Raj

2006-01-15

416

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

PubMed Central

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

2011-01-01

417

Curved Mirrors  

NSDL National Science Digital Library

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

Horton, Michael

2009-05-30

418

Aerobic Growth on Nitroglycerin as the Sole Carbon, Nitrogen, and Energy Source by a Mixed Bacterial Culture  

PubMed Central

Nitroglycerin (glycerol trinitrate [GTN]), an explosive and vasodilatory compound, was metabolized by mixed microbial cultures from aeration tank sludge previously exposed to GTN. Aerobic enrichment cultures removed GTN rapidly in the absence of a supplemental carbon source. Complete denitration of GTN, provided as the sole C and N source, was observed in aerobic batch cultures and proceeded stepwise via the dinitrate and mononitrate isomers, with successive steps occurring at lower rates. The denitration of all glycerol nitrate esters was found to be concomitant, and 1,2-glycerol dinitrate (1,2-GDN) and 2-glycerol mononitrate (2-GMN) were the primary GDN and GMN isomers observed. Denitration of GTN resulted in release of primarily nitrite-N, indicating a reductive denitration mechanism. Biomass growth at the expense of GTN was verified by optical density and plate count measurements. The kinetics of GTN biotransformation were 10-fold faster than reported for complete GTN denitration under anaerobic conditions. A maximum specific growth rate of 0.048 ± 0.005 h?1 (mean ± standard deviation) was estimated for the mixed culture at 25°C. Evidence of GTN toxicity was observed at GTN concentrations above 0.3 mM. To our knowledge, this is the first report of complete denitration of GTN used as a primary growth substrate by a bacterial culture under aerobic conditions.

Accashian, John V.; Vinopal, Robert T.; Kim, Byung-Joon; Smets, Barth F.

1998-01-01

419

Relationship of bacterial growth phase to killing of Listeria monocytogenes by oxidative agents generated by neutrophils and enzyme systems.  

PubMed Central

Listeria monocytogenes, a gram-positive motile bacterium which can cause severe bacterial infection in humans, is considered to be pathogenic by virtue of its ability to resist intracellular killing. Since the mechanism of intracellular survival is poorly understood, we assessed the sensitivity of L. monocytogenes to several potent antibacterial products. Phorbol myristate acetate (PMA)-stimulated polymorphonuclear cells (PMNs) produced extracellular antibacterial products which were inhibited completely by catalase, suggesting a role for oxidative agents in this process. L. monocytogenes in logarithmic (log) growth phase resisted PMA-stimulated PMN extracellular products significantly more than L. monocytogenes in stationary (stat) growth phase or Escherichia coli (three strains) in either phase of growth. The role of oxidative agents was studied further by using xanthine oxidase-xanthine, glucose oxidase-glucose, and myeloperoxidase enzyme systems to generate hydroxyl radical (.OH), hydrogen peroxide (H2O2), and hypochlorous acid (OCl-), respectively. L. monocytogenes in log phase resisted the antibacterial products of these enzyme systems under conditions which produced superoxide (O2-) and H2O2 at concentrations similar to those produced extracellularly by PMA-stimulated PMNs, while stat-growth-phase L. monocytogenes and E. coli in either phase of growth were susceptible. Antibacterial activity could be blocked or inhibited by exogenous catalase (for all oxygen radical-generating systems), mannitol, or desferoxamine (for xanthine oxidase-xanthine) and alanine (for myeloperoxidase), suggesting that .OH and OCl- were responsible for this activity. Log-phase L. monocytogenes had 2.5-fold higher bacteria-associated catalase activity, as compared with stat-phase L. monocytogenes. These experiments, therefore, suggest that log-phase L. monocytogenes resists oxidative antibacterial agents by producing sufficient catalase to inactivate these products. This may contribute to the ability of L. monocytogenes to survive intracellularly.

Bortolussi, R; Vandenbroucke-Grauls, C M; van Asbeck, B S; Verhoef, J

1987-01-01

420

Inhibition of bacterial and filamentous fungal growth in high moisture, nonsterile corn with intermittent pumping of trans-2-hexenal vapor.  

PubMed

Trans-2-hexenal (T2H), a plant-produced aldehyde, was intermittently pumped over a 7 d period into a small, bench top model of stored corn (nonsterile, moisture content about 23%). Naturally occurring bacteria and fungi, including added Aspergillus flavus, grew rapidly on corn not treated with T2H vapor. However, intermittently pumped T2H (30 min per 2 h or 30 min per 12 h) significantly reduced bacterial and fungal viable populations, with nearly 100% fungal viability loss observed after either (1) one day of pumping at the 30 min per 2 h rate or (2) pumping cycles of 30 min per 12 h period over the initial 48 to 72 h of incubation. Data suggest that short-term intermittent fumigation of stored corn with T2H could prevent growth of bacteria and mycotoxigenic fungi such as A. flavus. PMID:23865451

De Lucca, Anthony J; Carter-Wientjes, Carol H; Boué, Stephen M; Lovisa, Mary P; Bhatnagar, Deepak

2013-07-01

421

Methods for Intense Aeration, Growth, Storage, and Replication of Bacterial Strains in Microtiter Plates  

Microsoft Academic Search

Miniaturized growth systems for heterogeneous culture collections are not only attractive in reducing demands for incubation space and medium but also in making the parallel handling of large numbers of strains more practicable. We report here on the optimization of oxygen transfer rates in deep-well microtiter plates and the development of a replication system allowing the simultaneous and reproducible sampling

WOUTER A. DUETZ; LORENZ RUEDI; ROBERT HERMANN; K. O'Connor; J. Buchs; B. Witholt

2000-01-01

422

Review Paper A dynamic approach to predicting bacterial growth in food  

Microsoft Academic Search

A new member of the family of growth models described by Baranyi et al. (1993a) is introduced in which the physiological state of the cells is represented by a single variable. The duration of lag is determined by the value of that variable at inoculation and by the post-inoculation environment. When the subculturing procedure is standardized, as occurs in laboratory

Terry A. Roberts

423

The Mycobacterium tuberculosis CysQ phosphatase modulates the biosynthesis of sulfated glycolipids and bacterial growth  

PubMed Central

CysQ is a 3'-phosphoadenosine-5'-phosphatase that dephosphorylates intermediates from the sulfate assimilation pathway of Mycobacterium tuberculosis (Mtb). Here, we demonstrate that cysQ disruption attenuates Mtb growth in vitro and decreases the biosynthesis of sulfated glycolipids but not major thiols, suggesting that the encoded enzyme specifically regulates mycobacterial sulfation.

Hatzios, Stavroula K.; Schelle, Michael W.; Newton, Gerald L.; Sogi, Kimberly M.; Holsclaw, Cynthia M.; Fahey, Robert C.; Bertozzi, Carolyn R.

2011-01-01

424

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

Microsoft Academic Search

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

Patti M. Thorn; Roy M. Ventullo

1988-01-01

425

Bacterial Growth Dynamics, Limiting Factors, and Community Diversity in a Proposed Geological Nuclear Waste Repository Environment  

Microsoft Academic Search

Microbiological growth parameters, including limiting factors, kinetics, and minimal cell densities were assessed for subsurface microbiological communities collected with rock from an area proposed for a nuclear waste repository at Yucca Mountain, Nevada. Phospholipid fatty acid analysis revealed that approximately 10–10 viable cells per gram of dry rock are extant, and water availability was shown to be the primary factor

Joanne M. Horn; Brett A. Masterson; Angel Rivera; Anabel Miranda; Michael A. Davis; Sue Martin

2004-01-01

426

Assessment of the extent of bacterial growth in reverse osmosis system for improving drinking water quality  

Microsoft Academic Search

This study was carried out to assess reverse osmosis (RO) treatment efficacy of drinking water in terms of biological stability in the distribution system. Two flat-sheet RO membranes were used in this study. Experiments were designed to investigate the growth of biofilm and bulk phase bacteria for the RO-treated water flowing through a model distribution system under controlled conditions without

Se-keun Park; Jiang Yong Hu

2010-01-01

427

Body size change in various nematodes depending on bacterial food, sex and growth temperature  

PubMed Central

We previously reported significant body size change in the nematode Caenorhabditis elegans, depending on the food strain of E. coli. Here, we examined this body size change in 11 other nematode species as well, and found that it is common to most of these nematodes. Furthermore, this food-dependent body size change is influenced by sex and growth temperature.

So, Shuhei; Garan, Yohei; Miyahara, Kohji; Ohshima, Yasumi

2012-01-01

428

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

NASA Astrophysics Data System (ADS)

The sub-Antarctic zone (SAZ) of the Southern Ocean is considered one of the largest sinks for atmospheric CO 2 and as such is an important region for climate change research. To determine the importance of micro- and nano-heterotrophs in controlling microbial abundance within this region, we determined microbial standing stocks and rates of herbivory and bacterivory in relation to changes in the water masses south of Tasmania. The SAZ-Sense ('Sensitivity of the sub-Antarctic zone to environmental change') cruise traversed the SAZ during mid-late austral summer and focussed on process stations to the southeast (45°S, 153°E) and southwest (46°S, 140°E) of Tasmania and at the Polar Front (54°S, 147°E). Growth and grazing mortality of phytoplankton and bacteria were estimated by the grazing dilution technique using seawater from 10 m depth at 15 sites along the survey, along with concentrations of heterotrophic nanoflagellates (HNF), microzooplankton, bacteria, cyanobacteria and size fractionated (pico-, nano- and micro-sized) chlorophyll a (Chl a). Rates of herbivory ranged from 0.12 to 1.39 d -1 and were highest in the north-eastern SAZ (NE-SAZ) where concentrations of prey (as indicated by Chl a) and microzooplankton were also highest. Rates of herbivory were correlated with total rates of phytoplankton growth, bacterial growth and concentrations of microzooplankton. On average 82%, 67% and 42% primary production d -1 was consumed by microzooplankton and HNF at process stations in the north-western SAZ (NW-SAZ), NE-SAZ and polar frontal zone (PFZ), respectively. In the NW-SAZ, grazing pressure was highest on the pico-sized Chl a fraction, whereas in the NE-SAZ, grazing pressure was more evenly distributed across all three size fractions of Chl a. Bacterivory removed 77%, 93% and 39% of bacterial production d -1 in the NW-SAZ, NE-SAZ and PFZ, respectively, and rates of bacterivory ranged from 0.12 to 1.03 d -1. Rates of bacterivory were highest in the NE-SAZ where concentrations of bacteria were significantly higher than elsewhere in the region and bacterivory was correlated with bacterial growth rates and rates of cyanobacterivory. Cluster analysis of the concentrations of marine microbes and their rates of growth and grazing mortality identified 5 groups of sampling sites that differed in community structure. Analysis distinguished between high nutrient, low Chl a (HNLC) communities in the NW-SAZ that were iron-limited; iron-limited low Chl a PFZ communities; and iron-replete NE-SAZ communities where high rates of remineralisation correlated with higher concentrations of Chl a. Our findings show that much of the carbon sequestered by photosynthesis in the SAZ during summer is reprocessed via the microbial loop rather than contributing to vertical flux, particularly to the southeast of Tasmania. This suggests strong seasonality in carbon export in the region and that future climate-driven changes in oceanography may reduce carbon export from the region in summer.

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

2011-11-01

429

A new predictive dynamic model describing the effect of the ambient temperature and the convective heat transfer coefficient on bacterial growth.  

PubMed

In this study, predictive microbiology and food engineering were combined in order to develop a new analytical model predicting the bacterial growth under dynamic temperature conditions. The proposed model associates a simplified primary bacterial growth model without lag, the secondary Ratkowsky "square root" model and a simplified two-parameter heat transfer model regarding an infinite slab. The model takes into consideration the product thickness, its thermal properties, the ambient air temperature, the convective heat transfer coefficient and the growth parameters of the micro organism of concern. For the validation of the overall model, five different combinations of ambient air temperature (ranging from 8 degrees C to 12 degrees C), product thickness (ranging from 1 cm to 6 cm) and convective heat transfer coefficient (ranging from 8 W/(m(2) K) to 60 W/(m(2) K)) were tested during a cooling procedure. Moreover, three different ambient air temperature scenarios assuming alternated cooling and heating stages, drawn from real refrigerated food processes, were tested. General agreement between predicted and observed bacterial growth was obtained and less than 5% of the experimental data fell outside the 95% confidence bands estimated by the bootstrap percentile method, at all the tested conditions. Accordingly, the overall model was successfully validated for isothermal and dynamic refrigeration cycles allowing for temperature dynamic changes at the centre and at the surface of the product. The major impact of the convective heat transfer coefficient and the product thickness on bacterial growth during the product cooling was demonstrated. For instance, the time needed for the same level of bacterial growth to be reached at the product's half thickness was estimated to be 5 and 16.5 h at low and high convection level, respectively. Moreover, simulation results demonstrated that the predicted bacterial growth at the air ambient temperature cannot be assumed to be equivalent to the bacterial growth occurring at the product's surface or centre when convection heat transfer is taken into account. Our results indicate that combining food engineering and predictive microbiology models is an interesting approach providing very useful tools for food safety and process optimisation. PMID:19447512

Ben Yaghlene, H; Leguerinel, I; Hamdi, M; Mafart, P

2009-04-24

430

SIMULATION OF SINGLE-SPECIES BACTERIAL-BIOFILM GROWTH USING THE GLAZIER-GRANER-HOGEWEG MODEL AND THE COMPUCELL3D MODELING ENVIRONMENT  

Microsoft Academic Search

The CompuCell3D modeling environment provides a convenient platform for biofllm simulations using the Glazier-Graner-Hogeweg (GGH) model, a cell-oriented framework designed to simulate growth and pattern formation due to biological cells' behaviors. We show how to develop such a simulation, based on the hybrid (continuum-discrete) model of Picioreanu, van Loosdrecht, and Heijnen (PLH), simulate the growth of a single-species bacterial biofllm,

Abbas Shirinifard; Maciej Swat; James A. Glazier

2008-01-01

431

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

PubMed

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

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

2013-08-27

432

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

PubMed

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

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

2013-08-03

433

Growth responses of ciliate protozoa to the abundance of their bacterial prey  

Microsoft Academic Search

The growth rate or numerical response of five species of bactivorous ciliates to the abundance ofEnterobacter aerogenes was examined in monoxenic culture. The ciliatesColpidium campylum, C. colpoda, Glaucoma scintillons, G. frontata, andCyclidium glaucoma were isolated from a small pond. Four were grown in shaken cultures, while three were grown in cultures in which the bacteria were allowed to settle on

William D. Taylor

1977-01-01

434

Comparison of two bacterial azoreductases acquired during adaptation to growth on azo dyes  

Microsoft Academic Search

Selection for utilization of carboxy-Orange I [1-(4'-carboxyphenylazo)-4-naphthol] in the chemostat yielded Pseudomonas strain K24 which was unable to grow on carboxy-Orange II [1-(4'-carboxyphenylazo)-2naphthol] while selection for growth on carboxy-Orange II had previously led to strain KF 46 which did not utilize carboxy-Orange I. Orange I azoreductase of strain K24, the key enzyme of dye degradation, was purified 80-fold with 17%

Thomas Zimmermann; Franz Gasser; Hans G. Kulla; Thomas Leisinger

1984-01-01

435

Antitumor activity of bacterial infection. I. Effect of Listeria monocytogenes on growth of a murine fibrosarcoma.  

PubMed

Growth of a murine fibrosarcoma was suppressed when tumor cells were mixed with viable Listeria monocytogenes (LM) before intradermal injection into nonimmune syngeneic recepients. Immunization of recipients, by intravenous injection of LM 11 days before transplantation of LM-tumor cell mixtures, eliminated the mortality associated with large doses of LM but did not alter the antitumor activity of the microorganisms. Simultaneous injection of LM and tumor cells at separate sites failed to affect tumor growth, which suggested that contact between LM and tumor cells was required for tumor suppression. Tumor-specific immunity was not observed; mice surviving injection of LM and tumor cells did not resist a second tumor-cell challenge. At least 100 times more heat-killed LM was required to produce the antitumor effect of viable organisms. The ability of heat-killed LM to suppress tumor growth was abolished by treatment of recipients with rabbit antiserum to mouse thymocytes, which was consistent with a requirement for a host response to the LM. Regression of established fibrosarcoma transplants was produced by the intratumor injection of viable LM 5 days after injection of tumor cells. Intratumor injection of BCG at this interval was not effective. The incidence of tumor regression was not increased by multiple intratumor injections of LM, by intratumor injection of a combination of LM and BCG, or by preimmunization with LM prior to the intratumor injection of the same organism. PMID:804566

Bast, R C; Zbar, B; Mackaness, G B; Rapp, H J

1975-03-01

436

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

PubMed Central

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

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

1977-01-01