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Sample records for bacterial growth rate

  1. Bounds on bacterial cell growth rates

    CERN Document Server

    Landy, Jonathan

    2013-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, P.F.

    1995-12-31

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

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

    Science.gov (United States)

    Osella, Matteo; Lagomarsino, Marco Cosentino

    2013-01-01

    Gene networks exhibiting oscillatory dynamics are widespread in biology. The minimal regulatory designs giving rise to oscillations have been implemented synthetically and studied by mathematical modeling. However, most of the available analyses generally neglect the coupling of regulatory circuits with the cellular “chassis” in which the circuits are embedded. For example, the intracellular macromolecular composition of fast-growing bacteria changes with growth rate. As a consequence, important parameters of gene expression, such as ribosome concentration or cell volume, are growth-rate dependent, ultimately coupling the dynamics of genetic circuits with cell physiology. This work addresses the effects of growth rate on the dynamics of a paradigmatic example of genetic oscillator, the repressilator. Making use of empirical growth-rate dependencies of parameters in bacteria, we show that the repressilator dynamics can switch between oscillations and convergence to a fixed point depending on the cellular state of growth, and thus on the nutrients it is fed. The physical support of the circuit (type of plasmid or gene positions on the chromosome) also plays an important role in determining the oscillation stability and the growth-rate dependence of period and amplitude. This analysis has potential application in the field of synthetic biology, and suggests that the coupling between endogenous genetic oscillators and cell physiology can have substantial consequences for their functionality.

  4. Bacterial growth on surfaces: Automated image analysis for quantification of growth rate-related parameters

    DEFF Research Database (Denmark)

    Møller, S.; Sternberg, Claus; Poulsen, L. K.;

    1995-01-01

    species-specific hybridizations with fluorescence-labelled ribosomal probes to estimate the single-cell concentration of RNA. By automated analysis of digitized images of stained cells, we determined four independent growth rate-related parameters: cellular RNA and DNA contents, cell volume......, and the frequency of dividing cells in a cell population. These parameters were used to compare physiological states of liquid-suspended and surfacegrowing Pseudomonas putida KT2442 in chemostat cultures. The major finding is that the correlation between substrate availability and cellular growth rate found...

  5. Bacterial Respiration and Growth Rates Affect the Feeding Preferences, Brood Size and Lifespan of Caenorhabditis elegans.

    Directory of Open Access Journals (Sweden)

    Li Yu

    Full Text Available Bacteria serve as live food and nutrients for bacterial-feeding nematodes (BFNs in soils, and influence nematodes behavior and physiology through their metabolism. Five bacterial taxa (Bacillus amyloliquefaciens JX1, Variovorax sp. JX14, Bacillus megaterium JX15, Pseudomonas fluorescens Y1 and Escherichia coli OP50 and the typical BFN Caenorhabditis elegans were selected to study the effects of bacterial respiration and growth rates on the feeding preferences, brood size and lifespan of nematodes. P. fluorescens Y1 and E. coli OP50 were found to be more active, with high respiration and rapid growth, whereas B. amyloliquefaciens JX1 and B. megaterium JX15 were inactive. The nematode C. elegans preferred active P. fluorescens Y1 and E. coli OP50 obviously. Furthermore, worms that fed on these two active bacteria produced more offspring but had shorter lifespan, while inactive and less preferred bacteria had increased nematodes lifespan and decreased the brood size. Based on these results, we propose that the bacterial activity may influence the behavior and life traits of C. elegans in the following ways: (1 active bacteria reproduce rapidly and emit high levels of CO2 attracting C. elegans; (2 these active bacteria use more resources in the nematodes' gut to sustain their survival and reproduction, thereby reducing the worm's lifespan; (3 inactive bacteria may provide less food for worms than active bacteria, thus increasing nematodes lifespan but decreasing their fertility. Nematodes generally require a balance between their preferred foods and beneficial foods, only preferred food may not be beneficial for nematodes.

  6. Growth against entropy in bacterial metabolism: the phenotypic trade-off behind empirical growth rate distributions in E. coli

    Science.gov (United States)

    De Martino, Daniele; Capuani, Fabrizio; De Martino, Andrea

    2016-06-01

    The solution space of genome-scale models of cellular metabolism provides a map between physically viable flux configurations and cellular metabolic phenotypes described, at the most basic level, by the corresponding growth rates. By sampling the solution space of E. coli's metabolic network, we show that empirical growth rate distributions recently obtained in experiments at single-cell resolution can be explained in terms of a trade-off between the higher fitness of fast-growing phenotypes and the higher entropy of slow-growing ones. Based on this, we propose a minimal model for the evolution of a large bacterial population that captures this trade-off. The scaling relationships observed in experiments encode, in such frameworks, for the same distance from the maximum achievable growth rate, the same degree of growth rate maximization, and/or the same rate of phenotypic change. Being grounded on genome-scale metabolic network reconstructions, these results allow for multiple implications and extensions in spite of the underlying conceptual simplicity.

  7. Effects of Surface Area and Flow Rate on Marine Bacterial Growth in Activated Carbon Columns

    OpenAIRE

    Shimp, Robert J.; Pfaender, Frederic K.

    1982-01-01

    The colonization of granular activated carbon columns by bacteria can have both beneficial and potentially detrimental consequences. Bacterial growth on the carbon surface can remove adsorbed organics and thus partially regenerate the carbon bed. However, growth can also increase the levels of bacteria in the column effluents, which can adversely affect downstream uses of the treated water. This study of a sand column and several activated carbon columns demonstrated that considerable marine ...

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

    Science.gov (United States)

    Tobler, Dominique J; Benning, Liane G

    2011-07-01

    The microbial ecology associated with siliceous sinters was studied in five geochemically diverse Icelandic geothermal systems. Bacterial 16S rRNA clone libraries were constructed from water-saturated precipitates from each site resulting in a total of 342 bacterial clone sequences and 43 species level phylotypes. In near-neutral, saline (2.6-4.7% salinity) geothermal waters where sinter growth varied between 10 and ~300 kg year(-1) m(-2), 16S rRNA gene analyses revealed very low (no OTUs could be detected) to medium (9 OTUs) microbial activity. The most dominant phylotypes found in these waters belong to marine genera of the Proteobacteria. In contrast, in alkaline (pH = 9-10), meteoric geothermal waters with temperature = 66-96°C and geothermal waters; alkaliphilic thermophilic microbial communities with phylotypes related to heterotrophic and autotrophic microorganisms developed in alkaline high temperature waters, whereas halophilic mesophilic communities dominated coastal geothermal waters.

  9. Population dynamics of a Salmonella lytic phage and its host: implications of the host bacterial growth rate in modelling.

    Science.gov (United States)

    Santos, Sílvio B; Carvalho, Carla; Azeredo, Joana; Ferreira, Eugénio C

    2014-01-01

    The prevalence and impact of bacteriophages in the ecology of bacterial communities coupled with their ability to control pathogens turn essential to understand and predict the dynamics between phage and bacteria populations. To achieve this knowledge it is essential to develop mathematical models able to explain and simulate the population dynamics of phage and bacteria. We have developed an unstructured mathematical model using delay-differential equations to predict the interactions between a broad-host-range Salmonella phage and its pathogenic host. The model takes into consideration the main biological parameters that rule phage-bacteria interactions likewise the adsorption rate, latent period, burst size, bacterial growth rate, and substrate uptake rate, among others. The experimental validation of the model was performed with data from phage-interaction studies in a 5 L bioreactor. The key and innovative aspect of the model was the introduction of variations in the latent period and adsorption rate values that are considered as constants in previous developed models. By modelling the latent period as a normal distribution of values and the adsorption rate as a function of the bacterial growth rate it was possible to accurately predict the behaviour of the phage-bacteria population. The model was shown to predict simulated data with a good agreement with the experimental observations and explains how a lytic phage and its host bacteria are able to coexist. PMID:25051248

  10. Population dynamics of a Salmonella lytic phage and its host: implications of the host bacterial growth rate in modelling.

    Directory of Open Access Journals (Sweden)

    Sílvio B Santos

    Full Text Available The prevalence and impact of bacteriophages in the ecology of bacterial communities coupled with their ability to control pathogens turn essential to understand and predict the dynamics between phage and bacteria populations. To achieve this knowledge it is essential to develop mathematical models able to explain and simulate the population dynamics of phage and bacteria. We have developed an unstructured mathematical model using delay-differential equations to predict the interactions between a broad-host-range Salmonella phage and its pathogenic host. The model takes into consideration the main biological parameters that rule phage-bacteria interactions likewise the adsorption rate, latent period, burst size, bacterial growth rate, and substrate uptake rate, among others. The experimental validation of the model was performed with data from phage-interaction studies in a 5 L bioreactor. The key and innovative aspect of the model was the introduction of variations in the latent period and adsorption rate values that are considered as constants in previous developed models. By modelling the latent period as a normal distribution of values and the adsorption rate as a function of the bacterial growth rate it was possible to accurately predict the behaviour of the phage-bacteria population. The model was shown to predict simulated data with a good agreement with the experimental observations and explains how a lytic phage and its host bacteria are able to coexist.

  11. Conserved rates and patterns of transcription errors across bacterial growth states and lifestyles.

    Science.gov (United States)

    Traverse, Charles C; Ochman, Howard

    2016-03-22

    Errors that occur during transcription have received much less attention than the mutations that occur in DNA because transcription errors are not heritable and usually result in a very limited number of altered proteins. However, transcription error rates are typically several orders of magnitude higher than the mutation rate. Also, individual transcripts can be translated multiple times, so a single error can have substantial effects on the pool of proteins. Transcription errors can also contribute to cellular noise, thereby influencing cell survival under stressful conditions, such as starvation or antibiotic stress. Implementing a method that captures transcription errors genome-wide, we measured the rates and spectra of transcription errors in Escherichia coli and in endosymbionts for which mutation and/or substitution rates are greatly elevated over those of E. coli Under all tested conditions, across all species, and even for different categories of RNA sequences (mRNA and rRNAs), there were no significant differences in rates of transcription errors, which ranged from 2.3 × 10(-5) per nucleotide in mRNA of the endosymbiont Buchnera aphidicola to 5.2 × 10(-5) per nucleotide in rRNA of the endosymbiont Carsonella ruddii The similarity of transcription error rates in these bacterial endosymbionts to that in E. coli (4.63 × 10(-5) per nucleotide) is all the more surprising given that genomic erosion has resulted in the loss of transcription fidelity factors in both Buchnera and Carsonella.

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

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    Halyna Hrynash

    2014-01-01

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

  13. Theory of hydrokinetic clearance of bacteria from the urinary bladder. I. Effect of variations in bacterial growth rate.

    Science.gov (United States)

    Mackintosh, I P; Hammond, B J; Watson, B W; O'Grady, F

    1975-05-01

    If the bladder is regularly emptied in appropriate circumstances the concentration of bacteria in successively voided samples progressively falls. By making a number of assumptions about conditions of bacterial growth in the bladder the way in which this washout of bacteria will occur can be predicted. Such predictions give a form of washout curve which differs significantly from that commonly encountered in patients. The shape of the predicted washout curve is affected by the form of the bacterial growth curve but this influence is not sufficient to account for the observed difference between patients and predictions. PMID:1120639

  14. Influence of filtration and glucose amendment on bacterial growth rate at different tidal conditions in the Minho Estuary River (NW Portugal)

    DEFF Research Database (Denmark)

    Anne, I.; Fidalgo, M. L.; Thosthrup, L.;

    2006-01-01

    Bacterioplankton abundance, biomass and growth rates were studied in the Minho Estuary River (NW Portugal). The influence of tidal conditions, glucose amendment, and the filtration process on total bacterial abundance, total and faecal coliforms, as well as faecal streptococci, were evaluated....... In contrast, a significant decrease of bacterial indicators of faecal pollution at high tide was probably the result of various causes, such as the decrease of continental and agriculturalland mn-off effect by dilution, aml/or increase in the abundance of potential specific predators. Thus, drastic changes...

  15. Enteral nutrient solutions. Limiting bacterial growth.

    Science.gov (United States)

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

    1984-06-01

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

  16. Electromagnetism of Bacterial Growth

    Science.gov (United States)

    Ainiwaer, Ailiyasi

    2011-10-01

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

  17. Population Dynamics of a Salmonella Lytic Phage and Its Host: Implications of the Host Bacterial Growth Rate in Modelling

    OpenAIRE

    Santos, Sílvio Roberto Branco; Carvalho, Carla A. O. C. M.; Azeredo, Joana; Ferreira, E. C.

    2014-01-01

    The prevalence and impact of bacteriophages in the ecology of bacterial communities coupled with their ability to control pathogens turn essential to understand and predict the dynamics between phage and bacteria populations. To achieve this knowledge it is essential to develop mathematical models able to explain and simulate the population dynamics of phage and bacteria. We have developed an unstructured mathematical model using delay-differential equations to predict the interactions betwee...

  18. Comparative Study of Bacterial Growth in Magnet Fields

    Science.gov (United States)

    Smith, Derek; Masood, Samina

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

  19. MODELING AND SIMULATION TO PREDICT PARTIAL DEPOSITION OF AMMONIA AND SPECIFIC GROWTH RATE OF BACTERIAL IN HOMOGENEOUS FORMATION IN OBIO/AKPOR, RIVERS STATE OF NIGERIA

    OpenAIRE

    solomon Ndubuisi Eluozo

    2013-01-01

    Specific growth rate of bacteria has been expressed through characteristics influence deposition at various stratums to aquiferous zone. The growth rates of bacteria are under the influence of the substrate utilization that contaminates groundwater aquifers in various formations. Derived mathematical equations generated theoretical values that expressed the rate of exponential phase of ammonia deposition and bacteria growth rate in homogenous formation. Slight fluctuations were experienced in...

  20. Bacterial volatiles promote growth in Arabidopsis

    OpenAIRE

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

    2003-01-01

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

  1. MODELING AND SIMULATION TO PREDICT PARTIAL DEPOSITION OF AMMONIA AND SPECIFIC GROWTH RATE OF BACTERIAL IN HOMOGENEOUS FORMATION IN OBIO/AKPOR, RIVERS STATE OF NIGERIA

    Directory of Open Access Journals (Sweden)

    solomon Ndubuisi Eluozo

    2013-03-01

    Full Text Available Specific growth rate of bacteria has been expressed through characteristics influence deposition at various stratums to aquiferous zone. The growth rates of bacteria are under the influence of the substrate utilization that contaminates groundwater aquifers in various formations. Derived mathematical equations generated theoretical values that expressed the rate of exponential phase of ammonia deposition and bacteria growth rate in homogenous formation. Slight fluctuations were experienced in between the aquiferous zones under the influence of variation from degree of porosity and permeability of the stratum. Experimental values were compared with the theoretical values; both parameters produced a best fit. These expressed the application of the derived model that determines partial deposition of ammonia and bacteria growth rate in homogenous formation. The study is imperative because the model expressed partial depositions of ammonia that determine the growth rate of bacteria at various formations to groundwater aquifers in the study area.

  2. Asynchronous exponential growth of a bacterial population

    Directory of Open Access Journals (Sweden)

    Mohamed Boulanouar

    2014-01-01

    Full Text Available In this work, we complete a study started earlier in [1,2] wherein a model of growing bacterial population has been the matter of a mathematical analysis. We show that the full model is governed by a strongly continuous semigroup. Beside the positivity and the irreducibility of the generated semigroup, we describe its asymptotic behavior in the uniform topology which leads to the asynchronous exponential growth of the bacterial population.

  3. Evaluation of silicon oil on bacterial growth

    Directory of Open Access Journals (Sweden)

    Fabio Adams

    2012-04-01

    Full Text Available PURPOSE: To analyze the antimicrobial properties of silicon oil (Óleo de Silicone®, Ophthalmos, Brazil on in vitro bacterial growth of different microorganisms related to endophthalmitis. METHODS: The following microorganisms were analyzed: (1 Pseudomonas aeruginosa (ATCC 27583; (2 Escherichia coli (ATCC 25922; (3 Staphylococcus aureus (ATCC 25923; (4 Staphylococcus epidermidis (ATCC 12228; (5 Candida albicans (ATCC 10231; (6 Klebsiella pneumoniae (ATCC 13883; and (7 Streptococcus pneumoniae (ATCC 49619. The plates were incubated at 35 ± 2ºC and its growth examined after 24 hours. An empty disk was placed in the center of each plate as a control. RESULTS: No inhibition halos were verified in any of the plates containing the four different concentrations of the bacterial inocula. CONCLUSIONS: The silicon oil 1000 cps does not have any effect on bacterial growth of any of the studied microrganisms.

  4. Microcoupon Assay Of Adhesion And Growth Of Bacterial Films

    Science.gov (United States)

    Pierson, Duane L.; Koenig, David W.

    1994-01-01

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

  5. Bacterial growth laws and their applications

    OpenAIRE

    Scott, Matthew; Hwa, Terence

    2011-01-01

    Quantitative empirical relationships between cell composition and growth rate played an important role in the early days of microbiology. Gradually, the focus of the field began to shift from growth physiology to the ever more elaborate molecular mechanisms of regulation employed by the organisms. Advances in systems biology and biotechnology have renewed interest in the physiology of the cell as a whole. Furthermore, gene expression is known to be intimately coupled to the growth state of th...

  6. GROWTH RATE OF ARABIAN FOALS

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    M. PIESZKA

    2013-12-01

    Full Text Available Arabian horses are treated as one of the most noble horse breed in the world. It isalso one of the oldest breed known as a root of many other breeds. Opposite toThoroughbred horses Arabian ones are very healthy, easy to keep with low fodderdemand. They are still incredibly resistant to environmental conditions. Growth anddevelopment of foals is also very interesting because it is more similar to growth ofprimitive than to noble foals. The object of this study was to analyse the growth rateof Arabian foals bred in Poland. 382 foals born in Bialka Stud in 1983-2003 weretaken under consideration. The height at withers, girth and cannon circumferencemeasured at 1 day and 6 and 18 months of life were analysed. On this base thegrowth rate was calculated. Horses were divided into different groups accordingtheir year of birth, sex, coat colour and sire and dam lines. The statistical differencesbetween particular groups were evaluated. It was stated that year of birth affectedsignificantly the growth rate of Arabian foals. Colts were characterized bysignificantly higher growth rate of cannon circumference. Horses of different coatcolour did not differ in growth rate of any parameter. Affiliation to particular sireand dam lines had some effects on growth rate of Arabian foals.

  7. Archaeal Abundance across a pH Gradient in an Arable Soil and Its Relationship to Bacterial and Fungal Growth Rates

    OpenAIRE

    Bengtson, Per; Sterngren, Anna E.; Rousk, Johannes

    2012-01-01

    Soil pH is one of the most influential factors for the composition of bacterial and fungal communities, but the influence of soil pH on the distribution and composition of soil archaeal communities has yet to be systematically addressed. The primary aim of this study was to determine how total archaeal abundance (quantitative PCR [qPCR]-based estimates of 16S rRNA gene copy numbers) is related to soil pH across a pH gradient (pH 4.0 to 8.3). Secondarily, we wanted to assess how archaeal abund...

  8. A Brief History of Bacterial Growth Physiology

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    Moselio eSchaechter

    2015-04-01

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

  9. GDP growth rate and population

    OpenAIRE

    Kitov, Ivan O.

    2005-01-01

    Real GDP growth rate in developed countries is found to be a sum of two terms. The first term is the reciprocal value of the duration of the period of mean income growth with work experience, Tcr. The current value of Tcr in the USA is 40 years. The second term is inherently related to population and defined by the relative change in the number of people with a specific age (9 years in the USA), (1/2)*dN9(t) /N9(t), where N9(t) is the number of 9-year-olds at time t. The Tcr grows as the squa...

  10. Growth rate for blackhole instabilities

    Science.gov (United States)

    Prabhu, Kartik; Wald, Robert

    2015-04-01

    Hollands and Wald showed that dynamic stability of stationary axisymmetric black holes is equivalent to positivity of canonical energy on a space of linearised axisymmetric perturbations satisfying certain boundary and gauge conditions. Using a reflection isometry of the background, we split the energy into kinetic and potential parts. We show that the kinetic energy is positive. In the case that potential energy is negative, we show existence of exponentially growing perturbations and further obtain a variational formula for the growth rate.

  11. Metal loss growth rate distributions

    Energy Technology Data Exchange (ETDEWEB)

    Nicoletti, Erika S.M.; Olivier, Joao H.; Souza, Ricardo D. de; Addor, Pedro N. [PETROBRAS Transporte S.A. (TRANSPETRO), Rio de Janeiro, RJ (Brazil)

    2009-12-19

    Significant efforts have been dedicated in recent decades to the development of damage tolerance criteria and ILI tool technology and, by combining both, operators can nowadays determine their system's integrity condition at the time of inspection with considerable accuracy. However, to accomplish proper integrity management it is also necessary to estimate the damage progression over time. As corrosion is one of the most time-dependent threats to pipeline integrity, aging systems' operational reliability and cost-effectiveness mostly rely on the accuracy of their corrosion growth-rate estimations. The diversity of mechanisms acting concomitantly along a single pipeline, and the inherent stochastic nature of the corrosion process makes its mechanistic modeling a complex task. This paper introduces the use of exploratory statistical analysis combined with segmentation strategies to produce representative corrosion rates of metal-loss anomaly populations reported by ILI. The procedure could provide input suitable for both deterministic and probabilistic FFP analysis: for the latter, proper computational tools to process best fitting distributions being required. Three case studies, where diverse segmentation principles have been applied, are presented to illustrate methodology application. (author)

  12. Methods of modelling relative growth rate

    Institute of Scientific and Technical Information of China (English)

    Arne Pommerening; Anders Muszta

    2015-01-01

    Background:Analysing and modelling plant growth is an important interdisciplinary field of plant science. The use of relative growth rates, involving the analysis of plant growth relative to plant size, has more or less independently emerged in different research groups and at different times and has provided powerful tools for assessing the growth performance and growth efficiency of plants and plant populations. In this paper, we explore how these isolated methods can be combined to form a consistent methodology for modelling relative growth rates. Methods:We review and combine existing methods of analysing and modelling relative growth rates and apply a combination of methods to Sitka spruce (Picea sitchensis (Bong.) Carr.) stem-analysis data from North Wales (UK) and British Douglas fir (Pseudotsuga menziesi (Mirb.) Franco) yield table data. Results:The results indicate that, by combining the approaches of different plant-growth analysis laboratories and using them simultaneously, we can advance and standardise the concept of relative plant growth. Particularly the growth multiplier plays an important role in modelling relative growth rates. Another useful technique has been the recent introduction of size-standardised relative growth rates. Conclusions:Modelling relative growth rates mainly serves two purposes, 1) an improved analysis of growth performance and efficiency and 2) the prediction of future or past growth rates. This makes the concept of relative growth ideally suited to growth reconstruction as required in dendrochronology, climate change and forest decline research and for interdisciplinary research projects beyond the realm of plant science.

  13. A novel approach for estimating growth phases and parameters of bacterial population in batch culture

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Using mathematical analysis, a new method has been developed for studying the growth kinetics of bacterial populations in batch culture. First, sampling data were smoothed with the spline interpolation method. Second, the instantaneous rates were derived by numerical differential techniques and finally, the derived data were fitted with the Gaussian function to obtain growth parameters. We named this the Spline-Numerical-Gaussian or SNG method. This method yielded more accurate estimates of the growth rates of bacterial populations and new parameters. It was possible to divide the growth curve into four different but continuous phases based on changes in the instantaneous rates. The four phases are the accelerating growth phase, the constant growth phase, the decelerating growth phase and the declining phase. Total DNA content was measured by flow cytometry and varied depending on the growth phase. The SNG system provides a very powerful tool for describing the kinetics of bacterial population growth. The SNG method avoids the unrealistic assumptions generally used in the traditional growth equations.

  14. The evolution of growth trajectories: what limits growth rate?

    Science.gov (United States)

    Dmitriew, Caitlin M

    2011-02-01

    According to life-history theory, growth rates are subject to strong directional selection due to reproductive and survival advantages associated with large adult body size. Yet, growth is commonly observed to occur at rates lower than the maximum that is physiologically possible and intrinsic growth rates often vary among populations. This implies that slower growth is favoured under certain conditions. Realized growth rate is thus the result of a compromise between the costs and advantages of growing rapidly, and the optimal rate of growth is not equivalent to the fundamental maximum rate. The ecological and evolutionary factors influencing growth rate are reviewed, with particular emphasis on how growth might be constrained by direct fitness costs. Costs of accelerating growth might contribute to the variance in fitness that is not attributable to age or size at maturity, as well as to the variation in life-history strategies observed within and among species. Two main approaches have been taken to study the fitness trade-offs relating to growth rate. First, environmental manipulations can be used to produce treatment groups with different rates of growth. Second, common garden experiments can be used to compare fitness correlates among populations with different intrinsic growth rates. Data from these studies reveal a number of potential costs for growth over both the short and long term. In order to acquire the energy needed for faster growth, animals must increase food intake. Accordingly, in many taxa, the major constraint on growth rate appears to arise from the trade-off between predation risk and foraging effort. However, growth rates are also frequently observed to be submaximal in the absence of predation, suggesting that growth trajectories also impact fitness via other channels, such as the reallocation of finite resources between growth and other traits and functions. Despite the prevalence of submaximal growth, even when predators are absent, there

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

    Science.gov (United States)

    Lambert, Guillaume; Kussell, Edo

    2013-03-01

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

  16. Evolution of bacterial and fungal growth media

    OpenAIRE

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

    2015-01-01

    Microbial media has undergone several changes since its inception but some key challenges remain. In recent years, there has been exploration of several alternative nutrient sources, both to cater to the specificity in requirement of growth of “fussy microorganisms” and also to reduce costs for large-scale fermentation that is required for biotechnology. Our mini-review explores these developments and also points at lacunas in the present areas of exploration, such as a lack of concerted effo...

  17. Morphomechanics of bacterial biofilms undergoing anisotropic differential growth

    Science.gov (United States)

    Zhang, Cheng; Li, Bo; Huang, Xiao; Ni, Yong; Feng, Xi-Qiao

    2016-10-01

    Growing bacterial biofilms exhibit a number of surface morphologies, e.g., concentric wrinkles, radial ridges, and labyrinthine networks, depending on their physiological status and nutrient access. We explore the mechanisms underlying the emergence of these greatly different morphologies. Ginzburg-Landau kinetic method and Fourier spectral method are integrated to simulate the morphological evolution of bacterial biofilms. It is shown that the morphological instability of biofilms is triggered by the stresses induced by anisotropic and heterogeneous bacterial expansion, and involves the competition between membrane energy and bending energy. Local interfacial delamination further enriches the morphologies of biofilms. Phase diagrams are established to reveal how the anisotropy and spatial heterogeneity of growth modulate the surface patterns. The mechanics of three-dimensional microbial morphogenesis may also underpin self-organization in other development systems and provide a potential strategy for engineering microscopic structures from bacterial aggregates.

  18. Methods of modelling relative growth rate

    OpenAIRE

    Arne Pommerening; Anders Muszta

    2015-01-01

    Background Analysing and modelling plant growth is an important interdisciplinary field of plant science. The use of relative growth rates, involving the analysis of plant growth relative to plant size, has more or less independently emerged in different research groups and at different times and has provided powerful tools for assessing the growth performance and growth efficiency of plants and plant populations. In this paper, we explore how these isolated methods can be combined to form...

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

    Institute of Scientific and Technical Information of China (English)

    刘实

    1999-01-01

    By increasing viscosity of liquid media above 8.4 centipoise (cp) i.e. 0.084 g·cm-1·S-1 individual growth and family formation of Escherichia coli was continuously observed in real-time for up to 6 h. The observations showed primarily unidirectional growth and reproduction of E. coli and suggested more than one reproduction in the observed portion of E. coli life span. A new bacterial life model is proposed: each bacterium has a stable cell polarity that ultimately transforms into two bacteria of different generations; the life cycle of a bacterium can contain more than one reproduction cycle; and the age of a bacterium should be defined by its experienced chronological time. This new bacterial life model differs from the dominant concepts of bacterial life but complies with all basic life principles based on direct observation of macroorganisms.

  20. Effect of topical and systemic antibiotics on bacterial growth kinesis in generalized peritonitis in man.

    Science.gov (United States)

    Krukowski, Z H; Al-Sayer, H M; Reid, T M; Matheson, N A

    1987-04-01

    Quantitative bacteriology in peritoneal exudate was studied in 40 patients with generalized peritonitis of small intestinal, appendicular or colonic origin. Bacterial growth kinesis was measured in 28 of the patients. Systemic antibiotics given before operation resulted in a significant reduction in both the concentration and growth rate of viable bacteria in the peritoneal fluid. Lavage of the peritoneal cavity with saline resulted in a further reduction in growth rate in patients given pre-operative systemic antibiotics by an effect attributable to simple dilution. In contrast, peritoneal lavage with tetracycline (1 mg/ml) resulted in complete inhibition of bacterial growth in the residual peritoneal fluid. These observations support the policy of giving systemic antibiotics to patients with generalized peritonitis as soon as the diagnosis has been made and provide bacteriological evidence for the value of peroperative antibiotic peritoneal lavage.

  1. Measurements of Protein Crystal Face Growth Rates

    Science.gov (United States)

    Gorti, S.

    2014-01-01

    Protein crystal growth rates will be determined for several hyperthermophile proteins.; The growth rates will be assessed using available theoretical models, including kinetic roughening.; If/when kinetic roughening supersaturations are established, determinations of protein crystal quality over a range of supersaturations will also be assessed.; The results of our ground based effort may well address the existence of a correlation between fundamental growth mechanisms and protein crystal quality.

  2. Growth Rates of Microbes in the Oceans

    Science.gov (United States)

    Kirchman, David L.

    2016-01-01

    A microbe's growth rate helps to set its ecological success and its contribution to food web dynamics and biogeochemical processes. Growth rates at the community level are constrained by biomass and trophic interactions among bacteria, phytoplankton, and their grazers. Phytoplankton growth rates are approximately 1 d-1, whereas most heterotrophic bacteria grow slowly, close to 0.1 d-1; only a few taxa can grow ten times as fast. Data from 16S rRNA and other approaches are used to speculate about the growth rate and the life history strategy of SAR11, the most abundant clade of heterotrophic bacteria in the oceans. These strategies are also explored using genomic data. Although the methods and data are imperfect, the available data can be used to set limits on growth rates and thus on the timescale for changes in the composition and structure of microbial communities.

  3. Role of Rate of Specific Growth Rate in Different Growth Processes: A First Principle Approach

    CERN Document Server

    Biswas, Dibyendu; Patra, Sankar Nayaran

    2015-01-01

    In the present communication, effort is given for the development of a common platform that helps to address several growth processes found in literature. Based on first principle approach, the role of rate of specific growth rate in different growth processes has been considered in an unified manner. It is found that different growth equations can be derived from the same rate equation of specific growth rate. The dependence of growth features of different growth processes on the parameters of the rate equation of specific growth rate has been examined in detail. It is found that competitive environment may increase the saturation level of population size. The exponential growth could also be addressed in terms of two important factors of growth dynamics, as reproduction and competition. These features are, most probably, not reported earlier.

  4. Export growth, economic growth and real exchange rate in Indonesia

    OpenAIRE

    Wing-Keung Lo, K.

    2000-01-01

    The thesis studies the export growth, economic growth and real exchange rate in Indonesia. The research is a piece of empirical studies mainly covering the period from 1974 to 1993. Indonesia is an oil-exporting country. Economic recession with high inflation rate in the early eighties prompted the government to undertake a series of economic and financial reforms. It was believed that oil export earnings by itself could not sustain long-term economic growth. Trade reform and devaluation woul...

  5. Incubation Station for the Bacterial Growth Study in Biological Samples

    OpenAIRE

    Carlos Rafael Duharte Rodríguez; Ibrain Ceballo Acosta; Carmen B. Busoch Morlán; Ángel Regueiro Gómez

    2015-01-01

    This work shows the designing and characterization of a prototype of laboratory incubator as support of Microbiology research, in particular for the research of the bacterial growth in biological samples through optic methods (Turbidimetry) and electrometric measurements of bioimpedance. It shows the results of simulation and experimentation of the design proposed for the canals of measurement of the variables: temperature and humidity, with a high linearity from the adequate selection of the...

  6. Beyond growth: novel functions for bacterial cell wall hydrolases.

    Science.gov (United States)

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

    2012-11-01

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

  7. Thermodynamics of Growth, Non-Equilibrium Thermodynamics of Bacterial Growth : The Phenomenological and the Mosaic Approach

    NARCIS (Netherlands)

    Westerhoff, Hans V.; Lolkema, Juke S.; Otto, Roel; Hellingwerf, K

    1982-01-01

    Microbial growth is analyzed in terms of mosaic and phenomenological non-equilibrium thermodynamics. It turns out that already existing parameters devised to measure bacterial growth, such as YATP, µ, and Qsubstrate, have as thermodynamic equivalents flow ratio, output flow and input flow. With this

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

    Science.gov (United States)

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

    2011-03-01

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

  9. Experimental Results and Integrated Modeling of Bacterial Growth on an Insoluble Hydrophobic Substrate (Phenanthrene)

    DEFF Research Database (Denmark)

    Adam, Iris K. U.; Rein, Arno; Miltner, Anja;

    2014-01-01

    Metabolism of a low-solubility substrate is limited by dissolution and availability and can hardly be determined. We developed a numerical model for simultaneously calculating dissolution kinetics of such substrates and their metabolism and microbial growth (Monod kinetics with decay) and tested...... was fitted to the test results for the rates of dissolution, metabolism, and growth. The strains showed similar efficiency, with v(max) values of 12-18 g dw g(-1) d(-1), yields of 0.21 g g(-1), maximum growth rates of 2.5-3.8 d(-1), and decay rates of 0.04-0.05 d(-1). Sensitivity analysis with the model...... shows that (i) retention in crystals or NAPLs or by sequestration competes with biodegradation, (ii) bacterial growth conditions (dissolution flux and resulting chemical activity of substrate) are more relevant for the final state of the system than the initial biomass, and (iii) the desorption flux...

  10. Analysis of a stochastic model for bacterial growth and the lognormality in the cell-size distribution

    CERN Document Server

    Yamamoto, Ken

    2016-01-01

    This paper theoretically analyzes a phenomenological stochastic model for bacterial growth. This model comprises cell divisions and linear growth of cells, where growth rates and cell cycles are drawn from lognormal distributions. We derive that the cell size is expressed as a sum of independent lognormal variables. We show numerically that the quality of the lognormal approximation greatly depends on the distributions of the growth rate and cell cycle. Furthermore, we show that actual parameters of the growth rate and cell cycle take values which give good lognormal approximation, so the experimental cell-size distribution is in good agreement with a lognormal distribution.

  11. Analysis of a Stochastic Model for Bacterial Growth and the Lognormality of the Cell-Size Distribution

    Science.gov (United States)

    Yamamoto, Ken; Wakita, Jun-ichi

    2016-07-01

    This paper theoretically analyzes a phenomenological stochastic model for bacterial growth. This model comprises cell division and the linear growth of cells, where growth rates and cell cycles are drawn from lognormal distributions. We find that the cell size is expressed as a sum of independent lognormal variables. We show numerically that the quality of the lognormal approximation greatly depends on the distributions of the growth rate and cell cycle. Furthermore, we show that actual parameters of the growth rate and cell cycle take values that give a good lognormal approximation; thus, the experimental cell-size distribution is in good agreement with a lognormal distribution.

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

    Directory of Open Access Journals (Sweden)

    Katherine C Goldfarb

    2011-05-01

    Full Text Available 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, Enterobacterales, 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 8 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-04-18

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

  14. Incubation Station for the Bacterial Growth Study in Biological Samples

    Directory of Open Access Journals (Sweden)

    Carlos Rafael Duharte Rodríguez

    2015-12-01

    Full Text Available This work shows the designing and characterization of a prototype of laboratory incubator as support of Microbiology research, in particular for the research of the bacterial growth in biological samples through optic methods (Turbidimetry and electrometric measurements of bioimpedance. It shows the results of simulation and experimentation of the design proposed for the canals of measurement of the variables: temperature and humidity, with a high linearity from the adequate selection of the corresponding sensors and the analogue components of every canal, controlled with help of a microcontroller AT89C51 (ATMEL with adequate benefi ts for this type of application.

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

    Science.gov (United States)

    Ursell, Tristan

    2012-02-01

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

  16. Bacterial growth efficiency in a tropical estuary: Seasonal variability subsidized by allochthonous carbon

    Digital Repository Service at National Institute of Oceanography (India)

    Ram, A.S.P.; Nair, S.; Chandramohan, D.

    Bacterial growth efficiency (BGE) is a key factor in understanding bacterial influence on carbon flow in aquatic ecosystems. Intra-annual variability in BGE, and bacteria-mediated carbon flow in the tropical Mandovi and Zuari estuaries (southwest...

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

    Science.gov (United States)

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

    2009-04-01

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

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

    NARCIS (Netherlands)

    S. Zindel (Stephan); W.E. Kaman (Wendy); S. Fröls (Sabrina); F. Pfeifer (Felicitas); A. Peters (Annette); J.P. Hays (John); H.-L. Fuchsbauer (Hans-Lothar)

    2013-01-01

    textabstractA 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 ant

  19. Changes in urine composition after trauma facilitate bacterial growth

    Directory of Open Access Journals (Sweden)

    Aubron Cecile

    2012-11-01

    Full Text Available Abstract 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.

  20. An integral parametrization of the bacterial growth curve experimental demonstration with E. coli C600 bacteria

    International Nuclear Information System (INIS)

    In this work an integral parametrization of the bacterial growth curve is presented. The values of the parameters are obtained by fitting to the experimental data. Those parameters, with allow to describe the growth in its different phases, are the followings: slopes of the curve in its three parts and the time which divides the last two phases of the bacterial growth. The experimental data are bacterial densities measured by optical methods. The bacteria used was the E. coli C600. (Author)

  1. Effects of low-level deuterium enrichment on bacterial growth.

    Directory of Open Access Journals (Sweden)

    Xueshu Xie

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

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

    DEFF Research Database (Denmark)

    Hasman, Henrik; Bjerrum, Morten J.; Christiansen, Lasse Engbo;

    2009-01-01

    In this paper we examine how the bacterial growth is influenced by the availability of copper ions in complex Mueller Hinton growth media. The data shows that the free copper concentration is seven to eight orders of magnitude lower the total copper concentration and that there seems to be a bett...... is to be recommended, when working with bacterial copper testing....

  3. China's fertility drop lowers world growth rate.

    Science.gov (United States)

    Haub, C

    1993-06-01

    China practices a stringent and compulsory program of family planning and population control. This approach has, however, served to increase the number of domestic IUD insertions and sterilizations. Contraceptive prevalence has reached 83% and total fertility (TFR) is estimated to be 1.9. This Chinese accomplishment has helped reduce TFR for all East Asia to 1.8, which is lower than that for northern Europe, and bring the world population growth rate down from the 1992 level of 1.68% to 1.63%. This latter rate is reported in the 1993 Population Reference Bureau's (PRB) World Population Data Sheet and is the lowest world population growth rate since PRB's first annual edition in 1962. Despite these reductions, world population still grows by 90 million annually. No one can say for sure whether or not observed fertility decline in China is permanent. China's birth rate rose twice in the 1980s and it could certainly rebound once again. A popular backlash to population policy or a relaxing of policy due to international pressure to reduce the level of compulsion in the program are 2 factors which might increase overall fertility and population growth. Fertility is also declining in subSaharan Africa, but not universally. Birth rates are rapidly declining in eastern Europe and the former USSR as economic conditions and outlooks pale. The populations of Estonia, Latvia, Ukraine, and possible Russia are even declining, while only mixed data are available from Yugoslavia. New statistical publications reflect changing borders. Finally, while Slovakia is the only country added to this year's sheet, Eritrea and the Channel Islands will likely be included in next year's.

  4. Species Diversity Enhances Predator Growth Rates

    Directory of Open Access Journals (Sweden)

    Mark H. Olson

    2007-01-01

    Full Text Available Predators can be important top-down regulators of community structure and are known to have both positive and negative effects on species diversity. However, little is known about the reciprocal effects of species diversity on predators. Across a set of 80 lakes in Connecticut, USA, we found a strong positive correlation between prey species diversity (using the Shannon-Weiner Diversity Index and growth rates of largemouth bass (Micropterus salmoides. This correlation was strongest for small predators and decreased with body size. Although the underlying mechanisms are not known, the correlation is not driven by total fish abundance, predator abundance, or productivity.

  5. Impact of ZnO and Ag Nanoparticles on Bacterial Growth and Viability

    Science.gov (United States)

    Olson, M. S.; Digiovanni, K. A.

    2007-12-01

    Hundreds of consumer products containing nanomaterials are currently available in the U.S., including computers, clothing, cosmetics, sports equipment, medical devices and product packaging. Metallic nanoparticles can be embedded in or coated on product surfaces to provide antimicrobial, deodorizing, and stain- resistant properties. Although these products have the potential to provide significant benefit to the user, the impact of these products on the environment remains largely unknown. The purpose of this project is to study the effect of metallic nanoparticles released to the environment on bacterial growth and viability. Inhibition of bacterial growth was tested by adding doses of suspended ZnO and Ag nanoparticles into luria broth prior to inoculation of Escherichia coli cells. ZnO particles (approximately 40 nm) were obtained commercially and Ag particles (12-14 nm) were fabricated by reduction of silver nitrate with sodium borohydride. Toxicity assays were performed to test the viability of E. coli cells exposed to both ZnO and Ag nanoparticles using the LIVE/DEAD BacLight bacterial viability kit (Invitrogen). Live cells stain green whereas cells with compromised membranes that are considered dead or dying stain red. Cells were first grown, stained, and exposed to varying doses of metallic nanoparticles, and then bacterial viability was measured hourly using fluorescence microscopy. Results indicate that both ZnO and Ag nanoparticles inhibit the growth of E. coli in liquid media. Preliminary results from toxicity assays confirm the toxic effect of ZnO and Ag nanoparticles on active cell cultures. Calculated death rates resulting from analyses of toxicity studies will be presented.

  6. Effect of crushed mussel shell addition on bacterial growth in acid polluted soils

    DEFF Research Database (Denmark)

    Fernandez Calviño, David; Garrido-Rodríguez, B.; Arias-Estévez, M.;

    2015-01-01

    We applied three different doses of crushed mussel shell (CMS) on two Cu-polluted acid soils to study the effect of these amendments on the growth of the bacterial community during 730 days. Soil pH increased in the short and medium term due to CMS addition. In a first stage, bacterial growth...

  7. Bacterial Community Dynamics and Biodegradation Rates in Untreated and Oily Soils During PAH Exposure

    International Nuclear Information System (INIS)

    The approach taken in this study represents an attempt to address the possible selective effects of Polycyclic aromatic hydrocarbons (PAH) on the bacterial community structure of an untreated garden soil (S) and a chronically contaminated oily soil (CS). Untreated and chronically hydrocarbon polluted soils, collected from Egypt were enriched in shaking flasks containing 50 mg/l anthracene as a sole source of carbon over a period of 15 days. Bacterial communities in each soil were profiled by denaturing gradient gel electrophoresis (DGGE) analysis of the PCR amplified 16 S r DNA gene fragments after 0, 5, 10, and 15 days. Culture able biodegrading bacterial counts on minerals- Silica gel- Oil (MSD) plates as well as anthracene degradation for both soils were followed up at the same time intervals. Nine bacterial species were found to be dominant in the pristine soil before enrichment with the model polycyclic aromatic hydrocarbon (PAH), eight of them disappeared after live days of enrichment with the domination of one new species. It stayed dominant in soil until 15 days - exposure to anthracene. Therefore it can be used as a bio marker for PAH pollution. The chronically contaminated soil revealed a remarkable increase in the diversity directly after 5 days exposure to PAH HPLC analysis of the extracted anthracene remained in the biodegradation flasks after different degradation periods revealed that a higher biodegradation rates were accomplished by the oily soil consortium rather than by the pristine one. Before exposure to PAH, counts of culture able biodegrading bacteria were found to be higher in the untreated soil rather than in the oily one. After exposure the situation has been a bit altered as the counts in the untreated soil revealed a temporary suppression with a prolongation of the time required for growth as a result of the hydrocarbon stress

  8. Factors Affecting Bacterial Growth in Drinking Water Distribution System

    Institute of Scientific and Technical Information of China (English)

    WEI LU; XIAO-JIAN ZHANG

    2005-01-01

    Objective To define the influence of some parameters, including assimilable organic carbon (AOC), chloramine residual, etc. on the bacterial growth in drinking water distribution systems. Methods Three typical water treatment plants in a northern city (City T) of China and their corresponding distribution systems were investigated. Some parameters of the water samples, such as heterotrophic plate content (HPC), AOC, CODMn, TOC, and phosphate were measured. Results The AOC in most water samples were more than 100 μg/L, or even more than 200 μg/L in some cases. The HPC in distribution systems increased significantly with the decrease of residual chlorine. When the residual chlorine was less than 0.1 mg/L, the magnitude order of HPC was 104 CFU/mL; when it was 0.5-0.7 mg/L, the HPC was about 500 CFU/mL. Conclusion For controlling the biostability of drinking water, the controlling of AOC and residual chlorine should be considered simultaneously. The influence of phosphors on the AOC tests of water is not significant. Phosphors may not be the limiting nutrient in the water distribution systems.

  9. Bacterial growth on chitosan-coated polypropylene textile.

    Science.gov (United States)

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

    2012-01-01

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

  10. Modeling of Scale-Dependent Bacterial Growth by Chemical Kinetics Approach

    Directory of Open Access Journals (Sweden)

    Haydee Martínez

    2014-01-01

    Full Text Available We applied the so-called chemical kinetics approach to complex bacterial growth patterns that were dependent on the liquid-surface-area-to-volume ratio (SA/V of the bacterial cultures. The kinetic modeling was based on current experimental knowledge in terms of autocatalytic bacterial growth, its inhibition by the metabolite CO2, and the relief of inhibition through the physical escape of the inhibitor. The model quantitatively reproduces kinetic data of SA/V-dependent bacterial growth and can discriminate between differences in the growth dynamics of enteropathogenic E. coli, E. coli  JM83, and Salmonella typhimurium on one hand and Vibrio cholerae on the other hand. Furthermore, the data fitting procedures allowed predictions about the velocities of the involved key processes and the potential behavior in an open-flow bacterial chemostat, revealing an oscillatory approach to the stationary states.

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

    Science.gov (United States)

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

    2014-11-01

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

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

    Science.gov (United States)

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

    2014-11-01

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

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

    Directory of Open Access Journals (Sweden)

    Minna Pekkonen

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

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

    Science.gov (United States)

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

    2012-08-01

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

  15. Bacterial Growth in Amniotic Fluid Is Dependent on the Iron-Availability and the Activity of Bacterial Iron-Uptake System

    OpenAIRE

    Ahn, Young-Joon; Park, Sang-Kee; Oh, Jae-Wook; Sun, Hui-Yu; Shin, Sung-Heui

    2004-01-01

    In the present study, the relationship among iron-availability, antibacterial activity, role of meconium as an iron source and the activity of bacterial iron-uptake system (IUS) for bacterial growth in amniotic fluid (AF) were investigated. Staphylococcus aureus ATCC 6538 and its streptonigrin-resistant (SR) mutant with defective IUS were used as the test strains. The growth of S. aureus in AF was stimulated dosedependently by addition of meconium. Bacterial growth stimulated by meconium was ...

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

    Directory of Open Access Journals (Sweden)

    Vázquez José

    2011-11-01

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

  17. Effect of Vibration on Bacterial Growth and Antibiotic Resistance

    Science.gov (United States)

    Juergensmeyer, Elizabeth A.; Juergensmeyer, Margaret A.

    2004-01-01

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

  18. Bacterial growth efficiency in the tropical estuarine and coastal waters of Goa, southwest coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Ram, A.; Nair, S.; Chandramohan, D.

    Bacterial growth efficiency (BGE) is an index of organic carbon passing through bacteria in an aquatic system. BGE values of natural bacterioplankton assemblages were measured in tropical estuarine and adjacent coastal waters in Goa along...

  19. Fructose-enhanced reduction of bacterial growth on nanorough surfaces

    Directory of Open Access Journals (Sweden)

    Durmus NG

    2012-02-01

    Full Text Available Naside Gozde Durmus1, Erik N Taylor1, Fatih Inci3,4, Kim M Kummer1, Keiko M Tarquinio5, Thomas J Webster1,21School of Engineering, Brown University, Providence, RI, USA; 2Department of Orthopedics, Brown University, Providence, RI, USA; 3Bio-Acoustic-MEMS in Medicine (BAMM Laboratory, Center for Biomedical Engineering, Department of Medicine, Brigham and Women's Hospital, Harvard-MIT Health Sciences and Technology, Harvard Medical School, MA, USA; 4Istanbul Technical University, Molecular Biology-Genetics and Biotechnology Program, Mobgam, Maslak, Istanbul, Turkey; 5Division of Pediatric Critical Care Medicine, Rhode Island Hospital, Providence, RI, USAAbstract: Patients on mechanical ventilators for extended periods of time often face the risk of developing ventilator-associated pneumonia. During the ventilation process, patients incapable of breathing are intubated with polyvinyl chloride (PVC endotracheal tubes (ETTs. PVC ETTs provide surfaces where bacteria can attach and proliferate from the contaminated oropharyngeal space to the sterile bronchoalveolar area. To overcome this problem, ETTs can be coated with antimicrobial agents. However, such coatings may easily delaminate during use. Recently, it has been shown that changes in material topography at the nanometer level can provide antibacterial properties. In addition, some metabolites, such as fructose, have been found to increase the efficiency of antibiotics used to treat Staphylococcus aureus (S. aureus infections. In this study, we combined the antibacterial effect of nanorough ETT topographies with sugar metabolites to decrease bacterial growth and biofilm formation on ETTs. We present for the first time that the presence of fructose on the nanorough surfaces decreases the number of planktonic S. aureus bacteria in the solution and biofilm formation on the surface after 24 hours. We thus envision that this method has the potential to impact the future of surface engineering of

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

    Energy Technology Data Exchange (ETDEWEB)

    Hobbs, D.

    2011-01-19

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

  1. Bacterial strains from floodplain soils perform different plant-growth promoting processes and enhance cowpea growth

    Directory of Open Access Journals (Sweden)

    Elaine Martins da Costa

    2016-08-01

    Full Text Available ABSTRACT Certain nodulating nitrogen-fixing bacteria in legumes and other nodule endophytes perform different plant-growth promoting processes. The objective of this study was to evaluate 26 bacterial strains isolated from cowpea nodules grown in floodplain soils in the Brazilian savannas, regarding performance of plant-growth promoting processes and ability to enhance cowpea growth. We also identified these strains by 16S rRNA sequencing. The following processes were evaluated: free-living biological nitrogen fixation (BNF, solubilization of calcium, aluminum and iron phosphates and production of indole-3-acetic acid (IAA. The abilities to nodulate and promote cowpea growth were evaluated in Leonard jars. Partial sequencing of the 16S rRNA gene identified 60 % of the strains as belonging to genus Paenibacillus. The following four genera were also identified: Bacillus, Bradyrhizobium, Enterobacter and Pseudomonas. None of the strains fixed N2 free-living. Among the strains, 80 % solubilized Ca phosphate and one solubilized Al phosphate and none solubilized Fe phosphate. The highest IAA concentrations (52.37, 51.52 and 51.00 μg mL−1 were obtained in the 79 medium with tryptophan by Enterobacter strains UFPI B5-7A, UFPI B5-4 and UFPI B5-6, respectively. Only eight strains nodulated cowpea, however, all increased production of total dry matter. The fact that the strains evaluated perform different biological processes to promote plant growth indicates that these strains have potential use in agricultural crops to increase production and environmental sustainability.

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

    Science.gov (United States)

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

    2015-11-01

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

  3. Estimation of alga growth stage and lipid content growth rate

    Science.gov (United States)

    Embaye, Tsegereda N. (Inventor); Trent, Jonathan D. (Inventor)

    2012-01-01

    Method and system for estimating a growth stage of an alga in an ambient fluid. Measured light beam absorption or reflection values through or from the alga and through an ambient fluid, in each of two or more wavelength sub-ranges, are compared with reference light beam absorption values for corresponding wavelength sub-ranges for in each alga growth stage to determine (1) which alga growth stage, if any, is more likely and (2) whether estimated lipid content of the alga is increasing or has peaked. Alga growth is preferably terminated when lipid content has approximately reached a maximum value.

  4. Sweat secretion rates in growth hormone disorders

    DEFF Research Database (Denmark)

    Sneppen, S B; Main, K M; Juul, A;

    2000-01-01

    While increased sweating is a prominent symptom in patients with active acromegaly, reduced sweating is gaining status as part of the growth hormone deficiency (GHD) syndrome.......While increased sweating is a prominent symptom in patients with active acromegaly, reduced sweating is gaining status as part of the growth hormone deficiency (GHD) syndrome....

  5. EBSP studies of growth rates during recrystallization

    DEFF Research Database (Denmark)

    Juul Jensen, D.

    1996-01-01

    The use of the electron back scattering pattern (EBSP) technique to study effects of crystallographic orientation on growth is reviewed. The experimental set-up and data handling procedures are shortly introduced and two different approaches to study orientation effects on growth are described. T...

  6. Concurrent growth rate and transcript analyses reveal essential gene stringency in Escherichia coli.

    Directory of Open Access Journals (Sweden)

    Shan Goh

    Full Text Available BACKGROUND: Genes essential for bacterial growth are of particular scientific interest. Many putative essential genes have been identified or predicted in several species, however, little is known about gene expression requirement stringency, which may be an important aspect of bacterial physiology and likely a determining factor in drug target development. METHODOLOGY/PRINCIPAL FINDINGS: Working from the premise that essential genes differ in absolute requirement for growth, we describe silencing of putative essential genes in E. coli to obtain a titration of declining growth rates and transcript levels by using antisense peptide nucleic acids (PNA and expressed antisense RNA. The relationship between mRNA decline and growth rate decline reflects the degree of essentiality, or stringency, of an essential gene, which is here defined by the minimum transcript level for a 50% reduction in growth rate (MTL(50. When applied to four growth essential genes, both RNA silencing methods resulted in MTL(50 values that reveal acpP as the most stringently required of the four genes examined, with ftsZ the next most stringently required. The established antibacterial targets murA and fabI were less stringently required. CONCLUSIONS: RNA silencing can reveal stringent requirements for gene expression with respect to growth. This method may be used to validate existing essential genes and to quantify drug target requirement.

  7. Mechanisms and rates of bacterial colonization of sinking aggregates

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Grossart, H.P.; Ploug, H.;

    2002-01-01

    (0 to 2 s(-1)). The rates at which these bacteria colonized artificial aggregates (stationary and sinking) largely agreed with model predictions. We report several findings. (i) Motile bacteria rapidly colonize aggregates, whereas nonmotile bacteria do not. 00 Flow enhances colonization rates. (iii...... frequency, and turn angles) and the hydrodynamic environment (stationary versus sinking aggregates). We then experimentally tested the models with 10 strains of bacteria isolated from marine particles: two strains were nonmotile; the rest were swimming at 20 to 60 mum s(-1) with different tumbling frequency...

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

    OpenAIRE

    Zindel, S.; Kaman, W.E.; Frols, S.; Pfeifer, F; Peters, A.; Hays, J.P.; Fuchsbauer, H.-L.

    2013-01-01

    A novel papain inhibitory protein (SPI) from Streptomyces mobaraensis was studied to measure its inhibitory effect on bacterial cysteine protease activity (Staphylococcus aureus SspB) and culture supernatants (Porphyromonas gingivalis, Bacillus anthracis). Further, growth of Bacillus anthracis, Staphylococcus aureus, Pseudomonas aeruginosa, and Vibrio cholerae was completely inhibited by 10 μM SPI. At this concentration of SPI, no cytotoxicity was observed. We conclude that SPI inhibits bacte...

  9. Bacterial Growth on Photochemically Transformed Leachates from Aquatic and Terrestrial Primary Producers

    DEFF Research Database (Denmark)

    Anesio, A.M.; Nielsen, Jon Theil; Granéli, W.

    2000-01-01

    We measured bacterial growth on phototransformed dissolved organic matter (DOM) leached from eight different primary producers. Leachates (10 mg C liter-1) were exposed to artificial UVA + UVB radiation, or kept in darkness, for 20 h. DOM solutions were subsequently inoculated with lake water...... leachate and type of bacterial growth criterion. Bacterial carbon utilization (biomass production plus respiration) over the entire incubation period (120 h) was enhanced by UV radiation of leachate from the terrestrial leaves, relative to carbon utilization in non-irradiated leachates. Conversely, carbon...... utilization was reduced by radiation of the leachates from aquatic macrophytes. In a separate experiment, the stable C and N isotope composition of bacteria grown on irradiated and non-irradiated DOM was estimated. Bacterial growth on UV-irradiated DOM was enriched in 13C relative to the bacteria in the non...

  10. Bacterial cell curvature through mechanical control of cell growth

    DEFF Research Database (Denmark)

    Cabeen, M.; Charbon, Godefroid; Vollmer, W.;

    2009-01-01

    The cytoskeleton is a key regulator of cell morphogenesis. Crescentin, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus and localizes to the inner cell curvature. Here, we show that crescentin forms a single filamentous structure...

  11. The bacterial contamination rate of glucose meter test strips in the hospital setting

    Science.gov (United States)

    Al-Rubeaan, Khalid A.; Saeb, Amr T. M.; AlNaqeb, Dhekra M.; AlQumaidi, Hamed M.; AlMogbel, Turki A.

    2016-01-01

    Objectives: To assess the rate of bacterial contamination of the multi-use vial and single-use packed glucose meter strips, and to identify the type and frequency of various bacterial contamination in different hospital wards. Methods: This prospective observational study was conducted by a team from the Strategic Center for Diabetes Research in 7 general hospitals in the Central region of Saudi Arabia during the period from August to September 2014 to assess the bacterial contamination rate of the unused strips. A total of 10,447 strips were cultured using proper agar media and incubated both aerobically and anaerobically. Results: The total bacterial contamination rate for the multi-use vials glucose strips was 31.7%, while single-use packed strips were not contaminated at all. Ministry of Health hospitals had the highest contamination rates compared with other hospitals. Critical, obstetric, and surgical wards had the highest bacterial isolates number, where most were in the risk group 3 according to the National Institute of Health guidelines. Staphylococcus species were the most common bacteria found. Conclusion: Glucose meter strips should be recognized as a source of bacterial contamination that could be behind serious hospital acquired infections. The hospital infection control team should adopt proper measures to implement protocols for glucose meter cleaning and glucose strips handling. PMID:27570855

  12. CPI Overruns Deposit Reserve Rate Growth

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ The People's Bank of China has announced its intention to raise the deposit reserve rate again,less than one month after the last rate increase, this means that the deposit reserve rate has increased a total of ten times this year. However, this time the central bank increased the deposit reserve rate by a full 1 percent, a bigger increase than the last nine adjustments of 0.5 percent.

  13. Growth rates and aggregate welfare : an international comparison

    OpenAIRE

    Kakwani, Nanak

    1991-01-01

    This paper explores the relationship between growth rates and changes in welfare, using alternative procedures for measuring growth. The Bank and other organizations often compute growth rates by fitting a least-squares linear trend line to the logarithmic values of economic indicators for a period. This paper questions the use of the least-squares procedure for measuring people's economic welfare over time. Instead, the author develops a conceptual framework for deriving an aggregate growth ...

  14. The effect of temperature and bacterial growth phase on protein extraction by means of electroporation.

    Science.gov (United States)

    Haberl-Meglič, Saša; Levičnik, Eva; Luengo, Elisa; Raso, Javier; Miklavčič, Damijan

    2016-12-01

    Different chemical and physical methods are used for extraction of proteins from bacteria, which are used in variety of fields. But on a large scale, many methods have severe drawbacks. Recently, extraction by means of electroporation showed a great potential to quickly obtain proteins from bacteria. Since many parameters are affecting the yield of extracted proteins, our aim was to investigate the effect of temperature and bacterial growth phase on the yield of extracted proteins. At the same time bacterial viability was tested. Our results showed that the temperature has a great effect on protein extraction, the best temperature post treatment being 4°C. No effect on bacterial viability was observed for all temperatures tested. Also bacterial growth phase did not affect the yield of extracted proteins or bacterial viability. Nevertheless, further experiments may need to be performed to confirm this observation, since only one incubation temperature (4°C) and one incubation time before and after electroporation (0.5 and 1h) were tested for bacterial growth phase. Based on our results we conclude that temperature is a key element for bacterial membrane to stay in a permeabilized state, so more proteins flow out of bacteria into surrounding media. PMID:27561651

  15. Observational tests of Galileon gravity with growth rate

    Science.gov (United States)

    Hirano, Koichi

    2016-10-01

    We compare observational data of growth rate with the prediction by Galileon theory. For the same value of the energy density parameter Ω_{m,0}, the growth rate in Galileon models is enhanced compared with the Λ CDM case, due to the enhancement of Newton's constant. The smaller Ω_{m,0} is, the more suppressed growth rate is. Hence the best fit value of Ω_{m,0} in the Galileon model is 0.16 from only the growth rate data, which is considerably smaller than such value obtained from observations of supernovae Ia, the cosmic microwave background and baryon acoustic oscillations. We also find the upper limit of the Brans-Dicke parameter to be ω < -1000 (1σ ), from the growth rate data. In this paper, specific galileon models are considered, not the entire class. More and better growth rate data are required to distinguish between dark energy and modified gravity.

  16. Dependence of Limited Growth Rate of High-Quality Gem Diamond on Growth Conditions

    Institute of Scientific and Technical Information of China (English)

    TIAN Yu; MA Hong-An; LI Shang-Sheng; XIAO Hong-Yu; ZHANG Ya-Fei; HUANG Guo-Feng; MA Li-Qiu; JIA Xiao-Peng

    2007-01-01

    The growth rate of diamond has been investigated for a long time and researchers have been attempting to enhance the growth rate of high-quality gem diamond infinitely. However, it has been found according to previous research results that the quality of diamond is debased with the increase of growth rate. Thus, under specific conditions, the growth rate of high-quality diamond cannot exceed a limited value that is called the limited growth rate of diamond. We synthesize a series of type Ib gem diamonds by temperature gradient method under high pressure and high temperature (HPHT) using the as-grown {100} face. The dependence of limited growth rate on growth conditions is studied. The results show that the limited growth rate increases when synthetic temperature decreases, also when growth time is prolonged.

  17. Shaping the Growth Behaviour of Bacterial Aggregates in Biofilms

    CERN Document Server

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

    2015-01-01

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

  18. Resistive Wall Growth Rate Measurements in the Fermilab Recycler

    Energy Technology Data Exchange (ETDEWEB)

    Ainsworth, R. [Fermilab; Adamson, P. [Fermilab; Burov, A. [Fermilab; Kourbanis, I. [Fermilab

    2016-10-05

    Impedance could represent a limitation of running high intensity beams in the Fermilab recycler. With high intensity upgrades foreseen, it is important to quantify the impedance. To do this,studies have been performed measuring the growth rate of presumably the resistive wall instability. The growth rates at varying intensities and chromaticities are shown. The measured growth rates are compared to ones calculated with the resistive wall impedance.

  19. Prophylactic treatment with growth hormone improves intestinal barrier function and alleviates bacterial translocation in stressed rats

    Institute of Scientific and Technical Information of China (English)

    丁连安; 黎介寿; 李幼生; 刘放南; 谭力

    2004-01-01

    Background Damage to the gut barrier often occurs during critical illnesses. In such cases, it is very important to alleviate impairment of the intestinal barrier and protect intestinal barrier function. This study investigated the protective effect of growth hormone on intestinal barrier function in rats under stress.Methods This study consisted of prospective, randomized, and controlled animal experiments. Twenty-five Sprague-Dawley rats served as total parenteral nutrition (TPN) models and were divided into three groups: TPN group, sepsis (Sep) group, and growth hormone (GH) group. Another 8 rats served as normal controls. Each group received different stress stimuli. Rats were fed for 7 days, and samples were taken for examination 24 hours after garaging with dual saccharides. Results The architecture of the small intestinal mucosa in the Sep group showed the most severe damage among all groups. Nitric oxide levels in blood plasma and immunoglobulin A levels in the intestinal mucosa of the GH group were significantly lower than in the Sep group (P<0.02). There were no significant changes in CD3 counts and in the CD4/CD8 ratio between the four groups. Dual sugar tests and bacteriological examinations revealed that intestinal permeability and rate of bacterial translocation in the GH group were lower than in the Sep group (P<0.01, respectively).Conclusion Prophylactic treatment with growth hormone can alleviate damage to intestinal barrier function caused by trauma and endotoxemia in rats under stress.

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

    Science.gov (United States)

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

    2015-11-01

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

  1. Distribution of bacterial growth activity in flow-chamber biofilms

    DEFF Research Database (Denmark)

    Sternberg, Claus; Christensen, Bjarke B.; Johansen, Tove;

    1999-01-01

    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...... 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....

  2. Small Regulatory RNA-Induced Growth Rate Heterogeneity of Bacillus subtilis

    OpenAIRE

    Mars, Ruben A. T.; Nicolas, Pierre; Ciccolini, Mariano; Reilman, Ewoud; Reder, Alexander; Schaffer, Marc; Maeder, Ulrike; Voelker, Uwe; van Dijl, Jan Maarten; Denham, Emma L.

    2015-01-01

    Author Summary Bacterial cells that share the same genetic information can display very different phenotypes, even if they grow under identical conditions. Despite the relevance of this population heterogeneity for processes like drug resistance and development, the molecular players that induce heterogenic phenotypes are often not known. Here we report that in the Gram-positive model bacterium Bacillus subtilis a small regulatory RNA (sRNA) can induce heterogeneity in growth rates by increas...

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

    Science.gov (United States)

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

    2014-09-01

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

  4. Rates of gyrase supercoiling and transcription elongation control supercoil density in a bacterial chromosome.

    Directory of Open Access Journals (Sweden)

    Nikolay Rovinskiy

    Full Text Available Gyrase catalyzes negative supercoiling of DNA in an ATP-dependent reaction that helps condense bacterial chromosomes into a compact interwound "nucleoid." The supercoil density (σ of prokaryotic DNA occurs in two forms. Diffusible supercoil density (σ(D moves freely around the chromosome in 10 kb domains, and constrained supercoil density (σ(C results from binding abundant proteins that bend, loop, or unwind DNA at many sites. Diffusible and constrained supercoils contribute roughly equally to the total in vivo negative supercoil density of WT cells, so σ = σ(C+σ(D. Unexpectedly, Escherichia coli chromosomes have a 15% higher level of σ compared to Salmonella enterica. To decipher critical mechanisms that can change diffusible supercoil density of chromosomes, we analyzed strains of Salmonella using a 9 kb "supercoil sensor" inserted at ten positions around the genome. The sensor contains a complete Lac operon flanked by directly repeated resolvase binding sites, and the sensor can monitor both supercoil density and transcription elongation rates in WT and mutant strains. RNA transcription caused (- supercoiling to increase upstream and decrease downstream of highly expressed genes. Excess upstream supercoiling was relaxed by Topo I, and gyrase replenished downstream supercoil losses to maintain an equilibrium state. Strains with TS gyrase mutations growing at permissive temperature exhibited significant supercoil losses varying from 30% of WT levels to a total loss of σ(D at most chromosome locations. Supercoil losses were influenced by transcription because addition of rifampicin (Rif caused supercoil density to rebound throughout the chromosome. Gyrase mutants that caused dramatic supercoil losses also reduced the transcription elongation rates throughout the genome. The observed link between RNA polymerase elongation speed and gyrase turnover suggests that bacteria with fast growth rates may generate higher supercoil densities

  5. Gut Commensal E. coli Proteins Activate Host Satiety Pathways following Nutrient-Induced Bacterial Growth.

    Science.gov (United States)

    Breton, Jonathan; Tennoune, Naouel; Lucas, Nicolas; Francois, Marie; Legrand, Romain; Jacquemot, Justine; Goichon, Alexis; Guérin, Charlène; Peltier, Johann; Pestel-Caron, Martine; Chan, Philippe; Vaudry, David; do Rego, Jean-Claude; Liénard, Fabienne; Pénicaud, Luc; Fioramonti, Xavier; Ebenezer, Ivor S; Hökfelt, Tomas; Déchelotte, Pierre; Fetissov, Sergueï O

    2016-02-01

    The composition of gut microbiota has been associated with host metabolic phenotypes, but it is not known if gut bacteria may influence host appetite. Here we show that regular nutrient provision stabilizes exponential growth of E. coli, with the stationary phase occurring 20 min after nutrient supply accompanied by bacterial proteome changes, suggesting involvement of bacterial proteins in host satiety. Indeed, intestinal infusions of E. coli stationary phase proteins increased plasma PYY and their intraperitoneal injections suppressed acutely food intake and activated c-Fos in hypothalamic POMC neurons, while their repeated administrations reduced meal size. ClpB, a bacterial protein mimetic of α-MSH, was upregulated in the E. coli stationary phase, was detected in plasma proportional to ClpB DNA in feces, and stimulated firing rate of hypothalamic POMC neurons. Thus, these data show that bacterial proteins produced after nutrient-induced E. coli growth may signal meal termination. Furthermore, continuous exposure to E. coli proteins may influence long-term meal pattern. PMID:26621107

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

    Science.gov (United States)

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

    2016-01-01

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

  7. On the growth rate of the foliicolous lichen Strigula elegans

    NARCIS (Netherlands)

    Wilde-Duyfjes, de B.E.E.

    1967-01-01

    The diametral growth rate of the foliicolous lichen Strigula elegans (Fée) Müll. Arg., measured under natural conditions in the African tropical rainforest, has been established to amount to (0.7-)3-3-6(-8) mm annually. As compared to the diametral growth rate of lichens from temperate regions, whic

  8. Growth rates of intracranial aneurysms : exploring constancy

    NARCIS (Netherlands)

    Koffijberg, Hendrik; Buskens, Erik; Algra, Ale; Wermer, Marieke J. H.; Rinkel, Gabriel J. E.

    2008-01-01

    Object. The annual rate of rupture of intracranial aneurysms is often assumed to be constant, but it is unknown whether this assumption is true. Recent case reports have suggested that aneurysms grow fast in a short period of time. The authors of the present report investigated the plausibility of a

  9. An Economic Growth Model with Optimal Growth Rate and Individual Years of Schooling

    Directory of Open Access Journals (Sweden)

    Huan Yang

    2015-01-01

    Full Text Available An economic growth model with individual years of schooling is present. It is proved that there exist optimal individual years of schooling for fixed wage growth rate. On the other hand, the economy has balance growth path for given individual years of schooling. Finally, we prove that there exist optimal individual years of schooling and economic growth rate such that the individual lifetime utility reaches maximum and the economy grows on a balance growth path.

  10. Larval developmental rate, metabolic rate and future growth performance in Atlantic salmon

    DEFF Research Database (Denmark)

    Serrano, Jonathan Vaz; Åberg, Madelene; Gjoen, Hans Magnus;

    2009-01-01

    Previous studies in salmonids suggest a link between larval developmental rate, metabolic rate, and future growth. However, the connection between growth during exogenous and endogenous feeding is still debated. In the current study, a positive relationship between larval developmental rate, quan...

  11. Growth rates and feeding management of Irish thoroughbred foals

    OpenAIRE

    Griffin, Róisín

    2015-01-01

    peer-reviewed Limited studies have focused on the growth of Irish Thoroughbred (TB) foals. The objectives of this study were to track the growth of foals and to monitor growth rates based on nutritional intakes. The growth of 72 foals, on eight Irish stud farms were monitored monthly from birth to six months of age. Body weight (BW), average daily gain (ADG), wither height (WH), body length (BL), heart girth (HG) and cannon bone circumference (CC) were measured monthly. Representative samp...

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

    Science.gov (United States)

    Shao, Xinxian; Mugler, Andrew; Nemenman, Ilya

    2014-03-01

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

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

    Science.gov (United States)

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

    2011-12-01

    Previous research has linked measured changes in the bulk electrical conductivity (σb) 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 σb 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 σb in the iron-reducing column and a 10-fold increase in σb (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 σb 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

  14. Allometries of maximum growth rate versus body mass at maximum growth indicate that non-avian dinosaurs had growth rates typical of fast growing ectothermic sauropsids.

    Directory of Open Access Journals (Sweden)

    Jan Werner

    Full Text Available We tested if growth rates of recent taxa are unequivocally separated between endotherms and ectotherms, and compared these to dinosaurian growth rates. We therefore performed linear regression analyses on the log-transformed maximum growth rate against log-transformed body mass at maximum growth for extant altricial birds, precocial birds, eutherians, marsupials, reptiles, fishes and dinosaurs. Regression models of precocial birds (and fishes strongly differed from Case's study (1978, which is often used to compare dinosaurian growth rates to those of extant vertebrates. For all taxonomic groups, the slope of 0.75 expected from the Metabolic Theory of Ecology was statistically supported. To compare growth rates between taxonomic groups we therefore used regressions with this fixed slope and group-specific intercepts. On average, maximum growth rates of ectotherms were about 10 (reptiles to 20 (fishes times (in comparison to mammals or even 45 (reptiles to 100 (fishes times (in comparison to birds lower than in endotherms. While on average all taxa were clearly separated from each other, individual growth rates overlapped between several taxa and even between endotherms and ectotherms. Dinosaurs had growth rates intermediate between similar sized/scaled-up reptiles and mammals, but a much lower rate than scaled-up birds. All dinosaurian growth rates were within the range of extant reptiles and mammals, and were lower than those of birds. Under the assumption that growth rate and metabolic rate are indeed linked, our results suggest two alternative interpretations. Compared to other sauropsids, the growth rates of studied dinosaurs clearly indicate that they had an ectothermic rather than an endothermic metabolic rate. Compared to other vertebrate growth rates, the overall high variability in growth rates of extant groups and the high overlap between individual growth rates of endothermic and ectothermic extant species make it impossible to rule

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

    Science.gov (United States)

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

    1984-06-01

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

  16. Biocontrol of Fusarium graminearum Growth and Deoxynivalenol Production in Wheat Kernels with Bacterial Antagonists

    Directory of Open Access Journals (Sweden)

    Cuijuan Shi

    2014-01-01

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

  17. Aortic growth rates in chronic aortic dissection

    Energy Technology Data Exchange (ETDEWEB)

    Kelly, A.M. [Department of Radiology, Division of Thoracic Radiology, University of Michigan Medical Center (United States)]. E-mail: ainekell@med.umich.edu; Quint, L.E. [Department of Radiology, Division of Thoracic Radiology, University of Michigan Medical Center (United States); Nan, B. [School of Public Health, University of Michigan, Ann Arbor, Michigan (United States); Zheng, J. [School of Public Health, University of Michigan, Ann Arbor, Michigan (United States); Cronin, P. [Department of Radiology, Division of Thoracic Radiology, University of Michigan Medical Center (United States); Deeb, G.M. [Division of Cardiac Surgery, University of Michigan Medical Center (United States); Williams, D.M. [Division of Vascular Interventional Imaging, University of Michigan Medical Center (United States)

    2007-09-15

    Aim: To determine and compare rates of descending aortic enlargement and complications in chronic aortic dissection with and without a proximal aortic graft. Methods and materials: Fifty-two patients with dissection involving the descending aorta and who had undergone at least two computed tomography (CT) examinations at our institution between November, 1993 and February, 2004 were identified, including 24 non-operated patients (four type A, 20 type B) and 28 operated patients (type A). CT examinations per patient ranged from two to 10, and follow-up ranged from 1-123 months (mean 49 months, median 38.5 months). On each CT image, the aortic short axis (SA), false lumen (FL), and true lumen (TL) diameters were measured at the longitudinal midpoint of the dissection and at the point of maximum aortic diameter. Complications were tabulated, including aortic rupture and aortic enlargement requiring surgery. Results: For non-operated patients, the midpoint and maximum point SA, TL, and FL diameters increased significantly over time. For operated patients, the midpoint and maximum point SA and FL diameters increased significantly over time. In both groups, aortic enlargement was predominantly due to FL expansion. Diameter increases in non-operated patients were significantly larger than those in operated patients. The rate of change in aortic diameter was constant, regardless of aortic size. Four non-operated and six operated patients developed aortic complications. Conclusions: In patients with a dissection involving the descending thoracic aorta, the FL increased in diameter over time, at a constant rate, and to a greater degree in non-operated patients (mostly type B) compared with operated patients (all type A)

  18. Growth Rates in the Quaquaversal Tiling

    OpenAIRE

    Draco, Brimstone; Sadun, Lorenzo; Van Wieren, Douglas

    1998-01-01

    Conway and Radin's ``quaquaversal'' tiling of R^3 is known to exhibit statistical rotational symmetry in the infinite volume limit. A finite patch, however, cannot be perfectly isotropic, and we compute the rates at which the anisotropy scales with size. In a sample of volume N, tiles appear in O(N^{1/6}) distinct orientations. However, the orientations are not uniformly populated. A small (O(N^{1/84})) set of these orientations account for the majority of the tiles. Furthermore, these orient...

  19. Volatile emissions from Mycobacterium avium subsp. paratuberculosis mirror bacterial growth and enable distinction of different strains.

    Directory of Open Access Journals (Sweden)

    Phillip Trefz

    Full Text Available 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

  20. Population dynamics and growth rates of endosymbionts during Diaphorina citri (Hemiptera, Liviidae) ontogeny.

    Science.gov (United States)

    Dossi, Fabio Cleisto Alda; da Silva, Edney Pereira; Cônsoli, Fernando Luis

    2014-11-01

    The infection density of symbionts is among the major parameters to understand their biological effects in host-endosymbionts interactions. Diaphorina citri harbors two bacteriome-associated bacterial endosymbionts (Candidatus Carsonella ruddii and Candidatus Profftella armatura), besides the intracellular reproductive parasite Wolbachia. In this study, the density dynamics of the three endosymbionts associated with the psyllid D. citri was investigated by real-time quantitative PCR (qPCR) at different developmental stages. Bacterial density was estimated by assessing the copy number of the 16S rRNA gene for Carsonella and Profftella, and of the ftsZ gene for Wolbachia. Analysis revealed a continuous growth of the symbionts during host development. Symbiont growth and rate curves were estimated by the Gompertz equation, which indicated a negative correlation between the degree of symbiont-host specialization and the time to achieve the maximum growth rate (t*). Carsonella densities were significantly lower than those of Profftella at all host developmental stages analyzed, even though they both displayed a similar trend. The growth rates of Wolbachia were similar to those of Carsonella, but Wolbachia was not as abundant. Adult males displayed higher symbiont densities than females. However, females showed a much more pronounced increase in symbiont density as they aged if compared to males, regardless of the incorporation of symbionts into female oocytes and egg laying. The increased density of endosymbionts in aged adults differs from the usual decrease observed during host aging in other insect-symbiont systems. PMID:25037159

  1. Population dynamics and growth rates of endosymbionts during Diaphorina citri (Hemiptera, Liviidae) ontogeny.

    Science.gov (United States)

    Dossi, Fabio Cleisto Alda; da Silva, Edney Pereira; Cônsoli, Fernando Luis

    2014-11-01

    The infection density of symbionts is among the major parameters to understand their biological effects in host-endosymbionts interactions. Diaphorina citri harbors two bacteriome-associated bacterial endosymbionts (Candidatus Carsonella ruddii and Candidatus Profftella armatura), besides the intracellular reproductive parasite Wolbachia. In this study, the density dynamics of the three endosymbionts associated with the psyllid D. citri was investigated by real-time quantitative PCR (qPCR) at different developmental stages. Bacterial density was estimated by assessing the copy number of the 16S rRNA gene for Carsonella and Profftella, and of the ftsZ gene for Wolbachia. Analysis revealed a continuous growth of the symbionts during host development. Symbiont growth and rate curves were estimated by the Gompertz equation, which indicated a negative correlation between the degree of symbiont-host specialization and the time to achieve the maximum growth rate (t*). Carsonella densities were significantly lower than those of Profftella at all host developmental stages analyzed, even though they both displayed a similar trend. The growth rates of Wolbachia were similar to those of Carsonella, but Wolbachia was not as abundant. Adult males displayed higher symbiont densities than females. However, females showed a much more pronounced increase in symbiont density as they aged if compared to males, regardless of the incorporation of symbionts into female oocytes and egg laying. The increased density of endosymbionts in aged adults differs from the usual decrease observed during host aging in other insect-symbiont systems.

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

    Science.gov (United States)

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

    2015-02-01

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

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

    Science.gov (United States)

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

    2015-11-01

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

  4. Effect of holothurian and zoanthid extracts on growth of some bacterial and diatom species

    Digital Repository Service at National Institute of Oceanography (India)

    Gonsalves, C.

    . All the three extracts possessed antifouling activity bu their efficacy was found to be species specific. The highest bacterial inhibition zone ranged between 3-4 mm with both the zoanthid extracts. In case of diatoms, inducement of growth was observed...

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

    Energy Technology Data Exchange (ETDEWEB)

    Song, Hyun-Seob; Liu, Chongxuan

    2015-06-29

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

  6. The influence of low intensity microwave on some bacterial growth

    International Nuclear Information System (INIS)

    The action for of low intensity microwaves (power density 10 mW/cm2, frequency of about 10.75 GHz) on growth dynamics was searched in two microbial cultures: Staphylococcus aureus ATCC-6538 (Gram positive bacteria) and Escherichia coli ATCC-10536 (Gram negative bacteria). It was evaluated the number of living cells/ml using a JASCO spectrophotometer for measurements carried out at 3, 6 , 9, 12, 24, 36, 48 and 72 hours in samples and controls. The results obtained revealed a stimulatory effect of microwaves on cell multiplication in both tested bacteria all over the experiment. Statistical computation showed different mathematical functions for experimental graphs approach. Logarithmic function was found to fit to E. coli growth (correlation coefficient equal to 0.978) while exponential function was found to approximate S. aureus dynamics (correlation coefficient equal to 0.758). A low thermal effect could be the main cause of such behaviour, as expected. However, a non-thermal effect could also be involved in the dynamics of these pathogen microorganisms. (authors)

  7. Bacterial growth in a simulated Martian subsurface environment

    Science.gov (United States)

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

    2013-12-01

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

  8. Bacterial growth inhibition potential of annatto plant parts

    Institute of Scientific and Technical Information of China (English)

    Akshatha Venugopalan; Parvatam Giridhar

    2012-01-01

    Objective: To study the antibacterial efficacy of Bixa orellana leaves and deseeded fruit capsule extracts against both Gram positive and Gram negative bacteria. Methods: The antibacterial activity of the ethanolic, methanolic, acetone and dimethyl sulphoxide extracts of B. orellana were tested against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Bacillus subtilis,Bacillus cereus and Staphylococus aureus by disc diffusion method. Results: The antibacterial activity of leaf was more pronounced even at low concentrations and fruit extracts exhibited the same at relatively higher concentrations. Only DMSO extract of seeds showed growth inhibition of S. aureus, B. subtilis, B. cereus, and P. aeruginosa. Conclusions: The present study suggested that the leaves and deseeded capsule extracts of B. orellana possess significant antibacterial activity thereby providing substantial support for the ethanobotanical applications of this plant.

  9. Applicability of bacterial growth models in spreadable processed cheese

    Directory of Open Access Journals (Sweden)

    Dorota Weiss

    2015-09-01

    Full Text Available Background. Food spoilage is a process in which the quality parameters decrease and products are no longer edible. This is a cumulative effect of bacteria growth and their metabolite production, which is a factor limiting shelf life. Thus, the aim of the study was to evaluate whether microbiological growth models for total viable count (TVC and Clostridium strain bacteria are reliable tools for prediction of microbiological changes in spreadable processed cheese. Material and methods. Investigations were conducted for two types of bacteria: TVC and Clostridium in following temperature: 8°C, 20°C and 30°C. A total number of aerobic bacteria was determined based on standard PN-EN ISO 4833:2004 and Clostridium was detected by using microbiological procedure for sulphite-reducing anaerobic spore-bacteria with a selective nourishment. During the analysis nonlinear regression and Baranyi and Roberts primary model were used. Results. For temperatures 20°C and 30°C, Baranyi and Roberts model, for total viable count showed determination coeffi cient of 70%. The models prepared for Clostridium, in these temperatures, showed much lower R2, respectively 25% and 30%. At the abovementioned temperatures also the expiration of product shelf life was much shorter and amounted 70 days at 20°C and 7 days at 30°C. For both types of bacteria incubated at 8°C the numbers of bacteria decrease until the expiration of product shelf life. Conclusions. Models used in the analyses, Baranyi and Roberts and nonlinear regression, poorly matched the experimental data, hence they are not reliable tools. Nevertheless, they gave information about dynamic of microbiological changes in spreadable processed cheese.

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

    OpenAIRE

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

    2014-01-01

    Background: To study chlorhexidine digluconate disinfectant effects on planktonic growth and biofilm formation in some bacterial field isolates from animals. Objectives: The current study investigated chlorhexidine digluconate effects on planktonic growth and biofilm formation in some field isolates of veterinary bacterial pathogens. Materials and Methods: Forty clinical isolates of Escherichia coli, Salmonella serotypes, Staphylococcus. aureus and Streptococcus agalactiae (10 isolates for ea...

  11. Chlorhexidine Gluconate Dressings Reduce Bacterial Colonization Rates in Epidural and Peripheral Regional Catheters

    Directory of Open Access Journals (Sweden)

    Klaus Kerwat

    2015-01-01

    Full Text Available Introduction. Bacterial colonization of catheter tips is common in regional anesthesia and is a suspected risk factor for infectious complications. This is the first study evaluating the effect of CHG-impregnated dressings on bacterial colonization of regional anesthesia catheters in a routine clinical setting. Methods. In this prospective study, regional anesthesia catheter infection rates were examined in two groups of patients with epidural and peripheral regional catheters. In the first group, regional anesthesia was dressed with a conventional draping. The second group of patients underwent catheter dressing using a CHG-impregnated draping. Removed catheters and the insertion sites were both screened for bacterial colonization. Results. A total of 337 catheters from 308 patients were analysed. There was no significant reduction of local infections in either epidural or peripheral regional anesthesia catheters in both CHG and conventional groups. In the conventional group, 21% of the catheter tips and 41% of the insertion sites showed positive culture results. In the CHG-group, however, only 3% of the catheter tips and 8% of the insertion sites were colonised. Conclusion. CHG dressings significantly reduce bacterial colonization of the tip and the insertion site of epidural and peripheral regional catheters. However, no reductions in rates of local infections were seen.

  12. Protein thermodynamics can be predicted directly from biological growth rates.

    Directory of Open Access Journals (Sweden)

    Ross Corkrey

    Full Text Available Life on Earth is capable of growing from temperatures well below freezing to above the boiling point of water, with some organisms preferring cooler and others hotter conditions. The growth rate of each organism ultimately depends on its intracellular chemical reactions. Here we show that a thermodynamic model based on a single, rate-limiting, enzyme-catalysed reaction accurately describes population growth rates in 230 diverse strains of unicellular and multicellular organisms. Collectively these represent all three domains of life, ranging from psychrophilic to hyperthermophilic, and including the highest temperature so far observed for growth (122 °C. The results provide credible estimates of thermodynamic properties of proteins and obtain, purely from organism intrinsic growth rate data, relationships between parameters previously identified experimentally, thus bridging a gap between biochemistry and whole organism biology. We find that growth rates of both unicellular and multicellular life forms can be described by the same temperature dependence model. The model results provide strong support for a single highly-conserved reaction present in the last universal common ancestor (LUCA. This is remarkable in that it means that the growth rate dependence on temperature of unicellular and multicellular life forms that evolved over geological time spans can be explained by the same model.

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

    Directory of Open Access Journals (Sweden)

    Aisha Waheed Qurashi

    2012-09-01

    Full Text Available 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.

  14. Seasonal variations in ectotherm growth rates: Quantifying growth as an intermittent non steady state compensatory process

    Science.gov (United States)

    Guarini, J.-M.; Chauvaud, Laurent; Cloern, J.E.; Clavier, J.; Coston-Guarini, J.; Patry, Y.

    2011-01-01

    Generally, growth rates of living organisms are considered to be at steady state, varying only under environmental forcing factors. For example, these rates may be described as a function of light for plants or organic food resources for animals and these could be regulated (or not) by temperature or other conditions. But, what are the consequences for an individual's growth (and also for the population growth) if growth rate variations are themselves dynamic and not steady state? For organisms presenting phases of dormancy or long periods of stress, this is a crucial question. A dynamic perspective for quantifying short-term growth was explored using the daily growth record of the scallop Pecten maximus (L.). This species is a good biological model for ectotherm growth because the shell records growth striae daily. Independently, a generic mathematical function representing the dynamics of mean daily growth rate (MDGR) was implemented to simulate a diverse set of growth patterns. Once the function was calibrated with the striae patterns, the growth rate dynamics appeared as a forced damped oscillation during the growth period having a basic periodicity during two transitory phases (mean duration 43. days) and appearing at both growth start and growth end. This phase is most likely due to the internal dynamics of energy transfer within the organism rather than to external forcing factors. After growth restart, the transitory regime represents successive phases of over-growth and regulation. This pattern corresponds to a typical representation of compensatory growth, which from an evolutionary perspective can be interpreted as an adaptive strategy to coping with a fluctuating environment. ?? 2011 Elsevier B.V.

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

    Science.gov (United States)

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

    2013-02-01

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

  16. SPATULA links daytime temperature and plant growth rate.

    Science.gov (United States)

    Sidaway-Lee, Kate; Josse, Eve-Marie; Brown, Alanna; Gan, Yinbo; Halliday, Karen J; Graham, Ian A; Penfield, Steven

    2010-08-24

    Plants exhibit a wide variety of growth rates that are known to be determined by genetic and environmental factors, and different plants grow optimally at different temperatures, indicating that this is a genetically determined character. Moderate decreases in ambient temperature inhibit vegetative growth, but the mechanism is poorly understood, although a decrease in gibberellin (GA) levels is known to be required. Here we demonstrate that the basic helix-loop-helix transcription factor SPATULA (SPT), previously known to be a regulator of low temperature-responsive germination, mediates the repression of growth by cool daytime temperatures but has little or no growth-regulating role under warmer conditions. We show that only daytime temperatures affect vegetative growth and that SPT couples morning temperature to growth rate. In seedlings, warm temperatures inhibit the accumulation of the SPT protein, and SPT autoregulates its own transcript abundance in conjunction with diurnal effects. Genetic data show that repression of growth by SPT is independent of GA signaling and phytochrome B, as previously shown for PIF4. Our data suggest that SPT integrates time of day and temperature signaling to control vegetative growth rate.

  17. Effect of selection for relative growth rate and bodyweight of mice on rate, composition and efficiency of growth

    NARCIS (Netherlands)

    Bakker, H.

    1974-01-01

    To evaluate the effect of selection for parameters of a growth curve, four selection lines and a control line were started from one base population. In the selection lines is selected for a large and a small relative growth rate between 21 and 29 days (RGH and RGL) and for a large and small bodyweig

  18. GROWTH AND METABOLISM OF INDIVIDUAL BACTERIAL CELLS UTILIZING NANOSIMS

    Energy Technology Data Exchange (ETDEWEB)

    NEALSON, H. K.

    2007-08-03

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

  19. Insights for Analyzing Earnings Growth Rates: A Case Study.

    Science.gov (United States)

    Hannah, Richard L.

    1994-01-01

    A study at one public university investigated the annualized rate of salary/wage increase of employees from the time of hiring until July 1992. It examined promotion patterns, equity adjustments, employee degree acquisition, and certification of clerical workers. The study underscored the wide variation in earnings growth rates due in large part…

  20. An impedance response model for inhibitory effect of antibiotics on bacterial growth in biometallurgy

    Institute of Scientific and Technical Information of China (English)

    陶菡; 魏万之; 张书芬; 张进忠; 毛友安

    2004-01-01

    An impedance response model reflecting the inhibitory effect of antibiotics on bacterial growth in biometallurgy was established. Three inhibition parameters, i.e. the maximum amount inhibitory constant of the bacterial growth(K1 ), the maximum specific growth inhibitory constant(K2 ) and the lag time inhibitory constant(K3 ), were included in the model. The influence of these parameters on the response curve was discussed in detail. By fitting experimental data towards the proposed model, three growth parameters (A, μm and λ) in the presence of antibiotics were gained and compared. The results show that the growth ability of bacteria is decreased due to the influence of antibiotics. The experimental and fitted curves have goodness-of-fit in the range of 0. 987 - 1. 008. Moreover, the kinetic growth parameters obtained from this model are closed to those from the Logistics popular growth model.These results show that the proposed model is validity to reflect the inhibitory effect of antibiotics on bacteria.

  1. Seasonal growth rate of the sponge Haliclona oculata (Demospongiae: Haplosclerida).

    Science.gov (United States)

    Koopmans, Marieke; Wijffels, René H

    2008-01-01

    The interest in sponges has increased rapidly since the discovery of potential new pharmaceutical compounds produced by many sponges. A good method to produce these compounds by using aquaculture of sponges is not yet available, because there is insufficient knowledge about the nutritional needs of sponges. To gain more insight in the nutritional needs for growth, we studied the growth rate of Haliclona oculata in its natural environment and monitored environmental parameters in parallel. A stereo photogrammetry approach was used for measuring growth rates. Stereo pictures were taken and used to measure volumetric changes monthly during 1 year. Volumetric growth rate of Haliclona oculata showed a seasonal trend with the highest average specific growth rate measured in May: 0.012 +/- 0.004 day(-1). In our study a strong positive correlation (p rate with temperature, algal biomass (measured as chlorophyll a), and carbon and nitrogen content in suspended particulate matter. A negative correlation (p rate with salinity, ammonium, nitrate, nitrite, and phosphate. No correlation was found with dissolved organic carbon, suggesting that Haliclona oculata is more dependent on particulate organic carbon.

  2. Noise in gene expression is coupled to growth rate.

    Science.gov (United States)

    Keren, Leeat; van Dijk, David; Weingarten-Gabbay, Shira; Davidi, Dan; Jona, Ghil; Weinberger, Adina; Milo, Ron; Segal, Eran

    2015-12-01

    Genetically identical cells exposed to the same environment display variability in gene expression (noise), with important consequences for the fidelity of cellular regulation and biological function. Although population average gene expression is tightly coupled to growth rate, the effects of changes in environmental conditions on expression variability are not known. Here, we measure the single-cell expression distributions of approximately 900 Saccharomyces cerevisiae promoters across four environmental conditions using flow cytometry, and find that gene expression noise is tightly coupled to the environment and is generally higher at lower growth rates. Nutrient-poor conditions, which support lower growth rates, display elevated levels of noise for most promoters, regardless of their specific expression values. We present a simple model of noise in expression that results from having an asynchronous population, with cells at different cell-cycle stages, and with different partitioning of the cells between the stages at different growth rates. This model predicts non-monotonic global changes in noise at different growth rates as well as overall higher variability in expression for cell-cycle-regulated genes in all conditions. The consistency between this model and our data, as well as with noise measurements of cells growing in a chemostat at well-defined growth rates, suggests that cell-cycle heterogeneity is a major contributor to gene expression noise. Finally, we identify gene and promoter features that play a role in gene expression noise across conditions. Our results show the existence of growth-related global changes in gene expression noise and suggest their potential phenotypic implications. PMID:26355006

  3. Bacteriophage T4 development in Escherichia coli is growth rate dependent.

    Science.gov (United States)

    Rabinovitch, Avinoam; Fishov, Itzhak; Hadas, Hilla; Einav, Monica; Zaritsky, Arieh

    2002-05-01

    Three independent parameters (eclipse and latent periods, and rate of ripening during the rise period) are essential and sufficient to describe bacteriophage development in its bacterial host. A general model to describe the classical "one-step growth" experiment [Rabinovitch et al. (1999a) J. Bacteriol.181, 1687-1683] allowed their calculations from experimental results obtained with T4 in Escherichia coli B/r under different growth conditions [Hadas et al. (1997) Microbiology143, 179-185]. It is found that all three parameters could be described by their dependence solely on the culture doubling time tau before infection. Their functional dependence on tau, derived by a best-fit analysis, was used to calculate burst size values. The latter agree well with the experimental results. The dependence of the derived parameters on growth conditions can be used to predict phage development under other experimental manipulations.

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

    Directory of Open Access Journals (Sweden)

    Wanilada Rungrassamee

    Full Text Available 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.

  5. Greenhouse Gas Growth Rates from AIRS Hyperspectral Radiance Time Series

    Science.gov (United States)

    Strow, L. L.; Desouza-Machado, S. G.; Hannon, S.; Imbiriba, B.; Schou, P.

    2009-12-01

    The AIRS seven year hyperspectral radiance record provides an ideal platform for measurings growth rates of infrared active minor gases, especially carbon dioxide and methane. The largest changes in CLARREO radiances will likely be due to increasing carbon dioxide and other greenhouse gases. We have produced a 5+ year record of almost cloud-free AIRS radiances, from which we have derived the radiance anomaly and linear time rate of change. The source of these radiances are the L1b radiances corrected for small frequency drifts. Growth rates of carbon dioxide, nitrous oxide, methane, ozone, and CFC11 are simultaneously derived from zonal averages of these radiance rates for tropics, and mid-latitude northern and southern hemispheres. The effective linear rate of change of ~5 layers of water vapor and temperature, plus the surface temperature are also simultaneously derived with the minor gas rates. No model data or prior is needed and more than 1000 channels are used in the fit. Sampling issues may preclude the use of the mid-latitude temperature and water vapor rates for climate analysis, but possibly not for the tropics. The resulting greenhouse gas growth rates agree very well with in-situ measurements, which suggests high radiometric stability for AIRS. Radiance intercomparisons for climate analysis between IASI and AIRS will also be presented.

  6. Coral growth rates revisited after 31 years: what is causing lower extension rates in Acropora palmata?

    NARCIS (Netherlands)

    Bak, R.P.M.; Nieuwland, G.; Meesters, H.W.G.

    2009-01-01

    Linear extension of branches in the same Acropora palmata (Lamarck, 1816) population in Curaçao was measured, employing exactly the same methods, in 1971-1973 and in 2002-2004, and the resulting coral growth rates are compared. Linear growth shows the same pattern over seasons in both periods with g

  7. Growth rate in the dynamical dark energy models

    Energy Technology Data Exchange (ETDEWEB)

    Avsajanishvili, Olga [Ilia State University, Abastumani Astrophysical Observatory, Tbilisi (Georgia); Arkhipova, Natalia A. [Astro Space Center of P.N. Lebedev Physical Institute, Russia, Moscow (Russian Federation); Samushia, Lado [Kansas State University, Department of Physics, Manhattan, KS (United States); Ilia State University, Abastumani Astrophysical Observatory, Tbilisi (Georgia); Kahniashvili, Tina [Carnegie Mellon University, McWilliams Center for Cosmology and Department of Physics, Pittsburgh, PA (United States); Laurentian University, Department of Physics, Sudbury, ON (Canada); Ilia State University, Abastumani Astrophysical Observatory, Tbilisi (Georgia)

    2014-11-15

    Dark energy models with a slowly rolling cosmological scalar field provide a popular alternative to the standard, time-independent cosmological constant model. We study the simultaneous evolution of background expansion and growth in the scalar field model with the Ratra-Peebles self-interaction potential. We use recent measurements of the linear growth rate and the baryon acoustic oscillation peak positions to constrain the model parameter α that describes the steepness of the scalar field potential. (orig.)

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

    OpenAIRE

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

    1989-01-01

    The growth, toxicity, and associated bacterial flora of 10 clonal cultures of the toxic benthic dinoflagellates Ostreopsis lenticularis and Gambierdiscus toxicus isolated from the coastal waters of southwest Puerto Rico have been examined. Clonal cultures of O. lenticularis grew more rapidly and at broader temperature ranges than those of G. toxicus. All five Ostreopsis clones were toxic, while only one of the five Gambierdiscus clones was poisonous. The degree of toxicity among poisonous clo...

  9. Radiocarbon Based Ages and Growth Rates: Hawaiian Deep Sea Corals

    Energy Technology Data Exchange (ETDEWEB)

    Roark, E B; Guilderson, T P; Dunbar, R B; Ingram, B L

    2006-01-13

    The radial growth rates and ages of three different groups of Hawaiian deep-sea 'corals' were determined using radiocarbon measurements. Specimens of Corallium secundum, Gerardia sp., and Leiopathes glaberrima, were collected from 450 {+-} 40 m at the Makapuu deep-sea coral bed using a submersible (PISCES V). Specimens of Antipathes dichotoma were collected at 50 m off Lahaina, Maui. The primary source of carbon to the calcitic C. secundum skeleton is in situ dissolved inorganic carbon (DIC). Using bomb {sup 14}C time markers we calculate radial growth rates of {approx} 170 {micro}m y{sup -1} and ages of 68-75 years on specimens as tall as 28 cm of C. secundum. Gerardia sp., A. dichotoma, and L. glaberrima have proteinaceous skeletons and labile particulate organic carbon (POC) is their primary source of architectural carbon. Using {sup 14}C we calculate a radial growth rate of 15 {micro}m y{sup -1} and an age of 807 {+-} 30 years for a live collected Gerardia sp., showing that these organisms are extremely long lived. Inner and outer {sup 14}C measurements on four sub-fossil Gerardia spp. samples produce similar growth rate estimates (range 14-45 {micro}m y{sup -1}) and ages (range 450-2742 years) as observed for the live collected sample. Similarly, with a growth rate of < 10 {micro}m y{sup -1} and an age of {approx}2377 years, L. glaberrima at the Makapuu coral bed, is also extremely long lived. In contrast, the shallow-collected A. dichotoma samples yield growth rates ranging from 130 to 1,140 {micro}m y{sup -1}. These results show that Hawaiian deep-sea corals grow more slowly and are older than previously thought.

  10. Fatigue crack growth rates of rotor steel at elevated temperatures

    Institute of Scientific and Technical Information of China (English)

    LIU Chang-hai; MA Li-juan; TANG Li-qiang

    2008-01-01

    Low fatigue samples were obtained from the outer edges of rotor steel (30CrlMolV) which had operated under different temperatures conditions.Based on this data,the effects of temperature on fatigue crack growth rates were investigated.This paper presents a derivation of the superposition expression of two natural logarithms governing crack growth rates and also discusses the relationship between a material's constants and temperature.These results can provide experimental and theoretical references for fatigue life design of root steel in steam turbines.

  11. Nanocrystalline silicon prepared at high growth rate using helium dilution

    Indian Academy of Sciences (India)

    Koyel Bhattacharya; Debajyoti Das

    2008-06-01

    Growth and optimization of the nanocrystalline silicon (nc-Si : H) films have been studied by varying the electrical power applied to the helium diluted silane plasma in RF glow discharge. Wide optical gap and conducting intrinsic nanocrystalline silicon network of controlled crystalline volume fraction and oriented crystallographic lattice planes have been obtained at a reasonably high growth rate from helium diluted silane plasma, without using hydrogen. Improving crystallinity in the network comprising ∼ 10 nm Si-nanocrystallites and contributing optical gap widening, conductivity ascending and that obtained during simultaneous escalation of the deposition rate, promises significant technological impact.

  12. The growth rate of gas hydrate from refrigerant R12

    Energy Technology Data Exchange (ETDEWEB)

    Kendoush, Abdullah Abbas; Jassim, Najim Abid [Centre of Engineering Physics, Ministry of Sciences and Technology, P.O. Box 765, Baghdad (Iraq); Joudi, Khalid A. [Al-Nahrain University, Baghdad (Iraq)

    2006-07-15

    Experimental and theoretical investigations were presented dealing with three phase direct-contact heat transfer by evaporation of refrigerant drops in an immiscible liquid. Refrigerant R12 was used as the dispersed phase, while water and brine were the immiscible continuous phase. A numerical solution is presented to predict the formation rate of gas hydrates in test column. The solution provided an acceptable agreement when compared with experimental results. The gas hydrate growth rate increased with time. It increased with increasing dispersed phase flow rate. The presence of surface-active sodium chloride in water had a strong inhibiting effect on the gas hydrate formation rate. (author)

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

    Science.gov (United States)

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

    2013-10-28

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

  14. Impact of bacterial priming on some stress tolerance mechanisms and growth of cold stressed wheat seedlings

    Directory of Open Access Journals (Sweden)

    Mohammed E.H. Osman

    2014-01-01

    Full Text Available The potential to enhance growth of cold stressed wheat by seed treatment (priming with the beneficial bacteria Bacillus amyloliquefaciens 5113 and Azospirillum brasilense NO40 were tested. Results showed an improved ability of bacteria-treated seedlings to survive at −5°C up to 12 h. Cold stress increased transcript levels of three stress marker genes and increased activity for the ascorbate-glutathione redox enzymes. However, primed and stressed seedlings generally showed smaller effects on the stress markers correlating with better growth and improved stress tolerance. Bacterial priming to improve crop plant performance at low temperature seems a useful strategy to explore further.

  15. Food additives reduce lactic acid bacterial growth in culture medium and in meat products, increasing product shelf life

    Directory of Open Access Journals (Sweden)

    Cleonice Mendes Pereira Sarmento

    2015-12-01

    Full Text Available The uncontrolled growth of lactic acid bacteria (LAB in meat and meat products leads to product spoilage, and thus shortens product shelf life. Although food additives are known to decrease LAB growth, this effect has not been analyzed in detail. Here, a detailed analysis was performed of the effects of sodium chloride, sodium polyphosphate, sodium lactate, sodium nitrite/nitrate, and garlic on the growth of the Lactobacillus plantarum in culture medium. The results were used to design and test experimental formulations of meat products. Initially, the effect of food additives on L. plantarum was evaluated using a Fractional Factorial Design (FFD, followed by a Central Composite Rotatable Design (CCRD. The Modified Gompertz Model was adjusted to the growth curves to determine the Kinetic parameters of bacterial growth (logarithmic increase in the population, specific growth rate, and lag phase extension. Higher sodium lactate and sodium chloride levels had a negative impact on L. plantarum growth parameters (p?0.05. Therefore, we designed experimental formulations of mortadella and smoked pork sausages containing 4% sodium lactate (w w-1 and 2.4-3.5% sodium chloride (w w-1, and determined LAB growth from samples of stored products produced according to these formulations, in order to determine product shelf life. There was an increased lag phase of LAB growth for most experimental formulations. Also, the experimental smoked pork sausages had a longer shelf life, which was increased by at least 22 days, suggesting that the proposed formulation, with higher than standard lactate concentration, increased the product’s shelf life.

  16. Effect of microstructure on anomalous strain-rate-dependent behaviour of bacterial cellulose hydrogel.

    Science.gov (United States)

    Gao, Xing; Shi, Zhijun; Lau, Andrew; Liu, Changqin; Yang, Guang; Silberschmidt, Vadim V

    2016-05-01

    This study is focused on anomalous strain-rate-dependent behaviour of bacterial cellulose (BC) hydrogel that can be strain-rate insensitive, hardening, softening, or strain-rate insensitive in various ranges of strain rate. BC hydrogel consists of randomly distributed nanofibres and a large content of free water; thanks to its ideal biocompatibility, it is suitable for biomedical applications. Motivated by its potential applications in complex loading conditions of body environment, its time-dependent behaviour was studied by means of in-aqua uniaxial tension tests at constant temperature of 37 °C at various strain rates ranging from 0.000 1s(-1) to 0.3s(-1). Experimental results reflect anomalous strain-rate-dependent behaviour that was not documented before. Micro-morphological observations allowed identification of deformation mechanisms at low and high strain rates in relation to microstructural changes. Unlike strain-rate softening behaviours in other materials, reorientation of nanofibres and kinematics of free-water flow dominate the softening behaviour of BC hydrogel at high strain rates. PMID:26952406

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Kristufek, V.; Elhottova, D.; Chronakova, A.; Dostalkova, I.; Picek, T.; Kalcik, J. [Academy of Science in Czech Republic, Ceske Budejovice (Czech Republic). Inst. of Soil Biology

    2005-07-01

    The bacterial population of brown coal colliery spoil (Sokolov coal mining district, Czech Republic) was characterized by measuring viable bacterial biomass, the culturable to total cell ratio (C:T), colony-forming curve (CFC) analysis and species and/or biotype diversity. Bacterial representatives that differed in colony-forming growth (fast and/or slow growers) were used for growth-strategy investigation of heterotrophic bacteria. Spoil substrates from the surface (0-50 mm) and the mineral (100-150 mm) layers were sampled on 4 sites undergoing spontaneous succession corresponding to 1, 11, 21 and 43 years after deposition (initial, early, mid and late stages). The bacterial biomass of the surface layer increased during the initial and early stages with a maximum at mid stage and stabilized in the late stage while mineral layer biomass increased throughout the succession. The maxima of C:T ratios were at the early stage, minima at the late stage. Depending on the succession stage the C:T ratio was 1.5-2 times higher in the mineral than the surface layer of soil. An increase in the fraction of nonculturable bacteria was associated with the late succession stage. CFC analysis of the surface layer during a 3-d incubation revealed that the early-succession substrate contained more (75%) rapidly colonizing bacteria than successively older substrates. The culturable bacterial community of the mineral layer maintained a high genera and species richness of fast growers along the succession line in contrast to the surface layer community, where there was a maximum in the abundance of fast growers in the early stage. A markedly lower abundance of slow growers was observed in the mineral in contrast to the surface layer.

  19. Growth rates of modern science: A bibliometric analysis

    CERN Document Server

    Bornmann, Lutz

    2014-01-01

    Many studies in information science have looked at the growth of science. In this study, we re-examine the question of the growth of science. To do this we (i) use current data up to publication year 2012 and (ii) analyse it across all disciplines and also separately for the natural sciences and for the medical and health sciences. Furthermore, the data are analysed with an advanced statistical technique (segmented regression analysis) which can identify specific segments with similar growth rates in the history of science. The study is based on two different sets of bibliometric data: (1) The number of publications held as source items in the Web of Science (WoS, Thomson Reuters) per publication year and (2) the number of cited references in the publications of the source items per cited reference year. We have looked at the rate at which science has grown since the mid-1600s. In our analysis we identified three growth phases in the development of science, which each led to growth rates tripling in compariso...

  20. A generic mechanism for adaptive growth rate regulation.

    Directory of Open Access Journals (Sweden)

    Chikara Furusawa

    2008-01-01

    Full Text Available How can a microorganism adapt to a variety of environmental conditions despite the existence of a limited number of signal transduction mechanisms? We show that for any growing cells whose gene expression fluctuate stochastically, the adaptive cellular state is inevitably selected by noise, even without a specific signal transduction network for it. In general, changes in protein concentration in a cell are given by its synthesis minus dilution and degradation, both of which are proportional to the rate of cell growth. In an adaptive state with a higher growth speed, both terms are large and balanced. Under the presence of noise in gene expression, the adaptive state is less affected by stochasticity since both the synthesis and dilution terms are large, while for a nonadaptive state both the terms are smaller so that cells are easily kicked out of the original state by noise. Hence, escape time from a cellular state and the cellular growth rate are negatively correlated. This leads to a selection of adaptive states with higher growth rates, and model simulations confirm this selection to take place in general. The results suggest a general form of adaptation that has never been brought to light--a process that requires no specific mechanisms for sensory adaptation. The present scheme may help explain a wide range of cellular adaptive responses including the metabolic flux optimization for maximal cell growth.

  1. A generic mechanism for adaptive growth rate regulation.

    Science.gov (United States)

    Furusawa, Chikara; Kaneko, Kunihiko

    2008-01-01

    How can a microorganism adapt to a variety of environmental conditions despite the existence of a limited number of signal transduction mechanisms? We show that for any growing cells whose gene expression fluctuate stochastically, the adaptive cellular state is inevitably selected by noise, even without a specific signal transduction network for it. In general, changes in protein concentration in a cell are given by its synthesis minus dilution and degradation, both of which are proportional to the rate of cell growth. In an adaptive state with a higher growth speed, both terms are large and balanced. Under the presence of noise in gene expression, the adaptive state is less affected by stochasticity since both the synthesis and dilution terms are large, while for a nonadaptive state both the terms are smaller so that cells are easily kicked out of the original state by noise. Hence, escape time from a cellular state and the cellular growth rate are negatively correlated. This leads to a selection of adaptive states with higher growth rates, and model simulations confirm this selection to take place in general. The results suggest a general form of adaptation that has never been brought to light--a process that requires no specific mechanisms for sensory adaptation. The present scheme may help explain a wide range of cellular adaptive responses including the metabolic flux optimization for maximal cell growth.

  2. Upscaling Calcite Growth Rates From the Mesoscale to the Macroscale

    Energy Technology Data Exchange (ETDEWEB)

    Bracco, Jacquelyn N [ORNL; Stack, Andrew G [ORNL; Steefel, Carl I [Lawrence Berkeley National Laboratory (LBNL)

    2013-01-01

    Quantitative prediction of mineral reaction rates in the subsurface remains a daunting task partly because a key parameter for macroscopic models, the reactive site density, is poorly constrained. Here we report atomic force microscopy (AFM) measurements on the calcite surface of monomolecular step densities, treated as equivalent to the reactive site density, as a function of aqueous calcium-to-carbonate ratio and saturation index. Data for the obtuse step orientation are combined with existing step velocity measurements to generate a model that predicts overall macroscopic calcite growth rates. The model is quantitatively consistent with several published macroscopic rates under a range of alkaline solution conditions, particularly for two of the most comprehensive data sets without the need for additional fit parameters. The model reproduces peak growth rates and its functional form is simple enough to be incorporated into reactive transport or other macroscopic models designed for predictions in porous media. However, it currently cannot model equilibrium, pH effects, and may overestimate rates at high aqueous calcium-to-carbonate ratios. The discrepancies in rates at high calcium-to-carbonate ratios may be due to differences in pre-treatment, such as exposing the seed material to SI 1.0 to generate/develop growth hillocks, or other factors.

  3. Net Assimilation Rate Determines the Growth Rates of 14 Species of Subtropical Forest Trees.

    Directory of Open Access Journals (Sweden)

    Xuefei Li

    Full Text Available Growth rates are of fundamental importance for plants, as individual size affects myriad ecological processes. We determined the factors that generate variation in RGR among 14 species of trees and shrubs that are abundant in subtropical Chinese forests. We grew seedlings for two years at four light levels in a shade-house experiment. We monitored the growth of every juvenile plant every two weeks. After one and two years, we destructively harvested individuals and measured their functional traits and gas-exchange rates. After calculating individual biomass trajectories, we estimated relative growth rates using nonlinear growth functions. We decomposed the variance in log(RGR to evaluate the relationships of RGR with its components: specific leaf area (SLA, net assimilation rate (NAR and leaf mass ratio (LMR. We found that variation in NAR was the primary determinant of variation in RGR at all light levels, whereas SLA and LMR made smaller contributions. Furthermore, NAR was strongly and positively associated with area-based photosynthetic rate and leaf nitrogen content. Photosynthetic rate and leaf nitrogen concentration can, therefore, be good predictors of growth in woody species.

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

  7. Linear Stability of Binary Alloy Solidification for Unsteady Growth Rates

    Science.gov (United States)

    Mazuruk, K.; Volz, M. P.

    2010-01-01

    An extension of the Mullins and Sekerka (MS) linear stability analysis to the unsteady growth rate case is considered for dilute binary alloys. In particular, the stability of the planar interface during the initial solidification transient is studied in detail numerically. The rapid solidification case, when the system is traversing through the unstable region defined by the MS criterion, has also been treated. It has been observed that the onset of instability is quite accurately defined by the "quasi-stationary MS criterion", when the growth rate and other process parameters are taken as constants at a particular time of the growth process. A singular behavior of the governing equations for the perturbed quantities at the constitutional supercooling demarcation line has been observed. However, when the solidification process, during its transient, crosses this demarcation line, a planar interface is stable according to the linear analysis performed.

  8. Feed consumption, growth and growth efficiency of rainbow trout (Oncorhynchus mykiss (Walbaum)) fed on diets containing a bacterial single-cell protein.

    Science.gov (United States)

    Perera, W M; Carter, C G; Houlihan, D F

    1995-04-01

    The aim of the present study was to compare the nutritive value of bacterial single-cell protein (BSCP) with that of fishmeal in rainbow trout (Oncorhynchus mykiss (Walbaum)). Four diets were formulated to contain a total of 458 g crude protein/kg of which 0% was from BSCP in diet 1 (BSCP-0), 25% in diet 2 (BSCP-25), 62.5% in diet 3 (BSCP-62.5) and 100% in diet 4 (BSCP-100); the remainder of the protein was from fishmeal. There were two studies: in study 1, duplicate groups of twenty-five fish were fed on one of the four experimental diets at the rate of 20 g/kg body weight per d for 132 d. Feed consumption rates of individual fish were measured using radiography and the overall apparent absorption efficiency for N in each group was measured over a 2-week period. In study 2, N intake, consumption, absorption and accretion were measured for each fish under controlled environmental conditions (12 h: 12 h light-dark regime; 14 degrees). Higher dietary levels of BSCP resulted in significantly higher feed consumption rates but reduced N absorption efficiency and growth rates. However, a diet containing 25% BSCP (75% fishmeal) did not significantly influence growth rates, feed consumption and absorption efficiency compared with a 100% fishmeal diet. The N growth efficiencies were highest in fish fed on the diet containing the highest level of fishmeal and significantly decreased with increasing BSCP content. Construction of N budgets demonstrated that the reduction in growth in fish eating an increasingly larger proportion of BSCP was due to a decrease in N absorption and an increase in the excretion of urea.

  9. Sales Growth Rate Forecasting Using Improved PSO and SVM

    Directory of Open Access Journals (Sweden)

    Xibin Wang

    2014-01-01

    Full Text Available Accurate forecast of the sales growth rate plays a decisive role in determining the amount of advertising investment. In this study, we present a preclassification and later regression based method optimized by improved particle swarm optimization (IPSO for sales growth rate forecasting. We use support vector machine (SVM as a classification model. The nonlinear relationship in sales growth rate forecasting is efficiently represented by SVM, while IPSO is optimizing the training parameters of SVM. IPSO addresses issues of traditional PSO, such as relapsing into local optimum, slow convergence speed, and low convergence precision in the later evolution. We performed two experiments; firstly, three classic benchmark functions are used to verify the validity of the IPSO algorithm against PSO. Having shown IPSO outperform PSO in convergence speed, precision, and escaping local optima, in our second experiment, we apply IPSO to the proposed model. The sales growth rate forecasting cases are used to testify the forecasting performance of proposed model. According to the requirements and industry knowledge, the sample data was first classified to obtain types of the test samples. Next, the values of the test samples were forecast using the SVM regression algorithm. The experimental results demonstrate that the proposed model has good forecasting performance.

  10. Re-assessing copepod growth using the Moult Rate method

    DEFF Research Database (Denmark)

    Hirst, Andrew G.; Keister, J. E.; Richardson, A. J.;

    2014-01-01

    typically over-estimated growth rates (on 80% of occasions) for life stages where the subsequent stage is actively moulting; the median and mean MR values are 138 and 164%, respectively, of the corrected MMR values. We were unable to correct the original data for life stages that are followed by a non...

  11. 40 CFR 798.5500 - Differential growth inhibition of repair proficient and repair deficient bacteria: “Bacterial DNA...

    Science.gov (United States)

    2010-07-01

    ... repair proficient and repair deficient bacteria: âBacterial DNA damage or repair tests.â 798.5500 Section... CONTROL ACT (CONTINUED) HEALTH EFFECTS TESTING GUIDELINES Genetic Toxicity § 798.5500 Differential growth inhibition of repair proficient and repair deficient bacteria: “Bacterial DNA damage or repair tests.”...

  12. Computing the crystal growth rate by the interface pinning method

    DEFF Research Database (Denmark)

    Pedersen, Ulf Rørbæk; Hummel, Felix; Dellago, Christoph

    2015-01-01

    An essential parameter for crystal growth is the kinetic coefficient given by the proportionality between supercooling and average growth velocity. Here, we show that this coefficient can be computed in a single equilibrium simulation using the interface pinning method where two-phase configurati......An essential parameter for crystal growth is the kinetic coefficient given by the proportionality between supercooling and average growth velocity. Here, we show that this coefficient can be computed in a single equilibrium simulation using the interface pinning method where two...... is investigated in detail for the Lennard-Jones model. We find that the kinetic coefficient scales as the inverse square-root of temperature along the high temperature part of the melting line. The practical usability of the method is demonstrated by computing the kinetic coefficient of the elements...... Na and Si from first principles. A generalized version of the method may be used for computing the rates of crystal nucleation or other rare events....

  13. Exchange-Driven Growth with Birth Rate Less Than Death

    Institute of Scientific and Technical Information of China (English)

    LIN Zhen-Quan; KE Jian-Hong; YE Gao-Xiang

    2005-01-01

    We further study the kinetic behavior of the exchange-driven growth with birth and death for the case of birth rate kernel being less than that of death based on the mean-field theory. The symmetric exchange rate kernel is K(k,j) = K'(k,j) = Ikjv, and the birth and death rates are proportional to the aggregate's size. The long time asymptotic behavior of the aggregate size distribution ak(t) is found to obey a much unusual scaling law with an exponentially growing scaling function φ(x) = exp(x).

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Science.gov (United States)

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

    2011-12-01

    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.

  16. Growth of 48 built environment bacterial isolates on board the International Space Station (ISS).

    Science.gov (United States)

    Coil, David A; Neches, Russell Y; Lang, Jenna M; Brown, Wendy E; Severance, Mark; Cavalier, Darlene; Eisen, Jonathan A

    2016-01-01

    Background. While significant attention has been paid to the potential risk of pathogenic microbes aboard crewed spacecraft, the non-pathogenic microbes in these habitats have received less consideration. Preliminary work has demonstrated that the interior of the International Space Station (ISS) has a microbial community resembling those of built environments on Earth. Here we report the results of sending 48 bacterial strains, collected from built environments on Earth, for a growth experiment on the ISS. This project was a component of Project MERCCURI (Microbial Ecology Research Combining Citizen and University Researchers on ISS). Results. Of the 48 strains sent to the ISS, 45 of them showed similar growth in space and on Earth using a relative growth measurement adapted for microgravity. The vast majority of species tested in this experiment have also been found in culture-independent surveys of the ISS. Only one bacterial strain showed significantly different growth in space. Bacillus safensis JPL-MERTA-8-2 grew 60% better in space than on Earth. Conclusions. The majority of bacteria tested were not affected by conditions aboard the ISS in this experiment (e.g., microgravity, cosmic radiation). Further work on Bacillus safensis could lead to interesting insights on why this strain grew so much better in space.

  17. Relating Productivity Events to Holocene Bivalve Shell Growth Rates

    Science.gov (United States)

    Huntley, J. W.; Krause, R. A.; Kowalewski, M.; Romanek, C. S.; Kaufman, D. S.; Simoes, M. G.

    2007-12-01

    The growth rate of a bivalve can be influenced by many environmental factors that can change during the life of the organism. In this contribution we present initial data from a millennium scale chronology to assess the relationship between ontogenetic growth in the bivalve Semele casali and paleoenvironmental conditions preserved in the shell using growth increment analysis, radiocarbon-calibrated amino acid racemization dating techniques, stable isotopes (C and O) and high spatial resolution (125-150 samples per cm of shell profile) trace element (Ba, Mn) analysis (LA-ICPMS). Time-averaged specimens of S. casali were dredged from two sites at 10 meters and 30 meters depth along the inner continental shelf at Ubatuba Bay in the Southeast Brazilian Bight, an area influenced by productivity pulses triggered by coastal runoff events and coastal upwelling. Seventy-five individual valves were dated using amino acid racemization (aspartic acid). Dates were calculated using an expanded version of a previously published relationship (Barbour Wood et al., 2006 Quaternary Research 323- 331) between aspartic acid ratios and AMS radiocarbon dates of twelve S. casali individuals from the same sampling locations. The resulting time series has complete coverage for the past three thousand years at centennial resolution. From this time series, a sub-sample of dated valves was selected for more detailed growth increment, stable isotope and high-resolution trace element (Ba/Ca and Mn/Ca) analyses. Oceanic productivity is expressed differentially in the trace element profiles of S. casali with elevated Ba/Ca and Mn/Ca ratios capturing nutrient input through coastal runoff events while elevated Ba/Ca and depressed Mn/Ca ratios represent input through coastal upwelling. Fluctuations in Ba/Ca and Mn/Ca are not correlated to fluctuations in relative growth throughout the ontogeny of an individual bivalve, nor are they expected to be as periods of increased productivity are transient

  18. FACTORS LIMITING BACTERIAL GROWTH : III. CELL SIZE AND "PHYSIOLOGIC YOUTH" IN BACTERIUM COLI CULTURES.

    Science.gov (United States)

    Hershey, A D; Bronfenbrenner, J

    1938-07-20

    1. Measurements of the rate of oxygen uptake per cell in transplants of Bacterium coli from cultures of this organism in different phases of growth have given results in essential agreement with the observations of others. 2. Correlations of viable count, centrifugable nitrogen, and turbidity, with oxygen consumption, indicate that the increased metabolism during the early portion of the growth period is quantitatively referable to increased average size of cells. 3. Indirect evidence has suggested that the initial rate of growth of transplants is not related to the phase of growth of the parent culture.

  19. Scaling laws in the dynamics of crime growth rate

    CERN Document Server

    Alves, Luiz Gustavo de Andrade; Mendes, Renio dos Santos

    2013-01-01

    The increasing number of crimes in areas with large concentrations of people have made cities one of the main source of violence. Understanding characteristics of how crime rate expands and its relations with the cities size goes beyond an academic question, being a central issue for the contemporary society. Here, we characterize and analyze quantitative aspects of murders in the period from 1980 to 2009 in Brazilian cities. We find that the distribution of the annual, biannual and triannual logarithmic homicide growth rates exhibit the same functional form for distinct scales, that is, a scale invariant behaviour. We also identify asymptotic power-law decay relations between the standard deviations of these three growth rates and the initial size. Further, we discuss similarities with complex organizations.

  20. Inhibition of bacterial growth by different mixtures of propofol and thiopentone

    Directory of Open Access Journals (Sweden)

    K.E. Joubert

    2005-06-01

    Full Text Available Propofol is, as a result of its formulation, an ideal bacterial and yeast culture medium. An outbreak of sepsis in humans and an increase in wound infections in dogs has been ascribed to the use of propofol. It has been previously reported that a 1:1 mixture of propofol and thiopentone has bactericidal properties. This study was undertaken to determine if further serial mixtures of propofol and thiopentone maintained the bactericidal properties. Mixtures of 1:1 (solution A, 5:1 (solution B, 10:1 (solution C, 50:1 (solution D and 100:1 (solution E of 1 % propofol to 2.5 % thiopentone, 2.5 % thiopentone (solution T, 1 % propofol (solution P and saline (solution S were prepared and inoculated with between 105 and 106 colony-forming units of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. A sample was withdrawn from each solution at 0, 1, 6, 12, 48 and 120 hours after inoculation and a bacterial count was performed. This study showed that thiopentone and solution A behaved in similar fashion by inhibiting bacterial growth and was bactericidal after 48 hours. Solution B was not bactericidal against S. aureus and C. albicans. Propofol and solutions D and E all supported growth of all the organisms tested. These data indicate that mixtures of propofol and thiopentone at a ratio less than 1:1 do not maintain the bactericidal properties.

  1. Proximate causes of adaptive growth rates: growth efficiency variation among latitudinal populations of Rana temporaria.

    Science.gov (United States)

    Lindgren, B; Laurila, A

    2005-07-01

    In ectothermic organisms, declining season length and lower temperature towards higher latitudes often select for latitudinal variation in growth and development. However, the energetic mechanisms underlying this adaptive variation are largely unknown. We investigated growth, food intake and growth efficiency of Rana temporaria tadpoles from eight populations along a 1500 km latitudinal gradient across Sweden. To gain an insight into the mechanisms of adaptation at organ level, we also examined variation in tadpole gut length. The tadpoles were raised at two temperatures (16 and 20 degrees C) in a laboratory common garden experiment. We found increased growth rate towards higher latitudes, regardless of temperature treatment. This increase in growth was not because of a higher food intake rate, but populations from higher latitudes had higher growth efficiency, i.e. they were more efficient at converting ingested food into body mass. Low temperature reduced growth efficiency most strongly in southern populations. Relative gut length increased with latitude, and tadpoles at low temperature tended to have longer guts. However, variation in gut length was not the sole adaptive explanation for increased growth efficiency as latitude and body length still explained significant amounts of variation in growth efficiency. Hence, additional energetic adaptations are probably involved in growth efficiency variation along the latitudinal gradient.

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

    Science.gov (United States)

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

    1989-01-01

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

  3. Fatigue crack growth rate test using a frequency sweep method

    Institute of Scientific and Technical Information of China (English)

    Xun ZHOU; Xiao-li YU

    2008-01-01

    Fatigue crack propagation characteristics of a diesel engine crankshaft are studied by measuring the fatigue crack growth rate using a frequency sweep method on a resonant fatigue test rig. Based on the phenomenon that the system frequency will change when the crack becomes large, this method can be directly applied to a complex component or structure. Finite element analyses (FEAs) are performed to calibrate the relation between the frequency change and the crack size, and to obtain the natural frequency of the test rig and the stress intensity factor (SIF) of growing cracks. The crack growth rate i.e. da/dN-AK of each crack size is obtained by combining the testing-time monitored data and FEA results. The results show that the crack growth rate of engine crankshaft, which is a component with complex geometry and special surface treatment, is quite different from that of a pure material. There is an apparent turning point in the Paris's crack partition. The cause of the fatigue crack growth is also dis-cussed.

  4. THE INFLUENCE OF THE ECONOMIC GROWTH ON THE BIRTH RATE

    Directory of Open Access Journals (Sweden)

    SAVU MIHAELA

    2013-02-01

    Full Text Available The changes occurred over time in the population have effects on the economy, especially the reductions in thebirth rate which may lead to disturbances in the population structure. The relationship between the economic growthand the birth rate in Romania is analysed over an 11-year period, in order to see its intensity. The presentation of theevolution of the gross domestic product and of the birth rate is completed by the calculation of the Spearmancoefficient for determining the intensity of the relationship between the two indicators. The decrease of the birth rate isdetermined, to a modest extent, by the economic growth, with a wide range of factors that influence it. In this situation,the establishment and implementation of a birth rate recovery strategy is highly necessary to reduce the imbalancecreated in the population structure.

  5. Last Five Years Pakistan Economic Growth Rate GDP And Its Comparison With China India And Bangladesh

    OpenAIRE

    Abdul Rehman; Luan Jingdong; Yuneng Du

    2015-01-01

    Abstract This paper formulates and reviews Pakistans last five years economic growth rate and its comparison with the growth rate of China India and Bangladesh. As growth rate the amount of increment of a specific variable has gained within a specific period of time and context. In fact economic growth rate provides general direction and magnitude of growth for overall economy.

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

    Science.gov (United States)

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

    2012-12-01

    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.

  7. Functional properties of peanut fractions on the growth of probiotics and foodborne bacterial pathogens.

    Science.gov (United States)

    Peng, Mengfei; Bitsko, Elizabeth; Biswas, Debabrata

    2015-03-01

    Various compounds found in peanut (Arachis hypogaea) have been shown to provide multiple benefits to human health and may influence the growth of a broad range of gut bacteria. In this study, we investigated the effects of peanut white kernel and peanut skin on 3 strains of Lactobacillus and 3 major foodborne enteric bacterial pathogens. Significant (P microbes. We also found that within 72 h, PF inhibited growth of enterohemorrhagic Escherichia coli O157:H7 (EHEC), while PSE significantly (P < 0.05) inhibited Listeria monocytogenes but promoted the growth of both EHEC and Salmonella Typhimurium. The cell adhesion and invasion abilities of 3 pathogens to the host cells were also significantly (P < 0.05) reduced by 0.5% PF and 0.5% PSE. These results suggest that peanut white kernel might assist in improving human gut flora as well as reducing EHEC, whereas the beneficial effects of peanut skins require further research and investigation.

  8. Cationic Pillararenes Potently Inhibit Biofilm Formation without Affecting Bacterial Growth and Viability.

    Science.gov (United States)

    Joseph, Roymon; Naugolny, Alissa; Feldman, Mark; Herzog, Ido M; Fridman, Micha; Cohen, Yoram

    2016-01-27

    It is estimated that up to 80% of bacterial infections are accompanied by biofilm formation. Since bacteria in biofilms are less susceptible to antibiotics than are bacteria in the planktonic state, biofilm-associated infections pose a major health threat, and there is a pressing need for antibiofilm agents. Here we report that water-soluble cationic pillararenes differing in the quaternary ammonium groups efficiently inhibited the formation of biofilms by clinically important Gram-positive pathogens. Biofilm inhibition did not result from antimicrobial activity; thus, the compounds should not inhibit growth of natural bacterial flora. Moreover, none of the cationic pillararenes caused detectable membrane damage to red blood cells or toxicity to human cells in culture. The results indicate that cationic pillararenes have potential for use in medical applications in which biofilm formation is a problem. PMID:26745311

  9. Direct Observation of Aggregative Nanoparticle Growth: Kinetic Modeling of the Size Distribution and Growth Rate

    Energy Technology Data Exchange (ETDEWEB)

    Woehl, Taylor J.; Park, Chiwoo; Evans, James E.; Arslan, Ilke; Ristenpart, William D.; Browning, Nigel D.

    2014-01-08

    Direct observations of solution-phase nanoparticle growth using in situ liquid transmission electron microscopy (TEM) have demonstrated the importance of “non-classical” growth mechanisms, such as aggregation and coalescence, on the growth and final morphology of nanocrystals at the atomic and single nanoparticle scales. To date, groups have quantitatively interpreted the mean growth rate of nanoparticles in terms of the Lifshitz-Slyozov-Wagner (LSW) model for Ostwald ripening, but less attention has been paid to modeling the corresponding particle size distribution. Here we use in situ fluid stage scanning TEM to demonstrate that silver nanoparticles grow by a length-scale dependent mechanism, where individual nanoparticles grow by monomer attachment but ensemble-scale growth is dominated by aggregation. Although our observed mean nanoparticle growth rate is consistent with the LSW model, we show that the corresponding particle size distribution is broader and more symmetric than predicted by LSW. Following direct observations of aggregation, we interpret the ensemble-scale growth using Smoluchowski kinetics and demonstrate that the Smoluchowski model quantitatively captures the mean growth rate and particle size distribution.

  10. A study of the growth rates and growth habits of ice crystals in a solution of antifreeze (glyco) proteins

    Science.gov (United States)

    Li, Qianzhong; Luo, Liaofu

    1996-12-01

    The mechanism of the antifreeze glycoprotein/antifreeze protein interaction on the surface of ice is analyzed. The theory of ice crystal growth in an AF(G)P solution is presented. A quantitative calculation of the growth rates for gain growth has been obtained. The anisotropic growth habits and growth rates of ice crystals in an AF(G)P solution are explained.

  11. Improvements in plant growth rate using underwater discharge

    International Nuclear Information System (INIS)

    The drainage water from plant pots was irradiated by plasma and then recycled to irrigate plants for improving the growth rate by supplying nutrients to plants and inactivating the bacteria in the bed-soil. Brassica rapa var. perviridis (Chinese cabbage; Brassica campestris) plants were cultivated in pots filled with artificial soil, which included the use of chicken droppings as a fertiliser. The water was recycled once per day from a drainage water pool and added to the bed-soil in the pots. A magnetic compression type pulsed power generator was used to produce underwater discharge with repetition rate of 250 pps. The plasma irradiation times were set as 10 and 20 minutes per day over 28 days of cultivation. The experimental results showed that the growth rate increased significantly with plasma irradiation into the drainage water. The growth rate increased with the plasma irradiation time. The nitrogen concentration of the leaves increased as a result of plasma irradiation based on chlorophyll content analysis. The bacteria in the drainage water were inactivated by the plasma irradiation.

  12. 2,4,6-Trinitrotoluene mineralization and bacterial production rates of natural microbial assemblages from coastal sediments

    International Nuclear Information System (INIS)

    The nitrogenous energetic constituent, 2,4,6-Trinitrotoluene (TNT), is widely reported to be resistant to bacterial mineralization (conversion to CO2); however, these studies primarily involve bacterial isolates from freshwater where bacterial production is typically limited by phosphorus. This study involved six surveys of coastal waters adjacent to three biome types: temperate broadleaf, northern coniferous, and tropical. Capacity to catabolize and mineralize TNT ring carbon to CO2 was a common feature of natural sediment assemblages from these coastal environments (ranging to 270+/-38 μg C kg-1 d-1). More importantly, these mineralization rates comprised a significant proportion of total heterotrophic production. The finding that most natural assemblages surveyed from these ecosystems can mineralize TNT ring carbon to CO2 is consistent with recent reports that assemblage components can incorporate TNT ring carbon into bacterial biomass. These data counter the widely held contention that TNT is recalcitrant to bacterial catabolism of the ring carbon in natural environments. - Highlights: → TNT mineralization is a common feature of natural bacterial assemblages in coastal sediments. → TNT mineralization rates comprised a significant proportion of total heterotrophic production. → These data counter the widely held contention that TNT is recalcitrant to bacterial catabolism of the ring carbon in natural environments. - The capacity to mineralize TNT ring carbon to CO2 is a common feature of natural bacterial assemblages in coastal sediment.

  13. 2,4,6-Trinitrotoluene mineralization and bacterial production rates of natural microbial assemblages from coastal sediments

    Energy Technology Data Exchange (ETDEWEB)

    Montgomery, Michael T., E-mail: michael.montgomery@nrl.navy.mil [Naval Research Laboratory, Marine Biogeochemistry Section, Code 6114, 4555 Overlook Avenue, Washington, DC 20375 (United States); Coffin, Richard B., E-mail: richard.coffin@nrl.navy.mil [Naval Research Laboratory, Marine Biogeochemistry Section, Code 6114, 4555 Overlook Avenue, Washington, DC 20375 (United States); Boyd, Thomas J., E-mail: thomas.boyd@nrl.navy.mil [Naval Research Laboratory, Marine Biogeochemistry Section, Code 6114, 4555 Overlook Avenue, Washington, DC 20375 (United States); Smith, Joseph P., E-mail: joseph.smith@nrl.navy.mil [Naval Research Laboratory, Marine Biogeochemistry Section, Code 6114, 4555 Overlook Avenue, Washington, DC 20375 (United States); Walker, Shelby E., E-mail: Shelby.Walker@noaa.gov [Naval Research Laboratory, Marine Biogeochemistry Section, Code 6114, 4555 Overlook Avenue, Washington, DC 20375 (United States); Osburn, Christopher L., E-mail: chris_osburn@ncsu.edu [Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695 (United States)

    2011-12-15

    The nitrogenous energetic constituent, 2,4,6-Trinitrotoluene (TNT), is widely reported to be resistant to bacterial mineralization (conversion to CO{sub 2}); however, these studies primarily involve bacterial isolates from freshwater where bacterial production is typically limited by phosphorus. This study involved six surveys of coastal waters adjacent to three biome types: temperate broadleaf, northern coniferous, and tropical. Capacity to catabolize and mineralize TNT ring carbon to CO{sub 2} was a common feature of natural sediment assemblages from these coastal environments (ranging to 270+/-38 {mu}g C kg{sup -1} d{sup -1}). More importantly, these mineralization rates comprised a significant proportion of total heterotrophic production. The finding that most natural assemblages surveyed from these ecosystems can mineralize TNT ring carbon to CO{sub 2} is consistent with recent reports that assemblage components can incorporate TNT ring carbon into bacterial biomass. These data counter the widely held contention that TNT is recalcitrant to bacterial catabolism of the ring carbon in natural environments. - Highlights: > TNT mineralization is a common feature of natural bacterial assemblages in coastal sediments. > TNT mineralization rates comprised a significant proportion of total heterotrophic production. > These data counter the widely held contention that TNT is recalcitrant to bacterial catabolism of the ring carbon in natural environments. - The capacity to mineralize TNT ring carbon to CO{sub 2} is a common feature of natural bacterial assemblages in coastal sediment.

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

    Science.gov (United States)

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

    2014-07-01

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

  15. FINGERNAIL GROWTH RATE IN A NORMAL CHINESE POPULATION

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Objective To investigate fingernail growth rate (FNGR) role in the physiological or pathological status of the fingernails in normal Chinese population. Methods The FNGR was measured with vernier caliper. The data of 1 595 fingernails from 208 normal Chinese subjects (including 96 men and 112 women; age ranging from 14 to 78 years) were analyzed. Results The average FNGR was (0.104±0.027) mm per day. Higher growth rates were observed in males than in females, in the young individuals than in the old individuals, in summer than in winter, and in the right hand than in the left hand, respectively. The FNGR differed among fingernails and decreased in order of precedence: middle fingernails, index fingernails or ring fingernails, thumb and little fingernails. Conclusion FNGR was significantly associated with age, gender and temperature. Different fingernail grew at an individual speed.

  16. Noise in gene expression is coupled to growth rate

    OpenAIRE

    Keren, Leeat; van Dijk, David; Weingarten-Gabbay, Shira; Davidi, Dan; Jona, Ghil; Weinberger, Adina; Milo, Ron; Segal, Eran

    2015-01-01

    Genetically identical cells exposed to the same environment display variability in gene expression (noise), with important consequences for the fidelity of cellular regulation and biological function. Although population average gene expression is tightly coupled to growth rate, the effects of changes in environmental conditions on expression variability are not known. Here, we measure the single-cell expression distributions of approximately 900 Saccharomyces cerevisiae promoters across four...

  17. Impact of increased flow rate on specific growth rate of juvenile turbot (Scophthalmus maximus, Rafinesque 1810)

    NARCIS (Netherlands)

    Schram, E.; Verdegem, M.C.J.; Widjaja, R.T.O.B.H.; Kloet, C.J.; Foss, A.; Schelvis-Smit, A.A.M.

    2009-01-01

    The effect of flow rate on growth was investigated in juvenile turbot. Fish with a mean (SD) initial weight of 102 (10.4) g were reared at 6 different flow rates, equaling 1, 2, 3, 4, 6 or 8 tank volumes/h in 196 L tanks during 29 days at 18 ± 0.29 °C, a salinity of 18.0 ± 0.77¿ and a pH ranging fro

  18. Addition of selenium nanoparticles to electrospun silk scaffolds improves mammalian cell activity while reducing bacterial growth

    Directory of Open Access Journals (Sweden)

    Stanley Chung

    2016-07-01

    Full Text Available Silk possesses many beneficial wound healing properties, and electrospun scaffolds are especially applicable for skin applications, due to their smaller interstices and higher surface areas compared to non-electrospun equivalents. However, purified silk promotes microbial growth. In contrast, selenium nanoparticles have excellent antibacterial properties and are a novel antimicrobial chemistry. Here, electrospun silk scaffolds were doped with selenium nanoparticles to impart antibacterial properties to the silk scaffolds. Results showed significantly improved bacterial inhibition and improvement in human dermal fibroblast metabolic activity. These results suggest that the addition of selenium nanoparticles to electrospun silk is a promising approach to improve wound healing with reduced infection, without relying on antibiotics.

  19. Effect of growth rate and body mass on resting metabolic rate in galliform chicks

    NARCIS (Netherlands)

    Dietz, MW; Drent, RH

    1997-01-01

    In this study, we asked whether within-species variation in chick resting metabolic rate was related to variation in growth and whether this relationship changed during development in three galliform species (turkey, Meleagris gallopavo, guinea fowl, Numida meleagris, and Japanese quail, Coturnix co

  20. Temperature dependences of growth rates and carrying capacities of marine bacteria depart from metabolic theoretical predictions.

    Science.gov (United States)

    Huete-Stauffer, Tamara Megan; Arandia-Gorostidi, Nestor; Díaz-Pérez, Laura; Morán, Xosé Anxelu G

    2015-10-01

    Using the metabolic theory of ecology (MTE) framework, we evaluated over a whole annual cycle the monthly responses to temperature of the growth rates (μ) and carrying capacities (K) of heterotrophic bacterioplankton at a temperate coastal site. We used experimental incubations spanning 6ºC with bacterial physiological groups identified by flow cytometry according to membrane integrity (live), nucleic acid content (HNA and LNA) and respiratory activity (CTC+). The temperature dependence of μ at the exponential phase of growth was summarized by the activation energy (E), which was variable (-0.52 to 0.72 eV) but followed a seasonal pattern, only reaching the hypothesized value for aerobic heterotrophs of 0.65 eV during the spring bloom for the most active bacterial groups (live, HNA, CTC+). K (i.e. maximum experimental abundance) peaked at 4 × 10(6) cells mL(-1) and generally covaried with μ but, contrary to MTE predictions, it did not decrease consistently with temperature. In the case of live cells, the responses of μ and K to temperature were positively correlated and related to seasonal changes in substrate availability, indicating that the responses of bacteria to warming are far from homogeneous and poorly explained by MTE at our site. PMID:26362925

  1. Temperature dependences of growth rates and carrying capacities of marine bacteria depart from metabolic theoretical predictions

    KAUST Repository

    Huete-Stauffer, Tamara Megan

    2015-09-11

    Using the metabolic theory of ecology (MTE) framework, we evaluated over a whole annual cycle the monthly responses to temperature of the growth rates (μ) and carrying capacities (K) of heterotrophic bacterioplankton at a temperate coastal site. We used experimental incubations spanning 6oC with bacterial physiological groups identified by flow cytometry according to membrane integrity (live), nucleic acid content (HNA and LNA) and respiratory activity (CTC+). The temperature dependence of μat the exponential phase of growth was summarized by the activation energy (E), which was variable (-0.52 to 0.72 eV) but followed a seasonal pattern, only reaching the hypothesized value for aerobic heterotrophs of 0.65 eV during the spring bloom for the most active bacterial groups (live, HNA, CTC+). K (i.e. maximum experimental abundance) peaked at 4 × 106 cells mL-1 and generally covaried with μbut, contrary to MTE predictions, it did not decrease consistently with temperature. In the case of live cells, the responses of μand K to temperature were positively correlated and related to seasonal changes in substrate availability, indicating that the responses of bacteria to warming are far from homogeneous and poorly explained by MTE at our site. © FEMS 2015.

  2. In situ high rate growth of high temperature superconductor tapes

    Energy Technology Data Exchange (ETDEWEB)

    Hammond, M. R. B. (Malcom R. Beasley); Peng, L. S. (Luke S.); Wang, W. (Weizhi); Jo, W.; Ohnishi, T. (Tsuyoshi); Marshall, A. F. (Ann F.); Hammond, R. H. (Robert H.); Beasley, M. R. (Malcom R.); Peterson, E. J. (Eric J.); Ericson, R. (Richard)

    2001-01-01

    In situ high rate growth of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} superconducting films has been carried out using e-beam deposition. A deposition flux controller is developed to monitor and control the deposition rates using tunable diode laser based atomic absorption. Wide range of temperatures, deposition rates, and oxygen fluxes including atomic and molecular oxygen, as well as ozone, have been explored in order to understand both kinetic and thermodynamic stability. Critical current density above 1 MA/cm{sup 2} has been achieved on SrTiO{sub 3} substrate samples in growth rate up to 75 {angstrom}/sec. Samples prepared on IBAD YSZ/Ni tapes exhibit similar R(T)s and x-ray diffraction patterns. However, critical current densities of the tapes are around kA/cm{sup 2} or lower. The poor critical current density of the tape is attributed to interaction between the YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} film and the YSZ buffer layer.

  3. Salamander growth rates increase along an experimental stream phosphorus gradient.

    Science.gov (United States)

    Bumpers, Phillip M; Maerz, John C; Rosemond, Amy D; Benstead, Jonathan P

    2015-11-01

    Nutrient-driven perturbations to the resource base of food webs are predicted to attenuate with trophic distance, so it is unclear whether higher-level consumers will generally respond to anthropogenic nutrient loading. Few studies have tested whether nutrient (specifically, nitrogen [N] and phosphorus [P]) enrichment of aquatic ecosystems propagates through multiple trophic levels to affect predators, or whether N vs. P is relatively more important in driving effects on food webs. We conducted two-year whole-stream N and P additions to five streams to generate gradients in N and P concentration and N:P ratio (target N:P = 2, 8, 16, 32, 128). Larval salamanders are vertebrate predators of primary and secondary macroinvertebrate consumers in many heterotrophic headwater streams in which the basal resources are detritus and associated microorganisms. We determined the effects of N and P on the growth rates of caged and free-roaming larval Desmognathus quadramaculatus and the average body size of larval Eurycea wilderae. Growth rates and average body size increased by up to 40% and 60%, respectively, with P concentration and were negatively related to N:P ratio. These findings were consistent across both species of salamanders using different methodologies (cage vs. free-roaming) and at different temporal scales (3 months vs. 2 yr). Nitrogen concentration was not significantly related to increased growth rate or body size of the salamander species tested. Our findings suggest that salamander growth responds to the relaxation of ecosystem-level P limitation and that moderate P enrichment can have relatively large effects on vertebrate predators in detritus-based food webs. PMID:27070018

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

    Science.gov (United States)

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

    1984-02-01

    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

  5. Alcohol, intestinal bacterial growth, intestinal permeability to endotoxin, and medical consequences: summary of a symposium.

    Science.gov (United States)

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

    2008-08-01

    This report is a summary of the symposium on Alcohol, Intestinal Bacterial Growth, Intestinal Permeability to Endotoxin, and Medical Consequences, organized by National Institute on Alcohol Abuse and Alcoholism, Office of Dietary Supplements, and National Institute of Diabetes and Digestive and Kidney Diseases of National Institutes of Health in Rockville, Maryland, October 11, 2006. Alcohol exposure can promote the growth of Gram-negative bacteria in the intestine, which may result in accumulation of endotoxin. In addition, alcohol metabolism by Gram-negative bacteria and intestinal epithelial cells can result in accumulation of acetaldehyde, which in turn can increase intestinal permeability to endotoxin by increasing tyrosine phosphorylation of tight junction and adherens junction proteins. Alcohol-induced generation of nitric oxide may also contribute to increased permeability to endotoxin by reacting with tubulin, which may cause damage to microtubule cytoskeleton and subsequent disruption of intestinal barrier function. Increased intestinal permeability can lead to increased transfer of endotoxin from the intestine to the liver and general circulation where endotoxin may trigger inflammatory changes in the liver and other organs. Alcohol may also increase intestinal permeability to peptidoglycan, which can initiate inflammatory response in liver and other organs. In addition, acute alcohol exposure may potentiate the effect of burn injury on intestinal bacterial growth and permeability. Decreasing the number of Gram-negative bacteria in the intestine can result in decreased production of endotoxin as well as acetaldehyde which is expected to decrease intestinal permeability to endotoxin. In addition, intestinal permeability may be preserved by administering epidermal growth factor, l-glutamine, oats supplementation, or zinc, thereby preventing the transfer of endotoxin to the general circulation. Thus reducing the number of intestinal Gram-negative bacteria

  6. Sweet scents from good bacteria: Case studies on bacterial volatile compounds for plant growth and immunity.

    Science.gov (United States)

    Chung, Joon-hui; Song, Geun Cheol; Ryu, Choong-Min

    2016-04-01

    Beneficial bacteria produce diverse chemical compounds that affect the behavior of other organisms including plants. Bacterial volatile compounds (BVCs) contribute to triggering plant immunity and promoting plant growth. Previous studies investigated changes in plant physiology caused by in vitro application of the identified volatile compounds or the BVC-emitting bacteria. This review collates new information on BVC-mediated plant-bacteria airborne interactions, addresses unresolved questions about the biological relevance of BVCs, and summarizes data on recently identified BVCs that improve plant growth or protection. Recent explorations of bacterial metabolic engineering to alter BVC production using heterologous or endogenous genes are introduced. Molecular genetic approaches can expand the BVC repertoire of beneficial bacteria to target additional beneficial effects, or simply boost the production level of naturally occurring BVCs. The effects of direct BVC application in soil are reviewed and evaluated for potential large-scale field and agricultural applications. Our review of recent BVC data indicates that BVCs have great potential to serve as effective biostimulants and bioprotectants even under open-field conditions.

  7. Empirical formulas for description of the fatigue crack growth rate

    Energy Technology Data Exchange (ETDEWEB)

    Rozumek, D. [Opole University of Technology, Faculty of Mechanical Engineering, Opole (Poland)

    2010-02-15

    The paper presents the test results obtained for fatigue crack growth in flat specimens subjected to bending. The tests were conducted for different loading amplitudes and different load ratios using the {delta}J parameter. Accuracy of description of the fatigue crack growth rate was tested with use of different empirical formulas. One-side restrained specimens made of 10HNAP steel were tested. In each tested specimen, there was the external notch 5 mm in depth, and the notch rounding radius was {rho}=0.2 mm. The tests were carried out at the fatigue test stand MZGS-100 under loading frequency 28.8 Hz. It has been found that the obtained results depend on the applied empirical formula. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  8. Red and infrared laser therapy inhibits in vitro growth of major bacterial species that commonly colonize skin ulcers.

    Science.gov (United States)

    de Sousa, Natanael Teixeira Alves; Gomes, Rosana Caetano; Santos, Marcos Ferracioli; Brandino, Hugo Evangelista; Martinez, Roberto; de Jesus Guirro, Rinaldo Roberto

    2016-04-01

    Low-level laser therapy (LLLT) is used in chronic wounds due to its healing effects. However, bacterial species may colonize these wounds and the optimal parameters for effective bacterial inhibition are not clear. The aim of this study was to analyze the effect of LLLT on bacterial growth in vitro. Bacterial strains including Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were suspended in saline solution at a concentration of 10(3) cells/ml and exposed to laser irradiation at wavelengths of 660, 830, and 904 nm at fluences of 0 (control), 3, 6, 12, 18, and 24 J/cm(2). An aliquot of the irradiated suspension was spread on the surface of petri plates and incubated at 37 °C for quantification of colony-forming unit after 24, 48, and 72 h. Laser irradiation inhibited the growth of S. aureus at all wavelengths and fluences higher than 12 J/cm(2), showing a strong correlation between increase in fluence and bacterial inhibition. However, for P. aeruginosa, LLLT inhibited growth at all wavelengths only at a fluence of 24 J/cm(2). E. coli had similar growth inhibition at a wavelength of 830 nm at fluences of 3, 6, 12, and 24 J/cm(2). At wavelengths of 660 and 904 nm, growth inhibition was only observed at fluences of 12 and 18 J/cm(2), respectively. LLLT inhibited bacterial growth at all wavelengths, for a maximum of 72 h after irradiation, indicating a correlation between bacterial species, fluence, and wavelength. PMID:26886585

  9. Effects of sulfur chemistry and flow rate on fatigue crack growth rates in LWR environments

    International Nuclear Information System (INIS)

    Fatigue crack growth rate tests, at a load ratio of 0.2, have been conducted on steels of low, medium and high sulfur contents (0.004%, 0.013% and 0.025%) in PWR water at both low and high flow rates. Crack growth rates show no dependence on flow rate, but are strongly dependent on sulfur content, with a large proportion of environmental assistance for the highest sulfur contents. Tests of low and high sulfur content steels at a load ratio of 0.7 show relatively little environmental assistance in either case. The fractography of these specimens shows the usual brittle appearance for environmentally-assisted fatigue crack growth. In addition, the opposing fracture surfaces match perfectly, indicating that little or no dissolution of the metal matrix has occurred, and there is very little plastic flow associated with the fatigue cracking process. The x-ray photoelectron emission examination of the fracture surface oxides shows that FeS and FeS2 coexist in the oxide layer, suggesting that the conditions within the crack enclave involved near-neutral pH and cathodic potentials

  10. Combining prebiotics with probiotic bacteria can enhance bacterial growth and secretion of bacteriocins.

    Science.gov (United States)

    Pranckutė, Raminta; Kaunietis, Arnoldas; Kuisienė, Nomeda; Čitavičius, Donaldas J

    2016-08-01

    There is a growing interest in supporting human health by using prebiotics, such as oligosaccharides, and beneficial bacteria, also called probiotics. Combining these two components we can develop synbiotics. In order to create successful combination of synbiotic it is very important to evaluate the influence of prebiotic oligosaccharides to probiotic bacteria and their behavior, such as growth and secretion of health related biomolecules, including bacteriocins. In this study seven type strains of probiotic bacteria (five Lactobacillus sp. and two Lactococcus sp.) and two Lactobacillus sp. strains, isolated from probiotic yoghurt, were cultivated with various commercially available and extracted oligosaccharides (OS). The aim of this study was to evaluate the influence of these OS on type and isolated bacterial strains growth and antibacterial activity. Obtained results suggest that combination of certain OS with probiotic strains may considerably improve their growth and/or antibacterial activity. We also determined the antibacterial activity spectrum of investigated strains with combination of OS against common food borne pathogens. Results of this work show that prebiotic OS can be useful for modulating probiotic bacteria growth, antibacterial activity and even specificity of this activity. PMID:27181578

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

    Science.gov (United States)

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

    2014-08-01

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

  12. Effects of Interactions of Auxin-Producing Bacteria and Bacterial-Feeding Nematodes on Regulation of Peanut Growths

    OpenAIRE

    Li Xu; Wensi Xu; Ying Jiang; Feng Hu; Huixin Li

    2015-01-01

    The influences of an IAA (indole-3-acetic acid)-producing bacterium (Bacillus megaterium) and two bacterial-feeding nematodes (Cephalobus sp. or Mesorhabditis sp.) on the growth of peanut (Arachis hypogaea L. cv. Haihua 1) after various durations of time were investigated in natural soils. The addition of bacteria and nematodes and incubation time all significantly affected plant growth, plant root growth, plant nutrient concentrations, soil nutrient concentrations, soil microorganisms and so...

  13. Response of leaf endophytic bacterial community to elevated CO2 at different growth stages of rice plant

    OpenAIRE

    Ren, Gaidi; Zhang, Huayong; Lin, Xiangui; Zhu, Jianguo; Jia, Zhongjun

    2015-01-01

    Plant endophytic bacteria play an important role in plant growth and health. In the context of climate change, the response of plant endophytic bacterial communities to elevated CO2 at different rice growing stages is poorly understood. Using 454 pyrosequencing, we investigated the response of leaf endophytic bacterial communities to elevated CO2 (eCO2) at the tillering, filling, and maturity stages of the rice plant under different nitrogen fertilization conditions [low nitrogen fertilizatio...

  14. Response of leaf endophytic bacterial community to elevated CO2 at different growth stages of rice plant

    OpenAIRE

    Gaidi eRen; Huayong eZhang; Xiangui eLin; Jianguo eZhu; Zhongjun eJia

    2015-01-01

    Plant endophytic bacteria play an important role in plant growth and health. In the context of climate change, the response of plant endophytic bacterial communities to elevated CO2 at different rice growing stages is poorly understood. Using 454 pyrosequencing, we investigated the response of leaf endophytic bacterial communities to elevated CO2 (eCO2) at the tillering, filling and maturity stages of the rice plant under different nitrogen fertilization conditions (low nitrogen fertilization...

  15. Effects of assimilable organic carbon and free chlorine on bacterial growth in drinking water.

    Directory of Open Access Journals (Sweden)

    Xiaolu Liu

    Full Text Available Assimilable organic carbon (AOC is one of the most important factors affecting the re-growth of microorganisms in drinking water. High AOC concentrations result in biological instability, but disinfection kills microbes to ensure the safety of drinking water. Free chlorine is an important oxidizing agent used during the disinfection process. Therefore, we explored the combined effects of AOC and free chlorine on bacterial growth in drinking water using flow cytometry (FCM. The initial AOC concentration was 168 μg.L(-1 in all water samples. Without free chlorine, the concentrations of intact bacteria increased but the level of AOC decreased. The addition of sodium hypochlorite caused an increase and fluctuation in AOC due to the oxidation of organic carbon. The concentrations of intact bacteria decreased from 1.1 × 10(5 cells.mL(-1 to 2.6 × 10(4 cells.mL(-1 at an initial free chlorine dose of 0.6 mg.L(-1 to 4.8 × 10(4 cells.mL(-1 at an initial free chlorine dose of 0.3 mg.L(-1 due to free chlorine originating from sodium hypochlorite. Additionally, free chlorine might be more obviously affected AOC concentrations than microbial growth did. These results suggested that AOC and free chlorine might have combined effects on microbial growth. In this study, our results showed concentrations determined by FCM were higher than those by HPC, which indicated that some E. coli detected by FCM might not be detected using HPC in drinking water. The level of free chlorine might restrain the consumption of AOC by inhibiting the growth of E. coli; on the other hand, chlorination might increase the level of AOC, thereby increase the potential for microbial growth in the drinking water network.

  16. The plant pathogenic fungus Gaeumannomyces graminis var. tritici improves bacterial growth and triggers early gene regulations in the biocontrol strain Pseudomonas fluorescens Pf29Arp.

    Science.gov (United States)

    Barret, M; Frey-Klett, P; Boutin, M; Guillerm-Erckelboudt, A-Y; Martin, F; Guillot, L; Sarniguet, A

    2009-01-01

    In soil, some antagonistic rhizobacteria contribute to reduce root diseases caused by phytopathogenic fungi. Direct modes of action of these bacteria have been largely explored; however, commensal interaction also takes place between these microorganisms and little is known about the influence of filamentous fungi on bacteria. An in vitro confrontation bioassay between the pathogenic fungus Gaeumannomyces graminis var. tritici (Ggt) and the biocontrol bacterial strain Pseudomonas fluorescens Pf29Arp was set up to analyse bacterial transcriptional changes induced by the fungal mycelium at three time-points of the interaction before cell contact and up until contact. For this, a Pf29Arp shotgun DNA microarray was constructed. Specifity of Ggt effect was assessed in comparison with one of two other filamentous fungi, Laccaria bicolor and Magnaporthe grisea. During a commensal interaction, Ggt increased the growth rate of Pf29Arp. Before contact, Ggt induced bacterial genes involved in mycelium colonization. At contact, genes encoding protein of stress response and a patatin-like protein were up-regulated. Among all the bacterial genes identified, xseB was specifically up-regulated at contact by Ggt but down-regulated by the other fungi. Data showed that the bacterium sensed the presence of the fungus early, but the main gene alteration occurred during bacterial-fungal cell contact. PMID:19121038

  17. Nanoscale imaging of the growth and division of bacterial cells on planar substrates with the atomic force microscope

    Energy Technology Data Exchange (ETDEWEB)

    Van Der Hofstadt, M. [Institut de Bioenginyeria de Catalunya (IBEC), C/ Baldiri i Reixac 11-15, 08028 Barcelona (Spain); Hüttener, M.; Juárez, A. [Institut de Bioenginyeria de Catalunya (IBEC), C/ Baldiri i Reixac 11-15, 08028 Barcelona (Spain); Departament de Microbiologia, Universitat de Barcelona, Avinguda Diagonal 645, 08028 Barcelona (Spain); Gomila, G., E-mail: ggomila@ibecbarcelona.eu [Institut de Bioenginyeria de Catalunya (IBEC), C/ Baldiri i Reixac 11-15, 08028 Barcelona (Spain); Departament d' Electronica, Universitat de Barcelona, C/ Marti i Franqués 1, 08028 Barcelona (Spain)

    2015-07-15

    With the use of the atomic force microscope (AFM), the Nanomicrobiology field has advanced drastically. Due to the complexity of imaging living bacterial processes in their natural growing environments, improvements have come to a standstill. Here we show the in situ nanoscale imaging of the growth and division of single bacterial cells on planar substrates with the atomic force microscope. To achieve this, we minimized the lateral shear forces responsible for the detachment of weakly adsorbed bacteria on planar substrates with the use of the so called dynamic jumping mode with very soft cantilever probes. With this approach, gentle imaging conditions can be maintained for long periods of time, enabling the continuous imaging of the bacterial cell growth and division, even on planar substrates. Present results offer the possibility to observe living processes of untrapped bacteria weakly attached to planar substrates. - Highlights: • Gelatine coatings used to weakly attach bacterial cells onto planar substrates. • Use of the dynamic jumping mode as a non-perturbing bacterial imaging mode. • Nanoscale resolution imaging of unperturbed single living bacterial cells. • Growth and division of single bacteria cells on planar substrates observed.

  18. The Importance of Growth Kinetic Analysis in Determining Bacterial Susceptibility against Antibiotics and Silver Nanoparticles

    Directory of Open Access Journals (Sweden)

    Karsten eTheophel

    2014-11-01

    Full Text Available Routine antibiotics susceptibility testing still relies on standardized cultivation-based analyses, including measurement of inhibition zones in conventional agar diffusion tests and endpoint turbidity-based measurements. Here, we demonstrate that common off-line monitoring and endpoint determination after 18–24 h could be insufficient for reliable growth-dependent evaluation of antibiotic susceptibility. Different minimal inhibitory concentrations were obtained in 20- and 48-h microdilution plate tests using an Enterococcus faecium clinical isolate (strain UKI-MB07 as a model organism. Hence, we used an on-line kinetic assay for simultaneous cultivation and time-resolved growth analysis in a 96-well format instead of off-line susceptibility testing. Growth of the Enterococcus test organism was delayed up to 30 h in the presence of 0.25 µg mL-1 of vancomycin and 8 µg mL-1 of fosfomycin, after which pronounced growth was observed. Despite the delayed onset of growth, treatment with fosfomycin, daptomycin, fusidic acid, cefoxitin, or gentamicin resulted in higher maximum growth rates and/or higher final optical density values compared with antibiotic-free controls, indicating that growth stimulation and hormetic effects may occur with extended exposure to sublethal antibiotic concentrations. Whereas neither maximum growth rate nor final cell density correlated with antibiotic concentration, the lag phase duration for some antibiotics was a more meaningful indicator of dose-dependent growth inhibition. Our results also reveal that non-temporal growth profiles are only of limited value for cultivation-based antimicrobial silver nanoparticle susceptibility testing. The exposure to Ag(0 nanoparticles led to plasma membrane damage in a concentration-dependent manner and induced oxidative stress in Enterococcus faecium UKI-MB07, as shown by intracellular ROS accumulation.

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

    Science.gov (United States)

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

    2014-01-01

    Routine antibiotics susceptibility testing still relies on standardized cultivation-based analyses, including measurement of inhibition zones in conventional agar diffusion tests and endpoint turbidity-based measurements. Here, we demonstrate that common off-line monitoring and endpoint determination after 18-24 h could be insufficient for reliable growth-dependent evaluation of antibiotic susceptibility. Different minimal inhibitory concentrations were obtained in 20- and 48 h microdilution plate tests using an Enterococcus faecium clinical isolate (strain UKI-MB07) as a model organism. Hence, we used an on-line kinetic assay for simultaneous cultivation and time-resolved growth analysis in a 96-well format instead of off-line susceptibility testing. Growth of the Enterococcus test organism was delayed up to 30 h in the presence of 0.25 μg mL(-1) of vancomycin and 8 μg mL(-1) of fosfomycin, after which pronounced growth was observed. Despite the delayed onset of growth, treatment with fosfomycin, daptomycin, fusidic acid, cefoxitin, or gentamicin resulted in higher maximum growth rates and/or higher final optical density values compared with antibiotic-free controls, indicating that growth stimulation and hormetic effects may occur with extended exposure to sublethal antibiotic concentrations. Whereas neither maximum growth rate nor final cell density correlated with antibiotic concentration, the lag phase duration for some antibiotics was a more meaningful indicator of dose-dependent growth inhibition. Our results also reveal that non-temporal growth profiles are only of limited value for cultivation-based antimicrobial silver nanoparticle susceptibility testing. The exposure to Ag(0) nanoparticles led to plasma membrane damage in a concentration-dependent manner and induced oxidative stress in Enterococcus faecium UKI-MB07, as shown by intracellular ROS accumulation. PMID:25426104

  20. Phenomenology of infant death rates. Identification of the peaks of viral and bacterial diseases

    CERN Document Server

    Richmond, Peter

    2016-01-01

    After birth setting up an effective immune system is a major challenge for all living organisms. In this paper we show that this process can be explored by using the age-specific infant death rate as a kind of sensor. This is made possible because, as shown by the authors in Berrut et al. (2016), between birth and a critical age t_c, for all mammals the death rate decreases with age as an hyperbolic function. For humans t_c is equal to 10 years. At some ages the hyperbolic fall displays spikes which, it is assumed, correspond to specific events in the organism's response to exogenous factors. One of these spikes occurs 10 days after birth and there is another at the age of about 300 days. It is shown that the first spike is related to viral infections whereas the second is related to bacterial diseases. By going back to former time periods during which infant mortality was much higher than currently, it is possible to get a magnified view of these peaks which in turn may give us useful information about how a...

  1. Attached biomass growth and substrate utilization rate in a moving bed biofilm reactor

    Directory of Open Access Journals (Sweden)

    J. J. Marques

    2008-12-01

    Full Text Available A moving bed bioreactor containing cubes of polyether foam immersed in a synthetic wastewater (an aqueous mixture of meat extract, yeast extract, dextrose, meat peptone, ammonium chloride, potassium chloride, sodium chloride, sodium bicarbonate, potassium mono-hydrogen-phosphate and magnesium sulphate was used to evaluate bacterial growth and biomass yield parameters based on Monod's equation. The wastewater was supplied in the bottom of the equipment flowing ascending in parallel with a diffused air current that provided the mixing of the reactor content. Suspended and attached biomass concentration was measured through gravimetric methods. Good agreement was found between experimental kinetic parameters values and those obtained by other researchers. The only significant difference was the high global biomass content about 2 times the values obtained in conventional processes, providing high performance with volumetric loading rates up to 5.5 kg COD/m³/d.

  2. Standard test method for measurement of fatigue crack growth rates

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 This test method covers the determination of fatigue crack growth rates from near-threshold to Kmax controlled instability. Results are expressed in terms of the crack-tip stress-intensity factor range (ΔK), defined by the theory of linear elasticity. 1.2 Several different test procedures are provided, the optimum test procedure being primarily dependent on the magnitude of the fatigue crack growth rate to be measured. 1.3 Materials that can be tested by this test method are not limited by thickness or by strength so long as specimens are of sufficient thickness to preclude buckling and of sufficient planar size to remain predominantly elastic during testing. 1.4 A range of specimen sizes with proportional planar dimensions is provided, but size is variable to be adjusted for yield strength and applied force. Specimen thickness may be varied independent of planar size. 1.5 The details of the various specimens and test configurations are shown in Annex A1-Annex A3. Specimen configurations other than t...

  3. The Terminal Oxidase Cytochrome bd Promotes Sulfide-resistant Bacterial Respiration and Growth.

    Science.gov (United States)

    Forte, Elena; Borisov, Vitaliy B; Falabella, Micol; Colaço, Henrique G; Tinajero-Trejo, Mariana; Poole, Robert K; Vicente, João B; Sarti, Paolo; Giuffrè, Alessandro

    2016-01-01

    Hydrogen sulfide (H2S) impairs mitochondrial respiration by potently inhibiting the heme-copper cytochrome c oxidase. Since many prokaryotes, including Escherichia (E.) coli, generate H2S and encounter high H2S levels particularly in the human gut, herein we tested whether bacteria can sustain sulfide-resistant O2-dependent respiration. E. coli has three respiratory oxidases, the cyanide-sensitive heme-copper bo3 enzyme and two bd oxidases much less sensitive to cyanide. Working on the isolated enzymes, we found that, whereas the bo3 oxidase is inhibited by sulfide with half-maximal inhibitory concentration IC50 = 1.1 ± 0.1 μM, under identical experimental conditions both bd oxidases are insensitive to sulfide up to 58 μM. In E. coli respiratory mutants, both O2-consumption and aerobic growth proved to be severely impaired by sulfide when respiration was sustained by the bo3 oxidase alone, but unaffected by ≤200 μM sulfide when either bd enzyme acted as the only terminal oxidase. Accordingly, wild-type E. coli showed sulfide-insensitive respiration and growth under conditions favouring the expression of bd oxidases. In all tested conditions, cyanide mimicked the functional effect of sulfide on bacterial respiration. We conclude that bd oxidases promote sulfide-resistant O2-consumption and growth in E. coli and possibly other bacteria. The impact of this discovery is discussed. PMID:27030302

  4. Molecular mechanisms for the evolution of bacterial morphologies and growth modes

    Directory of Open Access Journals (Sweden)

    Amelia M Randich

    2015-06-01

    Full Text Available Bacteria exhibit a rich diversity of morphologies. Within this diversity, there is a uniformity of shape for each species that is replicated faithfully each generation, suggesting that bacterial shape is as selectable as any other biochemical adaptation. We describe the spatiotemporal mechanisms that target peptidoglycan synthesis to different subcellular zones to generate the rod-shape of model organisms Escherichia coli and Bacillus subtilis. We then demonstrate, using the related genera Caulobacter and Asticcacaulis as examples, how the modularity of the core components of the peptidoglycan synthesis machinery permits repositioning of the machinery to achieve different growth modes and morphologies. Finally, we highlight cases in which the mechanisms that underlie morphological evolution are beginning to be understood, and how they depend upon the expansion and diversification of the core components of the peptidoglycan synthesis machinery.

  5. Altering the growth conditions of Gluconacetobacter xylinus to maximize the yield of bacterial cellulose.

    Science.gov (United States)

    Ruka, Dianne R; Simon, George P; Dean, Katherine M

    2012-06-20

    An extensive matrix of different growth conditions including media, incubation time, inoculum volume, surface area and media volume were investigated in order to maximize the yield of bacterial cellulose produced by Gluconacetobacter xylinus, which will be used as reinforcement material to produce fully biodegradable composites. Crystallinity was shown to be controllable depending on the media and conditions employed. Samples with significant difference in crystallinity in a range from 50% to 95% were produced. Through experimental design, the yield of cellulose was maximized; primarily this involved reactor surface area design, optimized media and the use of mannitol being the highest cellulose-producing carbon source. Increasing the volume of the media did achieve a higher cellulose yield, however this increase was not found to be cost or time effective.

  6. Sevoflurane Contamination: Water Accumulation in Sevoflurane Vaporizers Can Allow Bacterial Growth in the Vaporizer.

    Science.gov (United States)

    Wallace, Arthur W

    2016-06-15

    Sevoflurane vaporizers (GE Tec 7) were difficult to fill with "slow flow" and a need to "burp." Evaluation of the bottle of sevoflurane (AbbVie Ultane) demonstrated a contaminant. Four of the facilities' 13 sevoflurane vaporizers had the contaminant. Unopened sevoflurane bottles did not have evidence of contamination. The contaminant was found to be water at pH 6.0 growing Staphylococcus epidermidis. Gas chromatography revealed the production of multiple metabolites of sevoflurane, including primarily urea and 1,3,5-triazine-2,4,6(1H,3H,5H)-trione (83% and 9.6% of volatiles) in addition to multiple other organic molecules. Sevoflurane contains water that can accumulate in vaporizers allowing bacterial growth. PMID:27301057

  7. Small regulatory RNA-induced growth rate heterogeneity of Bacillus subtilis.

    Science.gov (United States)

    Mars, Ruben A T; Nicolas, Pierre; Ciccolini, Mariano; Reilman, Ewoud; Reder, Alexander; Schaffer, Marc; Mäder, Ulrike; Völker, Uwe; van Dijl, Jan Maarten; Denham, Emma L

    2015-03-01

    Isogenic bacterial populations can consist of cells displaying heterogeneous physiological traits. Small regulatory RNAs (sRNAs) could affect this heterogeneity since they act by fine-tuning mRNA or protein levels to coordinate the appropriate cellular behavior. Here we show that the sRNA RnaC/S1022 from the Gram-positive bacterium Bacillus subtilis can suppress exponential growth by modulation of the transcriptional regulator AbrB. Specifically, the post-transcriptional abrB-RnaC/S1022 interaction allows B. subtilis to increase the cell-to-cell variation in AbrB protein levels, despite strong negative autoregulation of the abrB promoter. This behavior is consistent with existing mathematical models of sRNA action, thus suggesting that induction of protein expression noise could be a new general aspect of sRNA regulation. Importantly, we show that the sRNA-induced diversity in AbrB levels generates heterogeneity in growth rates during the exponential growth phase. Based on these findings, we hypothesize that the resulting subpopulations of fast- and slow-growing B. subtilis cells reflect a bet-hedging strategy for enhanced survival of unfavorable conditions. PMID:25790031

  8. Small regulatory RNA-induced growth rate heterogeneity of Bacillus subtilis.

    Directory of Open Access Journals (Sweden)

    Ruben A T Mars

    2015-03-01

    Full Text Available Isogenic bacterial populations can consist of cells displaying heterogeneous physiological traits. Small regulatory RNAs (sRNAs could affect this heterogeneity since they act by fine-tuning mRNA or protein levels to coordinate the appropriate cellular behavior. Here we show that the sRNA RnaC/S1022 from the Gram-positive bacterium Bacillus subtilis can suppress exponential growth by modulation of the transcriptional regulator AbrB. Specifically, the post-transcriptional abrB-RnaC/S1022 interaction allows B. subtilis to increase the cell-to-cell variation in AbrB protein levels, despite strong negative autoregulation of the abrB promoter. This behavior is consistent with existing mathematical models of sRNA action, thus suggesting that induction of protein expression noise could be a new general aspect of sRNA regulation. Importantly, we show that the sRNA-induced diversity in AbrB levels generates heterogeneity in growth rates during the exponential growth phase. Based on these findings, we hypothesize that the resulting subpopulations of fast- and slow-growing B. subtilis cells reflect a bet-hedging strategy for enhanced survival of unfavorable conditions.

  9. Growth rate controlled barium partitioning in calcite and aragonite

    Science.gov (United States)

    Goetschl, Katja Elisabeth; Mavromatis, Vasileios; Baldermann, Andre; Purgstaller, Bettina; Dietzel, Martin

    2016-04-01

    The barium (Ba) content and the Ba/Ca molar ratios in biogenic and abiotic carbonates have been widely used from the scientific community as a geochemical proxy especially in marine and early diagenetic settings. The Ba content of carbonate minerals has been earlier associated to changes in oceanic circulation that may have been caused by upwelling, changes in weathering regimes and river-runoff as well as melt water discharge. The physicochemical controls of Ba ion incorporation in the two most abundant CaCO3 polymorphs found in Earth's surface environments, i.e. calcite and aragonite, have adequately been studied only for calcite. These earlier studies (i.e. [1]) suggest that at increasing growth rate, Ba partitioning in calcite is increasing as well. In contrast, to date the effect of growth rate on the partitioning of Ba in aragonite remains questionable, despite the fact that this mineral phase is the predominant carbonate-forming polymorph in shallow marine environments. To shed light on the mechanisms controlling Ba ion uptake in carbonates in this study we performed steady-state Ba co-precipitation experiments with calcite and aragonite at 25°C. The obtained results for the partitioning of Ba in calcite are in good agreement with those reported earlier by [1], whereas those for aragonite indicate a reduction of Ba partitioning at elevated aragonite growth rates, with the partitioning coefficient value between solid and fluid to be approaching the unity. This finding is good agreement with the formation of a solid solution in the aragonite-witherite system, owing to the isostructural crystallography of the two mineral phases. Moreover, our data set provides new insights that are required for reconstructing the evolution of the Ba content of pristine marine versus diagenetically altered carbonate minerals commonly occurring in marine subfloor settings, as the thermodynamically less stable aragonite will transform to calcite enriched in Ba, whilst affecting

  10. Response of leaf endophytic bacterial community to elevated CO2 at different growth stages of rice plant

    Directory of Open Access Journals (Sweden)

    Gaidi eRen

    2015-08-01

    Full Text Available Plant endophytic bacteria play an important role in plant growth and health. In the context of climate change, the response of plant endophytic bacterial communities to elevated CO2 at different rice growing stages is poorly understood. Using 454 pyrosequencing, we investigated the response of leaf endophytic bacterial communities to elevated CO2 (eCO2 at the tillering, filling and maturity stages of the rice plant under different nitrogen fertilization conditions (low nitrogen fertilization (LN and high nitrogen fertilization (HN. The results revealed that the leaf endophytic bacterial community was dominated by Gammaproteobacteria-affiliated families, such as Enterobacteriaceae and Xanthomonadaceae, which represent 28.7-86.8% and 2.14-42.6% of the total sequence reads, respectively, at all tested growth stages. The difference in the bacterial community structure between the different growth stages was greater than the difference resulting from the CO2 and nitrogen fertilization treatments. The eCO2 effect on the bacterial communities differed greatly under different nitrogen application conditions and at different growth stages. Specifically, eCO2 revealed a significant effect on the community structure under both LN and HN levels at the tillering stage; however, the significant effect of eCO2 was only observed under HN, rather than under the LN condition at the filling stage; no significant effect of eCO2 on the community structure at both the LN and HN fertilization levels was found at the maturity stage. These results provide useful insights into the response of leaf endophytic bacterial communities to elevated CO2 across rice growth stages.

  11. Rating Growth of Scientific Knowledge and Risk from Theory Bubbles

    CERN Document Server

    Loeb, Abraham

    2011-01-01

    In physics the value of a theory is measured by its agreement with experimental data. But how should the physics community gauge the value of an emerging theory that has not been tested experimentally as of yet? With no reality check, a hypothesis like string theory may linger for a while before physicists will know its actual value in describing nature. In this short article, I advocate the need for a website operated by graduate students that will use various measures of publicly available data (such as the growth rate of newly funded experiments, research grants, publications, and faculty jobs) to gauge the future dividends of various research frontiers. The analysis can benefit from past experience (e.g. in research areas that suffered from limited experimental data over long periods of time) and aim to alert the community of the risk from future theory bubbles.

  12. Aerosol observations and growth rates in the tropical tropopause layer

    Directory of Open Access Journals (Sweden)

    D. A. Waddicor

    2012-01-01

    Full Text Available We present a case study of Aitken and accumulation mode aerosol observed downwind of the anvils of deep tropical thunderstorms. The measurements were made by condensation nuclei counters flown on the Egrett high-altitude aircraft from Darwin during the ACTIVE campaign, in monsoon conditions producing widespread convection over land and ocean. Maximum measured concentrations of aerosol in the size range 10–100 nm were 25 000 cm−3 STP. By calculating back-trajectories from the observations, and projecting on to infrared satellite images, the time since the air exited cloud was estimated. In this way a time scale of ~ 3–4 h was derived for the 10–100 nm aerosol concentration to reach its peak. We examine the hypothesis that the growth in aerosol concentrations can be explained by production of sulphuric acid from SO2 followed by particle nucleation and coagulation. Estimates of the sulphuric acid production rate show that the observations are only consistent with this hypothesis if the particles coagulate to sizes > 10 nm much more quickly than is suggested by current theory. Alternatively, other condensible gases (possibly organic drive the growth of aerosol particles in the TTL.

  13. Age, growth rates, and paleoclimate studies of deep sea corals

    Science.gov (United States)

    Prouty, Nancy G; Roark, E. Brendan; Andrews, Allen; Robinson, Laura; Hill, Tessa; Sherwood, Owen; Williams, Branwen; Guilderson, Thomas P.; Fallon, Stewart

    2015-01-01

    Deep-water corals are some of the slowest growing, longest-lived skeletal accreting marine organisms. These habitat-forming species support diverse faunal assemblages that include commercially and ecologically important organisms. Therefore, effective management and conservation strategies for deep-sea corals can be informed by precise and accurate age, growth rate, and lifespan characteristics for proper assessment of vulnerability and recovery from perturbations. This is especially true for the small number of commercially valuable, and potentially endangered, species that are part of the black and precious coral fisheries (Tsounis et al. 2010). In addition to evaluating time scales of recovery from disturbance or exploitation, accurate age and growth estimates are essential for understanding the life history and ecology of these habitat-forming corals. Given that longevity is a key factor for population maintenance and fishery sustainability, partly due to limited and complex genetic flow among coral populations separated by great distances, accurate age structure for these deep-sea coral communities is essential for proper, long-term resource management.

  14. Effect of inactive yeast cell wall on growth performance, survival rate and immune parameters in Pacific White Shrimp (Litopenaeus vannamei

    Directory of Open Access Journals (Sweden)

    Rutchanee Chotikachinda

    2008-10-01

    Full Text Available Effects of dietary inactive yeast cell wall on growth performance, survival rate, and immune parameters in pacific white shrimp (Litopenaeus vannamei was investigated. Three dosages of inactive yeast cell wall (0, 1, and 2 g kg-1 were tested in three replicate groups of juvenile shrimps with an average initial weight of 7.15±0.05 g for four weeks. There was no significant difference in final weight, survival rate, specific growth rate, feed conversion ratio, feed intake, protein efficiency ratio, and apparent net protein utilization of each treatments. However, different levels of inactive yeast cell wall showed an effect on certain immune parameters (p<0.05. Total hemocyte counts, granular hemocyte count, and bacterial clearance were better in shrimp fed diets supplemented with 1 and 2 g kg-1 inactive yeast cell wall as compared with thecontrol group.

  15. Error Growth Rate in the MM5 Model

    Science.gov (United States)

    Ivanov, S.; Palamarchuk, J.

    2006-12-01

    The goal of this work is to estimate model error growth rates in simulations of the atmospheric circulation by the MM5 model all the way from the short range to the medium range and beyond. The major topics are addressed to: (i) search the optimal set of parameterization schemes; (ii) evaluate the spatial structure and scales of the model error for various atmospheric fields; (iii) determine geographical regions where model errors are largest; (iv) define particular atmospheric patterns contributing to the fast and significant model error growth. Results are presented for geopotential, temperature, relative humidity and horizontal wind components fields on standard surfaces over the Atlantic-European region during winter 2002. Various combinations of parameterization schemes for cumulus, PBL, moisture and radiation are used to identify which one provides a lesser difference between the model state and analysis. The comparison of the model fields is carried out versus ERA-40 reanalysis of the ECMWF. Results show that the rate, at which the model error grows as well as its magnitude, varies depending on the forecast range, atmospheric variable and level. The typical spatial scale and structure of the model error also depends on the particular atmospheric variable. The distribution of the model error over the domain can be separated in two parts: the steady and transient. The first part is associated with a few high mountain regions including Greenland, where model error is larger. The transient model error mainly moves along with areas of high gradients in the atmospheric flow. Acknowledgement: This study has been supported by NATO Science for Peace grant #981044. The MM5 modelling system used in this study has been provided by UCAR. ERA-40 re-analysis data have been obtained from the ECMWF data server.

  16. Simultaneous Assessment of Acidogenesis-Mitigation and Specific Bacterial Growth-Inhibition by Dentifrices.

    Directory of Open Access Journals (Sweden)

    Sarah Forbes

    Full Text Available Dentifrices can augment oral hygiene by inactivating bacteria and at sub-lethal concentrations may affect bacterial metabolism, potentially inhibiting acidogenesis, the main cause of caries. Reported herein is the development of a rapid method to simultaneously measure group-specific bactericidal and acidogenesis-mitigation effects of dentifrices on oral bacteria. Saliva was incubated aerobically and anaerobically in Tryptone Soya Broth, Wilkins-Chalgren Broth with mucin, or artificial saliva and was exposed to dentifrices containing triclosan/copolymer (TD; sodium fluoride (FD; stannous fluoride and zinc lactate (SFD1; or stannous fluoride, zinc lactate and stannous chloride (SFD2. Minimum inhibitory concentrations (MIC were determined turbidometrically whilst group-specific minimum bactericidal concentrations (MBC were assessed using growth media and conditions selective for total aerobes, total anaerobes, streptococci and Gram-negative anaerobes. Minimum acid neutralization concentration (MNC was defined as the lowest concentration of dentifrice at which acidification was inhibited. Differences between MIC and MNC were calculated and normalized with respect to MIC to derive the combined inhibitory and neutralizing capacity (CINC, a cumulative measure of acidogenesis-mitigation and growth inhibition. The overall rank order for growth inhibition potency (MIC under aerobic and anaerobic conditions was: TD> SFD2> SFD1> FD. Acidogenesis-mitigation (MNC was ordered; TD> FD> SFD2> SFD1. CINC was ordered TD> FD> SFD2> SFD1 aerobically and TD> FD> SFD1> SFD2 anaerobically. With respect to group-specific bactericidal activity, TD generally exhibited the greatest potency, particularly against total aerobes, total anaerobes and streptococci. This approach enables the rapid simultaneous evaluation of acidity mitigation, growth inhibition and specific antimicrobial activity by dentifrices.

  17. The transport mechanism of bacterial Cu+-ATPases: distinct efflux rates adapted to different function.

    Science.gov (United States)

    Raimunda, Daniel; González-Guerrero, Manuel; Leeber, Blaise W; Argüello, José M

    2011-06-01

    Cu(+)-ATPases play a key role in bacterial Cu(+) homeostasis by participating in Cu(+) detoxification and cuproprotein assembly. Characterization of Archaeoglobus fulgidus CopA, a model protein within the subfamily of P(1B-1) type ATPases, has provided structural and mechanistic details on this group of transporters. Atomic resolution structures of cytoplasmic regulatory metal binding domains (MBDs) and catalytic actuator, phosphorylation, and nucleotide binding domains are available. These, in combination with whole protein structures resulting from cryo-electron microscopy analyses, have enabled the initial modeling of these transporters. Invariant residues in helixes 6, 7 and 8 form two transmembrane metal binding sites (TM-MBSs). These bind Cu(+) with high affinity in a trigonal planar geometry. The cytoplasmic Cu(+) chaperone CopZ transfers the metal directly to the TM-MBSs; however, loading both of the TM-MBSs requires binding of nucleotides to the enzyme. In agreement with the classical transport mechanism of P-type ATPases, occupancy of both transmembrane sites by cytoplasmic Cu(+) is a requirement for enzyme phosphorylation and subsequent transport into the periplasmic or extracellular milieus. Recent transport studies have shown that all Cu(+)-ATPases drive cytoplasmic Cu(+) efflux, albeit with quite different transport rates in tune with their various physiological roles. Archetypical Cu(+)-efflux pumps responsible for Cu(+) tolerance, like the Escherichia coli CopA, have turnover rates ten times higher than those involved in cuproprotein assembly (or alternative functions). This explains the incapability of the latter group to significantly contribute to the metal efflux required for survival in high copper environments. PMID:21210186

  18. Effect of Bacterial-Feeding Nematode Inoculation on{1mmWheatGrowth and N and P Uptake

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A 40-day gnotobiotic microcosm experiment was carried out to quantifythe effect of bacterial-feeding nematode on plant growth and nutrientabsorption. The results showed that inoculation of bacterial-feedingnematode { Protorhabditis sp. stimulated the growth of wheat(Triticum aestivum) and the uptake of N. By the end of the40-day incubation wheat biomass and N uptake in the treatment withnematode and bacteria (Pseudomonas sp.) increased by 6.5% and5.9%, respectively, compared with bacteria alone treatment. Thepresence of nematode mainly accelerated the growth of aboveground ofwheat, while it slightly inhibited the root development. There waslittle difference in plant tissue N concentration between treatments. Pconcentration and uptake of wheat, however, were generally reduced bynematode. It appears that the enhancement of plant growth and nitrogenuptake is attributed to the enhancement of nitrogen mineralizationinduced by nematode feeding on bacteria, and the reduction ofphosphorous uptake is the result of weak root status and competition bybacteria immobilization.

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

    Science.gov (United States)

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

    2013-11-01

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

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

    Directory of Open Access Journals (Sweden)

    Schrey Silvia D

    2012-08-01

    Full Text Available Abstract 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.

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

    Science.gov (United States)

    2012-01-01

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

  2. BACTERIAL BIOFILM FORMATION VERSUS MAMMALIAN CELL GROWTH ON TITANIUM-BASED MONO- AND BI-FUNCTIONAL COATINGS

    NARCIS (Netherlands)

    Subbiahdoss, Guruprakash; Pidhatika, Bidhari; Coullerez, Geraldine; Charnley, Mirren; Kuijer, Roel; van der Mei, Henny C.; Textor, Marcus; Busscher, Henk J.

    2010-01-01

    Biomaterials-associated-infections (BAI) are serious complications in modern medicine. Although non-adhesive coatings, like polymer-brush coatings, have been shown to prevent bacterial adhesion, they do not support cell growth. Bi-functional coatings are supposed to prevent biofilm formation while s

  3. Long-term warming of a subarctic heath decreases soil bacterial community growth but has no effects on its temperature adaptation

    DEFF Research Database (Denmark)

    Rinnan, Riikka; Michelsen, Anders; Bååth, E

    2011-01-01

    , respectively. The decrease was most likely due to decreased availability of labile substrate under warming. However, we found no evidence for temperature adaptation of soil bacterial communities. The optimum temperature for bacterial growth was on average 25 °C, and the apparent minimum temperature for growth......We tested whether bacterial communities of subarctic heath soil are adapted to elevated temperature after experimental warming by open-top greenhouses for 7 or 17 years. The long-term warming by 1–2 °C significantly decreased bacterial community growth, by 28% and 73% after 7 and 17 years...

  4. Bacterial and fungal growth for monitoring the impact of wildfire combined or not with different soil stabilization treatments

    Science.gov (United States)

    Barreiro, Ana; Baath, Erland; Díaz-Raviña, Montserrat

    2015-04-01

    Soil stabilization techniques are rapidly gaining acceptance as efficient tool for reducing post-fire erosion. However, despite its interest, information concerning their impact on soil biota is scarce. We examined, under field conditions, the bacterial and fungal medium-term responses in a hillslope area located in Laza (NW Spain) affected by a high severity wildfire with the following treatments established by triplicate (4 x 20 m plots): unburnt control soil, burnt control soil, burnt soil with rye seeding and burnt soil with straw mulch. The bacterial and fungal growth, as well as respiration, were measured 4 years after fire and application of treatments using leucine incorporation for bacterial growth and acetate-in-ergosterol incorporation for fungal growth. The results showed that soil respiration and fungal biomass were negatively affected by fire, in the top layer (0-5 cm), while bacterial and fungal growth was stimulated. These microbial changes induced by fire were associated with modifications in organic matter (50% reduction in C content) and soil pH (increase of 0.5-0.9 units). Thus, the results suggested that under acid environment (pH in water 3.5) post-fire conditions might have favoured both microbial groups, which is supported by the fact that estimated bacterial and fungal growth were positive and significant correlated with soil pH (range of 3.5-4.5). This contrast with the well-known reported investigations showing that bacteria rather than fungi proliferation occurred after prescribed fire or wildfire; it should be noticed, however, that soils with a higher pH than that in the present study were used. Our data also indicated that bacterial and fungal communities were not significantly affected by seeding and mulching treatments. The results highlighted the importance of pre-fire soil pH as key factor in determining the microbial response after fire. Acknowledgements. A. Barreiro is recipient of FPU grant from Spanish Ministry of Education

  5. Growth responses of Picea mongolica seedlings to defoliation rate

    Institute of Scientific and Technical Information of China (English)

    ZOU Chun-jing; HAN Shi-jie; QI Shu-yan; XU Wen-duo; LI Dao-tang

    2005-01-01

    Picea mongolica W. D. Xu. is an endemic species in China. The spruce forest is only found in semi-arid habitat in Inner Mongolia Autonomous Region of China. Based on the simulative defoliation experiment, it was proved that Picea mongolica seedlings had the compensatory and overcompensatory effects under the certain defoliation rate. The results of variance analysis on growth indexes showed that in PM Ⅰ (natural regeneration seedlings under Picea mongolica forest), the differences of H1 (height in June 23) and H2 (height in September 3) were extremely significant, and the difference of D(diameter at the breast height) were not significant. In PM Ⅱ (artificial regeneration seedlings under Betula platyphylla Suk. forest), the difference of H1 was significant, the difference of H2 was not significant, and the difference of D was extremely significant. The regression equations were established and the compensatory and overcompensatory points were obtained. In PM Ⅰ , the compensatory points of H1, H2, and D were 0.7628, 0.7436, 0.5725, and the overcompensatory points were 0.6056, 0.5802 and 0.2909 respectively. In PM Ⅱ, the compensatory points of H1, H2, and D are 0.5012, 0.3421, 0.2488, and the overcompensatory points are 0.4137, 0.2633 and 0.0747 respectively. These results suggested that the induction of compensatory growth mechanisms in spruce seedlings required a threshold level of defoliation, and the insects in Picea mongolica forest could be controlled in a certain degree.

  6. Clostridial necrotic enteritis in chicken associated with growth rate depression

    Directory of Open Access Journals (Sweden)

    Adin Priadi

    2008-03-01

    Full Text Available Clostridium perfringens (C. perfringens is a normal inhabitant of the intestinal tract of chickens as well as a potential pathogen causing necrotic enteritis. C. perfringens only causes necrotic enteritis when it transforms from non-toxin producing type to toxin producing type. The alpha toxin, (phospholipase C is believed to be a key to the occurrence of Clostridial necrotic enteritis (CNE. The best known predisposing factor is mucosal damage, caused by coccidiosis that damages the intestinal lining, making the gut susceptible to infections including C. perfringens. The purpose of this study was to observe the chicken performance in experimental CNE and field cases of CNE. Diagnosis of CNE were made by latex agglutination test, isolation and identification of the agent. Pathological and histopathological changes were also observed. Experimentally, NE could be reproduced when Eimeria sp and C. perfringens spores are inoculated in chicken. Signs of an NE are wet litter and diarrhea, and an increase in mortality is not often obvious. The depression of growth rate and feed efficiency of chicken become noticeable by week 5 because of damage to the intestine and the subsequent reduction in digestion and absorption of food. Subclinical form of CNE was also frequently found in the field, leading to significant decreases in performance. Chicken gut samples examinations revealed that subclinical form of CNE causes damage to the intestinal mucosa caused by C. perfringens leads to decreased digestion and absorption, increased feed conversion ratio and reduced weight gain. Dual infection with C. perfringens and Eimeria sp. was frequently found in field. The results of these studies provide evidence for C. perfringens as a causative bacteria for growth depression.

  7. Growth-rate regulated genes have profound impact on interpretation of transcriptome profiling in Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Regenberg, Birgitte; Grotkjaer, Thomas; Winther, Ole;

    2006-01-01

    Growth rate is central to the development of cells in all organisms. However, little is known about the impact of changing growth rates. We used continuous cultures to control growth rate and studied the transcriptional program of the model eukaryote Saccharomyces cerevisiae, with generation time...

  8. OPTIMAL CONTROL OF GROWTH RATE FOR A CLASS OF POPULATION SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    WUZhuoqun; GAOHang; 等

    2003-01-01

    In this paper,we discuss the optimal control of growth rate for a class of population systems governed by nonlinear degenerate parabolic equations.Given an ap-propriate cost functional,we prove the existence of the optimal growth rate and give some necessary conditions for optimal growth rate.

  9. OPTIMAL CONTROL OF GROWTH RATE FOR A CLASS OF POPULATION SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    WU Zhuoqun; YIN Jingxue; GAO Hang

    2003-01-01

    In this paper, we discuss the optimal control of growth rate for a class ofpopulation systems governed by nonlinear degenerate parabolic equations. Given an ap-propriate cost functional, we prove the existence of the optimal growth rate and give somenecessary conditions for optimal growth rate.

  10. Product formation from thiophene by a mixed bacterial culture. Influence of benzene as growth substrate

    DEFF Research Database (Denmark)

    Rivas, Isabelle Marie; Mosbæk, Hans; Arvin, Erik

    2003-01-01

    The influence of benzene as a growth substrate on the cometabolic conversion of thiophene was investigated in batch systems with microorganisms originating from an creosote contaminated site. Benzene was shown to stimulate the conversion of thiophene with a first-order rate, during the initial...... phase of transformation. The microorganisms were able to transform thiophene in the absence of benzene at a zero-order rate. Thiophene was converted to five oxidation products, regardless of the presence of benzene. Benzene had no influence on the distribution of these oxidation products. The main...

  11. Utility of phenomenological models for describing temperature dependence of bacterial growth.

    OpenAIRE

    Heitzer, A.; Kohler, H P; Reichert, P.; Hamer, G

    1991-01-01

    We compared three unstructured mathematical models, the master reaction, the square root, and the damage/repair models, for describing the relationship between temperature and the specific growth rates of bacteria. The models were evaluated on the basis of several criteria: applicability, ease of use, simple interpretation of model parameters, problem-free determination of model parameters, statistical evaluation of goodness of fit (chi 2 test), and biological relevance. Best-fit parameters f...

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

    Science.gov (United States)

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

    2003-08-01

    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.

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

    Science.gov (United States)

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

    2003-08-01

    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

  14. The Italian Patient (Why Italian Growth Rates Diverges)

    OpenAIRE

    Scognamiglio Pasini Carlo

    2010-01-01

    The performance of Italian economy has always been a fascinating puzzle for economists, both during the miraculous economic boom and in the current age of zero growth. This paper identifies the sluggish productivity dynamic as the main explanatory factor of Italian growth limits. It analyses the existing relationship between productivity and growth from three different points of view: the Keynesian approach, Neo-monetarism and Supply-Side Economics. The paper analyses the Italian growth disea...

  15. Growth rate of sheep fed high fat ration

    Directory of Open Access Journals (Sweden)

    Darwinsyah Lubis

    1998-10-01

    Full Text Available Incorporating high amount of fats into the ration for ruminants will affect the rumen microbes adversely and will reducefiber digestion potential. To correct such negative effects, the free fatty acids used for feed should be bond with Ca++, so it canpassing through the rumen savely (rumen by-pass fat. To test the Ca-fat utilization biologically, 20 growing male Garut shee pwere used and fed with 4 type of isocaloric-isoprotein concentrate feed which were allotted based on a randomized block desig nwith 5 replications. The concentrate (C-A was a positive control diet, while C-B was substituted with 10% free fatty acids (negative control, C-C was substituted with 10% Ca-fat, and C-D with 15% Ca-fat. The concentrate feed was fed at 500 g/d, while forage (King grass was 4 kg/d. Results of the experiment showed that the negative effect of free fatty acids can be corrected if it was given in the form of Ca-fat. Growth rate curve indicating a good growing pattern, with average daily gain was 100.18, 87.68, 112.86, and 115.00 g/d (P0.05. Carcass production was relatively good, where for C-A, C-B, C-C, and C-D were 14.84, 14.68, 16.34, and 15.72 kg (P<0.05 respectively, with final live weights of 34.00, 31.74, 34.58, and 34.30 kg (P<0.05. It can be concluded that Ca-fat (rumen by-pass fat can be used as an energy source component for growing sheep diet, and give the best result at 10% substitution rate in concentrate feed.

  16. Estimation of uncertainty for fatigue growth rate at cryogenic temperatures

    Science.gov (United States)

    Nyilas, Arman; Weiss, Klaus P.; Urbach, Elisabeth; Marcinek, Dawid J.

    2014-01-01

    Fatigue crack growth rate (FCGR) measurement data for high strength austenitic alloys at cryogenic environment suffer in general from a high degree of data scatter in particular at ΔK regime below 25 MPa√m. Using standard mathematical smoothing techniques forces ultimately a linear relationship at stage II regime (crack propagation rate versus ΔK) in a double log field called Paris law. However, the bandwidth of uncertainty relies somewhat arbitrary upon the researcher's interpretation. The present paper deals with the use of the uncertainty concept on FCGR data as given by GUM (Guidance of Uncertainty in Measurements), which since 1993 is a recommended procedure to avoid subjective estimation of error bands. Within this context, the lack of a true value addresses to evaluate the best estimate by a statistical method using the crack propagation law as a mathematical measurement model equation and identifying all input parameters. Each parameter necessary for the measurement technique was processed using the Gaussian distribution law by partial differentiation of the terms to estimate the sensitivity coefficients. The combined standard uncertainty determined for each term with its computed sensitivity coefficients finally resulted in measurement uncertainty of the FCGR test result. The described procedure of uncertainty has been applied within the framework of ITER on a recent FCGR measurement for high strength and high toughness Type 316LN material tested at 7 K using a standard ASTM proportional compact tension specimen. The determined values of Paris law constants such as C0 and the exponent m as best estimate along with the their uncertainty value may serve a realistic basis for the life expectancy of cyclic loaded members.

  17. Variation in coral growth rates with depth at Discovery Bay, Jamaica

    Energy Technology Data Exchange (ETDEWEB)

    Huston, M.

    1985-01-01

    Growth rates, determined by X-radiographic measurement of skeletal extension, decreased with depth for four of six species of coral examined at Discovery Bay, Jamaica. Growth of Porites astreoides, Montastrea annularis, Colpophyllia natans, and Siderastrea siderea decreased significantly with depth over a 1- to 30-m depth range. In Montastrea cavernosa, the highest growth rate occurred in the middle of the sampled depth range. Agaricia agaricites had no measurable change in growth rate with depth. A compilation of available growth data for Atlantic and Pacific corals shows a strong pattern of highest growth rates a short distance below the surface and a decrease with depth.

  18. The Influence of Ozonization For DO, BOD and Bacterial Growth in The Liquid Waste From Tanning Leather Industry

    International Nuclear Information System (INIS)

    The research of ozonization influence of dissolved oxygen (DO), biological oxygen demand (BOD) and the bacterial growth in the liquid waste from tanning leather industry has been done. The objectives of this research was to studied the influence of ozonization for decomposition process of the organic compound in these waste by indicator of BOD decreased, increased of DO and decomposer bacterial growth. The ozonization was carried out by time variation 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180, 195 and 210 minutes. Each samples of the waste has been ozonized keep in the sterile reaction tube for isolated of bacterial and the other keep in the bottle for BOD and DO measurement. These research results show that ozonization with 16.243 x 10-4 mg/second debit for 3 hours can decreased of BOD were 19.61 %, and ozonization for 3.5 hours can increased of DO were 82.5%. The other hand, 3 hours ozonization can decreased of kind of bacterial growth were 80 %. (author)

  19. Bacterial antigen induced release of soluble vascular endothelial growth factor (VEGF) and VEGFR1 before and after surgery

    DEFF Research Database (Denmark)

    Svendsen, Mads N; Lykke, J; Werther, Kim;

    2005-01-01

    OBJECTIVE: The influence of surgery on release of soluble vascular endothelial growth factor (sVEGF) and the soluble inhibitory receptor (sVEGFR1) is unknown. The effect of major and minor surgery on variations in sVEGF and sVEGFR1 concentrations in vivo was studied, and on bacterial antigen...... concentrations in plasma changed during surgery. In vitro stimulation of blood samples with bacteria-derived antigens resulted in a significant increase in sVEGF (p ... significantly with neutrophil cell counts (0.53 surgery. In vitro bacterial stimulation led to increased release of sVEGF, which...

  20. Bacterial growth and biofilm formation in household-stored groundwater collected from public wells.

    Science.gov (United States)

    Burkowska-But, Aleksandra; Kalwasińska, Agnieszka; Swiontek Brzezinska, Maria

    2015-06-01

    The research was aimed at assessing changes in the number of bacteria and evaluating biofilm formation in groundwater collected from public wells, both aspects directly related to the methods of household storage. In the research, water collected from Cretaceous aquifer wells in Toruń (Poland) was stored in a refrigerator and at room temperature. Microbiological parameters of the water were measured immediately after the water collection, and then after 3 and 7 days of storage under specified conditions. The microbiological examination involved determining the number of heterotrophic bacteria capable of growth at 22 and 37 °C, the number of spore-forming bacteria, and the total number of bacteria on membrane filters. The storage may affect water quality to such an extent that the water, which initially met the microbiological criteria for water intended for human consumption, may pose a health risk. The repeated use of the same containers for water storage results in biofilm formation containing live and metabolically active bacterial cells. PMID:26042968

  1. How Much Growth Can We Expect? A Conditional Analysis of R-CBM Growth Rates by Level of Performance

    Science.gov (United States)

    Silberglitt, Benjamin; Hintze, John M.

    2007-01-01

    This study examined the reading growth rates of 7,544 students in Grades 2-6, measured over 1 year using Reading-Curriculum-Based Measurement (R-CBM) benchmark assessments administered in the fall, winter, and spring. The authors used hierarchical linear modeling to establish and compare student rates of growth within each grade level based on…

  2. In vitro evaluation of Pseudomonas bacterial isolates from rice phylloplane for biocontrol of Rhizoctonia solani and plant growth promoting traits.

    Science.gov (United States)

    Akter, Shamima; Kadir, Jugah; Juraimi, Abdul Shukor; Saud, Halimi Mohd

    2016-07-01

    The ability for biocontrol and plant growth promotion of three Pseudomonas bacterial isolates namely Pseudomonas fluorescens (UMB20), Pseudomonas aeruginosa (KMB25) and Pseudomonas asplenii (BMB42) obtained from rice plants was investigated. Fungal growth inhibition by the isolates ranged from 86.85 to 93.15% in volatile and 100% in diffusible metabolites test. Among the isolates, BMB42 showed fungal growth inhibition significantly in the volatile metabolite test. Isolates UMB20 and BMB42 were able to synthesis chitinase with chitinolytic indices of 13.66 and 13.50, respectively. In case of -1,3-glucanase, all the isolates showed activity to produce this enzyme at varied levels and isolate KMB25 showed significantly highest activity (53.53 ppm). Among the three isolates, KMB25 showed positive response to protease production and all of them were negative to pectinase and lipase and positive to the production of siderophore, and HCN, and were able to solubilize tricalcium phosphate. All the three bacterial isolates were capable of forming biofilm at different levels. Above results suggest that phylloplane Pseudomonas bacterial isolates have potential for antifungal activities and plant growth promotion. PMID:27498507

  3. The lag-phase during diauxic growth is a trade-off between fast adaptation and high growth rate

    Science.gov (United States)

    Chu, Dominique; Barnes, David J.

    2016-04-01

    Bi-phasic or diauxic growth is often observed when microbes are grown in a chemically defined medium containing two sugars (for example glucose and lactose). Typically, the two growth stages are separated by an often lengthy phase of arrested growth, the so-called lag-phase. Diauxic growth is usually interpreted as an adaptation to maximise population growth in multi-nutrient environments. However, the lag-phase implies a substantial loss of growth during the switch-over. It therefore remains unexplained why the lag-phase is adaptive. Here we show by means of a stochastic simulation model based on the bacterial PTS system that it is not possible to shorten the lag-phase without incurring a permanent growth-penalty. Mechanistically, this is due to the inherent and well established limitations of biological sensors to operate efficiently at a given resource cost. Hence, there is a trade-off between lost growth during the diauxic switch and the long-term growth potential of the cell. Using simulated evolution we predict that the lag-phase will evolve depending on the distribution of conditions experienced during adaptation. In environments where switching is less frequently required, the lag-phase will evolve to be longer whereas, in frequently changing environments, the lag-phase will evolve to be shorter.

  4. Simplified Capacitance Monitoring for the Determination of Campylobacter spp. Growth Rates

    Science.gov (United States)

    Capacitance monitoring is commonly used as an efficient means to measure growth curves of bacterial pathogens. However, the use of capacitance monitoring with Campylobacter spp. was previously determined difficult due to the complexity of the required media. We investigated capacitance monitoring ...

  5. Discrete cyclic di-GMP-dependent control of bacterial predation versus axenic growth in Bdellovibrio bacteriovorus.

    Directory of Open Access Journals (Sweden)

    Laura Hobley

    2012-02-01

    Full Text Available Bdellovibrio bacteriovorus is a Delta-proteobacterium that oscillates between free-living growth and predation on Gram-negative bacteria including important pathogens of man, animals and plants. After entering the prey periplasm, killing the prey and replicating inside the prey bdelloplast, several motile B. bacteriovorus progeny cells emerge. The B. bacteriovorus HD100 genome encodes numerous proteins predicted to be involved in signalling via the secondary messenger cyclic di-GMP (c-di-GMP, which is known to affect bacterial lifestyle choices. We investigated the role of c-di-GMP signalling in B. bacteriovorus, focussing on the five GGDEF domain proteins that are predicted to function as diguanylyl cyclases initiating c-di-GMP signalling cascades. Inactivation of individual GGDEF domain genes resulted in remarkably distinct phenotypes. Deletion of dgcB (Bd0742 resulted in a predation impaired, obligately axenic mutant, while deletion of dgcC (Bd1434 resulted in the opposite, obligately predatory mutant. Deletion of dgcA (Bd0367 abolished gliding motility, producing bacteria capable of predatory invasion but unable to leave the exhausted prey. Complementation was achieved with wild type dgc genes, but not with GGAAF versions. Deletion of cdgA (Bd3125 substantially slowed predation; this was restored by wild type complementation. Deletion of dgcD (Bd3766 had no observable phenotype. In vitro assays showed that DgcA, DgcB, and DgcC were diguanylyl cyclases. CdgA lacks enzymatic activity but functions as a c-di-GMP receptor apparently in the DgcB pathway. Activity of DgcD was not detected. Deletion of DgcA strongly decreased the extractable c-di-GMP content of axenic Bdellovibrio cells. We show that c-di-GMP signalling pathways are essential for both the free-living and predatory lifestyles of B. bacteriovorus and that obligately predatory dgcC- can be made lacking a propensity to survive without predation of bacterial pathogens and thus possibly

  6. Export incentives, exchange rate policy and export growth in Turkey

    NARCIS (Netherlands)

    S.J.G. van Wijnbergen; I. Arslan

    1993-01-01

    The driving forces behind the Turkish export miracle, and in fact its very existence, have remained a matter of debate We show there was a boom. As to contributing factors, import growth in the Middle East in excess of import growth elsewhere made a negative contribution. On exports to non-oil count

  7. Effect of dietary supplementation of fructooligosaccharide (FOS) on growth performance, survival, lactobacillus bacterial population and hemato-immunological parameters of stellate sturgeon (Acipenser stellatus) juvenile.

    Science.gov (United States)

    Akrami, Reza; Iri, Yousef; Rostami, Hosseinali Khoshbavar; Razeghi Mansour, Majid

    2013-10-01

    The dietary supplementation of fructooligosaccharide (FOS) in stellate sturgeon juvenile, Acipenser stellatus (with mean initial body weight of 30.16 ± 0.14 g) was evaluated for the effect on growth, autochthonous intestinal microbiata and hemato-immunological parameters for 11 weeks. FOS was added at a level of 0, 1% and 2% to the commercial pellet diet (BioMar). At the end of the experiment, growth parameters, survival rate, lactobacillus bacterial population, hematological and immunological parameters were determined. The fish fed on 1% FOS significantly showed higher final weight, WG%, SGR and PER and lower FCR compared to those of the control group (P  0.05). However, FOS administration resulted in lower survival. The serum lysozyme activity was significantly affected by dietary 1% FOS (P  0.05). In fish fed on the diet with 1% FOS showed a significant increase of total heterotrophic autochthonous bacterial and presumptive LAB levels (P prebiotics. In addition to increase in WBC, RBC, MCV, hematocrit, hemoglobin and lymphocyte levels were observed in this group. These results indicated that dietary supplementation of FOS at a dose of 1% improved growth performance, beneficial intestinal microbiata and stimulate immune response of stellate sturgeon juvenile. PMID:23973846

  8. Valorization of lubricant-based wastewater for bacterial neutral lipids production: Growth-linked biosynthesis.

    Science.gov (United States)

    Da Silva, Pedro D M P; Lima, Filipa; Alves, Maria Madalena; Bijmans, Martijn F M; Pereira, Maria Alcina

    2016-09-15

    Lipids produced by microorganisms are currently of great interest as raw material for either biofuels or oleochemicals production. Significant biosynthesis of neutral lipids, such as triacylglycerol (TAG) and wax esters (WE) are thought to be limited to a few strains. Hydrocarbonoclastic bacteria (HCB), key players in bioremediation of hydrocarbon contaminated ecosystems, are among this group of strains. Hydrocarbon rich wastewaters have been overlooked concerning their potential as raw material for microbial lipids production. In this study, lubricant-based wastewater was fed, as sole carbon source, to two HCB representative wild strains: Alcanivorax borkumensis SK2, and Rhodococcus opacus PD630. Neutral lipid production was observed with both strains cultivated under uncontrolled conditions of pH and dissolved oxygen. A. borkumensis SK2 was further investigated in a pH- and OD-controlled fermenter. Different phases were assessed separately in terms of lipids production and alkanes removal. The maximum TAG production rate occurred during stationary phase (4 mg-TAG/L h). The maximum production rate of WE-like compounds was 15 mg/L h, and was observed during exponential growth phase. Hydrocarbons removal was 97% of the gas chromatography (GC) resolved straight-chain alkanes. The maximum removal rate was observed during exponential growth phase (6 mg-alkanes/L h). This investigation proposes a novel approach for the management of lubricant waste oil, aiming at its conversion into valuable lipids. The feasibility of the concept is demonstrated under low salt (0.3%) and saline (3.3%) conditions, and presents clues for its technological development, since growth associated oil production opens the possibility for establishing continuous fermentation processes. PMID:27244293

  9. Evaluation of bacterial contamination rate of the anterior chamber during phacoemulsification surgery using an automated microbial detection system

    Institute of Scientific and Technical Information of China (English)

    Ibrahim; Kocak; Funda; Kocak; Bahri; Teker; Ali; Aydin; Faruk; Kaya; Hakan; Baybora

    2014-01-01

    ·AIM: To assess the incidence of anterior chamber bacterial contamination during phacoemulsification surgery using an automated microbial detection system(BacT/Alert).·METHODS: Sixty-nine eyes of 60 patients who had uneventful phacoemulsification surgery, enrolled in this prospective study. No prophylactic topical or systemic antibiotics were used before surgery. After antisepsis with povidone-iodine, two intraoperative anterior chamber aqueous samples were obtained, the first whilst entering anterior chamber, and the second at the end of surgery. BacT/Alert culture system was used to detect bacterial contamination in the aqueous samples.·RESULTS: Neither aqueous samples obtained at the beginning nor conclusion of the surgery was positive for microorganisms on BacT/Alert culture system. The rate of bacterial contamination during surgery was 0%. None of the eyes developed acute-onset endophthalmitis after surgery.· CONCLUSION: In this study, no bacterial contamination of anterior chamber was observed during cataract surgery. This result shows that meticulous surgical preparation and technique can prevent anterior chamber contamination during phacoemulsification cataract surgery.

  10. Lowering GTP level increases survival of amino acid starvation but slows growth rate for Bacillus subtilis cells lacking (p)ppGpp.

    Science.gov (United States)

    Bittner, Alycia N; Kriel, Allison; Wang, Jue D

    2014-06-01

    Bacterial cells sense external nutrient availability to regulate macromolecular synthesis and consequently their growth. In the Gram-positive bacterium Bacillus subtilis, the starvation-inducible nucleotide (p)ppGpp negatively regulates GTP levels, both to resist nutritional stress and to maintain GTP homeostasis during growth. Here, we quantitatively investigated the relationship between GTP level, survival of amino acid starvation, and growth rate when GTP synthesis is uncoupled from its major homeostatic regulator, (p)ppGpp. We analyzed growth and nucleotide levels in cells that lack (p)ppGpp and found that their survival of treatment with a nonfunctional amino acid analog negatively correlates with both growth rate and GTP level. Manipulation of GTP levels modulates the exponential growth rate of these cells in a positive dose-dependent manner, such that increasing the GTP level increases growth rate. However, accumulation of GTP levels above a threshold inhibits growth, suggesting a toxic effect. Strikingly, adenine counteracts GTP stress by preventing GTP accumulation in cells lacking (p)ppGpp. Our results emphasize the importance of maintaining appropriate levels of GTP to maximize growth: cells can survive amino acid starvation by decreasing GTP level, which comes at a cost to growth, while (p)ppGpp enables rapid adjustment to nutritional stress by adjusting GTP level, thus maximizing fitness.

  11. Properties of bacterial endophytes and their proposed role in plant growth

    NARCIS (Netherlands)

    Hardoim, Pablo R.; van Overbeek, Leo S.; van Elsas, Jan Dirk

    2008-01-01

    Bacterial endophytes live inside plants for at least part of their life cycle. Studies of the interaction of endophytes with their host plants and their function within their hosts are important to address the ecological relevance of endophytes. The modulation of ethylene levels in plants by bacteri

  12. Adoption of multivariate copulae in prognostication of economic growth by means of interest rate

    Science.gov (United States)

    Saputra, Dewi Tanasia; Indratno, Sapto Wahyu, Dr.

    2015-12-01

    Inflation, at a healthy rate, is a sign of growing economy. Nonetheless, when inflation rate grows uncontrollably, it will negatively influence economic growth. Many tackle this problem by increasing interest rate to help protecting the value of money which is detained by inflation. There are few, however, who study the effects of interest rate in economic growth. The main purposes of this paper are to find how the change of interest rate affects economic growth and to use the relationship in prognostication of economic growth. By using expenditure model, a linear relationship between economic growth and interest rate is developed. The result is then used for prediction by normal copula and Vine Archimedean copula. It is shown that increasing interest rate to tackle inflation is a poor solution. Whereas implementation of copula in predicting economic growth yields an accurate result, with not more than 0.5% difference.

  13. Physical and bacterial controls on inorganic nutrients and dissolved organic carbon during a sea ice growth and decay experiment

    DEFF Research Database (Denmark)

    Zhou, J.; Delille, B.; Kaartokallio, H.;

    2014-01-01

    We investigated how physical incorporation, brine dynamics and bacterial activity regulate the distribution of inorganic nutrients and dissolved organic carbon (DOC) in artificial sea ice during a 19-day experiment that included periods of both ice growth and decay. The experiment was performed...... regulating the distribution of the dissolved compounds within sea ice are clearly a complex interaction of brine dynamics, biological activity and in the case of dissolved organic matter, the physico-chemical properties of the dissolved constituents themselves....

  14. Improving protein delivery of fibroblast growth factor-2 from bacterial inclusion bodies used as cell culture substrates

    OpenAIRE

    Seras Franzoso, Joaquin; Peebo, Karl; Garcia Fruitós, Elena; Vázquez Gómez, Esther; Rinas, Ursula; Villaverde Corrales, Antonio

    2014-01-01

    Altres ajuts: We are indebted CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN, Spain) for funding our research on inclusion bodies. Bacterial inclusion bodies (IBs) have recently been used to generate biocompatible cell culture interfaces, with diverse effects on cultured cells such as cell adhesion enhancement, stimulation of cell growth or induction of mesenchymal stem cell differentiation. Additionally, novel applications of IBs as sustained protein delivery systems with...

  15. Climate forcing growth rates: doubling down on our Faustian bargain

    Science.gov (United States)

    Hansen, James; Kharecha, Pushker; Sato, Makiko

    2013-03-01

    Rahmstorf et al 's (2012) conclusion that observed climate change is comparable to projections, and in some cases exceeds projections, allows further inferences if we can quantify changing climate forcings and compare those with projections. The largest climate forcing is caused by well-mixed long-lived greenhouse gases. Here we illustrate trends of these gases and their climate forcings, and we discuss implications. We focus on quantities that are accurately measured, and we include comparison with fixed scenarios, which helps reduce common misimpressions about how climate forcings are changing. Annual fossil fuel CO2 emissions have shot up in the past decade at about 3% yr-1, double the rate of the prior three decades (figure 1). The growth rate falls above the range of the IPCC (2001) 'Marker' scenarios, although emissions are still within the entire range considered by the IPCC SRES (2000). The surge in emissions is due to increased coal use (blue curve in figure 1), which now accounts for more than 40% of fossil fuel CO2 emissions. Figure 1. Figure 1. CO2 annual emissions from fossil fuel use and cement manufacture, an update of figure 16 of Hansen (2003) using data of British Petroleum (BP 2012) concatenated with data of Boden et al (2012). The resulting annual increase of atmospheric CO2 (12-month running mean) has grown from less than 1 ppm yr-1 in the early 1960s to an average ~2 ppm yr-1 in the past decade (figure 2). Although CO2 measurements were not made at sufficient locations prior to the early 1980s to calculate the global mean change, the close match of global and Mauna Loa data for later years suggests that Mauna Loa data provide a good approximation of global change (figure 2), thus allowing a useful estimate of annual global change beginning with the initiation of Mauna Loa measurements in 1958 by Keeling et al (1973). Figure 2. Figure 2. Annual increase of CO2 based on data from the NOAA Earth System Research Laboratory (ESRL 2012). CO2 change

  16. The transport mechanism of bacterial Cu+-ATPases: distinct efflux rates adapted to different function

    OpenAIRE

    Raimunda, Daniel; González-Guerrero, Manuel; Leeber, Blaise W.; Argüello, José M.

    2011-01-01

    Cu+-ATPases play a key role in bacterial Cu+ homeostasis by participating in Cu+ detoxification and cuproprotein assembly. Characterization of Archaeoglobus fulgidus CopA, a model protein within the subfamily of P1B-1 type ATPases, has provided structural and mechanistic details on this group of transporters. Atomic resolution structures of cytoplasmic regulatory metal binding domains (MBDs) and catalytic actuator, phosphorylation, and nucleotide binding domains are available. These, in combi...

  17. Constant growth rate can be supported by decreasing energy flux and increasing aerobic glycolysis

    NARCIS (Netherlands)

    Slavov, Nikolai; Budnik, Bogdan A; Schwab, David; Airoldi, Edoardo M; van Oudenaarden, Alexander

    2014-01-01

    Fermenting glucose in the presence of enough oxygen to support respiration, known as aerobic glycolysis, is believed to maximize growth rate. We observed increasing aerobic glycolysis during exponential growth, suggesting additional physiological roles for aerobic glycolysis. We investigated such ro

  18. Mycelium-Like Networks Increase Bacterial Dispersal, Growth, and Biodegradation in a Model Ecosystem at Various Water Potentials.

    Science.gov (United States)

    Worrich, Anja; König, Sara; Miltner, Anja; Banitz, Thomas; Centler, Florian; Frank, Karin; Thullner, Martin; Harms, Hauke; Kästner, Matthias; Wick, Lukas Y

    2016-05-15

    Fungal mycelia serve as effective dispersal networks for bacteria in water-unsaturated environments, thereby allowing bacteria to maintain important functions, such as biodegradation. However, poor knowledge exists on the effects of dispersal networks at various osmotic (Ψo) and matric (Ψm) potentials, which contribute to the water potential mainly in terrestrial soil environments. Here we studied the effects of artificial mycelium-like dispersal networks on bacterial dispersal dynamics and subsequent effects on growth and benzoate biodegradation at ΔΨo and ΔΨm values between 0 and -1.5 MPa. In a multiple-microcosm approach, we used a green fluorescent protein (GFP)-tagged derivative of the soil bacterium Pseudomonas putida KT2440 as a model organism and sodium benzoate as a representative of polar aromatic contaminants. We found that decreasing ΔΨo and ΔΨm values slowed bacterial dispersal in the system, leading to decelerated growth and benzoate degradation. In contrast, dispersal networks facilitated bacterial movement at ΔΨo and ΔΨm values between 0 and -0.5 MPa and thus improved the absolute biodegradation performance by up to 52 and 119% for ΔΨo and ΔΨm, respectively. This strong functional interrelationship was further emphasized by a high positive correlation between population dispersal, population growth, and degradation. We propose that dispersal networks may sustain the functionality of microbial ecosystems at low osmotic and matric potentials. PMID:26944849

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

    Directory of Open Access Journals (Sweden)

    Julie eDinasquet

    2012-08-01

    Full Text Available 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 16S 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.

  20. A systematic approach for the assessment of bacterial growth-controlling factors linked to biological stability of drinking water in distribution systems

    KAUST Repository

    Prest, E. I.

    2016-01-06

    A systematic approach is presented for the assessment of (i) bacterial growth-controlling factors in drinking water and (ii) the impact of distribution conditions on the extent of bacterial growth in full-scale distribution systems. The approach combines (i) quantification of changes in autochthonous bacterial cell concentrations in full-scale distribution systems with (ii) laboratoryscale batch bacterial growth potential tests of drinking water samples under defined conditions. The growth potential tests were done by direct incubation of water samples, without modification of the original bacterial flora, and with flow cytometric quantification of bacterial growth. This method was shown to be reproducible (ca. 4% relative standard deviation) and sensitive (detection of bacterial growth down to 5 μg L-1 of added assimilable organic carbon). The principle of step-wise assessment of bacterial growth-controlling factors was demonstrated on bottled water, shown to be primarily carbon limited at 133 (±18) × 103 cells mL-1 and secondarily limited by inorganic nutrients at 5,500 (±1,700) × 103 cells mL-1. Analysis of the effluent of a Dutch full-scale drinking water treatment plant showed (1) bacterial growth inhibition as a result of end-point chlorination, (2) organic carbon limitation at 192 (±72) × 103 cells mL-1 and (3) inorganic nutrient limitation at 375 (±31) × 103 cells mL-1. Significantly lower net bacterial growth was measured in the corresponding full-scale distribution system (176 (±25) × 103 cells mL-1) than in the laboratory-scale growth potential test of the same water (294 (±35) × 103 cells mL-1), highlighting the influence of distribution on bacterial growth. The systematic approach described herein provides quantitative information on the effect of drinking water properties and distribution system conditions on biological stability, which can assist water utilities in decision-making on treatment or distribution system improvements to

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

    OpenAIRE

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

    2014-01-01

    This research focused on the effects of different doses of Bacillus subtilis KN-42 on the growth performance, diarrhea incidence, faecal bacterial flora, and the relative number of Lactobacillus and Escherichia coli in faeces of weaned piglets to determine whether the strain can serve as a candidate antimicrobial growth promoter. A total of 360 piglets (initial body weight 7.14±0.63 kg) weaned at 26±2 days of age were randomly allotted to 5 treatment groups (4 pens per treatment with 18 pigs ...

  2. The effect of subminimal inhibitory concentrations of penicillin on growth rate and haemolysin activity of group G Streptococcus

    Directory of Open Access Journals (Sweden)

    Verônica V. Vieira

    1993-09-01

    Full Text Available The influence of the subminimal inhibitory concentrations (1/3 and 1/4 of the MIC of penicillin on growth rate and on haemolysin production of a strain of group G Streptococcus was studied. It was shown that 1/3 of the MIC almost completely inhibited the bacterial growth, but it was not able to inhibit haemolysin activity in the culture supernate. The generation time of bacteria grown in 1/4 of the MIC was approximately twice longer than that of the control culture. In all cultures, the haemolysin, after being produced (or liberated, reached a peak and decreased to low levels, which could suggest that group G Streptococcus produces some end products of metabolism that are able to inhibit haemolysin activity.

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Pedro Beschoren da Costa

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

  5. The Renminbi Exchange Rate Reform and the Rebalancing of China’s Growth Model

    Institute of Scientific and Technical Information of China (English)

    JIANBO; SONG; SEAN; MACKINNON; SONGTAO; TAN

    2015-01-01

    This paper posits that a proper way to estimate the Renminbi(RMB) exchange rate is to base the evaluation on the Balassa-Samuelson effect, and that the optimal way to facilitate China’s growth model transformation is gradual RMB internationalization and capital account liberalization. Regression estimates show that the gross domestic product per capita growth rate, or the productivity growth rate, has strong explanatory validity when estimating the RMB exchange rate. The findings further assert that, as the growth of gross fixed capital formation slows, and the growth of household consumption speeds up, China’s economic growth will be sustained. The RMB exchange rate regime is one in which gradual reforms must yield to interest rates levels and hence should only be revalued conditionally.

  6. The Long Run Growth Rate of the Kazakhstan’s Economy

    Directory of Open Access Journals (Sweden)

    Aloysius Ajab AMIN

    2012-05-01

    Full Text Available Kazakhstan’s economy has performed very well for almost the past decade – growing on an average annual growth rate of 9%. Furthermore, over this period there has been rapid increase in production in all the sectors of the economy. Can this economy continue to grow at such a high growth rate in the long run? The scanty existing literature on the topic suggests that growth is driven by exports from the extractive industry, while growth accounting studies on Kazakhstan’s economy reveal little contribution of total factor productivity to growth. In theory, the total factor productivity (TFP growth rate and long-run growth rate, or the steady state growth rate are equal. Hence, we examine this premise because it is as interesting and useful as policy input. In investigating the long run growth rate, we used parametric (econometric methods with extended production functions to include learning by doing through trade (openness. We find the estimates of the TFP steady state growth rate to be around 3 percent. This study gives us better insight into the economic growth of the country, although with transitional economies like Kazakhstan’s, there are huge institutional changes.

  7. Growth rate change driven by external perturbation in the azuki bean weevil

    CERN Document Server

    Fukano, T

    2003-01-01

    In laboratory experiments we obtain that the apparent growth rate of the population becomes larger than one under the normal condition, triggered by the external perturbation as the removal of individuals. The changed growth rate is stable for a while. We also propose a simple model of population dynamics allowing both matching and mis-matching the trend of the external perturbation, and show that the growth rate of the model population is changeable and stable to some extent.

  8. Impacts of Population and Income Growth Rates on Threatened Mammals and Birds

    OpenAIRE

    Pandit, Ram; Laband, David N.

    2011-01-01

    Per capita income and human population levels in a country have direct influences on its environmental outcomes. Countries with same level of income may have different rate of income growth and vice versa, suggesting that the influence of the rate of income growth on environmental outcomes could be different than that of income level. Similarly, the rate of population growth might have different impact in addition to the impacts of sheer number of population. We explore this empirical questio...

  9. Individual Growth Rates of Nikolsky’s Viper, Vipera berus nikolskii (Squamata, Viperidae

    Directory of Open Access Journals (Sweden)

    Bondarenko Z. S.

    2016-02-01

    Full Text Available Capture-mark-recapture data was used to infer growth rates of the Nikolsky’s viper, Vipera berus nikolskii (Vedmederja, Grubant et Rudaeva, 1986, in the Eastern Ukraine. We have found that growth rate is negatively correlated with age. The difference in growth rates before maturation is not significant between different sexes. Growth rates decrease rapidly after maturation in males and females, however adult males retain significantly higher average growth rates. There is large dispersion of growth rates in the group of adult females, which is caused, probably, by alteration of complete arrest of growth in the years with reproduction and more intensive growth in the years without it. Asymptotic snout-ventral length estimated after Von Bertalanffy model was 680 mm in females and 630 mm in males. Females mature after fifth and males mature after fourth hibernation. The larger females in vipers can not be the result of higher growth rates in females, but are the outcome of a combination of other factors including different maturation time and size (older and being larger, and, perhaps, longer life span due to lower mortality. Growth rates of the Nikolsky’s viper in the nature are higher than in other species in the group of small Eurasian vipers.

  10. Effect of cold work on initiation stage crack growth rate of nickel based alloys

    International Nuclear Information System (INIS)

    To investigate the effect of cold work on initiation stage crack growth rates of nickel based alloy, initiation stage crack growth rates were measured for simulated PWR primary water conditions using flat type specimens which were prepared from three different heats of alloy 600 and then 20 and 40% cold worked. Almost all data showed the stress had an increasing linear dependency on crack growth rate ; however there was some scattering of data and some materials showed a different tendency. Since yield strength was increased by cold work, for the same stress, the initiation stage crack growth rates were restrained or were not changed significantly by cold work. (author)

  11. Different Transcriptional Responses from Slow and Fast Growth Rate Strains of Listeria monocytogenes Adapted to Low Temperature

    Science.gov (United States)

    Cordero, Ninoska; Maza, Felipe; Navea-Perez, Helen; Aravena, Andrés; Marquez-Fontt, Bárbara; Navarrete, Paola; Figueroa, Guillermo; González, Mauricio; Latorre, Mauricio; Reyes-Jara, Angélica

    2016-01-01

    Listeria monocytogenes has become one of the principal foodborne pathogens worldwide. The capacity of this bacterium to grow at low temperatures has opened an interesting field of study in terms of the identification and classification of new strains of L. monocytogenes with different growth capacities at low temperatures. We determined the growth rate at 8°C of 110 strains of L. monocytogenes isolated from different food matrices. We identified a group of slow and fast strains according to their growth rate at 8°C and performed a global transcriptomic assay in strains previously adapted to low temperature. We then identified shared and specific transcriptional mechanisms, metabolic and cellular processes of both groups; bacterial motility was the principal process capable of differentiating the adaptation capacity of L. monocytogenes strains with different ranges of tolerance to low temperatures. Strains belonging to the fast group were less motile, which may allow these strains to achieve a greater rate of proliferation at low temperature. PMID:26973610

  12. Different transcriptional responses from slow and fast growth rate strains of Listeria monocytogenes adapted to low temperature

    Directory of Open Access Journals (Sweden)

    Ninoska eCordero

    2016-03-01

    Full Text Available Listeria monocytogenes has become one of the principal foodborne pathogens worldwide. The capacity of this bacterium to grow at low temperatures has opened an interesting field of study in terms of the identification and classification of new strains of L. monocytogenes with different growth capacities at low temperatures. We determined the growth rate at 8 ºC of 110 strains of L. monocytogenes isolated from different food matrices. We identified a group of slow and fast strains according to their growth rate at 8 °C and performed a global transcriptomic assay in strains previously adapted to low temperature. We then identified shared and specific transcriptional mechanisms, metabolic and cellular processes of both groups; bacterial motility was the principal process capable of differentiating the adaptation capacity of L. monocytogenes strains with different ranges of tolerance to low temperatures. Strains belonging to the fast group were less motile, which may allow these strains to achieve a greater rate of proliferation at low temperature.

  13. Effects of chemical and biological pesticides on plant growth parameters and rhizospheric bacterial community structure in Vigna radiata

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Sunil; Gupta, Rashi; Sharma, Shilpi, E-mail: shilpi@dbeb.iitd.ac.in

    2015-06-30

    Highlights: • Non-target effects of pesticides employing qualitative and quantitative approaches. • Qualitative shifts in resident and active bacterial community structure. • Abundance of 16S rRNA gene and transcripts were reduced significantly. • Effects of biological pesticide similar to chemical pesticides on rhizospheric bacteria. - Abstract: With increasing application of pesticides in agriculture, their non-target effects on soil microbial communities are critical to soil health maintenance. The present study aimed to evaluate the effects of chemical pesticides (chlorpyrifos and cypermethrin) and a biological pesticide (azadirachtin) on growth parameters and the rhizospheric bacterial community of Vigna radiata. Qualitative and quantitative analysis by PCR-denaturing gradient gel electrophoresis (DGGE) and q-PCR, respectively, of the 16S rRNA gene and transcript were performed to study the impact of these pesticides on the resident and active rhizospheric bacterial community. While plant parameters were not affected significantly by the pesticides, a shift in the bacterial community structure was observed with an adverse effect on the abundance of 16S rRNA gene and transcripts. Chlorpyrifos showed almost complete degradation toward the end of the experiment. These non-target impacts on soil ecosystems and the fact that the effects of the biopesticide mimic those of chemical pesticides raise serious concerns regarding their application in agriculture.

  14. Effects of chemical and biological pesticides on plant growth parameters and rhizospheric bacterial community structure in Vigna radiata

    International Nuclear Information System (INIS)

    Highlights: • Non-target effects of pesticides employing qualitative and quantitative approaches. • Qualitative shifts in resident and active bacterial community structure. • Abundance of 16S rRNA gene and transcripts were reduced significantly. • Effects of biological pesticide similar to chemical pesticides on rhizospheric bacteria. - Abstract: With increasing application of pesticides in agriculture, their non-target effects on soil microbial communities are critical to soil health maintenance. The present study aimed to evaluate the effects of chemical pesticides (chlorpyrifos and cypermethrin) and a biological pesticide (azadirachtin) on growth parameters and the rhizospheric bacterial community of Vigna radiata. Qualitative and quantitative analysis by PCR-denaturing gradient gel electrophoresis (DGGE) and q-PCR, respectively, of the 16S rRNA gene and transcript were performed to study the impact of these pesticides on the resident and active rhizospheric bacterial community. While plant parameters were not affected significantly by the pesticides, a shift in the bacterial community structure was observed with an adverse effect on the abundance of 16S rRNA gene and transcripts. Chlorpyrifos showed almost complete degradation toward the end of the experiment. These non-target impacts on soil ecosystems and the fact that the effects of the biopesticide mimic those of chemical pesticides raise serious concerns regarding their application in agriculture

  15. The physiological basis of reaction norms: the interaction among growth rate, the duration of growth and body size.

    Science.gov (United States)

    Davidowitz, Goggy; Nijhout, H Frederik

    2004-12-01

    The general effects of temperature and nutritional quality on growth rate and body size are well known. We know little, however, about the physiological mechanisms by which an organism translates variation in diet and temperature into reaction norms of body size or development time. We outline an endocrine-based physiological mechanism that helps explain how this translation occurs in the holometabolous insect Manduca sexta (Sphingidae). Body size and development time are controlled by three factors: (i) growth rate, (ii) the timing of the cessation of juvenile hormone secretion (measured by the critical weight) and (iii) the timing of ecdysteroid secretion leading to pupation (the interval to cessation of growth [ICG] after reaching the critical weight). Thermal reaction norms of body size and development time are a function of how these three factors interact with temperature. Body size is smaller at higher temperatures, because the higher growth rate decreases the ICG, thereby reducing the amount of mass that can accumulate. Development time is shorter at higher temperatures because the higher growth rate decreases the time required to attain the critical weight and, independently, controls the duration of the ICG. Life history evolution along altitudinal, latitudinal and seasonal gradients may occur through differential selection on growth rate and the duration of the two independently controlled determinants of the growth period. PMID:21676730

  16. Phytoplankton growth rate and nitrogen content: Implications for feeding and fecundity in a herbivorous copepod

    DEFF Research Database (Denmark)

    Kiørboe, Thomas

    1989-01-01

    Observations of natural feeding and egg-production rates of planktonic copepods have revealed distinct responses, independent of phytoplankton biomass, to oceanographic processes that fertilize the photic layer. Are such responses caused by changes in phytoplankton growth rate, influencing feedin...

  17. Frequency dependence of fatigue and corrosion fatigue crack growth rate

    Energy Technology Data Exchange (ETDEWEB)

    Marvasti, Mohammad Hassan; Chen, Weixing [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB (Canada); Kania, Richard; Worthingham, Robert [TransCanada Pipelines Limited, Calgary, AB (Canada); Van Boven, Gregory [Spectra Energy Transmission Limited, Vancouver, BC (Canada)

    2010-07-01

    It was in the mid-1980s that stress corrosion cracking (SCC) was first found in near-neutral pH conditions on the TransCanada pipeline system. Since then, there have been many reports of pipeline cracking in Canada in these conditions. The huge quantity of pipelines in Canada and the number of failures have brought great interest in investigation of this cracking. A study was conducted on one X52 pipeline steel. It used compact tension specimens for corrosion fatigue and fatigue tests in air. The following conclusions were drawn: 1) crack growth in near-neutral pH conditions can be explained by a factor, which reflects the combined action of the mechanical driving force and the hydrogen effects; 2) mechanical dormancy can be common when oil and gas pipelines are in operation; 3) hydrogen is a determining factor of crack growth when pipeline steels are exposed to near-neutral pH conditions.

  18. Energy and Growth under Flexible Exchange Rates: A Simulation Study

    OpenAIRE

    Sachs, Jeffrey D

    1980-01-01

    This paper offers a theoretical framework for studying the inter-actions of energy prices and economic growth. The incorporation of energy prices and quantities in a macroeconomic setting focuses on (1)the aggregate technology; (2) the interdependence of energy producers and consumers in the world economy; and (3) the asset markets as the channel through which energy price changes affect output and capital accumulation. While several existing studies consider aspects of these issues, none pro...

  19. Strictly Endogenous Growth with Non-renewable Resources Implies an Unbounded Growth Rate

    OpenAIRE

    Groth, Christian

    2003-01-01

    Conventional endogenous growth theory relies on the assumption of constant returns to ”broad capital”. As Solow pointed out, the strength of this assumption is revealed by recognizing that even the slightest touch of increasing returns creates explosive growth: infinite output in finite time! But Solow’s observation ignored natural resources. What happens if non-renewable resources enter the ”growth engine”? In this case (strictly) endogenous growth requires the technology to be such that the...

  20. Geometric analysis and estimation of the growth rate gradient on gastropod shells.

    Science.gov (United States)

    Noshita, Koji; Shimizu, Keisuke; Sasaki, Takenori

    2016-01-21

    The morphology of gastropod shells provides a record of the growth rate at the aperture of the shell, and molecular biological studies have shown that the growth rate gradient along the aperture of a gastropod shell can be closely related to gene expression at the aperture. Here, we develop a novel method for deriving microscopic growth rates from the macroscopic shapes of gastropod shells. The growth vector map of a shell provides information on the growth rate gradient as a vector field along the aperture, over the growth history. However, it is difficult to estimate the growth vector map directly from the macroscopic shape of a specimen, because the degree of freedom of the growth vector map is very high. In order to overcome this difficulty, we develop a method of estimating the growth vector map based on a growing tube model, where the latter includes fewer parameters to be estimated. In addition, we calculate an aperture map specifying the magnitude of the growth vector at each location, which can be compared with the expression levels of several genes or proteins that are important in morphogenesis. Finally, we show a concrete example of how macroscopic shell shapes evolve in a morphospace when microscopic growth rate gradient changes.

  1. Growth promotion and colonization of switchgrass (Panicum virgatum cv. Alamo by bacterial endophyte Burkholderia phytofirmans strain PsJN

    Directory of Open Access Journals (Sweden)

    Kim Seonhwa

    2012-05-01

    Full Text Available Abstract 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

  2. Family poverty affects the rate of human infant brain growth.

    Directory of Open Access Journals (Sweden)

    Jamie L Hanson

    Full Text Available Living in poverty places children at very high risk for problems across a variety of domains, including schooling, behavioral regulation, and health. Aspects of cognitive functioning, such as information processing, may underlie these kinds of problems. How might poverty affect the brain functions underlying these cognitive processes? Here, we address this question by observing and analyzing repeated measures of brain development of young children between five months and four years of age from economically diverse backgrounds (n = 77. In doing so, we have the opportunity to observe changes in brain growth as children begin to experience the effects of poverty. These children underwent MRI scanning, with subjects completing between 1 and 7 scans longitudinally. Two hundred and three MRI scans were divided into different tissue types using a novel image processing algorithm specifically designed to analyze brain data from young infants. Total gray, white, and cerebral (summation of total gray and white matter volumes were examined along with volumes of the frontal, parietal, temporal, and occipital lobes. Infants from low-income families had lower volumes of gray matter, tissue critical for processing of information and execution of actions. These differences were found for both the frontal and parietal lobes. No differences were detected in white matter, temporal lobe volumes, or occipital lobe volumes. In addition, differences in brain growth were found to vary with socioeconomic status (SES, with children from lower-income households having slower trajectories of growth during infancy and early childhood. Volumetric differences were associated with the emergence of disruptive behavioral problems.

  3. EXCHANGE RATE AND ECONOMIC GROWTH. THE CASE OF ROMANIA

    Directory of Open Access Journals (Sweden)

    Nicolae Ghiba

    2010-12-01

    Full Text Available Considering the difficulties created by the economic crisis, many exporters have criticized the National Bank of Romania (NBR’s policy regarding the exchange rate evolution. They argue that depreciation is a necessary condition for recovery and not financial stability. On the contrary, Romania cannot afford a shock in the exchange rate level. The risk associated with such a measure is too high for an emerging country and it annihilates any export competitive advantages. Therefore, depreciation may delay the imperative of Romanian economic recovery. A solid economic recovery should have as starting point a financial system sound and stable. Excessive exchange rate depreciation jeopardizes the financial soundness of banks and the borrower’s ability to repay their loans. Therefore, it creates inflationary flare-ups, particularly dangerous for the economy of any state.

  4. The impact of risk management on internal and sustainable growth rate: Evidence from Tehran Stock Exchange

    Directory of Open Access Journals (Sweden)

    Hamid Reza Vakili Fard

    2014-09-01

    Full Text Available Measuring the relative risk of firms has been an open discussion among researchers. There are many studies on learning how leverage may influence on growth of the firms. This article reviews the relationship between risk management, internal and sustainable growth of accepted companies in Tehran stock exchange. The survey considers three types of risks including operating, financial and compound and investigates their relationships with internal growth rate as well as sustainable growth rate. Using some regression techniques, the study has determined negative and meaningful relationships between different types of leverage on side and internal as well as sustainable growth on the other side.

  5. Effects of begging on growth rates of nestling chicks

    OpenAIRE

    Rodríguez-Gironés, Miguel Ángel; Jesús M Zúñiga; Redondo, T.

    2001-01-01

    We investigated whether an increase in begging levels delays growth of chicks. In experiment 1, we hand-reared nine pairs of ring dove squabs, divided into a control and a begging group. All squabs received similar amounts of food, but those in the begging group had to beg for a prolonged period in order to be fed, while squabs in the control group received food without begging. Squabs stopped responding to the treatment after 10 days and, at that time, there was no effect of induced begging ...

  6. [Qualitative and quantitative determination of bacterial populations in an aquatic environment. 7. Development of bacterial growth on raw materials exposed to potable water].

    Science.gov (United States)

    Dott, W; Schoenen, D

    1985-05-01

    Refined steel plates coated with different materials that contained available organic compounds led to a microbial growth on the surface. Even plastics and bitumen which were used in the sphere of drinking water showed after an exposure time of three months up to 192 ml slime per square meter. The number of viable bacteria within the Aufwuchs was in the range of 10(7) cfu/ml. The production of slime increased with time. The relation of carbohydrate and protein content significantly changed from 2 at the beginning to 30 after 12 months of incubation the bitumen coating test plates. This indicates an increase synthesis of carbohydrate containing extracellular polymeric substances during the late phase of growth. The bacteria isolated from the Aufwuchs mainly belonged to the genera Pseudomonas, Flavobacterium, Acinetobacter, Caulobacter, sheated bacteria and other gramnegative physiologically nonreactiv roads. During exposure of the plates the relation changed within the bacterial communities of the main groups. Comparing the bacteria communities of inlet and outflow water it became evident that the later one was influenced by bacteria of the Aufwuchs. PMID:4024773

  7. Transcription factor control of growth rate dependent genes in Saccharomyces cerevisiae: A three factor design

    DEFF Research Database (Denmark)

    Fazio, Alessandro; Jewett, Michael Christopher; Daran-Lapujade, Pascale;

    2008-01-01

    Background: Characterization of cellular growth is central to understanding living systems. Here, we applied a three-factor design to study the relationship between specific growth rate and genome-wide gene expression in 36 steady-state chemostat cultures of Saccharomyces cerevisiae. The three...... factors we considered were specific growth rate, nutrient limitation, and oxygen availability. Results: We identified 268 growth rate dependent genes, independent of nutrient limitation and oxygen availability. The transcriptional response was used to identify key areas in metabolism around which m...

  8. Economic growth and currency crisis: A real exchange rate entropic approach

    OpenAIRE

    Matesanz Gómez, David; Guillermo J. Ortega

    2005-01-01

    We propose a country classification of economic growth currency crisis consequences based on the entropic analysis of the real exchange rate. We show that this ranking is highly correlated with the annual minimum rate of growth, a proxy used to quantify real currency crisis effects.

  9. A re-examination of tigerfish growth rates in Lake Kariba

    OpenAIRE

    Beattie, I.H.

    1982-01-01

    Growth rates of male and female tigerfish Hydrocynus vittatus were determined from length/frequencies of fish from the Sanyati Basin and Sinamwenda estuary, Lake Kariba. Growth rates were similar in both sexes for the first two years, after which females grew faster and reached a greater length. Fish from the Sanyati Basin appeared to grow slightly faster than those from the Sinamwenda Estuary.

  10. Geographic After-Tax Real Income Differentials and Population Growth Rates

    OpenAIRE

    Alexander, Gigi; Cebula, Richard; Koch, James

    1989-01-01

    This empirical note investigates the impact of geographic after-tax real, as opposed to nominal, income differentials on geographic population growth rates. The focus is on Florida's 67 counties and the 1980-88 time period. The empirical results imply that the population growth rate in Florida counties was of after-tax real income.

  11. Relative growth rate variation of evergreen and deciduous savanna tree species is driven by different traits

    NARCIS (Netherlands)

    Tomlinson, K.W.; Poorter, L.; Bongers, F.; Borghetti, F.; Jacobs, L.; Langevelde, van F.

    2014-01-01

    Background and Aims Plant relative growth rate (RGR) depends on biomass allocation to leaves (leaf mass fraction, LMF), efficient construction of leaf surface area (specific leaf area, SLA) and biomass growth per unit leaf area (net assimilation rate, NAR). Functional groups of species may differ in

  12. THE GROWTH RATE AND STATISTICAL FLUCTUATION OF BOSE-EINSTEIN CONDENSATE FORMATION

    Institute of Scientific and Technical Information of China (English)

    Yan Ke-zhu; Tan Wei-han

    2000-01-01

    Using the generating function method to solve the master equation ofBose-Einstein condensate and to evaluate the growth rate, statisticalfluctuation of condensate atoms, we find out that there is a plateau inthe growth rate curve and a super-Poisson distribution observed.

  13. Two-Way Selection for Growth Rate in the Common Carp (CYPRINUS CARPIO L.)

    Science.gov (United States)

    Moav, R.; Wohlfarth, G.

    1976-01-01

    The domesticated European carp was subjected to a two-way selection for growth rate. Five generations of mass selection for faster growth rate did not yield any response, but subsequent selection between groups (families) resulted in considerable progress while maintaining a large genetic variance. Selection for slow growth rate yielded relatively strong response for the first three generations. Random-bred control lines suffered from strong inbreeding depression and when two lines were crossed, the F1 showed a high degree of heterosis. Selection was performed on pond-raised fish, but growth rate was also tested in cages. A strong pond-cage genetic interaction was found. A theoretical explanation was suggested involving overdominance for fast growth rate and amplification through competition of intra-group but not inter-group variation. PMID:1248737

  14. How Do Output Growth Rate Distributions Look Like? Some Time-Series Evidence on OECD Countries

    CERN Document Server

    Fagiolo, G; Roventini, A; Fagiolo, Giorgio; Napoletano, Mauro; Roventini, Andrea

    2006-01-01

    This paper investigates the statistical properties of within-country GDP and industrial production (IP) growth rate distributions. Many empirical contributions have recently pointed out that cross-section growth rates of firms, industries and countries all follow Laplace distributions. In this work, we test whether also within-country, time-series GDP and IP growth rates can be approximated by tent-shaped distributions. We fit output growth rates with the exponential-power (Subbotin) family of densities, which includes as particular cases both the Gaussian and the Laplace distributions. We find that, for a large number of OECD countries including the U.S., both GDP and IP growth rates are Laplace distributed. Moreover, we show that fat-tailed distributions robustly emerge even after controlling for outliers, autocorrelation and heteroscedasticity.

  15. Effects of Eucommia ulmoides extract on longitudinal bone growth rate in adolescent female rats.

    Science.gov (United States)

    Kim, Ji Young; Lee, Jeong-Il; Song, MiKyung; Lee, Donghun; Song, Jungbin; Kim, Soo Young; Park, Juyeon; Choi, Ho-Young; Kim, Hocheol

    2015-01-01

    Eucommia ulmoides is one of the popular tonic herbs for the treatment of low back pain and bone fracture and is used in Korean medicine to reinforce muscles and bones. This study was performed to investigate the effects of E. ulmoides extract on longitudinal bone growth rate, growth plate height, and the expressions of bone morphogenetic protein 2 (BMP-2) and insulin-like growth factor 1 (IGF-1) in adolescent female rats. In two groups, we administered a twice-daily dosage of E. ulmoides extract (at 30 and 100 mg/kg, respectively) per os over 4 days, and in a control group, we administered vehicle only under the same conditions. Longitudinal bone growth rate in newly synthesized bone was observed using tetracycline labeling. Chondrocyte proliferation in the growth plate was observed using cresyl violet dye. In addition, we analyzed the expressions of BMP-2 and IGF-1 using immunohistochemistry. Eucommia ulmoides extract significantly increased longitudinal bone growth rate and growth plate height in adolescent female rats. In the immunohistochemical study, E. ulmoides markedly increased BMP-2 and IGF-1 expressions in the proliferative and hypertrophic zones. In conclusion, E. ulmoides increased longitudinal bone growth rate by promoting chondrogenesis in the growth plate and the levels of BMP-2 and IGF-1. Eucommia ulmoides could be helpful for increasing bone growth in children who have growth retardation. PMID:25087723

  16. Native bacterial endophytes promote host growth in a species-specific manner; phytohormone manipulations do not result in common growth responses.

    Directory of Open Access Journals (Sweden)

    Hoang Hoa Long

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

  17. Effects of interactions of auxin-producing bacteria and bacterial-feeding nematodes on regulation of peanut growths.

    Science.gov (United States)

    Xu, Li; Xu, Wensi; Jiang, Ying; Hu, Feng; Li, Huixin

    2015-01-01

    The influences of an IAA (indole-3-acetic acid)-producing bacterium (Bacillus megaterium) and two bacterial-feeding nematodes (Cephalobus sp. or Mesorhabditis sp.) on the growth of peanut (Arachis hypogaea L. cv. Haihua 1) after various durations of time were investigated in natural soils. The addition of bacteria and nematodes and incubation time all significantly affected plant growth, plant root growth, plant nutrient concentrations, soil nutrient concentrations, soil microorganisms and soil auxin concentration. The addition of nematodes caused greater increases in these indices than those of bacteria, while the addition of the combination of bacteria and nematodes caused further increases. After 42-day growth, the increases in soil respiration differed between the additions of two kinds of nematodes because of differences in their life strategies. The effects of the bacteria and nematodes on the nutrient and hormone concentrations were responsible for the increases in plant growth. These results indicate the potential for promoting plant growth via the addition of nematodes and bacteria to soil.

  18. Effects of interactions of auxin-producing bacteria and bacterial-feeding nematodes on regulation of peanut growths.

    Science.gov (United States)

    Xu, Li; Xu, Wensi; Jiang, Ying; Hu, Feng; Li, Huixin

    2015-01-01

    The influences of an IAA (indole-3-acetic acid)-producing bacterium (Bacillus megaterium) and two bacterial-feeding nematodes (Cephalobus sp. or Mesorhabditis sp.) on the growth of peanut (Arachis hypogaea L. cv. Haihua 1) after various durations of time were investigated in natural soils. The addition of bacteria and nematodes and incubation time all significantly affected plant growth, plant root growth, plant nutrient concentrations, soil nutrient concentrations, soil microorganisms and soil auxin concentration. The addition of nematodes caused greater increases in these indices than those of bacteria, while the addition of the combination of bacteria and nematodes caused further increases. After 42-day growth, the increases in soil respiration differed between the additions of two kinds of nematodes because of differences in their life strategies. The effects of the bacteria and nematodes on the nutrient and hormone concentrations were responsible for the increases in plant growth. These results indicate the potential for promoting plant growth via the addition of nematodes and bacteria to soil. PMID:25867954

  19. Effects of interactions of auxin-producing bacteria and bacterial-feeding nematodes on regulation of peanut growths.

    Directory of Open Access Journals (Sweden)

    Li Xu

    Full Text Available The influences of an IAA (indole-3-acetic acid-producing bacterium (Bacillus megaterium and two bacterial-feeding nematodes (Cephalobus sp. or Mesorhabditis sp. on the growth of peanut (Arachis hypogaea L. cv. Haihua 1 after various durations of time were investigated in natural soils. The addition of bacteria and nematodes and incubation time all significantly affected plant growth, plant root growth, plant nutrient concentrations, soil nutrient concentrations, soil microorganisms and soil auxin concentration. The addition of nematodes caused greater increases in these indices than those of bacteria, while the addition of the combination of bacteria and nematodes caused further increases. After 42-day growth, the increases in soil respiration differed between the additions of two kinds of nematodes because of differences in their life strategies. The effects of the bacteria and nematodes on the nutrient and hormone concentrations were responsible for the increases in plant growth. These results indicate the potential for promoting plant growth via the addition of nematodes and bacteria to soil.

  20. Rate limits in silicon sheet growth - The connections between vertical and horizontal methods

    Science.gov (United States)

    Thomas, Paul D.; Brown, Robert A.

    1987-01-01

    Meniscus-defined techniques for the growth of thin silicon sheets fall into two categories: vertical and horizontal growth. The interactions of the temperature field and the crystal shape are analyzed for both methods using two-dimensional finite-element models which include heat transfer and capillarity. Heat transfer in vertical growth systems is dominated by conduction in the melt and the crystal, with almost flat melt/crystal interfaces that are perpendicular to the direction of growth. The high axial temperature gradients characteristic of vertical growth lead to high thermal stresses. The maximum growth rate is also limited by capillarity which can restrict the conduction of heat from the melt into the crystal. In horizontal growth the melt/crystal interface stretches across the surface of the melt pool many times the crystal thickness, and low growth rates are achievable with careful temperature control. With a moderate axial temperature gradient in the sheet a substantial portion of the latent heat conducts along the sheet and the surface of the melt pool becomes supercooled, leading to dendritic growth. The thermal supercooling is surpressed by lowering the axial gradient in the crystal; this configuration is the most desirable for the growth of high quality crystals. An expression derived from scaling analysis relating the growth rate and the crucible temperature is shown to be reliable for horizontal growth.

  1. Bacterial growth in humic waters exposed to UV-radiation and simulated sunlight

    DEFF Research Database (Denmark)

    Corin, N.; Backlund, P.; Wiklund, T.

    1998-01-01

    Sterile filtered (0.45 mu m) humic lake water was exposed to simulated sunlight (300-800 nm) or W-radiation (254 run)for various periods of times and the dissolved organic carbon content, absorbance at 254 and 460 nm and PH were recorded. The irradiated water was inoculated with a natural bacterial...

  2. Growth rates of atmospheric molecular clusters determined from cluster appearance times and collision-evaporation fluxes

    Science.gov (United States)

    Kontkanen, Jenni; Olenius, Tinja; Lehtipalo, Katrianne; Vehkamäki, Hanna; Kulmala, Markku

    2015-04-01

    The probability of freshly formed particles to survive to climatically relevant sizes is determined by the competition between the coagulation loss rate and the particle growth rate. Therefore, various methods have been developed to deduce the growth rates from measured particle size distributions. Recently, the growth rates of sub-3nm clusters have been determined based on the appearance times of different cluster sizes. However, it is not clear to what extent these growth rates are consistent with the growth rates corresponding to molecular fluxes between clusters. In this work, we simulated the time evolution of a population of sub-3 nm molecular clusters and compared the growth rates determined (1) from the cluster appearance times and (2) from the collision-evaporation fluxes between different cluster sizes. We performed a number of simulations by varying the ambient conditions and the properties of the model substance. In the first simulation set, the Gibbs free energy of the formation of the clusters was assumed to have a single maximum and no minima, corresponding to a monotonically increasing stability as a function of cluster size. The saturation vapor pressure was selected so that the growth proceeded solely via monomer additions. The growth rates were determined separately for each cluster. However, to see the effect of finite size resolution, we also performed simulations where the clusters were grouped into size bins, for which we determined the growth rates. In the second simulation set, the saturation vapor pressure was lowered so that the collisions of small clusters significantly contributed to the growth. As the growth rate of a single cluster is ambiguous in this case, the growth rates were determined only for different size bins. We performed simulations using a similar free energy profile as in other simulations but we also used a free energy profile containing a local minimum, corresponding to small stable clusters. Our simulations show that

  3. Whole genome sequencing of Mycobacterium tuberculosis reveals slow growth and low mutation rates during latent infections in humans.

    Directory of Open Access Journals (Sweden)

    Roberto Colangeli

    Full Text Available Very little is known about the growth and mutation rates of Mycobacterium tuberculosis during latent infection in humans. However, studies in rhesus macaques have suggested that latent infections have mutation rates that are higher than that observed during active tuberculosis disease. Elevated mutation rates are presumed risk factors for the development of drug resistance. Therefore, the investigation of mutation rates during human latency is of high importance. We performed whole genome mutation analysis of M. tuberculosis isolates from a multi-decade tuberculosis outbreak of the New Zealand Rangipo strain. We used epidemiological and phylogenetic analysis to identify four cases of tuberculosis acquired from the same index case. Two of the tuberculosis cases occurred within two years of exposure and were classified as recently transmitted tuberculosis. Two other cases occurred more than 20 years after exposure and were classified as reactivation of latent M. tuberculosis infections. Mutation rates were compared between the two recently transmitted pairs versus the two latent pairs. Mean mutation rates assuming 20 hour generation times were 5.5 X 10(-10 mutations/bp/generation for recently transmitted tuberculosis and 7.3 X 10(-11 mutations/bp/generation for latent tuberculosis. Generation time versus mutation rate curves were also significantly higher for recently transmitted tuberculosis across all replication rates (p = 0.006. Assuming identical replication and mutation rates among all isolates in the final two years before disease reactivation, the u 20 hr mutation rate attributable to the remaining latent period was 1.6 × 10(-11 mutations/bp/generation, or approximately 30 fold less than that calculated during the two years immediately before disease. Mutations attributable to oxidative stress as might be caused by bacterial exposure to the host immune system were not increased in latent infections. In conclusion, we did not find any

  4. Whole genome sequencing of Mycobacterium tuberculosis reveals slow growth and low mutation rates during latent infections in humans.

    Science.gov (United States)

    Colangeli, Roberto; Arcus, Vic L; Cursons, Ray T; Ruthe, Ali; Karalus, Noel; Coley, Kathy; Manning, Shannon D; Kim, Soyeon; Marchiano, Emily; Alland, David

    2014-01-01

    Very little is known about the growth and mutation rates of Mycobacterium tuberculosis during latent infection in humans. However, studies in rhesus macaques have suggested that latent infections have mutation rates that are higher than that observed during active tuberculosis disease. Elevated mutation rates are presumed risk factors for the development of drug resistance. Therefore, the investigation of mutation rates during human latency is of high importance. We performed whole genome mutation analysis of M. tuberculosis isolates from a multi-decade tuberculosis outbreak of the New Zealand Rangipo strain. We used epidemiological and phylogenetic analysis to identify four cases of tuberculosis acquired from the same index case. Two of the tuberculosis cases occurred within two years of exposure and were classified as recently transmitted tuberculosis. Two other cases occurred more than 20 years after exposure and were classified as reactivation of latent M. tuberculosis infections. Mutation rates were compared between the two recently transmitted pairs versus the two latent pairs. Mean mutation rates assuming 20 hour generation times were 5.5 X 10(-10) mutations/bp/generation for recently transmitted tuberculosis and 7.3 X 10(-11) mutations/bp/generation for latent tuberculosis. Generation time versus mutation rate curves were also significantly higher for recently transmitted tuberculosis across all replication rates (p = 0.006). Assuming identical replication and mutation rates among all isolates in the final two years before disease reactivation, the u 20 hr mutation rate attributable to the remaining latent period was 1.6 × 10(-11) mutations/bp/generation, or approximately 30 fold less than that calculated during the two years immediately before disease. Mutations attributable to oxidative stress as might be caused by bacterial exposure to the host immune system were not increased in latent infections. In conclusion, we did not find any evidence to suggest

  5. Beyond Thermal Performance Curves: Modeling Time-Dependent Effects of Thermal Stress on Ectotherm Growth Rates.

    Science.gov (United States)

    Kingsolver, Joel G; Woods, H Arthur

    2016-03-01

    Thermal performance curves have been widely used to model the ecological responses of ectotherms to variable thermal environments and climate change. Such models ignore the effects of time dependence-the temporal pattern and duration of temperature exposure-on performance. We developed and solved a simple mathematical model for growth rate of ectotherms, combining thermal performance curves for ingestion rate with the temporal dynamics of gene expression and protein production in response to high temperatures to predict temporal patterns of growth rate in constant and diurnally fluctuating temperatures. We used the model to explore the effects of heat shock proteins on larval growth rates of Manduca sexta. The model correctly captures two empirical patterns for larval growth rate: first, maximal growth rate and optimal temperature decline with increasing duration of temperature exposure; second, mean growth rates decline with time in diurnally fluctuating temperatures at higher mean temperatures. These qualitative results apply broadly to cases where proteins or other molecules produced in response to high temperatures reduce growth rates. We discuss some of the critical assumptions and predictions of the model and suggest potential extensions and alternatives. Incorporating time-dependent effects will be essential for making more realistic predictions about the physiological and ecological consequences of temperature fluctuations and climate change. PMID:26913942

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

    Science.gov (United States)

    Kristula, M A; Dou, Z; Toth, J D; Smith, B I; Harvey, N; Sabo, M

    2008-05-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

  8. Study of failures in a rabbit line selected for growth rate

    OpenAIRE

    C. Naturil-Alfonso; R. Lavara; Millán , P.; Rebollar, P.G.; J.S. Vicente; F. Marco-Jiménez

    2016-01-01

    Selection for growth rate is negatively related with reproductive fitness. The aim of this work was to analyse the causes of fertility failure in rabbit does selected for growth rate and characterised for reproductive deficiencies (line R). In the experiment, 82 does were divided into 2 groups: naturally mated (NM) and artificially inseminated (AI), to relate luteinizing hormone (LH) concentration with ovulation induction and pregnancy rate by laparoscopic determination. Additionally, in 38 o...

  9. Bilateral Trade and SEE–Eurozone Countries Growth Rate Alignment

    Directory of Open Access Journals (Sweden)

    Valerija Botrić

    2016-06-01

    Full Text Available The aim of the paper is to explore the role of trade in aligning the synchronisation patterns between the South Eastern European (see countries – Albania, Bosnia and Herzegovina, Bulgaria, Croatia, FYR of Macedonia, Kosovo, Montenegro, Romania and Serbia – and members of the euro area. More precisely, we investigate whether bilateral trade flows affect output synchronisation between the euro area countries and see countries and compare trade-synchronisation patterns between the see countries and new member states that have not yet introduced the euro (NMS. The results show that the levels of output similarities between the see countries and NMS are different and that the see countries exhibit lower output correlation with the euro area members than the NMS. Exploring the role of trade in aligning growth patterns has in some cases found positive effects, much stronger for the see countries, which have lower trade intensity levels. We argue that the reason for these results is related to the fact that other factors could be dominant in the NMS countries (policy measures alignment within the EU, while for the see countries only trade relationships had the opportunity to exert noticeable effects in the analysed period.

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

    Directory of Open Access Journals (Sweden)

    Ramona Marasco

    2013-01-01

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

  11. Effects of chemical and biological pesticides on plant growth parameters and rhizospheric bacterial community structure in Vigna radiata.

    Science.gov (United States)

    Singh, Sunil; Gupta, Rashi; Sharma, Shilpi

    2015-06-30

    With increasing application of pesticides in agriculture, their non-target effects on soil microbial communities are critical to soil health maintenance. The present study aimed to evaluate the effects of chemical pesticides (chlorpyrifos and cypermethrin) and a biological pesticide (azadirachtin) on growth parameters and the rhizospheric bacterial community of Vigna radiata. Qualitative and quantitative analysis by PCR-denaturing gradient gel electrophoresis (DGGE) and q-PCR, respectively, of the 16S rRNA gene and transcript were performed to study the impact of these pesticides on the resident and active rhizospheric bacterial community. While plant parameters were not affected significantly by the pesticides, a shift in the bacterial community structure was observed with an adverse effect on the abundance of 16S rRNA gene and transcripts. Chlorpyrifos showed almost complete degradation toward the end of the experiment. These non-target impacts on soil ecosystems and the fact that the effects of the biopesticide mimic those of chemical pesticides raise serious concerns regarding their application in agriculture. PMID:25791643

  12. Temperature responses of substrate carbon conversion efficiencies and growth rates of plant tissues.

    Science.gov (United States)

    Hansen, Lee D; Thomas, Nathan R; Arnholdt-Schmitt, Birgit

    2009-12-01

    Growth rates of plant tissues depend on both the respiration rate and the efficiency with which carbon is incorporated into new structural biomass. Calorespirometric measurement of respiratory heat and CO2 rates, from which both efficiency and growth rate can be calculated, is a well established method for determining the effects of rapid temperature changes on the respiratory and growth properties of plant tissues. The effect of the alternative oxidase/cytochrome oxidase activity ratio on efficiency is calculated from first principles. Data on the temperature dependence of the substrate carbon conversion efficiency are tabulated. These data show that epsilon is maximum and approximately constant through the optimum growth temperature range and decreases rapidly as temperatures approach temperature limits to growth. The width of the maximum and the slopes of decreasing epsilon at high and low temperatures vary greatly with species, cultivars and accessions.

  13. A NOVEL PARAMETER FOR EVALUATING THE FATIGUE CRACK GROWTH RATE IN CARBON STEELS

    Institute of Scientific and Technical Information of China (English)

    X.S.Wang; S.Q.Zhu; N.Kawagoishi; H.Nisitani

    2001-01-01

    A novel parameter is suggested for evaluating the fatigue crack growth rate in carbonsteels.Fatigue crack propagation tests of an annealed 0.42% carbon steel were carriedout under different conditions to investigate the relationship between this dominatingparameter and the crack opening displacement (COD).A new equation of fatiguecrack growth rate is formulated in terms of the suggested parameter.The physicalmeanings of the material parameters in this equation are explored experimentally.Considering the relation of crack growth and deformation properties,a simple andapplicable method is proposed to evaluate the fatigue crack growth rate.It is alsoobserved that the material parameters in the fatigue crack growth rate equation ofcarbon steels are related linearly to the material strength.The results are in a goodagreement with experimental results.

  14. ppGpp is the major source of growth rate control in E. coli.

    Science.gov (United States)

    Potrykus, Katarzyna; Murphy, Helen; Philippe, Nadège; Cashel, Michael

    2011-03-01

    It is widely accepted that the DNA, RNA and protein content of Enterobacteriaceae is regulated as a function of exponential growth rates; macromolecular content increases with faster growth regardless of specific composition of the growth medium. This phenomenon, called growth rate control, primarily involves regulation of ribosomal RNA and ribosomal protein synthesis. However, it was uncertain whether the global regulator ppGpp is the major determinant for growth rate control. Therefore, here we re-evaluate the effect of ppGpp on macromolecular content for different balanced growth rates in defined media. We find that when ppGpp is absent, RNA/protein and RNA/DNA ratios are equivalent in fast and slow growing cells. Moreover, slow growing ppGpp-deficient cells with increased RNA content, display a normal ribosomal subunit composition although polysome content is reduced when compared with fast growing wild-type cells. From this we conclude that growth rate control does not occur in the absence of ppGpp. Also, artificial elevation of ppGpp or introduction of stringent RNA polymerase mutants in ppGpp-deficient cells restores this control. We believe these findings strongly argue in favour of ppGpp and against redundant regulation of growth rate control by other factors in Escherichia coli and other enteric bacteria.

  15. Stool consistency is strongly associated with gut microbiota richness and composition, enterotypes and bacterial growth rates

    OpenAIRE

    Vandeputte, Doris; Falony, Gwen; Araujo Vieira Da Silva, Sara Manuel; Tito Tadeo, Raul Yhossef; Joossens, Marie; Raes, Jeroen

    2016-01-01

    Objective The assessment of potentially confounding factors affecting colon microbiota composition is essential to the identification of robust microbiome based disease markers. Here, we investigate the link between gut microbiota variation and stool consistency using Bristol Stool Scale classification, which reflects faecal water content and activity, and is considered a proxy for intestinal colon transit time. Design Through 16S rDNA Illumina profiling of faecal samples of 53 healthy women,...

  16. Rapid Growth Reduces Cold Resistance: Evidence from Latitudinal Variation in Growth Rate, Cold Resistance and Stress Proteins

    OpenAIRE

    Robby Stoks; Marjan De Block

    2011-01-01

    BACKGROUND: Physiological costs of rapid growth may contribute to the observation that organisms typically grow at submaximal rates. Although, it has been hypothesized that faster growing individuals would do worse in dealing with suboptimal temperatures, this type of cost has never been explored empirically. Furthermore, the mechanistic basis of the physiological costs of rapid growth is largely unexplored. METHODOLOGY/PRINCIPAL FINDING: Larvae of the damselfly Ischnura elegans from two univ...

  17. Interactive effect of biochar and plant growth-promoting bacterial endophytes on ameliorating salinity stress in maize

    DEFF Research Database (Denmark)

    Saleem Akhtar, Saqib; Andersen, Mathias Neumann; Naveed, Muhammad;

    2015-01-01

    The objective of this work was to study the interactive effect of biochar and plant growth-promoting endophytic bacteria containing 1-aminocyclopropane-1-carboxylate deaminase and exopolysaccharide activity on mitigating salinity stress in maize (Zea mays L.). The plants were grown in a greenhouse...... under controlled conditions, and were subjected to separate or combined treatments of biochar (0% and 5%, w/w) and two endophytic bacterial strains (Burkholderia phytofirmans (PsJN) and Enterobacter sp. (FD17)) and salinity stress. The results indicated that salinity significantly decreased the growth...... of maize, whereas both biochar and inoculation mitigated the negative effects of salinity on maize performance either by decreasing the xylem Na+ concentration ([Na+]xylem) uptake or by maintaining nutrient balance within the plant, especially when the two treatments were applied in combination. Moreover...

  18. Effect of PGR producing bacterial strains isolated from vermisources on germination and growth of Vigna unguiculata (L. Walp.

    Directory of Open Access Journals (Sweden)

    Anandharaj Marimuthu

    2014-12-01

    Full Text Available Nineteen bacterial strains were isolated from vermisources andscreened for Indole-3-acetic acid (IAA production among themonly nine strains produce IAA and they were identified asStreptococcus spp., Micrococcus spp., Klebsiella spp., Bacillus spp., Enterobacter spp., Escherichia spp., Alcaligenes spp., Erwinia spp., and Pseudomonas spp. Among all other strains Bacillus sp. showed the higher IAA production hence selected for further molecular analysis and confirmed as Bacillus cereus. The B. cereus was grown in nutrient broth supplemented with different concentrations (1, 2, 3, 4 and 5mg/ml of tryptophan for seven days at pH 7 and at 37ºC. Crude IAA was used for in vitro phytostimulatory studies using Vigna unguiculata (L. Walp. The plant growth parameters were analyzed at different day intervals (5, 10 and 15 days. Supplementation of 5 ml crude IAA (2mg/ml of tryptophan dynamically enhances the plant growth parameters after 15 days.

  19. Radiation Sterilization of Two Commonly Culture Media Used for Bacterial Growth

    International Nuclear Information System (INIS)

    Radiation sterilization of culture media used for the cultivation of bacteria by Co-60 gamma ray was investigated. Nutrient agar and tryptone glucose yeast extract (TGY) media widely used for the propagation of bacteria were sterilized with 15 kGy dose gamma radiation. Seven different bacterial species were grown as well on the radiation sterilized media as on media sterilized by autoclaving in a conventional way

  20. Data compilation of respiration, feeding, and growth rates of marine pelagic organisms

    DEFF Research Database (Denmark)

    2013-01-01

    's adaptation to the environment, with consequently less universal mass scaling properties. Data on body mass, maximum ingestion and clearance rates, respiration rates and maximum growth rates of animals living in the ocean epipelagic were compiled from the literature, mainly from original papers but also from...

  1. Geographic after-tax real income differentials and population growth rates.

    Science.gov (United States)

    Alexander, G; Cebula, R J; Koch, J V

    1990-03-01

    "The purpose of this [one-page] note is to empirically investigate the impact of geographic after-tax real income differentials on geographic population growth rate differentials. The focus is on population growth rates in Florida's 67 counties over the period 1980-88." The authors conclude that "even after allowing for a variety of other location-influencing factors, including coastal access, after-tax real income differentials exercise a positive and significant impact on population growth rate differentials among Florida's counties."

  2. Growth rate enhancement of free-electron laser by two consecutive wigglers with axial magnetic field

    Indian Academy of Sciences (India)

    A Hasanbeigi; A Farhadian; E Khademi Bidhendi

    2014-06-01

    The operative mechanism for a free-electron laser (FEL) with two consecutive helical wigglers having opposite circular polarization in the presence of an axial magnetic field is proposed and analysed. With the help of fluid theory, a tenth-degree polynomial dispersion equation for electromagnetic and space-charge waves is derived. The results are used to illustrate and discuss the dependence of growth rate on different system parameters. Finally, it is shown that for the same system parameters the growth rate of the proposed structure is more than the growth rate of instability in a conventional FEL.

  3. Characterization of culturable bacterial endophytes and their capacity to promote plant growth from plants grown using organic or conventional practices.

    Science.gov (United States)

    Xia, Ye; DeBolt, Seth; Dreyer, Jamin; Scott, Delia; Williams, Mark A

    2015-01-01

    Plants have a diverse internal microbial biota that has been shown to have an important influence on a range of plant health attributes. Although these endophytes have been found to be widely occurring, few studies have correlated agricultural production practices with endophyte community structure and function. One agricultural system that focuses on preserving and enhancing soil microbial abundance and biodiversity is organic farming, and numerous studies have shown that organically managed system have increased microbial community characteristics. Herein, the diversity and specificity of culturable bacterial endophytes were evaluated in four vegetable crops: corn, tomato, melon, and pepper grown under organic or conventional practices. Endophytic bacteria were isolated from surface-sterilized shoot, root, and seed tissues and sequence identified. A total of 336 bacterial isolates were identified, and grouped into 32 species and five phyla. Among these, 239 isolates were from organically grown plants and 97 from those grown conventionally. Although a diverse range of bacteria were documented, 186 were from the Phylum Firmicutes, representing 55% of all isolates. Using the Shannon diversity index, we observed a gradation of diversity in tissues, with shoots and roots having a similar value, and seeds having the least diversity. Importantly, endophytic microbial species abundance and diversity was significantly higher in the organically grown plants compared to those grown using conventional practices, potentially indicating that organic management practices may increase endophyte presence and diversity. The impact that these endophytes could have on plant growth and yield was evaluated by reintroducing them into tomato plants in a greenhouse environment. Of the bacterial isolates tested, 61% were found to promote tomato plant growth and 50-64% were shown to enhance biomass accumulation, illustrating their potential agroecosystem application. PMID:26217348

  4. Characterization of culturable bacterial endophytes and their capacity to promote plant growth from plants grown using organic or conventional practices.

    Science.gov (United States)

    Xia, Ye; DeBolt, Seth; Dreyer, Jamin; Scott, Delia; Williams, Mark A

    2015-01-01

    Plants have a diverse internal microbial biota that has been shown to have an important influence on a range of plant health attributes. Although these endophytes have been found to be widely occurring, few studies have correlated agricultural production practices with endophyte community structure and function. One agricultural system that focuses on preserving and enhancing soil microbial abundance and biodiversity is organic farming, and numerous studies have shown that organically managed system have increased microbial community characteristics. Herein, the diversity and specificity of culturable bacterial endophytes were evaluated in four vegetable crops: corn, tomato, melon, and pepper grown under organic or conventional practices. Endophytic bacteria were isolated from surface-sterilized shoot, root, and seed tissues and sequence identified. A total of 336 bacterial isolates were identified, and grouped into 32 species and five phyla. Among these, 239 isolates were from organically grown plants and 97 from those grown conventionally. Although a diverse range of bacteria were documented, 186 were from the Phylum Firmicutes, representing 55% of all isolates. Using the Shannon diversity index, we observed a gradation of diversity in tissues, with shoots and roots having a similar value, and seeds having the least diversity. Importantly, endophytic microbial species abundance and diversity was significantly higher in the organically grown plants compared to those grown using conventional practices, potentially indicating that organic management practices may increase endophyte presence and diversity. The impact that these endophytes could have on plant growth and yield was evaluated by reintroducing them into tomato plants in a greenhouse environment. Of the bacterial isolates tested, 61% were found to promote tomato plant growth and 50-64% were shown to enhance biomass accumulation, illustrating their potential agroecosystem application.

  5. Characterization of culturable bacterial endophytes and their capacity to promote plant growth from plants grown using organic or conventional practices

    Directory of Open Access Journals (Sweden)

    Ye eXia

    2015-07-01

    Full Text Available Plants have a diverse internal microbial biota that has been shown to have an important influence on a range of plant health attributes. Although these endophytes have been found to be widely occurring, few studies have correlated agricultural production practices with endophyte community structure and function. One agricultural system that focuses on preserving and enhancing soil microbial abundance and biodiversity is organic farming, and numerous studies have shown that organically managed system have increased microbial community characteristics. Herein, the diversity and specificity of culturable bacterial endophytes were evaluated in four vegetable crops: corn, tomato, melon and pepper grown under organic or conventional practices. Endophytic bacteria were isolated from surface-sterilized shoot, root and seed tissues and sequence identified. A total of 336 bacterial isolates were identified, and grouped into 32 species and 5 phyla. Among these, 239 isolates were from organically grown plants and 97 from those grown conventionally. Although a diverse range of bacteria were documented, 186 were from the Phylum Firmicutes, representing 55% of all isolates. Using the Shannon diversity index, we observed a gradation of diversity in tissues, with shoots and roots having a similar value, and seeds having the least diversity. Importantly, endophytic microbial species abundance and diversity was significantly higher in the organically grown plants compared to those grown using conventional practices, potentially indicating that organic management practices may increase endophyte presence and diversity. The impact that these endophytes could have on plant growth and yield was evaluated by reintroducing them into tomato plants in a greenhouse environment. Of the bacterial isolates tested, 61% were found to promote tomato plant growth and 50%-64% were shown to enhance biomass accumulation, illustrating their potential agroecosystem application.

  6. Influence of biogas flow rate on biomass composition during the optimization of biogas upgrading in microalgal-bacterial processes.

    Science.gov (United States)

    Serejo, Mayara L; Posadas, Esther; Boncz, Marc A; Blanco, Saúl; García-Encina, Pedro; Muñoz, Raúl

    2015-03-01

    The influence of biogas flow rate (0, 0.3, 0.6, and 1.2 m(3) m(-2) h(-1)) on the elemental and macromolecular composition of the algal-bacterial biomass produced from biogas upgrading in a 180 L photobioreactor interconnected to a 2.5 L external bubbled absorption column was investigated using diluted anaerobically digested vinasse as cultivation medium. The influence of the external liquid recirculation/biogas ratio (0.5 biogas, was also evaluated. A L/G ratio of 10 was considered optimum to support CO2 and H2S removals of 80% and 100%, respectively, at all biogas flow rates tested. Biomass productivity increased at increasing biogas flow rate, with a maximum of 12 ± 1 g m(-2) d(-1) at 1.2 m(3) m(-2) h(-1), while the C, N, and P biomass content remained constant at 49 ± 2%, 9 ± 0%, and 1 ± 0%, respectively, over the 175 days of experimentation. The high carbohydrate contents (60-76%), inversely correlated to biogas flow rates, would allow the production of ≈100 L of ethanol per 1000 m(3) of biogas upgraded under a biorefinery process approach.

  7. Daily changes in temperature, not the circadian clock, regulate growth rate in Brachypodium distachyon.

    Directory of Open Access Journals (Sweden)

    Dominick A Matos

    Full Text Available Plant growth is commonly regulated by external cues such as light, temperature, water availability, and internal cues generated by the circadian clock. Changes in the rate of growth within the course of a day have been observed in the leaves, stems, and roots of numerous species. However, the relative impact of the circadian clock on the growth of grasses has not been thoroughly characterized. We examined the influence of diurnal temperature and light changes, and that of the circadian clock on leaf length growth patterns in Brachypodium distachyon using high-resolution time-lapse imaging. Pronounced changes in growth rate were observed under combined photocyles and thermocycles or with thermocycles alone. A considerably more rapid growth rate was observed at 28°C than 12°C, irrespective of the presence or absence of light. In spite of clear circadian clock regulated gene expression, plants exhibited no change in growth rate under conditions of constant light and temperature, and little or no effect under photocycles alone. Therefore, temperature appears to be the primary cue influencing observed oscillations in growth rate and not the circadian clock or photoreceptor activity. Furthermore, the size of the leaf meristem and final cell length did not change in response to changes in temperature. Therefore, the nearly five-fold difference in growth rate observed across thermocycles can be attributed to proportionate changes in the rate of cell division and expansion. A better understanding of the growth cues in B. distachyon will further our ability to model metabolism and biomass accumulation in grasses.

  8. Daily changes in temperature, not the circadian clock, regulate growth rate in Brachypodium distachyon.

    Science.gov (United States)

    Matos, Dominick A; Cole, Benjamin J; Whitney, Ian P; MacKinnon, Kirk J-M; Kay, Steve A; Hazen, Samuel P

    2014-01-01

    Plant growth is commonly regulated by external cues such as light, temperature, water availability, and internal cues generated by the circadian clock. Changes in the rate of growth within the course of a day have been observed in the leaves, stems, and roots of numerous species. However, the relative impact of the circadian clock on the growth of grasses has not been thoroughly characterized. We examined the influence of diurnal temperature and light changes, and that of the circadian clock on leaf length growth patterns in Brachypodium distachyon using high-resolution time-lapse imaging. Pronounced changes in growth rate were observed under combined photocyles and thermocycles or with thermocycles alone. A considerably more rapid growth rate was observed at 28°C than 12°C, irrespective of the presence or absence of light. In spite of clear circadian clock regulated gene expression, plants exhibited no change in growth rate under conditions of constant light and temperature, and little or no effect under photocycles alone. Therefore, temperature appears to be the primary cue influencing observed oscillations in growth rate and not the circadian clock or photoreceptor activity. Furthermore, the size of the leaf meristem and final cell length did not change in response to changes in temperature. Therefore, the nearly five-fold difference in growth rate observed across thermocycles can be attributed to proportionate changes in the rate of cell division and expansion. A better understanding of the growth cues in B. distachyon will further our ability to model metabolism and biomass accumulation in grasses.

  9. Diameter growth rates in tropical dry forests: contributions to the sustainable management of forests in the Bolivian Cerrado biogeographical province

    NARCIS (Netherlands)

    Lopez, L.; Villalba, R.; Peña-Claros, M.

    2012-01-01

    Growth ring variations were used to provide the rates in diameter growth for seven tree species in the Bolivian Cerrado biogeographical province. Ten to 50 trees were measured per species. Ring width measurements provided accurate data on the rates of tree growth. Variations in growth rates were det

  10. Crack growth rate in core shroud horizontal welds using two models for a BWR

    Energy Technology Data Exchange (ETDEWEB)

    Arganis Juárez, C.R., E-mail: carlos.arganis@inin.gob.mx; Hernández Callejas, R.; Medina Almazán, A.L.

    2015-05-15

    Highlights: • Two models were used to predict SCC growth rate in a core shroud of a BWR. • A weld residual stress distribution with 30% stress relaxation by neutron was used. • Agreement is shown between the measurements of SCC growth rate and the predictions. • Slip–oxidation model is better at low fluences and empirical model at high fluences. - Abstract: An empirical crack growth rate correlation model and a predictive model based on the slip–oxidation mechanism for Stress Corrosion Cracking (SCC) were used to calculate the crack growth rate in a BWR core shroud. In this study, the crack growth rate was calculated by accounting for the environmental factors related to aqueous environment, neutron irradiation to high fluence and the complex residual stress conditions resulting from welding. In estimating the SCC behavior the crack growth measurements data from a Boiling Water Reactor (BWR) plant are referred to, and the stress intensity factor vs crack depth throughout thickness is calculated using a generic weld residual stress distribution for a core shroud, with a 30% stress relaxation induced by neutron irradiation. Quantitative agreement is shown between the measurements of SCC growth rate and the predictions of the slip–oxidation mechanism model for relatively low fluences (5 × 10{sup 24} n/m{sup 2}), and the empirical model predicted better the SCC growth rate than the slip–oxidation model for high fluences (>1 × 10{sup 25} n/m{sup 2}). The relevance of the models predictions for SCC growth rate behavior depends on knowing the model parameters.

  11. Rates and mechanisms of bacterial mutagenesis from maximum-depth sequencing.

    Science.gov (United States)

    Jee, Justin; Rasouly, Aviram; Shamovsky, Ilya; Akivis, Yonatan; Steinman, Susan R; Mishra, Bud; Nudler, Evgeny

    2016-06-30

    In 1943, Luria and Delbrück used a phage-resistance assay to establish spontaneous mutation as a driving force of microbial diversity. Mutation rates are still studied using such assays, but these can only be used to examine the small minority of mutations conferring survival in a particular condition. Newer approaches, such as long-term evolution followed by whole-genome sequencing, may be skewed by mutational ‘hot’ or ‘cold’ spots. Both approaches are affected by numerous caveats. Here we devise a method, maximum-depth sequencing (MDS), to detect extremely rare variants in a population of cells through error-corrected, high-throughput sequencing. We directly measure locus-specific mutation rates in Escherichia coli and show that they vary across the genome by at least an order of magnitude. Our data suggest that certain types of nucleotide misincorporation occur 10(4)-fold more frequently than the basal rate of mutations, but are repaired in vivo. Our data also suggest specific mechanisms of antibiotic-induced mutagenesis, including downregulation of mismatch repair via oxidative stress, transcription–replication conflicts, and, in the case of fluoroquinolones, direct damage to DNA. PMID:27338792

  12. Effects of Phlomis umbrosa Root on Longitudinal Bone Growth Rate in Adolescent Female Rats.

    Science.gov (United States)

    Lee, Donghun; Kim, Young-Sik; Song, Jungbin; Kim, Hyun Soo; Lee, Hyun Jung; Guo, Hailing; Kim, Hocheol

    2016-01-01

    This study aimed to investigate the effects of Phlomis umbrosa root on bone growth and growth mediators in rats. Female adolescent rats were administered P. umbrosa extract, recombinant human growth hormone or vehicle for 10 days. Tetracycline was injected intraperitoneally to produce a glowing fluorescence band on the newly formed bone on day 8, and 5-bromo-2'-deoxyuridine was injected to label proliferating chondrocytes on days 8-10. To assess possible endocrine or autocrine/paracrine mechanisms, we evaluated insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3) or bone morphogenetic protein-2 (BMP-2) in response to P. umbrosa administration in either growth plate or serum. Oral administration of P. umbrosa significantly increased longitudinal bone growth rate, height of hypertrophic zone and chondrocyte proliferation of the proximal tibial growth plate. P. umbrosa also increased serum IGFBP-3 levels and upregulated the expressions of IGF-1 and BMP-2 in growth plate. In conclusion, P. umbrosa increases longitudinal bone growth rate by stimulating proliferation and hypertrophy of chondrocyte with the increment of circulating IGFBP-3. Regarding the immunohistochemical study, the effect of P. umbrosa may also be attributable to upregulation of local IGF-1 and BMP-2 expressions in the growth plate, which can be considered as a GH dependent autocrine/paracrine pathway. PMID:27070559

  13. Effects of Phlomis umbrosa Root on Longitudinal Bone Growth Rate in Adolescent Female Rats

    Directory of Open Access Journals (Sweden)

    Donghun Lee

    2016-04-01

    Full Text Available This study aimed to investigate the effects of Phlomis umbrosa root on bone growth and growth mediators in rats. Female adolescent rats were administered P. umbrosa extract, recombinant human growth hormone or vehicle for 10 days. Tetracycline was injected intraperitoneally to produce a glowing fluorescence band on the newly formed bone on day 8, and 5-bromo-2′-deoxyuridine was injected to label proliferating chondrocytes on days 8–10. To assess possible endocrine or autocrine/paracrine mechanisms, we evaluated insulin-like growth factor-1 (IGF-1, insulin-like growth factor binding protein-3 (IGFBP-3 or bone morphogenetic protein-2 (BMP-2 in response to P. umbrosa administration in either growth plate or serum. Oral administration of P. umbrosa significantly increased longitudinal bone growth rate, height of hypertrophic zone and chondrocyte proliferation of the proximal tibial growth plate. P. umbrosa also increased serum IGFBP-3 levels and upregulated the expressions of IGF-1 and BMP-2 in growth plate. In conclusion, P. umbrosa increases longitudinal bone growth rate by stimulating proliferation and hypertrophy of chondrocyte with the increment of circulating IGFBP-3. Regarding the immunohistochemical study, the effect of P. umbrosa may also be attributable to upregulation of local IGF-1 and BMP-2 expressions in the growth plate, which can be considered as a GH dependent autocrine/paracrine pathway.

  14. Combinative effects of a bacterial type-III effector and a biocontrol bacterium on rice growth and disease resistance

    Indian Academy of Sciences (India)

    Haiying Ren; Ganyu Gu; Juying Long; Qian Yin; Tingquan Wu; Tao Song; Shujian Zhang; Zhiyi Chen; Hansong Dong

    2006-12-01

    Expression of HpaGXoo, a bacterial type-III effector, in transgenic plants induces disease resistance. Resistance also can be elicited by biocontrol bacteria. In both cases, plant growth is often promoted. Here we address whether biocontrol bacteria and HpaGXoo can act together to provide better results in crop improvement. We studied effects of Pseudomonas cepacia on the rice variety R109 and the hpaGXoo-expressing rice line HER1. Compared to R109, HER1 showed increased growth, grain yield, and defense responses toward diseases and salinity stress. Colonization of roots by P. cepacia caused 20% and 13% increase, in contrast to controls, in root growth of R109 and HER1. Growth of leaves and stems also increased in R109 but that of HER1 was inhibited. When P. cepacia colonization was subsequent to plant inoculation with Rhizoctonia solani, a pathogen that causes sheath blight, the disease was less severe than controls in both R109 and HER1; HER1, nevertheless, was more resistant, suggesting that P. cepacia and HpaGXoo cooperate in inducing disease resistance. Several genes that critically regulate growth and defense behaved differentially in HER1 and R109 while responding to P. cepacia. In R109 leaves, the OsARF1 gene, which regulates plant growth, was expressed in consistence with growth promotion by P. cepacia. Inversely, OsARF1 expression was coincident with inhibition in growth of HER1 leaves. In both plants, the expression of OsEXP1, which encodes an expansin protein involved in plant growth, was concomitant with growth promotion in leaves instead of roots, in response to P. cepacia. We also studied OsMAPK, a gene that encodes a mitogen-activated protein kinase and controls defense responses toward salinity and infection by pathogens in rice. In response to P. cepacia, an early expression of OsMAPK was coincident with R109 resistance to the disease, while HER1 expressed the gene similarly whether P. cepacia was present or not. Evidently, P. cepacia and GXoo

  15. The Effects of Population Density on Juvenile Growth Rate in White-Tailed Deer

    Science.gov (United States)

    Barr, Brannon; Wolverton, Steve

    2014-10-01

    Animal body size is driven by habitat quality, food availability, and nutrition. Adult size can relate to birth weight, to length of the ontogenetic growth period, and/or to the rate of growth. Data requirements are high for studying these growth mechanisms, but large datasets exist for some game species. In North America, large harvest datasets exist for white-tailed deer ( Odocoileus virginianus), but such data are collected under a variety of conditions and are generally dismissed for ecological research beyond local population and habitat management. We contend that such data are useful for studying the ecology of white-tailed deer growth and body size when analyzed at ordinal scale. In this paper, we test the response of growth rate to food availability by fitting a logarithmic equation that estimates growth rate only to harvest data from Fort Hood, Texas, and track changes in growth rate over time. Results of this ordinal scale model are compared to previously published models that include additional parameters, such as birth weight and adult weight. It is shown that body size responds to food availability by variation in growth rate. Models that estimate multiple parameters may not work with harvest data because they are prone to error, which renders estimates from complex models too variable to detect interannual changes in growth rate that this ordinal scale model captures. This model can be applied to harvest data, from which inferences about factors that influence animal growth and body size (e.g., habitat quality and nutritional availability) can be drawn.

  16. The Role Of Industry Structure, Costs, And Economic Spillovers In Determining State Employment Growth Rates

    OpenAIRE

    Mark D. Partridge; Rickman, Dan S.

    1996-01-01

    We examine differential state employment growth by appraising the relative effects of traditional cost factors versus knowledge and technology spillovers. One emphasis is the influence that industry composition has on employment growth. Traditional cost factors examined include wage rates, unionization, taxes, and government policies such as unemployment insurance and welfare programs. The results suggest that industry composition does influence growth, working through several different avenu...

  17. Effects of properties of metal-contaminated soils on bacterial bioluminescence activity, seed germination, and root and shoot growth.

    Science.gov (United States)

    Kang, Il-Mo; Kong, In Chul

    2016-01-01

    This study examined the effects of several factors (metal contents and soil properties) on bacterial bioluminescence activity, seed germination and root/shoot growth of Lactuca in metal-contaminated soils. Each bioassay showed different sensitivities to extractants of soil samples. Average sensitivities of the bioassay were in the following order: root growth > bioluminescence ≥ shoot growth ≥ seed germination. Both total and weak acid-extracted metal contents showed no observable correlations with the activity of any bioassays (r(2) bioluminescence activity and organics (r(2) = 0.7198) as well as between root growth and CEC (r(2) = 0.6676). Effects of soils were difficult to generalize since they were dependent on many factors, such as soil properties, metal contents, and the organism used in each test. Nonetheless, these results indicated that a battery of bioassays is an effective strategy for assessment of contaminated soils. Furthermore, specific soil factors were shown to more influence on soil toxicity, depending on the type of bioassay.

  18. Density but not climate affects the population growth rate of guanacos ( Lama guanicoe) (Artiodactyla, Camelidae)

    Science.gov (United States)

    Zubillaga, María; Skewes, Oscar; Soto, Nicolás; Rabinovich, Jorge E

    2014-01-01

    We analyzed the effects of population density and climatic variables on the rate of population growth in the guanaco ( Lama guanicoe), a wild camelid species in South America. We used a time series of 36 years (1977-2012) of population sampling in Tierra del Fuego, Chile. Individuals were grouped in three age-classes: newborns, juveniles, and adults; for each year a female population transition matrix was constructed, and the population growth rate (λ) was estimated for each year as the matrix highest positive eigenvalue. We applied a regression analysis with finite population growth rate (λ) as dependent variable, and total guanaco population, sheep population, annual mean precipitation, and winter mean temperature as independent variables, with and without time lags. The effect of guanaco population size was statistically significant, but the effects of the sheep population and the climatic variables on guanaco population growth rate were not statistically significant. PMID:25187878

  19. Growth rate of Usnea aurantiacoatra (Jacq.) Bory on Fildes Peninsula, Antarctica and its climatic background.

    Science.gov (United States)

    Li, Ying; Kromer, Bernd; Schukraft, Gerd; Bubenzer, Olaf; Huang, Man-Rong; Wang, Ze-Min; Bian, Lin-Gen; Li, Cheng-Sen

    2014-01-01

    The ages of a fruticose lichen of Usnea aurantiacoatra (Jacq.) Bory, from Fildes Peninsula, King George Island, Southwest Antarctic, were determined by radiocarbon (14C), and it is 1993-1996 at bottom and 2006-2007 at top of the lichen branch. The growth rates of U. aurantiacoatra calculated are 4.3 to 5.5 mm year(-1) based on its length and ages. The comparisons show that the growth rates of U. aurantiacoatra are higher than those of U. antarctica (0.4 to 1.1 mm year(-1)). The growth rates of fruticose lichens are always higher, usually >2 mm year(-1), than those of crustose ones, usually lichen growth rates in polar areas may respond to the climatic and environmental changes, and the lichens may act as bio-monitor of natural condition. PMID:24968131

  20. Modelling the effect of ethanol on growth rate of food spoilage moulds

    NARCIS (Netherlands)

    Dantigny, P.; Guilmart, A.; Radoi, F.; Bensoussan, M.; Zwietering, M.H.

    2005-01-01

    The effect of ethanol (E) on the radial growth rate (¿) of food spoilage moulds (Aspergillus candidus, Aspergillus flavus, Aspergillus niger, Cladosporium cladosporioides, Eurotium herbariorum, Mucor circinelloides, Mucor racemosus, Paecilomyces variotii, Penicillium chrysogenum, Penicillium digitat

  1. Growth rates of alien Oreochromis niloticus and indigenous Oreochromis mortimeri in Lake Kariba, Zimbabwe

    NARCIS (Netherlands)

    Chifamba, P. C.; Videler, J. J.

    2014-01-01

    Growth rates of indigenous Oreochromis mortimeri and alien Oreochromis niloticus from Lake Kariba were estimated from samples collected in 1997-2000, 2003-2005 and 2010-2011. Growth zones on scales and otoliths of O. niloticus and on the otoliths and opercula of O. mortimeri were deposited annually.

  2. In Search of Inflation Rate Compatible with Growth Target in CEMAC Countries

    OpenAIRE

    Mantsie, Rufin-Willy

    2012-01-01

    Inflation produces adverse effects to growth in economies. However, economic analysis faces aproblem of determining the threshold at which inflation becomes harmful to the economy. Inthis article we try to determine the inflation rate favorable to growth or not for the CEMACcountries and to make contributions to economic policy.

  3. Thermal effects on growth and respiration rates of the mayfly, Dolania americana (ephemeroptera)

    International Nuclear Information System (INIS)

    The mayfly Dolania Americana, common in the sand of Upper Three Runs Creek, Savannah River Plant, was studied to determine the effects of seasonal changes in temperature on population growth rates and to determine the effects of slight elevations in water temperature on respiration rates of this benthic species. Growth of the population increased with stream temperature until peak emergence of adults in June and July. There was a strong inverse correlation between body weight and respiration rates of immature nymphs. Respiration rates at 2.5, 5, and 100C above ambient creekwater temperatures were not significantly higher than those measured at ambient creekwater temperatures. (auth)

  4. Phylogenetic, functional, and structural components of variation in bone growth rate of amniotes.

    Science.gov (United States)

    Cubo, Jorge; Legendre, Pierre; de Ricqlès, Armand; Montes, Laëtitia; de Margerie, Emmanuel; Castanet, Jacques; Desdevises, Yves

    2008-01-01

    The biological features observed in every living organism are the outcome of three sets of factors: historical (inherited by homology), functional (biological adaptation), and structural (properties inherent to the materials with which organs are constructed, and the morphogenetic rules by which they grow). Integrating them should bring satisfactory causal explanations of empirical data. However, little progress has been accomplished in practice toward this goal, because a methodologically efficient tool was lacking. Here we use a new statistical method of variation partitioning to analyze bone growth in amniotes. (1) Historical component. The variation of bone growth rates contains a significant phylogenetic signal, suggesting that the observed patterns are partly the outcome of shared ancestry. (2) Functional causation. High growth rates, although energy costly, may be adaptive (i.e., they may increase survival rates) in taxa showing short growth periods (e.g., birds). In ectothermic amniotes, low resting metabolic rates may limit the maximum possible growth rates. (3) Structural constraint. Whereas soft tissues grow through a multiplicative process, growth of mineralized tissues is accretionary (additive, i.e., mineralization fronts occur only at free surfaces). Bone growth of many amniotes partially circumvents this constraint: it is achieved not only at the external surface of the bone shaft, but also within cavities included in the bone cortex as it grows centrifugally. Our approach contributes to the unification of historicism, functionalism, and structuralism toward a more integrated evolutionary biology. PMID:18315815

  5. Measuring the growth rate of UK dairy heifers to improve future productivity.

    Science.gov (United States)

    Bazeley, Katrine J; Barrett, David C; Williams, Paul D; Reyher, Kristen K

    2016-06-01

    Sub-optimal heifer growth is associated with higher disease rates and reduced future performance and longevity in the dairy herd. This report describes a system for measuring heifer growth from birth to first calving that was used on commercial dairy farms in South West England, in order to gather benchmarking data to feed back to farmers. Weights (n = 8443) were collected from 20 farms. There was a marked variation in individual and herd mean growth rates. Overall, calves gained no weight in the first 8 days after birth and had a very low growth rate (median 0.12 kg/day) up to 30 days, a period when feed conversion efficiency is high and calves are vulnerable to disease. Heifers whose growth rate up to 180 days was low were significantly less likely to achieve target service weight (374 kg) by 420 days. Monitoring heifer growth during the rearing period enables farmers to improve heifer growth rates and so impact both the efficiency of heifer rearing and, potentially, the productivity and performance of the adult herd. PMID:27256019

  6. Phylogenetic, functional, and structural components of variation in bone growth rate of amniotes.

    Science.gov (United States)

    Cubo, Jorge; Legendre, Pierre; de Ricqlès, Armand; Montes, Laëtitia; de Margerie, Emmanuel; Castanet, Jacques; Desdevises, Yves

    2008-01-01

    The biological features observed in every living organism are the outcome of three sets of factors: historical (inherited by homology), functional (biological adaptation), and structural (properties inherent to the materials with which organs are constructed, and the morphogenetic rules by which they grow). Integrating them should bring satisfactory causal explanations of empirical data. However, little progress has been accomplished in practice toward this goal, because a methodologically efficient tool was lacking. Here we use a new statistical method of variation partitioning to analyze bone growth in amniotes. (1) Historical component. The variation of bone growth rates contains a significant phylogenetic signal, suggesting that the observed patterns are partly the outcome of shared ancestry. (2) Functional causation. High growth rates, although energy costly, may be adaptive (i.e., they may increase survival rates) in taxa showing short growth periods (e.g., birds). In ectothermic amniotes, low resting metabolic rates may limit the maximum possible growth rates. (3) Structural constraint. Whereas soft tissues grow through a multiplicative process, growth of mineralized tissues is accretionary (additive, i.e., mineralization fronts occur only at free surfaces). Bone growth of many amniotes partially circumvents this constraint: it is achieved not only at the external surface of the bone shaft, but also within cavities included in the bone cortex as it grows centrifugally. Our approach contributes to the unification of historicism, functionalism, and structuralism toward a more integrated evolutionary biology.

  7. ENDOSULFAN INDUCED CHANGES IN GROWTH RATE, PIGMENT COMPOSITION AND PHOTOSYNTHETIC ACTIVITY OF MOSQUITO FERN AZOLLA MICROPHYLLA

    OpenAIRE

    Raja W.; Rathaur P.; John S. A.; Ramteke P. W.

    2012-01-01

    This paper is the first in a series reporting a study on the effects of different concentrations of insecticide, Endosulfan (0-600ppm) was premeditated on 5th day after insecticide exposure with respect to growth rate, pigment composition and photosynthetic activity of Azolla microphylla under laboratory conditions which become non-target organism in the rice fields. Endosulfan inhibited the relative growth rate, pigment content and photosynthetic O2 evolution. Phycocyanin was main target fo...

  8. Density but not climate affects the population growth rate of guanacos ( Lama guanicoe) (Artiodactyla, Camelidae)

    OpenAIRE

    María Zubillaga; Oscar Skewes; Nicolás Soto; Jorge E Rabinovich

    2014-01-01

    We analyzed the effects of population density and climatic variables on the rate of population growth in the guanaco ( Lama guanicoe), a wild camelid species in South America. We used a time series of 36 years (1977-2012) of population sampling in Tierra del Fuego, Chile. Individuals were grouped in three age-classes: newborns, juveniles, and adults; for each year a female population transition matrix was constructed, and the population growth rate (λ) was estimated for each year as the matri...

  9. Anti-Candida albicans activity of Pichia anomala as determined by a growth rate reduction assay.

    OpenAIRE

    Sawant, A D; Abdelal, A T; Ahearn, D G

    1988-01-01

    Killer toxin activity of Pichia anomala WC65 appeared fungicidal for P. bimundalis WC38 and fungistatic for Candida albicans RC1. Inhibitory activity against sensitive C. albicans showed a linear relationship between toxin concentrations and the inverse of the reduced growth rates. The plot of toxin concentrations against growth rates was hyperbolic, as is characteristic of saturation kinetics. Sensitivity of C. albicans to the toxin decreased with increased cell age. The measurement of growt...

  10. SCC crack growth rate of cold worked 316L stainless steel in PWR environment

    Energy Technology Data Exchange (ETDEWEB)

    Du, Donghai; Chen, Kai; Yu, Lun; Lu, Hui [School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Zhang, Lefu, E-mail: lfzhang@sjtu.edu.cn [School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Shi, Xiuqiang; Xu, Xuelian [Shanghai Nuclear Engineering Research and Design Institute, Shanghai 200233 (China)

    2015-01-15

    Many component failures in nuclear power plants were found to be caused by stress corrosion cracking (SCC) of cold worked austenitic steels. Some of the pressure boundary component materials are even cold worked up to 35% plastic deformation, leaving high residual stress and inducing high growth rate of corrosion crack. Controlling water chemistry is one of the best counter measure to mitigate this problem. In this work, the effects of temperature (200 up to 325 °C) and dissolved oxygen (0 up to 2000 μg/L) on SCC crack growth rates of cold worked austenitic stainless steel type 316L have been tested by using direct current potential drop (DCPD) method. The results showed that temperature affected SCC crack growth rates more significantly in oxygenated water than in deaerated water. In argon deaerated water, the crack growth rate exhibited a peak at about 250 °C, which needs further verification. At 325 °C, the SCC crack growth rate increased rapidly with the increase of dissolved oxygen concentration within the range from 0 up to 200 μg/L, while when dissolved oxygen was above 200 μg/L, the crack growth rate followed a shallower dependence on dissolved oxygen concentration.

  11. Factors influencing crystal growth rates from undercooled liquids of pharmaceutical compounds.

    Science.gov (United States)

    Trasi, Niraj S; Baird, Jared A; Kestur, Umesh S; Taylor, Lynne S

    2014-08-21

    Amorphous forms of drugs are increasingly being used to deliver poorly water-soluble compounds. Therefore, understanding the magnitude and origin of differences in crystallization kinetics is highly important. The goal of this study was to better understand the factors that influence crystal growth rates from pharmaceutically relevant undercooled liquids and to evaluate the range of growth rates observed. The crystal growth rates of 31 drugs were determined using an optical microscope in the temperature region between the glass transition temperature (Tg) and the melting temperature (Tm). Thermodynamic parameters such as Tm, melting enthalpy, and Tg were determined using a differential scanning calorimeter (DSC). Selected viscosity values for the undercooled liquid were taken from the literature. The growth rates of the different compounds were found to be very different from each other with a variation of about 5 orders of magnitude between the fastest growing compounds and the slowest growing compounds. A comparison of the physicochemical properties showed that compounds that had fast crystal growth rates had smaller molecular weights, higher melting temperatures, lower melt entropies, lower melt viscosities, and higher crystal densities. Variations in the growth rates of the compounds could be rationalized to a large extent by considering the thermodynamic driving force for crystallization, the viscosity, and the entropy difference between the melt and undercooled liquid. This study therefore provides important insight into factors that may compromise the stability of amorphous pharmaceuticals. PMID:25076138

  12. Effect of growth rate on characteristic lengths of microstructure in directionally solidified

    Directory of Open Access Journals (Sweden)

    Zhang Yuan

    2013-09-01

    Full Text Available The microstructure of TiAl based alloys is sensitive to growth rates. In this paper, Bridgman directional solidification of Ti-46Al-2Cr-2Nb-0.2B (at.% alloy was carried out at a constant temperature gradient (G to investigate the effects of various growth rates (v on characteristic lengths (primary dendritic arm spacing, secondary dendritic arm spacing and lamellar spacing of the microstructure. Results show that under the experimental conditions of G = 18 K·m-1 and v = 15 μm·s-1 to 70 μm·s-1, the primary phase of directionally solidified Ti-46Al-2Cr-2Nb-0.2B alloy is α phase, the values of primary dendritic arm spacing (λ1, secondary dendritic arm spacing (λ2 and lamellar spacing (λ1a decrease with the increase in growth rate. The results were compared with theoretical models and similar experimental results of TiAl based alloys. The Bouchard-Kirkaldy model agrees well with the relationship between primary dendritic arm spacing and growth rate obtained in the experiment; the relationship between them can be expressed by λ1 = 758.6v-0.39. The relationship between the secondary dendritic arm spacing and the growth rate can be expressed by λ2 = 113.9v-0.45, while the relationship between the lamellar spacing and growth rate can be expressed by λ1a = 22.88v-0.94.

  13. On the measurement of fatigue crack growth rates of steels using non-standard specimens

    International Nuclear Information System (INIS)

    Fatigue crack growth rates were measured using K-Decreasing Method during precracking of standard (Compact Tension) and non-standard (Charpy V -notch and Three-Point-Bend) specimens of four ferritic steels. Crack growth rates from the specimens were then inter-compared. The results from Compact Tension specimens were within ±15% error bar of the results from Three-Point-Bend specimens and were within ±6% error bar of the results from Charpy V -notch. The inter-comparison of the mean crack growth rates of any of the steels as obtained using different specimen geometries did not reveal any systematic dependence of crack growth rates vis-a-vis the specimens utilized. The experimental results suggested the possibility of generating material crack growth rate data as a bonus during fatigue precracking of fracture toughness specimens including Charpy V-notch and Three-Point-Bend specimens. The results also indicated distinct possibility of the measurement of steady state fatigue crack growth rate of irradiated steels using either Compact Tension and Three-Point-Bend fracture toughness specimens with a/W ≤ 0.65 or during precrackingstep of a few designated impact specimens from surveillance locations to be used as fracture toughness specimens for generation of irradiated material fracture toughness data. (author)

  14. Crack growth rate under cyclic bending in the explosively welded steel/titanium bimetals

    International Nuclear Information System (INIS)

    Highlights: ► The results of the tests on fatigue crack growth in a steel/titanium composite under oscillatory bending. ► Hardness of both joined materials in all their section is higher than hardness of the materials before cladding. ► The main crack propagated in the direction parallel to the loading action and they did not include secondary cracks. ► When the crack growth was being passed along the interface line, decrease of the crack growth rate took place. -- Abstract: The paper presents the results of the tests on fatigue crack growth in a steel/titanium composite under oscillatory bending. Two kinds of specimens of rectangular cross sections were tested. In the tested specimens, the ratio of heights of basic and overlaid materials was h1:h2 = 2.5:1 and 1:1. In the specimens, the fatigue crack growth was parallel to the applied loading and its direction changed at the interface line. Next, the crack growth along the interface line or the crack growth passing through the interface line were observed. When the crack growth passed along the interface line, decrease of the crack growth rate took place. The specimens have the uniform crack growth at both sides of lateral surfaces. At the composite fractures in the steel and titanium, transcrystalline cracks are dominating.

  15. Small regulatory RNA-induced growth rate heterogeneity of Bacillus subtilis.

    OpenAIRE

    Mars, Ruben A. T.; Pierre Nicolas; Mariano Ciccolini; Ewoud Reilman; Alexander Reder; Marc Schaffer; Ulrike Mäder; Uwe Völker; Jan Maarten van Dijl; Denham, Emma L.

    2015-01-01

    Isogenic bacterial populations can consist of cells displaying heterogeneous physiological traits. Small regulatory RNAs (sRNAs) could affect this heterogeneity since they act by fine-tuning mRNA or protein levels to coordinate the appropriate cellular behavior. Here we show that the sRNA RnaC/S1022 from the Gram-positive bacterium Bacillus subtilis can suppress exponential growth by modulation of the transcriptional regulator AbrB. Specifically, the post-transcriptional abrB-RnaC/S1022 inter...

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

    Science.gov (United States)

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

  17. Diagnostic Accuracy of Growth Rate in Differentiating Etiologies of Short Stature in Children

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Alaei

    2016-08-01

    Full Text Available Background  Short stature is a manifestation of a wide variety of conditions that some of which may be amenable to timely treatment and a suboptimal growth rate may be an early marker pointing to the cause of growth retardation. This study was conducted to evaluate the diagnostic utility of growth rate in differential diagnosis of children with short stature. Materials and Methods All children between the ages of 2 and 18 years who visited in pediatric endocrinology clinic in a five years period were recruited in a prospective cohort study. Children with standing height Results One hundred forty three patients fulfilled the inclusion criteria. Mean follow up period was 14.4±10.9 months. Etiologies of short stature were: constitutional growth delay (CGD 46.9%, familial short stature (FSS 28.7%, hypothyroidism 4.2%, growth hormone deficiency (GHD 4.2% and miscellaneous causes in 16% of patients.  Mean Z- score for children with constitutional growth delay was -2.3±0.69, in familial short stature was -2.3±0.65 and for other condition was -2.7±1.49. There was a meaningful statistical correlation between growth rate and etiology of short stature (P0.05. Conclusion There was significant difference in growth rate between children with constitutional growth delay and familial short stature in comparing to short stature due to endocrine problem and other etiologies. Assessment of growth rate has some utility in diagnosing the etiology of short stature.

  18. A quantitative theory of solid tumor growth, metabolic rate and vascularization.

    Directory of Open Access Journals (Sweden)

    Alexander B Herman

    Full Text Available The relationships between cellular, structural and dynamical properties of tumors have traditionally been studied separately. Here, we construct a quantitative, predictive theory of solid tumor growth, metabolic rate, vascularization and necrosis that integrates the relationships between these properties. To accomplish this, we develop a comprehensive theory that describes the interface and integration of the tumor vascular network and resource supply with the cardiovascular system of the host. Our theory enables a quantitative understanding of how cells, tissues, and vascular networks act together across multiple scales by building on recent theoretical advances in modeling both healthy vasculature and the detailed processes of angiogenesis and tumor growth. The theory explicitly relates tumor vascularization and growth to metabolic rate, and yields extensive predictions for tumor properties, including growth rates, metabolic rates, degree of necrosis, blood flow rates and vessel sizes. Besides these quantitative predictions, we explain how growth rates depend on capillary density and metabolic rate, and why similar tumors grow slower and occur less frequently in larger animals, shedding light on Peto's paradox. Various implications for potential therapeutic strategies and further research are discussed.

  19. An inverse modeling procedure to determine particle growth and nucleation rates from measured aerosol size distributions

    Directory of Open Access Journals (Sweden)

    B. Verheggen

    2006-01-01

    Full Text Available Classical nucleation theory is unable to explain the ubiquity of nucleation events observed in the atmosphere. This shows a need for an empirical determination of the nucleation rate. Here we present a novel inverse modeling procedure to determine particle nucleation and growth rates based on consecutive measurements of the aerosol size distribution. The particle growth rate is determined by regression analysis of the measured change in the aerosol size distribution over time, taking into account the effects of processes such as coagulation, deposition and/or dilution. This allows the growth rate to be determined with a higher time-resolution than can be deduced from inspecting contour plots ('banana-plots''. Knowing the growth rate as a function of time enables the evaluation of the time of nucleation of measured particles of a certain size. The nucleation rate is then obtained by integrating the particle losses from time of measurement to time of nucleation. The regression analysis can also be used to determine or verify the optimum value of other parameters of interest, such as the wall loss or coagulation rate constants. As an example, the method is applied to smog chamber measurements. This program offers a powerful interpretive tool to study empirical aerosol population dynamics in general, and nucleation and growth in particular.

  20. Effects of climate change on plant population growth rate and community composition change.

    Directory of Open Access Journals (Sweden)

    Xiao-Yu Chang

    Full Text Available The impacts of climate change on forest community composition are still not well known. Although directional trends in climate change and community composition change were reported in recent years, further quantitative analyses are urgently needed. Previous studies focused on measuring population growth rates in a single time period, neglecting the development of the populations. Here we aimed to compose a method for calculating the community composition change, and to testify the impacts of climate change on community composition change within a relatively short period (several decades based on long-term monitoring data from two plots-Dinghushan Biosphere Reserve, China (DBR and Barro Colorado Island, Panama (BCI-that are located in tropical and subtropical regions. We proposed a relatively more concise index, Slnλ, which refers to an overall population growth rate based on the dominant species in a community. The results indicated that the population growth rate of a majority of populations has decreased over the past few decades. This decrease was mainly caused by population development. The increasing temperature had a positive effect on population growth rates and community change rates. Our results promote understanding and explaining variations in population growth rates and community composition rates, and are helpful to predict population dynamics and population responses to climate change.

  1. Stature of Sub-arctic Birch in Relation to Growth Rate, Lifespan and Tree Form

    OpenAIRE

    JÓNSSON, THORBERGUR HJALTI

    2004-01-01

    • Background and Aims Sub-arctic mountain birch Betula pubescens var. pumila communities in the North Atlantic region are of variable stature, ranging from prostrate scrubs to forests with trees up to 12 m high. Four hypotheses were tested, relating growth and population characteristics of sub-arctic birch woodland and scrub to tree stature; i.e. the variable stature of birch woods is due to differences in (1) the mean growth rate; (2) the age-related patterns of growth rate; (3) the life exp...

  2. Context-specific influence of water temperature on brook trout growth rates in the field

    Science.gov (United States)

    Xu, C.; Letcher, B.H.; Nislow, K.H.

    2010-01-01

    1. Modelling the effects of climate change on freshwater fishes requires robust field-based estimates accounting for interactions among multiple factors.2. We used data from an 8-year individual-based study of a wild brook trout (Salvelinus fontinalis) population to test the influence of water temperature on season-specific growth in the context of variation in other environmental (i.e. season, stream flow) or biotic factors (local brook trout biomass density and fish age and size) in West Brook, a third-order stream in western Massachusetts, U.S.A.3. Changes in ambient temperature influenced individual growth rates. In general, higher temperatures were associated with higher growth rates in winter and spring and lower growth rates in summer and autumn. However, the effect of temperature on growth was strongly context-dependent, differing in both magnitude and direction as a function of season, stream flow and fish biomass density.4. We found that stream flow and temperature had strong and complex interactive effects on trout growth. At the coldest temperatures (in winter), high stream flows were associated with reduced trout growth rates. During spring and autumn and in typical summers (when water temperatures were close to growth optima), higher flows were associated with increased growth rates. In addition, the effect of flow at a given temperature (the flow-temperature interaction) differed among seasons.5. Trout density negatively affected growth rate and had strong interactions with temperature in two of four seasons (i.e. spring and summer) with greater negative effects at high temperatures.6. Our study provided robust, integrative field-based estimates of the effects of temperature on growth rates for a species which serves as a model organism for cold-water adapted ectotherms facing the consequences of environmental change. Results of the study strongly suggest that failure to derive season-specific estimates, or to explicitly consider interactions with

  3. Experimental design and estimation of growth rate distributions in size-structured shrimp populations

    International Nuclear Information System (INIS)

    We discuss inverse problem results for problems involving the estimation of probability distributions using aggregate data for growth in populations. We begin with a mathematical model describing variability in the early growth process of size-structured shrimp populations and discuss a computational methodology for the design of experiments to validate the model and estimate the growth-rate distributions in shrimp populations. Parameter-estimation findings using experimental data from experiments so designed for shrimp populations cultivated at Advanced BioNutrition Corporation are presented, illustrating the usefulness of mathematical and statistical modeling in understanding the uncertainty in the growth dynamics of such populations

  4. DIFFERENCES IN POST HATCH METABOLIC RATE AND DEVELOPMENTAL RATE IN ATLANTIC SALMON (SALMO SALAR L): EVIDENCE FOR COMPENSATORY GROWTH?

    DEFF Research Database (Denmark)

    Steffensen, John Fleng

    2010-01-01

    in six out of 91 families, the three families with earliest and the three families with latest time to hatch. Measurements were done on two occasions, at 570-580 (T1) and 600-610 (T2) day degrees from fertilization. Generally, VO2 increased and yolk was consumed between T1 and T2. Late hatching larvae...... and had higher metabolic rate in T1 suggests that these inherited differences can be even out by accelerated post hatch growth....

  5. Effects of soil nitrogen:phosphorus ratio on growth rate of Artemisia ordosica seedlings

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    To address how the ratios of nitrogen and phosphorus (N:P ratios) in soil affect plant growth, we performed a two-factor (soil available N:P ratios and plant density) randomized block pot experiment to examine the relationships between soil N:P ratios, and the N:P ratios and growth rate of Artemisia ordosica seedlings. Under moderate water stress and adequate nutrient status, both soil N:P and plant density influenced the N:P ratios and growth rates of A. ordosica. With the increase of soil N:P ratios, the growth rates of A. ordosica seedlings decreased significantly. With the increase of soil N:P ratios, N:P ratios in A. ordosica seedlings increased significantly. While the nitrogen concentrations in the plant increased slightly, the phosphorus concentrations significantly decreased. With the increase of plant density, the shoot N:P ratios and growth rates significantly decreased, which resulted from soil N:P ratios. Thus, soil N:P ratios influenced the N:P ratios in A. ordosica seedlings, and hence, influenced its growth. Our results suggest that, under adequate nutrient environment, soil N:P ratios can be a limiting factor for plant growth.

  6. Maximum Rate of Growth of Enstrophy in Solutions of the Fractional Burgers Equation

    CERN Document Server

    Yun, Dongfang

    2016-01-01

    This investigation is a part of a research program aiming to characterize the extreme behavior possible in hydrodynamic models by probing the sharpness of estimates on the growth of certain fundamental quantities. We consider here the rate of growth of the classical and fractional enstrophy in the fractional Burgers equation in the subcritical, critical and supercritical regime. First, we obtain estimates on these rates of growth and then show that these estimates are sharp up to numerical prefactors. In particular, we conclude that the power-law dependence of the enstrophy rate of growth on the fractional dissipation exponent has the same global form in the subcritical, critical and parts of the supercritical regime. This is done by numerically solving suitably defined constrained maximization problems and then demonstrating that for different values of the fractional dissipation exponent the obtained maximizers saturate the upper bounds in the estimates as the enstrophy increases. In addition, nontrivial be...

  7. Model of apparent crystal growth rate and kinetics of seeded precipitation from sodium aluminate solution

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-bin; LIU Zhi-jian; XU Xiao-hui; ZHOU Qiu-sheng; PENG Zhi-hong; LIU Gui-hua

    2005-01-01

    Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was deve-loped. The simulation results indicate that the rate of apparent crystal growth during seeded precipitation exhibits a manifest dependence on the crystal size. In general, there is an obvious increase in the apparent crystal growth rate with the augment in crystal size. The apparent activation energy increases with the increase of characteristic crystal size, which indicates that the growth of small crystals is controlled by surface chemical reaction; it is gradually controlled by both the surface reaction and diffusion with the augment in crystal size.

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

    Science.gov (United States)

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

    2013-01-01

    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

  9. Evaluation of coral pathogen growth rates after exposure to atmospheric African dust samples

    Science.gov (United States)

    Lisle, John T.; Garrison, Virginia H.; Gray, Michael A.

    2014-01-01

    Laboratory experiments were conducted to assess if exposure to atmospheric African dust stimulates or inhibits the growth of four putative bacterial coral pathogens. Atmospheric dust was collected from a dust-source region (Mali, West Africa) and from Saharan Air Layer masses over downwind sites in the Caribbean [Trinidad and Tobago and St. Croix, U.S. Virgin Islands (USVI)]. Extracts of dust samples were used to dose laboratory-grown cultures of four putative coral pathogens: Aurantimonas coralicida (white plague type II), Serratia marcescens (white pox), Vibrio coralliilyticus, and V. shiloi (bacteria-induced bleaching). Growth of A. coralicida and V. shiloi was slightly stimulated by dust extracts from Mali and USVI, respectively, but unaffected by extracts from the other dust sources. Lag time to the start of log-growth phase was significantly shortened for A. coralicida when dosed with dust extracts from Mali and USVI. Growth of S. marcescens and V. coralliilyticus was neither stimulated nor inhibited by any of the dust extracts. This study demonstrates that constituents from atmospheric dust can alter growth of recognized coral disease pathogens under laboratory conditions.

  10. Generation time, net reproductive rate, and growth in stage-age-structured populations

    DEFF Research Database (Denmark)

    Steiner, Uli; Tuljapurkar, Shripad; Coulson, Tim

    2014-01-01

    to age-structured populations. Here we generalize this result to populations structured by stage and age by providing a new, unique measure of reproductive timing (Tc) that, along with net reproductive rate (R0), has a direct mathematical relationship to and approximates growth rate (r). We use simple...

  11. Hydrogen Isotope Effect on the Fatigue Crack Growth Rate in Pipeline Steel

    Science.gov (United States)

    Connolly, Matthew; Slifka, Andrew; Drexler, Elizabeth; Hydrogen Pipeline Safety Team

    Hydrogen (H2) is desirable for energy storage as it is cleaner burning and can store a larger amount of energy than an equal mass of gasoline. One problem in the development of a hydrogen economy is to find or develop materials that ensure the safe, reliable, and cost-effective flow of energy from the source to the user. It is expected steels will be needed to serve this function. However, the existing network of natural gas pipeline, for example, is constructed of ferrous materials which are susceptible to embrittlement and subsequent increased fatigue crack growth rates after exposure to hydrogen. It is expected that diffusion rates play an important role on fatigue crack growth rates. We report the measurement of the fatigue crack growth rate in a high strength pipeline steel in a gaseous deuterium (D2) environment, in an effort to determine the role of diffusion rate on FCGR, because D2 is chemically identical to H2, but with twice the mass. We found that the D2 fatigue crack growth rate was not enhanced compared to air as is seen in an H2 environment; in fact our D2 rate measurement was slightly slower than in air, a result which is not expected to be due to diffusion rates alone. NIST Materials Measurement Laboratory, Applied Chemicals and Materials Division.

  12. Effects of light intensity and temperature on Cryptomonas ovata (Cryptophyceae) growth and nutrient uptake rates

    Science.gov (United States)

    Cloern, James E.

    1977-01-01

    Specific growth rate of Cryptomonas ovata var. palustris Pringsheim was measured in batch culture at 14 light-temperature combinations. Both the maximum growth rate (μm) and optimum light intensity (Iopt) fit an empirical function that increases exponentially with temperature up to an optimum (Topt), then declines rapidly as temperature exceeds Topt. Incorporation of these functions into Steele's growth equation gives a good estimate of specific growth rate over a wide range of temperature and light intensity. Rates of phosphate, ammonium and nitrate uptake were measured separately at 16 combinations of irradiance and temperature and following a spike addition of all starved cells initially took up nutrient at a rapid rate. This transitory surge was followed by a period of steady, substrate-saturated uptake that persisted until external nutrient concentration fell. Substrate-saturated NO3−-uptake proceeded at very slow rates in the dark and was stimulated by both increased temperature and irradiance; NH4+-uptake apparently proceeded at a basal rate at 8 and l4 C and was also stimulated by increased temperature and irradiance. Rates of NH4−-uptake were much higher than NO3−-uptake at all light-temperature combinations. Below 20 C, PO4−3-uptake was more rapid in dark than in light, but was light enhanced at 26 C.

  13. Size-dependent standard deviation for growth rates: Empirical results and theoretical modeling

    Science.gov (United States)

    Podobnik, Boris; Horvatic, Davor; Pammolli, Fabio; Wang, Fengzhong; Stanley, H. Eugene; Grosse, I.

    2008-05-01

    We study annual logarithmic growth rates R of various economic variables such as exports, imports, and foreign debt. For each of these variables we find that the distributions of R can be approximated by double exponential (Laplace) distributions in the central parts and power-law distributions in the tails. For each of these variables we further find a power-law dependence of the standard deviation σ(R) on the average size of the economic variable with a scaling exponent surprisingly close to that found for the gross domestic product (GDP) [Phys. Rev. Lett. 81, 3275 (1998)]. By analyzing annual logarithmic growth rates R of wages of 161 different occupations, we find a power-law dependence of the standard deviation σ(R) on the average value of the wages with a scaling exponent β≈0.14 close to those found for the growth of exports, imports, debt, and the growth of the GDP. In contrast to these findings, we observe for payroll data collected from 50 states of the USA that the standard deviation σ(R) of the annual logarithmic growth rate R increases monotonically with the average value of payroll. However, also in this case we observe a power-law dependence of σ(R) on the average payroll with a scaling exponent β≈-0.08 . Based on these observations we propose a stochastic process for multiple cross-correlated variables where for each variable (i) the distribution of logarithmic growth rates decays exponentially in the central part, (ii) the distribution of the logarithmic growth rate decays algebraically in the far tails, and (iii) the standard deviation of the logarithmic growth rate depends algebraically on the average size of the stochastic variable.

  14. Further laboratory investigations into the Relative Diffusional Growth Rate theory of thunderstorm electrification

    Science.gov (United States)

    Emersic, C.; Saunders, C. P. R.

    2010-11-01

    Predictions from the Relative Diffusional Growth Rate theory have allowed us to further examine controls over the sign of graupel charge in laboratory experiments involving collisions between ice crystals and riming graupel. This has been achieved primarily through the use of two-cloud experiments in which a supercooled droplet cloud and an ice crystal cloud are mixed together. A range of crystal-cloud nucleation techniques has enabled substantial control over the preconditioning of ice crystal surface growth rates such as to control transient rapid crystal growth on mixing with a droplet cloud prior to interaction with a riming target. We have qualitatively identified the effects that crystal surface growth rate and size have on the rate of transient rapid growth after mixing. Crystals with higher surface growth rates in environments nearer to water saturation reduce the effect of transient rapid growth on mixing leading to positive graupel charging. Crystals with lower surface growth rates in environments nearer to ice saturation enhance transient rapid growth on mixing - particularly for smaller crystal sizes - to promote negative graupel charging. This is consistent with the Relative Diffusional Growth Rate theory which has been developed from many laboratory studies and shows that in collisions between ice particles, the surface growing faster by diffusion charges positively. Using both the shortest and longest nucleation techniques developed, it was possible to extend negative charging to approximately -20 °C and -14 °C respectively. Being able to control cloud microphysics and determine its effect on charge sign has led to the conclusion that numerical models of thunderstorm charge development need to take account of the wide range of specific microphysical conditions and their effects on cloud particle charging throughout many regions and the lifetime of a thunderstorm. We also provide evidence in support of new interpretations of the results of other

  15. Element content of Ochromonas danica: a replicated chemostat study controlling the growth rate and temperature.

    Science.gov (United States)

    Simonds, Savannah; Grover, James P; Chrzanowski, Thomas H

    2010-11-01

    Ecological stoichiometry focuses on the balance between multiple nutrient elements in resources and in consumers of those resources. The major consumers of bacteria in aquatic food webs are heterotrophic and mixotrophic nanoflagellates. Despite the importance of this consumer-resource interaction to understanding nutrient dynamics in the aquatic food web, few data are available addressing the element stoichiometry of flagellate consumers. Ochromonas danica, a mixotrophic bacterivore, was used as a model organism to study the relationships among temperature, growth rate and element stoichiometry. Ochromonas danica was grown in chemostats at dilution rates ranging between 0.03 and 0.10 h(-1) and temperatures ranging between 15 and 28 °C. Cells accumulated elements as interactive functions of temperature and growth rate, with the highest element concentrations corresponding to cells grown at a low temperature and high growth rates. The highest concentrations of elements were associated with small cells. Temperature and growth rate affected the element stoichiometry (as C:N, C:P and N:P) of O. danica in a complex manner, but the growth rate had a greater effect on ratios than did temperature. PMID:21039649

  16. Effect of cell size and shear stress on bacterium growth rate

    Science.gov (United States)

    Fadlallah, Hadi; Jarrahi, Mojtaba; Herbert, Éric; Peerhossaini, Hassan; PEF Team

    2015-11-01

    Effect of shear stress on the growth rate of Synechocystis and Chlamydomonas cells is studied. An experimental setup was prepared to monitor the growth rate of the microorganisms versus the shear rate inside a clean room, under atmospheric pressure and 20 °C temperature. Digital magnetic agitators are placed inside a closed chamber provided with airflow, under a continuous uniform light intensity over 4 weeks. In order to study the effect of shear stress on the growth rate, different frequencies of agitation are tested, 2 vessels filled with 150 ml of each specie were placed on different agitating system at the desired frequency. The growth rate is monitored daily by measuring the optical density and then correlate it to the cellular concentration. The PH was adjusted to 7 in order to maintain the photosynthetic activity. Furthermore, to measure the shear stress distribution, the flow velocity field was measured using PIV. Zones of high and low shear stress were identified. Results show that the growth rate is independent of the shear stress magnitude, mostly for Synechocystis, and with lower independency for Chlamydomonas depending on the cell size for each species.

  17. Capital accumulation, structural change and real exchange rate in a Keynesian-Structuralist growth model

    Directory of Open Access Journals (Sweden)

    Oreiro José Luis

    2015-01-01

    Full Text Available The aim of this paper is to show at theoretical level that maintaining a competitive real exchange rate positively affects the economic growth of developing countries by means of a Keynesian-Structuralist model that combines elements of Kaleckian growth models with the balance of payments constrained growth models pioneered developed by Thirlwall. In this setting, the level of real exchange rate is capable, due to its effect over capital accumulation, to induce a structural change in the economy, making endogenous income elasticities of exports and imports. For reasonable parameter values it is shown that in steady-state growth there is two long-run equilibrium values for real exchange rate, one that corresponds to an under-valued currency and another that corresponds to an over-valued currency. If monetary authorities run exchange rate policy in order to target a competitive level for real exchange rate, than under-valued equilibrium is stable and the economy will show a high growth rate in the long-run.

  18. Joint effects of heavy metal binary mixtures on seed germination, root and shoot growth, bacterial bioluminescence, and gene mutation

    Institute of Scientific and Technical Information of China (English)

    In Chul Kong

    2013-01-01

    This investigation was to assess the joint effects of metal binary mixtures on seed germination,root and shoot growth,bacterial bioluminescence,and gene mutation based on the one toxic unit (1 TU) approach.Different sensitivities and orders of toxicity of metal mixtures were observed among the bioassays.In general,mostly additive or antagonistic effects were observed,while almost no synergistic effects by the binary metal mixtures in all bioassays.Therefore,the combined effects of heavy metals in the different bioassays were difficult to generalize since they were dependent on both chemical type and the organism used in each bioassay.However,these results indicate that a battery of bioassays with mixture chemicals as opposed to just a single assay with single metal is a better strategy for the bioassessment of environmental pollutants.

  19. How to determine control of growth rate in a chemostat. Using metabolic control analysis to resolve the paradox

    DEFF Research Database (Denmark)

    Snoep, Jacky L.; Jensen, Peter Ruhdal; Groeneveld, Philip;

    1994-01-01

    how, paradoxically, one can determine control of growth rate, of growth yield and of other fluxes in a chemostat. We develop metabolic control analysis for the chemostat. this analysis does not depend on the particular way in which specific growth rate varies with the concentration of the growth...

  20. Effect of Temperature on the Void Growth in Pure Aluminium at High Strain-Rate Loading

    Institute of Scientific and Technical Information of China (English)

    QI Mei-Lan; HE Hong-Liang; YAN Shi-Lin

    2007-01-01

    @@ With the environment temperature varying from 273K to 773K, the dynamic process of void growth in pure aluminium at high strain-rate loading is calculated based on the dynamic growth equation of a void with internal pressure. The result shows that the effect of temperature on the growth of void should be emphasized. Because the initial pressure of void with gas will increase and the viscosity of materials will decrease with the rising of temperature, the growth of void is accelerated. Furthermore, material inertia restrains the growth of void evidently when the diameter exceeds 10μm. The effect of surface tension is very weak in the whole process of void growth.

  1. Systems Level Regulation of Rhythmic Growth Rate and Biomass Accumulation in Grasses

    Energy Technology Data Exchange (ETDEWEB)

    Kay, Steve A. [University of California San Diego

    2013-05-02

    Several breakthroughs have been recently made in our understanding of plant growth and biomass accumulation. It was found that plant growth is rhythmically controlled throughout the day by the circadian clock through a complex interplay of light and phytohormone signaling pathways. While plants such as the C4 energy crop sorghum (Sorghum bicolor (L.) Moench) and possibly the C3 grass (Brachypodium distachyon) also exhibit daily rhythms in growth rate, the molecular details of its regulation remain to be explored. A better understanding of diurnally regulated growth behavior in grasses may lead to species-specific mechanisms highly relevant to future strategies to optimize energy crop biomass yield. Here we propose to devise a systems approach to identify, in parallel, regulatory hubs associated with rhythmic growth in C3 and C4 plants. We propose to use rhythmicity in daily growth patterns to drive the discovery of regulatory network modules controlling biomass accumulation.

  2. Value of volume measurements in evaluating abdominal aortic aneurysms growth rate and need for surgical treatment

    Energy Technology Data Exchange (ETDEWEB)

    Kontopodis, Nikolaos, E-mail: kontopodisn@yahoo.gr [Department of Vascular Surgery, University of Crete Medical School, Heraklion (Greece); Metaxa, Eleni, E-mail: emmetaxa@gmail.com [Institute of Applied and Computational Mathematics, Foundation for Research and Technology-Hellas, Heraklion, Crete (Greece); Papaharilaou, Yannis, E-mail: yannisp@iacm.forth.gr [Institute of Applied and Computational Mathematics, Foundation for Research and Technology-Hellas, Heraklion, Crete (Greece); Georgakarakos, Efstratios, E-mail: efstratiosgeorg@gmail.com [Vascular Surgery Department, “Demokritus” University of Thrace Medical School, Alexandroupolis (Greece); Tsetis, Dimitris, E-mail: tsetis@med.uoc.gr [Interventional Radiology Unit, Department of Radiology, University of Crete Medical School, Heraklion, Crete (Greece); Ioannou, Christos V., E-mail: ioannou@med.uoc.gr [Department of Vascular Surgery, University of Crete Medical School, Heraklion (Greece)

    2014-07-15

    Purpose: To examine whether indices other than the traditionally used abdominal aortic aneurysm (AAA) maximum diameter, such as AAA volume, intraluminal thrombus (ILT) thickness and ILT volume, may be superior to evaluate aneurismal enlargement. Materials and methods: Thirty-four small AAAs (initially presenting a maximum diameter <5.5 cm which is the threshold for surgical repair) with an initial and a follow-up CT were examined. Median increase and percentile annual change of these variables was calculated. Correlation between growth rates as determined by the new indices under evaluation and those of maximum diameter were assessed. AAAs were divided according to outcome (surveillance vs. elective repair after follow-up which is based on the maximum diameter criterion) and according to growth rate (high vs. low) based on four indices. Contingency between groups of high/low growth rate regarding each of the four indices on one hand and those regarding need for surgical repair on the other was assessed. Results: A strong correlation between growth rates of maximum diameter and those of AAA and ILT volumes could be established. Evaluation of contingency between groups of outcome and those of growth rate revealed significant associations only for AAA and ILT volumes. Subsequently AAAs with a rapid volumetric increase over time had a likelihood ratio of 10 to be operated compared to those with a slower enlargement. Regarding increase of maximum diameter, likelihood ratio between AAAs with rapid and those with slow expansion was only 3. Conclusion: Growth rate of aneurysms regarding 3Dimensional indices of AAA and ILT volumes is significantly associated with the need for surgical intervention while the same does not hold for growth rates determined by 2Dimensional indices of maximum diameter and ILT thickness.

  3. Value of volume measurements in evaluating abdominal aortic aneurysms growth rate and need for surgical treatment

    International Nuclear Information System (INIS)

    Purpose: To examine whether indices other than the traditionally used abdominal aortic aneurysm (AAA) maximum diameter, such as AAA volume, intraluminal thrombus (ILT) thickness and ILT volume, may be superior to evaluate aneurismal enlargement. Materials and methods: Thirty-four small AAAs (initially presenting a maximum diameter <5.5 cm which is the threshold for surgical repair) with an initial and a follow-up CT were examined. Median increase and percentile annual change of these variables was calculated. Correlation between growth rates as determined by the new indices under evaluation and those of maximum diameter were assessed. AAAs were divided according to outcome (surveillance vs. elective repair after follow-up which is based on the maximum diameter criterion) and according to growth rate (high vs. low) based on four indices. Contingency between groups of high/low growth rate regarding each of the four indices on one hand and those regarding need for surgical repair on the other was assessed. Results: A strong correlation between growth rates of maximum diameter and those of AAA and ILT volumes could be established. Evaluation of contingency between groups of outcome and those of growth rate revealed significant associations only for AAA and ILT volumes. Subsequently AAAs with a rapid volumetric increase over time had a likelihood ratio of 10 to be operated compared to those with a slower enlargement. Regarding increase of maximum diameter, likelihood ratio between AAAs with rapid and those with slow expansion was only 3. Conclusion: Growth rate of aneurysms regarding 3Dimensional indices of AAA and ILT volumes is significantly associated with the need for surgical intervention while the same does not hold for growth rates determined by 2Dimensional indices of maximum diameter and ILT thickness

  4. Selenium hyperaccumulators harbor a diverse endophytic bacterial community characterized by high selenium resistance and plant growth promoting properties

    Directory of Open Access Journals (Sweden)

    Martina eSura - de Jong

    2015-03-01

    Full Text Available Selenium (Se-rich plants may be used to provide dietary Se to humans and livestock, and also to clean up Se-polluted soils or waters. This study focused on endophytic bacteria of plants that hyperaccumulate selenium (Se to 0.5-1% of dry weight. Terminal restriction fragment length polymorphism (T-RFLP analysis was used to compare the diversity of endophytic bacteria of hyperaccumulators Stanleya pinnata (Brassicaceae and Astragalus bisulcatus (Fabaceae with those from related non-accumulators Physaria bellii (Brassicaceae and Medicago sativa (Fabaceae collected on the same, seleniferous site. Hyperaccumulators and non-accumulators showed equal T-RF diversity. Parsimony analysis showed that T-RFs from individuals of the same species were more similar to each other than to those from other species, regardless of plant Se content or spatial proximity. Cultivable endophytes from hyperaccumulators S. pinnata and A. bisulcatus were further identified and characterized. The 66 bacterial morphotypes were shown by MS MALDI-TOF Biotyper analysis and 16S rRNA gene sequencing to include strains of Bacillus, Pseudomonas, Pantoea, Staphylococcus, Paenibacillus, Advenella, Arthrobacter and Variovorax. Most isolates were highly resistant to selenate and selenite (up to 200 mM and all could reduce selenite to red elemental Se, reduce nitrite and produce siderophores. Seven isolates were selected for plant inoculation and found to have plant growth promoting properties, both in pure culture and when co-cultivated with crop species Brassica juncea (Brassicaceae or M. sativa. There were no effects on plant Se accumulation. We conclude that Se hyperaccumulators harbor an endophytic bacterial community in their natural seleniferous habitat that is equally diverse to that of comparable non-accumulators. The hyperaccumulator endophytes are characterized by high Se resistance, capacity to produce elemental Se and plant growth promoting properties.

  5. Bacterial growth in ground beef prepared from electrically stimulated and nonstimulated muscles.

    OpenAIRE

    Butler, J L; Smith, G. C.; Savell, J W; Vanderzant, C.

    1981-01-01

    Ground beef samples prepared from electrically stimulated and nonstimulated biceps femoris and infraspinatus muscles were inoculated with Lactobacillus sp., Pseudomonas sp., Acinetobacter sp., or a mixture of Lactobacillus spp., Pseudomonas spp., Acinetobacter spp., Moraxella sp., Microbacterium thermosphactum, and Erwinia herbicola. There were no significant differences in growth of various bacteria in ground beef made from electrically stimulated and nonstimulated muscles.

  6. Characteristics of Growth Rate of Coral Porites from Sanya Bay, Hainan Island and its Relationship to Environmental Variables

    Institute of Scientific and Technical Information of China (English)

    Shi Qi; Zhang Yechun; Sun Donghuai

    2003-01-01

    The time series of annual and seasonal growth rate of two coral Porites, collected at different sites of fringe reef in the Sanya Bay, Hainan Island have been obtained by analyzing X-radiograph of skeletal band. There are obvious seasonal variations of the growth rate in two corals, the average low rate in winter and the average high rate from spring to autumn. Compared with the time series of environmental variables, the coral growth rate is only correlated statistically with seawater temperature and not related to rainfall and sunshine. Furthermore, the growth rate in spring and summer is correlated directly with seawater temperature of the winter-early spring ( between December and March ) and the other seasonal growth rate has no relationship with seasonal variations of seawater temperature. We propose that seawater temperature is one of the factors affecting the coral growth rate in the area and the low seawater temperature is a primary control of the seasonal growth rate.

  7. Pretreatment Growth Rate Predicts Radiation Response in Vestibular Schwannomas

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Nina N. [Department of Radiation Oncology, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts (United States); Harvard Medical School, Department of Medicine, Brigham and Women' s Hospital, Boston, Massachusetts (United States); Niemierko, Andrzej [Department of Radiation Oncology, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts (United States); Larvie, Mykol [Harvard Medical School, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts (United States); Curtin, Hugh [Harvard Medical School, Department of Radiology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts (United States); Loeffler, Jay S. [Department of Radiation Oncology, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts (United States); McKenna, Michael J. [Harvard Medical School, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts (United States); Shih, Helen A., E-mail: hshih@partners.org [Department of Radiation Oncology, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts (United States)

    2014-05-01

    Purpose: Vestibular schwannomas (VS) are often followed without initial therapeutic intervention because many tumors do not grow and radiation therapy is associated with potential adverse effects. In an effort to determine whether maximizing initial surveillance predicts for later treatment response, the predictive value of preirradiation growth rate of VS on response to radiation therapy was assessed. Methods and Materials: Sixty-four patients with 65 VS were treated with single-fraction stereotactic radiation surgery or fractionated stereotactic radiation therapy. Pre- and postirradiation linear expansion rates were estimated using volumetric measurements on sequential magnetic resonance images (MRIs). In addition, postirradiation tumor volume change was classified as demonstrating shrinkage (ratio of volume on last follow-up MRI to MRI immediately preceding irradiation <80%), stability (ratio 80%-120%), or expansion (ratio >120%). The median pre- and postirradiation follow-up was 20.0 and 27.5 months, respectively. Seven tumors from neurofibromatosis type 2 (NF2) patients were excluded from statistical analyses. Results: In the 58 non-NF2 patients, there was a trend of correlation between pre- and postirradiation volume change rates (slope on linear regression, 0.29; P=.06). Tumors demonstrating postirradiation expansion had a median preirradiation growth rate of 89%/year, and those without postirradiation expansion had a median preirradiation growth rate of 41%/year (P=.02). As the preirradiation growth rate increased, the probability of postirradiation expansion also increased. Overall, 24.1% of tumors were stable, 53.4% experienced shrinkage, and 22.5% experienced expansion. Predictors of no postirradiation tumor expansion included no prior surgery (P=.01) and slower tumor growth rate (P=.02). The control of tumors in NF2 patients was only 43%. Conclusions: Radiation therapy is an effective treatment for VS, but tumors that grow quickly preirradiation may be

  8. Influence of water relations and growth rate on plant element uptake and distribution

    Energy Technology Data Exchange (ETDEWEB)

    Greger, Maria [Stockholm Univ. (Sweden). Dept. of Botany

    2006-02-15

    Plant uptake of Ni, Sr, Mo, Cs, La, Th, Se, Cl and I was examined to determine how plant water relations and growth rate influence the uptake and distribution of these elements in the studied plants. The specific questions were how water uptake and growth rate influenced the uptake of various nuclides and how transpiration influenced translocation to the shoot. The knowledge gained will be used in future modelling of radionuclide leakage from nuclear waste deposits entering the ecosystem via plants. The plant studied was willow, Salix viminalis, a common plant in the areas suggested for waste disposal; since there can be clone variation, two different clones having different uptake properties for several other heavy metals were used. The plants were grown in nutrient solution and the experiments on 3-month-old plants were run for 3 days. Polyethylene glycol was added to the medium to decrease the water uptake rate, a fan was used to increase the transpiration rate, and different light intensities were used to produce different growth rates. Element concentration was analysed in roots and shoots. The results show that both the uptake and distribution of various elements are influenced in different ways and to various extents by water flow and plant growth rate, and that it is not possible from the chemical properties of these elements to know how they will react. However, in most cases increased growth rate diluted the concentration of the element in the tissue, reduced water uptake reduced the element uptake, while transpiration had no effect on the translocation of elements to the shoot. The clones did not differ in terms of either the uptake or translocation of the elements, except that I was not taken up and translocated to the shoot in one of the clones when the plant water flow or growth rate was too low. Not all of the elements were found in the plant in the same proportions as they had been added to the nutrient solution.

  9. Influence of water relations and growth rate on plant element uptake and distribution

    International Nuclear Information System (INIS)

    Plant uptake of Ni, Sr, Mo, Cs, La, Th, Se, Cl and I was examined to determine how plant water relations and growth rate influence the uptake and distribution of these elements in the studied plants. The specific questions were how water uptake and growth rate influenced the uptake of various nuclides and how transpiration influenced translocation to the shoot. The knowledge gained will be used in future modelling of radionuclide leakage from nuclear waste deposits entering the ecosystem via plants. The plant studied was willow, Salix viminalis, a common plant in the areas suggested for waste disposal; since there can be clone variation, two different clones having different uptake properties for several other heavy metals were used. The plants were grown in nutrient solution and the experiments on 3-month-old plants were run for 3 days. Polyethylene glycol was added to the medium to decrease the water uptake rate, a fan was used to increase the transpiration rate, and different light intensities were used to produce different growth rates. Element concentration was analysed in roots and shoots. The results show that both the uptake and distribution of various elements are influenced in different ways and to various extents by water flow and plant growth rate, and that it is not possible from the chemical properties of these elements to know how they will react. However, in most cases increased growth rate diluted the concentration of the element in the tissue, reduced water uptake reduced the element uptake, while transpiration had no effect on the translocation of elements to the shoot. The clones did not differ in terms of either the uptake or translocation of the elements, except that I was not taken up and translocated to the shoot in one of the clones when the plant water flow or growth rate was too low. Not all of the elements were found in the plant in the same proportions as they had been added to the nutrient solution

  10. Shape of Growth Rate Distribution determines the type of Non-Gibrat's Law

    CERN Document Server

    Ishikawa, Atushi; Mizuno, Takayuki

    2010-01-01

    In this study, by employing exhaustive business data on Japanese firms that approximately fully cover the middle- and large-scale ranges in terms of firm size, the authors confirm the following findings. Detailed Balance is observed not only in profits data but also in sales data. The growth-rate distribution of sales has wider tails than the linear growth-rate distribution of profits in log-log scale. On one hand, in the middle-scale range of profits, the probability of positive growth decreases and the probability of negative growth increases symmetrically as the initial value increases. This is called Non-Gibrat's First Law. On the other hand, in the middle-scale range of sales, the probability of positive growth decreases as the initial value increases, while the probability of negative growth hardly changes. This is called Non-Gibrat's Second Law. Under Detailed Balance, Non-Gibrat's First and Second Laws are analytically induced from the linear and quadratic growth-rate distributions in log-log scale, r...

  11. No trade-off between growth rate and temperature stress resistance in four insect species.

    Directory of Open Access Journals (Sweden)

    Isabell Karl

    Full Text Available Although fast growth seems to be generally favored by natural selection, growth rates are rarely maximized in nature. Consequently, fast growth is predicted to carry costs resulting in intrinsic trade-offs. Disentangling such trade-offs is of great ecological importance in order to fully understand the prospects and limitations of growth rate variation. A recent study provided evidence for a hitherto unknown cost of fast growth, namely reduced cold stress resistance. Such relationships could be especially important under climate change. Against this background we here investigate the relationships between individual larval growth rate and adult heat as well as cold stress resistance, using eleven data sets from four different insect species (three butterfly species: Bicyclus anynana, Lycaena tityrus, Pieris napi; one Dipteran species: Protophormia terraenovae. Despite using different species (and partly different populations within species and an array of experimental manipulations (e.g. different temperatures, photoperiods, feeding regimes, inbreeding levels, we were not able to provide any consistent evidence for trade-offs between fast growth and temperature stress resistance in these four insect species.

  12. Human disturbance influences reproductive success and growth rate in California sea lions (Zalophus californianus).

    Science.gov (United States)

    French, Susannah S; González-Suárez, Manuela; Young, Julie K; Durham, Susan; Gerber, Leah R

    2011-01-01

    The environment is currently undergoing changes at both global (e.g., climate change) and local (e.g., tourism, pollution, habitat modification) scales that have the capacity to affect the viability of animal and plant populations. Many of these changes, such as human disturbance, have an anthropogenic origin and therefore may be mitigated by management action. To do so requires an understanding of the impact of human activities and changing environmental conditions on population dynamics. We investigated the influence of human activity on important life history parameters (reproductive rate, and body condition, and growth rate of neonate pups) for California sea lions (Zalophus californianus) in the Gulf of California, Mexico. Increased human presence was associated with lower reproductive rates, which translated into reduced long-term population growth rates and suggested that human activities are a disturbance that could lead to population declines. We also observed higher body growth rates in pups with increased exposure to humans. Increased growth rates in pups may reflect a density dependent response to declining reproductive rates (e.g., decreased competition for resources). Our results highlight the potentially complex changes in life history parameters that may result from human disturbance, and their implication for population dynamics. We recommend careful monitoring of human activities in the Gulf of California and emphasize the importance of management strategies that explicitly consider the potential impact of human activities such as ecotourism on vertebrate populations. PMID:21436887

  13. Human disturbance influences reproductive success and growth rate in California sea lions (Zalophus californianus).

    Science.gov (United States)

    French, Susannah S; González-Suárez, Manuela; Young, Julie K; Durham, Susan; Gerber, Leah R

    2011-03-16

    The environment is currently undergoing changes at both global (e.g., climate change) and local (e.g., tourism, pollution, habitat modification) scales that have the capacity to affect the viability of animal and plant populations. Many of these changes, such as human disturbance, have an anthropogenic origin and therefore may be mitigated by management action. To do so requires an understanding of the impact of human activities and changing environmental conditions on population dynamics. We investigated the influence of human activity on important life history parameters (reproductive rate, and body condition, and growth rate of neonate pups) for California sea lions (Zalophus californianus) in the Gulf of California, Mexico. Increased human presence was associated with lower reproductive rates, which translated into reduced long-term population growth rates and suggested that human activities are a disturbance that could lead to population declines. We also observed higher body growth rates in pups with increased exposure to humans. Increased growth rates in pups may reflect a density dependent response to declining reproductive rates (e.g., decreased competition for resources). Our results highlight the potentially complex changes in life history parameters that may result from human disturbance, and their implication for population dynamics. We recommend careful monitoring of human activities in the Gulf of California and emphasize the importance of management strategies that explicitly consider the potential impact of human activities such as ecotourism on vertebrate populations.

  14. Human disturbance influences reproductive success and growth rate in California sea lions (Zalophus californianus.

    Directory of Open Access Journals (Sweden)

    Susannah S French

    Full Text Available The environment is currently undergoing changes at both global (e.g., climate change and local (e.g., tourism, pollution, habitat modification scales that have the capacity to affect the viability of animal and plant populations. Many of these changes, such as human disturbance, have an anthropogenic origin and therefore may be mitigated by management action. To do so requires an understanding of the impact of human activities and changing environmental conditions on population dynamics. We investigated the influence of human activity on important life history parameters (reproductive rate, and body condition, and growth rate of neonate pups for California sea lions (Zalophus californianus in the Gulf of California, Mexico. Increased human presence was associated with lower reproductive rates, which translated into reduced long-term population growth rates and suggested that human activities are a disturbance that could lead to population declines. We also observed higher body growth rates in pups with increased exposure to humans. Increased growth rates in pups may reflect a density dependent response to declining reproductive rates (e.g., decreased competition for resources. Our results highlight the potentially complex changes in life history parameters that may result from human disturbance, and their implication for population dynamics. We recommend careful monitoring of human activities in the Gulf of California and emphasize the importance of management strategies that explicitly consider the potential impact of human activities such as ecotourism on vertebrate populations.

  15. Lifespan, growth rate, and body size across latitude in marine Bivalvia, with implications for Phanerozoic evolution.

    Science.gov (United States)

    Moss, David K; Ivany, Linda C; Judd, Emily J; Cummings, Patrick W; Bearden, Claire E; Kim, Woo-Jun; Artruc, Emily G; Driscoll, Jeremy R

    2016-08-17

    Mean body size in marine animals has increased more than 100-fold since the Cambrian, a discovery that brings to attention the key life-history parameters of lifespan and growth rate that ultimately determine size. Variation in these parameters is not well understood on the planet today, much less in deep time. Here, we present a new global database of maximum reported lifespan and shell growth coupled with body size data for 1 148 populations of marine bivalves and show that (i) lifespan increases, and growth rate decreases, with latitude, both across the group as a whole and within well-sampled species, (ii) growth rate, and hence metabolic rate, correlates inversely with lifespan, and (iii) opposing trends in lifespan and growth combined with high variance obviate any demonstrable pattern in body size with latitude. Our observations suggest that the proposed increase in metabolic activity and demonstrated increase in body size of organisms over the Phanerozoic should be accompanied by a concomitant shift towards faster growth and/or shorter lifespan in marine bivalves. This prediction, testable from the fossil record, may help to explain one of the more fundamental patterns in the evolutionary and ecological history of animal life on this planet. PMID:27488653

  16. Lifespan, growth rate, and body size across latitude in marine Bivalvia, with implications for Phanerozoic evolution.

    Science.gov (United States)

    Moss, David K; Ivany, Linda C; Judd, Emily J; Cummings, Patrick W; Bearden, Claire E; Kim, Woo-Jun; Artruc, Emily G; Driscoll, Jeremy R

    2016-08-17

    Mean body size in marine animals has increased more than 100-fold since the Cambrian, a discovery that brings to attention the key life-history parameters of lifespan and growth rate that ultimately determine size. Variation in these parameters is not well understood on the planet today, much less in deep time. Here, we present a new global database of maximum reported lifespan and shell growth coupled with body size data for 1 148 populations of marine bivalves and show that (i) lifespan increases, and growth rate decreases, with latitude, both across the group as a whole and within well-sampled species, (ii) growth rate, and hence metabolic rate, correlates inversely with lifespan, and (iii) opposing trends in lifespan and growth combined with high variance obviate any demonstrable pattern in body size with latitude. Our observations suggest that the proposed increase in metabolic activity and demonstrated increase in body size of organisms over the Phanerozoic should be accompanied by a concomitant shift towards faster growth and/or shorter lifespan in marine bivalves. This prediction, testable from the fossil record, may help to explain one of the more fundamental patterns in the evolutionary and ecological history of animal life on this planet.

  17. Fluoroquinolone-macrolide combination therapy for chronic bacterial prostatitis: retrospective analysis of pathogen eradication rates, inflammatory findings and sexual dysfunction

    Institute of Scientific and Technical Information of China (English)

    Vittorio Magri; Emanuele Montanari; Vi(s)nja (S)kerk; Alemka Markoti(c); Emanuela Marras; Antonella Restelli; Kurt G Naber; Gianpaolo Perletti

    2011-01-01

    We previously demonstrated the safety and efficacy of fluoroquinolone-macrolide combination therapy in category Ⅱ chronic bacterial prostatitis (CBP).The aim of this study is to retrospectively compare the microbiological and clinical findings of two treatment schemes for CBP based on the combination of azithromycin (500 mg,thrice-weekly) with a once-daily 500-or 750-mg dose of ciprofloxacin (Cipro-500 or Cipro-750 cohort,respectively).Combined administration of azithromycin (1500 mg week-1) with ciprofloxacin at the rate of 750 mg day-1 for 4 weeks rather than at 500 mg day-1 for 6 weeks increased the eradication rates from 62.35% to 77.32% and the total bacteriological success from 71.76% to 85.57%.A significant decrease in pain and voiding signs/symptoms and a significant reduction in inflammatory leukocyte counts and serum prostate-specific antigen (PSA) were sustained throughout an 18-month follow-up period in both groups.Ejaculatory pain,haemospermia and premature ejaculation were significantly attenuated on microbiological eradication in both groups,but the latter subsided more promptly in the Cipro-750 cohort.In total,59 Cipro-750 patients showed mild-to-severn erectile dysfunction (ED) at baseline,while 22 patients had no ED on microbiological eradication and throughout the follow-up period.In conclusion fluoroquinolone-macrolide therapy resulted in pathogen eradication and CBP symptom attenuation,including pain,voiding disturbances and sexual dysfunction.A once-daily 750-mg dose of ciprofloxacin for 4 weeks showed enhanced eradication rates and lower inflammatory white blood cell counts compared to the 500-mg dose for 6 weeks.Our results are open to further prospective validation.

  18. Trace incorporation of heavy water reveals slow and heterogeneous pathogen growth rates in cystic fibrosis sputum

    Science.gov (United States)

    Kopf, Sebastian H.; Sessions, Alex L.; Cowley, Elise S.; Reyes, Carmen; Van Sambeek, Lindsey; Hu, Yang; Orphan, Victoria J.; Kato, Roberta; Newman, Dianne K.

    2016-01-01

    Effective treatment for chronic infections is undermined by a significant gap in understanding of the physiological state of pathogens at the site of infection. Chronic pulmonary infections are responsible for the morbidity and mortality of millions of immunocompromised individuals worldwide, yet drugs that are successful in laboratory culture are far less effective against pathogen populations persisting in vivo. Laboratory models, upon which preclinical development of new drugs is based, can only replicate host conditions when we understand the metabolic state of the pathogens and the degree of heterogeneity within the population. In this study, we measured the anabolic activity of the pathogen Staphylococcus aureus directly in the sputum of pediatric patients with cystic fibrosis (CF), by combining the high sensitivity of isotope ratio mass spectrometry with a heavy water labeling approach to capture the full range of in situ growth rates. Our results reveal S. aureus generation times with a median of 2.1 d, with extensive growth rate heterogeneity at the single-cell level. These growth rates are far below the detection limit of previous estimates of CF pathogen growth rates, and the rates are slowest in acutely sick patients undergoing pulmonary exacerbations; nevertheless, they are accessible to experimental replication within laboratory models. Treatment regimens that include specific antibiotics (vancomycin, piperacillin/tazobactam, tobramycin) further appear to correlate with slow growth of S. aureus on average, but follow-up longitudinal studies must be performed to determine whether this effect holds for individual patients.

  19. Empirical Analysis of Non-Performing Loans Trend and Growth Rate in Nigerian Banking System

    Directory of Open Access Journals (Sweden)

    Aniefiok Akpan Umoren

    2016-04-01

    Full Text Available Increasing trend in Non-performing loans (NPLs adversely affected availability of credits to economic agents in all sectors of the economy thereby constraining financial intermediation and economic activities. The study examined the trend and growth rates of NPLs in the Nigerian banking system during the major banking policy reforms regimes namely: pre-consolidation (1979 – 2004 and post consolidation era (2005 – 2014. Time series data collected were analyzed using descriptive and regression analyses. Results indicated irregular fluctuations in NPLs’ trend in both periods. This result suggested prevalent of high credit risk and corresponding reduction in lending capability of banks in the economy. Regression estimates of NPLs’ trend in the two regimes showed significant negative growth rates. This implies that, financial policies implemented in the country yielded positive impacts over time. NPLs assumed an exponential growth rate of -1.39% and -15.55% during the pre and post consolidated eras respectively. An average exponential growth rate of -5.2% was obtained during the entire period. Quadratic trend analysis revealed that, increase influence of time variable significantly reduced NPLs during pre- consolidation regime and the entire period considered. However, this influence was stagnated during post consolidation period. Based on the result, it is recommended that, prudent lending coupled with swift and orderly clean-up of banking system loan portfolios should be adopted to decelerate NPLs trend and growth rate in Nigeria. Time is an important element in designing and implementing any banking and macroeconomic policy.

  20. Rapid growth reduces cold resistance: evidence from latitudinal variation in growth rate, cold resistance and stress proteins.

    Directory of Open Access Journals (Sweden)

    Robby Stoks

    Full Text Available BACKGROUND: Physiological costs of rapid growth may contribute to the observation that organisms typically grow at submaximal rates. Although, it has been hypothesized that faster growing individuals would do worse in dealing with suboptimal temperatures, this type of cost has never been explored empirically. Furthermore, the mechanistic basis of the physiological costs of rapid growth is largely unexplored. METHODOLOGY/PRINCIPAL FINDING: Larvae of the damselfly Ischnura elegans from two univoltine northern and two multivoltine southern populations were reared at three temperatures and after emergence given a cold shock. Cold resistance, measured by chill coma recovery times in the adult stage, was lower in the southern populations. The faster larval growth rates in the southern populations contributed to this latitudinal pattern in cold resistance. In accordance with their assumed role in cold resistance, Hsp70 levels were lower in the southern populations, and faster growing larvae had lower Hsp70 levels. Yet, individual variation in Hsp70 levels did not explain variation in cold resistance. CONCLUSIONS/SIGNIFICANCE: WE PROVIDE EVIDENCE FOR A NOVEL COST OF RAPID GROWTH: reduced cold resistance. Our results indicate that the reduced cold resistance in southern populations of animals that change voltinism along the latitudinal gradient may not entirely be explained by thermal selection per se but also by the costs of time constraint-induced higher growth rates. This also illustrates that stressors imposed in the larval stage may carry over and shape fitness in the adult stage and highlights the importance of physiological costs in the evolution of life-histories at macro-scales.

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

    CERN Document Server

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

    2014-01-01

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

  2. A bacterial artificial chromosome transgenic mouse model for visualization of neurite growth.

    Science.gov (United States)

    Tao, Tao; Chen, Chen; Sun, Jie; Peng, YaJing; Zhu, MinSheng

    2015-04-01

    Class III β-tubulin (Tubb3) is a component of the microtubules in neurons and contributes to microtubule dynamics that are required for axon outgrowth and guidance during neuronal development. We here report a novel bacterial artificial chromosome (BAC) transgenic mouse line that expresses Class III β-tubulin fused to mCherry, an improved monomeric red fluorescent protein, for the visualization of microtubules during neuronal development. A BAC containing Tubb3 gene was modified by insertion of mCherry complementary DNA downstream of Tubb3 coding sequence via homologous recombination. mCherry fusion protein was expressed in the nervous system and testis of the transgenic animal, and the fluorescent signal was observed in the neurons that located in the olfactory bulb, cerebral cortex, hippocampal formation, cerebellum, as well as the retina. Besides, Tubb3-mCherry fusion protein mainly distributed in neurites and colocalized with endogenous Class III β-tubulin. The fusion protein labels Purkinje cell dendrites during cerebellar circuit formation. Therefore, this transgenic line might be a novel tool for scientific community to study neuronal development both in vitro and in vivo.

  3. Discrete cyclic di-GMP-dependent control of bacterial predation versus axenic growth in Bdellovibrio bacteriovorus

    OpenAIRE

    Laura Hobley; Fung, Rowena K. Y.; Carey Lambert; Maximilian A T S Harris; Dabhi, Jayesh M.; King, Simon S.; Basford, Sarah M; Kaoru Uchida; Robert Till; Rashidah Ahmad; Shin-Ichi Aizawa; Mark Gomelsky; R Elizabeth Sockett

    2012-01-01

    Bdellovibrio bacteriovorus is a Delta-proteobacterium that oscillates between free-living growth and predation on Gram-negative bacteria including important pathogens of man, animals and plants. After entering the prey periplasm, killing the prey and replicating inside the prey bdelloplast, several motile B. bacteriovorus progeny cells emerge. The B. bacteriovorus HD100 genome encodes numerous proteins predicted to be involved in signalling via the secondary messenger cyclic di-GMP (c-di-GMP)...

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

    OpenAIRE

    Aisha Waheed Qurashi; Anjum Nasim Sabri

    2012-01-01

    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 developi...

  5. The effect of material properties on growth rates of folding and boudinage: Experiments with wax models

    Science.gov (United States)

    Neurath, C.; Smith, R. B.

    The growth of unstable structures was studied experimentally in layered wax models. The rheological properties of the two wax types were determined independently by a series of cylinder compression tests. Both waxes enhibited (1) a non-Newtonian stress vs strain-rate relationship (2) strain softening and (3) temperature-dependent viscosity. The stress-strain-rate relationships approximated a power-law, with stress exponents of 5 for the microcrystalline wax and 1.8 for paraffin wax. Blocks of paraffin with a single embedded layer of microcrystalline wax were deformed in two-dimensional pure shear with the layer oriented either parallel to the compressive strain axis so that it shortened and folded, or perpendicular to that axis so that it would stretch and boundinage would form. The growth rates of tiny initial disturbances were measured. The growth rates for folding and boudinage were much higher than could be accounted for by theories assuming Newtonian material properties. Theories taking non-Newtonian behaviour into account (Smith, R. B. 1975. Bull. geol. Soc. Am.86, 1601-1609; Fletcher, R. C. 1974. Am. J. Sci.274, 1029-1043) better describe the folding growth rates. Boudinage, however, grew almost three times faster than would be predicted even by existing non-Newtonian theory. A possible reason for this discrepancy is that the waxes do not exhibit steady-state creep as assumed in the theory. We, therefore, extend the theory to include strain-softening. The crucial step in this theory is the use of a scalar measure of the deformation as a state variable in the constitutive law. In this way the isotropic manifestation of strain-softening can be taken into account. The analysis shows that strain-softening can lead to greatly increased boudinage growth rates while having little influence on the growth rates of folds, which is in agreement with the experiments.

  6. Characterization of the sulfate uptake and assimilation pathway from Xanthomonas citri - targets for bacterial growth inhibitors

    International Nuclear Information System (INIS)

    Full text: Microorganisms require sulfur for growth and obtain it either for inorganic sulfate or organosulfur compounds. ATP-Binding Cassete (SulT family) or major facilitator superfamily-type (SulP) transporters are responsible for the sulfate transport into the cell. In Xanthomonas citri, the phytopathogenic bacterium that causes the canker citrus disease, there are no reports related to the importance of these transporters during in vitro or in vivo infection. We identified in X. citri genome all the genes that belong to the well-characterized cys regulon from Escherichia coli and Salmonella typhimurium, which includes three ABC transporters and all the enzymes necessary for sulfate oxide reduction to sulfide and cysteine. Once these genes have been shown to be extremely important for bacteria growth and development in different environments, we chose the sbpcysWUA and cysDNCHIJG operons, which encodes the ABC inorganic sulfate ABC transporter and all the enzymes necessary for conversion of sulfate in cysteine, respectively. As a step for crystallization trials and resolution of their tridimensional structures, the referred genes were amplified and cloned into the cloning vector pGEM T-easy. In addition, using bioinformatics tools and molecular modeling we characterized all the protein functions as well as built tridimensional models of their structure for determination of the active sites. The importance of each protein is discussed aiming the discovery of a good target for development of inhibitors that could block the bacterium growth. (author)

  7. Inhibitory Concentration and Minimum Contact Time Gambir Extract (Uncaria gambier Roxb Against Bacterial Growth Enterococcus faecalis

    Directory of Open Access Journals (Sweden)

    Hafsah Katu

    2016-06-01

    Full Text Available Enterococcus faecalis (E.Faecalis gram-positive bacteria commonly found in endodontic retreatment cases. Extract Gambir, a type of dried sap from the leaves and young stems of plants gambier (Uncaria gambier Roxb contains catechins, which are potent antibacterial and anti fungal with minimal side effects. This study aimed to determine the inhibitory concentrations and minimal contact time Gambir extract on the growth of the bacteria E. faecalis. Research applied a design with lab experiments, conducted on May 30-June 16, 2011 at the Laboratory of Pharmacognosy-Phytochemicals Faculty of Pharmacy and Laboratory of Microbiology, Faculty of Medicine, University of Hasanuddin. Materials and methods; 600 gr Gambir which has been crushed, extracted with reflux and rotary method. Minimal Inhibitory Concentration is determined with 5 ml of 5.25% NaOCl as a positive control and sterile distilled water negative control. Antibacterial activity is determined based on the time zone diameter hambat.Analisis contact and SPSS version 16.0 for windows with One-way ANOVA test and LSD on (p <0.05. Results indicated that Statistical analysis showed a 1% concentration and contact time of 24 hours, effectively inhibits the growth of bacteria E.faecalis. in conclusion, Gambir extract effectively inhibits the growth of bacteria E. faecalis.

  8. Characterization of the sulfate uptake and assimilation pathway from Xanthomonas citri - targets for bacterial growth inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Tambascia, C.; Balan, A. [Laboratorio Nacional de Biociencias - LNBIO, Campinas, SP (Brazil)

    2012-07-01

    Full text: Microorganisms require sulfur for growth and obtain it either for inorganic sulfate or organosulfur compounds. ATP-Binding Cassete (SulT family) or major facilitator superfamily-type (SulP) transporters are responsible for the sulfate transport into the cell. In Xanthomonas citri, the phytopathogenic bacterium that causes the canker citrus disease, there are no reports related to the importance of these transporters during in vitro or in vivo infection. We identified in X. citri genome all the genes that belong to the well-characterized cys regulon from Escherichia coli and Salmonella typhimurium, which includes three ABC transporters and all the enzymes necessary for sulfate oxide reduction to sulfide and cysteine. Once these genes have been shown to be extremely important for bacteria growth and development in different environments, we chose the sbpcysWUA and cysDNCHIJG operons, which encodes the ABC inorganic sulfate ABC transporter and all the enzymes necessary for conversion of sulfate in cysteine, respectively. As a step for crystallization trials and resolution of their tridimensional structures, the referred genes were amplified and cloned into the cloning vector pGEM T-easy. In addition, using bioinformatics tools and molecular modeling we characterized all the protein functions as well as built tridimensional models of their structure for determination of the active sites. The importance of each protein is discussed aiming the discovery of a good target for development of inhibitors that could block the bacterium growth. (author)

  9. Spatial distribution of soda straws growth rates of the Coufin Cave (Vercors, France

    Directory of Open Access Journals (Sweden)

    Perrette Yves

    2010-07-01

    Full Text Available The Choranche Cave system (Vercors, France is an excellent locality for measuring the growth rates of large numbers soda straws. This is especially the case for the Coufin Cave, as enlargement of the cave entrance in 1875 led to a change in stalactite color from brown to white, thus providing a reliable chronomarker. The date of this brown-to-white calcite transition has been confirmed by lamina counting. We measured and georeferenced the growth-lengths of 306 soda straws in a 1m2 area of the roof of the Coufin Cave entrance chamber. Because of the very slow and sometimes inexistent water feeding of those stalactites, hydrochemistry analysis were not achieved and drop rate effect on growth were neglected; this study is based on a geomorphological and geostatistical work. By measuring a large number of soda straws in a very small area for which most of the parameters affecting stalactite growth could be considered uniform, and because flow rates are very slow (frequencies are always superior to 1 drop per half hour, we could ascribe differences in growth rates to variations in the global increase of water flow through the unsaturated matrix. Statistical and geostatistical analyses of the measurements showed that this set of similarly shaped stalactites actually consisted of three Gaussian populations with different mean growth rates: fast growth rate (FGR- mean of 0.92 mm.y-1, medium growth rate (MGR- mean of 0.47 mm.y-1 and low growth rate (LGR- 0.09 mm.y-1. Plotting the lengths and spatial distribution of the 20 longest FGR soda straws revealed that there is a rough pattern to the water flow through the cave roof. Even if no direction is statisticaly different from others, the observed directional pattern is consistent with local and regional tectonic observations. Plots of the spatial distribution of the soda straws show that FGR soda straws follow lines of regional geological stress, whereas MGR and LGR soda straws are more dispersed.

  10. Phase and its morphologies of Ti-45 %Al alloy directionally solidified at different growth rates

    Institute of Scientific and Technical Information of China (English)

    LIU Chang; SU Yan-qing; BI Wei-sheng; GUO Jing-Jie; JIA Jun; FU Heng-zhi

    2005-01-01

    The microstructures of Ti-45%Al(molar fraction) alloy directionally solidified at different growth rates in alumina tube by electromagnetic heating zone melting were studied. The measured temperature gradient of the system is about 104K/m. The microstructures show that the primary solidified phase is β phase at different growth rates. The growth at low rates from 1.94 × 10-6 m/s to 4. 16 × 10-6 m/s results in a transient solid/liquid interface structure from planar to shallow cellular. This transient rate is larger than the theoretical value of vc = 6.94 × 10-7 m/s.Compared with vt = vc/k = 1.01 × 10-6 m/s, the cellular-dendritic transient rate of experiment is observed in the range of 1.67 × 10-5- 2.50 × 10-5 m/s. The primary arm spacing decreases with increasing growth rate.

  11. Plasma deposition of boron films with high growth rate and efficiency using carborane

    International Nuclear Information System (INIS)

    The injection of carborane (C2B10H12) on the PISCES-B linear plasma device has been used to produce boron containing films on various target species. Film growth rates achieved are extremely high (up to 30 nm/s) compared to those typically found for glow discharges (∼0.01 nm/s). For low-Z target materials (C and Al) the film production is highly efficient, with the boron film growth rate comparable to the incident ion flux and the injection rate of boron atoms. The boron to carbon ratio is 3.0-3.6 for these films. Similarly high growth rates (∼10 nm/s) are obtained with high-Z target (W), but with lower deposition efficiency and higher B/C film ratio. The high film growth rate/efficiency are apparently linked to the high degree of carborane ionization and dissociation caused by the ∼40 eV PISCES-B plasma, compared with T<1 eV plasmas of glow discharges. This technique opens the possibility of continuously producing protective B films in thermonuclear devices where net erosion rates approach 10 nm/s

  12. Can Uzbekistan Economy Retain Its High Growth Rates? Scenarios of Economic Development in 2015-30

    OpenAIRE

    Popov, Vladimir

    2014-01-01

    Uzbekistan in recent 10 years is an extremely successful economy – high growth (8%), low domestic and international debt, undervalued exchange rate, relatively even distribution of income, creation from scratch competitive export oriented auto industry. It is important though to avoid “dizziness from success” and to envisage possible growth traps in the future. This paper discusses two unfavourable scenarios – negative terms of trade shock due to the decline in cotton, gas and gold prices (a ...

  13. Are international growth rates constrained by the balance of payments? A comment on Professor Thirlwall

    Directory of Open Access Journals (Sweden)

    J.S.L. MCCOMBIE

    2013-12-01

    Full Text Available In a recent article A.P. Thirlwall derived what he termed a “fundamental law” which he argued explains the disparate post-war growth rates of advanced countries. In this note, the author takes issue with Thirlwall’s model, showing that together with the empirical evidence it is not capable of discriminating between the demand and the supply orientated approaches to growth.

  14. Horizon Instability of Extremal Kerr Black Holes: Nonaxisymmetric Modes and Enhanced Growth Rate

    CERN Document Server

    Casals, Marc; Zimmerman, Peter

    2016-01-01

    We show that the horizon instability of the extremal Kerr black hole is associated with a singular branch point in the Green function at the superradiant bound frequency. We study generic initial data supported away from the horizon and find an enhanced growth rate due to nonaxisymmetric modes. The growth is controlled by the conformal weight of each mode. We speculate on connections to near-extremal black holes and holographic duality.

  15. Economic Growth, Financial Depth and Lending Rate Nexus: A Case of Oil Dependant Economy

    OpenAIRE

    Najeeb Muhammad Nasir; Nasir Ali; Imran Khokhar

    2014-01-01

    This research empirically investigates the long and short run causal relationships between economic growth, financial depth and lending rate in the unique economic setup of Saudi Arabia where 92% of total GDP comes from oil exports. Study uses two proxies for financial depth namely liquid liability indicator and banks claim to the private sector to GDP ratio, while economic growth is measured by real GDP per capita. This study intends to get answers for such questions as, if financial depth e...

  16. Simple Predicting Method for Fatigue Crack Growth Rate Based on Tensile Strength of Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Three types of fatigue tests for an annealed carbon steel containing carbon of 0.42 % were carried out on smooth specimens and specimens with a small blind hole in order to investigate the fatigue crack growth law. A simple predicting method for crack growth rates has been proposed involving strength σb and the relation between cyclic stress and strain. The validity of proposed method has been confirmed by experiments on several carbon steels with different loadings.

  17. Poor correlation between phytoplankton community growth rates and nutrient concentration in the sea

    OpenAIRE

    Regaudie-de-gioux, A.; Sal, S; Á. López-Urrutia

    2015-01-01

    Nutrient availability is one of the major factors regulating marine productivity and phytoplankton community structure. While the response of phytoplankton species to nutrient variation is relatively well known, that of phytoplankton community remains unclear. We question whether phytoplankton community growth rates respond to nutrient concentration in a similar manner to phytoplankton species composing the community, that is, following Monod's model. Data on in situ marine community growth r...

  18. Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation

    Science.gov (United States)

    Reddy, Michael M.

    2012-01-01

    Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (Ωc). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and Ωc=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10−4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10−4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates.

  19. Variability of rRNA operon copy number and growth rate dynamics of Bacillus isolated from an extremely oligotrophic aquatic ecosystem

    Directory of Open Access Journals (Sweden)

    Jorge Antonio Valdivia-Anistro

    2016-01-01

    Full Text Available The ribosomal RNA (rrn operon is a key suite of genes related to the production of protein synthesis machinery and thus to bacterial growth physiology. Experimental evidence has suggested an intrinsic relationship between the number of copies of this operon and environmental resource availability, especially the availability of phosphorus (P, because bacteria that live in oligotrophic ecosystems usually have few rrn operons and a slow growth rate. The Cuatro Ciénegas Basin (CCB is a complex aquatic ecosystem that contains an unusually high microbial diversity that is able to persist under highly oligotrophic conditions. These environmental conditions impose a variety of strong selective pressures that shape the genome dynamics of their inhabitants. The genus Bacillus is one of the most abundant cultivable bacterial groups in the CCB and usually possesses a relatively large number of rrn operon copies (6-15 copies. The main goal of this study was to analyze the variation in the number of rrn operon copies of Bacillus in the CCB and to assess their growth-related properties as well as their stoichiometric balance (N and P content. We defined 18 phylogenetic groups within the Bacilli clade and documented a range of from six to 14 copies of the rrn operon. The growth dynamic of these Bacilli was heterogeneous and did not show a direct relation to the number of operon copies. Physiologically, our results were not consistent with the Growth Rate Hypothesis, since the copies of the rrn operon were decoupled from growth rate. However, we speculate that the diversity of the growth properties of these Bacilli as well as the low P content of their cells in an ample range of rrn copy number is an adaptive response to oligotrophy of the CCB and could represent an ecological mechanism that allows these taxa to coexist. These findings increase the knowledge of the variability in the number of copies of the rrn operon in the genus Bacillus and give insights

  20. Slow Growth Rates of Amazonian Trees: Consequences for Carbon Sequestration and Forest Management.

    Science.gov (United States)

    Vieira, S. A.; Camargo, P. B.; Selhorst, D.; Chambers, J.; Higuchi, N.; Martinelli, L. A.; Trumbore, S.

    2004-12-01

    Growth rates for tropical forest trees estimated from radiocarbon ages and dendrometer measurements illustrate differences in forest age and structure among three sites located in the eastern, central and western Amazon basin. Although growth rates vary dramatically among individual trees overall the slowest growing trees (averaging \\sim0.1mm yr-1 as opposed to 0.3mm yr-1 diameter increment) are found in the central Amazon. Small individuals (DBH \\500 yr are encountered at all sites. Only \\sim2MgC ha-1 year-1, or \\SIM7% of annual photosynthesis, is allocated to growth of living wood at the eastern and central Amazon sites. Rates of C allocation to stem growth are similar across the three sites we studied because slowest growth occurs at the central Amazon site that has highest stem density and greatest biomass. Extrapolating our growth increment data to forest stand, we estimate the mean age of individual trees is \\SIM350 years in the central Amazon but \\SIM200\\-250 years in the other two areas. The mean age of C making up the trees has a smaller range of \\SIM250\\-310 years, because of the greater fraction of biomass in larger individuals in the eastern and western Amazon sites. These residence times for C are longer than those of 100\\-180 years obtained by simply dividing the total biomass C by the rate of C allocation to new wood for the same reason. We estimate that >20% of trees at all sites should have ages >300 years, and that maximum tree ages of >1000 years, though not common, are in accord with the growth rates we find. The fact that many Amazon trees attain ages greater than several centuries should be accounted for in management practices in these forests.

  1. Investigation of the growth rate for joint fast breeder reactor and light water reactor operation

    International Nuclear Information System (INIS)

    An investigation of fuel consumption and breeding characteristics of FBR-LWR joint operation is presented. The FBR operates in a closed cycle with joint-reprocessing of core and blanket material. The LWR-portion that runs on FBR plutonium operates in an open cycle. The growth rate of the system is defined based upon the fact that the discharge from the system will make up a fraction of an identical system; the system growth rate is found to have an almost linear dependence on the fraction of the LWR fed by plutonium from the FBR. The LWR growth rate, which is negative, is a constant and represents the fraction of the fuel burnt in the LWR-fraction that runs on FBR plutonium per year

  2. ANALYSIS OF TUITION GROWTH RATES BASED ON CLUSTERING AND REGRESSION MODELS

    Directory of Open Access Journals (Sweden)

    Long Cheng

    2016-07-01

    Full Text Available Tuition plays a significant role in determining whether a student could afford higher education, which is one of the major driving forces for country development and social prosperity. So it is necessary to fully understand what factors might affect the tuition and how they affect it. However, many existing studies on the tuition growth rate either lack sufficient real data and proper quantitative models to support their conclusions, or are limited to focus on only a few factors that might affect the tuition growth rate, failing to make a comprehensive analysis. In this paper, we explore a wide variety of factors that might affect the tuition growth rate by use of large amounts of authentic data and different quantitative methods such as clustering and regression models.

  3. STRATIFIED MODEL FOR ESTIMATING FATIGUE CRACK GROWTH RATE OF METALLIC MATERIALS

    Institute of Scientific and Technical Information of China (English)

    YANG Yong-yu; LIU Xin-wei; YANG Fan

    2005-01-01

    The curve of relationship between fatigue crack growth rate and the stress strength factor amplitude represented an important fatigue property in designing of damage tolerance limits and predicting life of metallic component parts. In order to have a morereasonable use of testing data, samples from population were stratified suggested by the stratified random sample model (SRAM). The data in each stratum corresponded to the same experiment conditions. A suitable weight was assigned to each stratified sample according to the actual working states of the pressure vessel, so that the estimation of fatigue crack growth rate equation was more accurate for practice. An empirical study shows that the SRAM estimation by using fatigue crack growth rate data from different stoves is obviously better than the estimation from simple random sample model.

  4. Measurement of fatigue crack growth rate in pipe and pipe weld

    International Nuclear Information System (INIS)

    Striation spacing on the fracture surface developed during fatigue crack growth in pipes and pipe welds have been examined under scanning electron microscope (SEM). Striation spacing was measured on the fracture surface in maximum depth (radial) and surface (circumferential) direction at several locations. Striation spacing increases with crack growth in thickness (depth) direction of pipe and pipe weld. Local direction of striation spacing is different from the global direction of crack growth in cracked pipe. Striation spacing was compared with the conventionally evaluated crack growth rate where crack growth was measured using Alternate Current Potential Difference (ACPD) based instrument. Striation spacing is marginally lower for carbon steel and higher for stainless steel in comparison to da/dN in the Paris regime (evaluated from 'a Vs N' plot). Striation spacing form fracture surface of pipe was also compared with those measured on CT specimen. (author)

  5. Does warming affect growth rate and biomass production of shrubs in the High Arctic?

    DEFF Research Database (Denmark)

    Campioli, Matteo; Schmidt, Niels Martin; Albert, Kristian Rost;

    2013-01-01

    Few studies have assessed directly the impact of warming on plant growth and biomass production in the High Arctic. Here, we aimed to investigate the impact of 7 years of warming (open greenhouses) on the aboveground relative growth rate (RGR) of Cassiope tetragona and Salix arctica in North...... the secondary growth of old stem segments of Cassiope formed before the treatment began. The increase in Cassiope RGR was associated with an increase in gross photosynthetic uptake, branching and C concentration in old green tissues. Overall, the different growth measures consistently indicated that temperature......-Eastern Greenland. RGR was assessed for apical (leaves, stem, reproductive organs) and lateral meristems (secondary growth of stem and branches) and accompanied by measures of gross ecosystem production (GEP), branching and tissue carbon (C) concentration. Measurements were based on harvest and biometric methods...

  6. Effects of elaidic acid, a predominant industrial trans fatty acid, on bacterial growth and cell surface hydrophobicity of lactobacilli.

    Science.gov (United States)

    Wu, Qinglong; Shah, Nagendra P

    2014-12-01

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

  7. Effects of varying media, temperature, and growth rates on the intracellular concentrations of yeast amino acids.

    Science.gov (United States)

    Martínez-Force, E; Benítez, T

    1995-01-01

    Variations of the yeast free amino acid pool under different culture conditions were studied in two Saccharomyces strains, the laboratory haploid strain S288C and the industrial fermentative yeast IFI256. The internal amino acid pool of both strains was measured when grown in laboratory (minimal and complete) versus semiindustrial (molasses with or without added biotin and/or diammonium phosphate) media, in fermentable (glucose, fructose, sucrose) versus respirable (glycerol) carbon sources, in different temperatures (22, 30, and 37 degrees C), pHs (2.0-4.75), and growth rates (0.018-0.24 h-1) in continuous culture, and at different phases of the growth curve in batch culture (lag, exponential, early and late stationary). Results indicated that environmental conditions, particularly the presence of amino acids in the media, enormously influenced the intracellular amino acid concentration. Higher values were detected in molasses than in laboratory media and in fermentable carbon sources (glucose, fructose, sucrose) than in glycerol. Variations in the amino acid pool along the growth curve were greater at 37 degrees C than at other temperatures; in all cases, the highest values were measured at the beginning of the exponential phase. In continuous culture and at different growth rates, intracellular free amino acid concentrations increased by 3-10-fold when the growth rate was lower than 0.05 h-1, representing 20-35% of the total (free plus protein) amino acid content and indicating that amino acid yield was a partly growth-linked parameter. PMID:7654310

  8. Non-monotonic growth rates of sawtooth precursors evidenced with a new method on ASDEX Upgrade

    Science.gov (United States)

    Vezinet, D.; Igochine, V.; Weiland, M.; Yu, Q.; Gude, A.; Meshcheriakov, D.; Sertoli, M.; the Asdex Upgrade Team; the EUROfusion MST1 Team

    2016-08-01

    This paper describes a new method to derive, from soft x-ray (SXR) tomography, robust estimates of the core displacement, growth rate and frequency of a 1/1 sawtooth crash precursor. The method is valid for very peaked SXR profiles and is robust against both the inversion algorithm and the presence of tungsten in a rotating plasma. Three typical ASDEX Upgrade crashes are then analysed. In all cases a postcursor is observed, suggesting incomplete reconnection. Despite different dynamics, in all three cases the growth rate of the core displacement shows similar features. First, it is not constant, supporting the idea of non-linear growth. Second, it can be divided into clearly identified phases with quasi-constant growth rates, suggesting sudden change of growth regime rather than smooth transitions. Third, its evolution is non-monotonic, with phases of accelerated growth followed by damped phases. This damping is interpreted for two cases respectively as an effect of fast ions and of mode coupling, based on the result of a MHD simulation. The mode frequency is observed in all cases to be closely related to the plasma bulk rotation profile, with little or no visible effect of the electron diamagnetic drift frequency. The onset criterion could not be clearly identified and it is shown that the role of the pressure gradient is not as expected from a naive extrapolation of the linear stability theory.

  9. A Generalized Preferential Attachment Model for Business Firms Growth Rates: I. Empirical Evidence

    CERN Document Server

    Pammolli, F; Buldyrev, S V; Riccaboni, M; Matia, K; Yamasaki, K; Stanley, H E; Pammolli, Fabio; Fu, Dongfeng; Riccaboni, Massimo; Matia, Kaushik; Yamasaki, Kazuko

    2006-01-01

    We introduce a model of proportional growth to explain the distribution $P(g)$ of business firm growth rates. The model predicts that $P(g)$ is Laplace in the central part and depicts an asymptotic power-law behavior in the tails with an exponent $\\zeta=3$. Because of data limitations, previous studies in this field have been focusing exclusively on the Laplace shape of the body of the distribution. We test the model at different levels of aggregation in the economy, from products, to firms, to countries, and we find that the its predictions are in good agreement with empirical evidence on both growth distributions and size-variance relationships.

  10. Improved growth rates and purity of basic ammonothermal GaN

    Science.gov (United States)

    Pimputkar, S.; Kawabata, S.; Speck, J. S.; Nakamura, S.

    2014-10-01

    Improvements to the experimental setup for the basic ammonothermal growth of GaN and the introduction of a silver capsule into the autoclave have yielded an ultrahigh purity (UHP) growth environment with reproducible external wall temperature profiles to within the error of the thermocouples (type K with special limits of error (SLE), ±2.5 °C). 40 basic ammonothermal growth runs were performed on hydride vapor phase epitaxy (HVPE) GaN seed crystals with different crystal orientations to optimize the growth system. Due to the UHP growth environment, transition metal impurities in the GaN crystals were reduced to less than 1×1017 cm-3 and oxygen impurity concentrations were comparable to those of the polycrystalline HVPE GaN source material (1×1019 cm-3). Total growth rates improved to 344±30 μm/day for c-plane growth and 46±2 μm/day for m-plane growth. The crystal quality, as measured by the full width at half maximum (FWHM) of the ω-rocking curve using X-ray diffraction (ω-XRC), was comparable to that of the seed crystal, except for Ga-face growth on c-plane oriented seeds due to poor nucleation and cracking in thick growth layers due to strain originating from the HVPE seed crystals. The difference in total system pressure profiles during growth runs using autoclaves with and without a silver capsule was analyzed and the pressure drop due to outward diffusion of hydrogen during growth was modeled.

  11. Inhibitors of bacterial growth in urine: what is the role of betaines?

    Science.gov (United States)

    Chambers, S T; Peddie, B A; Randall, K; Lever, M

    1999-05-01

    It has long been recognised that some individuals produce urine that is inhibitory to uropathogens. This may be partly explained by inhibitors. Several inhibitors have been identified in urine including urea and organic acids. Bacteria adapt to high osmolarity by activating osmoregulated betaine porters and accumulating organic osmolytes intracellularly. The preferred substrate is glycine betaine, which is present in urine, and promotes rapid growth by balancing osmotic forces and stabilising macromolecular structures against the toxicity of urea and low pH. Other dietary betaines such as trigonelline may also be taken but enhance urea toxicity. The importance of such compounds in vivo is unknown. PMID:10394986

  12. DNA segregation by the bacterial actin AlfA during Bacillus subtilis growth and development

    OpenAIRE

    Becker, Eric; Herrera, Nick C; Gunderson, Felizza Q.; Derman, Alan I.; Dance, Amber L; Sims, Jennifer; Larsen, Rachel A.; Pogliano, Joe

    2006-01-01

    We here identify a protein (AlfA; actin like filament) that defines a new family of actins that are only distantly related to MreB and ParM. AlfA is required for segregation of Bacillus subtilis plasmid pBET131 (a mini pLS32-derivative) during growth and sporulation. A 3-kb DNA fragment encoding alfA and a downstream gene (alfB) is necessary and sufficient for plasmid stability. AlfA-GFP assembles dynamic cytoskeletal filaments that rapidly turn over (t1/2

  13. Growth rate effects on Mg/Ca and Sr/Ca ratios constrained by belemnite calcite

    Science.gov (United States)

    Vinzenz Ullmann, Clemens

    2016-04-01

    Multiple temperature proxies from single species are important to achieve robust palaeotemperature estimates. Besides the commonly employed oxygen isotope thermometer, also Mg/Ca and Sr/Ca ratios perform well as proxies for calcification temperature in the shells of some species. While salinity changes affect the ratios of earth alkaline elements much less than the δ18O thermometer, metabolic effects may exert a strong control on the expression of element ratios. Such effects are hard to study because biomineralization experiments have to overcome large intraspecific variability and can hardly ever isolate the controls of a single parameter on shell geochemistry. The unique geometry of the belemnite rostrum constitutes an exception to this rule. Its shape, large size, and the visibility of growth increments as bands enable the analysis of multiple, correlatable, high resolution geochemical profiles in a single fossil. The effects of the growth rate variability amongst these profiles on Mg/Ca and Sr/Ca ratios has been tested here. Within a specimen of Passaloteuthis bisulcata (Early Toarcian, Cleveland Basin, UK), Mg/Ca and Sr/Ca data were obtained from four profiles. With respect to growth rate in the first profile, which was taken as a reference, the relative growth rates in the remaining three profiles varied by a factor of 0.9 to 2.7. Results suggest that relative growth rate is linearly correlated with Mg/Ca and Sr/Ca, with a decrease of Mg/Ca by 8 % and increase of Sr/Ca by 6 % per 100 % increase in relative growth rate. The observed trends are consistent with abiogenic precipitation experiments and suggest that crystal precipitation rate exerts a significant, predictable control on the element distribution in biogenic calcite.

  14. Airborne measurements of nucleation mode particles I: coastal nucleation and growth rates

    Directory of Open Access Journals (Sweden)

    C. D. O'Dowd

    2007-01-01

    Full Text Available A light aircraft was equipped with a bank of Condensation Particle Counters (CPCs (50% cut from 3–5.4–9.6 nm and a nano-Scanning Mobility Particle Sizer (nSMPS and deployed along the west coast of Ireland, in the vicinity of Mace Head. The objective of the exercise was to provide high resolution micro-physical measurements of the coastal nucleation mode in order to map the spatial extent of new particle production regions and to evaluate the evolution, and associated growth rates of the coastal nucleation-mode aerosol plume. Results indicate that coastal new particle production is occurring over most areas along the land-sea interface with peak concentrations at the coastal plume-head in excess of 106 cm−3. Pseudo-Lagrangian studies of the coastal plume evolution illustrated significant growth of new particles to sizes in excess of 8 nm approximately 10 km downwind of the source region. Close to the plume head (<1 km growth rates can be as high as 123–171 nm h−1, decreasing gradually to 53–72 nm h−1 at 3 km. Further along the plume, at distances up to 10 km, the growth rates are calculated to be 17–32 nm h−1. Growth rates of this magnitude suggest that after a couple of hours, coastal nucleation mode particles can reach significant sizes where they can contribution to the regional aerosol loading.

  15. Effects of lowered pH on marine phytoplankton growth rates

    DEFF Research Database (Denmark)

    Berge, Terje; Daugbjerg, Niels; Andersen, Betinna Balling;

    2010-01-01

    concentration of seawater. Ocean acidification may potentially both stimulate and reduce primary production by marine phytoplankton. Data are scarce on the response of marine phytoplankton growth rates to lowered pH/increased CO2. Using the acid addition method to lower the seawater pH and manipulate...... the carbonate system, we determined in detail the lower pH limit for growth rates of 2 model species of common marine phytoplankton. We also tested whether growth and production rates of 6 other common species of phytoplankton were affected by ocean acidification (lowered to pH 7.0). The lower pH limits...... statistically similar in the pH range of ~7.0 to 8.5. Our results and literature reports on growth at lowered pH indicate that marine phytoplankton in general are resistant to climate change in terms of ocean acidification, and do not increase or decrease their growth rates according to ecological relevant...

  16. Importance of inoculum properties on the structure and growth of bacterial communities during Recolonisation of humus soil with different pH.

    Science.gov (United States)

    Pettersson, Marie; Bååth, Erland

    2013-08-01

    The relationship between community structure and growth and pH tolerance of a soil bacterial community was studied after liming in a reciprocal inoculum study. An unlimed (UL) humus soil with a pH of 4.0 was fumigated with chloroform for 4 h, after which < 1 % of the initial bacterial activity remained. Half of the fumigated soil was experimentally limed (EL) to a pH of 7.6. Both the UL and the EL soil were then reciprocally inoculated with UL soil or field limed (FL) soil with a pH of 6.2. The FL soil was from a 15-year-old experiment. The structural changes were measured on both bacteria in soil and on bacteria able to grow on agar plates using phospholipids fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analysis. The developing community pH tolerance and bacterial growth were also monitored over time using thymidine incorporation. The inoculum source had a significant impact on both growth and pH tolerance of the bacterial community in the EL soil. These differences between the EL soil inoculated with UL soil and FL soil were correlated to structural changes, as evidenced by both PLFA and DGGE analyses on the soil. Similar correlations were seen to the fraction of the community growing on agar plates. There were, however, no differences between the soil bacterial communities in the unlimed soils with different inocula. This study showed the connection between the development of function (growth), community properties (pH tolerance) and the structure of the bacterial community. It also highlighted the importance of both the initial properties of the community and the selection pressure after environmental changes in shaping the resulting microbial community.

  17. L-harmonic functions with polynomial growth of a fixed rate

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Yau made the following conjecture:For a complete noncompact manifold with nonnegative Ricci curvature the space of harmonic functions with polynomial growth of a fixed rate is finite dimensional.we extend the result on the Laplace operator to that on the symmetric diffusion operator,and prove the space of L-harmonic functions with polynomial growth of a fixed rate is finitedimensional,when m-dimensional Bakery-Emery Ricci curvature of the symmetric diffusion operator on the complete noncompact Riemannian manifold is nonnegative.

  18. L-harmonic functions with polynomial growth of a fixed rate

    Institute of Scientific and Technical Information of China (English)

    ZHOU ChaoHui; CHEN ZhiHua

    2009-01-01

    Yau made the following conjecture: For a complete noncompact manifold with nonnegative Ricci curvature the space of harmonic functions with polynomial growth of a fixed rate is finite dimensional,we extend the result on the Laplace operator to that on the symmetric diffusion operator,and prove the space of L-harmonic functions with polynomial growth of a fixed rate is finitedimensional,when m-dimensional Bakery-Emery Ricci curvature of the symmetric diffusion operator on the complete noncompact Riemannian manifold is nonnegative.

  19. Effects of distributions of growth rates on recrystallization kinetics and microstructure

    DEFF Research Database (Denmark)

    Godiksen, Rasmus Brauner; Schmidt, Søren; Juul Jensen, Dorte

    2007-01-01

    The effects on recrystallization kinetics and microstructure of growth rate distributions rather than a single growth rate for recrystallizing grains were investigated by geometric simulations. The grains were set to grow as spheres with radii r = At1-alpha. The results show that distributions in A...... and alpha may produce significant changes in the microstructure and texture, whereas only distributions in alpha may change the overall evolution in kinetics represented by V-v(t) by completely changing the shape of the kinetics curve. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All...

  20. Collaborative Project: Understanding the Chemical Processes tat Affect Growth rates of Freshly Nucleated Particles

    Energy Technology Data Exchange (ETDEWEB)

    McMurry, Peter [Univ. of Minnesota, Minneapolis, MN (United States); Smuth, James [University Corporation for Atmospheric Research, Irvine, CA (United States)

    2015-11-12

    This final technical report describes our research activities that have, as the ultimate goal, the development of a model that explains growth rates of freshly nucleated particles. The research activities, which combine field observations with laboratory experiments, explore the relationship between concentrations of gas-phase species that contribute to growth and the rates at which those species are taken up. We also describe measurements of the chemical composition of freshly nucleated particles in a variety of locales, as well as properties (especially hygroscopicity) that influence their effects on climate.

  1. A study on the rate of contribution of education investment to the economic growth in China

    Institute of Scientific and Technical Information of China (English)

    Fan Bo-nai; Lai Xiong-xiang

    2006-01-01

    There is an evident bi-directional causality relationship between education investment and economic growth based on an analysis of statistics from 1952 to 2003 released by the State Statistics Bureau.A generalized difference regression model is set up to investigate the relationship between the two.Studies show that the rate of contribution of education investment to economic growth was 24.4 percent from 1952 to 2003.Further examination indicates that after the market-oriented economy restructuring,this rate increased by a wide margin of 7 percent,from 22.8 percent to 29.7 percent.

  2. The uniqueness of company size distribution function from tent-shaped growth rate distribution

    CERN Document Server

    Ishikawa, A

    2007-01-01

    We report the proof that the extension of Gibrat's law in the middle scale region is unique and the probability distribution function (pdf) is also uniquely derived from the extended Gibrat's law and the law of detailed balance. In the proof, two approximations are employed. The pdf of growth rate is described as tent-shaped exponential functions and the value of the origin of the growth rate distribution is constant. These approximations are confirmed in profits data of Japanese companies 2003 and 2004. The resultant profits pdf fits with the empirical data with high accuracy. This guarantees the validity of the approximations.

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

    Science.gov (United States)

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

    2006-01-01

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

  4. Microscopic Rate Constants of Crystal Growth from Molecular Dynamic Simulations Combined with Metadynamics

    Directory of Open Access Journals (Sweden)

    Dániel Kozma

    2012-01-01

    Full Text Available Atomistic simulation of crystal growth can be decomposed into two steps: the determination of the microscopic rate constants and a mesoscopic kinetic Monte Carlo simulation. We proposed a method to determine kinetic rate constants of crystal growth. We performed classical molecular dynamics on the equilibrium liquid/crystal interface of argon. Metadynamics was used to explore the free energy surface of crystal growth. A crystalline atom was selected at the interface, and it was displaced to the liquid phase by adding repulsive Gaussian potentials. The activation free energy of this process was calculated as the maximal potential energy density of the Gaussian potentials. We calculated the rate constants at different interfacial structures using the transition state theory. In order to mimic real crystallization, we applied a temperature difference in the calculations of the two opposite rate constants, and they were applied in kinetic Monte Carlo simulation. The novelty of our technique is that it can be used for slow crystallization processes, while the simple following of trajectories can be applied only for fast reactions. Our method is a possibility for determination of elementary rate constants of crystal growth that seems to be necessary for the long-time goal of computer-aided crystal design.

  5. Growth rates in modern speleothems from Santana Cave, Brazil, by the 210Pb-method

    International Nuclear Information System (INIS)

    The Santana Cave is located at the Upper Ribeira Touristic State Park (PETAR-Parque Estadual Turístico do Alto Ribeira) in southern São Paulo State, Brazil. This paper describes 210Pb activity concentration data in soda straw stalactites samples collected at Salão das Flores in Santana Cave that is a fossil tributary of the cave river. Non-expensive alpha counting following some analytical steps for extracting and depositing 210Po were used for providing the 210Pb data. In the analyzed samples, 210Pb values of increasingly older samples fitted an exponential curve, thus suggesting that the production of 210Pb has been constant with time. Also, the near-ideal fit indicated that the growth was uniform and there was no break in the continuous growth. The soda straw growth rates were determined from the best fit to the exponential curve through the 210Pb activity concentration. The results of the measurements allowed estimate a longitudinal rate corresponding to 1.3 mm/yr and a lateral rate of 0.01 mm/yr, which permitted calculate times of 70 years and 317–498 years for their formation, respectively. The lateral growth rate is compatible with values from studies of chemical weathering rates held under laboratory and natural conditions.

  6. Dependence of microstructures on growth rate in YBCO films by TFA-MOD method

    International Nuclear Information System (INIS)

    YBa2Cu3Oy (YBCO) films grown by starting solutions with Ba-poor (Y:Ba:Cu = 1:1.5:3, Ba/Y = 1.5) have been reported to perform higher Jc than that for YBCO films with stoichiometric one due to smaller and less pores in YBCO films by metal organic deposition (MOD) using tri-fluoroacetates (TFA). However, we have reported that a lot of non-reacted particles such as Y and Cu oxides were remained for the YBCO film surface grown by the precursors using Ba-poor solution. In this study, influences of YBCO growth rate on microstructures of the YBCO film were discussed to control microstructures of these second phase particles. As a result, microstructures of the YBCO film depended strongly on the YBCO growth rate, residues of Y and Cu oxides were dispersed randomly throughout the YBCO film grown at higher growth rate. Consequently, it was succeeded to control the segregated phases as seen in the previous YBCO film with Ba/Y = 1.5 at the film surface into the YBCO film. Jc of the YBCO film grown at higher rate was a value almost equal to that grown at previous growth rate.

  7. Proteomic analysis of growth phase-dependent expression of Legionella pneumophila proteins which involves regulation of bacterial virulence traits.

    Directory of Open Access Journals (Sweden)

    Tsuyoshi Hayashi

    Full Text Available Legionella pneumophila, which is a causative pathogen of Legionnaires' disease, expresses its virulent traits in response to growth conditions. In particular, it is known to become virulent at a post-exponential phase in vitro culture. In this study, we performed a proteomic analysis of differences in expression between the exponential phase and post-exponential phase to identify candidates associated with L. pneumophila virulence using 2-Dimentional Fluorescence Difference Gel Electrophoresis (2D-DIGE combined with Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry (MALDI-TOF-MS. Of 68 identified proteins that significantly differed in expression between the two growth phases, 64 were up-regulated at a post-exponential phase. The up-regulated proteins included enzymes related to glycolysis, ketone body biogenesis and poly-3-hydroxybutyrate (PHB biogenesis, suggesting that L. pneumophila may utilize sugars and lipids as energy sources, when amino acids become scarce. Proteins related to motility (flagella components and twitching motility-associated proteins were also up-regulated, predicting that they enhance infectivity of the bacteria in host cells under certain conditions. Furthermore, 9 up-regulated proteins of unknown function were found. Two of them were identified as novel bacterial factors associated with hemolysis of sheep red blood cells (SRBCs. Another 2 were found to be translocated into macrophages via the Icm/Dot type IV secretion apparatus as effector candidates in a reporter assay with Bordetella pertussis adenylate cyclase. The study will be helpful for virulent analysis of L. pneumophila from the viewpoint of physiological or metabolic modulation dependent on growth phase.

  8. Carbon and phosphorus regulating bacterial metabolism in oligotrophic boreal lakes

    DEFF Research Database (Denmark)

    Vidal, L. O.; Graneli, W.; Daniel, C. B.;

    2011-01-01

    -P and glucose-C alone or in combination (0.01 and 0.3 mg L(-1), respectively) was added to 1.0 mu m filtered lake water and incubated in darkness at 20 degrees C. Additions of glucose (C) and phosphorus (P) alone did not lead to changes in the rates of bacterial metabolic processes, whereas bacterial...... respiration and bacterial production responded positively to C + P enrichment for most of the lakes sampled. Bacterial growth efficiency showed a wide range (2.5-28.7%) and low mean value (12%). These variations were not correlated with the DOC concentration. Our results show that heterotrophic bacterial...

  9. Sex-based differences in Adelie penguin (Pygoscelis adeliae) chick growth rates.

    Science.gov (United States)

    Jennings, Scott; Varsani, Arvind; Dugger, Catherine; Ballard, Grant; Ainley, David G.

    2016-01-01

    Sexually size-dimorphic species must show some difference between the sexes in growth rate and/or length of growing period. Such differences in growth parameters can cause the sexes to be impacted by environmental variability in different ways, and understanding these differences allows a better understanding of patterns in productivity between individuals and populations. We investigated differences in growth rate and diet between male and female Adélie Penguin (Pygoscelis adeliae) chicks during two breeding seasons at Cape Crozier, Ross Island, Antarctica. Adélie Penguins are a slightly dimorphic species, with adult males averaging larger than adult females in mass (~11%) as well as bill (~8%) and flipper length (~3%). We measured mass and length of flipper, bill, tibiotarsus, and foot at 5-day intervals for 45 male and 40 female individually-marked chicks. Chick sex was molecularly determined from feathers. We used linear mixed effects models to estimate daily growth rate as a function of chick sex, while controlling for hatching order, brood size, year, and potential variation in breeding quality between pairs of parents. Accounting for season and hatching order, male chicks gained mass an average of 15.6 g d-1 faster than females. Similarly, growth in bill length was faster for males, and the calculated bill size difference at fledging was similar to that observed in adults. There was no evidence for sex-based differences in growth of other morphological features. Adélie diet at Ross Island is composed almost entirely of two species—one krill (Euphausia crystallorophias) and one fish (Pleuragramma antarctica), with fish having a higher caloric value. Using isotopic analyses of feather samples, we also determined that male chicks were fed a higher proportion of fish than female chicks. The related differences in provisioning and growth rates of male and female offspring provides a greater understanding of the ways in which ecological factors may impact

  10. Tropical dendrochemistry: A novel approach for reconstructing seasonally-resolved growth rates from ringless tropical trees

    Science.gov (United States)

    Poussart, P. M.; Myneni, S. C.

    2005-12-01

    Although tropical forests play an active role in the global carbon cycle and are host to a variety of pristine paleoclimate archives, they remain poorly characterized as compared to other ecosystems on the planet. In particular, dating and reconstructing the growth rate history of tropical trees remains a challenge and continues to delay research efforts towards understanding tropical forest dynamics. Traditional dendrochronological techniques have found limited applications in the tropics because temperature seasonality is often too small to initiate the production of visible annual growth rings. Dendrometers, cambium scarring methods and sub-annual records of oxygen and carbon isotopes from tree cellulose may be used to estimate growth rate histories when growth rings are absent. However, dendrometer records rarely extend beyond the past couple of decades and the generation of seasonally-resolved isotopic records remains labour intensive, currently prohibiting the level of record replication necessary for statistical analysis. Here, we present evidence that Ca may also be used as a proxy for dating and reconstructing growth rates of trees lacking visible growth rings. Using the Brookhaven National Lab Synchrotron, we recover a radial record of cyclic variations in Ca from a Miliusa velutina tree from northern Thailand. We determine that the Ca cycles are seasonal based on a comparison between radiocarbon age estimates and a trace element age model, which agree within 2 years over the period of 1955 to 2000. The amplitude of the Ca annual cycle is significantly correlated with growth rate estimates, which are also correlated to the amount of dry season rainfall. The measurements at the Synchrotron are fast, non-destructive and require little sample preparation. Application of this technique in the tropics holds the potential to resolve longstanding questions about tropical forest dynamics and interannual to decadal changes in the carbon cycle.

  11. Morphology and mycelial growth rate of Pleurotus spp. strains from the Mexican mixtec region

    Directory of Open Access Journals (Sweden)

    P.C. Guadarrama-Mendoza

    2014-09-01

    Full Text Available Two native Pleurotus spp. strains (white LB-050 and pale pink LB-051 were isolated from rotten tree trunks of cazahuate (Ipomoea murucoides from the Mexican Mixtec Region. Both strains were chemically dedikaryotized to obtain their symmetrical monokaryotic components (neohaplonts. This was achieved employing homogenization time periods from 60 to 65 s, and 3 day incubation at 28 °C in a peptone-glucose solution (PGS. Pairing of compatible neohaplonts resulted in 56 hybrid strains which were classified into the four following hybrid types: (R1-n xB1-n, R1-n xB2-1, R2-n xB1-n and R2-n xB2-1. The mycelial growth of Pleurotus spp. monokaryotic and dikaryotic strains showed differences in texture (cottony or floccose, growth (scarce, regular or abundant, density (high, regular or low, and pigmentation (off-white, white or pale pink. To determine the rate and the amount of mycelium growth in malt extract agar at 28 °C, the diameter of the colony was measured every 24 h until the Petri dish was completely colonized. A linear model had the best fit to the mycelial growth kinetics. A direct relationship between mycelial morphology and growth rate was observed. Cottony mycelium presented significantly higher growth rates (p < 0.01 in comparison with floccose mycelium. Thus, mycelial morphology can be used as criterion to select which pairs must be used for optimizing compatible-mating studies. Hybrids resulting from cottony neohaplonts maintained the characteristically high growth rates of their parental strains with the hybrid R1-n xB1-n being faster than the latter.

  12. Sex-Based Differences in Adelie Penguin (Pygoscelis adeliae Chick Growth Rates and Diet.

    Directory of Open Access Journals (Sweden)

    Scott Jennings

    Full Text Available Sexually size-dimorphic species must show some difference between the sexes in growth rate and/or length of growing period. Such differences in growth parameters can cause the sexes to be impacted by environmental variability in different ways, and understanding these differences allows a better understanding of patterns in productivity between individuals and populations. We investigated differences in growth rate and diet between male and female Adélie Penguin (Pygoscelis adeliae chicks during two breeding seasons at Cape Crozier, Ross Island, Antarctica. Adélie Penguins are a slightly dimorphic species, with adult males averaging larger than adult females in mass (~11% as well as bill (~8% and flipper length (~3%. We measured mass and length of flipper, bill, tibiotarsus, and foot at 5-day intervals for 45 male and 40 female individually-marked chicks. Chick sex was molecularly determined from feathers. We used linear mixed effects models to estimate daily growth rate as a function of chick sex, while controlling for hatching order, brood size, year, and potential variation in breeding quality between pairs of parents. Accounting for season and hatching order, male chicks gained mass an average of 15.6 g d(-1 faster than females. Similarly, growth in bill length was faster for males, and the calculated bill size difference at fledging was similar to that observed in adults. There was no evidence for sex-based differences in growth of other morphological features. Adélie diet at Ross Island is composed almost entirely of two species--one krill (Euphausia crystallorophias and one fish (Pleuragramma antarctica, with fish having a higher caloric value. Using isotopic analyses of feather samples, we also determined that male chicks were fed a higher proportion of fish than female chicks. The related differences in provisioning and growth rates of male and female offspring provides a greater understanding of the ways in which ecological factors

  13. Etabolism in compensatory growth . III. The urea, glucose and C02 entry rates in animal undergoing compensatory growth

    Directory of Open Access Journals (Sweden)

    Pram Mahyudin

    1996-03-01

    Full Text Available Glucose (GER, Urea (UER and C02 (C02 ER entry rates were studied at four points in the growth curve viz: before feed restriction (PI after 8 weeks of feed restriction (P2, after 3 weeks (P3 and 15 weeks (P4 following resumption ofad libitum feeding. Sixteen Merino wethers were used and offerred pelleted lucerne (Medicago sativa ad libitum for 3 weeks; then they were divided into 2 groups of eight. Group I continued to be fed ad libitum and Group 11 was fed pelleted lucerne at half maintenance level for 8 weeks and then fed ad libitum until the end of experiment. During feed restriction (P2, UER, urinary urea and urea transferred from the blood to the gut were 74% lower in group II than those in group I due to the reduction of N intake . At P2 GER and C02ER were also lower (53% and 56%, respectively because of the reduction of available glucose precursor and metabolic rate. Similarly AV concentration difference of glucose, glucose taken up by the hind-limb muscle and the percentage of glucose taken up by muscle that was oxidised were reduced by 52%, 86% and 48%, respectively . When animals resumed ad libitum feeding, the components of urea entry rate (except plasma urea concentration, GER and C02ER were markedly increased indicating A switch to the anabolic mode, followed by increased glucose taken up and oxidised by the hind-limb muscle . The significance of glucose in muscle metabolism during compensatory growth was shown in the dramatic increase in the actual rate of glucose oxidation per unit muscle weight . It appears that the priority of usage of glucose taken up by muscle during compensatory growth is for oxidation to both C02 and lactate.

  14. Simple and Versatile Turbidimetric Monitoring of Bacterial Growth in Liquid Cultures Using a Customized 3D Printed Culture Tube Holder and a Miniaturized Spectrophotometer: Application to Facultative and Strictly Anaerobic Bacteria

    Science.gov (United States)

    Maia, Margarida R. G.; Marques, Sara; Cabrita, Ana R. J.; Wallace, R. John; Thompson, Gertrude; Fonseca, António J. M.; Oliveira, Hugo M.

    2016-01-01

    Here we introduce a novel strategy for turbidimetric monitoring of bacterial growth in liquid culture. The instrumentation comprises a light source, a customized 3D printed culture tube holder and a miniaturized spectrophotometer, connected through optical cables. Due to its small footprint and the possibility to operate with external light, bacterial growth was directly monitored from culture tubes in a simple and versatile fashion. This new portable measurement technique was used to monitor the growth of facultative (Escherichia coli ATCC/25922, and Staphylococcus aureus ATCC/29213) and strictly (Butyrivibrio fibrisolvens JW11, Butyrivibrio proteoclasticus P18, and Propionibacterium acnes DSMZ 1897) anaerobic bacteria. For E. coli and S. aureus, the growth rates calculated from normalized optical density values were compared with those ones obtained using a benchtop spectrophotometer without significant differences (P = 0.256). For the strictly anaerobic species, a high precision (relative standard deviation < 3.5%) was observed between replicates up to 48 h. Regarding its potential for customization, this manifold could accommodate further developments for customized turbidimetric monitoring, such as the use of light-emitting diodes as a light source or flow cells. PMID:27630632

  15. Simple and versatile turbidimetric monitoring of bacterial growth in liquid cultures using a customized 3D printed culture tube holder and a miniaturized spectrophotometer: application to facultative and strictly anaerobic bacteria

    Directory of Open Access Journals (Sweden)

    Margarida R. G. Maia

    2016-08-01

    Full Text Available Here we introduce a novel strategy for turbidimetric monitoring of bacterial growth in liquid culture. The instrumentation comprises a light source, a customized 3D printed culture tube holder and a miniaturized spectrophotometer, connected through optical cables. Due to its small footprint and the possibility to operate with external light, bacterial growth was directly monitored from culture tubes in a simple and versatile fashion. This new portable measurement technique was used to monitor the growth of facultative (Escherichia coli ATCC/25922, and Staphylococcus aureus ATCC/29213 and strictly (Butyrivibrio fibrisolvens JW11, Butyrivibrio proteoclasticus P18, and Propionibacterium acnes DSMZ 1897 anaerobic bacteria. For E. coli and S. aureus, the growth rates calculated from normalized optical density values were compared with those ones obtained using a benchtop spectrophotometer without significant differences (P = 0.256. For the strictly anaerobic species, a high precision (RSD < 3.5% was observed between replicates up to 48 h. Regarding its potential for customization, this manifold could accommodate further developments for customized turbidimetric monitoring, such as the use of light-emitting diodes as a light source or flow cells.

  16. Simple and Versatile Turbidimetric Monitoring of Bacterial Growth in Liquid Cultures Using a Customized 3D Printed Culture Tube Holder and a Miniaturized Spectrophotometer: Application to Facultative and Strictly Anaerobic Bacteria.

    Science.gov (United States)

    Maia, Margarida R G; Marques, Sara; Cabrita, Ana R J; Wallace, R John; Thompson, Gertrude; Fonseca, António J M; Oliveira, Hugo M

    2016-01-01

    Here we introduce a novel strategy for turbidimetric monitoring of bacterial growth in liquid culture. The instrumentation comprises a light source, a customized 3D printed culture tube holder and a miniaturized spectrophotometer, connected through optical cables. Due to its small footprint and the possibility to operate with external light, bacterial growth was directly monitored from culture tubes in a simple and versatile fashion. This new portable measurement technique was used to monitor the growth of facultative (Escherichia coli ATCC/25922, and Staphylococcus aureus ATCC/29213) and strictly (Butyrivibrio fibrisolvens JW11, Butyrivibrio proteoclasticus P18, and Propionibacterium acnes DSMZ 1897) anaerobic bacteria. For E. coli and S. aureus, the growth rates calculated from normalized optical density values were compared with those ones obtained using a benchtop spectrophotometer without significant differences (P = 0.256). For the strictly anaerobic species, a high precision (relative standard deviation < 3.5%) was observed between replicates up to 48 h. Regarding its potential for customization, this manifold could accommodate further developments for customized turbidimetric monitoring, such as the use of light-emitting diodes as a light source or flow cells.

  17. Growth rates and the prevalence and progression of scoliosis in short-statured children on Australian growth hormone treatment programmes

    Directory of Open Access Journals (Sweden)

    McPhee Ian

    2007-02-01

    Full Text Available Abstract Study design and aim This was a longitudinal chart review of a diverse group (cohort of patients undergoing HGH (Human Growth Hormone treatment. Clinical and radiological examinations were performed with the aim to identify the presence and progression of scoliosis. Methods and cohort 185 patients were recruited and a database incorporating the age at commencement, dose and frequency of growth hormone treatment and growth charts was compiled from their Medical Records. The presence of any known syndrome and the clinical presence of scoliosis were included for analysis. Subsequently, skeletally immature patients identified with scoliosis were followed up over a period of a minimum four years and the radiologic type, progression and severity (Cobb angle of scoliosis were recorded. Results Four (3.6% of the 109 with idiopathic short stature or hormone deficiency had idiopathic scoliosis (within normal limits for a control population and scoliosis progression was not prospectively observed. 13 (28.8% of 45 with Turner syndrome had scoliosis radiologically similar to idiopathic scoliosis. 11 (48% of 23 with varying syndromes, had scoliosis. In the entire cohort, the growth rates of those with and without scoliosis were not statistically different and HGH treatment was not ceased because of progression of scoliosis. Conclusion In this study, there was no evidence of HGH treatment being responsible for progression of scoliosis in a small number of non-syndromic patients (four. An incidental finding was that scoliosis, similar to the idiopathic type, appears to be more prevalent in Turner syndrome than previously believed.

  18. Effect of reactor pressure on the growth rate and structural properties of GaN films

    Institute of Scientific and Technical Information of China (English)

    NI JinYu; HAO Yue; ZHANG JinCheng; YANG LinAn

    2009-01-01

    The effect of reactor pressure on the growth rate,surface morphology and crystalline quality of GaN films grown on sapphire by metalorganic chemical vapor deposition is studied.The results show that as the reactor pressure increases from 2500 to 20000 Pa,the GaN surface becomes rough and the growth rate of GaN films decreases.The rough surface morphology is associated with the initial high temperature GaN islands,which are large with low density due to low adatom surface diffusion under high reactor pressure.These islands prolong the occurrence of 2D growth mode and decrease the growth rate of GaN film.Meanwhile,the large GaN islands with low density lead to the reduction of threading dislocation density during subsequent island growth and coalescence,and consequently decrease the full width at half maximum of X-ray rocking curve of the GaN film.

  19. Temperature Effects on the Growth Rates and Photosynthetic Activities of Symbiodinium Cells

    Directory of Open Access Journals (Sweden)

    Widiastuti Karim

    2015-06-01

    Full Text Available Coral bleaching is caused by environmental stress and susceptibility to bleaching stress varies among types of coral. The physiological properties of the algal symbionts (Symbiodinium spp., especially extent of damage to PSII and its repair capacity, contribute importantly to this variability in stress susceptibility. The objective of the present study was to investigate the relationship between the growth rates and photosynthetic activities of six cultured strains of Symbiodinium spp. (clades A, B, C, D, and F at elevated temperature (33 °C. We also observed the recovery of photodamaged-PSII in the presence or absence of a chloroplast protein synthesis inhibitor (lincomycin. The growth rates and photochemical efficiencies of PSII (Fv/Fm decreased in parallel at high temperature in thermally sensitive strains, B-K100 (clade B followed by culture name and A-Y106, but not in thermally tolerant strains, F-K102 and D-K111. In strains A-KB8 and C-Y103, growth declined markedly at high temperature, but Fv/Fm decreased only slightly. These strains may reallocate energy from growth to the repair of damaged photosynthetic machineries or protection pathways. Alternatively, since recoveries of photo-damaged PSII at 33 °C were modest in strains A-KB8 and C-Y103, thermal stressing of other metabolic pathways may have reduced growth rates in these two strains. This possibility should be explored in future research efforts.

  20. A transcription factor links growth rate and metabolism in the hypersaline adapted archaeon Halobacterium salinarum.

    Science.gov (United States)

    Todor, Horia; Dulmage, Keely; Gillum, Nicholas; Bain, James R; Muehlbauer, Michael J; Schmid, Amy K

    2014-09-01

    Co-ordinating metabolism and growth is a key challenge for all organisms. Despite fluctuating environments, cells must produce the same metabolic outputs to thrive. The mechanisms underlying this 'growth homeostasis' are known in bacteria and eukaryotes, but remain unexplored in archaea. In the model archaeon Halobacterium salinarum, the transcription factor TrmB regulates enzyme-coding genes in diverse metabolic pathways in response to glucose. However, H. salinarum is thought not to catabolize glucose. To resolve this discrepancy, we demonstrate that TrmB regulates the gluconeogenic production of sugars incorporated into the cell surface S-layer glycoprotein. Additionally, we show that TrmB-DNA binding correlates with instantaneous growth rate, likely because S-layer glycosylation is proportional to growth. This suggests that TrmB transduces a growth rate signal to co-regulated metabolic pathways including amino acid, purine, and cobalamin biosynthesis. Remarkably, the topology and function of this growth homeostatic network appear conserved across domains despite extensive alterations in protein components.

  1. Rate-dependent morphology of Li2O2 growth in Li-O2 batteries

    CERN Document Server

    Horstmann, B; Mitchell, R; Bessler, W G; Shao-Horn, Y; Bazant, M Z

    2013-01-01

    Compact solid discharge products enable energy storage devices with high gravimetric and volumetric energy densities, but solid deposits on active surfaces can disturb charge transport and induce mechanical stress. In this Letter we develop a nanoscale continuum model for the growth of Li2O2 crystals in lithium-oxygen batteries with organic electrolytes, based on a theory of electrochemical non-equilibrium thermodynamics originally applied to Li-ion batteries. As in the case of lithium insertion in phase-separating LiFePO4 nanoparticles, the theory predicts a transition from complex to uniform morphologies of Li2O2 with increasing current. Discrete particle growth at low discharge rates becomes suppressed at high rates, resulting in a film of electronically insulating Li2O2 that limits cell performance. We predict that the transition between these surface growth modes occurs at current densities close to the exchange current density of the cathode reaction, consistent with experimental observations.

  2. Final Report: "Collaborative Project. Understanding the Chemical Processes That Affect Growth Rates of Freshly Nucleated Particles"

    Energy Technology Data Exchange (ETDEWEB)

    Smith, James N. [NCAR, Boulder, CO (United States); McMurry, Peter H. [NCAR, Boulder, CO (United States)

    2015-11-12

    This final technical report describes our research activities that have, as the ultimate goal, the development of a model that explains growth rates of freshly nucleated particles. The research activities, which combine field observations with laboratory experiments, explore the relationship between concentrations of gas-phase species that contribute to growth and the rates at which those species are taken up. We also describe measurements of the chemical composition of freshly nucleated particles in a variety of locales, as well as properties (especially hygroscopicity) that influence their effects on climate. Our measurements include a self-organized, DOE-ARM funded project at the Southern Great Plains site, the New Particle Formation Study (NPFS), which took place during spring 2013. NPFS data are available to the research community on the ARM data archive, providing a unique suite observations of trace gas and aerosols that are associated with the formation and growth of atmospheric aerosol particles.

  3. Radiocarbon-Based Ages and Growth Rates of Bamboo Corals from the Gulf of Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Roark, E B; Guilderson, T P; Flood-Page, S; Dunbar, R B; Ingram, B L; Fallon, S J; McCulloch, M

    2004-12-12

    Deep-sea coral communities have long been recognized by fisherman as areas that support large populations of commercial fish. As a consequence, many deep-sea coral communities are threatened by bottom trawling. Successful management and conservation of this widespread deep-sea habitat requires knowledge of the age and growth rates of deep-sea corals. These organisms also contain important archives of intermediate and deep-water variability, and are thus of interest in the context of decadal to century-scale climate dynamics. Here, we present {Delta}{sup 14}C data that suggest that bamboo corals from the Gulf of Alaska are long-lived (75-126 years) and that they acquire skeletal carbon from two distinct sources. Independent verification of our growth rate estimates and coral ages is obtained by counting seasonal Sr/Ca cycles and probable lunar cycle growth bands.

  4. Wavy membranes and the growth rate of a planar chemical garden: Enhanced diffusion and bioenergetics

    CERN Document Server

    Ding, Yang; Steinbock, Oliver; Cartwright, Julyan H E; Cardoso, Silvana S S

    2016-01-01

    In order to model ion transport across protocell membranes in Hadean hydrothermal vents, we consider both theoretically and experimentally the planar growth of a precipitate membrane formed at the interface between two parallel fluid streams in a two-dimensional microfluidic reactor. The growth rate of the precipitate is found to be proportional to the square root of time, which is characteristic of diffusive transport. However, the dependence of the growth rate on the concentrations of hydroxide and metal ions is approximately linear and quadratic, respectively. We show that such a difference in ionic transport dynamics arises from the enhanced transport of metal ions across a thin gel layer present at the surface of the precipitate. The fluctuations in transverse velocity in this wavy porous gel layer allow an enhanced transport of the cation, so that the effective diffusivity is about an order of magnitude higher than that expected from molecular diffusion alone. Our theoretical predictions are in excellen...

  5. Beyond reduced-impact logging: silvicultural treatments to increase growth rates of tropical trees

    NARCIS (Netherlands)

    Peña-Claros, M.; Fredericksen, T.S.; Alarcón, A.; Blate, G.M.; Choque, U.; Leaño, C.; Licona, J.C.; Mostacedo, B.; Pariona, W.; Villegas, Z.; Putz, F.E.

    2008-01-01

    Use of reduced-impact logging (RIL) techniques has repeatedly been shown to reduce damage caused by logging. Unfortunately, these techniques do not necessarily ameliorate the low growth rates of many commercial species or otherwise assure recovery of the initial volume harvested during the next cutt

  6. STRONG LAW OF LARGE NUMBERS AND GROWTH RATE FOR NOD SEQUENCES

    Institute of Scientific and Technical Information of China (English)

    MA Song-lin; WANG Xue-jun

    2015-01-01

    In the paper, we get the precise results of Hájek-Rényi type inequalities for the par-tial sums of negatively orthant dependent sequences, which improve the results of Theorem 3.1 and Corollary 3.2 in Kim (2006) and the strong law of large numbers and strong growth rate for negatively orthant dependent sequences.

  7. Effect of temperature on fatigue crack growth rate in inconel 690

    International Nuclear Information System (INIS)

    The effect of temperature on fatigue crack growth rate in Inconel 690 steam generator tube was investigated at room temperature, 150 .deg. C, 300 .deg. C and 400 .deg. C in air environment. Fatigue tests was performed on compact tension(CT) specimens made to thickness 8mm. Heat treatment was performed to obtain various microstructures. Tests was conducted at load ratio 0.1, at frequency 10Hz using sinusoidal waveform. Crack length was monitored by compliance method using sensor probe. Tensile tests was performed to obtain yield strength for fatigue test at each testing temperature. Fracture modes were studied using scanning electron microscopy(SEM). Tensile properties of Inconel 690 were dependent on grain size and testing temperature. As temperature and grain size increased, yield strength decreased. At temperature above 300 .deg. C, the serrations which were an evidence of dynamic strain aging (DSA) were observed for all cases of materials. Fatigue crack growth rate decreased with increasing grain size. At low Δ K, grain size effect was significant at room temperature, which was due to roughness induced crack closure. With increasing temperature, fatigue crack growth rate increased and grain size effect decreased. Chormium carbides which have large size and semi-continuous distribution in the grain boundaries decreased fatigue crack growth rate

  8. A methodology to study cyclic debond growth at constant mode-mixity and energy release rate

    DEFF Research Database (Denmark)

    Quispitupa, Amilcar; Berggreen, Christian; Carlsson, Leif A.

    2010-01-01

    It is well known that face/core debond crack propagation is governed by the critical energy release rate (fracture toughness) and mode-mixity at the crack tip. Thus, the current study focuses on the developing of a methodology to perform fatigue crack growth experiments of debonded sandwich...

  9. Capitalizing on the Dynamic Features of Excel to Consider Growth Rates and Limits

    Science.gov (United States)

    Taylor, Daniel; Moore-Russo, Deborah

    2012-01-01

    It is common for both algebra and calculus instructors to use power functions of various degrees as well as exponential functions to examine and compare rates of growth. This can be done on a chalkboard, with a graphing calculator, or with a spreadsheet. Instructors often are careful to connect the symbolic and graphical (and occasionally the…

  10. Extracting growth rates from the non-laminated coralline sponge Astrosclera willeyana using "bomb" radiocarbon

    Energy Technology Data Exchange (ETDEWEB)

    Fallon, S; Guilderson, T

    2004-06-30

    Coralline sponges have the potential to fill in gaps in our understanding of subsurface oceanographic variability. However, one disadvantage they have compared to hermatypic reef building coral proxies is that they do not have annual density bands and need to be radiometrically dated for an age determination. To elucidate growth rate variability we have measured radiocarbon in 1 mm increments from Astrosclera willeyana sponges collected off the Central and Northern Great Barrier Reef (GBR) and from Truk in the Caroline Islands and compared these radiocarbon profiles to independently dated coral radiocarbon records. Growth rates of the GBR sponges average 1.2 {+-} 0.3 and 1.0 {+-} 0.3 mm yr{sup -1}, north and central respectively but can vary by a factor of two. The growth rate of the Truk sponge averages 1.2 {+-} 0.1 mm yr{sup -1}. These growth rates are significantly faster to those measured for other GBR Astrosclera willeyana sponges (0.2 mm yr{sup -1}) by Calcein staining (Woerheide 1988).

  11. Contemporary evolution of plant growth rate following experimental removal of herbivores.

    Science.gov (United States)

    Turley, Nash E; Odell, Walter C; Schaefer, Hanno; Everwand, Georg; Crawley, Michael J; Johnson, Marc T J

    2013-05-01

    Herbivores are credited with driving the evolutionary diversification of plant defensive strategies over macroevolutionary time. For this to be true, herbivores must also cause short-term evolution within plant populations, but few studies have experimentally tested this prediction. We addressed this gap using a long-term manipulative field experiment where exclosures protected 22 plant populations from natural rabbit herbivory for growth rate, tolerance to herbivory, competitive ability, and the concentration of secondary metabolites (tannins and oxalate) implicated in defense against herbivores. In 26 years without rabbit herbivory, plant growth rate decreased linearly by 30%. We argue that plant growth rate has evolved as a defense against intense rabbit herbivory. In contrast, we found no change in tolerance to herbivory or concentrations of secondary metabolites. We also found no change in competitive ability, suggesting that contemporary evolution may not feed back to alter ecological interactions within this plant community. Our results combined with those of other studies show that the evolution of gross morphological traits such as growth rate in response to herbivory may be common, which calls into question assumptions about some of the most popular theories of plant defense.

  12. Growth rate of Usnea aurantiacoatra (Jacq. Bory on Fildes Peninsula, Antarctica and its climatic background.

    Directory of Open Access Journals (Sweden)

    Ying Li

    Full Text Available The ages of a fruticose lichen of Usnea aurantiacoatra (Jacq. Bory, from Fildes Peninsula, King George Island, Southwest Antarctic, were determined by radiocarbon (14C, and it is 1993-1996 at bottom and 2006-2007 at top of the lichen branch. The growth rates of U. aurantiacoatra calculated are 4.3 to 5.5 mm year(-1 based on its length and ages. The comparisons show that the growth rates of U. aurantiacoatra are higher than those of U. antarctica (0.4 to 1.1 mm year(-1. The growth rates of fruticose lichens are always higher, usually >2 mm year(-1, than those of crustose ones, usually <1 mm year(-1, in polar areas. A warming trend on Fildes Peninsula is recorded in the period from 1969 to 2010 obviously: the mean annual temperature rose from -2.75 to -1.9°C and the average temperature of summer months from 0.95 to 1.4°C, as well as the average temperature of winter months from -6.75 to -5.5°C. The alteration of lichen growth rates in polar areas may respond to the climatic and environmental changes, and the lichens may act as bio-monitor of natural condition.

  13. Predicting Lexical Density Growth Rate in Young Children with Autism Spectrum Disorders

    Science.gov (United States)

    Yoder, Paul J.

    2006-01-01

    Purpose: The purpose of this longitudinal correlational study was to test whether an environmental variable and 4 child variables predicted growth rate of number of different nonimitative words used (i.e., lexical density). Method: Thirty-five young (age range = 21-54 months) children with autism spectrum disorders (ASD) who were initially…

  14. Growth rate of multiple intracranial hydatid cysts assessed by CT from the time of embolisation

    Energy Technology Data Exchange (ETDEWEB)

    Evliyaoglu, C.; Yuksel, M.; Gul, B.; Kaptanoglu, E.; Yaman, M. [Ankara Numune Hastanesi, Beyin Cerrahisi Klinigi, Ankara (Turkey)

    1998-06-01

    We report the case of a 25-year-old man with multiple bilateral hydatid cysts of the brain in whom we were able to assess the growth rate of the cysts on repeated examination. On average, the cysts increased in diameter by 1 cm per month. (orig.) With 5 figs., 6 refs.

  15. Wavelength dependence of the linear growth rate of the Es layer instability

    Directory of Open Access Journals (Sweden)

    R. B. Cosgrove

    2007-06-01

    Full Text Available It has recently been shown, by computation of the linear growth rate, that midlatitude sporadic-E (Es layers are subject to a large scale electrodynamic instability. This instability is a logical candidate to explain certain frontal structuring events, and polarization electric fields, which have been observed in Es layers by ionosondes, by coherent scatter radars, and by rockets. However, the original growth rate derivation assumed an infinitely thin Es layer, and therefore did not address the short wavelength cutoff. Also, the same derivation ignored the effects of F region loading, which is a significant wavelength dependent effect. Herein is given a generalized derivation that remedies both these short comings, and thereby allows a computation of the wavelength dependence of the linear growth rate, as well as computations of various threshold conditions. The wavelength dependence of the linear growth rate is compared with observed periodicities, and the role of the zeroth order meridional wind is explored. A three-dimensional paper model is used to explain the instability geometry, which has been defined formally in previous works.

  16. A Study on the Rate of Contribution of Education Investment to the Economic Growth in China

    Science.gov (United States)

    Fan, Bo-nai; Lai, Xiong-xiang

    2006-01-01

    There is an evident bi-directional causality relationship between education investment and economic growth based on an analysis of statistics from 1952 to 2003 released by the State Statistics Bureau. A generalized difference regression model is set up to investigate the relationship between the two. Studies show that the rate of contribution of…

  17. Quantitative physiology of Lactococcus lactis at extreme low-growth rates

    NARCIS (Netherlands)

    Ercan, O.; Smid, E.J.; Kleerebezem, M.

    2013-01-01

    This paper describes the metabolic adaptation of Lactococcus lactis during the transition from a growing to a non-growing state using retentostat cultivation. Under retentostat cultivation, the specific growth rate decreased from 0.025 h-1 to 0.0001 h-1 in 42 days, while doubling time increased to m

  18. Influence of High Strength Steel Microstructure on Fatigue Crack Growth Rate

    Directory of Open Access Journals (Sweden)

    Enefola S. Ameh

    2016-07-01

    Full Text Available This study examines the effect of high strength steel microstructure morphology on fatigue crack growth rate (FCGR. To achieve this aim, three different heat treatment methods (normalizing, austempering quenching and tempering were considered and all the steel specimens were initially heated to 9500C austenization temperature for ninety minutes and then processed via the different heat treatment methods before viewing the resultant microstructures under light optical microscope (LOM. Fatigue crack growth rate tests were conducted on the resultant microstructures with compact tension specimens at room temperature as prescribed by American standard testing method E647. Results of FCGR tests showed normalized microstructure has the lowest FCGR (6.2698E-06, followed by quenched and tempered (7.9519E-06, asreceived (8.15E-06 and austempered (9.6667E-06 microstructure considering a low stress intensity factor range. The trend of results showed insignificant effect of microstructure over the Paris regime growth indicating fatigue crack growth rate is not a reliable parameter for correlating rate of crack propagation to microstructure

  19. Population Growth Rates: Connecting Mathematics to Studies of Society and the Environment

    Science.gov (United States)

    Ninbet, Steven; Hurley, Gabrielle; Weldon, Elizabeth

    2006-01-01

    This article reports on the teaching of a unit of lessons which integrates mathematics with studies of society and the environment. The unit entitled "Population Growth Rates" was taught to a double class of Year 6 students by a team of three teachers. The objectives of the unit were: (1) to provide students with a real-world context in which to…

  20. Maximum Likelihood based comparison of the specific growth rates for P. aeruginosa and four mutator strains

    DEFF Research Database (Denmark)

    Philipsen, Kirsten Riber; Christiansen, Lasse Engbo; Mandsberg, Lotte Frigaard;

    2008-01-01

    that the specific growth rate is the same for all bacteria strains. This study highlights the importance of carrying out an explorative examination of residuals in order to make a correct parametrization of a model including the covariance structure. The ML method is shown to be a strong tool as it enables...