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Sample records for biofilm growth kinetics

  1. An experimental model of COD abatement in MBBR based on biofilm growth dynamic and on substrates' removal kinetics.

    PubMed

    Siciliano, Alessio; De Rosa, Salvatore

    2016-08-01

    In this study, the performance of a lab-scale Moving Bed Biofilm Reactor (MBBR) under different operating conditions was analysed. Moreover, the dependence of the reaction rates both from the concentration and biodegradability of substrates and from the biofilm surface density, by means of several batch kinetic tests, was investigated. The reactor controls exhibited an increasing COD (Chemical Oxygen Demand) removal, reaching maximum yields (close to 90%) for influent loadings of up to12.5 gCOD/m(2)d. From this value, the pilot plant performance decreased to yields of only about 55% for influent loadings greater than 16 gCOD/m(2)d. In response to the influent loading increase, the biofilm surface density exhibited a logistic growing trend until reaching a maximum amount of total attached solids of about 9.5 g/m(2). The kinetic test results indicated that the COD removal rates for rapidly biodegradable, rapidly hydrolysable and slowly biodegradable substrates were not affected by the organic matter concentrations. Instead, first-order kinetics were detected with respect to biofilm surface density. The experimental results permitted the formulation of a mathematical model to predict the MBBR organic matter removal efficiency. The validity of the model was successfully tested in the lab-scale plant. PMID:26758696

  2. Dissipative-particle-dynamics model of biofilm growth

    SciTech Connect

    Xu, Zhijie; Meakin, Paul; Tartakovsky, Alexandre M.; Scheibe, Timothy D.

    2011-06-13

    A dissipative particle dynamics (DPD) model for the quantitative simulation of biofilm growth controlled by substrate (nutrient) consumption, advective and diffusive substrate transport, and hydrodynamic interactions with fluid flow (including fragmentation and reattachment) is described. The model was used to simulate biomass growth, decay, and spreading. It predicts how the biofilm morphology depends on flow conditions, biofilm growth kinetics, the rheomechanical properties of the biofilm and adhesion to solid surfaces. The morphology of the model biofilm depends strongly on its rigidity and the magnitude of the body force that drives the fluid over the biofilm.

  3. Comparative Kinetic Studies and Performance Evaluation of Biofilm and Biomass Characteristics of Pseudomonas fluorescens in Degrading Synthetic Phenolic Effluent in Inverse Fluidized Bed Biofilm Reactor.

    PubMed

    Begum, S Sabarunisha; Radha, K V

    2016-05-01

    The bioremediation potential of Pseudomonas fluorescens was studied in an Inverse Fluidized Bed Biofilm Reactor under batch recirculation conditions using synthetic phenolic effluent of various concentrations (400, 600, 800, 1000 and 1200 mg/l). The performance of the reactor was investigated and the characteristics of biomass and biofilm were determined by evaluating biofilm dry density and thickness, bioparticle density, suspended and attached biomass concentration, chemical oxygen demand and phenol removal efficiency. Biodegradation kinetics had been studied for suspended biomass culture and biofilm systems with respect to its specific growth and substrate consumption rates. Suspended biomass followed substrate inhibition kinetics and the experimental data fitted well with the Haldane model. The degradation kinetic behavior of biofilm revealed that a well adapted biofilm system with effective control of biofilm thickness in an inverse fluidized bed biofilm reactor overcomes substrate inhibition effects by tolerating higher phenol concentration and fitted well to the Monod model. PMID:27131305

  4. Biofilm growth on rugose surfaces

    NASA Astrophysics Data System (ADS)

    Rodriguez, D.; Einarsson, B.; Carpio, A.

    2012-12-01

    A stochastic model is used to assess the effect of external parameters on the development of submerged biofilms on smooth and rough surfaces. The model includes basic cellular mechanisms, such as division and spreading, together with an elementary description of the interaction with the surrounding flow and probabilistic rules for extracellular polymeric substance matrix generation, cell decay, and adhesion. Insight into the interplay of competing mechanisms such as the flow or the nutrient concentration change is gained. Erosion and growth processes combined produce biofilm structures moving downstream. A rich variety of patterns are generated: shrinking biofilms, patches, ripplelike structures traveling downstream, fingers, mounds, streamerlike patterns, flat layers, and porous and dendritic structures. The observed regimes depend on the carbon source and the type of bacteria.

  5. Differential growth of wrinkled biofilms

    NASA Astrophysics Data System (ADS)

    Espeso, D. R.; Carpio, A.; Einarsson, B.

    2015-02-01

    Biofilms are antibiotic-resistant bacterial aggregates that grow on moist surfaces and can trigger hospital-acquired infections. They provide a classical example in biology where the dynamics of cellular communities may be observed and studied. Gene expression regulates cell division and differentiation, which affect the biofilm architecture. Mechanical and chemical processes shape the resulting structure. We gain insight into the interplay between cellular and mechanical processes during biofilm development on air-agar interfaces by means of a hybrid model. Cellular behavior is governed by stochastic rules informed by a cascade of concentration fields for nutrients, waste, and autoinducers. Cellular differentiation and death alter the structure and the mechanical properties of the biofilm, which is deformed according to Föppl-Von Kármán equations informed by cellular processes and the interaction with the substratum. Stiffness gradients due to growth and swelling produce wrinkle branching. We are able to reproduce wrinkled structures often formed by biofilms on air-agar interfaces, as well as spatial distributions of differentiated cells commonly observed with B. subtilis.

  6. Biofilm Formation Mechanisms of Pseudomonas aeruginosa Predicted via Genome-Scale Kinetic Models of Bacterial Metabolism

    PubMed Central

    Vital-Lopez, Francisco G.; Reifman, Jaques; Wallqvist, Anders

    2015-01-01

    A hallmark of Pseudomonas aeruginosa is its ability to establish biofilm-based infections that are difficult to eradicate. Biofilms are less susceptible to host inflammatory and immune responses and have higher antibiotic tolerance than free-living planktonic cells. Developing treatments against biofilms requires an understanding of bacterial biofilm-specific physiological traits. Research efforts have started to elucidate the intricate mechanisms underlying biofilm development. However, many aspects of these mechanisms are still poorly understood. Here, we addressed questions regarding biofilm metabolism using a genome-scale kinetic model of the P. aeruginosa metabolic network and gene expression profiles. Specifically, we computed metabolite concentration differences between known mutants with altered biofilm formation and the wild-type strain to predict drug targets against P. aeruginosa biofilms. We also simulated the altered metabolism driven by gene expression changes between biofilm and stationary growth-phase planktonic cultures. Our analysis suggests that the synthesis of important biofilm-related molecules, such as the quorum-sensing molecule Pseudomonas quinolone signal and the exopolysaccharide Psl, is regulated not only through the expression of genes in their own synthesis pathway, but also through the biofilm-specific expression of genes in pathways competing for precursors to these molecules. Finally, we investigated why mutants defective in anthranilate degradation have an impaired ability to form biofilms. Alternative to a previous hypothesis that this biofilm reduction is caused by a decrease in energy production, we proposed that the dysregulation of the synthesis of secondary metabolites derived from anthranilate and chorismate is what impaired the biofilms of these mutants. Notably, these insights generated through our kinetic model-based approach are not accessible from previous constraint-based model analyses of P. aeruginosa biofilm

  7. Cellular growth in biofilms

    SciTech Connect

    Wood, B.D.; Whitaker, S.

    1999-09-20

    In this paper the authors develop a macroscopic evolutionary equation for the growth of the cellular phase starting from a microscopic description of mass transport and a simple structured model for product formation. The methods of continuum mechanics and volume averaging are used to develop the macroscopic representation by carefully considering the fluxes of chemical species that pertain to cell growth. The concept of structured models is extended to include the transport of reacting chemical species at the microscopic scale. The resulting macroscopic growth model is similar in form to previously published models for the transport of a single substrate and electron donor and for the production of cellular mass and exopolymer. The method of volume averaging indicated under what conditions the developed growth model is valid and provides an explicit connection between the relevant microscopic model parameters and their corresponding macroscopic counterparts.

  8. On growth and form of Bacillus subtilis biofilms.

    PubMed

    Dervaux, Julien; Magniez, Juan Carmelo; Libchaber, Albert

    2014-12-01

    A general feature of mature biofilms is their highly heterogeneous architecture that partitions the microbial city into sectors with specific micro-environments. To understand how this heterogeneity arises, we have investigated the formation of a microbial community of the model organism Bacillus subtilis. We first show that the growth of macroscopic colonies is inhibited by the accumulation of ammoniacal by-products. By constraining biofilms to grow approximately as two-dimensional layers, we then find that the bacteria which differentiate to produce extracellular polymeric substances form tightly packed bacterial chains. In addition to the process of cellular chaining, the biomass stickiness also strongly hinders the reorganization of cells within the biofilm. Based on these observations, we then write a biomechanical model for the growth of the biofilm where the cell density is constant and the physical mechanism responsible for the spreading of the biomass is the pressure generated by the division of the bacteria. Besides reproducing the velocity field of the biomass across the biofilm, the model predicts that, although bacteria divide everywhere in the biofilm, fluctuations in the growth rates of the bacteria lead to a coarsening of the growing bacterial layer. This process of kinetic roughening ultimately leads to the formation of a rough biofilm surface exhibiting self-similar properties. Experimental measurements of the biofilm texture confirm these predictions. PMID:25485075

  9. On growth and form of Bacillus subtilis biofilms

    PubMed Central

    Dervaux, Julien; Magniez, Juan Carmelo; Libchaber, Albert

    2014-01-01

    A general feature of mature biofilms is their highly heterogeneous architecture that partitions the microbial city into sectors with specific micro-environments. To understand how this heterogeneity arises, we have investigated the formation of a microbial community of the model organism Bacillus subtilis. We first show that the growth of macroscopic colonies is inhibited by the accumulation of ammoniacal by-products. By constraining biofilms to grow approximately as two-dimensional layers, we then find that the bacteria which differentiate to produce extracellular polymeric substances form tightly packed bacterial chains. In addition to the process of cellular chaining, the biomass stickiness also strongly hinders the reorganization of cells within the biofilm. Based on these observations, we then write a biomechanical model for the growth of the biofilm where the cell density is constant and the physical mechanism responsible for the spreading of the biomass is the pressure generated by the division of the bacteria. Besides reproducing the velocity field of the biomass across the biofilm, the model predicts that, although bacteria divide everywhere in the biofilm, fluctuations in the growth rates of the bacteria lead to a coarsening of the growing bacterial layer. This process of kinetic roughening ultimately leads to the formation of a rough biofilm surface exhibiting self-similar properties. Experimental measurements of the biofilm texture confirm these predictions. PMID:25485075

  10. A new approach for development of kinetics of wastewater treatment in aerobic biofilm reactor

    NASA Astrophysics Data System (ADS)

    Goswami, S.; Sarkar, S.; Mazumder, D.

    2016-02-01

    Biofilm process is widely used for the treatment of a variety of wastewater especially containing slowly biodegradable substances. It provides resistance against toxic environment and is capable of retaining biomass under continuous operation. Development of kinetics is very much pertinent for rational design of a biofilm process for the treatment of wastewater with or without inhibitory substances. A simple approach for development of such kinetics for an aerobic biofilm reactor has been presented using a novel biofilm model. The said biofilm model is formulated from the correlations between substrate concentrations in the influent/effluent and at biofilm liquid interface along with substrate flux and biofilm thickness complying Monod's growth kinetics. The methodology for determining the kinetic coefficients for substrate removal and biomass growth has been demonstrated stepwise along with graphical representations. Kinetic coefficients like K, k, Y, b t, b s, and b d are determined either from the intercepts of X- and Y-axis or from the slope of the graphical plots.

  11. Biofilm Growth and Detachment of Actinobacillus actinomycetemcomitans

    PubMed Central

    Kaplan, Jeffrey B.; Meyenhofer, Markus F.; Fine, Daniel H.

    2003-01-01

    The gram-negative, oral bacterium Actinobacillus actinomycetemcomitans has been implicated as the causative agent of several forms of periodontal disease in humans. When cultured in broth, fresh clinical isolates of A. actinomycetemcomitans form tenacious biofilms on surfaces such as glass, plastic, and saliva-coated hydroxyapatite, a property that probably plays an important role in the ability of this bacterium to colonize the oral cavity and cause disease. We examined the morphology of A. actinomycetemcomitans biofilm colonies grown on glass slides and in polystyrene petri dishes by using light microscopy and scanning and transmission electron microscopy. We found that A. actinomycetemcomitans developed asymmetric, lobed biofilm colonies that displayed complex architectural features, including a layer of densely packed cells on the outside of the colony and nonaggregated cells and large, transparent cavities on the inside of the colony. Mature biofilm colonies released single cells or small clusters of cells into the medium. These released cells adhered to the surface of the culture vessel and formed new colonies, enabling the biofilm to spread. We isolated three transposon insertion mutants which produced biofilm colonies that lacked internal, nonaggregated cells and were unable to release cells into the medium. All three transposon insertions mapped to genes required for the synthesis of the O polysaccharide (O-PS) component of lipopolysaccharide. Plasmids carrying the complementary wild-type genes restored the ability of mutant strains to synthesize O-PS and release cells into the medium. Our findings suggest that A. actinomycetemcomitans biofilm growth and detachment are discrete processes and that biofilm cell detachment evidently involves the formation of nonaggregated cells inside the biofilm colony that are destined for release from the colony. PMID:12562811

  12. Hierarchical simulator of biofilm growth and dynamics in granular porous materials

    NASA Astrophysics Data System (ADS)

    Kapellos, George E.; Alexiou, Terpsichori S.; Payatakes, Alkiviades C.

    2007-06-01

    A new simulator is developed for the prediction of the rate and pattern of growth of biofilms in granular porous media. The biofilm is considered as a heterogeneous porous material that exhibits a hierarchy of length scales. An effective-medium model is used to calculate the local hydraulic permeability and diffusion coefficient in the biofilm, as functions of the local geometric and physicochemical properties. The Navier-Stokes equations and the Brinkman equation are solved numerically to determine the velocity and pressure fields within the pore space and the biofilm, respectively. Biofilm fragments become detached if they are exposed to shear stress higher than a critical value. The detached fragments re-enter into the fluid stream and move within the pore space until they exit from the system or become reattached to downstream grain or biofilm surfaces. A Lagrangian-type simulation is used to determine the trajectories of detached fragments. The spatiotemporal distributions of a carbon source, an electron acceptor and a cell-to-cell signaling molecule are determined from the numerical solution of the governing convection-diffusion-reaction equations. The simulator incorporates growth and apoptosis kinetics for the bacterial cells and production and lysis kinetics for the EPS. The specific growth rate of active bacterial cells depends on the local concentrations of nutrients, mechanical stresses, and a quorum sensing mechanism. Growth-induced deformation of the biofilms is implemented with a cellular automaton approach. In this work, the spatiotemporal evolution of biofilms in the pore space of a 2D granular medium is simulated under high flow rate and nutrient-rich conditions. Transient changes in the pore geometry caused by biofilm growth lead to the formation of preferential flowpaths within the granular porous medium. The decrease of permeability caused by clogging of the porous medium is calculated and is found to be in qualitative agreement with published

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  14. Embedded biofilm, a new biofilm model based on the embedded growth of bacteria.

    PubMed

    Jung, Yong-Gyun; Choi, Jungil; Kim, Soo-Kyoung; Lee, Joon-Hee; Kwon, Sunghoon

    2015-01-01

    A variety of systems have been developed to study biofilm formation. However, most systems are based on the surface-attached growth of microbes under shear stress. In this study, we designed a microfluidic channel device, called a microfluidic agarose channel (MAC), and found that microbial cells in the MAC system formed an embedded cell aggregative structure (ECAS). ECASs were generated from the embedded growth of bacterial cells in an agarose matrix and better mimicked the clinical environment of biofilms formed within mucus or host tissue under shear-free conditions. ECASs were developed with the production of extracellular polymeric substances (EPS), the most important feature of biofilms, and eventually burst to release planktonic cells, which resembles the full developmental cycle of biofilms. Chemical and genetic effects have also confirmed that ECASs are a type of biofilm. Unlike the conventional biofilms formed in the flow cell model system, this embedded-type biofilm completes the developmental cycle in only 9 to 12 h and can easily be observed with ordinary microscopes. We suggest that ECASs are a type of biofilm and that the MAC is a system for observing biofilm formation. PMID:25326307

  15. Embedded Biofilm, a New Biofilm Model Based on the Embedded Growth of Bacteria

    PubMed Central

    Jung, Yong-Gyun; Choi, Jungil; Kim, Soo-Kyoung

    2014-01-01

    A variety of systems have been developed to study biofilm formation. However, most systems are based on the surface-attached growth of microbes under shear stress. In this study, we designed a microfluidic channel device, called a microfluidic agarose channel (MAC), and found that microbial cells in the MAC system formed an embedded cell aggregative structure (ECAS). ECASs were generated from the embedded growth of bacterial cells in an agarose matrix and better mimicked the clinical environment of biofilms formed within mucus or host tissue under shear-free conditions. ECASs were developed with the production of extracellular polymeric substances (EPS), the most important feature of biofilms, and eventually burst to release planktonic cells, which resembles the full developmental cycle of biofilms. Chemical and genetic effects have also confirmed that ECASs are a type of biofilm. Unlike the conventional biofilms formed in the flow cell model system, this embedded-type biofilm completes the developmental cycle in only 9 to 12 h and can easily be observed with ordinary microscopes. We suggest that ECASs are a type of biofilm and that the MAC is a system for observing biofilm formation. PMID:25326307

  16. Rock Physics Models of Biofilm Growth in Porous Media

    NASA Astrophysics Data System (ADS)

    Jaiswal, P.; alhadhrami, F. M.; Atekwana, E. A.

    2013-12-01

    Recent studies suggest the potential to use acoustic techniques to image biofilm growth in porous media. Nonetheless the interpretation of the seismic response to biofilm growth and development remains speculative because of the lack of quantitative petrophysical models that can relate changes in biofilm saturation to changes in seismic attributes. Here, we report our efforts in developing quantitative rock physics models to biofilm saturation with increasing and decreasing P-wave velocity (VP) and amplitudes recorded in the Davis et al. [2010] physical scale experiment. We adapted rock physics models developed for modeling gas hydrates in unconsolidated sediments. Two distinct growth models, which appear to be a function of pore throat size, are needed to explain the experimental data. First, introduction of biofilm as an additional mineral grain in the sediment matrix (load-bearing mode) is needed to explain the increasing time-lapse VP. Second, introduction of biofilm as part of the pore fluid (pore-filling mode) is required to explain the decreasing time-lapse VP. To explain the time-lapse VP, up to 15% of the pore volume was required to be saturated with biofilm. The recorded seismic amplitudes, which can be expressed as a function of porosity, permeability and grain size, showed a monotonic time-lapse decay except on Day 3 at a few selected locations, where it increased. Since porosity changes are constrained by VP, amplitude increase could be modeled by increasing hydraulic conductivity. Time lapse VP at locations with increasing amplitudes suggest that these locations have a load-bearing growth style. We conclude that permeability can increase by up to 10% at low (~2%) biofilm saturation in load-bearing growth style due to the development of channels within the biofilm structure. Developing a rock physics model for the biofilm growth in general may help create a field guide for interpreting porosity and permeability changes in bioremediation, MEOR and

  17. A novel fluidized bed respirometric technique for determination of in situ biofilm kinetics.

    PubMed

    Chowdhury, Nabin; Nakhla, George; Zhu, Jesse

    2012-01-01

    A respirometric approach has been developed to determine heterotrophic biofilm kinetics using fluidized bioparticles--particles with attached biomass. Lava rock particles of 600 microm were used as a biomass carrier medium. The modified respirometer successfully estimates in situ biofilm kinetics of the bioparticles collected from a pilot-scale liquid-solid circulating fluidized bed (LSCFB) bioreactor. The observed maximum specific growth rates (micro(max)) of 3.69 +/- 0.44 d(-1) and biomass yields (Y(H)) of 0.36 +/- 0.03 g COD/g COD in the fluidized bed respirometers were significantly different from the micro(max) of 5.57-5.72 d(-1) and Y(H) of 0.54-0.59 g COD/g COD observed in the conventional respirometric tests for bioparticles and detached biomass. The higher Monod half-saturation coefficient (K(S)) of 186-219mg COD/L observed in the fluidized bed respirometers relative to the 49-58 mg COD/L in the conventional respirometers reveals the presence of mass transfer resistance in the LSCFB despite fluidization. Significantly reduced yields in the fluidized bed respirometers and the estimated maintenance coefficient of 1.16 d(-1) for the particulate biofilm in the LSCFB clearly emphasize that a substantial amount of substrate was utilized for cell maintenance at the low food to microorganism (S/X) ratio of 0.5 g COD/g VSS. PMID:22629617

  18. Pherotype Influences Biofilm Growth and Recombination in Streptococcus pneumoniae

    PubMed Central

    Carrolo, Margarida; Pinto, Francisco Rodrigues; Melo-Cristino, José; Ramirez, Mário

    2014-01-01

    In Streptococcus pneumoniae the competence-stimulating peptide (CSP), encoded by the comC gene, controls competence development and influences biofilm growth. We explored the influence of pherotype, defined by the two major comC allelic variants (comC1 and comC2), on biofilm development and recombination efficiency. Among isolates recovered from human infections those presenting comC1 show a higher capacity to form in vitro biofilms. The influence of pherotype on biofilm growth was confirmed by experiments with isogenic strains differing in their comC alleles. Biofilm architecture evaluated by confocal laser scanning microscopy showed that strains carrying comC1 form biofilms that are denser and thicker than those carrying the comC2 allele. Isogenic strains carrying the comC1 allele yielded more transformants than those carrying the comC2 allele in both planktonic and biofilm growth. Transformation assays with comC knockout strains show that ComD1 needs lower doses of the signaling peptide to reach the same biological outcomes. In contrast to mixed planktonic growth, within mixed biofilms inter-pherotype genetic exchange is less frequent than that occurring between bacteria of the same pherotype. Since biofilms are a major bacterial lifestyle, these observations may explain the genetic differentiation between populations with different pherotypes reported previously. Considering that biofilms have been associated with colonization our results suggest that strains carrying the comC1 allele may be more transmissible and more efficient at persisting in carriage. Both effects may help explain the higher prevalence of the comC1 allele in the pneumococcal population. PMID:24646937

  19. Spatial & Temporal Geophysical Monitoring of Microbial Growth and Biofilm Formation

    EPA Science Inventory

    Previous studies have examined the effect of biogenic gases and biomineralization on the acoustic properties of porous media. In this study, we investigated the spatiotemporal effect of microbial growth and biofilm formation on compressional waves and complex conductivity in sand...

  20. The BioFilm Ring Test: a Rapid Method for Routine Analysis of Pseudomonas aeruginosa Biofilm Formation Kinetics

    PubMed Central

    Olivares, Elodie; Badel-Berchoux, Stéphanie; Provot, Christian; Jaulhac, Benoît; Prévost, Gilles; Bernardi, Thierry

    2015-01-01

    Currently, few techniques are available for the evaluation of bacterial biofilm adhesion. These detection tools generally require time for culture and/or arduous handling steps. In this work, the BioFilm Ring Test (BRT), a new technology, was used to estimate the biofilm formation kinetics of 25 strains of Pseudomonas aeruginosa, isolated from the sputum of cystic fibrosis (CF) patients. The principle of the new assay is based on the mobility measurement of magnetic microbeads mixed with a bacterial suspension in a polystyrene microplate. If free to move under the magnetic action, particles gather to a visible central spot in the well bottom. Therefore, the absence of spot formation in the plate reflects the bead immobilization by a biofilm in formation. The BRT device allowed us to classify the bacterial strains into three general adhesion profiles. Group 1 consists of bacteria, which are able to form a solid biofilm in <2 h. Group 2 comprises the strains that progressively set up a biofilm during 24 h. Lastly, group 3 includes the strains that stay in a planktonic form. The grouping of our strains did not differ according to culture conditions, i.e., the use of different sets of beads or culture media. The BRT is shown to be an informative tool for the characterization of biofilm-forming bacteria. Various application perspectives may be investigated for this device, such as the addition of antibiotics to the bacterial suspension to select which would have the ability to inhibit the biofilm formation. PMID:26719437

  1. The BioFilm Ring Test: a Rapid Method for Routine Analysis of Pseudomonas aeruginosa Biofilm Formation Kinetics.

    PubMed

    Olivares, Elodie; Badel-Berchoux, Stéphanie; Provot, Christian; Jaulhac, Benoît; Prévost, Gilles; Bernardi, Thierry; Jehl, François

    2016-03-01

    Currently, few techniques are available for the evaluation of bacterial biofilm adhesion. These detection tools generally require time for culture and/or arduous handling steps. In this work, the BioFilm Ring Test (BRT), a new technology, was used to estimate the biofilm formation kinetics of 25 strains of Pseudomonas aeruginosa, isolated from the sputum of cystic fibrosis (CF) patients. The principle of the new assay is based on the mobility measurement of magnetic microbeads mixed with a bacterial suspension in a polystyrene microplate. If free to move under the magnetic action, particles gather to a visible central spot in the well bottom. Therefore, the absence of spot formation in the plate reflects the bead immobilization by a biofilm in formation. The BRT device allowed us to classify the bacterial strains into three general adhesion profiles. Group 1 consists of bacteria, which are able to form a solid biofilm in <2 h. Group 2 comprises the strains that progressively set up a biofilm during 24 h. Lastly, group 3 includes the strains that stay in a planktonic form. The grouping of our strains did not differ according to culture conditions, i.e., the use of different sets of beads or culture media. The BRT is shown to be an informative tool for the characterization of biofilm-forming bacteria. Various application perspectives may be investigated for this device, such as the addition of antibiotics to the bacterial suspension to select which would have the ability to inhibit the biofilm formation. PMID:26719437

  2. Reduction Kinetics of Manganese Dioxide by Geobacter Sulfurreducens and Associated Biofilm Morphology in a Flow-Through Reactor

    NASA Astrophysics Data System (ADS)

    Berns, E.; Werth, C. J.; Valocchi, A. J.; Sanford, R. A.

    2015-12-01

    Biogeochemical interactions have been investigated extensively to characterize natural nutrient cycling and predict contaminant transport in surface and groundwater. Dissimilatory metal reducing bacteria, many of which form biofilms, play an important role in reducing a variety of metals in these systems. It has been shown that biofilm morphology is impacted by flow conditions, but there has been little work that explores how reduction kinetics change as a result of these different morphologies. Different flow rates may affect physical properties of the biofilm that influence the rate of substrate reduction. We introduce an approach to calculate changes in Monod kinetic parameters while simultaneously evaluating biofilm morphologies under different flow rates. A vertical, cylindrical flow cell with removable glass slide sections coated in manganese dioxide (electron acceptor) was used to grow a biofilm of Geobacter sulfurreducens with acetate as the electron donor under both high (50 mL/hr) and low (5 mL/h) flow rates. The removable sections allowed for visualization of the biofilm at different time points with a confocal microscope, and quantification of the biomass on the surface using a combination of a protein assay and image analysis. Data collected from the experiments was used to determine yield and specific growth rate at the different flow rates, and a simple numerical model was used to estimate the half saturation constant of manganese dioxide at both flow rates. A smaller half saturation constant was estimated at the higher flow rate, indicating that the biofilm was more efficient in the high flow system, but a strong correlation between morphology and the faster reduction rate was not observed. Monod kinetic parameters are important for the development of accurate nutrient cycling and contaminant transport models in natural environments, and understanding how they are impacted by flow will be important for the development of new, improved models.

  3. Probing phenotypic growth in expanding Bacillus subtilis biofilms.

    PubMed

    Wang, Xiaoling; Koehler, Stephan A; Wilking, James N; Sinha, Naveen N; Cabeen, Matthew T; Srinivasan, Siddarth; Seminara, Agnese; Rubinstein, Shmuel; Sun, Qingping; Brenner, Michael P; Weitz, David A

    2016-05-01

    We develop an optical imaging technique for spatially and temporally tracking biofilm growth and the distribution of the main phenotypes of a Bacillus subtilis strain with a triple-fluorescent reporter for motility, matrix production, and sporulation. We develop a calibration procedure for determining the biofilm thickness from the transmission images, which is based on Beer-Lambert's law and involves cross-sectioning of biofilms. To obtain the phenotype distribution, we assume a linear relationship between the number of cells and their fluorescence and determine the best combination of calibration coefficients that matches the total number of cells for all three phenotypes and with the total number of cells from the transmission images. Based on this analysis, we resolve the composition of the biofilm in terms of motile, matrix-producing, sporulating cells and low-fluorescent materials which includes matrix and cells that are dead or have low fluorescent gene expression. We take advantage of the circular growth to make kymograph plots of all three phenotypes and the dominant phenotype in terms of radial distance and time. To visualize the nonlocal character of biofilm growth, we also make kymographs using the local colonization time. Our technique is suitable for real-time, noninvasive, quantitative studies of the growth and phenotype distribution of biofilms which are either exposed to different conditions such as biocides, nutrient depletion, dehydration, or waste accumulation. PMID:27003268

  4. Influence of substrate micropatterning on biofilm growth

    NASA Astrophysics Data System (ADS)

    Koehler, Stephan; Li, Yiwei; Liu, Bi-Feng Liu; Weitz, David

    2015-11-01

    We culture triple reporter Bacillus Subtilis biofilm on micropatterned agar substrates. We track the biofilm development in terms of size, thickness, shape, and phenotype expression. For a tiling composed of elevated rectangles, we observe the biofilm develops an oval shape or triangular shape depending on the rectangle's aspect ratio and orientation. The motile cells are primarily located in the valleys between the rectangles and the matrix producing cells are mostly located on the rectangles. Wrinkles form at the edges of the elevated surfaces, and upon merging form channels centered on the elevated surface. After a few days, the spore-forming cells appear at the periphery. Since biofilms in nature grow on irregular surfaces, our work may provide insight into the complex patterns observed.

  5. Effects of Nicotine on Streptococcus gordonii Growth, Biofilm Formation, and Cell Aggregation.

    PubMed

    Huang, R; Li, M; Ye, M; Yang, K; Xu, X; Gregory, R L

    2014-12-01

    Streptococcus gordonii is a commensal species of human oral flora. It initiates dental biofilm formation and provides binding sites for later colonizers to attach to and generate mature biofilm. Smoking is the second highest risk factor for periodontal disease, and cigarette smoke extract has been reported to facilitate Porphyromonas gingivalis-S. gordonii dual-species biofilm formation. Our hypothesis is that nicotine, one of the most important and active components of tobacco, stimulates S. gordonii multiplication and aggregation. In the present study, S. gordonii planktonic cell growth (kinetic absorbance and CFU), biofilm formation (crystal violet stain and confocal laser scanning microscopy [CLSM]), aggregation with/without sucrose, and 11 genes that encode binding proteins or regulators of gene expression were investigated. Results demonstrated planktonic cell growth was stimulated by 1 to 4 mg/ml nicotine treatment. Biofilm formation was increased at 0.5 to 4 mg/ml nicotine. CLSM indicated bacterial cell mass was increased by 2 and 4 mg/ml nicotine, but biofilm extracellular polysaccharide was not significantly affected by nicotine. Cell aggregation was upregulated by 4, 8, and 16 mg/ml nicotine with sucrose and by 16 mg/ml nicotine without sucrose. Quantitative reverse transcriptase PCR indicated S. gordonii abpA, scaA, ccpA, and srtA were upregulated in planktonic cells by 2 mg/ml nicotine. In conclusion, nicotine stimulates S. gordonii planktonic cell growth, biofilm formation, aggregation, and gene expression of binding proteins. Those effects may promote later pathogen attachment to tooth surfaces, the accumulation of tooth calculus, and the development of periodontal disease in cigarette smokers. PMID:25217021

  6. Monitoring of microbial adhesion and biofilm growth using electrochemical impedancemetry.

    PubMed

    Dheilly, A; Linossier, I; Darchen, A; Hadjiev, D; Corbel, C; Alonso, V

    2008-05-01

    Electrochemical impedance spectroscopy was tested to monitor the cell attachment and the biofilm proliferation in order to identify characteristic events induced on the metal surface by Gram-negative (Pseudomonas aeruginosa PAO1) and Gram-positive (Bacillus subtilis) bacteria strains. Electrochemical impedance spectra of AISI 304 electrodes during cell attachment and initial biofilm growth for both strains were obtained. It can be observed that the resistance increases gradually with the culture time and decreases with the biofilm detachment. So, the applicability of electric cell-substrate impedance sensing (ECIS) for studying the attachment and spreading of cells on a metal surface has been demonstrated. The biofilm formation was also characterized by the use of scanning electron microscopy and confocal laser scanning microscopy and COMSTAT image analysis. The electrochemical results roughly agree with the microscope image observations. The ECIS technique used in this study was used for continuous real-time monitoring of the initial bacterial adhesion and the biofilm growth. It provides a simple and non-expensive electrochemical method for in vitro assessment of the presence of biofilms on metal surfaces. PMID:18330564

  7. The effect of light direction and suspended cell concentrations on algal biofilm growth rates.

    PubMed

    Schnurr, Peter J; Espie, George S; Allen, D Grant

    2014-10-01

    Algae biofilms were grown in a semicontinuous flat plate biofilm photobioreactor to study the effects of light direction and suspended algal cell populations on algal biofilm growth. It was determined that, under the growth conditions and biofilm thicknesses studied, light direction had no effect on long-term algal biofilm growth (26 days); however, light direction did affect the concentration of suspended algal cells by influencing the photon flux density in the growth medium in the photobioreactors. This suspended algal cell population affected short-term (7 days) algae cell recruitment and algal biofilm growth, but additional studies showed that enhanced suspended algal cell populations did not affect biofilm growth rates over the long term (26 days). Studying profiles of light transmittance through biofilms as they grew showed that most of the light became attenuated by the biomass after just a few days of growth (88 % after 3 days). The estimated biofilm thicknesses after these few days of growth were approximately 150 μm. The light attenuation data suggests that, although the biofilms grew to 700-900 μm, under these light intensities, only the first few hundred micrometers of the biofilm is receiving enough light to be photosynthetically active. We postulate that this photosynthetically active layer of the biofilm grows adjacent to the light source, while the rest of the biofilm is in a stationary growth phase. The results of this study have implications for algal biofilm photobioreactor design and operation. PMID:25149444

  8. Evaluation of Anaerobic Biofilm Reactor Kinetic Parameters Using Ant Colony Optimization.

    PubMed

    Satya, Eswari Jujjavarapu; Venkateswarlu, Chimmiri

    2013-09-01

    Fixed bed reactors with naturally attached biofilms are increasingly used for anaerobic treatment of industry wastewaters due their effective treatment performance. The complex nature of biological reactions in biofilm processes often poses difficulty in analyzing them experimentally, and mathematical models could be very useful for their design and analysis. However, effective application of biofilm reactor models to practical problems suffers due to the lack of knowledge of accurate kinetic models and uncertainty in model parameters. In this work, an inverse modeling approach based on ant colony optimization is proposed and applied to estimate the kinetic and film thickness model parameters of wastewater treatment process in an anaerobic fixed bed biofilm reactor. Experimental data of pharmaceutical industry wastewater treatment process are used to determine the model parameters as a consequence of the solution of the rigorous mathematical models of the process. Results were evaluated for different modeling configurations derived from the combination of mathematical models, kinetic expressions, and optimization algorithms. Analysis of results showed that the two-dimensional mathematical model with Haldane kinetics better represents the pharmaceutical wastewater treatment in the biofilm reactor. The mathematical and kinetic modeling of this work forms a useful basis for the design and optimization of industry wastewater treating biofilm reactors. PMID:24065871

  9. Evaluation of Anaerobic Biofilm Reactor Kinetic Parameters Using Ant Colony Optimization

    PubMed Central

    Satya, Eswari Jujjavarapu; Venkateswarlu, Chimmiri

    2013-01-01

    Abstract Fixed bed reactors with naturally attached biofilms are increasingly used for anaerobic treatment of industry wastewaters due their effective treatment performance. The complex nature of biological reactions in biofilm processes often poses difficulty in analyzing them experimentally, and mathematical models could be very useful for their design and analysis. However, effective application of biofilm reactor models to practical problems suffers due to the lack of knowledge of accurate kinetic models and uncertainty in model parameters. In this work, an inverse modeling approach based on ant colony optimization is proposed and applied to estimate the kinetic and film thickness model parameters of wastewater treatment process in an anaerobic fixed bed biofilm reactor. Experimental data of pharmaceutical industry wastewater treatment process are used to determine the model parameters as a consequence of the solution of the rigorous mathematical models of the process. Results were evaluated for different modeling configurations derived from the combination of mathematical models, kinetic expressions, and optimization algorithms. Analysis of results showed that the two-dimensional mathematical model with Haldane kinetics better represents the pharmaceutical wastewater treatment in the biofilm reactor. The mathematical and kinetic modeling of this work forms a useful basis for the design and optimization of industry wastewater treating biofilm reactors. PMID:24065871

  10. Modeling of the Bacillus subtilis Bacterial Biofilm Growing on an Agar Substrate.

    PubMed

    Wang, Xiaoling; Wang, Guoqing; Hao, Mudong

    2015-01-01

    Bacterial biofilms are organized communities composed of millions of microorganisms that accumulate on almost any kinds of surfaces. In this paper, a biofilm growth model on an agar substrate is developed based on mass conservation principles, Fick's first law, and Monod's kinetic reaction, by considering nutrient diffusion between biofilm and agar substrate. Our results show biofilm growth evolution characteristics such as biofilm thickness, active biomass, and nutrient concentration in the agar substrate. We quantitatively obtain biofilm growth dependence on different parameters. We provide an alternative mathematical method to describe other kinds of biofilm growth such as multiple bacterial species biofilm and also biofilm growth on various complex substrates. PMID:26355542

  11. Modeling of the Bacillus subtilis Bacterial Biofilm Growing on an Agar Substrate

    PubMed Central

    Wang, Xiaoling; Wang, Guoqing; Hao, Mudong

    2015-01-01

    Bacterial biofilms are organized communities composed of millions of microorganisms that accumulate on almost any kinds of surfaces. In this paper, a biofilm growth model on an agar substrate is developed based on mass conservation principles, Fick's first law, and Monod's kinetic reaction, by considering nutrient diffusion between biofilm and agar substrate. Our results show biofilm growth evolution characteristics such as biofilm thickness, active biomass, and nutrient concentration in the agar substrate. We quantitatively obtain biofilm growth dependence on different parameters. We provide an alternative mathematical method to describe other kinds of biofilm growth such as multiple bacterial species biofilm and also biofilm growth on various complex substrates. PMID:26355542

  12. Nucleation and growth transformation kinetics

    NASA Astrophysics Data System (ADS)

    Erukhimovitch, V.; Baram, J.

    1995-03-01

    As a result of the reassessment of the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory for the kinetics of nucleation and growth transformations, an integral-equation formulation has been developed instead of the well-known and widely used Avrami equation. The presented formulation considers interfacial and diffusional growths, in one, two, and three dimensions, with both time-dependent and time-invariant nucleation and growth rates. The integral-equation model corrects reported inadequacies of the KJMA theory when applied in numerous experiments and various solid-state transformations. It is shown that in the example cases examined in this paper, crystallization from the amorphous state in melt-spun ribbons, isothermal aging of CuAlZn, pearlitic transition in an eutectoid steel, and crystallization in a PEKK polymer, the thermodynamic and kinetic interpretation and parameters extracted from best fits of the Avrami equations to the experimental data are erroneous. The KJMA formulation is a simplification of the real physical conditions. The main limitation of the new model is that almost all the integral equations representing the kinetics of solid-state transformations have no analytical solutions.

  13. Effect of Honey on Streptococcus mutans Growth and Biofilm Formation

    PubMed Central

    Li, Mingyun

    2012-01-01

    Because of the tradition of using honey as an antimicrobial medicament, we investigated the effect of natural honey (NH) on Streptococcus mutans growth, viability, and biofilm formation compared to that of an artificial honey (AH). AH contained the sugars at the concentrations reported for NH. NH and AH concentrations were obtained by serial dilution with tryptic soy broth (TSB). Several concentrations of NH and AH were tested for inhibition of bacterial growth, viability, and biofilm formation after inoculation with S. mutans UA159 in 96-well microtiter plates to obtain absorbance and CFU values. Overall, NH supported significantly less (P < 0.05) bacterial growth than AH at 25 and 12.5% concentrations. At 50 and 25% concentrations, both honey groups provided significantly less bacterial growth and biofilm formation than the TSB control. For bacterial viability, the results for all honey concentrations except 50% NH were not significantly different from those for the TSB control. NH was able to decrease the maximum velocity of S. mutans growth compared to AH. In summary, NH demonstrated more inhibition of bacterial growth, viability, and biofilm formation than AH. This study highlights the potential antibacterial properties of NH and could suggest that the antimicrobial mechanism of NH is not solely due to its high sugar content. PMID:22038612

  14. Inactivation kinetics of various chemical disinfectants on Aeromonas hydrophila planktonic cells and biofilms.

    PubMed

    Jahid, Iqbal Kabir; Ha, Sang-Do

    2014-05-01

    The present article focuses on the inactivation kinetics of various disinfectants including ethanol, sodium hypochlorite, hydrogen peroxide, peracetic acid, and benzalkonium chloride against Aeromonas hydrophila biofilms and planktonic cells. Efficacy was determined by viable plate count and compared using a modified Weibull model. The removal of the biofilms matrix was determined by the crystal violet assay and was confirmed by field-emission scanning electron microscope. The results revealed that all the experimental data and calculated Weibull α (scale) and β (shape) parameters had a good fit, as the R(2) values were between 0.88 and 0.99. Biofilms are more resistant to disinfectants than planktonic cells. Ethanol (70%) was the most effective in killing cells in the biofilms and significantly reduced (p<0.05) the biofilms matrix. The Weibull parameter b-value correlated (R(2)=0.6835) with the biofilms matrix removal. The present findings deduce that the Weibull model is suitable to determine biofilms matrix reduction as well as the effectiveness of chemical disinfectants on biofilms. The study showed that the Weibull model could successfully be used on food and food contact surfaces to determine the exact contact time for killing biofilms-forming foodborne pathogens. PMID:24552163

  15. Mechanistic models of biofilm growth in porous media

    NASA Astrophysics Data System (ADS)

    Jaiswal, Priyank; Al-Hadrami, Fathiya; Atekwana, Estella A.; Atekwana, Eliot A.

    2014-07-01

    Nondestructive acoustics methods can be used to monitor in situ biofilm growth in porous media. In practice, however, acoustic methods remain underutilized due to the lack of models that can translate acoustic data into rock properties in the context of biofilm. In this paper we present mechanistic models of biofilm growth in porous media. The models are used to quantitatively interpret arrival times and amplitudes recorded in the 29 day long Davis et al. (2010) physical scale biostimulation experiment in terms of biofilm morphologies and saturation. The model pivots on addressing the sediment elastic behavior using the lower Hashin-Shtrikman bounds for grain mixing and Gassmann substitution for fluid saturation. The time-lapse P wave velocity (VP; a function of arrival times) is explained by a combination of two rock models (morphologies); "load bearing" which assumes the biofilm as an additional mineral in the rock matrix and "pore filling" which assumes the biofilm as an additional fluid phase in the pores. The time-lapse attenuation (QP-1; a function of amplitudes), on the other hand, can be explained adequately in two ways; first, through squirt flow where energy is lost from relative motion between rock matrix and pore fluid, and second, through an empirical function of porosity (φ), permeability (κ), and grain size. The squirt flow model-fitting results in higher internal φ (7% versus 5%) and more oblate pores (0.33 versus 0.67 aspect ratio) for the load-bearing morphology versus the pore-filling morphology. The empirical model-fitting results in up to 10% increase in κ at the initial stages of the load-bearing morphology. The two morphologies which exhibit distinct mechanical and hydraulic behavior could be a function of pore throat size. The biofilm mechanistic models developed in this study can be used for the interpretation of seismic data critical for the evaluation of biobarriers in bioremediation, microbial enhanced oil recovery, and CO2

  16. Micropollutant removal by attached and suspended growth in a hybrid biofilm-activated sludge process.

    PubMed

    Falås, P; Longrée, P; la Cour Jansen, J; Siegrist, H; Hollender, J; Joss, A

    2013-09-01

    Removal of organic micropollutants in a hybrid biofilm-activated sludge process was investigated through batch experiments, modeling, and full-scale measurements. Batch experiments with carriers and activated sludge from the same full-scale reactor were performed to assess the micropollutant removal rates of the carrier biofilm under oxic conditions and the sludge under oxic and anoxic conditions. Clear differences in the micropollutant removal kinetics of the attached and suspended growth were demonstrated, often with considerably higher removal rates for the biofilm compared to the sludge. For several micropollutants, the removal rates were also affected by the redox conditions, i.e. oxic and anoxic. Removal rates obtained from the batch experiments were used to model the micropollutant removal in the full-scale process. The results from the model and plant measurements showed that the removal efficiency of the process can be predicted with acceptable accuracy (± 25%) for most of the modeled micropollutants. Furthermore, the model estimations indicate that the attached growth in hybrid biofilm-activated sludge processes can contribute significantly to the removal of individual compounds, such as diclofenac. PMID:23764599

  17. Adhesion and removal kinetics of Bacillus cereus biofilms on Ni-PTFE modified stainless steel.

    PubMed

    Huang, Kang; McLandsborough, Lynne A; Goddard, Julie M

    2016-01-01

    Biofilm control remains a challenge to food safety. A well-studied non-fouling coating involves codeposition of polytetrafluoroethylene (PTFE) during electroless plating. This coating has been reported to reduce foulant build-up during pasteurization, but opportunities remain in demonstrating its efficacy in inhibiting biofilm formation. Herein, the initial adhesion, biofilm formation, and removal kinetics of Bacillus cereus on Ni-PTFE-modified stainless steel (SS) are characterized. Coatings lowered the surface energy of SS and reduced biofilm formation by > 2 log CFU cm(-2). Characterization of the kinetics of biofilm removal during cleaning demonstrated improved cleanability on the Ni-PTFE coated steel. There was no evidence of biofilm after cleaning by either solution on the Ni-PTFE coated steel, whereas more than 3 log and 1 log CFU cm(-2) of bacteria remained on the native steel after cleaning with water and an alkaline cleaner, respectively. This work demonstrates the potential application of Ni-PTFE non-fouling coatings on SS to improve food safety by reducing biofilm formation and improving the cleaning efficiency of food processing equipment. PMID:27020838

  18. Inverse modeling approach for evaluation of kinetic parameters of a biofilm reactor using tabu search.

    PubMed

    Kumar, B Shiva; Venkateswarlu, Ch

    2014-08-01

    The complex nature of biological reactions in biofilm reactors often poses difficulties in analyzing such reactors experimentally. Mathematical models could be very useful for their design and analysis. However, application of biofilm reactor models to practical problems proves somewhat ineffective due to the lack of knowledge of accurate kinetic models and uncertainty in model parameters. In this work, we propose an inverse modeling approach based on tabu search (TS) to estimate the parameters of kinetic and film thickness models. TS is used to estimate these parameters as a consequence of the validation of the mathematical models of the process with the aid of measured data obtained from an experimental fixed-bed anaerobic biofilm reactor involving the treatment of pharmaceutical industry wastewater. The results evaluated for different modeling configurations of varying degrees of complexity illustrate the effectiveness of TS for accurate estimation of kinetic and film thickness model parameters of the biofilm process. The results show that the two-dimensional mathematical model with Edward kinetics (with its optimum parameters as mu(max)rho(s)/Y = 24.57, Ks = 1.352 and Ki = 102.36) and three-parameter film thickness expression (with its estimated parameters as a = 0.289 x 10(-5), b = 1.55 x 10(-4) and c = 15.2 x 10(-6)) better describes the biofilm reactor treating the industry wastewater. PMID:25306783

  19. Transcriptomic and proteomic analyses of Desulfovibrio vulgaris biofilms: Carbon and energy flow contribute to the distinct biofilm growth state

    PubMed Central

    2012-01-01

    Background Desulfovibrio vulgaris Hildenborough is a sulfate-reducing bacterium (SRB) that is intensively studied in the context of metal corrosion and heavy-metal bioremediation, and SRB populations are commonly observed in pipe and subsurface environments as surface-associated populations. In order to elucidate physiological changes associated with biofilm growth at both the transcript and protein level, transcriptomic and proteomic analyses were done on mature biofilm cells and compared to both batch and reactor planktonic populations. The biofilms were cultivated with lactate and sulfate in a continuously fed biofilm reactor, and compared to both batch and reactor planktonic populations. Results The functional genomic analysis demonstrated that biofilm cells were different compared to planktonic cells, and the majority of altered abundances for genes and proteins were annotated as hypothetical (unknown function), energy conservation, amino acid metabolism, and signal transduction. Genes and proteins that showed similar trends in detected levels were particularly involved in energy conservation such as increases in an annotated ech hydrogenase, formate dehydrogenase, pyruvate:ferredoxin oxidoreductase, and rnf oxidoreductase, and the biofilm cells had elevated formate dehydrogenase activity. Several other hydrogenases and formate dehydrogenases also showed an increased protein level, while decreased transcript and protein levels were observed for putative coo hydrogenase as well as a lactate permease and hyp hydrogenases for biofilm cells. Genes annotated for amino acid synthesis and nitrogen utilization were also predominant changers within the biofilm state. Ribosomal transcripts and proteins were notably decreased within the biofilm cells compared to exponential-phase cells but were not as low as levels observed in planktonic, stationary-phase cells. Several putative, extracellular proteins (DVU1012, 1545) were also detected in the extracellular fraction from

  20. Kinetics of phenol degradation in an anaerobic fixed-biofilm process

    SciTech Connect

    Lin, Y.H.; Lee, K.K.

    2006-06-15

    A mathematical model was developed to describe phenol degradation in an anaerobic fixed-biofilm process. The model incorporates the mechanisms of diffusive mass transport and Monod kinetics. The model was solved using a combination of the orthogonal collocation method and Gear's method. A pilot-scale column reactor was used to verify the model. Batch kinetic tests were conducted independently to determine the biokinetic parameters used in the model, while shear loss and initial thickness of biofilm were assumed so that the model simulated the substrate concentration results well. The removal efficiency for phenol was approximately 98.5% at a steady-state condition. The model accurately described the effluent substrate concentrations and the sequence of biodegradation in the reactor. The model simulations are in agreement with the experimental results. The approaches presented in this paper could be used to design full-scale anaerobic fixed-biofilm reactor systems for the biodegradation of phenolic substrates.

  1. Effects of ambroxol on Candida albicans growth and biofilm formation.

    PubMed

    Rene, Hernandez-Delgadillo; José, Martínez-Sanmiguel Juan; Isela, Sánchez-Nájera Rosa; Claudio, Cabral-Romero

    2014-04-01

    Typically, the onset of candidiasis is characterised by the appearance of a biofilm of Candida albicans, which is associated with several diseases including oral candidiasis in young and elderly people. The objective of this work was to investigate the in vitro fungicidal activity as well as the antibiofilm activity of ambroxol (AMB) against C. albicans growth. In the present investigation, the fungicidal activity of AMB was established using the cell viability 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Also the minimum inhibitory concentration (MIC) of AMB required to inhibit the fungal growth was determined. Simultaneously, the antibiofilm activity of AMB was evaluated using fluorescence microscopy. The study revealed that 2 mg ml(-1) of AMB exhibited higher fungicidal activity than 3.3 mg ml(-1) of terbinafine, one of most common commercial antifungals. A MIC of 1 mg ml(-1) was determined for AMB to interfere with C. albicans growth. Furthermore, AMB was found to be effective in inhibiting the biofilm formation of C. albicans and exerted its fungicidal activity against the fungal cells interspersed in the preformed biofilm. The study suggests a potential role of the mucolytic agent, AMB, as an interesting therapeutic alternative in the treatment of oral candidiasis. PMID:24224742

  2. Nonlinear Dynamics of Biofilm Growth on Sediment Surfaces

    NASA Astrophysics Data System (ADS)

    Molz, F. J.; Murdoch, L. C.; Faybishenko, B.

    2013-12-01

    Bioclogging often begins with the establishment of small colonies (microcolonies), which then form biofilms on the surfaces of a porous medium. These biofilm-porous media surfaces are not simple coatings of single microbes, but complex assemblages of cooperative and competing microbes, interacting with their chemical environment. This leads one to ask: what are the underlying dynamics involved with biofilm growth? To begin answering this question, we have extended the work of Kot et al. (1992, Bull. Mathematical Bio.) from a fully mixed chemostat to an idealized, one-dimensional, biofilm environment, taking into account a simple predator-prey microbial competition, with the prey feeding on a specified food source. With a variable (periodic) food source, Kot et al. (1992) were able to demonstrate chaotic dynamics in the coupled substrate-prey-predator system. Initially, deterministic chaos was thought by many to be mainly a mathematical phenomenon. However, several recent publications (e.g., Becks et al, 2005, Nature Letters; Graham et al. 2007, Int. Soc Microb. Eco. J.; Beninca et al., 2008, Nature Letters; Saleh, 2011, IJBAS) have brought together, using experimental studies and relevant mathematics, a breakthrough discovery that deterministic chaos is present in relatively simple biochemical systems. Two of us (Faybishenko and Molz, 2013, Procedia Environ. Sci)) have numerically analyzed a mathematical model of rhizosphere dynamics (Kravchenko et al., 2004, Microbiology) and detected patterns of nonlinear dynamical interactions supporting evidence of synchronized synergetic oscillations of microbial populations, carbon and oxygen concentrations driven by root exudation into a fully mixed system. In this study, we have extended the application of the Kot et al. model to investigate a spatially-dependent biofilm system. We will present the results of numerical simulations obtained using COMSOL Multi-Physics software, which we used to determine the nature of the

  3. Monitoring of biofilm growth in marine sediment by metal electrodes

    NASA Astrophysics Data System (ADS)

    Cristiani, P.; Guandalini, R.; Del Negro, P.; Cataletto, B.

    2009-04-01

    Electrochemical monitoring of biofilm growing in marine sediments is evaluating in laboratory experiments, still in progress. The interesting preliminary results obtained during six month experiments are presented in this paper. A concept of electrochemically active bacteria has recently pointed out by several studies, showing that bacteria forming biofilms on conductive materials can achieve a direct electrochemical connection with the substrate using it as electron exchanger, also without the aid of additional mediators [1]. The electric current generated by bacteria is more than enough as signal for bio-sensors. Thanks to the developing of bio-sensors based on electrochemical probes and able to monitoring the biofilm growth on metal surfaces, this "bio-electricity" has been already exploited with success for the biofilm monitoring in industrial equipment exposed to natural waters [2]. The same, very simple, electrochemical biofilm probes, in which electrical signal is proportional to biofilm growth, already successfully used for aerobic environments, have been here tested in the anaerobic environment of marine sediments. A laboratory microcosm has been prepared by filling a large polycarbonate cylinder about one-third full with organic-rich coastal marine sediment collected in the Gulf of Trieste (Northern Adriatic Sea). The sediment was packed tightly in the container to avoid entrapping air and then covered with O2 depleted seawater. Three identical electrochemical sensors were buried in the sediment of microcosm. The cylinder was placed in the dark under controlled temperature and anaerobic conditions. During the six months of monitoring, bacterial communities developing at the water-sediment interface were periodically sampled by inserting a long thin pipette into the column and removing some coloured mud or water. The microrganisms were used to inoculate enriched media and to extract bulk DNA. The results pointed out the possibility of set up simple device

  4. Mechanical signatures of microbial biofilms in micropillar-embedded growth chambers.

    PubMed

    Chew, S C; Kundukad, B; Teh, W K; Doyle, P; Yang, L; Rice, S A; Kjelleberg, S

    2016-06-21

    Biofilms are surface-attached communities of microorganisms embedded in an extracellular matrix and are essential for the cycling of organic matter in natural and engineered environments. They are also the leading cause of many infections, for example, those associated with chronic wounds and implanted medical devices. The extracellular matrix is a key biofilm component that determines its architecture and defines its physical properties. Herein, we used growth chambers embedded with micropillars to study the net mechanical forces (differential pressure) exerted during biofilm formation in situ. Pressure from the biofilm is transferred to the micropillars via the extracellular matrix, and reduction of major matrix components decreases the magnitude of micropillar deflections. The spatial arrangement of micropillar deflections caused by pressure differences in the different biofilm strains may potentially be used as mechanical signatures for biofilm characterization. Hence, we submit that micropillar-embedded growth chambers provide insights into the mechanical properties and dynamics of the biofilm and its matrix. PMID:27191395

  5. Biofilms of vaginal Lactobacillus reuteri CRL 1324 and Lactobacillus rhamnosus CRL 1332: kinetics of formation and matrix characterization.

    PubMed

    Leccese Terraf, María Cecilia; Juárez Tomás, María Silvina; Rault, Lucie; Le Loir, Yves; Even, Sergine; Nader-Macías, María Elena Fátima

    2016-09-01

    Adhesion and biofilm formation are strain properties that reportedly contribute to the permanence of lactobacilli in the human vagina. The kinetics of biofilm formation and the chemical nature of the biofilm matrix formed by Lactobacillus reuteri CRL (Centro de Referencia para Lactobacilos Culture Collection) 1324 and Lactobacillus rhamnosus CRL 1332, vaginal beneficial strains, were evaluated in this work. Crystal violet-stained microplate assay and techniques of epifluorescence, electron and confocal microscopy were applied. The highest density and complexity of biofilms of both vaginal lactobacilli were observed at 72 h of incubation. Protease, proteinase K, α-chymotrypsin and trypsin treatments efficiently detached L. reuteri CRL 1324 biofilm that was also partially affected by α-amylase. However, L. rhamnosus CRL 1332 biofilm was slightly affected by protease, proteinase K and α-amylase. Confocal microscopy revealed greater amount of polysaccharides in L. rhamnosus CRL 1332 biofilm matrix than in L. reuteri CRL 1324 biofilm matrix. The results indicate that proteins are one of the main components of the L. reuteri CRL 1324 biofilm, while the biofilm matrix of L. rhamnosus CRL 1332 is composed of carbohydrates and proteins. The results obtained support the knowledge, understanding and characterization of two biofilm-forming vaginal Lactobacillus strains. PMID:27146055

  6. Pseudomonas aeruginosa facilitates Campylobacter jejuni growth in biofilms under oxic flow conditions.

    PubMed

    Culotti, Alessandro; Packman, Aaron I

    2015-12-01

    We investigated the growth of Campylobacter jejuni in biofilms with Pseudomonas aeruginosa under oxic flow conditions. We observed the growth of C. jejuni in mono-culture, deposited on pre-established P. aeruginosa biofilms, and co-inoculated with P. aeruginosa. In mono-culture, C. jejuni was unable to form biofilms. However, deposited C. jejuni continuously grew on pre-established P. aeruginosa biofilms for a period of 3 days. The growth of scattered C. jejuni clusters was strictly limited to the P. aeruginosa biofilm surface, and no intergrowth was observed. Co-culturing of C. jejuni and P. aeruginosa also enabled the growth of both organisms in biofilms, with C. jejuni clusters developing on the surface of the P. aeruginosa biofilm. Dissolved oxygen (DO) measurements in the medium showed that P. aeruginosa biofilms depleted the effluent DO from 9.0 to 0.5 mg L(-1) 24 hours after inoculation. The localized microaerophilic environment generated by P. aeruginosa promoted the persistence and growth of C. jejuni. Our findings show that P. aeruginosa not only prolongs the survival of C. jejuni under oxic conditions, but also enables the growth of C. jejuni on the surface of P. aeruginosa biofilms. PMID:26610432

  7. Biofilms

    PubMed Central

    van Hoek, Monique L

    2013-01-01

    Our understanding of the virulence and pathogenesis of Francisella spp. has significantly advanced in recent years, including a new understanding that this organism can form biofilms. What is known so far about Francisella spp. biofilms is summarized here and future research questions are suggested. The molecular basis of biofilm production has begun to be studied, especially the role of extracellular carbohydrates and capsule, quorum sensing and two-component signaling systems. Further work has explored the contribution of amoebae, pili, outer-membrane vesicles, chitinases, and small molecules such as c-di-GMP to Francisella spp. biofilm formation. A role for Francisella spp. biofilm in feeding mosquito larvae has been suggested. As no strong role in virulence has been found yet, Francisella spp. biofilm formation is most likely a key mechanism for environmental survival and persistence. The significance and importance of Francisella spp.’s biofilm phenotype as a critical aspect of its microbial physiology is being developed. Areas for further studies include the potential role of Francisella spp. biofilms in the infection of mammalian hosts and virulence regulation. PMID:24225421

  8. Dissolved inorganic carbon enhanced growth, nutrient uptake, and lipid accumulation in wastewater grown microalgal biofilms.

    PubMed

    Kesaano, Maureen; Gardner, Robert D; Moll, Karen; Lauchnor, Ellen; Gerlach, Robin; Peyton, Brent M; Sims, Ronald C

    2015-03-01

    Microalgal biofilms grown to evaluate potential nutrient removal options for wastewaters and feedstock for biofuels production were studied to determine the influence of bicarbonate amendment on their growth, nutrient uptake capacity, and lipid accumulation after nitrogen starvation. No significant differences in growth rates, nutrient removal, or lipid accumulation were observed in the algal biofilms with or without bicarbonate amendment. The biofilms possibly did not experience carbon-limited conditions because of the large reservoir of dissolved inorganic carbon in the medium. However, an increase in photosynthetic rates was observed in algal biofilms amended with bicarbonate. The influence of bicarbonate on photosynthetic and respiration rates was especially noticeable in biofilms that experienced nitrogen stress. Medium nitrogen depletion was not a suitable stimulant for lipid production in the algal biofilms and as such, focus should be directed toward optimizing growth and biomass productivities to compensate for the low lipid yields and increase nutrient uptake. PMID:25585252

  9. Growth kinetics and morphology of polymer crystals

    NASA Astrophysics Data System (ADS)

    Toda, Akihiko

    2007-03-01

    Originating from the nature of chain folding, polymer single crystals are quite unique in the growth kinetics and morphology. The developments of the understanding in the past 50 years are discussed and the unsolved important issues will be suggested. Polymer single crystals are thin lamellae with the thickness in the order of 10nm determined by the period of chain folding, which keeps a constant value for the isothermal crystallization. The growth of polymer single crystals is modeled by the kinetics of creation and annihilation of growth steps on a rectangular substrate with the pre-determined thickness. The growth face is therefore regarded as a one-dimensional substrate and the kinks and anti-kinks on the substrate correspond to the growth steps propagating in the opposite directions. The kinetic equations of those kinks proposed by Seto and Frank well describe the transition of growth regime as a crossover from single nucleation to multi-nucleation on the basis of the standard model of chain-folded polymer crystallization with surface nucleation proposed by Lauritzen and Hoffman. However, the analysis of the growth kinetics and morphology of single crystals having curved growth front suggests an unusual behavior of the step propagation velocity. The anomaly can be accounted for by a self-poisoning of the growth step interrupted by polymer chains with folding shorter than required. An entropic barrier of pinning proposed by Sadler and Gilmer is a possible candidate of the self-poisoning and is in accordance with recent computer simulation results suggesting the kinetics on a rugged free energy landscape having a resemblance to protein folding. Therefore, the quantitative evaluation of the kinetic barriers of surface nucleation and pinning has been an important issue. In addition, examination of the kinetics of melting will have valuable information because melting of a crystal must be free from nucleation but can still be limited by the entropic barrier.

  10. Assessment of Heterotrophic Growth Supported by Soluble Microbial Products in Anammox Biofilm using Multidimensional Modeling.

    PubMed

    Liu, Yiwen; Sun, Jing; Peng, Lai; Wang, Dongbo; Dai, Xiaohu; Ni, Bing-Jie

    2016-01-01

    Anaerobic ammonium oxidation (anammox) is known to autotrophically convert ammonium to dinitrogen gas with nitrite as the electron acceptor, but little is known about their released microbial products and how these are relative to heterotrophic growth in anammox system. In this work, we applied a mathematical model to assess the heterotrophic growth supported by three key microbial products produced by bacteria in anammox biofilm (utilization associated products (UAP), biomass associated products (BAP), and decay released substrate). Both One-dimensional and two-dimensional numerical biofilm models were developed to describe the development of anammox biofilm as a function of the multiple bacteria-substrate interactions. Model simulations show that UAP of anammox is the main organic carbon source for heterotrophs. Heterotrophs are mainly dominant at the surface of the anammox biofilm with small fraction inside the biofilm. 1-D model is sufficient to describe the main substrate concentrations/fluxes within the anammox biofilm, while the 2-D model can give a more detailed biomass distribution. The heterotrophic growth on UAP is mainly present at the outside of anammox biofilm, their growth on BAP (HetB) are present throughout the biofilm, while the growth on decay released substrate (HetD) is mainly located in the inner layers of the biofilm. PMID:27273460

  11. Assessment of Heterotrophic Growth Supported by Soluble Microbial Products in Anammox Biofilm using Multidimensional Modeling

    PubMed Central

    Liu, Yiwen; Sun, Jing; Peng, Lai; Wang, Dongbo; Dai, Xiaohu; Ni, Bing-Jie

    2016-01-01

    Anaerobic ammonium oxidation (anammox) is known to autotrophically convert ammonium to dinitrogen gas with nitrite as the electron acceptor, but little is known about their released microbial products and how these are relative to heterotrophic growth in anammox system. In this work, we applied a mathematical model to assess the heterotrophic growth supported by three key microbial products produced by bacteria in anammox biofilm (utilization associated products (UAP), biomass associated products (BAP), and decay released substrate). Both One-dimensional and two-dimensional numerical biofilm models were developed to describe the development of anammox biofilm as a function of the multiple bacteria–substrate interactions. Model simulations show that UAP of anammox is the main organic carbon source for heterotrophs. Heterotrophs are mainly dominant at the surface of the anammox biofilm with small fraction inside the biofilm. 1-D model is sufficient to describe the main substrate concentrations/fluxes within the anammox biofilm, while the 2-D model can give a more detailed biomass distribution. The heterotrophic growth on UAP is mainly present at the outside of anammox biofilm, their growth on BAP (HetB) are present throughout the biofilm, while the growth on decay released substrate (HetD) is mainly located in the inner layers of the biofilm. PMID:27273460

  12. The growth of Gardnerella vaginalis and Lactobacillus acidophilus in Sorbarod biofilms.

    PubMed

    Muli, F W; Struthers, J K

    1998-05-01

    Sorbarod biofilms were investigated for their suitability in establishing continuous culture biofilms for the study of bacterial vaginosis. Two important organisms in the condition, Gardnerella vaginalis and Lactobacillus acidophilus, were studied. In contrast to growth in broth culture, both organisms were maintained for at least 96 h in a steady state on the biofilms. With G. vaginalis, the haemolytic activity was consistently maintained in the biofilms in contrast to short-term activity in broth culture which matched the bacterial titre. The simple Sorbarod system appears to be suitable for studying the growth conditions of bacteria in continuous culture and has potential for investigating interactions between micro-organisms. PMID:9879940

  13. Acoustic and Electrical Property Changes Due to Microbial Growth and Biofilm Formation in Porous Media

    EPA Science Inventory

    A laboratory study was conducted to investigate the effect of microbial growth and biofilm formation on compressional waves, and complex conductivity during stimulated microbial growth. Over the 29 day duration of the experiment, compressional wave amplitudes and arrival times f...

  14. Experimental and Computational Investigation of Biofilm Formation by Rhodopseudomonas palustris Growth under Two Metabolic Modes.

    PubMed

    Kernan, Chase; Chow, Philicia P; Christianson, Rebecca J; Huang, Jean

    2015-01-01

    We examined biofilms formed by the metabolically versatile bacterium Rhodopseudomonas palustris grown via different metabolic modes. R. palustris was grown in flow cell chambers with identical medium conditions either in the presence or absence of light and oxygen. In the absence of oxygen and the presence of light, R. palustris grew and formed biofilms photoheterotrophically, and in the presence of oxygen and the absence of light, R. palustris grew and formed biofilms heterotrophically. We used confocal laser scanning microscopy and image analysis software to quantitatively analyze and compare R. palustris biofilm formation over time in these two metabolic modes. We describe quantifiable differences in structure between the biofilms formed by the bacterium grown heterotrophically and those grown photoheterotrophically. We developed a computational model to explore ways in which biotic and abiotic parameters could drive the observed biofilm architectures, as well as a random-forest machine-learning algorithm based on structural differences that was able to identify growth conditions from the confocal imaging of the biofilms with 87% accuracy. Insight into the structure of phototrophic biofilms and conditions that influence biofilm formation is relevant for understanding the generation of biofilm structures with different properties, and for optimizing applications with phototrophic bacteria growing in the biofilm state. PMID:26087200

  15. Experimental and Computational Investigation of Biofilm Formation by Rhodopseudomonas palustris Growth under Two Metabolic Modes

    PubMed Central

    Kernan, Chase; Chow, Philicia P.; Christianson, Rebecca J.; Huang, Jean

    2015-01-01

    We examined biofilms formed by the metabolically versatile bacterium Rhodopseudomonas palustris grown via different metabolic modes. R. palustris was grown in flow cell chambers with identical medium conditions either in the presence or absence of light and oxygen. In the absence of oxygen and the presence of light, R. palustris grew and formed biofilms photoheterotrophically, and in the presence of oxygen and the absence of light, R. palustris grew and formed biofilms heterotrophically. We used confocal laser scanning microscopy and image analysis software to quantitatively analyze and compare R. palustris biofilm formation over time in these two metabolic modes. We describe quantifiable differences in structure between the biofilms formed by the bacterium grown heterotrophically and those grown photoheterotrophically. We developed a computational model to explore ways in which biotic and abiotic parameters could drive the observed biofilm architectures, as well as a random-forest machine-learning algorithm based on structural differences that was able to identify growth conditions from the confocal imaging of the biofilms with 87% accuracy. Insight into the structure of phototrophic biofilms and conditions that influence biofilm formation is relevant for understanding the generation of biofilm structures with different properties, and for optimizing applications with phototrophic bacteria growing in the biofilm state. PMID:26087200

  16. U-shaped, double-tapered, fiber-optic sensor for effective biofilm growth monitoring

    PubMed Central

    Zhong, Nianbing; Zhao, Mingfu; Li, Yishan

    2016-01-01

    To monitor biofilm growth on polydimethylsiloxane in a photobioreactor effectively, the biofilm cells and liquids were separated and measured using a sensor with two U-shaped, double-tapered, fiber-optic probes (Sen. and Ref. probes). The probes’ Au-coated hemispherical tips enabled double-pass evanescent field absorption. The Sen. probe sensed the cells and liquids inside the biofilm. The polyimide–silica hybrid-film-coated Ref. probe separated the liquids from the biofilm cells and analyzed the liquid concentration. The biofilm structure and active biomass were also examined to confirm the effectiveness of the measurement using a simulation model. The sensor was found to effectively respond to the biofilm growth in the adsorption through exponential phases at thicknesses of 0–536 μm. PMID:26977344

  17. U-shaped, double-tapered, fiber-optic sensor for effective biofilm growth monitoring.

    PubMed

    Zhong, Nianbing; Zhao, Mingfu; Li, Yishan

    2016-02-01

    To monitor biofilm growth on polydimethylsiloxane in a photobioreactor effectively, the biofilm cells and liquids were separated and measured using a sensor with two U-shaped, double-tapered, fiber-optic probes (Sen. and Ref. probes). The probes' Au-coated hemispherical tips enabled double-pass evanescent field absorption. The Sen. probe sensed the cells and liquids inside the biofilm. The polyimide-silica hybrid-film-coated Ref. probe separated the liquids from the biofilm cells and analyzed the liquid concentration. The biofilm structure and active biomass were also examined to confirm the effectiveness of the measurement using a simulation model. The sensor was found to effectively respond to the biofilm growth in the adsorption through exponential phases at thicknesses of 0-536 μm. PMID:26977344

  18. Vibrio cholerae biofilm growth program and architecture revealed by single-cell live imaging.

    PubMed

    Yan, Jing; Sharo, Andrew G; Stone, Howard A; Wingreen, Ned S; Bassler, Bonnie L

    2016-09-01

    Biofilms are surface-associated bacterial communities that are crucial in nature and during infection. Despite extensive work to identify biofilm components and to discover how they are regulated, little is known about biofilm structure at the level of individual cells. Here, we use state-of-the-art microscopy techniques to enable live single-cell resolution imaging of a Vibrio cholerae biofilm as it develops from one single founder cell to a mature biofilm of 10,000 cells, and to discover the forces underpinning the architectural evolution. Mutagenesis, matrix labeling, and simulations demonstrate that surface adhesion-mediated compression causes V. cholerae biofilms to transition from a 2D branched morphology to a dense, ordered 3D cluster. We discover that directional proliferation of rod-shaped bacteria plays a dominant role in shaping the biofilm architecture in V. cholerae biofilms, and this growth pattern is controlled by a single gene, rbmA Competition analyses reveal that the dense growth mode has the advantage of providing the biofilm with superior mechanical properties. Our single-cell technology can broadly link genes to biofilm fine structure and provides a route to assessing cell-to-cell heterogeneity in response to external stimuli. PMID:27555592

  19. Rock physics models for constraining quantitative interpretation of ultrasonic data for biofilm growth and development

    NASA Astrophysics Data System (ADS)

    Alhadhrami, Fathiya Mohammed

    This study examines the use of rock physics modeling for quantitative interpretation of seismic data in the context of microbial growth and biofilm formation in unconsolidated sediment. The impetus for this research comes from geophysical experiments by Davis et al. (2010) and Kwon and Ajo-Franklin et al. (2012). These studies observed that microbial growth has a small effect on P-wave velocities (VP) but a large effect on seismic amplitudes. Davis et al. (2010) and Kwon and Ajo-Franklin et al. (2012) speculated that the amplitude variations were due to a combination of rock mechanical changes from accumulation of microbial growth related features such as biofilms. A more definite conclusion can be drawn by developing rock physics models that connect rock properties to seismic amplitudes. The primary objective of this work is to provide an explanation for high amplitude attenuation due to biofilm growth. The results suggest that biofilm formation in the Davis et al. (2010) experiment exhibit two growth styles: a loadbearing style where biofilm behaves like an additional mineral grain and a non-loadbearing mode where the biofilm grows into the pore spaces. In the loadbearing mode, the biofilms contribute to the stiffness of the sediments. We refer to this style as "filler." In the non-loadbearing mode, the biofilms contribute only to change in density of sediments without affecting their strength. We refer to this style of microbial growth as "mushroom." Both growth styles appear to be changing permeability more than the moduli or the density. As the result, while the VP velocity remains relatively unchanged, the amplitudes can change significantly depending on biofilm saturation. Interpreting seismic data from biofilm growths in term of rock physics models provide a greater insight into the sediment-fluid interaction. The models in turn can be used to understand microbial enhanced oil recovery and in assisting in solving environmental issues such as creating bio

  20. Phosphorus removal coupled to bioenergy production by three cyanobacterial isolates in a biofilm dynamic growth system.

    PubMed

    Gismondi, Alessandra; Pippo, Francesca Di; Bruno, Laura; Antonaroli, Simonetta; Congestri, Roberta

    2016-09-01

    In the present study a closed incubator, designed for biofilm growth on artificial substrata, was used to grow three isolates of biofilm-forming heterocytous cyanobacteria using an artificial wastewater secondary effluent as the culture medium. We evaluated biofilm efficiency in removing phosphorus, by simulating biofilm-based tertiary wastewater treatment and coupled this process with biodiesel production from the developed biomass. The three strains were able to grow in the synthetic medium and remove phosphorus in percentages, between 6 and 43%, which varied between strains and also among each strain according to the biofilm growth phase. Calothrix sp. biofilm turned out to be a good candidate for tertiary treatment, showing phosphorus reducing capacity (during the exponential biofilm growth) at the regulatory level for the treated effluent water being discharged into natural water systems. Besides phosphorus removal, the three cyanobacterial biofilms produced high quality lipids, whose profile showed promising chemical stability and combustion behavior. Further integration of the proposed processes could include the integration of oil extracted from these cyanobacterial biofilms with microalgal oil known for high monounsaturated fatty acids content, in order to enhance biodiesel cold flow characteristics. PMID:26939844

  1. Use of Bioluminescence to Study Reactive Solute Transport and Biofilm Growth and Activity in Porous Media

    NASA Astrophysics Data System (ADS)

    Sharp, R. R.; Gerlach, R.; Al, C. B.

    2004-12-01

    Using a meso-scale porous media flat plate reactor we utilized a naturally bioluminescent biofilm (V. fischeri) and tracer studies to obtain information on the interactions between biofilms and reactive flow in porous media. The growth and development of the V. fischeri biofilm in a porous media geometry was studied using digital time lapse images of the bioluminescent signal given off by the developing biofilm. The effect of biofilm development on porous media hydrodynamics was examined using dye tracer studies and image analysis. The natural bioluminescence of the V. fischeri allowed real-time, in-situ study of biofilm development in porous media, without destruction of the biofilm. Dye studies and image analysis enabled the study of effects of biofilm accumulation on porous media hydraulics, with comparisons to plug flow and completely mixed systems with varying degrees of biofilm accumulation. The hydraulic conductivity of the porous media/biofilm system was continuously monitored showing a 1 to 4 order of magnitude decrease in hydraulic conductivity as a function of biofilm thickness and accumulation. The real-time nature of the study permitted us to visualize dynamic flow channel formation within the biofilm/porous media system. In addition, the sensitivity of the V. fischeri biofilm to dissolved oxygen allowed us to capture real-time images of reactive transport within the system. Using bioluminescent imaging, the location of active biomass, as well as the relative degree of biological activity, could be visualized and monitored over time. This work is the first meso-scale visualization of the interactions between biofilm and flow in porous media.

  2. High-throughput dental biofilm growth analysis for multiparametric microenvironmental biochemical conditions using microfluidics.

    PubMed

    Lam, Raymond H W; Cui, Xin; Guo, Weijin; Thorsen, Todd

    2016-04-26

    Dental biofilm formation is not only a precursor to tooth decay, but also induces more serious systematic health problems such as cardiovascular disease and diabetes. Understanding the conditions promoting colonization and subsequent biofilm development involving complex bacteria coaggregation is particularly important. In this paper, we report a high-throughput microfluidic 'artificial teeth' device offering controls of multiple microenvironmental factors (e.g. nutrients, growth factors, dissolved gases, and seeded cell populations) for quantitative characteristics of long-term dental bacteria growth and biofilm development. This 'artificial teeth' device contains multiple (up to 128) incubation chambers to perform parallel cultivation and analyses (e.g. biofilm thickness, viable-dead cell ratio, and spatial distribution of multiple bacterial species) of bacteria samples under a matrix of different combinations of microenvironmental factors, further revealing possible developmental mechanisms of dental biofilms. Specifically, we applied the 'artificial teeth' to investigate the growth of two key dental bacteria, Streptococci species and Fusobacterium nucleatum, in the biofilm under different dissolved gas conditions and sucrose concentrations. Together, this high-throughput microfluidic platform can provide extended applications for general biofilm research, including screening of the biofilm properties developing under combinations of specified growth parameters such as seeding bacteria populations, growth medium compositions, medium flow rates and dissolved gas levels. PMID:27045372

  3. Spatio-temporal Kinetics of Nontypeable Haemophilus influenzae(NTHi) Biofilms

    NASA Astrophysics Data System (ADS)

    Dhanji, Aleya; Rosas, Lucia; Ray, William; Jayaprakash, Ciriyam; Bakaletz, Lauren; Das, Jayajit

    2014-03-01

    Bacteria can form complex spatial structures known as biofilms. Biofilm formation is frequently associated with chronic infections due to the greatly enhanced antibiotic resistance of resident bacteria. However, our understanding of the role of basic processes, such as bacteria replication and resource consumption, in controlling the development and temporal change of the spatial structure remains rudimentary. Here, we examine the growth of cultured biofilms by the opportunistic pathogen NTHi. Through spatial information extracted from confocal microscopy images, we quantitatively characterize the biofilm structure as it evolves over time. We find that the equal-time height-height pair correlation function decreases with distance and scales with time for small length scales. Furthermore, both the surface roughness and the correlation length perpendicular to the surface growth direction increase with time initially and then decrease. We construct a spatially resolved agent based model beginning with the simplest possible case of a single bacteria species Fisher-Kolmogorov-Petrovsky-Piscounov equation. We show that it cannot describe the observed spatio-temporal behavior and suggest an improved two-species model that better captures the dynamics of the NTHi system. Supported by The Research Institute at Nationwide Children's Hospital.

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

    PubMed

    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

  5. Transport and Growth Kinetics in Microgravity Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    Otalora, F.; Garcia-Ruiz, J. M.; Carotenuto, L.; Castagnolo, D.; Novella, M. L.; Chernov, A. A.

    2002-01-01

    The dynamic coupling between mass transport and incorporation of growth units into the surface of a crystal growing from solution in microgravity is used to derive quantitative information on the crystal growth kinetics. To this end, new procedures for experiment preparation, interferometric data processing and model fitting have been developed. The use of experimental data from the bulk diffusive maw transport together with a model for steady state stagnant crystal growth allows the detailed quantitative understanding of the kinetics of both the concentration depletion zone around the crystal and the growth of the crystal interface. The protein crystal used in the experiment is shown to be growing in the mixed kinetic regime (0.2 x 10(exp -6) centimeters per second less than beta R/D less than 0.9 x 10(exp -6) centimeters per second).

  6. The Small Molecule DAM Inhibitor, Pyrimidinedione, Disrupts Streptococcus pneumoniae Biofilm Growth In Vitro.

    PubMed

    Yadav, Mukesh Kumar; Go, Yoon Young; Chae, Sung-Won; Song, Jae-Jun

    2015-01-01

    Streptococcus pneumoniae persist in the human nasopharynx within organized biofilms. However, expansion to other tissues may cause severe infections such as pneumonia, otitis media, bacteremia, and meningitis, especially in children and the elderly. Bacteria within biofilms possess increased tolerance to antibiotics and are able to resist host defense systems. Bacteria within biofilms exhibit different physiology, metabolism, and gene expression profiles than planktonic cells. These differences underscore the need to identify alternative therapeutic targets and novel antimicrobial compounds that are effective against pneumococcal biofilms. In bacteria, DNA adenine methyltransferase (Dam) alters pathogenic gene expression and catalyzes the methylation of adenine in the DNA duplex and of macromolecules during the activated methyl cycle (AMC). In pneumococci, AMC is involved in the biosynthesis of quorum sensing molecules that regulate competence and biofilm formation. In this study, we examine the effect of a small molecule Dam inhibitor, pyrimidinedione, on Streptococcus pneumoniae biofilm formation and evaluate the changes in global gene expression within biofilms via microarray analysis. The effects of pyrimidinedione on in vitro biofilms were studied using a static microtiter plate assay, and the architecture of the biofilms was viewed using confocal and scanning electron microscopy. The cytotoxicity of pyrimidinedione was tested on a human middle ear epithelium cell line by CCK-8. In situ oligonucleotide microarray was used to compare the global gene expression of Streptococcus pneumoniae D39 within biofilms grown in the presence and absence of pyrimidinedione. Real-time RT-PCR was used to study gene expression. Pyrimidinedione inhibits pneumococcal biofilm growth in vitro in a concentration-dependent manner, but it does not inhibit planktonic cell growth. Confocal microscopy analysis revealed the absence of organized biofilms, where cell-clumps were scattered

  7. The Small Molecule DAM Inhibitor, Pyrimidinedione, Disrupts Streptococcus pneumoniae Biofilm Growth In Vitro

    PubMed Central

    Yadav, Mukesh Kumar; Go, Yoon Young; Chae, Sung-Won; Song, Jae-Jun

    2015-01-01

    Streptococcus pneumoniae persist in the human nasopharynx within organized biofilms. However, expansion to other tissues may cause severe infections such as pneumonia, otitis media, bacteremia, and meningitis, especially in children and the elderly. Bacteria within biofilms possess increased tolerance to antibiotics and are able to resist host defense systems. Bacteria within biofilms exhibit different physiology, metabolism, and gene expression profiles than planktonic cells. These differences underscore the need to identify alternative therapeutic targets and novel antimicrobial compounds that are effective against pneumococcal biofilms. In bacteria, DNA adenine methyltransferase (Dam) alters pathogenic gene expression and catalyzes the methylation of adenine in the DNA duplex and of macromolecules during the activated methyl cycle (AMC). In pneumococci, AMC is involved in the biosynthesis of quorum sensing molecules that regulate competence and biofilm formation. In this study, we examine the effect of a small molecule Dam inhibitor, pyrimidinedione, on Streptococcus pneumoniae biofilm formation and evaluate the changes in global gene expression within biofilms via microarray analysis. The effects of pyrimidinedione on in vitro biofilms were studied using a static microtiter plate assay, and the architecture of the biofilms was viewed using confocal and scanning electron microscopy. The cytotoxicity of pyrimidinedione was tested on a human middle ear epithelium cell line by CCK-8. In situ oligonucleotide microarray was used to compare the global gene expression of Streptococcus pneumoniae D39 within biofilms grown in the presence and absence of pyrimidinedione. Real-time RT-PCR was used to study gene expression. Pyrimidinedione inhibits pneumococcal biofilm growth in vitro in a concentration-dependent manner, but it does not inhibit planktonic cell growth. Confocal microscopy analysis revealed the absence of organized biofilms, where cell-clumps were scattered

  8. Start-up of membrane bioreactor and hybrid moving bed biofilm reactor-membrane bioreactor: kinetic study.

    PubMed

    Leyva-Díaz, J C; Poyatos, J M

    2015-01-01

    A hybrid moving bed biofilm reactor-membrane bioreactor (hybrid MBBR-MBR) system was studied as an alternative solution to conventional activated sludge processes and membrane bioreactors. This paper shows the results obtained from three laboratory-scale wastewater treatment plants working in parallel in the start-up and steady states. The first wastewater treatment plant was a MBR, the second one was a hybrid MBBR-MBR system containing carriers both in anoxic and aerobic zones of the bioreactor (hybrid MBBR-MBRa), and the last one was a hybrid MBBR-MBR system which contained carriers only in the aerobic zone (hybrid MBBR-MBRb). The reactors operated with a hydraulic retention time of 30.40 h. A kinetic study for characterizing heterotrophic biomass was carried out and organic matter and nutrients removals were evaluated. The heterotrophic biomass of the hybrid MBBR-MBRb showed the best kinetic performance in the steady state, with yield coefficient for heterotrophic biomass=0.30246 mg volatile suspended solids per mg chemical oxygen demand, maximum specific growth rate for heterotrophic biomass=0.00308 h(-1) and half-saturation coefficient for organic matter=3.54908 mg O2 L(-1). The removal of organic matter was supported by the kinetic study of heterotrophic biomass. PMID:26606088

  9. Impact of growth temperature and surface type on the resistance of Pseudomonas aeruginosa and Staphylococcus aureus biofilms to disinfectants.

    PubMed

    Abdallah, Marwan; Khelissa, Oussama; Ibrahim, Ali; Benoliel, Corinne; Heliot, Laurent; Dhulster, Pascal; Chihib, Nour-Eddine

    2015-12-01

    Biofilm formation of Pseudomonas aeruginosa and Staphylococcus aureus on food-contact-surfaces represents a significant risk for the public health. In this context, the present study investigates the relationship between the environmental conditions of biofilm formation and the resistance to disinfectants. Therefore, a static biofilm reactor, called NEC-Biofilm System, was established in order to study the effect of growth temperature (20, 30 and 37°C), and of the surface type (stainless steel and polycarbonate), on biofilm resistance to disinfectants. These conditions were selected to mimic the biofilm formation on abiotic surfaces of food processing industries. The antibiofilm assays were performed on biofilms grown during 24 h. The results showed that the growth temperature influenced significantly the biofilm resistance to disinfectants. These data also revealed that the growth temperature has a significant effect on the biofilm structure of both bacteria. Furthermore, the increase of the biofilm growth temperature increased significantly the algD transcript level in sessile P. aeruginosa cells, whereas the icaA one was not affected in S. aureus cells. Overall, our findings show that the biofilm structure and matrix cannot fully explain the biofilm resistance to disinfectant agents. Nevertheless, it underlines the intimate link between environmental conditions, commonly met in food sectors, and the biofilm resistance to disinfectants. PMID:26233298

  10. INVESTIGATING THE EFFECT OF MICROBIAL GROWTH AND BIOFILM FORMATION ON SEISMIC WAVE PROPAGATION IN SEDIMENT

    EPA Science Inventory

    Previous laboratory investigations have demonstrated that the seismic methods are sensitive to microbially-induced changes in porous media through the generation of biogenic gases and biomineralization. The seismic signatures associated with microbial growth and biofilm formation...

  11. Effect of gas accumulation and biofilm growth on the dispersivity of porous media

    NASA Astrophysics Data System (ADS)

    Ye, S.; Sleep, B. E.; Chien, C.

    2009-12-01

    The effects of biofilm growth and methane gas accumulation on the transport in porous media were investigated in an anaerobic two-dimensional sand-filled cell. Inoculation of the lower portion of the cell with a methanogenic culture and addition of methanol to the bottom of the cell led to biomass growth and formation of a gas phase. Gas generated at the bottom of the cell in the biologically active zone moved upwards in discrete fingers, so that gas saturations in the biologically active zone at the bottom of the cell did not exceed 40-50%, while gas accumulation at the top of the cell produced gas saturations as high as 80%. In the most biologically active zone at the bottom of the cell, porosity reductions due to biofilm growth were estimated to be 80-95%. The effects of biofilm and gas generation on the dispersivity were separated by performing one tracer test in the presence of both biofilm and a gas phase and a second tracer test after removal of the gas phase through water flushing. The dispersivity increased by 20 times in the presence of both biofilm and a gas phase, and increased by 4.8 times in the presence of only biofilm. The results of tracer tests demonstrated that transport in the two-dimensional cell were significantly affected by gas accumulation and biofilm growth, and especially by gas accumulation.

  12. Micro-structured surfaces for algal biofilm growth

    NASA Astrophysics Data System (ADS)

    Sathananthan, Suthamathy; Genin, Scott N.; Aitchison, J. Stewart; Allen, D. Grant

    2013-12-01

    It is well known that cells respond to structured surface cues that are on the micro/nanometer scale. Tissue engineering and bio-fouling fields have utilized the semiconductor device fabrication processes to make micro- and nanometer patterned surfaces to study animal cell tissue formation and to prevent algae attachment on marine surfaces respectively. In this paper we describe the use of micro-structured surfaces to study the attachment and growth of algal films. This paper gives an overview of how micro-structured surfaces are made for this purpose, how they are incorporated into a photo bioreactor and how this patterning influences the growth of an algal biofilm. Our results suggest that surface patterning with deeper V-groove patterns that are of the same size scale as the algal species has resulted in higher biomass productivity giving them a chance to embed and attach on the slope and flat surfaces whereas shallower size grooves and completely flat surfaces did not show this trend.

  13. Kinetics of Indigenous Nitrate Reducing Sulfide Oxidizing Activity in Microaerophilic Wastewater Biofilms

    PubMed Central

    Villahermosa, Desirée; Corzo, Alfonso; Garcia-Robledo, Emilio; González, Juan M.; Papaspyrou, Sokratis

    2016-01-01

    Nitrate decreases sulfide release in wastewater treatment plants (WWTP), but little is known on how it affects the microzonation and kinetics of related microbial processes within the biofilm. The effect of nitrate addition on these properties for sulfate reduction, sulfide oxidation, and oxygen respiration were studied with the use of microelectrodes in microaerophilic wastewater biofilms. Mass balance calaculations and community composition analysis were also performed. At basal WWTP conditions, the biofilm presented a double-layer system. The upper microaerophilic layer (~300 μm) showed low sulfide production (0.31 μmol cm-3 h-1) and oxygen consumption rates (0.01 μmol cm-3 h-1). The anoxic lower layer showed high sulfide production (2.7 μmol cm-3 h-1). Nitrate addition decreased net sulfide production rates, caused by an increase in sulfide oxidation rates (SOR) in the upper layer, rather than an inhibition of sulfate reducing bacteria (SRB). This suggests that the indigenous nitrate reducing-sulfide oxidizing bacteria (NR-SOB) were immediately activated by nitrate. The functional vertical structure of the biofilm changed to a triple-layer system, where the previously upper sulfide-producing layer in the absence of nitrate split into two new layers: 1) an upper sulfide-consuming layer, whose thickness is probably determined by the nitrate penetration depth within the biofilm, and 2) a middle layer producing sulfide at an even higher rate than in the absence of nitrate in some cases. Below these layers, the lower net sulfide-producing layer remained unaffected. Net SOR varied from 0.05 to 0.72 μmol cm-3 h-1 depending on nitrate and sulfate availability. Addition of low nitrate concentrations likely increased sulfate availability within the biofilm and resulted in an increase of both net sulfate reduction and net sulfide oxidation by overcoming sulfate diffusional limitation from the water phase and the strong coupling between SRB and NR-SOB syntrophic

  14. Pronounced Metabolic Changes in Adaptation to Biofilm Growth by Streptococcus pneumoniae

    PubMed Central

    Allan, Raymond N.; Skipp, Paul; Jefferies, Johanna; Clarke, Stuart C.; Faust, Saul N.

    2014-01-01

    Streptococcus pneumoniae accounts for a significant global burden of morbidity and mortality and biofilm development is increasingly recognised as important for colonization and infection. Analysis of protein expression patterns during biofilm development may therefore provide valuable insights to the understanding of pneumococcal persistence strategies and to improve vaccines. iTRAQ (isobaric tagging for relative and absolute quantification), a high-throughput gel-free proteomic approach which allows high resolution quantitative comparisons of protein profiles between multiple phenotypes, was used to interrogate planktonic and biofilm growth in a clinical serotype 14 strain. Comparative analyses of protein expression between log-phase planktonic and 1-day and 7-day biofilm cultures representing nascent and late phase biofilm growth were carried out. Overall, 244 proteins were identified, of which >80% were differentially expressed during biofilm development. Quantitatively and qualitatively, metabolic regulation appeared to play a central role in the adaptation from the planktonic to biofilm phenotype. Pneumococci adapted to biofilm growth by decreasing enzymes involved in the glycolytic pathway, as well as proteins involved in translation, transcription, and virulence. In contrast, proteins with a role in pyruvate, carbohydrate, and arginine metabolism were significantly increased during biofilm development. Downregulation of glycolytic and translational proteins suggests that pneumococcus adopts a covert phenotype whilst adapting to an adherent lifestyle, while utilization of alternative metabolic pathways highlights the resourcefulness of pneumococcus to facilitate survival in diverse environmental conditions. These metabolic proteins, conserved across both the planktonic and biofilm phenotypes, may also represent target candidates for future vaccine development and treatment strategies. Data are available via ProteomeXchange with identifier PXD001182. PMID

  15. Roles of ionic strength and biofilm roughness on adhesion kinetics of Escherichia coli onto groundwater biofilm grown on PVC surfaces

    PubMed Central

    Janjaroen, Dao; Ling, Fangqiong; Monroy, Guillermo; Derlon, Nicolas; Mogenroth, Eberhard; Boppart, Stephen A.; Liu, Wen-Tso; Nguyen, Thanh H.

    2013-01-01

    Mechanisms of Escherichia coli attachment on biofilms grown on PVC coupons were investigated. Biofilms were grown in CDC reactors using groundwater as feed solution over a period up to 27 weeks. Biofilm physical structure was characterized at the micro- and meso-scales using Scanning Electron Microscopy (SEM) and Optical Coherence Tomography (OCT), respectively. Microbial community diversity was analyzed with Terminal Restricted Fragment Length Polymorphism (T-RFLP). Both physical structure and microbial community diversity of the biofilms were shown to be changing from 2 weeks to 14 weeks, and became relatively stable after 16 weeks. A parallel plate flow chamber coupled with an inverted fluorescent microscope was also used to monitor the attachment of fluorescent microspheres and E. coli on clean PVC surfaces and biofilms grown on PVC surfaces for different ages. Two mechanisms of E. coli attachment were identified. The adhesion rate coefficients (kd) of E. coli on nascent PVC surfaces and 2-week biofilms increased with ionic strength. However, after biofilms grew for 8 weeks, the adhesion was found to be independent of solution chemistry. Instead, a positive correlation between kd and biofilm roughness as determined by OCT was obtained, indicating that the physical structure of biofilms could play an important role in facilitating the adhesion of E. coli cells. PMID:23497979

  16. 2-Deoxy-d-glucose is a potent inhibitor of biofilm growth in Escherichia coli.

    PubMed

    Sutrina, Sarah L; Griffith, Melanie S J; Lafeuillee, Chad

    2016-06-01

    Escherichia coli strain 15 (ATCC 9723), which forms robust biofilms, was grown under optimal biofilm conditions in NaCl-free Luria-Bertani broth (LB*) or in LB* supplemented with one of the non-metabolizable analogues 2-deoxy-d-glucose (2DG), methyl α-d-mannopyranoside (αMM), or methyl α-d-glucopyranoside (αMG). Biofilm growth was inhibited by mannose analogue 2DG even at very low concentration in unbuffered medium, and the maximal inhibition was enhanced in the presence of either 100 mM KPO4 or 100 mM MOPS, pH 7.5; in buffered medium, concentrations of 0.02 % (1.2 mM) or more inhibited growth nearly completely. In contrast, mannose analogue αMM, which should not be able to enter the cells but has been reported to inhibit biofilm growth by binding to FimH, did not exhibit strong inhibition even at concentrations up to 1.8 % (108 mM). The glucose analogue αMG inhibited biofilm growth, but much less strongly than did 2DG. None of the analogues inhibited planktonic growth or caused a change in pH of the unbuffered medium. Similar inhibitory effects of the analogues were observed in minimal medium. The effects were not strain-specific, as 2DG and αMG also inhibited the weak biofilm growth of E. coli K12. PMID:27045200

  17. Microscopic kinetic model for polymer crystal growth

    NASA Astrophysics Data System (ADS)

    Hu, Wenbing

    2011-03-01

    Linear crystal growth rates characterize the net result of competition between growth and melting at the liquid-solid interfaces. The rate equation for polymer crystal growth can be derived with a barrier term for crystal growth and with a driving force term of excess lamellar thickness, provided that growth and melting share the same rate-determining steps at the growth front. Such an ansatz can be verified by the kinetic symmetry between growth and melting around the melting point of lamellar crystals, as made in our recent dynamic Monte Carlo simulations. The profile of the growth/melting front appears as wedge-shaped, with the free energy barrier for intramolecular secondary crystal nucleation at its top, and with the driving force gained via instant thickening at its bottom. Such a scenario explains unique phenomena on polymer crystal growth, such as chain folding, regime transitions, molecular segregation of polydisperse polymers, self-poisoning with integer-number chain-folding of short chains, and colligative growth rates of binary mixtures of two chain lengths. Financial support from NNSFC No. 20825415 and NBRPC No. 2011CB606100 is acknowledged.

  18. Sinefungin, a Natural Nucleoside Analogue of S-Adenosylmethionine, Inhibits Streptococcus pneumoniae Biofilm Growth

    PubMed Central

    Park, Seok-Won; Chae, Sung-Won

    2014-01-01

    Pneumococcal colonization and disease is often associated with biofilm formation, in which the bacteria exhibit elevated resistance both to antibiotics and to host defense systems, often resulting in infections that are persistent and difficult to treat. We evaluated the effect of sinefungin, a nucleoside analogue of S-adenosylmethionine, on pneumococcal in vitro biofilm formation and in vivo colonization. Sinefungin is bacteriostatic to pneumococci and significantly decreased biofilm growth and inhibited proliferation and structure of actively growing biofilms but did not alter growth or the matrix structure of established biofilms. Sinefungin significantly reduced pneumococcal colonization in rat middle ear. The quorum sensing molecule (autoinducer-2) production was significantly reduced by 92% in sinefungin treated samples. The luxS, pfs, and speE genes were downregulated in biofilms grown in the presence of sinefungin. This study shows that sinefungin inhibits pneumococcal biofilm growth in vitro and colonization in vivo, decreases AI-2 production, and downregulates luxS, pfs, and speE gene expressions. Therefore, the S-adenosylmethionine (SAM) inhibitors could be used as lead compounds for the development of novel antibiofilm agents against pneumococci. PMID:25050323

  19. Simulation of Bacillus subtilis biofilm growth on agar plate by diffusion-reaction based continuum model.

    PubMed

    Zhang, Xianlong; Wang, Xiaoling; Nie, Kai; Li, Mingpeng; Sun, Qingping

    2016-01-01

    Various species of bacteria form highly organized spatially-structured aggregates known as biofilms. To understand how microenvironments impact biofilm growth dynamics, we propose a diffusion-reaction continuum model to simulate the formation of Bacillus subtilis biofilm on an agar plate. The extended finite element method combined with level set method are employed to perform the simulation, numerical results show the quantitative relationship between colony morphologies and nutrient depletion over time. Considering that the production of polysaccharide in wild-type cells may enhance biofilm spreading on the agar plate, we inoculate mutant colony incapable of producing polysaccharide to verify our results. Predictions of the glutamate source biofilm's shape parameters agree with the experimental mutant colony better than that of glycerol source biofilm, suggesting that glutamate is rate limiting nutrient for Bacillus subtilis biofilm growth on agar plate, and the diffusion-limited is a better description to the experiment. In addition, we find that the diffusion time scale is of the same magnitude as growth process, and the common-employed quasi-steady approximation is not applicable here. PMID:27434099

  20. Growth and Detachment of Cell Clusters from Mature Mixed-Species Biofilms

    PubMed Central

    Stoodley, Paul; Wilson, Suzanne; Hall-Stoodley, Luanne; Boyle, John D.; Lappin-Scott, Hilary M.; Costerton, J. W.

    2001-01-01

    Detachment from biofilms is an important consideration in the dissemination of infection and the contamination of industrial systems but is the least-studied biofilm process. By using digital time-lapse microscopy and biofilm flow cells, we visualized localized growth and detachment of discrete cell clusters in mature mixed-species biofilms growing under steady conditions in turbulent flow in situ. The detaching biomass ranged from single cells to an aggregate with a diameter of approximately 500 μm. Direct evidence of local cell cluster detachment from the biofilms was supported by microscopic examination of filtered effluent. Single cells and small clusters detached more frequently, but larger aggregates contained a disproportionately high fraction of total detached biomass. These results have significance in the establishment of an infectious dose and public health risk assessment. PMID:11722913

  1. Protein crystal growth - Growth kinetics for tetragonal lysozyme crystals

    NASA Technical Reports Server (NTRS)

    Pusey, M. L.; Snyder, R. S.; Naumann, R.

    1986-01-01

    Results are reported from theoretical and experimental studies of the growth rate of lysozyme as a function of diffusion in earth-gravity conditions. The investigations were carried out to form a comparison database for future studies of protein crystal growth in the microgravity environment of space. A diffusion-convection model is presented for predicting crystal growth rates in the presence of solutal concentration gradients. Techniques used to grow and monitor the growth of hen egg white lysozyme are detailed. The model calculations and experiment data are employed to discuss the effects of transport and interfacial kinetics in the growth of the crystals, which gradually diminished the free energy in the growth solution. Density gradient-driven convection, caused by presence of the gravity field, was a limiting factor in the growth rate.

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

    PubMed

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

    2016-01-01

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

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

    PubMed Central

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

    2016-01-01

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

  4. Growth kinetics of Bacillus stearothermophilus BR219

    SciTech Connect

    Worden, R.M.; Subramanian, R.; Bly, M.J.; Winter, S.; Aronson, C.L.

    1991-12-31

    Bacillus stearothermophilus BR219, a phenol-resistant thermophile, can convert phenol to the specialty chemical catechol. The growth kinetics of this organism were studied in batch, continuous, and immobilized-cell culture. Batch growth was insensitive to pH between 6.0 and 8.0, but little growth occurred at 5.5. In continuous culture on a dilute medium supplemented with 10 mM phenol, several steady states were achieved between dilution rates of 0.25 and 1.3 h{sup -1}. Phenol degradation was found to be uncoupled from growth. Immobilized cells grew rapidly in a rich medium, but cell viability plummeted following a switch to a dilute medium supplemented with 5 mM phenol.

  5. Biofilm feeding: Microbial colonization of food promotes the growth of a detritivorous arthropod.

    PubMed

    Horváthová, Terézia; Babik, Wiesław; Bauchinger, Ulf

    2016-01-01

    Feeding on plant material is common among animals, but how different animals overcome the dietary deficiencies imposed by this feeding strategy is not well understood. Microorganisms are generally considered to play a vital role in the nutritional ecology of plant feeding animals. Commonly microbes living inside animal bodies are considered more important, but recent studies suggest external microbes significantly shape plant-feeding strategies in invertebrates. Here we investigate how external microbes that typically form biofilm on primary plant material affect growth rates in a terrestrial isopod species Porcellio scaber. We experimentally manipulated the amount of biofilm on three different primary diet sources and quantified growth and survival of individuals that fed on food with either a small or large amount of biofilm. In addition, we tested how dietary manipulation shapes the composition of bacterial communities in the gut. The presence of visible biofilm significantly affected the growth of isopods: individuals that fed on the primary diet source with a large amount of biofilm gained more mass than individuals feeding on a diet with marginal biofilm. Diet also significantly affected the bacterial gut community. The primary diet source mainly determined the taxonomic composition of the bacterial community in the isopod gut, whereas the amount of biofilm affected the relative abundance of bacterial taxa. Our study suggests that terrestrial isopods may cope with low-quality plant matter by feeding on biofilm, with decomposition of plant material by organisms outside of the feeding organism (here a terrestrial isopod) probably playing a major role. Future investigations may be directed towards the primary diet source, plant matter, and the secondary diet source, biofilm, and should assess if both components are indeed uptaken in detritivorous species. PMID:27110187

  6. Biofilm feeding: Microbial colonization of food promotes the growth of a detritivorous arthropod

    PubMed Central

    Horváthová, Terézia; Babik, Wiesław; Bauchinger, Ulf

    2016-01-01

    Abstract Feeding on plant material is common among animals, but how different animals overcome the dietary deficiencies imposed by this feeding strategy is not well understood. Microorganisms are generally considered to play a vital role in the nutritional ecology of plant feeding animals. Commonly microbes living inside animal bodies are considered more important, but recent studies suggest external microbes significantly shape plant-feeding strategies in invertebrates. Here we investigate how external microbes that typically form biofilm on primary plant material affect growth rates in a terrestrial isopod species Porcellio scaber. We experimentally manipulated the amount of biofilm on three different primary diet sources and quantified growth and survival of individuals that fed on food with either a small or large amount of biofilm. In addition, we tested how dietary manipulation shapes the composition of bacterial communities in the gut. The presence of visible biofilm significantly affected the growth of isopods: individuals that fed on the primary diet source with a large amount of biofilm gained more mass than individuals feeding on a diet with marginal biofilm. Diet also significantly affected the bacterial gut community. The primary diet source mainly determined the taxonomic composition of the bacterial community in the isopod gut, whereas the amount of biofilm affected the relative abundance of bacterial taxa. Our study suggests that terrestrial isopods may cope with low-quality plant matter by feeding on biofilm, with decomposition of plant material by organisms outside of the feeding organism (here a terrestrial isopod) probably playing a major role. Future investigations may be directed towards the primary diet source, plant matter, and the secondary diet source, biofilm, and should assess if both components are indeed uptaken in detritivorous species. PMID:27110187

  7. Morphological stability and kinetics in crystal growth from vapors

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz

    1990-01-01

    The following topics are discussed: (1) microscopy image storage and processing system; (2) growth kinetics and morphology study with carbon tetrabromide; (3) photothermal deflection vapor growth setup; (4) bridgman growth of iodine single crystals; (5) vapor concentration distribution measurement during growth; and (6) Monte Carlo modeling of anisotropic growth kinetics and morphology. A collection of presentations and publications of these results are presented.

  8. Understanding, Monitoring, and Controlling Biofilm Growth in Drinking Water Distribution Systems.

    PubMed

    Liu, Sanly; Gunawan, Cindy; Barraud, Nicolas; Rice, Scott A; Harry, Elizabeth J; Amal, Rose

    2016-09-01

    In drinking water distribution systems (DWDS), biofilms are the predominant mode of microbial growth, with the presence of extracellular polymeric substance (EPS) protecting the biomass from environmental and shear stresses. Biofilm formation poses a significant problem to the drinking water industry as a potential source of bacterial contamination, including pathogens, and, in many cases, also affecting the taste and odor of drinking water and promoting the corrosion of pipes. This article critically reviews important research findings on biofilm growth in DWDS, examining the factors affecting their formation and characteristics as well as the various technologies to characterize and monitor and, ultimately, to control their growth. Research indicates that temperature fluctuations potentially affect not only the initial bacteria-to-surface attachment but also the growth rates of biofilms. For the latter, the effect is unique for each type of biofilm-forming bacteria; ammonia-oxidizing bacteria, for example, grow more-developed biofilms at a typical summer temperature of 22 °C compared to 12 °C in fall, and the opposite occurs for the pathogenic Vibrio cholerae. Recent investigations have found the formation of thinner yet denser biofilms under high and turbulent flow regimes of drinking water, in comparison to the more porous and loosely attached biofilms at low flow rates. Furthermore, in addition to the rather well-known tendency of significant biofilm growth on corrosion-prone metal pipes, research efforts also found leaching of growth-promoting organic compounds from the increasingly popular use of polymer-based pipes. Knowledge of the unique microbial members of drinking water biofilms and, importantly, the influence of water characteristics and operational conditions on their growth can be applied to optimize various operational parameters to minimize biofilm accumulation. More-detailed characterizations of the biofilm population size and structure are now

  9. Towards optimum permeability reduction in porous media using biofilm growth simulations.

    PubMed

    Pintelon, T R R; Graf von der Schulenburg, D A; Johns, M L

    2009-07-01

    While biological clogging of porous systems can be problematic in numerous processes (e.g., microbial enhanced oil recovery-MEOR), it is targeted during bio-barrier formation to control sub-surface pollution plumes in ground water. In this simulation study, constant pressure drop (CPD) and constant volumetric flow rate (CVF) operational modes for nutrient provision for biofilm growth in a porous system are considered with respect to optimum (minimum energy requirement for nutrient provision) permeability reduction for bio-barrier applications. Biofilm growth is simulated using a Lattice-Boltzmann (LB) simulation platform complemented with an individual-based biofilm model (IbM). A biomass detachment technique has been included using a fast marching level set (FMLS) method that models the propagation of the biofilm-liquid interface with a speed proportional to the adjacent velocity shear field. The porous medium permeability reduction is simulated for both operational modes using a range of biofilm strengths. For stronger biofilms, less biomass deposition and energy input are required to reduce the system permeability during CPD operation, whereas CVF is more efficient at reducing the permeability of systems containing weaker biofilms. PMID:19309753

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

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

    2015-01-01

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

  12. Physiological activities associated with biofilm growth in attached and suspended growth bioreactors under aerobic and anaerobic conditions.

    PubMed

    Naz, Iffat; Seher, Shama; Perveen, Irum; Saroj, Devendra P; Ahmed, Safia

    2015-01-01

    This research work evaluated the biofilm succession on stone media and compared the biochemical changes of sludge in attached and suspended biological reactors operated under aerobic and anaerobic conditions. Stones incubated (30±2°C) with activated sludge showed a constant increase in biofilm weight up to the fifth and seventh week time under anaerobic and aerobic conditions, respectively, where after reduction (>80%) the most probable number index of pathogen indicators on ninth week was recorded. Reduction in parameters such as biological oxygen demand (BOD) (47.7%), chemical oxygen demand (COD, 41%), nitrites (60.2%), nitrates (105.5%) and phosphates (58.9%) and increase in dissolved oxygen (176.5%) of sludge were higher in aerobic attached growth reactors as compared with other settings. While, considerable reductions in these values were also observed (BOD, 53.8%; COD, 2.8%; nitrites, 28.6%; nitrates, 31.7%; phosphates, 41.4%) in the suspended growth system under anaerobic conditions. However, higher sulphate removal was observed in suspended (40.9% and 54.9%) as compared with biofilm reactors (28.2% and 29.3%). Six weeks biofilm on the stone media showed maximum physiological activities; thus, the operational conditions should be controlled to keep the biofilm structure similar to six-week-old biofilm, and can be used in fixed biofilm reactors for wastewater treatment. PMID:25609155

  13. Effect of alcohols on filamentation, growth, viability and biofilm development in Candida albicans.

    PubMed

    Chauhan, Nitin M; Shinde, Ravikumar B; Karuppayil, S Mohan

    2013-12-01

    In this study we report the potential of alcohols as morphogenetic regulators in Candida albicans. All the alcohols tested influenced various modes of growth like planktonic as well as biofilm forms. Viability was affected at high concentrations. Among the alcohols, the response of C. albicans to amyl alcohol (pentanol) was noteworthy. Amyl alcohol at a concentration 0.5% which was not inhibitory to growth and viability specifically inhibited morphogenetic switching from yeast to hyphal forms. It also inhibited normal biofilm development favoring yeast dominated biofilms. Based on this study we hypothesize that alcohols produced under anaerobic conditions may not favor biofilm development and support dissemination of yeast cells. Since anaerobic conditions are not found to favor production of quorum sensing molecules like farnesol, the alcohols may play a role in morphogenetic regulation. PMID:24688528

  14. Effect of alcohols on filamentation, growth, viability and biofilm development in Candida albicans

    PubMed Central

    Chauhan, Nitin M; Shinde, Ravikumar B; Karuppayil, S. Mohan

    2013-01-01

    In this study we report the potential of alcohols as morphogenetic regulators in Candida albicans. All the alcohols tested influenced various modes of growth like planktonic as well as biofilm forms. Viability was affected at high concentrations. Among the alcohols, the response of C. albicans to amyl alcohol (pentanol) was noteworthy. Amyl alcohol at a concentration 0.5% which was not inhibitory to growth and viability specifically inhibited morphogenetic switching from yeast to hyphal forms. It also inhibited normal biofilm development favoring yeast dominated biofilms. Based on this study we hypothesize that alcohols produced under anaerobic conditions may not favor biofilm development and support dissemination of yeast cells. Since anaerobic conditions are not found to favor production of quorum sensing molecules like farnesol, the alcohols may play a role in morphogenetic regulation. PMID:24688528

  15. Prostaglandin E2 from Candida albicans Stimulates the Growth of Staphylococcus aureus in Mixed Biofilms

    PubMed Central

    Krause, Jan; Geginat, Gernot; Tammer, Ina

    2015-01-01

    Background Previous studies showed that Staphylococcus aureus and Candida albicans interact synergistically in dual species biofilms resulting in enhanced mortality in animal models. Methodology/Principal Findings The aim of the current study was to test possible candidate molecules which might mediate this synergistic interaction in an in vitro model of mixed biofilms, such as farnesol, tyrosol and prostaglandin (PG) E2. In mono-microbial and dual biofilms of C.albicans wild type strains PGE2 levels between 25 and 250 pg/mL were measured. Similar concentrations of purified PGE2 significantly enhanced S.aureus biofilm formation in a mode comparable to that observed in dual species biofilms. Supernatants of the null mutant deficient in PGE2 production did not stimulate the proliferation of S.aureus and the addition of the cyclooxygenase inhibitor indomethacin blocked the S.aureus biofilm formation in a dose-dependent manner. Additionally, S. aureus biofilm formation was boosted by low and inhibited by high farnesol concentrations. Supernatants of the farnesol-deficient C. albicans ATCC10231 strain significantly enhanced the biofilm formation of S. aureus but at a lower level than the farnesol producer SC5314. However, C. albicans ATCC10231 also produced PGE2 but amounts were significantly lower compared to SC5314. Conclusion/Significance In conclision, we identified C. albicans PGE2 as a key molecule stimulating the growth and biofilm formation of S. aureus in dual S. aureus/C. albicans biofilms, although C. albicans derived farnesol, but not tyrosol, may also contribute to this effect but to a lesser extent. PMID:26262843

  16. Growth of Escherichia coli in Model Distribution System Biofilms Exposed to Hypochlorous Acid or Monochloramine

    PubMed Central

    Williams, Margaret M.; Braun-Howland, Ellen B.

    2003-01-01

    Bacteria indigenous to water distribution systems were used to grow multispecies biofilms within continuous-flow slide chambers. Six flow chambers were also inoculated with an Escherichia coli isolate obtained from potable water. The effect of disinfectants on bacterial populations was determined after exposure of established biofilms to 1 ppm of hypochlorous acid (ClOH) for 67 min or 4 ppm of monochloramine (NH2Cl) for 155 min. To test the ability of bacterial populations to initiate biofilm formation in the presence of disinfectants, we assessed the biofilms after 2 weeks of exposure to residual concentrations of 0.2 ppm of ClOH or 4 ppm of NH2Cl. Lastly, to determine the effect of recommended residual concentrations on newly established biofilms, we treated systems with 0.2 ppm of ClOH after 5 days of growth in the absence of disinfectant. Whole-cell in situ hybridizations using fluorescently tagged, 16S rRNA-targeted oligonucleotide probes performed on cryosectioned biofilms permitted the direct observation of metabolically active bacterial populations, including certain phylogenetic groups and species. The results of these studies confirmed the resistance of established bacterial biofilms to treatment with recommended levels of disinfectants. Specifically, Legionella pneumophila, E. coli, and β and δ proteobacteria were identified within biofilms both before and after treatment. Furthermore, although it was undetected using routine monitoring techniques, the observation of rRNA-containing E. coli within biofilms demonstrated not only survival but also metabolic activity of this organism within the model distribution systems. The persistence of diverse bacterial species within disinfectant-treated biofilms suggests that current testing practices underestimate the risk to immunocompromised individuals of contracting waterborne disease. PMID:12957935

  17. Growth of Streptococcus mutans in Biofilms Alters Peptide Signaling at the Sub-population Level

    PubMed Central

    Shields, Robert C.; Burne, Robert A.

    2016-01-01

    Streptococcus mutans activates multiple cellular processes in response to the formation of a complex between comX-inducing peptide (XIP) and the ComR transcriptional regulator. Bulk phase and microfluidic experiments previously revealed that ComR-dependent activation of comX is altered by pH and by carbohydrate source. Biofilm formation is a major factor in bacterial survival and virulence in the oral cavity. Here, we sought to determine the response of S. mutans biofilm cells to XIP during different stages of biofilm maturation. Using flow cytometry and confocal microscopy, we showed that exogenous addition of XIP to early biofilms resulted in robust comX activation. However, as the biofilms matured, increasing amounts of XIP were required to activate comX expression. Single-cell analysis demonstrated that the entire population was responding to XIP with activation of comX in early biofilms, but only a sub-population was responding in mature biofilms. The sub-population response of mature biofilms was retained when the cells were dispersed and then treated with XIP. The proportion and intensity of the bi-modal response of mature biofilm cells was altered in mutants lacking the Type II toxins MazF and RelE, or in a strain lacking the (p)ppGpp synthase/hydrolase RelA. Thus, competence signaling is markedly altered in cells growing in mature biofilms, and pathways that control cell death and growth/survival decisions modulate activation of comX expression in these sessile populations. PMID:27471495

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

    PubMed Central

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

    2014-01-01

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

  19. Simulation of Bacillus subtilis biofilm growth on agar plate by diffusion–reaction based continuum model

    NASA Astrophysics Data System (ADS)

    Zhang, Xianlong; Wang, Xiaoling; Nie, Kai; Li, Mingpeng; Sun, Qingping

    2016-08-01

    Various species of bacteria form highly organized spatially-structured aggregates known as biofilms. To understand how microenvironments impact biofilm growth dynamics, we propose a diffusion–reaction continuum model to simulate the formation of Bacillus subtilis biofilm on an agar plate. The extended finite element method combined with level set method are employed to perform the simulation, numerical results show the quantitative relationship between colony morphologies and nutrient depletion over time. Considering that the production of polysaccharide in wild-type cells may enhance biofilm spreading on the agar plate, we inoculate mutant colony incapable of producing polysaccharide to verify our results. Predictions of the glutamate source biofilm’s shape parameters agree with the experimental mutant colony better than that of glycerol source biofilm, suggesting that glutamate is rate limiting nutrient for Bacillus subtilis biofilm growth on agar plate, and the diffusion-limited is a better description to the experiment. In addition, we find that the diffusion time scale is of the same magnitude as growth process, and the common-employed quasi-steady approximation is not applicable here.

  20. Microbial growth and biofilm formation in geologic media is detected with complex conductivity measurements

    NASA Astrophysics Data System (ADS)

    Davis, Caroline A.; Atekwana, Estella; Atekwana, Eliot; Slater, Lee D.; Rossbach, Silvia; Mormile, Melanie R.

    2006-09-01

    Complex conductivity measurements (0.1-1000 Hz) were obtained from biostimulated sand-packed columns to investigate the effect of microbial growth and biofilm formation on the electrical properties of porous media. Microbial growth was verified by direct microbial counts, pH measurements, and environmental scanning electron microscope imaging. Peaks in imaginary (interfacial) conductivity in the biostimulated columns were coincident with peaks in the microbial cell concentrations extracted from sands. However, the real conductivity component showed no discernible relationship to microbial cell concentration. We suggest that the observed dynamic changes in the imaginary conductivity (σ″) arise from the growth and attachment of microbial cells and biofilms to sand surfaces. We conclude that complex conductivity techniques, specifically imaginary conductivity measurements are a proxy indicator for microbial growth and biofilm formation in porous media. Our results have implications for microbial enhanced oil recovery, CO2 sequestration, bioremediation, and astrobiology studies.

  1. Droplet Growth Kinetics in Various Environments

    NASA Astrophysics Data System (ADS)

    Raatikainen, T. E.; Lathem, T. L.; Moore, R.; Lin, J. J.; Cerully, K. M.; Padro, L.; Lance, S.; Cozic, J.; Anderson, B. E.; Nenes, A.

    2012-12-01

    The largest uncertainties in the effects of atmospherics aerosols on the global radiation budget are related to their indirect effects on cloud properties (IPCC, the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007). Cloud formation is a kinetic process where the resulting cloud properties depend on aerosol properties and meteorological parameters such as updraft velocity (e.g. McFiggans et al., Atmos. Chem. Phys., 6, 2593-2649, 2006). Droplet growth rates are limited by the water vapor diffusion, but additional kinetic limitations, e.g., due to organic surface films, slow solute dissociation or highly viscous or glassy aerosol states have been hypothesized. Significant additional kinetic limitations can lead to increased cloud droplet number concentration, thus the effect is similar to those of increased aerosol number concentration or changes in vertical velocity (e.g. Nenes et al., Geophys. Res. Lett., 29, 1848, 2002). There are a few studies where slow droplet growth has been observed (e.g. Ruehl et al., Geophys. Res. Lett., 36, L15814, 2009), however, little is currently known about their global occurrence and magnitude. Cloud micro-physics models often describe kinetic limitations by an effective water vapor uptake coefficient or similar parameter. Typically, determining aerosol water vapor uptake coefficients requires experimental observations of droplet growth which are interpreted by a numerical droplet growth model where the uptake coefficient is an adjustable parameter (e.g. Kolb et al., Atmos. Chem. Phys., 10, 10561-10605, 2010). Such methods have not been practical for high time-resolution or long term field measurements, until a model was recently developed for analyzing Droplet Measurement Technologies (DMT) cloud condensation nuclei (CCN) counter data (Raatikainen et al., Atmos. Chem. Phys., 12, 4227-4243, 2012). Model verification experiments showed that the calibration aerosol droplet size can be predicted accurately

  2. Volume Diffusion Growth Kinetics and Step Geometry in Crystal Growth

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Ramachandran, Narayanan

    1998-01-01

    The role of step geometry in two-dimensional stationary volume diff4sion process used in crystal growth kinetics models is investigated. Three different interface shapes: a) a planar interface, b) an equidistant hemispherical bumps train tAx interface, and c) a train of right angled steps, are used in this comparative study. The ratio of the super-saturation to the diffusive flux at the step position is used as a control parameter. The value of this parameter can vary as much as 50% for different geometries. An approximate analytical formula is derived for the right angled steps geometry. In addition to the kinetic models, this formula can be utilized in macrostep growth models. Finally, numerical modeling of the diffusive and convective transport for equidistant steps is conducted. In particular, the role of fluid flow resulting from the advancement of steps and its contribution to the transport of species to the steps is investigated.

  3. Amyloid growth: combining experiment and kinetic theory

    NASA Astrophysics Data System (ADS)

    Knowles, Tuomas; Cohen, Samuel; Vendruscolo, Michele; Dobson, Christopher

    2012-02-01

    The conversion of proteins from their soluble forms into fibrillar amyloid nanostructures is a general type of behaviour encountered for many different proteins in the context of disease as well as for the generation of a select class of functional materials in nature. This talk focuses on the problem of defining the rates of the individual molecular level processes involved in the overall conversion reaction. A master equation approach is discussedootnotetextCohen et al, J Chem Phys 2011, 135, 065106 ootnotetextKnowles et al, Science, 2009, 326, 1533-1537 and used in combination with kinetic measurements to yield mechanistic insights into the amyloid growth phenomenon.

  4. Modelling biofilm growth in the presence of carbon dioxide and water flow in the subsurface

    NASA Astrophysics Data System (ADS)

    Ebigbo, Anozie; Helmig, Rainer; Cunningham, Alfred B.; Class, Holger; Gerlach, Robin

    2010-07-01

    The concentration of greenhouse gases - particularly carbon dioxide (CO 2) - in the atmosphere has been on the rise in the past decades. One of the methods which have been proposed to help reduce anthropogenic CO 2 emissions is the capture of CO 2from large, stationary point sources and storage in deep geological formations. The caprock is an impermeable geological layer which prevents the leakage of stored CO 2, and its integrity is of utmost importance for storage security. Due to the high pressure build-up during injection, the caprock in the vicinity of the well is particularly at risk of fracturing. Biofilms could be used as biobarriers which help prevent the leakage of CO 2 through the caprock in injection well vicinity by blocking leakage pathways. The biofilm could also protect well cement from corrosion by CO 2-rich brine. The goal of this paper is to develop and test a numerical model which is capable of simulating the development of a biofilm in a CO 2 storage reservoir. This involves the description of the growth of the biofilm, flow and transport in the geological formation, and the interaction between the biofilm and the flow processes. Important processes which are accounted for in the model include the effect of biofilm growth on the permeability of the formation, the hazardous effect of supercritical CO 2 on suspended and attached bacteria, attachment and detachment of biomass, and two-phase fluid flow processes. The model is tested by comparing simulation results to experimental data.

  5. Quantum dots conjugated zinc oxide nanosheets: Impeder of microbial growth and biofilm

    NASA Astrophysics Data System (ADS)

    Patil, Rajendra; Gholap, Haribhau; Warule, Sambhaji; Banpurkar, Arun; Kulkarni, Gauri; Gade, Wasudeo

    2015-01-01

    The grieving problem of the 21st century has been the antimicrobial resistance in pathogenic microorganisms to conventional antibiotics. Therefore, developments of novel antibacterial materials which effectively inhibit or kill such resistant microorganisms have become the need of the hour. In the present study, we communicate the synthesis of quantum dots conjugated zinc oxide nanostructures (ZnO/CdTe) as an impeder of microbial growth and biofilm. The as-synthesized nanostructures were characterized by X-ray diffraction, ultraviolet-visible spectroscopy, photoluminescence spectroscopy, field emission scanning electron microscopy and high resolution transmission electron microscopy. The growth impedance property of ZnO and ZnO/CdTe on Gram positive organism, Bacillus subtilis NCIM 2063 and Gram negative, Escherichia coli NCIM 2931 and biofilm impedance activity in Pseudomonas aeruginosa O1 was found to occur due to photocatalytical action on the cell biofilm surfaces. The impedance in microbial growth and biofilm formation was further supported by ruptured appearances of cells and dettrered biofilm under field emission scanning electron and confocal laser scanning microscope. The ZnO/CdTe nanostructures array synthesized by hydrothermal method has an advantage of low growth temperature, and opportunity to fabricate inexpensive material for nano-biotechnological applications.

  6. Impact of Actinobacillus pleuropneumoniae biofilm mode of growth on the lipid A structures and stimulation of immune cells.

    PubMed

    Hathroubi, Skander; Beaudry, Francis; Provost, Chantale; Martelet, Léa; Segura, Mariela; Gagnon, Carl A; Jacques, Mario

    2016-07-01

    Actinobacillus pleuropneumoniae (APP), the etiologic agent of porcine pleuropneumonia, forms biofilms on biotic and abiotic surfaces. APP biofilms confers resistance to antibiotics. To our knowledge, no studies have examined the role of APP biofilm in immune evasion and infection persistence. This study was undertaken to (i) investigate biofilm-associated LPS modifications occurring during the switch to biofilm mode of growth; and (ii) characterize pro-inflammatory cytokines expression in porcine pulmonary alveolar macrophages (PAMs) and proliferation in porcine PBMCs challenged with planktonic or biofilm APP cells. Extracted lipid A samples from biofilm and planktonic cultures were analyzed by HPLC high-resolution, accurate mass spectrometry. Biofilm cells displayed significant changes in lipid A profiles when compared with their planktonic counterparts. Furthermore, in vitro experiments were conducted to examine the inflammatory response of PAMs exposed to UV-inactivated APP grown in biofilm or in suspension. Relative mRNA expression of pro-inflammatory genes IL1, IL6, IL8 and MCP1 decreased in PAMs when exposed to biofilm cells compared to planktonic cells. Additionally, the biofilm state reduced PBMCs proliferation. Taken together, APP biofilm cells show a weaker ability to stimulate innate immune cells, which could be due, in part, to lipid A structure modifications. PMID:27226465

  7. Growth kinetics of Si and Ge nanowires

    NASA Astrophysics Data System (ADS)

    Kodambaka, S.; Tersoff, J.; Reuter, M. C.; Ross, F. M.

    2009-02-01

    Si and Ge nanowires have potential applications in a wide variety of areas including thermoelectrics, optoelectronics, and sensors. Nanowires are most commonly grown via the vapor-liquid-solid (VLS) process. In this method, a vapor phase containing the material of interest preferentially dissociates at a liquid catalyst and is incorporated as a solid at the solid-liquid interface. However, despite 40 years of research in this area, several aspects of nanowire growth remain unclear, even for relatively simple elemental Si and Ge wires. Here, we will review our in situ transmission electron microscopy (TEM) investigations of Si and Ge nanowire growth kinetics. The observations are carried out in an ultra-high vacuum TEM (the IBM UHV-TEM) equipped with facilities for deposition during observation. Using Au as the catalyst, we study the VLS growth of Si and Ge nanowires as a function of disilane or digermane pressure and substrate temperature. We find surprisingly different growth mechanisms for the two materials. The insights gained from in situ results may help devise methods for large-scale fabrication of wires with controlled architecture.

  8. Demonstrating benthic control of anomalous solute transport: biofilm growth interacts with substrate size.

    NASA Astrophysics Data System (ADS)

    Aubeneau, A. F.; Tank, J. L.; Bolster, D.; Hanrahan, B.

    2014-12-01

    In fluvial systems, biofilms are the main driver of biogeochemical transformations. Biofilms grow on most surfaces in the benthic and hyporheic regions, where they process waterborne solutes. These solutes are transported in the regional flow and their fluxes near the biofilms are controlled by local physical properties, such as head gradients and hydraulic conductivity. These properties are in turn influenced by the growth of the biofilm itself, which can clog porous media and/or develop its own network of porous space. Therefore, the residence time of a solute in proximity to biofilm surfaces, where it can be processed, should be influenced by the properties not only of the physical environment, but by that of the biofilm itself. We hypothesized that the presence of biofilms would increase residence times in the benthic and shallow subsurface regions of the stream bed. We performed controlled experiments in 4 experimental streams at Notre Dame's Linked Experimental Ecosystem Facility (ND-LEEF) to quantify the interaction between substrate and biofilm in controlling anomalous solute transport. Each stream at ND-LEEF had a different substrate configuration: 2 with homogeneous substrate but with different sizes (pea gravel vs. coarse gravel) and 2 with heterogeneous substrate (alternating sections vs. well-mixed reaches). We measured the evolution of the residence time distributions in the streams by injecting rhodamine tracer (RWT) multiple times over the course of a 5 month colonization gradient. Analysis of breakthrough curves demonstrated that in addition to the influence of substrate, biofilm colonization and growth significantly influenced the residence time in the system. Specifically, as biofilms grew, the power-law exponent of the RTD decreased, i.e. the tails of the distributions became heavier, suggesting prolonged retention due to the presence of the biofilms. Although the substrate signature persisted over time, with the coarser gravel bed washing out

  9. Tyrosine Phosphorylation and Dephosphorylation in Burkholderia cenocepacia Affect Biofilm Formation, Growth under Nutritional Deprivation, and Pathogenicity

    PubMed Central

    Andrade, Angel; Tavares-Carreón, Faviola; Khodai-Kalaki, Maryam

    2015-01-01

    Burkholderia cenocepacia, a member of the B. cepacia complex (Bcc), is an opportunistic pathogen causing serious chronic infections in patients with cystic fibrosis. Tyrosine phosphorylation has emerged as an important posttranslational modification modulating the physiology and pathogenicity of Bcc bacteria. Here, we investigated the predicted bacterial tyrosine kinases BCAM1331 and BceF and the low-molecular-weight protein tyrosine phosphatases BCAM0208, BceD, and BCAL2200 of B. cenocepacia K56-2. We show that BCAM1331, BceF, BCAM0208, and BceD contribute to biofilm formation, while BCAL2200 is required for growth under nutrient-limited conditions. Multiple deletions of either tyrosine kinase or low-molecular-weight protein tyrosine phosphatase genes resulted in the attenuation of B. cenocepacia intramacrophage survival and reduced pathogenicity in the Galleria mellonella larval infection model. Experimental evidence indicates that BCAM1331 displays reduced tyrosine autophosphorylation activity compared to that of BceF. With the artificial substrate p-nitrophenyl phosphate, the phosphatase activities of the three low-molecular-weight protein tyrosine phosphatases demonstrated similar kinetic parameters. However, only BCAM0208 and BceD could dephosphorylate BceF. Further, BCAL2200 became tyrosine phosphorylated in vivo and catalyzed its autodephosphorylation. Together, our data suggest that despite having similar biochemical activities, low-molecular-weight protein tyrosine phosphatases and tyrosine kinases have both overlapping and specific roles in the physiology of B. cenocepacia. PMID:26590274

  10. The role of iron in Mycobacterium smegmatis biofilm formation: the exochelin siderophore is essential in limiting iron conditions for biofilm formation but not for planktonic growth

    PubMed Central

    Ojha, Anil; Hatfull, Graham F

    2007-01-01

    Many species of mycobacteria form structured biofilm communities at liquid–air interfaces and on solid surfaces. Full development of Mycobacterium smegmatis biofilms requires addition of supplemental iron above 1 μM ferrous sulphate, although addition of iron is not needed for planktonic growth. Microarray analysis of the M. smegmatis transcriptome shows that iron-responsive genes – especially those involved in siderophore synthesis and iron uptake – are strongly induced during biofilm formation reflecting a response to iron deprivation, even when 2 μM iron is present. The acquisition of iron under these conditions is specifically dependent on the exochelin synthesis and uptake pathways, and the strong defect of an iron–exochelin uptake mutant suggests a regulatory role of iron in the transition to biofilm growth. In contrast, although the expression of mycobactin and iron ABC transport operons is highly upregulated during biofilm formation, mutants in these systems form normal biofilms in low-iron (2 μM) conditions. A close correlation between iron availability and matrix-associated fatty acids implies a possible metabolic role in the late stages of biofilm maturation, in addition to the early regulatory role. M. smegmatis surface motility is similarly dependent on iron availability, requiring both supplemental iron and the exochelin pathway to acquire it. PMID:17854402

  11. Development of a simplified biofilm model

    NASA Astrophysics Data System (ADS)

    Sarkar, Sushovan; Mazumder, Debabrata

    2015-11-01

    A simplified approach for analyzing the biofilm process in deriving an easy model has been presented. This simplified biofilm model formulated correlations between substrate concentration in the influent/effluent and at biofilm-liquid interface along with substrate flux and biofilm thickness. The model essentially considered the external mass transport according to Fick's Law, steady state substrate as well as biomass balance for attached growth microorganisms. In substrate utilization, Monod growth kinetics has been followed incorporating relevant boundary conditions at the liquid-biofilm interface and at the attachment surface. The numerical solution of equations was accomplished using Runge-Kutta method and accordingly an integrated computer program was developed. The model has been successfully applied in a distinct set of trials with varying range of representative input variables. The model performance was compared with available existing methods and it was found an easy, accurate method that can be used for process design of biofilm reactor.

  12. Domain Growth Kinetics in Stratifying Foam Films

    NASA Astrophysics Data System (ADS)

    Zhang, Yiran; Sharma, Vivek

    2015-03-01

    Baking bread, brewing cappuccino, pouring beer, washing dishes, shaving, shampooing, whipping eggs and blowing bubbles all involve creation of aqueous foam films. Typical foam films consist of two surfactant-laden surfaces that are μ 5 nm - 10 micron apart. Sandwiched between these interfacial layers is a fluid that drains primarily under the influence of viscous and interfacial forces, including disjoining pressure. Interestingly, for certain low molecular weight surfactants, a layered ordering of micelles inside the foam films (thickness <100 nm) leads to a stepwise thinning phenomena called stratification. We experimentally elucidate the influence of these different driving forces, and confinement on drainage kinetics of horizontal stratifying foam films. Thinner, darker domains spontaneously grow within foam films. Quantitative characterization of domain growth visualized in a using Scheludko-type thin film cell and a theoretical model based on lubrication analysis, provide critical insights into hydrodynamics of thin foam films, and the strength and nature of surface forces, including supramolecular oscillatory structural forces.

  13. Human Serum Promotes Candida albicans Biofilm Growth and Virulence Gene Expression on Silicone Biomaterial

    PubMed Central

    Samaranayake, Yuthika Hemamala; Cheung, Becky P. K.; Yau, Joyce Y. Y.; Yeung, Shadow K. W.; Samaranayake, Lakshman P.

    2013-01-01

    Objectives Systemic candidal infections are a common problem in hospitalized patients due to central venous catheters fabricated using silicone biomaterial (SB). We therefore evaluated the effect of human serum on C. albicans biofilm morphology, growth, and the expression of virulence-related genes on SB in vitro. Methods We cultivated C. albicans SC5314 (wild-type strain, WT) and its derivative HLC54 (hyphal mutant, HM) for 48 h in various conditions, including the presence or absence of SB discs, and human serum. The growth of planktonic and biofilm cells of both strains was monitored at three time points by a tetrazolium salt reduction assay and by scanning electron microscopy. We also analyzed by RT-PCR its expression of the virulence-related genes ALS3, HWP1, EAP1, ECE1, SAP1 - SAP10, PLB1, PLB2, PLC and PLD. Results At each time point, planktonic cells of WT strain cultured in yeast nitrogen base displayed a much higher expression of EAP1 and HWP1, and a moderately higher ALS3 expression, than HM cells. In planktonic cells, expression of the ten SAP genes was higher in the WT strain initially, but were highly expressed in the HM strain by 48 h. Biofilm growth of both strains on SB was promoted in the presence of human serum than in its absence. Significant upregulation of ALS3, HWP1, EAP1, ECE1, SAP1, SAP4, SAP6 - SAP10, PLB1, PLB2 and PLC was observed for WT biofilms grown on serum-treated SB discs for at least one time point, compared with biofilms on serum-free SB discs. Conclusions Human serum stimulates C. albicans biofilm growth on SB discs and upregulates the expression of virulence genes, particularly adhesion genes ALS3 and HWP1, and hydrolase-encoding genes SAP, PLB1 and PLB2. This response is likely to promote the colonization of this versatile pathogen within the human host. PMID:23704884

  14. Microbial biofilm growth on irradiated, spent nuclear fuel cladding

    NASA Astrophysics Data System (ADS)

    Bruhn, D. F.; Frank, S. M.; Roberto, F. F.; Pinhero, P. J.; Johnson, S. G.

    2009-02-01

    A fundamental criticism regarding the potential for microbial influenced corrosion in spent nuclear fuel cladding or storage containers concerns whether the required microorganisms can, in fact, survive radiation fields inherent in these materials. This study was performed to unequivocally answer this critique by addressing the potential for biofilm formation, the precursor to microbial-influenced corrosion, in radiation fields representative of spent nuclear fuel storage environments. This study involved the formation of a microbial biofilm on irradiated spent nuclear fuel cladding within a hot cell environment. This was accomplished by introducing 22 species of bacteria, in nutrient-rich media, to test vessels containing irradiated cladding sections and that was then surrounded by radioactive source material. The overall dose rate exceeded 2 Gy/h gamma/beta radiation with the total dose received by some of the bacteria reaching 5 × 10 3 Gy. This study provides evidence for the formation of biofilms on spent-fuel materials, and the implication of microbial influenced corrosion in the storage and permanent deposition of spent nuclear fuel in repository environments.

  15. Microbial Biofilm Growth on Irradiated, Spent Nuclear Fuel Cladding

    SciTech Connect

    S.M. Frank

    2009-02-01

    A fundamental criticism regarding the potential for microbial influenced corrosion in spent nuclear fuel cladding or storage containers concerns whether the required microorganisms can, in fact, survive radiation fields inherent in these materials. This study was performed to unequivocally answer this critique by addressing the potential for biofilm formation, the precursor to microbial-influenced corrosion, in radiation fields representative of spent nuclear fuel storage environments. This study involved the formation of a microbial biofilm on irradiated spent nuclear fuel cladding within a hot cell environment. This was accomplished by introducing 22 species of bacteria, in nutrient-rich media, to test vessels containing irradiated cladding sections and that was then surrounded by radioactive source material. The overall dose rate exceeded 2 Gy/h gamma/beta radiation with the total dose received by some of the bacteria reaching 5 × 103 Gy. This study provides evidence for the formation of biofilms on spent-fuel materials, and the implication of microbial influenced corrosion in the storage and permanent deposition of spent nuclear fuel in repository environments.

  16. Optimizing and real-time control of biofilm formation, growth and renewal in denitrifying biofilter.

    PubMed

    Liu, Xiuhong; Wang, Hongchen; Long, Feng; Qi, Lu; Fan, Haitao

    2016-06-01

    A pilot-scale denitrifying biofilter (DNBF) with a treatment capacity of 600m(3)/d was used to study real-time control of biofilm formation, removal and renewal. The results showed biofilm formation, growth and removal can be well controlled using on-line monitored turbidity. The status of filter layer condition can be well indicated by Turb break points on turbidity profile. There was a very good linear relationship between biofilm growth degree (Xbiof) and filter clogging degree (Cfilter) with R(2) higher than 0.99. Filter layer clogging coefficient (Yc) lower than 0.27 can be used to determine stable filter layer condition. Since variations of turbidity during backwash well fitted normal distribution with R(2) higher than 0.96, biofilm removal during backwash also can be well optimized by turbidity. Although biofilm structure and nirK-coding denitrifying communities using different carbon sources were much more different, DNBF was still successfully and stably optimized and real-time controlled via on-line turbidity. PMID:26994461

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

    USGS Publications Warehouse

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

    2006-01-01

    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.

  18. Effect of negative pressure on growth, secretion and biofilm formation of Staphylococcus aureus.

    PubMed

    Li, Tongtong; Wang, Guoqi; Yin, Peng; Li, Zhirui; Zhang, Licheng; Liu, Jianheng; Li, Ming; Zhang, Lihai; Han, Li; Tang, Peifu

    2015-10-01

    Negative pressure wound therapy (NPWT) has gained popularity in the management of contaminated wounds as an effective physical therapy, although its influence on the bacteria in the wounds remains unclear. In this study, we attempted to explore the effect of negative pressure conditions on Staphylococcus aureus, the most frequently isolated pathogen during wound infection. S. aureus was cultured in Luria-Bertani medium at subatmospheric pressure of -125 mmHg for 24 h, with the bacteria grown at ambient pressure as the control. The application of negative pressure was found to slow down the growth rate and inhibit biofilm development of S. aureus, which was confirmed by static biofilm assays. Furthermore, decreases in the total amount of virulence factors and biofilm components were observed, including α-hemolysin, extracellular adherence protein, polysaccharide intercellular adhesin and extracellular DNA. With quantitative RT-PCR analysis, we also revealed a significant inhibition in the transcription of virulence and regulatory genes related to wound infections and bacterial biofilms. Together, these findings indicated that negative pressure could inhibit the growth, virulence and biofilm formation of S. aureus. A topical subatmospheric pressure condition, such as NPWT, may be a potential antivirulence and antibiofilm strategy in the field of wound care. PMID:26272011

  19. Influence of Lysogeny of Tectiviruses GIL01 and GIL16 on Bacillus thuringiensis Growth, Biofilm Formation, and Swarming Motility

    PubMed Central

    Gillis, Annika

    2014-01-01

    Bacillus thuringiensis is an entomopathogenic bacterium that has been used as an efficient biopesticide worldwide. Despite the fact that this bacterium is usually described as an insect pathogen, its life cycle in the environment is still largely unknown. B. thuringiensis belongs to the Bacillus cereus group of bacteria, which has been associated with many mobile genetic elements, such as species-specific temperate or virulent bacteriophages (phages). Temperate (lysogenic) phages are able to establish a long-term relationship with their host, providing, in some cases, novel ecological traits to the bacterial lysogens. Therefore, this work focuses on evaluating the potential influence of temperate tectiviruses GIL01 and GIL16 on the development of different life traits of B. thuringiensis. For this purpose, a B. thuringiensis serovar israelensis plasmid-cured (nonlysogenic) strain was used to establish bacterial lysogens for phages GIL01 and GIL16, and, subsequently, the following life traits were compared among the strains: kinetics of growth, metabolic profiles, antibiotics susceptibility, biofilm formation, swarming motility, and sporulation. The results revealed that GIL01 and GIL16 lysogeny has a significant influence on the bacterial growth, sporulation rate, biofilm formation, and swarming motility of B. thuringiensis. No changes in metabolic profiles or antibiotic susceptibilities were detected. These findings provide evidence that tectiviruses have a putative role in the B. thuringiensis life cycle as adapters of life traits with ecological advantages. PMID:25261525

  20. Influence of lysogeny of Tectiviruses GIL01 and GIL16 on Bacillus thuringiensis growth, biofilm formation, and swarming motility.

    PubMed

    Gillis, Annika; Mahillon, Jacques

    2014-12-01

    Bacillus thuringiensis is an entomopathogenic bacterium that has been used as an efficient biopesticide worldwide. Despite the fact that this bacterium is usually described as an insect pathogen, its life cycle in the environment is still largely unknown. B. thuringiensis belongs to the Bacillus cereus group of bacteria, which has been associated with many mobile genetic elements, such as species-specific temperate or virulent bacteriophages (phages). Temperate (lysogenic) phages are able to establish a long-term relationship with their host, providing, in some cases, novel ecological traits to the bacterial lysogens. Therefore, this work focuses on evaluating the potential influence of temperate tectiviruses GIL01 and GIL16 on the development of different life traits of B. thuringiensis. For this purpose, a B. thuringiensis serovar israelensis plasmid-cured (nonlysogenic) strain was used to establish bacterial lysogens for phages GIL01 and GIL16, and, subsequently, the following life traits were compared among the strains: kinetics of growth, metabolic profiles, antibiotics susceptibility, biofilm formation, swarming motility, and sporulation. The results revealed that GIL01 and GIL16 lysogeny has a significant influence on the bacterial growth, sporulation rate, biofilm formation, and swarming motility of B. thuringiensis. No changes in metabolic profiles or antibiotic susceptibilities were detected. These findings provide evidence that tectiviruses have a putative role in the B. thuringiensis life cycle as adapters of life traits with ecological advantages. PMID:25261525

  1. In situ monitoring of Shewanella oneidensis MR-1 biofilm growth on gold electrodes by using a Pt microelectrode.

    PubMed

    Bao, Han; Zheng, Zhanwang; Yang, Bin; Liu, Ding; Li, Feifang; Zhang, Xingwang; Li, Zhongjian; Lei, Lecheng

    2016-06-01

    Much attention has been focused on electrochemically active bacteria (EAB) in the application of bioelectrochemical systems (BESs). Studying the EAB biofilm growth mechanism as well as electron transfer mechanism provides a route to upgrade BES performance. But an effective bacterial growth monitoring method on the biofilm scale is still absent in this field. In this work, electrode-attached bacterial biofilms formed by Shewanella oneidensis MR-1 were dynamically monitored through a microelectrode method. For S. oneidensis MR-1, a respiratory electron transport chain is associated with the secretion of riboflavin, severing as the cofactor to the outer membrane c-type cytochromes. The biofilm growth was monitored through adopting riboflavin as an electrochemical probe during the approach of the microelectrode to the biofilm external surface. This method allows in vivo and in situ biofilm monitoring at different growth stages without destructive manipulation. Furthermore, the biofilm growth monitoring results have been proved to be relatively accurate through observation under confocal laser scanning microscopy. We further applied this method to investigate the effects of four environmental factors (the concentrations of dissolved oxygen, sodium lactate, riboflavin as well as the electrode potential) on S. oneidensis MR-1 biofilm development. PMID:26850925

  2. Selected dietary (poly)phenols inhibit periodontal pathogen growth and biofilm formation.

    PubMed

    Shahzad, Muhammad; Millhouse, Emma; Culshaw, Shauna; Edwards, Christine A; Ramage, Gordon; Combet, Emilie

    2015-03-01

    Periodontitis (PD) is a chronic infectious disease mediated by bacteria in the oral cavity. (Poly)phenols (PPs), ubiquitous in plant foods, possess antimicrobial activities and may be useful in the prevention and management of periodontitis. The objective of this study was to test the antibacterial effects of selected PPs on periodontal pathogens, on both planktonic and biofilm modes of growth. Selected PPs (n = 48) were screened against Streptococcus mitis (S. mitis), Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), Fusobacterium nucleatum (F. nucleatum) and Porphyromonas gingivalis (P. gingivalis). The antibacterial potential of each compound was evaluated in terms of planktonic minimum inhibitory concentration (PMIC) and planktonic minimum bactericidal concentration (PMBC) using standardized broth microdilution assays. The most active PPs were further tested for their effect on mono-species and multi-species biofilms using a colorimetric resazurin-based viability assay and scanning electron microscopy. Of the 48 PPs tested, 43 showed effective inhibition of planktonic growth of one or more test strains, of which curcumin was the most potent (PMIC range = 7.8-62.5 μg mL(-1)), followed by pyrogallol (PMIC range = 2.4-2500 μg mL(-1)), pyrocatechol (MIC range = 4.9-312.5 μg mL(-1)) and quercetin (PMIC range = 31.2-500 μg mL(-1)). At this concentration, adhesion of curcumin and quercetin to the substrate also inhibited adhesion of S. mitis, and biofilm formation and maturation. While both curcumin and quercetin were able to alter architecture of mature multi-species biofilms, only curcumin-treated biofilms displayed a significantly reduced metabolic activity. Overall, PPs possess antibacterial activities against periodontopathic bacteria in both planktonic and biofilm modes of growth. Further cellular and in vivo studies are necessary to confirm their beneficial activities and potential use in the prevention and or treatment of periodontal

  3. Effect of estradiol on planktonic growth, coaggregation, and biofilm formation of the Prevotella intermedia group bacteria.

    PubMed

    Fteita, Dareen; Könönen, Eija; Söderling, Eva; Gürsoy, Ulvi Kahraman

    2014-06-01

    Alterations in the quantity and quality of biofilms at gingival margin are considered to play a role in the initiation and development of pregnancy-related gingivitis. Prevotella intermedia sensu lato is able to consume estradiol, the major sex hormone secreted during pregnancy, in the absence of vitamin K. The aim of the study was to examine the effect of estradiol on the planktonic growth, coaggregation, polysaccharide production, and biofilm formation of the P. intermedia group bacteria, namely P. intermedia, Prevotella nigrescens, and Prevotella pallens. In all experiments, the type strain (ATCC) and a clinical strain (AHN) of P. intermedia, P. nigrescens, and P. pallens were incubated with the concentrations of 0, 30, 90, and 120 nmol/L of estradiol. Planktonic growth was assessed by means of the colony forming unit method, while coaggregation and biofilm formation were assessed by spectrophotometric methods. In the determination of protein and polysaccharide levels, the Bradford and phenol-sulfuric acid methods were used, respectively. P. pallens AHN 9283 and P. nigrescens ATCC 33563 increased their numbers at planktonic stage with increasing estradiol concentrations. In 48-h biofilm tests, elevated protein levels were found for both strains of P. intermedia, and the strains P. nigrescens ATCC 33563 and P. pallens AHN 9283 in the presence of estradiol. The P. intermedia strains also increased the levels of polysaccharide formation in the biofilm. Coaggregation of the P. intermedia group organisms with Fusobacterium nucleatum was enhanced only in P. intermedia AHN 8290. In conclusion, our in vitro experiments indicate that estradiol regulates planktonic growth, coaggregation, polysaccharide production, and biofilm formation characteristics of P. intermedia, P. nigrescens, and P. pallens differently. These results may, at least partly, explain the differences seen in their contribution to the pathogenesis of pregnancy-related gingivitis. PMID

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  5. Thin films of silk fibroin and its blend with chitosan strongly promote biofilm growth of Synechococcus sp. BDU 140432.

    PubMed

    Kaushik, Sharbani; Sarma, Mrinal K; Thungon, Phurpa Dema; Santhosh, Mallesh; Goswami, Pranab

    2016-10-01

    The activating role of different polymer thin films coated over polystyrene support on the Synechococcus sp. biofilm growth was examined concurrently by measuring biofilm florescence using a dye and by measuring cell density in the isolated biofilm. Compared to blank (no coating), the increase in biofilm formation (%) on silk, chitosan, silk-chitosan (3:2) blend, polyaniline, osmium, and Nafion films were 27.73 (31.16), 21.55 (23.74), 37.21 (38.34), 5.35 (8.96), 6.70 (6.55) and (nil), respectively with corresponding cell density (%) shown in the parentheses. This trend of biofilm formation on the films did not significantly vary for Escherichia coli and Lactobacillus plantarum strains. The films of 20 residues long each of glycine-alanine repeat peptide, which mimics a silk fibroin motif, and a hydrophobic glycine-valine repeat peptide, increased the biofilm growth by 13.53 % and 26.08 %, respectively. Silk and blend films showed highest adhesion unit (0.48-0.49), adhesion rate ((4.2-4.8)×10(-6), m/s) and Gibbs energy of adhesion (-8.5 to -8.6kT) with Synechococcus sp. The results confirmed interplay of electrostatic and hydrophobic interaction between cell-surface and polymer films for promoting rapid biofilm growth. This study established that the thin films of silk and the blend (3:2) promote rapid biofilm growth for all the tested microorganisms. PMID:27393887

  6. Burkholderia BcpA mediates biofilm formation independently of interbacterial contact dependent growth inhibition

    PubMed Central

    Garcia, Erin C.; Anderson, Melissa S.; Hagar, Jon A.; Cotter, Peggy A.

    2013-01-01

    SUMMARY Contact dependent growth inhibition (CDI) is a phenomenon in which Gram-negative bacteria use the toxic C-terminus of a large surface-exposed exoprotein to inhibit the growth of susceptible bacteria upon cell-cell contact. Little is known about when and where bacteria express the genes encoding CDI system proteins and how these systems contribute to the survival of bacteria in their natural niche. Here we establish that, in addition to mediating interbacterial competition, the Burkholderia thailandensis CDI system exoprotein BcpA is required for biofilm development. We also provide evidence that the catalytic activity of BcpA and extracellular DNA are required for the characteristic biofilm pillars to form. We show using a bcpA-gfp fusion that within the biofilm, expression of the CDI system-encoding genes is below the limit of detection for the majority of bacteria and only a subset of cells express the genes strongly at any given time. Analysis of a strain constitutively expressing the genes indicates that native expression is critical for biofilm architecture. Although CDI systems have so far only been demonstrated to be involved in interbacterial competition, constitutive production of the system’s immunity protein in the entire bacterial population did not alter biofilm formation, indicating a CDI-independent role for BcpA in this process. We propose, therefore, that bacteria may use CDI proteins in cooperative behaviors, like building biofilm communities, and in competitive behaviors that prevent non-self bacteria from entering the community. PMID:23879629

  7. The effect of blue light on periodontal biofilm growth in vitro.

    PubMed

    Fontana, Carla R; Song, Xiaoqing; Polymeri, Angeliki; Goodson, J Max; Wang, Xiaoshan; Soukos, Nikolaos S

    2015-11-01

    We have previously shown that blue light eliminates the black-pigmented oral bacteria Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, and Prevotella melaninogenica. In the present study, the in vitro photosensitivity of the above black-pigmented microorganisms and four Fusobacteria species (Fusobacterium nucleatum ss. nucleatum, F. nucleatum ss. vincentii, F. nucleatum ss. polymorphum, Fusobacterium periodonticum) was investigated in pure cultures and human dental plaque suspensions. We also tested the hypothesis that phototargeting the above eight key periodontopathogens in plaque-derived biofilms in vitro would control growth within the dental biofilm environment. Cultures of the eight bacteria were exposed to blue light at 455 nm with power density of 80 mW/cm2 and energy fluence of 4.8 J/cm2. High-performance liquid chromatography (HPLC) analysis of bacteria was performed to demonstrate the presence and amounts of porphyrin molecules within microorganisms. Suspensions of human dental plaque bacteria were also exposed once to blue light at 455 nm with power density of 50 mW/cm2 and energy fluence of 12 J/cm2. Microbial biofilms developed from the same plaque were exposed to 455 nm blue light at 50 mW/cm2 once daily for 4 min (12 J/cm2) over a period of 3 days (4 exposures) in order to investigate the cumulative action of phototherapy on the eight photosensitive pathogens as well as on biofilm growth. Bacterial growth was evaluated using the colony-forming unit (CFU) assay. The selective phototargeting of pathogens was studied using whole genomic probes in the checkerboard DNA-DNA format. In cultures, all eight species showed significant growth reduction (p < 0.05). HPLC demonstrated various porphyrin patterns and amounts of porphyrins in bacteria. Following phototherapy, the mean survival fractions were reduced by 28.5 and 48.2% in plaque suspensions and biofilms, respectively, (p < 0.05). DNA probe analysis showed significant

  8. Domain growth kinetics in stratifying foam films

    NASA Astrophysics Data System (ADS)

    Zhang, Yiran; Sharma, Vivek

    2015-11-01

    Baking bread, brewing cappuccino, pouring beer, washing dishes, shaving, shampooing, whipping eggs and blowing bubbles all involve creation of aqueous foam films. Typical foam films consist of two surfactant-laden surfaces that are ~ 5 nm - 10 micron apart. Sandwiched between these interfacial layers is a fluid that drains primarily under the influence of viscous and interfacial forces, including disjoining pressure. Interestingly, a layered ordering of micelles inside the foam films (thickness <100 nm) leads to a stepwise thinning phenomena called stratification, which results in a thickness-dependent variation in reflected light intensity, visualized as progressively darker shades of gray. Thinner, darker domains spontaneously grow within foam films. We show that the domain expansion dynamics exhibit two distinct growth regimes with characteristic scaling laws. Though several studies have focused on the expansion dynamics of isolated domains that exhibit a diffusion-like scaling, the change in expansion kinetics observed after domains contact with the Plateau border has not been reported and analyzed before.

  9. Candida-streptococcal mucosal biofilms display distinct structural and virulence characteristics depending on growth conditions and hyphal morphotypes

    PubMed Central

    Bertolini, Martinna M.; Xu, Hongbin; Sobue, Takanori; Nobile, Clarissa J.; Cury, Altair; Dongari-Bagtzoglou, Anna

    2015-01-01

    Summary Candida albicans and Streptococci of the Mitis group form communities in multiple oral sites, where moisture and nutrient availability can change spatially or temporally. This study evaluated structural and virulence characteristics of Candida-streptococcal biofilms formed on moist or semidry mucosal surfaces, and tested the effects of nutrient availability and hyphal morphotype on dual-species biofilms. Three-dimensional models of the oral mucosa formed by immortalized keratinocytes on a fibroblast-embedded collagenous matrix were used. Infections were carried out using Streptococcus oralis strain 34, in combination with a C. albicans wild-type strain, or pseudohyphal-forming mutant strains. Increased moisture promoted a homogeneous surface biofilm by C. albicans. Dual biofilms had a stratified structure, with streptococci growing in close contact to the mucosa and fungi growing on the bacterial surface. Under semi-dry conditions, Candida formed localized foci of dense growth, which promoted focal growth of streptococci in mixed biofilms. Candida biofilm biovolume was greater under moist conditions, albeit with minimal tissue invasion, compared to semidry conditions. Supplementing the infection medium with nutrients under semidry conditions intensified growth, biofilm biovolume and tissue invasion/damage, without changing biofilm structure. Under these conditions, the pseudohyphal mutants and S. oralis formed defective superficial biofilms, with most bacteria in contact with the epithelial surface, below a pseudohyphal mass, resembling biofilms growing in moist environment. The presence of S. oralis promoted fungal invasion and tissue damage under all conditions. We conclude that moisture, nutrient availability, hyphal morphotype and presence of commensal bacteria influence the architecture and virulence characteristics of mucosal fungal biofilms. PMID:25754666

  10. Visualization experiments of biofilm growth in the presence of carbon dioxide

    NASA Astrophysics Data System (ADS)

    Manariotis, I. D.; Sygouni, V.; Chrysikopoulos, C. V.

    2013-12-01

    Capturing and storing CO2 emissions in properly selected deep geologic formations is considered a promising solution for the reduction of CO2 in the atmosphere. However, CO2 leakage may potentially occur from the storage geologic formation. Partition of CO2 in water may result in pH decrease. This change in aqueous phase may contribute to solubilization of undesired heavy metals from the solid matrix. In this work we investigate experimentally the impact of CO2 to shallow groundwater systems. A series of visualization experiments in a glass-etched micromodel were performed in order to estimate the effect of CO2 on biofilm formation. Biofilms were developed using Pseudomonas putida. Nutrient saturated with CO2 was injected in the micromodel through an inlet port, and fluid samples were collected at the outlet port. The transient growth of the biofilm was monitored by taking high-resolution digital photographs at various times, and the effect of CO2 on biofilm growth was estimated.

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

    PubMed Central

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

    2011-01-01

    Biofilm embedded bacterial pathogens such as Staphylococcus spp., Escherichia coli, Pseudomonas aeruginosa, and Acinetobacter baumannii are difficult to eradicate and are major sources of bacterial infections. New drugs are needed to combat these pathogens. Hypericum is a plant genus that contains species known to have antimicrobial properties. However, the specific constituents responsible for the antimicrobial properties are not entirely known, nor have most compounds been tested as inhibitors of biofilm development. The investigation presented here tested seven secondary metabolites isolated from the species Hypericum densiflorum, Hypericumellipticum, Hypericum prolificum and Hypericum punctatum as inhibitors of bacterial growth and biofilm production. Assays were conducted against Staphylococcus epidermidis, Staphylococcusaureus, clinical methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Escherichia coli, and Acinetobacter baumannii. Five of the seven compounds demonstrated growth inhibition against the Gram-positive bacteria with minimum inhibitory concentrations (MIC) ranging from 1.95 μg/mL to 7.81 μg/mL. Four of the secondary metabolites inhibited biofilm production by certain Gram-positive strains at sub-MIC concentrations. PMID:22170780

  12. Influence of oxyR on Growth, Biofilm Formation, and Mobility of Vibrio parahaemolyticus

    PubMed Central

    Chung, Chun-Hui; Fen, Shin-yuan; Yu, Shu-Chuan

    2015-01-01

    Vibrio parahaemolyticus is a common marine food-borne enteropathogen. In this study, we examined the antioxidative activity, growth, biofilm formation, and cell mobility of an oxyR deletion mutant and its genetically complementary strain of V. parahaemolyticus. oxyR is the regulator of catalase and ahpC genes. Protection against extrinsic H2O2 and against the organic peroxides cumene hydroperoxide and tert-butyl hydroperoxide was weaker in the deletion mutant than in its parent strain. Expression of the major functional antioxidative genes, ahpC1 and VPA1418, was markedly decreased in the oxyR mutant. Growth of this mutant on agar medium was significantly inhibited by autoclaved 0.25% glucose and by 0.25% dipotassium hydrogen phosphate, 0.5% monosaccharides (glucose, galactose, xylose, and arabinose), or 114.8 mM phosphates. The inhibition of the growth of this oxyR mutant by extrinsic peroxides, autoclaved sugars, and phosphates was eliminated by the complementary oxyR gene or by the addition of catalase to the autoclaved medium, while no inhibition of growth was observed when filter-sterilized sugars were used. The formation of biofilm and swimming mobility were significantly inhibited in the oxyR mutant relative to that in the wild-type strain. This investigation demonstrates the antioxidative function of oxyR in V. parahaemolyticus and its possible roles in biofilm formation, cell mobility, and the protection of growth in heated rich medium. PMID:26590276

  13. Large-scale epitaxial growth kinetics of graphene: A kinetic Monte Carlo study

    SciTech Connect

    Jiang, Huijun; Hou, Zhonghuai

    2015-08-28

    Epitaxial growth via chemical vapor deposition is considered to be the most promising way towards synthesizing large area graphene with high quality. However, it remains a big theoretical challenge to reveal growth kinetics with atomically energetic and large-scale spatial information included. Here, we propose a minimal kinetic Monte Carlo model to address such an issue on an active catalyst surface with graphene/substrate lattice mismatch, which facilitates us to perform large scale simulations of the growth kinetics over two dimensional surface with growth fronts of complex shapes. A geometry-determined large-scale growth mechanism is revealed, where the rate-dominating event is found to be C{sub 1}-attachment for concave growth-front segments and C{sub 5}-attachment for others. This growth mechanism leads to an interesting time-resolved growth behavior which is well consistent with that observed in a recent scanning tunneling microscopy experiment.

  14. Biofilm supported increase of chemical weathering and decrease of chemical denudation in pine growth experiments

    NASA Astrophysics Data System (ADS)

    Balogh, Z.; Keller, C.; Gill, R. A.

    2006-12-01

    Vascular plants and associated microbial communities produced biofilm coatings increase weathering by extending contact periods of minerals with low pH liquids. We performed an experiment to isolate the effects of ectomycorrhiza-forming fungi and ectomycorrhiza- helper bacteria on chemical weathering and chemical denudation (i.e. chemical erosion), and their effects on these fluxes in association with red pine as a host. The study was conducted in a growth chamber using sandy growth medium in replicated flow-through columns. Biotite and anorthite supplied Ca, Mg and K. Concentrations of these cations were measured in input and output solutions, in tree biomass and on exchangeable cation sites of the growth medium; then weathering and denudation fluxes were estimated by mass-balance. In addition, mineral surface changes, biofilm cover and microbial attachment to surfaces were investigated with scanning electron microscopy. The column experiment demonstrated that both bacteria and fungi had a large weathering potential for Ca- bearing minerals, but the microbial communities were not able to regulate denudation losses without a vascular host. Chemical weathering and denudation were about equal in each microbe-only treatment. By the second 6 months of the experiment treatment effects became significant for the seedling systems (p<0.005). The ectomycorrhizal treatments produced the greatest weathering and least denudation, but non- ectomycorrhizal seedlings lowered denudation as well. The differences between the fluxes were significant in both ectomycorrhizal and non-ectomycorrhizal treatments, but the ectomycorrhizal treatment difference was larger, while abiotic weathering was less and equaled the abiotic denudation flux. The ability to retard denudation in both ectomycorrhizal and non-ectomycorrhizal treatment was linked to biofilm formation on mineral surfaces. An ectomycorrhizal hyphal network, as part of the biofilm or covered by the biofilm, was apparently able

  15. C. albicans growth, transition, biofilm formation, and gene expression modulation by antimicrobial decapeptide KSL-W

    PubMed Central

    2013-01-01

    Background Antimicrobial peptides have been the focus of much research over the last decade because of their effectiveness and broad-spectrum activity against microbial pathogens. These peptides also participate in inflammation and the innate host defense system by modulating the immune function that promotes immune cell adhesion and migration as well as the respiratory burst, which makes them even more attractive as therapeutic agents. This has led to the synthesis of various antimicrobial peptides, including KSL-W (KKVVFWVKFK-NH2), for potential clinical use. Because this peptide displays antimicrobial activity against bacteria, we sought to determine its antifungal effect on C. albicans. Growth, hyphal form, biofilm formation, and degradation were thus examined along with EFG1, NRG1, EAP1, HWP1, and SAP 2-4-5-6 gene expression by quantitative RT-PCR. Results This study demonstrates that KSL-W markedly reduced C. albicans growth at both early and late incubation times. The significant effect of KSL-W on C. albicans growth was observed beginning at 10 μg/ml after 5 h of contact by reducing C. albicans transition and at 25 μg/ml by completely inhibiting C. albicans transition. Cultured C. albicans under biofilm-inducing conditions revealed that both KSL-W and amphotericin B significantly decreased biofilm formation at 2, 4, and 6 days of culture. KSL-W also disrupted mature C. albicans biofilms. The effect of KSL-W on C. albicans growth, transition, and biofilm formation/disruption may thus occur through gene modulation, as the expression of various genes involved in C. albicans growth, transition and biofilm formation were all downregulated when C. albicans was treated with KSL-W. The effect was greater when C. albicans was cultured under hyphae-inducing conditions. Conclusions These data provide new insight into the efficacy of KSL-W against C. albicans and its potential use as an antifungal therapy. PMID:24195531

  16. Probiotic lactobacilli inhibit early stages of Candida albicans biofilm development by reducing their growth, cell adhesion, and filamentation.

    PubMed

    Matsubara, Victor Haruo; Wang, Yi; Bandara, H M H N; Mayer, Marcia Pinto Alves; Samaranayake, Lakshman P

    2016-07-01

    We evaluated the inhibitory effects of the probiotic Lactobacillus species on different phases of Candida albicans biofilm development. Quantification of biofilm growth and ultrastructural analyses were performed on C. albicans biofilms treated with Lactobacillus rhamnosus, Lactobacillus casei, and Lactobacillus acidophilus planktonic cell suspensions as well as their supernatants. Planktonic lactobacilli induced a significant reduction (p < 0.05) in the number of biofilm cells (25.5-61.8 %) depending on the probiotic strain and the biofilm phase. L. rhamnosus supernatants had no significant effect on the mature biofilm (p > 0.05), but significantly reduced the early stages of Candida biofilm formation (p < 0.01). Microscopic analyses revealed that L. rhamnosus suspensions reduced Candida hyphal differentiation, leading to a predominance of budding growth. All lactobacilli negatively impacted C. albicans yeast-to-hyphae differentiation and biofilm formation. The inhibitory effects of the probiotic Lactobacillus on C. albicans entailed both cell-cell interactions and secretion of exometabolites that may impact on pathogenic attributes associated with C. albicans colonization on host surfaces and yeast filamentation. This study clarifies, for the first time, the mechanics of how Lactobacillus species may antagonize C. albicans host colonization. Our data elucidate the inhibitory mechanisms that define the probiotic candicidal activity of lactobacilli, thus supporting their utility as an adjunctive therapeutic mode against mucosal candidal infections. PMID:27087525

  17. Biofilm growth of Chlorella sorokiniana in a rotating biological contactor based photobioreactor.

    PubMed

    Blanken, W; Janssen, M; Cuaresma, M; Libor, Z; Bhaiji, T; Wijffels, R H

    2014-12-01

    Microalgae biofilms could be used as a production platform for microalgae biomass. In this study, a photobioreactor design based on a rotating biological contactor (RBC) was used as a production platform for microalgae biomass cultivated in biofilm. In the photobioreactor, referred to as Algadisk, microalgae grow in biofilm on vertical rotating disks partially submerged in a growth medium. The objective is to evaluate the potential of the Algadisk photobioreactor with respect to the effects of disk roughness, disk rotation speed and CO2 concentration. These objectives where evaluated in relationship to productivity, photosynthetic efficiency, and long-term cultivation stability in a lab-scale Algadisk system. Although the lab-scale Algadisk system is used, operation parameters evaluated are relevant for scale-up. Chlorella Sorokiniana was used as model microalgae. In the lab-scale Algadisk reactor, productivity of 20.1 ± 0.7 g per m(2) disk surface per day and a biomass yield on light of 0.9 ± 0.04 g dry weight biomass per mol photons were obtained. Different disk rotation speeds did demonstrate minimal effects on biofilm growth and on the diffusion of substrate into the biofilm. CO2 limitation, however, drastically reduced productivity to 2-4 g per m(2) disk surface per day. Productivity could be maintained over a period of 21 weeks without re-inoculation of the Algadisk. Productivity decreased under extreme conditions such as pH 9-10, temperature above 40°C, and with low CO2 concentrations. Maximal productivity, however, was promptly recovered when optimal cultivation conditions were reinstated. These results exhibit an apparent opportunity to employ the Algadisk photobioreactor at large scale for microalgae biomass production if diffusion does not limit the CO2 supply. PMID:24895246

  18. Determining crystal growth kinetic parameters using optical fibre sensors

    NASA Astrophysics Data System (ADS)

    Boerkamp, M.; Lamb, D. W.; Lye, P. G.

    2012-12-01

    The capability of an 'intrinsic exposed core optical fibre sensor' (IECOFS) as a monitoring device of scale formation has been evaluated. The IECOFS has been used to measure kinetics parameters of calcium carbonate heterogeneous crystal growth such as the activation energy, the crystal growth rate and the induction time. The IECOFS was able to evaluate crystal growth inhibition through the use of chemical inhibitors.

  19. General Theory for Integrated Analysis of Growth, Gene, and Protein Expression in Biofilms

    PubMed Central

    Zhang, Tianyu; Pabst, Breana; Klapper, Isaac; Stewart, Philip S.

    2013-01-01

    A theory for analysis and prediction of spatial and temporal patterns of gene and protein expression within microbial biofilms is derived. The theory integrates phenomena of solute reaction and diffusion, microbial growth, mRNA or protein synthesis, biomass advection, and gene transcript or protein turnover. Case studies illustrate the capacity of the theory to simulate heterogeneous spatial patterns and predict microbial activities in biofilms that are qualitatively different from those of planktonic cells. Specific scenarios analyzed include an inducible GFP or fluorescent protein reporter, a denitrification gene repressed by oxygen, an acid stress response gene, and a quorum sensing circuit. It is shown that the patterns of activity revealed by inducible stable fluorescent proteins or reporter unstable proteins overestimate the region of activity. This is due to advective spreading and finite protein turnover rates. In the cases of a gene induced by either limitation for a metabolic substrate or accumulation of a metabolic product, maximal expression is predicted in an internal stratum of the biofilm. A quorum sensing system that includes an oxygen-responsive negative regulator exhibits behavior that is distinct from any stage of a batch planktonic culture. Though here the analyses have been limited to simultaneous interactions of up to two substrates and two genes, the framework applies to arbitrarily large networks of genes and metabolites. Extension of reaction-diffusion modeling in biofilms to the analysis of individual genes and gene networks is an important advance that dovetails with the growing toolkit of molecular and genetic experimental techniques. PMID:24376726

  20. Growth Kinetics of Suspended Microbial Cells: From Single-Substrate-Controlled Growth to Mixed-Substrate Kinetics

    PubMed Central

    Kovárová-Kovar, Karin; Egli, Thomas

    1998-01-01

    Growth kinetics, i.e., the relationship between specific growth rate and the concentration of a substrate, is one of the basic tools in microbiology. However, despite more than half a century of research, many fundamental questions about the validity and application of growth kinetics as observed in the laboratory to environmental growth conditions are still unanswered. For pure cultures growing with single substrates, enormous inconsistencies exist in the growth kinetic data reported. The low quality of experimental data has so far hampered the comparison and validation of the different growth models proposed, and only recently have data collected from nutrient-controlled chemostat cultures allowed us to compare different kinetic models on a statistical basis. The problems are mainly due to (i) the analytical difficulty in measuring substrates at growth-controlling concentrations and (ii) the fact that during a kinetic experiment, particularly in batch systems, microorganisms alter their kinetic properties because of adaptation to the changing environment. For example, for Escherichia coli growing with glucose, a physiological long-term adaptation results in a change in KS for glucose from some 5 mg liter−1 to ca. 30 μg liter−1. The data suggest that a dilemma exists, namely, that either “intrinsic” KS (under substrate-controlled conditions in chemostat culture) or μmax (under substrate-excess conditions in batch culture) can be measured but both cannot be determined at the same time. The above-described conventional growth kinetics derived from single-substrate-controlled laboratory experiments have invariably been used for describing both growth and substrate utilization in ecosystems. However, in nature, microbial cells are exposed to a wide spectrum of potential substrates, many of which they utilize simultaneously (in particular carbon sources). The kinetic data available to date for growth of pure cultures in carbon-controlled continuous culture

  1. A non-destructive method for characterizing phenotypes and growth of a Bacillus subtilis biofilm using fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Koehler, Stephan; Wang, Xiaoling; Wilking, James; Weitz, Dave

    2015-11-01

    We develop an imaging technique for characterizing growth of biofilms using a triple fluorescent labeled strain for the three main phenotypes of a Bacillus subtilis biofilm on an agar substrate. We find that the biofilm does not flow across the substrate and thus growth is due to colonization at the periphery and thickening of the interior regions. We obtain local height and its composition of the three main phenotypes, which are motile, matrix-producing and sporulating, as well as the non-fluorescent material, which can be spores, dormant or dead cells or extracellular matrix. This technique is suitable for the study of biofilm growth and inhibition for different conditions such as biocides or bioremediation.

  2. ZnO Nanoparticles Affect Bacillus subtilis Cell Growth and Biofilm Formation

    PubMed Central

    Hsueh, Yi-Huang; Ke, Wan-Ju; Hsieh, Chien-Te; Lin, Kuen-Song; Tzou, Dong-Ying; Chiang, Chao-Lung

    2015-01-01

    Zinc oxide nanoparticles (ZnO NPs) are an important antimicrobial additive in many industrial applications. However, mass-produced ZnO NPs are ultimately disposed of in the environment, which can threaten soil-dwelling microorganisms that play important roles in biodegradation, nutrient recycling, plant protection, and ecological balance. This study sought to understand how ZnO NPs affect Bacillus subtilis, a plant-beneficial bacterium ubiquitously found in soil. The impact of ZnO NPs on B. subtilis growth, FtsZ ring formation, cytosolic protein activity, and biofilm formation were assessed, and our results show that B. subtilis growth is inhibited by high concentrations of ZnO NPs (≥ 50 ppm), with cells exhibiting a prolonged lag phase and delayed medial FtsZ ring formation. RedoxSensor and Phag-GFP fluorescence data further show that at ZnO-NP concentrations above 50 ppm, B. subtilis reductase activity, membrane stability, and protein expression all decrease. SDS-PAGE Stains-All staining results and FT-IR data further demonstrate that ZnO NPs negatively affect exopolysaccharide production. Moreover, it was found that B. subtilis biofilm surface structures became smooth under ZnO-NP concentrations of only 5–10 ppm, with concentrations ≤ 25 ppm significantly reducing biofilm formation activity. XANES and EXAFS spectra analysis further confirmed the presence of ZnO in co-cultured B. subtilis cells, which suggests penetration of cell membranes by either ZnO NPs or toxic Zn+ ions from ionized ZnO NPs, the latter of which may be deionized to ZnO within bacterial cells. Together, these results demonstrate that ZnO NPs can affect B. subtilis viability through the inhibition of cell growth, cytosolic protein expression, and biofilm formation, and suggest that future ZnO-NP waste management strategies would do well to mitigate the potential environmental impact engendered by the disposal of these nanoparticles. PMID:26039692

  3. Biofilms of Lactobacillus plantarum and Lactobacillus fermentum: Effect on stress responses, antagonistic effects on pathogen growth and immunomodulatory properties.

    PubMed

    Aoudia, Nabil; Rieu, Aurélie; Briandet, Romain; Deschamps, Julien; Chluba, Johanna; Jego, Gaëtan; Garrido, Carmen; Guzzo, Jean

    2016-02-01

    Few studies have extensively investigated probiotic functions associated with biofilms. Here, we show that strains of Lactobacillus plantarum and Lactobacillus fermentum are able to grow as biofilm on abiotic surfaces, but the biomass density differs between strains. We performed microtiter plate biofilm assays under growth conditions mimicking to the gastrointestinal environment. Osmolarity and low concentrations of bile significantly enhanced Lactobacillus spatial organization. Two L. plantarum strains were able to form biofilms under high concentrations of bile and mucus. We used the agar well-diffusion method to show that supernatants from all Lactobacillus except the NA4 isolate produced food pathogen inhibitory molecules in biofilm. Moreover, TNF-α production by LPS-activated human monocytoid cells was suppressed by supernatants from Lactobacillus cultivated as biofilms but not by planktonic culture supernatants. However, only L. fermentum NA4 showed anti-inflammatory effects in zebrafish embryos fed with probiotic bacteria, as assessed by cytokine transcript level (TNF-α, IL-1β and IL-10). We conclude that the biofilm mode of life is associated with beneficial probiotic properties of lactobacilli, in a strain dependent manner. Those results suggest that characterization of isolate phenotype in the biofilm state could be additional valuable information for the selection of probiotic strains. PMID:26611169

  4. Cancer Progression and Tumor Growth Kinetics

    NASA Astrophysics Data System (ADS)

    Blagoev, Krastan; Kalpathy-Cramer, Jayashree; Wilkerson, Julia; Sprinkhuizen, Sara; Song, Yi-Qiao; Bates, Susan; Rosen, Bruce; Fojo, Tito

    2013-03-01

    We present and analyze tumor growth data from prostate and brain cancer. Scaling the data from different patients shows that early stage prostate tumors show non-exponential growth while advanced prostate and brain tumors enter a stage of exponential growth. The scaling analysis points to the existence of cancer stem cells and/or massive apoptosis in early stage prostate cancer and that late stage cancer growth is not dominated by cancer stem cells. Statistical models of these two growth modes are discussed. Work supported by the National Science Foundation and the National Institutes of Health

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

    PubMed

    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

  6. Growth of Listeria monocytogenes in Salmon Roe - a kinetic analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to investigate the growth kinetics of Listeria monocytogenes in unsalted and salted (3%) salmon roe. Growth curves, developed using inoculated samples incubated at constant temperatures between 5 and 30 degrees C, were analyzed by curve-fitting to the Huang and Baran...

  7. Effect of oxygen on the growth and biofilm formation of Xylella fastidiosa in liquid media.

    PubMed

    Shriner, Anthony D; Andersen, Peter C

    2014-12-01

    Xylella fastidiosa is a xylem-limited bacterial pathogen, and is the causative agent of Pierce's disease of grapevines and scorch diseases of many other plant species. The disease symptoms are putatively due to blocking of the transpiration stream by bacterial-induced biofilm formation and/or by the formation of plant-generated tylosis. Xylella fastidiosa has been classified as an obligate aerobe, which appears unusual given that dissolved O2 levels in the xylem during the growing season are often hypoxic (20-60 μmol L(-1)). We examined the growth and biofilm formation of three strains of X. fastidiosa under variable O2 conditions (21, 2.1, 0.21 and 0 % O2), in comparison to that of Pseudomonas syringae (obligate aerobe) and Erwinia carotovora (facultative anaerobe) under similar conditions. The growth of X. fastidiosa more closely resembled that of the facultative anaerobe, and not the obligate aerobe. Xanthomonas campestris, the closest genetic relative of X. fastidiosa, exhibited no growth in an N2 environment, whereas X. fastidiosa was capable of growing in an N2 environment in PW(+), CHARDS, and XDM2-PR media. The magnitude of growth and biofilm formation in the N2 (0 % O2) treatment was dependent on the specific medium. Additional studies involving the metabolism of X. fastidiosa in response to low O2 are warranted. Whether X. fastidiosa is classified as an obligate aerobe or a facultative anaerobe should be confirmed by gene activation and/or the quantification of the metabolic profiles under hypoxic conditions. PMID:25100224

  8. Staphylococcus aureus and MRSA Growth and Biofilm Formation after Treatment with Antibiotics and SeNPs

    PubMed Central

    Cihalova, Kristyna; Chudobova, Dagmar; Michalek, Petr; Moulick, Amitava; Guran, Roman; Kopel, Pavel; Adam, Vojtech; Kizek, Rene

    2015-01-01

    Methicillin-resistant Staphylococcus aureus (MRSA) is a dangerous pathogen resistant to β-lactam antibiotics. Due to its resistance, it is difficult to manage the infections caused by this strain. We examined this issue in terms of observation of the growth properties and ability to form biofilms in sensitive S. aureus and MRSA after the application of antibiotics (ATBs)—ampicillin, oxacillin and penicillin—and complexes of selenium nanoparticles (SeNPs) with these ATBs. The results suggest the strong inhibition effect of SeNPs in complexes with conventional ATBs. Using the impedance method, a higher disruption of biofilms was observed after the application of ATB complexes with SeNPs compared to the group exposed to ATBs without SeNPs. The biofilm formation was intensely inhibited (up to 99% ± 7% for S. aureus and up to 94% ± 4% for MRSA) after application of SeNPs in comparison with bacteria without antibacterial compounds whereas ATBs without SeNPs inhibited S. aureus up to 79% ± 5% and MRSA up to 16% ± 2% only. The obtained results provide a basis for the use of SeNPs as a tool for the treatment of bacterial infections, which can be complicated because of increasing resistance of bacteria to conventional ATB drugs. PMID:26501270

  9. First-order kinetics of landfill leachate treatment in a pilot-scale anaerobic sequence batch biofilm reactor.

    PubMed

    Contrera, Ronan Cleber; da Cruz Silva, Katia Cristina; Morita, Dione Mari; Domingues Rodrigues, José Alberto; Zaiat, Marcelo; Schalch, Valdir

    2014-12-01

    This paper reports the kinetics evaluation of landfill leachate anaerobic treatment in a pilot-scale Anaerobic Sequence Batch Biofilm Reactor (AnSBBR). The experiment was carried out at room temperature (23.8 ± 2.1 °C) in the landfill area in São Carlos-SP, Brazil. Biomass from the bottom of a local landfill leachate stabilization pond was used as inoculum. After acclimated and utilizing leachate directly from the landfill, the AnSBBR presented efficiency over 70%, in terms of COD removal, with influent COD ranging from 4825 mg L(-1) to 12,330 mg L(-1). To evaluate the kinetics of landfill leachate treatment, temporal profiles of CODFilt. concentration were performed and a first-order kinetics model was adjusted for substrate consumption, obtaining an average k1 = 4.40 × 10(-5) L mgTVS(-1) d(-1), corrected to 25 °C. Considering the temperature variations, a temperature-activity coefficient θ = 1.07 was obtained. Statistical "Randomness" and "F" tests were used to successfully validate the model considered. Thus, the results demonstrate that the first-order kinetic model is adequate to model the anaerobic treatment of the landfill leachate in the AnSBBR. PMID:25127066

  10. Controlled positions and kinetic analysis of spontaneous tin whisker growth

    NASA Astrophysics Data System (ADS)

    Su, Chien-Hao; Chen, Hao; Lee, Hsin-Yi; Wu, Albert T.

    2011-09-01

    This study achieved controlling the positions of spontaneous growth of tin whiskers. We surmounted the unpredictable growing nature of such whiskers and performed accurately quantitative analyses of the growth kinetics and yielded precise measurement of the growth rate. Furthermore, using synchrotron radiation x-ray, this study determined the stress variations in conjunction with whisker growth that fitted appropriately to the model. Accordingly, the results could address the debate held for decades and prove that forming a surface oxide layer is one of the required and necessary conditions for controlling the positions of spontaneous growth of tin whiskers.

  11. Multiple substrate growth kinetics of Leptothrix discophora SP-6.

    PubMed

    Yurt, Nurdan; Sears, John; Lewandowski, Zbigniew

    2002-01-01

    The growth parameters of Leptothrix discophora SP-6 were quantified on the basis of the steady-state concentrations and utilization rates of pyruvate, dissolved oxygen, and concentration of microorganisms in a chemostat operated at 25 degrees C, pH 7.2, and an agitation rate of 350 rpm. The results showed that the microbial growth was limited by both pyruvate and dissolved oxygen. A combined growth kinetics model using Monod growth kinetics for pyruvate and Tessier growth kinetics for oxygen showed the best correlation with the experimental data when analyzed using an interactive multiple substrate model. The growth kinetics parameters and the respective confidence limits, estimated using the Monte Carlo simulation, were mu(max) = 0.576 +/- 0.021 h(-1), K(sMp) = 38.81 +/- 4.24 mg L(-1), K(sTo) = 0.39 +/- 0.04 mg L(-1), Y(X/p) = 0.150 (mg microorganism mg(-1) pyruvate), Y(X/o) = 1.24 (mg microorganism mg(-1) oxygen), the maintenance factors for pyruvate and oxygen were m(p) = 0.129 (mg pyruvate consumed mg(-1) microorganism h(-1)) and m(o) = 0.076 (mg oxygen consumed mg(-1) microorganism h(-1)), respectively. PMID:12363350

  12. An investigation of Pseudomonas aeruginosa biofilm growth on novel nanocellulose fibre dressings.

    PubMed

    Powell, Lydia C; Khan, Saira; Chinga-Carrasco, Gary; Wright, Chris J; Hill, Katja E; Thomas, David W

    2016-02-10

    Nanocellulose from wood is a novel biomaterial, which is highly fibrillated at the nanoscale. This affords the material a number of advantages, including self-assembly, biodegradability and the ability to absorb and retain moisture, which highlights its potential usefulness in clinical wound-dressing applications. In these in vitro studies, the wound pathogen Pseudomonas aeruginosa PAO1 was used to assess the ability of two nanocellulose materials to impair bacterial growth (<48 h). The two nanocelluloses had a relatively small fraction of residual fibres (<4%) and thus a large fraction of nanofibrils (widths <20 nm). Scanning electron microscopy and confocal laser scanning microscopy imaging demonstrated impaired biofilm growth on the nanocellulose films and increased cell death when compared to a commercial control wound dressing, Aquacel(®). Nanocellulose suspensions inhibited bacterial growth, whilst UV-vis spectrophotometry and laser profilometry also revealed the ability of nanocellulose to form smooth, translucent films. Atomic force microscopy studies of the surface properties of nanocellulose demonstrated that PAO1 exhibited markedly contrasting morphology when grown on the nanocellulose film surfaces compared to an Aquacel(®) control dressing (p<0.05). This study highlights the potential utility of these biodegradable materials, from a renewable source, for wound dressing applications in the prevention and treatment of biofilm development. PMID:26686120

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

    NASA Astrophysics Data System (ADS)

    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.

  14. [Methods for extraction of exopolymeric complex in plankton and biofilm growth mode of Stenotrophomonas maltophilia 22M].

    PubMed

    Boretskaia, M A; Suslova, O S

    2013-01-01

    The optimal methods for the extraction of exopolymeric complex (EPS) of Stenotrophomonas maltophilia 22M was determined. That EPS was synthesized in plankton and biofilm growth mode on the mild steel surface. It is desirable to use different physical and chemical methods for studying the EPS composition (carbohydrates and proteins) depending on the bacteria growth mode. In this way the interaction with ion exchange resin was the most effective for plankton growth mode to determine the maximum amount of carbohydrates (9.5 microg/ml), and the impact of heating to determine protein (3.9 microg/ml). For EPS biofilm in order to obtain maximum amount of carbohydrate it is desirable to use heating (30 microg/ml) and centrifugation (35 microg/ml). It is recommended to determine protein in the biofilm EPS after treatment with heating (3.75 microg/ml) and centrifugation (3.75 microg/ml). PMID:23720963

  15. Growth and Nitrogen Uptake Kinetics in Cultured Prorocentrum donghaiense

    PubMed Central

    Hu, Zhangxi; Duan, Shunshan; Xu, Ning; Mulholland, Margaret R.

    2014-01-01

    We compared growth kinetics of Prorocentrum donghaiense cultures on different nitrogen (N) compounds including nitrate (NO3−), ammonium (NH4+), urea, glutamic acid (glu), dialanine (diala) and cyanate. P. donghaiense exhibited standard Monod-type growth kinetics over a range of N concentraions (0.5–500 μmol N L−1 for NO3− and NH4+, 0.5–50 μmol N L−1 for urea, 0.5–100 μmol N L−1 for glu and cyanate, and 0.5–200 μmol N L−1 for diala) for all of the N compounds tested. Cultures grown on glu and urea had the highest maximum growth rates (μm, 1.51±0.06 d−1 and 1.50±0.05 d−1, respectively). However, cultures grown on cyanate, NO3−, and NH4+ had lower half saturation constants (Kμ, 0.28–0.51 μmol N L−1). N uptake kinetics were measured in NO3−-deplete and -replete batch cultures of P. donghaiense. In NO3−-deplete batch cultures, P. donghaiense exhibited Michaelis-Menten type uptake kinetics for NO3−, NH4+, urea and algal amino acids; uptake was saturated at or below 50 μmol N L−1. In NO3−-replete batch cultures, NH4+, urea, and algal amino acid uptake kinetics were similar to those measured in NO3−-deplete batch cultures. Together, our results demonstrate that P. donghaiense can grow well on a variety of N sources, and exhibits similar uptake kinetics under both nutrient replete and deplete conditions. This may be an important factor facilitating their growth during bloom initiation and development in N-enriched estuaries where many algae compete for bioavailable N and the nutrient environment changes as a result of algal growth. PMID:24710151

  16. Development of a simplified model for the fixed biofilm reactor.

    PubMed

    Sarkar, Sushovan; Mazumder, Debabrata

    2015-01-01

    A simplified fixed biofilm model was developed to formulate the relationship between the substrate concentrations at both the entry and exit, at the biofilm-liquid interface and at the biofilm attached surface along with average substrate flux in the biofilm, substrate flux at the biofilm-liquid interface and effective biofilm thickness. The model considered the substrate mass transport external to the biofilm and into the biofilm as per Fick's law and the steady state substrate as well as biomass balance for attached growth microorganisms. Monod's growth kinetics has been adopted in substrate utilization, incorporating relevant boundary conditions. The numerical solution of model equations was accomplished for calculating average flux and exit substrate concentration and thereafter the Runge-Kutta method was employed for determining effective biofilm thickness. Consequently, two computer programs were developed for the purpose of rapid solution. The model was satisfactorily applied to data available from the literature for checking its accuracy and was validated with the experimental results. The model was found to be an easy, accurate and fast method that can be used for process design of a fixed biofilm reactor. PMID:26524452

  17. Cell Differentiation in a Bacillus thuringiensis Population during Planktonic Growth, Biofilm Formation, and Host Infection

    PubMed Central

    Verplaetse, Emilie; Slamti, Leyla; Gohar, Michel

    2015-01-01

    ABSTRACT Bacillus thuringiensis (Bt) is armed to complete a full cycle in its insect host. During infection, virulence factors are expressed under the control of the quorum sensor PlcR to kill the host. After the host’s death, the quorum sensor NprR controls a necrotrophic lifestyle, allowing the vegetative cells to use the insect cadaver as a bioincubator and to survive. Only a part of the Bt population sporulates in the insect cadaver, and the precise composition of the whole population and its evolution over time are unknown. Using fluorescent reporters to record gene expression at the single-cell level, we have determined the differentiation course of a Bt population and explored the lineage existing among virulent, necrotrophic, and sporulating cells. The dynamics of cell differentiation were monitored during growth in homogenized medium, biofilm formation, and colonization of insect larvae. We demonstrated that in the insect host and in planktonic culture in rich medium, the virulence, necrotrophism, and sporulation regulators are successively activated in the same cell. In contrast, in biofilms, activation of PlcR is dispensable for NprR activation and we observed a greater heterogeneity than under the other two growth conditions. We also showed that sporulating cells arise almost exclusively from necrotrophic cells. In biofilm and in the insect cadaver, we identified an as-yet-uncharacterized category of cells that do not express any of the reporters used. Overall, we showed that PlcR, NprR, and Spo0A act as interconnected integrators to allow finely tuned adaptation of the pathogen to its environment. PMID:25922389

  18. Kinetic model of particle-inhibited grain growth

    NASA Astrophysics Data System (ADS)

    Thompson, Gary Scott

    The effects of second phase particles on matrix grain growth kinetics were investigated using Al2O3-SiC as a model system. In particular, the validity of the conclusion drawn from a previous kinetic analysis that the kinetics of particle-inhibited grain growth in Al2 O3-SiC samples with an intermediate volume fraction of second phase could be well quantified by a modified-Zener model was investigated. A critical analysis of assumptions made during the previous kinetic analysis revealed oversimplifications which affect the validity of the conclusion. Specifically, the degree of interaction between particles and grain boundaries was assumed to be independent of the mean second phase particle size and size distribution. In contrast, current measurements indicate that the degree of interaction in Al2O3-SiC is dependent on these parameters. An improved kinetic model for particle-inhibited grain growth in Al 2O3-SiC was developed using a modified-Zener approach. The comparison of model predictions with experimental grain growth data indicated that significant discrepancies (as much as 4--5 orders of magnitude) existed. Based on this, it was concluded that particles had a much more significant effect on grain growth kinetics than that caused by a simple reduction of the boundary driving force due to the removal of boundary area. Consequently, it was also concluded that the conclusion drawn from the earlier kinetic analysis regarding the validity of a modified-Zener model was incorrect. Discrepancies between model and experiment were found to be the result of a significant decrease in experimental growth rate constant not predicted by the model. Possible physical mechanisms for such a decrease were investigated. The investigation of a small amount of SiO2 on grain growth in Al2O3 indicated that the decrease was not the result of a decrease in grain boundary mobility due to impurity contamination by particles. By process of elimination and based on previous observations

  19. Utilization of moving bed biofilm reactor for industrial wastewater treatment containing ethylene glycol: kinetic and performance study.

    PubMed

    Hassani, Amir Hessam; Borghei, Seyed Mehdi; Samadyar, Hassan; Ghanbari, Bastam

    2014-01-01

    One of the requirements for environmental engineering, which is currently being considered, is the removal of ethylene glycol (EG) as a hazardous environmental pollutant from industrial wastewater. Therefore, in a recent study, a moving bed biofilm reactor (MBBR) was applied at pilot scale to treat industrial effluents containing different concentrations of EG (600, 800, 1200, and 1800 mg L-1 ). The removal efficiency and kinetic analysis of the system were examined at different hydraulic retention times of 6, 8, 10, and 12 h as well as influent chemical oxygen demand (COD) ranged between values of 1000 and 3000mg L-1. In minimum and maximum COD Loadings, the MBBR showed 95.1% and 60.7% removal efficiencies, while 95.9% and 66.2% EG removal efficiencies were achieved in the lowest and highest EG concentrations. The results of the reactor modelling suggested compliance of the well-known modified Stover-Kincannon model with the system. PMID:24600890

  20. Metastable Solution Thermodynamic Properties and Crystal Growth Kinetics

    NASA Technical Reports Server (NTRS)

    Kim, Soojin; Myerson, Allan S.

    1996-01-01

    The crystal growth rates of NH4H2PO4, KH2PO4, (NH4)2SO4, KAl(SO4)2 central dot 12H2O, NaCl, and glycine and the nucleation rates of KBr, KCl, NaBr central dot 2H2O, (NH4)2Cl, and (NH4)2SO4 were expressed in terms of the fundamental driving force of crystallization calculated from the activity of supersaturated solutions. The kinetic parameters were compared with those from the commonly used kinetic expression based on the concentration difference. From the viewpoint of thermodynamics, rate expressions based on the chemical potential difference provide accurate kinetic representation over a broad range of supersaturation. The rates estimated using the expression based on the concentration difference coincide with the true rates of crystallization only in the concentration range of low supersaturation and deviate from the true kinetics as the supersaturation increases.

  1. Growth and characterization of Escherichia coli DH5α biofilm on concrete surfaces as a protective layer against microbiologically influenced concrete deterioration (MICD).

    PubMed

    Soleimani, Sahar; Ormeci, Banu; Isgor, O Burkan

    2013-02-01

    Biofilms of selected bacteria strains were previously used on metal coupons as a protective layer against microbiologically influenced corrosion of metals. Unlike metal surfaces, concrete surfaces present a hostile environment for growing a protective biofilm. The main objective of this research was to investigate whether a beneficial biofilm can be successfully grown on mortar surfaces. Escherichia coli DH5α biofilm was grown on mortar surfaces for 8 days, and the structure and characteristics of the biofilm were studied using advanced microscopy techniques such as scanning electron microscopy and confocal laser scanning microscopy in combination with fluorescence in situ hybridization, live/dead, extracellular polymer staining, ATP analysis, and membrane filtration. A biofilm layer with a varying thickness of 20-40 μm was observed on the mortar surface. The distribution of live and dead bacteria and extracellular polymers varied with depth. The density of the live population near the mortar surface was the lowest. The bacteria reached their highest density at three fourths of the biofilm depth and then decreased again near the biofilm-liquid interface. Overall, the results indicated a healthy biofilm growth in the chosen growth period of 8 days, and it is expected that longer growth periods would lead to formation of a more resistant biofilm with more coverage of mortar surfaces. PMID:22961420

  2. Linking biofilm growth to fouling and aeration performance of fine-pore diffuser in activated sludge.

    PubMed

    Garrido-Baserba, Manel; Asvapathanagul, Pitiporn; McCarthy, Graham W; Gocke, Thomas E; Olson, Betty H; Park, Hee-Deung; Al-Omari, Ahmed; Murthy, Sudhir; Bott, Charles B; Wett, Bernhard; Smeraldi, Joshua D; Shaw, Andrew R; Rosso, Diego

    2016-03-01

    Aeration is commonly identified as the largest contributor to process energy needs in the treatment of wastewater and therefore garners significant focus in reducing energy use. Fine-pore diffusers are the most common aeration system in municipal wastewater treatment. These diffusers are subject to fouling and scaling, resulting in loss in transfer efficiency as biofilms form and change material properties producing larger bubbles, hindering mass transfer and contributing to increased plant energy costs. This research establishes a direct correlation and apparent mechanistic link between biofilm DNA concentration and reduced aeration efficiency caused by biofilm fouling. Although the connection between biofilm growth and fouling has been implicit in discussions of diffuser fouling for many years, this research provides measured quantitative connection between the extent of biofouling and reduced diffuser efficiency. This was clearly established by studying systematically the deterioration of aeration diffusers efficiency during a 1.5 year period, concurrently with the microbiological study of the biofilm fouling in order to understand the major factors contributing to diffuser fouling. The six different diffuser technologies analyzed in this paper included four different materials which were ethylene-propylene-diene monomer (EPDM), polyurethane, silicone and ceramic. While all diffusers foul eventually, some novel materials exhibited fouling resistance. The material type played a major role in determining the biofilm characteristics (i.e., growth rate, composition, and microbial density) which directly affected the rate and intensity at what the diffusers were fouled, whereas diffuser geometry exerted little influence. Overall, a high correlation between the increase in biofilm DNA and the decrease in αF was evident (CV < 14.0 ± 2.0%). By linking bacterial growth with aeration efficiency, the research was able to show quantitatively the causal connection

  3. Kinetics of laser-assisted carbon nanotube growth.

    PubMed

    van de Burgt, Y; Bellouard, Y; Mandamparambil, R

    2014-03-21

    Laser-assisted chemical vapour deposition (CVD) growth is an attractive mask-less process for growing locally aligned carbon nanotubes (CNTs) in selected places on temperature sensitive substrates. The nature of the localized process results in fast carbon nanotube growth with high experimental throughput. Here, we report on the detailed investigation of growth kinetics related to physical and chemical process characteristics. Specifically, the growth kinetics is investigated by monitoring the dynamical changes in reflected laser beam intensity during growth. Benefiting from the fast growth and high experimental throughput, we investigate a wide range of experimental conditions and propose several growth regimes. Rate-limiting steps are determined using rate equations linked to the proposed growth regimes, which are further characterized by Raman spectroscopy and Scanning Electron Microscopy (SEM), therefore directly linking growth regimes to the structural quality of the CNTs. Activation energies for the different regimes are found to be in the range of 0.3-0.8 eV. PMID:24481313

  4. Grain boundary curvature and grain growth kinetics with particle pinning

    NASA Astrophysics Data System (ADS)

    Shahandeh, Sina; Militzer, Matthias

    2013-08-01

    Second-phase particles are used extensively in design of polycrystalline materials to control the grain size. According to Zener's theory, a distribution of particles creates a pinning pressure on a moving grain boundary. As a result, a limiting grain size is observed, but the effect of pinning on the detail of grain growth kinetics is less known. The influence of the particles on the microstructure occurs in multiple length scales, established by particle radius and the grain size. In this article, we use a meso-scale phase-field model that simulates grain growth in the presence of a uniform pinning pressure. The curvature of the grain boundary network is measured to determine the driving pressure of grain growth in 2D and 3D systems. It was observed that the grain growth continues, even under conditions where the average driving pressure is smaller than the pinning pressure. The limiting grain size is reached when the maximum of driving pressure distribution in the structure is equal to the pinning pressure. This results in a limiting grain size, larger than the one predicted by conventional models, and further analysis shows consistency with experimental observations. A physical model is proposed for the kinetics of grain growth using parameters based on the curvature analysis of the grain boundaries. This model can describe the simulated grain growth kinetics.

  5. Kinetics of bacterial growth on chlorinated aliphatic compounds

    SciTech Connect

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

    1993-07-01

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

  6. Subdiffusion kinetics of nanoprecipitate growth and destruction in solid solutions

    NASA Astrophysics Data System (ADS)

    Sibatov, R. T.; Svetukhin, V. V.

    2015-06-01

    Based on fractional differential generalizations of the Ham and Aaron-Kotler precipitation models, we study the kinetics of subdiffusion-limited growth and dissolution of new-phase precipitates. We obtain the time dependence of the number of impurities and dimensions of new-phase precipitates. The solutions agree with the Monte Carlo simulation results.

  7. Growth Kinetics and Modeling of ZnO Nanoparticles

    ERIC Educational Resources Information Center

    Hale, Penny S.; Maddox, Leone M.; Shapter, Joe G.; Voelcker, Nico H.; Ford, Michael J.; Waclawik, Eric R.

    2005-01-01

    The technique for producing quantum-sized zinc oxide (ZnO) particles is much safer than a technique that used hydrogen sulfide gas to produce cadmium sulfide and zinc sulfide nanoparticles. A further advantage of this method is the ability to sample the solution over time and hence determine the growth kinetics.

  8. The biofilm inhibitor Carolacton inhibits planktonic growth of virulent pneumococci via a conserved target

    PubMed Central

    Donner, Jannik; Reck, Michael; Bergmann, Simone; Kirschning, Andreas; Müller, Rolf; Wagner-Döbler, Irene

    2016-01-01

    New antibacterial compounds, preferentially exploiting novel cellular targets, are urgently needed to fight the increasing resistance of pathogens against conventional antibiotics. Here we demonstrate that Carolacton, a myxobacterial secondary metabolite previously shown to damage Streptococcus mutans biofilms, inhibits planktonic growth of Streptococcus pneumoniae TIGR4 and multidrug-resistant clinical isolates of serotype 19A at nanomolar concentrations. A Carolacton diastereomer is inactive in both streptococci, indicating a highly specific interaction with a conserved cellular target. S. mutans requires the eukaryotic-like serine/threonine protein kinase PknB and the cysteine metabolism regulator CysR for susceptibility to Carolacton, whereas their homologues are not needed in S. pneumoniae, suggesting a specific function for S. mutans biofilms only. A bactericidal effect of Carolacton was observed for S. pneumoniae TIGR4, with a reduction of cell numbers by 3 log units. The clinical pneumonia isolate Sp49 showed immediate growth arrest and cell lysis, suggesting a bacteriolytic effect of Carolacton. Carolacton treatment caused a reduction in membrane potential, but not membrane integrity, and transcriptome analysis revealed compensatory reactions of the cell. Our data show that Carolacton might have potential for treating pneumococcal infections. PMID:27404808

  9. Waste Water Derived Electroactive Microbial Biofilms: Growth, Maintenance, and Basic Characterization

    PubMed Central

    Gimkiewicz, Carla; Harnisch, Falk

    2013-01-01

    The growth of anodic electroactive microbial biofilms from waste water inocula in a fed-batch reactor is demonstrated using a three-electrode setup controlled by a potentiostat. Thereby the use of potentiostats allows an exact adjustment of the electrode potential and ensures reproducible microbial culturing conditions. During growth the current production is monitored using chronoamperometry (CA). Based on these data the maximum current density (jmax) and the coulombic efficiency (CE) are discussed as measures for characterization of the bioelectrocatalytic performance. Cyclic voltammetry (CV), a nondestructive, i.e. noninvasive, method, is used to study the extracellular electron transfer (EET) of electroactive bacteria. CV measurements are performed on anodic biofilm electrodes in the presence of the microbial substrate, i.e. turnover conditions, and in the absence of the substrate, i.e. nonturnover conditions, using different scan rates. Subsequently, data analysis is exemplified and fundamental thermodynamic parameters of the microbial EET are derived and explained: peak potential (Ep), peak current density (jp), formal potential (Ef) and peak separation (ΔEp). Additionally the limits of the method and the state-of the art data analysis are addressed. Thereby this video-article shall provide a guide for the basic experimental steps and the fundamental data analysis. PMID:24430581

  10. Zoocin A and lauricidin in combination reduce Streptococcus mutans growth in a multispecies biofilm.

    PubMed

    Lester, K; Simmonds, R S

    2012-01-01

    Dental caries is the most prevalent human infection. It is a multifactorial disease in which the microbial composition of dental plaque plays a major role in the development of clinical symptoms. The bacteria most often implicated in the development of caries are that group of streptococci referred to as the mutans streptococci, in particular Streptococcus mutans and Streptococcus sobrinus. One approach to the prevention of caries is to reduce the numbers of mutans streptococci in plaque to a level insufficient to support demineralization of the tooth. In this study, zoocin A, a peptidoglycan hydrolase, combined with lauricidin, a cell membrane active lipid, was shown over a 72 h period to selectively suppress the growth of S. mutans in a triple species biofilm. Growth of the non-target species Streptococcus oralis and Actinomyces viscosus was not inhibited. In treated systems the amount of extracellular polysaccharide matrix produced was much reduced as determined by use of fluorescein isothiocyanate conjugated wheat germ agglutinin. The pH of treated biofilms remained above neutral as opposed to a value of 4.3 in untreated controls. We conclude that use of antimicrobial compounds that specifically target cariogenic bacteria should be further explored. PMID:22508519

  11. The biofilm inhibitor Carolacton inhibits planktonic growth of virulent pneumococci via a conserved target.

    PubMed

    Donner, Jannik; Reck, Michael; Bergmann, Simone; Kirschning, Andreas; Müller, Rolf; Wagner-Döbler, Irene

    2016-01-01

    New antibacterial compounds, preferentially exploiting novel cellular targets, are urgently needed to fight the increasing resistance of pathogens against conventional antibiotics. Here we demonstrate that Carolacton, a myxobacterial secondary metabolite previously shown to damage Streptococcus mutans biofilms, inhibits planktonic growth of Streptococcus pneumoniae TIGR4 and multidrug-resistant clinical isolates of serotype 19A at nanomolar concentrations. A Carolacton diastereomer is inactive in both streptococci, indicating a highly specific interaction with a conserved cellular target. S. mutans requires the eukaryotic-like serine/threonine protein kinase PknB and the cysteine metabolism regulator CysR for susceptibility to Carolacton, whereas their homologues are not needed in S. pneumoniae, suggesting a specific function for S. mutans biofilms only. A bactericidal effect of Carolacton was observed for S. pneumoniae TIGR4, with a reduction of cell numbers by 3 log units. The clinical pneumonia isolate Sp49 showed immediate growth arrest and cell lysis, suggesting a bacteriolytic effect of Carolacton. Carolacton treatment caused a reduction in membrane potential, but not membrane integrity, and transcriptome analysis revealed compensatory reactions of the cell. Our data show that Carolacton might have potential for treating pneumococcal infections. PMID:27404808

  12. Kinetics of microbial growth and biodegradation of methanol and toluene in biofilters and an analysis of the energetic indicators.

    PubMed

    Avalos Ramirez, Antonio; Bénard, Sandrine; Giroir-Fendler, Anne; Jones, J Peter; Heitz, Michèle

    2008-11-25

    The kinetics of microbial growth and the biodegradation of methanol and toluene in (a) biofilters (BFs), and (b) biotrickling filters (BTFs), packed with inert materials, has been studied and analyzed. The specific growth rate, mu, for the treatment of methanol was 0.037h(-1) for a wide range of operating conditions. In the BF, mu was found to be a function of the methanol and toluene concentrations in the biofilm. In the BF used for treating methanol, mu was found to be affected by (1) the nitrogen concentration present in the nutrient solution, and (2) the kind of packing material employed. The kinetics of the methanol and toluene biodegradations were also analyzed using "mixed order" models. A Michaelis-Menten model type provided a good fit for the elimination capacity (EC) of the BTF treating methanol, while a Haldane model type provided a good fit to the EC of the BF treating methanol and toluene. The carbon dioxide production rate was related to the packed bed temperature and the content of the volatile solids within the biofilm. For the BF, the ratio of temperature/carbon dioxide production rate (PCO(2)) was 0.024 degrees C per unit of PCO(2), and for the BTF it was 0.15 degrees C per unit of PCO(2). PMID:18778740

  13. Growth kinetics of sulfur nanoparticles in aqueous surfactant solutions.

    PubMed

    Chaudhuri, Rajib Ghosh; Paria, Santanu

    2011-02-15

    Sulfur is an important element has many practical applications when present as nanoparticles. Despite the practicable applications, limited studies are available in the literature related to synthesis of sulfur nanoparticles. Growth kinetics of colloidal sulfur particles synthesized from aqueous solutions using different surfactants have been studied here. The effects of different parameters such as reactant concentration, temperature, sonication, types of acids, types of surfactants, and even surfactant concentration are studied on the growth kinetics. Since the reaction rate is fast, particle growth depends on the parameters which affect diffusion of sulfur molecules. There is a linear relationship found among the reactant concentration and the particle coarsening rate constant. The growth kinetics was studied in the presence of different surfactants such as nonionic (poly(oxyethylene) p-tert-octylphenyl ether, TX-100), anionic (sodium dodecylbenzene sulfonate, SDBS), cationic (cetyltrimethyammonium bromide, CTAB) and results show the coarsening constant changes according to the following order: water>TX-100>SDBS>CTAB. The particle growth rate also depends on the surfactant concentration, coarsening rate constant decreases with the increase in surfactant concentration and become constant close to the critical micellar concentration (CMC). The coarsening rate constant also highly depends on the types of acid used as catalyst. PMID:21147482

  14. Effects of antimicrobial peptides on Staphylococcus aureus growth and biofilm formation in vitro following isolation from implant-associated infections

    PubMed Central

    Zhao, Guangfeng; Zhong, Huiming; Zhang, Mao; Hong, Yucai

    2015-01-01

    To prevent biomaterial-associated infections, antibiotic agents are recommended for various medical conditions requiring biomaterial implants, but resistance often appears after the introduction of antibiotics into clinical use. Therefore, new strategies for the prevention or treatment for biomaterial-associated infections are required. The purpose of this study was to evaluate the effects of antimicrobial peptides on growth and biofilm formation of Staphylococcus aureus isolated from implant-associated infections. A total of 20 patients with culture-proven staphylococcal infection associated with stable orthopedic implants were selected as the experimental group. S. aureus were isolated from tissue biopsies for identification, the isolated strains were mixed with Tet213 incubated at 37°C and viable bactrial number of S. aureus was counted. For the biofilm formation, the broad spectrum AMP Tet213 was selected and loaded onto the Ti coating first. At the same time Ti coated with Tet213 were mixed with S. aureus in vitro to form biofilm. After 30 min, 2 h, 4 h, 6 h, 8 h, the population of S. aureus in the biofilm was counted. Tet213 showed significant antibacterial effect on 16 strains (P < 0.05, Table 1). The inhibition rate reached above 80% among 12 strains of the clinically isolated strain. In biofilm experiments, counts of the NO. 1, 2, 3, 4 strains in biofilms decreased significantly after 2 h (P < 0.05), while there was no obvious difference in counts of NO. 5 strain (P > 0.05). The broad spectrum AMP Tet213 could strongly reduce the growth and biofilm formation of S. aureus in vitro, and the use of this might be an important new approach to target implant-associated infections. PMID:25785171

  15. Effects of nisin and lysozyme on growth inhibition and biofilm formation capacity of Staphylococcus aureus strains isolated from raw milk and cheese samples.

    PubMed

    Sudagidan, Mert; Yemenicioğlu, Ahmet

    2012-09-01

    Effects of nisin and lysozyme on growth inhibition and biofilm formation capacity of 25 Staphylococcus aureus strains isolated from raw milk (13 strains) and cheese (12 strains) were studied. Nisin was tested at concentrations between 0.5 and 25 μg/ml; the growth of all strains was inhibited at 25 μg/ml, but the resistances of strains showed a great variation at lower nisin concentrations. In contrast, lysozyme tested at concentrations up to 5.0 mg/ml showed no inhibition on the growth of strains. Nisin used at the growth inhibitory concentration prevented the biofilm formation of strains, but strains continued biofilm formation at subinhibitory nisin concentrations. Lysozyme did not affect the biofilm formation of 19 of the strains, but it caused a considerable activation in the biofilm formation capacity of six strains. Twelve of the strains contained both biofilm-related protease genes (sspA, sspB, and aur) and active proteases; eight of these strains were nisin resistant. These results suggest a potential risk of S. aureus growth and biofilm formation when lysozyme is used in the biopreservation of dairy products. Nisin can be used to control growth and biofilm formation of foodborne S. aureus, unless resistance against this biopreservative develops. PMID:22947470

  16. Growth kinetics of Staphylococcus aureus on Brie and Camembert cheeses.

    PubMed

    Lee, Heeyoung; Kim, Kyungmi; Lee, Soomin; Han, Minkyung; Yoon, Yohan

    2014-05-01

    In this study, we developed mathematical models to describe the growth kinetics of Staphylococcus aureus on natural cheeses. A five-strain mixture of Staph. aureus was inoculated onto 15 g of Brie and Camembert cheeses at 4 log CFU/g. The samples were then stored at 4, 10, 15, 25, and 30 °C for 2-60 d, with a different storage time being used for each temperature. Total bacterial and Staph. aureus cells were enumerated on tryptic soy agar and mannitol salt agar, respectively. The Baranyi model was fitted to the growth data of Staph. aureus to calculate kinetic parameters such as the maximum growth rate in log CFU units (r max; log CFU/g/h) and the lag phase duration (λ; h). The effects of temperature on the square root of r max and on the natural logarithm of λ were modelled in the second stage (secondary model). Independent experimental data (observed data) were compared with prediction and the respective root mean square error compared with the RMSE of the fit on the original data, as a measure of model performance. The total growth of bacteria was observed at 10, 15, 25, and 30 °C on both cheeses. The r max values increased with storage temperature (P<0·05), but a significant effect of storage temperature on λ values was only observed between 4 and 15 °C (P<0·05). The square root model and linear equation were found to be appropriate for description of the effect of storage temperature on growth kinetics (R 2=0·894-0·983). Our results indicate that the models developed in this study should be useful for describing the growth kinetics of Staph. aureus on Brie and Camembert cheeses. PMID:24731395

  17. Effects of extracts from Italian medicinal plants on planktonic growth, biofilm formation and adherence of methicillin-resistant Staphylococcus aureus

    PubMed Central

    Quave, Cassandra L.; Plano, Lisa R.W.; Pantuso, Traci; Bennett, Bradley C.

    2008-01-01

    One-third of botanical remedies from southern Italy are used to treat skin and soft tissue infection (SSTI). Staphylococcus aureus, a common cause of SSTI, has generated increasing concern due to drug resistance. Many plants possess antimicrobial agents and provide effective remedies for SSTI. Our aim was to investigate plants from different ethnobotanical usage groups for inhibition of growth and biofilms in methicillin-resistant S. aureus (MRSA). Three groups were assessed: plant remedies for SSTI, plant remedies not involving the skin, and plants with no ethnomedical application. We screened 168 extracts, representing 104 botanical species, for activity against MRSA (ATCC 33593). We employed broth dilution methods to determine the MIC after 18 hours growth using an optical density (OD600nm) reading. Anti-biofilm effects were assessed by growing biofilms for 40 hours, then fixing and staining with crystal violet. After washing, 10% Tween 80 was added and OD570nm readings were taken. Extracts from 10 plants exhibited an IC50 ≤32 μg/ml for biofilm inhibition: Lonicera alpigena, Castanea sativa, Juglans regia, Ballota nigra, Rosmarinus officinalis, Leopoldia comosa, Malva sylvestris, Cyclamen hederifolium, Rosa canina, and Rubus ulmifolius. Limited bacteriostatic activity was evident. The anti-biofilm activity of medicinal plants was significantly greater than plants without any ethnomedical applications. PMID:18556162

  18. Biofilm growth and the related changes in the physical properties of a porous medium: 2. Permeability

    NASA Astrophysics Data System (ADS)

    Taylor, Stewart W.; Milly, P. C. D.; Jaffé, Peter R.

    1990-09-01

    Growth of a biofilm in a porous medium reduces the total volume and the average size of the pores. The change in the pore size distributions is easily quantified when certain geometric assumptions are made. Existing models of permeability or of relative permeability can be manipulated to yield estimates of the resulting reduction in permeability as a function of biofilm thickness. The associated reductions in porosity and specific surface can be estimated as well. Based on a sphere model of the medium, the Kozeny-Carman permeability model predicts physically realistic results for this problem. Using a cut-and-random-rejoin-type model of the medium, the permeability model of Childs and Collis-George yields qualitatively reasonable results for this problem, as does a generalization of the relative permeability model of Mualem. Permeability models of Kozeny-Carman and of Millington and Quirk lead to unrealistic results for a cut-and-random-rejoin-type medium. The Childs and Collis-George and the Mualem models predict that the permeability reduction for a given volume of biomass is greatest when the porous medium has uniform pore sizes.

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

    PubMed

    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

  20. Growth Morphologies of Wax in the Presence Kinetic Inhibitors

    NASA Astrophysics Data System (ADS)

    Tetervak, Alexander; Hutter, Jeffrey

    2004-03-01

    Kinetic inhibitors are molecules that alter crystal growth rates and morphologies by adsorbing to growth faces. Such species are used in many commercial processes to control microsctructure, and in other cases to prevent crystallization altogether. Despite their importance, the details of their mechanisms are largely unverified. We are studying the effects of such inhibitors on the crystallization of normal alkanes from solution. We find that inhibitors drastically alter the crystal morphology. As in similar systems, we see ``burst growth,'' in which newly formed solid is able to grow faster due to lower inhibitor coverage. Our experiments show several growth morphologies as a function of conditions: a tree-like structure that in some cases forms bands, and spherulites with characteristics very similar to those seen in polymers. Here, we characterize the front morphology as a function of these conditions and compare the results to numerical models that capture the essential growth behavior.

  1. Listeria monocytogenes LO28: Surface Physicochemical Properties and Ability To Form Biofilms at Different Temperatures and Growth Phases

    PubMed Central

    Chavant, Patrick; Martinie, Brigitte; Meylheuc, Thierry; Bellon-Fontaine, Marie-Noëlle; Hebraud, Michel

    2002-01-01

    The surface physicochemical properties of Listeria monocytogenes LO28 under different conditions (temperature and growth phase) were determined by use of microelectrophoresis and microbial adhesion to solvents. The effect of these parameters on adhesion and biofilm formation by L. monocytogenes LO28 on hydrophilic (stainless steel) and hydrophobic (polytetrafluoroethylene [PTFE]) surfaces was assessed. The bacterial cells were always negatively charged and possessed hydrophilic surface properties, which were negatively correlated with growth temperature. The colonization of the two surfaces, monitored by scanning electron microscopy, epifluorescence microscopy, and cell enumeration, showed that the strain had a great capacity to colonize both surfaces whatever the incubation temperature. However, biofilm formation was faster on the hydrophilic substratum. After 5 days at 37 or 20°C, the biofilm structure was composed of aggregates with a three-dimensional shape, but significant detachment took place on PTFE at 37°C. At 8°C, only a bacterial monolayer was visible on stainless steel, while no growth was observed on PTFE. The growth phase of bacteria used to inoculate surfaces had a significant effect only in some cases during the first steps of biofilm formation. The surface physicochemical properties of the strain are correlated with adhesion and surface colonization. PMID:11823213

  2. Kinetic Roughening Transition and Energetics of Tetragonal Lysozyme Crystal Growth

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

    2004-01-01

    Interpretation of lysozyme crystal growth rates using well-established physical theories enabled the discovery of a phenomenon possibly indicative of kinetic roughening. For example, lysozyme crystals grown above a critical supersaturation sigma, (where supersaturation sigma = ln c/c(sub eq), c = the protein concentration and c(sub eq) = the solubility concentration) exhibit microscopically rough surfaces due to the continuous addition of growth units anywhere on the surface of a crystal. The rate of crystal growth, V(sub c), for the continuous growth process is determined by the continuous flux of macromolecules onto a unit area of the crystal surface, a, from a distance, xi, per unit time due to diffusion, and a probability of attachment onto the crystal surface, expressed. Based upon models applied, the energetics of lysozyme crystal growth was determined. The magnitudes of the energy barriers of crystal growth for both the (110) and (101) faces of tetragonal lysozyme crystals are compared. Finally, evidence supportive of the kinetic roughening hypothesis is presented.

  3. Bactericidal Compounds Controlling Growth of the Plant Pathogen Pseudomonas syringae pv. actinidiae, Which Forms Biofilms Composed of a Novel Exopolysaccharide

    PubMed Central

    Ghods, Shirin; Sims, Ian M.; Moradali, M. Fata

    2015-01-01

    Pseudomonas syringae pv. actinidiae is the major cause of bacterial canker and is a severe threat to kiwifruit production worldwide. Many aspects of the disease caused by P. syringae pv. actinidiae, such as the pathogenicity-relevant formation of a biofilm composed of extracellular polymeric substances (EPSs), are still unknown. Here, a highly virulent strain of P. syringae pv. actinidiae, NZ V-13, was studied with respect to biofilm formation and architecture using a flow cell system combined with confocal laser scanning microscopy. The biofilm formed by P. syringae pv. actinidiae NZ V-13 was heterogeneous, consisting of a thin cellular base layer 5 μm thick and microcolonies with irregular structures. The major component of the EPSs produced by P. syringae pv. actinidiae NZ V-13 bacteria was isolated and identified to be an exopolysaccharide. Extensive compositional and structural analysis showed that rhamnose, fucose, and glucose were the major constituents, present at a ratio of 5:1.5:2. Experimental evidence that P. syringae pv. actinidiae NZ V-13 produces two polysaccharides, a branched α-d-rhamnan with side chains of terminal α-d-Fucf and an α-d-1,4-linked glucan, was obtained. The susceptibility of the cells in biofilms to kasugamycin and chlorine dioxide was assessed. About 64 and 73% of P. syringae pv. actinidiae NZ V-13 cells in biofilms were killed when kasugamycin and chlorine dioxide were used at 5 and 10 ppm, respectively. Kasugamycin inhibited the attachment of P. syringae pv. actinidiae NZ V-13 to solid surfaces at concentrations of 80 and 100 ppm. Kasugamycin was bacteriostatic against P. syringae pv. actinidiae NZ V-13 growth in the planktonic mode, with the MIC being 40 to 60 ppm and a bactericidal effect being found at 100 ppm. Here we studied the formation, architecture, and composition of P. syringae pv. actinidiae biofilms as well as used the biofilm as a model to assess the efficacies of bactericidal compounds. PMID:25841017

  4. Bactericidal Compounds Controlling Growth of the Plant Pathogen Pseudomonas syringae pv. actinidiae, Which Forms Biofilms Composed of a Novel Exopolysaccharide.

    PubMed

    Ghods, Shirin; Sims, Ian M; Moradali, M Fata; Rehm, Bernd H A

    2015-06-15

    Pseudomonas syringae pv. actinidiae is the major cause of bacterial canker and is a severe threat to kiwifruit production worldwide. Many aspects of the disease caused by P. syringae pv. actinidiae, such as the pathogenicity-relevant formation of a biofilm composed of extracellular polymeric substances (EPSs), are still unknown. Here, a highly virulent strain of P. syringae pv. actinidiae, NZ V-13, was studied with respect to biofilm formation and architecture using a flow cell system combined with confocal laser scanning microscopy. The biofilm formed by P. syringae pv. actinidiae NZ V-13 was heterogeneous, consisting of a thin cellular base layer 5 μm thick and microcolonies with irregular structures. The major component of the EPSs produced by P. syringae pv. actinidiae NZ V-13 bacteria was isolated and identified to be an exopolysaccharide. Extensive compositional and structural analysis showed that rhamnose, fucose, and glucose were the major constituents, present at a ratio of 5:1.5:2. Experimental evidence that P. syringae pv. actinidiae NZ V-13 produces two polysaccharides, a branched α-d-rhamnan with side chains of terminal α-d-Fucf and an α-d-1,4-linked glucan, was obtained. The susceptibility of the cells in biofilms to kasugamycin and chlorine dioxide was assessed. About 64 and 73% of P. syringae pv. actinidiae NZ V-13 cells in biofilms were killed when kasugamycin and chlorine dioxide were used at 5 and 10 ppm, respectively. Kasugamycin inhibited the attachment of P. syringae pv. actinidiae NZ V-13 to solid surfaces at concentrations of 80 and 100 ppm. Kasugamycin was bacteriostatic against P. syringae pv. actinidiae NZ V-13 growth in the planktonic mode, with the MIC being 40 to 60 ppm and a bactericidal effect being found at 100 ppm. Here we studied the formation, architecture, and composition of P. syringae pv. actinidiae biofilms as well as used the biofilm as a model to assess the efficacies of bactericidal compounds. PMID:25841017

  5. Inhibitory Effect of Sophorolipid on Candida albicans Biofilm Formation and Hyphal Growth

    PubMed Central

    Haque, Farazul; Alfatah, Md.; Ganesan, K.; Bhattacharyya, Mani Shankar

    2016-01-01

    Candida albicans causes superficial and life-threatening systemic infections. These are difficult to treat often due to drug resistance, particularly because C. albicans biofilms are inherently resistant to most antifungals. Sophorolipid (SL), a glycolipid biosurfactant, has been shown to have antimicrobial and anticancer properties. In this study, we investigated the effect of SL on C. albicans biofilm formation and preformed biofilms. SL was found to inhibit C. albicans biofilm formation as well as reduce the viability of preformed biofilms. Moreover, SL, when used along with amphotericin B (AmB) or fluconazole (FLZ), was found to act synergistically against biofilm formation and preformed biofilms. Effect of SL on C. albicans biofilm formation was further visualized by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), which revealed absence of hyphae, typical biofilm architecture and alteration in the morphology of biofilm cells. We also found that SL downregulates the expression of hypha specific genes HWP1, ALS1, ALS3, ECE1 and SAP4, which possibly explains the inhibitory effect of SL on hyphae and biofilm formation. PMID:27030404

  6. Coalescence kinetics under the action of alternative grain growth mechanisms

    SciTech Connect

    Gubanov, P. Yu. Maksimov, I. L.

    2008-01-15

    The coalescence process is considered for the case where the prevailing grain growth mechanism is block-to-block diffusion, during which the motion of atoms in a solution occurs in the form of diffusion flux along the block boundaries. Numerical and analytical investigation of the coalescence kinetics in a homogeneous supersaturated solution is performed with allowance for the finite maximum grain size, and the time evolution of the size distribution function of new-phase grains is theoretically described. Possible transition regimes arising during coalescence at a change in the dominant grain growth mechanism are considered.

  7. Modeling and validation of single-chamber microbial fuel cell cathode biofilm growth and response to oxidant gas composition

    DOE PAGESBeta

    Ou, Shiqi; Zhao, Yi; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

    2016-08-15

    This work describes experiments and computational simulations to analyze single-chamber, air-cathode microbial fuel cell (MFC) performance and cathodic limitations in terms of current generation, power output, mass transport, biomass competition, and biofilm growth. Steady-state and transient cathode models were developed and experimentally validated. Two cathode gas mixtures were used to explore oxygen transport in the cathode: the MFCs exposed to a helium-oxygen mixture (heliox) produced higher current and power output than the group of MFCs exposed to air or a nitrogen-oxygen mixture (nitrox), indicating a dependence on gas-phase transport in the cathode. Multi-substance transport, biological reactions, and electrochemical reactions inmore » a multi-layer and multi-biomass cathode biofilm were also simulated in a transient model. The transient model described biofilm growth over 15 days while providing insight into mass transport and cathodic dissolved species concentration profiles during biofilm growth. Lastly, simulation results predict that the dissolved oxygen content and diffusion in the cathode are key parameters affecting the power output of the air-cathode MFC system, with greater oxygen content in the cathode resulting in increased power output and fully-matured biomass.« less

  8. Biofilm growth mode promotes maximum carrying capacity and community stability during product inhibition syntrophy

    PubMed Central

    Brileya, Kristen A.; Camilleri, Laura B.; Zane, Grant M.; Wall, Judy D.; Fields, Matthew W.

    2014-01-01

    Sulfate-reducing bacteria (SRB) can interact syntrophically with other community members in the absence of sulfate, and interactions with hydrogen-consuming methanogens are beneficial when these archaea consume potentially inhibitory H2 produced by the SRB. A dual continuous culture approach was used to characterize population structure within a syntrophic biofilm formed by the SRB Desulfovibrio vulgaris Hildenborough and the methanogenic archaeum Methanococcus maripaludis. Under the tested conditions, monocultures of D. vulgaris formed thin, stable biofilms, but monoculture M. maripaludis did not. Microscopy of intact syntrophic biofilm confirmed that D. vulgaris formed a scaffold for the biofilm, while intermediate and steady-state images revealed that M. maripaludis joined the biofilm later, likely in response to H2 produced by the SRB. Close interactions in structured biofilm allowed efficient transfer of H2 to M. maripaludis, and H2 was only detected in cocultures with a mutant SRB that was deficient in biofilm formation (ΔpilA). M. maripaludis produced more carbohydrate (uronic acid, hexose, and pentose) as a monoculture compared to total coculture biofilm, and this suggested an altered carbon flux during syntrophy. The syntrophic biofilm was structured into ridges (∼300 × 50 μm) and models predicted lactate limitation at ∼50 μm biofilm depth. The biofilm had structure that likely facilitated mass transfer of H2 and lactate, yet maximized biomass with a more even population composition (number of each organism) when compared to the bulk-phase community. Total biomass protein was equivalent in lactate-limited and lactate-excess conditions when a biofilm was present, but in the absence of biofilm, total biomass protein was significantly reduced. The results suggest that multispecies biofilms create an environment conducive to resource sharing, resulting in increased biomass retention, or carrying capacity, for cooperative populations. PMID:25566209

  9. Growth morphologies of wax in the presence of kinetic inhibitors

    NASA Astrophysics Data System (ADS)

    Tetervak, Alexander A.

    Driven by the need to prevent crystallization of normal alkanes from diesel fuels in cold climates, the petroleum industry has developed additives to slow the growth of these crystals and alter their morphologies. Although the utility of these kinetic inhibitors has been well demonstrated in the field, few studies have directly monitored their effect at microscopic morphology, and the mechanisms by which they act remain poorly understood. Here we present a study of the effects of such additives on the crystallization of long-chain n-alkanes from solution. The additives change the growth morphology from plate-like crystals to a microcrystalline mesh. When we impose a front velocity by moving the sample through a temperature gradient, the mesh growth may form a macroscopic banded pattern and also exhibit a burst-crystallization behavior. In this study, we characterize these crystallization phenomena and also two growth models: a continuum model that demonstrates the essential behavior of the banded crystallization, and a simple qualitative cellular automata model that captures basics of the burst-crystallization process. Keywords: solidification; mesh crystallization; kinetic inhibitor; burst growth.

  10. Role of Transport and Kinetics in Growth of Renal Stones

    NASA Technical Reports Server (NTRS)

    Kassemi, Mohammad; Iskovitz, Ilana

    2012-01-01

    Renal stone disease is not only a concern on earth but could conceivably pose as a serious risk to the astronauts health and safety in Space. In this paper, a combined transport-kinetics model for growth of calcium oxalate crystals is presented. The model is used to parametrically investigate the growth of renal calculi in urine with a focus on the coupled effects of transport and surface reaction on the ionic concentrations at the surface of the crystal and their impact on the resulting growth rates. It is shown that under nominal conditions of low solution supersaturation and low Damkohler number that typically exist on Earth, the surface concentrations of calcium and oxalate approach their bulk solution values in the urine and the growth rate is most likely limited by the surface reaction kinetics. But for higher solution supersaturations and larger Damkohler numbers that may be prevalent in the microgravity environment of Space, the calcium and oxalate surface concentrations tend to shift more towards their equilibrium or saturation values and thus the growth process may be limited by the transport through the medium. Furthermore, parametric numerical studies suggest that changes to the renal biochemistry of astronauts due in space may promote development of renal calculi during long duration space expeditions.

  11. Development of a rotating algal biofilm growth system for attached microalgae growth with in situ biomass harvest.

    PubMed

    Gross, Martin; Henry, Wesley; Michael, Clayton; Wen, Zhiyou

    2013-12-01

    This work aimed to develop a rotating algal biofilm (RAB) cultivation system that can be widely adopted by microalgae producers for easy biomass harvest. Algal cells were grown on the surface of a material rotating between nutrient-rich liquid and CO2-rich gaseous phase. Scrapping biomass from the attached surface avoided the expensive harvest operations such as centrifugation. Among various attachment materials, cotton sheet resulted in best algal growth, durability, and cost effectiveness. A lab-scale RAB system was further optimized with harvest frequency, rotation speed, and CO2 levels. The algal biomass from the RAB system had a similar water content as that in centrifuged biomass. An open pond raceway retrofitted with a pilot-scale RAB system resulted in a much higher biomass productivity when compared to a control open pond. Collectively, the research shows that the RAB system is an efficient algal culture system for easy biomass harvest with enhanced biomass productivity. PMID:24161650

  12. Computer Simulation of Grain Growth Kinetics with Solute Drag

    SciTech Connect

    Chen, L.; Chen, S.P.; Fan, D.

    1998-12-23

    The effects of solute dragon grain growth kinetics were studied in two dimensional (2-D) computer simulations by using a diffuse-interface field model. It is shown that, in the low velocity / low driving force regime, the velocity of a grain boundary motion departs from a linear relation with driving force (curvature) with solute drag. The nonlinear relation of migration velocity and driving force comes from the dependence of grain boundary energy and width on the curvature. The growth exponent m of power growth law for a polycrystalline system is affected by the segregation of solutes to grain boundaries. With the solute drag, the growth exponent m can take any value between 2 and 3 depending on the ratio of lattice diffusion to grain boundary mobility. The grain size and topological distributions are unaffected by solute drag, which are the same as those in a pure system.

  13. Morphology and Growth Kinetics of Straight and Kinked Tin Whiskers

    NASA Astrophysics Data System (ADS)

    Susan, Donald; Michael, Joseph; Grant, Richard P.; McKenzie, Bonnie; Yelton, W. Graham

    2013-03-01

    Time-lapse SEM studies of Sn whiskers were conducted to estimate growth kinetics and document whisker morphologies. For straight whiskers, growth rates of 3 to 4 microns per day were measured at room temperature. Two types of kinked whiskers were observed. For Type A kinks, the original growth segment spatial orientation remains unchanged, there are no other changes in morphology or diameter, and growth continues. For Type B kinks, the spatial orientation of the original segment changes and it appears that the whisker bends over. Whiskers with Type B kinks show changes in morphology and diameter at the base, indicating grain boundary motion in the film, which eliminates the conditions suitable for long-term whisker growth. To estimate the errors in the whisker growth measurements, a technique is presented to correct for SEM projection effects. With this technique, the actual growth angles and lengths of a large number of whiskers were collected. It was found that most whiskers grow at moderate or shallow angles with respect to the surface; few straight whiskers grow nearly normal to the surface. In addition, there is no simple correlation between growth angles and lengths for whiskers observed over an approximate 2-year period.

  14. Calcite growth kinetics: Modeling the effect of solution stoichiometry

    NASA Astrophysics Data System (ADS)

    Wolthers, Mariëtte; Nehrke, Gernot; Gustafsson, Jon Petter; Van Cappellen, Philippe

    2012-01-01

    Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth rate on the cation to anion ratio in solution, we extend the growth model for binary symmetrical electrolyte crystals of Zhang and Nancollas (1998) by combining it with the surface complexation model for the chemical structure of the calcite-aqueous solution interface of Wolthers et al. (2008). To maintain crystal stoichiometry, the rate of attachment of calcium ions to step edges is assumed to equal the rate of attachment of carbonate plus bicarbonate ions. The model parameters are optimized by fitting the model to the step velocities obtained previously by atomic force microscopy (AFM, Teng et al., 2000; Stack and Grantham, 2010). A variable surface roughness factor is introduced in order to reconcile the new process-based growth model with bulk precipitation rates measured in seeded calcite growth experiments. For practical applications, we further present empirical parabolic rate equations fitted to bulk growth rates of calcite in common background electrolytes and in artificial seawater-type solutions. Both the process-based and empirical growth rate equations agree with measured calcite growth rates over broad ranges of ionic strength, pH, solution stoichiometry and degree of supersaturation.

  15. Analysis of Network Topologies Underlying Ethylene Growth Response Kinetics.

    PubMed

    Prescott, Aaron M; McCollough, Forest W; Eldreth, Bryan L; Binder, Brad M; Abel, Steven M

    2016-01-01

    Most models for ethylene signaling involve a linear pathway. However, measurements of seedling growth kinetics when ethylene is applied and removed have resulted in more complex network models that include coherent feedforward, negative feedback, and positive feedback motifs. The dynamical responses of the proposed networks have not been explored in a quantitative manner. Here, we explore (i) whether any of the proposed models are capable of producing growth-response behaviors consistent with experimental observations and (ii) what mechanistic roles various parts of the network topologies play in ethylene signaling. To address this, we used computational methods to explore two general network topologies: The first contains a coherent feedforward loop that inhibits growth and a negative feedback from growth onto itself (CFF/NFB). In the second, ethylene promotes the cleavage of EIN2, with the product of the cleavage inhibiting growth and promoting the production of EIN2 through a positive feedback loop (PFB). Since few network parameters for ethylene signaling are known in detail, we used an evolutionary algorithm to explore sets of parameters that produce behaviors similar to experimental growth response kinetics of both wildtype and mutant seedlings. We generated a library of parameter sets by independently running the evolutionary algorithm many times. Both network topologies produce behavior consistent with experimental observations, and analysis of the parameter sets allows us to identify important network interactions and parameter constraints. We additionally screened these parameter sets for growth recovery in the presence of sub-saturating ethylene doses, which is an experimentally-observed property that emerges in some of the evolved parameter sets. Finally, we probed simplified networks maintaining key features of the CFF/NFB and PFB topologies. From this, we verified observations drawn from the larger networks about mechanisms underlying ethylene

  16. Analysis of Network Topologies Underlying Ethylene Growth Response Kinetics

    PubMed Central

    Prescott, Aaron M.; McCollough, Forest W.; Eldreth, Bryan L.; Binder, Brad M.; Abel, Steven M.

    2016-01-01

    Most models for ethylene signaling involve a linear pathway. However, measurements of seedling growth kinetics when ethylene is applied and removed have resulted in more complex network models that include coherent feedforward, negative feedback, and positive feedback motifs. The dynamical responses of the proposed networks have not been explored in a quantitative manner. Here, we explore (i) whether any of the proposed models are capable of producing growth-response behaviors consistent with experimental observations and (ii) what mechanistic roles various parts of the network topologies play in ethylene signaling. To address this, we used computational methods to explore two general network topologies: The first contains a coherent feedforward loop that inhibits growth and a negative feedback from growth onto itself (CFF/NFB). In the second, ethylene promotes the cleavage of EIN2, with the product of the cleavage inhibiting growth and promoting the production of EIN2 through a positive feedback loop (PFB). Since few network parameters for ethylene signaling are known in detail, we used an evolutionary algorithm to explore sets of parameters that produce behaviors similar to experimental growth response kinetics of both wildtype and mutant seedlings. We generated a library of parameter sets by independently running the evolutionary algorithm many times. Both network topologies produce behavior consistent with experimental observations, and analysis of the parameter sets allows us to identify important network interactions and parameter constraints. We additionally screened these parameter sets for growth recovery in the presence of sub-saturating ethylene doses, which is an experimentally-observed property that emerges in some of the evolved parameter sets. Finally, we probed simplified networks maintaining key features of the CFF/NFB and PFB topologies. From this, we verified observations drawn from the larger networks about mechanisms underlying ethylene

  17. Spherulitic growth of wax in the presence of kinetic inhibitors

    NASA Astrophysics Data System (ADS)

    Hutter, Jeffrey L.; Smith, Chris; Khmaladze, Alexander

    2001-03-01

    The petroleum industry has developed polymeric additives to prevent the precipitation of wax from diesel fuels in cold climates. These additives affect the crystallization kinetics of wax growth without affecting the thermodynamics. Some additives apparently operate by adsorbing to crystalline surfaces and blocking step flow, though direct evidence is lacking. We have used optical microscopy to study this process in model n-alkane systems with inhibitors added as a 1 wt% impurity. We find that the presence of the polymer dramatically alters the growth morphology of the wax --- rather than the usual plate-like growth, we see forms with all of the attributes of spherulites typical of bulk polymer growth, including radially oriented lamellae and banding. Since models for spherulitic growth postulate lamellar alignment by entropic pressure due to dangling polymer chains, the surface-adsorbed polymers are likely responsible for the similar alignment in wax spherulites. The banding seen in this case, however, results from periodic growth, rather than from the lamellar twisting seen in traditional polymer spherulites. We have modeled this effect as a coupling between the polymer adsorption rate and the growth rate of wax crystals.

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

    PubMed

    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

  19. Autotrophic hydrogen-producing biofilm growth sustained by a cathode as the sole electron and energy source.

    PubMed

    Jourdin, Ludovic; Freguia, Stefano; Donose, Bogdan C; Keller, Jurg

    2015-04-01

    It is still unclear whether autotrophic microbial biocathode biofilms are able to self-regenerate under purely cathodic conditions without any external electron or organic carbon sources. Here we report on the successful development and long-term operation of an autotrophic biocathode whereby an electroactive biofilm was able to grow and sustain itself with CO2 as a sole carbon source and using the cathode as electron source, with H2 as sole product. From a small inoculum of 15 mg COD (in 250 mL), containing 30.3% Archaea, the bioelectrochemical system operating at -0.5 V vs. SHE enabled an estimated biofilm growth of 300 mg as COD over a period of 276 days. A dramatic change in the microbial population was observed during this period with Archaea disappearing completely (<0.1% of population). The predominant phyla enriched were Proteobacteria (57.3%), Firmicutes (12.4%), Bacteroidetes (11.6%) and Actinobacteria (1.1%). Up to 9.2 L H2 m(-2) day(-1) (1.88 A m(-2)) was achieved when the cathode potential was decreased to -0.75 V vs. SHE. This study demonstrates that purely autotrophic biofilm growth coupled to proton reduction to hydrogen alone can be sustained with a cathode as the sole electron source, while avoiding the development of H2-consuming microorganisms such as methanogens and acetogens. PMID:25497168

  20. Solution growth kinetics and mechanism: Prismatic face of ADP

    NASA Astrophysics Data System (ADS)

    Chernov, A. A.; Rashkovich, L. N.; Mkrtchan, A. A.

    1986-01-01

    Laser Michelson interferometry has been applied to in situ study the (001) ADP growth kinetics in aqueous solution in the kinetic regime. The technique allows one to simultaneously measure the slope p of a growth hillock and normal growth rate R provided by this hillock. From these data, the average step growth rate v=R/p has been determined as a function of relative supersaturation σ. The dependencev(σ) is found to be linear, demonstrating the unimportance of surface and bulk diffusion. The direct incorporation at steps is characterized by the step kinetic coefficient βl=(5.1-6.4)X10-3 cm/s. The specific step free energy αl=(1.2-1.9) X10-6 erg/cm was determined from the measured linear dependence of the hillock slope on supersaturation for the hillock around presumably single elementary dislocation. For complex dislocation sources with large total Burgers vectors, the tendency to saturationin the hillock slope-supersaturation curves has been found. The curve perfectly fits the BCF expression which takes into account the perimeter 2L of the region occupied by the points in which the dislocation of the complex step source cross the growing face. For two dislocation sources,L=0.92 μm andL=0.31 μm and total Burgers vectors ⋍12h and 6h (h=7.53Å) have been found. The supersaturation dependence of activities for various complex dislocation sources have been directly demonstrated.

  1. A dynamic void growth model governed by dislocation kinetics

    NASA Astrophysics Data System (ADS)

    Wilkerson, J. W.; Ramesh, K. T.

    2014-10-01

    Here we examine the role of dislocation kinetics and substructure evolution on the dynamic growth of voids under very high strain rates, and develop a methodology for accounting for these effects in a computationally efficient manner. In particular, we account for the combined effects of relativistic dislocation drag and an evolving mobile dislocation density on the dynamics of void growth. We compare these effects to the constraints imposed by micro-inertia and discuss the conditions under which each mechanism governs the rate of void growth. The consequences of these constraints may be seen in a number of experimental observations associated with dynamic tensile failure, including the extreme rate-sensitivity of spall strength observed in laser shock experiments, an apparent anomalous temperate dependence of spall strength, and some particular features of void size distributions on spall surfaces.

  2. Kinetics of growth and aniline degradation by Stenotrophomonas maltophilia

    SciTech Connect

    Zissi, U.S.; Lyberatos, G.C.

    1999-01-01

    A pure bacterial culture of Stenotrophomonas maltophilia, capable of using aniline as a sole carbon source, was isolated. Kinetic experiments were conducted to develop a mathematical model that describes accurately the growth and utilization rates of the microorganism on the aniline and an alternate carbon source (glucose) individually and on their mixture. The growth of microorganisms and substrate utilization could be well described by using Monod expressions for limiting substrates. The presence of glucose in the culture medium did not repress aniline catabolism but simultaneous utilization was observed. When both substrates were present, the utilization of one substrate had a considerable effect on the utilization of the other. These effects were shown to be predicted by a mathematical model based on a modified Monod expression. The proposed model was found capable of describing accurately cellular growth as well as aniline and glucose biodegradation.

  3. Energetics and kinetics unveiled on helium cluster growth in tungsten

    NASA Astrophysics Data System (ADS)

    Wang, Jinlong; Niu, Liang-Liang; Shu, Xiaolin; Zhang, Ying

    2015-09-01

    The energetics and kinetics regarding helium (He) cluster growth in bcc tungsten (W) are unveiled using combined techniques of molecular statics and molecular dynamics. The principal mechanisms accounting for the decrease of system potential energy are identified to be trap mutation, < 100>   →  1/2< 111> cluster transformation, loop punching, coalescence between 1/2[1 1-1] and 1/2[1-1-1] loops, and loop capturing. The kinetic barriers associated with these key atomistic events are estimated. This work provides new insights into the complex yet intriguing atomistic evolution sequence of the He cluster and interstitial loop in W-based nuclear fusion materials under irradiation.

  4. Host stress hormone norepinephrine stimulates pneumococcal growth, biofilm formation and virulence gene expression

    PubMed Central

    2014-01-01

    Background Host signals are being shown to have a major impact on the bacterial phenotype. One of them is the endogenously produced catecholamine stress hormones, which are also used therapeutically as inotropes. Recent work form our laboratories have found that stress hormones can markedly increase bacterial growth and virulence. This report reveals that Streptococcus pneumoniae, a commensal that can also be a major cause of community acquired and nosocomial pneumonia, is highly inotrope responsive. Therapeutic levels of the stress hormone norepinephrine increased pneumococcal growth via a mechanism involving provision of iron from serum-transferrin and inotrope uptake, as well as enhancing expression of key genes in central metabolism and virulence. Collectively, our data suggests that Streptococcus pneumoniae recognises host stress as an environmental cue to initiate growth and pathogenic processes. Results Effects of a clinically attainable concentration of norepinephrine on S. pneumoniae pathogenicity were explored using in vitro growth and virulence assays, and RT-PCR gene expression profiling of genes involved in metabolism and virulence. We found that norepinephrine was a potent stimulator of growth, via a mechanism involving norepinephrine-delivery of transferrin-iron and internalisation of the inotrope. Stress hormone exposure also markedly increased biofilm formation. Importantly, gene profiling showed that norepinephrine significantly enhanced expression of genes involved in central metabolism and host colonisation. Analysis of the response of the pneumococcal pspA and pspC mutants to the stress hormone showed them to have a central involvement in the catecholamine response mechanism. Conclusions Collectively, our evidence suggests that the pneumococcus has mechanisms to recognise and process host stress hormones to augment its virulence properties. The ability to respond to host stress signals may be important for the pneumococcal transition from

  5. Development and Validation of a Chemostat Gut Model To Study Both Planktonic and Biofilm Modes of Growth of Clostridium difficile and Human Microbiota

    PubMed Central

    Crowther, Grace S.; Chilton, Caroline H.; Todhunter, Sharie L.; Nicholson, Scott; Freeman, Jane; Baines, Simon D.; Wilcox, Mark H.

    2014-01-01

    The human gastrointestinal tract harbours a complex microbial community which exist in planktonic and sessile form. The degree to which composition and function of faecal and mucosal microbiota differ remains unclear. We describe the development and characterisation of an in vitro human gut model, which can be used to facilitate the formation and longitudinal analysis of mature mixed species biofilms. This enables the investigation of the role of biofilms in Clostridium difficile infection (CDI). A well established and validated human gut model of simulated CDI was adapted to incorporate glass rods that create a solid-gaseous-liquid interface for biofilm formation. The continuous chemostat model was inoculated with a pooled human faecal emulsion and controlled to mimic colonic conditions in vivo. Planktonic and sessile bacterial populations were enumerated for up to 46 days. Biofilm consistently formed macroscopic structures on all glass rods over extended periods of time, providing a framework to sample and analyse biofilm structures independently. Whilst variation in biofilm biomass is evident between rods, populations of sessile bacterial groups (log10 cfu/g of biofilm) remain relatively consistent between rods at each sampling point. All bacterial groups enumerated within the planktonic communities were also present within biofilm structures. The planktonic mode of growth of C. difficile and gut microbiota closely reflected observations within the original gut model. However, distinct differences were observed in the behaviour of sessile and planktonic C. difficile populations, with C. difficile spores preferentially persisting within biofilm structures. The redesigned biofilm chemostat model has been validated for reproducible and consistent formation of mixed species intestinal biofilms. This model can be utilised for the analysis of sessile mixed species communities longitudinally, potentially providing information of the role of biofilms in CDI. PMID

  6. Biofilm Growth and Near-Infrared Radiation-Driven Photosynthesis of the Chlorophyll d-Containing Cyanobacterium Acaryochloris marina

    PubMed Central

    Behrendt, Lars; Schrameyer, Verena; Qvortrup, Klaus; Lundin, Luisa; Sørensen, Søren J.; Larkum, Anthony W. D.

    2012-01-01

    The cyanobacterium Acaryochloris marina is the only known phototroph harboring chlorophyll (Chl) d. It is easy to cultivate it in a planktonic growth mode, and A. marina cultures have been subject to detailed biochemical and biophysical characterization. In natural situations, A. marina is mainly found associated with surfaces, but this growth mode has not been studied yet. Here, we show that the A. marina type strain MBIC11017 inoculated into alginate beads forms dense biofilm-like cell clusters, as in natural A. marina biofilms, characterized by strong O2 concentration gradients that change with irradiance. Biofilm growth under both visible radiation (VIS, 400 to 700 nm) and near-infrared radiation (NIR, ∼700 to 730 nm) yielded maximal cell-specific growth rates of 0.38 per day and 0.64 per day, respectively. The population doubling times were 1.09 and 1.82 days for NIR and visible light, respectively. The photosynthesis versus irradiance curves showed saturation at a photon irradiance of Ek (saturating irradiance) >250 μmol photons m−2 s−1 for blue light but no clear saturation at 365 μmol photons m−2 s−1 for NIR. The maximal gross photosynthesis rates in the aggregates were ∼1,272 μmol O2 mg Chl d−1 h−1 (NIR) and ∼1,128 μmol O2 mg Chl d−1 h−1 (VIS). The photosynthetic efficiency (α) values were higher in NIR-irradiated cells [(268 ± 0.29) × 10−6 m2 mg Chl d−1 (mean ± standard deviation)] than under blue light [(231 ± 0.22) × 10−6 m2 mg Chl d−1]. A. marina is well adapted to a biofilm growth mode under both visible and NIR irradiance and under O2 conditions ranging from anoxia to hyperoxia, explaining its presence in natural niches with similar environmental conditions. PMID:22467501

  7. Kinetic model of impurity poisoning during growth of calcite

    SciTech Connect

    DeYoreo, J; Wasylenki, L; Dove, P; Wilson, D; Han, N

    2004-05-18

    The central role of the organic component in biologically controlled mineralization is widely recognized. These proteins are characterized by a high proportion of acidic amino acid residues, especially aspartate, Asp. At the same time, biomineralization takes place in the presence of a number of naturally-occurring, inorganic impurities, particularly Mg and Sr. In an attempt to decipher the controls on calcite growth imposed by both classes of modifiers, we have used in situ AFM to investigate the dependence of growth morphology and step kinetics on calcite in the presence of Sr{sup 2+}, as well as a wide suite of Aspartic acid-bearing polypeptides. In each case, we observe a distinct and step-specific modification. Most importantly, we find that the step speed exhibits a characteristic dependence on impurity concentration not predicted by existing crystal growth models. While all of the impurities clearly induce appearance of a 'dead zone,' neither the width of that dead zone nor the dependence of step speed on activity or impurity content can be explained by invoking the Gibbs-Thomson effect, which is the basis for the Cabrera-Vermilyea model of impurity poisoning. Common kink-blocking models also fail to explain the observed dependencies. Here we propose a kinetic model of inhibition based on a 'cooperative' effect of impurity adsorption at adjacent kink sites. The model is in qualitative agreement with the experimental results in that it predicts a non-linear dependence of dead zone width on impurity concentration, as well as a sharp drop in step speed above a certain impurity content. However, a detailed model of impurity adsorption kinetics that give quantitative agreement with the data has yet to be developed.

  8. Zerovalent bismuth nanoparticles inhibit Streptococcus mutans growth and formation of biofilm

    PubMed Central

    Hernandez-Delgadillo, Rene; Velasco-Arias, Donaji; Diaz, David; Arevalo-Niño, Katiushka; Garza-Enriquez, Marianela; De la Garza-Ramos, Myriam A; Cabral-Romero, Claudio

    2012-01-01

    Background and methods Despite continuous efforts, the increasing prevalence of resistance among pathogenic bacteria to common antibiotics has become one of the most significant concerns in modern medicine. Nanostructured materials are used in many fields, including biological sciences and medicine. While some bismuth derivatives has been used in medicine to treat vomiting, nausea, diarrhea, and stomach pain, the biocidal activity of zerovalent bismuth nanoparticles has not yet been studied. The objective of this investigation was to analyze the antimicrobial activity of bismuth nanoparticles against oral bacteria and their antibiofilm capabilities. Results Our results showed that stable colloidal bismuth nanoparticles had 69% antimicrobial activity against Streptococcus mutans growth and achieved complete inhibition of biofilm formation. These results are similar to those obtained with chlorhexidine, the most commonly used oral antiseptic agent. The minimal inhibitory concentration of bismuth nanoparticles that interfered with S. mutans growth was 0.5 mM. Conclusion These results suggest that zerovalent bismuth nanoparticles could be an interesting antimicrobial agent to be incorporated into an oral antiseptic preparation. PMID:22619547

  9. Bismuth oxide aqueous colloidal nanoparticles inhibit Candida albicans growth and biofilm formation

    PubMed Central

    Hernandez-Delgadillo, Rene; Velasco-Arias, Donaji; Martinez-Sanmiguel, Juan Jose; Diaz, David; Zumeta-Dube, Inti; Arevalo-Niño, Katiushka; Cabral-Romero, Claudio

    2013-01-01

    Multiresistance among microorganisms to common antimicrobials has become one of the most significant concerns in modern medicine. Nanomaterials are a new alternative to successfully treat the multiresistant microorganisms. Nanostructured materials are used in many fields, including biological sciences and medicine. Recently, it was demonstrated that the bactericidal activity of zero-valent bismuth colloidal nanoparticles inhibited the growth of Streptococcus mutans; however the antimycotic potential of bismuth nanostructured derivatives has not yet been studied. The main objective of this investigation was to analyze the fungicidal activity of bismuth oxide nanoparticles against Candida albicans, and their antibiofilm capabilities. Our results showed that aqueous colloidal bismuth oxide nanoparticles displayed antimicrobial activity against C. albicans growth (reducing colony size by 85%) and a complete inhibition of biofilm formation. These results are better than those obtained with chlorhexidine, nystatin, and terbinafine, the most effective oral antiseptic and commercial antifungal agents. In this work, we also compared the antimycotic activities of bulk bismuth oxide and bismuth nitrate, the precursor metallic salt. These results suggest that bismuth oxide colloidal nanoparticles could be a very interesting candidate as a fungicidal agent to be incorporated into an oral antiseptic. Additionally, we determined the minimum inhibitory concentration for the synthesized aqueous colloidal Bi2O3 nanoparticles. PMID:23637533

  10. Glass susceptibility: Growth kinetics and saturation under shear

    NASA Astrophysics Data System (ADS)

    Nandi, Saroj Kumar; Ramaswamy, Sriram

    2016-07-01

    We study the growth kinetics of glassy correlations in a structural glass by monitoring the evolution, within mode-coupling theory, of a suitably defined three-point function χC(t ,tw) with time t and waiting time tw. From the complete wave-vector-dependent equations of motion for domain growth, we pass to a schematic limit to obtain a numerically tractable form. We find that the peak value χCP of χC(t ,tw) , which can be viewed as a correlation volume, grows as tw0.5, and the relaxation time as tw0.8, following a quench to a point deep in the glassy state. These results constitute a theoretical explanation of the simulation findings of Parisi [J. Phys. Chem. B 103, 4128 (1999), 10.1021/jp983967m] and Kob and Barrat [Phys. Rev. Lett. 78, 4581 (1997), 10.1103/PhysRevLett.78.4581], and they are also in qualitative agreement with Parsaeian and Castillo [Phys. Rev. E 78, 060105(R) (2008), 10.1103/PhysRevE.78.060105]. On the other hand, if the quench is to a point on the liquid side, the correlation volume grows to saturation. We present a similar calculation for the growth kinetics in a p -spin spin glass mean-field model where we find a slower growth, χCP˜tw0.13 . Further, we show that a shear rate γ ˙ cuts off the growth of glassy correlations when tw˜1 /γ ˙ for quench in the glassy regime and tw=min(tr,1 /γ ˙) in the liquid, where tr is the relaxation time of the unsheared liquid. The relaxation time of the steady-state fluid in this case is ∝γ˙-0.8 .

  11. Electrical spiking in bacterial biofilms

    PubMed Central

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

    2015-01-01

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

  12. Two-step nitrification in a pure moving bed biofilm reactor-membrane bioreactor for wastewater treatment: nitrifying and denitrifying microbial populations and kinetic modeling.

    PubMed

    Leyva-Díaz, J C; González-Martínez, A; Muñío, M M; Poyatos, J M

    2015-12-01

    The moving bed biofilm reactor-membrane bioreactor (MBBR-MBR) is a novel solution to conventional activated sludge processes and membrane bioreactors. In this study, a pure MBBR-MBR was studied. The pure MBBR-MBR mainly had attached biomass. The bioreactor operated with a hydraulic retention time (HRT) of 9.5 h. The kinetic parameters for heterotrophic and autotrophic biomasses, mainly nitrite-oxidizing bacteria (NOB), were evaluated. The analysis of the bacterial community structure of the ammonium-oxidizing bacteria (AOB), NOB, and denitrifying bacteria (DeNB) from the pure MBBR-MBR was carried out by means of pyrosequencing to detect and quantify the contribution of the nitrifying and denitrifying bacteria in the total bacterial community. The relative abundance of AOB, NOB, and DeNB were 5, 1, and 3%, respectively, in the mixed liquor suspended solids (MLSS), and these percentages were 18, 5, and 2%, respectively, in the biofilm density (BD) attached to carriers. The pure MBBR-MBR had a high efficiency of total nitrogen (TN) removal of 71.81±16.04%, which could reside in the different bacterial assemblages in the fixed biofilm on the carriers. In this regard, the kinetic parameters for autotrophic biomass had values of YA=2.3465 mg O2 mg N(-1), μm, A=0.7169 h(-1), and KNH=2.0748 mg NL(-1). PMID:26264139

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

    SciTech Connect

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

    1994-04-15

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

  14. Effect of Algae and Plant Lectins on Planktonic Growth and Biofilm Formation in Clinically Relevant Bacteria and Yeasts

    PubMed Central

    Vasconcelos, Mayron Alves; Arruda, Francisco Vassiliepe Sousa; Carneiro, Victor Alves; Silva, Helton Colares; Nascimento, Kyria Santiago; Sampaio, Alexandre Holanda; Cavada, Benildo; Teixeira, Edson Holanda; Henriques, Mariana

    2014-01-01

    This study aimed to evaluate the abilities of plant and algae lectins to inhibit planktonic growth and biofilm formation in bacteria and yeasts. Initially, ten lectins were tested on Staphylococcus epidermidis, Staphylococcus aureus, Klebsiella oxytoca, Pseudomonas aeruginosa, Candida albicans, and C. tropicalis at concentrations of 31.25 to 250 μg/mL. The lectins from Cratylia floribunda (CFL), Vatairea macrocarpa (VML), Bauhinia bauhinioides (BBL), Bryothamnion seaforthii (BSL), and Hypnea musciformis (HML) showed activities against at least one microorganism. Biofilm formation in the presence of the lectins was also evaluated; after 24 h of incubation with the lectins, the biofilms were analyzed by quantifying the biomass (by crystal violet staining) and by enumerating the viable cells (colony-forming units). The lectins reduced the biofilm biomass and/or the number of viable cells to differing degrees depending on the microorganism tested, demonstrating the different characteristics of the lectins. These findings indicate that the lectins tested in this study may be natural alternative antimicrobial agents; however, further studies are required to better elucidate the functional use of these proteins. PMID:24982871

  15. C-di-GMP regulates Pseudomonas aeruginosa stress response to tellurite during both planktonic and biofilm modes of growth

    PubMed Central

    Chua, Song Lin; Sivakumar, Krishnakumar; Rybtke, Morten; Yuan, Mingjun; Andersen, Jens Bo; Nielsen, Thomas E.; Givskov, Michael; Tolker-Nielsen, Tim; Cao, Bin; Kjelleberg, Staffan; Yang, Liang

    2015-01-01

    Stress response plays an important role on microbial adaptation under hostile environmental conditions. It is generally unclear how the signaling transduction pathway mediates a stress response in planktonic and biofilm modes of microbial communities simultaneously. Here, we showed that metalloid tellurite (TeO32–) exposure induced the intracellular content of the secondary messenger cyclic di-GMP (c-di-GMP) of Pseudomonas aeruginosa. Two diguanylate cyclases (DGCs), SadC and SiaD, were responsible for the increased intracellular content of c-di-GMP. Enhanced c-di-GMP levels by TeO32– further increased P. aeruginosa biofilm formation and resistance to TeO32–. P. aeruginosa ΔsadCΔsiaD and PAO1/plac-yhjH mutants with low intracellular c-di-GMP content were more sensitive to TeO32– exposure and had low relative fitness compared to the wild-type PAO1 planktonic and biofilm cultures exposed to TeO32–. Our study provided evidence that c-di-GMP level can play an important role in mediating stress response in microbial communities during both planktonic and biofilm modes of growth. PMID:25992876

  16. Effect of algae and plant lectins on planktonic growth and biofilm formation in clinically relevant bacteria and yeasts.

    PubMed

    Vasconcelos, Mayron Alves; Arruda, Francisco Vassiliepe Sousa; Carneiro, Victor Alves; Silva, Helton Colares; Nascimento, Kyria Santiago; Sampaio, Alexandre Holanda; Cavada, Benildo; Teixeira, Edson Holanda; Henriques, Mariana; Pereira, Maria Olivia

    2014-01-01

    This study aimed to evaluate the abilities of plant and algae lectins to inhibit planktonic growth and biofilm formation in bacteria and yeasts. Initially, ten lectins were tested on Staphylococcus epidermidis, Staphylococcus aureus, Klebsiella oxytoca, Pseudomonas aeruginosa, Candida albicans, and C. tropicalis at concentrations of 31.25 to 250  μ g/mL. The lectins from Cratylia floribunda (CFL), Vatairea macrocarpa (VML), Bauhinia bauhinioides (BBL), Bryothamnion seaforthii (BSL), and Hypnea musciformis (HML) showed activities against at least one microorganism. Biofilm formation in the presence of the lectins was also evaluated; after 24 h of incubation with the lectins, the biofilms were analyzed by quantifying the biomass (by crystal violet staining) and by enumerating the viable cells (colony-forming units). The lectins reduced the biofilm biomass and/or the number of viable cells to differing degrees depending on the microorganism tested, demonstrating the different characteristics of the lectins. These findings indicate that the lectins tested in this study may be natural alternative antimicrobial agents; however, further studies are required to better elucidate the functional use of these proteins. PMID:24982871

  17. Effect of silver nanoparticle coatings on mycobacterial biofilm attachment and growth: Implications for ceramic water filters

    NASA Astrophysics Data System (ADS)

    Larimer, Curtis James

    Silver is a natural, broad-spectrum antibacterial metal and its toxicity can be enhanced when surface area is maximized. As a result, silver nanoparticles (AgNP) have been investigated for use in novel water treatment technologies. The hypothesis of this work is that deposited AgNPs can enhance water treatment technologies by inhibiting growth of planktonic bacteria and biofilms. This was investigated by evaluating the antibacterial efficacy of AgNPs both in solution and as deposited on surfaces. AgNPs were found to be toxic to three species of environmental mycobacteria, M. smegmatis, M. avium, and M. marinum and the level of susceptibility varied widely, probably owing to the varying levels of silver that each species is exposed to in its natural environment. When cultured in a AgNP enriched environment M. smegmatis developed resistance to the toxic effects of both the nanoparticles and silver ions. The resistant mutant was as viable as the unmodified strain and was also resistant to antibiotic isoniazid. However, the strain was more susceptible to other toxic metal ions from ZnSO4 and CuSO4. AgNPs were deposited on silicon wafer substrates by vertical colloidal deposition (VCD). Manipulating deposition speed and also concentration of AgNPs in the depositing liquid led to a range of AgNP coatings with distinctive deposition lines perpendicular to the motion of the meniscus. Experimental results for areal coverage, which was measured from SEM images of AgNP coatings, were compared to Diao's theory of VCD but did not show agreement due to a stick-slip mechanism that is not accounted for by the theory. Durability of AgNP coatings is critical for antibacterial efficacy and to mitigate the risks of exposing the environment to nanomaterials and it was measured by exposing AgNP coatings to liquid flow in a flow cell. Durability was improved by modifying processing to include a heat treatment after deposition. Finally, the antibiofilm efficacy of deposited AgNPs was

  18. Radiochemical study of the kinetics of crystal growth in gels

    NASA Astrophysics Data System (ADS)

    Cecal, Alexandru; Palamaru, Mircea; Juverdeanu, Anca; Giosan, Marcel

    1996-01-01

    A kinetic study was performed on nucleation and growth of crystals containing radioactive ions in gelatin and agar gels. The investigated crystals were: 60CoHPO 4, 60CoS, 60Co(OH) 2, 60Co(SCN) 2, 204Tl(OH) 3, and 204Tl[(C 2H 5) 2NCS 2] 3. The study shows that the crystal growth rate depends on the cation size and charge, the nature of anion as well as on the colloidal medium. The crystallisation process in the gel has two distinctive steps: diffusion of reactant ions in the gel followed by a chemical reaction which leads to nucleation of the crystal. Both steps are described quantitatively.

  19. Kinetically controlled growth of gallium on stepped Si (553) surface

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh; Pasha, Syed Khalid; Govind

    2013-10-01

    Kinetically controlled growth of gallium (Ga) metal has been reported on high index stepped Si (553) surface and its thermal stability with various novel superstructural phases has been analyzed. Auger electron spectroscopy studies revealed that the adsorption of Ga at room temperature (RT) follows Frank-van der Merwe (FM) growth mode while for higher substrate temperature, Ga adsorption remains within the submonolayer range. Thermal desorption and low energy electron diffraction studies investigated the formation of thermally stable Ga-islands and the various Ga induced superstructural phase on Si (553). During room temperature adsorption, (1 1 1)7 × 7 facet of Si (553) reconstructed into (1 1 1)6 × 6 facet while during desorption process, stable (1 1 1)6 × 6 and (1 1 1)√3 × √3-R30° surface reconstructions has been observed.

  20. Continuous growth kinetics of Candida utilis in pineapple cannery effluent

    SciTech Connect

    Prior, B.A.

    1984-01-01

    Candida utilis was grown on a pineapple cannery effluent as the sole carbon and energy source in a chemostat at dilution rates between 0.10 and 0.62 h/sup -1/ to determine the growth kinetics. The principal sugars in the effluent were sucrose, glucose, and fructose. The cell yield coefficient on carbohydrate varied with dilution rate and a maximum value of 0.63 was observed at a dilution rate of 0.33 h/sup -1/. The steady-state concentrations of carbohydrate, reducing sugar, and chemical oxygen demand (COD) appeared to follow Monod saturation kinetics with increasing dilution rate, although none of the measured parameters represented a pure substrate. The maximum specific growth rate and reducing sugar saturation constant were 0.64 h/sup -1/ and 0.060 g/L, respectively. A maximum cell mass productivity of 2.3 g/L h was observed at a dilution rate of 0.51 h/sup -1/. At this dilution rate, only 68% of the COD was removed. A 95% COD removal was attained at a dilution rate of 0.10 h/sup -1/. Optimal yeast productivity and COD reduction occurred at a dilution rate of 0.33 h/sup -1/.

  1. Thermodynamic-kinetic simulation of constrained dendrite growth in steels

    SciTech Connect

    Miettinen, J.

    2000-04-01

    A model of constrained dendritic growth for steels, based on thermodynamic and kinetic theory, is presented. The model links thermodynamic chemical potential-equality equations to an existing, approximate treatment of constrained dendritic growth in multicomponent steels, taking into account the deviation from the local thermodynamic equilibrium of the phase interface caused by interface friction, capillarity, and solute trapping. Due to the thermodynamic approach, with a thermodynamic model and recently assessed data, the present treatment yields a more accurate determination of phase stabilities than the earlier methods. Depending on the steel composition and the growth conditions (growth rate and temperature gradient), the model determines the dendrite tip undercooling, the primary solid phase (ferrite or austenite), the stability of that phase, certain dimensions of the microstructure, and the solute accumulation ahead of the dendrite tip. A special optional calculations is that of the equally probable formation of ferrite and austenite in stainless steels. Calculations for testing the model and for validation it with experimental data are presented.

  2. Characterization of membrane lipidome changes in Pseudomonas aeruginosa during biofilm growth on glass wool.

    PubMed

    Benamara, Hayette; Rihouey, Christophe; Abbes, Imen; Ben Mlouka, Mohamed Amine; Hardouin, Julie; Jouenne, Thierry; Alexandre, Stéphane

    2014-01-01

    Bacteria cells within biofilms are physiologically distinct from their planktonic counterparts. In particular they are more resistant to detrimental environmental conditions. In this study, we monitored the evolution of the phospholipid composition of the inner and outer membranes of P. aeruginosa during the biofilm formation (i.e., from 1-, 2-, to 6-day-old biofilm). Lipidome analyses were performed by electrospray ionization mass spectrometry. In addition to the lipidomic analysis, the fatty acid composition was analysed by gas chromatography/mass spectrometry. We found that the lipidome alterations of the inner and the outer membranes varied with the biofilm age. These alterations in phospholipid compositions reflect a higher diversity in sessile organisms than in planktonic counterparts. The diversity is characterized by the presence of PE 30∶1, PE 31∶0 and PG 31∶0 for the lower masses as well as PE 38∶1, 38∶2, 39∶1, 39∶2 and PG 38∶0, 38∶1, 38∶2, 39∶1, 39∶2 for the higher masses. However, this lipidomic feature tends to disappear with the biofilm age, in particular the high mass phospholipids tend to disappear. The amount of branched chains phospholipids mainly located in the outer membrane decreased with the biofilm age, whereas the proportion of cyclopropylated phospholipids increased in both membranes. In bacteria present in oldest biofilms, i.e., 6-day-old, the phospholipid distribution moved closer to that of planktonic bacteria. PMID:25265483

  3. Characterization of Membrane Lipidome Changes in Pseudomonas aeruginosa during Biofilm Growth on Glass Wool

    PubMed Central

    Benamara, Hayette; Rihouey, Christophe; Abbes, Imen; Ben Mlouka, Mohamed Amine; Hardouin, Julie; Jouenne, Thierry; Alexandre, Stéphane

    2014-01-01

    Bacteria cells within biofilms are physiologically distinct from their planktonic counterparts. In particular they are more resistant to detrimental environmental conditions. In this study, we monitored the evolution of the phospholipid composition of the inner and outer membranes of P. aeruginosa during the biofilm formation (i.e., from 1-, 2-, to 6-day-old biofilm). Lipidome analyses were performed by electrospray ionization mass spectrometry. In addition to the lipidomic analysis, the fatty acid composition was analysed by gas chromatography/mass spectrometry. We found that the lipidome alterations of the inner and the outer membranes varied with the biofilm age. These alterations in phospholipid compositions reflect a higher diversity in sessile organisms than in planktonic counterparts. The diversity is characterized by the presence of PE 30∶1, PE 31∶0 and PG 31∶0 for the lower masses as well as PE 38∶1, 38∶2, 39∶1, 39∶2 and PG 38∶0, 38∶1, 38∶2, 39∶1, 39∶2 for the higher masses. However, this lipidomic feature tends to disappear with the biofilm age, in particular the high mass phospholipids tend to disappear. The amount of branched chains phospholipids mainly located in the outer membrane decreased with the biofilm age, whereas the proportion of cyclopropylated phospholipids increased in both membranes. In bacteria present in oldest biofilms, i.e., 6-day-old, the phospholipid distribution moved closer to that of planktonic bacteria. PMID:25265483

  4. IsdC from Staphylococcus lugdunensis Induces Biofilm Formation under Low-Iron Growth Conditions

    PubMed Central

    Missineo, Antonino; Di Poto, Antonella; Geoghegan, Joan A.; Rindi, Simonetta; Heilbronner, Simon; Gianotti, Valentina; Arciola, Carla Renata; Foster, Timothy J.; Pietrocola, Giampiero

    2014-01-01

    Staphylococcus lugdunensis is a coagulase-negative staphylococcus that is a commensal of humans and an opportunistic pathogen. It can cause a spectrum of infections, including those that are associated with the ability to form biofilm, such as occurs with endocarditis or indwelling medical devices. The genome sequences of two strains revealed the presence of orthologues of the ica genes that are responsible for synthesis of poly-N-acetylglucosamine (PNAG) that is commonly associated with biofilm in other staphylococci. However, we discovered that biofilm formed by a panel of S. lugdunensis isolates growing in iron-restricted medium was susceptible to degradation by proteases and not by metaperiodate, suggesting that the biofilm matrix comprised proteins and not PNAG. When the iron concentration was raised to 1 mM biofilm formation by all strains tested was greatly reduced. A mutant of strain N920143 lacking the entire locus that encodes iron-regulated surface determinant (Isd) proteins was defective in biofilm formation under iron-limited conditions. An IsdC-null mutant was defective, whereas IsdK, IsdJ, and IsdB mutants formed biofilm to the same level as the parental strain. Expression of IsdC was required both for the primary attachment to unconditioned polystyrene and for the accumulation phase of biofilm involving cell-cell interactions. Purified recombinant IsdC protein formed dimers in solution and Lactococcus lactis cells expressing only IsdC adhered to immobilized recombinant IsdC but not to IsdJ, IsdK, or IsdB. This is consistent with a specific homophilic interaction between IsdC molecules on neighboring cells contributing to accumulation of S. lugdunensis biofilm in vivo. PMID:24686057

  5. A Microplate-Based System as In Vitro Model of Biofilm Growth and Quantification.

    PubMed

    Vandecandelaere, Ilse; Van Acker, Heleen; Coenye, Tom

    2016-01-01

    We describe a 96-well microtiter plate-based system as an in vitro model for biofilm formation and quantification. Although in vitro assays are artificial systems and thus significantly differ from in vivo conditions, they represent an important tool to evaluate biofilm formation and the effect of compounds on biofilms. Stainings to evaluate the amount of biomass (crystal violet staining) and the number of metabolically active cells (resazurin assay) are discussed and specific attention is paid to the use of this model to quantify persisters in sessile populations. PMID:26468099

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  7. Multi-Channel Microfluidic Biosensor Platform Applied for Online Monitoring and Screening of Biofilm Formation and Activity

    PubMed Central

    Bruchmann, Julia; Sachsenheimer, Kai; Rapp, Bastian E.; Schwartz, Thomas

    2015-01-01

    Bacterial colonization of surfaces and interfaces has a major impact on various areas including biotechnology, medicine, food industries, and water technologies. In most of these areas biofilm development has a strong impact on hygiene situations, product quality, and process efficacies. In consequence, biofilm manipulation and prevention is a fundamental issue to avoid adverse impacts. For such scenario online, non-destructive biofilm monitoring systems become important in many technical and industrial applications. This study reports such a system in form of a microfluidic sensor platform based on the combination of electrical impedance spectroscopy and amperometric current measurement, which allows sensitive online measurement of biofilm formation and activity. A total number of 12 parallel fluidic channels enable real-time online screening of various biofilms formed by different Pseudomonas aeruginosa and Stenotrophomonas maltophilia strains and complex mixed population biofilms. Experiments using disinfectant and antibiofilm reagents demonstrate that the biofilm sensor is able to discriminate between inactivation/killing of bacteria and destabilization of biofilm structures. The impedance and amperometric sensor data demonstrated the high dynamics of biofilms as a consequence of distinct responses to chemical treatment strategies. Gene expression of flagellar and fimbrial genes of biofilms grown inside the microfluidic system supported the detected biofilm growth kinetics. Thus, the presented biosensor platform is a qualified tool for assessing biofilm formation in specific environments and for evaluating the effectiveness of antibiofilm treatment strategies. PMID:25706987

  8. Multi-channel microfluidic biosensor platform applied for online monitoring and screening of biofilm formation and activity.

    PubMed

    Bruchmann, Julia; Sachsenheimer, Kai; Rapp, Bastian E; Schwartz, Thomas

    2015-01-01

    Bacterial colonization of surfaces and interfaces has a major impact on various areas including biotechnology, medicine, food industries, and water technologies. In most of these areas biofilm development has a strong impact on hygiene situations, product quality, and process efficacies. In consequence, biofilm manipulation and prevention is a fundamental issue to avoid adverse impacts. For such scenario online, non-destructive biofilm monitoring systems become important in many technical and industrial applications. This study reports such a system in form of a microfluidic sensor platform based on the combination of electrical impedance spectroscopy and amperometric current measurement, which allows sensitive online measurement of biofilm formation and activity. A total number of 12 parallel fluidic channels enable real-time online screening of various biofilms formed by different Pseudomonas aeruginosa and Stenotrophomonas maltophilia strains and complex mixed population biofilms. Experiments using disinfectant and antibiofilm reagents demonstrate that the biofilm sensor is able to discriminate between inactivation/killing of bacteria and destabilization of biofilm structures. The impedance and amperometric sensor data demonstrated the high dynamics of biofilms as a consequence of distinct responses to chemical treatment strategies. Gene expression of flagellar and fimbrial genes of biofilms grown inside the microfluidic system supported the detected biofilm growth kinetics. Thus, the presented biosensor platform is a qualified tool for assessing biofilm formation in specific environments and for evaluating the effectiveness of antibiofilm treatment strategies. PMID:25706987

  9. Inhibition of Aspergillus fumigatus and Its Biofilm by Pseudomonas aeruginosa Is Dependent on the Source, Phenotype and Growth Conditions of the Bacterium

    PubMed Central

    Ferreira, Jose A. G.; Penner, John C.; Moss, Richard B.; Haagensen, Janus A. J.; Clemons, Karl V.; Spormann, Alfred M.; Nazik, Hasan; Cohen, Kevin; Banaei, Niaz; Carolino, Elisabete; Stevens, David A.

    2015-01-01

    Aspergillus fumigatus (Af) and Pseudomonas aeruginosa (Pa) are leading fungal and bacterial pathogens, respectively, in many clinical situations. Relevant to this, their interface and co-existence has been studied. In some experiments in vitro, Pa products have been defined that are inhibitory to Af. In some clinical situations, both can be biofilm producers, and biofilm could alter their physiology and affect their interaction. That may be most relevant to airways in cystic fibrosis (CF), where both are often prominent residents. We have studied clinical Pa isolates from several sources for their effects on Af, including testing involving their biofilms. We show that the described inhibition of Af is related to the source and phenotype of the Pa isolate. Pa cells inhibited the growth and formation of Af biofilm from conidia, with CF isolates more inhibitory than non-CF isolates, and non-mucoid CF isolates most inhibitory. Inhibition did not require live Pa contact, as culture filtrates were also inhibitory, and again non-mucoid>mucoid CF>non-CF. Preformed Af biofilm was more resistant to Pa, and inhibition that occurred could be reproduced with filtrates. Inhibition of Af biofilm appears also dependent on bacterial growth conditions; filtrates from Pa grown as biofilm were more inhibitory than from Pa grown planktonically. The differences in Pa shown from these different sources are consistent with the extensive evolutionary Pa changes that have been described in association with chronic residence in CF airways, and may reflect adaptive changes to life in a polymicrobial environment. PMID:26252384

  10. Glass susceptibility: Growth kinetics and saturation under shear.

    PubMed

    Nandi, Saroj Kumar; Ramaswamy, Sriram

    2016-07-01

    We study the growth kinetics of glassy correlations in a structural glass by monitoring the evolution, within mode-coupling theory, of a suitably defined three-point function χ_{C}(t,t_{w}) with time t and waiting time t_{w}. From the complete wave-vector-dependent equations of motion for domain growth, we pass to a schematic limit to obtain a numerically tractable form. We find that the peak value χ_{C}^{P} of χ_{C}(t,t_{w}), which can be viewed as a correlation volume, grows as t_{w}^{0.5}, and the relaxation time as t_{w}^{0.8}, following a quench to a point deep in the glassy state. These results constitute a theoretical explanation of the simulation findings of Parisi [J. Phys. Chem. B 103, 4128 (1999)JPCBFK1520-610610.1021/jp983967m] and Kob and Barrat [Phys. Rev. Lett. 78, 4581 (1997)PRLTAO0031-900710.1103/PhysRevLett.78.4581], and they are also in qualitative agreement with Parsaeian and Castillo [Phys. Rev. E 78, 060105(R) (2008)PLEEE81539-375510.1103/PhysRevE.78.060105]. On the other hand, if the quench is to a point on the liquid side, the correlation volume grows to saturation. We present a similar calculation for the growth kinetics in a p-spin spin glass mean-field model where we find a slower growth, χ_{C}^{P}∼t_{w}^{0.13}. Further, we show that a shear rate γ[over ̇] cuts off the growth of glassy correlations when t_{w}∼1/γ[over ̇] for quench in the glassy regime and t_{w}=min(t_{r},1/γ[over ̇]) in the liquid, where t_{r} is the relaxation time of the unsheared liquid. The relaxation time of the steady-state fluid in this case is ∝γ[over ̇]^{-0.8}. PMID:27575179

  11. Modeling of anaerobic formate kinetics in mixed biofilm culture using dynamic membrane mass spectrometric measurement.

    PubMed

    Dornseiffer, P; Meyer, B; Heinzle, E

    1995-02-01

    The dynamics of the anaerobic conversion of formate in a microbial mixed culture taken from an anaerobic fluidized bed reactor was studied using a new stirred micro reactor equipped with a membrane mass spectrometer. The microreactor with a toroidally shaped bottom and pitched blade turbine and a cylindrical flow guide was thermostated and additionally equipped with a pH electrode and pH control. During fed-batch experiments using formate, the dissolved gases (methane, hydrogen, and carbon dioxide), as well as the acid consumption rates for pH control were monitored continuously. Initially and at the end of each experiment, organic acids were analyzed using ion chromatography (IC). It was found that about 50% of the formate was converted to methane via hydrogen and carbon dioxide, 40% gave methane either directly or via acetate. This was calculated from experiments using H(13)CO(3) (-) pulses and measurement of (12)CH(4) and (13)CH(4) production rates. About 10% of the formate was converted to lactate, acetate, and propionate, thereby increasing the measured CO(2)/CH(4) production ratio. The nondissociated formic acid was shown to be rate determining. From the relatively high K(s) value of 2.5 mmol m(-3), it was concluded that formate cannot play an important role in electron transfer. During dynamic feeding of formate, hydrogen concentration always increased to a maximum before decreasing again. This peak was found to be very discriminative during modeling. From the various models set up, only those with two-stage degradation and double Monod kinetics, both for CO(2) and hydrogen, were able to describe the experimental data adequately. Additional discrimination was possible with the IC measurement of organic acids. (c) 1995 John Wiley & Sons, Inc. PMID:18623141

  12. Arabidopsis thaliana root growth kinetics and lunisolar tidal acceleration.

    PubMed

    Fisahn, Joachim; Yazdanbakhsh, Nima; Klingele, Emile; Barlow, Peter

    2012-07-01

    • All living organisms on Earth are continually exposed to diurnal variations in the gravitational tidal force due to the Sun and Moon. • Elongation of primary roots of Arabidopsis thaliana seedlings maintained at a constant temperature was monitored for periods of up to 14 d using high temporal- and spatial-resolution video imaging. The time-course of the half-hourly elongation rates exhibited an oscillation which was maintained when the roots were placed in the free-running condition of continuous illumination. • Correlation between the root growth kinetics collected from seedlings initially raised under several light protocols but whose roots were subsequently in the free-running condition and the lunisolar tidal profiles enabled us to identify that the latter is the probable exogenous determinant of the rhythmic variation in root elongation rate. Similar observations and correlations using roots of Arabidopsis starch mutants suggest a central function of starch metabolism in the response to the lunisolar tide. The periodicity of the lunisolar tidal signal and the concomitant adjustments in root growth rate indicate that an exogenous timer exists for the modulation of root growth and development. • We propose that, in addition to the sensitivity to Earthly 1G gravity, which is inherent to all animals and plants, there is another type of responsiveness which is attuned to the natural diurnal variations of the lunisolar tidal force. PMID:22583121

  13. Inhibitory effects of Lactobacillus fermentum on microbial growth and biofilm formation.

    PubMed

    Rybalchenko, Oxana V; Bondarenko, Viktor M; Orlova, Olga G; Markov, Alexander G; Amasheh, S

    2015-10-01

    Beneficial effects of Lactobacilli have been reported, and lactic bacteria are employed for conservation of foods. Therefore, the effects of a Lactobacillus fermentum strain were analyzed regarding inhibitory effects on staphylococci, Candida albicans and enterotoxigenic enterobacteria by transmission electron microscopy (TEM). TEM of bacterial biofilms was performed using cocultures of bacteriocin-producing L. fermentum 97 with different enterotoxigenic strains: Staphylococcus epidermidis expressing the ica gene responsible for biofilm formation, Staphylococcus aureus producing enterotoxin type A, Citrobacter freundii, Enterobacter cloaceae, Klebsiella oxytoca, Proteus mirabilis producing thermolabile and thermostable enterotoxins determined by elt or est genes, and Candida albicans. L. fermentum 97 changed morphological features and suppressed biofilm formation of staphylococci, enterotoxigenic enterobacteria and Candida albicans; a marked transition to resting states, a degradation of the cell walls and cytoplasm, and a disruption of mature bacterial biofilms were observed, the latter indicating efficiency even in the phase of higher cell density. PMID:26267163

  14. Growth kinetics in a phase field model with continuous symmetry

    NASA Astrophysics Data System (ADS)

    Marini Bettolo Marconi, Umberto; Crisanti, Andrea

    1996-07-01

    We discuss the static and kinetic properties of a Ginzburg-Landau spherically symmetric O(N) model recently introduced [U. Marini Bettolo Marconi and A. Crisanti, Phys. Rev. Lett. 75, 2168 (1995)] in order to generalize the so-called phase field model of Langer [Rev. Mod. Phys. 52, 1 (1980); Science 243, 1150 (1989)]. The Hamiltonian contains two O(N) invariant fields φ and U bilinearly coupled. The order parameter field φ evolves according to a nonconserved dynamics, whereas the diffusive field U follows a conserved dynamics. In the limit N-->∞ we obtain an exact solution, which displays an interesting kinetic behavior characterized by three different growth regimes. In the early regime the system displays normal scaling and the average domain size grows as t1/2; in the intermediate regime one observes a finite wave-vector instability, which is related to the Mullins-Sekerka instability; finally, in the late stage the structure function has a multiscaling behavior, while the domain size grows as t1/4.

  15. Oxidation kinetics and chemostat growth kinetics of Thiobacillus ferrooxidans on tetrathionate and thiosulfate.

    PubMed

    Eccleston, M; Kelly, D P

    1978-06-01

    Growth of Thiobacillus ferrooxidans in batch culture on 10 mM potassium tetrathionate was optimal at pH 2.5 (specific growth rate, 0.092 h-1). Oxygen electrode studies on resting cell suspensions showed that the apparent Km for tetrathionate oxidation (0.13 to 8.33 mM) was pH dependent, suggesting higher substrate affinity at higher pH. Conversely, oxidation rates were greatest at low pH. High substrate concentrations (7.7 to 77 mM) did not affect maximum oxidation rates at pH 3.0, but produced substrate inhibition at other pH values. Tetrathionate-grown cell suspensions also oxidized thiosulfate at pH 2.0 to 4.0. Apparent Km values (1.2 to 25 mM) were of the same order as for tetrathionate, but kinetics were complex. Continuous culture on growth-limiting tetrathionate at pH 2.5, followed by continuous culture on growth-limiting thiosulfate at pH 2.5, indicated true growth yield values (grams [dry weight] per gram-molecule of substrate) of 12.2 and 7.5, and maintenance coefficient values (millimoles of substrate per gram [dry weight) of organisms per hour) of 1.01 and 0.97 for tetrathionate and thiosulfate, respectively. Yield was increased on both media at low dilution rates by increase in CO2 supply. The apparent maintenance coefficient was lowered without affecting YG, suggesting better energy coupling in CO2-rich environments. Prolonged continuous cultivation on tetrathionate or thiosulfate did not affect the ability of the organism to grow subsequently in ferrous iron medium. PMID:26665

  16. Tryptophan Inhibits Biofilm Formation by Pseudomonas aeruginosa

    PubMed Central

    Brandenburg, Kenneth S.; Rodriguez, Karien J.; McAnulty, Jonathan F.; Murphy, Christopher J.; Abbott, Nicholas L.; Schurr, Michael J.

    2013-01-01

    Biofilm formation by Pseudomonas aeruginosa has been implicated in the pathology of chronic wounds. Both the d and l isoforms of tryptophan inhibited P. aeruginosa biofilm formation on tissue culture plates, with an equimolar ratio of d and l isoforms producing the greatest inhibitory effect. Addition of d-/l-tryptophan to existing biofilms inhibited further biofilm growth and caused partial biofilm disassembly. Tryptophan significantly increased swimming motility, which may be responsible in part for diminished biofilm formation by P. aeruginosa. PMID:23318791

  17. Biofilm formation of Salmonella serotypes in simulated meat processing environments and its relationship to cell characteristics.

    PubMed

    Wang, Huhu; Ding, Shijie; Dong, Yang; Ye, Keping; Xu, Xinglian; Zhou, Guanghong

    2013-10-01

    Salmonella attached to meat contact surfaces encountered in meat processing facilities may serve as a source of cross-contamination. In this study, the influence of serotypes and media on biofilm formation of Salmonella was investigated in a simulated meat processing environment, and the relationships between biofilm formation and cell characteristics were also determined. All six serotypes (Salmonella enterica serotype Heidelberg, Salmonella Derby, Salmonella Agona, Salmonella Indiana, Salmonella Infantis, and Salmonella Typhimurium) can readily form biofilms on stainless steel surfaces, and the amounts of biofilms were significantly influenced by the serotypes, incubation media, and incubation time used in this study. Significant differences in cell surface hydrophobicity, autoaggregation, motility, and growth kinetic parameters were observed between individual serotypes tested. Except for growth kinetic parameters, the cell characteristics were correlated with the ability of biofilm formation incubated in tryptic soy broth, whereas no correlation with biofilm formation incubated in meat thawing-loss broth (an actual meat substrate) was found. Salmonella grown in meat thawing-loss broth showed a "cloud-shaped" morphology in the mature biofilm, whereas when grown in tryptic soy broth it had a "reticulum-shaped" appearance. Our study provides some practical information to understand the process of biofilm formation on meat processing contact surfaces. PMID:24112581

  18. Pattern Formation and Growth Kinetics in Eutectic Systems

    SciTech Connect

    Teng, Jing

    2007-01-01

    Growth patterns during liquid/solid phase transformation are governed by simultaneous effects of heat and mass transfer mechanisms, creation of new interfaces, jump of the crystallization units from liquid to solid and their rearrangement in the solid matrix. To examine how the above processes influence the scale of microstructure, two eutectic systems are chosen for the study: a polymeric system polyethylene glycol-p-dibromobenzene (PEG-DBBZ) and a simple molecular system succinonitrile (SCN)-camphor. The scaling law for SCN-camphor system is found to follow the classical Jackson-Hunt model of circular rod eutectic, where the diffusion in the liquid and the interface energy are the main physics governing the two-phase pattern. In contrast, a significantly different scaling law is observed for the polymer system. The interface kinetics of PEG phase and its solute concentration dependence thus have been critically investigated for the first time by directional solidification technique. A model is then proposed that shows that the two-phase pattern in polymers is governed by the interface diffusion and the interface kinetics. In SCN-camphor system, a new branch of eutectic, elliptical shape rodl, is found in thin samples where only one layer of camphor rods is present. It is found that the orientation of the ellipse can change from the major axis in the direction of the thickness to the direction of the width as the velocity and/or the sample thickness is decreased. A theoretical model is developed that predicts the spacing and orientation of the elliptical rods in a thin sample. The single phase growth patterns of SCN-camphor system were also examined with emphasis on the three-dimensional single cell and cell/dendrite transition. For the 3D single cell in a capillary tube, the entire cell shape ahead of the eutectic front can be described by the Saffmann-Taylor finger only at extremely low growth rate. A 3D directional solidification model is developed to

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

    SciTech Connect

    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.

  20. Physiologic growth hormone replacement improves fasting lipid kinetics in patients with HIV lipodystrophy syndrome

    Technology Transfer Automated Retrieval System (TEKTRAN)

    HIV lipodystrophy syndrome (HLS) is characterized by accelerated lipolysis, inadequate fat oxidation, increased hepatic reesterification, and a high frequency of growth hormone deficiency (GHD). The effect of growth hormone (GH) replacement on these lipid kinetic abnormalities is unknown. We aimed ...

  1. Role of Intracellular Stochasticity in Biofilm Growth. Insights from Population Balance Modeling

    PubMed Central

    Shu, Che-Chi; Chatterjee, Anushree; Hu, Wei-Shou; Ramkrishna, Doraiswami

    2013-01-01

    There is increasing recognition that stochasticity involved in gene regulatory processes may help cells enhance the signal or synchronize expression for a group of genes. Thus the validity of the traditional deterministic approach to modeling the foregoing processes cannot be without exception. In this study, we identify a frequently encountered situation, i.e., the biofilm, which has in the past been persistently investigated with intracellular deterministic models in the literature. We show in this paper circumstances in which use of the intracellular deterministic model appears distinctly inappropriate. In Enterococcus faecalis, the horizontal gene transfer of plasmid spreads drug resistance. The induction of conjugation in planktonic and biofilm circumstances is examined here with stochastic as well as deterministic models. The stochastic model is formulated with the Chemical Master Equation (CME) for planktonic cells and Reaction-Diffusion Master Equation (RDME) for biofilm. The results show that although the deterministic model works well for the perfectly-mixed planktonic circumstance, it fails to predict the averaged behavior in the biofilm, a behavior that has come to be known as stochastic focusing. A notable finding from this work is that the interception of antagonistic feedback loops to signaling, accentuates stochastic focusing. Moreover, interestingly, increasing particle number of a control variable could lead to an even larger deviation. Intracellular stochasticity plays an important role in biofilm and we surmise by implications from the model, that cell populations may use it to minimize the influence from environmental fluctuation. PMID:24232571

  2. Role of intracellular stochasticity in biofilm growth. Insights from population balance modeling.

    PubMed

    Shu, Che-Chi; Chatterjee, Anushree; Hu, Wei-Shou; Ramkrishna, Doraiswami

    2013-01-01

    There is increasing recognition that stochasticity involved in gene regulatory processes may help cells enhance the signal or synchronize expression for a group of genes. Thus the validity of the traditional deterministic approach to modeling the foregoing processes cannot be without exception. In this study, we identify a frequently encountered situation, i.e., the biofilm, which has in the past been persistently investigated with intracellular deterministic models in the literature. We show in this paper circumstances in which use of the intracellular deterministic model appears distinctly inappropriate. In Enterococcus faecalis, the horizontal gene transfer of plasmid spreads drug resistance. The induction of conjugation in planktonic and biofilm circumstances is examined here with stochastic as well as deterministic models. The stochastic model is formulated with the Chemical Master Equation (CME) for planktonic cells and Reaction-Diffusion Master Equation (RDME) for biofilm. The results show that although the deterministic model works well for the perfectly-mixed planktonic circumstance, it fails to predict the averaged behavior in the biofilm, a behavior that has come to be known as stochastic focusing. A notable finding from this work is that the interception of antagonistic feedback loops to signaling, accentuates stochastic focusing. Moreover, interestingly, increasing particle number of a control variable could lead to an even larger deviation. Intracellular stochasticity plays an important role in biofilm and we surmise by implications from the model, that cell populations may use it to minimize the influence from environmental fluctuation. PMID:24232571

  3. Urinary catheter indwelling clinical pathogen biofilm formation, exopolysaccharide characterization and their growth influencing parameters

    PubMed Central

    Murugan, Kasi; Selvanayaki, Krishnasamy; Al-Sohaibani, Saleh

    2015-01-01

    Self-reproducing microbial biofilm community mainly involved in the contamination of indwelling medical devices including catheters play a vital role in nosocomial infections. The catheter-associated urinary tract infection (CA-UTI) causative Staphylococcus aureus, Enterobacter faecalis, and Pseudomonas aeruginosa were selectively isolated, their phenotypic as well as genotypic biofilm formation, production and monomeric sugar composition of EPS as well as sugar, salt, pH and temperature influence on their in vitro biofilm formation were determined. From 50 culture positive urinary catheters S. aureus (24%), P. aeruginosa (18%), E. faecalis (14%) and others (44%) were isolated. The performed assays revealed their varying biofilm forming ability. The isolated S. aureus ica, E. faecalis esp, and P. aeruginosa cup A gene sequencing and phylogenetic analysis showed their close branching and genetic relationship. The analyzed sugar, salt, pH, and temperature showed that the degree of CA-UTI isolates biofilm formation is an environmentally sensitive process. EPS monosaccharide HPLC analysis showed the presence of neutral sugars (ng/μl) as follows: glucose (P. aeruginosa: 44.275; E. faecalis: 4.23), lactose (P. aeruginosa: 7.29), mannitol (P. aeruginosa: 2.53; S. aureus: 2.62; E. faecalis: 2.054) and maltose (E. faecalis: 7.0042) revealing species-specific presence and variation. This study may have potential clinical relevance for the easy diagnosis and management of CA-UTI. PMID:26858552

  4. Growth kinetics of forsterite reaction rims at high-pressure

    NASA Astrophysics Data System (ADS)

    Nishihara, Yu; Maruyama, Genta; Nishi, Masayuki

    2016-08-01

    Growth kinetics of forsterite (Fo) reaction rims between periclase (Per) and enstatite (En) were studied experimentally at pressure (P) and temperature (T) conditions of 3.0-11.1 GPa and 1473-1873 K, respectively. Pt markers originally placed at the Per-En interface were always observed at the Per-Fo interface, which indicates that Mg and O are the diffusing species in Fo rim growth (Mg-O coupled diffusion). The presence of some En inclusions in Fo grains and the growth rate of the Fo rim suggests that grain boundary diffusion is dominant rather than lattice diffusion. Considering the very fast grain boundary diffusion of O in olivine, the Mg-O coupled grain boundary diffusion in Fo is deduced to be rate-limited by the diffusivity of Mg. Based on an analysis of data collected under dry conditions, the product of the Mg grain boundary diffusion coefficient (Dgb) and the effective grain boundary width (δ) was determined to be δDgb = δDgb,0exp[-(E∗ + PV∗)/RT] with δDgb,0 = 10-9.68 ± 1.51 m3/s, E∗ = 379 ± 44 kJ/mol and V∗ = -1.9 ± 1.4 cm3/mol. Our results, combined with previously reported data on Mg lattice diffusion in Fo, suggest that for Mg, the significance of grain boundary diffusion increases with depth in the Earth's upper mantle, although lattice diffusion is still dominant for typical mantle grain sizes of 1-10 mm.

  5. Staphylococcus aureus biofilms

    PubMed Central

    Archer, Nathan K; Mazaitis, Mark J; Costerton, J William; Leid, Jeff G; Powers, Mary Elizabeth

    2011-01-01

    Increasing attention has been focused on understanding bacterial biofilms and this growth modality's relation to human disease. In this review we explore the genetic regulation and molecular components involved in biofilm formation and maturation in the context of the Gram-positive cocci, Staphylococcus aureus. In addition, we discuss diseases and host immune responses, along with current therapies associated with S. aureus biofilm infections and prevention strategies. PMID:21921685

  6. End-growth/evaporation living polymerization kinetics revisited

    NASA Astrophysics Data System (ADS)

    Semenov, A. N.; Nyrkova, I. A.

    2011-03-01

    End-growth/evaporation kinetics in living polymer systems with "association-ready" free unimers (no initiator) is considered theoretically. The study is focused on the systems with long chains (typical aggregation number N ≫ 1) at long times. A closed system of continuous equations is derived and is applied to study the kinetics of the chain length distribution (CLD) following a jump of a parameter (T-jump) inducing a change of the equilibrium mean chain length from N0 to N. The continuous approach is asymptotically exact for t ≫ t1, where t1 is the dimer dissociation time. It yields a number of essentially new analytical results concerning the CLD kinetics in some representative regimes. In particular, we obtained the asymptotically exact CLD response (for N ≫ 1) to a weak T-jump (ɛ = N0/N - 1 ≪ 1). For arbitrary T-jumps we found that the longest relaxation time tmax = 1/γ is always quadratic in N (γ is the relaxation rate of the slowest normal mode). More precisely tmax ∝4N2 for N0 < 2N and tmax ∝NN0/(1 - N/N0) for N0 > 2N. The mean chain length Nn is shown to change significantly during the intermediate slow relaxation stage t1 ≪ t ≪ tmax . We predict that N_n(t)-N_n(0)∝ √{t} in the intermediate regime for weak (or moderate) T-jumps. For a deep T-quench inducing strong increase of the equilibrium Nn (N ≫ N0 ≫ 1), the mean chain length follows a similar law, N_n(t)∝ √{t}, while an opposite T-jump (inducing chain shortening, N0 ≫ N ≫ 1) leads to a power-law decrease of Nn: Nn(t)∝t-1/3. It is also shown that a living polymer system gets strongly polydisperse in the latter regime, the maximum polydispersity index r = Nw/Nn being r* ≈ 0.77N0/N ≫ 1. The concentration of free unimers relaxes mainly during the fast process with the characteristic time tf ˜ t1N0/N2. A nonexponential CLD dominated by short chains develops as a result of the fast stage in the case of N0 = 1 and N ≫ 1. The obtained analytical results are supported

  7. Effects of Grape Xylem Sap and Cell-Wall Constituents on In Vitro Growth, Biofilm Formation and Cellular Aggregation of Xylella fastidiosa

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Purified cell-wall constituents or grape xylem sap added to media affected in vitro growth, biofilm formation, cell aggregation and gene expression of Xylella fastidiosa. Media containing xylem sap from Pierce’s disease (PD)-susceptible plants provided better support for bacterial growth and biofil...

  8. Pseudomonas aeruginosa Exhibits Deficient Biofilm Formation in the Absence of Class II and III Ribonucleotide Reductases Due to Hindered Anaerobic Growth

    PubMed Central

    Crespo, Anna; Pedraz, Lucas; Astola, Josep; Torrents, Eduard

    2016-01-01

    Chronic lung infections by the ubiquitous and extremely adaptable opportunistic pathogen Pseudomonas aeruginosa correlate with the formation of a biofilm, where bacteria grow in association with an extracellular matrix and display a wide range of changes in gene expression and metabolism. This leads to increased resistance to physical stress and antibiotic therapies, while enhancing cell-to-cell communication. Oxygen diffusion through the complex biofilm structure generates an oxygen concentration gradient, leading to the appearance of anaerobic microenvironments. Ribonucleotide reductases (RNRs) are a family of highly sophisticated enzymes responsible for the synthesis of the deoxyribonucleotides, and they constitute the only de novo pathway for the formation of the building blocks needed for DNA synthesis and repair. P. aeruginosa is one of the few bacteria encoding all three known RNR classes (Ia, II, and III). Class Ia RNRs are oxygen dependent, class II are oxygen independent, and class III are oxygen sensitive. A tight control of RNR activity is essential for anaerobic growth and therefore for biofilm development. In this work we explored the role of the different RNR classes in biofilm formation under aerobic and anaerobic initial conditions and using static and continuous-flow biofilm models. We demonstrated the importance of class II and III RNR for proper cell division in biofilm development and maturation. We also determined that these classes are transcriptionally induced during biofilm formation and under anaerobic conditions. The molecular mechanism of their anaerobic regulation was also studied, finding that the Anr/Dnr system is responsible for class II RNR induction. These data can be integrated with previous knowledge about biofilms in a model where these structures are understood as a set of layers determined by oxygen concentration and contain cells with different RNR expression profiles, bringing us a step closer to the understanding of this

  9. Influence of deformation on dolomite rim growth kinetics

    NASA Astrophysics Data System (ADS)

    Helpa, Vanessa; Rybacki, Erik; Grafulha Morales, Luiz Fernando; Dresen, Georg

    2015-04-01

    Using a gas-deformation apparatus stacks of oriented calcite (CaCO3) and magnesite (MgCO3) single crystals were deformed at T = 750° C and P = 400 MPa to examine the influence of stress and strain on magnesio-calcite and dolomite (CaMg[CO3]2) growth kinetics. Triaxial compression and torsion tests performed at constant stresses between 7 and 38 MPa and test durations between 4 and 171 hours resulted in bulk strains of 0.03-0.2 and maximum shear strains of 0.8-5.6, respectively. The reaction rims consist of fine-grained (2-7 μm) dolomite with palisade-shaped grains growing into magnesite reactants and equiaxed granular dolomite grains next to calcite. In between dolomite and pure calcite, magnesio-calcite grains evolved with an average grain size of 20-40 μm. Grain boundaries tend to be straighter at high bulk strains and equilibrium angles at grain triple junctions are common within the magnesio-calcite layer. Transmission electron microscopy shows almost dislocation free palisades and increasing dislocation density within granular dolomite towards the magnesio-calcite boundary. Within magnesio-calcite grains, dislocations are concentrated at grain boundaries. Variation of time at fixed stress (˜17 MPa) yields a parabolic time dependence of dolomite rim width, indicating diffusion-controlled growth, similar to isostatic rim growth behavior. In contrast, the magnesio-calcite layer growth is enhanced compared to isostatic conditions. Triaxial compression at given time shows no significant change of dolomite rim thickness (11±2 μm) and width of magnesio-calcite layers (33±5 μm) with increasing stress. In torsion experiments, reaction layer thickness and grain size decrease from the center (low stress/strain) to the edge (high strain/stress) of samples. Chemical analysis shows nearly stoichiometric composition of dolomite palisades, but enhanced Ca content within granular grains, indicating local disequilibrium with magnesio-calcite, in particular for twisted

  10. Kinetics of nitrate and perchlorate reduction in ion exchange brine using the membrane biofilm reactor (MBfR)

    EPA Science Inventory

    Several sources of bacterial inocula were tested for their ability to reduce nitrate and perchlorate in synthetic ion-exchange spent brine (3-4.5% salinity) using a hydrogen-based membrane biofilm reactor (MBfR). Nitrate and perchlorate removal fluxes reached as high as 5.4 g N ...

  11. Kinetics and mechanisms of creep crack growth in a creep-resisting steel

    SciTech Connect

    Vainshtok, V.A.; Baumshtein, M.V.; Makovetskaya, I.A.; Man'ko, V.D.

    1986-02-01

    This paper discusses the nature of kinetic diagrams of growth of fatigue cracks in the temperature range typical of operation of important components of power equipment and examines the proportion of the incubation period of crack growth in the total life. The relationship of the kinetic diagrams of crack growth with the fracture mechanisms are examined and the effect of running life on creep crack propagation is reviewed.

  12. Growth, biofilm formation, antifungal susceptibility and oxidative stress resistance of Candida glabrata are affected by different glucose concentrations.

    PubMed

    Ng, Tzu Shan; Desa, Mohd Nasir Mohd; Sandai, Doblin; Chong, Pei Pei; Than, Leslie Thian Lung

    2016-06-01

    Glucose is an important fuel source to support many living organisms. Its importance in the physiological fitness and pathogenicity of Candida glabrata, an emerging human fungal pathogen has not been extensively studied. The present study aimed to investigate the effects of glucose on the growth, biofilm formation, antifungal susceptibility and oxidative stress resistance of C. glabrata. In addition, its effect on the expression of a putative high affinity glucose sensor gene, SNF3 was also investigated. Glucose concentrations were found to exert effects on the physiological responses of C. glabrata. The growth rate of the species correlated positively to the amount of glucose. In addition, low glucose environments were found to induce C. glabrata to form biofilm and resist amphotericin B. Conversely, high glucose environments promoted oxidative stress resistance of C. glabrata. The expression of CgSNF3 was found to be significantly up-regulated in low glucose environments. The expression of SNF3 gene in clinical isolates was found to be higher compared to ATCC laboratory strains in low glucose concentrations, which may explain the better survivability of clinical isolates in the low glucose environment. These observations demonstrated the impact of glucose in directing the physiology and virulence fitness of C. glabrata through the possible modulation by SNF3 as a glucose sensor, which in turn aids the species to adapt, survive and thrive in hostile host environment. PMID:26358577

  13. Biofilms and biofilm reactors. (Latest citations from the Life Sciences Collection database). Published Search

    SciTech Connect

    Not Available

    1993-05-01

    The bibliography contains citations concerning the formation and characterization of biofilms. Biofilms occur in fermentation, wastewater treatment, packed-bed reactors, fluidized-bed reactors, medical prostheses, fouling, biomass reactors, waste supply systems, and other aquatic systems. Topics include microorganism makeup of biofilms, controlling biofilm formation, biological and chemical properties, model studies, kinetic studies, and biofilm identification and detection. (Contains a minimum of 209 citations and includes a subject term index and title list.)

  14. Cellular automata-based modelling and simulation of biofilm structure on multi-core computers.

    PubMed

    Skoneczny, Szymon

    2015-01-01

    The article presents a mathematical model of biofilm growth for aerobic biodegradation of a toxic carbonaceous substrate. Modelling of biofilm growth has fundamental significance in numerous processes of biotechnology and mathematical modelling of bioreactors. The process following double-substrate kinetics with substrate inhibition proceeding in a biofilm has not been modelled so far by means of cellular automata. Each process in the model proposed, i.e. diffusion of substrates, uptake of substrates, growth and decay of microorganisms and biofilm detachment, is simulated in a discrete manner. It was shown that for flat biofilm of constant thickness, the results of the presented model agree with those of a continuous model. The primary outcome of the study was to propose a mathematical model of biofilm growth; however a considerable amount of focus was also placed on the development of efficient algorithms for its solution. Two parallel algorithms were created, differing in the way computations are distributed. Computer programs were created using OpenMP Application Programming Interface for C++ programming language. Simulations of biofilm growth were performed on three high-performance computers. Speed-up coefficients of computer programs were compared. Both algorithms enabled a significant reduction of computation time. It is important, inter alia, in modelling and simulation of bioreactor dynamics. PMID:26606102

  15. Exploring growth kinetics of carbon nanotube arrays by in situ optical diagnostics and modeling

    SciTech Connect

    Puretzky, Alexander A; Geohegan, David B; Pannala, Sreekanth; Rouleau, Christopher

    2014-01-01

    Simple kinetic models of carbon nanotube growth have been able to successfully link together many experimental parameters involved in the growth of carbon nanotubes for practical applications including the prediction of growth rates, terminal lengths, number of walls, activation energies, and their dependences on the growth environment. The implications of recent experiments utilizing in situ monitoring of carbon nanotube growth on our past kinetic model are first reviewed. Then, sub-second pulsed feedstock gas introduction is discussed to explore the nucleation and initial growth of carbon nanotubes in the context of the kinetic model. Moreover, kinetic effects in "pulsed CVD" - using repeated pulsed gas introduction to stop and restart nanotube growth - are explored to understand renucleation, the origin of alignment in nanotube arrays, and incremental growth. Time-resolved reflectivity of the surface is used to remotely understand the kinetics of nucleation and the coordinated growth of arrays. This approach demonstrates that continuous vertically aligned single wall carbon nanotubes can be grown incrementally by pulsed CVD, and that the first exposure of fresh catalyst to feedstock gas is critical to nanotubes site density required for coordinated growth. Aligned nanotube arrays (as short as 60 nm) are shown to nucleate and grow within single, sub-second gas pulses. The multiple-pulse growth experiments (> 100 pulses) show that a high fraction of nanotubes renucleate on subsequent gas pulses.

  16. Free convection and surface kinetics in crystal growth from solution

    NASA Astrophysics Data System (ADS)

    Baird, James K.; Guo, Lihong

    1998-08-01

    As a crystal grows from solution, there is ordinarily a boundary layer depleted in solute, which forms at the crystal-solution interface. When the normal to the growing crystal surface is oriented in any direction other than parallel to gravity, the boundary layer is set into motion by the force of buoyancy. Using a similarity transformation and a boundary layer approximation, we have solved the Navier-Stokes equation and the equation for convective diffusion for a crystal in the form of a flat plate growing with normal perpendicular to gravity. Parameters in the theory include solute concentration, c0, and diffusion coefficient, D; solution shear viscosity, μ, mass density, ρ, and logarithmic density derivative with respect to concentration, α; crystal solubility, cs, height, h, and linear growth rate, kG; the specific rate, k (sticking coefficient), of the reaction which transfers molecules from the solution to the crystal and the kinetic order, n, of this reaction; and the acceleration due to gravity, g. We find these parameters to be related by the equation log[1-Sh/a (Sc) 1/4(Gr) 1/4φ s1/4]=(1/n) log[a(5/4) n(D/hkc 0n-1)(Sc)1/4(Gr) 1/4]+[(5/4-n)/n]log φs, where a=0.9, Sh=kGh/D, Sc=μ/ρD, Gr=gαh3ρ2/4μ2, and φs=(c0-cs)/c0. Given a knowledge of the solution physical properties, if Sh is measured as a function of φs and the results plotted in accord with the above equation, both n and k can be determined.

  17. Anodic biofilms as the interphase for electroactive bacterial growth on carbon veil.

    PubMed

    Artyushkova, Kateryna; Roizman, Dan; Santoro, Carlo; Doyle, Lucinda Elizabeth; Fatima Mohidin, Abeed; Atanassov, Plamen; Marsili, Enrico

    2016-01-01

    The structure and activity of electrochemically active biofilms (EABs) are usually investigated on flat electrodes. However, real world applications such as wastewater treatment and bioelectrosynthesis require tridimensional electrodes to increase surface area and facilitate EAB attachment. The structure and activity of thick EABs grown on high surface area electrodes are difficult to characterize with electrochemical and microscopy methods. Here, the authors adopt a stacked electrode configuration to simulate the high surface and the tridimensional structure of an electrode for large-scale EAB applications. Each layer of the stacked electrode is independently characterized using confocal laser scanning microscopy (CLSM) and digital image processing. Shewanella oneidensis MR-1 biofilm on stacked carbon veil electrodes is grown under constant oxidative potentials (0, +200, and +400 mV versus Ag/AgCl) until a stable current output is obtained. The textural, aerial, and volumetric parameters extracted from CLSM images allow tracking of the evolution of morphological properties within the stacked electrodes. The electrode layers facing the bulk liquid show higher biovolumes compared with the inner layer of the stack. The electrochemical performance of S. oneidensis MR-1 is directly linked to the overall biofilm volume as well as connectivity between cell clusters. PMID:27609094

  18. High Performance Bioanode Development for Fermentable Substrates via Controlled Electroactive Biofilm Growth

    SciTech Connect

    Ichihashi, Osamu; Vishnivetskaya, Tatiana A; Borole, Abhijeet P

    2014-11-11

    A bioanode was optimized to generate current densities reaching 38.4 4.9 A m-2, which brings bioelectrochemical systems closer to commercial consideration. Glucose and lactate were fed together in a continuous or fed-batch mode. The current density increased from 2.3 A m-2 to 38.4 A m-2 over a 33 day period and remained stable thereafter. The coulombic efficiency ranged from 50% to 80%. A change in substrate concentration from 200 mg L-1 to 5 mg L-1 decreased maximum current density from 38.4 A m-2 to 12.3 A m-2. The anode consortia included Firmicutes (55.0%), Proteobacteria (41.8%) and Bacteroidetes (2.1%) constituting two potential electrogenic genera: Geobacter (6.8%) and Aeromonas (31.9%). The current production was found to be limited by kinetics during the growth period (33 days), and mass transfer, thereafter. The results indicate the necessity of removing spent biomass for efficient long term operation and treatment of wastewater streams.

  19. Phase-field Model for Interstitial Loop Growth Kinetics and Thermodynamic and Kinetic Models of Irradiated Fe-Cr Alloys

    SciTech Connect

    Li, Yulan; Hu, Shenyang Y.; Sun, Xin; Khaleel, Mohammad A.

    2011-06-15

    Microstructure evolution kinetics in irradiated materials has strongly spatial correlation. For example, void and second phases prefer to nucleate and grow at pre-existing defects such as dislocations, grain boundaries, and cracks. Inhomogeneous microstructure evolution results in inhomogeneity of microstructure and thermo-mechanical properties. Therefore, the simulation capability for predicting three dimensional (3-D) microstructure evolution kinetics and its subsequent impact on material properties and performance is crucial for scientific design of advanced nuclear materials and optimal operation conditions in order to reduce uncertainty in operational and safety margins. Very recently the meso-scale phase-field (PF) method has been used to predict gas bubble evolution, void swelling, void lattice formation and void migration in irradiated materials,. Although most results of phase-field simulations are qualitative due to the lake of accurate thermodynamic and kinetic properties of defects, possible missing of important kinetic properties and processes, and the capability of current codes and computers for large time and length scale modeling, the simulations demonstrate that PF method is a promising simulation tool for predicting 3-D heterogeneous microstructure and property evolution, and providing microstructure evolution kinetics for higher scale level simulations of microstructure and property evolution such as mean field methods. This report consists of two parts. In part I, we will present a new phase-field model for predicting interstitial loop growth kinetics in irradiated materials. The effect of defect (vacancy/interstitial) generation, diffusion and recombination, sink strength, long-range elastic interaction, inhomogeneous and anisotropic mobility on microstructure evolution kinetics is taken into account in the model. The model is used to study the effect of elastic interaction on interstitial loop growth kinetics, the interstitial flux, and sink

  20. Host Responses to Biofilm.

    PubMed

    Watters, C; Fleming, D; Bishop, D; Rumbaugh, K P

    2016-01-01

    From birth to death the human host immune system interacts with bacterial cells. Biofilms are communities of microbes embedded in matrices composed of extracellular polymeric substance (EPS), and have been implicated in both the healthy microbiome and disease states. The immune system recognizes many different bacterial patterns, molecules, and antigens, but these components can be camouflaged in the biofilm mode of growth. Instead, immune cells come into contact with components of the EPS matrix, a diverse, hydrated mixture of extracellular DNA (bacterial and host), proteins, polysaccharides, and lipids. As bacterial cells transition from planktonic to biofilm-associated they produce small molecules, which can increase inflammation, induce cell death, and even cause necrosis. To survive, invading bacteria must overcome the epithelial barrier, host microbiome, complement, and a variety of leukocytes. If bacteria can evade these initial cell populations they have an increased chance at surviving and causing ongoing disease in the host. Planktonic cells are readily cleared, but biofilms reduce the effectiveness of both polymorphonuclear neutrophils and macrophages. In addition, in the presence of these cells, biofilm formation is actively enhanced, and components of host immune cells are assimilated into the EPS matrix. While pathogenic biofilms contribute to states of chronic inflammation, probiotic Lactobacillus biofilms cause a negligible immune response and, in states of inflammation, exhibit robust antiinflammatory properties. These probiotic biofilms colonize and protect the gut and vagina, and have been implicated in improved healing of damaged skin. Overall, biofilms stimulate a unique immune response that we are only beginning to understand. PMID:27571696

  1. [Biofilms and public health].

    PubMed

    Choisy, Claude

    2011-01-01

    Micro-organisms do not always exist in planctonic forms (single cells or small groups). To survive, especially in limiting media, they may adhere to inert or living surfaces. This enables them to multiply within a community protected by an extracellular matrix, thus forming a biofilm which protects them from antimicrobials. Biofilms have many potential consequences for public health. Some are positive, such as the commensal biofilms that protect against pathogenic bacteria, while environmental biofilms may be a source of outbreaks of respiratory or gastrointestinal diseases or infections associated with implanted medical devices. Respiratory tract infection can be caused by aerosols of fragmented biofilms growing in warm humid conditions (air cooling towers, hot springs, showers, etc.). Digestive tract infection can arise from biofilms formed during food manufacturing or packaging processes. Colonized implanted medical devices can lead to sepsis. This article examines the role of central venous catheters, taking into account the surgical site. In vivo studies show that the source of catheter infection may be exogenous or endogenous, while in vitro studies of biofilms show that ablation of the device is the best solution. Prevention is difficult, as biofilm formation is multifactorial. Physical and biological knowledge of biofilms may help to limit their formation and growth. PMID:22375373

  2. Enhancement of plant growth and yields in Chickpea (Cicer arietinum L.) through novel cyanobacterial and biofilmed inoculants.

    PubMed

    Bidyarani, Ngangom; Prasanna, Radha; Babu, Santosh; Hossain, Firoz; Saxena, Anil Kumar

    2016-01-01

    The use of Rhizobium inoculants in chickpea is well established; however, meagre efforts have been directed towards the use of other microbial supplements for improving nutrient uptake and yields. A set of novel cyanobacterial and biofilmed inoculants were evaluated in chickpea under field conditions. A significant two-fold enhancement in leghaemoglobin content of nodules and plant biomass was recorded with Anabaena laxa treatment. The inoculants - Anabaena laxa and Anabaena - Rhizobium biofilmed formulation proved to be the top-ranking treatments. Soil chlorophyll, nitrogen-fixation and available N possessed high positive direct effects on grain yield through positive - correlations and - high direct effects and also had high positive indirect effects through other component traits. The cumulative effect of improved plant growth and nutrient uptake exhibited a positive correlation with microbiological activity, especially nitrogen fixation, soil chlorophyll and soil available nitrogen. This may account for the significantly higher yield parameters in the A. laxa treatment, which recorded 50% higher grain yield (1724kgha(-1)) as compared to control (847kgha(-1)). PMID:27296967

  3. Comparative Genomics of Iron-Transporting Systems in Bacillus cereus Strains and Impact of Iron Sources on Growth and Biofilm Formation

    PubMed Central

    Hayrapetyan, Hasmik; Siezen, Roland; Abee, Tjakko; Nierop Groot, Masja

    2016-01-01

    Iron is an important element for bacterial viability, however it is not readily available in most environments. We studied the ability of 20 undomesticated food isolates of Bacillus cereus and two reference strains for capacity to use different (complex) iron sources for growth and biofilm formation. Studies were performed in media containing the iron scavenger 2,2-Bipyridine. Transcriptome analysis using B. cereus ATCC 10987 indeed showed upregulation of predicted iron transporters in the presence of 2,2-Bipyridine, confirming that iron was depleted upon its addition. Next, the impact of iron sources on growth performance of the 22 strains was assessed and correlations between growth stimulation and presence of putative iron transporter systems in the genome sequences were analyzed. All 22 strains effectively used Fe citrate and FeCl3 for growth, and possessed genes for biosynthesis of the siderophore bacillibactin, whereas seven strains lacked genes for synthesis of petrobactin. Hemoglobin could be used by all strains with the exception of one strain that lacked functional petrobactin and IlsA systems. Hemin could be used by the majority of the tested strains (19 of 22). Notably, transferrin, ferritin, and lactoferrin were not commonly used by B. cereus for growth, as these iron sources could be used by 6, 3, and 2 strains, respectively. Furthermore, biofilm formation was found to be affected by the type of iron source used, including stimulation of biofilms at liquid-air interphase (FeCl3 and Fe citrate) and formation of submerged type biofilms (hemin and lactoferrin). Our results show strain variability in the genome-encoded repertoire of iron-transporting systems and differences in efficacy to use complex iron sources for growth and biofilm formation. These features may affect B. cereus survival and persistence in specific niches. PMID:27375568

  4. The 3-D spatial structure of multicellular aggregates can give them a competition-dependent growth advantage in early biofilm development

    NASA Astrophysics Data System (ADS)

    Gordon, Vernita; Kragh, Kasper; Hutchison, Jaime; Melaugh, Gavin; Rodesney, Chris; Roberts, Aled; Irie, Yasuhiko; Jensen, Peter; Diggle, Stephen; Allen, Rosalind; Bjarnsholt, Thomas

    Biofilms are structured communities of sessile microbes. Traditional models of biofilm development begin with single bacteria seeding a surface. However, biofilms can also be seeded by multicellular aggregates. How the three-dimensional structure of aggregates impacts the initiation and development of biofilms is not known. Here we use a combination of experiments and simulations to determine the impact of the seeding structure. We find that whether aggregates or single cells grow better depends on the density of single cells initially seeded. The density of single cells, which we take as our measure of the level of competition, impacts per-cell access to growth resource. The overall biomass accumulation arising from an aggregate is a combination of slow growth in the resource-limited interior, and faster growth on the sides and top. When competition is low, aggregates are disadvantaged, compared with single cells. However, when competition is high, aggregates are fitter than single cells, because the cells at the top of the aggregates have better access to growth resources than do high-density single cells on the surface.

  5. Temperature dependence of protein solubility-determination, application to crystallization, and growth kinetics studies

    NASA Technical Reports Server (NTRS)

    Rosenberger, Franz

    1993-01-01

    A scintillation method was developed for determinations of the temperature dependence of the solubility, and of nucleation induction times of proteins, in 50-100 mu(l) volumes of solution. Solubility data for lysozyme and horse serum albumin were obtained for various combinations of pH and precipitant concentrations. These data and the nucleation induction information were used for dynamic crystallization control, that is, for the controlled separation of nucleation and growth stages. Individual lysozyme and horse serum albumin crystals were grown in 15-20 mu(l) solution volumes contained in x-ray capillaries. The morphology and kinetics of the growth and dissolution of lysozyme in aqueous solutions with 2.5 percent NaCl and at pH = 4.5 was studied in situ with a depth resolution of 300 A (4 unit cells) by high resolution optical microscopy and digital image processing. The bulk super- or under saturation, sigma, of the solution inside a closed growth cell was controlled by temperature. The growth habit was bound by (110) and (101) faces that grew through layer spreading, although with different growth rate dependencies on supersaturation/temperature. At sigma less than 10 (obtained at higher temperatures) growth was purely kinetic ally controlled, with impurity effects (macrostep formation and kinetic hindrance) becoming significant for sigma less than 2. At sigma greater than 10 (lower temperatures), anisotropies in the interfacial kinetics were more pronounced, with interfacial kinetics and bulk transport becoming equally important to the growth morphology. Growth rates were growth history dependent. The formation of striations (layers of irregularly incorporated solution) was unambiguously correlated with growth temperature variations. Etching exposed dislocations and various high-index faces whose growth morphologies were studied during return to the steady state growth form. Growth steps were observed to originate from two-dimensional nuclei or from outcrops

  6. Biofilms: Microbial Life on Surfaces

    PubMed Central

    2002-01-01

    Microorganisms attach to surfaces and develop biofilms. Biofilm-associated cells can be differentiated from their suspended counterparts by generation of an extracellular polymeric substance (EPS) matrix, reduced growth rates, and the up- and down- regulation of specific genes. Attachment is a complex process regulated by diverse characteristics of the growth medium, substratum, and cell surface. An established biofilm structure comprises microbial cells and EPS, has a defined architecture, and provides an optimal environment for the exchange of genetic material between cells. Cells may also communicate via quorum sensing, which may in turn affect biofilm processes such as detachment. Biofilms have great importance for public health because of their role in certain infectious diseases and importance in a variety of device-related infections. A greater understanding of biofilm processes should lead to novel, effective control strategies for biofilm control and a resulting improvement in patient management. PMID:12194761

  7. Manipulation of Biofilm Microbial Ecology

    SciTech Connect

    White, D.C.; Palmer, R.J., Jr.; Zinn, M.; Smith, C.A.; Burkhalter, R.; Macnaughton, S.J.; Whitaker, K.W.; Kirkegaard, R.D.

    1998-08-15

    The biofilm mode of growth provides such significant advantages to the members of the consortium that most organisms in important habitats are found in biofilms. The study of factors that allow manipulation of biofilm microbes in the biofilm growth state requires that reproducible biofilms be generated. The most effective monitoring of biofilm formation, succession and desaturation is with on-line monitoring of microbial biofilms with flowcell for direct observation. The biofilm growth state incorporates a second important factor, the heterogeneity in distribution in time and space of the component members of the biofilm consortium. This heterogeneity is reflected not only in the cellular distribution but in the metabolic activity within a population of cells. Activity and cellular distribution can be mapped in four dimensions with confocal microscopy, and function can be ascertained by genetically manipulated reporter functions for specific genes or by vital stains. The methodology for understanding the microbial ecology of biofilms is now much more readily available and the capacity to manipulate biofilms is becoming an important feature of biotechnology.

  8. Manipulatiaon of Biofilm Microbial Ecology

    SciTech Connect

    Burkhalter, R.; Macnaughton, S.J.; Palmer, R.J.; Smith, C.A.; Whitaker, K.W.; White, D.C.; Zinn, M.; kirkegaard, R.

    1998-08-09

    The Biofilm mode of growth provides such significant advantages to the members of the consortium that most organisms in important habitats are found in biofilms. The study of factors that allow manipulation of biofilm microbes in the biofilm growth state requires that reproducible biofilms by generated. The most effective monitoring of biofilm formation, succession and desquamation is with on-line monitoring of microbial biofilms with flowcell for direct observation. The biofilm growth state incorporates a second important factor, the heterogeneity in the distribution in time and space of the component members of the biofilm consortium. This heterogeneity is reflected not only in the cellular distribution but in the metabolic activity within a population of cells. Activity and cellular distribution can be mapped in four dimensions with confocal microscopy, and function can be ascertained by genetically manipulated reporter functions for specific genes or by vital stains. The methodology for understanding the microbial ecology of biofilms is now much more readily available and the capacity to manipulate biofilms is becoming an important feature of biotechnology.

  9. Plasma-Mediated Inactivation of Pseudomonas aeruginosa Biofilms Grown on Borosilicate Surfaces under Continuous Culture System

    PubMed Central

    Vandervoort, Kurt G.; Brelles-Mariño, Graciela

    2014-01-01

    Biofilms are microbial communities attached to a surface and embedded in a matrix composed of exopolysaccharides and excreted nucleic acids. Bacterial biofilms are responsible for undesirable effects such as disease, prostheses colonization, biofouling, equipment damage, and pipe plugging. Biofilms are also more resilient than free-living cells to regular sterilization methods and therefore it is indispensable to develop better ways to control and remove them. The use of gas discharge plasmas is a good alternative since plasmas contain a mixture of reactive agents well-known for their decontamination potential against free microorganisms. We have previously reported that Pseudomonas aeruginosa biofilms were inactivated after a 1-min plasma exposure. We determined that the adhesiveness and the thickness of Pseudomonas biofilms grown on borosilicate were reduced. We also reported sequential morphological changes and loss of viability upon plasma treatment. However, the studies were carried out in batch cultures. The use of a continuous culture results in a more homogenous environment ensuring reproducible biofilm growth. The aim of this work was to study plasma-mediated inactivation of P. aeruginosa biofilms grown on borosilicate in a continuous culture system. In this paper we show that biofilms grown on glass under continuous culture can be inactivated by using gas discharge plasma. Both biofilm architecture and cell culturabilty are impacted by the plasma treatment. The inactivation kinetics is similar to previously described ones and cells go through sequential changes ranging from minimal modification without loss of viability at short plasma exposure times, to major structure and viability loss at longer exposure times. We report that changes in biofilm structure leading to the loss of culturability and viability are related to a decrease of the biofilm matrix adhesiveness. To our knowledge, there has been no attempt to evaluate the inactivation

  10. Natural plant products inhibits growth and alters the swarming motility, biofilm formation, and expression of virulence genes in enteroaggregative and enterohemorrhagic Escherichia coli.

    PubMed

    García-Heredia, Alam; García, Santos; Merino-Mascorro, José Ángel; Feng, Peter; Heredia, Norma

    2016-10-01

    The purpose of this study was to determine the effects of plant products on the growth, swarming motility, biofilm formation and virulence gene expression in enterohemorrhagic Escherichia coli O157:H7 and enteroaggregative E. coli strain 042 and a strain of O104:H4 serotype. Extracts of Lippia graveolens and Haematoxylon brassiletto, and carvacrol, brazilin were tested by an antimicrobial microdilution method using citral and rifaximin as controls. All products showed bactericidal activity with minimal bactericidal concentrations ranging from 0.08 to 8.1 mg/ml. Swarming motility was determined in soft LB agar. Most compounds reduced swarming motility by 7%-100%; except carvacrol which promoted motility in two strains. Biofilm formation studies were done in microtiter plates. Rifaximin inhibited growth and reduced biofilm formation, but various concentrations of other compounds actually induced biofilm formation. Real time PCR showed that most compounds decreased stx2 expression. The expression of pic and rpoS in E. coli 042 were suppressed but in E. coli O104:H4 they varied depending on compounds. In conclusion, these extracts affect E. coli growth, swarming motility and virulence gene expression. Although these compounds were bactericidal for pathogenic E. coli, sublethal concentrations had varied effects on phenotypic and genotypic traits, and some increased virulence gene expression. PMID:27375253

  11. Computer Simulations of Interstitial Loop Growth Kinetics in irradiated bcc Fe

    SciTech Connect

    Li, Yulan; Hu, Shenyang Y.; Henager, Charles H.; Deng, Huiqiu; Gao, Fei; Sun, Xin; Khaleel, Mohammad A.

    2012-08-01

    The growth kinetics of (001) [001] interstitial loops in bcc Fe is studied by phase-field modeling. The effect of defect (vacancy/interstitial) concentration, generation, recombination, sink strength, and elastic interaction on the growth kinetics of interstitial loops is systematically simulated. Results show that the elastic interaction between the defects and interstitial loops speeds up the growth kinetics and affects the morphology of the interstitial loops. Linear growth rate, i.e., the loop average radius is linear to time, under both aging and irradiation are predicted, which is in agreement with experimental observation. The results also show that the interstitial loop growth rate, which is directly related to the sink strength of the interstitial loop for interstitials, increases linearly with the initial interstitial concentration during aging while changing logarithmically with the interstitial generation rate under irradiation.

  12. The Secreted Protease PrtA Controls Cell Growth, Biofilm Formation and Pathogenicity in Xylella fastidiosa

    PubMed Central

    Gouran, Hossein; Gillespie, Hyrum; Nascimento, Rafael; Chakraborty, Sandeep; Zaini, Paulo A.; Jacobson, Aaron; Phinney, Brett S.; Dolan, David; Durbin-Johnson, Blythe P.; Antonova, Elena S.; Lindow, Steven E.; Mellema, Matthew S.; Goulart, Luiz R.; Dandekar, Abhaya M.

    2016-01-01

    Pierce’s disease (PD) is a deadly disease of grapevines caused by the Gram-negative bacterium Xylella fastidiosa. Though disease symptoms were formerly attributed to bacteria blocking the plant xylem, this hypothesis is at best overly simplistic. Recently, we used a proteomic approach to characterize the secretome of X. fastidiosa, both in vitro and in planta, and identified LesA as one of the pathogenicity factors of X. fastidiosa in grapevines that leads to leaf scorching and chlorosis. Herein, we characterize another such factor encoded by PD0956, designated as an antivirulence secreted protease “PrtA” that displays a central role in controlling in vitro cell proliferation, length, motility, biofilm formation, and in planta virulence. The mutant in X. fastidiosa exhibited reduced cell length, hypermotility (and subsequent lack of biofilm formation) and hypervirulence in grapevines. These findings are supported by transcriptomic and proteomic analyses with corresponding plant infection data. Of particular interest, is the hypervirulent response in grapevines observed when X. fastidiosa is disrupted for production of PrtA, and that PD-model tobacco plants transformed to express PrtA exhibited decreased symptoms after infection by X. fastidiosa. PMID:27492542

  13. The Secreted Protease PrtA Controls Cell Growth, Biofilm Formation and Pathogenicity in Xylella fastidiosa.

    PubMed

    Gouran, Hossein; Gillespie, Hyrum; Nascimento, Rafael; Chakraborty, Sandeep; Zaini, Paulo A; Jacobson, Aaron; Phinney, Brett S; Dolan, David; Durbin-Johnson, Blythe P; Antonova, Elena S; Lindow, Steven E; Mellema, Matthew S; Goulart, Luiz R; Dandekar, Abhaya M

    2016-01-01

    Pierce's disease (PD) is a deadly disease of grapevines caused by the Gram-negative bacterium Xylella fastidiosa. Though disease symptoms were formerly attributed to bacteria blocking the plant xylem, this hypothesis is at best overly simplistic. Recently, we used a proteomic approach to characterize the secretome of X. fastidiosa, both in vitro and in planta, and identified LesA as one of the pathogenicity factors of X. fastidiosa in grapevines that leads to leaf scorching and chlorosis. Herein, we characterize another such factor encoded by PD0956, designated as an antivirulence secreted protease "PrtA" that displays a central role in controlling in vitro cell proliferation, length, motility, biofilm formation, and in planta virulence. The mutant in X. fastidiosa exhibited reduced cell length, hypermotility (and subsequent lack of biofilm formation) and hypervirulence in grapevines. These findings are supported by transcriptomic and proteomic analyses with corresponding plant infection data. Of particular interest, is the hypervirulent response in grapevines observed when X. fastidiosa is disrupted for production of PrtA, and that PD-model tobacco plants transformed to express PrtA exhibited decreased symptoms after infection by X. fastidiosa. PMID:27492542

  14. Kinetics of nickel silicide growth in silicon nanowires: From linear to square root growth

    NASA Astrophysics Data System (ADS)

    Yaish, Y. E.; Katsman, A.; Cohen, G. M.; Beregovsky, M.

    2011-05-01

    The common practice for nickel silicide formation in silicon nanowires (SiNWs) relies on axial growth of silicide along the wire that is initiated from nickel reservoirs at the source and drain contacts. In the present work the silicide intrusions were studied for various parameters including wire diameter (25-50 nm), annealing time (15-120 s), annealing temperature (300-440∘C), and the quality of the initial Ni/Si interface. The silicide formation was investigated by high-resolution scanning electron microscopy, high-resolution transmission electron microscopy (TEM), and atomic force microscopy. The main part of the intrusion formed at 420∘C consists of monosilicide NiSi, as was confirmed by energy dispersive spectroscopy STEM, selected area diffraction TEM, and electrical resistance measurements of fully silicided SiNWs. The kinetics of nickel silicide axial growth in the SiNWs was analyzed in the framework of a diffusion model through constrictions. The model calculates the time dependence of the intrusion length, L, and predicts crossover from linear to square root time dependency for different wire parameters, as confirmed by the experimental data.

  15. Anticandidal efficacy of cinnamon oil against planktonic and biofilm cultures of Candida parapsilosis and Candida orthopsilosis.

    PubMed

    Pires, Regina Helena; Montanari, Lilian Bueno; Martins, Carlos Henrique G; Zaia, José Eduardo; Almeida, Ana Marisa Fusco; Matsumoto, Marcelo T; Mendes-Giannini, Maria José S

    2011-12-01

    Candida parapsilosis is yeast capable of forming biofilms on medical devices. Novel approaches for the prevention and eradication of the biofilms are desired. This study investigated the anticandidal activity of sixteen essential oils on planktonic and biofilm cultures of C. parapsilosis complex. We used molecular tools, enumeration of colony-forming units, the colourimetric MTT assay, scanning electron microscopy (SEM) and a chequerboard assay coupled with software analyses to evaluate the growth kinetics, architecture, inhibition and reduction in biofilms formed from environmental isolates of the Candida parapsilosis complex; further, we also evaluated whether essential oils would interact synergistically with amphotericin B to increase their anticandidal activities. Of the environmental C. parapsilosis isolates examined, C. parapsilosis and C. orthopsilosis were identified. Biofilm growth on polystyrene substrates peaked within 48 h, after which growth remained relatively stable up to 72 h, when it began to decline. Details of the architectural analysis assessed by SEM showed that C. parapsilosis complex formed less complex biofilms compared with C. albicans biofilms. The most active essential oil was cinnamon oil (CO), which showed anticandidal activity against C. orthopsilosis and C. parapsilosis in both suspension (minimum inhibitory concentration-MIC-250 and 500 μg/ml) and biofilm (minimum biofilm reduction concentration-MBRC-1,000 and 2,000 μg/ml) cultures. CO also inhibited biofilm formation (MBIC) at concentrations above 250 μg/ml for both species tested. However, synergism with amphotericin B was not observed. Thus, CO is a natural anticandidal agent that can be effectively utilised for the control of the yeasts tested. PMID:21761153

  16. Modeling of kinetically limited growth rate for solution-synthesized germanium nanocrystals

    NASA Astrophysics Data System (ADS)

    Shoop, Nicholas; Tribby, Louis J.; Han, Sang M.

    2015-08-01

    Solution synthesis is a common method for preparing semiconductor nanocrystals (NCs). For such solution synthesis, many investigations have considered diffusion-limited growth, in which the diffusion of reactants through the boundary layer (BL) limits the NC growth rate. These studies often model the growth rate with a diffusion BL thickness much larger than the NC size and with unphysically low diffusion constants on the order of 10-12 cm2 s-1. In this work, we have examined the growth of Ge NCs synthesized by injecting Ge amide precursors into a solution of 1-octadecene, oleylamine, and hexadecylamine. We have previously established this low-temperature, low-pressure synthesis route. The resulting Ge growth rate compares well with our model, in which we consider both BL diffusion and surface kinetics of Ge precursors and organic ligand adsorbates. Our modeling results suggest that the NC growth is limited not by diffusion, but by the surface adsorption and desorption kinetics. The BL thickness in the stirred reaction vessel is calculated to be on the same order of magnitude as the crystal radius; therefore, the surface kinetics cannot be ignored. Furthermore, the synthesis temperature is near 300 °C, where the Ge monomer diffusion coefficient within the growth solution is substantially increased and estimated to be on the order of 10-5 cm2 s-1. These considerations agree well with our experimentally measured growth rate and strongly suggest that the NC size evolution is controlled primarily by the surface kinetics.

  17. COMPARATIVE KINETIC STUDIES OF NITRATE-LIMITED GROWTH AND NITRATE UPTAKE IN PHYTOPLANKTON IN CONTINUOUS CULTURE

    EPA Science Inventory

    A comparative kinetic study of nitrate-limited growth and nitrate uptake was carried out in chemostat cultures of Ankistrodesmus falcatus, Asterionella formosa, Fragilaria crotonensis. In each species growth rate (microgram) was related to total cell nitrogen or cell quota (q) by...

  18. Biofilm Formation by Neisseria gonorrhoeae

    PubMed Central

    Greiner, L. L.; Edwards, J. L.; Shao, J.; Rabinak, C.; Entz, D.; Apicella, M. A.

    2005-01-01

    Studies were performed in continuous-flow chambers to determine whether Neisseria gonorrhoeae could form a biofilm. Under these growth conditions, N. gonorrhoeae formed a biofilm with or without the addition of 10 μM sodium nitrite to the perfusion medium. Microscopic analysis of a 4-day growth of N. gonorrhoeae strain 1291 revealed evidence of a biofilm with organisms embedded in matrix, which was interlaced with water channels. N. gonorrhoeae strains MS11 and FA1090 were found to also form biofilms under the same growth conditions. Cryofield emission scanning electron microscopy and transmission electron microscopy confirmed that organisms were embedded in a continuous matrix with membranous structures spanning the biofilm. These studies also demonstrated that N. gonorrhoeae has the capability to form a matrix in the presence and absence of CMP-N-acetylneuraminic acid (CMP-Neu5Ac). Studies with monoclonal antibody 6B4 and the lectins soy bean agglutinin and Maackia amurensis indicated that the predominate terminal sugars in the biofilm matrix formed a lactosamine when the biofilm was grown in the absence of CMP-Neu5Ac and sialyllactosamine in the presence of CMP-Neu5Ac. N. gonorrhoeae strain 1291 formed a biofilm on primary urethral epithelial cells and cervical cells in culture without loss of viability of the epithelial cell layer. Our studies demonstrated that N. gonorrhoeae can form biofilms in continuous-flow chambers and on living cells. Studies of these biofilms may have implications for understanding asymptomatic gonococcal infection. PMID:15784536

  19. Domain growth and ordering kinetics in dense quark matter

    SciTech Connect

    Singh, A.; Puri, S.; Mishra, H.

    2012-06-15

    The kinetics of chiral transitions in quark matter is studied in a two-flavor Nambu-Jona-Lasinio model. We focus on the phase-ordering dynamics subsequent to a temperature quench from the massless quark phase to the massive quark phase. We study the dynamics by considering a phenomenological model (Ginzburg-Landau free-energy functional). The morphology of the ordering system is characterized by the scaling of the order-parameter correlation function.

  20. Interactions of microbial biofilms with toxic trace metals; 1: Observation and modeling of cell growth, attachment, and production of extracellular polymer

    SciTech Connect

    Hsieh, K.M.; Murgel, G.A.; Lion, L.W.; Shuler, M.L. )

    1994-06-20

    Adsorbent surfaces in natural and engineered systems are frequently modified by bacterial attachment, growth of a biofilm, and bacterial production of extracellular polymer. Attached cells or sorbed polymers may alter the metal-binding characteristics of the supporting substratum and influence metal partitioning. The interdependent behavior of toxic trace metal partitioning and biofilm development requires description of the interaction between cell growth with its accompanying polymer production and metal speciation. In this article, the first of a two part series, a mechanistic model is developed to describe the growth of a film-forming bacterium which adheres to a substratum through the production of extracellular biopolymers. Each bacterial cell was modeled as a two-component structure consisting of active cell mass and biopolymer. The biopolymer component was further divided into cell-associated and dissolved categories to distinguish biopolymer which remained naturally bound to cell surfaces from that which did not. Use of this structured model permitted independent description of the dynamics of cell growth, and polymer production, both of which may influence trace metal behavior. Employing parameters obtained from independent experiments as well as published values, the model satisfactorily predicts experimental observations of bacterial growth, attachment and detachment, biopolymer production, and adsorption of polymer onto solid (glass) surfaces. The model simulated transient and steady-state biofilm systems equally well.

  1. Triclosan-loaded Tooth-binding Micelles for Prevention and Treatment of Dental Biofilm

    PubMed Central

    Chen, Fu; Rice, Kelly C.; Liu, Xin-Ming; Reinhardt, Richard A.; Bayles, Kenneth W.; Wang, Dong

    2010-01-01

    The purpose of the present study was to develop tooth-binding micelle formulations and evaluate their ability to both inhibit initial biofilm formation as well as decrease the viability of preformed biofilm using an in vitro dental biofilm model. Alendronate (ALN, a bisphosphonate) was covalently attached to the ends of different Pluronic copolymers to confer tooth-binding ability to the micelles, and triclosan was used as a model drug. Based on different micelle preparation methods, Pluronic copolymers and ALN-terminated Pluronic copolymers were used to prepare triclosan-loaded tooth-binding micelles. The formulation was optimized for triclosan solubility, particle size, hydroxyapatite (HA) binding capacity and kinetics, and in vitro drug release behavior. In vitro biofilm treatment studies demonstrated that the triclosan-loaded tooth-binding micelles were able to inhibit initial biofilm growth of Streptococcus mutans UA159 by 6-log CFU/HA disc compared to the untreated control. These tooth-binding micelles were also capable of reducing the viability of preformed biofilm by 4-log CFU/HA disc compared to untreated control biofilm. In summary, triclosan-loaded tooth-binding micelles have been successfully developed and optimized in this study. These micelles demonstrated promising anti-biofilm capabilities that have the potential for use in the future treatment and prevention of dental diseases. PMID:20387099

  2. Determining the Kinetic Parameters Characteristic of Microalgal Growth.

    ERIC Educational Resources Information Center

    Martinez Sancho, Maria Eugenie; And Others

    1991-01-01

    An activity in which students obtain a growth curve for algae, identify the exponential and linear growth phases, and calculate the parameters which characterize both phases is described. The procedure, a list of required materials, experimental conditions, analytical technique, and a discussion of the interpretations of individual results are…

  3. Nanowire growth kinetics in aberration corrected environmental transmission electron microscopy.

    PubMed

    Chou, Yi-Chia; Panciera, Federico; Reuter, Mark C; Stach, Eric A; Ross, Frances M

    2016-04-14

    We visualize atomic level dynamics during Si nanowire growth using aberration corrected environmental transmission electron microscopy, and compare with lower pressure results from ultra-high vacuum microscopy. We discuss the importance of higher pressure observations for understanding growth mechanisms and describe protocols to minimize effects of the higher pressure background gas. PMID:27041654

  4. Comparative proteomic analysis of extracellular proteins expressed by various clonal types of Staphylococcus aureus and during planktonic growth and biofilm development

    PubMed Central

    Atshan, Salman S.; Shamsudin, Mariana N.; Sekawi, Zamberi; Thian Lung, Leslie T.; Barantalab, Fatemeh; Liew, Yun K.; Alreshidi, Mateg Ali; Abduljaleel, Salwa A.; Hamat, Rukman A.

    2015-01-01

    Staphylococcus aureus is well known for its biofilm formation with rapid emergence of new clones circulating worldwide. The main objectives of the study were (1) to identify possible differences in protein expression among various and closely related clonal types of S. aureus, (2) to establish the differences in protein expression in terms of size of protein spots and its intensities between bacteria which are grown statically (biofilm formation) with that of under aeration and agitation, and (3) to compare the differences in protein expression as a function of time (in hours). In this study, we selected six clinical isolates comprising two similar (MRSA-527 and MRSA-524) and four different (MRSA-139, MSSA-12E, MSSA-22d, and MSSA-10E) types identified by spa typing, MLST and SCCmec typing. We performed 2D gel migration comparison. Also, two MRSA isolates (527 and 139) were selected to determine quantitative changes in the level of extracellular proteins at different biofilm growth time points of 12, 24, and 48 h. The study was done using a strategy that combines 2-DGE and LC-MS/MS analysis for absolute quantification and identification of the extracellular proteins. The 2DGE revealed that the proteomic profiles for the isolates belonging to the similar spa, MLST, and SCCmec types were still quite different. Among the extracellular proteins secreted at different time points of biofilm formation, significant changes in protein expression were observed at 48 h incubation as compared to the exponential growth at 12 h incubation. The main conclusion of the work is that the authors do observe differences among isolates, and growth conditions do influence the protein content at different time points of biofilm formation. PMID:26089817

  5. Discovering Biofilms: Inquiry-Based Activities for the Classroom

    ERIC Educational Resources Information Center

    Redelman, Carly V.; Marrs, Kathleen; Anderson, Gregory G.

    2012-01-01

    In nature, bacteria exist in and adapt to different environments by forming microbial communities called "biofilms." We propose simple, inquiry-based laboratory exercises utilizing a biofilm formation assay, which allows controlled biofilm growth. Students will be able to qualitatively assess biofilm growth via staining. Recently, we developed a…

  6. Zinc oxide and titanium dioxide nanoparticles induce oxidative stress, inhibit growth, and attenuate biofilm formation activity of Streptococcus mitis.

    PubMed

    Khan, Shams Tabrez; Ahmad, Javed; Ahamed, Maqusood; Musarrat, Javed; Al-Khedhairy, Abdulaziz A

    2016-06-01

    Streptococcus mitis from the oral cavity causes endocarditis and other systemic infections. Rising resistance against traditional antibiotics amongst oral bacteria further aggravates the problem. Therefore, antimicrobial and antibiofilm activities of zinc oxide and titanium dioxide nanoparticles (NPs) synthesized and characterized during this study against S. mitis ATCC 6249 and Ora-20 were evaluated in search of alternative antimicrobial agents. ZnO and TiO2-NPs exhibited an average size of 35 and 13 nm, respectively. The IC50 values of ZnO and TiO2-NPs against S. mitis ATCC 6249 were 37 and 77 µg ml(-1), respectively, while the IC50 values against S. mitis Ora-20 isolate were 31 and 53 µg ml(-1), respectively. Live and dead staining, biofilm formation on the surface of polystyrene plates, and extracellular polysaccharide production show the same pattern. Exposure to these nanoparticles also shows an increase (26-83 %) in super oxide dismutase (SOD) activity. Three genes, namely bapA1, sodA, and gtfB like genes from these bacteria were identified and sequenced for quantitative real-time PCR analysis. An increase in sodA gene (1.4- to 2.4-folds) levels and a decrease in gtfB gene (0.5- to 0.9-folds) levels in both bacteria following exposure to ZnO and TiO2-NPs were observed. Results presented in this study verify that ZnO-NPs and TiO2-NPs can control the growth and biofilm formation activities of these strains at very low concentration and hence can be used as alternative antimicrobial agents for oral hygiene. PMID:26837748

  7. Bifidobacteria inhibit the growth of Porphyromonas gingivalis but not of Streptococcus mutans in an in vitro biofilm model.

    PubMed

    Jäsberg, Heli; Söderling, Eva; Endo, Akihito; Beighton, David; Haukioja, Anna

    2016-06-01

    There is growing interest in the use of probiotic bifidobacteria for enhancement of the therapy, and in the prevention, of oral microbial diseases. However, the results of clinical studies assessing the effects of bifidobacteria on the oral microbiota are controversial, and the mechanisms of actions of probiotics in the oral cavity remain largely unknown. In addition, very little is known about the role of commensal bifidobacteria in oral health. Our aim was to study the integration of the probiotic Bifidobacterium animalis subsp. lactis Bb12 and of oral Bifidobacterium dentium and Bifidobacterium longum isolates in supragingival and subgingival biofilm models and their effects on other bacteria in biofilms in vitro using two different in vitro biofilms and agar-overlay assays. All bifidobacteria integrated well into the subgingival biofilms composed of Porphyromonas gingivalis, Actinomyces naeslundii, and Fusobacterium nucleatum and decreased significantly only the number of P. gingivalis in the biofilms. The integration of bifidobacteria into the supragingival biofilms containing Streptococcus mutans and A. naeslundii was less efficient, and bifidobacteria did not affect the number of S. mutans in biofilms. Therefore, our results suggest that bifidobacteria may have a positive effect on subgingival biofilm and thereby potential in enhancing gingival health; however, their effect on supragingival biofilm may be limited. PMID:27061393

  8. Biofilm in endodontics: A review.

    PubMed

    Jhajharia, Kapil; Parolia, Abhishek; Shetty, K Vikram; Mehta, Lata Kiran

    2015-01-01

    Endodontic disease is a biofilm-mediated infection, and primary aim in the management of endodontic disease is the elimination of bacterial biofilm from the root canal system. The most common endodontic infection is caused by the surface-associated growth of microorganisms. It is important to apply the biofilm concept to endodontic microbiology to understand the pathogenic potential of the root canal microbiota as well as to form the basis for new approaches for disinfection. It is foremost to understand how the biofilm formed by root canal bacteria resists endodontic treatment measures. Bacterial etiology has been confirmed for common oral diseases such as caries and periodontal and endodontic infections. Bacteria causing these diseases are organized in biofilm structures, which are complex microbial communities composed of a great variety of bacteria with different ecological requirements and pathogenic potential. The biofilm community not only gives bacteria effective protection against the host's defense system but also makes them more resistant to a variety of disinfecting agents used as oral hygiene products or in the treatment of infections. Successful treatment of these diseases depends on biofilm removal as well as effective killing of biofilm bacteria. So, the fundamental to maintain oral health and prevent dental caries, gingivitis, and periodontitis is to control the oral biofilms. From these aspects, the formation of biofilms carries particular clinical significance because not only host defense mechanisms but also therapeutic efforts including chemical and mechanical antimicrobial treatment measures have the most difficult task of dealing with organisms that are gathered in a biofilm. The aim of this article was to review the mechanisms of biofilms' formation, their roles in pulpal and periapical pathosis, the different types of biofilms, the factors influencing biofilm formation, the mechanisms of their antimicrobial resistance, techniques to

  9. Kinetics of monolayer graphene growth by segregation on Pd(111)

    SciTech Connect

    Mok, H. S.; Murata, Y.; Kodambaka, S.; Ebnonnasir, A.; Ciobanu, C. V.; Nie, S.; McCarty, K. F.

    2014-03-10

    Using in situ low-energy electron microscopy and density functional theory calculations, we follow the growth of monolayer graphene on Pd(111) via surface segregation of bulk-dissolved carbon. Upon lowering the substrate temperature, nucleation of graphene begins on graphene-free Pd surface and continues to occur during graphene growth. Measurements of graphene growth rates and Pd surface work functions establish that this continued nucleation is due to increasing C adatom concentration on the Pd surface with time. We attribute this anomalous phenomenon to a large barrier for attachment of C adatoms to graphene coupled with a strong binding of the non-graphitic C to the Pd surface.

  10. Monoculture parameters successfully predict coculture growth kinetics of Bacteroides thetaiotaomicron and two Bifidobacterium strains.

    PubMed

    Van Wey, A S; Cookson, A L; Roy, N C; McNabb, W C; Soboleva, T K; Shorten, P R

    2014-11-17

    Microorganisms rarely live in isolation but are most often found in a consortium. This provides the potential for cross-feeding and nutrient competition among the microbial species, which make it challenging to predict the growth kinetics in coculture. In this paper we developed a mathematical model to describe substrate consumption and subsequent microbial growth and metabolite production for bacteria grown in monoculture. The model characterized substrate utilization kinetics of 18 Bifidobacterium strains. Some bifidobacterial strains demonstrated preferential degradation of oligofructose in that sugars with low degree of polymerization (DP) (DP≤3 or 4) were metabolized before sugars of higher DP, or vice versa. Thus, we expanded the model to describe the preferential degradation of oligofructose. In addition, we adapted the model to describe the competition between human colonic bacteria Bacteroides thetaiotaomicron LMG 11262 and Bifidobacterium longum LMG 11047 or Bifidobacterium breve Yakult for inulin as well as cross-feeding of breakdown products from the extracellular hydrolysis of inulin by B. thetaiotaomicron LMG 11262. We found that the coculture growth kinetics could be predicted based on the respective monoculture growth kinetics. Using growth kinetics from monoculture experiments to predict coculture dynamics will reduce the number of in vitro experiments required to parameterize multi-culture models. PMID:25282609

  11. Kinetic constants of abnormal grain growth in nanocrystalline nickel

    NASA Astrophysics Data System (ADS)

    Aleshin, A. N.

    2016-02-01

    The grain growth in nanocrystalline nickel with a purity of 99.5 at % during non-isothermal annealing was experimentally investigated using differential scanning calorimetry and transmission electron microscopy. Nanocrystalline nickel was prepared by electrodeposition and had an average grain size of approximately 20 nm. It was shown that, at a temperature corresponding to the calorimetric signal peak, abnormal grain growth occurs with the formation of a bimodal grain microstructure. Calorimeters signals were processed within the Johnson-Mehl-Avrami formalism. This made it possible to determine the exponent of the corresponding equation, the frequency factor, and the activation energy of the grain growth, which was found to be equal to the activation energy of the vacancy migration. The reasons for the abnormal grain growth in nanocrystalline nickel were discussed.

  12. Biofilm initiation and growth of Pseudomonas aeruginosa on 316L stainless steel in low gravity in orbital space flight

    NASA Astrophysics Data System (ADS)

    Todd, Paul; Pierson, Duane L.; Allen, Britt; Silverstein, JoAnn

    The formation of biofilms by water microorganisms such as Pseudomonas aeruginosa in spacecraft water systems has been a matter of concern for long-duration space flight. Crewed spacecraft plumbing includes internal surfaces made of 316L stainless steel. Experiments were therefore undertaken to compare the ability of P. aeruginosa to grow in suspension, attach to stainless steel and to grow on stainless steel in low gravity on the space shuttle. Four categories of cultures were studied during two space shuttle flights (STS-69 and STS-77). Cultures on the ground were held in static horizontal or vertical cylindrical containers or were tumbled on a clinostat and activated under conditions identical to those for the flown cultures. The containers used on the ground and in flight were BioServe Space Technologies’ Fluid Processing Apparatus (FPA), an open-ended test tube with rubber septa that allows robotic addition of bacteria to culture media to initiate experiments and the addition of fixative to conclude experiments. Planktonic growth was monitored by spectrophotometry, and biofilms were characterized quantitatively by epifluorescence and scanning electron microscopy. In these experiments it was found that: (1) Planktonic growth in flown cultures was more extensive than in static cultures, as seen repeatedly in the history of space microbiology, and closely resembled the growth of tumbled cultures. (2) Conversely, the attachment of cells in flown cultures was as much as 8 times that in tumbled cultures but not significantly different from that in static horizontal and vertical cultures, consistent with the notion that flowing fluid reduces microbial attachment. (3) The final surface coverage in 8 days was the same for flown and static cultures but less by a factor of 15 in tumbled cultures, where coverage declined during the preceding 4 days. It is concluded that cell attachment to 316L stainless steel in the low gravity of orbital space flight is similar to that

  13. Growth kinetics and H-shaped crystals of SAPO-40

    NASA Astrophysics Data System (ADS)

    Di Renzo, F.; Dumont, Nathalie; Trens, P.; Gabelica, Zelimir

    2003-11-01

    Crystal morphologies with well-defined macroscopic cavities are very rare occurrences. Tabular crystals of SAPO-40 with a symmetrical notch at each end have been obtained by selective inhibition of the growth of the large-pore faces. Crystal growth has continued on the small-pores (0 1 0) faces, circumvented the inhibited sphenoidal faces formed a protruding tab at the corners of the crystals.

  14. Growth Physiology of the Hyperthermophilic Archaeon Thermococcus litoralis: Development of a Sulfur-Free Defined Medium, Characterization of an Exopolysaccharide, and Evidence of Biofilm Formation

    PubMed Central

    Rinker, K. D.; Kelly, R. M.

    1996-01-01

    Nutritional characteristics of the hyperthermophilic archaeon Thermococcus litoralis have been investigated with emphasis on the development of a sulfur-free, defined growth medium, analysis of an exocellular polysaccharide, and formation of a biofilm. An artificial-seawater-based medium, containing 16 amino acids, adenine, uracil, vitamins, and trace elements, allowed T. litoralis to attain growth rates and cell densities similar to those found with complex media. Four amino acids (alanine, asparagine, glutamine, and glutamate) were not included due to their lack of effect on growth rates and cell yields. In this medium, cultures reached densities of 10(sup8) cells per ml, with doubling times of 55 min (without maltose) or 43 min (with maltose). Neither the addition of elemental sulfur nor the presence of H(inf2) significantly affected cell growth. A sparingly soluble exopolysaccharide was produced by T. litoralis grown in either defined or complex media. Analysis of the acid-hydrolyzed exopolysaccharide yielded mannose as the only monosaccharidic constituent. This exopolysaccharide is apparently involved in the formation of a biofilm on polycarbonate filters and glass slides, which is inhabited by high levels of T. litoralis. Biofilm formation by hyperthermophilic microorganisms in geothermal environments has not been examined to any extent, but further work in this area may provide information related to the interactions among high-temperature organisms. PMID:16535464

  15. Proteome changes during yeast-like and pseudohyphal growth in the biofilm-forming yeast Pichia fermentans.

    PubMed

    Maserti, Biancaelena; Podda, Alessandra; Giorgetti, Lucia; Del Carratore, Renata; Chevret, Didier; Migheli, Quirico

    2015-06-01

    The Pichia fermentans strain DISAABA 726 is a biofilm-forming yeast that has been proposed as biocontrol agent to control brown rot on apple. How ever, when inoculated on peach, strain 726 shows yeast-like to pseudohyphal transition coupled to a pathogenic behaviour. To identify the proteins potentially involved in such transition process, a comparative proteome analysis of P. fermentans 726 developed on peach (filamentous growth) vs apple (yeast-like growth) was carried out using two-dimensional gel electrophoresis coupled with mass spectrometry analysis. The proteome comparison was also performed between the two different cell morphologies induced in a liquid medium amended with urea (yeast-like cells) or methionine (filamentous cells) to exclude fruit tissue impact on the transition. Seventy-three protein spots showed significant variations in abundance (±twofold, p < 0.01, confidence intervals 99 %) between pseudohyphal vs yeast-like morphology produced on fruits. Among them, 30 proteins changed their levels when the two morphologies were developed in liquid medium. The identified proteins belong to several pathways and functions, such as glycolysis, amino acid synthesis, chaperones, and signalling transduction. The possible role of a group of proteins belonging to the carbohydrate pathway in the metabolic re-organisation during P. fermentans dimorphic transition is discussed. PMID:25743163

  16. Growth Kinetics and Mechanics of Hydrate Films by Interfacial Rheology.

    PubMed

    Leopércio, Bruna C; de Souza Mendes, Paulo R; Fuller, Gerald G

    2016-05-01

    A new approach to study and understand the kinetics and mechanical properties of hydrates by interfacial rheology is presented. This is made possible using a "double wall ring" interfacial rheology cell that has been designed to provide the necessary temperature control. Cyclopentane and water are used to form hydrates, and this model system forms these structures at ambient pressures. Different temperature and water/hydrocarbon contact protocols are explored. Of particular interest is the importance of first contacting the hydrocarbon against ice crystals in order to initiate hydrate formation. Indeed, this is found to be the case, even though the hydrates may be created at temperatures above the melting point of ice. Once hydrates completely populate the hydrocarbon/water interface, strain sweeps of the interfacial elastic and viscous moduli are conducted to interrogate the mechanical response and fragility of the hydrate films. The dependence on temperature, Tf, by the kinetics of formation and the mechanical properties is reported, and the cyclopentane hydrate dissociation temperature was found to be between 6 and 7 °C. The formation time (measured from the moment when cyclopentane first contacts ice crystals) as well as the elastic modulus and the yield strain increase as Tf increases. PMID:27076092

  17. Kinetic-structural analysis of neuronal growth cone veil motility.

    PubMed

    Mongiu, Anne K; Weitzke, Elizabeth L; Chaga, Oleg Y; Borisy, Gary G

    2007-03-15

    Neuronal growth cone advance was investigated by correlative light and electron microscopy carried out on chick dorsal root ganglion cells. Advance was analyzed in terms of the two principal organelles responsible for protrusive motility in the growth cone - namely, veils and filopodia. Veils alternated between rapid phases of protrusion and retraction. Electron microscopy revealed characteristic structural differences between the phases. Our results provide a significant advance in three respects: first, protruding veils are comprised of a densely branched network of actin filaments that is lamellipodial in appearance and includes the Arp2/3 complex. On the basis of this structural and biomarker evidence, we infer that the dendritic nucleation and/or array-treadmilling mechanism of protrusive motility is conserved in veil protrusion of growth cones as in the motility of fibroblasts; second, retracting veils lack dendritic organization but contain a sparse network of long filaments; and third, growth cone filopodia have the capacity to nucleate dendritic networks along their length, a property consistent with veil formation seen at the light microscopic level but not previously understood in supramolecular terms. These elements of veil and filopodial organization, when taken together, provide a conceptual framework for understanding the structural basis of growth cone advance. PMID:17327278

  18. Kinetic Monte Carlo Simulation of Epitaxial Thin Film Growth: Formation of Submonolayer Islands and Multilayer Mounds

    SciTech Connect

    Evans, J. W.; Thiel, P. A.; Li, Maozhi

    2007-06-14

    We consider homoepitaxy (or low-misfit heteroepitaxy) via vapor deposition or MBE under UHV conditions. Thin film growth is initiated by nucleation and growth of 2D islands in the submonolayer regime. For atoms subsequently deposited on top of islands, a step edge barrier often inhibits downward transport and produces kinetic roughening during multilayer growth. Such unstable growth is characterized by the formation of 3D mounds (multilayer stacks of 2D islands). Kinetic Monte Carlo (KMC) simulation of suitable atomistic lattice-gas models can address fundamental or general issues related to both submonolayer and multilayer film evolution, and can also provide a predictive tool for morphological evolution in specific systems. Examples of the successes of KMC modeling are provided for metal homoepitaxial film growth, specifically for contrasting behavior in the classic Ag/Ag(100) and Ag/Ag(111) systems.

  19. Natural History, Growth Kinetics and Outcomes of Untreated Clinically Localized Renal Tumors Under Active Surveillance

    PubMed Central

    Crispen, Paul L.; Viterbo, Rosalia; Boorjian, Stephen A.; Greenberg, Richard E.; Chen, David Y.T.; Uzzo, Robert G.

    2010-01-01

    Background The growth kinetics of untreated solid organ malignancies are not defined. Radiographic active surveillance (AS) of renal tumors in patient unfit or unwilling to undergo intervention provides an opportunity to quantitate the natural history of untreated localized tumors. Here we report the radiographic growth kinetics of renal neoplasms during a period of surveillance. Methods We identified patients with enhancing renal masses who were radiographically observed for at least 12 months. Clinical and pathological records were reviewed to determine tumor growth kinetics and clinical outcomes. Tumor growth kinetics were expressed in terms of absolute and relative linear and volumetric growth. Results We identified 172 renal tumors in 154 patients under AS. Median tumor diameter and volume on presentation was 2.0 cm (mean 2.5, range 0.4 - 12.0) and 4.18 cm3 (mean 20.0, range 0.0033 – 904). Median duration of follow-up was 24 months (mean 31, range 12 – 156). A significant association between presenting tumor size and proportional growth was noted, with smaller tumors growing faster than larger tumors. 39% (68/173) of tumors underwent delayed intervention and 84% (57/68) were pathologically malignant. Progression to metastatic disease was noted in 1.3% (2/154) of patients. Conclusions We demonstrate the association between a tumor’s volume and subsequent growth with smaller tumors exhibiting significantly faster volumetric growth than larger tumors, consistent with Gompertzian kinetics. Surveillance of localized renal tumors is associated with a low rate of disease progression in the intermediate term and suggests potential over-treatment biases in select patients. PMID:19402168

  20. Microalgal growth in municipal wastewater treated in an anaerobic moving bed biofilm reactor.

    PubMed

    Hultberg, Malin; Olsson, Lars-Erik; Birgersson, Göran; Gustafsson, Susanne; Sievertsson, Bertil

    2016-05-01

    Nutrient removal from the effluent of an anaerobic moving bed biofilm reactor (AnMBBR) treated with microalgae was evaluated. Algal treatment was highly efficient in removal of nutrients and discharge limits were met after 3days. Extending the cultivation time from 3 to 5days resulted in a large increase in biomass, from 233.3±49.3 to 530.0±72.1mgL(-1), despite nutrients in the water being exhausted after 3days (ammonium 0.04mgL(-1), orthophosphate <0.05mgL(-1)). Biomass productivity, lipid content and quality did not differ in microalgal biomass produced in wastewater sampled before the AnMBBR. The longer cultivation time resulted in a slight increase in total lipid concentration and a significant decrease in linolenic acid concentration in all treatments. Differences were observed in chemical oxygen demand, which decreased after algal treatment in wastewater sampled before the AnMBBR whereas it increased after algal treatment in the effluent from the AnMBBR. PMID:26868151

  1. Graphene CVD growth on copper and nickel: role of hydrogen in kinetics and structure.

    PubMed

    Losurdo, Maria; Giangregorio, Maria Michela; Capezzuto, Pio; Bruno, Giovanni

    2011-12-14

    Understanding the chemical vapor deposition (CVD) kinetics of graphene growth is important for advancing graphene processing and achieving better control of graphene thickness and properties. In the perspective of improving large area graphene quality, we have investigated in real-time the CVD kinetics using CH(4)-H(2) precursors on both polycrystalline copper and nickel. We highlighted the role of hydrogen in differentiating the growth kinetics and thickness of graphene on copper and nickel. Specifically, the growth kinetics and mechanism is framed in the competitive dissociative chemisorption of H(2) and dehydrogenating chemisorption of CH(4), and in the competition of the in-diffusion of carbon and hydrogen, being hydrogen in-diffusion faster in copper than nickel, while carbon diffusion is faster in nickel than copper. It is shown that hydrogen acts as an inhibitor for the CH(4) dehydrogenation on copper, contributing to suppress deposition onto the copper substrate, and degrades quality of graphene. Additionally, the evidence of the role of hydrogen in forming C-H out of plane defects in CVD graphene on Cu is also provided. Conversely, resurfacing recombination of hydrogen aids CH(4) decomposition in the case of Ni. Understanding better and providing other elements to the kinetics of graphene growth is helpful to define the optimal CH(4)/H(2) ratio, which ultimately can contribute to improve graphene layer thickness uniformity even on polycrystalline substrates. PMID:22006173

  2. Role of plasma activation in the kinetics of CNT growth in PECVD process

    NASA Astrophysics Data System (ADS)

    Lebedeva, Irina; Gavrikov, Alexey; Baranov, Alexey; Belov, Maxim; Knizhnik, Andrey; Potapkin, Boris; Sommerer, Timothy

    2009-10-01

    The work presents kinetic modeling of the effect of acceleration for the growth kinetics of carbon nanotubes by hydrocarbon gas mixture modification with plasma discharge. The plasma activation creates active species in hydrocarbon gas mixture, which can easily adsorb and dissociate on the catalyst surface. So plasma treatment of the gas mixture in the CVD process allows to increase the carbon supply rate by a few orders of magnitude compared to that in thermal CVD process. On the other hand, plasma can also provide etching of carbon species from the catalyst surface. To correctly reproduce both of these effects of plasma, the kinetic model of growth of carbon nanotubes is developed based on first-principles analysis of heterogeneous processes on the catalyst surface and detailed kinetics of gas phase chemistry. The model is used to compare the growth rates of carbon nanotubes in thermal and plasma-enhanced CVD processes and to determine critical gas pressures, at which CNT growth kinetics switches from the adsorption limitation to the limitation by reaction and diffusion on the catalyst.

  3. Listeria monocytogenes Impact on Mature or Old Pseudomonas fluorescens Biofilms During Growth at 4 and 20°C

    PubMed Central

    Puga, Carmen H.; Orgaz, Belen; SanJose, Carmen

    2016-01-01

    Changes in spatial organization, as observed by confocal laser scanning microscopy (CLSM), viable cell content, biovolume, and substratum surface coverage of the biofilms formed on glass by Pseudomonas fluorescens resulting from co-culture with Listeria monocytogenes, were examined. Two strains of L. monocytogenes, two culture temperatures and two biofilm developmental stages were investigated. Both L. monocytogenes strains, a persistently sampled isolate (collected repeatedly along 3 years from a meat factory) and Scott A, induced shrinkage in matrix volume, both at 20°C and 4°C, in mature or old biofilms, without loss of P. fluorescens cell count per surface unit. The nearly homogeneous pattern of surface coverage shown by mono-species P. fluorescens biofilms, turned into more irregular layouts in co-culture with L. monocytogenes. The upper layer of both mono and dual-species biofilms turned to predominantly consist of matrix, with plenty of viable cells underneath, in old biofilms cultured at 20°C, but not in those grown at 4°C. Between 15 and 56% of the substratum area was covered by biofilm, the extent depending on temperature, time and L. monocytogenes strain. Real biofilms in food-related surfaces may thus be very heterogeneous regarding their superficial components, i.e., those more accessible to disinfectants. It is therefore a hygienic challenge to choose an adequate agent to disrupt them. PMID:26913024

  4. Crystallization of pumpkin seed globulin: growth and dissolution kinetics

    NASA Astrophysics Data System (ADS)

    Malkin, Alexander J.; McPherson, Alexander

    1993-10-01

    Quasi-elastic light scattering was used to investigate the nucleation and crystallization of pumpkin ( Cucurbita) seed globulin. The diameter of the pumpkin globulin monomer was measured to be ≈ 5-6 nm. The supersaturation dependence of critical nucleus size was obtained, and this allowed an estimate of the interfacial free energy to be α ≈ 6.1 x 10 -2 erg/cm 2. The crystallization and dissolution kinetics were investigated for 4.9-16 mg/ml protein solutions containing 1-7% NaCl. The solubility data as a function of precipitant concentration and temperature were obtained and these will be utilized for optimization of the crystallization conditions for the pumpkin globulin.

  5. Self-consistent ion-by-ion growth model for kinetic isotopic fractionation during calcite precipitation

    NASA Astrophysics Data System (ADS)

    Nielsen, Laura C.; DePaolo, Donald J.; De Yoreo, James J.

    2012-06-01

    Microscopic mechanisms operating at the mineral-aqueous interface control rates of growth and dissolution, isotope fractionation and trace element partitioning during crystal growth. Despite the importance of characterizing surface kinetic controls on isotopic partitioning, no self-consistent microscopic theory has yet been presented which can simultaneously model both mineral growth rate and isotopic composition. Using a kinetic theory for AB or di-ionic crystal growth, we derive a model to predict precipitation rate and isotope fractionation as a function of growth solution oversaturation and solution stoichiometry and apply the theory to calcium isotope fractionation during calcite precipitation. Our model assimilates the current understanding of surface controlled isotope fractionation with kinetic theories of ion-by-ion mineral growth to predict isotopic partitioning during the growth of ionic crystals. This approach accounts for the effect of solution composition on microscopic mineral surface structure and composition, providing numerous testable hypotheses for growth of sparingly soluble AB crystals such as calcite, namely: Both oversaturation and solution stoichiometry control growth rate and partitioning of isotopes during precipitation; for growth driven primarily by step propagation, distinct expressions describe dislocation- and 2D nucleation-driven growth rates, while the expression for isotope fractionation is the same for both mechanisms; mineral precipitation occurring via the formation of an amorphous precursor will generate isotope effects that are not compatible with ion-by-ion growth theory and may therefore be excluded from comparison; and, the absolute kinetic limit of isotope fractionation may not be accessible at high oversaturation due to the formation of amorphous precursors. Using calcite as a model system, we derive expressions for growth rate and isotopic fractionation as a function of oversaturation and Ca:CO32- in solution

  6. Application and kinetic evaluation of upflow anaerobic biofilm reactor for nitrogen removal from wastewater by Anammox process

    PubMed Central

    2013-01-01

    The lab-scale upflow anaerobic biofilm reactor was successfully operated for the treatment of synthetic wastewater with high nitrogen load by Anammox (anaerobic ammonium oxidation) process. During the entire period of operation, the reactor temperature was kept at 35±1°C. The operational strategy consisted of both increasing the ammonium and nitrite concentrations from 60 to 700mgN/L and from 80 to 920 mgN/L, respectively and decreasing the hydraulic retention time from 24 to 6 h, at each step. The highest achieved removal efficiency of ammonium and nitrite were 91 and 93%, respectively. Consequently, due to their acceptable performance for nitrogen removal in previous researches, modified Stover-Kincannon and Grau second-order models were used in this study. According to the experiment results, the model validity testing showed that the Stover-Kincannon model was a little more appropriate for the description of nitrogen removal in the reactor, even though both models gave high correlation coefficients (R2=0.999). PMID:23414202

  7. Permeabilizing biofilms

    DOEpatents

    Soukos, Nikolaos S.; Lee, Shun; Doukas, Apostolos G.

    2008-02-19

    Methods for permeabilizing biofilms using stress waves are described. The methods involve applying one or more stress waves to a biofilm, e.g., on a surface of a device or food item, or on a tissue surface in a patient, and then inducing stress waves to create transient increases in the permeability of the biofilm. The increased permeability facilitates delivery of compounds, such as antimicrobial or therapeutic agents into and through the biofilm.

  8. The kinetics of parasitic growth in GaAs MOVPE

    NASA Astrophysics Data System (ADS)

    Clayton, A. J.; Irvine, S. J. C.

    2007-03-01

    Gallium arsenide (GaAs) deposition was carried out in a horizontal quartz reactor tube with trimethylgallium (TMGa) and arsine (AsH 3) as precursors, using a hydrogen (H 2) carrier gas. Temperatures were in the range 400-500 °C, where surface reactions limit deposition rate. Nucleation time and deposition rate were monitored using laser interferometry, optimum reflectance was gained by aligning a quartz wafer to back reflect the incident beam. The 980 nm infrared laser beam was sufficiently long in wavelength to be able to penetrate the wall deposit. Results showing the effect of temperature and V/III ratio on the nucleation time and deposition rate are presented, where with temperature the nucleation delay was observed to reduce and the growth rate to increase. The nucleation delay is consistent with a thermally activated surface nucleation for the parasitic GaAs. A theoretical growth rate model, based on a restricted set of reaction steps was used to compare with the experimental growth rates. Without any free parameters, the growth rates from theoretical calculation and experiment agreed within a factor of two and showed the same trends with V/III ratio and temperature. The non-linearity of the theoretical growth rates on an Arrhenius plot indicates that there is more than one dominant reaction step over the temperature range investigated. The range of experimental activation energies, calculated from Arrhenius plots, was 17.56-23.59 kJ mol -1. A comparison of these activation energies and minimum deposition temperature with the literature indicates that the wall temperature measurement on an Aixtron reactor is over 100 °C higher than previously reported.

  9. Optimization of the moving-bed biofilm sequencing batch reactor (MBSBR) to control aeration time by kinetic computational modeling: Simulated sugar-industry wastewater treatment.

    PubMed

    Faridnasr, Maryam; Ghanbari, Bastam; Sassani, Ardavan

    2016-05-01

    A novel approach was applied for optimization of a moving-bed biofilm sequencing batch reactor (MBSBR) to treat sugar-industry wastewater (BOD5=500-2500 and COD=750-3750 mg/L) at 2-4h of cycle time (CT). Although the experimental data showed that MBSBR reached high BOD5 and COD removal performances, it failed to achieve the standard limits at the mentioned CTs. Thus, optimization of the reactor was rendered by kinetic computational modeling and using statistical error indicator normalized root mean square error (NRMSE). The results of NRMSE revealed that Stover-Kincannon (error=6.40%) and Grau (error=6.15%) models provide better fits to the experimental data and may be used for CT optimization in the reactor. The models predicted required CTs of 4.5, 6.5, 7 and 7.5h for effluent standardization of 500, 1000, 1500 and 2500mg/L influent BOD5 concentrations, respectively. Similar pattern of the experimental data also confirmed these findings. PMID:26943932

  10. Biofilm in endodontics: A review

    PubMed Central

    Jhajharia, Kapil; Parolia, Abhishek; Shetty, K Vikram; Mehta, Lata Kiran

    2015-01-01

    Endodontic disease is a biofilm-mediated infection, and primary aim in the management of endodontic disease is the elimination of bacterial biofilm from the root canal system. The most common endodontic infection is caused by the surface-associated growth of microorganisms. It is important to apply the biofilm concept to endodontic microbiology to understand the pathogenic potential of the root canal microbiota as well as to form the basis for new approaches for disinfection. It is foremost to understand how the biofilm formed by root canal bacteria resists endodontic treatment measures. Bacterial etiology has been confirmed for common oral diseases such as caries and periodontal and endodontic infections. Bacteria causing these diseases are organized in biofilm structures, which are complex microbial communities composed of a great variety of bacteria with different ecological requirements and pathogenic potential. The biofilm community not only gives bacteria effective protection against the host's defense system but also makes them more resistant to a variety of disinfecting agents used as oral hygiene products or in the treatment of infections. Successful treatment of these diseases depends on biofilm removal as well as effective killing of biofilm bacteria. So, the fundamental to maintain oral health and prevent dental caries, gingivitis, and periodontitis is to control the oral biofilms. From these aspects, the formation of biofilms carries particular clinical significance because not only host defense mechanisms but also therapeutic efforts including chemical and mechanical antimicrobial treatment measures have the most difficult task of dealing with organisms that are gathered in a biofilm. The aim of this article was to review the mechanisms of biofilms’ formation, their roles in pulpal and periapical pathosis, the different types of biofilms, the factors influencing biofilm formation, the mechanisms of their antimicrobial resistance, techniques to

  11. Imaging Pseudomonas aeruginosa Biofilm Extracellular Polymer Scaffolds with Amphiphilic Carbon Dots.

    PubMed

    Ritenberg, Margarita; Nandi, Sukhendu; Kolusheva, Sofiya; Dandela, Rambabu; Meijler, Michael M; Jelinek, Raz

    2016-05-20

    Biofilm formation is a critical facet of pathogenesis and resilience of human, animal, and plant bacteria. Extracellular polymeric substances (EPS) constitute the physical scaffolding for bacterial biofilms and thus play central roles in their development and virulence. We show that newly synthesized amphiphilic fluorescent carbon dots (C-dots) readily bind to the EPS scaffold of Pseudomonas aeruginosa, a major biofilm-forming pathogen, resulting in unprecedented microscopic visualization of the EPS structural features. Fluorescence microscopy analysis utilizing the C-dots reveals that the P. aeruginosa EPS matrix exhibits a remarkable dendritic morphology. The experiments further illuminate the growth kinetics of the EPS and the effect of external factors such as temperature. We also show that the amphiphilic C-dot platform enabled screening of substances disrupting biofilm development, specifically quorum sensing inhibitors. PMID:26882175

  12. Crystal Growth Kinetics and Viscous Behavior in Ge2Sb2Se5 Undercooled Melt.

    PubMed

    Barták, Jaroslav; Koštál, Petr; Podzemná, Veronika; Shánělová, Jana; Málek, Jiří

    2016-08-18

    Crystal growth, viscosity, and melting were studied in Ge2Sb2Se5 bulk samples. The crystals formed a compact layer on the surface of the sample and then continued to grow from the surface to the central part of the sample. The formed crystalline layer grew linearly with time, which suggests that the crystal growth is controlled by liquid-crystal interface kinetics. Combining the growth data with the measured viscosities and melting data, crystal growth could be described on the basis of standard crystal growth models. The screw dislocation growth model seems to be operative in describing the temperature dependence of the crystal growth rate in the studied material in a wide temperature range. A detailed discussion on the relation between the kinetic coefficient of crystal growth and viscosity (ukin ∝ η(-ξ)) is presented. The activation energy of crystal growth was found to be higher than the activation energy of crystallization obtained from differential scanning calorimetry, which covers the whole nucleation-growth process. This difference is considered and explained under the experimental conditions. PMID:27441575

  13. Modified Gompertz equation for electrotherapy murine tumor growth kinetics: predictions and new hypotheses

    PubMed Central

    2010-01-01

    Background Electrotherapy effectiveness at different doses has been demonstrated in preclinical and clinical studies; however, several aspects that occur in the tumor growth kinetics before and after treatment have not yet been revealed. Mathematical modeling is a useful instrument that can reveal some of these aspects. The aim of this paper is to describe the complete growth kinetics of unperturbed and perturbed tumors through use of the modified Gompertz equation in order to generate useful insight into the mechanisms that underpin this devastating disease. Methods The complete tumor growth kinetics for control and treated groups are obtained by interpolation and extrapolation methods with different time steps, using experimental data of fibrosarcoma Sa-37. In the modified Gompertz equation, a delay time is introduced to describe the tumor's natural history before treatment. Different graphical strategies are used in order to reveal new information in the complete kinetics of this tumor type. Results The first stage of complete tumor growth kinetics is highly non linear. The model, at this stage, shows different aspects that agree with those reported theoretically and experimentally. Tumor reversibility and the proportionality between regions before and after electrotherapy are demonstrated. In tumors that reach partial remission, two antagonistic post-treatment processes are induced, whereas in complete remission, two unknown antitumor mechanisms are induced. Conclusion The modified Gompertz equation is likely to lead to insights within cancer research. Such insights hold promise for increasing our understanding of tumors as self-organizing systems and, the possible existence of phase transitions in tumor growth kinetics, which, in turn, may have significant impacts both on cancer research and on clinical practice. PMID:21029411

  14. Model for computing kinetics of the graphene edge epitaxial growth on copper

    NASA Astrophysics Data System (ADS)

    Khenner, Mikhail

    2016-06-01

    A basic kinetic model that incorporates a coupled dynamics of the carbon atoms and dimers on a copper surface is used to compute growth of a single-layer graphene island. The speed of the island's edge advancement on Cu[111] and Cu[100] surfaces is computed as a function of the growth temperature and pressure. Spatially resolved concentration profiles of the atoms and dimers are determined, and the contributions provided by these species to the growth speed are discussed. Island growth under the conditions of a thermal cycling is studied.

  15. The logistic growth of duckweed (Lemna minor) and kinetics of ammonium uptake.

    PubMed

    Zhang, Kun; Chen, You-Peng; Zhang, Ting-Ting; Zhao, Yun; Shen, Yu; Huang, Lei; Gao, Xu; Guo, Jin-Song

    2014-01-01

    Mathematical models have been developed to describe nitrogen uptake and duckweed growth experimentally to study the kinetics of ammonium uptake under various concentrations. The kinetics of duckweed ammonium uptake was investigated using the modified depletion method after plants were grown for two weeks at different ammonium concentrations (0.5-14 mg/L) in the culture medium. The maximum uptake rate and Michaelis-Menten constant for ammonium were estimated as 0.082 mg/(g fresh weight x h) and 1.877 mg/L, respectively. Duckweed growth was assessed when supplied at different total nitrogen (TN) concentrations (1-5 mg/L) in the culture medium. The results showed that the intrinsic growth rate was from 0.22 to 0.26 d(-1), and TN concentrations had no significant influence on the duckweed growth rate. PMID:24645435

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

    PubMed Central

    Robinson, J A; Tiedje, J M

    1983-01-01

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

  17. Streptococcus mutans Extracellular DNA Is Upregulated during Growth in Biofilms, Actively Released via Membrane Vesicles, and Influenced by Components of the Protein Secretion Machinery

    PubMed Central

    Liao, Sumei; Klein, Marlise I.; Heim, Kyle P.; Fan, Yuwei; Bitoun, Jacob P.; Ahn, San-Joon; Burne, Robert A.; Koo, Hyun; Brady, L. Jeannine

    2014-01-01

    Streptococcus mutans, a major etiological agent of human dental caries, lives primarily on the tooth surface in biofilms. Limited information is available concerning the extracellular DNA (eDNA) as a scaffolding matrix in S. mutans biofilms. This study demonstrates that S. mutans produces eDNA by multiple avenues, including lysis-independent membrane vesicles. Unlike eDNAs from cell lysis that were abundant and mainly concentrated around broken cells or cell debris with floating open ends, eDNAs produced via the lysis-independent pathway appeared scattered but in a structured network under scanning electron microscopy. Compared to eDNA production of planktonic cultures, eDNA production in 5- and 24-h biofilms was increased by >3- and >1.6-fold, respectively. The addition of DNase I to growth medium significantly reduced biofilm formation. In an in vitro adherence assay, added chromosomal DNA alone had a limited effect on S. mutans adherence to saliva-coated hydroxylapatite beads, but in conjunction with glucans synthesized using purified glucosyltransferase B, the adherence was significantly enhanced. Deletion of sortase A, the transpeptidase that covalently couples multiple surface-associated proteins to the cell wall peptidoglycan, significantly reduced eDNA in both planktonic and biofilm cultures. Sortase A deficiency did not have a significant effect on membrane vesicle production; however, the protein profile of the mutant membrane vesicles was significantly altered, including reduction of adhesin P1 and glucan-binding proteins B and C. Relative to the wild type, deficiency of protein secretion and membrane protein insertion machinery components, including Ffh, YidC1, and YidC2, also caused significant reductions in eDNA. PMID:24748612

  18. In situ biofilm coupon device

    SciTech Connect

    Peyton, Brent M.; Truex, Michael J.

    1997-01-01

    An apparatus for characterization of in-situ microbial biofilm populations in subsurface groundwater. The device permits biofilm-forming microorganisms to adhere to packing material while emplaced in a groundwater strata, so that the packing material can be later analyzed for quantity and type of microorganisms, growth rate, and nutrient requirements.

  19. In situ biofilm coupon device

    DOEpatents

    Peyton, B.M.; Truex, M.J.

    1997-06-24

    An apparatus is disclosed for characterization of in-situ microbial biofilm populations in subsurface groundwater. The device permits biofilm-forming microorganisms to adhere to packing material while emplaced in a groundwater strata, so that the packing material can be later analyzed for quantity and type of microorganisms, growth rate, and nutrient requirements. 3 figs.

  20. Kinetic Roughening and Energetics of Tetragonal Lysozyme Crystal Growth: A Preliminary Atomic Force Microscopy Investigation

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Forsythe, Elizabeth L.; Pusey, Marc L.

    2004-01-01

    We examined particulars of crystal growth from measurements obtained at both microscopic and molecular levels. The crystal growth measurements performed at the microscopic level are well characterized by a model that balances the flux of macromolecules towards the crystal surface with the flux of the crystal surface. Numerical evaluation of model with measurements of crystal growth, in time, provided accurate estimates for the average growth velocities. Growth velocities thus obtained were also interpreted using well-established phenomenological theories. Moreover, we find that microscopic measurements of growth velocity measurements obtained as a function of temperature best characterizes changes in crystal growth modes, when present. We also examined the possibility of detecting a change in crystal growth modes at the molecular level using atomic force microscopy, AFM. From preliminary AFM measurements performed at various supersaturations, we find that magnitude of surface height fluctuations, h(x), increases with supersaturation. Further examination of surface height fluctuations using methods established for fluctuation spectroscopy also enabled the discovery of the existence of a characteristic length, c, which may possibly determine the mode of crystal growth. Although the results are preliminary, we establish the non- critical divergence of 5 and the root-mean-square (rms) magnitude of height-height fluctuations as the kinetic roughening transition temperatures are approached. Moreover, we also examine approximate models for interpreting the non-critical behavior of both 6 and rms magnitude of height-height fluctuations, as the solution supersaturation is increased towards the kinetic roughening supersaturation.

  1. Growth Kinetics of Intracellular RNA/Protein Droplets: Signature of a Liquid-Liquid Phase Transition?

    NASA Astrophysics Data System (ADS)

    Berry, Joel; Weber, Stephanie C.; Vaidya, Nilesh; Zhu, Lian; Haataja, Mikko; Brangwynne, Clifford P.

    2015-03-01

    Nonmembrane-bound organelles are functional, dynamic assemblies of RNA and/or protein that can self-assemble and disassemble within the cytoplasm or nucleoplasm. The possibility that underlying intracellular phase transitions may drive and mediate the morphological evolution of some membrane-less organelles has been supported by several recent studies. In this talk, results from a collaborative experimental-theoretical study of the growth and dissolution kinetics of nucleoli and extranucleolar droplets (ENDs) in C. elegans embryos will be presented. We have employed Flory-Huggins solution theory, reaction-diffusion kinetics, and quantitative statistical dynamic scaling analysis to characterize the specific growth mechanisms at work. Our findings indicate that both in vivo and in vitro droplet scaling and growth kinetics are consistent with those resulting from an equilibrium liquid-liquid phase transition mediated by passive nonequilibrium growth mechanisms - simultaneous Brownian coalescence and Ostwald ripening. This supports a view in which cells can employ phase transitions to drive structural organization, while utilizing active processes, such as local transcriptional activity, to fine tune the kinetics of these phase transitions in response to given conditions.

  2. Growth kinetics of Al–Fe intermetallic compounds during annealing treatment of friction stir lap welds

    SciTech Connect

    Movahedi, M.; Kokabi, A.H.; Seyed Reihani, S.M.; Najafi, H.; Farzadfar, S.A.; Cheng, W.J.; Wang, C.J.

    2014-04-01

    In this study, we explored the growth kinetics of the Al–Fe intermetallic (IM) layer at the joint interface of the St-12/Al-5083 friction stir lap welds during post-weld annealing treatment at 350, 400 and 450 °C for 30 to 180 min. Optical microscope (OM), field emission gun scanning electron microscope (FEG-SEM) and transmission electron microscope (TEM) were employed to investigate the structure of the weld zone. The thickness and composition of the IM layers were evaluated using image analysis system and electron back-scatter diffraction (EBSD), respectively. Moreover, kernel average misorientation (KAM) analysis was performed to evaluate the level of stored energy in the as-welded state. The results showed that the growth kinetics of the IM layer was not governed by a parabolic diffusion law. Presence of the IM compounds as well as high stored energy near the joint interface of the as-welded sample was recognized to be the origin of the observed deviation from the parabolic diffusion law. - Highlights: • This work provided a new insight into growth kinetics of Al–Fe IM thickness. • The growth kinetics of IM layer was not governed by a parabolic diffusion law. • IM near the joint interface was the origin of deviation from the parabolic law. • High stored energy at joint interface was origin of deviation from parabolic law.

  3. Mathematical modeling and growth kinetics of Clostridium sporogenes in cooked beef

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Clostridium sporogenes PA 3679 is a common surrogate for proteolytic Clostridium botulinum for thermal process development and validation. However, little information is available concerning the growth kinetics of C. sporogenes in food. Therefore, the objective of this study was to investigate the...

  4. COMPARATIVE KINETIC STUDIES OF PHOSPHATE-LIMITED GROWTH AND PHOSPHATE UPTAKE IN PHYTOPLANKTON IN CONTINUOUS CULTURE

    EPA Science Inventory

    A comparative kinetic study of phosphate-limited growth and phosphate uptake was carried out in chemostat cultures of Anabaena flos-aquae Lyng. Breb., Ankistrodesmus falcatus (Corda) Ralfs, Asterionella formosa Hass., Fragilaria crotonensis Kitt., and Microcystis sp. Lemm. For ea...

  5. Evaluating algal growth performance and water use efficiency of pilot-scale revolving algal biofilm (RAB) culture systems.

    PubMed

    Gross, Martin; Mascarenhas, Vernon; Wen, Zhiyou

    2015-10-01

    A Revolving Algal Biofilm (RAB) growth system in which algal cells are attached to a flexible material rotating between liquid and gas phases has been developed. In this work, different configurations of RAB systems were developed at pilot-scale by retrofitting the attachment materials to a raceway pond (2000-L with 8.5 m(2) footprint area) and a trough reservoir (150 L with 3.5 m(2) footprint area). The algal growth performance and chemical composition, as well as the water evaporative loss and specific water consumption were evaluated over a period of nine months in a greenhouse environment near Boone, Iowa USA. Additionally a raceway pond was run in parallel, which served as a control. On average the raceway-based RAB and the trough-based RAB outperformed the control pond by 309% and 697%, respectively. A maximum productivity of 46.8 g m(-2) day(-1) was achieved on the trough-based RAB system. The evaporative water loss of the RAB system was modeled based on an energy balance analysis and was experimentally validated. While the RAB system, particularly the trough-based RAB, had higher water evaporative loss, the specific water consumption per unit of biomass produced was only 26% (raceway-based RAB) and 7% (trough-based RAB) of that of the control pond. Collectively, this research shows that the RAB system is an efficient algal culture system and has great potential to commercially produce microalgae with high productivity and efficient water use. PMID:25899246

  6. Outer membrane protein OmpQ of Bordetella bronchiseptica is required for mature biofilm formation.

    PubMed

    Cattelan, Natalia; Villalba, María Inés; Parisi, Gustavo; Arnal, Laura; Serra, Diego Omar; Aguilar, Mario; Yantorno, Osvaldo

    2016-02-01

    Bordetella bronchiseptica, an aerobic Gram-negative bacterium, is capable of colonizing the respiratory tract of diverse animals and chronically persists inside the hosts by forming biofilm. Most known virulence factors in Bordetella species are regulated by the BvgAS two-component transduction system. The Bvg-activated proteins play a critical role during host infection. OmpQ is an outer membrane porin protein which is expressed under BvgAS control. Here, we studied the contribution of OmpQ to the biofilm formation process by B. bronchiseptica. We found that the lack of expression of OmpQ did not affect the growth kinetics and final biomass of B. bronchiseptica under planktonic growth conditions. The ΔompQ mutant strain displayed no differences in attachment level and in early steps of biofilm formation. However, deletion of the ompQ gene attenuated the ability of B. bronchiseptica to form a mature biofilm. Analysis of ompQ gene expression during the biofilm formation process by B. bronchiseptica showed a dynamic expression pattern, with an increase of biofilm culture at 48 h. Moreover, we demonstrated that the addition of serum anti-OmpQ had the potential to reduce the biofilm biomass formation in a dose-dependent manner. In conclusion, we showed for the first time, to the best of our knowledge, evidence of the contribution of OmpQ to a process of importance for B. bronchiseptica pathobiology. Our results indicate that OmpQ plays a role during the biofilm development process, particularly at later stages of development, and that this porin could be a potential target for strategies of biofilm formation inhibition. PMID:26673448

  7. Growth kinetics of three species of Tetrahymena on solid agar

    SciTech Connect

    Dobra, K.W.; McArdle, E.W.; Ehret, C.F.

    1980-01-01

    A nutrient-agar method without liquid overlay has been developed for cultivation of ciliates. Three species of Tetrahymena-T. pyriformis strain W, T. rostrata strain UNI, and T. vorax strain V/sub 2/S, representing the 3 main groups of Tetrahymena species, were used; however the method should apply to other ciliates. Growth on the surface of the agar was facilitated by an optimal surface-to-volume ratio yielding a high density of ciliates and short generation times. At the highest density achieved, the cells became irregularly hexagonal and formed a monolayer tissue on the agar. Ciliates grown on agar were like those in liquid culture, typical oral ciliature, food-vacuole formation, and typical cortical patterns being retained. Advantages of this method include high cell density, easy recovery, and optimal O/sub 2/ supply. The organisms can also be cultivated on the surface of sterile cellulose-nitrate filters, facilitating in situ fixation and staining as well as transfer into different media by transfer of filters with cells, without prior centrifugation and resuspension.

  8. The kinetic boundary layer around an absorbing sphere and the growth of small droplets

    SciTech Connect

    Widder, M.E.; Titulaer, U.M. )

    1989-06-01

    Deviations from the classical Smoluchowski expression for the growth rate of a droplet in a supersaturated vapor can be expected when the droplet radius is not large compared to the mean free path of a vapor molecule. The growth rate then depends significantly on the structure of the kinetic boundary layer around a sphere. The authors consider this kinetic boundary layer for a dilute system of Brownian particles. For this system a large class of boundary layer problems for a planar wall have been solved. They show how the spherical boundary layer can be treated by a perturbation expansion in the reciprocal droplet radius. In each order one has to solve a finite number of planar boundary layer problems. The first two corrections to the planar problem are calculated explicitly. For radii down to about two velocity persistence lengths (the analog of the mean free path for a Brownian particle) the successive approximations for the growth rate agree to within a few percent. A reasonable estimate of the growth rate for all radii can be obtained by extrapolating toward the exactly known value at zero radius. Kinetic boundary layer effects increase the time needed for growth from 0 to 10 (or 2{1/2}) velocity persistence lengths by roughly 35% (or 175%).

  9. Intermetallic compound layer growth kinetics in non-lead bearing solders

    SciTech Connect

    Vianco, P.T.; Kilgo, A.C.; Grant, R.

    1995-04-01

    The introduction of alternative, non-lead bearing solders into electronic assemblies requires a thorough investigation of product manufacturability and reliability. Both of these attributes can be impacted by the excessive growth of intermetallic compound (IMC) layers at the solder/substrate interface. An extensive study has documented the stoichiometry and solid state growth kinetics of IMC layers formed between copper and the lead-free solders: 96.5Sn-3.5Ag (wt.%), 95Sn-5Sb, 100Sn, and 58Bi-42Sn. Aging temperatures were 70--205 C for the Sn-based solders and 55--120 C for the Bi-rich solder. Time periods were 1--400 days for all of the alloys. The Sn/Cu, Sn-Ag/Cu, and Sn-Sb/Cu IMC layers exhibited sub-layers of Cu{sub 6}Sn{sub 5} and Cu{sub 3}Sn; the latter composition was present only following prolonged aging times or higher temperatures. The total layer growth exhibited a time exponent of n = 0.5 at low temperatures and a value of n = 0.42 at higher temperatures in each of the solder/Cu systems. Similar growth kinetics were observed with the low temperature 58Bi-42Sn solder; however, a considerably more complex sub-layer structure was observed. The kinetic data will be discussed with respect to predicting IMC layer growth based upon solder composition.

  10. Multiple effects of Escherichia coli Nissle 1917 on growth, biofilm formation and inflammation cytokines profile of Clostridium perfringens type A strain CP4

    PubMed Central

    Jiang, Yanlong; Kong, Qingke; Roland, Kenneth L.; Wolf, Amanda; Curtiss, Roy

    2014-01-01

    Clostridium perfringens is an important Gram-positive pathogen responsible for food poisoning, necrotic enteritis, gas gangrene, and even death. Escherichia coli Nissle 1917 (EcN) is a well-characterized probiotic strain with demonstrated benefits. In this study we evaluated the effects of EcN on growth, toxin production, biofilm formation and inflammatory cytokine responses of C. perfringens. In vitro co-culture experiments demonstrated that EcN inhibited growth, gas production and toxin production (α-toxin and NetB) of C. perfringens in a dose dependent manner. The growth inhibition effect was not observed when C. perfringens was incubated with EcN cell free supernatants (CFSE), suggesting that growth inhibition was caused by nutrition competition during co-incubation. In vitro studies demonstrated that pre-incubation with EcN did not inhibit C. perfringens attachment to Caco-2 cells, but did reduce C. perfringens total number, toxin production and cytotoxicity after 24 h. The similar growth inhibition results were also observed during the formation of C. perfringens biofilm. Finally, pre-incubation of EcN with RAW264.7 cells significantly decreased the production of inflammatory cytokines caused by introduction of C. perfringens. Our results indicate that EcN can inhibit many of the pathological effects of C. perfringens in vitro conditions. PMID:24532573

  11. Multiple effects of Escherichia coli Nissle 1917 on growth, biofilm formation, and inflammation cytokines profile of Clostridium perfringens type A strain CP4.

    PubMed

    Jiang, Yanlong; Kong, Qingke; Roland, Kenneth L; Wolf, Amanda; Curtiss, Roy

    2014-04-01

    Clostridium perfringens is an important Gram-positive pathogen responsible for food poisoning, necrotic enteritis, gas gangrene, and even death. Escherichia coli Nissle 1917 (EcN) is a well-characterized probiotic strain with demonstrated benefits. In this study, we evaluated the effects of EcN on growth, toxin production, biofilm formation, and inflammatory cytokine responses of C. perfringens. In vitro co-culture experiments demonstrated that EcN inhibited growth, gas production, and toxin production (α-toxin and NetB) of C. perfringens in a dose-dependent manner. The growth inhibition effect was not observed when C. perfringens was incubated with EcN cell-free supernatants (CFSE), suggesting that growth inhibition was caused by nutrition competition during co-incubation. In vitro studies demonstrated that pre-incubation with EcN did not inhibit C. perfringens attachment to Caco-2 cells, but did reduce C. perfringens total number, toxin production, and cytotoxicity after 24 h. The similar growth inhibition results were also observed during the formation of C. perfringens biofilm. Finally, pre-incubation of EcN with RAW264.7 cells significantly decreased the production of inflammatory cytokines caused by the introduction of C. perfringens. Our results indicate that EcN can inhibit many of the pathological effects of C. perfringens in vitro conditions. PMID:24532573

  12. Diameter-Independent Kinetics in the Vapor-Liquid-Solid Growth of Si Nanowires

    NASA Astrophysics Data System (ADS)

    Kodambaka, S.; Tersoff, J.; Reuter, M. C.; Ross, F. M.

    2006-03-01

    We examine individual Si nanowires grown by the vapor-liquid-solid mechanism, using real-time in situ ultra high vacuum transmission electron microscopy. By directly observing Au-catalyzed growth of Si wires from disilane, we show that the growth rate is independent of wire diameter, contrary to the expected behavior. Our measurements show that the unique rate-limiting step here is the irreversible, kinetically limited, dissociative adsorption of disilane directly on the catalyst surface. We also identify a novel dependence of growth rate on wire taper.

  13. Diameter-independent kinetics in the vapor-liquid-solid growth of Si nanowires.

    PubMed

    Kodambaka, S; Tersoff, J; Reuter, M C; Ross, F M

    2006-03-10

    We examine individual Si nanowires grown by the vapor-liquid-solid mechanism, using real-time in situ ultra high vacuum transmission electron microscopy. By directly observing Au-catalyzed growth of Si wires from disilane, we show that the growth rate is independent of wire diameter, contrary to the expected behavior. Our measurements show that the unique rate-limiting step here is the irreversible, kinetically limited, dissociative adsorption of disilane directly on the catalyst surface. We also identify a novel dependence of growth rate on wire taper. PMID:16606284

  14. Kinetic Simulation of Gold Nanorod Growth in Solution Based on Optical Spectra

    NASA Astrophysics Data System (ADS)

    Wang, Ying-ying; Li, Bo-xuan; Vdovic, Silvije; Wang, Xue-fei; Xia, An-dong

    2012-04-01

    By monitoring the time evolution of the optical absorption spectrum corresponding to dynamic information of aspect ratio (AR) and volume, we succeeded in following the growth kinetics of gold nanorods. The results indicate that the rods growth consists of two stages: seeds develop into rods with a fast AR increase and the rods grow big with constant AR. Here, a charge transfer model, involving positive charge transfer from Au(I) to seed and neutralization by electron from ascorbic acid, has been introduced to explain the autocatalysis mechanism of rod growth. The good agreement between the numerical simulation based on this model and experimental results supports the proposed mechanism.

  15. Presence of extracellular DNA in the Candida albicans biofilm matrix and its contribution to biofilms

    PubMed Central

    Martins, Margarida; Uppuluri, Priya; Thomas, Derek P.; Cleary, Ian A.; Henriques, Mariana; Lopez-Ribot, José L.; Oliveira, Rosário

    2014-01-01

    DNA has been described as a structural component of the extracellular matrix (ECM) in bacterial biofilms. In Candida albicans there is a scarce knowledge concerning the contribution of extracellular DNA (eDNA) to biofilm matrix and overall structure. This work examined the presence and quantified the amount of eDNA in C.albicans biofilm ECM and the effect of DNase treatment and the addition of exogenous DNA on C. albicans biofilm development as indicators of a role for eDNA in biofilm development. We were able to detect the accumulation of eDNA in biofilm ECM extracted from C. albicans biofilms formed under conditions of flow, although the quantity of eDNA detected differed according to growth conditions, in particular with regards to the medium used to grow the biofilms. Experiments with C. albicans biofilms formed statically using a microtiter plate model indicated that the addition of exogenous DNA (>160 ng/ml) increases biofilm biomass and, conversely, DNase treatment (>0.03 mg/ml) decreases biofilm biomass at later time points of biofilm development. We present evidence for the role of eDNA in C. albicans biofilm structure and formation, consistent with eDNA being a key element of the ECM in mature C. albicans biofilms and playing a predominant role in biofilm structural integrity and maintenance. PMID:20012895

  16. Kinetic characteristics and modelling of growth and substrate removal by Alcaligenes faecalis strain NR.

    PubMed

    Chen, Jie; Zhao, Bin; An, Qiang; Wang, Xia; Zhang, Yi Xin

    2016-04-01

    Alcaligenes faecalis strain NR has the capability of simultaneous ammonium and organic carbon removal under sole aerobic conditions. The growth and substrate removal characteristics of A. faecalis strain NR were studied and appropriate kinetic models were developed. The maximum substrate removal rate of NH4 (+)-N and TOC were determined as 2.27 mg NH4 (+)-N/L/h and 30.00 mg TOC/L/h, respectively with initial NH4 (+)-N = 80 mg/L and TOC = 800 mg/L. Single-substrate models and double-substrate models based on Monod, Contois, Moser and Teissier were employed to describe the bioprocess kinetic coefficients. As a result, two double-substrate models, Teissier-Contois and Contois-Contois, were considered to be appropriate to model growth kinetics with both NH4 (+)-N and TOC as limiting substrates. The kinetic constants of maximum growth rate (μ max) and half-saturation constant (K S and B S) were obtained by solving multiple equations with regression. This work can be used to further understand and predict the performance of heterotrophic nitrifiers, and thus provides specific guidance of these functional strains in practical wastewater treatment process. PMID:26796583

  17. Lack of a unique kinetic pathway in the growth and decay of Pluronic micelles.

    PubMed

    Arranja, Alexandra; Waton, Gilles; Schosseler, François; Mendes, Eduardo

    2016-01-21

    We report kinetic experiments on dilute brine solutions of P84, P94 and P104 Pluronic copolymer micelles. The growth and the decay of micelles after temperature steps are measured by non-standard time resolved multi-angle photon correlation spectroscopy. Several concurrent mechanisms are at work during the very slow equilibration of solutions, namely insertion/expulsion of unimers, aggregation/dissociation of micellar aggregates, and fusion/budding of micellar aggregates. Their relative rates determine both the kinetic pathways and the morphologies of the micellar assemblies, which depend markedly on modest changes in the copolymer molecular weight. For the typical Pluronic copolymers investigated here, none of these elementary processes can be neglected if the resulting morphology is to be explained. This feature imposes multiple kinetic behaviours where growth and decay of Pluronic micelles become strongly dependent on the thermal history. We point out to some possible shortcomings in the studies of micellar growth kinetics by light scattering techniques. Extensive time-resolved multiangle measurements are a prerequisite for avoiding these pitfalls. PMID:26523415

  18. Kinetics of cesium lead halide perovskite nanoparticle growth; focusing and de-focusing of size distribution

    NASA Astrophysics Data System (ADS)

    Koolyk, Miriam; Amgar, Daniel; Aharon, Sigalit; Etgar, Lioz

    2016-03-01

    In this work we study the kinetics of cesium lead halide perovskite nanoparticle (NP) growth; the focusing and de-focusing of the NP size distribution. Cesium lead halide perovskite NPs are considered to be attractive materials for optoelectronic applications. Understanding the kinetics of the formation of these all-inorganic perovskite NPs is critical for reproducibly and reliably generating large amounts of uniformly sized NPs. Here we investigate different growth durations for CsPbI3 and CsPbBr3 NPs, tracking their growth by high-resolution transmission electron microscopy and size distribution analysis. As a result, we are able to provide a detailed model for the kinetics of their growth. It was observed that the CsPbI3 NPs exhibit focusing of the size distribution in the first 20 seconds of growth, followed by de-focusing over longer growth durations, while the CsPbBr3 NPs show de-focusing of the size distribution starting from the beginning of the growth. The monomer concentration is depleted faster in the case of CsPbBr3 than in the case of CsPbI3, due to faster diffusion of the monomers, which increases the critical radius and results in de-focusing of the population. Accordingly, focusing is not observed within 40 seconds of growth in the case of CsPbBr3. This study provides important knowledge on how to achieve a narrow size distribution of cesium lead halide perovskite NPs when generating large amounts of these promising, highly luminescent NPs.In this work we study the kinetics of cesium lead halide perovskite nanoparticle (NP) growth; the focusing and de-focusing of the NP size distribution. Cesium lead halide perovskite NPs are considered to be attractive materials for optoelectronic applications. Understanding the kinetics of the formation of these all-inorganic perovskite NPs is critical for reproducibly and reliably generating large amounts of uniformly sized NPs. Here we investigate different growth durations for CsPbI3 and CsPbBr3 NPs, tracking

  19. Insitu Measurements and Modeling of Carbon Nanotube Array Growth Kinetics during Chemical Vapor Deposition

    SciTech Connect

    Puretzky, Alexander A; Geohegan, David B; Jesse, Stephen; Ivanov, Ilia N; Eres, Gyula

    2005-01-01

    Direct measurements of carbon nanotube growth kinetics are described based upon time-resolved reflectivity (TRR) of a HeNe laser beam from vertically aligned nanotube arrays (VANTAs) as they grow during chemical vapor deposition (CVD). Growth rates and terminal lengths were measured in situ for VANTAs growing during CVD between 535 C and 900 C on Si substrates with evaporated Al/Fe/Mo multi-layered catalysts and acetylene feedstock at different feedstock partial pressures. Methods of analysis of the TRR signals are presented to interpret catalyst particle formation and oxidation, as well as the porosity of the VANTAs. A rate-equation model is developed to describe the measured kinetics in terms of activation energies and rate constants for surface carbon formation and diffusion on the catalyst nanoparticle, nanotube growth, and catalyst over-coating. Taken together with the TRR data, this model enables basic understanding and optimization of growth conditions for any catalyst/feedstock combination. The model lends insight into the main processes responsible for the growth of VANTAs, the measured number of walls in the nanotubes at different temperatures, conditions for growth of single-wall carbon nanotube arrays, and likely catalyst poisoning mechanisms responsible for the sharp decline in growth rates observed at high temperatures.

  20. Phosphate-limited growth of the marine diatom Thalassiosira weissflogii (Bacillariophyceae): evidence of non-monod growth kinetics(1).

    PubMed

    Laws, Edward A; Pei, Shaofeng; Bienfang, Paul

    2013-04-01

    The marine diatom Thalassiosira weissflogii (Grunow) G. A. Fryxell & Hasle was grown in a chemostat over a series of phosphate-limited growth rates. Ambient substrate concentrations were determined from bioassays involving picomolar spikes of (33) P-labeled phosphate, and maximum uptake rates were determined from analogous bioassays that included the addition of micromolar concentrations of unlabeled phosphate and tracer concentrations of (33) P. The relationship between cell phosphorus quotas and growth rates was well described by the Droop equation. Maximum uptake rates of phosphate spikes were several orders of magnitude higher than steady state uptake rates. Despite the large size of the T. weissflogii cells, diffusion of phosphate through the boundary layer around the cells had little effect on growth kinetics, in part because the cellular N:P ratios exceeded the Redfield ratio at all growth rates. Fitting the Monod equation to the experimental data produced an estimate of the nutrient-saturated growth rate that was ~50% greater than the maximum growth rate observed in batch culture. A modified hyperbolic equation with a curvature that is a maximum in magnitude at positive growth rates gave a better fit to the data and an estimate of the maximum growth rate that was consistent with observations. The failure of the Monod equation to describe the data may reflect a transition from substrate to co-substrate limitation and/or the presence of an inducible uptake system. PMID:27008513

  1. The effects of indoor and outdoor dust exposure on the growth, sensitivity to oxidative-stress, and biofilm production of three opportunistic bacterial pathogens.

    PubMed

    Suraju, Mohammed O; Lalinde-Barnes, Sloan; Sanamvenkata, Sachindra; Esmaeili, Mahsa; Shishodia, Shishir; Rosenzweig, Jason A

    2015-12-15

    Within the last decade, many studies have highlighted the radical changes in the components of indoor and outdoor dust. For example, agents like automobile emitted platinum group elements and different kinds of organic phthalates and esters have been reported to be accumulating in the biosphere. Humans consistently face dermal, respiratory, and dietary exposures to these particles while indoors and outdoors. In fact, dust particulate matter has been associated with close to 500,000 deaths per year in Europe and about 200,000 deaths per year in the United States. To date, there has been limited examination of the physiological impact of indoor and outdoor dust exposure on normal flora microbes. In this study, the effect of indoor- and outdoor-dust exposure on three opportunistic bacterial species (Escherichia coli, Enterococcus faecalis, and Pseudomonas aeruginosa) was assessed. Specifically, bacterial growth, oxidative stress resistance, and biofilm production were measured following indoor- and outdoor-dust exposures. Studies were conducted in nutritionally-rich and -poor environments typically encountered by bacteria. Surprisingly, indoor-dust (200μg/mL), enhanced the growth of all three bacterial species in nutrient-poor conditions, but slowed growth in nutrient-rich conditions. In nutrient-rich medium, 100μg/mL exposure of either indoor- or outdoor-dust resulted in significantly reduced oxidative stress resistance in E. coli. Most interestingly, dust (indoor and outdoor), either in nutrient-rich or -poor conditions, significantly increased biofilm production in all three bacterial species. These data suggest that indoor and outdoor dust, can modify opportunistic bacteria through altering growth, sensitivity to oxidative stress, and their virulence potential through enhanced biofilm formation. PMID:26363607

  2. Candida Biofilms: Development, Architecture, and Resistance

    PubMed Central

    CHANDRA, JYOTSNA; MUKHERJEE, PRANAB K.

    2015-01-01

    Intravascular device–related infections are often associated with biofilms (microbial communities encased within a polysaccharide-rich extracellular matrix) formed by pathogens on the surfaces of these devices. Candida species are the most common fungi isolated from catheter-, denture-, and voice prosthesis–associated infections and also are commonly isolated from contact lens–related infections (e.g., fungal keratitis). These biofilms exhibit decreased susceptibility to most antimicrobial agents, which contributes to the persistence of infection. Recent technological advances have facilitated the development of novel approaches to investigate the formation of biofilms and identify specific markers for biofilms. These studies have provided extensive knowledge of the effect of different variables, including growth time, nutrients, and physiological conditions, on biofilm formation, morphology, and architecture. In this article, we will focus on fungal biofilms (mainly Candida biofilms) and provide an update on the development, architecture, and resistance mechanisms of biofilms. PMID:26350306

  3. Directional grain growth from anisotropic kinetic roughening of grain boundaries in sheared colloidal crystals

    PubMed Central

    Gokhale, Shreyas; Nagamanasa, K. Hima; Santhosh, V.; Sood, A. K.; Ganapathy, Rajesh

    2012-01-01

    The fabrication of functional materials via grain growth engineering implicitly relies on altering the mobilities of grain boundaries (GBs) by applying external fields. Although computer simulations have alluded to kinetic roughening as a potential mechanism for modifying GB mobilities, its implications for grain growth have remained largely unexplored owing to difficulties in bridging the widely separated length and time scales. Here, by imaging GB particle dynamics as well as grain network evolution under shear, we present direct evidence for kinetic roughening of GBs and unravel its connection to grain growth in driven colloidal polycrystals. The capillary fluctuation method allows us to quantitatively extract shear-dependent effective mobilities. Remarkably, our experiments reveal that for sufficiently large strains, GBs with normals parallel to shear undergo preferential kinetic roughening, resulting in anisotropic enhancement of effective mobilities and hence directional grain growth. Single-particle level analysis shows that the mobility anisotropy emerges from strain-induced directional enhancement of activated particle hops normal to the GB plane. We expect our results to influence materials fabrication strategies for atomic and block copolymeric polycrystals as well. PMID:23169661

  4. Kinetics of growth and caffeine demethylase production of Pseudomonas sp. in bioreactor.

    PubMed

    Gummadi, Sathyanarayana N; Santhosh, Devarai

    2010-09-01

    The effect of various initial caffeine concentrations on growth and caffeine demethylase production by Pseudomonas sp. was studied in bioreactor. At initial concentration of 6.5 g l(-1) caffeine, Pseudomonas sp. showed a maximum specific growth rate of 0.2 h(-1), maximum degradation rate of 1.1 g h(-1), and caffeine demethylase activity of 18,762 U g CDW(-1) (CDW: cell dry weight). Caffeine degradation rate was 25 times higher in bioreactor than in shake flask. For the first time, we show highest degradation of 75 g caffeine (initial concentration 20 g l(-1)) in 120 h, suggesting that the tested strain has potential for successful bioprocess for caffeine degradation. Growth kinetics showed substrate inhibition phenomenon. Various substrate inhibition models were fitted to the kinetic data, amongst which the double-exponential (R(2) = 0.94), Luong (R(2) = 0.92), and Yano and Koga 2 (R(2) = 0.94) models were found to be the best. The Luedeking-Piret model showed that caffeine demethylase production kinetics was growth related. This is the first report on production of high levels of caffeine demethylase in batch bioreactor with faster degradation rate and high tolerance to caffeine, hence clearly suggesting that Pseudomonas sp. used in this study is a potential biocatalyst for industrial decaffeination. PMID:20495941

  5. On the Effect of Atoms in Solid Solution on Grain Growth Kinetics

    NASA Astrophysics Data System (ADS)

    Hersent, Emmanuel; Marthinsen, Knut; Nes, Erik

    2014-10-01

    The discrepancy between the classical grain growth law in high purity metals (grain size ) and experimental measurements has long been a subject of debate. It is generally believed that a time growth exponent less than 1/2 is due to small amounts of impurity atoms in solid solution even in high purity metals. The present authors have recently developed a new approach to solute drag based on solute pinning of grain boundaries, which turns out to be mathematically simpler than the classic theory for solute drag. This new approach has been combined with a simple parametric law for the growth of the mean grain size to simulate the growth kinetics in dilute solid solution metals. Experimental grain growth curves in the cases of aluminum, iron, and lead containing small amounts of impurities have been well accounted for.

  6. Kinetic modeling of Moorella thermoacetica growth on single and dual-substrate systems.

    PubMed

    Schmitt, Elliott; Bura, Renata; Gustafson, Rick; Ehsanipour, Mandana

    2016-10-01

    Acetic acid is an important chemical raw material that can be produced directly from sugars in lignocellulosic biomass. Development of kinetic models that capture the bioconversion dynamics of multiple sugar systems will be critical to optimization and process control in future lignocellulosic biorefinery processes. In this work, a kinetic model was developed for the single- and dual-substrate conversion of xylose and glucose to acetic acid using the acetogen Moorella thermoacetica. Batch fermentations were performed experimentally at 20 g L(-1) total sugar concentration using synthetic glucose, xylose, and a mixture of glucose and xylose at a 1:1 ratio. The product yield, calculated as total product formed divided by total sugars consumed, was 79.2, 69.9, and 69.7 % for conversion of glucose, xylose, and a mixture of glucose and xylose (1:1 ratio), respectively. During dual-substrate fermentation, M. thermoacetica demonstrated diauxic growth where xylose (the preferred substrate) was almost entirely consumed before consumption of glucose began. Kinetic parameters were similar for the single-substrate fermentations, and a strong linear correlation was determined between the maximum specific growth rate μ max and substrate inhibition constant, K s . Parameters estimated for the dual-substrate system demonstrated changes in the specific growth rate of both xylose and glucose consumption. In particular, the maximum growth rate related to glucose tripled compared to the single-substrate system. Kinetic growth is affected when multiple substrates are present in a fermentation system, and models should be developed to reflect these features. PMID:27262717

  7. Azo dye load-shock on relative behavior of biofilm and suspended growth configured periodic discontinuous batch mode operations: critical evaluation with enzymatic and bio-electrocatalytic analysis.

    PubMed

    Naresh Kumar, A; Nagendranatha Reddy, C; Hari Prasad, R; Venkata Mohan, S

    2014-09-01

    Effect of dye (C.I.Acid Black 10B) load-shock was comparatively evaluated in biofilm (self-immobilized) and suspended growth systems operated in periodic discontinuous batch mode (PDBR, anoxic-aerobic-anoxic) was investigated. At higher dye load (1250 mg dye/l), biofilm system showed relatively higher dye (74.5%) and COD (46%) removal efficiencies than the corresponding suspended mode operation (dye/COD removal efficiency, 42%/65%). Increment in dye load showed increment in azo reductase and dehydrogenase enzyme activities. Voltammograms (cyclic) showed higher reduction currents (RC) with increment in dye load specifically in biofilm system. Derivative cyclic voltammograms analysis depicted the involvement of mediators (NAD (+), FAD(+), etc.) which presumably played a major role in electron transport chain and dye degradation. Disappearance of peak (1612 cm(-1)) specific to azo group in FTIR spectrum, at higher loading rate in both the systems indicates the non-inhibitory and robust nature of PDBR operation. PMID:24859232

  8. Quantitative exploration of the contribution of settlement, growth, dispersal and grazing to the accumulation of natural marine biofilms on antifouling and fouling-release coatings

    PubMed Central

    Van Mooy, Benjamin A. S.; Hmelo, Laura R.; Fredricks, Helen F.; Ossolinski, Justin E.; Pedler, Byron E.; Bogorff, Daniel J.; Smith, Peter J.S.

    2014-01-01

    The accumulation of microbial biofilms on ships' hulls negatively affects ships' performance and efficiency while also moderating the establishment of even more detrimental hard-fouling communities. However, there is little quantitative information on how the accumulation rate of microbial biofilms is impacted by the balance of the rates of cell settlement, in situ production (ie growth), dispersal to surrounding waters and mortality induced by grazers. These rates were quantified on test panels coated with copper-based antifouling or polymer-based fouling-release coatings by using phospholipids as molecular proxies for microbial biomass. The results confirmed the accepted modes of efficacy of these two types of coatings. In a more extensive set of experiments with only the fouling-release coatings, it was found that seasonally averaged cellular production rates were 1.5 ± 0.5 times greater than settlement and the dispersal rates were 2.7 ± 0.8 greater than grazing. The results of this study quantitatively describe the dynamic balance of processes leading to microbial biofilm accumulation on coatings designed for ships' hulls. PMID:24417212

  9. Kinetics and mechanisms of cadmium carbonate heteroepitaxial growth at the calcite (10 1bar 4) surface

    NASA Astrophysics Data System (ADS)

    Xu, Man; Kovarik, Libor; Arey, Bruce W.; Felmy, Andrew R.; Rosso, Kevin M.; Kerisit, Sebastien

    2014-06-01

    Elucidating the kinetics and mechanisms of heteroepitaxial nucleation and growth at mineral-water interfaces is essential to understanding surface reactivity in geochemical systems. In the present work, the formation of heteroepitaxial cadmium carbonate coatings at calcite-water interfaces was investigated by exposing calcite (10 1bar 4) surfaces to Cd-bearing aqueous solutions. In situ atomic force microscopy (AFM) was employed as the primary technique. The AFM results indicate that the heteroepitaxial growth of cadmium carbonate proceeds via three different mechanisms depending on the initial supersaturation of the aqueous solution: advancement of existing steps, nucleation and growth of three-dimensional (3D) islands, and nucleation and spread of two-dimensional (2D) nuclei. The 3D islands and 2D nuclei exhibit different morphologies and growth kinetics. The effects of supersaturation on heteroepitaxial growth mechanisms can be interpreted in terms of the free energy barrier for nucleation. At low initial supersaturation, where 3D nucleation dominates, it is hypothesized, from the growth rate and morphology of the 3D islands observed with AFM, that the crystallization of the overgrowth follows a non-classical pathway involving the formation of a surface precursor that is not fully crystalline, whereas high supersaturation favors the formation of crystalline 2D nuclei whose morphology is based on the atomic structure of the calcite substrate. Cross-sectional transmission electron microscopy (TEM) images reveal that the atomic structure of the interface between the cadmium carbonate coating and calcite shows perfect, dislocation-free epitaxy.

  10. Kinetics and Mechanisms of Cadmium Carbonate Heteroepitaxial Growth at the Calcite (101¯4) Surface

    SciTech Connect

    Xu, Man; Kovarik, Libor; Arey, Bruce W.; Felmy, Andrew R.; Rosso, Kevin M.; Kerisit, Sebastien N.

    2014-06-01

    Elucidating the kinetics and mechanisms of heteroepitaxial nucleation and growth at mineral-water interfaces is essential to understanding surface reactivity in geochemical systems. In the present work, the formation of heteroepitaxial cadmium carbonate coatings at calcite-water interfaces was investigated by exposing calcite (10-14) surfaces to Cd-bearing aqueous solutions. In situ atomic force microscopy (AFM) was employed as the primary technique. The AFM results indicate that the heteroepitaxial growth of cadmium carbonate proceeds via three different mechanisms depending on the initial supersaturation of the aqueous solution: advancement of existing steps, nucleation and growth of three-dimensional (3D) islands, and nucleation and spread of two-dimensional (2D) nuclei. The 3D islands and 2D nuclei exhibit different morphologies and growth kinetics. The effects of supersaturation on heteroepitaxial growth mechanisms can be interpreted in terms of the free energy barrier for nucleation. At low initial supersaturation, where 3D nucleation dominates, it is hypothesized, from the growth rate and morphology of the 3D islands observed with AFM, that the crystallization of the overgrowth follows a non-classical pathway involving the formation of a surface precursor that is not fully crystalline, whereas high supersaturation favors the formation of crystalline 2D nuclei whose morphology is based on the atomic structure of the calcite substrate. Cross-sectional transmission electron microscopy (TEM) images reveal that the atomic structure of the interface between the cadmium carbonate coating and calcite shows perfect, dislocation-free epitaxy.

  11. Estimation of the growth kinetics for the cooling crystallisation of paracetamol and ethanol solutions

    NASA Astrophysics Data System (ADS)

    Mitchell, Niall A.; Ó'Ciardhá, Clifford T.; Frawley, Patrick J.

    2011-08-01

    This work details the estimation of the growth kinetics of paracetamol in ethanol solutions for cooling crystallisation processes, by means of isothermal seeded batch experiments. The growth kinetics of paracetamol crystals were evaluated in isolation, with the growth rate assumed to be size independent. Prior knowledge of the Metastable Zone Width (MSZW) was required, so that supersaturation ratios of 1.7-1.1 could be induced in solution without the occurrence of nucleation. The technique involved the utilisation of two in-situ Process Analytical Techniques (PATs), with a Focused Beam Reflectance Measurement (FBRM ®) utilised to ensure that negligible nucleation occurred and an Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) probe employed for online monitoring of solute concentration. Initial Particle Size Distributions (PSDs) were used in conjunction with desupersaturation profiles to determine the growth rate as a function of temperature and supersaturation. Furthermore, the effects of seed loading and size on the crystal growth rate were investigated. A numerical model, incorporating the population balance equation and the method of moments, was utilised to describe the crystal growth process. Experimental parameters were compared to the model simulation, with the accuracy of the model validated by means of the final product PSDs and solute concentration.

  12. MODELING CHEMICAL INTERACTIONS IN ANAEROBIC BIOFILM SYSTEMS

    EPA Science Inventory

    Rigorous steady-state models of acetate- and methanol-utilizing methanogenic biofilms are developed taking into account the mass transfer of neutral and ionic species, pH changes within the biofilm, pH-dependent Monod kinetics, chemical equilibrium,, electronueutrality, gas produ...

  13. Denitrification and biofilm growth in a pilot-scale biofilter packed with suspended carriers for biological nitrogen removal from secondary effluent.

    PubMed

    Shi, Yunhong; Wu, Guangxue; Wei, Nan; Hu, Hongying

    2015-06-01

    Tertiary denitrification is an effective method for nitrogen removal from wastewater. A pilot-scale biofilter packed with suspended carriers was operated for tertiary denitrification with ethanol as the organic carbon source. Long-term performance, biokinetics of denitrification and biofilm growth were evaluated under filtration velocities of 6, 10 and 14 m/hr. The pilot-scale biofilter removed nitrate from the secondary effluent effectively, and the nitrate nitrogen (NO3-N) removal percentage was 82%, 78% and 55% at the filtration velocities of 6, 10 and 14 m/hr, respectively. At the filtration velocities of 6 and 10 m/hr, the nitrate removal loading rate increased with increasing influent nitrate loading rates, while at the filtration velocity of 14 m/hr, the removal loading rate and the influent loading rate were uncorrelated. During denitrification, the ratio of consumed chemical oxygen demand to removed NO3-N was 3.99-4.52 mg/mg. Under the filtration velocities of 6, 10 and 14 m/hr, the maximum denitrification rate was 3.12, 4.86 and 4.42 g N/(m2·day), the half-saturation constant was 2.61, 1.05 and 1.17 mg/L, and the half-order coefficient was 0.22, 0.32 and 0.24(mg/L)1/2/min, respectively. The biofilm biomass increased with increasing filtration velocity and was 2845, 5124 and 7324 mg VSS/m2 at filtration velocities of 6, 10 and 14 m/hr, respectively. The highest biofilm density was 44 mg/cm3 at the filtration velocity of 14 m/hr. Due to the low influent loading rate, biofilm biomass and thickness were lowest at the filtration velocity of 6m/hr. PMID:26040729

  14. Functional genomics of probiotic Escherichia coli Nissle 1917 and 83972, and UPEC strain CFT073: comparison of transcriptomes, growth and biofilm formation.

    PubMed

    Hancock, Viktoria; Vejborg, Rebecca Munk; Klemm, Per

    2010-12-01

    Strain CFT073 is a bona fide uropathogen, whereas strains 83972 and Nissle 1917 are harmless probiotic strains of urinary tract and faecal origin, respectively. Despite their different environmental origins and dispositions the three strains are very closely related and the ancestors of 83972 and Nissle 1917 must have been very similar to CFT073. Here, we report the first functional genome profiling of Nissle 1917 and the first biofilm profiling of a uropathogen. Transcriptomic profiling revealed that Nissle 1917 expressed many UPEC-associated genes and showed that the active genomic profiles of the three strains are closely related. The data demonstrate that the distance from a pathogen to a probiotic strain can be surprisingly short. We demonstrate that Nissle 1917, in spite of its intestinal niche origin, grows well in urine, and is a good biofilm former in this medium in which it also out-competes CFT073 during planktonic growth. The role in biofilm formation of three up-regulated genes, yhaK, yhcN and ybiJ, was confirmed by knockout mutants in Nissle 1917 and CFT073. Two of these mutants CFT073∆yhcN and CFT073∆ybiJ had significantly reduced motility compared with the parent strain, arguably accounting for the impaired biofilm formation. Although the three strains have very different strategies vis-à-vis the human host their functional gene profiles are surprisingly similar. It is also interesting to note that the only two Escherichia coli strains used as probiotics are in fact deconstructed pathogens. PMID:20886356

  15. Biological Selenite Reduction and Biofilm Growth in a Microfluidic Flow Cell

    NASA Astrophysics Data System (ADS)

    Tang, Y.; Valocchi, A. J.; Werth, C. J.; Liu, W. T.; Sanford, R. A.; Singh, R.; Nobu, M.; Michelson, K.; Xue, Z.

    2014-12-01

    Selenite-contaminated groundwater can be biologically remediated in-situ by supplying an electron donor to promote the growth of selenite-reducing bacteria. We studied the fate of selenite during in-situ bioremediation using a microfluidic flow cell containing a homogeneous distribution of pores. The flow cell had two inlets: one for selenite supply, and the other for propionate (electron donor) supply. The media contained sulfate, which is common in groundwater and can affect selenite reduction. During the 5-month operation, biomass and selenite reduction products were periodically imaged using a phase contrast microscope and an environmental scanning electron microscope. Selenite reduction products were further characterized using Raman spectroscopy and energy-dispersive X-ray spectroscopy. Three types of crystals were detected in the mixing zone between selenite and propionate, and they occurred in different locations of the mixing zone. On the selenite side, selenite was biologically reduced to elemental selenium in the monoclinic form. Along the centerline, sulfate was biologically reduced to sulfide, which chemically reacted with selenite to form the second type of crystal (selenium sulfide). On the propionate side, selenium sulfide was biologically reduced to elemental selenium in the trigonal form. A mathematical model was developed to explain the segregation of the three crystals. On the selenite side, bacteria preferred selenite to sulfate since selenite can provide more energy for bacteria growth according to thermodynamics. On the propionate side, selenite was limiting; thus bacteria used selenium sulfide as their electron acceptor. Understanding this segregation can help to predict in-situ bioremediation of selenite-contaminated groundwater. Conventional prediction models consider the reaction on the selenite side as the only path of selenite removal, while a model considering the three paths of selenite removal would increase the prediction accuracy.

  16. Nonlinear Growth Kinetics of Breast Cancer Stem Cells: Implications for Cancer Stem Cell Targeted Therapy

    NASA Astrophysics Data System (ADS)

    Liu, Xinfeng; Johnson, Sara; Liu, Shou; Kanojia, Deepak; Yue, Wei; Singn, Udai; Wang, Qian; Wang, Qi; Nie, Qing; Chen, Hexin

    2013-08-01

    Cancer stem cells (CSCs) have been identified in primary breast cancer tissues and cell lines. The CSC population varies widely among cancerous tissues and cell lines, and is often associated with aggressive breast cancers. Despite of intensive research, how the CSC population is regulated within a tumor is still not well understood so far. In this paper, we present a mathematical model to explore the growth kinetics of CSC population both in vitro and in vivo. Our mathematical models and supporting experiments suggest that there exist non-linear growth kinetics of CSCs and negative feedback mechanisms to control the balance between the population of CSCs and that of non-stem cancer cells. The model predictions can help us explain a few long-standing questions in the field of cancer stem cell research, and can be potentially used to predict the efficicacy of anti-cancer therapy.

  17. Growth kinetics and island evolution during double-pulsed molecular beam epitaxy of InN

    NASA Astrophysics Data System (ADS)

    Kraus, A.; Hein, C.; Bremers, H.; Rossow, U.; Hangleiter, A.

    2016-06-01

    The kinetic processes of InN growth using alternating source fluxes with sub-monolayer In pulses in plasma-assisted molecular beam epitaxy have been investigated. Growth at various temperatures reveals the existence of two growth regimes. While growth at low temperatures is solely governed by surface diffusion, a combination of decomposition, desorption, and diffusion becomes decisive at growth temperatures of 470 °C and above. At this critical temperature, the surface morphology changes from a grainy structure to a structure made of huge islands. The formation of those islands is attributed to the development of an indium adlayer, which can be observed via reflection high energy electron diffraction monitoring. Based on the growth experiments conducted at temperatures below TGrowth = 470 °C, an activation energy for diffusion of 0.54 ± 0.02 eV has been determined from the decreasing InN island density. A comparison between growth on metalorganic vapor phase epitaxy GaN templates and pseudo bulk GaN indicates that step edges and dislocations are favorable nucleation sites. Based on the results, we developed a growth model, which describes the main mechanisms of the growth.

  18. Intrinsic Kinetics Fluctuations as Cause of Growth Inhomogeneity in Protein Crystals

    NASA Technical Reports Server (NTRS)

    Vekilov, Peter G.; Rosenberger, Franz

    1998-01-01

    Intrinsic kinetics instabilities in the form of growth step bunching during the crystallization of the protein lysozyme from solution were characterized by in situ high-resolution optical interferometry. Compositional variations (striations) in the crystal, which potentially decrease its utility, e.g., for molecular structure studies by diffraction methods, were visualized by polarized light reflection microscopy. A spatiotemporal correlation was established between the sequence of moving step bunches and the striations.

  19. Mg doping and its effect on the semipolar GaN(1122) growth kinetics

    SciTech Connect

    Lahourcade, L.; Wirthmueller, A.; Monroy, E.; Chauvat, M. P.; Ruterana, P.; Laufer, A.; Eickhoff, M.

    2009-10-26

    We report the effect of Mg doping on the growth kinetics of semipolar GaN(1122) synthesized by plasma-assisted molecular-beam epitaxy. Mg tends to segregate on the surface, inhibiting the formation of the self-regulated Ga film which is used as a surfactant for the growth of undoped and Si-doped GaN(1122). We observe an enhancement of Mg incorporation in GaN(1122) compared to GaN(0001). Typical structural defects or polarity inversion domains found in Mg-doped GaN(0001) were not observed for the semipolar films investigated in the present study.

  20. Effect of clofibrate on the growth-kinetics of the murine P 1798(sc) lymphoma.

    PubMed Central

    Ubeira, F. M.; Seoane, R.; Puentes, E.; Faro, J.; Regueiro, B. J.

    1983-01-01

    Clofibrate (CPIB) is a drug applied as an antilipidaemic agent in mammals. In this work we have tested its efficacy in vivo on the growth kinetics of P 1798(sc) lymphoma transplanted to recipient (BALB/c x AKR)F1 mice. Our results show a facilitation of the tumour growth rate in treated recipients. This fact may be related to an effect of the agent on the recipient which produces a decrease in the immune response as was confirmed on testing CPIB on thymus-dependent antigens in haemolytic plaque assays. Images Figure 3 PMID:6351886

  1. Generalization of Monod kinetics for analysis of growth data with substrate inhibition

    SciTech Connect

    Luong, J.H.T.

    1987-02-05

    The inhibitory effect of butanol on yeast growth has been studied for the strain Candida utilis ATCC 8205 growing aerobically on butanol under batch conditions. A mathematical expression was then proposed to fit the kinetic pattern of butanol inhibition on the specific growth rate. The maximum allowable butanol concentration above which cells do not grow was predicted to be 9.16 g/l. The proposed model appears to accurately represent the experimental data obtained in this study and the literature data developed for a variety of batch culture systems at widely ranging substrate concentrations. 20 references.

  2. Investigation of the kinetics of surface-limited thin film growth of SiGe alloys

    SciTech Connect

    Sharp, J.W. . Dept. of Physics and Astronomy); Eres, G. )

    1992-11-01

    The kinetics of surface-limited thin film growth of SiGe alloys was investigated by time-resolved surface differential reflectometry. The source gas, mixtures of disilane and digermane in ratios from 1:1 to 6:1 in helium carrier gas, was delivered to a heated substrate by a fast-acting pulsed molecular jet valve. The adsorption and desorption kinetics were determined from the surface differential reflectance signal obtained using a polarized, high-stability HeNe probe laser. Thin film growth was studied in the temperature range of 400--600[degrees]C on Si(001) substrates. Preferential incorporation of digermane into the film produces an alloy composition that depends upon but does not mirror the gas composition. For all gas mixtures, there is a strong temperature dependence of the rate at which the adsorption layer decomposes into film plus by-product. The kinetic data and the alloy compositions provide a basis for deducing some of the characteristics of the reaction sequence that leads to SiGe alloy thin film growth.

  3. Investigation of the kinetics of surface-limited thin film growth of SiGe alloys

    SciTech Connect

    Sharp, J.W.; Eres, G.

    1992-11-01

    The kinetics of surface-limited thin film growth of SiGe alloys was investigated by time-resolved surface differential reflectometry. The source gas, mixtures of disilane and digermane in ratios from 1:1 to 6:1 in helium carrier gas, was delivered to a heated substrate by a fast-acting pulsed molecular jet valve. The adsorption and desorption kinetics were determined from the surface differential reflectance signal obtained using a polarized, high-stability HeNe probe laser. Thin film growth was studied in the temperature range of 400--600{degrees}C on Si(001) substrates. Preferential incorporation of digermane into the film produces an alloy composition that depends upon but does not mirror the gas composition. For all gas mixtures, there is a strong temperature dependence of the rate at which the adsorption layer decomposes into film plus by-product. The kinetic data and the alloy compositions provide a basis for deducing some of the characteristics of the reaction sequence that leads to SiGe alloy thin film growth.

  4. Effect of nitrogen and vanadium on austenite grain growth kinetics of a low alloy steel

    SciTech Connect

    Stasko, Renata . E-mail: rstasko@ap.Cracow.pl; Adrian, Henryk . E-mail: adrian@uci.agh.edu.pl; Adrian, Anna . E-mail: adrian@metal.agh.edu.pl

    2006-06-15

    Austenite grain growth kinetics in a steel containing 0.4% C, 1.8% Cr with different nitrogen contents (in the range 0.0038-0.0412%) and a micralloying addition of 0.078% V were investigated. The investigations were carried out in an austenitising temperature range of 840-1200 deg. C for 30 min. The results of investigations showed that N promotes the grain growth of austenite. The microalloying addition of vanadium protects the austenite grain growth because of carbonitride V(C,N) precipitation and the grain boundary pinning effect of undissolved particles of V(C,N). Using a thermodynamic model, the carbonitride V(C,N) content, undissolved at the austenitising temperature was calculated. At temperatures when a coarsening and dissolution of carbonitride occurs, the austenite grains start to growth. The effect of nitrogen on the type of chord length distribution of austenite grains was analysed.

  5. Effects of Alloying on Nanoscale Grain Growth in Substitutional Binary Alloy System: Thermodynamics and Kinetics

    NASA Astrophysics Data System (ADS)

    Peng, Haoran; Chen, Yuzeng; Liu, Feng

    2015-11-01

    Applying the regular solution model, the Gibbs free energy of mixing for substitutional binary alloy system was constructed. Then, thermodynamic and kinetic parameters, e.g., driving force and solute drag force, controlling nanoscale grain growth of substitutional binary alloy systems were derived and compared to their generally accepted definitions and interpretations. It is suggested that for an actual grain growth process, the classical driving force P = γ/D ( γ the grain boundary (GB) energy, D the grain size) should be replaced by a new expression, i.e., P^' = γ /D - Δ P . Δ P represents the energy required to adjust nonequilibrium solute distribution to equilibrium solute distribution, which is equivalent to the generally accepted solute drag force impeding GB migration. By incorporating the derived new driving force for grain growth into the classical grain growth model, the reported grain growth behaviors of nanocrystalline Fe-4at. pct Zr and Pd-19at. pct Zr alloys were analyzed. On this basis, the effect of thermodynamic and kinetic parameters ( i.e., P, Δ P and the GB mobility ( M GB)) on nanoscale grain growth, were investigated. Upon grain growth, the decrease of P is caused by the reduction of γ as a result of solute segregation in GBs; the decrease of Δ P is, however, due to the decrease of grain growth velocity; whereas the decrease of M GB is attributed to the enhanced difference of solute molar fractions between the bulk and the GBs as well as the increased activation energy for GB diffusion.

  6. Bacterial interactions in dental biofilm.

    PubMed

    Huang, Ruijie; Li, Mingyun; Gregory, Richard L

    2011-01-01

    Biofilms are masses of microorganisms that bind to and multiply on a solid surface, typically with a fluid bathing the microbes. The microorganisms that are not attached but are free floating in an aqueous environment are termed planktonic cells. Traditionally, microbiology research has addressed results from planktonic bacterial cells. However, many recent studies have indicated that biofilms are the preferred form of growth of most microbes and particularly those of a pathogenic nature. Biofilms on animal hosts have significantly increased resistance to various antimicrobials compared to planktonic cells. These microbial communities form microcolonies that interact with each other using very sophisticated communication methods (i.e., quorum-sensing). The development of unique microbiological tools to detect and assess the various biofilms around us is a tremendously important focus of research in many laboratories. In the present review, we discuss the major biofilm mechanisms and the interactions among oral bacteria. PMID:21778817

  7. Bacterial interactions in dental biofilm

    PubMed Central

    Huang, Ruijie; Li, Mingyun

    2011-01-01

    Biofilms are masses of microorganisms that bind to and multiply on a solid surface, typically with a fluid bathing the microbes. The microorganisms that are not attached but are free-floating in an aqueous environment are termed planktonic cells. Traditionally, microbiology research has addressed results from planktonic bacterial cells. However, many recent studies have indicated that biofilms are the preferred form of growth of most microbes and particularly those of a pathogenic nature. Biofilms on animal hosts have significantly increased resistance to various antimicrobials compared to planktonic cells. These microbial communities form microcolonies that interact with each other using very sophisticated communication methods (i.e., quorum-sensing). The development of unique microbiological tools to detect and assess the various biofilms around us is a tremendously important focus of research in many laboratories. In the present review, we discuss the major biofilm mechanisms and the interactions among oral bacteria. PMID:21778817

  8. Genetic dissection of mycobacterial biofilms.

    PubMed

    Ojha, Anil K; Jacobs, William R; Hatfull, Graham F

    2015-01-01

    Our understanding of the biological principles of mycobacterial tolerance to antibiotics is crucial for developing shorter anti-tuberculosis regimens. Various in vitro approaches have been developed to identify the conditions that promote mycobacterial persistence against antibiotics. In our laboratories, we have developed a detergent-free in vitro growth model, in which mycobacteria spontaneously grow at the air-medium interface as self-organized multicellular structures, called biofilms. Mycobacterial biofilms harbor a subpopulation of drug tolerant persisters at a greater frequency than their planktonic counterpart. Importantly, development of these structures is genetically programmed, and defective biofilms of isogenic mutants harbor fewer persisters. Thus, genetic analysis of mycobacterial biofilms in vitro could potentially be a powerful tool to unravel the biology of drug tolerance in mycobacteria. In this chapter we describe a method for screening biofilm-defective mutants of mycobacteria in a 96-well format, which readily yields a clonally pure mutant for further studies. PMID:25779318

  9. A phase-field model coupled with lattice kinetics solver for modeling crystal growth in furnaces

    SciTech Connect

    Lin, Guang; Bao, Jie; Xu, Zhijie; Tartakovsky, Alexandre M.; Henager, Charles H.

    2014-02-02

    In this study, we present a new numerical model for crystal growth in a vertical solidification system. This model takes into account the buoyancy induced convective flow and its effect on the crystal growth process. The evolution of the crystal growth interface is simulated using the phase-field method. Two novel phase-field models are developed to model the crystal growth interface in vertical gradient furnaces with two temperature profile setups: 1) fixed wall temperature profile setup and 2) time-dependent temperature profile setup. A semi-implicit lattice kinetics solver based on the Boltzmann equation is employed to model the unsteady incompressible flow. This model is used to investigate the effect of furnace operational conditions on crystal growth interface profiles and growth velocities. For a simple case of macroscopic radial growth, the phase-field model is validated against an analytical solution. Crystal growth in vertical gradient furnaces with two temperature profile setups have been also investigated using the developed model. The numerical simulations reveal that for a certain set of temperature boundary conditions, the heat transport in the melt near the phase interface is diffusion dominant and advection is suppressed.

  10. Role of Environmental and Antibiotic Stress on Staphylococcus epidermidis Biofilm Microstructure

    PubMed Central

    Stewart, Elizabeth J.; Satorius, Ashley E.; Younger, John G.; Solomon, Michael J.

    2014-01-01

    Cellular clustering and separation of Staphylococcus epidermidis surface adherent biofilms were found to depend significantly on both antibiotic and environmental stress present during growth under steady flow. Image analysis techniques common to colloidal science were applied to image volumes acquired with high-resolution confocal laser scanning microscopy to extract spatial positions of individual bacteria in volumes of size ~30 × 30 × 15 μm3. The local number density, cluster distribution, and radial distribution function were determined at each condition by analyzing the statistics of the bacterial spatial positions. Environmental stressors of high osmotic pressure (776 mM NaCl) and sublethal antibiotic dose (1.9 μg/mL vancomycin) decreased the average bacterial local number density 10-fold. Device-associated bacterial biofilms are frequently exposed to these environmental and antibiotic stressors while undergoing flow in the bloodstream. Characteristic density phenotypes associated with low, medium, and high local number densities were identified in unstressed S. epidermidis biofilms, while stressed biofilms contained medium- and low-density phenotypes. All biofilms exhibited clustering at length scales commensurate with cell division (~1.0 μm). However, density phenotypes differed in cellular connectivity at the scale of ~6 μm. On this scale, nearly all cells in the high- and medium-density phenotypes were connected into a single cluster with a structure characteristic of a densely packed disordered fluid. However, in the low-density phenotype, the number of clusters was greater, equal to 4% of the total number of cells, and structures were fractal in nature with df =1.7 ± 0.1. The work advances the understanding of biofilm growth, informs the development of predictive models of transport and mechanical properties of biofilms, and provides a method for quantifying the kinetics of bacterial surface colonization as well as biofilm fracture and

  11. A novel microculture kinetic assay (MiCK assay) for malignant cell growth and chemosensitivity.

    PubMed

    Kravtsov, V D

    1994-01-01

    The THERMOmax microplate reader was adapted for monitoring the growth kinetics of human leukaemic OCI/AML-2 and mouse tumour J-774.1 cell lines in continuous culture. Fluid evaporation from wells, CO2 escape and contamination were prevented by hermetic sealing of the microcultures in wells of a 96-well microplate, thus enabling the cells to grow exponentially for 72 h under the conditions of the incubated microplate reader. For both OCI/AML-2 cells, which grow in suspension, and adherent J-774.1 cells, a linear correlation was demonstrated between the number of unstained cells seeded in a given microplate well and the optical density (OD) of that well. Therefore, the OD/time curve of the culture could be deemed to be its growth curve. By the use of the linear fit equation, the actual number of the cells in the wells was computable at any time point of the assay. In the chemosensitivity test, an inhibitory effect of ARA-C on the growth of the cells could be estimated by viewing of the growth curves plotted on the screen. The maximum kinetic rates (Vmax) of the curves in the control and the ARA-C-treated wells were compared, yielding a growth inhibition index (GII). Comparison of results of the kinetic chemosensitivity assay with those of a [3H]thymidine incorporation assay revealed that the novel assay is suitable for precise quantitation of the cell chemosensitivity, is more informative and has the added technical advantage of performance without recourse to radioactive or chemically hazardous substances. PMID:7833120

  12. Quantifying the Nucleation and Growth Kinetics of Microwave Nanochemistry Enabled by in Situ High-Energy X-ray Scattering.

    PubMed

    Liu, Qi; Gao, Min-Rui; Liu, Yuzi; Okasinski, John S; Ren, Yang; Sun, Yugang

    2016-01-13

    The fast reaction kinetics presented in the microwave synthesis of colloidal silver nanoparticles was quantitatively studied, for the first time, by integrating a microwave reactor with in situ X-ray diffraction at a high-energy synchrotron beamline. Comprehensive data analysis reveals two different types of reaction kinetics corresponding to the nucleation and growth of the Ag nanoparticles. The formation of seeds (nucleation) follows typical first-order reaction kinetics with activation energy of 20.34 kJ/mol, while the growth of seeds (growth) follows typical self-catalytic reaction kinetics. Varying the synthesis conditions indicates that the microwave colloidal chemistry is independent of concentration of surfactant. These discoveries reveal that the microwave synthesis of Ag nanoparticles proceeds with reaction kinetics significantly different from the synthesis present in conventional oil bath heating. The in situ X-ray diffraction technique reported in this work is promising to enable further understanding of crystalline nanomaterials formed through microwave synthesis. PMID:26625184

  13. Dynamic kinetic analysis of growth of Listeria monocytogenes in a simulated comminuted, non-cured cooked pork product

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to directly construct a tertiary growth model for Listeria monocytogenes in cooked pork and simultaneously determine the kinetic parameters using a combination of dynamic and isothermal growth curves. Growth studies were conducted using a cocktail of 5 strains of L. ...

  14. Modeling the effect of tides and waves on benthic biofilms

    NASA Astrophysics Data System (ADS)

    Mariotti, G.; Fagherazzi, S.

    2012-12-01

    We propose a simple model for growth of benthic biofilm subject to variable hydrodynamic disturbances and with a biofilm-dependent erodibility (biostabilization). Model results show that, for disturbances with equal intensity, the biofilm is eroded or not depending on its current biomass, which is a function of the past evolution trajectory. Because of the finite time needed for a biofilm to develop, both the intensity and frequency of periodical disturbances, such as tidal currents, determine whether the biofilm can approach its equilibrium biomass. Spring-neap tidal modulation favors biofilm development, since the reduction of the current shear stress associated with neap tides allows biofilm growth, thus increasing biostabilization and the biofilm's likelihood to withstand the subsequent energetic spring tides. On the other hand, diurnal tidal modulations are negative for biofilm development, because the diel biofilm growth is almost negligible. Under stochastic disturbances associated with wind waves, there are two most-likely states for the biofilm biomass: either close to zero or close to the equilibrium value, depending on wave intensity. If biostabilization is reduced or eliminated, the probability of intermediate values for biofilm biomass becomes also significant. The role of biostabilization is hence to exacerbate the probability of the end-member states. Finally, because of the nonmonotonic relationship between water depth and wave induced bed stresses, only extremely shallow and deep areas favor biofilm persistence. If light attenuation with depth is considered, deep water becomes unsuitable for biofilm growth when water turbidity is high.

  15. Diverse Growth Kinetics in Suspension Culture of a Model Eukaryote Dictyostelium discoideum, Confirmation of Lagless Growth

    NASA Astrophysics Data System (ADS)

    Franck, Carl; Zhou, Xaio-Qiao S.; Deshmukh, Amrish; Bogart, Elijah; Lau, Sharon; Daie, Kayvon; Bae, Albert

    2010-03-01

    In recent work we explored the notion that the transition between slow and fast growth, the lag-log transition, with increasing density seen in shaken cell culture represents a collective effect. (Phys. Rev. E 77, 041905 (2008)). We reported preliminary observations in which the lag phase was apparently missing. Here, we present significantly more measurements than in our original work as well as increased sensitivity at low densities. We confirm that instances of nearly exponential (``log'') growth do in fact appear, but more frequently, we find evidence of lagging. The degree of lagging fluctuates significantly from run to run, in contrast to our earlier observations and theory, but in all cases exponential growth is established with increasing density once the range of 10^4 to 10^5 cells/ml is reached. We present evidence against two natural explanations for these fluctuations: 1) a mixture of strains which have different growth phenotypes or 2) a single strain variation due to an epigenetic switch which can be set to the low growth state by subjecting cells to high density environments. The appearance of such growth variations has considerable practical significance and suggests that there is an additional dynamical variable besides density in play.

  16. Simulation studies on shape and growth kinetics for fractal aggregates in aerosol and colloidal systems

    NASA Astrophysics Data System (ADS)

    Heinson, William Raymond

    The aim of this work is to explore, using computational techniques that simulate the motion and subsequent aggregation of particles in aerosol and colloidal systems, many common but not well studied systems that form fractal clusters. Primarily the focus is on cluster shape and growth kinetics. The structure of clusters made under diffusion limited cluster-cluster aggregation (DLCA) is looked at. More specifically, the shape anisotropy is found to have an inverse relationship on the scaling prefactor k0 and have no effect on the fractal dimension Df . An analytical model that predicts the shape and fractal dimension of diffusion limited cluster-cluster aggregates is tested and successfully predicts cluster shape and dimensionality. Growth kinetics of cluster-cluster aggregation in the free molecular regime where the system starts with ballistic motion and then transitions to diffusive motion as the aggregates grow in size is studied. It is shown that the kinetic exponent will crossover from the ballistic to the diffusional values and the onset of this crossover is predicted by when the nearest neighbor Knudsen number reaches unity. Simulations were carried out for a system in which molten particles coalesce into spheres, then cool till coalescing stops and finally the polydispersed monomers stick at point contacts to form fractal clusters. The kinetic exponent and overall cluster structure for these aggregates was found to be in agreement with DLCA that started with monodispersed monomers. Colloidal aggregation in the presence of shear was studied in detail. Study of a colloidal system characterized a by short-range attractive potential showed that weak shear enhanced the aggregation process. Strong shear led to fragmentation and subsequent nucleation as cluster growth rebounded after an induction time.

  17. Implications of solution chemistry effects: Direction-specific restraints on the step kinetics of calcite growth

    NASA Astrophysics Data System (ADS)

    Hong, Mina; Teng, H. Henry

    2014-09-01

    Classical crystallization models successfully depict the dependence of growth kinetics on thermodynamic driving force but cannot predict the roles of solution chemistry. Yet, it has become increasingly clear that crystal growth rate at fixed supersaturations depends on pH, ionic strength, and the relative abundance of cations and anions in the parent solutions. We conducted experiments to isolate the effect of individual solution-chemistry parameters on calcite step growth kinetics. Our results revealed a distinct correlation between step velocity and pH in acute and obtuse directions and a simultaneous trend change at pH ∼9.5. Step speeds varied with solution stoichiometry, and each direction reached its maximal rate at a different [Ca]/[CO32-] value. In addition, the solution cation/anion at which maximal step speed occurred appeared to be pH dependent as well. Limited effect of ionic strength on step growth was observed in the obtuse direction at low background electrolyte concentrations, but no obvious change was found for growth at the acute side. We proposed a growth model based upon independent incorporation of cations and anions and interpreted these observations as: (1) solute constituents enter kinks through direct solution diffusion at obtuse steps but surface diffusion at acute steps; (2) growth is limited by Ca2+ dehydration at the obtuse side, but by surface adsorption and reorientation and rearrangement of CO32- in the acute direction; and (3) background electrolyte (NaCl in our study) competes with solutes for surface sites at more easily accessible kinks.

  18. Experimental evolution in biofilm populations

    PubMed Central

    Steenackers, Hans P.; Parijs, Ilse; Foster, Kevin R.; Vanderleyden, Jozef

    2016-01-01

    Biofilms are a major form of microbial life in which cells form dense surface associated communities that can persist for many generations. The long-life of biofilm communities means that they can be strongly shaped by evolutionary processes. Here, we review the experimental study of evolution in biofilm communities. We first provide an overview of the different experimental models used to study biofilm evolution and their associated advantages and disadvantages. We then illustrate the vast amount of diversification observed during biofilm evolution, and we discuss (i) potential ecological and evolutionary processes behind the observed diversification, (ii) recent insights into the genetics of adaptive diversification, (iii) the striking degree of parallelism between evolution experiments and real-life biofilms and (iv) potential consequences of diversification. In the second part, we discuss the insights provided by evolution experiments in how biofilm growth and structure can promote cooperative phenotypes. Overall, our analysis points to an important role of biofilm diversification and cooperation in bacterial survival and productivity. Deeper understanding of both processes is of key importance to design improved antimicrobial strategies and diagnostic techniques. PMID:26895713

  19. Experimental evolution in biofilm populations.

    PubMed

    Steenackers, Hans P; Parijs, Ilse; Foster, Kevin R; Vanderleyden, Jozef

    2016-05-01

    Biofilms are a major form of microbial life in which cells form dense surface associated communities that can persist for many generations. The long-life of biofilm communities means that they can be strongly shaped by evolutionary processes. Here, we review the experimental study of evolution in biofilm communities. We first provide an overview of the different experimental models used to study biofilm evolution and their associated advantages and disadvantages. We then illustrate the vast amount of diversification observed during biofilm evolution, and we discuss (i) potential ecological and evolutionary processes behind the observed diversification, (ii) recent insights into the genetics of adaptive diversification, (iii) the striking degree of parallelism between evolution experiments and real-life biofilms and (iv) potential consequences of diversification. In the second part, we discuss the insights provided by evolution experiments in how biofilm growth and structure can promote cooperative phenotypes. Overall, our analysis points to an important role of biofilm diversification and cooperation in bacterial survival and productivity. Deeper understanding of both processes is of key importance to design improved antimicrobial strategies and diagnostic techniques. PMID:26895713

  20. Kinetics of grain growth in the weld heat-affected zone of Alloy 718

    SciTech Connect

    Radhakrishnan, B.; Thompson, R.G.

    1993-12-01

    Grain-boundary liquation occurs in the weld heat-affected zone (HAZ) of the Ni-base superalloy 718 at locations where the peak temperatures are greater than about 1,200 C. The evolution of the grain structure at the HAZ locations depends upon the interaction between the grains and the grain-boundary liquid. The evolution of grain structure in the presence of grain-boundary liquid was simulated by subjecting samples to controlled thermal cycles using resistance heating. A measurement of grain size as a function of isothermal hold at two peak temperatures of 1,200 C and 1,227 C indicated that in alloy 718, the kinetics of grain growth depended upon the prior thermal history of the alloy. In the solution-treated alloy, the presence of grain-boundary liquid did not arrest grain growth at either peak temperature. In the homogenized and aged alloy, a grain refinement was observed at the peak temperature of 1,227 C, while an arrest of grain growth was observed at a peak temperature of 1,200 C. Liquid film migration (LFM) and subgrain coalescence, either acting alone or simultaneously, are shown to explain most of the observed microstructural phenomena and the kinetics of grain growth in the alloy.

  1. Kinetics of grain growth in the weld heat-affected zone of alloy 718

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, B.; Thompson, R. G.

    1993-12-01

    Grain-boundary liquation occurs in the weld heat-affected zone (HAZ) of the Ni-base superalloy 718 at locations where the peak temperatures are greater than about 1200 ‡C. The evolution of the grain structure at these HAZ locations depends upon the interaction between the grains and the grain-boundary liquid. The evolution of grain structure in the presence of grain-boundary liquid was simulated by subjecting samples to controlled thermal cycles using resistance heating. A measurement of grain size as a function of isothermal hold at two peak temperatures of 1200 ‡C and 1227 ‡C indicated that in alloy 718, the kinetics of grain growth depended upon the prior thermal history of the alloy. In the solution-treated alloy, the presence of grain-boundary liquid did not arrest grain growth at either peak temperature. In the homogenized and aged alloy, a grain refinement was observed at the peak temperature of 1227 ‡C, while an arrest of grain growth was observed at a peak temperature of 1200‡C. Liquid film migration (LFM) and subgrain coalescence, either acting alone or simultaneously, are shown to explain most of the observed microstructural phenomena and the kinetics of grain growth in the alloy.

  2. From atoms to layers: in situ gold cluster growth kinetics during sputter deposition

    NASA Astrophysics Data System (ADS)

    Schwartzkopf, Matthias; Buffet, Adeline; Körstgens, Volker; Metwalli, Ezzeldin; Schlage, Kai; Benecke, Gunthard; Perlich, Jan; Rawolle, Monika; Rothkirch, André; Heidmann, Berit; Herzog, Gerd; Müller-Buschbaum, Peter; Röhlsberger, Ralf; Gehrke, Rainer; Stribeck, Norbert; Roth, Stephan V.

    2013-05-01

    The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction of morphological real space parameters, such as cluster size and shape, correlation distance, layer porosity and surface coverage, directly from reciprocal space scattering data. This approach enables a large variety of future investigations of the influence of different process parameters on the thin metal film morphology. Furthermore, our study allows for deducing the wetting behavior of gold cluster films on solid substrates and provides a better understanding of the growth kinetics in general, which is essential for optimization of manufacturing parameters, saving energy and resources.The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction

  3. Evaluation of a kinetic model for computer simulation of growth and fermentation by Scheffersomyces (Pichia) stipitis fed D-xylose

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Scheffersomyces (formly Pichia) stipitis is a potential biocatalyst for converting lignocelluloses to ethanol because the yeast natively ferments xylose. An unstructured kinetic model based upon a system of linear differential equations has been formulated that describes growth and ethanol productio...

  4. Crystal growth kinetics in Lennard-Jones and Weeks-Chandler-Andersen systems along the solid-liquid coexistence line

    NASA Astrophysics Data System (ADS)

    Benjamin, Ronald; Horbach, Jürgen

    2015-07-01

    Kinetics of crystal-growth is investigated along the solid-liquid coexistence line for the (100), (110), and (111) orientations of the Lennard-Jones (LJ) and Weeks-Chandler-Andersen (WCA) fcc crystal-liquid interface, using non-equilibrium molecular dynamics simulations. A slowing down of the growth kinetics along the coexistence line is observed, which is due to the decrease of the melting enthalpy with increasing coexistence temperature and pressure. Other quantities such as the melting pressure and liquid self-diffusion coefficient have a comparatively lesser impact on the kinetic growth coefficient. Growth kinetics of the LJ and WCA potentials become similar at large values of the melting temperature and pressure, when both resemble a purely repulsive soft-sphere potential. Classical models of crystallization from the melt are in reasonable qualitative agreement with our simulation data. Finally, several one-phase empirical melting/freezing rules are studied with respect to their validity along the coexistence line.

  5. Control of Electron Beam-Induced Au Nanocrystal Growth Kinetics through Solution Chemistry.

    PubMed

    Park, Jeung Hun; Schneider, Nicholas M; Grogan, Joseph M; Reuter, Mark C; Bau, Haim H; Kodambaka, Suneel; Ross, Frances M

    2015-08-12

    Measurements of solution-phase crystal growth provide mechanistic information that is helpful in designing and synthesizing nanostructures. Here, we examine the model system of individual Au nanocrystal formation within a defined liquid geometry during electron beam irradiation of gold chloride solution, where radiolytically formed hydrated electrons reduce Au ions to solid Au. By selecting conditions that favor the growth of well-faceted Au nanoprisms, we measure growth rates of individual crystals. The volume of each crystal increases linearly with irradiation time at a rate unaffected by its shape or proximity to neighboring crystals, implying a growth process that is controlled by the arrival of atoms from solution. Furthermore, growth requires a threshold dose rate, suggesting competition between reduction and oxidation processes in the solution. Above this threshold, the growth rate follows a power law with dose rate. To explain the observed dose rate dependence, we demonstrate that a reaction-diffusion model is required that explicitly accounts for the species H(+) and Cl(-). The model highlights the necessity of considering all species present when interpreting kinetic data obtained from beam-induced processes, and suggest conditions under which growth rates can be controlled with higher precision. PMID:26207841

  6. Domain growth kinetics in the isosceles triangular Ising antiferromagnet CoNb2O6

    NASA Astrophysics Data System (ADS)

    Kobayashi, S.; Okano, H.; Jogetsu, T.; Miyamoto, J.; Mitsuda, S.

    2004-04-01

    We have studied the domain-growth kinetics of fourfold-degenerate antiferromagnetic (AF) and threefold-degenerate ferrimagnetic states in the isosceles triangular Ising antiferromagnet CoNb2O6 by ac susceptibility measurements and Monte Carlo simulations. In both magnetic phases ac susceptibility after the field quench is found to decrease with time according to the power-growth law with an universal growth exponent n=0.21±0.01. The prefactor in the power-growth law suggests that the zero-field growth of the AF state is strongly suppressed by the application of magnetic fields along the direction perpendicular to the frustrated isosceles-triangular lattice. Monte Carlo results show the unusual domain growth dominated by the reversal of the free magnetic spins near favorable domain walls where the exchange field is effectively canceled out due to the isosceles triangular geometry of spins. The obtained domain configuration strongly supports our neutron-diffraction results that revealed the temporal shift of the magnetic Bragg peak position during the growth.

  7. Antifreeze effect of carboxylated ε-poly-L-lysine on the growth kinetics of ice crystals.

    PubMed

    Vorontsov, Dmitry A; Sazaki, Gen; Hyon, Suong-Hyu; Matsumura, Kazuaki; Furukawa, Yoshinori

    2014-08-28

    Some biological substances control the nucleation and growth of inorganic crystals. Antifreeze proteins, which prohibit ice crystal growth in living organisms, promise are also important as biological antifreezes for medical applications and in the frozen food industries. In this work, we investigated the crystallization of ice in the presence of a new cryoprotector, carboxylated ε-poly-L-lysine (COOH-PLL). In order to reveal the characteristics and the mechanism of its antifreeze effect, free-growth experiments of ice crystals were carried out in solutions with various COOH-PLL concentrations and degrees of supercooling, and the depression of the freezing point and growth rates of the tips of ice dendrites were obtained using optical microscopy. Hysteresis of growth rates and depression of the freezing point was revealed in the presence of COOH-PLL. The growth-inhibition effect of COOH-PLL molecules could be explained on the basis of the Gibbs-Thomson law and the use of Langmuir's adsorption isotherm. Theoretical kinetic curves for hysteresis calculated on the basis of Punin-Artamonova's model were in good agreement with experimental data. We conclude that adsorption of large biological molecules in the case of ice crystallization has a non-steady-state character and occurs more slowly than the process of embedding of crystal growth units. PMID:25113284

  8. Growth Kinetics and Transmission Potential of Existing and Emerging Field Strains of Infectious Laryngotracheitis Virus

    PubMed Central

    Coppo, Mauricio J. C.; Vaz, Paola K.; Legione, Alistair R.; Quinteros, José A.; Noormohammadi, Amir H.; Markham, Phillip F.; Browning, Glenn F.; Devlin, Joanne M.

    2015-01-01

    Attenuated live infectious laryngotracheitis virus (ILTV) vaccines are widely used in the poultry industry to control outbreaks of disease. Natural recombination between commercial ILTV vaccines has resulted in virulent recombinant viruses that cause severe disease, and that have now emerged as the dominant field strains in important poultry producing regions in Australia. Genotype analysis using PCR—restriction fragment length polymorphism has shown one recombinant virus (class 9) has largely replaced the previously dominant class 2 field strain. To examine potential reasons for this displacement we compared the growth kinetics and transmission potential of class 2 and class 9 viruses. The class 9 ILTV grew to higher titres in cell culture and embryonated eggs, but no differences were observed in entry kinetics or egress into the allantoic fluid from the chorioallantoic membrane. In vivo studies showed that birds inoculated with class 9 ILTV had more severe tracheal pathology and greater weight loss than those inoculated with the class 2 virus. Consistent with the predominance of class 9 field strains, birds inoculated with 102 or 103 plaque forming units of class 9 ILTV consistently transmitted virus to in-contact birds, whereas this could only be seen in birds inoculated with 104 PFU of the class 2 virus. Taken together, the improved growth kinetics and transmission potential of the class 9 virus is consistent with improved fitness of the recombinant virus over the previously dominant field strain. PMID:25785629

  9. Growth kinetics and transmission potential of existing and emerging field strains of infectious laryngotracheitis virus.

    PubMed

    Lee, Sang-Won; Hartley, Carol A; Coppo, Mauricio J C; Vaz, Paola K; Legione, Alistair R; Quinteros, José A; Noormohammadi, Amir H; Markham, Phillip F; Browning, Glenn F; Devlin, Joanne M

    2015-01-01

    Attenuated live infectious laryngotracheitis virus (ILTV) vaccines are widely used in the poultry industry to control outbreaks of disease. Natural recombination between commercial ILTV vaccines has resulted in virulent recombinant viruses that cause severe disease, and that have now emerged as the dominant field strains in important poultry producing regions in Australia. Genotype analysis using PCR-restriction fragment length polymorphism has shown one recombinant virus (class 9) has largely replaced the previously dominant class 2 field strain. To examine potential reasons for this displacement we compared the growth kinetics and transmission potential of class 2 and class 9 viruses. The class 9 ILTV grew to higher titres in cell culture and embryonated eggs, but no differences were observed in entry kinetics or egress into the allantoic fluid from the chorioallantoic membrane. In vivo studies showed that birds inoculated with class 9 ILTV had more severe tracheal pathology and greater weight loss than those inoculated with the class 2 virus. Consistent with the predominance of class 9 field strains, birds inoculated with 10(2) or 10(3) plaque forming units of class 9 ILTV consistently transmitted virus to in-contact birds, whereas this could only be seen in birds inoculated with 10(4) PFU of the class 2 virus. Taken together, the improved growth kinetics and transmission potential of the class 9 virus is consistent with improved fitness of the recombinant virus over the previously dominant field strain. PMID:25785629

  10. Kinetics of substrate utilization and bacterial growth of crude oil degraded by Pseudomonas aeruginosa.

    PubMed

    Talaiekhozani, Amirreza; Jafarzadeh, Nematollah; Fulazzaky, Mohamad Ali; Talaie, Mohammad Reza; Beheshti, Masoud

    2015-01-01

    Pollution associated with crude oil (CO) extraction degrades the quality of waters, threatens drinking water sources and may ham air quality. The systems biology approach aims at learning the kinetics of substrate utilization and bacterial growth for a biological process for which very limited knowledge is available. This study uses the Pseudomonas aeruginosa to degrade CO and determines the kinetic parameters of substrate utilization and bacterial growth modeled from a completely mixed batch reactor. The ability of Pseudomonas aeruginosa can remove 91 % of the total petroleum hydrocarbons and 83 % of the aromatic compounds from oily environment. The value k of 9.31 g of substrate g(-1) of microorganism d(-1) could be far higher than the value k obtained for petrochemical wastewater treatment and that for municipal wastewater treatment. The production of new cells of using CO as the sole carbon and energy source can exceed 2(3) of the existing cells per day. The kinetic parameters are verified to contribute to improving the biological removal of CO from oily environment. PMID:26413306

  11. Bacillus cereus ATCC 14579 RpoN (Sigma 54) Is a Pleiotropic Regulator of Growth, Carbohydrate Metabolism, Motility, Biofilm Formation and Toxin Production

    PubMed Central

    Hayrapetyan, Hasmik; Tempelaars, Marcel; Nierop Groot, Masja; Abee, Tjakko

    2015-01-01

    Sigma 54 is a transcriptional regulator predicted to play a role in physical interaction of bacteria with their environment, including virulence and biofilm formation. In order to study the role of Sigma 54 in Bacillus cereus, a comparative transcriptome and phenotypic study was performed using B. cereus ATCC 14579 WT, a markerless rpoN deletion mutant, and its complemented strain. The mutant was impaired in many different cellular functions including low temperature and anaerobic growth, carbohydrate metabolism, sporulation and toxin production. Additionally, the mutant showed lack of motility and biofilm formation at air-liquid interphase, and this correlated with absence of flagella, as flagella staining showed only WT and complemented strain to be highly flagellated. Comparative transcriptome analysis of cells harvested at selected time points during growth in aerated and static conditions in BHI revealed large differences in gene expression associated with loss of phenotypes, including significant down regulation of genes in the mutant encoding enzymes involved in degradation of branched chain amino acids, carbohydrate transport and metabolism, flagella synthesis and virulence factors. Our study provides evidence for a pleiotropic role of Sigma 54 in B. cereus supporting its adaptive response and survival in a range of conditions and environments. PMID:26241851

  12. Kinetic Analysis of Spontaneous Whisker Growth on Pre-treated Surfaces with Weak Oxide

    NASA Astrophysics Data System (ADS)

    Su, Chien-Hao; Chen, Hao; Lee, Hsin-Yi; Liu, Cheng Yi; Ku, Ching-Shun; Wu, Albert T.

    2014-09-01

    This study sought to clarify the relationship between cracks in surface oxide layers and the growth behavior of tin whiskers. The number, length, and total volume of extrusions were precisely calculated and residual stress was measured using synchrotron radiation x-ray diffractometry. The aim was to elucidate the influence of stress on the driving force and flux involved in atomic diffusion. The distance between weak spots was shown to be the most significant factor involved in the growth of whiskers. The results could explain why increasing the density of the surface weak spots could reduce the number of long whiskers. Measuring the dimensions of whiskers yielded a precise kinetic model capable of describing the migration of atoms to the root of whiskers, resulting in their spontaneous growth.

  13. Kinetics of crystal nucleation and growth in Pd(40)Ni(40)P(20) glass

    NASA Technical Reports Server (NTRS)

    Drehman, A. J.; Greer, A. L.

    1984-01-01

    Samples of Pd(40)Ni(40)P(20) glass, produced by cooling the melt at 1 or 800 K/s, are heated in a differential scanning calorimeter to determine the crystallization kinetics. Optical microscopy shows that eutectic crystallization proceeds both by growth from the surface of the samples and by the growth of spherical regions around preexisting nuclei in the interior. A modified Kissinger (1957) analysis is used to obtain the activation energy for crystal growth (3.49 eV). The steady state homogeneous nucleation frequency at 590 K is about 10 million/cu m per sec. This is estimated to be the maximum nucleation frequency: it is too low to account for the observed population of quenched-in nuclei, which are therefore presumed to be heterogeneous. The major practical obstacle to glass formation in this system is heterogeneous nucleation.

  14. Impact of sustaining a controlled residual growth on polyhydroxybutyrate yield and production kinetics in Cupriavidus necator.

    PubMed

    Grousseau, Estelle; Blanchet, Elise; Déléris, Stéphane; Albuquerque, Maria G E; Paul, Etienne; Uribelarrea, Jean-Louis

    2013-11-01

    In this study a complementary modeling and experimental approach was used to explore how growth controls the NADPH generation and availability, and the resulting impact on PHB (polyhydroxybutyrate) yields and kinetics. The results show that the anabolic demand allowed the NADPH production through the Entner-Doudoroff (ED) pathway, leading to a high maximal theoretical PHB production yield of 0.89 C mole C mole(-1); whereas without biomass production, NADPH regeneration is only possible via the isocitrate dehydrogenase leading to a theoretical yield of 0.67 C mole C mole(-1). Furthermore, the maximum specific rate of NADPH produced at maximal growth rate (to fulfil biomass requirement) was found to be the maximum set in every conditions, which by consequence determines the maximal PHB production rate. These results imply that sustaining a controlled residual growth improves the PHB specific production rate without altering production yield. PMID:24035890

  15. Effects of substrate crystallinity and dopant on the growth kinetics of platinum silicides

    NASA Astrophysics Data System (ADS)

    Takai, H.; Psaras, P. A.; Tu, K. N.

    1985-12-01

    The growth kinetics of platinum silicides have been studied on four substrate categories: single-crystal, amorphous, undoped polycrystalline, and phosphorus-doped (8×1020 at./cm3) polycrystalline silicon. The sequential growth of Pt2Si and PtSi were analyzed by Rutherford backscattering spectroscopy (RBS), Seeman-Bohlin x-ray diffraction, and cross-section transmission electron microscopy. Phosphorus depth profiles were measured by secondary ion mass spectroscopy (SIMS). Our results conclude that the activation energies for the growth of Pt2Si and PtSi are not affected by substrate crystallinity and doping of phosphorus. Analysis of the phosphorus profile by SIMS clearly showed that phosphorus atoms are segregated near the interface between PtSi and polycrystalline silicon, but not at the Pt2Si/polycrystalline silicon interface.

  16. Growth of Ni2Si by rapid thermal annealing: Kinetics and moving species

    NASA Astrophysics Data System (ADS)

    Ma, E.; Lim, B. S.; Nicolet, M.-A.; Natan, M.

    1987-10-01

    The growth kinetics is characterized and the moving species is identified for the formation of Ni2Si by Rapid Thermal Annealing (RTA) of sequentially deposited Si and Ni films on a <100> Si substrate. The interfacial Ni2Si layer grows as the square root of time, indicating that the suicide growth process is diffusion-limited. The activation energy is 1.25±0.2 eV in the RTA temperature range of 350 450° C. The results extend those of conventional steady-state furnace annealing quite fittingly, and a common activation energy of 1.3±0.2 eV is deduced from 225° to 450° C. The marker experiment shows that Ni is the dominant moving species during Ni2Si formation by RTA, as is the case for furnace annealing. It is concluded that the two annealing techniques induce the same growth mechanisms in Ni2Si formation.

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

    PubMed Central

    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

  18. Kinetically Controlled Sequential Growth of Surface-Grafted Chiral Supramolecular Copolymers.

    PubMed

    Frisch, Hendrik; Fritz, Eva-Corinna; Stricker, Friedrich; Schmüser, Lars; Spitzer, Daniel; Weidner, Tobias; Ravoo, Bart Jan; Besenius, Pol

    2016-06-13

    We report a facile strategy to grow supramolecular copolymers on Au surfaces by successively exposing a surface-anchored monomer to solutions of oppositely charged peptide comonomers. Charge regulation on the active chain end of the polymer sufficiently slows down the kinetics of the self-assembly process to produce kinetically trapped copolymers at near-neutral pH. We thereby achieve architectural control at three levels: The β-sheet sequences direct the polymerization away from the surface, the height of the supramolecular copolymer brushes is well-controlled by the stepwise nature of the alternating copolymer growth, and 2D spatial resolution is realized by using micropatterned initiating monomers. The programmable nature of the resulting architectures renders this concept attractive for the development of customized biomaterials or chiral interfaces for optoelectronics and sensor applications. PMID:26989886

  19. Nonlinear kinetic description of Raman growth using an envelope code, and comparisons with Vlasov simulations

    NASA Astrophysics Data System (ADS)

    Bénisti, Didier; Morice, Olivier; Gremillet, Laurent; Siminos, Evangelos; Strozzi, David J.

    2010-10-01

    In this paper, we present our nonlinear kinetic modeling of stimulated Raman scattering in a uniform and collisionless plasma using envelope equations. We recall the derivation of these equations, as well as our theoretical predictions for each of the nonlinear kinetic terms, the precision of which having been carefully checked against Vlasov simulations. We particularly focus here on the numerical resolution of these equations, which requires the additional concept of "self-optimization" that we explain, and we describe the envelope code BRAMA that we used. As an application of our modeling, we present one-dimensional BRAMA simulations of stimulated Raman scattering which predict threshold intensities, as well as time scales for Raman growth above threshold, in very good agreement with those inferred from Vlasov simulations. Finally, we discuss the differences between our modeling and other published ones.

  20. Growth kinetics of CVD TiO sub 2; Influence of carrier gas

    SciTech Connect

    Siefering, K.L.; Griffin, G.L. )

    1990-04-01

    This paper reports on the growth rate of TiO{sub 2} thin films deposited by the decomposition of titanium tetraisopropoxide (TTIP) in the presence of N{sub 2} carrier gas. Experiments are performed at TTIP partial pressures between 0.005 and 0.7 torr and a substrate temperature of 573 K, conditions where second-order kinetics have previously been observed in the presence of TTIP alone. When 5 torr of N{sub 2} is present as a carrier gas, the kinetics become first order in TTIP concentration. By fitting the observed rates to the rate expression for the bimolecular reaction mechanism proposed in the earlier study, the authors obtain a value of {phi} = 0.43 for the relative efficiency of N{sub 2} for collisional energy transfer, compared to TTIP.

  1. Effects of spill-treating agents on growth kinetics of marine microalgae.

    PubMed

    Rial, Diego; Murado, Miguel A; Menduiña, Araceli; Fuciños, Pablo; González, Pilar; Mirón, Jesús; Vázquez, José A

    2013-12-15

    The effects of four spill-treating agents (STAs) (CytoSol, Finasol(®) OSR 51, Agma OSD 569 and OD4000) on the growth kinetics of three marine microalgae (Isochrysis galbana, Chaetoceros gracilis, Phaeodactylum tricornutum) were studied. Chlorophyll a concentration and optical density at 700 nm were assessed to describe the logistic growth of algae in batch cultures. The optical density data were initially analyzed as described for standard algal growth inhibition tests and subsequently modelled by a bivariate model, as a function of time and dose, to assess the toxic effects on growth parameters. Increasing trends in EC50 and EC10 values with time were found with the standard approach. In 8 of the 11 tests, the lag phase (λ) or the time required to achieve half the maximum biomass (τ) was significantly dependent on the STA concentration. A global parameter (EC50,τ) was calculated to summarize the effects of STAs on growth parameters in the bivariate model. The ranking of sensitivity as EC50,τ values was I. galbana>C. gracilis>P. tricornutum. For all species tested, the least toxic agent was Agma OSD 569, followed by CytoSol. The mathematical model allowed successful ecotoxicological evaluation of chemicals on microalgal growth. PMID:23911058

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

    PubMed

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

    2014-03-01

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

  3. Step-flow kinetics model for the vapor-solid-solid Si nanowires growth.

    PubMed

    Cui, H; Lü, Y Y; Yang, G W; Chen, Y M; Wang, C X

    2015-05-13

    Vapor-solid-solid (VSS) process has recently received continued attention as an alternative to grow Si nanowire. In comparison with common vapor-liquid-solid (VLS) growth with liquid catalyst, VSS growth can prevent the catalyst species from incorporating into nanowires with deep-level impurity, and achieve the compositionally abrupt interfaces by restraining the so-called "reservoir effect". However, despite the huge advances in experimental observations with in situ electron microscopy, VSS growth still remains much less understood in theory. Here, we developed a general mass-transport-limited kinetic model to describe the VSS growth process of Si nanowires by considering three surface diffusion processes and a slow interface diffusion process, where the former determines the atoms supplies way, while the latter dominates the growth of nanowires. The present model is not only well consistent with the available experimental data of Si nanowire, but also gives a clear physical image for the successive side-to-side ledge flow VSS growth. PMID:25928836

  4. Growth kinetics of physical vapor transport processes: Crystal growth of the optoelectronic material mercurous chloride

    NASA Technical Reports Server (NTRS)

    Singh, N. B.; Duval, W. M.

    1991-01-01

    Physical vapor transport processes were studied for the purpose of identifying the magnitude of convective effects on the crystal growth process. The effects of convection on crystal quality were were studied by varying the aspect ratio and those thermal conditions which ultimately affect thermal convection during physical vapor transport. An important outcome of the present study was the observation that the convection growth rate increased up to a certain value and then dropped to a constant value for high aspect ratios. This indicated that a very complex transport had occurred which could not be explained by linear stability theory. Better quality crystals grown at a low Rayleigh number confirmed that improved properties are possible in convectionless environments.

  5. The Powder-Pack Nitriding Process: Growth Kinetics of Nitride Layers on Pure Iron

    NASA Astrophysics Data System (ADS)

    Campos-Silva, I.; Ortiz-Dominguez, M.; Elias-Espinosa, M.; Vega-Morón, R. C.; Bravo-Bárcenas, D.; Figueroa-López, U.

    2015-09-01

    In this study, the growth kinetics of nitride layers that develop during the powder-pack nitriding process on the surface of ARMCO pure iron was estimated. The powder-pack nitriding of pure iron was performed according to the Pulnieren© (H.E.F. Durferrit) method using a "Pulnier" powder and an activator, at 798-848 K with different exposure times (2-12 h) for each temperature. In addition, for the entire set of nitriding conditions, three different activator/"Pulnier" powder ratios (0.20, 0.25, and 0.35) were used to evaluate the activation level during the growth of nitride layers. The kinetics of the nitride layers over the surface of ARMCO pure iron were estimated by two mathematical approaches, that consider the mass balance equations at the growth interphases. The resulting expressions for the effective diffusion coefficients in the nitride layers were evaluated as a function of nitriding temperatures and activator/"Pulnier" powder ratio. Finally, based on the experimental parameters ascribed to the powder-pack nitriding process, two expressions were proposed to estimate the nitride layer thicknesses at 798 and 823 K after 9 h of exposure for each temperature, to validate the diffusion models used in this work.

  6. [Growth kinetics and phenol degradation of highly efficient phenol-degrading Ochrobactrum sp. CH10].

    PubMed

    Chen, Xiao-Hua; Wei, Gang; Liu, Si-Yuan; Sun, Jiang-Man; Wang, Fang-Fang; Li, Hao-Yuan; Liu, Yu-Jun

    2012-11-01

    The strain Ochrobactrum sp. CH10 was a highly efficient phenol degrading bacterial strain isolated from soil in a constructed wetland in Yuan Dynasty Capital City Wall Relics in Beijing. Growth and biodegradation were investigated in details with phenol as the sole carbon and energy source. The best growth and most efficient phenol biodegradation occurred when the strain was cultured in medium containing 400 mg x L(-1) phenol at initial pH of 7.0 and 30 degrees C, with 5% inoculation volume. The phenol degradation rate was around 100% , 92.3 and 82.2% with an initial concentration of 400, 900 and 1 000 mg x L(-1) phenol in 24, 44 and 48 h, respectively. Phenol degradation kinetic studies indicated that the strain followed Haldane's model, and the parameters were: upsilon(max) (maximum specific rate) = 0.126 h(-1), K(s) (half-saturation constant) = 23.53 mg x L(-1) and K(I) (inhibition constant) = 806.1 mg x L(-1). The phenol-limited growth kinetics of CH10 by Andrews's model also followed a similar trend to that of phenol degradation. Among all the strains belonging to Ochrobactrum genus, this strain is the most efficient at present. The strain has a good application potential for the phenolic wastewater treatment. PMID:23323431

  7. The effect of Co alloying content on the kinetics of reaction zone growth in tungsten fiber reinforced superalloy composites

    NASA Technical Reports Server (NTRS)

    Rodriguez, A.; Tien, J. K.; Caulfield, T.; Petrasek, D. W.

    1988-01-01

    A Co-free modified superalloy similar in composition to Waspaloy is investigated in an effort to understand the effect of Co on reaction zone growth kinetics and verify the chemistry dependence of reaction zone growth in the matrix of tungsten fiber reinforced superalloy composites. The values of the parabolic rate constant, characterizing the kinetics of reaction zone growth, for the Waspaloy matrix and the C-free alloy as well as five other alloys from a previous study confirm the dependence of reaction zone growth kinetics on cobalt content of the matrix. The Co-free alloy composite exhibits the slowest reaction zone growth among all tungsten fiber reinforced composites studied to date.

  8. Influence of flow velocity on biofilm growth in a tubular heat exchanger-condenser cooled by seawater.

    PubMed

    Trueba, Alfredo; García, Sergio; Otero, Félix M; Vega, Luis M; Madariaga, Ernesto

    2015-01-01

    The influence of flow velocity (FV) on the heat transfer process in tubes made from AISI 316L stainless steel in a heat exchanger-condenser cooled by seawater was evaluated based on the characteristics of the resulting biofilm that adhered to the internal surface of the tubes at velocities of 1, 1.2, 1.6, and 3 m s(-1). The results demonstrated that at a higher FV, despite being more compact and consistent, the biofilm was thinner with a lower concentration of solids, and smoother, which favoured the heat transfer process within the equipment. However, higher velocities increase the initial cost of the refrigerating water-pumping equipment and its energy consumption cost to compensate for the greater pressure drops produced in the tube. The velocity of 1.6 m s(-1) represented the equilibrium between the advantages and disadvantages of the variables analysed for the test conditions in this study. PMID:26222187

  9. Polymorph-specific kinetics and thermodynamics of β-amyloid fibril growth

    PubMed Central

    Qiang, Wei; Kelley, Kevin; Tycko, Robert

    2013-01-01

    Amyloid fibrils formed by the 40-residue β-amyloid peptide (Aβ1–40) are highly polymorphic, with molecular structures that depend on the details of growth conditions. Underlying differences in physical properties are not well understood. Here, we investigate differences in growth kinetics and thermodynamic stabilities of two Aβ1–40 fibril polymorphs for which detailed structural models are available from solid state nuclear magnetic resonance (NMR) studies. Rates of seeded fibril elongation in the presence of excess soluble Aβ1–40 and shrinkage in the absence of soluble Aβ1–40 are determined with atomic force microscopy (AFM). From these rates, we derive polymorph-specific values for the soluble Aβ1–40 concentration at quasi-equilibrium, from which relative stabilities can be derived. The AFM results are supported by direct measurements by ultraviolet absorbance, using a novel dialysis system to establish quasi-equilibrium. At 24° C, the two polymorphs have significantly different elongation and shrinkage kinetics but similar thermodynamic stabilities. At 37° C, differences in kinetics are reduced, and thermodynamic stabilities are increased significantly. Fibril length distributions in AFM images provide support for an intermittent growth model, in which fibrils switch randomly between an "on" state (capable of elongation) and an "off" state (incapable of elongation). We also monitor interconversion between polymorphs at 24° C by solid state NMR, showing that the two-fold symmetric "agitated" () polymorph is more stable than the three-fold symmetric "quiescent" polymorph. Finally, we show that the two polymorphs have significantly different rates of fragmentation in the presence of shear forces, a difference that helps explain the observed predominance of the structure when fibrils are grown in agitated solutions. PMID:23627695

  10. Kinetics of phase growth in Nb3Sn formation for heat treatment optimization

    SciTech Connect

    Emanuela Barzi; Sara Mattafirri

    2002-10-25

    The kinetics of growth and superconducting properties of Nb{sub 3}Sn are investigated as a function of the heat treatment (HT) duration and temperature for Internal Tin and Powder-in-Tube strands at 650, 700 and 750 C. For all times and temperatures, the Nb{sub 3}Sn layer thickness is measured, the critical current at 4.2 K is tested as a function of magnetic field, and the upper critical field is evaluated. Results of the layer critical current density are also shown as a function of HT duration and temperature.

  11. Evidence of enzymatic catalysis of oxygen reduction on stainless steels under marine biofilm.

    PubMed

    Faimali, Marco; Benedetti, Alessandro; Pavanello, Giovanni; Chelossi, Elisabetta; Wrubl, Federico; Mollica, Alfonso

    2011-04-01

    Cathodic current trends on stainless steel samples with different surface percentages covered by biofilm and potentiostatically polarized in natural seawater were studied under oxygen concentration changes, temperature increases, and additions of enzymic inhibitors to the solution. The results showed that on each surface fraction covered by biofilm the oxygen reduction kinetics resembled a reaction catalyzed by an immobilised enzyme with high oxygen affinity (apparent Michaelis-Menten dissociation constant close to K(O(2))(M)  ≈ 10 μM) and low activation energy (W ≈ 20 KJ mole(-1)). The proposed enzyme rapidly degraded when the temperature was increased above the ambient (half-life time of ∼1 day at 25°C, and of a few minutes at 50°C). Furthermore, when reversible enzymic inhibitors (eg sodium azide and cyanide) were added, the cathodic current induced by biofilm growth was inhibited. PMID:21526439

  12. Innovative Strategies to Overcome Biofilm Resistance

    PubMed Central

    Taraszkiewicz, Aleksandra; Fila, Grzegorz; Grinholc, Mariusz; Nakonieczna, Joanna

    2013-01-01

    We review the recent literature concerning the efficiency of antimicrobial photodynamic inactivation toward various microbial species in planktonic and biofilm cultures. The review is mainly focused on biofilm-growing microrganisms because this form of growth poses a threat to chronically infected or immunocompromised patients and is difficult to eradicate from medical devices. We discuss the biofilm formation process and mechanisms of its increased resistance to various antimicrobials. We present, based on data in the literature, strategies for overcoming the problem of biofilm resistance. Factors that have potential for use in increasing the efficiency of the killing of biofilm-forming bacteria include plant extracts, enzymes that disturb the biofilm structure, and other nonenzymatic molecules. We propose combining antimicrobial photodynamic therapy with various antimicrobial and antibiofilm approaches to obtain a synergistic effect to permit efficient microbial growth control at low photosensitizer doses. PMID:23509680

  13. Comparison of the growth kinetics and proteolytic activities of Chryseobacterium species and Pseudomonas fluorescens.

    PubMed

    Bekker, A; Steyn, L; Charimba, G; Jooste, P; Hugo, C

    2015-12-01

    The effect of temperature on the growth kinetics and proteolytic activity of Chryseobacterium joostei and Chryseobacterium bovis was determined during this study. The results were compared with the activities of Pseudomonas fluorescens, which is regarded to be a major food spoilage psychrotolerant microorganism. For the growth studies, cultures were incubated in nutrient broth in a temperature gradient incubator (from 9 to 50 °C) and separately at 4 °C, and the optical density was measured at different time intervals. Growth temperature profiles for each organism were constructed. For determination of proteolytic activity, the cultures were incubated in fat-free ultra-high temperature processed milk in the temperature gradient incubator for 72 h (temperature range as above). Cell-free extracts were used to determine the proteolytic activity using the azocasein method. Results of the growth studies showed that C. joostei had the ability to grow over a wider temperature range than C. bovis and P. fluorescens without being affected by changes in the temperature. For the proteolytic activity, C. joostei had significantly (p < 0.001) higher activity per milligram of protein at 15.5 °C, followed by C. bovis and P. fluorescens. The results showed that C. joostei potentially has an even greater spoilage capacity in milk on the basis of growth rate and proteolytic activity than did P. fluorescens. PMID:26451905

  14. Alginate Sulfates Mitigate Binding Kinetics of Proangiogenic Growth Factors with Receptors toward Revascularization.

    PubMed

    Schmidt, John; Lee, Min Kyung; Ko, Eunkyung; Jeong, Jae Hyun; DiPietro, Luisa A; Kong, Hyunjoon

    2016-07-01

    Ever since proangiogenic growth factors have been used as a vascular medicine to treat tissue ischemia, efforts have been increasingly made to develop a method to enhance efficacy of growth factors in recreating microvascular networks, especially at low dose. To this end, we hypothesized that polysaccharides substituted with sulfate groups would amplify growth factor receptor activation and stimulate phenotypic activities of endothelial cells involved in neovascularization. We examined this hypothesis by modifying alginate with a controlled number of sulfates and using it to derive a complex with vascular endothelial growth factor (VEGF), as confirmed with fluorescence resonance energy transfer (FRET) assay. Compared with the bare VEGF and with a mixture of VEGF and unmodified alginates, the VEGF complexed with alginate sulfates significantly reduced the dissociation rate with the VEGFR-2, elevated VEGFR-2 phosphorylation level, and increased the number of endothelial sprouts in vitro. Furthermore, the VEGF-alginate sulfate complex improved recovery of perfusion in an ischemic hindlimb of a mouse due to the increase of the capillary density. Overall, this study not only demonstrates an important cofactor of VEGF but also uncovers an underlying mechanism by which the cofactor mitigates the VEGF-induced signaling involved in the binding kinetics and activation of VEGFR. We therefore believe that the results of this study will be highly useful in improving the therapeutic efficacy of various growth factors and expediting their uses in clinical treatments of wounds and tissue defects. PMID:26881299

  15. Kinetics of Bacillus thuringiensis var. israelensis growth on high glucose concentrations.

    PubMed

    Berbert-Molina, M A; Prata, A M R; Pessanha, L G; Silveira, M M

    2008-11-01

    The kinetic and general growth features of Bacillus thuringiensis var. israelensis were evaluated. Initial glucose concentration (S0) in fermentation media varied from 10 to 152 g/l. The results afforded to characterize four morphologically and physiologically well-defined culture phases, independent of S0 values: Phase I, vegetative growth; Phase II, transition to sporulation; Phase III, sporulation; and Phase IV, spores maturation and cell lysis. Important process parameters were also determined. The maximum specific growth rates (microX,m) were not affected with S0 up to 75 g/l (1.0-1.1 per hour), but higher glucose concentrations resulted in growth inhibition by substrate, revealed by a reduction in microX,m values. These higher S0 values led to longer Phases III and IV and delayed sporulation. Similar biomass concentrations (Xm=15.2-15.9 g/l) were achieved with S0 over 30.8 g/l, with increasing residual substrate, suggesting a limitation in some other nutrients and the use of glucose to form other metabolites. In this case, with S0 from 30.8 to 152 g/l, cell yield (YX/S) decreased from 0.58 to 0.41 g/g. On the other hand, with S0=10 g/l growth was limited by substrate, and YX/S has shown its maximum value (0.83 g/g). PMID:18712542

  16. Flux-Dependent Growth Kinetics and Diameter Selectivity in Single-Wall Carbon Nanotube Arrays

    SciTech Connect

    Geohegan, David B; Puretzky, Alexander A; Jackson, Jeremy Joseph; Rouleau, Christopher M; Eres, Gyula; More, Karren Leslie

    2011-01-01

    The nucleation and growth kinetics of single-wall carbon nanotubes in aligned arrays have been measured using fast pulses of acetylene and in situ optical diagnostics in conjunction with low pressure chemical vapor deposition (CVD). Increasing the acetylene partial pressure is shown to decrease nucleation times by three orders of magnitude, permitting aligned nanotube arrays to nucleate and grow to microns lengths within single gas pulses at high (up to 7 micron/s) peak growth rates and short ~ 0.5 s times.Low-frequency Raman scattering (> 10 cm-1) and transmission electron microscopy measurements show that increasing the feedstock flux in both continuous-CVD and pulsed-CVD shifts the product distribution to large single-wall carbon nanotube diameters > 2.5 nm. Sufficiently high acetylene partial pressures in pulsed-CVD appear to temporarily terminate the growth of the fastest- growing, small-diameter nanotubes by overcoating the more catalytically-active, smaller catalyst nanoparticles within the ensemble with non-nanotube carbon in agreement with a growth model. The results indicate that subsets of catalyst nanoparticle ensembles nucleate, grow, and terminate growth within different flux ranges according to their catalytic activity.

  17. Kinetics and mechanisms of crystal growth inhibition of indomethacin by model precipitation inhibitors

    NASA Astrophysics Data System (ADS)

    Patel, Dhaval

    Supersaturating Drug Delivery Systems (SDDS) could enhance oral bioavailability of poorly water soluble drugs (PWSD). Precipitation inhibitors (PIs) in SDDS could maintain supersaturation by inhibiting nucleation, crystal growth, or both. The mechanisms by which these effects are realized are generally unknown. The goal of this dissertation was to explore the mechanisms underpinning the effects of model PIs including hydroxypropyl beta-cyclodextrins (HP-beta-CD), hydroxypropyl methylcellulose (HPMC), and polyvinylpyrrolidone (PVP) on the crystal growth of indomethacin, a model PWSD. At high degrees of supersaturation (S), the crystal growth kinetics of indomethacin was bulk diffusion-controlled, which was attributed to a high energy form deposited on the seed crystals. At lower S, indomethacin growth kinetics was surface integration-controlled. The effect of HP-beta-CD at high S was successfully modeled using the reactive diffusion layer theory. The superior effects of PVP and HPMC as compared to HP-beta-CD at high S were attributed to a change in the rate limiting step from bulk diffusion to surface integration largely due to prevention of the high energy form formation. The effects of PIs at low S were attributed to significant retardation of the surface integration rate, a phenomenon that may reflect the adsorption of PIs onto the growing surface. PVP was selected to further understand the relationship between adsorption and crystal growth inhibition. The Langmuir adsorption isotherm model fit the adsorption isotherms of PVP and N-vinylpyrrolidone well. The affinity and extent of adsorption of PVP were significantly higher than those of N-vinylpyrrolidone, which was attributed to cooperative interactions between PVP and indomethacin. The extent of PVP adsorption on a weight-basis was greater for higher molecular weight PVP but less on a molar-basis indicating an increased percentage of loops and tails for higher molecular weight PVPs. PVP significantly inhibited

  18. New insights into the lifestyle of the cold-loving SM1 euryarchaeon: natural growth as a monospecies biofilm in the subsurface.

    PubMed

    Henneberger, Ruth; Moissl, Christine; Amann, Thomas; Rudolph, Christian; Huber, Robert

    2006-01-01

    In the surface waters of sulfidic springs near Regensburg, Bavaria, Germany, the SM1 euryarchaeon, together with filamentous bacteria, forms the recently described unique string-of-pearls community. In addition to naturally occurring string-of-pearls communities, the growth of these communities was also observed on polyethylene nets provided as an artificial attachment material in the streamlets of springs. In order to learn more about the distribution and origin of the SM1 euryarchaeon and its possible occurrence in the subsurface, polyethylene nets were incubated as deeply as possible in different spring holes. After a short residence time, slime-like, milky drops, almost completely composed of SM1 euryarchaeon, were attached to the nets, indicating that this organism grows independent of a partner in deeper earth layers. A newly designed in situ biofilm trapping system allowed the quantitative harvesting of organisms exhibiting this newly discovered lifestyle of the SM1 euryarchaeon for detailed biological studies. The discovery of naturally occurring archaeal biofilms extends our knowledge of the biology and ecological significance of archaea in their environments. PMID:16391042

  19. [Kinetic patterns in the growth of transplantable mouse tumor RShM-1].

    PubMed

    Svinogeeva, T P; Konopliannikov, A G; Shtein, L V

    1976-01-01

    Under study was the kinetics of growth of cervical cancer (CCM-1) transplanted on mice CBA, also the mitotic cycle and diurnal activity of tumor cells division. The tumor growth can well be described with the Hompertz equation, the constants of acceleration and retardation being equal to 0.34 day-1 and 0.004 day-1 accordingly. A linear dependence between the size, weight and number of CCM-1 celos is shown. In the tumor under study a persistant diurnal rhythm of the cell division was found with the maximum at 7 and 19 hours and the minimum at 13. The basis parameters of the mitotic cycle of tumor cells were determined: Tc=17.8 hr., G2 approximately 40 min.; S=9 hr., M approximately 24 min., G1 approximately 18.4 hr. The time of tumor doubling was 48.7 hr. The cell loss factor is as much as 42.1 per cent. PMID:1034368

  20. Experimental Studies of the Growth Kinetics of Methane Clathrate Hydrates & Superfluid Hydrodynamics on the Nanoscale

    NASA Astrophysics Data System (ADS)

    Botimer, Jeffrey David

    This thesis details the experimental findings of three distinct research projects. The first studies the growth kinetics of methane clathrate hydrates grown under the influence of multiple factors including surfactants, porous media, substrate wetting properties, and salt content. The second investigates the flow behaviors of superfluid helium through single, high aspect ratio nanopipes. The third models the frequency response of a quartz tuning fork in high pressure normal and superfluid helium and demonstrates how quartz tuning forks can be used as cheap, small, in situ, cryogenic pressure gauges. The first project reports studies of the kinetics of growth of methane hydrates from liquid water containing small amounts of surfactant (<500 ppm of sodium dodecyl sulfate, SDS). The kinetics are monitored using simultaneous measurements of the uptake of methane detected by a pressure drop in the gas phase, and either visual observations of the amount of liquid water and solid phase in the reaction vessel, or in situ micro-Raman measurements or in situ NMR measurements. These diagnostics show that the uptake of methane and the conversion of liquid water to a solid phase do not occur simultaneously; the uptake of gas always lags the visual and spectroscopic signatures of the disappearance of liquid water and the formation of solid. The evidence suggests that the SDS causes water to form an intermediate immobile solid-like state before combining with the methane to form hydrate. The growth mechanism is related to the surfactant and disappears for low SDS concentrations (<25 ppm). Also reported are studies of the growth rates of methane hydrates as a function of substrate wetting properties, driving force, and growth media. The second project studies pressure driven flow of superfluid helium through single high aspect ratio glass nanopipes into a vacuum has been studied for a wide range of pressure drop (0--30 atm), reservoir temperature (0.8--2.5K), pipe lengths (1-30mm

  1. Direct dynamic kinetic analysis and computer simulation of growth of Clostridium perfringens in cooked turkey during cooling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This research applied a new one-step methodology to directly construct a tertiary model for describing the growth of C. perfringens in cooked turkey meat under dynamically cooling conditions. The kinetic parameters of the growth models were determined by numerical analysis and optimization using mu...

  2. Shape transition of endotaxial islands growth from kinetically constrained to equilibrium regimes

    SciTech Connect

    Li, Zhi-Peng; Tok, Engsoon; Foo, Yonglim

    2013-09-01

    Graphical abstract: - Highlights: • All Fe{sub 13}Ge{sub 8} islands will grow into Ge(0 0 1) substrate at temperatures from 350 to 675 °C. • Shape transition occurred from kinetically constrained to equilibrium regime. • All endotaxial islands can be clarified into two types. • The mechanisms of endotaxial growth and shape transition have been rationalized. - Abstract: A comprehensive study of Fe grown on Ge(0 0 1) substrates has been conducted at elevated temperatures, ranging from 350 to 675 °C. All iron germinide islands, with the same Fe{sub 13}Ge{sub 8} phase, grow into the Ge substrate with the same epitaxial relationship. Shape transition occurs from small square islands (low temperatures), to elongated orthogonal islands or orthogonal nanowires (intermediate temperatures), and then finally to large square orthogonal islands (high temperatures). According to both transmission electron microscopy (TEM) and atomic force microscopy (AFM) investigations, all islands can be defined as either type-I or type-II. Type-I islands usually form at kinetically constrained growth regimes, like truncated pyramids. Type-II islands usually appear at equilibrium growth regimes forming a dome-like shape. Based on a simple semi-quantitative model, type-II islands have a lower total energy per volume than type-I, which is considered as the dominant mechanism for this type of shape transition. Moreover, this study not only elucidates details of endotaxial growth in the Fe–Ge system, but also suggests the possibility of controlled fabrication of temperature-dependent nanostructures, especially in materials with dissimilar crystal structures.

  3. Wound biofilms: lessons learned from oral biofilms

    PubMed Central

    Mancl, Kimberly A.; Kirsner, Robert S.; Ajdic, Dragana

    2013-01-01

    Biofilms play an important role in the development and pathogenesis of many chronic infections. Oral biofilms, more commonly known as dental plaque,are a primary cause of oral diseases including caries, gingivitis and periodontitis. Oral biofilms are commonly studied as model biofilm systems as they are easily accessible, thus biofilm research in oral diseases is advanced with details of biofilm formation and bacterial interactions being well-elucidated. In contrast, wound research has relatively recently directed attentionto the role biofilms have in chronic wounds. This review discusses the biofilms in periodontal disease and chronic wounds with comparisons focusing on biofilm detection, biofilm formation, the immune response to biofilms, bacterial interaction and quorum sensing. Current treatment modalities used by both fields as well as future therapies are also discussed. PMID:23551419

  4. Biofilm formation by Helicobacter pylori.

    PubMed

    Stark, R M; Gerwig, G J; Pitman, R S; Potts, L F; Williams, N A; Greenman, J; Weinzweig, I P; Hirst, T R; Millar, M R

    1999-02-01

    Helicobacter pylori NCTC 11637 produces a water-insoluble biofilm when grown under defined conditions with a high carbon:nitrogen ratio in continuous culture and in 10% strength Brucella broth supplemented with 3 g l-1 glucose. Biofilm accumulated at the air/liquid interface of the culture. Light microscopy of frozen sections of the biofilm material showed few bacterial cells in the mass of the biofilm. The material stained with periodic acid Schiff's reagent. Fucose, glucose, galactose, and glycero-manno-heptose, N-acetylglucosamine and N-acetylmuramic acid were identified in partially purified and in crude material, using gas chromatography and mass spectrometry. The sugar composition strongly indicates the presence of a polysaccharide as a component of the biofilm material. Antibodies (IgG) to partially purified material were found in both sero-positive and sero-negative individuals. Treatment of the biofilm material with periodic acid reduced or abolished immunoreactivity. Treatment with 5 mol l-1 urea at 100 degrees C and with phenol did not remove antigenic recognition by patient sera. The production of a water-insoluble biofilm by H. pylori may be important in enhancing resistance to host defence factors and antibiotics, and in microenvironmental pH homeostasis facilitating the growth and survival of H. pylori in vivo. PMID:10063642

  5. The composition and compression of biofilms developed on ultrafiltration membranes determine hydraulic biofilm resistance.

    PubMed

    Derlon, Nicolas; Grütter, Alexander; Brandenberger, Fabienne; Sutter, Anja; Kuhlicke, Ute; Neu, Thomas R; Morgenroth, Eberhard

    2016-10-01

    This study aimed at identifying how to improve the level of permeate flux stabilisation during gravity-driven membrane filtration without control of biofilm formation. The focus was therefore on understanding (i) how the different fractions of the biofilms (inorganics particles, bacterial cells, EPS matrix) influence its hydraulic resistance and (ii) how the compression of biofilms impacts its hydraulic resistance, i.e., can water head be increased to increase the level of permeate flux stabilisation. Biofilms were developed on ultrafiltration membranes at 88 and 284 cm water heads with dead-end filtration for around 50 days. A larger water head resulted in a smaller biofilm permeability (150 and 50 L m(-2) h(-1) bar(-1) for biofilms grown at 88 cm and 284 cm water head, respectively). Biofilms were mainly composed of EPS (>90% in volume). The comparison of the hydraulic resistances of biofilms to model fouling layers indicated that most of the hydraulic resistance is due to the EPS matrix. The compressibility of the biofilm was also evaluated by subjecting the biofilms to short-term (few minutes) and long-term variations of transmembrane pressures (TMP). A sudden change of TMP resulted in an instantaneous and reversible change of biofilm hydraulic resistance. A long-term change of TMP induced a slow change in the biofilm hydraulic resistance. Our results demonstrate that the response of biofilms to a TMP change has two components: an immediate variation of resistance (due to compression/relaxation) and a long-term response (linked to biofilm adaptation/growth). Our results provide relevant information about the relationship between the operating conditions in terms of TMP, the biofilm structure and composition and the resulting biofilm hydraulic resistance. These findings have practical implications for a broad range of membrane systems. PMID:27318448

  6. Effects of Kinetic Roughening and Liquid-Liquid Phase Transition on Lysozyme Crystal Growth Velocities

    NASA Technical Reports Server (NTRS)

    Gorti, Sridhar; Konnert, John; Forsythe, Elizabeth L.; Pusey, Marc L.

    2004-01-01

    We measured the growth velocities of the (110) face of tetragonal lysozyme, V (centimeters per second), at four different concentrations, c (milligrams per milliliter), as the solution temperature, T (Centigrade), was reduced. For a broad range of T dependent on c, we find that the growth velocities increased as the solution temperature was reduced. The initial increase in V is well characterized by the 2D nucleation model for crystal growth, yielding the magnitude of an effective barrier for growth, gamma(sub s) = 1.2 plus or minus 0.1 x 10(exp -13) erg/molecule. Below certain temperatures, T(sub cr), dependent on c, however, a kinetic roughening hypothesis that considers the continuous addition of molecules anywhere on the crystal surface better describes the observed growth velocities. The application of the continuous growth model, up to the solution cloud-point temperatures, T(sub cl), enabled the determinations of the crossover concentration, c(sub r), from estimated values of T(sub cr). For all conditions presented, we find that the crossover from growth by 2D nucleation to continuous addition occurs at a supersaturation, sigma (sub c), = 2.0 plus or minus 0.1. Moreover, we find the energy barrier for the continuous addition, E(sub c), within the temperature range T(sub cl) less than T less than T less than T (sub cr), to be 6 plus or minus 1 x 10(exp -13) erg/molecule. Further reduction of T below approximately 2-3 C of T(sub cl), also revealed a rapid slowing of crystal growth velocities. From quasi-elastic light scattering investigations, we find that the rapid diminishment of crystal growth velocities can be accounted for by the phase behavior of lysozyme solutions. Namely, we find the reversible formation of dense fluid proto-droplets comprised of lysozyme molecules to occur below approximately 0.3 C of T(sub cl). Hence, the rapid slowing of growth velocities may occur as a result of the sudden depletion of "mobile" molecules within crystal growth

  7. Confined growth of poly(butylene succinate) in its miscible blends with poly(vinylidene fluoride): morphology and growth kinetics.

    PubMed

    Wang, Tianchang; Li, Huihui; Wang, Feng; Yan, Shouke; Schultz, Jerold M

    2011-06-23

    The morphology and confined crystallization behavior of poly(butylene succinate) (PBS) in miscible poly(vinylidene fluoride) (PVDF)/PBS blends has been studied using differential scanning calorimetry (DSC) and optical and atomic force microscopy (OM and AFM). It was found that PBS crystal lamellae nucleated and grew confined inside the matrix of PVDF spherulites. Crystallized PBS domains grow with an ellipsoidal outline within PVDF spherulites formed at a relatively high PVDF crystallization temperature (T(c,PVDF)), while circular domains, engulfing several PVDF spherulites, are seen when growing in the PVDF spherulites created at lower T(c,PVDF). The growth kinetics of PBS confined in the PVDF matrix was investigated under various conditions. The growth rate of PBS (G(PBS)) increases with decreasing crystallization temperature and increasing PBS content under a given PVDF crystallization temperature (T(c,VDF)). For T(c,PVDF) above 145 °C, G(PBS) decreases with T(c,PVDF) for both 50:50 and 30:70 PVDF/PBS blends. However, for T(c,PVDF) below 145 °C, 50:50 and 30:70 PVDF/PBS blends exhibit the opposite G(PBS) trend; that is, G(PBS) for the 50:50 blend decreases with decreasing T(c,PVDF), while for the 30:70 PVDF/PBS blend G(PBS) increases with decreasing T(c,PVDF). It is shown that this behavior cannot be associated with the effect of crossing the boundary of smaller PVDF spherulites formed at a lower temperature. Rather, the behavior appears to be related to the interleaving growth of PBS lamellae among PVDF lamellae or between bundles of PVDF lamellae (fibrils), as in situ AFM observation shows. It is found that the interconnectedness of the molten pockets within the PVDF spherulites, which depends on the PVDF crystallization temperature, is an important factor determining the growth kinetics of PBS confined within the PVDF scaffold. PMID:21595485

  8. Grain Growth Kinetics of BaTiO3 Nanocrystals During Calcining Process

    NASA Astrophysics Data System (ADS)

    Song, Xiao-lan; He, Xi; Yang, Hai-ping; Qu, Yi-xin; Qiu, Guan-zhou

    2008-06-01

    BaTiO3 nanocrystals were synthesized by sol-gel method using barium acetate (Ba(CH3COO)2) and tetra-butyl titanate (Ti(OC4H9)4) as raw materials. Xerogel precursors and products were characterized by means of thermogravimetric/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD) and transmission electron microscope (TEM). The influence of the calcination temperature and duration on the lattice constant, the lattice distortion, and the grain size of BaTiO3 nanocrystals was discussed based on the XRD results. The grain growth kinetics of BaTiO3 nanocrystals during the calcination process were simulated with a conventional grain growth model which only takes into account diffusion, and an isothermal model proposed by Qu and Song, which takes into account both diffusion and surface reactions. Using these models, the pre-exponential factor and the activation energy of the rate constant were estimated. The simulation results indicate that the isothermal model is superior to the conventional one in describing the grain growth process, implying that both diffusion and surface reactions play important roles in the grain growth process.

  9. Process development for hydrogen production with Chlamydomonas reinhardtii based on growth and product formation kinetics.

    PubMed

    Lehr, Florian; Morweiser, Michael; Rosello Sastre, Rosa; Kruse, Olaf; Posten, Clemens

    2012-11-30

    Certain strains of microalgae are long known to produce hydrogen under anaerobic conditions. In Chlamydomonas reinhardtii the oxygen-sensitive hydrogenase enzyme recombines electrons from the chloroplast electron transport chain with protons to form molecular hydrogen directly inside the chloroplast. A sustained hydrogen production can be obtained under low sulfur conditions in C. reinhardtii, reducing the net oxygen evolution by reducing the photosystem II activity and thereby overcoming the inhibition of the hydrogenases. The development of specially adapted hydrogen production strains led to higher yields and optimized biological process preconditions. So far sustainable hydrogen production required a complete exchange of the growth medium to establish sulfur-deprived conditions after biomass growth. In this work we demonstrate the transition from the biomass growth phase to the hydrogen production phase in a single batch culture only by exact dosage of sulfur. This eliminates the elaborate and energy intensive solid-liquid separation step and establishes a process strategy to proceed further versus large scale production. This strategy has been applied to determine light dependent biomass growth and hydrogen production kinetics to assess the potential of H₂ production with C. reinhardtii as a basis for scale up and further process optimization. PMID:22750091

  10. Cell growth kinetics of Chlorella sorokiniana and nutritional values of its biomass.

    PubMed

    Kumar, Kanhaiya; Dasgupta, Chitralekha Nag; Das, Debabrata

    2014-09-01

    The present study investigates the effects of different physico-chemical parameters for the growth of Chlorella sorokiniana and subsequently determination of nutritional values of its biomass. Most suitable temperature, light intensity, pH, and acetic acid concentration were 30°C, 100 μmol m(-2)s(-1), pH 7.5, and 34.8mM, respectively for the growth of this microorganism. Arrhenius growth activation energy, Ea was calculated as 7.08 kJ mol(-1). Monod kinetics constants: maximum specific growth rate (μ max) and substrate (acetic acid) affinity coefficient (Ks) were determined as 0.1 ± 0.01 h(-1) and 76 ± 8 mg L(-1), respectively. Stoichiometric analysis revealed the capture of 1.83 g CO2 and release of 1.9 g O2 for 1g algal biomass synthesis. Algal biomass of C. sorokiniana was found rich in protein and several important minerals such as Mg, Ca, and Fe. Astaxanthin and β-carotene were extracted and quantified using high performance liquid chromatography. PMID:24997380

  11. Three-dimensional kinetic Monte Carlo simulations of cubic transition metal nitride thin film growth

    NASA Astrophysics Data System (ADS)

    Nita, F.; Mastail, C.; Abadias, G.

    2016-02-01

    A three-dimensional kinetic Monte Carlo (KMC) model has been developed and used to simulate the microstructure and growth morphology of cubic transition metal nitride (TMN) thin films deposited by reactive magnetron sputtering. Results are presented for the case of stoichiometric TiN, chosen as a representative TMN prototype. The model is based on a NaCl-type rigid lattice and includes deposition and diffusion events for both N and Ti species. It is capable of reproducing voids and overhangs, as well as surface faceting. Simulations were carried out assuming a uniform flux of incoming particles approaching the surface at normal incidence. The ballistic deposition model is parametrized with an interaction parameter r0 that mimics the capture distance at which incoming particles may stick on the surface, equivalently to a surface trapping mechanism. Two diffusion models are implemented, based on the different ways to compute the site-dependent activation energy for hopping atoms. The influence of temperature (300-500 K), deposition flux (0.1-100 monolayers/s), and interaction parameter r0 (1.5-6.0 Å) on the obtained growth morphology are presented. Microstructures ranging from highly porous, [001]-oriented straight columns with smooth top surface to rough columns emerging with different crystallographic facets are reproduced, depending on kinetic restrictions, deposited energy (seemingly captured by r0), and shadowing effect. The development of facets is a direct consequence of the diffusion model which includes an intrinsic (minimum energy-based) diffusion anisotropy, although no crystallographic diffusion anisotropy was explicitly taken into account at this stage. The time-dependent morphological evolution is analyzed quantitatively to extract the growth exponent β and roughness exponent α , as indicators of kinetic roughening behavior. For dense TiN films, values of α ≈0.7 and β =0.24 are obtained in good agreement with existing experimental data. At this

  12. Revealing the surface and bulk regimes of isothermal graphene growth on Ni with in situ kinetic measurements and modeling

    SciTech Connect

    Puretzky, Alexander A; Merkulov, Igor A; Rouleau, Christopher M; Eres, Gyula; Geohegan, David B

    2014-01-01

    In situ optical diagnostics are used to reveal the isothermal nucleation and growth mechanisms of graphene on Ni across a wide temperature range (560 C < T < 840 C) by chemical vapor deposition from single, sub-second pulses of acetylene. An abrupt, two-orders of magnitude change in growth times (~ 100s to 1s) is revealed at T = 680 C. Below and above this temperature, similar sigmoidal kinetics are measured and attributed to autocatalytic growth reactions but by two different mechanisms, surface assembly and dissolution/precipitation, respectively. These data are used to develop a simple and general kinetic model for graphene growth that includes the nucleation phase and includes the effects of carbon solubility in metals, describes delayed nucleation, and allows the interpretation of the competition between surface and bulk growth modes. The sharp transition in growth kinetics at T = 680 C is explained by a change in defect site density required for nucleation due to a transition in the carbon-induced mobility of the Ni surface. The easily-implemented optical reflectivity diagnostics and the simple kinetic model described here allow a pathway to optimize the growth of graphene on metals with arbitrary carbon solubility.

  13. Methods for Characterizing the Co-development of Biofilm and Habitat Heterogeneity

    PubMed Central

    Li, Xiaobao; Song, Jisun L.; Culotti, Alessandro; Zhang, Wei; Chopp, David L.; Lu, Nanxi; Packman, Aaron I.

    2016-01-01

    Biofilms are surface-attached microbial communities that have complex structures and produce significant spatial heterogeneities. Biofilm development is strongly regulated by the surrounding flow and nutritional environment. Biofilm growth also increases the heterogeneity of the local microenvironment by generating complex flow fields and solute transport patterns. To investigate the development of heterogeneity in biofilms and interactions between biofilms and their local micro-habitat, we grew mono-species biofilms of Pseudomonas aeruginosa and dual-species biofilms of P. aeruginosa and Escherichia coli under nutritional gradients in a microfluidic flow cell. We provide detailed protocols for creating nutrient gradients within the flow cell and for growing and visualizing biofilm development under these conditions. We also present protocols for a series of optical methods to quantify spatial patterns in biofilm structure, flow distributions over biofilms, and mass transport around and within biofilm colonies. These methods support comprehensive investigations of the co-development of biofilm and habitat heterogeneity. PMID:25866914

  14. Methods for characterizing the co-development of biofilm and habitat heterogeneity.

    PubMed

    Li, Xiaobao; Song, Jisun L; Culotti, Alessandro; Zhang, Wei; Chopp, David L; Lu, Nanxi; Packman, Aaron I

    2015-01-01

    Biofilms are surface-attached microbial communities that have complex structures and produce significant spatial heterogeneities. Biofilm development is strongly regulated by the surrounding flow and nutritional environment. Biofilm growth also increases the heterogeneity of the local microenvironment by generating complex flow fields and solute transport patterns. To investigate the development of heterogeneity in biofilms and interactions between biofilms and their local micro-habitat, we grew mono-species biofilms of Pseudomonas aeruginosa and dual-species biofilms of P. aeruginosa and Escherichia coli under nutritional gradients in a microfluidic flow cell. We provide detailed protocols for creating nutrient gradients within the flow cell and for growing and visualizing biofilm development under these conditions. We also present protocols for a series of optical methods to quantify spatial patterns in biofilm structure, flow distributions over biofilms, and mass transport around and within biofilm colonies. These methods support comprehensive investigations of the co-development of biofilm and habitat heterogeneity. PMID:25866914

  15. Kinetics-controlled growth of bimetallic RhAg on Au nanorods and their catalytic properties

    NASA Astrophysics Data System (ADS)

    Ye, Wei; Guo, Xia; Xie, Fang; Zhu, Rui; Zhao, Qing; Yang, Jian

    2014-03-01

    Controlled growth of hybrid metallic nanocomposites for a desirable structure in a combination of selected components is highly important for their applications. Herein, the controllable growth of RhAg on the gold nanorods is achieved from the dumbbell-like RhAg-tipped nanorods to the brushy RhAg-coated nanorods, or the rod-like Au@Ag-Rh nanorattles. These different growth modes of RhAg on the gold nanorods are correlated with the reducing kinetics of RhCl3 and AgNO3. In view of the promising catalytic properties of Rh, the gold nanorods modified by RhAg in different structures are examined as catalysts for the oxidation of o-phenylenediamine. It is found that brushy RhAg-coated nanorods present a higher catalytic efficiency than dumbbell-like RhAg-tipped nanorods and rod-like Au@Ag-Rh nanorattles. These results would benefit the overgrowth control on the one-dimensional metallic nanorods and the rational design of new generation heterogeneous catalysts and optical devices.Controlled growth of hybrid metallic nanocomposites for a desirable structure in a combination of selected components is highly important for their applications. Herein, the controllable growth of RhAg on the gold nanorods is achieved from the dumbbell-like RhAg-tipped nanorods to the brushy RhAg-coated nanorods, or the rod-like Au@Ag-Rh nanorattles. These different growth modes of RhAg on the gold nanorods are correlated with the reducing kinetics of RhCl3 and AgNO3. In view of the promising catalytic properties of Rh, the gold nanorods modified by RhAg in different structures are examined as catalysts for the oxidation of o-phenylenediamine. It is found that brushy RhAg-coated nanorods present a higher catalytic efficiency than dumbbell-like RhAg-tipped nanorods and rod-like Au@Ag-Rh nanorattles. These results would benefit the overgrowth control on the one-dimensional metallic nanorods and the rational design of new generation heterogeneous catalysts and optical devices. Electronic

  16. Suppression in droplet growth kinetics by the addition of organics to sulfate particles

    NASA Astrophysics Data System (ADS)

    Wong, Jenny P. S.; Liggio, John; Li, Shao-Meng; Nenes, Athanasios; Abbatt, Jonathan P. D.

    2014-11-01

    Aerosol-cloud interactions are affected by the rate at which water vapor condenses onto particles during cloud droplet growth. Changes in droplet growth rates can impact cloud droplet number and size distribution. The current study investigated droplet growth kinetics of acidic and neutral sulfate particles which contained various amounts and types of organic compounds, from model compounds (carbonyls) to complex mixtures (α-pinene secondary organic aerosol and diesel engine exhaust). In most cases, the formed droplet size distributions were shifted to smaller sizes relative to control experiments (pure sulfate particles), due to suppression in droplet growth rates in the cloud condensation nuclei counter. The shift to smaller droplets correlated with increasing amounts of organic material, with the largest effect observed for acidic seed particles at low relative humidity. For all organics incorporated onto acidic particles, formation of high molecular weight compounds was observed, probably by acid-catalyzed Aldol condensation reactions in the case of carbonyls. To test the reversibility of this process, carbonyl experiments were conducted with acidic particles exposed to higher relative humidity. High molecular weight compounds were not measured in this case and no shift in droplet sizes was observed, suggesting that high molecular weight compounds are the species affecting the rate of water uptake. While these results provide laboratory evidence that organic compounds can slow droplet growth rates, the modeled mass accommodation coefficient of water on these particles (α > 0.1) indicates that this effect is unlikely to significantly affect cloud properties, consistent with infrequent field observations of slower droplet growth rates.

  17. [The kinetic characteristics of mycelium growth of medicinal mushroom Ganoderma sinense in liquid-submerged cultivation].

    PubMed

    Gong, Jianhua; Wang, Yijun

    2002-02-01

    The study was carried out to investigate the kinetic characteristics of Ganoderma sinense mycelium growth in liquid-submerged cultivation, using a air-lift bioreactor ALR/ff specially designed for the cultivation of mushrooms' suspending mycelia cultures. Mycelia of G. sinense grew in the range of 25 degrees C-35 degrees C, and at the different temperature in which the specific growth rate showed by the mycelia much differed. The specific growth rates with the maximum of 0.0444(h-1) at 1.64 vvm of aeration in the cultivation were more than at 0.93 vvm, also more than at 2.50 vvm. In comparison with the less glucose concentration, the culture of 2.80 g glucose/100 mL in the medium had a shorter lag-period, and the more concentration of glucose favoured mycelia growth in the latter cultivation course with the denser pellets of mycelia. Then the culture of the less concentration of glucose in the medium had the higher conversion-rates of glucose to G. sinense biomass all along the cultivation course, than of the more concentration of glucose. Futhermore, in the continuous cultivations with growth-limiting substrate of carbon source the mycelia displaying different growing activities, demonstrated the varied forms of mycelium-gathering. In that cases the relationships among mycelia biomass, growth-limiting substrate and productivity of mycelium biomass obviously differed from the ones in the case of bacteria. Also in the range of dilution rates 0.010-0.220 (h-1) the growing of G. sinense mycelia followed the function of Contois equation. PMID:12557355

  18. Biomechanical Analysis of Infectious Biofilms.

    PubMed

    Head, David

    2016-01-01

    The removal of infectious biofilms from tissues or implanted devices and their transmission through fluid transport systems depends in part of the mechanical properties of their polymeric matrix. Linking the various physical and chemical microscopic interactions to macroscopic deformation and failure modes promises to unveil design principles for novel therapeutic strategies targeting biofilm eradication, and provide a predictive capability to accelerate the development of devices, water lines, etc, that minimise microbial dispersal. Here, our current understanding of biofilm mechanics is appraised from the perspective of biophysics , with an emphasis on constitutive modelling that has been highly successful in soft matter. Fitting rheometric data to viscoelastic models has quantified linear and nonlinear stress relaxation mechanisms, how they vary between species and environments, and how candidate chemical treatments alter the mechanical response. The rich interplay between growth, mechanics and hydrodynamics is just becoming amenable to computational modelling and promises to provide unprecedented characterisation of infectious biofilms in their native state. PMID:27193540

  19. Prognostic markers and tumour growth kinetics in melanoma patients progressing on vemurafenib.

    PubMed

    Seifert, Heike; Fisher, Rosalie; Martin-Liberal, Juan; Edmonds, Kim; Hughes, Peta; Khabra, Komel; Gore, Martin; Larkin, James

    2016-04-01

    The BRAF inhibitor vemurafenib is an effective drug in patients with BRAF mutant metastatic melanoma, but resistance occurs after a median of 6 months. The anti-CTLA4-antibody, ipilimumab, is a standard first-line and second-line treatment option in Europe, with a median time to response of 2-3 months, but some patients show rapid clinical deterioration before that. The aim of this analysis was to identify prognostic markers for survival after failure of vemurafenib treatment to identify patients who have a sufficient life expectancy to respond to new immunotherapy treatments. We retrospectively analysed 101 consecutive unselected patients treated with vemurafenib for metastatic melanoma at a single institution. The association between clinical parameters and death within 3 months after cessation of vemurafenib (n=69) was assessed by binary logistic and Cox regression. Of the patients, 45% died within 3 months of progression on vemurafenib. Elevated baseline serum lactate dehydrogenase, absence of normalization of serum lactate dehydrogenase on vemurafenib therapy, performance status of at least 2 at progression and time from primary tumour to metastatic disease less than 5 years were identified as poor prognostic markers. In an exploratory tumour growth kinetics analysis (n=16), we found that following cessation of vemurafenib, approximately a third each showed a stable, decelerated or accelerated rate of tumour growth. Patients with these poor prognostic markers are unlikely to have sufficient life expectancy to complete ipilimumab treatment after failure with vemurafenib. Consideration needs to be given to the elective use of immunotherapy before patients become resistant to vemurafenib. This requires prospective randomized evaluation. Our tumour growth kinetics analysis requires confirmation; however, it may suggest that intermittent vemurafenib treatment should be investigated in clinical trials. PMID:26684061

  20. Effects Of Myrcia Ovata Cambess. Essential Oil On Planktonic Growth Of Gastrointestinal Microorganisms and Biofilm Formation Of Enterococcus Faecalis

    PubMed Central

    Cândido, Cinthya S.; Portella, Cadmo Silton A.; Laranjeira, Bruno J.; da Silva, Sérgio S.; Arriaga, Angela M.C.; Santiago, Gilvandete M. P.; Gomes, Geovany A.; Almeida, Paulo César; Carvalho, Cibele B. M.

    2010-01-01

    The essential oil from the leaves of Myrcia ovata Cambess., commonly used in Brazil for the treatment of gastric illnesses, was screened for antimicrobial activity and action in the formation of microbial biofilms by Enterococcus faecalis. The oil was obtained by hydrodistillation using a clevenger-type system. Its chemical composition was analyzed using GC and GC-MS. Both MIC and MBC of the essential oil were determined by broth microdilution techniques and agar dilution method. The essential oil showed antimicrobial activity against E. faecalis, Escherichia coli, Pseudomonas aeruginosa, Salmonella choleraesuis, Staphylococcus aureus, Streptococcus pneumoniae and Candida parapsilosis. The results showed that the essential oil of M. ovata Cambess. was effective against the formation of biofilm by E. faecalis when compared with the control. Four volatile compounds, representing 92.1 % of the oil, were identified and geranial was the major component (50.4 %). At the best of our knowledge, this is the first report of the chemical composition and antimicrobial activity of the essential oil from leaves of M. ovata. PMID:24031537

  1. The Influence of Kinetic Growth Factors on the Clumped Isotope Composition of Calcite

    NASA Astrophysics Data System (ADS)

    Hunt, J. D.; Watkins, J. M.; Tripati, A.; Ryerson, F. J.; DePaolo, D. J.

    2014-12-01

    Clumped isotope paleothermometry is based on the association of 13C and 18O within carbonate minerals. Although the influence of temperature on equilibrium 13C-18O bond ordering has been studied, recent oxygen isotope studies of inorganic calcite demonstrate that calcite grown in laboratory experiments and in many natural settings does not form in equilibrium with water. It is therefore likely that the carbon and clumped isotope composition of these calcite crystals are not representative of true thermodynamic equilibrium. To isolate kinetic clumped isotope effects that arise at the mineral-solution interface, clumped isotopic equilibrium of DIC species must be maintained. This can be accomplished by dissolving the enzyme carbonic anhydrase (CA) into the solution, thereby reducing the time required for isotopic equilibration of DIC species by approximately two orders of magnitude between pH 7.7 and 9.3. We conduct calcite growth experiments aimed specifically at measuring the pH-dependence of kinetic clumped isotope effects during non-equilibrium precipitation of calcite. We precipitated calcite from aqueous solution at a constant pH and controlled supersaturation over the pH range 7.7-9.3 in the presence of CA. For each experiment, a gas mixture of N2 and CO2 is bubbled through a beaker of solution without seed crystals. As CO2 from the gas dissolves into solution, calcite crystals grow on the beaker walls. The pH of the solution is maintained by use of an autotitrator with NaOH as the titrant. We control the temperature, pH, the pCO2 of the gas inflow, and the gas inflow rate, and monitor the total alkalinity, the pCO2 of the gas outflow, and the amount of NaOH added. A constant crystal growth rate of ~1.6 mmol/m2/hr is maintained over all experiments. Results from these experiments are compared to predictions from a recently-developed isotopic ion-by-ion growth model of calcite. The model describes the rate, temperature and pH dependence of oxygen isotope uptake

  2. Mechanisms of biofilm resistance to antimicrobial agents.

    PubMed

    Mah, T F; O'Toole, G A

    2001-01-01

    Biofilms are communities of microorganisms attached to a surface. It has become clear that biofilm-grown cells express properties distinct from planktonic cells, one of which is an increased resistance to antimicrobial agents. Recent work has indicated that slow growth and/or induction of an rpoS-mediated stress response could contribute to biocide resistance. The physical and/or chemical structure of exopolysaccharides or other aspects of biofilm architecture could also confer resistance by exclusion of biocides from the bacterial community. Finally, biofilm-grown bacteria might develop a biofilm-specific biocide-resistant phenotype. Owing to the heterogeneous nature of the biofilm, it is likely that there are multiple resistance mechanisms at work within a single community. Recent research has begun to shed light on how and why surface-attached microbial communities develop resistance to antimicrobial agents. PMID:11166241

  3. The Challenging World of Biofilm Physiology.

    PubMed

    Donné, Joke; Dewilde, Sylvia

    2015-01-01

    Worldwide, infectious diseases are one of the leading causes of death among children. At least 65% of all infections are caused by the biofilm mode of bacterial growth. Bacteria colonise surfaces and grow as multicellular biofilm communities surrounded by a polymeric matrix as a common survival strategy. These sessile communities endow bacteria with high tolerance to antimicrobial agents and hence cause persistent and chronic bacterial infections, such as dental caries, periodontitis, otitis media, cystic fibrosis and pneumonia. The highly complex nature and the rapid adaptability of the biofilm population impede our understanding of the process of biofilm formation, but an important role for oxygen-binding proteins herein is clear. Much research on this bacterial lifestyle is already performed, from genome/proteome analysis to in vivo antibiotic susceptibility testing, but without significant progress in biofilm treatment or eradication. This review will present the multiple challenges of biofilm research and discuss possibilities to cross these barriers in future experimental studies. PMID:26616519

  4. Multicellular Organization in a Degradative Biofilm Community

    PubMed Central

    Wolfaardt, G. M.; Lawrence, J. R.; Robarts, R. D.; Caldwell, S. J.; Caldwell, D. E.

    1994-01-01

    Diclofop methyl, a commercial herbicide, was used as the sole carbon source to cultivate diclofop-degrading biofilms in continuous-flow slide culture. The biofilms were analyzed by using scanning confocal laser microscopy and image analysis. Spatial relationships among members of the community were distinctive to diclofop-grown biofilms. These relationships did not develop when the biofilms were grown on more labile substrates but were conserved when the biofilms were cultivated with other chlorinated ring compounds. The structures included conical bacterial consortia rising to 30 μm above the surrounding biofilm, grape-like clusters of cocci embedded in a matrix of perpendicularly oriented bacilli, and other highly specific patterns of intra- and intergeneric cellular coaggregation and growth. These unique consortial relationships indicated that syntrophic interactions may be necessary for optimal degradation of diclofop methyl and other chlorinated ring compounds. Images PMID:16349173

  5. Notes on Interface Growth Kinetics 50 Years after Burton, Cabrera and Frank

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    2004-01-01

    This overview is devoted to some unresolved basic problems in crystal growth kinetics. The density wave approach to propagation of a spatially diffuse interface between a growing crystal and its simple (e.g., metallic) melt is discussed is Section 2. This approach allows for the calculation of kinetic coefficients and is an alternative to the localized interface concept in which each atom belongs to either a solid or a liquid. Sections 3 and 4 deals mainly with layer growth from solution. Mutual retardation of the growth steps via their bulk and d a c e diffusion fields is the major subject. The influence of solution flow on step bunching (Section 4) suggests the essential influence of bulk diffusion on the surface morphology. The flow within the solution boundary layer enhances step-step interaction, influences the step bunching process and the resulting step pattern morphology on the growing surface. Recent experiments on the rates at which strongly polygonized steps on protein and small molecule crystals propagate during growth from solution are analyzed in Section 5 . We have shown that the step segments may be "singular" and that "one-dimensional nucleation" may be the rate limiting stage for the segments that are shorter or comparable in length to the thermodynamically equilibrium interlink distance. In this case, the reciprocal dependence of the segment propagation rate on the segment length that follow from the Gibbs-Thompson law, should be replaced by an abrupt switch from zero to a finite constant velocity. Until recently, the Kossel crystal remained the only model used in crystal growth theory. In such Kossel Gibbs-Thomson law, should be replaced by an abrupt switch &om zero to a finite constant velocity. crystals, all kinks at the steps are identical and the kink rate is a linear function of the supersaturation. In the non-Kossel crystals, there may be several kink configurations characterized by different geometries and energies. These configurations

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

    PubMed Central

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

    2009-01-01

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

  7. Aspartate inhibits Staphylococcus aureus biofilm formation.

    PubMed

    Yang, Hang; Wang, Mengyue; Yu, Junping; Wei, Hongping

    2015-04-01

    Biofilm formation renders Staphylococcus aureus highly resistant to conventional antibiotics and host defenses. Four D-amino acids (D-Leu, D-Met, D-Trp and D-Tyr) have been reported to be able to inhibit biofilm formation and disassemble established S. aureus biofilms. We report here for the first time that both D- and L-isoforms of aspartate (Asp) inhibited S. aureus biofilm formation on tissue culture plates. Similar biofilm inhibition effects were also observed against other staphylococcal strains, including S. saprophyticus, S. equorum, S. chromogenes and S. haemolyticus. It was found that Asp at high concentrations (>10 mM) inhibited the growth of planktonic N315 cells, but at subinhibitory concentrations decreased the cellular metabolic activity without influencing cell growth. The decreased cellular metabolic activity might be the reason for the production of less protein and DNA in the matrix of the biofilms formed in the presence of Asp. However, varied inhibition efficacies of Asp were observed for biofilms formed by clinical staphylococcal isolates. There might be mechanisms other than decreasing the metabolic activity, e.g. the biofilm phenotypes, affecting biofilm formation in the presence of Asp. PMID:25687923

  8. A diffusion-controlled kinetic model for growth of Au-catalyzed ZnO nanorods: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Hejazi, S. R.; Madaah Hosseini, H. R.

    2007-11-01

    A kinetic model for growth of ZnO nanorods via vapor-liquid-solid (VLS) mechanism based on the bulk diffusion of Zn atoms through the Au-Zn droplet is presented. The dependences of the growth rate on size are given quantitatively. A general expression for the growth rate of nanorods during VLS process is derived. The derived formula shows the dependences of growth rate on lateral size of nanorods, concentration and supersaturation of Zn atoms in the liquid droplet. Based on the presented kinetic model the smaller nanorods have faster growth rate. Au-catalyzed ZnO nanorods are grown by chemical vapor transport and condensation (CVTC) process experimentally. Theoretical and experimental rate/radius curves are compared to each other. Theoretical predictions are in good agreement with the experimental results.

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

    PubMed

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

    2003-06-01

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

  10. Influence of Nitrogen Content on Thermal Stability and Grain Growth Kinetics of Cryomilled Al Nanocomposites

    NASA Astrophysics Data System (ADS)

    Hashemi-Sadraei, L.; Mousavi, S. E.; Vogt, R.; Li, Y.; Zhang, Z.; Lavernia, E. J.; Schoenung, J. M.

    2012-02-01

    Nanocomposite powders of Al 5083/B4C were produced via cryogenic milling (cryomilling) of boron carbide (B4C) particles in Al 5083 matrix. The effect of milling time (up to 24 hours), and consequential nitrogen content, on grain growth in the nanocrystalline Al 5083 matrix was investigated. Thermal stability was studied at temperatures as high as ~0.96 T m and annealing times of up to 24 hours. Average grain sizes increased with time and temperature and tended to stabilize after longer annealing times, regardless of nitrogen content. Higher thermal stability was observed in samples with higher nitrogen content, with the average grain size remaining in the range of 30 nm, even after exposure to the most extreme annealing conditions. This behavior was attributed to the retarding effect that nitrides have on grain growth, as a result of pinning grain boundaries. Kinetic studies based on the Burke equation showed two thermally activated grain growth regimes—a low-temperature regime with an activation energy of 15 kJ/mol and a high-temperature regime with an activation energy of 58 kJ/mol.

  11. Use of fermentative metabolites for heterotrophic microalgae growth: Yields and kinetics.

    PubMed

    Turon, V; Baroukh, C; Trably, E; Latrille, E; Fouilland, E; Steyer, J-P

    2015-01-01

    The growth of two lipid-producing Chlorella species on fermentative end-products acetate, butyrate and lactate, was investigated using a kinetic modeling approach. Chlorella sorokiniana and Auxenochlorella protothecoides were grown on synthetic media with various (acetate:butyrate:lactate) ratios. Both species assimilated efficiently acetate and butyrate with yields between 0.4 and 0.5g carbon of biomass/g carbon of substrate, but did not use lactate. The highest growth rate on acetate, 2.23d(-1), was observed for C. sorokiniana, and on butyrate, 0.22d(-1), for A. protothecoides. Butyrate removal started after complete acetate exhaustion (diauxic effect). However, butyrate consumption may be favored by the increase of biomass concentration induced by the initial use of acetate. A model combining Monod and Haldane functions was then built and fitted the experimental data well for both species. Butyrate concentration and (acetate:butyrate) ratios were identified as key parameters for heterotrophic growth of microalgae on fermentative metabolites. PMID:25459841

  12. Photobiotreatment: influence of nitrogen and phosphorus ratio in wastewater on growth kinetics of Scenedesmus obliquus.

    PubMed

    Arbib, Z; Ruiz, J; Alvarez-Díaz, Pablo; Garrido-Pérez, C; Barragan, J; Perales, J A

    2013-01-01

    Nitrogen and phosphorus concentration in the effluent of a wastewater treatment plant can vary significantly, which could affect the growth kinetic and chemical composition of microalgae when cultivated in this medium. The aim of this work was to study the rate of growth, nutrient removal and carbon dioxide biofixation as well as biomass composition of Scenedesmus obliquus (S. obliquus) when it is cultivated in wastewater at different nitrogen and phosphorus ratio, from 1:1 to 35:1. A more homogeneous method for calculating productivities in batch reactors was proposed. The proper N:P ratio for achieving optimum batch biomass productivity ranged between 9 and 13 (263 and 322 mg L(-1) d(-1) respectively). This was also the ratio range for achieving a total N and P removal. Above and below this range (9-13) the maximum biomass concentration changed, instead of the specific growth rate.The maximum carbon dioxide biofixation rate was achieved at N:P ratio between 13 and 22 (553 and 557 mg CO2 L(-1) d(-1) respectively). Lipid and crude protein content, both depend on the aging culture, reaching the maximum lipid content (34%) at the lowest N:P (1:1) and the maximum crude protein content (34.2%) at the highest N:P (35:1). PMID:23819274

  13. The clinical impact of bacterial biofilms

    PubMed Central

    Høiby, Niels; Ciofu, Oana; Johansen, Helle Krogh; Song, Zhi-jun; Moser, Claus; Jensen, Peter Østrup; Molin, Søren; Givskov, Michael; Tolker-Nielsen, Tim; Bjarnsholt, Thomas

    2011-01-01

    Bacteria survive in nature by forming biofilms on surfaces and probably most, if not all, bacteria (and fungi) are capable of forming biofilms. A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and extracellular DNA. Bacterial biofilms are resistant to antibiotics, disinfectant chemicals and to phagocytosis and other components of the innate and adaptive inflammatory defense system of the body. It is known, for example, that persistence of staphylococcal infections related to foreign bodies is due to biofilm formation. Likewise, chronic Pseudomonas aeruginosa lung infections in cystic fibrosis patients are caused by biofilm growing mucoid strains. Gradients of nutrients and oxygen exist from the top to the bottom of biofilms and the bacterial cells located in nutrient poor areas have decreased metabolic activity and increased doubling times. These more or less dormant cells are therefore responsible for some of the tolerance to antibiotics. Biofilm growth is associated with an increased level of mutations. Bacteria in biofilms communicate by means of molecules, which activates certain genes responsible for production of virulence factors and, to some extent, biofilm structure. This phenomenon is called quorum sensing and depends upon the concentration of the quorum sensing molecules in a certain niche, which depends on the number of the bacteria. Biofilms can be prevented by antibiotic prophylaxis or early aggressive antibiotic therapy and they can be treated by chronic suppressive antibiotic therapy. Promising strategies may include the use of compounds which can dissolve the biofilm matrix and quorum sensing inhibitors, which increases biofilm susceptibility to antibiotics and phagocytosis. PMID:21485309

  14. The kinetics of dolomite reaction rim growth under isostatic and non-isostatic pressure conditions

    NASA Astrophysics Data System (ADS)

    Helpa, V.; Rybacki, E.; Morales, L. G.; Abart, R.; Dresen, G. H.

    2013-12-01

    During burial and exhumation, rocks are simultaneously exposed to metamorphic reactions and tectonic stresses. Therefore, the reaction rate of newly formed minerals may depend on chemical and mechanical driving forces. Here, we investigate the reaction kinetics of dolomite (CaMg[CO3]2) rim growth by solid-state reactions experiments on oriented calcite (CaCO3) and magnesite (MgCO3) single crystals under isostatic and non-isostatic pressure conditions. Cylindrical samples of 3-5 mm length and 7 mm diameter were drilled and polished perpendicular to the rhombohedral cleavage planes of natural clear crystals. The tests were performed using a Paterson-type deformation apparatus at P = 400 MPa confining pressure, temperatures, T, between 750 and 850°C, and reaction durations, t, of 2 - 146 h to calculate the kinetic parameters of dolomite rim growth under isostatic stress conditions. For non-isostatic reaction experiments we applied in addition differential stresses, σ, up to 40 MPa perpendicular to the contact interface at T = 750°C for 4 - 171 h duration, initiating minor inelastic deformation of calcite. The thickness of the resulting dolomite reaction rims increases linearly with the square root of time, indicating a diffusion-controlled reaction. The rims consist of two different textural domains. Granular dolomite grains (≈ 2 -5 μm grain size) form next to calcite and elongated palisade-shaped grains (1-6 μm diameter) grow perpendicular to the magnesite interface. Texture measurements with the electron backscatter diffraction technique indicate that the orientations of dolomite grains are mainly influenced by the orientation of the calcite educt crystal, in particular in the granular rim. To some extent, the texture of dolomite palisades is also influenced by the orientation of magnesite. The thickness of the two individual layers increases with temperature. At 400 MPa isostatic pressure, T = 750°C and t = 29 hours, a 5 μm thick granular dolomite layer

  15. Kinetics of subdiffusive growth of new phase particles in supersaturated solid solutions

    NASA Astrophysics Data System (ADS)

    Svetukhin, V. V.; Sibatov, R. T.

    2015-04-01

    The kinetics of the subdiffusion-limited growth of spherical precipitates is studied. The process is described by the equation of anomalous diffusion with a fractional derivative with respect to time. It is shown that a decrease in the concentration of monomers is described by the law exp(- kt 3α/2) at the initial stage and the power law t -α at large times, where 0 < α ≤ 1 is the dispersion parameter coinciding with the order of time derivative in the subdiffusion equation. The time dependence of the size of a spherical precipitate is obtained. The results generalize the Ham diffusion theory and are in agreement with the Monte Carlo simulation data.

  16. Kinetics of subdiffusive growth of new phase particles in supersaturated solid solutions

    SciTech Connect

    Svetukhin, V. V. Sibatov, R. T.

    2015-04-15

    The kinetics of the subdiffusion-limited growth of spherical precipitates is studied. The process is described by the equation of anomalous diffusion with a fractional derivative with respect to time. It is shown that a decrease in the concentration of monomers is described by the law exp(−kt{sup 3α/2}) at the initial stage and the power law t{sup −α} at large times, where 0 < α ≤ 1 is the dispersion parameter coinciding with the order of time derivative in the subdiffusion equation. The time dependence of the size of a spherical precipitate is obtained. The results generalize the Ham diffusion theory and are in agreement with the Monte Carlo simulation data.

  17. Kinetics of low pressure CVD growth of SiO2 on InP and Si

    NASA Technical Reports Server (NTRS)

    Iyer, R.; Lile, D. L.

    1988-01-01

    The kinetics of low pressure CVD growth of SiO2 from SiH4 and O2 has been investigated for the case of an indirect (remote) plasma process. Homogeneous (gas phase) and heterogeneous operating ranges have been experimentally identified. The process was shown to be consistent within the heterogeneous surface-reaction dominated range of operation. A kinetic rate equation is given for growth at 14 W RF power input and 400 mtorr total pressure on both InP and Si substrates. The process exhibits an activation energy of 8.4 + or - 0.6 kcal/mol.

  18. Enhanced Generic Phase-field Model of Irradiation Materials: Fission Gas Bubble Growth Kinetics in Polycrystalline UO2

    SciTech Connect

    Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert O.; Gao, Fei; Sun, Xin

    2012-05-30

    Experiments show that inter-granular and intra-granular gas bubbles have different growth kinetics which results in heterogeneous gas bubble microstructures in irradiated nuclear fuels. A science-based model predicting the heterogeneous microstructure evolution kinetics is desired, which enables one to study the effect of thermodynamic and kinetic properties of the system on gas bubble microstructure evolution kinetics and morphology, improve the understanding of the formation mechanisms of heterogeneous gas bubble microstructure, and provide the microstructure to macroscale approaches to study their impact on thermo-mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking. In our previous report 'Mesoscale Benchmark Demonstration, Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing', we developed a phase-field model to simulate the intra-granular gas bubble evolution in a single crystal during post-irradiation thermal annealing. In this work, we enhanced the model by incorporating thermodynamic and kinetic properties at grain boundaries, which can be obtained from atomistic simulations, to simulate fission gas bubble growth kinetics in polycrystalline UO2 fuels. The model takes into account of gas atom and vacancy diffusion, vacancy trapping and emission at defects, gas atom absorption and resolution at gas bubbles, internal pressure in gas bubbles, elastic interaction between defects and gas bubbles, and the difference of thermodynamic and kinetic properties in matrix and grain boundaries. We applied the model to simulate gas atom segregation at grain boundaries and the effect of interfacial energy and gas mobility on gas bubble morphology and growth kinetics in a bi-crystal UO2 during post-irradiation thermal annealing. The preliminary results demonstrate that the model can produce the equilibrium thermodynamic properties and the morphology of gas bubbles at

  19. Kinetics and gas-surface dynamics of GaN homoepitaxial growth using NH 3-seeded supersonic molecular beams

    NASA Astrophysics Data System (ADS)

    McGinnis, A. J.; Thomson, D.; Davis, R. F.; Chen, E.; Michel, A.; Lamb, H. H.

    2001-11-01

    The kinetics of homoepitaxial growth of GaN thin films on metal-organic chemical vapor deposition (MOCVD)-grown GaN(0 0 0 1)/AlN/6H-SiC substrates was probed using NH 3-seeded supersonic molecular beams. NH 3 was seeded in H 2 and He and antiseeded in N 2 and Ar in order to obtain incident kinetic energies of 0.08-1.8 eV. Nozzle temperatures of 35-600 °C were used to adjust the NH 3 internal energy. Intense NH 3 beams (fluxes >2×10 15 cm-2 s-1 at the substrate) are produced for low seeding percentages (<5%) in the lighter carrier gases, because the heavier species (NH 3) is focused along the centerline of the beam. The NH 3 flux is proportional to the ratio of its molecular weight to the average molecular weight of the binary gas mixture. A steady-state Langmuir-Hinshelwood kinetics model was used to extract zero-coverage NH 3 sticking coefficient ( αNH 30) values from GaN growth kinetics data. An αNH 30 value of 0.14 at 750 °C was determined using seeded supersonic beams of NH 3 in He with incident kinetic energies of 0.4-0.5 eV. In comparison, GaN growth rates using low-energy NH 3 molecules (0.03 eV) from a leak valve indicate an αNH 30 of 0.29. Growth rate measurements using NH 3 beams with kinetic energies of 0.08-1.8 eV confirmed that αNH 30 generally decreases with increasing incident kinetic energy, leading us to conclude that NH 3 chemisorption on GaN(0 0 0 1) is unactivated and occurs via a precursor-mediated mechanism. Internal energy enhancement of NH 3 chemisorption via a precursor-mediated channel is proposed to explain the effects of nozzle temperature on GaN growth kinetics. The effects of NH 3 incident kinetic energy on film morphology are indirect. Rough, highly faceted films are observed under Ga-limited growth conditions. The surface morphology of films grown under NH 3-limited conditions changes from rough to smooth as the effective V/III ratio is decreased.

  20. FocVel1 influences asexual production, filamentous growth, biofilm formation, and virulence in Fusarium oxysporum f. sp. cucumerinum

    PubMed Central

    Li, Peiqian; Pu, Xiaoming; Feng, Baozhen; Yang, Qiyun; Shen, Huifang; Zhang, Jingxin; Lin, Birun

    2015-01-01

    Velvet genes play critical roles in the regulation of diverse cellular processes. In current study, we identified the gene FocVel1, a homolog of Fusarium graminearum VelA, in the plant pathogenic fungus F. oxysporum f. sp. cucumerinum. This pathogen causes the destructive disease called cucumber Fusarium wilt (CFW), which severely affects the production and marketing of this vegetable worldwide. Transcript analyses revealed high expression of FocVel1 during conidiophore development. Disruption of the FocVel1 gene led to several phenotypic defects, including reduction in aerial hyphal formation and conidial production. The deletion mutant ΔFocVel1 showed increased resistance to both osmotic stress and cell wall-damaging agents, but increased sensitivity to iprodione and prochloraz fungicides, which may be related to changes in cell wall components. In the process of biofilm formation in vitro, the mutant strain ΔFocVel1 displayed not only a reduction in spore aggregation but also a delay in conidial germination on the polystyrene surface, which may result in defects in biofilm formation. Moreover, pathogenicity assays showed that the mutant ΔFocVel1 exhibited impaired virulence in cucumber seedlings. And the genetic complementation of the mutant with the wild-type FocVel1 gene restored all the defects of the ΔFocVel1. Taken together, the results of this study indicated that FocVel1 played a critical role in the regulation of various cellular processes and pathogenicity in F. oxysporum f. sp. cucumerinum. PMID:25999976

  1. Non-classical nuclei and growth kinetics of Cr precipitates in FeCr alloys during ageing

    SciTech Connect

    Li, Yulan; Hu, Shenyang Y.; Zhang, Lei; Sun, Xin

    2014-01-10

    In this manuscript, we quantitatively calculated the thermodynamic properties of critical nuclei of Cr precipitates in FeCr alloys. The concentration profiles of the critical nuclei and nucleation energy barriers were predicted by the constrained shrinking dimer dynamics (CSDD) method. It is found that Cr concentration distribution in the critical nuclei strongly depend on the overall Cr concentration as well as temperature. The critical nuclei are non-classical because the concentration in the nuclei is smaller than the thermodynamic equilibrium value. These results are in agreement with atomic probe observation. The growth kinetics of both classical and non-classical nuclei was investigated by the phase field approach. The simulations of critical nucleus evolution showed a number of interesting phenomena: 1) a critical classical nucleus first shrinks toward its non-classical nucleus and then grows; 2) a non-classical nucleus has much slower growth kinetics at its earlier growth stage compared to the diffusion-controlled growth kinetics. 3) a critical classical nucleus grows faster at the earlier growth stage than the non-classical nucleus. All of these results demonstrate that it is critical to introduce the correct critical nuclei in order to correctly capture the kinetics of precipitation.

  2. Non-classical nuclei and growth kinetics of Cr precipitates in FeCr alloys during ageing

    NASA Astrophysics Data System (ADS)

    Li, Yulan; Hu, Shenyang; Zhang, Lei; Sun, Xin

    2014-03-01

    In this manuscript, we have quantitatively calculated the thermodynamic properties of the critical nuclei of Cr precipitates in FeCr alloys. The concentration profiles of the critical nuclei and nucleation energy barriers were predicted by the constrained shrinking dimer dynamics method. It is found that Cr concentration distribution in the critical nuclei strongly depends on the overall Cr concentration as well as on the temperature. The critical nuclei are non-classical because the concentration in the nuclei is smaller than the thermodynamic equilibrium value. These results are in agreement with atomic probe observation. The growth kinetics of both classical and non-classical nuclei was investigated by the phase-field approach. The simulations of critical nucleus evolution showed a number of interesting phenomena: (1) a critical classical nucleus first shrinks toward its non-classical nucleus and then grows; (2) a non-classical nucleus has much slower growth kinetics at its earlier growth stage compared to the diffusion-controlled growth kinetics and (3) a critical classical nucleus grows faster at the earlier growth stage than does a non-classical nucleus. All of these results demonstrate that it is critical to introduce the correct critical nuclei in order to correctly capture the kinetics of precipitation.

  3. Growth of Staphylococcus aureus in Cooked Potato and Potato Salad--A One-Step Kinetic Analysis.

    PubMed

    Huang, Lihan

    2015-12-01

    Staphylococcus aureus is a Gram-positive spherically-shaped bacterium capable of producing heat-stable enterotoxins that cause acute gastrointestinal diseases. The growth of this pathogen in food is a major threat to public health worldwide. Potato salad is a frequent vehicle for infection and food poisoning caused by S. aureus. Therefore, the objective of this study was to investigate the growth kinetics of S. aureus in cooked potato and potato salad. Samples of potato cubes and potato salad inoculated with S. aureus were incubated at temperatures between 8 and 43 °C to observe its growth for developing growth models. No growth was observed at 8 °C. The experimental results showed that the growth curves did not exhibit lag phases, and can be described by a 3-parameter logistic model. A one-step kinetic analysis approach was used to simultaneously analyze all growth curves by direct construction of both the primary and secondary (Ratkowsky square root) models using nonlinear regression to minimize the global residual error. The estimated nominal minimum growth temperature of S. aureus was 6.12 °C in potato cubes and 8.80 °C in potato salad. The estimated maximum growth temperatures of S. aureus in potato cubes and potato salad were very close to each other (46.3 and 46.8 °C, respectively). On the average, the specific growth rates of S. aureus in potato cubes were approximately 70% higher than those in potato salad. This study suggests that cooked potato and potato salad should be stored below 6 °C or above 47 °C to prevent the growth of S. aureus. The mathematical models and kinetic parameters can be used to accurately evaluate the effect of temperature abuse on the growth of S. aureus and conduct risk assessments of S. aureus in cooked potato and potato salad. PMID:26539902

  4. Oral biofilm models for mechanical plaque removal.

    PubMed

    Verkaik, Martinus J; Busscher, Henk J; Rustema-Abbing, Minie; Slomp, Anje M; Abbas, Frank; van der Mei, Henny C

    2010-08-01

    In vitro plaque removal studies require biofilm models that resemble in vivo dental plaque. Here, we compare contact and non-contact removal of single and dual-species biofilms as well as of biofilms grown from human whole saliva in vitro using different biofilm models. Bacteria were adhered to a salivary pellicle for 2 h or grown after adhesion for 16 h, after which, their removal was evaluated. In a contact mode, no differences were observed between the manual, rotating, or sonic brushing; and removal was on average 39%, 84%, and 95% for Streptococcus mutans, Streptococcus oralis, and Actinomyces naeslundii, respectively, and 90% and 54% for the dual- and multi-species biofilms, respectively. However, in a non-contact mode, rotating and sonic brushes still removed considerable numbers of bacteria (24-40%), while the manual brush as a control (5-11%) did not. Single A. naeslundii and dual-species (A. naeslundii and S. oralis) biofilms were more difficult to remove after 16 h growth than after 2 h adhesion (on average, 62% and 93% for 16- and 2-h-old biofilms, respectively), while in contrast, biofilms grown from whole saliva were easier to remove (97% after 16 h and 54% after 2 h of growth). Considering the strong adhesion of dual-species biofilms and their easier more reproducible growth compared with biofilms grown from whole saliva, dual-species biofilms of A. naeslundii and S. oralis are suggested to be preferred for use in mechanical plaque removal studies in vitro. PMID:19565279

  5. A growth kinetics model of rate decomposition for Si1-xGex alloy based on dimer theory

    NASA Astrophysics Data System (ADS)

    Dai, Xian-Ying; Ji, Yao; Hao, Yue

    2014-01-01

    According to the dimer theory on semiconductor surface and chemical vapor deposition(CVD) growth characteristics of Si1-xGex, two mechanisms of rate decomposition and discrete flow density are proposed. Based on these two mechanisms, the Grove theory and Fick's first law, a CVD growth kinetics model of Si1-xGex alloy is established. In order to make the model more accurate, two growth control mechanisms of vapor transport and surface reaction are taken into account. The paper also considers the influence of the dimer structure on the growth rate. The results show that the model calculated value is consistent with the experimental values at different temperatures.

  6. Kinetic aspects of the thermostatted growth of ice from supercooled water in simulations

    NASA Astrophysics Data System (ADS)

    Weiss, Volker C.; Rullich, Markus; Köhler, Christof; Frauenheim, Thomas

    2011-07-01

    In experiments, the growth rate of ice from supercooled water is seen to increase with the degree of supercooling, that is, the lower the temperature, the faster the crystallization takes place. In molecular dynamics simulations of the freezing process, however, the temperature is usually kept constant by means of a thermostat that artificially removes the heat released during the crystallization by scaling the velocities of the particles. This direct removal of energy from the system replaces a more realistic heat-conduction mechanism and is believed to be responsible for the curious observation that the thermostatted ice growth proceeds fastest near the melting point and more slowly at lower temperatures, which is exactly opposite to the experimental findings [M. A. Carignano, P. B. Shepson, and I. Szleifer, Mol. Phys. 103, 2957 (2005), 10.1080/00268970500243796]. This trend is explained by the diffusion and the reorientation of molecules in the liquid becoming the rate-determining steps for the crystal growth, both of which are slower at low temperatures. Yet, for a different set of simulations, a kinetic behavior analogous to the experimental finding has been reported [H. Nada and Y. Furukawa, J. Crystal Growth 283, 242 (2005), 10.1016/j.jcrysgro.2005.05.057]. To clarify this apparent contradiction, we perform relatively long simulations of the TIP4P/Ice model in an extended range of temperatures. The temperature dependence of the thermostatted ice growth is seen to be more complex than was previously reported: The crystallization process is very slow close to the melting point at 270 K, where the thermodynamic driving force for the phase transition is weak. On lowering the temperature, the growth rate initially increases, but displays a maximum near 260 K. At even lower temperatures, the freezing process slows down again due to the reduced diffusivity in the liquid. The velocity of the thermostatted melting process, in contrast, shows a monotonic increase upon

  7. Kinetic aspects of the thermostatted growth of ice from supercooled water in simulations.

    PubMed

    Weiss, Volker C; Rullich, Markus; Köhler, Christof; Frauenheim, Thomas

    2011-07-21

    In experiments, the growth rate of ice from supercooled water is seen to increase with the degree of supercooling, that is, the lower the temperature, the faster the crystallization takes place. In molecular dynamics simulations of the freezing process, however, the temperature is usually kept constant by means of a thermostat that artificially removes the heat released during the crystallization by scaling the velocities of the particles. This direct removal of energy from the system replaces a more realistic heat-conduction mechanism and is believed to be responsible for the curious observation that the thermostatted ice growth proceeds fastest near the melting point and more slowly at lower temperatures, which is exactly opposite to the experimental findings [M. A. Carignano, P. B. Shepson, and I. Szleifer, Mol. Phys. 103, 2957 (2005)]. This trend is explained by the diffusion and the reorientation of molecules in the liquid becoming the rate-determining steps for the crystal growth, both of whic