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Sample records for biofilm growth kinetics

  1. Mechanism and kinetics of biofilm growth process influenced by shear stress in sewers.

    PubMed

    Ai, Hainan; Xu, Jingwei; Huang, Wei; He, Qiang; Ni, Bingjie; Wang, Yinliang

    2016-01-01

    Sewer biofilms play an important role in the biotransformation of substances for methane and sulfide emission in sewer networks. The dynamic flows and the particular shear stress in sewers are the key factors determining the growth of the sewer biofilm. In this work, the development of sewer biofilm with varying shear stress is specifically investigated to gain a comprehensive understanding of the sewer biofilm dynamics. Sewer biofilms were cultivated in laboratory-scale gravity sewers under different hydraulic conditions with the corresponding shell stresses are 1.12 Pa, 1.29 Pa and 1.45 Pa, respectively. The evolution of the biofilm thickness were monitored using microelectrodes, and the variation in total solids (TS) and extracellular polymer substance (EPS) levels in the biofilm were also measured. The results showed that the steady-state biofilm thickness were highly related to the corresponding shear stresses with the biofilm thickness of 2.4 ± 0.1 mm, 2.7 ± 0.1 mm and 2.2 ± 0.1 mm at shear stresses of 1.12 Pa, 1.29 Pa and 1.45 Pa, respectively, which the chemical oxygen demand concentration is 400 mg/L approximately. Based on these observations, a kinetic model for describing the development of sewer biofilms was developed and demonstrated to be capable of reproducing all the experimental data.

  2. 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.

  3. 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.

  4. Growth dilution of metals in microalgal biofilms.

    PubMed

    Hill, Walter R; Larsen, Ingvar L

    2005-03-15

    Despite the key role microalgae play in introducing toxicants into aquatic food webs, little is known about the effects of environmental factors on metal accumulation by these primary producers. Environmental factors such as light and nutrients alter growth rates and may consequently influence metal concentrations in microalgae through growth dilution. Laboratory experiments suggested that metal uptake and elimination by microalgal biofilms were gradual enough to enable dilution of metals within the biofilms by photosynthetically accrued carbon, and a simple kinetic model of metal accumulation predicted significant variation in metal content due to growth dilution over the natural range of microalgal growth rates. The ratio of metal uptake to carbon uptake by microalgal biofilms decreased exponentially with increasing light in short-term laboratory experiments because photosynthesis was much more sensitive to a light gradient than was metal uptake. The effect of light on biofilm metal concentrations was confirmed in situ with a long-term experiment in which experimental shading of biofilms in a metal-contaminated stream decreased biofilm growth rates and caused a 3x increase in biofilm concentrations of twelve metals, including methylmercury. Slow growth at the primary producer level is a likely contributor to higher biotic metal concentrations in shaded, oligotrophic, or cold ecosystems.

  5. Kinetic Theories for Biofilms (Preprint)

    DTIC Science & Technology

    2011-01-01

    species of biomass and thereby allow a full coupling of quorum sensing mechanism. This work will be forthcoming in a sequel. Acknowledgment and...genetic dynamics in the presence of foreign agents [10, 13, 28]. Biofilms essentially behave like biogels in which small solvent and nutrient molecule can...γ2 = νN is proportional to the reciprocal of the volume of the solvent molecule and ∥·∥ denotes the l2 norm of a vector. The entropic conformational

  6. 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.

  7. 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.

  8. 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

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

    PubMed

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

    2015-10-01

    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

  10. Morphomechanics of bacterial biofilms undergoing anisotropic differential growth

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  11. Kinetic development of biofilm on NF membranes at the Méry-sur-Oise plant, France.

    PubMed

    Houari, Ahmed; Seyer, Damien; Kecili, Karima; Heim, Véronique; Martino, Patrick Di

    2013-01-01

    The kinetic formation of biofilms developing on nanofiltration (NF) membranes was studied for 2 years in the water production unit of Méry-sur-Oise, France. New membranes were set up in a pilot train integrated to the plant and autopsied after operation for 7, 80, 475 and 717 days. The biofouling layer was studied by confocal laser scanning microscope after 4',6-diamidino-2-phenyindole dihydrochloride and lectin staining, and by attenuated total reflectance-Fourier transform infrared spectroscopy and rheology experiments. Three stages of biofilm growth were discriminated: (1) the presence of sessile microcolonies embedded in an exopolymeric matrix (after filtration for seven days); (2) membrane coverage expansion through microcolony development and biofilm growth in three dimensions (up to 80 days filtration); and (3) biofilm maturation by densification (after filtration for 80-717 days). Biofilm maturation resulted in total coverage of the membrane surface and matrix residue diversification, development of the polysaccharide network, and the strengthening of matrix cohesion through viscosity and elasticity increases. The wettability and permeability of the fouled NF membranes decreased quickly and continuously throughout the biofilm development process. The longitudinal pressure drop (LPD) increased only after the biofilm reached a quantitative threshold. The decline in membrane permeability may be the result of contributions from many fouling mechanisms but the LPD was more substantially influenced by biofilm development.

  12. Growth Kinetics in Epitaxial Growth

    NASA Astrophysics Data System (ADS)

    Hessinger, Uwe

    Growth kinetics in heteroepitaxial growth are related to the nucleation and growth of atomic-height islands during the deposition of a material on a dissimilar substrate. Experimental measurements of the initial morphology of CaF_2 films deposited on Si(111) substrates were performed. These measurements consisted of photoemission spectroscopy and diffraction, which give sub-nanometer scale information averaged over the entire sample, and plan-view transmission electron microscopy, which gives localized information on a scale of several nanometers. These results, combined with others in the literature, revealed four distinct growth morphologies dependent on the deposition rate, substrate temperature and spacing between atomic-height steps on the surface, two of which had not been previously explained. A model based on two extant theories of homoepitaxial growth kinetics was developed to explain the different observed growth morphologies for the heteroepitaxial system CaF_2/Si(111). The first theory deals with whether the initial nucleation will occur at substrate steps or through adatom collisions on flat terraces, while the second deals with the nucleation of subsequent layers as these initial atomic islands increase in size. In extending these theories to heteroepitaxy, very different rates of upper-layer nucleation for the different size islands that nucleated at steps and on terraces are predicted. By applying this theory to CaF_2/Si(111), the diffusion barriers for CaF_2 molecule migration both on the reacted Si-Ca-F interface layer and on subsequent CaF_2 layers was extracted. The four different growth morphologies are explained within a common framework. The theory is quite general, and should apply to most heteroepitaxial systems. These theories were extended to predict a means by which the upper-layer nucleation may be inhibited while the underlying layer is completed. This method involves initiating the growth at conditions favoring many, small islands on

  13. Kinetics of carbendazim degradation in a horizontal tubular biofilm reactor.

    PubMed

    Alvarado-Gutiérrez, María Luisa; Ruiz-Ordaz, Nora; Galíndez-Mayer, Juvencio; Santoyo-Tepole, Fortunata; Curiel-Quesada, Everardo; García-Mena, Jaime; Ahuatzi-Chacón, Deifilia

    2016-12-22

    The fungicide carbendazim is an ecotoxic agent affecting aquatic biota. Due to its suspected hormone-disrupting effects, it is considered a "priority hazard substance" by the Water Framework Directive of the European Commission, and its degradation is of major concern. In this work, a horizontal tubular biofilm reactor (HTBR) operating in plug-flow regime was used to study the kinetics of carbendazim removal by an acclimated microbial consortium. The reactor was operated in steady state continuous culture at eight different carbendazim loading rates. The concentrations of the fungicide were determined at several distances of the HTBR. At the loading rates tested, the highest instantaneous removal rates were observed in the first section of the tubular biofilm reactor. No evidence of inhibition of the catabolic activity of the microbial community was found. Strains of the genera Flectobacillus, Klebsiella, Stenotrophomonas, and Flavobacterium were identified in the biofilm; the last three degrade carbendazim in axenic culture.

  14. 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

  15. 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.

  16. 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.

  17. Biofilm growth and characteristics in an alternating pumped sequencing batch biofilm reactor (APSBBR).

    PubMed

    Zhan, Xin-Min; Rodgers, Michael; O'Reilly, Edmond

    2006-02-01

    A novel biofilm reactor-alternating pumped sequencing batch biofilm reactor (APSBBR)-was developed to treat synthetic dairy wastewater at a volumetric chemical oxygen demand (COD) loading rate of 487 g COD m(-3) d(-1) and an areal loading rate of 5.4 g COD m(-2) d(-1). This biofilm reactor comprised two tanks, Tanks 1 and 2, with two identical plastic biofilm modules in each tank. The maximum volume of bulk fluid in the two-tank reactor was the volume of one tank. The APSBBR was operated as a sequencing batch biofilm reactor with five operational phases-fill (25 min), anoxic (9 h), aerobic (9 h), settle (6 h) and draw (5 min). The fill, anoxic, settle and draw phases occurred in Tank 1. In the aerobic phase, the wastewater was circulated between the two tanks with centrifugal pumps and aeration was mainly achieved through oxygen absorption by micro-organisms in the biofilms when they were exposed to the air. In this paper, the biofilm growth and characteristics in the APSBBR were studied in a 98-day laboratory-scale experiment. During the course of the study, it was found that the biofilm thickness (delta) in Tank 1 ranged from 1.2 to 7.2 mm and that in Tank 2 from 0.5 to 2.2 mm; the biofilm growth against time (t) can be simulated as delta=0.07t0.99 (R2 = 0.97, P = 0.002) in Tank 1 and delta = 0.08t0.66 (R2 = 0.81, P = 0.04) in Tank 2. The biomass yield coefficient, Y, was 0.18 g volatile solids (VS) g(-1) COD removal. The biofilm density in both tanks, X, decreased as the biofilm thickness increased and can be correlated to the biofilm thickness, delta .

  18. In vitro study of biofilm growth on biologic prosthetics.

    PubMed

    Bellows, Charles; Smith, Alison

    2014-01-01

    Biologic prosthetics are increasingly used for the repair of abdominal wall hernia defects but can become infected as a result of peri- or early post-operative bacterial contamination. Data evaluating biofilm formation on biologic prosthetics is lacking. The aim of this study was to investigate the influence of different biologic prosthetics on the growth behavior of two different bacterial species and their ability to form biofilms. Methicillin resistant Staphylococcus aureus (MRSA) or Pseudomrnonas aeruginosa were incubated on disks of two biologic prosthetics-human acellular dermis (ADM), and porcine small intestinal submucosa (SIS). The bacteria were allowed to attach to the prosthetics and propagate into mature biofilms for 24 hours at 370C. Images of biofilms were obtained using confocal microscopy and scanning electron microscopy (SEM). The number of viable cells and the biofilm biomass were quantified by colony forming units (CFUs) and crystal violet staining respectively. Analysis of variance was performed to compare the mean values for the different prosthetics. Each biologic matrix had a distinct surface characteristic. SEM visualized mature biofilms characterized by highly organized multi-cellular structures on surface of both biologic prosthetics. Quantification of bacterial growth over time showed that ADM had the lowest CFUs and biofilm biomass at 24 hours post-inoculation compared to SIS for both bacterial strains. MRSA and P. aeruginosa can form mature biofilms on biologic prosthetics but the relative abundance of the biofilm varies on different prosthetic constructs. Biologic material composition and manufacturing methods may influence bacterial adherence.

  19. 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.

  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. 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...

  2. Biofilm Growth in Porous Media: Validation of three-dimensional characterization of biofilm growth in packed bead columns

    NASA Astrophysics Data System (ADS)

    Iltis, G.; Armstrong, R. T.; Jansik, D. P.; Wood, B. D.; Wildenschild, D.

    2009-12-01

    Current understanding of subsurface microbial biofilm formation and the impact on fluid hydrodynamics associated with biofilm growth is limited by our ability to observe the in situ pore-scale geometry of developed biofilms. Biomass distribution in porous media has been observed primarily in two-dimensional systems to date; currently, no high-resolution three-dimensional structural data sets exist for opaque porous media that provide sufficient information about biomass distribution such that the impact on flow and solute transport at the pore-scale can be directly assessed. A new method for resolving high-resolution three-dimensional tomographic images of biofilms in porous media using synchrotron-based x-ray microtomography has been developed. As a part of this method, silver coated, neutrally buoyant microspheres are used to delineate the surface of the biofilm within porous media. Quantitative validation of this method will be presented along with three-dimensional characterization of biofilm growth in packed bead columns. Current and future applications for this imaging method include quantitative experimental validation of mathematical models pertaining to spatial distribution of biofilm and variation in hydrodynamic flow pathways within porous media. Our current research into this area focuses on evaluating microbially mediated co-precipitation of heavy metals in porous media. Results will be presented from new imaging experiments comparing different microbes and varying flow rates to address effects of biofilm type and density on the image quality.

  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.

  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. Kinetics of biofilm formation by drinking water isolated Penicillium expansum.

    PubMed

    Simões, Lúcia Chaves; Simões, Manuel; Lima, Nelson

    2015-01-01

    Current knowledge on drinking water (DW) biofilms has been obtained mainly from studies on bacterial biofilms. Very few reports on filamentous fungi (ff) biofilms are available, although they can contribute to the reduction in DW quality. This study aimed to assess the dynamics of biofilm formation by Penicillium expansum using microtiter plates under static conditions, mimicking water flow behaviour in stagnant regions of drinking water distribution systems. Biofilms were analysed in terms of biomass (crystal violet staining), metabolic activity (resazurin, fluorescein diacetate and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide [MTT]) and morphology (epifluorescence [calcofluor white M2R, FUN-1, FDA and acridine orange] and bright-field microscopies). Biofilm development over time showed the typical sigmoidal curve with noticeable different phases in biofilm formation (induction, exponential, stationary, and sloughing off). The methods used to assess metabolic activity provided similar results. The microscope analysis allowed identification of the involvement of conidia in initial adhesion (4 h), germlings (8 h), initial monolayers (12 h), a monolayer of intertwined hyphae (24 h), mycelial development, hyphal layering and bundling, and development of the mature biofilms (≥48 h). P. expansum grows as a complex, multicellular biofilm in 48 h. The metabolic activity and biomass of the fungal biofilms were shown to increase over time and a correlation between metabolism, biofilm mass and hyphal development was found.

  6. Estimating biofilm reaction kinetics using hybrid mechanistic-neural network rate function model.

    PubMed

    Kumar, B Shiva; Venkateswarlu, Ch

    2012-01-01

    This work describes an alternative method for estimation of reaction rate of a biofilm process without using a model equation. A first principles model of the biofilm process is integrated with artificial neural networks to derive a hybrid mechanistic-neural network rate function model (HMNNRFM), and this combined model structure is used to estimate the complex kinetics of the biofilm process as a consequence of the validation of its steady state solution. The performance of the proposed methodology is studied with the aid of the experimental data of an anaerobic fixed bed biofilm reactor. The statistical significance of the method is also analyzed by means of the coefficient of determination (R2) and model efficiency (ME). The results demonstrate the effectiveness of HMNNRFM for estimating the complex kinetics of the biofilm process involved in the treatment of industry wastewater.

  7. 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.

  8. 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.

  9. 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.

  10. Kinetic parameter estimation in N. europaea biofilms using a 2-D reactive transport model.

    PubMed

    Lauchnor, Ellen G; Semprini, Lewis; Wood, Brian D

    2015-06-01

    Biofilms of the ammonia oxidizing bacterium Nitrosomonas europaea were cultivated to study microbial processes associated with ammonia oxidation in pure culture. We explored the hypothesis that the kinetic parameters of ammonia oxidation in N. europaea biofilms were in the range of those determined with batch suspended cells. Oxygen and pH microelectrodes were used to measure dissolved oxygen (DO) concentrations and pH above and inside biofilms and reactive transport modeling was performed to simulate the measured DO and pH profiles. A two dimensional (2-D) model was used to simulate advection parallel to the biofilm surface and diffusion through the overlying fluid while reaction and diffusion were simulated in the biofilm. Three experimental studies of microsensor measurements were performed with biofilms: i) NH3 concentrations near the Ksn value of 40 μM determined in suspended cell tests ii) Limited buffering capacity which resulted in a pH gradient within the biofilms and iii) NH3 concentrations well below the Ksn value. Very good fits to the DO concentration profiles both in the fluid above and in the biofilms were achieved using the 2-D model. The modeling study revealed that the half-saturation coefficient for NH3 in N. europaea biofilms was close to the value measured in suspended cells. However, the third study of biofilms with low availability of NH3 deviated from the model prediction. The model also predicted shifts in the DO profiles and the gradient in pH that resulted for the case of limited buffering capacity. The results illustrate the importance of incorporating both key transport and chemical processes in a biofilm reactive transport model.

  11. Population dynamics and in situ kinetics of nitrifying bacteria in autotrophic nitrifying biofilms as determined by real-time quantitative PCR.

    PubMed

    Kindaichi, Tomonori; Kawano, Yoshiko; Ito, Tsukasa; Satoh, Hisashi; Okabe, Satoshi

    2006-08-20

    Population dynamics of ammonia-oxidizing bacteria (AOB) and uncultured Nitrospira-like nitrite-oxidizing bacteria (NOB) dominated in autotrophic nitrifying biofilms were determined by using real-time quantitative polymerase chain reaction (RTQ-PCR) and fluorescence in situ hybridization (FISH). Although two quantitative techniques gave the comparable results, the RTQ-PCR assay was easier and faster than the FISH technique for quantification of both nitrifying bacteria in dense microcolony-forming nitrifying biofilms. Using this RTQ-PCR assay, we could successfully determine the maximum specific growth rate (mu = 0.021/h) of uncultured Nitrospira-like NOB in the suspended enrichment culture. The population dynamics of nitrifying bacteria in the biofilm revealed that once they formed the biofilm, the both nitrifying bacteria grew slower than in planktonic cultures. We also calculated the spatial distributions of average specific growth rates of both nitrifying bacteria in the biofilm based on the concentration profiles of NH4+, NO2-, and O2, which were determined by microelectrodes, and the double-Monod model. This simple model estimation could explain the stratified spatial distribution of AOB and Nitrospira-like NOB in the biofilm. The combination of culture-independent molecular techniques and microelectrode measurements is a very powerful approach to analyze the in situ kinetics and ecophysiology of nitrifying bacteria including uncultured Nitrospira-like NOB in complex biofilm communities.

  12. Catalase Enhances Growth and Biofilm Production of Mycoplasma pneumoniae

    PubMed Central

    Simmons, Warren L.; Dybvig, Kevin

    2015-01-01

    Mycoplasma pneumoniae causes chronic respiratory disease in humans. Factors thought to be important for colonization include the ability of the mycoplasma to form a biofilm on epithelial surfaces and the production of hydrogen peroxide to damage host tissue. Almost all of the mycoplasmas, including M. pneumoniae, lack superoxide dismutase and catalase and a balance should exist between peroxide production and growth. We show here that the addition of catalase to cultures enhanced the formation of biofilms and altered the structure. The incorporation of catalase in agar increased the number of colony-forming units detected and hence could improve the clinical diagnosis of mycoplasmal diseases. PMID:25894997

  13. Growth dynamic of Naegleria fowleri in a microbial freshwater biofilm.

    PubMed

    Goudot, Sébastien; Herbelin, Pascaline; Mathieu, Laurence; Soreau, Sylvie; Banas, Sandrine; Jorand, Frédéric

    2012-09-01

    The presence of pathogenic free-living amoebae (FLA) such as Naegleria fowleri in freshwater environments is a potential public health risk. Although its occurrence in various water sources has been well reported, its presence and associated factors in biofilm remain unknown. In this study, the density of N. fowleri in biofilms spontaneously growing on glass slides fed by raw freshwater were followed at 32 °C and 42 °C for 45 days. The biofilms were collected with their substrata and characterized for their structure, numbered for their bacterial density, thermophilic free-living amoebae, and pathogenic N. fowleri. The cell density of N. fowleri within the biofilms was significantly affected both by the temperature and the nutrient level (bacteria/amoeba ratio). At 32 °C, the density remained constantly low (1-10 N. fowleri/cm(2)) indicating that the amoebae were in a survival state, whereas at 42 °C the density reached 30-900 N. fowleri/cm(2) indicating an active growth phase. The nutrient level, as well, strongly affected the apparent specific growth rate (μ) of N. fowleri in the range of 0.03-0.23 h(-1). At 42 °C a hyperbolic relationship was found between μ and the bacteria/amoeba ratio. A ratio of 10(6) to 10(7) bacteria/amoeba was needed to approach the apparent μ(max) value (0.23 h(-1)). Data analysis also showed that a threshold for the nutrient level of close to 10(4) bacteria/amoeba is needed to detect the growth of N. fowleri in freshwater biofilm. This study emphasizes the important role of the temperature and bacteria as prey to promote not only the growth of N. fowleri, but also its survival.

  14. Kinetics and equilibrium adsorption of nano-TiO 2 particles on synthetic biofilm

    NASA Astrophysics Data System (ADS)

    Sahle-Demessie, Endalkachew; Tadesse, Haregewine

    2011-07-01

    Understanding the environmental behavior of nanoparticles includes their interaction with biofilms, which is a covering on the surface of a living or nonliving substrate composed of microorganisms. This study focuses on nano-TiO2 sorption mechanism by synthetic biofilm that was prepared as superporous spherical beads from agarose, using batch stirred flasks kept at room temperature. The pH plays an important part in these phenomena, by its influence on the nanoparticles and biofilm chemistry, where the biofilm nanoTiO2 uptake at neutral pH was enhanced over acidic conditions. Hydroxylation of TiO2 nanoparticles, dependent on pH and the salinity of the solution, influences the stability of colloids, the sorption kinetics via the nature of limiting phases: diffusion through the boundary layer or intrabiofilm mass transfer and the sorption mechanism. The sorption follows pseudo first-order adsorption kinetics with estimated average rate constants of 2.2 (min- 1). Equilibrium isotherms were evaluated using Langmuir and Freundlich isotherms to obtain the maximum uptake at different solution pH and the free energy of the adsorption. The adsorption is apparently irreversible because biofilm limits diffusion of particles out of the pores and the complexation active binding sites on the surface hydrated biofilm to the hydrophilic TiO2 nanoparticles.

  15. Sensitivity analysis of a biofilm model describing mixed growth of nitrite oxidisers in a CSTR.

    PubMed

    Kornaros, M; Dokianakis, S N; Lyberatos, G

    2006-01-01

    A simple kinetic model has been developed for describing nitrite oxidation by autotrophic aerobic nitrifiers in a CSTR reactor, in which mixed (suspended and attached) growth conditions are prevailing. In this work, a critical dimensionless parameter is identified containing both biofilm characteristics and microbial kinetic parameters, as well as the specific (per volume) surface of the reactor configuration used. Evaluation of this dimensionless parameter can easily provide information on whether or not wall attachment is critical, and should be taken into account either in kinetic studies or in reactor design, when specific pollutants are to be removed from the waste influent stream. The effect of bulk dissolved oxygen (DO) concentration on the validity of this model is addressed and minimum non-limiting DO concentrations are proposed depending on the reactor configuration.

  16. 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.

  17. Uncertainty in bulk-liquid hydrodynamics and biofilm dynamics creates uncertainties in biofilm reactor design.

    PubMed

    Boltz, J P; Daigger, G T

    2010-01-01

    While biofilm reactors may be classified as one of seven different types, the design of each is unified by fundamental biofilm principles. It follows that state-of-the art design of each biofilm reactor type is subject to the same uncertainties (although the degree of uncertainty may vary). This paper describes unifying biofilm principles and uncertainties of importance in biofilm reactor design. This approach to biofilm reactor design represents a shift from the historical approach which was based on empirical criteria and design formulations. The use of such design criteria was largely due to inherent uncertainty over reactor-scale hydrodynamics and biofilm dynamics, which correlate with biofilm thickness, structure and function. An understanding of two fundamental concepts is required to rationally design biofilm reactors: bioreactor hydrodynamics and biofilm dynamics (with particular emphasis on mass transfer resistances). Bulk-liquid hydrodynamics influences biofilm thickness control, surface area, and development. Biofilm dynamics influences biofilm thickness, structure and function. While the complex hydrodynamics of some biofilm reactors such as trickling filters and biological filters have prevented the widespread use of fundamental biofilm principles and mechanistic models in practice, reactors utilizing integrated fixed-film activated sludge or moving bed technology provide a bulk-liquid hydrodynamic environment allowing for their application. From a substrate transformation perspective, mass transfer in biofilm reactors defines the primary difference between suspended growth and biofilm systems: suspended growth systems are kinetically (i.e., biomass) limited and biofilm reactors are primarily diffusion (i.e., biofilm growth surface area) limited.

  18. Growth and dissolution kinetics of tetragonal lysozyme

    NASA Technical Reports Server (NTRS)

    Monaco, L. A.; Rosenberger, F.

    1993-01-01

    The growth and dissolution kinetics of lysozyme in a 25 ml solution bridge inside a closed growth cell was investigated. It was found that, under all growth conditions, the growth habit forming (110) and (101) faces grew through layer spreading with different growth rate dependence on supersaturation/temperature. On the other hand, (100) faces which formed only at low temperatures underwent a thermal roughening transition around 12 C.

  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. 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.

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

    NASA Astrophysics Data System (ADS)

    Davis, C. A.; Pyrak-Nolte, L. J.; Atekwana, E. A.; Werkema, D. D.; Haugen, M. E.

    2009-12-01

    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 columns. A control column (non-biostimulated) and a biostimulated column were studied in a 2D acoustic scanning apparatus, and a second set of columns were constructed with Ag-AgCl electrodes for complex conductivity measurements. At the completion of the 29-day experiment, compressional wave amplitudes and arrival times for the control column were observed to be relatively uniform over the scanned 2D region. However, the biostimulated sample exhibited a high degree of spatial variability within the column for both the amplitude and arrival times. Furthermore, portions of the sample exhibited increased attenuation (~ 80%) concurrent with an increase in the arrival times, while other portions exhibited decreased attenuation (~ 45%) and decreased arrival time. The acoustic amplitude and arrival times changed significantly in the biostimulated column between Days 5 and 7 of the experiment and are consistent with a peak in the imaginary conductivity (σ”) values. The σ” response corresponds to different stages of biofilm development. That is, we interpret the peak σ” with the maximum biofilm thickness and decreasing σ” due to cell death or detachment. Environmental scanning electron microscope (ESEM) imaging confirmed microbial cell attachment to sand surfaces in the biostimulated columns, showed apparent differences in the morphology of attached biomass between regions of increased and decreased attenuation, and indicated no mineral precipitation or biomineralization. The heterogeneity in the elastic properties arises from the differences in the morphology and structure of attached biofilms. These results suggest that combining acoustic imaging and complex conductivity techniques

  2. Impact of initial biofilm growth on the anode impedance of microbial fuel cells.

    PubMed

    Ramasamy, Ramaraja P; Ren, Zhiyong; Mench, Matthew M; Regan, John M

    2008-09-01

    Electrochemical impedance spectroscopy (EIS) was used to study the behavior of a microbial fuel cell (MFC) during initial biofilm growth in an acetate-fed, two-chamber MFC system with ferricyanide in the cathode. EIS experiments were performed both on the full cell (between cathode and anode) as well as on individual electrodes. The Nyquist plots of the EIS data were fitted with an equivalent electrical circuit to estimate the contributions of various intrinsic resistances to the overall internal MFC impedance. During initial development of the anode biofilm, the anode polarization resistance was found to decrease by over 70% at open circuit and by over 45% at 27 microA/cm(2), and a simultaneous increase in power density by about 120% was observed. The exchange current density for the bio-electrochemical reaction on the anode was estimated to be in the range of 40-60 nA/cm(2) for an immature biofilm after 5 days of closed circuit operation, which increased to around 182 nA/cm(2) after more than 3 weeks of operation and stable performance in an identical parallel system. The polarization resistance of the anode was 30-40 times higher than that of the ferricyanide cathode for the conditions tested, even with an established biofilm. For a two-chamber MFC system with a Nafion 117 membrane and an inter-electrode spacing of 15 cm, the membrane and electrolyte solution dominate the ohmic resistance and contribute to over 95% of the MFC internal impedance. Detailed EIS analyses provide new insights into the dominant kinetic resistance of the anode bio-electrochemical reaction and its influence on the overall power output of the MFC system, even in the high internal resistance system used in this study. These results suggest that new strategies to address this kinetic constraint of the anode bio-electrochemical reactions are needed to complement the reduction of ohmic resistance in modern designs.

  3. 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

  4. 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

  5. Analysis of uropathogenic Escherichia coli biofilm formation under different growth conditions.

    PubMed

    Adamus-Białek, Wioletta; Kubiak, Anna; Czerwonka, Grzegorz

    2015-01-01

    The ability to form different types of biofilm enables bacteria to survive in a harsh or toxic environment. Different structures of biofilms are related to different surfaces and environment of bacterial growth. The aim of this study was analysis of the biofilm formation of 115 clinical uropathogenic Escherichia coli strains under different growth conditions: surface for biofilm formation, medium composition and time of incubation. The biofilm formation after 24 h, 48 h, 72 h and 96 h was determined spectrophotometrically (A531) after crystal violet staining and it was correlated with bacterial growth (A600). The live and dead cells in biofilm structures was also observed on the glass surface by an epi-fluorescence microscope. Additionally, the presence of rpoS, sdiA and rscA genes was analyzed. The statistical significance was estimated by paired T-test. The observed biofilms were different for each particular strain. The biofilm formation was the highest in the rich medium (LB) after 24 h and its level hasn't changed in time. When biofilm level was compared to bacterial growth (relative biofilm) - it was higher in a minimal medium in comparison to enriched medium. These results suggest that most of the bacterial cells prefer to live in a biofilm community under the difficult environmental conditions. Moreover, biofilm formation on polyurethane surface did not correlate with biofilm formation on glass. It suggests that mechanisms of biofilm formation can be correlated with other bacterial properties. This phenomenon may explain different types of biofilm formation among one species and even one pathotype - uropathogenic Escherichia coli.

  6. 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.

  7. Kinetics of microbial growth on pentachlorophenol.

    PubMed Central

    Klecka, G M; Maier, W J

    1985-01-01

    Batch and fed-batch experiments were conducted to examine the kinetics of pentachlorophenol utilization by an enrichment culture of pentachlorophenol-degrading bacteria. The Haldane modification of the Monod equation was found to describe the relationship between the specific growth rate and substrate concentration. Analysis of the kinetic parameters indicated that the maximum specific growth rate and yield coefficients are low, with values of 0.074 h-1 and 0.136 g/g, respectively. The Monod constant (Ks) was estimated to be 60 micrograms/liter, indicating a high affinity of the microorganisms for the substrate. However, high concentrations (KI = 1,375 micrograms/liter) were shown to be inhibitory for metabolism and growth. These kinetic parameters can be used to define the optimal conditions for the removal of pentachlorophenol in biological treatment systems. PMID:3977315

  8. Biofilms.

    PubMed

    Callow, J A; Callow, M E

    2006-01-01

    Biofilms of bacteria, frequently in association with algae, protozoa and fungi, are found on all submerged structures in the marine environment. Although it is likely that for the majority of organisms a biofilmed surface is not a pre-requisite for settlement, in practice, colonization by spores and larvae of fouling organisms almost always takes place via a biofilmed surface. Therefore, the properties of the latter may be expected to influence colonization, positively or negatively. Biofilms are responsible for a range of surface-associated and diffusible signals, which may moderate the settling behaviour of cells, spores and larvae. However, there is no consensus view regarding either cause and effect or the mechanism(s) by which biofilms moderate settlement. Studies with mixed biofilms, especially field experiments, are difficult to interpret because of the conflicting signals produced by different members of the biofilm community as well as their spatial organisation. Molecular techniques highlight the deficiencies of culture methods in identifying biofilm bacteria; hence, the strains with the most impact on settlement of spores and larvae may not yet have been isolated and cultured. Furthermore, secondary products isolated from cultured organisms may not reflect the situation that pertains in nature. The evidence that bacterial quorum sensing signal molecules stimulate settlement of spores of the green macroalga, Ulva, is discussed in some detail. New molecular and analytical tools should provide the opportunity to improve our fundamental understanding of the interactions between fouling organisms and biofilms, which in turn may inform novel strategies to control biofouling.

  9. 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.

  10. Polyphosphate-mediated modulation of Campylobacter jejuni biofilm growth and stability.

    PubMed

    Drozd, Mary; Chandrashekhar, Kshipra; Rajashekara, Gireesh

    2014-08-15

    Biofilms increase C. jejuni's resilience to detergents, antibiotics, and environmental stressors. In these investigations, we studied the modulation of biofilm in response to phosphate related stressors. We found that the deletion of ppk1, phoX, and ppk2 (polyphosphate associated [poly P] genes) in C. jejuni modulated different stages of biofilm formation such as attached microcolonies, air-liquid biofilms, and biofilm shedding. Additionally, inorganic phosphate also modulated attached microcolonies, air-liquid biofilms, and biofilm shedding both independently of and additively in the poly P associated mutants. Furthermore, we observed that these different biofilm stages were affected by biofilm age: for example, the adherent microcolonies were maximum on day 2, while biofilm growth at the air-liquid interface and shedding was highest on day 3. Also, we observed altered calcofluor white reactive polysaccharides in poly P-associated mutants, as well as increased secretion of autoinducer-2 (AI-2) quorum sensing molecules in the ∆ppk2 mutant. Further, the polysaccharide and flagellar biosynthesis genes, that are associated with biofilm formation, were altered in these poly P-associated mutants. We conclude that the phosphate limiting condition modulates C. jejuni biofilm formation.

  11. Cell growth and protein expression of Shewanella oneidensis in biofilms and hydrogel-entrapped cultures.

    PubMed

    Zhang, Yingdan; Ng, Chun Kiat; Cohen, Yehuda; Cao, Bin

    2014-05-01

    The performance of biofilm-based bioprocesses is difficult to predict and control because of the intrinsic heterogeneous and dynamic properties of microbial biofilms. Biofilm mimics, such as microbial cells entrapped in polymeric scaffolds that are permeable for nutrients, have been proposed to replace real biofilms to achieve long-term robust performance in engineering applications. However, the physiological differences between cells that are physically entrapped in a synthetic polymeric matrix and biofilm cells that are encased in a self-produced polymeric matrix remain unknown. In this study, using Shewanella oneidensis as a model organism and alginate hydrogel as a model synthetic matrix, we compared the cell growth and protein expression in entrapped cultures and biofilms. The hydrogel-entrapped cultures were found to exhibit a growth rate comparable with biofilms. There was no substantial difference in cell viability, surface charge, as well as hydrophobicity between the cells grown in alginate hydrogel and those grown in biofilms. However, the gel-entrapped cultures were found to be physiologically different from biofilms. The gel-entrapped cultures had a higher demand for metabolic energy. The siderophore-mediated iron uptake was repressed in the gel-entrapped cells. The presence of the hydrogel matrix decreased the expression of proteins involved in biofilm formation, while inducing the production of extracellular DNA (eDNA) in the gel-entrapped cultures. These results advance the fundamental understanding of the physiology of hydrogel-entrapped cells, which can lead to more efficient biofilm mimic-based applications.

  12. 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.

  13. 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

  14. Pseudomonas aeruginosa biofilm growth inhibition on medical plastic materials by immobilized esterases and acylase.

    PubMed

    Kisch, Johannes Martin; Utpatel, Christian; Hilterhaus, Lutz; Streit, Wolfgang R; Liese, Andreas

    2014-09-05

    Biofilms are matrix-encapsulated cell aggregates that cause problems in technical and health-related areas; for example, 65 % of all human infections are biofilm associated. This is mainly due to their ameliorated resistance against antimicrobials and immune systems. Pseudomonas aeruginosa, a biofilm-forming organism, is commonly responsible for nosocomial infections. Biofilm development is partly mediated by signal molecules, such as acyl-homoserine lactones (AHLs) in Gram-negative bacteria. We applied horse liver esterase, porcine kidney acylase, and porcine liver esterase; these can hydrolyze AHLs, thereby inhibiting biofilm formation. As biofilm infections are often related to foreign material introduced into the human body, we immobilized the enzymes on medical plastic materials. Biofilm formation was quantified by Crystal Violet staining and confocal laser scanning microscopy, revealing up to 97 % (on silicone), 54 % (on polyvinyl chloride), and 77 % (on polyurethane) reduced biomass after 68 h growth.

  15. 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).

  16. 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...

  17. 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

  18. 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

  19. Effects of streambed morphology and biofilm growth on the transient storage of solutes.

    PubMed

    Bottacin-Busolin, Andrea; Singer, Gabriel; Zaramella, Mattia; Battin, Tom J; Marion, Andrea

    2009-10-01

    Microbial biofilms are the prime site of nutrient and contaminant removal in streams. It is therefore essential to understand how biofilms affect hydrodynamic exchange, solute transport, and retention in systems where geomorphology end induced hydrodynamics shape their growth and structure. We experimented with large-scale streamside flumes with streambed landscapes constructed from graded bedforms of constant height and wavelength. Each flume had a different bedform height and was covered with a layer of gravel as substratum for benthic microbial biofilms. Biofilms developed different biomass and physical structures in response to the hydrodynamic conditions induced by the streambed morphology. Step injections of conservative tracers were performed at different biofilm growth stages. The experimental breakthrough curves were analyzed with the STIR model, using a residence time approach to characterize the retention effects associated with biofilms. The retained mass of the solute increased with biofilm biomass and the biofilm-associated retention was furthermore related to bedform height. We tentatively relate this behavior to biofilm structural differentiation induced by bed morphology, which highlights the strong linkage between geomorphology, hydrodynamics, and biofilms in natural streams and provide important clues for stream restoration.

  20. 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

    2016-09-06

    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.

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

    PubMed Central

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

    2016-01-01

    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

  2. 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.

  3. 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

  4. 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.

  5. Kinetics of nitrate and perchlorate removal and biofilm stratification in an ion exchange membrane bioreactor.

    PubMed

    Ricardo, Ana R; Carvalho, Gilda; Velizarov, Svetlozar; Crespo, João G; Reis, Maria A M

    2012-09-15

    The biological degradation of nitrate and perchlorate was investigated in an ion exchange membrane bioreactor (IEMB) using a mixed anoxic microbial culture and ethanol as the carbon source. In this process, a membrane-supported biofilm reduces nitrate and perchlorate delivered through an anion exchange membrane from a polluted water stream, containing 60 mg/L of NO₃⁻ and 100 μg/L of ClO₄⁻. Under ammonia limiting conditions, the perchlorate reduction rate decreased by 10%, whereas the nitrate reduction rate was unaffected. Though nitrate and perchlorate accumulated in the bioreactor, their concentrations in the treated water (2.8 ± 0.5 mg/L of NO₃⁻ and 7.0 ± 0.8 μg/L of ClO₄⁻, respectively) were always below the drinking water regulatory levels, due to Donnan dialysis control of the ionic transport in the system. Kinetic parameters determined for the mixed microbial culture in suspension showed that the nitrate reduction rate was 35 times higher than the maximum perchlorate reduction rate. It was found that perchlorate reduction was inhibited by nitrate, since after nitrate depletion perchlorate reduction rate increased by 77%. The biofilm developed in the IEMB was cryosectioned and the microbial population was analyzed by fluorescence in situ hybridization (FISH). The results obtained seem to indicate that the kinetic advantage of nitrate reduction favored accumulation of denitrifiers near the membrane, whereas per(chlorate) reducing bacteria were mainly positioned at the biofilm outer surface, contacting the biomedium. As a consequence of the biofilm stratification, the reduction of perchlorate and nitrate occur sequentially in space allowing for the removal of both ions in the IEMB.

  6. 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.

  7. Biofilm growth on polyvinylchloride surface incubated in suboptimal microbial warm water and effect of sanitizers on biofilm removal post biofilm formation.

    PubMed

    Maharjan, Pramir; Huff, Geraldine; Zhang, Wen; Watkins, Susan

    2017-01-01

    An in vitro experiment was conducted to understand the nature of biofilm growth on polyvinyl chloride (PVC) surface when exposed to suboptimal-quality microbial water (>4 log10 cfu/mL) obtained from a poultry drinking water source mimicking water in waterlines during the first week of poultry brooding condition. PVC sections (internal surface area of 15.16 cm(2)) were utilized in the study to grow biofilm. After a 7-d test period, test coupons with 7-day-old biofilm were transferred into autoclaved municipal water and then treated with either chlorine-based or hydrogen peroxide-based sanitizer at bird drinking water rate, to see the impact on removal of biofilm formed on test coupons. Two trials (T1 and T2) were conducted. Test coupons used in T1 and T2 had the bacterial growth of 3.67 (SEM 0.04) and 3.97 (SEM 0.11) log10 cfu/cm(2) on d 7. After sanitizer application, chlorine-based sanitizer removed bacteria in biofilm completely (0 cfu/cm(2)) within 24 h post treatment whereas hydrogen peroxide-based sanitizer reduced the counts to 1.68 log10 cfu/cm(2) (P < 0.05) by 48 h post sanitizer application. Control remained the same (P > 0.05). Results indicated that biofilm formation can occur quickly under suboptimal water condition on PVC surface, and sanitizer application helped mitigate already formed biofilm, yet chlorine proved to be more effective than hydrogen peroxide.

  8. Culture media profoundly affect Candida albicans and Candida tropicalis growth, adhesion and biofilm development

    PubMed Central

    Weerasekera, Manjula M; Wijesinghe, Gayan K; Jayarathna, Thilini A; Gunasekara, Chinthika P; Fernando, Neluka; Kottegoda, Nilwala; Samaranayake, Lakshman P

    2016-01-01

    As there are sparse data on the impact of growth media on the phenomenon of biofilm development for Candida we evaluated the efficacy of three culture media on growth, adhesion and biofilm formation of two pathogenic yeasts, Candida albicans and Candida tropicalis. The planktonic phase yeast growth, either as monocultures or mixed cultures, in sabouraud dextrose broth (SDB), yeast nitrogen base (YNB), and RPMI 1640 was compared, and adhesion as well as biofilm formation were monitored using MTT and crystal violet (CV) assays and scanning electron microscopy. Planktonic cells of C. albicans, C. tropicalis and their 1:1 co-culture showed maximal growth in SDB. C. albicans/C. tropicalis adhesion was significantly facilitated in RPMI 1640 although the YNB elicited the maximum growth for C. tropicalis. Similarly, the biofilm growth was uniformly higher for both species in RPMI 1640, and C. tropicalis was the slower biofilm former in all three media. Scanning electron microscopy images tended to confirm the results of MTT and CV assay. Taken together, our data indicate that researchers should pay heed to the choice of laboratory culture media when comparing relative planktonic/biofilm growth of Candida. There is also a need for standardisation of biofilm development media so as to facilitate cross comparisons between laboratories. PMID:27706381

  9. Inhibition of Streptococcus mutans Growth and Biofilm Formation by Probiotics in vitro.

    PubMed

    Schwendicke, Falk; Korte, Franziska; Dörfer, Christof E; Kneist, Susanne; Fawzy El-Sayed, Karim; Paris, Sebastian

    2017-01-01

    To exert anticaries effects, probiotics are described to inhibit growth and biofilm formation of cariogenic bacteria such as Streptococcus mutans (SM). We screened 8 probiotics and assessed how SM growth or biofilm formation inhibition affects cariogenicity of probiotic-SM mixed-species biofilms in vitro. Growth inhibition was assessed by cocultivating probiotics and 2 SM strains (ATCC 20532/25175) on agar. Probiotics were either precultured before SM cultivation (exclusion), or SM precultured prior to probiotic cultivation (displacement). Inhibition of SM culture growth was assessed visually. Inhibition of SM biofilm formation on bovine enamel was assessed using a continuous-flow short-term biofilm model, again in exclusion or displacement mode. The cariogenicity of mixed-species biofilms of SM with the most promising growth and biofilm formation inhibiting probiotic strains was assessed using an artificial mouth model, and enamel mineral loss (ΔZ) was measured microradiographically. We found limited differences in SM growth inhibition in exclusion versus displacement mode, and in inhibition of SM 20532 versus 25175. Results were therefore pooled. Lactobacillus acidophilus LA-5 inhibited significantly more SM culture growth than most other probiotics. L. casei LC-11 inhibited SM biofilm formation similarly to other alternatives but showed the highest retention of probiotics in the biofilms (p < 0.05). Mineral loss from SM monospecies biofilms (ΔZ = 9,772, 25th/75th percentiles: 6,277/13,558 vol% × µm) was significantly lower than from mixed-species SM × LA-5 biofilms (ΔZ = 24,578, 25th/75th percentiles: 19,081/28,768 vol% × µm; p < 0.01) but significantly higher than from SM × LC-11 biofilms (ΔZ = 4,835, 25th/75th percentiles: 263/7,865 vol% × µm; p < 0.05). Probiotics inhibiting SM culture growth do not necessarily reduce the cariogenicity of SM-probiotic biofilms. Nevertheless, SM biofilm formation inhibition may be relevant in the reduction of

  10. [Biofilm--short characteristic of microbial growth related to drinking water distribution systems].

    PubMed

    Szczotko, Maciej

    2007-01-01

    General information about drinking water biofilms containing few steps biofilm forming process, microorganisms' short characterization and potential risk related to microbial presence in water installations has been presented. A part of review concerns European Acceptance Scheme (EAS) basis and current methods applied for assessment of susceptibility of materials contacting with drinking water to microbial growth.

  11. Biofilm growth on polyvinylchloride surface incubated in suboptimal microbial warm water and effect of sanitizers on biofilm removal post biofilm formation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An in vitro experiment was conducted to understand the nature of biofilm growth on polyvinyl chloride (PVC) surface when exposed to sub optimal quality microbial water (> 4 log10 cfu/ml) obtained from poultry drinking water source mimicking water in waterlines during the first week of poultry broodi...

  12. 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.

  13. 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.

  14. A Genome-Scale Modeling Approach to Quantify Biofilm Component Growth of Salmonella Typhimurium.

    PubMed

    Ribaudo, Nicholas; Li, Xianhua; Davis, Brett; Wood, Thomas K; Huang, Zuyi Jacky

    2017-01-01

    Salmonella typhimurium (S. typhimurium) is an extremely dangerous foodborne bacterium that infects both animal and human subjects, causing fatal diseases around the world. Salmonella's robust virulence, antibiotic-resistant nature, and capacity to survive under harsh conditions are largely due to its ability to form resilient biofilms. Multiple genome-scale metabolic models have been developed to study the complex and diverse nature of this organism's metabolism; however, none of these models fully integrated the reactions and mechanisms required to study the influence of biofilm formation. This work developed a systems-level approach to study the adjustment of intracellular metabolism of S. typhimurium during biofilm formation. The most advanced metabolic reconstruction currently available, STM_v1.0, was 1st extended to include the formation of the extracellular biofilm matrix. Flux balance analysis was then employed to study the influence of biofilm formation on cellular growth rate and the production rates of biofilm components. With biofilm formation present, biomass growth was examined under nutrient rich and nutrient deficient conditions, resulting in overall growth rates of 0.8675 and 0.6238 h(-1) respectively. Investigation of intracellular flux variation during biofilm formation resulted in the elucidation of 32 crucial reactions, and associated genes, whose fluxes most significantly adapt during the physiological response. Experimental data were found in the literature to validate the importance of these genes for the biofilm formation of S. typhimurium. This preliminary investigation on the adjustment of intracellular metabolism of S. typhimurium during biofilm formation will serve as a platform to generate hypotheses for further experimental study on the biofilm formation of this virulent bacterium.

  15. 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

  16. 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

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

    PubMed

    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

  18. 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

  19. Effects of Carbon Source, Carbon Concentration, and Chlorination on Growth Related Parameters of Heterotrophic Biofilm Bacteria.

    PubMed

    Ellis; Butterfield; Jones; McFeters; Camper

    1999-11-01

    To investigate growth of heterotrophic biofilm bacteria, a model biofilm reactor was developed to simulate a drinking water distribution system. Controlled addition of three different carbon sources (amino acids, carbohydrates, and humics) at three different concentrations (500, 1,000, and 2,000 ppb carbon) in the presence and absence of chlorine were used in separate experiments. An additional experiment was run with a 1:1:2 mixture of the above carbon sources. Biofilm and effluent total and culturable cells in addition to total and dissolved organic carbon were measured in order to estimate specific growth rates (SGRs), observed yields, population densities, and bacterial carbon production rates. Bacterial carbon production rates (µg C/L day) were extremely high in the control biofilm communities (range = 295-1,738). Both growth rate and yield decreased with increasing carbon concentrations. Therefore, biofilm growth rates were zero-order with respect to the carbon concentrations used in these experiments. There was no correlation between growth rate and carbon concentration, but there was a significant negative correlation between growth rate and biofilm cell density (r = -0.637, p = 0.001 control and r = -0.57, p = 0.021 chlorinated biofilms). Growth efficiency was highest at the lowest carbon concentration (range = 12-4.5%, amino acids and humics respectively). Doubling times ranged from 2.3-15.4 days in the control biofilms and 1-12.3 days in the chlorinated biofilms. Growth rates were significantly higher in the presence of chlorine for the carbohydrates, humics, and mixed carbon sources (p = 0.004, < 0.0005, 0.013, respectively). The concept of r/K selection theory was used to explain the results with respect to specific growth rates and yields. Humic removal by the biofilm bacteria (78% and 56% for the control and chlorinated biofilms, respectively) was higher than previously reported literature values for planktonic bacteria. A number of control

  20. [Denitrification and kinetic characteristics using biodegradable polymers as carbon source and biofilm carrier].

    PubMed

    Lai, Cai-sheng; Tan, Hong-xin; Luo, Guo-zhi; Ruan, Yun-jie; Zhou, Wei; Sun, Da-chuan

    2010-08-01

    The PBS material that in the form of insoluble biodegradable polymers pellets was investigated as the solid carbon source and the biofilm carrier for nitrate removal from wastewater. The denitrification of nitrate removal and kinetic process were carried out in a packed-bed reactor in order to remove nitrate in recirculation aquaculture system. The experimental results indicated that the optimal influent loading rate was in the range of 0.107-1.098 kg/(m3 x d), when the water temperature was (29 +/- 1) degrees C and the influent nitrate concentration was in the range of 25-334 mg/L. The maximum nitrate volumetric removal rate of 0.577 kg/(m3 x d) was achieved at the influent loading rate of 1.098 kg/(m3 x d). When the influent loading rate exceeded 1.098 kg/(m3 x d), the nitrate volumetric removal rate was declined. The kinetic experimental results show that the denitrification rate of PBS as the solid carbon source and the biofilm carrier corresponds to first-order kinetics. Based on the kinetics characteristics, constants n and K used in Eckenfelder model were deduced, which can be successfully applied for the prediction of effluent nitrate concentration. The two groups' predictive values and actual values were analyzed by using SPSS 16.0 software for Paired-Samples t test analysis. The Paired-Samples t test analysis indicates that the corresponding p > 0.05 values are 0.553 and 0.632, which proved that no significant differences exist between the predictive values and actual values of the model.

  1. 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

    2015-12-02

    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.

  2. 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...

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

    PubMed

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

    2013-05-01

    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.

  4. 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

  5. Growth morphology with anisotropic surface kinetics

    NASA Technical Reports Server (NTRS)

    Xiao, Rong-Fu; Alexander, J. Iwan D.; Rosenberger, Franz

    1990-01-01

    The morphological evolution of crystals growing from an incongruent vapor phase is studied using a Monte Carlo model, and the full range of growth morphologies is recovered. The diffusion in the bulk nutrient and the anisotropy in the interface kinetics are morphologically destabilizing and stabilizing, respectively. For a given set of simulation parameters and lattice symmetries there is a critical size, which scales linearly with the mean free path in the vapor, beyond which a crystal cannot retain its stable, macroscopically faceted growth shape. Surface diffusion stabilizes faceted growth on the shorter scale of the mean surface diffusion length. In simulations with a uniform drift superimposed on the random walk nutrient transport, crystal faces oriented toward the drift show enhanced morphological stability compared to the purely diffusive situation. Rotational drifts with periodic reversal of direction are morphologically stabilizing for all crystal facets.

  6. 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.

  7. Measurement of biofilm growth and local hydrodynamics using optical coherence tomography

    PubMed Central

    Weiss, Nicolás; Obied, Khalid El Tayeb El; Kalkman, Jeroen; Lammertink, Rob G.H.; van Leeuwen, Ton G.

    2016-01-01

    We report on localized and simultaneous measurement of biofilm growth and local hydrodynamics in a microfluidic channel using optical coherence tomography. We measure independently with high spatio-temporal resolution the longitudinal flow velocity component parallel to the imaging beam and the transverse flow velocity component perpendicular to the imaging beam. Based on the measured velocities we calculate the shear-rates in the flow channel. We show the relation between the measured biofilm structure and flow velocities as biofilm growth progresses over the course of 48 hours. PMID:27699116

  8. Kinetic analysis of microbial sulfate reduction by Desulfovibrio desulfuricans in an anaerobic upflow porous media biofilm reactor

    SciTech Connect

    Chen, Chingi; Mueller, R.F.; Griebe, T. . National Science Foundation Engineering Research Center for Biofilm Engineering)

    1994-02-20

    An anaerobic upflow porous media biofilm reactor was designed to study the kinetics and stoichiometry of hydrogen sulfide production by the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans (ATCC 5575) as the first step for the modeling and control of formation souring (H[sub 2]S) in oil field porous media. The initial indication of souring was the appearance of well-separated black spots (precipitates of iron sulfide) in the sand bed. Analysis of the pseudo-steady state column shows that there were concentration gradients for lactate and hydrogen sulfide along the column. The results indicate that most of the lactate was consumed at the front part of the column. Measurements of SRB biomass on the solid phase (sand) and in the liquid phase indicate that the maximum concentration of SRB biomass resided at the front part of the column while the maximum in the liquid phase occurred further downstream. The stoichiometry regarding lactate consumption and hydrogen sulfide production observed in the porous media reactor was different from that in a chemostat. After analyzing the radial dispersion coefficient for the SRB in porous media and kinetics of microbial growth, it was deduced that transport phenomena dominate the souring process in the porous media reactor system.

  9. Bulk water phase and biofilm growth in drinking water at low nutrient conditions.

    PubMed

    Boe-Hansen, Rasmus; Albrechtsen, Hans-Jørgen; Arvin, Erik; Jørgensen, Claus

    2002-11-01

    In this study, the bacterial growth dynamics of a drinking water distribution system at low nutrient conditions was studied in order to determine bacterial growth rates by a range of methods, and to compare growth rates in the bulk water phase and the biofilm. A model distribution system was used to quantify the effect of retention times at hydraulic conditions similar to those in drinking water distribution networks. Water and pipe wall samples were taken and examined during the experiment. The pipes had been exposed to drinking water at approximately 13 degrees C, for at least 385 days to allow the formation of a mature quasi-stationary biofilm. At retention times of 12 h, total bacterial counts increased equivalent to a net bacterial growth rate of 0.048 day(-1). The bulk water phase bacteria exhibited a higher activity than the biofilm bacteria in terms of culturability, cell-specific ATP content, and cell-specific leucine incorporation rate. Bacteria in the bulk water phase incubated without the presence of biofilm exhibited a bacterial growth rate of 0.30 day(-1). The biofilm was radioactively labelled by the addition of 14C-benzoic acid. Subsequently, a biofilm detachment rate of 0.013 day(-1) was determined by measuring the release of 14C-labelled bacteria of the biofilm. For the quasi-stationary phase biofilm, the detachment rate was equivalent to the net growth rate. The growth rates determined in this study by different independent experimental approaches were comparable and within the range of values reported in the literature.

  10. 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.

  11. Linear surface roughness growth and flow smoothening in a three-dimensional biofilm model

    NASA Astrophysics Data System (ADS)

    Head, D. A.

    2013-09-01

    The sessile microbial communities known as biofilms exhibit varying architectures as environmental factors are varied, which for immersed biofilms includes the shear rate of the surrounding flow. Here we modify an established agent-based biofilm model to include affine flow and employ it to analyze the growth of surface roughness of single-species, three-dimensional biofilms. We find linear growth laws for surface geometry in both horizontal and vertical directions and measure the thickness of the active surface layer, which is shown to anticorrelate with roughness. Flow is shown to monotonically reduce surface roughness without affecting the thickness of the active layer. We argue that the rapid roughening is due to nonlocal surface interactions mediated by the nutrient field, which are curtailed when advection competes with diffusion. We further argue the need for simplified models to elucidate the underlying mechanisms coupling flow to growth.

  12. 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

  13. 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.

  14. 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

  15. 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

    2016-09-06

    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

  16. 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.

  17. 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

  18. 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

  19. 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

  20. Numerical simulation of biofilm growth in flow channels using a cellular automaton approach coupled with a macro flow computation.

    PubMed

    Yamamoto, Takehiro; Ueda, Shuya

    2013-01-01

    Biofilm is a slime-like complex aggregate of microorganisms and their products, extracellular polymer substances, that grows on a solid surface. The growth phenomenon of biofilm is relevant to the corrosion and clogging of water pipes, the chemical processes in a bioreactor, and bioremediation. In these phenomena, the behavior of the biofilm under flow has an important role. Therefore, controlling the biofilm behavior in each process is important. To provide a computational tool for analyzing biofilm growth, the present study proposes a computational model for the simulation of biofilm growth in flows. This model accounts for the growth, decay, detachment and adhesion of biofilms. The proposed model couples the computation of the surrounding fluid flow, using the finite volume method, with the simulation of biofilm growth, using the cellular automaton approach, a relatively low-computational-cost method. Furthermore, a stochastic approach for considering the adhesion process is proposed. Numerical simulations for the biofilm growth on a planar wall and that in an L-shaped rectangular channel were carried out. A variety of biofilm structures were observed depending on the strength of the flow. Moreover, the importance of the detachment and adhesion processes was confirmed.

  1. Bacterial activity in plant (Schoenoplectus validus) biofilms of constructed wetlands.

    PubMed

    Pollard, Peter C

    2010-12-01

    Biofilm-bacterial communities have been exploited in the treatment of wastewater in 'fixed-film' processes. Our understanding of biofilm dynamics requires a quantitative knowledge of bacterial growth-kinetics in these microenvironments. The aim of this paper was to apply the thymidine assay to quantify bacterial growth without disturbing the biofilm on the surfaces of emergent macrophytes (Schoenoplectus validus) of a constructed wetland. The isotope was rapidly and efficiently taken-up and incorporated into dividing biofilm-bacteria. Isotope diffusion into the biofilm did not limit the growth rate measurement. Isotope dilution was inhibited at >12 μM thymidine. Biofilm-bacterial biomass and growth rates were not correlated to the plant surface area (r(2) < 0.02). The measurements of in situ biofilm-bacterial growth rates both displayed, and accommodated, the inherent heterogeneity of the complex wetland ecosystem. Biofilm-bacterial respiratory activities, measured using the redox dye CTC, and growth rates were measured simultaneously. The dye did not interfere with bacterial growth. Biofilm-bacterial specific growth rates ranged from 1.4 ± 0.6 d(-1) to 3.3 ± 1.3 d(-1). In the constructed wetlands of this study biofilm-bacterial specific growth rates, compared to those of natural ecosystems, could be markedly improved through changes in wetland design that increased bacterial respiration while minimising biofilm growth.

  2. Candida albicans survival, growth and biofilm formation are differently affected by mouthwashes: an in vitro study.

    PubMed

    Paulone, Simona; Malavasi, Giulia; Ardizzoni, Andrea; Orsi, Carlotta Francesca; Peppoloni, Samuele; Neglia, Rachele Giovanna; Blasi, Elisabetta

    2017-01-01

    Candida albicans is the most common cause of oral mycoses. The aim of the present study was to investigate in vitro the susceptibility of C. albicans to mouthwashes, in terms of growth, survival and biofilm formation. Candida albicans, laboratory strain SC5314, and 7 commercial mouthwashes were employed: 3 with 0.2% chlorhexidine digluconate; 1 with 0.06% chlorhexidine digluconate and 250 ppm F- sodium fluoride; 3 with fluorine-containing molecules. None of the mouthwashes contained ethanol in their formulations. The anti-Candida effects of the mouthwashes were assessed by disk diffusion, crystal violet and XTT assays. By using five protocols combining different dilutions and contact times the mouthwashes were tested against: 1) C. albicans growth; 2) biofilm formation; 3) survival of fungal cells in early, developing and mature Candida biofilm. Chlorhexidine digluconate-containing mouthwashes consistently exhibited the highest anti-Candida activity, irrespective of the protocols employed. Fungal growth, biofilm formation and survival of Candida cells within biofilm were impaired, the effects strictly depending on both the dilution employed and the time of contact. These in vitro studies provide evidence that mouthwashes exert anti-Candida activity against both planktonic and biofilm fungal structures, but to a different extent depending on their composition. This suggests special caution in the choice of mouthwashes for oral hygiene, whether aimed at prevention or treatment of oral candidiasis.

  3. Effects of cranberry extracts on growth and biofilm production of Escherichia coli and Staphylococcus species.

    PubMed

    LaPlante, Kerry L; Sarkisian, Simon A; Woodmansee, Suzanne; Rowley, David C; Seeram, Navindra P

    2012-09-01

    Biofilm producing bacteria such as Staphylococcus species and Escherichia coli are the most common cause of catheter related urinary tract infections (UTIs). The American cranberry (Vaccinium macrocarpon) is utilized widely as a prophylaxis for UTIs due to its prevention of microbial adhesion. Cranberry contains proanthocyanidins (PACs), which have been implicated as active constituents responsible for its bacterial antiadhesive properties. Despite overwhelming data supporting cranberry's beneficial effects against human pathogenic bacteria, there is limited information regarding its effects on biofilm formation. This study evaluated the effects of three proprietary PAC-standardized cranberry extracts on the inhibition of bacterial growth and biofilm production against a panel of clinically relevant pathogens: Staphylococcus epidermidis, Staphylococcus aureus, clinical methicillin-resistant S. aureus (MRSA), Staphylococcus saprophyticus and Escherichia coli. The extracts inhibited the growth of the Gram-positive bacteria (Staphylococcus spp.) but not the Gram-negative species (E. coli) with minimum inhibitory concentrations in the range 0.02-5 mg/mL. The extracts also inhibited biofilm production by the Gram-positive bacteria but did not eradicate their established biofilm. These results suggest that cranberry may have beneficial effects against the growth and biofilm producing capability of Gram-positive bacteria pathogens.

  4. 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.

  5. 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.

  6. The effect of flow velocity on the distribution and composition of extracellular polymeric substances in biofilms and the detachment mechanism of biofilms.

    PubMed

    Wang, Chao; Miao, Lingzhan; Hou, Jun; Wang, Peifang; Qian, Jin; Dai, Shanshan

    2014-01-01

    Flume experiments were conducted to investigate the distribution and composition of extracellular polymeric substances (EPS) in biofilms and the detachment mechanism of biofilms grown under different flow velocity conditions. The results of biofilm growth kinetics showed that the growth trends were coincident with the logistic growth model. The growth kinetics parameters reached their maximum under intermediate velocity (IV) condition. Biofilms exhibited different profiles of EPS composition and distribution, depending on the flow conditions in which the biofilms were grown. The amounts of total polysaccharide and total protein in the thin biofilm (high velocity condition 2 - HV2) were both generally greater than those in the thick biofilm (IV). As compared to the heterogeneous distribution of EPS in the thick biofilms (IV), the EPS in the thin biofilms (HV2) exhibited more homogeneous distribution, and the bound EPS in the thin biofilms (HV2) were much greater than those in the thick biofilms (IV). From the detachment tests, an inverse relationship was observed between the proportion of detached biomass and the value of flow velocity during growth. Biofilms grown under higher velocities showed stronger cohesion than those grown under lower velocities. Therefore, water velocity during biofilm growth conditioned the distribution and composition of EPS, as well as its detachment characteristics under higher shear stress.

  7. Investigating Filamentous Growth and Biofilm/Mat Formation in Budding Yeast

    PubMed Central

    Cullen, Paul J.

    2015-01-01

    In response to nutrient limitation, budding yeast can undergo filamentous growth by differentiating into elongated chains of interconnected cells. Filamentous growth is regulated by signal transduction pathways that oversee the reorganization of cell polarity, changes to the cell cycle, and an increase in cell adhesion that occur in response to nutrient limitation. Each of these changes can be easily measured. Yeast can also grow colonially atop surfaces in a biofilm or mat of connected cells. Filamentous growth and biofilm/mat formation require cooperation among individuals; therefore, studying these responses can shed light on the origin and genetic basis of multicellular behaviors. The assays introduced here can be used to study analogous behaviors in fungal pathogens, which require filamentous growth and biofilm/mat formation for virulence. PMID:25734073

  8. Biofilm mode of growth of Streptococcus intermedius favored by a competence-stimulating signaling peptide.

    PubMed

    Petersen, Fernanda C; Pecharki, Daniele; Scheie, Anne A

    2004-09-01

    Gram-positive and gram-negative bacteria use quorum sensing to coordinate population behavior. In several streptococci, quorum sensing mediated by competence-stimulating peptides (CSP) is associated with development of competence for transformation. We show here that a synthetic CSP favored the biofilm mode of growth of Streptococcus intermedius without affecting the rate of culture growth.

  9. Characterizing the Growth Kinetics in Estrogen Responsive ...

    EPA Pesticide Factsheets

    There is a need to develop high-throughput screening (HTS) tests capable of testing thousands of environmental chemicals for endocrine disrupting potential. The estrogen signaling pathway is a known xenobiotic target that has been implicated in a variety of adverse health effects including reproductive deficits and cancer promotion. Using real-time measurements of growth kinetics by electrode impedance, the estrogen-responsive human ductal carcinoma cell line, T47D, was treated with 2000 chemicals of environmental relevance. Cells were treated in concentration response and measurements of cellular impedance were recorded every hour for six days. Exponential impedance, signifying increased proliferation, was observed by prototypical estrogen receptor agonists (17β-estradiol, genestein, bisphenol-A, nonylphenol, 4-tert-octylphenol). Several compounds, including bisphenol-A and genestein, induced cell proliferation at comparable levels to 17β-estradiol, although at much higher concentrations. Progestins, and mineralocortocoids (progesterone, dihydrotestosterone, aldosterone) invoked a biphasic impedance signature. In conclusion, the real-time nature of this assay allows for rapid detection of differential growth characteristics shows potential, in combination with other ToxCast HTS assays, to detect environmental chemicals with potential endocrine activity. [This abstract does not necessarily reflect Agency policy]. Several compounds, including bisphenol-A and

  10. Microbial competition in porous environments can select against rapid biofilm growth.

    PubMed

    Coyte, Katharine Z; Tabuteau, Hervé; Gaffney, Eamonn A; Foster, Kevin R; Durham, William M

    2017-01-10

    Microbes often live in dense communities called biofilms, where competition between strains and species is fundamental to both evolution and community function. Although biofilms are commonly found in soil-like porous environments, the study of microbial interactions has largely focused on biofilms growing on flat, planar surfaces. Here, we use microfluidic experiments, mechanistic models, and game theory to study how porous media hydrodynamics can mediate competition between bacterial genotypes. Our experiments reveal a fundamental challenge faced by microbial strains that live in porous environments: cells that rapidly form biofilms tend to block their access to fluid flow and redirect resources to competitors. To understand how these dynamics influence the evolution of bacterial growth rates, we couple a model of flow-biofilm interaction with a game theory analysis. This investigation revealed that hydrodynamic interactions between competing genotypes give rise to an evolutionarily stable growth rate that stands in stark contrast with that observed in typical laboratory experiments: cells within a biofilm can outcompete other genotypes by growing more slowly. Our work reveals that hydrodynamics can profoundly affect how bacteria compete and evolve in porous environments, the habitat where most bacteria live.

  11. Kinetic analysis of microbial sulfate reduction by desulfovibrio desulfuricans in an anaerobic upflow porous media biofilm reactor.

    PubMed

    Chen, C I; Mueller, R F; Griebe, T

    1994-02-20

    An anaerobic upflow porous media biofilm reactor was designed to study the kinetics and stoichiometry of hydrogen sulfide production by the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans (ATCC 5575) as the first step for the modeling and control of formation souring (H(2)S) in oil field porous media. The reactor was a packed bed (50 x 5.5 cm) tubular reactor. Sea sand (140 to 375 mum) was used as the porous media. The initial indication of souring was the appearance of well-separated black spots (precipitates of iron sulfide) in the sand bed. The blackened zones expanded radially and upward through the column. New spots also appeared and expanded into the cone shapes. Lactate (substrate) was depleted and hydrogen sulfide appeared in the effluent.Analysis of the pseudo-steady state column shows that there were concentration gradients for lactate and hydrogen sulfide along the column. The results indicate that most of the lactate was consumed at the front part of the column. Measurements of SRB biomass on the solid phase (sand) and in the liquid phase indicate that the maximum concentration of SRB biomass resided at the front part of the column while the maximum in the liquid phase occurred further downstream. The stoichiometry regarding lactate consumption and hydrogen sulfide production observed in the porous media reactor was different from that in a chemostat. After analyzing the radial dispersion coefficient for the SRB in porous media and kinetics of microbial growth, it was deduced that transport phenomena dominate the souring process in our porous media reactor system. (c) 1994 John Wiley & Sons, Inc.

  12. 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

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

    PubMed

    Andrade, Angel; Tavares-Carreón, Faviola; Khodai-Kalaki, Maryam; Valvano, Miguel A

    2015-11-20

    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.

  14. 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

  15. Electron donors supporting growth and electroactivity of Geobacter sulfurreducens anode biofilms.

    PubMed

    Speers, Allison M; Reguera, Gemma

    2012-01-01

    Geobacter bacteria efficiently oxidize acetate into electricity in bioelectrochemical systems, yet the range of fermentation products that support the growth of anode biofilms and electricity production has not been thoroughly investigated. Here, we show that Geobacter sulfurreducens oxidized formate and lactate with electrodes and Fe(III) as terminal electron acceptors, though with reduced efficiency compared to acetate. The structure of the formate and lactate biofilms increased in roughness, and the substratum coverage decreased, to alleviate the metabolic constraints derived from the assimilation of carbon from the substrates. Low levels of acetate promoted formate carbon assimilation and biofilm growth and increased the system's performance to levels comparable to those with acetate only. Lactate carbon assimilation also limited biofilm growth and led to the partial oxidization of lactate to acetate. However, lactate was fully oxidized in the presence of fumarate, which redirected carbon fluxes into the tricarboxylic acid (TCA) cycle, and by acetate-grown biofilms. These results expand the known ranges of electron donors for Geobacter-driven fuel cells and identify microbial constraints that can be targeted to develop better-performing strains and increase the performance of bioelectrochemical systems.

  16. 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.

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

    PubMed Central

    Qurashi, Aisha Waheed; Sabri, Anjum Nasim

    2012-01-01

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

  18. Influence of glyphosate in planktonic and biofilm growth of Pseudomonas aeruginosa

    PubMed Central

    Lima, Ilana Schneider; Baumeier, Nicole Carmo; Rosa, Rosimeire Takaki; Campelo, Patrícia Maria Stuelp; Rosa, Edvaldo Antonio Ribeiro

    2014-01-01

    This study evaluated the impact of different concentrations of glyphosate (Rondup®) on planktonic and biofilm growth of P. aeruginosa. Aerobic and anaerobic cultures of P. aeruginosa ATCC®15442 inoculated in MHB + glyphosate (0.845 ppm, 1.690 ppm, 8.45 ppm, 16.90 ppm, 84.50 ppm, 169 ppm, 845 ppm, and 1690 ppm) and cultured in normoxia and anoxia, following their OD560nm every hour for 24 h. Biofilms of adapted cells were formed in the presence of glyphosate (0.845 to 1690 ppm) in normoxia and anoxia for 36 h. Glyphosate at concentrations higher than 84.5 ppm reduces the cell density of planktonic aerobic cultures (p < 0.05). However, these same concentrations favor the planktonic anaerobic growth (p < 0.05). On the other hand, the herbicide favors a slight growth of biofilms in a concentration-dependent manner up to 84.5 ppm (p > 0.05), and more pronounced over 169 ppm. Anaerobic biofilms have their growth more readily favored (p < 0.05), regardless of concentration. In a concentration-dependent manner, glyphosate interferes with the growth ability of P. aeruginosa ATCC®15442. PMID:25477933

  19. 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.

  20. 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

  1. 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.

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

    USGS Publications Warehouse

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

    2006-01-01

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

  3. Effects of tea tree (Melaleuca alternifolia) oil on Staphylococcus aureus in biofilms and stationary growth phase.

    PubMed

    Kwieciński, Jakub; Eick, Sigrun; Wójcik, Kinga

    2009-04-01

    Tea tree oil (TTO) is known for its antimicrobial activity. In this study, we determined whether TTO is effective against Staphylococcus aureus in biofilms and how TTO activity is affected by the S. aureus growth phase. All clinical strains tested were killed by TTO both as planktonic cells and as biofilms. The minimum biofilm eradication concentration was usually two times higher than the minimum bactericidal concentration, yet it was never higher than 1% v/v. The fastest killing of biofilm occurred during the first 15min of contact with TTO and was not influenced by increasing TTO concentration above 1% v/v. Planktonic stationary phase cells exhibited decreased susceptibility to TTO compared with exponential phase cells. The killing rate for stationary phase cells was also less affected by increasing TTO concentration than that for exponential phase cells. These data show that TTO efficiently kills S. aureus in the stationary growth phase and within biofilms and is therefore a promising tool for S. aureus eradication.

  4. 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.

  5. Theory of a microfluidic serial dilution bioreactor for growth of planktonic and biofilm populations.

    PubMed

    Hsu, Sze-Bi; Yang, Ya-Tang

    2016-04-01

    We present the theory of a microfluidic bioreactor with a two-compartment growth chamber and periodic serial dilution. In the model, coexisting planktonic and biofilm populations exchange by adsorption and detachment. The criteria for coexistence and global extinction are determined by stability analysis of the global extinction state. Stability analysis yields the operating diagram in terms of the dilution and removal ratios, constrained by the plumbing action of the bioreactor. The special case of equal uptake function and logistic growth is analytically solved and explicit growth curves are plotted. The presented theory is applicable to generic microfluidic bioreactors with discrete growth chambers and periodic dilution at discrete time points. Therefore, the theory is expected to assist the design of microfluidic devices for investigating microbial competition and microbial biofilm growth under serial dilution conditions.

  6. Silver-decorated orthorhombic nanotubes of lithium vanadium oxide: an impeder of bacterial growth and biofilm.

    PubMed

    Diggikar, Rahul S; Patil, Rajendra H; Kale, Sheetal B; Thombre, Dipalee K; Gade, Wasudeo N; Kulkarni, Milind V; Kale, Bharat B

    2013-09-01

    Reoccurrence of infectious diseases and ability of pathogens to resist antibacterial action has raised enormous challenges which may possibly be confronted by nanotechnology routes. In the present study, uniformly embedded silver nanoparticles in orthorhombic nanotubes of lithium vanadium oxide (LiV2O5/Ag) were explored as an impeder of bacterial growth and biofilm. The LiV2O5/Ag nanocomposites have impeded growth of Gram-positive Bacillus subtilis NCIM 2063 and Gram-negative Escherichia coli NCIM 2931 at 60 to 120 μg/mL. It also impeded the biofilm in Pseudomonas aeruginosa NCIM 2948 at 12.5 to 25 μg/mL. Impedance in the growth and biofilm occurs primarily by direct action of the nanocomposites on the cell surfaces of test organisms as revealed by surface perturbation in scanning electron microscopy. As the metabolic growth and biofilm formation phenomena of pathogens play a central role in progression of pathogenesis, LiV2O5/Ag nanocomposite-based approach is likely to curb the menace of reoccurrence of infectious diseases. Thus, LiV2O5/Ag nanocomposites can be viewed as a promising candidate in biofabrication of biomedical materials.

  7. 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

  8. 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.

  9. Biofilm growth of individual and dual strains of Klebsiella oxytoca from the dairy industry on ultrafiltration membranes.

    PubMed

    Tang, Xuemei; Flint, Steve H; Bennett, Rod J; Brooks, John D; Morton, R Hugh

    2009-12-01

    Formation of biofilms in dairy membrane plants causes membrane pore blocking, product contamination and subsequent economic loss. To investigate the biofilm growth, two Klebsiella oxytoca strains, K. B006 and TR002, previously isolated from New Zealand dairy membrane plants, were grown both individually and combined on three types of ultrafiltration (UF) membranes in different concentrations of whey medium in biofilm reactors (CBR 90, BioSurface Technologies, Bozeman, USA). Biofilms of both the individual and combined strains grew on the membrane surfaces to levels of 4.9-7.99 log colony-forming units (CFU) cm(-2) measured by standard plate counting after removing the cells by sonication. More biofilm grew on used polyethersulfone (PES) membranes than on new PES and polyvinylidene fluoride (PVDF) membranes. Both strains formed good biofilms, although K. B006 formed a denser biofilm than TR002. This corresponded to our previous study on the attachment of these organisms, where K. B006 attached in greater numbers than K. TR002. The dual strains produced a higher biofilm density than single strains on the new membranes. Biofilm density tended to increase with increased whey concentration. The saturated biofilm was approximately 10(8) CFU cm(-2). PES membranes appeared to support biofilm growth less readily than did PVDF membranes and therefore may be the preferred material for UF membranes to reduce problems with microbial colonisation. Used membranes were more readily colonised with biofilm than were new membranes. Therefore, selecting a membrane type and monitoring membrane age will help manage biofilm development during UF.

  10. Patterns of metal accumulation by natural river biofilms during their growth and seasonal succession.

    PubMed

    Tien, Chien-Jung; Chen, Colin S

    2013-05-01

    To evaluate the factors influencing patterns of metal accumulation by river biofilms, concentrations of chromium (Cr), nickel (Ni), copper (Cu), and lead (Pb) in biofilms from Erh-Jen River and San-Yeh-Kung Creek were investigated during their growth and seasonal succession. Different metal-accumulation patterns during biofilm development were observed between the two rivers. Mature biofilms (grown for 21-28 days) in both rivers showed maximum metal accumulation (≤3.24 × 10(4), 1.55 × 10(4), 7.40 × 10(3), and 7.80 × 10(2) μg g(-1) of Cr, Ni, Cu, and Pb, respectively) and bioconcentration factors (≤7.15 × 10(5), 1.60 × 10(5), 2.60 × 10(5), and 4.22 × 10(5) l kg(-1) of Cr, Ni, Cu, and Pb, respectively). These types of biofilms had the characteristics of being good metal accumulators and the ability to integrate metal-exposure conditions, suggesting that they were suitable biomonitors for metal-contaminated water. Seasonal succession in metal-accumulation ability of 1-month-old biofilms from Erh-Jen River was mainly affected by changes in bacterial and algal biomass and chemical oxygen demand in water, whereas that from San-Yeh-Kung Creek was primary influenced by concentrations of total nitrogen in water. Synergistic interaction between these four metals on metal-binding sites within biofilms was also shown.

  11. Nanostructured microspheres of silver @ zinc oxide: an excellent impeder of bacterial growth and biofilm

    NASA Astrophysics Data System (ADS)

    Patil, Santosh S.; Patil, Rajendra H.; Kale, Sheetal B.; Tamboli, Mohaseen S.; Ambekar, Jalindar D.; Gade, Wasudev N.; Kolekar, Sanjay S.; Kale, Bharat B.

    2014-11-01

    Nanostructured (metal/semiconductor) Ag@ZnO a photoactive material is synthesized by facile hydrothermal method. The FESEM analysis of as synthesized Ag@ZnO nanostructures showed formation of submicron-sized microspheres, composed of small nanoparticles of size in the range of 10-20 nm. The as synthesized Ag@ZnO nanostructures possess wurtzite hexagonal structure of ZnO with band edge transition to visible region due to surface plasmon effect of silver which ultimately is responsible for the improved photocatalytic performance. The photocatalytic action of Ag@ZnO nanostructures impede the growth of model organisms Bacillus subtilis NCIM 2063 and Escherichia coli NCIM 2931, and biofilm in Pseudomonas aeruginosa O1. The present study is important as it introduces an excellent functionality of Ag@ZnO, an agent for impeding the biofilm and bacterial communities inside the biofilm.

  12. Inhibition of Gallic Acid on the Growth and Biofilm Formation of Escherichia coli and Streptococcus mutans.

    PubMed

    Shao, Dongyan; Li, Jing; Li, Ji; Tang, Ruihua; Liu, Liu; Shi, Junling; Huang, Qingsheng; Yang, Hui

    2015-06-01

    New strategies for biofilm inhibition are becoming highly necessary because of the concerns to synthetic additives. As gallic acid (GA) is a hydrolysated natural product of tannin in Chinese gall, this research studied the effects of GA on the growth and biofilm formation of bacteria (Escherichia coli [Gram-negative] and Streptococcus mutans [Gram-positive]) under different conditions, such as nutrient levels, temperatures (25 and 37 °C) and incubation times (24 and 48 h). The minimum antimicrobial concentration of GA against the two pathogenic organisms was determined as 8 mg/mL. GA significantly affected the growth curves of both test strains at 25 and 37 °C. The nutrient level, temperature, and treatment time influenced the inhibition activity of GA on both growth and biofim formation of tested pathogens. The inhibition effect of GA on biofilm could be due to other factors in addition to the antibacterial effect. Overall, GA was most effective against cultures incubated at 37 °C for 24 h and at 25 °C for 48 h in various concentrations of nutrients and in vegetable wash waters, which indicated the potential of GA as emergent sources of biofilm control products.

  13. Comparison of biofilm ecology supporting growth of individual Naegleria species in a drinking water distribution system.

    PubMed

    Puzon, Geoffrey J; Wylie, Jason T; Walsh, Tom; Braun, Kalan; Morgan, Matthew J

    2017-02-21

    Free-living amoebae (FLA) are common components of microbial communities in drinking water distribution systems (DWDS). FLA are of clinical importance both as pathogens and as reservoirs for bacterial pathogens, so identifying the conditions promoting amoebae colonisation of DWDSs is an important public health concern for water utilities. We used high-throughput amplicon sequencing to compare eukaryotic and bacterial communities associated with DWDS biofilms supporting distinct FLA species (N. fowleri, N. lovaniensis or Vermamoeba sp.) at sites with similar physical/chemical conditions. Eukaryote and bacterial communities were characteristic of different FLA species presence, and biofilms supporting Naegleria growth had higher bacterial richness and higher abundance of Proteobacteria, Bacteroidetes (bacteria), Nematoda and Rotifera (eukaryota). The eukaryotic community in the biofilms had the greatest difference in relation to the presence of N. fowleri, while the bacterial community identified individual bacterial families associated with the presence of different Naegleria species. Our results demonstrate that ecogenomics data provide a powerful tool for studying the microbial and meiobiotal content of biofilms, and, in these samples can effectively discriminate biofilm communities supporting pathogenic N. fowleri. The identification of microbial species associated with N. fowleri could further be used in the management and control of N. fowleri in DWDSs.

  14. 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.

  15. 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.

  16. A spatially stabilized TDG based finite element framework for modeling biofilm growth with a multi-dimensional multi-species continuum biofilm model

    NASA Astrophysics Data System (ADS)

    Feng, D.; Neuweiler, I.; Nackenhorst, U.

    2017-02-01

    We consider a model for biofilm growth in the continuum mechanics framework, where the growth of different components of biomass is governed by a time dependent advection-reaction equation. The recently developed time-discontinuous Galerkin (TDG) method combined with two different stabilization techniques, namely the Streamline Upwind Petrov Galerkin (SUPG) method and the finite increment calculus (FIC) method, are discussed as solution strategies for a multi-dimensional multi-species biofilm growth model. The biofilm interface in the model is described by a convective movement following a potential flow coupled to the reaction inside of the biofilm. Growth limiting substrates diffuse through a boundary layer on top of the biofilm interface. A rolling ball method is applied to obtain a boundary layer of constant height. We compare different measures of the numerical dissipation and dispersion of the simulation results in particular for those with non-trivial patterns. By using these measures, a comparative study of the TDG-SUPG and TDG-FIC schemes as well as sensitivity studies on the time step size, the spatial element size and temporal accuracy are presented.

  17. Biofilm growth in porous media: Experiments, computational modeling at the porescale, and upscaling

    NASA Astrophysics Data System (ADS)

    Peszynska, Malgorzata; Trykozko, Anna; Iltis, Gabriel; Schlueter, Steffen; Wildenschild, Dorthe

    2016-09-01

    Biofilm growth changes many physical properties of porous media such as porosity, permeability and mass transport parameters. The growth depends on various environmental conditions, and in particular, on flow rates. Modeling the evolution of such properties is difficult both at the porescale where the phase morphology can be distinguished, as well as during upscaling to the corescale effective properties. Experimental data on biofilm growth is also limited because its collection can interfere with the growth, while imaging itself presents challenges. In this paper we combine insight from imaging, experiments, and numerical simulations and visualization. The experimental dataset is based on glass beads domain inoculated by biomass which is subjected to various flow conditions promoting the growth of biomass and the appearance of a biofilm phase. The domain is imaged and the imaging data is used directly by a computational model for flow and transport. The results of the computational flow model are upscaled to produce conductivities which compare well with the experimentally obtained hydraulic properties of the medium. The flow model is also coupled to a newly developed biomass-nutrient growth model, and the model reproduces morphologies qualitatively similar to those observed in the experiment.

  18. Kinetic experiments for evaluating the Nernst-Monod model for anode-respiring bacteria (ARB) in a biofilm anode.

    PubMed

    Torres, César I; Marcus, Andrew Kato; Parameswaran, Prathap; Rittmann, Bruce E

    2008-09-01

    Anode-respiring bacteria (ARB) are able to transfer electrons from reduced substrates to a solid electrode. Previously, we developed a biofilm model based on the Nernst-Monod equation to describe the anode potential losses of ARB that transfer electrons through a solid conductive matrix. In this work, we develop an experimental setup to demonstrate how well the Nernst-Monod equation is able to represent anode potential losses in an ARB biofilm. We performed low-scan cyclic voltammetry (LSCV) throughout the growth phase of an ARB biofilm on a graphite electrode growing on acetate in continuous mode. The (j)V response of 9 LSCVs corresponded well to the Nernst-Monod equation, and the half-saturation potential (E(KA)) was -0.425 +/- 0.002 V vs Ag/AgCl at 30 degrees C (-0.155 +/- 0.002 V vs SHE). Anode-potential losses from the potential of acetate reached approximately 0.225 V at current density saturation, and this loss was determined by our microbial community's E(KA) value. The LSCVs at high current densities showed no significant deviation from the Nernst-Monod ideal shape, indicating that the conductivity of the biofilm matrix (kappa(bio)) was high enough (> or = 0.5 mS/cm) that potential loss did not affect the performance of the biofilm anode. Our results confirm the applicability of the Nernst-Monod equation for a conductive biofilm anode and give insights of the processes that dominate anode potential losses in microbial fuel cells.

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

    PubMed

    Bertolini, M M; Xu, H; Sobue, T; Nobile, C J; Del Bel Cury, A A; Dongari-Bagtzoglou, A

    2015-08-01

    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 with the mucosa and fungi growing on the bacterial surface. Under semidry 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 with 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 a 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 the presence of commensal bacteria influence the architecture and virulence characteristics of mucosal fungal biofilms.

  20. Control of pathogen growth and biofilm formation using a urinary catheter that releases antimicrobial nitrogen oxides.

    PubMed

    Kishikawa, Hiroaki; Ebberyd, Anette; Römling, Ute; Brauner, Annelie; Lüthje, Petra; Lundberg, Jon O; Weitzberg, Eddie

    2013-12-01

    Antibacterial nitrogen oxides including nitric oxide are formed from nitrite under acidic conditions. In a continuous-flow model of the urinary bladder we used the retention cuff of an all-silicone Foley catheter as a depot for export of nitrogen oxides. The cuff was filled with sodium nitrite (50mM) and an acidic buffer solution (pH 3.6) and the growth of nine common uropathogens in the surrounding artificial urine was measured along with biofilm formation on the catheter surface. In experiments with control catheters (NaCl) bacteria grew readily and biofilm developed within hours in five of nine strains. In contrast, with test catheters bacterial counts were markedly reduced and biofilm formation by Pseudomonas aeruginosa, Klebsiella pneumoniae, and Enterobacter cloace was prevented, whereas Escherichia coli and Staphylococcus aureus were unaffected. We conclude that antibacterial nitrogen oxides generated in the retention cuff of a urinary catheter diffuse into urine and prevent the growth of urinary pathogens and biofilm formation. Although promising, future studies will reveal if this novel approach can be clinically useful for the prevention of catheter-associated urinary tract infections.

  1. Inhibition of bacterial growth and biofilm production by constituents from Hypericum spp.

    PubMed

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

    2012-07-01

    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, Hypericum ellipticum, Hypericum prolificum, and Hypericum punctatum as inhibitors of bacterial growth and biofilm production. Assays were conducted against Staphylococcus epidermidis, Staphylococcus aureus, 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.

  2. 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.

  3. Effect of growth temperature, surface type and incubation time on the resistance of Staphylococcus aureus biofilms to disinfectants.

    PubMed

    Abdallah, Marwan; Chataigne, Gabrielle; Ferreira-Theret, Pauline; Benoliel, Corinne; Drider, Djamel; Dhulster, Pascal; Chihib, Nour-Eddine

    2014-03-01

    The goal of this study was to investigate the effect of the environmental conditions such as the temperature change, incubation time and surface type on the resistance of Staphylococcus aureus biofilms to disinfectants. The antibiofilm assays were performed against biofilms grown at 20 °C, 30 °C and 37 °C, on the stainless steel and polycarbonate, during 24 and 48 h. The involvement of the biofilm matrix and the bacterial membrane fluidity in the resistance of sessile cells were investigated. Our results show that the efficiency of disinfectants was dependent on the growth temperature, the surface type and the disinfectant product. The increase of growth temperature from 20 °C to 37 °C, with an incubation time of 24 h, increased the resistance of biofilms to cationic antimicrobials. This change of growth temperature did not affect the major content of the biofilm matrix, but it decreased the membrane fluidity of sessile cells through the increase of the anteiso-C19 relative amount. The increase of the biofilm resistance to disinfectants, with the rise of the incubation time, was dependent on both growth temperature and disinfectant product. The increase of the biofilm age also promoted increases in the matrix production and the membrane fluidity of sessile cells. The resistance of S. aureus biofilm seems to depend on the environment of the biofilm formation and involves both extracellular matrix and membrane fluidity of sessile cells. Our study represents the first report describing the impact of environmental conditions on the matrix production, sessile cells membrane fluidity and resistance of S. aureus biofilms to disinfectants.

  4. 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

  5. Effects of nutritional and environmental conditions on planktonic growth and biofilm formation of Citrobacter werkmanii BF-6.

    PubMed

    Zhou, Gang; Li, Long-jie; Shi, Qing-shan; Ouyang, You-sheng; Chen, Yi-ben; Hu, Wen-feng

    2013-12-01

    Citrobacter sp. is a cause of significant opportunistic nosocomial infection and is frequently found in human and animal feces, soil, and sewage water, and even in industrial waste or putrefaction. Biofilm formation is an important virulence trait of Citrobacter sp. pathogens but the process and characteristics of this formation are unclear. Therefore, we employed in vitro assays to study the nutritional and environmental parameters that might influence biofilm formation of C. werkmanii BF-6 using 96-well microtiter plates. In addition, we detected the relative transcript levels of biofilm formation genes by RT-PCR. Our results indicated that the capacity of C. werkmanii BF-6 to form biofilms was affected by culture temperature, media, time, pH, and the osmotic agents glucose, sucrose, NaCl, and KCl. Confocal laser scanning microscopy results illustrated that the structure of biofilms and extracellular polysaccharide was influenced by 100 mM NaCl or 100 mM KCl. In addition, nine biofilm formation genes (bsmA, bssR, bssS, csgD, csgE, csgF, mrkA, mrkB, and mrkE) were found to contribute to planktonic and biofilm growth. Our data suggest that biofilm formation by C. werkmanii BF-6 is affected by nutritional and environmental factors, which could pave the way to the prevention and elimination of biofilm formation using proper strategies.

  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. 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

  8. Battling Bacterial Biofilms with Gas Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Zelaya, Anna; Vandervoort, Kurt; Brelles-Mariño, Graciela

    Most studies dealing with growth and physiology of bacteria have been carried out using free-living cells. However, most bacteria live in communities referred to as biofilms where cooperative interactions among their members make conventional methods of controlling microbial growth often ineffective. The use of gas discharge plasmas represents an alternative to traditional decontamination/sterilization methods. We studied biofilms using two organisms, Chromobacterium violaceum and Pseudomonas aeruginosa. With the first organism we demonstrated almost complete loss of cell culturability after a 5-min plasma treatment. However, additional determinations showed that non-culturable cells were still alive after short exposure times. We have recently reported the effect of plasma on P. aeruginosa biofilms grown on borosilicate coupons. In this paper, we present results for plasma treatments of 1-, 3-, and 7-day old P. aeruginosa biofilms grown on polycarbonate or stainless-steel coupons. Results indicate nearly 100% of ­biofilm inactivation after 5 min of exposure with similar inactivation kinetics for 1-, 3-, and 7-day-old biofilms, and for both materials used. The inactivation kinetics is similar for both organisms, suggesting that the method is useful regardless of the type of biofilm. AFM images show changes in biofilm structure for various plasma exposure times.

  9. 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.

  10. The Growth Kinetics of Salmonella Enteritidis in Raw Ground Beef.

    PubMed

    Sabike, Islam I; Fujikawa, Hiroshi; Edris, Abobakr M

    2015-01-01

    The growth kinetics of Salmonella Enteritidis in raw beef has been little studied so far. Thus, this study aimed to clarify the growth kinetics of the pathogen in ground beef using a growth model. When Salmonella cells inoculated at various initial doses into ground beef were incubated at a given temperature (24℃), the maximum population (Nmax) of the microbe at the stationary phase varied with the doses. This relationship was expressed with a polynomialequation for Nmax using the initial dose. The combination of the growth model and the polynomial equation successfully predicted Salmonella growth at a given initial dose. When Salmonella cells inoculated in ground beef were incubated at various constant temperatures, the growth curves of the pathogen and natural microflora (NM) were well described with the growth model. The rate constant of growth and the Nmax values for Salmonella and NM were then analyzed kinetically. From these results, growth curves of Salmonella and NM in ground beef stored at dynamic temperatures were successfully predicted. Competition between Salmonella and NM in ground beef was also found during the storage. This study could give usable information on the growth of Salmonella and NM in ground beef at various temperatures.

  11. Inhibitory effects of lactoferrin on growth and biofilm formation of Porphyromonas gingivalis and Prevotella intermedia.

    PubMed

    Wakabayashi, Hiroyuki; Yamauchi, Koji; Kobayashi, Tetsuo; Yaeshima, Tomoko; Iwatsuki, Keiji; Yoshie, Hiromasa

    2009-08-01

    Lactoferrin (LF) is an iron-binding antimicrobial protein present in saliva and gingival crevicular fluids, and it is possibly associated with host defense against oral pathogens, including periodontopathic bacteria. In the present study, we evaluated the in vitro effects of LF-related agents on the growth and biofilm formation of two periodontopathic bacteria, Porphyromonas gingivalis and Prevotella intermedia, which reside as biofilms in the subgingival plaque. The planktonic growth of P. gingivalis and P. intermedia was suppressed for up to 5 h by incubation with >or=130 microg/ml of human LF (hLF), iron-free and iron-saturated bovine LF (apo-bLF and holo-bLF, respectively), and >or=6 microg/ml of bLF-derived antimicrobial peptide lactoferricin B (LFcin B); but those effects were weak after 8 h. The biofilm formation of P. gingivalis and P. intermedia over 24 h was effectively inhibited by lower concentrations (>or=8 microg/ml) of various iron-bound forms (the apo, native, and holo forms) of bLF and hLF but not LFcin B. A preformed biofilm of P. gingivalis and P. intermedia was also reduced by incubation with various iron-bound bLFs, hLF, and LFcin B for 5 h. In an examination of the effectiveness of native bLF when it was used in combination with four antibiotics, it was found that treatment with ciprofloxacin, clarithromycin, and minocycline in combination with native bLF for 24 h reduced the amount of a preformed biofilm of P. gingivalis compared with the level of reduction achieved with each agent alone. These results demonstrate the antibiofilm activity of LF with lower iron dependency against P. gingivalis and P. intermedia and the potential usefulness of LF for the prevention and treatment of periodontal diseases and as adjunct therapy for periodontal diseases.

  12. Differences between single- and dual-species biofilms of Streptococcus mutans and Veillonella parvula in growth, acidogenicity and susceptibility to chlorhexidine.

    PubMed

    Kara, Duygu; Luppens, Suzanne B I; Cate, Jacob M

    2006-02-01

    Streptococcus mutans, considered a primary pathogen in dental caries, thrives in dental plaque, which is a multispecies biofilm. Metabolic interactions between S. mutans and Veillonella parvula have been suggested. In this study we developed a biofilm model to quantify single-species (S. mutans or V. parvula) and dual-species (S. mutans and V. parvula) biofilm formation, and we identified the differences between the respective biofilms in terms of growth, acid formation, and response to chlorhexidine. Polystyrene 96-well microtiter plates were used for biofilm formation. These biofilms were exposed to various chlorhexidine concentrations (0.025-0.4 mg ml(-1)) and treatment conditions. Growth of the biofilms and the effects of chlorhexidine were evaluated by viable counts. Viability of the two species in all biofilm types was similar ( approximately 10(8) colony-forming units per well) after 72 h. Lactic acid accumulation of dual-species biofilms was significantly lower at 48 and 72 h than single-species biofilms of S. mutans. Dual-species biofilms were less susceptible to chlorhexidine than single-species biofilms when a neutralization step was included. These results indicate that bacteria in dual-species biofilms have different properties from bacteria in single-species biofilms.

  13. General theory for integrated analysis of growth, gene, and protein expression in biofilms.

    PubMed

    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.

  14. Label-free interdigitated microelectrode based biosensors for bacterial biofilm growth monitoring using Petri dishes.

    PubMed

    Paredes, Jacobo; Becerro, Sheila; Arana, Sergio

    2014-05-01

    Impedance microbiology (IM) is a known technique that has been applied during the last decades to detect the presence of microorganisms in real samples in different fields: food industry, healthcare, environment, etc. Bacterial biofilms however have not been so far studied despite the fact that they are the most common microbiological formation and that they present resistance to antimicrobial agents. In situ early detection of bacterial biofilm is still a challenge nowadays that causes huge impact in many different scenarios. The ability to detect biofilm generation early will allow better and more efficient treatments preventing high costs and important problems. In this work a new performance of this technique with interdigitated microelectrode sensors (IDE) is proposed. A specific culturing setup where the sensors have been integrated in Petri Dishes has been developed. From the results it can be highlighted that low frequencies are more sensitive for detection than higher ones. The results achieved record variations of approximately 40% in the equivalent serial resistance after 10h of culture. Electrical models have been successfully simulated to find the electrical behavior of the development of biofilms. Variations in both the capacitance and resistance were recorded during the growth of the microbes.

  15. 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.

  16. Janus particle rotator-to-lamellar nucleation and growth kinetics

    NASA Astrophysics Data System (ADS)

    Beltran-Villegas, Daniel J.; Zhang, Yulei; Larson, Ronald G.

    2017-03-01

    We determine the free energy barrier, critical nucleus size, and kinetics of a Janus particle solid-solid transition by nucleation and growth of lamellar clusters within a metastable rotator phase. The transition involves negligible change in particle position and phase volume and entails only particle orientational ordering. Fast kinetics enable the analysis of unbiased crystal growth and shrinkage trajectories from Brownian dynamic simulations. By fitting simulation trajectories to a diffusion-migration equation, the nucleus free energy and growth coefficient as a function of nucleus size are extracted. Observed transition times are on the order of hundreds of characteristic particle rotation times. Lamellar crystal nuclei are oblate rather than spherical, but otherwise classical nucleation theory applies, with the bulk free energy contribution following closely the Maier-Saupe theory for purely orientational transitions and the interfacial energy contribution following trends from 3-dimensional Ising spin kinetics.

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

    PubMed

    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.

  18. 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

  19. 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.

  20. [Growth and development kinetics of Bacillus thuringiensis in batch culture].

    PubMed

    Sakharova, Z V; Ignatenko, Iu N; Schulz, F; Khovrychev, M P; Rabotnova, I L

    1985-01-01

    The kinetics of Bacillus thuringiensis growth and its assimilation of nutrient substances were studied under the conditions of batch cultivation in a complex medium containing yeast extract and in a chemically defined medium with amino acids. The growth of B. thuringiensis can be divided into five phases: exponential growth; decelerated growth; stationary phase when protein crystals are formed; stationary phase when spores are formed; lysis of sporangia releasing spores. The first phase may in turn be subdivided into three stages according to changes in the specific growth rate and substrate assimilation: a high specific growth rate and no glucose assimilation; an abrupt drop in mu and the beginning of intensive glucose assimilation from the medium; a new rise in the specific growth rate. As follows from the results of studying the kinetics of B. thuringiensis growth in a chemically defined medium, the above changes in the exponential growth phase are due to the fact that the culture assimilates yeast extract components in the complex medium or amino acids in the chemically defined medium during this phase, and then starts to assimilate glucose and ammonium in the following phases of growth.

  1. 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.

  2. Thermodynamic and kinetic control of the lateral Si wire growth

    SciTech Connect

    Dedyulin, Sergey N. Goncharova, Lyudmila V.

    2014-03-24

    Reproducible lateral Si wire growth has been realized on the Si (100) surface. In this paper, we present experimental evidence showing the unique role that carbon plays in initiating lateral growth of Si wires on a Si (100) substrate. Once initiated in the presence of ≈5 ML of C, lateral growth can be achieved in the range of temperatures, T = 450–650 °C, and further controlled by the interplay of the flux of incoming Si atoms with the size and areal density of Au droplets. Critical thermodynamic and kinetic aspects of the growth are discussed in detail.

  3. An autocatalytic kinetic model for describing microbial growth during fermentation.

    PubMed

    Ibarz, Albert; Augusto, Pedro E D

    2015-01-01

    The mathematical modelling of the behaviour of microbial growth is widely desired in order to control, predict and design food and bioproduct processing, stability and safety. This work develops and proposes a new semi-empirical mathematical model, based on an autocatalytic kinetic, to describe the microbial growth through its biomass concentration. The proposed model was successfully validated using 15 microbial growth patterns, covering the three most important types of microorganisms in food and biotechnological processing (bacteria, yeasts and moulds). Its main advantages and limitations are discussed, as well as the interpretation of its parameters. It is shown that the new model can be used to describe the behaviour of microbial growth.

  4. Development and calibration of a microfluidic biofilm growth cell with flow-templating and multi-modal characterization.

    PubMed

    Paquet-Mercier, Francois; Karas, Adnane; Safdar, Muhammad; Aznaveh, Nahid Babaei; Zarabadi, Mirpouyan; Greener, Jesse

    2014-01-01

    We report the development of a microfluidic flow-templating platform with multi-modal characterization for studies of biofilms and their precursor materials. A key feature is a special three inlet flow-template compartment, which confines and controls the location of biofilm growth against a template wall. Characterization compartments include Raman imaging to study the localization of the nutrient solutions, optical microscopy to quantify biofilm biomass and localization, and cyclic voltammetry for flow velocity measurements. Each compartment is tested and then utilized to make preliminary measurements.

  5. 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.

  6. 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

  7. Effects of Tween 80 on Growth and Biofilm Formation in Laboratory Media

    PubMed Central

    Nielsen, Christina K.; Kjems, Jørgen; Mygind, Tina; Snabe, Torben; Meyer, Rikke L.

    2016-01-01

    Tween 80 is a widely used non-ionic emulsifier that is added to cosmetics, pharmaceuticals, and foods. Because of its widespread use we need to understand how it affects bacteria on our skin, in our gut, and in food products. The aim of this study is to investigate how Tween 80 affects the growth and antimicrobial susceptibility of Staphylococcus aureus, Listeria monocytogenes, and Pseudomonas fluorescens, which are common causes of spoilage and foodborne illnesses. Addition of 0.1% Tween 80 to laboratory growth media increased the growth rate of planktonic S. aureus batch cultures, and it also increased the total biomass when S. aureus was grown as biofilms. In contrast, Tween 80 had no effect on batch cultures of L. monocytogenes, it slowed the growth rate of P. fluorescens, and it led to formation of less biofilm by both L. monocytogenes and P. fluorescens. Furthermore, Tween 80 lowered the antibacterial efficacy of two hydrophobic antimicrobials: rifampicin and the essential oil isoeugenol. Our findings underline the importance of documenting indirect effects of emulsifiers when studying the efficacy of hydrophobic antimicrobials that are dispersed in solution by emulsification, or when antimicrobials are applied in food matrixes that include emulsifiers. Furthermore, the species-specific effects on microbial growth suggests that Tween 80 in cosmetics and food products could affect the composition of skin and gut microbiota, and the effect of emulsifiers on the human microbiome should therefore be explored to uncover potential health effects. PMID:27920774

  8. Effects of Tween 80 on Growth and Biofilm Formation in Laboratory Media.

    PubMed

    Nielsen, Christina K; Kjems, Jørgen; Mygind, Tina; Snabe, Torben; Meyer, Rikke L

    2016-01-01

    Tween 80 is a widely used non-ionic emulsifier that is added to cosmetics, pharmaceuticals, and foods. Because of its widespread use we need to understand how it affects bacteria on our skin, in our gut, and in food products. The aim of this study is to investigate how Tween 80 affects the growth and antimicrobial susceptibility of Staphylococcus aureus, Listeria monocytogenes, and Pseudomonas fluorescens, which are common causes of spoilage and foodborne illnesses. Addition of 0.1% Tween 80 to laboratory growth media increased the growth rate of planktonic S. aureus batch cultures, and it also increased the total biomass when S. aureus was grown as biofilms. In contrast, Tween 80 had no effect on batch cultures of L. monocytogenes, it slowed the growth rate of P. fluorescens, and it led to formation of less biofilm by both L. monocytogenes and P. fluorescens. Furthermore, Tween 80 lowered the antibacterial efficacy of two hydrophobic antimicrobials: rifampicin and the essential oil isoeugenol. Our findings underline the importance of documenting indirect effects of emulsifiers when studying the efficacy of hydrophobic antimicrobials that are dispersed in solution by emulsification, or when antimicrobials are applied in food matrixes that include emulsifiers. Furthermore, the species-specific effects on microbial growth suggests that Tween 80 in cosmetics and food products could affect the composition of skin and gut microbiota, and the effect of emulsifiers on the human microbiome should therefore be explored to uncover potential health effects.

  9. 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.

  10. Quantifying the rate of biofilm growth of S. meliloti strains in microfluidics via the diffusion coefficient of microspheres

    NASA Astrophysics Data System (ADS)

    Dorian, Matthew; Seitaridou, Effrosyni

    2014-03-01

    Understanding the rate of biofilm growth is essential for studying genes and preventing unwanted biofilms. In this study, the diffusion coefficient (D) of polystyrene microspheres was used to quantify biofilm growth rates of Sinorhizobia meliloti, a nitrogen fixing bacteria that forms a symbiotic relationship with alfalfa plants. Five strains were studied, two wild types (8530 expR+ and 1021) and three mutants in the exopolysaccharide (EPS I, EPS II) synthesis (8530 exoY , 9034 expG , and 9030-2 expA 1); 1021 and 9030-2 expA 1 are known to be unable to form biofilms. Each strain was inserted into a microfluidic channel with the microspheres. As the cultures grew, the spheres' D values were obtained every 24 hours for 4 days using fluorescence microscopy. Although the D values for 9030-2 expA 1 were inconclusive, 8530 expR+ , 8530 exoY , and 9034 expG showed significant decreases in D between 3 days of growth (| z | > 2 . 25 , p < 0 . 025). The data also indicated that 8530 expR+ and 8530 exoY grew at similar rates. There was no significant change in D for 1021 (χ2(2) = 5 . 76 , p > 0 . 05), which shows the lack of a structured biofilm community. Thus, D can be used as an indicator of the presence of a biofilm and its development.

  11. 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.

  12. The Influence of Prior Modes of Growth, Temperature, Medium, and Substrate Surface on Biofilm Formation by Antibiotic-Resistant Campylobacter jejuni.

    PubMed

    Teh, Amy Huei Teen; Lee, Sui Mae; Dykes, Gary A

    2016-12-01

    Campylobacter jejuni is one of the most common causes of bacterial gastrointestinal food-borne infection worldwide. It has been suggested that biofilm formation may play a role in survival of these bacteria in the environment. In this study, the influence of prior modes of growth (planktonic or sessile), temperatures (37 and 42 °C), and nutrient conditions (nutrient broth and Mueller-Hinton broth) on biofilm formation by eight C. jejuni strains with different antibiotic resistance profiles was examined. The ability of these strains to form biofilm on different abiotic surfaces (stainless steel, glass, and polystyrene) as well as factors potentially associated with biofilm formation (bacterial surface hydrophobicity, auto-aggregation, and initial attachment) was also determined. The results showed that cells grown as sessile culture generally have a greater ability to form biofilm (P < 0.05) compared to their planktonic counterparts. Biofilm was also greater (P < 0.05) in lower nutrient media, while growth at different temperatures affects biofilm formation in a strain-dependent manner. The strains were able to attach and form biofilms on different abiotic surfaces, but none of them demonstrated strong, complex, or structured biofilm formation. There were no clear trends between the bacterial surface hydrophobicity, auto-aggregation, attachment, and biofilm formation by the strains. This finding suggests that environmental factors did affect biofilm formation by C. jejuni, and they are more likely to persist in the environment in the form of mixed-species rather than monospecies biofilms.

  13. Maximising electricity production by controlling the biofilm specific growth rate in microbial fuel cells.

    PubMed

    Ledezma, Pablo; Greenman, John; Ieropoulos, Ioannis

    2012-08-01

    The aim of this work is to study the relationship between growth rate and electricity production in perfusion-electrode microbial fuel cells (MFCs), across a wide range of flow rates by co-measurement of electrical output and changes in population numbers by viable counts and optical density. The experiments hereby presented demonstrate, for the first time to the authors' knowledge, that the anodic biofilm specific growth rate can be determined and controlled in common with other loose matrix perfusion systems. Feeding with nutrient-limiting conditions at a critical flow rate (50.8 mL h(-1)) resulted in the first experimental determination of maximum specific growth rate μ(max) (19.8 day(-1)) for Shewanella spp. MFC biofilms, which is considerably higher than those predicted or assumed via mathematical modelling. It is also shown that, under carbon-energy limiting conditions there is a strong direct relationship between growth rate and electrical power output, with μ(max) coinciding with maximum electrical power production.

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

    PubMed

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

    2015-10-16

    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.

  15. Flexible camphor diamond-like carbon coating on polyurethane to prevent Candida albicans biofilm growth.

    PubMed

    Santos, Thaisa B; Vieira, Angela A; Paula, Luciana O; Santos, Everton D; Radi, Polyana A; Khouri, Sônia; Maciel, Homero S; Pessoa, Rodrigo S; Vieira, Lucia

    2017-04-01

    Camphor was incorporated in diamond-like carbon (DLC) films to prevent the Candida albicans yeasts fouling on polyurethane substrates, which is a material commonly used for catheter manufacturing. The camphor:DLC and DLC film for this investigation was produced by plasma enhanced chemical vapor deposition (PECVD), using an apparatus based on the flash evaporation of organic liquid (hexane) containing diluted camphor for camphor:DLC and hexane/methane, mixture for DLC films. The film was deposited at a low temperature of less than 25°C. We obtained very adherent camphor:DLC and DLC films that accompanied the substrate flexibility without delamination. The adherence of camphor:DLC and DLC films on polyurethane segments were evaluated by scratching test and bending polyurethane segments at 180°. The polyurethane samples, with and without camphor:DLC and DLC films were characterized by Raman spectroscopy, scanning electron microscopy, atomic force microscopy, and optical profilometry. Candida albicans biofilm formation on polyurethane, with and without camphor:DLC and DLC, was assessed. The camphor:DLC and DLC films reduced the biofilm growth by 99.0% and 91.0% of Candida albicans, respectively, compared to bare polyurethane. These results open the doors to studies of functionalized DLC coatings with biofilm inhibition properties used in the production of catheters or other biomedical applications.

  16. 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

  17. Nucleation and growth kinetics of biochemicals measured at high supersaturations

    NASA Astrophysics Data System (ADS)

    Mahajan, Amarjit J.; Kirwan, Donald J.

    1994-12-01

    A grid mixer device (characteristic micromixing time < 3 ms) was successfully used to measure both nucleation and growth kinetics of lovastatin in 60 vol% methanol and asparagine monohydrate in 50 vol% 2-propanol at 23°C at high supersaturations but in the absence of mixing limitations. The supersaturation ratios investigated were in the range 1.25-8.8 for the lovastatin system and 1.17-4.1 for the asparagine system. When plotted according to primary nucleation theory, the induction time and nucleation rate measurements for both systems exhibited a homogeneous nucleation region at high supersaturations and a heterogeneous nucleation region at low supersaturations. The values of interfacial free energy extracted from these measurements for lovastatin (1.4-1.6 mJ/m 2) and asparagine (4.5-6.1 mJ/m 2) were an order-of-magnitude lower than those for inorganic salts reflecting the weaker intermolecular bonding in such biochemical solutes. The measured crystal growth rates for both solutes over the entire range of supersaturation could be represented with a power law dependence on chemical potential driving force. The kinetic orders of crystal growth were found to be 6.7 and 2.9 for lovastatin and asparagine, respectively. These unusually high kinetic orders could be represented by a polynuclear surface nucleation growth mechanism. The activation energy for the growth of lovastatin was measured as 280 kJ/mol.

  18. Cyclosporine A decreases the fluconazole minimum inhibitory concentration of Candida albicans clinical isolates but not biofilm formation and cell growth.

    PubMed

    Wibawa, T; Nurrokhman; Baly, I; Daeli, P R; Kartasasmita, G; Wijayanti, N

    2015-03-01

    Among the genus Candida, Candida albicans is the most abundant species in humans. One of the virulent factors of C. albicans is its ability to develop biofilm. Biofilm forming microbes are characterized by decreasing of its susceptibility to antibiotics and antifungal. The fungicidal effect of fluconazole may be enhanced by cyclosporine A in laboratory engineered C. albicans strains. The aim of this work is to analyze the synergistic effect of cyclosporine A with fluconazole in C. albicans clinical isolates and the effect of cycolsporine A alone in the biofilm formation. Six fluconazole resistant and six sensitive C. albicans clinical isolates were analyzed for its minimum inhibitory concentration (MICs), biofilm formation, and cell growths. A semi-quantitative XTT [2,3-bis(2-methoxy-4-nitro-5- sulfo-phenyl)-2H-tetrazolium-5-carboxanilide] reduction assay was conducted to measure the biofilm formation. Cyclosporine A has synergistic effect with fluconazole that was shown by decreasing MICs of both fluconazole resistant and sensitive C. albicans clinical isolates. However, cyclosporine A alone did not influence the biofilm formation and cell growth of both fluconazole resistant and sensitive C. albicans clinical isolates. These results indicated that cyclosporine A might be a promising candidate of adjuvant therapy for fluconazole against both fluconazole resistant and sensitive C. albicans clinical isolates.

  19. 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.

  20. Dendritic growth shapes in kinetic Monte Carlo models

    NASA Astrophysics Data System (ADS)

    Krumwiede, Tim R.; Schulze, Tim P.

    2017-02-01

    For the most part, the study of dendritic crystal growth has focused on continuum models featuring surface energies that yield six pointed dendrites. In such models, the growth shape is a function of the surface energy anisotropy, and recent work has shown that considering a broader class of anisotropies yields a correspondingly richer set of growth morphologies. Motivated by this work, we generalize nanoscale models of dendritic growth based on kinetic Monte Carlo simulation. In particular, we examine the effects of extending the truncation radius for atomic interactions in a bond-counting model. This is done by calculating the model’s corresponding surface energy and equilibrium shape, as well as by running KMC simulations to obtain nanodendritic growth shapes. Additionally, we compare the effects of extending the interaction radius in bond-counting models to that of extending the number of terms retained in the cubic harmonic expansion of surface energy anisotropy in the context of continuum models.

  1. 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.

  2. [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).

  3. 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.

  4. Growth condition-dependent Esp expression by Enterococcus faecium affects initial adherence and biofilm formation.

    PubMed

    Van Wamel, Willem J B; Hendrickx, Antoni P A; Bonten, Marc J M; Top, Janetta; Posthuma, George; Willems, Rob J L

    2007-02-01

    A genetic subpopulation of Enterococcus faecium, called clonal complex 17 (CC-17), is strongly associated with hospital outbreaks and invasive infections. Most CC-17 strains contain a putative pathogenicity island encoding the E. faecium variant of enterococcal surface protein (Esp). Western blotting, flow cytometric analyses, and electron microscopy showed that Esp is expressed and exposed on the surface of E. faecium, though Esp expression and surface exposure are highly varied among different strains. Furthermore, Esp expression depends on growth conditions like temperature and anaerobioses. When grown at 37 degrees C, five of six esp-positive E. faecium strains showed significantly increased levels of surface-exposed Esp compared to bacteria grown at 21 degrees C, which was confirmed at the transcriptional level by real-time PCR. In addition, a significant increase in surface-exposed Esp was found in half of these strains when grown at 37 degrees C under anaerobic conditions compared to the level in bacteria grown under aerobic conditions. Finally, amounts of surface-exposed Esp correlated with initial adherence to polystyrene (R(2) = 0.7146) and biofilm formation (R(2) = 0.7535). Polystyrene adherence was competitively inhibited by soluble recombinant N-terminal Esp. This study demonstrates that Esp expression on the surface of E. faecium (i) varies consistently between strains, (ii) is growth condition dependent, and (iii) is quantitatively correlated with initial adherence and biofilm formation. These data indicate that E. faecium senses and responds to changing environmental conditions, which might play a role in the early stages of infection when bacteria transit from oxygen-rich conditions at room temperature to anaerobic conditions at body temperature. In addition, variation of surface exposure may explain the contrasting findings reported on the role of Esp in biofilm formation.

  5. 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

  6. Biofilm Composition and Threshold Concentration for Growth of Legionella pneumophila on Surfaces Exposed to Flowing Warm Tap Water without Disinfectant.

    PubMed

    van der Kooij, Dick; Bakker, Geo L; Italiaander, Ronald; Veenendaal, Harm R; Wullings, Bart A

    2017-03-01

    Legionella pneumophila in potable water installations poses a potential health risk, but quantitative information about its replication in biofilms in relation to water quality is scarce. Therefore, biofilm formation on the surfaces of glass and chlorinated polyvinyl chloride (CPVC) in contact with tap water at 34 to 39°C was investigated under controlled hydraulic conditions in a model system inoculated with biofilm-grown L. pneumophila The biofilm on glass (average steady-state concentration, 23 ± 9 pg ATP cm(-2)) exposed to treated aerobic groundwater (0.3 mg C liter(-1); 1 μg assimilable organic carbon [AOC] liter(-1)) did not support growth of the organism, which also disappeared from the biofilm on CPVC (49 ± 9 pg ATP cm(-2)) after initial growth. L. pneumophila attained a level of 4.3 log CFU cm(-2) in the biofilms on glass (1,055 ± 225 pg ATP cm(-2)) and CPVC (2,755 ± 460 pg ATP cm(-2)) exposed to treated anaerobic groundwater (7.9 mg C liter(-1); 10 μg AOC liter(-1)). An elevated biofilm concentration and growth of L. pneumophila were also observed with tap water from the laboratory. The Betaproteobacteria Piscinibacter and Methyloversatilis and amoeba-resisting Alphaproteobacteria predominated in the clones and isolates retrieved from the biofilms. In the biofilms, the Legionella colony count correlated significantly with the total cell count (TCC), heterotrophic plate count, ATP concentration, and presence of Vermamoeba vermiformis This amoeba was rarely detected at biofilm concentrations of <100 pg ATP cm(-2) A threshold concentration of approximately 50 pg ATP cm(-2) (TCC = 1 × 10(6) to 2 × 10(6) cells cm(-2)) was derived for growth of L. pneumophila in biofilms.IMPORTANCELegionella pneumophila is the etiologic agent in more than 10,000 cases of Legionnaires' disease that are reported annually worldwide and in most of the drinking water-associated disease outbreaks reported in the United States. The organism proliferates in biofilms on

  7. Kinetics of Denitrifying Growth by Fast-Growing Cowpea Rhizobia

    PubMed Central

    El Hassan, G. A.; Zablotowicz, R. M.; Focht, D. D.

    1985-01-01

    Two fast-growing strains of cowpea rhizobia (A26 and A28) were found to grow anaerobically at the expense of NO3−, NO2−, and N2O as terminal electron acceptors. The two major differences between aerobic and denitrifying growth were lower yield coefficients (Y) and higher saturation constants (Ks) with nitrogenous oxides as electron acceptors. When grown aerobically, A26 and A28 adhered to Monod kinetics, respectively, as follows: Ks, 3.4 and 3.8 μM; Y, 16.0 and 14.0 g · cells eq−1; μmax, 0.41 and 0.33 h−1. Yield coefficients for denitrifying growth ranged from 40 to 70% of those for aerobic growth. Only A26 adhered to Monod kinetics with respect to growth on all three nitrogenous oxides. The apparent Ks values were 41, 270, and 460 μM for nitrous oxide, nitrate, and nitrite, respectively; the Ks for A28 grown on nitrate was 250 μM. The results are kinetically and thermodynamically consistent in explaining why O2 is the preferred electron acceptor. Although no definitive conclusions could be drawn regarding preferential utilization of nitrogenous oxides, nitrite was inhibitory to both strains and effected slower growth. However, growth rates were identical (μmax, 0.41 h−1) when A26 was grown with either O2 or NO3− as an electron acceptor and were only slightly reduced when A28 was grown with NO3− (0.25 h−1) as opposed to O2 (0.33 h−1). PMID:16346745

  8. Kinetic model for microbial growth and desulphurisation with Enterobacter sp.

    PubMed

    Liu, Long; Guo, Zhiguo; Lu, Jianjiang; Xu, Xiaolin

    2015-02-01

    Biodesulphurisation was investigated by using Enterobacter sp. D4, which can selectively desulphurise and convert dibenzothiophene into 2-hydroxybiphenyl (2-HBP). The experimental values of growth, substrate consumption and product generation were obtained at 95 % confidence level of the fitted values using three models: Hinshelwood equation, Luedeking-Piret and Luedeking-Piret-like equations. The average error values between experimental values and fitted values were less than 10 %. These kinetic models describe all the experimental data with good statistical parameters. The production of 2-HBP in Enterobacter sp. was by "coupled growth".

  9. 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.

  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. Waste water derived electroactive microbial biofilms: growth, maintenance, and basic characterization.

    PubMed

    Gimkiewicz, Carla; Harnisch, Falk

    2013-12-29

    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 (E(f)) 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.

  12. 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.

  13. 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

  14. Bioelectrochemical Reduction of Fe(II)EDTA-NO in a Biofilm Electrode Reactor: Performance, Mechanism, and Kinetics.

    PubMed

    Xia, Yinfeng; Zhao, Jingkai; Li, Meifang; Zhang, Shihan; Li, Sujing; Li, Wei

    2016-04-05

    A biofilm electrode reactor (BER) is proposed to effectively regenerate Fe(II)EDTA, a solvent for NOx removal from flue gas, from Fe(II)EDTA-NO, a spent solution. In this study, the performance, mechanism, and kinetics of the bioelectrochemical reduction of Fe(II)EDTA-NO were investigated. The pathways of Fe(II)EDTA-NO reduction were investigated via determination of nitrogen element balance in the BER and an abiotic electrode reactor. The experimental results indicate that the chelated NO (Fe(II)EDTA-NO) is reduced to N2 with N2O as an intermediate. However, the oxidation of NO occurred in the absence of Fe(II)EDTA in abiotic reactors. Furthermore, the accumulation of N2O was suppressed with the help of electricity. The preponderant electron donor for reduction of Fe(II)EDTA-NO was also confirmed via analysis of the electron conservation. About 87% of Fe(II)EDTA-NO was reduced using Fe(II)EDTA as the electron donor in the presence of both glucose and cathode electrons while the cathode electrons were utilized for the reduction of Fe(III)EDTA to Fe(II)EDTA. Michaelis-Menten kinetic constants of bioelectrochemical reduction of Fe(II)EDTA-NO were also calculated. The maximum reduction rate of Fe(II)EDTA-NO was 13.04 mol m(-3) h(-1), which is 50% higher than that in a conventional biofilter.

  15. Physiological adaptation of growth kinetics in activated sludge.

    PubMed

    Friedrich, M; Takács, I; Tränckner, J

    2015-11-15

    Physiological adaptation as it occurs in bacterial cells at variable environmental conditions influences characteristic properties of growth kinetics significantly. However, physiological adaptation to growth related parameters in activated sludge modelling is not yet recognised. Consequently these parameters are regarded to be constant. To investigate physiological adaptation in activated sludge the endogenous respiration in an aerobic degradation batch experiment and simultaneous to that the maximum possible respiration in an aerobic growth batch experiment was measured. The activated sludge samples were taken from full scale wastewater treatment plants with different sludge retention times (SRTs). It could be shown that the low SRT sludge adapts by growth optimisation (high maximum growth rate and high decay rate) to its particular environment where a high SRT sludge adapts by survival optimization (low maximum growth rate and low decay rate). Thereby, both the maximum specific growth rate and the decay rate vary in the same pattern and are strongly correlated to each other. To describe the physiological state of mixed cultures like activated sludge quantitatively a physiological state factor (PSF) is proposed as the ratio of the maximum specific growth rate and the decay rate. The PSF can be expressed as an exponential function with respect to the SRT.

  16. Mucin can enhance growth, biofilm formation, and survival of Streptococcus mutans.

    PubMed

    Mothey, Deepa; Buttaro, Bettina A; Piggot, Patrick J

    2014-01-01

    Streptococcus mutans is a member of the dental plaque and is the primary causative agent of dental caries. It can survive extended periods of starvation, which may occur in different niches within the oral cavity. We have found that mucin compensated for the absence of amino acids to promote exponential growth and biofilm formation of S. mutans in minimal medium supplemented with glucose and sucrose, respectively. Mucin extended survival in conditions where there was no net growth provided the operon encoding the pyruvate dehydrogenase complex was intact. Mucin extended survival in conditions of amino acid sufficiency provided the tagatose pathway for galactose utilization was intact, suggesting that S. mutans can scavenge sufficient galactose from mucin to enhance survival, although not to serve as a primary carbon and energy source. The results suggest that mucin has a metabolic role in promoting survival of S. mutans.

  17. 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

  18. 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

  19. 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.

  20. 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

  1. 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.

  2. Rapid quantitative and qualitative analysis of biofilm production by Staphylococcus epidermidis under static growth conditions.

    PubMed

    Waters, Elaine M; McCarthy, Hannah; Hogan, Siobhan; Zapotoczna, Marta; O'Neill, Eoghan; O'Gara, James P

    2014-01-01

    Rapid screening of biofilm forming capacity by Staphylococcus epidermidis is possible using in vitro assays with 96-well plates. This method first developed by Christensen et al. in 1985 is fast and does not require specialized instruments. Thus, laboratories with standard microbiology infrastructure and a 96-well plate reader can easily use this technique to generate data on the biofilm phenotypes of multiple S. epidermidis strains and clinical isolates. Furthermore, this method can be adapted to gain insights into biofilm regulation and the characteristics of biofilms produced by different S. epidermidis isolates. Although this assay is extremely useful for showing whether individual strains are biofilm-positive or biofilm-negative and distinguishing between form weak, moderate or strong biofilm, it is important to acknowledge that the absolute levels of biofilm produced by an individual strain can vary significantly between experiments meaning that strict adherence to the protocol used is of paramount importance. Furthermore, measuring biofilm under static conditions does not generally reflect in vivo conditions in which bacteria are often subjected to shear stresses under flow conditions. Hence, the biofilm characteristics of some strains are dramatically different under flow and static conditions. Nevertheless, rapid measurement of biofilm production under static conditions is a useful tool in the analysis of the S. epidermidis biofilm phenotype.

  3. Comparing Resistance, Resilience, and Stability of Replicate Moving Bed Biofilm and Suspended Growth Combined Nitritation-Anammox Reactors.

    PubMed

    Wells, G F; Shi, Y; Laureni, M; Rosenthal, A; Szivák, I; Weissbrodt, D G; Joss, A; Buergmann, H; Johnson, D R; Morgenroth, E

    2017-04-04

    Combined partial nitritation-anammox (PN/A) systems are increasingly employed for sustainable nitrogen removal from wastewater, but process instabilities present ongoing challenges for practitioners. The goal of this study was to elucidate differences in process stability between PN/A process variations employing two distinct aggregate types-biofilm (in moving bed biofilm reactors, MBBRs) and suspended growth biomass. Triplicate reactors for each process variation were studied under baseline conditions and in response to a series of transient perturbations. MBBRs displayed elevated NH4+ removal rates relative to suspended growth counterparts over six months of unperturbed baseline operation, but also exhibited significantly greater variability in performance. Transient perturbations led to strikingly divergent yet reproducible behavior in biofilm versus suspended growth systems. A temperature perturbation prompted a sharp reduction in NH4+ removal rates with no NO2- accumulation and rapid recovery in MBBRs, compared to a similar reduction in NH4+ removal rates but strong NO2- accumulation in suspended growth reactors. Pulse additions of a nitrification inhibitor (allylthiourea) prompted only moderate declines in performance in suspended growth reactors compared to sharp decreases in NH4+ removal rates in MBBRs. Quantitative FISH demonstrated a significant enrichment of anammox in MBBRs compared to suspended growth reactors, and conversely a proportionally higher AOB abundance in suspended growth reactors. Overall, MBBRs displayed significantly increased susceptibility to transient perturbations employed in this study compared to suspended growth counterparts (stability parameter), including significantly longer recovery times (resilience). No significant difference in maximum impact of perturbations (resistance) was apparent. Taken together, our results suggest that aggregate architecture (biofilm versus suspended growth) in PN/A processes exerts an unexpectedly

  4. 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 .

  5. Kinetic growth walk on critical percolation clusters and lattice animals

    NASA Astrophysics Data System (ADS)

    Lam, P. M.; Zhang, Z. Q.

    1984-03-01

    The statistics of recently proposed kinetic growth walk (KGW) model for linear polymers (or growing self avoiding walk (GSAW)) on two dimensional critical percolation clusters and lattice animals are studied using real-space renormalization group method. The correlation length exponents ν's are found to be ν{KGW/ Pc } = 0.68 and ν{KGW/LA} respectively for the critical percolation clusters and lattice animals. Close agreements are found between these results and a generalized Flory formula for linear polymers at theta point ν{KGW/F} = 2/bar d+1),, wherebar d is the fractal dimension of the fractal object F.

  6. 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

  7. Growth of Pseudomonas taiwanensis VLB120∆C biofilms in the presence of n-butanol.

    PubMed

    Halan, Babu; Vassilev, Igor; Lang, Karsten; Schmid, Andreas; Buehler, Katja

    2016-10-03

    Biocatalytic processes often encounter problems due to toxic reactants and products, which reduce biocatalyst viability. Thus, robust organisms capable of tolerating or adapting towards such compounds are of high importance. This study systematically investigated the physiological response of Pseudomonas taiwanensis VLB120∆C biofilms when exposed to n-butanol, one of the potential next generation biofuels as well as a toxic substance using microscopic and biochemical methods. Initially P. taiwanensis VLB120∆C biofilms did not show any observable growth in the presence of 3% butanol. Prolonged cultivation of 10 days led to biofilm adaptation, glucose and oxygen uptake doubled and consequently it was possible to quantify biomass. Complementing the medium with yeast extract and presumably reducing the metabolic burden caused by butanol exposure further increased the biomass yield. In course of cultivation cells reduced their size in the presence of n-butanol which results in an enlarged surface-to-volume ratio and thus increased nutrient uptake. Finally, biofilm enhanced its extracellular polymeric substances (EPS) production when exposed to n-butanol. The predominant response of these biofilms under n-butanol stress are higher energy demand, increased biomass yield upon medium complements, larger surface-to-volume ratio and enhanced EPS production. Although we observed a distinct increase in biomass in the presence of 3% butanol it was not possible to cultivate P. taiwanensis VLB120∆C biofilms at higher n-butanol concentrations. Thereby this study shows that biofilms are not per se tolerant against solvents, and need to adapt to toxic n-butanol concentrations.

  8. Effect of tannic and gallic acids alone or in combination with carbenicillin or tetracycline on Chromobacterium violaceum CV026 growth, motility, and biofilm formation.

    PubMed

    Dusane, Devendra H; O'May, Che; Tufenkji, Nathalie

    2015-07-01

    Chromobacterium violaceum is an opportunistic pathogen that causes infections that are difficult to treat. The goal of this research was to evaluate the effect of selected tannins (tannic acid (TA) and gallic acid (GA)) on bacterial growth, motility, antibiotic (carbenicillin, tetracycline) susceptibility, and biofilm formation. Both tannins, particularly TA, impaired bacterial growth levels and swimming motilities at sub-minimum inhibitory concentrations (sub-MICs). In combination with tannins, antibiotics showed increased MICs, suggesting that tannins interfered with antibacterial activity. Sub-MICs of tetracycline or TA alone enhanced biofilm formation of C. violaceum; however, in combination, these compounds inhibited biofilm formation. In contrast, carbenicillin at sub-MICs was effective in inhibiting C. violaceum biofilm formation; however, in combination with lower concentrations of TA or GA, biofilms were enhanced. These results provide insights into the effects of tannins on C. violaceum growth and their varying interaction with antibiotics used to target C. violaceum infections.

  9. 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

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

    PubMed

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

    2016-03-31

    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.

  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.

  12. Kinetic 15N-isotope effects on algal growth

    PubMed Central

    Andriukonis, Eivydas; Gorokhova, Elena

    2017-01-01

    Stable isotope labeling is a standard technique for tracing material transfer in molecular, ecological and biogeochemical studies. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism metabolism and growth, which is not consistent with current theoretical and empirical knowledge on kinetic isotope effects. Here, we demonstrate profound changes in growth dynamics of the green alga Raphidocelis subcapitata grown in 15N-enriched media. With increasing 15N concentration (0.37 to 50 at%), the lag phase increased, whereas maximal growth rate and total yield decreased; moreover, there was a negative relationship between the growth and the lag phase across the treatments. The latter suggests that a trade-off between growth rate and the ability to adapt to the high 15N environment may exist. Remarkably, the lag-phase response at 3.5 at% 15N was the shortest and deviated from the overall trend, thus providing partial support to the recently proposed Isotopic Resonance hypothesis, which predicts that certain isotopic composition is particularly favorable for living organisms. These findings confirm the occurrence of KIE in isotopically enriched algae and underline the importance of considering these effects when using stable isotope labeling in field and experimental studies. PMID:28281640

  13. Kinetic 15N-isotope effects on algal growth

    NASA Astrophysics Data System (ADS)

    Andriukonis, Eivydas; Gorokhova, Elena

    2017-03-01

    Stable isotope labeling is a standard technique for tracing material transfer in molecular, ecological and biogeochemical studies. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism metabolism and growth, which is not consistent with current theoretical and empirical knowledge on kinetic isotope effects. Here, we demonstrate profound changes in growth dynamics of the green alga Raphidocelis subcapitata grown in 15N-enriched media. With increasing 15N concentration (0.37 to 50 at%), the lag phase increased, whereas maximal growth rate and total yield decreased; moreover, there was a negative relationship between the growth and the lag phase across the treatments. The latter suggests that a trade-off between growth rate and the ability to adapt to the high 15N environment may exist. Remarkably, the lag-phase response at 3.5 at% 15N was the shortest and deviated from the overall trend, thus providing partial support to the recently proposed Isotopic Resonance hypothesis, which predicts that certain isotopic composition is particularly favorable for living organisms. These findings confirm the occurrence of KIE in isotopically enriched algae and underline the importance of considering these effects when using stable isotope labeling in field and experimental studies.

  14. Cigarette smoke condensate increases C. albicans adhesion, growth, biofilm formation, and EAP1, HWP1 and SAP2 gene expression

    PubMed Central

    2014-01-01

    Background Smokers are more prone to oral infections than are non-smokers. Cigarette smoke reaches the host cells but also microorganisms present in the oral cavity. The contact between cigarette smoke and oral bacteria promotes such oral diseases as periodontitis. Cigarette smoke can also modulate C. albicans activities that promote oral candidiasis. The goal of this study was to investigate the effect of cigarette smoke condensate on C. albicans adhesion, growth, and biofilm formation as well as the activation of EAP1, HWP1 and secreted aspartic protease 2. Results Cigarette smoke condensate (CSC) increased C. albicans adhesion and growth, as well as biofilm formation. These features may be supported by the activation of certain important genes. Using quantitative RT-PCR, we demonstrated that CSC-exposed C. albicans expressed high levels of EAP1, HWP1 and SAP2 mRNA and that this gene expression increased with increasing concentrations of CSC. Conclusion CSC induction of C. albicans adhesion, growth, and biofilm formation may explain the increased persistence of this pathogen in smokers. These findings may also be relevant to other biofilm-induced oral diseases. PMID:24618025

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

    SciTech Connect

    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 in 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.

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

    DOE PAGES

    Ou, Shiqi; Zhao, Yi; Aaron, Douglas S.; ...

    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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    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 in 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. 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.

  18. Immobilized growth of the peridinin-producing marine dinoflagellate Symbiodinium in a simple biofilm photobioreactor.

    PubMed

    Benstein, Ruben Maximilian; Cebi, Zehra; Podola, Björn; Melkonian, Michael

    2014-12-01

    Products from phototrophic dinoflagellates such as toxins or pigments are potentially important for applications in the biomedical sciences, especially in drug development. However, the technical cultivation of these organisms is often problematic due to their sensitivity to hydrodynamic (shear) stress that is a characteristic of suspension-based closed photobioreactors (PBRs). It is thus often thought that most species of dinoflagellates are non-cultivable at a technical scale. Recent advances in the development of biofilm PBRs that rely on immobilization of microalgae may hold potential to circumvent this major technical problem in dinoflagellate cultivation. In the present study, the dinoflagellate Symbiodinium voratum was grown immobilized on a Twin-Layer PBR for isolation of the carotenoid peridinin, an anti-cancerogenic compound. Biomass productivities ranged from 1.0 to 11.0 g m(-2) day(-1) dry matter per vertical growth surface and a maximal biomass yield of 114.5 g m(-2), depending on light intensity, supplementary CO2, and type of substrate (paper or polycarbonate membrane) used. Compared to a suspension culture, the performance of the Twin-Layer PBRs exhibited significantly higher growth rates and maximal biomass yield. In the Twin-Layer PBR a maximal peridinin productivity of 24 mg m(-2) day(-1) was determined at a light intensity of 74 μmol m(-2) s(-1), although the highest peridinin content per dry weight (1.7 % w/w) was attained at lower light intensities. The results demonstrate that a biofilm-based PBR that minimizes hydrodynamic shear forces is applicable to technical-scale cultivation of dinoflagellates and may foster biotechnological applications of these abundant marine protists.

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

    PubMed

    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.

  20. 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

  1. Steps in Cu(111) thin films affect graphene growth kinetics

    NASA Astrophysics Data System (ADS)

    Miller, David L.; Gannett, Will; Keller, Mark W.

    2014-03-01

    The kinetics of chemical vapor deposition of graphene on Cu substrates depend on the relative rates of C diffusion on the surface, C attachment to graphene islands, and removal of C from the surface or from graphene islands by etching processes involving H atoms. Using Cu(111) thin films with centimeter-sized grains, we have grown graphene under a variety of conditions and examined the edges of graphene islands with SEM and AFM. The Cu surface shows a series of regular steps, roughly 2 nm in height, and the graphene islands are diamond-shaped with faster growth along the edges of Cu steps. In contrast, growth on polycrystalline Cu foils under the same conditions shows hexagonal graphene islands with smooth edges.

  2. 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/.

  3. Kinetics of growth and sugar consumption in yeasts.

    PubMed

    van Dijken, J P; Weusthuis, R A; Pronk, J T

    1993-01-01

    An overview is presented of the steady- and transient state kinetics of growth and formation of metabolic byproducts in yeasts. Saccharomyces cerevisiae is strongly inclined to perform alcoholic fermentation. Even under fully aerobic conditions, ethanol is produced by this yeast when sugars are present in excess. This so-called 'Crabtree effect' probably results from a multiplicity of factors, including the mode of sugar transport and the regulation of enzyme activities involved in respiration and alcoholic fermentation. The Crabtree effect in S. cerevisiae is not caused by an intrinsic inability to adjust its respiratory activity to high glycolytic fluxes. Under certain cultivation conditions, for example during growth in the presence of weak organic acids, very high respiration rates can be achieved by this yeast. S. cerevisiae is an exceptional yeast since, in contrast to most other species that are able to perform alcoholic fermentation, it can grow under strictly anaerobic conditions. 'Non-Saccharomyces' yeasts require a growth-limiting supply of oxygen (i.e. oxygen-limited growth conditions) to trigger alcoholic fermentation. However, complete absence of oxygen results in cessation of growth and therefore, ultimately, of alcoholic fermentation. Since it is very difficult to reproducibly achieve the right oxygen dosage in large-scale fermentations, non-Saccharomyces yeasts are therefore not suitable for large-scale alcoholic fermentation of sugar-containing waste streams. In these yeasts, alcoholic fermentation is also dependent on the type of sugar. For example, the facultatively fermentative yeast Candida utilis does not ferment maltose, not even under oxygen-limited growth conditions, although this disaccharide supports rapid oxidative growth.

  4. 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.

  5. 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.

  6. Rethinking growth and decay kinetics in activated sludge - towards a new adaptive kinetics approach.

    PubMed

    Friedrich, Michael; Jimenez, Jose; Pruden, Amy; Miller, Jennifer H; Metch, Jacob; Takács, Imre

    2017-02-01

    Growth kinetics in activated sludge modelling (ASM) are typically assumed to be the result of intrinsic growth and decay properties and thus process parameters are deemed to be constant. The activity change in a microbial population is expressed in terms of variance of the active biomass fraction and not actual shifts in bacterial cellular activities. This approach is limited, in that it does not recognise the reality that active biomass is highly physiologically adaptive. Here, a strong correlation between maximum specific growth rate (μmax) and decay rate (be) of ordinary heterotrophic organisms was revealed in both low solids retention times (SRT) and high SRT activated sludge systems. This relationship is indicative of physiological adaptation either for growth (high μmax and be) or survival optimization (low μmax and be). Further, the nitrifier decay process was investigated using molecular techniques to measure decay rates of ammonia oxidizing bacteria and nitrite oxidizing bacteria over a range of temperatures. This approach revealed decay rates 10-12% lower than values previously accepted and used in ASM. These findings highlight potential benefits of incorporating physiological adaptation of heterotrophic and nitrifying populations in future ASM.

  7. Kinetics of droplet growth observed in recent field campaigns

    NASA Astrophysics Data System (ADS)

    Mei, F.; Wang, J.

    2012-12-01

    Atmospheric aerosols can indirectly influence global climate budget by changing the microphysical structure, lifetime, and coverage of clouds. While it is generally agreed that aerosol indirect effects act to cool the Earth-atmosphere system by increasing cloud reflectivity and coverage, the magnitudes of the indirect effects are poorly understood. The formation of cloud droplets from aerosol particles is kinetically controlled by the availability of water vapor, equilibrium water vapor pressure above the growing droplet surface, and both the gas phase and aerosol phase mass transfer resistances. It has been hypothesized that the formation of surface organic films or the delay in dissolution of solute could significantly delay the growth of cloud droplets. Such delay could lead to a higher maximum supersaturation within a rising cloud parcel, therefore higher droplet number concentration and smaller droplet size at constant liquid water content. When only a subset of the droplets experiences significant growth delay, the overall droplet size spectrum will be broadened, which facilitates the formation of precipitation. During three recent field campaigns (CalNex-LA, CARES, and Aerosol Intensive Observation Period at Brookhaven National Laboratory), the CCN activity and droplet growth of size selected particles ranging from 25 to 320 nm were characterized by a CCN counter under supersaturations from 0.1% to 0.8%. The three campaigns allow us to examine the droplet growth for many representative organic aerosol types, including biogenic SOA, anthropogenic SOA, and organic aerosols from biomass burning. The droplet growth of size-selected ambient particles inside the CCN counter was found to be influenced by a number of parameters, including particle critical supersaturation, heterogeneity in particle composition, and particle concentration. For example, reduced droplet growth due to water vapor depletion was observed when particle concentration was higher than 200 cm

  8. Growth Kinetics and Morphology of Barite Crystals Derived from Face-Specific Growth Rates

    DOE PAGES

    Godinho, Jose R. A.; Stack, Andrew G.

    2015-03-30

    Here we investigate the growth kinetics and morphology of barite (BaSO4) crystals by measuring the growth rates of the (001), (210), (010), and (100) surfaces using vertical scanning interferometry. Solutions with saturation indices 1.1, 2.1, and 3.0 without additional electrolyte, in 0.7 M NaCl, or in 1.3 mM SrCl2 are investigated. Face-specific growth rates are inhibited in the SrCl2 solution relative to a solution without electrolyte, except for (100). Contrarily, growth of all faces is promoted in the NaCl solution. The variation of face-specific rates is solution-specific, which leads to a. change of the crystal morphology and overall growth ratemore » of crystals. The measured face-specific growth rates are used to model the growth of single crystals. Modeled crystals have a morphology and size similar to those grown from solution. Based on the model the time dependence of surface area and growth rates is analyzed. Growth rates change with time due to surface area normalization for small crystals and large growth intervals. By extrapolating rates to crystals with large surfaces areas, time-independent growth rates are 0.783, 2.96, and 0.513 mmol∙m-2∙h-1, for saturation index 2.1 solutions without additional electrolyte, NaCl, and SrCl2, respectively.« less

  9. Growth Kinetics and Morphology of Barite Crystals Derived from Face-Specific Growth Rates

    SciTech Connect

    Godinho, Jose R. A.; Stack, Andrew G.

    2015-03-30

    Here we investigate the growth kinetics and morphology of barite (BaSO4) crystals by measuring the growth rates of the (001), (210), (010), and (100) surfaces using vertical scanning interferometry. Solutions with saturation indices 1.1, 2.1, and 3.0 without additional electrolyte, in 0.7 M NaCl, or in 1.3 mM SrCl2 are investigated. Face-specific growth rates are inhibited in the SrCl2 solution relative to a solution without electrolyte, except for (100). Contrarily, growth of all faces is promoted in the NaCl solution. The variation of face-specific rates is solution-specific, which leads to a. change of the crystal morphology and overall growth rate of crystals. The measured face-specific growth rates are used to model the growth of single crystals. Modeled crystals have a morphology and size similar to those grown from solution. Based on the model the time dependence of surface area and growth rates is analyzed. Growth rates change with time due to surface area normalization for small crystals and large growth intervals. By extrapolating rates to crystals with large surfaces areas, time-independent growth rates are 0.783, 2.96, and 0.513 mmol∙m-2∙h-1, for saturation index 2.1 solutions without additional electrolyte, NaCl, and SrCl2, respectively.

  10. Biofilm growth in gravel bed streams controls solute residence time distributions

    NASA Astrophysics Data System (ADS)

    Aubeneau, A. F.; Hanrahan, Brittany; Bolster, Diogo; Tank, Jennifer

    2016-07-01

    Streambed substrates harbor a rich biome responsible for biogeochemical processing in riverine waters. Beyond their biological role, the presence of benthic and hyporheic biofilms can play an important role in influencing large-scale transport of solutes, even for conservative tracers. As biofilms grow and accumulate biomass, they actively interact with and influence surface and subsurface flow patterns. To explore this effect, we conducted experiments at the Notre Dame Linked Ecosystems Experimental Facility in four outdoor streams, each with different gravel beds. Over the course of 20 weeks we conducted transport experiments in each of these streams and observed different patterns in breakthrough curves as biofilms grew on the substrate. Biofilms played a major role in shaping the observed conservative transport patterns. Overall, while the presence of biofilms led to a decreased exchange rate between the fast (mobile) and slow (immobile) parts of the flow domain, water that was exchanged tended to be stored in the slow regions for longer times once biofilms had established. More specifically, we observed enhanced longitudinal dispersion in breakthrough curves as well as broader residence time distributions when biofilms were present. Biofilm colonization over time homogenized transport patterns across the four streams that were originally very distinct. These results indicate that stream biofilms exert a strong control on conservative solute transport in streams, a role that to date has not received enough attention.

  11. Growth, viability and architecture of biofilms of Listeria monocytogenes formed on abiotic surfaces.

    PubMed

    Reis-Teixeira, Fernanda Barbosa Dos; Alves, Virgínia Farias; de Martinis, Elaine Cristina Pereira

    2017-02-09

    The pathogenic bacterium Listeria monocytogenes can persist in food processing plants for many years, even when appropriate hygienic measures are in place, with potential for contaminating ready-to-eat products and, its ability to form biofilms on abiotic surfaces certainly contributes for the environmental persistence. In this research, L. monocytogenes was grown in biofilms up 8 days attached to stainless steel and glass surfaces, contributing for advancing the knowledge on architecture of mature biofilms, since many literature studies carried out on this topic considered only early stages of cell adhesion. In this study, biofilm populations of two strains of L. monocytogenes (serotypes 1/2a and 4b) on stainless steel coupons and glass were examined using regular fluorescence microscopy, confocal laser scanning microscopy and classic culture method. The biofilms formed were not very dense and microscopic observations revealed uneven biofilm structures, with presence of exopolymeric matrix surrounding single cells, small aggregates and microcolonies, in a honeycomb-like arrangement. Moreover, planktonic population of L. monocytogenes (present in broth media covering the abiotic surface) remained stable throughout the incubation time, which indicates an efficient dispersal mechanism, since the culture medium was replaced daily. In conclusion, even if these strains of L. monocytogenes were not able to form thick multilayer biofilms, it was noticeable their high persistence on abiotic surfaces, reinforcing the need to focus on measures to avoid biofilm formation, instead of trying to eradicate mature biofilms.

  12. Kinetics of faceting of crystals in growth, etching, and equilibrium

    NASA Astrophysics Data System (ADS)

    Vlachos, D. G.; Schmidt, L. D.; Aris, R.

    1993-03-01

    The faceting of crystals in equilibrium with the gas phase and also during crystal growth and etching conditions is studied using the Monte Carlo method. The dynamics of the transformation of unstable crystallographic orientations into hill and valley structures and the spatial patterns that develop are examined as functions of surface temperature, crystallographic orientation, and strength of interatomic potential for two transport processes: adsorption-desorption and surface diffusion. The results are compared with the continuum theory for facet formation. Thermodynamically unstable orientations break into hill and valley structures, and faceting exhibits three time regimes: disordering, facet nucleation, and coarsening of small facets to large facets. Faceting is accelerated as temperature increases, but thermal roughening can occur at high temperatures. Surface diffusion is the dominant mechanism at short times and small facets but adsorption-desorption becomes important at long times and large facets. Growth and etching promote faceting for conditions close to equilibrium but induce kinetic roughening for conditions far from equilibrium. Simultaneous irreversible growth and etching conditions with fast surface diffusion result in enhanced faceting.

  13. 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.

  14. Development and validation of a chemostat gut model to study both planktonic and biofilm modes of growth of Clostridium difficile and human microbiota.

    PubMed

    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.

  15. 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

  16. Biofilm growth and near-infrared radiation-driven photosynthesis of the chlorophyll d-containing cyanobacterium Acaryochloris marina.

    PubMed

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

    2012-06-01

    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 O(2) 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 E(k) (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 O(2) mg Chl d(-1) h(-1) (NIR) and ∼1,128 μmol O(2) mg Chl d(-1) h(-1) (VIS). The photosynthetic efficiency (α) values were higher in NIR-irradiated cells [(268 ± 0.29) × 10(-6) m(2) mg Chl d(-1) (mean ± standard deviation)] than under blue light [(231 ± 0.22) × 10(-6) m(2) mg Chl d(-1)]. A. marina is well adapted to a biofilm growth mode under both visible and NIR irradiance and under O(2) conditions ranging from anoxia to hyperoxia, explaining its presence in natural niches with similar environmental conditions.

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

    PubMed

    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.

  18. Iron oxide nanoparticles induce Pseudomonas aeruginosa growth, induce biofilm formation, and inhibit antimicrobial peptide function†

    PubMed Central

    Borcherding, Jennifer; Baltrusaitis, Jonas; Chen, Haihan; Stebounova, Larissa; Wu, Chia-Ming; Rubasinghege, Gayan; Mudunkotuwa, Imali A.; Caraballo, Juan Carlos; Zabner, Joseph

    2014-01-01

    Given the increased use of iron-containing nanoparticles in a number of applications, it is important to understand any effects that iron-containing nanoparticles can have on the environment and human health. Since iron concentrations are extremely low in body fluids, there is potential that iron-containing nanoparticles may influence the ability of bacteria to scavenge iron for growth, affect virulence and inhibit antimicrobial peptide (AMP) function. In this study, Pseudomonas aeruginosa (PA01) and AMPs were exposed to iron oxide nanoparticles, hematite (α-Fe2O3), of different sizes ranging from 2 to 540 nm (2 ± 1, 43 ± 6, 85 ± 25 and 540 ± 90 nm) in diameter. Here we show that the greatest effect on bacterial growth, biofilm formation, and AMP function impairment is found when exposed to the smallest particles. These results are attributed in large part to enhanced dissolution observed for the smallest particles and an increase in the amount of bioavailable iron. Furthermore, AMP function can be additionally impaired by adsorption onto nanoparticle surfaces. In particular, lysozyme readily adsorbs onto the nanoparticle surface which can lead to loss of peptide activity. Thus, this current study shows that co-exposure of nanoparticles and known pathogens can impact host innate immunity. Therefore, it is important that future studies be designed to further understand these types of impacts. PMID:25221673

  19. 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

  20. 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

  1. Kinetic transition during the growth of proeutectoid ferrite in Fe-C-Mn-Si quaternary steel

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Hong; Heo, Yoon-Uk; Song, Eun-Ju; Suh, Dong-Woo

    2013-03-01

    The kinetics of ferrite growth in Fe-0.1C-1.5Mn-0.94Si (mass pct) quaternary steel is investigated through the characterization of isothermal growth behavior, the thermodynamic prediction of kinetic boundary and the diffusional growth simulations using DICTRA. The change in microstructural evolution from slow growth to fast one is consistent with the calculated change of interface condition from the partitioning local equilibrium (PLE) to the negligible partitioning local equilibrium (NPLE). Compared with the DICTRA simulation, the observed growth kinetics of ferrite are between the calculated ones assuming local equilibrium (LE) and paraequilibrium (PE) criterions. At temperatures below the PLE/NPLE kinetic boundary, the observed growth behavior can be reasonably described by kinetic transition from PE to NPLE condition as isothermal time elapses, taking into account the critical velocity of interface at which trans-interface diffusion of subsitutional element permits the transition from PE to NPLE growth.

  2. 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

  3. 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

  4. Secreted Proteases Control Autolysin-mediated Biofilm Growth of Staphylococcus aureus*

    PubMed Central

    Chen, Chen; Krishnan, Vengadesan; Macon, Kevin; Manne, Kartik; Narayana, Sthanam V. L.; Schneewind, Olaf

    2013-01-01

    Staphylococcus epidermidis, a commensal of humans, secretes Esp protease to prevent Staphylococcus aureus biofilm formation and colonization. Blocking S. aureus colonization may reduce the incidence of invasive infectious diseases; however, the mechanism whereby Esp disrupts biofilms is unknown. We show here that Esp cleaves autolysin (Atl)-derived murein hydrolases and prevents staphylococcal release of DNA, which serves as extracellular matrix in biofilms. The three-dimensional structure of Esp was revealed by x-ray crystallography and shown to be highly similar to that of S. aureus V8 (SspA). Both atl and sspA are necessary for biofilm formation, and purified SspA cleaves Atl-derived murein hydrolases. Thus, S. aureus biofilms are formed via the controlled secretion and proteolysis of autolysin, and this developmental program appears to be perturbed by the Esp protease of S. epidermidis. PMID:23970550

  5. Exact solutions of kinetic equations in an autocatalytic growth model.

    PubMed

    Jędrak, Jakub

    2013-02-01

    Kinetic equations are introduced for the transition-metal nanocluster nucleation and growth mechanism, as proposed by Watzky and Finke [J. Am. Chem. Soc. 119, 10382 (1997)]. Equations of this type take the form of Smoluchowski coagulation equations supplemented with the terms responsible for the chemical reactions. In the absence of coagulation, we find complete analytical solutions of the model equations for the autocatalytic rate constant both proportional to the cluster mass, and the mass-independent one. In the former case, ξ(k)=s(k)(ξ(1))[proportionality]ξ(1)(k)/k was obtained, while in the latter, the functional form of s(k)(ξ(1)) is more complicated. In both cases, ξ(1)(t)=h(μ)(M(μ)(t)) is a function of the moments of the mass distribution. Both functions, s(k)(ξ(1)) and h(μ)(M(μ)), depend on the assumed mechanism of autocatalytic growth and monomer production, and not on other chemical reactions present in a system.

  6. Pattern formation and growth kinetics in eutectic systems

    NASA Astrophysics Data System (ADS)

    Teng, Jing

    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 rod, 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

  7. 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

  8. 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.

  9. 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.

  10. Interactive effect of trivalent iron on activated sludge digestion and biofilm structure in attached growth reactor of waste tire rubber.

    PubMed

    Sharafat, Iqra; Saeed, Dania Khalid; Yasmin, Sumera; Imran, Asma; Zafar, Zargona; Hameed, Abdul; Ali, Naeem

    2017-03-16

    Waste tire rubber (WTR) has been introduced as an alternative, novel media for biofilm development in several experimental systems including attached growth bioreactors. In this context, four laboratory-scale static batch bioreactors containing WTR as a support material for biofilm development were run under anoxic condition for 90 days using waste activated sludge as an inoculum under the influence of different concentrations (2.5, 6.5, 8.5 mg/l) of trivalent ferric iron (Fe(3+)). The data revealed that activated sludge with a Fe(3+) concentration of 8.5 mg/l supported the maximum bacterial biomass [4.73E + 10 CFU/ml cm(2)]; besides, it removed 38% more Chemical oxygen demand compared to Fe(3+) free condition from the reactor. Biochemical testing and 16S rDNA phylogenetic analysis of WTR-derived biofilm communities further suggested the role of varying concentrations of Fe(3+) on the density and diversity of members of Enterobacteria(ceae), ammonium (AOB) and nitrite oxidizing bacteria. Furthermore, Fluorescent in situ hybridization with phylogenetic oligonucleotide probes and confocal laser scanning microscopy of WTR biofilms indicated a significant increase in density of eubacteria (3.00E + 01 to.05E + 02 cells/cm(2)) and beta proteobacteria (8.10E + 01 to 1.42E + 02 cells/cm(2)), respectively, with an increase in Fe(3+) concentration in the reactors, whereas, the cell density of gamma proteobacteria in biofilms decreased.

  11. From Mouth to Model: Combining in vivo and in vitro Oral Biofilm Growth

    PubMed Central

    Klug, Barbara; Santigli, Elisabeth; Westendorf, Christian; Tangl, Stefan; Wimmer, Gernot; Grube, Martin

    2016-01-01

    Background: Oral biofilm studies based on simplified experimental setups are difficult to interpret. Models are limited mostly by the number of bacterial species observed and the insufficiency of artificial media. Few studies have attempted to overcome these limitations and to cultivate native oral biofilm. Aims: This study aimed to grow oral biofilm in vivo before transfer to a biofilm reactor for ex situ incubation. The in vitro survival of this oral biofilm and the changes in bacterial composition over time were observed. Methods: Six human enamel-dentin slabs embedded buccally in dental splints were used as biofilm carriers. Fitted individually to the upper jaw of 25 non-smoking male volunteers, the splints were worn continuously for 48 h. During this time, tooth-brushing and alcohol-consumption were not permitted. The biofilm was then transferred on slabs into a biofilm reactor and incubated there for 48 h while being nourished in BHI medium. Live/dead staining and confocal laser scanning microscopy were used to observe bacterial survival over four points in time: directly after removal (T0) and after 1 (T1), 24 (T2), and 48 h (T3) of incubation. Bacterial diversity at T0 and T3 was compared with 454-pyrosequencing. Fluorescence in situ hybridization (FISH) was performed to show specific taxa. Survival curves were calculated with a specially designed MATLAB script. Acacia and QIIME 1.9.1 were used to process pyrosequencing data. SPSS 21.0 and R 3.3.1 were used for statistical analysis. Results: After initial fluctuations at T1, survival curves mostly showed approximation of the bacterial numbers to the initial level at T3. Pyrosequencing analysis resulted in 117 OTUs common to all samples. The genera Streptococcus and Veillonella (both Firmicutes) dominated at T0 and T3. They make up two thirds of the biofilm. Genera with lower relative abundance had grown significantly at T3. FISH analysis confirmed the pyrosequencing results, i.e., the predominant staining

  12. From Mouth to Model: Combining in vivo and in vitro Oral Biofilm Growth.

    PubMed

    Klug, Barbara; Santigli, Elisabeth; Westendorf, Christian; Tangl, Stefan; Wimmer, Gernot; Grube, Martin

    2016-01-01

    Background: Oral biofilm studies based on simplified experimental setups are difficult to interpret. Models are limited mostly by the number of bacterial species observed and the insufficiency of artificial media. Few studies have attempted to overcome these limitations and to cultivate native oral biofilm. Aims: This study aimed to grow oral biofilm in vivo before transfer to a biofilm reactor for ex situ incubation. The in vitro survival of this oral biofilm and the changes in bacterial composition over time were observed. Methods: Six human enamel-dentin slabs embedded buccally in dental splints were used as biofilm carriers. Fitted individually to the upper jaw of 25 non-smoking male volunteers, the splints were worn continuously for 48 h. During this time, tooth-brushing and alcohol-consumption were not permitted. The biofilm was then transferred on slabs into a biofilm reactor and incubated there for 48 h while being nourished in BHI medium. Live/dead staining and confocal laser scanning microscopy were used to observe bacterial survival over four points in time: directly after removal (T0) and after 1 (T1), 24 (T2), and 48 h (T3) of incubation. Bacterial diversity at T0 and T3 was compared with 454-pyrosequencing. Fluorescence in situ hybridization (FISH) was performed to show specific taxa. Survival curves were calculated with a specially designed MATLAB script. Acacia and QIIME 1.9.1 were used to process pyrosequencing data. SPSS 21.0 and R 3.3.1 were used for statistical analysis. Results: After initial fluctuations at T1, survival curves mostly showed approximation of the bacterial numbers to the initial level at T3. Pyrosequencing analysis resulted in 117 OTUs common to all samples. The genera Streptococcus and Veillonella (both Firmicutes) dominated at T0 and T3. They make up two thirds of the biofilm. Genera with lower relative abundance had grown significantly at T3. FISH analysis confirmed the pyrosequencing results, i.e., the predominant staining

  13. Effect of growth conditions and substratum composition on the persistence of coliforms in mixed-population biofilms.

    PubMed Central

    Camper, A K; Jones, W L; Hayes, J T

    1996-01-01

    Laboratory reactors operated under oligotrophic conditions were used to evaluate the importance of initial growth rate and substratum composition on the long-term persistence of coliforms in mixed-population biofilms. The inoculum growth rate had a dramatic effect on the ability of coliforms to remain on surfaces. The most slowly grown coliforms (mu = 0.05/h) survived at the highest cell concentration. Antibody staining revealed that Klebsiella pneumoniae existed primarily as discrete microcolonies on the surface. Both coliforms and heterotrophic plate count bacteria were supported in larger numbers on a reactive substratum, mild steel, than on polycarbonate. PMID:8899991

  14. Enhancing plant productivity while suppressing biofilm growth in a windowfarm system using beneficial bacteria and ultraviolet irradiation.

    PubMed

    Lee, Seungjun; Ge, Chongtao; Bohrerova, Zuzana; Grewal, Parwinder S; Lee, Jiyoung

    2015-07-01

    Common problems in a windowfarm system (a vertical and indoor hydroponic system) are phytopathogen infections in plants and excessive buildup of biofilms. The objectives of this study were (i) to promote plant health by making plants more resistant to infection by using beneficial biosurfactant-producing Pseudomonas chlororaphis around the roots and (ii) to minimize biofilm buildup by ultraviolet (UV) irradiation of the water reservoir, thereby extending the lifespan of the whole system with minimal maintenance. Pseudomonas chlororaphis-treated lettuce grew significantly better than nontreated lettuce, as indicated by enhancement of color, mass, length, and number of leaves per head (p < 0.05). The death rate of the lettuce was reduced by ∼ 50% when the lettuce was treated with P. chlororaphis. UV irradiation reduced the bacteria (4 log reduction) and algae (4 log reduction) in the water reservoirs and water tubing systems. Introduction of P. chlororaphis into the system promoted plant growth and reduced damage caused by the plant pathogen Pythium ultimum. UV irradiation of the water reservoir reduced algal and biofilm growth and extended the lifespan of the system.

  15. 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.

  16. 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

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

    PubMed

    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.

  18. 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

  19. Effect of the antimicrobial peptide D-Nal-Pac-525 on the growth of Streptococcus mutans and its biofilm formation.

    PubMed

    Li, Huajun; Cheng, Jya-Wei; Yu, Hui-Yuan; Xin, Yi; Tang, Li; Ma, Yufang

    2013-08-01

    Streptococcus mutans is the primary etiological agent of dental caries. The antimicrobial peptide D-Nal-Pac-525 was designed by replacing the tryptophans of the Trp-rich peptide Pac-525 with D-β-naphthyalanines. To assess the effect of D-Nal-Pac-525 on cariogenic bacteria, the activity of D-Nal-Pac-525 on the growth of S. mutans and its biofilm formation were examined. D-Nal- Pac-525 showed robust antimicrobial activity against S. mutans (minimum inhibitory concentration of 4 μg/ml). Using scanning electron microscopy and transmission electron microscopy, it was shown that D-Nal-Pac-525 caused morphological changes and damaged the cell membrane of S. mutans. D-Nal-Pac-525 inhibited biofilm formation of S. mutans at 2 μg/ml. The results of this study suggest that D-Nal-Pac-525 has great potential for clinical application as a dental caries-preventing agent.

  20. Effect of cobalt enrichment on growth and hydrocarbon accumulation of Botryococcus braunii with immobilized biofilm attached cultivation.

    PubMed

    Cheng, Pengfei; Wang, Junfeng; Liu, Tianzhong

    2015-02-01

    The effects of cobalt enrichment on the growth and hydrocarbon accumulation were studied with biofilm attached cultivation. Under biofilm attached cultivation conditions, the microalga Botryococcus braunii survived high concentration of cobalt (50× normal level). The crude hydrocarbon content as well as the long C chain component (C31) increased under Co enrichment treatment indicating the activity of key enzyme that catalyze hydrocarbon synthesis might be enhanced by Co enrichment. The reduced carbohydrate and protein contents accompanied by increased hydrocarbon content for Co enrichment treatment indicating the Co was also an effective factor that controls the carbon flow of B. braunii. Under Co enrichment treatment, totally 1473.9 μmol of Co element was consumed to produce one gram of algal biomass, indicating this attached cultivation method is high efficient in heavy metal elements removal.

  1. 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.

  2. Growth kinetics and inhibition of growth of chemical vapor deposited thin tungsten films on silicon from tungsten hexafluoride

    NASA Astrophysics Data System (ADS)

    Leusink, G. J.; Kleijn, C. R.; Oosterlaken, T. G. M.; Janssen, G. C. A. M.; Radelaar, S.

    1992-07-01

    The growth kinetics and inhibition of growth of chemical vapor deposited thin W films on Si(100) from WF6 was studied with in situ growth stress and reflectivity measurements and ex situ weight gain measurements. A systematic series of experiments at varying WF6 flow, total pressure, and temperature show that the thickening kinetics and inhibition of the growth are controlled by two processes: WF6 diffusion through the gas phase and Si diffusion through the thickening columnar film. The steady state growth kinetics are controlled by WF6 diffusion in the gas phase whereas inhibition of the growth occurs at the transition from WF6 gas diffusion limited to Si solid state diffusion limited growth. A simple model based on WF6 gas phase diffusion and Si solid state diffusion is presented which gives a quantitative description of the experimental results.

  3. Regulated expression of polysaccharide utilization and capsular biosynthesis loci in biofilm and planktonic Bacteroides thetaiotaomicron during growth in chemostats

    PubMed Central

    TerAvest, Michaela A.; He, Zhen; Rosenbaum, Miriam A.; Martens, Eric C.; Cotta, Michael A.; Gordon, Jeffrey I.; Angenent, Largus T.

    2014-01-01

    Bacteroides thetaiotaomicron is a prominent member of the human distal gut microbiota that specializes in breaking down diet and host-derived polysaccharides. While polysaccharide utilization has been well studied in B. thetaiotaomicron, other aspects of its behavior are less well characterized, including the factors that allow it to maintain itself in the gut. Biofilm formation may be a mechanism for bacterial retention in the gut. Therefore, we used custom GeneChips to compare the transcriptomes of biofilm and planktonic B. thetaiotaomicron during growth in mono-colonized chemostats. We identified 1154 genes with a fold-change greater than 2, with confidence greater than or equal to 95%. Among the prominent changes observed in biofilm populations were: (i) greater expression of genes in polysaccharide utilization loci that are involved in foraging of O-glycans normally found in the gut mucosa; and (ii) regulated expression of capsular polysaccharide biosynthesis loci. Hierarchical clustering of the data with different datasets, which were obtained during growth under a range of conditions in minimal media and in intestinal tracts of gnotobiotic mice, revealed that within this group of differentially expressed genes, biofilm communities were more similar to the in vivo samples than to planktonic cells and exhibited features of substrate limitation. The current study also validates the use of chemostats as an in vitro ‘gnotobiotic’ model to study gene expression of attached populations of this bacterium. This is important to gut microbiota research, because bacterial attachment and the consequences of disruptions in attachment are difficult to study in vivo. PMID:23996813

  4. Major components of orange oil inhibit Staphylococcus aureus growth and biofilm formation, and alter its virulence factors.

    PubMed

    Federman, Cassandra; Ma, Christopher; Biswas, Debabrata

    2016-07-01

    Bovine mastitis is a costly disease in the dairy industry and does not always respond to antibiotic treatment. The major components of terpeneless, cold-pressed Valencia orange oil - citral, linalool, decanal and valencene - were examined as potential alternative treatments for Staphylococcus aureus-associated mastitis. The minimum inhibitory concentration (MIC) of all four components against S. aureus was determined after incubation for 24 h. Growth inhibition assays were performed for all effective components on S. aureus for either a 3 h or 72 h treatment. These components were tested for the ability to disrupt pre-formed S. aureus biofilms after 24 h of treatment by measuring absorbance at 540 nm. Cytotoxicity against immortalized bovine mammary epithelial (MAC-T) cells was measured using an MTT assay following a 1 h exposure. Only concentrations below the 50 % cytostatic concentration (CC50) were used in an adherence and invasion assay of S. aureus on MAC-T cells, and for measurements of virulence and biofilm gene expression via qPCR. The MICs of citral and linalool were 0.02 % and 0.12 %, respectively, but decanal and valencene were ineffective. Citral and linalool were capable of inhibiting growth of S. aureus after 24 h at their MIC values and inhibited pre-formed biofilms of S. aureus . The concentrations below the CC50 were 0.02 % for citral and 0.12 % for linalool. These concentrations inhibited the adhesion and invasion ability of S. aureus and downregulated virulence genes. Only 0.12 % linalool downregulated the expression of S. aureus biofilm-forming genes. These components should be considered for further in vivo study.

  5. Respiratory syncytial virus infection enhances Pseudomonas aeruginosa biofilm growth through dysregulation of nutritional immunity

    PubMed Central

    Hendricks, Matthew R.; Lashua, Lauren P.; Fischer, Douglas K.; Flitter, Becca A.; Eichinger, Katherine M.; Durbin, Joan E.; Sarkar, Saumendra N.; Coyne, Carolyn B.; Empey, Kerry M.; Bomberger, Jennifer M.

    2016-01-01

    Clinical observations link respiratory virus infection and Pseudomonas aeruginosa colonization in chronic lung disease, including cystic fibrosis (CF) and chronic obstructive pulmonary disease. The development of P. aeruginosa into highly antibiotic-resistant biofilm communities promotes airway colonization and accounts for disease progression in patients. Although clinical studies show a strong correlation between CF patients’ acquisition of chronic P. aeruginosa infections and respiratory virus infection, little is known about the mechanism by which chronic P. aeruginosa infections are initiated in the host. Using a coculture model to study the formation of bacterial biofilm formation associated with the airway epithelium, we show that respiratory viral infections and the induction of antiviral interferons promote robust secondary P. aeruginosa biofilm formation. We report that the induction of antiviral IFN signaling in response to respiratory syncytial virus (RSV) infection induces bacterial biofilm formation through a mechanism of dysregulated iron homeostasis of the airway epithelium. Moreover, increased apical release of the host iron-binding protein transferrin during RSV infection promotes P. aeruginosa biofilm development in vitro and in vivo. Thus, nutritional immunity pathways that are disrupted during respiratory viral infection create an environment that favors secondary bacterial infection and may provide previously unidentified targets to combat bacterial biofilm formation. PMID:26729873

  6. Respiratory syncytial virus infection enhances Pseudomonas aeruginosa biofilm growth through dysregulation of nutritional immunity.

    PubMed

    Hendricks, Matthew R; Lashua, Lauren P; Fischer, Douglas K; Flitter, Becca A; Eichinger, Katherine M; Durbin, Joan E; Sarkar, Saumendra N; Coyne, Carolyn B; Empey, Kerry M; Bomberger, Jennifer M

    2016-02-09

    Clinical observations link respiratory virus infection and Pseudomonas aeruginosa colonization in chronic lung disease, including cystic fibrosis (CF) and chronic obstructive pulmonary disease. The development of P. aeruginosa into highly antibiotic-resistant biofilm communities promotes airway colonization and accounts for disease progression in patients. Although clinical studies show a strong correlation between CF patients' acquisition of chronic P. aeruginosa infections and respiratory virus infection, little is known about the mechanism by which chronic P. aeruginosa infections are initiated in the host. Using a coculture model to study the formation of bacterial biofilm formation associated with the airway epithelium, we show that respiratory viral infections and the induction of antiviral interferons promote robust secondary P. aeruginosa biofilm formation. We report that the induction of antiviral IFN signaling in response to respiratory syncytial virus (RSV) infection induces bacterial biofilm formation through a mechanism of dysregulated iron homeostasis of the airway epithelium. Moreover, increased apical release of the host iron-binding protein transferrin during RSV infection promotes P. aeruginosa biofilm development in vitro and in vivo. Thus, nutritional immunity pathways that are disrupted during respiratory viral infection create an environment that favors secondary bacterial infection and may provide previously unidentified targets to combat bacterial biofilm formation.

  7. Effect of Bacoside A on growth and biofilm formation by Staphylococcus aureus and Pseudomonas aeruginosa.

    PubMed

    Parai, Debaprasad; Islam, Ekramul; Mitra, Jayati; Mukherjee, Samir Kumar

    2017-02-01

    The goal of this study was to evaluate the antibiofilm and antimicrobial activities of Bacoside A, a formulation of phytochemicals from Bacopa monnieri, against Staphylococcus aureus and Pseudomonas aeruginosa, which are known to form biofilms as one of their virulence traits. The antimicrobial effects of Bacoside A were tested using the minimum inhibitory concentration and minimum bactericidal concentration assays. A cell membrane disruption assay was performed to find its possible target site. MTT assay, crystal violet assay, and microscopic studies were performed to assess the antibiofilm activity. Bacoside A showed antimicrobial activity against both test organisms in their planktonic and biofilm states. At a subminimum inhibitory concentration of 200 μg·mL(-1), Bacoside A significantly removed ∼88%-93% of bacterial biofilm developed on microtiter plates. Biochemical and microscopic studies suggested that the eradication of biofilm might be due to the loss of extracellular polymeric substances and to a change in cell membrane integrity of the selected bacterial strains treated with Bacoside A. These results indicate that Bacoside A might be considered as an antimicrobial having the ability to disrupt biofilms. Thus, either alone or in combination with other therapeutics, Bacoside A could be useful to treat biofilm-related infections caused by opportunistic bacterial pathogens.

  8. Nucleation kinetics and crystal growth with fluctuating rates at the intermediate stage of phase transitions

    NASA Astrophysics Data System (ADS)

    Alexandrov, D. V.; Malygin, A. P.

    2014-01-01

    Crystal growth kinetics accompanied by particle growth with fluctuating rates at the intermediate stage of phase transitions is analyzed theoretically. The integro-differential model of governing equations is solved analytically for size-independent growth rates and arbitrary dependences of the nucleation frequency on supercooling/supersaturation. Two important cases of Weber-Volmer-Frenkel-Zel'dovich and Mier nucleation kinetics are detailed. A Fokker-Plank type equation for the crystal-size density distribution function is solved explicitly.

  9. Development of Mesorhizobium ciceri-Based Biofilms and Analyses of Their Antifungal and Plant Growth Promoting Activity in Chickpea Challenged by Fusarium Wilt.

    PubMed

    Das, Krishnashis; Rajawat, Mahendra Vikram Singh; Saxena, Anil Kumar; Prasanna, Radha

    2017-03-01

    Biofilmed biofertilizers have emerged as a new improved inoculant technology to provide efficient nutrient and pest management and sustain soil fertility. In this investigation, development of a Trichoderma viride-Mesorhizobium ciceri biofilmed inoculant was undertaken, which we hypothesized, would possess more effective biological nitrogen fixing ability and plant growth promoting properties. As a novel attempt, we selected Mesorhizobium ciceri spp. with good antifungal attributes with the assumption that such inoculants could also serve as biocontrol agents. These biofilms exhibited significant enhancement in several plant growth promoting attributes, including 13-21 % increase in seed germination, production of ammonia, IAA and more than onefold to twofold enhancement in phosphate solubilisation, when compared to their individual partners. Enhancement of 10-11 % in antifungal activity against Fusarium oxysporum f. sp. ciceri was also recorded, over the respective M. ciceri counterparts. The effect of biofilms and the M. ciceri cultures individual on growth parameters of chickpea under pathogen challenged soil illustrated that the biofilms performed at par with the M. ciceri strains for most plant biometrical and disease related attributes. Elicitation of defense related enzymes like l-phenylalanine ammonia lyase, peroxidase and polyphenol oxidase was higher in M. ciceri/biofilm treated plants as compared to uninoculated plants under pathogen challenged soil. Further work on the signalling mechanisms among the partners and their tripartite interactions with host plant is envisaged in future studies.

  10. 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.

  11. Pharmaceuticals suppress algal growth and microbial respiration and alter bacterial communities in stream biofilms.

    PubMed

    Rosi-Marshall, Emma J; Kincaid, Dustin W; Bechtold, Heather A; Royer, Todd V; Rojas, Miguel; Kelly, John J

    2013-04-01

    Pharmaceutical and personal care products are ubiquitous in surface waters but their effects on aquatic biofilms and associated ecosystem properties are not well understood. We measured in situ responses of stream biofilms to six common pharmaceutical compounds (caffeine, cimetidine, ciprofloxacin, diphenhydramine, metformin, ranitidine, and a mixture of each) by deploying pharmaceutical-diffusing substrates in streams in Indiana, Maryland, and New York. Results were consistent across seasons and geographic locations. On average, algal biomass was suppressed by 22%, 4%, 22%, and 18% relative to controls by caffeine, ciprofloxacin, diphenhydramine, and the mixed treatment, respectively. Biofilm respiration was significantly suppressed by caffeine (53%), cimetidine (51%), ciprofloxacin (91%), diphenhydramine (63%), and the mixed treatment (40%). In autumn in New York, photosynthesis was also significantly suppressed by diphenhydramine (99%) and the mixed treatment (88%). Pyrosequencing of 16S rRNA genes was used to examine the effects of caffeine and diphenhydramine on biofilm bacterial community composition at the three sites. Relative to the controls, diphenhydramine exposure significantly altered bacterial community composition and resulted in significant relative increases in Pseudomonas sp. and decreases in Flavobacterium sp. in all three streams. These ubiquitous pharmaceuticals, alone or in combination, influenced stream biofilms, which could have consequences for higher trophic levels and important ecosystem processes.

  12. Effects of penconazole on two yeast strains: growth kinetics and molecular studies.

    PubMed

    Jawich, Dalal; Lteif, Roger; Pfohl-Leszkowicz, Annie; Strehaiano, Pierre

    2006-05-01

    The aim of this study consisted to evaluate the impact of a pesticide (penconazole) on the growth kinetics and genotoxicity on two yeast strains (Saccharomyces cerevisiae and Metschnikowia pulcherrima). When the penconazole was added at different phases of the growth of M. pulcherrima, no effect was noticed on the kinetics of yeast growth but DNA adducts were observed when penconazole was added in the exponential phase. Increasing doses (1-15 maximum residue limit) of the pesticide added at the beginning of the fermentation did not induce DNA adducts while kinetics were affected.

  13. ygiW and qseBC are co-expressed in Aggregatibacter actinomycetemcomitans and regulate biofilm growth.

    PubMed

    Juárez-Rodríguez, María Dolores; Torres-Escobar, Ascención; Demuth, Donald R

    2013-06-01

    The quorum-sensing Escherichia coli regulators B and C (QseBC) two-component system were previously shown to regulate biofilm growth of the oral pathogen Aggregatibacter actinomycetemcomitans and to be essential for virulence. In this study, we use RT-PCR to show that an open reading frame, ygiW, residing upstream of qseBC and encoding a hypothetical protein is co-expressed with qseBC. In addition, using a series of lacZ transcriptional fusion constructs and 5'-rapid amplification of cDNA Ends (RACE), the promoter that drives expression of the ygiW-qseBC operon and the transcriptional start site was mapped to the 372 bp intergenic region upstream from ygiW. No internal promoters drive qseBC expression independently from ygiW. However, qseBC expression is attenuated by approximately ninefold by a putative attenuator stem-loop (ΔG = -77.0 KJ/mol) that resides in the 137 bp intergenic region between ygiW and qseB. The QseB response regulator activates expression of the ygiW-qseBC operon and transcription from the ygiW promoter is drastically reduced in ΔqseB and ΔqseBC mutants of A. actinomycetemcomitans. In addition, transcriptional activity of the ygiW promoter is significantly reduced in a mutant expressing an in-frame deletion of qseC that lacks the sensor domain of QseC, suggesting that a periplasmic signal is required for QseB activation. Finally, a non-polar in-frame deletion in ygiW had little effect on biofilm depth but caused a significant increase in surface coverage relative to wild-type. Complementation of the mutant with a plasmid-borne copy of ygiW reduced surface coverage back to wild-type levels. Interestingly, deletion of the sensor domain of QseC or of the entire qseC open reading frame resulted in significant reductions in biofilm depth, biomass and surface coverage, indicating that the sensor domain is essential for optimal biofilm formation by A. actinomycetemcomitans. Thus, although ygiW and qseBC are co-expressed, they regulate biofilm

  14. 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

  15. The influence of crystal morphology on the kinetics of growth of calcium oxalate monohydrate

    NASA Astrophysics Data System (ADS)

    Millan, A.; Sohnel, O.; Grases, F.

    1997-08-01

    The growth of several calcium oxalate monohydrate seeds in the presence and absence of additives (phytate, EDTA and citrate) has been followed by potentiometry measurements. Growth rates have been calculated from precipitate curves by a cubic spline method and represented in logarithmic plots versus supersaturation. Crystal growth kinetics were found to be dependent on crystal morphology, crystal perfection and degree of aggregation. Some seeds were dissolving in supersaturated solutions. Other seeds showed an initial growth phase of high-order kinetics. The effect of the additives was also different on each seed. Three alternative mechanisms for calcium oxalate crystal growth are proposed.

  16. Effect of flow rate on growth and oxygen consumption of biofilm in gravity sewer.

    PubMed

    Xu, Jingwei; Li, Muzhi; He, Qiang; Sun, Xingfu; Zhou, Xiangren; Su, Zhenping; Ai, Hainan

    2017-01-01

    The function of sewer as reactors must rely on the biofilm in it. In this paper, the formation, structure, oxygen transfer, and activity of the biofilm under different hydraulic conditions were studied by the microelectrode technology, oxygen uptake rate (OUR) technology, and 454 high-throughput pyrosequencing technology. Results showed that when the wall-shear stresses were 1.12, 1.29, and 1.45 Pa, the porosity of the steady-state biofilm were 69.1, 64.4, and 55.1 %, respectively. The maximum values of OUR were 0.033, 0.027, and 0.022 mg/(L*s), respectively, and the COD removal efficiency in the sewers reached 40, 35, and 32 %, respectively. The research findings had an important significance on how to improve the treatment efficiency of the sewers. Fig. a Graphical Abstract.

  17. Fungal Biofilms, Drug Resistance, and Recurrent Infection

    PubMed Central

    Desai, Jigar V.; Mitchell, Aaron P.; Andes, David R.

    2014-01-01

    A biofilm is a surface-associated microbial community. Diverse fungi are capable of biofilm growth. The significance of this growth form for infection biology is that biofilm formation on implanted devices is a major cause of recurrent infection. Biofilms also have limited drug susceptibility, making device-associated infection extremely difficult to treat. Biofilm-like growth can occur during many kinds of infection, even when an implanted device is not present. Here we summarize the current understanding of fungal biofilm formation, its genetic control, and the basis for biofilm drug resistance. PMID:25274758

  18. Modeling growth kinetics and statistical distribution of oligometastases.

    PubMed

    Withers, H Rodney; Lee, Steve P

    2006-04-01

    The kinetics of development of micrometastases, and especially of small numbers of metastases (oligometastases), was explored by using simple assumptions to develop concepts that may be useful for framing future research. The conclusions depend on the assumptions and hence must be considered speculative. It is assumed that beyond a threshold size for initiation of metastatic spread, which varies widely from tumor to tumor, the rate at which a primary tumor sheds new metastases increases exponentially, in parallel with its exponential growth. This increasing rate of release of new metastatic clonogens from the primary tumor is accompanied by a similar exponential growth of each of the micrometastases newly established at a secondary site. This creates a log-log linear relationship between the volume distribution of metastases and number of metastases, there being one largest metastasis followed by an exponentially expanding number of logarithmically smaller micrometastases. For example, if the micrometastases and the primary tumor grew at the same rate for 6 doublings after initiation of the first metastasis, then the primary tumor would have increased its volume by a factor of 64 (2(6)) and would be shedding metastatic clonogens at 64 times the initial rate. The first metastasis would undergo 6 doublings and contain 64 cells; the succeeding 2 metastases, released as the primary doubled in volume, would undergo 5 doublings and each would contain 32 cells; and so forth down to the 64 most recently developed single-cell metastases. However, the growth rate of metastases is expected to be faster than that of the primary tumor so that the rate of increase in volume of the micrometastases would be faster than the rate of increase in their numbers (through release of new metastases from the primary). Thus, although the log-log linear relationship is maintained, the slope of the volume frequency curve is changed; if the micrometastases grew 5 times faster than the primary

  19. 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

  20. Gel-Entrapped Staphylococcus aureus Bacteria as Models of Biofilm Infection Exhibit Growth in Dense Aggregates, Oxygen Limitation, Antibiotic Tolerance, and Heterogeneous Gene Expression

    PubMed Central

    Pabst, Breana; Pitts, Betsey; Lauchnor, Ellen

    2016-01-01

    An experimental model that mimicked the structure and characteristics of in vivo biofilm infections, such as those occurring in the lung or in dermal wounds where no biomaterial surface is present, was developed. In these infections, microbial biofilm forms as cell aggregates interspersed in a layer of mucus or host matrix material. This structure was modeled by filling glass capillary tubes with an agarose gel that had been seeded with Staphylococcus aureus bacteria and then incubating the gel biofilm in medium for up to 30 h. Confocal microscopy showed that the bacteria formed in discrete pockets distributed throughout the gel matrix. These aggregates enlarged over time and also developed a size gradient, with the clusters being larger near the nutrient- and oxygen-supplied interface and smaller at greater depths. Bacteria entrapped in gels for 24 h grew slowly (specific growth rate, 0.06 h−1) and were much less susceptible to oxacillin, minocycline, or ciprofloxacin than planktonic cells. Microelectrode measurements showed that the oxygen concentration decreased with depth into the gel biofilm, falling to values less than 3% of air saturation at depths of 500 μm. An anaerobiosis-responsive green fluorescent protein reporter gene for lactate dehydrogenase was induced in the region of the gel where the measured oxygen concentrations were low, confirming biologically relevant hypoxia. These results show that the gel biofilm model captures key features of biofilm infection in mucus or compromised tissue: formation of dense, distinct aggregates, reduced specific growth rates, local hypoxia, and antibiotic tolerance. PMID:27503656

  1. 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 ...

  2. Notes on Interface Growth Kinetics 50 Years After Burton, Cabrera and Frank

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    2003-01-01

    This is an overview of basic problems of crystal growth kinetics controlled by processes on the crystal interface with solution and melt. Included, also, are results on fundamental issues concerning morphological stability of crystal-solution interface that engage both interface kinetics and mass transport by diffusion and convection.

  3. Trichosporon inkin biofilms produce extracellular proteases and exhibit resistance to antifungals.

    PubMed

    de Aguiar Cordeiro, Rossana; Serpa, Rosana; Flávia Uchoa Alexandre, Camila; de Farias Marques, Francisca Jakelyne; Vladia Silva de Melo, Charlline; da Silva Franco, Jônatas; José de Jesus Evangelista, Antonio; Pires de Camargo, Zoilo; Samia Nogueira Brilhante, Raimunda; Fabio Gadelha Rocha, Marcos; Luciano Bezerra Moreira, José; de Jesus Pinheiro Gomes Bandeira, Tereza; Júlio Costa Sidrim, José

    2015-11-01

    The aim of this study was to determine experimental conditions for in vitro biofilm formation of clinical isolates of Trichosporon inkin, an important opportunistic pathogen in immunocompromised patients. Biofilms were formed in microtitre plates in three different media (RPMI, Sabouraud and CLED), with inocula of 104, 105 or 106 cells ml- 1, at pH 5.5 and 7.0, and at 35 and 28 °C, under static and shaking conditions for 72 h. Growth kinetics of biofilms were evaluated at 6, 24, 48 and 72 h. Biofilm milieu analysis were assessed by counting viable cells and quantification of nucleic acids released into biofilm supernatants. Biofilms were also analysed for proteolytic activity and antifungal resistance against amphotericin B, caspofungin, fluconazole, itraconazole and voriconazole. Finally, ultrastructural characterization of biofilms formed in microtitre plates and catheter disks was performed by scanning electron microscopy. Greater biofilm formation was observed with a starter inoculum of 106 cells ml- 1, at pH 7.0 at 35 °C and 80 r.p.m., in both RPMI and Sabouraud media. Growth kinetics showed an increase in both viable cells and biomass with increasing incubation time, with maximum production at 48 h. Biofilms were able to disperse viable cells and nucleic acids into the supernatant throughout the developmental cycle. T. inkin biofilms produced more protease than planktonic cells and showed high tolerance to amphotericin B, caspofungin and azole derivatives. Mature biofilms were formed by different morphotypes, such as blastoconidia, arthroconidia and hyphae, in a strain-specific manner. The present article details the multicellular lifestyle of T. inkin and provides perspectives for further research.

  4. 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

  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. The Effects of Cationic Surfactants on Marine Biofilm Growth on Hydrogels

    NASA Astrophysics Data System (ADS)

    Smith, M. J.; Adam, G.; Duncan, H. J.; Cowling, M. J.

    2002-09-01

    A method for the quantification of biofilm formation on hydrogel protective coatings for optical sensors and cameras has been developed using fluorescein diacetate (FDA) hydrolysis. In conjunction with these measurements the release of the fouling resistant cationic surfactants benzalkonium chloride, tallowbenzyldimethylammonium chloride and dicocodimethylammonium chloride was measured, using high performance liquid chromatography (HPLC), to enable correlation to be made between release and biofilm resistance and thus determine the active lifetime of such coatings. Results indicate that the twin-chained material, dicocodimethylammonium chloride, produced superior biofouling resistance as, at the 12 week time point, little fouling was detected on this coating. The hydrogel containing the long-chained tallowbenzyldimethylammonium chloride (mainly C16 and C18 chains) was the next best fouling resistant material, withstanding biofilm formation for 9 weeks. This correlates with the fact that each of these materials had an extremely slow to zero release rate, due to their irreversible binding to the hydrogel over the experimental timescale. In comparison the shorter chained benzalkonium chloride (mainly C12 and C14), showed signs of biofilm formation at the 3 week time point.

  7. 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.

  8. 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.)

  9. Activity of essential oil-based microemulsions against Staphylococcus aureus biofilms developed on stainless steel surface in different culture media and growth conditions.

    PubMed

    Raffaella, Campana; Casettari, Luca; Fagioli, Laura; Cespi, Marco; Bonacucina, Giulia; Baffone, Wally

    2017-01-16

    Food safety is a fundamental concern for both consumers and the food industry, especially as the numbers of reported cases of food-associated infections continue to increase. Industrial surfaces can provide a suitable substrate for the development and persistence of bacterial organized in biofilms that represent a potential source of food contamination. The negative consumer perception of chemical disinfectants has shifted the attention to natural substances, such as plant extracts. The aim of this study was to investigate the possibility of using the essential oils (EOs) in the fight against S. aureus biofilms. First, the Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Minimum Biofilm Inhibitory Concentration (MBIC), Minimum Biofilm Eradication Concentration (MBEC) of eleven EOs against S. aureus were determined. Cinnamomum cassia and Salvia officinalis EOs showed the greatest antibacterial properties with 1.25% MIC and MBC, 1.25% MBIC and 2.5% MBEC respectively. Gas Chromatography/Mass Spectrometry analysis revealed cinnamaldehyde (82.66%) and methoxy cinnamaldehyde (10.12%) as the most abundant substances of C. cassia, while cis-thujone (23.90%), camphor (19.22%) and 1.8-cineole (10.62%) of S. officinalis. Three different microemulsions, formulated with C. cassia, S. officinalis or both, were finally tested against S. aureus biofilms in different culture media and growth conditions, causing a >3 logarithmic reductions in S. aureus 24h-old biofilms and desiccated biofilms, and up to 68% of biofilm removal after 90min of exposure. The obtained data suggest the potential use of EOs, alone or in combination, for the formulation of sanitizers as alternative or in support in the disinfection of contaminated surfaces.

  10. Methods for obtaining reliable and reproducible results in studies of Candida biofilms formed in vitro.

    PubMed

    Costa, Anna C B P; Pereira, Cristiane A; Freire, Fernanda; Junqueira, Juliana C; Jorge, Antonio O C

    2013-11-01

    Biofilm formation is one of the most important attributes for virulence in Candida species and contributes to increased resistance to antifungal drugs and host immune mechanisms. These features have led to the development of several methodologies to reproduce a sessile community in vitro that can be used to study the development of a biofilm, its interaction with other microorganisms and the environment, and its susceptibility to available antifungal agents and also to search for new therapy strategies. The purpose of this review is to describe the most commonly used methods to study Candida biofilms in vitro, to discuss the benefits and limitations of the different methods to induce biofilm formation, and to analyse the architecture, viability and growth kinetics of Candida biofilms.

  11. 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.

  12. A fluid dynamics multidimensional model of biofilm growth: stability, influence of environment and sensitivity.

    PubMed

    Clarelli, F; Di Russo, C; Natalini, R; Ribot, M

    2016-12-01

    In this article, we study in detail the fluid dynamics system proposed in Clarelli et al. (2013, J. Math. Biol., 66, 1387-1408) to model the formation of cyanobacteria biofilms. After analysing the linear stability of the unique non-trivial equilibrium of the system, we introduce in the model the influence of light and temperature, which are two important factors for the development of a cyanobacteria biofilm. Since the values of the coefficients we use for our simulations are estimated through information found in the literature, some sensitivity and robustness analyses on these parameters are performed. All these elements enable us to control and to validate the model we have already derived and to present some numerical simulations in the 2D and the 3D cases.

  13. C. albicans Growth, Transition, Biofilm Formation, and Gene Expression Modulation by Antimicrobial Decapeptide KSL-W

    DTIC Science & Technology

    2013-11-07

    is essential to biofilm formation [4]. The involvement of HWP1 in C. albicans adhesion is supported by the EAP1 gene which encodes a glucan -crosslinked...KSL-W. Furthermore, the EAP1 gene, which encodes a glycosylphosphatidylinositol- anchored, glucan -crosslinked cell wall protein in both ad- hesion and...control in agriculture. J Sci Food Agric 2013, 93:1525–1536. 27. Dhople V, Krukemeyer A, Ramamoorthy A: The human beta -defensin-3, an antibacterial

  14. Modeling multidimensional and multispecies biofilms in porous media.

    PubMed

    Tang, Youneng; Liu, Haihu

    2017-03-21

    Modeling multidimensional and multispecies biofilm in porous media at the pore scale is challenging due to the need to simultaneously track the microbial community in the biofilms and the interfaces between the biofilms and the fluid. Therefore, researchers usually assume that the model has only one dimension in space or has only one microbial species. This work uses bioremediation of U(VI)-contaminated groundwater as the context to develop a two-dimensional and multispecies biofilm model. The model simulates the transverse mixing zone in which U(VI) is mixed with propionate, a nutrient externally supplied to stimulate the growth of microorganisms. The model considers multiple interactions among fluid flow, transport and reaction of chemical species, and growth of biofilm. The biofilm consists of two types of active biomass (syntrophs and dissimilatory metal reducing bacteria) and inert biomass. The two types of active biomass collaboratively remove U(VI). The model outputs biomass distribution, chemical species concentrations, and fluid flow at the pore scale to fundamentally study the multiple interactions. The model also outputs the contaminant removal rate that can be potentially used for up-scaling studies. The simulated results are generally consistent with experimental observations from other studies in trend. The trend can be explained by the multiple interactions based on thermodynamics and microbial kinetics. This article is protected by copyright. All rights reserved.

  15. New observations and insights into the morphology and growth kinetics of hydrate films.

    PubMed

    Li, Sheng-Li; Sun, Chang-Yu; Liu, Bei; Li, Zhi-Yun; Chen, Guang-Jin; Sum, Amadeu K

    2014-02-19

    The kinetics of film growth of hydrates of methane, ethane, and methane-ethane mixtures were studied by exposing a single gas bubble to water. The morphologies, lateral growth rates, and thicknesses of the hydrate films were measured for various gas compositions and degrees of subcooling. A variety of hydrate film textures was revealed. The kinetics of two-dimensional film growth was inferred from the lateral growth rate and initial thickness of the hydrate film. A clear relationship between the morphology and film growth kinetics was observed. The shape of the hydrate crystals was found to favour heat or mass transfer and favour further growth of the hydrate film. The quantitative results on the kinetics of film growth showed that for a given degree of subcooling, the initial film thicknesses of the double hydrates were larger than that of pure methane or ethane hydrate, whereas the thickest hydrate film and the lowest lateral growth rate occurred when the methane mole fraction was approximately 0.6.

  16. Simulation of single-species bacterial-biofilm growth using the Glazier-Graner-Hogeweg model and the CompuCell3D modeling environment.

    PubMed

    Popławski, Nikodem J; Shirinifard, Abbas; Swat, Maciej; Glazier, James A

    2008-04-01

    The CompuCell3D modeling environment provides a convenient platform for biofilm simulations using the Glazier-Graner-Hogeweg (GGH) model, a cell-oriented framework designed to simulate growth and pattern formation due to biological cells' behaviors. We show how to develop such a simulation, based on the hybrid (continuum-discrete) model of Picioreanu, van Loosdrecht, and Heijnen (PLH), simulate the growth of a single-species bacterial biofilm, and study the roles of cell-cell and cell-field interactions in determining biofilm morphology. In our simulations, which generalize the PLH model by treating cells as spatially extended, deformable bodies, differential adhesion between cells, and their competition for a substrate (nutrient), suffice to produce a fingering instability that generates the finger shapes of biofilms. Our results agree with most features of the PLH model, although our inclusion of cell adhesion, which is difficult to implement using other modeling approaches, results in slightly different patterns. Our simulations thus provide the groundwork for simulations of medically and industrially important multispecies biofilms.

  17. Time-Lapse Imaging to Examine the Growth Kinetics of Arabidopsis Seedlings in Response to Ethylene.

    PubMed

    Binder, Brad M

    2017-01-01

    Ethylene is well known to inhibit the growth of dark-grown eudicot seedlings. Most studies examine this inhibition after several days of exposure to ethylene. However, such end-point analysis misses transient responses and the dynamic nature of growth regulation. Here, high-resolution, time-lapse imaging is described as a method to gather data about ethylene growth kinetics and movement responses of the hypocotyls of dark-grown seedlings of Arabidopsis thaliana. These methods allow for the characterization of short-term kinetic responses and can be modified for the analysis of roots and seedlings from other species.

  18. Modeling of scale-dependent bacterial growth by chemical kinetics approach.

    PubMed

    Martínez, Haydee; Sánchez, Joaquín; Cruz, José-Manuel; Ayala, Guadalupe; Rivera, Marco; Buhse, Thomas

    2014-01-01

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

  19. 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)).

  20. 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…

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

    SciTech Connect

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

    2016-03-15

    Here, 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.

  2. 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

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

    PubMed

    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.

  4. 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.

  5. Growth kinetics of coliform bacteria under conditions relevant to drinking water distribution systems.

    PubMed

    Camper, A K; McFeters, G A; Characklis, W G; Jones, W L

    1991-08-01

    The growth of environmental and clinical coliform bacteria under conditions typical of drinking water distribution systems was examined. Four coliforms (Klebsiella pneumoniae, Escherichia coli, Enterobacter aerogenes, and Enterobacter cloacae) were isolated from an operating drinking water system for study; an enterotoxigenic E. coli strain and clinical isolates of K. pneumoniae and E. coli were also used. All but one of the coliforms tested were capable of growth in unsupplemented mineral salts medium; the environmental isolates had greater specific growth rates than did the clinical isolates. This trend was maintained when the organisms were grown with low levels (less than 1 mg liter-1) of yeast extract. The environmental K. pneumoniae isolate had a greater yield, higher specific growth rates, and a lower Ks value than the other organisms. The environmental E. coli and the enterotoxigenic E. coli strains had comparable yield, growth rate, and Ks values to those of the environmental K. pneumoniae strain, and all three showed significantly more successful growth than the clinical isolates. The environmental coliforms also grew well at low temperatures on low concentrations of yeast extract. Unsupplemented distribution water from the collaborating utility supported the growth of the environmental isolates. Growth of the K. pneumoniae water isolate was stimulated by the addition of autoclaved biofilm but not by tubercle material. These findings indicate that growth of environmental coliforms is possible under the conditions found in operating municipal drinking water systems and that these bacteria could be used in tests to determine assimilable organic carbon in potable water.

  6. 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.

  7. Flowtube experiments on diamond formation: separating the growth and nucleation kinetics

    NASA Astrophysics Data System (ADS)

    Martin, L. R.; Hill, Michael W.

    1990-12-01

    We have done a series of experiments on diamond microcrystal formation in flowtubes. The system is designed to separate the discharge used to create atomic hydrogen from the organic molecules used as a carbon source. This creates a simplified chemical environment in which the species concentrations are kinetically rather than thermodynamically controlled. The flowtube enables us to examine kinetics of diamond formation under a variety of conditions and gives us some information about the rate of nucleation independently of the growth rate. 1.

  8. 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

  9. Plasma-mediated inactivation of Pseudomonas aeruginosa biofilms grown on borosilicate surfaces under continuous culture system.

    PubMed

    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 culturability 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. 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

  11. 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.

  12. 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.

  13. 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.

  14. Quantitative Polymerase Chain Reaction for Microbial Growth Kinetics of Mixed Culture System.

    PubMed

    Cotto, Ada; Looper, Jessica K; Mota, Linda C; Son, Ahjeong

    2015-11-01

    Microbial growth kinetics is often used to optimize environmental processes owing to its relation to the breakdown of substrate (contaminants). However, the quantification of bacterial populations in the environment is difficult owing to the challenges of monitoring a specific bacterial population within a diverse microbial community. Conventional methods are unable to detect and quantify the growth of individual strains separately in the mixed culture reactor. This work describes a novel quantitative PCR (qPCR)-based genomic approach to quantify each species in mixed culture and interpret its growth kinetics in the mixed system. Batch experiments were performed for both single and dual cultures of Pseudomonas putida and Escherichia coli K12 to obtain Monod kinetic parameters (μmax and Ks). The growth curves and kinetics obtained by conventional methods (i.e., dry weight measurement and absorbance reading) were compared with that obtained by qPCR assay. We anticipate that the adoption of this qPCR-based genomic assay can contribute significantly to traditional microbial kinetics, modeling practice, and the operation of bioreactors, where handling of complex mixed cultures is required.

  15. Crystal nucleation and cluster-growth kinetics in a model glass under shear

    NASA Astrophysics Data System (ADS)

    Mokshin, Anatolii V.; Barrat, Jean-Louis

    2010-08-01

    Crystal nucleation and growth processes induced by an externally applied shear strain in a model metallic glass are studied by means of nonequilibrium molecular dynamics simulations, in a range of temperatures. We observe that the nucleation-growth process takes place after a transient, induction regime. The critical cluster size and the lag-time associated with this induction period are determined from a mean first-passage time analysis. The laws that describe the cluster-growth process are studied as a function of temperature and strain rate. A theoretical model for crystallization kinetics that includes the time dependence for nucleation and cluster growth is developed within the framework of the Kolmogorov-Johnson-Mehl-Avrami scenario and is compared with the molecular dynamics data. Scalings for the cluster-growth laws and for the crystallization kinetics are also proposed and tested. The observed nucleation rates are found to display a nonmonotonic strain rate dependency.

  16. 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.

  17. Reactive Dependent Growth Kinetics and Morphology of A-B Ternary Mixtures

    NASA Astrophysics Data System (ADS)

    Feng, Wen-Qiang; Wang, Kai-Ming; Zhu, Yue-Jin

    2013-08-01

    In this paper, we present Monte Carlo simulations of A-B-diblock-copolymer ternary mixtures simultaneously undergoing phase separation and reversible chemical reaction A + B ⇌ C. The results demonstrate that the competition of chemical reaction and thermal diffusion dynamics co-determine the self-assembling morphology and growth kinetics of the reactive ternary mixtures. The role of the chemical reaction on the growth kinetics count mainly on the copolymer-polymer interaction strength Jp. If Jp < 1.0, the introduction of chemical reaction speeds up the domain growth; while for Jp > 1.0, the chemical reaction slows down the domain growth. The domain growth exponent decreases linearly with increasing of the copolymer-polymer interaction strength. At a later stage, <1, 0> and <0, 1> oriented strip pattern formations are observed when Jp is strong.

  18. 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

  19. Relationship between kinetics of growth and production of exo-electrons: Case study with Geobacter toluenoxydans.

    PubMed

    Szöllősi, Attila; Narr, László; Kovács, Attila G; Styevkó, Gabriella

    2015-09-01

    Kinetics of growth and product formation of G. toluenoxydans DSMZ 19350 strain were investigated using sodium-acetate as substrate and Fe(3+)-ions and fumarate as electron acceptor. Response surface method was adapted for evaluation of growth of bacteria. Results showed that maximum growth was detected in the case of 2.2 g/L substrate concentration. Application of higher substrate concentration (>2.5 g/L sodium acetate) significantly inhibits the bacterial growth. Luong's model was found to be the most suitable to determine kinetic parameters (μ(max) = 0.033 1/h, KS = 0.205 g/L) of growth of G.toluenoxydans strain, and the growth was completely inhibited at substrate concentration higher than 3.1 g/L. In the case of product formation the Haldane model was used and kinetic parameters are μ(Pmax) = 0.123 mg/h, K(PS)= 0.184 g/L. Correlation between microbial growth and product formation was observed using the Luedeking-Piret empirical method. Both factors (growth and number of cells) affected significantly iron(III)-reduction, thus the product formation. These results are important and open the possibility to design a continuous MFC setting operating with G. toluenoxydans as biocatalyst.

  20. 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.

  1. Dependence of morphometric allometries on the growth kinetics of body parts.

    PubMed

    Nijhout, H Frederik

    2011-11-07

    As overall size varies, the sizes of body parts of many animals often appear to be related to each other by a power law, commonly called the allometric equation. Orderly scaling relationships among body parts are widespread in the animal world, but there is no general agreement about how these relationships come about. Presumably they depend on the patterns of growth of body parts, and simple analyses have shown that exponential growth can lead to size relationships that are well-described by the allometric equation. Exponential growth kinetics also allow for a simple biological interpretation of the coefficients of the power relationship. Nevertheless, many tissues do not grow with exponential kinetics, nor do they grow for the same period of time, and the consequences of more realistic growth patterns on the resulting allometric relationships of body parts are not well understood. In this paper I derive a set of allometric equations that assume different kinetics of growth: linear, exponential and sigmoidal. In these derivations I also include differences in development times as a variable, in addition to differences in the growth rates and initial sizes of the two structures whose allometric relationship is compared. I show how these equations can be used to deduce the effect of different causes of variation in absolute size on the resulting allometry. Variation in size can be due to variation in the duration of development, variation in growth rate or variation in initial size. I show that the meaning of the coefficients of the allometric equation depends on exactly how size variation comes about. I show that if two structures are assumed to grow with sigmoidal kinetics (logistic and Gompertz) the resulting allometric equations do not have a simple and intuitive structure and produce graphs that, over a sufficiently large range of sizes, can vary from linear, to sigmoidal to hump-shaped. Over a smaller range of absolute sizes, these sigmoid growth kinetics can

  2. 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.

  3. 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

  4. Domain and rim growth kinetics in stratifying foam films

    NASA Astrophysics Data System (ADS)

    Zhang, Yiran; Yilixiati, Subinuer; Sharma, Vivek

    Foam films are freely standing thin liquid films that typically 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. During the initial expansion, a rim forms near the contact line between the growing thinner domain and the surrounding region, which influences the dynamics of domain growth as well as stratification Using newly developed interferometry digitial imaging optical microscopy (IDIOM) technique, we capture the rim evolution dynamics. Finally, we also develop a theoretical model to describe both rim evolution and domain growth dynamics.

  5. Phosphate-limited continuous culture of Rhodotorula rubra: kinetics of transport, leakage, and growth.

    PubMed Central

    Robertson, B R; Button, D K

    1979-01-01

    The phosphate-limited growth kinetics of Rhodotorula rubra, a small yeast of marine origin, were examined by analysis of 32P distributions in continuous cultures. Isotope relaxation procedures were used to identify unidirectional flows of Pi and organic phosphate among compartments modeled during growth. The concentrations of phosphates in these compartments at various growth rates were used, together with attendant flows, to produce a mathematical model of growth. Both Pi and phosphate-containing metabolic intermediates leaked from cells during growth. Total leakage ranged from 4 to 10% of influx and was comprised mostly of Pi. Transport capacity was at least 10 times that required for growth at saturating Pi concentrations, so that influx was linear with concentration during growth. This led to the realization that the curvature of Monod plots (Kmu = 12 nM mumax = 0.18/h, and the threshold At = 2.5 nM) is due to change in yield with growth rate. Growth rate related to Pi by the affinity, aA (= 0.43 liter/mg of cells.h) of cells for Pi and the growth rate-dependent yield. It was also specified by a series of kinetic constants that specified flow among the various compartments and equilibrium compartment concentrations as they were set by extracellular Pi. The importance of leakage by healthy cells to the organic chemistry of aquatic systems is noted. PMID:37231

  6. Antimicrobial GL13K Peptide Coatings Killed and Ruptured the Wall of Streptococcus gordonii and Prevented Formation and Growth of Biofilms

    PubMed Central

    Chen, Xi; Hirt, Helmut; Li, Yuping; Gorr, Sven-Ulrik; Aparicio, Conrado

    2014-01-01

    Infection is one of the most prevalent causes for dental implant failure. We have developed a novel antimicrobial peptide coating on titanium by immobilizing the antimicrobial peptide GL13K. GL13K was developed from the human salivary protein BPIFA2. The peptide exhibited MIC of 8 µg/ml against planktonic Pseudonomas aeruginosa and their biofilms were reduced by three orders of magnitude with 100 µg/ml GL13K. This peptide concentration also killed 100% of Streptococcus gordonii. At 1 mg/ml, GL13K caused less than 10% lysis of human red blood cells, suggesting low toxicity to mammalian cells. Our GL13K coating has also previously showed bactericidal effect and inhibition of biofilm growth against peri-implantitis related pathogens, such as Porphyromonas gingivalis. The GL13K coating was cytocompatible with human fibroblasts and osteoblasts. However, the bioactivity of antimicrobial coatings has been commonly tested under (quasi)static culture conditions that are far from simulating conditions for biofilm formation and growth in the oral cavity. Oral salivary flow over a coating is persistent, applies continuous shear forces, and supplies sustained nutrition to bacteria. This accelerates bacteria metabolism and biofilm growth. In this work, the antimicrobial effect of the coating was tested against Streptococcus gordonii, a primary colonizer that provides attachment for the biofilm accretion by P. gingivalis, using a drip-flow biofilm bioreactor with media flow rates simulating salivary flow. The GL13K peptide coatings killed bacteria and prevented formation and growth of S. gordonii biofilms in the drip-flow bioreactor and under regular mild-agitation conditions. Surprisingly the interaction of the bacteria with the GL13K peptide coatings ruptured the cell wall at their septum or polar areas leaving empty shell-like structures or exposed protoplasts. The cell wall rupture was not detected under regular culture conditions, suggesting that cell wall rupture induced

  7. Secondary Flow Mixing due to Biofilm Growth in Capillaries of Varying Dimensions

    PubMed Central

    Hornemann, Jennifer A.; Codd, Sarah L.; Fell, Robert J.; Stewart, Philip S.; Seymour, Joseph D.

    2009-01-01

    Using a magnetic resonance microscopy (MRM) technique, velocity perturbations due to biofouling in capillaries were detected in 3-D velocity maps. The velocity images in each of the three square capillary sizes (2 mm, 0.9 mm, and 0.5 mm i.d.) tested indicate secondary flow in both the x and y directions for the biofouled capillaries. Similar flow maps generated in a clean square capillary show only an axial component. Investigation of these secondary flows and their geometric and dynamic similarity is the focus of this paper. The results showed significant secondary flows present in the 0.9 mm i.d. capillary, on the scale of 20% of the bulk fluid flow. Since this is the “standard 1 mm” size capillary used in confocal microscopy laboratory bioreactors to investigate biofilm properties, it is important to understand how these enhanced flows impact bioreactor transport. PMID:19191352

  8. 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.

  9. Kinetic growth mode of epitaxial GaAs on Si(001) micro-pillars

    NASA Astrophysics Data System (ADS)

    Bergamaschini, Roberto; Bietti, Sergio; Castellano, Andrea; Frigeri, Cesare; Falub, Claudiu V.; Scaccabarozzi, Andrea; Bollani, Monica; von Känel, Hans; Miglio, Leo; Sanguinetti, Stefano

    2016-12-01

    Three-dimensional, epitaxial GaAs crystals are fabricated on micro-pillars patterned into Si(001) substrates by exploiting kinetically controlled growth conditions in Molecular Beam Epitaxy. The evolution of crystal morphology during growth is assessed by considering samples with increasing GaAs deposit thickness. Experimental results are interpreted by a kinetic growth model, which takes into account the fundamental aspects of the growth and mutual deposition flux shielding between neighboring crystals. Different substrate pattern geometries with dissimilar lateral sizes and periodicities of the Si micro-pillars are considered and self-similar crystal structures are recognized. It is demonstrated that the top faceting of the GaAs crystals is tunable, which can pave the way to locally engineer compound semiconductor quantum structures on Si(001) substrates.

  10. 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.

  11. A growth kinetic model of Kluyveromyces marxianus cultures on cheese whey as substrate.

    PubMed

    Longhi, Luís G S; Luvizetto, Débora J; Ferreira, Luciane S; Rech, Rosane; Ayub, Marco A Z; Secchi, Argimiro R

    2004-01-01

    This work presents a multi-route, non-structured kinetic model for determination of microbial growth and substrate consumption in an experimental batch bioreactor in which beta-galactosidase is produced by Kluyveromyces marxianus growing on cheese whey. The main metabolic routes for lactose, and oxygen consumption, cell growth, and ethanol production are derived based on experimental data. When these individual rates are combined into a single growth rate, by rewriting the model equations, the model re-interpretation has a complexity similar to that of the usual variations of the Monod kinetic model, available in the literature. Furthermore, the proposed model is in good agreement with the experimental data for different growth temperatures, being acceptable for dynamic simulations, processes optimization, and implementations of model-based control technologies.

  12. Growth kinetics of Listeria monocytogenes and spoilage microorganisms in fresh-cut cantaloupe.

    PubMed

    Fang, Ting; Liu, Yanhong; Huang, Lihan

    2013-05-01

    The main objective of this study was to investigate the growth kinetics of Listeria monocytogenes and background microorganisms in fresh-cut cantaloupe. Fresh-cut cantaloupe samples, inoculated with three main serotypes (1/2a, 1/2b, and 4b) of L. monocytogenes, were incubated at different temperatures, ranging from 4 to 43 °C, to develop kinetic growth models. During storage studies, the population of both background microorganisms and L. monocytogenes began to increase almost immediately, with little or no lag phase for most growth curves. All growth curves, except for two growth curves of L. monocytogenes 1/2a at 4 °C, developed to full curves (containing exponential and stationary phases), and can be described by a 3-parameter logistic model. There was no significant difference (P = 0.28) in the growth behaviors and the specific growth rates of three different serotypes of L. monocytogenes inoculated to fresh-cut cantaloupe. The effect of temperature on the growth of L. monocytogenes and spoilage microorganisms was evaluated using three secondary models. For L. monocytogenes, the minimum and maximum growth temperatures were estimated by both the Ratkowsky square-root and Cardinal parameter models, and the optimum temperature and the optimum specific growth rate by the Cardinal parameter model. An Arrhenius-type model provided more accurate estimation of the specific growth rate of L. monocytogenes at temperatures <4 °C. The kinetic models developed in this study can be used by regulatory agencies and food processors for conducting risk assessment of L. monocytogenes in fresh-cut cantaloupe, and for estimating the shelf-life of fresh-cut products.

  13. 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

  14. Growth in glucose-based medium and exposure to subinhibitory concentrations of imipenem induce biofilm formation in a multidrug-resistant clinical isolate of Acinetobacter baumannii

    PubMed Central

    2009-01-01

    Background Acinetobacter baumannii is emerging as an important nosocomial pathogen. Multidrug resistance, as well as ability to withstand environmental stresses, makes eradication of A. baumannii difficult, particularly from hospital settings. Results Over a six-year period, 73 isolates of A. baumannii were collected from infected patients in two hospitals in Italy. While 69 out of the 73 isolates displayed identical multidrug antibiotic resistance pattern, they were susceptible to carbapenems. Genetic profiles of these 69 isolates, determined by Pulsed Field Gel Electrophoresis (PFGE), indicated that they were genetically related and could be clustered in a specific clone, called SMAL. We tested the ability of the SMAL clone to form biofilm, an important determinant for bacterial colonization of the human host and for persistence in the hospital environment. Biofilm formation by A. baumannii SMAL, measured as surface adhesion to polystyrene, is strongly affected by growth conditions, being impaired in rich growth media such as LB, while being favoured in glucose-based medium. Surface adhesion in glucose-based media is inhibited by treatment with cellulase, suggesting that it depends on production of cellulose or of a chemically related extracellular polysaccharide. Exposure of A. baumannii SMAL to subinhibitory concentrations of imipenem resulted in biofilm stimulation and increased production of iron uptake proteins. Growth in iron-supplemented medium also stimulated surface adhesion, thus suggesting that increased intracellular iron concentrations might act as an environmental signal for biofilm formation in A. baumannii SMAL. Conclusions Our results indicate that exposure to subinhibitory concentrations of imipenem can stimulate biofilm formation and induce iron uptake in a pathogenic strain of A. baumannii, with potential implications on antibiotic susceptibility and ability to persist in the human host. PMID:20028528

  15. Kinetics of biofilm formation and desiccation survival of Listeria monocytogenes in single and dual species biofilms with Pseudomonas fluorescens, Serratia proteamaculans or Shewanella baltica on food-grade stainless steel surfaces.

    PubMed

    Daneshvar Alavi, Hessam Edin; Truelstrup Hansen, Lisbeth

    2013-01-01

    This study investigated the dynamics of static biofilm formation (100% RH, 15 °C, 48-72 h) and desiccation survival (43% RH, 15 °C, 21 days) of Listeria monocytogenes, in dual species biofilms with the common spoilage bacteria, Pseudomonas fluorescens, Serratia proteamaculans and Shewanella baltica, on the surface of food grade stainless steel. The Gram-negative bacteria reduced the maximum biofilm population of L. monocytogenes in dual species biofilms and increased its inactivation during desiccation. However, due to the higher desiccation resistance of Listeria relative to P. fluorescens and S. baltica, the pathogen survived in greater final numbers. In contrast, S. proteamaculans outcompeted the pathogen during the biofilm formation and exhibited similar desiccation survival, causing the N21 days of Serratia to be ca 3 Log10(CFU cm(-2)) greater than that of Listeria in the dual species biofilm. Microscopy revealed biofilm morphologies with variable amounts of exopolymeric substance and the presence of separate microcolonies. Under these simulated food plant conditions, the fate of L. monocytogenes during formation of mixed biofilms and desiccation depended on the implicit characteristics of the co-cultured bacterium.

  16. Effect of wall growth on the kinetic modeling of nitrite oxidation in a CSTR.

    PubMed

    Dokianakis, Spiros N; Kornaros, Michael; Lyberatos, Gerasimos

    2006-03-05

    A simple kinetic model was developed for describing nitrite oxidation by autotrophic aerobic nitrifiers in a continuous stirred tank reactor (CSTR), in which mixed (suspended and attached) growth conditions prevail. The CSTR system was operated under conditions of constant nitrite feed concentration and varying volumetric flow rates. Experimental data from steady-state conditions in the CSTR system and from batch experiments were used for the determination of the model's kinetic parameters. Model predictions were verified against experimental data obtained under transient operating conditions, when volumetric flow rate and nitrite feed concentration disturbances were imposed on the CSTR. The presented kinetic modeling procedure is quite simple and general and therefore can also be applied to other mixed growth biological systems.

  17. 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.

  18. 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...

  19. Dynamic identification of growth and survival kinetic parameters of microorganisms in foods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Inverse analysis is a mathematical method used in predictive microbiology to determine the kinetic parameters of microbial growth and survival in foods. The traditional approach in inverse analysis relies on isothermal experiments that are time-consuming and labor-intensive, and errors are accumula...

  20. Physicochemical regulation of biofilm formation

    PubMed Central

    Renner, Lars D.; Weibel, Douglas B.

    2011-01-01

    This article reviews the physical and chemical constraints of environments on biofilm formation. We provide a perspective on how materials science and engineering can address fundamental questions and unmet technological challenges in this area of microbiology, such as biofilm prevention. Specifically, we discuss three factors that impact the development and organization of bacterial communities. (1) Physical properties of surfaces regulate cell attachment and physiology and affect early stages of biofilm formation. (2) Chemical properties influence the adhesion of cells to surfaces and their development into biofilms and communities. (3) Chemical communication between cells attenuates growth and influences the organization of communities. Mechanisms of spatial and temporal confinement control the dimensions of communities and the diffusion path length for chemical communication between biofilms, which, in turn, influences biofilm phenotypes. Armed with a detailed understanding of biofilm formation, researchers are applying the tools and techniques of materials science and engineering to revolutionize the study and control of bacterial communities growing at interfaces. PMID:22125358

  1. 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…

  2. 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

  3. Understanding the isothermal growth kinetics of cdse quantum dots through microfluidic reactor assisted combinatorial synthesis

    NASA Astrophysics Data System (ADS)

    Swain, Basudev; Hong, Myung Hwan; Kang, Lee-Seung; Lee, Chan Gi

    2016-11-01

    With the use of a microfluidic-assisted combinatorial reactor, the synthesis of CdSe quantum dots was optimized by varying one parameter at a time, and the isothermal growth kinetics of CdSe quantum dots using various models was analyzed. To understand precisely the nucleation and growth characteristics of CdSe quantum dots (QDs), we synthesized the CdSe QDs using various experimental conditions. Different model equations, like acceleratory growth-time curves, sigmoidal growth-time curves or Johnson-Mehl-Avrami-Kolmogorov (JMAK), acceleratory growthtime curves based on diffusion, geometric model growth-time curves, and nth order growth-time curves were fitted. Among all growth models, the JMAK model with α = 1 - {e^{ - {{(kt)}^n}}}, and n = 1 was the best fitting model with the MATLAB interactive curve-fitting procedure were used. Errors associated with the best-fitting model and statistics for the goodness of fit were analyzed. Most of the models were not as good as the other than the proposed model. The errors associated with the proposed model were minimal, and the growth kinetics and other associated statistical factors are very similar, for all the variables investigated. The minimal error associated with the reproducibility and the similar data for growth kinetics for all studied parameters indicated that microfluidic-assisted combinatorial synthesis can be used in the industrial production of QDs. By using the proposed model to obtain an understanding of growth of QDs, their size and properties can be managed and simulated.

  4. Performance and kinetic evaluation of anaerobic moving bed biofilm reactor for treating milk permeate from dairy industry.

    PubMed

    Wang, S; Rao, N Chandrasekhara; Qiu, R; Moletta, R

    2009-12-01

    High strength milk permeate derived from ultra-filtration based cheese making process was treated in an anaerobic moving bed biofilm reactor (AMBBR) under mesophilic (35 degrees C) condition. Total chemical oxygen demand (TCOD) removal efficiencies of 86.3-73.2% were achieved at organic loading rates (OLR) of 2.0-20.0 g TCOD L(-1) d(-1). A mass balance model gave values of methane yield coefficient (Y(G/S)) and cell maintenance coefficient (k(m)) of 0.341 L CH(4) g(-1) TCOD(removed) and 0.1808 g TCOD(removed) g(-1) VSS d(-1), respectively. The maximum substrate utilization rate U(max) was determined as 89.3 g TCOD L(-1) d(-1) by a modified Stover-Kincannon model. Volumetric methane production rates (VMPR) were shown to correlate with the biodegradable TCOD concentration through a Michaelis-Menten type equation. Moreover, based on VMPR and OLR removed from the reactor, the sludge production yield was determined as 0.0794 g VSS g(-1) TCOD(removed).

  5. 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 2-4 h 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 7.5 h for effluent standardization of 500, 1000, 1500 and 2500 mg/L influent BOD5 concentrations, respectively. Similar pattern of the experimental data also confirmed these findings.

  6. 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

  7. 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%).

  8. Analytical solution of Luedeking-Piret equation for a batch fermentation obeying Monod growth kinetics.

    PubMed

    Garnier, Alain; Gaillet, Bruno

    2015-12-01

    Not so many fermentation mathematical models allow analytical solutions of batch process dynamics. The most widely used is the combination of the logistic microbial growth kinetics with Luedeking-Piret bioproduct synthesis relation. However, the logistic equation is principally based on formalistic similarities and only fits a limited range of fermentation types. In this article, we have developed an analytical solution for the combination of Monod growth kinetics with Luedeking-Piret relation, which can be identified by linear regression and used to simulate batch fermentation evolution. Two classical examples are used to show the quality of fit and the simplicity of the method proposed. A solution for the combination of Haldane substrate-limited growth model combined with Luedeking-Piret relation is also provided. These models could prove useful for the analysis of fermentation data in industry as well as academia.

  9. 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.

  10. 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

  11. Growth model and metabolic activity of brewing yeast biofilm on the surface of spent grains: a biocatalyst for continuous beer fermentation.

    PubMed

    Brányik, Tomás; Vicente, António A; Kuncová, Gabriela; Podrazký, Ondrej; Dostálek, Pavel; Teixeira, José A

    2004-01-01

    In the continuous systems, such as continuous beer fermentation, immobilized cells are kept inside the bioreactor for long periods of time. Thus an important factor in the design and performance of the immobilized yeast reactor is immobilized cell viability and physiology. Both the decreasing specific glucose consumption rate (q(im)) and intracellular redox potential of the cells immobilized to spent grains during continuous cultivation in bubble-column reactor implied alterations in cell physiology. It was hypothesized that the changes of the physiological state of the immobilized brewing yeast were due to the aging process to which the immobilized yeast are exposed in the continuous reactor. The amount of an actively growing fraction (X(im)act) of the total immobilized biomass (X(im)) was subsequently estimated at approximately X(im)act = 0.12 g(IB) g(C)(-1) (IB = dry immobilized biomass, C = dry carrier). A mathematical model of the immobilized yeast biofilm growth on the surface of spent grain particles based on cell deposition (cell-to-carrier adhesion and cell-to-cell attachment), immobilized cell growth, and immobilized biomass detachment (cell outgrowth, biofilm abrasion) was formulated. The concept of the active fraction of immobilized biomass (X(im)act) and the maximum attainable biomass load (X(im)max) was included into the model. Since the average biofilm thickness was estimated at ca. 10 microm, the limitation of the diffusion of substrates inside the yeast biofilm could be neglected. The model successfully predicted the dynamics of the immobilized cell growth, maximum biomass load, free cell growth, and glucose consumption under constant hydrodynamic conditions in a bubble-column reactor. Good agreement between model simulations and experimental data was achieved.

  12. Kinetics of cesium lead halide perovskite nanoparticle growth; focusing and de-focusing of size distribution.

    PubMed

    Koolyk, Miriam; Amgar, Daniel; Aharon, Sigalit; Etgar, Lioz

    2016-03-28

    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.

  13. Edge-controlled growth and kinetics of single-crystal graphene domains by chemical vapor deposition.

    PubMed

    Ma, Teng; Ren, Wencai; Zhang, Xiuyun; Liu, Zhibo; Gao, Yang; Yin, Li-Chang; Ma, Xiu-Liang; Ding, Feng; Cheng, Hui-Ming

    2013-12-17

    The controlled growth of large-area, high-quality, single-crystal graphene is highly desired for applications in electronics and optoelectronics; however, the production of this material remains challenging because the atomistic mechanism that governs graphene growth is not well understood. The edges of graphene, which are the sites at which carbon accumulates in the two-dimensional honeycomb lattice, influence many properties, including the electronic properties and chemical reactivity of graphene, and they are expected to significantly influence its growth. We demonstrate the growth of single-crystal graphene domains with controlled edges that range from zigzag to armchair orientations via growth-etching-regrowth in a chemical vapor deposition process. We have observed that both the growth and the etching rates of a single-crystal graphene domain increase linearly with the slanted angle of its edges from 0° to ∼19° and that the rates for an armchair edge are faster than those for a zigzag edge. Such edge-structure-dependent growth/etching kinetics of graphene can be well explained at the atomic level based on the concentrations of the kinks on various edges and allow the evolution and control of the edge and morphology in single-crystal graphene following the classical kinetic Wulff construction theory. Using these findings, we propose several strategies for the fabrication of wafer-sized, high-quality, single-crystal graphene.

  14. Monte Carlo simulation of the kinetic effects on GaAs/GaAs(001) MBE growth

    NASA Astrophysics Data System (ADS)

    Ageev, Oleg A.; Solodovnik, Maxim S.; Balakirev, Sergey V.; Mikhaylin, Ilya A.; Eremenko, Mikhail M.

    2017-01-01

    The molecular beam epitaxial growth of GaAs on the GaAs(001)-(2×4) surface is investigated using a kinetic Monte Carlo-based method. The developed algorithm permits to focus on the kinetic effects in a wide range of growth conditions and enables considerable computational speedup. The simulation results show that the growth rate has a dramatic influence upon both the island morphology and Ga surface diffusion length. The average island size reduces with increasing growth rate while the island density increases with increasing growth rate as well as As4/Ga beam equivalent pressure ratio. As the growth rate increases, the island density becomes weaker dependent upon the As4/Ga pressure ratio and approaches to a saturation value. We also discuss three characteristics of Ga surface diffusion, namely a diffusion length of a Ga adatom deposited first, an average diffusion length, and an island spacing as an average distance between islands. The calculations show that the As4/Ga pressure ratio dependences of these characteristics obey the same law, but with different coefficients. An increase of the As4/Ga pressure ratio leads to a decrease in both the diffusion length and island spacing. However, its influence becomes stronger with increasing growth rate for the first Ga adatom diffusion length and weaker for the average diffusion length and for the island spacing.

  15. A Kinetic Model for GaAs Growth by Hydride Vapor Phase Epitaxy

    SciTech Connect

    Schulte, Kevin L.; Simon, John; Jain, Nikhil; Young, David L.; Ptak, Aaron J.

    2016-11-21

    Precise control of the growth of III-V materials by hydride vapor phase epitaxy (HVPE) is complicated by the fact that the growth rate depends on the concentrations of nearly all inputs to the reactor and also the reaction temperature. This behavior is in contrast to metalorganic vapor phase epitaxy (MOVPE), which in common practice operates in a mass transport limited regime where growth rate and alloy composition are controlled almost exclusively by flow of the Group III precursor. In HVPE, the growth rate and alloy compositions are very sensitive to temperature and reactant concentrations, which are strong functions of the reactor geometry. HVPE growth, particularly the growth of large area materials and devices, will benefit from the development of a growth model that can eventually be coupled with a computational fluid dynamics (CFD) model of a specific reactor geometry. In this work, we develop a growth rate law using a Langmuir-Hinshelwood (L-H) analysis, fitting unknown parameters to growth rate data from the literature that captures the relevant kinetic and thermodynamic phenomena of the HVPE process. We compare the L-H rate law to growth rate data from our custom HVPE reactor, and develop quantitative insight into reactor performance, demonstrating the utility of the growth model.

  16. Kinetics of grain-growth in wadsleyite: implications for point defect chemistry

    NASA Astrophysics Data System (ADS)

    Nishihara, Y.; Shinmei, T.; Karato, S.

    2003-12-01

    We investigate the kinetics of grain-growth in wadsleyite for two reasons. First, grain-growth kinetics controls the grain-size of wadsleyite in the mantle transition zone which in turn controls the rheology in that region. Second, the detailed knowledge of grain-growth kinetics will provide us with important constraints on the defect-related properties of this mineral which may control other properties such as diffusion, electrical conductivity and creep. We carried out the grain-growth experiments by using KIWI 1000-ton Kawai-type multi-anvil apparatus installed at Yale University. Starting material was synthesized from powdered San Carlos olivine. The grain-growth experiments were conducted at 15 GPa and 1100-1500° C for 1-24 hours. We used Mo, Ni and Re foil capsules, in order to control the oxygen fugacity by metal-oxide buffer. For ''wet'' experiments (water-saturated), a mixture of talc and brucite was packed into a capsule together with a wadsleyite sample separated by metal foils. We used a Au-Pd outer capsule which is known to be a good barrier for hydrogen diffusion. Water content in each sample was determined after an experiment by FTIR analysis of a doubly polished thin section. Grain-size was measured on a polished section using an intercept method. One of the difficulties in these experiments is to reduce the amount of water in wadsleyite. Even in nominally ''dry'' experiments in which no water is added, a significant amount of water (upto ˜25,000 H/106 Si) was detected, which comes presumably from some components in the sample assembly such as the cement. This water-uptake by wadsleyite can be minimized by surrounding it with a Au-Pd capsule. In this truly ''dry'' sample assembly, the water content of wadsleyite (after an experiment) is reduced to less than ˜100 H/106 Si, a water content similar to typical ''dry'' experiments on olivine. Compared at similar water content, the kinetics of grain-growth in wadsleyite is significantly slower than

  17. A kinetic model to simulate protein crystal growth in an evaporation-based crystallization platform

    SciTech Connect

    Talreja, S.; Kenis, P; Zukoski, C

    2007-01-01

    The quality, size, and number of protein crystals grown under conditions of continuous solvent extraction are dependent on the rate of solvent extraction and the initial protein and salt concentration. An increase in the rate of solvent extraction leads to a larger number of crystals. The number of crystals decreases, however, when the experiment is started with an initial protein concentration that is closer to the solubility boundary. Here we develop a kinetic model capable of predicting changes in the number and size of protein crystals as a function of time under continuous evaporation. Moreover, this model successfully predicts the initial condition of drops that will result in gel formation. We test this model with experimental crystal growth data of hen egg white lysozyme for which crystal nucleation and growth rate parameters are known from other studies. The predicted and observed rates of crystal growth are in excellent agreement, which suggests that kinetic constants for nucleation and crystal growth for different proteins can be extracted by applying a kinetic model in combination with observations from a few evaporation-based crystallization experiments.

  18. 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.

  19. 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.

  20. Growth kinetics of cubic carbide free layers in graded cemented carbides

    NASA Astrophysics Data System (ADS)

    Shi, Liu-Yong; Liu, Yi-Min; Huang, Ji-Hua; Zhang, Shou-Quan; Zhao, Xing-Ke

    2012-01-01

    In order to reveal the formation mechanism of cubic carbide free layers (CCFL), graded cemented carbides with CCFL in the surface zone were fabricated by a one-step sintering procedure in vacuum, and the analysis on microstructure and element distribution were performed by scanning electron microscopy (SEM) and electron probe micro-analyzer (EPMA), respectively. A new physical model and kinetic equation were established based on experimental results. Being different from previous models, this model suggests that nitrogen diffusion outward is only considered as an induction factor, and the diffusion of titanium through liquid phase plays a dominative role. The driving force of diffusion is expressed as the differential value between nitrogen partial pressure and nitrogen equilibrium pressure essentially. Simulation results by the kinetic equation are in good agreement with experimental values, and the effect of process parameters on the growth kinetics of CCFL can also be explained reasonably by the current model.

  1. 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

  2. Metabolism links bacterial biofilms and colon carcinogenesis

    PubMed Central

    Johnson, Caroline H.; Dejea, Christine M.; Edler, David; Hoang, Linh T.; Santidrian, Antonio F.; Felding, Brunhilde H.; Cho, Kevin; Wick, Elizabeth C.; Hechenbleikner, Elizabeth M.; Uritboonthai, Winnie; Goetz, Laura; Casero, Robert A.; Pardoll, Drew M.; White, James R.; Patti, Gary J.; Sears, Cynthia L.; Siuzdak, Gary

    2015-01-01

    SUMMARY Bacterial biofilms in the colon alter the host tissue microenvironment. A role for biofilms in colon cancer metabolism has been suggested but to date has not been evaluated. Using metabolomics, we investigated the metabolic influence that microbial biofilms have on colon tissues and the related occurrence of cancer. Patient-matched colon cancers and histologically normal tissues, with or without biofilms, were examined. We show the upregulation of polyamine metabolites in tissues from cancer hosts with significant enhancement of N1, N12-diacetylspermine in both biofilm positive cancer and normal tissues. Antibiotic treatment, which cleared biofilms, decreased N1, N12-diacetylspermine levels to those seen in biofilm negative tissues, indicating that host cancer and bacterial biofilm structures contribute to the polyamine metabolite pool. These results show that colonic mucosal biofilms alter the cancer metabolome, to produce a regulator of cellular proliferation and colon cancer growth potentially affecting cancer development and progression. PMID:25959674

  3. Metabolism links bacterial biofilms and colon carcinogenesis.

    PubMed

    Johnson, Caroline H; Dejea, Christine M; Edler, David; Hoang, Linh T; Santidrian, Antonio F; Felding, Brunhilde H; Ivanisevic, Julijana; Cho, Kevin; Wick, Elizabeth C; Hechenbleikner, Elizabeth M; Uritboonthai, Winnie; Goetz, Laura; Casero, Robert A; Pardoll, Drew M; White, James R; Patti, Gary J; Sears, Cynthia L; Siuzdak, Gary

    2015-06-02

    Bacterial biofilms in the colon alter the host tissue microenvironment. A role for biofilms in colon cancer metabolism has been suggested but to date has not been evaluated. Using metabolomics, we investigated the metabolic influence that microbial biofilms have on colon tissues and the related occurrence of cancer. Patient-matched colon cancers and histologically normal tissues, with or without biofilms, were examined. We show the upregulation of polyamine metabolites in tissues from cancer hosts with significant enhancement of N(1), N(12)-diacetylspermine in both biofilm-positive cancer and normal tissues. Antibiotic treatment, which cleared biofilms, decreased N(1), N(12)-diacetylspermine levels to those seen in biofilm-negative tissues, indicating that host cancer and bacterial biofilm structures contribute to the polyamine metabolite pool. These results show that colonic mucosal biofilms alter the cancer metabolome to produce a regulator of cellular proliferation and colon cancer growth potentially affecting cancer development and progression.

  4. Analysis of Arabidopsis thaliana root growth kinetics with high temporal and spatial resolution

    PubMed Central

    Yazdanbakhsh, Nima; Fisahn, Joachim

    2010-01-01

    Background Methods exist to quantify the distribution of growth rate over the root axis. However, non-destructive, high-throughput evaluations of total root elongation in controlled environments and the field are lacking in growth studies. A new imaging approach to analyse total root elongation is described. Scope High pixel resolution of the images enables the study of growth in short time intervals and provides high temporal resolution. Using the method described, total root elongation rates are calculated from the displacement of the root tip. Although the absolute root elongation rate changes in response to growth conditions, this set-up enables root growth of Arabidopsis wild-type seedlings to be followed for more than 1 month after germination. The method provides an easy approach to decipher root extension rate and much simpler calculations compared with other methods that use segmental growth to address this question. Conclusions The high temporal resolution allows small modifications of total root elongation growth to be revealed. Furthermore, with the options to investigate growth of various mutants in diverse growth conditions the present tool allows modulations in root growth kinetics due to different biotic and abiotic stimuli to be unravelled. Measurements performed on Arabidopsis thaliana wild-type (Col0) plants revealed rhythms superimposed on root elongation. Results obtained from the starchless mutant pgm, however, present a clearly modified pattern. As expected, deviation is strongest during the dark period. PMID:20421235

  5. 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.

  6. Catastrophic growth of gas hydrates in the presence of kinetic hydrate inhibitors.

    PubMed

    Cha, Minjun; Shin, Kyuchul; Seo, Yutaek; Shin, Ju-Young; Kang, Seong-Pil

    2013-12-27

    The effect of the concentration of kinetic hydrate inhibitors, polyvinylpyrrolidone (PVP), and polyvinylcaprolactam (PVCap) on the onset and growth of synthetic natural gas hydrates is investigated by measuring the hydrate onset time and gas consumption rate. Although the hydrate onset time is extended by increasing the concentration from 0.5 to 3.0 wt % for both PVP and PVCap, the growth rate of hydrates shows that the different tendency depends on the type of kinetic hydrate inhibitor and its concentration. For PVCap solution, the hydrate growth was slow for more than 1000 min after the onset at the concentration of 0.5 and 1.5 wt %. However, the growth rate becames almost 8 times faster at the concentration of 3.0 wt %, representing the catastrophic growth of hydrate just after the hydrate onset. (13)C NMR spectra of hydrates formed at 3.0 wt % of PVP and PVCap indicate the existence of both structures I and II. Cage occupancy of methane in large cages of structure II decreases significantly when compared to that for pure water. These results suggest that increasing the concentration of KHI up to 3.0 wt % may induce the earlier appearance of catastrophic hydrate growth and the existence of metastable structure I; thus, there needs to be an upper limit for using KHI to manage the formation of gas hydrates.

  7. 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.

  8. 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.

  9. 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

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

    2014-07-01

    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.

  10. Quantitative nucleation and growth kinetics of gold nanoparticles via model-assisted dynamic spectroscopic approach.

    PubMed

    Zhou, Yao; Wang, Huixuan; Lin, Wenshuang; Lin, Liqin; Gao, Yixian; Yang, Feng; Du, Mingming; Fang, Weiping; Huang, Jiale; Sun, Daohua; Li, Qingbiao

    2013-10-01

    Lacking of quantitative experimental data and/or kinetic models that could mathematically depict the redox chemistry and the crystallization issue, bottom-to-up formation kinetics of gold nanoparticles (GNPs) remains a challenge. We measured the dynamic regime of GNPs synthesized by l-ascorbic acid (representing a chemical approach) and/or foliar aqueous extract (a biogenic approach) via in situ spectroscopic characterization and established a redox-crystallization model which allows quantitative and separate parameterization of the nucleation and growth processes. The main results were simplified as the following aspects: (I) an efficient approach, i.e., the dynamic in situ spectroscopic characterization assisted with the redox-crystallization model, was established for quantitative analysis of the overall formation kinetics of GNPs in solution; (II) formation of GNPs by the chemical and the biogenic approaches experienced a slow nucleation stage followed by a growth stage which behaved as a mixed-order reaction, and different from the chemical approach, the biogenic method involved heterogeneous nucleation; (III) also, biosynthesis of flaky GNPs was a kinetic-controlled process favored by relatively slow redox chemistry; and (IV) though GNPs formation consists of two aspects, namely the redox chemistry and the crystallization issue, the latter was the rate-determining event that controls the dynamic regime of the whole physicochemical process.

  11. Semirigorous synchronous sublattice algorithm for parallel kinetic Monte Carlo simulations of thin film growth

    NASA Astrophysics Data System (ADS)

    Shim, Yunsic; Amar, Jacques G.

    2005-03-01

    The standard kinetic Monte Carlo algorithm is an extremely efficient method to carry out serial simulations of dynamical processes such as thin film growth. However, in some cases it is necessary to study systems over extended time and length scales, and therefore a parallel algorithm is desired. Here we describe an efficient, semirigorous synchronous sublattice algorithm for parallel kinetic Monte Carlo simulations. The accuracy and parallel efficiency are studied as a function of diffusion rate, processor size, and number of processors for a variety of simple models of epitaxial growth. The effects of fluctuations on the parallel efficiency are also studied. Since only local communications are required, linear scaling behavior is observed, e.g., the parallel efficiency is independent of the number of processors for fixed processor size.

  12. 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.

  13. 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.

  14. Nonlinear Response of Layer Growth Dynamics in the Mixed Kinetics-Bulk-Transport Regime

    NASA Technical Reports Server (NTRS)

    Vekilov, Peter G.; Alexander, J. Iwan D.; Rosenberger, Franz

    1996-01-01

    In situ high-resolution interferometry on horizontal facets of the protein lysozyme reveal that the local growth rate R, vicinal slope p, and tangential (step) velocity v fluctuate by up to 80% of their average values. The time scale of these fluctuations, which occur under steady bulk transport conditions through the formation and decay of step bunches (macrosteps), is of the order of 10 min. The fluctuation amplitude of R increases with growth rate (supersaturation) and crystal size, while the amplitude of the v and p fluctuations changes relatively little. Based on a stability analysis for equidistant step trains in the mixed transport-interface-kinetics regime, we argue that the fluctuations originate from the coupling of bulk transport with nonlinear interface kinetics. Furthermore, step bunches moving across the interface in the direction of or opposite to the buoyancy-driven convective flow increase or decrease in height, respectively. This is in agreement with analytical treatments of the interaction of moving steps with solution flow. Major excursions in growth rate are associated with the formation of lattice defects (striations). We show that, in general, the system-dependent kinetic Peclet number, Pe(sub k) , i.e., the relative weight of bulk transport and interface kinetics in the control of the growth process, governs the step bunching dynamics. Since Pe(sub k) can be modified by either forced solution flow or suppression of buoyancy-driven convection under reduced gravity, this model provides a rationale for the choice of specific transport conditions to minimize the formation of compositional inhomogeneities under steady bulk nutrient crystallization conditions.

  15. Prediction of microbial growth rate versus biomass yield by a metabolic network with kinetic parameters.

    PubMed

    Adadi, Roi; Volkmer, Benjamin; Milo, Ron; Heinemann, Matthias; Shlomi, Tomer

    2012-01-01

    Identifying the factors that determine microbial growth rate under various environmental and genetic conditions is a major challenge of systems biology. While current genome-scale metabolic modeling approaches enable us to successfully predict a variety of metabolic phenotypes, including maximal biomass yield, the prediction of actual growth rate is a long standing goal. This gap stems from strictly relying on data regarding reaction stoichiometry and directionality, without accounting for enzyme kinetic considerations. Here we present a novel metabolic network-based approach, MetabOlic Modeling with ENzyme kineTics (MOMENT), which predicts metabolic flux rate and growth rate by utilizing prior data on enzyme turnover rates and enzyme molecular weights, without requiring measurements of nutrient uptake rates. The method is based on an identified design principle of metabolism in which enzymes catalyzing high flux reactions across different media tend to be more efficient in terms of having higher turnover numbers. Extending upon previous attempts to utilize kinetic data in genome-scale metabolic modeling, our approach takes into account the requirement for specific enzyme concentrations for catalyzing predicted metabolic flux rates, considering isozymes, protein complexes, and multi-functional enzymes. MOMENT is shown to significantly improve the prediction accuracy of various metabolic phenotypes in E. coli, including intracellular flux rates and changes in gene expression levels under different growth rates. Most importantly, MOMENT is shown to predict growth rates of E. coli under a diverse set of media that are correlated with experimental measurements, markedly improving upon existing state-of-the art stoichiometric modeling approaches. These results support the view that a physiological bound on cellular enzyme concentrations is a key factor that determines microbial growth rate.

  16. Linking genes to microbial growth kinetics: an integrated biochemical systems engineering approach.

    PubMed

    Koutinas, Michalis; Kiparissides, Alexandros; Silva-Rocha, Rafael; Lam, Ming-Chi; Martins Dos Santos, Vitor A P; de Lorenzo, Victor; Pistikopoulos, Efstratios N; Mantalaris, Athanasios

    2011-07-01

    The majority of models describing the kinetic properties of a microorganism for a given substrate are unstructured and empirical. They are formulated in this manner so that the complex mechanism of cell growth is simplified. Herein, a novel approach for modelling microbial growth kinetics is proposed, linking biomass growth and substrate consumption rates to the gene regulatory programmes that control these processes. A dynamic model of the TOL (pWW0) plasmid of Pseudomonas putida mt-2 has been developed, describing the molecular interactions that lead to the transcription of the upper and meta operons, known to produce the enzymes for the oxidative catabolism of m-xylene. The genetic circuit model was combined with a growth kinetic model decoupling biomass growth and substrate consumption rates, which are expressed as independent functions of the rate-limiting enzymes produced by the operons. Estimation of model parameters and validation of the model's predictive capability were successfully performed in batch cultures of mt-2 fed with different concentrations of m-xylene, as confirmed by relative mRNA concentration measurements of the promoters encoded in TOL. The growth formation and substrate utilisation patterns could not be accurately described by traditional Monod-type models for a wide range of conditions, demonstrating the critical importance of gene regulation for the development of advanced models closely predicting complex bioprocesses. In contrast, the proposed strategy, which utilises quantitative information pertaining to upstream molecular events that control the production of rate-limiting enzymes, predicts the catabolism of a substrate and biomass formation and could be of central importance for the design of optimal bioprocesses.

  17. 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.

  18. Synthesis and characterization of lipophilic bismuth dimercaptopropanol nanoparticles and their effects on oral microorganisms growth and biofilm formation

    NASA Astrophysics Data System (ADS)

    Badireddy, Appala Raju; Hernandez-Delgadillo, Rene; Sánchez-Nájera, Rosa Isela; Chellam, Shankararaman; Cabral-Romero, Claudio

    2014-06-01

    The increasing prevalence of resistance among pathogenic microorganisms to common antibiotics has become one of the most significant concerns in modern medicine. Nanotechnology offers a new alternative to develop materials with interesting applications in many areas of biological sciences and medicine. While some bismuth derivatives have been employed to treat vomiting, nausea, diarrhea, and stomach pain, the antimicrobial properties of bismuth in its nanoparticulate form have not been extensively studied. The objective of this investigation was to analyze the bactericidal, fungicidal, and antibiofilm activities of bismuth dimercaptopropanol nanoparticles (BisBAL NPs) against oral microbes. The nanoparticles are composed of 18.7 nm crystallites on average and have a rhombohedral structure, agglomerating into chains-like or clusters of small nanoparticles. Our results showed that stable colloidal BisBAL NPs inhibited Streptococcus mutans and Streptococcus gordonii growth by more than 70 % at 0.1 µM, showing a twelve thousand fold higher effectiveness compared with 1.2 mM chlorhexidine, the oral antiseptic most used by dentists. The minimal inhibitory concentration (MIC) of BisBAL NPs for S. mutans and S. gordonii was 5 µM. MIC of BisBAL NPs for Candida albicans was 10 µM. However, 100 µM of BisBAL NPs were required to interfere with planktonic growth of and biofilm formation by a multi-species population of bacteria. Our experiments show that bactericidal activity of BisBAL NPs was similar to antibiotics such as vancomycin and rifampicin. Based on MTT cell viability assays, we hypothesize that BisBAL NPs potentially act on key enzymes, altering their metabolism, and cause cell lysis. All together, these findings show the efficacy of BisBAL NPs as a broad spectrum antimicrobial agent which could reduce antibiotic usage.

  19. In situ biofilm coupon device

    DOEpatents

    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.

  20. 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.

  1. Growth kinetics of biopigment production by Thai isolated Monascus purpureus in a stirred tank bioreactor.

    PubMed

    Kongruang, Sasithorn

    2011-01-01

    Monascus purpureus is a biopigment-producing fungi whose pigments can be used in many biotechnological and food industries. The growth kinetics of biopigment production were investigated in a liquid fermentation medium in a 5-l stirred tank bioreactor at 30°C, pH 7, for 8 days with 100 rpm agitation and 1.38 × 10(5) N/m(2) aeration. Thai Monascus purpureus strains TISTR 3002, 3180, 3090 and 3385 were studied for color production, growth kinetics and productivity. Citrinin as a toxic metabolite was measured from the Monascus fermentation broth. The biopigment productions were detected from fermentation broth by scanning spectra of each strain produced. Results showed a mixture of yellow, orange and red pigments with absorption peaks of pigments occurring at different wavelengths for the four strains. It was found that for each pigment color, the color production from the strains increased in the order TISTR 3002, 3180, 3090, 3385 with 3385 production being approximately 10 times that of 3002. Similar results were found for growth kinetics and productivity. HPLC results showed that citrinin was not produced under the culture conditions of this study. The L*, a* and b* values of the CIELAB color system were also obtained for the yellow, orange and red pigments produced from the TISTR 3002, 3180, 3090 and 3385 strains. The colors of the pigments ranged from burnt umber to deep red.

  2. 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

  3. 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.

  4. Medical Biofilms

    PubMed Central

    2009-01-01

    For more than two decades, Biotechnology and Bioengineering has documented research focused on natural and engineered microbial biofilms within aquatic and subterranean ecosystems, wastewater and waste-gas treatment systems, marine vessels and structures, and industrial bioprocesses. Compared to suspended culture systems, intentionally engineered biofilms are heterogeneous reaction systems that can increase reactor productivity, system stability, and provide inherent cell: product separation. Unwanted biofilms can create enormous increases in fluid frictional resistances, unacceptable reductions in heat transfer efficiency, product contamination, enhanced material deterioration, and accelerated corrosion. Missing from B&B has been an equivalent research dialogue regarding the basic molecular microbiology, immunology, and biotechnological aspects of medical biofilms. Presented here are the current problems related to medical biofilms; current concepts of biofilm formation, persistence, and interactions with the host immune system; and emerging technologies for controlling medical biofilms. PMID:18366134

  5. Relative performance of biofilm configuration over suspended growth operation on azo dye based wastewater treatment in periodic discontinuous batch mode operation.

    PubMed

    Mohan, S Venkata; Reddy, C Nagendranatha; Kumar, A Naresh; Modestra, J Annie

    2013-11-01

    Functional role of biofilm and suspended growth bioreactor configurations in response to the treatment of azo-dye (C.I. Acid Black 10B) bearing wastewater was evaluated in periodic discontinuous batch mode operation at varying dye concentrations. The biofilm system depicted higher dye removal efficiency (93.14%) compared to suspended mode (84.29%) at 350 mg dye/l operation. Both the reactor configurations did not show much process inhibition at higher dye loads studied. Azo reductase and dehydrogenase enzyme activities showed significant variation indicating the different metabolic capabilities of the native-microflora, stable proton shuttling between metabolic intermediates and differences in the delivery of reducing powers from the substrate metabolism towards dye removal. Voltammograms visualized marked variations in electron discharge properties with the function of reactor configuration, time intervals and dye load. Higher redox catalytic currents, lower Tafel slopes and polarization resistance showed good correlation with enzyme activities and dye removal.

  6. Kinetic simulation of filament growth dynamics in memristive electrochemical metallization devices

    NASA Astrophysics Data System (ADS)

    Dirkmann, Sven; Ziegler, Martin; Hansen, Mirko; Kohlstedt, Hermann; Trieschmann, Jan; Mussenbrock, Thomas

    2015-12-01

    In this work, we report on kinetic Monte-Carlo calculations of resistive switching and the underlying growth dynamics of filaments in an electrochemical metallization device consisting of an Ag/TiO2/Pt sandwich-like thin film system. The developed model is not limited to (i) fast time scale dynamics and (ii) only one growth and dissolution cycle of metallic filaments. In particular, we present results from the simulation of consecutive cycles. We find that the numerical results are in excellent agreement with experimentally obtained data. Additionally we observe an unexpected filament growth mode that is in contradiction to the widely acknowledged picture of filament growth but consistent with recent experimental findings.

  7. In situ X-ray diffraction study on the growth kinetics of NiO nanoparticles.

    PubMed

    Meneses, C T; Almeida, J M A; Sasaki, J M

    2010-05-01

    The growth kinetics of NiO nanoparticles have been studied by in situ X-ray diffraction using two detection systems (conventional and imaging plate). NiO nanoparticles were formed by thermal decomposition after heating of an amorphous compound formed by the coprecipitation method. It was found that the detection method using an imaging plate is more efficient than the conventional detection mode for observing changes in the crystallite growth of nanocrystalline materials. Studies have been carried out to investigate the effects of the heating rates on the particles growth. The results suggest that the growth process of the particles is accelerated when the samples are treated at low heating rates. The evolution of particles size and the diffusion coefficient obtained from X-ray powder diffraction patterns are discussed in terms of the thermal conditions for the two types of detection.

  8. 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.

  9. A photosynthetic rotating annular bioreactor (Taylor-Couette type flow) for phototrophic biofilm cultures.

    PubMed

    Paule, A; Lauga, B; Ten-Hage, L; Morchain, J; Duran, R; Paul, E; Rols, J L

    2011-11-15

    In their natural environment, the structure and functioning of microbial communities from river phototrophic biofilms are driven by biotic and abiotic factors. An understanding of the mechanisms that mediate the community structure, its dynamics and the biological succession processes during phototrophic biofilm development can be gained using laboratory-scale systems operating with controlled parameters. For this purpose, we present the design and description of a new prototype of a rotating annular bioreactor (RAB) (Taylor-Couette type flow, liquid working volume of 5.04 L) specifically adapted for the cultivation and investigation of phototrophic biofilms. The innovation lies in the presence of a modular source of light inside of the system, with the biofilm colonization and development taking place on the stationary outer cylinder (onto 32 removable polyethylene plates). The biofilm cultures were investigated under controlled turbulent flowing conditions and nutrients were provided using a synthetic medium (tap water supplemented with nitrate, phosphate and silica) to favour the biofilm growth. The hydrodynamic features of the water flow were characterized using a tracer method, showing behaviour corresponding to a completely mixed reactor. Shear stress forces on the surface of plates were also quantified by computer simulations and correlated with the rotational speed of the inner cylinder. Two phototrophic biofilm development experiments were performed for periods of 6.7 and 7 weeks with different inoculation procedures and illumination intensities. For both experiments, biofilm biomasses exhibited linear growth kinetics and produced 4.2 and 2.4 mg cm(-)² of ash-free dry matter. Algal and bacterial community structures were assessed by microscopy and T-RFLP, respectively, and the two experiments were different but revealed similar temporal dynamics. Our study confirmed the performance and multipurpose nature of such an innovative photosynthetic bioreactor

  10. Altered Cellular Kinetics in Growth Plate according to Alterations in Weight Bearing

    PubMed Central

    Park, Hoon; Kong, Sun Young; Kim, Hyun Woo

    2012-01-01

    Purpose To examine the effects of change in weight bearing on the growth plate metabolism, a simulated animal model of weightlessness was introduced and the chondrocytes' cellular kinetics was evaluated. Materials and Methods Unloading condition on the hind-limb of Sprague-Dawley rats was created by fixing a tail and lifting the hind-limb. Six rats aged 6 weeks old were assigned to each group of unloading, reloading, and control groups of unloading or reloading. Unloading was maintained for three weeks, and then reloading was applied for another one week thereafter. Histomorphometry for the assessment of vertical length of the growth plate, 5-bromo-2'-deoxyuridin immunohistochemistry for cellular kinetics, and biotin nick end labeling transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) assay for chondrocytes apoptosis in the growth plate were performed. Results The vertical length of the growth plate and the proliferative potential of chondrocytes were decreased in the unloading group compared to those of control groups. Inter-group differences were more significant in the proliferative and hypertrophic zones. Reloading increased the length of growth plate and proliferative potential of chondrocytes. However, apoptotic changes in the growth plate were not affected by the alterations of weight bearing. Conclusion Alterations in the weight bearing induced changes in the chondrocytic proliferative potential of the growth plate, however, had no effects on the apoptosis. This may explain why non-weight bearing in various clinical situations hampers normal longitudinal bone growth. Further studies on the factors for reversibility of chondrocytic proliferation upon variable mechanical stresses are needed. PMID:22477008

  11. 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.

  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.

  13. Release kinetics of platelet-derived and plasma-derived growth factors from autologous plasma rich in growth factors.

    PubMed

    Anitua, Eduardo; Zalduendo, Mari Mar; Alkhraisat, Mohammad Hamdan; Orive, Gorka

    2013-10-01

    Many studies have evaluated the biological effects of platelet rich plasma reporting the final outcomes on cell and tissues. However, few studies have dealt with the kinetics of growth factor delivery by plasma rich in growth factors. Venous blood was obtained from three healthy volunteers and processed with PRGF-Endoret technology to prepare autologous plasma rich in growth factors. The gel-like fibrin scaffolds were then incubated in triplicate, in a cell culture medium to monitor the release of PDGF-AB, VEGF, HGF and IGF-I during 8 days of incubation. A leukocyte-platelet rich plasma was prepared employing the same technology and the concentrations of growth factors and interleukin-1β were determined after 24h of incubation. After each period, the medium was collected, fibrin clot was destroyed and the supernatants were stored at -80°C until analysis. The growth factor delivery is diffusion controlled with a rapid initial release by 30% of the bioactive content after 1h of incubation and a steady state release when almost 70% of the growth factor content has been delivered. Autologous fibrin matrix retained almost 30% of the amount of the growth factors after 8 days of incubation. The addition of leukocytes to the formula of platelet rich plasma did not increase the concentration of the growth factors, while it drastically increased the presence of pro-inflammatory IL-1β. Further studies employing an in vitro inflammatory model would be interesting to study the difference in growth factors and pro-inflammatory cytokines between leukocyte-free and leukocyte-rich platelet rich plasma.

  14. Altered hypertrophic chondrocyte kinetics in GDF-5 deficient murine tibial growth plates.

    PubMed

    Mikic, B; Clark, R T; Battaglia, T C; Gaschen, V; Hunziker, E B

    2004-05-01

    The growth/differentiation factors (GDFs) are a subgroup of the bone morphogenetic proteins best known for their role in joint formation and chondrogenesis. Mice deficient in one of these signaling proteins, GDF-5, exhibit numerous skeletal abnormalities, including shortened limb bones. The primary aim of this study was determine whether GDF-5 deficiency would alter the growth rate in growth plates from the long bones in mice and, if so, how this is achieved. Stereologic and cell kinetic parameters in proximal tibial growth plates from 5-week-old female GDF-5 -/- mice and control littermates were examined. GDF-5 deficiency resulted in a statistically significant reduction in growth rate (-14%, p=0.03). The effect of genotype on growth rate was associated with an altered hypertrophic phase duration, with hypertrophic cells from GDF-5 deficient mice exhibiting a significantly longer phase duration compared to control littermates (+25%, p=0.006). These data suggest that one way in which GDF-5 might modulate the rate of endochondral bone growth could be by affecting the duration of the hypertrophic phase in growth plate chondrocytes.

  15. Integrating carbon nanotube forests into polysilicon MEMS: Growth kinetics, mechanisms, and adhesion

    SciTech Connect

    Ubnoske, Stephen M.; Radauscher, Erich J.; Meshot, Eric R.; Stoner, Brian R.; Parker, Charles B.; Glass, Jeffrey T.

    2016-11-19

    The growth of carbon nanotubes (CNTs) on polycrystalline silicon substrates was studied to improve the design of CNT field emission sources for microelectromechanical systems (MEMS) applications and vacuum microelectronic devices (VMDs). Microwave plasma-enhanced chemical vapor deposition (PECVD) was used for CNT growth, resulting in CNTs that incorporate the catalyst particle at their base. The kinetics of CNT growth on polysilicon were compared to growth on Si (100) using the model of Deal and Grove, finding activation energies of 1.61 and 1.54 eV for the nucleation phase of growth and 1.90 and 3.69 eV for the diffusion-limited phase on Si (100) and polysilicon, respectively. Diffusivity values for growth on polysilicon were notably lower than the corresponding values on Si (100) and the growth process became diffusion-limited earlier. Evidence favors a surface diffusion growth mechanism involving diffusion of carbon precursor species along the length of the CNT forest to the catalyst at the base. Explanations for the differences in activation energies and diffusivities were elucidated by SEM analysis of the catalyst nanoparticle arrays and through wide-angle X-ray scattering (WAXS) of CNT forests. As a result, methods are presented to improve adhesion of CNT films during operation as field emitters, resulting in a 2.5× improvement.

  16. Integrating carbon nanotube forests into polysilicon MEMS: Growth kinetics, mechanisms, and adhesion

    DOE PAGES

    Ubnoske, Stephen M.; Radauscher, Erich J.; Meshot, Eric R.; ...

    2016-11-19

    The growth of carbon nanotubes (CNTs) on polycrystalline silicon substrates was studied to improve the design of CNT field emission sources for microelectromechanical systems (MEMS) applications and vacuum microelectronic devices (VMDs). Microwave plasma-enhanced chemical vapor deposition (PECVD) was used for CNT growth, resulting in CNTs that incorporate the catalyst particle at their base. The kinetics of CNT growth on polysilicon were compared to growth on Si (100) using the model of Deal and Grove, finding activation energies of 1.61 and 1.54 eV for the nucleation phase of growth and 1.90 and 3.69 eV for the diffusion-limited phase on Si (100)more » and polysilicon, respectively. Diffusivity values for growth on polysilicon were notably lower than the corresponding values on Si (100) and the growth process became diffusion-limited earlier. Evidence favors a surface diffusion growth mechanism involving diffusion of carbon precursor species along the length of the CNT forest to the catalyst at the base. Explanations for the differences in activation energies and diffusivities were elucidated by SEM analysis of the catalyst nanoparticle arrays and through wide-angle X-ray scattering (WAXS) of CNT forests. As a result, methods are presented to improve adhesion of CNT films during operation as field emitters, resulting in a 2.5× improvement.« less

  17. 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.

  18. 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. ...

  19. Role of Step and Terrace Nucleation in Heteroepitaxial Growth Morphology: Growth Kinetics of CaF2/Si(111)

    NASA Astrophysics Data System (ADS)

    Hessinger, Uwe; Leskovar, M.; Olmstead, Marjorie A.

    1995-09-01

    The thickness uniformity and the spatial distribution of lattice relaxation in thin ( <8 nm) CaF2/Si(111) films, observed with photoelectron spectroscopy and transmission electron microscopy, are seen to depend strongly on the initial nucleation kinetics. We develop a general model for heteroepitaxial growth that explains both these and literature results. Terrace or step nucleation leads to laminar films, although with different relaxation patterns; combined step and terrace nucleation leads to rough films due to different upper-layer nucleation rates on the differently sized islands.

  20. Temperature-dependent growth kinetics of Escherichia coli ML 30 in glucose-limited continuous culture.

    PubMed Central

    Kovárová, K; Zehnder, A J; Egli, T

    1996-01-01

    Detailed comparison of growth kinetics at temperatures below and above the optimal temperature was carried out with Escherichia coli ML 30 (DSM 1329) in continuous culture. The culture was grown with glucose as the sole limiting source of carbon and energy (100 mg liter(-1) in feed medium), and the resulting steady-state concentrations of glucose were measured as a function of the dilution rate at 17.4, 28.4, 37, and 40 degrees C. The experimental data could not be described by the conventional Monod equation over the entire temperature range, but an extended form of the Monod model [mu = mu(max) x (s - s(min))/(Ks + s - s(min))], which predicts a finite substrate concentration at 0 growth rate (s(min)), provided a good fit. The two parameters mu(max) and s(min) were temperature dependent, whereas, surprisingly, fitting the model to the experimental data yielded virtually identical Ks values (approximately 33 microg liter(-1)) at all temperatures. A model that describes steady-state glucose concentrations as a function of temperature at constant growth rates is presented. In similar experiments with mixtures of glucose and galactose (1:1 mixture), the two sugars were utilized simultaneously at all temperatures examined, and their steady-state concentrations were reduced compared with to growth with either glucose or galactose alone. The results of laboratory-scale kinetic experiments are discussed with respect to the concentrations observed in natural environments. PMID:8755881

  1. Crystal growth kinetics in Lennard-Jones and Weeks-Chandler-Andersen systems along the solid-liquid coexistence line.

    PubMed

    Benjamin, Ronald; Horbach, Jürgen

    2015-07-07

    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.

  2. 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...

  3. 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

  4. 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

  5. Presence of extracellular DNA in the Candida albicans biofilm matrix and its contribution to biofilms.

    PubMed

    Martins, Margarida; Uppuluri, Priya; Thomas, Derek P; Cleary, Ian A; Henriques, Mariana; Lopez-Ribot, José L; Oliveira, Rosário

    2010-05-01

    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.

  6. A mathematical model of the kinetics of beta-amyloid fibril growth from the denatured state.

    PubMed Central

    Pallitto, M M; Murphy, R M

    2001-01-01

    Spontaneous conversion of beta-amyloid peptide (Abeta) from soluble monomer to insoluble fibril may underlie the neurodegeneration associated with Alzheimer's disease. A complete description of Abeta self-association kinetics requires identification of the oligomeric species present and the pathway of association, as well as quantitation of rate constants and reaction order. Abeta was rendered monomeric and denatured by dissolution in 8 M urea, pH 10. "Refolding" and fibrillization were initiated by rapid dilution into phosphate-buffered saline, pH 7.4. The kinetics of growth were followed at three different concentrations, using size exclusion chromatography, dynamic light scattering, and static light scattering. A multi-step pathway for fibril formation and growth was postulated. This pathway included 1) rapid commitment to either stable monomer/dimer or unstable intermediate, 2) cooperative association of intermediate into a multimeric "nucleus," 3) elongation of the "nucleus" into filaments via addition of intermediate, 4) lateral aggregation of filaments into fibrils, and 5) fibril elongation via end-to-end association. Differential and algebraic equations describing this kinetic pathway were derived, and model parameters were determined by fitting the data. The utility of the model for identifying toxic Abeta oligomeric specie(s) is demonstrated. The model should prove useful for designing compounds that inhibit Abeta aggregation and/or toxicity. PMID:11509390

  7. Theoretical consideration of the growth kinetics for GaAs and GaSb

    NASA Astrophysics Data System (ADS)

    Kaneko, T.; Asahi, H.; Gonda, S.

    1992-05-01

    An extended MOMBE growth kinetics model is proposed, based on the Robertson model, to explain both the GaAs growth rate variation and modulated beam mass spectroscopy data reported by Martin and Whitehouse. In this model, we assume that (1) MEGa molecules react with ethyl-radicals to form DEGa, (2) excessive group-V molecules on the surface suppress the decomposition of DEGa and enhance the desorption of DEGa, (3) reaction of DEGa with ethyl-radicals to form TEGa is negligible, and (4) effective surface coverage of excessive group-V atoms during growth is determined by the double layer adsorption model including desorption parameters for group-V molecules. The first assumption (1) is found to be a dominant process to explain the behaviour of DEGa desorption at high temperatures. This model can reproduce the dependences of both growth rate and desorbing rate of Ga alkyls on substrate temperature during GaAs MOMBE growth. The use of Sb instead of As produces a significant change in the growth rate variation with substrate temperature and group-V flux for the growth of GaSb, in spite of the use of the same TEGa flow rate. This can be rationalized by the difference in the desorption parameters for Sb and As.

  8. 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.

  9. 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.

  10. Nucleation and growth kinetics of struvite in a fluidized bed reactor

    NASA Astrophysics Data System (ADS)

    Bhuiyan, M. Iqbal H.; Mavinic, D. S.; Beckie, R. D.

    2008-03-01

    Kinetics of struvite crystallization were studied to gain a better understanding of intentional struvite formation in fluidized bed reactors. Mechanisms controlling nucleation were studied in the laboratory by induction time experiments. pH monitoring proved to be an effective method of induction time determination, during the induction period. The induction period, when nucleation was the controlling process for struvite crystal formation, was found to be primarily reaction controlled, with minor transport influence. The metastable region for struvite was explored in this study. The solubility and supersolubility curves, which are the boundaries of the metastable region, were observed to be almost parallel straight lines in the concentration range studied. The growth rate of struvite determined in a fluidized bed reactor was mainly transport controlled. With the determination of the mass-transfer coefficient and surface-reaction coefficient for a specified condition, a two-step linear growth rate model for struvite growth determination in a fluidized bed reactor has been proposed.

  11. 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

    Van Mooy, Benjamin A S; Hmelo, Laura R; Fredricks, Helen F; Ossolinski, Justin E; Pedler, Byron E; Bogorff, Daniel J; Smith, Peter J S

    2014-02-01

    The accumulation of microbial biofilms on ships' hulls negatively affects ship performance and efficiency while also playing a role in 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 (AF) or polymer-based fouling-release (FR) 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 FR 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 the accumulation of microbial biofilm on coatings designed for ships' hulls.

  12. 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

  13. Flux balancing of light and nutrients in a biofilm photobioreactor for maximizing photosynthetic productivity.

    PubMed

    Murphy, Thomas E; Berberoglu, Halil

    2014-01-01

    This article reports a combined experimental and numerical study on the efficient operation of Porous Substrate Bioreactors. A comprehensive model integrating light transport, mass transport, and algal growth kinetics was used to understand the productivity of photosynthetic biofilms in response to delivery rates of photons and nutrients. The reactor under consideration was an evaporation driven Porous Substrate Bioreactor (PSBR) cultivating the cyanobacteria Anabaena variabilis as a biofilm on a porous substrate which delivers water and nutrients to the cells. In an unoptimized experimental case, this reactor was operated with a photosynthetic efficiency of 2.3%, competitive with conventional photobioreactors. Moreover, through a scaling analysis, the location at which the phosphate delivery rate decreased the growth rate to half of its uninhibited value was predicted as a function of microorganism and bioreactor properties. The numerical model along with the flux balancing techniques presented herein can serve as tools for designing and selecting operating parameters of biofilm based cultivation systems for maximum productivity.

  14. 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.

  15. Altered Cellular Kinetics in the Growth Plate of the Femoral Head of Spontaneously Hypertensive Rats

    PubMed Central

    Park, Hoon; Kong, Sun Young

    2012-01-01

    Purpose Pathologic changes in the growth plate remain unknown in Legg-Calvé-Perthes (LCP) disease. Spontaneously hypertensive rats have proven to be a good model for studying LCP disease. This study investigated the histopathologic changes and the expression of vascular endothelial growth factor in the growth plate of spontaneously hypertensive rats (SHR). Materials and Methods Sixty SHR rats were divided into two groups: those showing osteonecrosis (SHR+n group: 32), and those showing normal ossification (SHR-n group: 28). Thirty Wister Kyoto rats served as a control. For histomorphological measurement, the length of each zone of the growth plate was measured. Cell kinetics was measured by 5-bromo-2'-deoxyuridin (BrdU) immunohistochemistry and transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) assays. Vascular endothelial growth factor (VEGF) immunohistochemistry was used to identify of expression of VEGF. Results The lengths of growth plates of the SHR+n group were significantly shorter in the initial growth period than those of the other groups. The lowest proliferative rate and the highest apoptosis rate were observed in the SHR+n group at the initial growth period. The expression of VEGF in the growth plate of the SHR group was lower than the control group, and it was lower in the SHR+n group than in the SHR-n group. Conclusion The growth plate of the SHR+n group was found to be affected by disease process of ischemic necrosis of the femoral head, and this might explain the relative overgrowth of the greater trochanter in the later stages of LCP disease. PMID:22477009

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

    PubMed

    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.

  17. Candida Biofilms: Development, Architecture, and Resistance.

    PubMed

    Chandra, Jyotsna; Mukherjee, Pranab K

    2015-08-01

    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.

  18. 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

  19. Kinetics of gypsum nucleation and crystal growth from Dead Sea brine

    NASA Astrophysics Data System (ADS)

    Reznik, Itay J.; Gavrieli, Ittai; Ganor, Jiwchar

    2009-10-01

    The Dead Sea brine is supersaturated with respect to gypsum ( Ω = 1.42). Laboratory experiments and evaluation of historical data show that gypsum nucleation and crystal growth kinetics from Dead Sea brine are both slower in comparison with solutions at a similar degree of supersaturation. The slow kinetics of gypsum precipitation in the Dead Sea brine is mainly attributed to the low solubility of gypsum which is due to the high Ca 2+/SO 42- molar ratio (115), high salinity (˜280 g/kg) and to Na + inhibition. Experiments with various clay minerals (montmorillonite, kaolinite) indicate that these minerals do not serve as crystallization seeds. In contrast, calcite and aragonite which contain traces of gypsum impurities do prompt precipitation of gypsum but at a considerable slower rate than with pure gypsum. This implies that transportation inflow of clay minerals, calcite and local crystallization of minerals in the Dead Sea does not prompt significant heterogeneous precipitation of gypsum. Based on historical analyses of the Dead Sea, it is shown that over the last decades, as inflows to the lake decreased and its salinity increased, gypsum continuously precipitated from the brine. The increasing salinity and Ca 2+/SO 42- ratio, which results from the precipitation of gypsum, lead to even slower kinetics of nucleation and crystal growth, which resulted in an increasing degree of supersaturation with respect to gypsum. Therefore, we predict that as the salinity of the Dead Sea brine continues to increase (accompanied by Dead Sea water level decline), although gypsum will continuously precipitate, the degree of supersaturation will increase furthermore due to progressively slower kinetics.

  20. Does viscosity describe the kinetic barrier for crystal growth from the liquidus to the glass transition?

    PubMed

    Nascimento, Marcio Luis Ferreira; Zanotto, Edgar Dutra

    2010-11-07

    An analysis of the kinetic coefficient of crystal growth U(kin), recently proposed by Ediger et al. [J. Chem. Phys. 128, 034709 (2008)], indicates that the Stokes-Einstein/Eyring (SE/E) equation does not describe the diffusion process controlling crystal growth rates in fragile glass-forming liquids. U(kin) was defined using the normal growth model and tested for crystal data for inorganic and organic liquids covering a viscosity range of about 10(4)-10(12) Pa  s. Here, we revisit their interesting finding considering two other models: the screw dislocation (SD) and the two-dimensional surface nucleated (2D) growth models for nine undercooled oxide liquids, in a wider temperature range, from slightly below the melting point down to the glass transition region T(g), thus covering a wider viscosity range: 10(1)-10(13) Pa  s. We then propose and use normalized kinetic coefficients (M(kin)) for the SD and 2D growth models. These new kinetic coefficients restore the ability of viscosity to describe the transport part of crystal growth rates (M(kin)∼1/η and ξ∼1) from low to moderate viscosities (η<10(6) Pa  s), and thus the SE/E equation works well in this viscosity range for all systems tested. For strong glasses, the SE/E equation works well from low to high viscosities, from the melting point down to T(g)! However, for at least three fragile liquids, diopside (kink at 1.08T(g), η=1.6×10(8) Pa  s), lead metasilicate (kink at 1.14T(g), η=4.3×10(6) Pa  s), and lithium disilicate (kink at 1.11T(g), η=1.6×10(8) Pa  s), there are clear signs of a breakdown of the SE/E equation at these higher viscosities. Our results corroborate the findings of Ediger et al. and demonstrate that viscosity data cannot be used to describe the transport part of the crystal growth (via the SE/E equation) in fragile glasses in the neighborhood of T(g).

  1. Acoustic vibration can enhance bacterial biofilm formation.

    PubMed

    Murphy, Mark F; Edwards, Thomas; Hobbs, Glyn; Shepherd, Joanna; Bezombes, Frederic

    2016-12-01

    This paper explores the use of low-frequency-low-amplitude acoustic vibration on biofilm formation. Biofilm development is thought to be governed by a diverse range of environmental signals and much effort has gone into researching the effects of environmental factors including; nutrient availability, pH and temperature on the growth of biofilms. Many biofilm-forming organisms have evolved to thrive in mechanically challenging environments, for example soil yet, the effects of the physical environment on biofilm formation has been largely ignored. Exposure of Pseudomonas aeruginosa to vibration at 100, 800 and 1600 Hz for 48 h, resulted in a significant increase in biofilm formation compared with the control, with the greatest growth seen at 800 Hz vibration. The results also show that this increase in biofilm formation is accompanied with an increase in P. aeruginosa cell number. Acoustic vibration was also found to regulate the spatial distribution of biofilm formation in a frequency-dependent manner. Exposure of Staphylococcus aureus to acoustic vibration also resulted in enhanced biofilm formation with the greatest level of biofilm being formed following 48 h exposure at 1600 Hz. These results show that acoustic vibration can be used to control biofilm formation and therefore presents a novel and potentially cost effective means to manipulate the development and yield of biofilms in a range of important industrial and medical processes.

  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.

  3. Relationship between grain boundary complexion and grain growth kinetics in alumina

    NASA Astrophysics Data System (ADS)

    Dillon, Shen J.

    2007-12-01

    This work investigated the effect of different grain boundary phases (complexions) on the grain growth kinetics of doped and undoped aluminas. This was achieved by relating quantitative grain growth kinetics to high-resolution electron microscopy of the grain boundaries. It was found that there are 6 different regimes into which the grain growth kinetics may be categorized. These regimes corresponded to the existence of six different grain boundary complexions. Grain boundaries in alumina were observed to show sub-monolayer adsorption, 'clean' intrinsic behavior, bilayer adsorption, multilayer adsorption, equilibrium thickness intergranular films, and wetting intergranular films. These different grain boundary types are listed in order of increasing grain boundary mobility. In general there is an increase in grain boundary mobility with an increase in the disorder within the core of the grain boundary. This broad range of grain boundaries produces a multiplicity of different microstructural effects that until now have been difficult to understand experimentally or theoretically. For example, abnormal grain growth in alumina simply results from the coexistence of two or more different complexions within the same microstructure. Therefore, there may be multiple distinct types of normal and abnormal grain growth behavior. Transitions from one type of boundary to another are chemically and thermally activated, and depend on the crystallography of the adjacent grains. It is found that the number of transitions that occur increases linearly with increasing grain size, and exponentially with temperature. In this regard, different dopants produce very different effects, which appear to be the major role of most dopants in affecting the grain boundary transport kinetics. Low energy planes and grain boundaries are the least likely to undergo such transitions. This experimental data compliments some theoretical derivations within the literature and has provided new insight

  4. Correlation between former alpha boundary growth kinetics and superplastic flow in Zn-22 pct Al

    SciTech Connect

    Yousefiani, A.; Mohamed, F.A.

    2000-01-01

    Former {alpha} boundaries (F{alpha}Bs) are residual grain boundaries that develop in Zn-22 pct Al during a heat treatment, which is normally applied to produce the fine structure necessary for micrograin superplasticity. They represent domains consisting of fine elongated {alpha} grains, which encompass groups of fine {alpha} (Al-rich) and {beta} (Zn-rich) phases (the superplastic microstructure). The results of a detailed investigation conducted on F{alpha}B growth kinetics in five grades of Zn-22 pct Al with various impurity contents reveal a direct correspondence between the level of impurities in the alloy and the characteristics associated with F{alpha}Bs (average size of F{alpha}Bs and the value of the F{alpha} B growth exponent). This correspondence, which, according to available evidence, is the result of impurity segregation at F{alpha}Bs, lends strong support to the interpretation of superplastic behavior at low stresses in terms of phenomena arising from boundary segregation. It is suggested that information on F{alpha}B growth kinetics in Zn-22 pct Al can be utilized to predict the low-stress superplastic characteristics of the alloy, such as the existence of region 1 or the occurrence of extensive cavitation.

  5. From atoms to layers: in situ gold cluster growth kinetics during sputter deposition.

    PubMed

    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

    2013-06-07

    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.

  6. Model-driven experimental evaluation of struvite nucleation, growth and aggregation kinetics.

    PubMed

    Galbraith, S C; Schneider, P A; Flood, A E

    2014-06-01

    Nutrient stewardship is emerging as an issue of global importance, which will drive the development of nutrient recovery in the near to medium future. This will impact wastewater treatment practices, environmental protection, sustainable agriculture and global food security. A modelling framework for precipitation-based nutrient recovery systems has been developed, incorporating non-ideal solution thermodynamics, a dynamic mass balance and a dynamic population balance to track the development of the precipitating particles. The mechanisms of crystal nucleation and growth and, importantly, aggregation are considered. A novel approach to the population balance embeds the nucleation rate into the model, enabling direct regression of its kinetic parameters. The case study chosen for the modelling framework is that of struvite precipitation, given its wide interest and commercial promise as one possible nutrient recovery pathway. Power law kinetic parameters for nucleation, crystal growth and particle aggregation rates were regressed from an ensemble data set generated from 14 laboratory seeded batch experiments using synthetic solutions. These experiments were highly repeatable, giving confidence to the regressed parameter values. The model successfully describes the dynamic responses of solution pH, the evolving particle size distribution subject to nucleation, growth and aggregation effects and the aqueous magnesium concentration in the liquid phase. The proposed modelling framework could well be extended to other, more complex systems, leading to an improved understanding and commensurately greater confidence in the design, operation and optimisation of large-scale nutrient recovery processes from complex effluents.

  7. 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.

  8. Controlling the Growth of Au on Icosahedral Seeds of Pd by Manipulating the Reduction Kinetics

    DOE PAGES

    Lv, Tian; Yang, Xuan; Zheng, Yiqun; ...

    2016-03-29

    This article reports a systematic study of how Au atoms nucleate and grow on Pd icosahedral seeds with a multiply twinned structure. By manipulating the reduction kinetics, we obtained Pd–Au bimetallic nanocrystals with two distinct shapes and structures. Specifically, Pd@Au core–shell icosahedra were formed when a relatively fast reduction rate was used for the HAuCl4 precursor. At a slow reduction rate, in contrast, the nucleation and growth of Au atoms were mainly confined to one of the vertices of a Pd icosahedral seed, resulting in the formation of a Au icosahedron by sharing five adjacent faces with the Pd seed.more » The same growth pattern was observed for Pd icosahedral seeds with both sizes of 32 and 20 nm. Also, we have also investigated the effects of other kinetic parameters, including the concentration of reducing agent and reaction temperature, on the growth pathway undertaken by the Au atoms. In conclusion, we believe that the mechanistic insights obtained from this study can be extended to other systems, including the involvement of different metals and/or seeds with different morphologies.« less

  9. Controlling the Growth of Au on Icosahedral Seeds of Pd by Manipulating the Reduction Kinetics

    SciTech Connect

    Lv, Tian; Yang, Xuan; Zheng, Yiqun; Huang, Hongwen; Zhang, Lei; Tao, Jing; Pan, Likun; Xia, Younan

    2016-03-29

    This article reports a systematic study of how Au atoms nucleate and grow on Pd icosahedral seeds with a multiply twinned structure. By manipulating the reduction kinetics, we obtained Pd–Au bimetallic nanocrystals with two distinct shapes and structures. Specifically, Pd@Au core–shell icosahedra were formed when a relatively fast reduction rate was used for the HAuCl4 precursor. At a slow reduction rate, in contrast, the nucleation and growth of Au atoms were mainly confined to one of the vertices of a Pd icosahedral seed, resulting in the formation of a Au icosahedron by sharing five adjacent faces with the Pd seed. The same growth pattern was observed for Pd icosahedral seeds with both sizes of 32 and 20 nm. Also, we have also investigated the effects of other kinetic parameters, including the concentration of reducing agent and reaction temperature, on the growth pathway undertaken by the Au atoms. In conclusion, we believe that the mechanistic insights obtained from this study can be extended to other systems, including the involvement of different metals and/or seeds with different morphologies.

  10. 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.

  11. Nutritional versatility and growth kinetics of an Aeromonas hydrophila strain isolated from drinking water.

    PubMed Central

    van der Kooij, D; Hijnen, W A

    1988-01-01

    The nutritional versatility and growth kinetics of Aeromonas hydrophila were studied to determine the nature and the growth-promoting properties of organic compounds which may serve as substrates for the growth of this organism in drinking water during treatment and distribution. As an initial screening, a total of 69 different organic compounds were tested at a concentration of 2.5 g/liter as growth substrates for 10 A. hydrophila strains. Of these strains, strain M800 attained the highest maximum colony counts in various types of drinking water and river water and was therefore used in further measurements of growth at low substrate concentrations. A mixture of 21 amino acids and a mixture of 10 long-chain fatty acids, when added to drinking water, promoted growth of strain M800 at individual compound concentrations as low as 0.1 microgram of C per liter. Mixtures of 18 carbohydrates and 18 carboxylic acids clearly enhanced growth of the organism at individual compound concentrations above 1 microgram of C per liter. Growth measurements with 63 individual substrates at a concentration of 10 micrograms of C per liter gave growth rates of greater than or equal to 0.1/h with two amino acids, nine carbohydrates, and six long-chain fatty acids. Ks values were determined for arginine (less than or equal to 0.3 micrograms of C per liter), glucose (15.9 micrograms of C per liter), acetate (11.1 micrograms of C per liter), and oleate (2.1 micrograms of C per liter). The data obtained indicate that biomass components, such as amino acids and long-chain fatty acids, can promote multiplication of aeromonads in drinking water distribution systems at concentrations as low as a few micrograms per liter. PMID:3214162

  12. How Biofilms Evade Host Defenses.

    PubMed

    Roilides, Emmanuel; Simitsopoulou, Maria; Katragkou, Aspasia; Walsh, Thomas J

    2015-06-01

    The steps involved during the biofilm growth cycle include attachment to a substrate followed by more permanent adherence of the microorganisms, microcolony arrangement, and cell detachment required for the dissemination of single or clustered cells to other organ systems. Various methods have been developed for biofilm detection and quantitation. Biofilm-producing microorganisms can be detected in tissue culture plates, using silicone tubes and staining methods, and by visual assessment using scanning electron microscopy or confocal scanning laser microscopy. Quantitative measurement of biofilm growth is determined by using methods that include dry cell weight assays, colony-forming-unit counting, DNA quantification, or XTT 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium hydroxide reduction assay. Upon infection, innate immune defense strategies are able to establish an immediate response through effector mechanisms mediated by immune cells, receptors, and several humoral factors. We present an overview of the life cycle of biofilms and their diversity, detection methods for biofilm development, and host immune responses to pathogens. We then focus on current concepts in bacterial and fungal biofilm immune evasion mechanisms. This appears to be of particular importance because the use of host immune responses may represent a novel therapeutic approach against biofilms.

  13. 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.

  14. Hydromagnesite solubility product and growth kinetics in aqueous solution from 25 to 75 °C

    NASA Astrophysics Data System (ADS)

    Gautier, Quentin; Bénézeth, Pascale; Mavromatis, Vasileios; Schott, Jacques

    2014-08-01

    Hydromagnesite Mg5(CO3)4(OH)2·4H2O is the most widespread form of hydrated Mg-carbonate minerals. To better understand the factors controlling the precipitation of hydrated Mg-carbonates, we measured hydromagnesite solubility product at 25 and 50 °C and its growth rate between 25 and 75 °C, using natural hydromagnesite from a cave as seed material. The solubility products values derived in this study, Ksp-Hmgs = -37.08 ± 0.50 and -38.90 ± 0.54 at 25 and 50 °C, respectively, are in the upper range of published values. Hydromagnesite growth rate normalized to the BET surface area at 8 ⩽ pH ⩽ 10 is consistent with the direct and reversible attachment of the reactants at the solid surface being rate-limiting. It may be described by: RHmgs=A0·e(ΩHmgs1/5-1) where A0, the pre-exponential factor, and Ea, the activation energy, are equal to 5.12 × 10-7 mol/cm2/s and 45.5 ± 9 kJ/mol, respectively, and ΩHmgs stands for the saturation state of the solution with respect to hydromagnesite. Comparison of hydromagnesite growth rates with recently published magnesite growth rates (Saldi et al., 2009, 2012) show that: (1) hydromagnesite apparent growth activation energy is lower by more than 100 kJ/mol compared to the activation energy for magnesite obtuse step advancement, and (2) hydromagnesite growth rate constant extrapolated to 90 °C is 2.5 orders of magnitude higher than corresponding magnesite growth rate constant. Thus, our results confirm the long-standing hypothesis that the slow dehydration kinetics of the Mg2+ cation is responsible for the sluggish magnesite formation at low temperature, and that the kinetic barrier for hydromagnesite growth is much lower. Nevertheless, simulation of hydromagnesite and magnesite growth rates as a function of solution composition at 50 and 90 °C, and pH 7 and 9 reveal that, because of its much higher solubility, hydromagnesite would grow more quickly than magnesite in natural or industrial environments only at 50 °C and

  15. Growth kinetics and processings of copper indium diselenide-based thin films

    NASA Astrophysics Data System (ADS)

    Kim, Suku

    CuInSe2 (CIS)-based compound semiconductors are increasingly important absorber layer materials for thin film solar cells. A better understanding of the growth kinetics of CuInSe2 thin films as a function of the process parameters would benefit the development of this technology. The reaction kinetics for formation of CuInSe2 from the bilayer structure InSe/CuSe was studied in-situ by high-temperature X-ray diffraction. The reaction pathway produces a diffusion barrier layer that can be schematically represented as InSe|CuSe → InSe|CuInSe 2|CuSe. Two different analyses based on the Avrami and the parabolic rate laws suggest that the reaction is one-dimensional diffusion controlled. The estimated apparent activation energy from each model is 66.0 and 65.2 kJ/mol, respectively. The result demonstrates that the time-resolved high temperature X-ray diffraction provides a powerful method for studying the reaction kinetics of CuInSe2 growth. The thermodynamic driving force for formation of copper selenide phase and the grain size distribution in CuInSe2 films was investigated. Large grains (˜a few mum) were observed in the CuInSe2 films annealed with a CuSe layer while films annealed without this layer exhibited very small grain size (<0.2 mum). This result suggests a secondary grain growth mechanism driven by the surface-energy anisotropy is responsible for the increased grain size. Epitaxial growth of CuInSe2 and CuGaSe2 on (001) GaAs substrates was attempted. The result shows that the crystalline structure and its quality strongly depends on the film stoichiometry, especially the [Cu]/[III] atomic ratio, with Cu-rich compositions showing higher crystalline quality. A two-dimensional model of heat transfer in the growth reactor was developed for a rotating platen/substrate in the molecular beam epitaxial reactor that was used for film growth. Time-varying view factors were included in the model to solve the problem dynamically and to account for the fact that the

  16. Dynamic Scaling and Island Growth Kinetics in Pulsed Laser Deposition of SrTiO3

    NASA Astrophysics Data System (ADS)

    Eres, Gyula; Tischler, J. Z.; Rouleau, C. M.; Lee, Ho Nyung; Christen, H. M.; Zschack, P.; Larson, B. C.

    2016-11-01

    We use real-time diffuse surface x-ray diffraction to probe the evolution of island size distributions and its effects on surface smoothing in pulsed laser deposition (PLD) of SrTiO3 . We show that the island size evolution obeys dynamic scaling and two distinct regimes of island growth kinetics. Our data show that PLD film growth can persist without roughening despite thermally driven Ostwald ripening, the main mechanism for surface smoothing, being shut down. The absence of roughening is concomitant with decreasing island density, contradicting the prevailing view that increasing island density is the key to surface smoothing in PLD. We also report a previously unobserved crossover from diffusion-limited to attachment-limited island growth that reveals the influence of nonequilibrium atomic level surface transport processes on the growth modes in PLD. We show by direct measurements that attachment-limited island growth is the dominant process in PLD that creates step flowlike behavior or quasistep flow as PLD "self-organizes" local step flow on a length scale consistent with the substrate temperature and PLD parameters.

  17. Influence of heavy metals on microbial growth kinetics including lag time: mathematical modeling and experimental verification.

    PubMed

    Sengör, S Sevinç; Barua, Sutapa; Gikas, Petros; Ginn, Timothy R; Peyton, Brent; Sani, Rajesh K; Spycher, Nicolas F

    2009-10-01

    Heavy metals can significantly affect the kinetics of substrate biodegradation and microbial growth, including lag times and specific growth rates. A model to describe microbial metabolic lag as a function of the history of substrate concentration has been previously described by Wood et al. (Water Resour Res 31:553-563) and Ginn (Water Resour Res 35:1395-1408). In the present study, this model is extended by including the effect of heavy metals on metabolic lag by developing an inhibitor-dependent functional to account for the metabolic state of the microorganisms. The concentration of the inhibiting metal is explicitly incorporated into the functional. The validity of the model is tested against experimental data on the effects of zinc on Pseudomonas species isolated from Lake Coeur d'Alene sediments, Idaho, U.S.A., as well as the effects of nickel or cobalt on a mixed microbial culture collected from the aeration tank of a wastewater treatment plant in Athens, Greece. The simulations demonstrate the ability to incorporate the effect of metals on metabolism through lag, yield coefficient, and specific growth rates. The model includes growth limitation due to insufficient transfer of oxygen into the growth medium.

  18. Predicting crystal growth via a unified kinetic three-dimensional partition model.

    PubMed

    Anderson, Michael W; Gebbie-Rayet, James T; Hill, Adam R; Farida, Nani; Attfield, Martin P; Cubillas, Pablo; Blatov, Vladislav A; Proserpio, Davide M; Akporiaye, Duncan; Arstad, Bjørnar; Gale, Julian D

    2017-04-03

    Understanding and predicting crystal growth is fundamental to the control of functionality in modern materials. Despite investigations for more than one hundred years, it is only recently that the molecular intricacies of these processes have been revealed by scanning probe microscopy. To organize and understand this large amount of new information, new rules for crystal growth need to be developed and tested. However, because of the complexity and variety of different crystal systems, attempts to understand crystal growth in detail have so far relied on developing models that are usually applicable to only one system. Such models cannot be used to achieve the wide scope of understanding that is required to create a unified model across crystal types and crystal structures. Here we describe a general approach to understanding and, in theory, predicting the growth of a wide range of crystal types, including the incorporation of defect structures, by simultaneous molecular-scale simulation of crystal habit and surface topology using a unified kinetic three-dimensional partition model. This entails dividing the structure into 'natural tiles' or Voronoi polyhedra that are metastable and, consequently, temporally persistent. As such, these units are then suitable for re-construction of the crystal via a Monte Carlo algorithm. We demonstrate our approach by predicting the crystal growth of a diverse set of crystal types, including zeolites, metal-organic frameworks, calcite, urea and l-cystine.

  19. 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).

  20. Growth behavior and kinetics of self-assembled silica-carbonate biomorphs.

    PubMed

    Kellermeier, Matthias; Melero-García, Emilio; Glaab, Fabian; Eiblmeier, Josef; Kienle, Lorenz; Rachel, Reinhard; Kunz, Werner; García-Ruiz, Juan Manuel

    2012-02-20

    Upon slow crystallization from silica-containing solutions or gels at elevated pH, alkaline-earth carbonates spontaneously self-assemble into remarkable nanocrystalline ultrastructures. These so-called silica biomorphs exhibit curved morphologies beyond crystallographic symmetry and ordered textures reminiscent of the hierarchical design found in many biominerals. The formation of these fascinating materials is thought to be driven by a dynamic coupling of the components' speciations in solution, which causes concerted autocatalytic mineralization of silica-stabilized nanocrystals over hours. In the present work, we have studied the precipitation kinetics of this unique system by determining growth rates of individual aggregates using video microscopy, and correlated the results with time-dependent data on the concentration of metal ions and pH acquired online during crystallization. In this manner, insight to the evolution of chemical conditions during growth was gained. It is shown that crystallization proceeds linearly with time and is essentially reaction controlled, which fits well in the proposed morphogenetic scenario, and thus, indirectly supports it. Measurements of the silica concentration in solution, combined with analyses of crystal aggregates isolated at distinct stages of morphogenesis, further demonstrate that the fraction of silica coprecipitated with carbonate during active growth is rather small. We discuss our findings with respect to the role of silica in the formation of biomorphs, and moreover, prove that the external silica skins that occasionally sheath the aggregates--previously supposed to be involved in the growth mechanism--originate from secondary precipitation after growth is already terminated.

  1. Dynamic Scaling and Island Growth Kinetics in Pulsed Laser Deposition of SrTiO3

    DOE PAGES

    Eres, Gyula; Tischler, J. Z.; Rouleau, C. M.; ...

    2016-11-11

    We use real-time diffuse surface x-ray diffraction to probe the evolution of island size distributions and its effects on surface smoothing in pulsed laser deposition (PLD) of SrTiO3. In this study, we show that the island size evolution obeys dynamic scaling and two distinct regimes of island growth kinetics. Our data show that PLD film growth can persist without roughening despite thermally driven Ostwald ripening, the main mechanism for surface smoothing, being shut down. The absence of roughening is concomitant with decreasing island density, contradicting the prevailing view that increasing island density is the key to surface smoothing in PLD.more » We also report a previously unobserved crossover from diffusion-limited to attachment-limited island growth that reveals the influence of nonequilibrium atomic level surface transport processes on the growth modes in PLD. We show by direct measurements that attachment-limited island growth is the dominant process in PLD that creates step flowlike behavior or quasistep flow as PLD “self-organizes” local step flow on a length scale consistent with the substrate temperature and PLD parameters.« less

  2. Environmental effects of realistic pesticide mixtures on natural biofilm communities with different exposure histories.

    PubMed

    Kim Tiam, Sandra; Morin, Soizic; Pesce, Stephane; Feurtet-Mazel, Agnès; Moreira, Aurélie; Gonzalez, Patrice; Mazzella, Nicolas

    2014-03-01

    This study deals with the use of Polar Organic Chemical Integrative Sampler (POCIS) extracts to assess the impact of low-dose pesticide mixtures on natural