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1
Micali, Gabriele. "Bacterial chemotaxis : from information processing to behaviour." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/50712.
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Chemotaxis allows flagellated bacteria to navigate in complex chemical environments, following nutrients and escaping toxins. The sensory system made up of chemoreceptors is constantly monitoring the extracellular concentrations of nutrients and toxins, while the signalling pathway processes and transmits the external information to the flagellated motors for movement. In the case of Escherichia coli, the chemotaxis pathway has been extensively characterised experimentally using genetics, biochemistry, and a wide range of imaging tools. This makes E. coli an ideal model organism for quantitative analysis and modelling. Several remarkable properties of the E. coli chemotaxis pathway have been summarised in terms of design principles. However, the swimming behaviour remains poorly understood, even for genetically identical cells in the artificial conditions normally used in a laboratory. Here, I propose an interdisciplinary approach, which combines theory, computational simulations, and experimental data from my collaborators, to study E. coli chemotaxis from an information-theoretic point of view. I demonstrate that the E. coli chemotaxis pathway is designed to optimally transmit environmental information over a certain range of concentrations and gradients. To do so, I develop a theory that identifies both the responses and the environmental conditions that transmit maximal environmental in- formation. Interestingly, when maximal information is transmitted, the behaviour characterised in terms of the drift velocity towards the nutrient is also maximised. A new design principle is proposed: maximal information transmission leads to maximal drift. Furthermore, the energetic cost of chemotaxis is much lower than the energy consumed to maintain the biological signalling pathway. Hence, thermodynamics does not seem to set constraints on information transmission and drift. However, to fully capitalise on my results, a closer connection with single-cell experiments is suggested.
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Farrell, Fred Desmond Casimir. "Modelling collective behaviour and pattern formation in bacterial colonies." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10452.
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In this Thesis I present simulation- and theory-based studies of pattern formation and growth in collections of micro-organisms, in particular bacterial colonies. The aim of these studies is to introduce simple models of the 'micro-scale' behaviour of bacterial cells in order to study the emergent behaviour of large collections of them. To do this, computer simulations and theoretical techniques from statistical physics, and in particular non-equilibrium statistical physics, were used, as the systems under study are far from thermodynamic equilibrium, in common with most biological systems. Since the elements making up these sytems - the micro-organisms - are active, constantly transducing energy from their environment in order to move and grow, they can be viewed as `active matter' systems. First, I describe my work on a generalization of an archetypal model of active matter - the Vicsek model of flocking behaviour - in which the speed of motion of active particles depends on the local density of particles. Such an interaction had previously been shown to be responsible for some forms of pattern formation in bacterial colonies grown on agar plates in the laboratory. Simulations and theory demonstrated a variety of pattern formation in this system, and these results may be relevant to explaining behaviour observed in experiments done on collections of molecular motors and actin fibres. I then go on to describe work on modelling pattern formation and growth in bacterial biofilms - dense colonies of cells growing on top of solid surfaces. I introduce a simple simulation model for the growth of non-motile cells on a flat surface, whereby they move only by growing and pushing on each other as they grow. Such colonies have previously been observed experimentally to demonstrate a transition from round to 'branched' colonies, with a pattern similar to diffusion-limited aggregation. From these simulations and analytical modelling, a theory of the growth of such colonies is developed which is quite different from previous theories. For example, I find that the colony cannot grow at a constant speed if the cells are not compressible. Finally, I present some results on genetic drift and evolution in growing bacterial colonies. Genetic drift is greatly enhanced in colonies which are expanding in space, as only a few individuals at the edge of the population are able to pass on their genes onto their progeny. The individual-based simulations of biofilms described above are used to analyse which factors - such as the shape of the colony, the thickness of the growing layer of cells, and the interactions between the cells - affect the rate of genetic drift and the probability of fixation of beneficial mutations. This has implications, for example, for the evolution of antibiotic resistance in such colonies.
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Chacko, Sarah Jane. "Surface attachment behaviour in Rhodobacter sphaeroides." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:943eb194-b147-4cb9-bbc2-a9fd04a45949.
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Motility and chemotaxis have been implicated in the process of biofilm formation in a wide range of species. Using a combination of microscopy and image analysis, genetics, microbiology and biochemistry, the initial approach of Rhodobacter sphaeroides cells to a solid surface has been characterised. Interestingly, these data suggest that for R. sphaeroides alterations in motility and swimming behaviour may result in differences in biofilm formation simply by changing the number of cells which reach the surface. This is in contrast to a few other well-studied species where the motility apparatus, the flagellum, has been shown to play an active role in surface sensing and the transition to biofilm growth. Tracking swimming cells and measuring surface attachment revealed that changes in motility affect the ability of cells to attach to a surface, with non-motile cells attaching least and mutants with frequent stops attaching less than smooth swimming cells with few stops. Tracking attaching cells and classifying their method of attachment revealed that flagellar tethering is not essential for R. sphaeroides attachment. Competition assays with fluorescently labelled strains showed that the initial imbalance between motile and non-motile cells remains as microcolonies develop over 48 hours,and the proportion of non-motile cells remains fairly constant. Development on a surface over 48 hours was similar for motile and non-motile strains, including aflagellate strains, once attached. Using parameters calculated by tracking swimming cells to calculate the effective diffusion coefficient in a simple model of cell movement suggested that motion alone could explain the differences in attachment without assuming different cell properties. In particular, aflagellate strains might be hindered from surface attachment by their reduced motility alone. This is interesting since some other bacterial species use the flagellum as a surface sensor.
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Jeziorska, Wanda. "The behavioural responses of Rhodobacter sphaeroides to carbohydrates." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305506.
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Mina, Petros. "Mathematical modelling and analysis of emergent behaviour in bacterial populations." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.628994.
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This thesis develops and analyses an agent based model of a bacterial Eschericia coli population in a quorum motivated by published experimental work The E. coli cells harbour a synthetic genetic regulatory network that is responsible for oscillatory behaviour across the population. The model is used to understand whether the collective oscillations seen in the experiments are an outcome of coupled oscillators synchronising or if they are an emergent property of the population. A bottom-up approach is used whereby an ordinary differential equation model is developed based on the biochemical dynamics that result from the introduced genetic network This model is studied using numerical bifurcation analysis, from the single cell level to see whether oscillatory behaviour exists and if such behaviour persists when groups of coupled cells are considered. Subsequently, the model is extended and an explicit spatial dimension is included to study any spatiotemporal effects that can affect the nature of oscillations. The spatial model is implemented in BSim, a novel software platform developed in Bristol, by students of the Bristol Centre for Complexity Sciences, to study bacterial population dynamics in silica. Finally, we study the possibility of controlling the cellular population, an area that has received a lot of attention recently in cellular biology. Specifically, we compare the performance of open and closed loop control in entraining the population to follow a non-native oscillating period. Vve also compare the ability to make the population track a non-oscillating signal. Our results indicate that the oscillatory behaviour seen in the published experiments is an emergent population level property. The onset and synchronisation of oscillations are dependent on cell density and the speed of diffusion of the coupling chemical in the environment medium. Also, the oscillating population is best controlled with closed loop methods.
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Reise, Franziska [Verfasser]. "Functional glycomimetics to explore bacterial adhesion and membrane behaviour: Synthesis and applications / Franziska Reise." Kiel : Universitätsbibliothek Kiel, 2019. http://d-nb.info/1177033623/34.
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Bass, Catherine Jennifer. "Survival of sulphate-reducing bacteria from oil field reservoirs : characteristics and behaviour of sulphidogenic bacterial consortia from oil field reservoirs under simulated laboratory conditions." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324131.
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Li, Martin. "Experimental study of swimming flagellated bacteria and their collective behaviour in concentrated suspensions." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4787.
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This thesis investigates bacterial motility from the mechanism permitting individual selfpropulsion to the complex collective flocking motility in Escherichia coli and Bacillus subtilis cells. Understanding bacterial swimming has intrigued scientists for decades and recently there has been a growing interest in collective swimming behaviour. The first part of this thesis reviews the characteristics of E. coli and B. subtilis cells subsequently describing the governing physics and constraints of self-propulsion in the low Reynolds regime. The second part of this thesis presents three self-contained experimental sections, examining individual swimming in non-conventional body shaped cells and subsequently focusing on concentrated bacterial swimming in normal cells. We first investigated motility in mutant spherical E. coli cells KJB24 motivated by simulations, which often model bacteria as self-propelled spheres. Somewhat unexpectedly these spherical cells do not exhibit runs and tumbles but diffuse slower than expected. As an introduction to working with microbiology and to familiarise with microbiology techniques we investigated why these spherical cells do not swim. Secondly we investigated how cellular motility varies as a function of body length by inhibiting cell division in wild-type E. coli with cephalexin; which remained motile despite body elongation. Fluorescent flagella visualization provided evidence of multiple bundle formations along the lateral walls as a mechanism to sustain motility. The average swimming velocity, body and flagella rotation rates, the number of flagella and number of flagella bundles were extracted experimentally as a function of length. The extracted experimental parameters for normal sized cells were consistent with Purcell’s model. We explored simple adaptations and scaling of this model to describe motility for filamentous cells, which agrees with experimental values. The main focus is on collective behaviour of B. subtilis by examining the onset from individual swimming to collective motility using time-lapse microscopy. Results demonstrated a smooth transition where cells self-organize into domains expanding rapidly by recruiting cells. We present advancements in B. subtilis fluorescent flagella staining which revealed unexpected multiple flagella bundle arrangements during runs, contradictory to general conjectures. Novel visualisation of flagella filaments during reversal events is presented in both E. coli and B. subtilis cells, providing experimental evidence for complex flagella ‘flipping’. Cellular reversal is hypothesized as a mechanism for quorum polarity facilitating collective swimming. We present novel flagella imaging in the setting of collective behaviour showing evidence to support quorum polarity. Subsequently we extracted the run length distributions of cells as a function of concentration, yielding a decreasing trend with increasing concentration. Using particle tracking we quantitatively extracted the mean squared displacement of swimming cells versus passive tracers at different concentrations during collective swimming, these novel results are discussed in respect to recent simulations. These presented experiments provide new insights into collective behaviour improving current understanding of this phenomenon.
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Sekora, Michael David. "Tactic behaviors in bacterial dynamics." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32915.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2005.Includes bibliographical references (leaves 89-90).
The locomotion of a wide class of motile bacteria can be mathematically described as a biased random walk in three-dimensional space. Fluid mechanics and probability theory are invoked to model the dynamics of bacteria swimming using tactic behaviors (movements or reorientation in response to chemical, physical or environmental stimuli) in flowing, viscous media. Physical descriptions are developed for bacterial chemotaxis (response to chemical agents) near particles exuding attractants, a small-scale process with global-scale implications for the biogeochemistry of the oceans. Three cases were investigated: a stationary particle, a slowly moving particle and a particle that generates a hydrodynamic wake in the form of attached vortices. The key finding of this thesis consists in the discovery of several scenarios in which motile bacteria swimming via random walks put themselves at a disadvantage in their quest for food with respect to non-motile pacteria. Thus, there exist threshold values in nutrient gradients and bacterial chemosensory ability below which bacteria would be better served if they did not swim. In the presence of vortices, it was discovered that bacteria can exploit the recirculating flow field to vastly increase their nutrient supply, but only if they alter their swimming behavior as a function of the concentration field.
(cont.) Otherwise, slow bacteria completely miss the hydrodynamic wake (and the high nutrient region) behind a nearby moving particle, while fast bacteria end up colonizing the particle (i.e. clustering around the particle and potentially anchoring themselves to it). These processes are currently under investigation in laboratory experiments using high-speed digital photography, for which software (BacTrackTM) was written that can locate and track multiple bacteria over time, with the aim of providing trajectories and their statistics and ultimately establish the importance of these phenomena for marine ecology and biogeochemistry. Preliminary experiments were conducted with Escherichia coli being exposed to ultraviolet radiation, documenting the known result of E. coli being repelled by UV radiation and providing a successful test bed for the reliability of the tracking software.
by Michael David Sekora.
S.B.
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Massé, Cécile. "Effets de la bioturbation sur la diversité des communautés bactériennes du sédiment : approches expérimentale et in-situ : de Melinna palmata aux communautés de la vasière Ouest-Gironde." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0039/document.
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Le lien entre la macrofaune et les communautés bactériennes benthiques a été déterminé selon deux approches : (1) une approche expérimentale à l’échelle de l’individu ciblée sur les effets de l’activité et de la bioturbation du polychète déposivore de surface Melinna palmata sur la distribution des communautés bactériennes des premiers millimètres de l’interface eau-sédiment ; (2) une approche in situ à l’échelle de la communauté de mise en corrélation des patrons spatiaux de distribution des communautés de macrofaune et de bactéries.Melinna palmata appartient à un nouveau groupe fonctionnel de bioturbation décrit pour la première fois, convoyeur de surface. L’utilisation de ce nouveau modèle biologique a permis de mettre en évidence que les activités de prospection et d’égestions modifient significativement la distribution des communautés bactériennes de la couche oxique de l’interface eau-sédiment. Ce lien est à la fois influencé par l’apport de matière organique de différentes qualités, et impacte la consommation et la minéralisation de cette matière organique.Le lien entre les patrons spatiaux de distribution des communautés de macrofaune et de bactéries a été étudié in situ, dans la vasière Ouest-Gironde. Les deux compartiments ont évolué le long d’un gradient avéré de teneur en matière organique et de taille des particules dans cette vasière.La corrélation des matrices biologiques n’a cependant pas été statistiquement significative et nécessite d’être approfondiThe link between benthic macrofauna and bacterial communities was assessed with two different approaches: (1) an experimental approach at the individual scale, focused on the effects of behaviour and bioturbation of the deposit feeder polychaete Melinna palmata on the bacteria lcommunity distribution on the very sediment-water interface; (2) an in situ approach at the scale of the community, focused on the correlation between spatial distribution patterns of the two biological compartments. Melinna palmata belongs to a new functional group of bioturbation described for the first time: surface conveyor. Its use allowed determining that prospection and egestion induced a significant change of bacterial communities on the sediment-water interface. This link was influenced by organic matter enrichment while influencing its fate. In a second part, the link between spatial distribution patterns of the communities was assessed in situ in the West-Gironde mud patch. Both macrofauna and bacteria changed along a gradient of organic matter quantity and quality and of particles size described in this system. However, the correlation between matrices was not statistically significant and needs to be more developed
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Dombrowski, Christopher Charles. "Bacterial Motility: From Propulsion to Collective Behavior." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/195677.
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This work explores bacterial motility from the mechanisms of propulsion of an individual cell to the complex behavior of collective motility. The shear modulus of bacterial flagella was measured by stretching isolated flagella with an optical trap and by measuring force extension curves of the stretched flagella shedding light onto the me-chanics involved in the motility of single micro-organisms. Experiments in concentrated suspensions of bacteria show collective behavior with large scale mixing on a time and length scale greater than can be understood from the standard model of "run and tumble" motility of a single organism are reported. To further understand the transition from individual to collective motility a novel form of motility where an individual bacterium can reverse direction without changing cell orientation is reported here. These experiments further the understanding of bacterial motility.
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Angelin, Martin. "Travel – a risk factor for disease and spread of antibiotic resistance." Doctoral thesis, Umeå universitet, Infektionssjukdomar, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-111057.
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As international travel is rapidly increasing, more people are being exposed to potentially more antibiotic resistant bacteria, a changed infectious disease epidemiology, and an increased risk of accidents and crime. Research-based advice is needed to adequately inform travellers about these risks. We studied travellers who sought advice from the Travel Medicine Clinic at the Department of Infectious Diseases, Umeå University Hospital, as well as university students from Umeå, Stockholm, and Gothenburg travelling abroad for study, research, and clinical exchange programs. From retrospective data at the Travel Medicine Clinic, we found that pre-existing health problems were rare among travellers from Umeå seeking pre- travel health advice and vaccinations. In addition, we found that the travel destination and the sex of the traveller affected vaccination levels. Although hepatitis A is endemic to both Thailand and Turkey, compared to travellers to Thailand few travellers to Turkey visited the clinic for hepatitis A vaccination. The data also revealed that more women than men were vaccinated against Japanese encephalitis despite comparable trips. A prospective survey study showed that travellers felt that the pre-travel health advice they received was helpful. Two-thirds of the travellers followed the advice given although they still fell ill to the same extent as those who were not compliant with the advice. Factors outside the control of travellers likely affect the travel-related morbidity. Compared to older travellers, younger travellers were less compliant with advice, fell ill to a greater extent, and took greater risks during travel. In a prospective survey study, we found that healthcare students had higher illness rates and risk exposure when abroad compared to students from other disciplines. This difference was mainly due to the fact that healthcare students more often travelled to developing regions during their study period abroad. When abroad, half of all students increased their alcohol consumption and this was linked to an increased risk of theft and higher likelihood of meeting a new sex partner. The healthcare students participating in the survey study also submitted stool samples before and after travel. These samples were tested for the presence of antibiotic resistance, both by selective culturing for ESBL-PE (Extended-Spectrum Beta-Lactamase Producing Enterobacteriaceae) as well as by metagenomic sequencing. About one-third (35%) of the students became colonised by ESBL-PE following their study abroad. The strongest risk factor for colonisation was travel destination; for example, 70% of students who had travelled to India became colonised. Antibiotic treatment during travel was also a significant risk factor for colonisation. The stool samples from a subset of study subjects were analysed using metagenomic sequencing. From this we learned that although the majority of resistance genes in the gut microbiome remained unchanged following travel, several clinically important resistance genes increased, most prominently genes encoding resistance to sulphonamide, trimethoprim, and beta-lactams. Overall, taxonomic changes associated with travel were small but the proportion of Proteobacteria, which includes several clinically important bacteria (e.g., Enterobacteriaceae), increased in a majority of the study subjects. Clearly, there are risks associated with international travel and these risks include outside factors as well as the personal behaviour of travellers. We believe our results can be used to develop better pre-travel advice for tourists as well as university students studying abroad resulting in safer travel.
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Cornforth, Daniel Michael. "Social behaviour in bacteria : regulation, coinfection, and virulence." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/17609.
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Bacteria interact with one another in many ways, through helpful behaviours like producing fitness-enhancing secretions and signals as well as harmful ones like the release of anti-competitor toxins. These interactions are essential for bacterial growth and survival and can have substantial impacts on the virulence of bacterial pathogens. This thesis explores the theory of social interactions among bacteria, focusing on both the mechanisms that underlie them as well the consequences for pathogens coinfecting a host. I first propose a hypothesis for the regulation of competitive traits in bacteria. By analysing published literature on anti-competitor toxin regulation I suggest that one of the principal mediators of antagonistic behaviour in bacteria is sensing harm from competitors. In particular, I argue that certain types of stress responses, known to protect bacteria from environmental assault, are fundamental in allowing bacteria to sense competitive threats. Next I focus on another mechanism of sensing social partners, quorum sensing, which has been argued alternatively to either sense bacterial cell density or the mass transfer properties of an environment. I propose a hypothesis on how the use of multiple quorum sensing signals molecules, a common feature across many bacteria, can potentially help resolve ambiguity between social and physical aspects of a cell’s environment. The rest of the thesis focuses on the epidemiology of coinfection, bacterial and otherwise. In some parasites, high coinfection rates lead to an increased level of evolved virulence due to competition between lineages inside the host. In contrast, when cooperative secretions contribute to virulence, the opposite can occur because high producing virulent strains are out-competed by parasites that do not produce public goods. I develop a mathematical model to show that the structure of parasites inside the host largely determines the fate of virulence when there is social interaction at a local level within the host. This analysis shows that multiplicity of infection can have either a positive or negative effect on virulence depending on structuring within the host. Lastly I explore how host contact structure influences coinfection rates and show that when hosts have very heterogeneous numbers of contacts, a small fraction of individuals in the population has a disproportionate effect on coinfection, which in turn shapes pathogen evolution.
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Rütschlin, Sina [Verfasser]. "Small Molecule Modulators of Bacterial Swarming Behavior / Sina Rütschlin." Konstanz : KOPS Universität Konstanz, 2019. http://d-nb.info/1189586592/34.
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Pierce, Christopher J. "Hydrodynamics and Collective Behavior of Magnetotactic Bacteria." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574761477220177.
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Wu, Xinyu Wu. "Control of the mechanical behavior of bacterial cellulose by mercerization." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case151092096578873.
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Liu, Xinliang [Verfasser]. "The Binding Behavior of Daptomycin on the Bacterial Membranes / Xinliang Liu." Bonn : Universitäts- und Landesbibliothek Bonn, 2018. http://d-nb.info/1192821394/34.
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Bertuccio, Alex Joseph. "Metal Species and Surfactant Impact on Bacterial Populations and Community Behavior." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1003.
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This work is motivated by the need to understand the environmental risks posed by antimicrobial silver and copper nanoparticles, from consumer products and pesticides, and surfactants, used for oil remediation. Silver and copper nanoparticles have biocidal properties, and surfactants have similar chemical structures as autoinducers, molecules bacteria use to communicate (known as quorum sensing), which may alter bacterial communication. The introduction of both classes of chemicals may pose different threats to bacterial populations to affect normal ecosystem functions. The dissertation addresses the role natural organic matter and bacterial concentrations play to serve as silver and copper sinks to mitigate toxicity and probes the effects that surfactants have on bacterial quorum sensing. Pseudomonas fluorescens was used as a model biofilm forming bacterium to understand the role natural organic matter (NOM) and bacterial concentration play on bacterial survival and colonization of AgNP-decorated surfaces. It was seen that both NOM and P. fluorescens serve as silver sinks and the critical amount of bacteria-bound silver necessary to inhibit growth was on the same order of magnitude for each initial bacterial concentration. An increased silver sensitivity was observed when NOM was present. Escherichia coli was used as a model Gram-negative bacterium to study Cu2+ toxicity in the presence of NOM. NOM increased bacterial tolerance to Cu2+ over ten-fold. Copper responsive genes were measured with and without NOM at the same initial bacterial concentration and it was observed that copper sensitive gene expression was lowered with NOM. Vibrio harveyi was used as a model quorum sensing bacterium to study the effect of Tween 80 surfactant on quorum sensing. Bioluminescence is one form of quorum sensing response for V. harveyi, and the addition of Tween 80 caused a decrease in luminescence for similar bacterial concentrations. Liquid chromatography-mass spectrometry was used to study interactions between Tween 80 and N-butyryl homoserine lactone (AI-2). A decrease in autoinducer AI-2 signal was observed with Tween 80 suggesting that there is some interaction between the surfactant and AI-2 that may result in a decrease of available signal. These results indicate that further studies should be performed to better understand these observations.
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Cornelis, Karen. "Behaviour of the phytopathogenic bacterium Rhodococcus fascians on plants." Doctoral thesis, Universite Libre de Bruxelles, 2000. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211753.
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Akter, Nousin. "Rheological behaviour of probiotic bacteria dispersed in maltodextrin and sucrose solutions." Thesis, Malmö universitet, Fakulteten för hälsa och samhälle (HS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-26378.
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Probiotic bacteria are live microorganisms, which manifest health benefits in humans. The goal of this work was to characterize rheological properties of probiotic bacteria (Lactobacillus reuteri) formulation in which maltodextrin and sucrose used as excipients. To fulfil the goal, first, thermal, structural and rheological properties of maltodextrin, sucrose solutions and probiotic bacteria slurry were investigated. Probiotic bacteria formulations were prepared by adding probiotic bacteria slurry to maltodextrin and sucrose solutions at different mass fractions. Finally, rheological properties of probiotic bacteria formulations were evaluated. From TGA, the water content of PB slurry including intracellular water found 81%. In DLS, three different types of aggregations of maltodextrin were observed and characteristic size of Probiotic bacteria found 1μm. The optical microscopy results indicate that at the liquid - air interface and in dehydrated state the bacteria are birefringent and arranged in an ordered fashion resembling a nematic phase. Most of the MD, SU and MD+SU solutions show Newtonian behaviour. MD and SU solutions show strong increase of viscosity with increasing concentration. This dependence can be described by using the Spurlin–Martin–Tennent’s model. The viscosities of MD+SU solutions increase with increasing proportion of maltodextrin. The oscillation data of MD and MD+SU solutions can be described by Maxwell model. The viscosities of MD, SU, MD+SU mixed solutions decrease with increasing temperature. This temperature dependency can be described by Arrhenius model of viscosity. At very high concentrations of MD, a deviation from this behaviour is observed. The probiotic bacteria slurry shows shear thinning behaviour at low shear stress and Newtonian behaviour at higher stresses. All probiotic formulations in which probiotic bacteria dispersed in maltodextrin and sucrose solutions show Newtonian behaviour. The viscosities of maltodextrin solutions and MD+SU mixed solutions decrease by addition of probiotic bacteria whereas mixed effects of probiotic bacteria addition on the viscosity of sucrose solutions were observed. The viscosity of probiotic bacteria slurry decreases with increasing temperature, although deviations from this behavior are seen at certain conditions.
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Curatolo, Agnese. "Collective behaviours in living systems : from bacteria to molecular motors." Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC244/document.
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La première partie de ma thèse est consacrée à l’étude de l’auto-organisation de souches génétiquement modifiées de bactéries Escherichia coli. Ce projet, réalisé en collaboration avec des biologistes synthétiques de l’Université de Hong Kong, a pour objectif l’exploration et le décryptage d’un nouveau mécanisme d’auto-organisation dans des colonies bactériennes multi-espèces. Cela a été inspiré par la question fascinante de comment les écosystèmes bactériens comprenant plusieurs espèces de bactéries peuvent s’auto-organiser dans l’espace. En considérant des systèmes dans lesquels deux souches de bactéries régulent mutuellement leurs motilités, j’ai pu montrer que le contrôle de densité réciproque est une voie générique de formation de motifs: si deux souches tendent à faire augmenter mutuellement leur motilité (la souche A se déplace plus vite quand la souche B est présent, et vice versa), ils subissent un processus de formation de motifs conduisant à la démixtion entre les deux souches. Inversement, l’inhibition mutuelle de la motilité conduit à la formation de motifs avec colocalisation. Ces résultats ont étévalidés expérimentalement par nos collaborateurs biologistes. Par la suite, j’ai étendu mon étude à des systèmes composés de plus de deux espèces en interaction, trouvant des règles simples permettant de prédire l’auto-organisation spatiale d’un nombre arbitraire d’espèces dont la motilité est sous contrôle mutuel. Cette partie de ma thèse ouvre une nouvelle voie pour comprendre l’auto-organisation des colonies bactériennes avec des souches concurrentes, ce qui est une question importante pour comprendre la dynamique des biofilms ou des écosystèmes bactériens dans les sols. Le deuxième problème traité dans ma thèse est inspiré par le comportement collectif des moteurs moléculaires se déplaçant le long des microtubules dans le cytoplasme des cellules eucaryotes. Un modèle pertinent pour le mouvement des moteurs moléculaires est donné par un système paradigmatique de non-équilibre appelé Processus Asymmetrique d’Exclusion Simple, en anglais Asymmetric Simple Exclusion Process (ASEP). Dans ce modèle sur réseau unidimensionnel, les particules se déplacent dans les sites voisins vides à des taux constants, avec un biais gauche-droite qui déséquilibre le système.Lorsqu’il est connecté à ses extrémités à des réservoirs de particules, l’ASEP est un exemple prototypique de transitions de phase unidimensionnelles guidées par les conditions aux limites. Les exemples réalistes, cependant, impliquent rarement une seule voie:les microtubules sont constitués de plusieurs pistes de tubuline auxquelles les moteurs peuvent s’attacher. Dans ma thèse, j’explique comment on peut théoriquement prédire le comportement de phase de systèmes à plusieurs voies complexes, dans lesquels les particules peuvent également sauter entre des voies parallèles. En particulier, je montre que la transition de phase unidimensionnelle vue dans l’ASEP survit cette complexité supplémentaire mais implique de nouvelles caractéristiques telles que des courants transversaux stables non-nulles et une localisation de cisaillementThe first part of my thesis is devoted to studying the self-organization of engineered strains of run-and-tumble bacteria Escherichia coli. This project, carried out in collaboration with synthetic biologists at Hong Kong University, has as its objective the exploration and decipherment of a novel self-organization mechanism in multi-species bacterial colonies. This was inspired by the fascinating question of how bacterial ecosystems comprising several species of bacteria can self-organize in space. By considering systems in which two strains of bacteria mutually regulate their motilities, I was able to show that reciprocal density control is a generic pattern-formation pathway: if two strains tend tomutually enhance their motility (strain A moves faster when strain B is present, and conversely),they undergo a pattern formation process leading to demixing between the two strains. Conversely, mutual inhibition of motility leads to pattern formation with colocalization. These results were validated experimentally by our biologist collaborators. Subsequently, I extended my study to systems composed of more than two interacting species, finding simple rules that can predict the spatial self-organization of an arbitrary number of species whose motility is under mutual control. This part of my thesis opens up a new route to understand the self-organization of bacterial colonies with competing strains, which is an important question to understand the dynamics of biofilms or bacterial ecosystems in soils.The second problem treated in my thesis is inspired by the collective behaviour ofmolecular motorsmoving along microtubules in the cytoplasm of eukaryotic cells. A relevant model for the molecularmotors’ motion is given by a paradigmatic non-equilibrium system called Asymmetric Simple Exclusion Process (ASEP). In this one-dimensional lattice- based model, particles hop on empty neighboring sites at constant rates, with a leftright bias that drives the systemout of equilibrium. When connected at its ends to particle reservoirs, the ASEP is a prototypical example of one-dimensional boundary driven phase transitions. Realistic examples, however, seldom involve only one lane: microtubules are made of several tubulin tracks to which the motors can attach. In my thesis, I explained how one can theoretically predict the phase behaviour of complex multilane systems, in which particles can also hop between parallel lanes. In particular, I showed that the onedimensional phase transition seen in the ASEP survives this additional complexity but involves new features such as non-zero steady transverse currents and shear localization
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Brown, Adrian. "Molecular characterisation of behavioural functions in Agrobacterium tumefaciens." Thesis, Durham University, 1992. http://etheses.dur.ac.uk/6019/.
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Tn5 insertion behavioural mutants of A. tumefaciens C58C(^1) were available. Cloning of the kanamycin resistance gene allowed isolation of Tn5 flanking sequences from a number of the mutants. Flanking sequences from five mutants were used to isolate cosmids, overlapping the Tn5 insertion sites of the mutantsfrom a C58C(^1) library. Two cosmids, pDUB1900 and 1905 have been characterised. pDUB1900 contains the insertion sites of eight motility mutants, with another immediately adjacent. The pDUB1905 insert overlaps sequences interrupted in another three mutants. Behavioural genes in Agrobacterium are clustered together on the chromosome, as in other motile bacteria. Restriction maps of the isolated cosmids show that none of motility mutants analysed was the result of mactivation of pscA or chvB which would lead to an altered behavioural phenotype. Flanking sequences from three of the mutants hybridised to R. meliloti chromosomal DNA, but not to DNA from other motile genera. DNA adjacent to the insertion site of fla-11 hybridised to the insert of pRZ-2, a cosmid containing behavioural genes from R. meliloti. Experiments were undertaken to investigate the occurrence of proteins homologous to the MCP's of enteric bacteria in C58C(^1) DNA hybridisation to oligonucleotide probes showed DNA that could potentially code for MCP-like proteins exists m both Agrobacterium and Rhizobium spp. In addition, an antibody raised against the E. coli MCP Tar cross-reacted with a protein of approximately 60kDa. in C58C(^1). In vivo protein methylation experiments using C58C(^1) resulted in the labelling of a 45kDa protein, whose methylation pattern did not change upon addition of chemostimuli. Possible reasons for the difference in size between the labelled protein and that revealed by the antibodv are discussed.
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McGivney, Eric. "Understanding the Relationship Between Nanoparticles and Bacterial Group Behavior: Autolysis and Quorum Sensing." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1111.
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Nano-sized materials are being used to address some of humanities greatest challenges— cancer therapy, food and water security, and environmental remediation. While extremely promising for these applications, the production, use, and disposal of nanomaterials have resulted in their release into environmental compartments. One major concern of any novel contaminant is how it interacts with bacteria. Bacteria play essential roles in human health, engineered systems, and ecological functioning. Bacteria are capable of macro-scale influence because they have evolved communication systems that enable coordinated behaviors. Communication among cells involves chemical signals that enter the environment, where they are subjected to its biogeochemistry, which now includes novel nanomaterials. The overall goal of this thesis was to improve understanding of the relationship between nanoparticles and cell-to-cell signaling behavior in bacteria focusing on two population-level behaviors: autolysis and quorum sensing. Specifically, this project sought to: (1) improve our understanding of how metal-oxide nanoparticles affect the autolytic process in Bacillus subtilis, by elucidating the biological response of the interactions between titanium dioxide nanoparticles and biomolecules; (2) reveal the interactions between quorum sensing signaling molecules and metal cations commonly used in antimicrobial nanomaterials, silver and copper; and (3) demonstrate the potential of quorum sensing-regulated cyanide production to affect oxidation and dissolution of gold nanoparticles in an environmentally relevant system. By addressing these objectives, the work demonstrated that: 1. TiO2 nanoparticles disrupt the autolytic process by delaying the onset of autolysis, and intercepting released autolytic enzymes, preventing the enzymes from degrading peptidoglycan in neighboring cells. 2. Quorum sensing signaling molecules form complexes with Ag+ and Cu2+, removing the most bioavailable form (free HHL, Ag+, and Cu2+) from the cells’ environment. 3. Quorum sensing-regulated cyanide production induces oxidative dissolution in Au nanoparticles, which were previously assumed to be inert in environmental systems. Taken together, this body of work highlights the relationship between nanoparticles and population-level behavior in bacteria. The presence of nanoparticles can have significant effects on population-level behaviors, and the activity of population-level behaviors can have significant effects on nanoparticles behavior. This inter-connected relationship, where the nanoparticles are both acted on and act upon their environment, must be considered in nanoparticle-based studies and applications.
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Lewis, Matthew R. (Matthew Robert) 1969. "The behavior of uranium in the environment : bacterial reduction of an aqueous uranium species." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8840.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2000.Includes bibliographical references (p. 379-382).
Experimental and analytical studies were performed to investigate the behavior of uranium with bacteria in an anaerobic environment. Laboratory studies used Shewanella putrefaciens because of its ability to grow rapidly in aerobic conditions and reduce metals in anaerobic conditions. Under anaerobic conditions, Shewanella putrefaciens use aqueous uranium as the electron acceptor in lieu of oxygen. The reduction of U(VI) to U(IV) removes uranium from solution and forms an insoluble compound known as uraninite. Ultraviolet/Visible Spectroscopy was used to analyze uranium ion complexion with several oxazine dyes that included Brilliant Cresyl Blue, Celestine Blue, and Gallomine Triethoiodide. Complexion and resultant color changes with U(VI) and U(IV) with the dye solutions were tested at a variety of pH levels. The dye behavior was evaluated for future use as a visible reduction indicator for microbial reduction when performing direct plating experiments. These studies showed the best visual indicator to be Celestine Blue. Significant absorbance changes in the 400 to 800 nm wavelength range for Brilliant Cresyl Blue and Gallomine Triethoiodide solutions were not detected. X Ray Diffraction and Electron Microprobe Spectroscopy characterized the solid precipitates by the bacteria. The dark black precipitate exhibited visible characteristics of both UO2(s) and U3O8 (s). Electron microprobe showed a very small crystal formed by the bacteria, but was inconclusive with respect to the elemental composition of the mineral. The XRD spectra determined that precipitate was uranium dioxide U02(s). The investigation included a time phased uranium isotope analysis in the precipitate and supernatant samples. Thermal Ionization Mass Spectrometry (TIMS) measured the uranium isotopic ratio of 238U /235U to determine if microbial reduction of U(VI) to U(IV) affected these ratios. The isotopic ratios of both the supernatant and precipitate were measured at times ranging from zero to 95 hours. An enriched uranium solution was created by dissolving an enriched sample of U308(s) in nitric acid. The U308(s) was standard reference material (SRM) from the New Brunswick National Laboratory, and was enriched to roughly 50 percent 235U. The results of the TIMS experiment showed that there was not a detectable level of fractionation.
by Matthew R. Lewis.
S.M.
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Leaman, Eric Joshua. "An Experimentally-validated Agent-based Model to Study the Emergent Behavior of Bacterial Communities." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/78072.
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Swimming bacteria are ubiquitous in aqueous environments ranging from oceans to fluidic environments within a living host. Furthermore, engineered bacteria are being increasingly utilized for a host of applications including environmental bioremediation, biosensing, and for the treatment of diseases. Often driven by chemotaxis (i.e. biased migration in response to gradients of chemical effectors) and quorum sensing (i.e. number density dependent regulation of gene expression), bacterial population dynamics and emergent behavior play a key role in regulating their own life and their impact on their immediate environment. Computational models that accurately and robustly describe bacterial population behavior and response to environmental stimuli are crucial to both understanding the dynamics of microbial communities and efficiently utilizing engineered microbes in practice. Many existing computational frameworks are finely-detailed at the cellular level, leading to extended computational time requirements, or are strictly population scale models, which do not permit population heterogeneities or spatiotemporal variability in the environment. To bridge this gap, we have created and experimentally validated a scalable, computationally-efficient, agent-based model of bacterial chemotaxis and quorum sensing (QS) which robustly simulates the stochastic behavior of each cell across a wide range of bacterial populations, ranging from a few to several hundred cells. We quantitatively and accurately capture emergent behavior in both isogenic QS populations and the altered QS response in a mixed QS and quorum quenching (QQ) microbial community. Finally, we show that the model can be used to predictively design synthetic genetic components towards programmed microbial behavior.Master of Science
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Sedlacek-Bassani, Juliana. "Uso de especiarias como aditivos naturais na produção de hambúrguer bovino /." Araçatuba, 2018. http://hdl.handle.net/11449/155847.
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Orientador: Elisa Helena Giglio PonsanoBanca: Marcia Marinho
Banca: Aparecida de Fátima Michelin
Resumo: O interesse da população pelo consumo de alimentos saudáveis, práticos e com maior durabilidade é cada vez mais frequente. Para atender a essa demanda, as indústrias de alimentos têm buscado trabalhar com ingredientes naturais, visando minimizar o uso de aditivos sintéticos. O estudo objetivou investigar se a inclusão de diferentes especiarias em hambúrguer bovino afeta o crescimento bacteriano, a oxidação lipídica e as características sensoriais dos produtos. Foram elaboradas 4 formulações de hambúrguer: controle (sem aditivos), açafrão (1%), gengibre (1%) e urucum (1%). Os produtos foram analisados quanto à contagem bacteriana total (CBT) nos dias 0, 7 e 15 (armazenamento a 4 °C) e 0, 15 e 60 (armazenamento a -30 °C) e quanto à rancidez, nos dias 0, 30 e 60 (armazenamento a -30 °C). A aceitação dos atributos sensoriais e a intenção de compra foram avaliadas com o uso de escalas hedônicas. Todos os hambúrgueres formulados com especiarias e mantidos a 4 °C apresentaram menor CBT que a formulação controle, enquanto que, para os armazenados a -30 °C, o mesmo ocorreu apenas com os que continham gengibre. Menores valores de oxidação lipídica foram encontrados nas formulações contendo as especiarias, com 0, 30 e 60 dias de armazenamento a -30 °C. As formulações controle e gengibre lideraram a aceitação dos provadores nos atributos aparência e cor, enquanto que, para os demais atributos, não houve diferença entre as formulações com especiarias. Na intenção de compra, tanto os hambú... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The population's interest in consuming healthier, more practical and durable foods is increasingly frequent. In order to meet this demand, the food industry has sought to work with natural ingredients in order to minimize the use of synthetic additives. The study aimed to investigate if the inclusion of different spices in bovine burger affects bacterial growth, lipid oxidation and sensorial characteristics of the products. Four hamburger formulations were prepared: control (without additives), saffron (1%), ginger (1%) and annatto (1%). The products were analyzed for total bacterial count (TBC) on days 0, 7 and 15 (storage at 4 °C) and 0, 15 and 60 (storage at -30 °C) and, for rancidity, on days 0, 30 and 60 (storage at -30 °C). The acceptance of the sensory attributes and the purchase intent were evaluated using hedonic scales. All burgers formulated with spices and kept at 4 °C had lower TBC than the control formulation, whereas for those stored at -30 °C, the same occurred only with the ginger-made ones. Lower lipid oxidation was found for the formulations containing the spices, with 0, 30 and 60 days of storage at -30 °C. Control and ginger formulations led the acceptance of the tasters for the attributes appearance and color, while for the other attributes no differences among the formulations with spices were detected. In the purchase intention trial, both the ginger-made and the control group burgers aroused greater interest from the tasters. It was concluded that the... (Complete abstract click electronic access below)
Mestre
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Batmanghelich, Farhad. "Effect of mixed denitrifying and sulfate reducing bacterial biofilms on corrosion behavior of cast iron." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1451311653.
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Nako, Entela. "Using E. coli as an experimental system to study the behavior of prion-like proteins." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11065.
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Prions are infectious, self-propagating protein aggregates that have been uncovered in evolutionary divergent members of the eukaryotic domain of life. It is not known whether prokaryotic organisms contain proteins that exhibit prion-like behavior. However, studies have shown that the E. coli cytoplasm can support conversion of the well-characterized Saccharomyces cerevisiae yeast prion protein Sup35 into the prion form and that this conversion, like in the yeast system, is dependent on the presence of amyloid aggregates of another yeast prion protein, a so-called PIN factor. It is interesting that the bacterial system recapitulates the in vivo requirements for Sup35 prion formation in the native yeast system despite the fact that bacteria diverged from eukaryotes ~2.2 billion years ago. In yeast, once formed, the Sup35 prion is stably propagated and this process is independent of the PIN factor. Using the same yeast prion protein, Sup35, in CHAPTER 2 we show that prion aggregates can be maintained for up to 90 generations in the bacterial cytoplasm and that these aggregates are still infectious when transformed into yeast.
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Hu, An. "Investigation of sulfate-reducing bacteria growth behavior for the mitigation of microbiologically influenced corrosion (MIC)." Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1176404403.
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Castro, A. Felipe (Castro Arancibia) 1979. "Influence of dissolved oxygen on the physicochemical properties and migration behavior of selected bacterial pathogens." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116013.
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Protection of potable water supplies demands a better understanding of the factors controlling migration of disease causing bacteria in subsurface environments. In this study, the migration behaviour of the waterborne pathogenic microorganisms Escherichia coli O157:H7 and Yersinia enterocolitica was investigated in water saturated granular systems. Both facultative bacteria were grown under aerobic and anaerobic conditions and further acclimatized to a microaerophilic or fully aerated environment for 21 h. Experiments were conducted using laboratory-scale packed columns over controlled extreme dissolved oxygen (DO) concentrations. The observed differences in the transport potential of these pathogens were found to depend strongly on the antecedent growth conditions under the tested environmental settings as well with the environmental DO in certain conditions. Further microbial characterization using cell titrations and FTIR spectroscopy gave a greater insight on the source of the surface charge that was found to dominate the attachment phenomena in sand packed columns. Techniques also revealed a probable role of other cell surface macromolecules (LPS) that could account for non-DLVO behaviour. The results illustrate the importance of considering physicochemical conditions relevant to the natural subsurface environment when designing laboratory transport experiments as evidenced by variations in microbe migration as a function of the DO under growth and acclimation.Keywords: bacterial adhesion, bacterial transport, DLVO, physicochemical characterization, dissolved oxygen, porous media.
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Vaitkevičius, Karolis. "Effects of Vibrio cholerae protease and pigment production on environmental survival and host interaction /." Umeå : Univ, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1474.
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Pichel, Marc Philippe [Verfasser], and Leon [Akademischer Betreuer] Abelmann. "The behaviour of magnetotactic bacteria in changing magnetic fields / Marc Philippe Pichel ; Betreuer: Leon Abelmann." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2018. http://d-nb.info/1155760549/34.
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Waisbord, Nicolas. "Magnetotactic bacteria as a driven active fluid : from single swimmer behavior to collective effects." Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10223.
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We report the work we lead on magneto tactic bacteria, from the point of view of active matter. The ability of this bacterium to swim at 100µm/s directed by the magnetic field makes it a good candidate to study driven active matter. Indeed, in this configuration, the self-propelled system is not dragged by an external force, and its directed motion comes from its biased orientation. We choose the strain MC-1 for our study, for the robustness of its individual behavior and its swimming speed. We studied the individual behavior, confirming previous results where the bacteria passively aligns on the magnetic field being disoriented solely by the magnetic field, but also succeeded in triggering activity in their reorientation, suspending it in different chemical environments, or directing them against a solid interface, where this bacteria could tumble. This tumbling behavior, very common amongst non-magnetic bacteria, was not reported for Mangetotactic bacteria. These new results leaded us to develop a model of Run and Tumble under a magnetic field. We studied their behavior when densely concentrated in a micro-channel, in jammed configuration, using standard microfluidics tools. We observed their motion in hour glass shaped micro-channels, without any flow, and characterized the chronology of the jamming process. We investigated the interaction of their swim with a shear, in a counter flow experiments, where MC-1 would be directed against a Poiseuille flow. Due to equilibrium between the magnetic torque and the hydrodynamic shear, bacteria would focus instantly in the middle of the channel. We studied this phenomenon theoretically, and checked our model with the experiments. We discovered a instability of a new kind in the same configuration, for high magnetic fields. Indeed, beyond a threshold the focused suspension would become wavy to end up in segregated droplets of bacteria. We characterized experimentally this phenomenon which reminds us of Rayleigh-Plateau and Kelvin-Helmholtz instabilities, varying the flow rate, the Magnetic field and the density of the suspension. Recirculation in the droplets is observed and explained. We interpret these convection droplets as the source of the instability of the focused suspension
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Rodrigues, Pedro A. D. P., and Pedro A. D. P. Rodrigues. "Bacterial Symbionts at the Colony and Individual Levels: Integration through Behavior and Morphology in a Social Insect." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/621295.
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The determination of a symbiotic association as beneficial requires good assessment of the costs and benefits involved in the maintenance and transmission of these microbes across generations. In social insects, symbiotic associations are complex as they may involve a network of interactions between individual and colony that result in stable associations over evolutionary time. My goal was to investigate the roles of behavior and morphology as integrators that have enabled the benefits of harboring gut microbes to reach both adult and growing brood in a colony. To achieve this goal, I used turtle ants (Cephalotes), a group that has co-evolved with their gut microbes since the Eocene (Sanders et al. 2014) and that shows a variety of morphological and behavioral specializations likely connected to this symbiotic association. In my dissertation I present evidence that the specialized behavior and morphology of Cephalotes are indeed strongly associated with mechanisms that ensure stability of ant-gut microbe interactions over evolutionary time. In Appendix A, I show that a valve between the crop and midgut (proventriculus) of C. rohweri works as a filtration organ, capable of excluding possible pathogens from the mostly liquid diet consumed by turtle ants. In addition, the proventricular filter is also associated with the structuring of the gut microbiota, dividing it in at least two great groups: one upstream and another downstream of the proventriculus. Through behavioral observation and microscopy, we also suggest that the formation of the proventricular filter is only complete after young and sterile workers (callows) are inoculated with the core group of symbiotic bacteria. In Appendix B, I present results confirming that the compartmentalization of gut microbiota is also present in the congener C. varians. I compare these results with previously published data, defining the meta-communities of the gut microbiota, and demonstrate that the previously recognized core microbiota is composed of compartment-specific microbial communities and lineages. This compartmentalization of the gut microbiota is similar to the one found in highly specialized herbivores, both vertebrates and invertebrates. In addition, I also sampled the infrabuccal pocket, a characteristic oral cavity found in ants and that has largely been ignored in studies of gut symbiosis. Based on my results, I provide compelling evidence that hindgut microbes are inoculated into food particles trapped in the infrabuccal pocket, aiding in digestion of this substrate. Moreover, I suggest that trophallaxis olays a central role in inoculation of food and individuals, and might be responsible for the transmission of nutrients that are predicted to result from the gut bacteria metabolism. Finally, in Appendix C I characterize abdominal trophallaxis in C. rohweri to gain insight on its role in the context of symbiotic associations with gut microbes. I show that the hindgut contents, including bacteria, can be transmitted via abdominal trophallaxis. This interaction is found to occur between all combinations of major and minor workers, in addition to callows. The rate of solicitation of abdominal trophallaxis is higher when individuals are protein starved, indicating that hindgut content may also be nutritive. Using shotgun metagenomic data, we show that the microbiota present in the infrabuccal pocket (mostly hindgut bacteria) are indeed capable of re-utilizing nitrogen and synthesizing essential amino acids, in addition to breaking down plant material. We also report that oral trophallaxis is a possible route for transmission of crop-specific bacteria for callows, as this group has performed oral trophallaxis at a relatively higher rate than older workers. Put together, these results highlight the importance of nestmate interactions and gut morphology in the establishment and maintenance of symbiotic microbes in a social insect, introducing a new model for explaining the evolution and functioning of ant-gut microbe symbiosis.
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Ozturkoglu, Sebnem. "Behaviour And Control Of Listeria Innocua During Manufacture And Storage Of Turkish White Cheese." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605543/index.pdf.
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Growth and survival of L. innocua and TAC in artificially inoculated Turkish White Cheese during manufacturing and storage periods, with respect to different level of contamination of L. innocua were investigated.
Cheese products were manufactured by the short-set procedure in pilot-plant-sized vats, as in AOÇdairy factory. Pasteurized cow&rsquo
s milk was inoculated with L. innocua for obtaining the initial loads of 3.84 and 7.12 log CFU/ml. Bacterial load of inoculated milk, whey, post-ripened curd and post-salted cheese was determined during processing at 20±
5º
C. Cheeses were stored in 16% saline solution at 4 ±
2º
C for up to 45 days. Samples were taken from each treatment and analysed on 5, 10, 15, 20, 30 and 45 days. Total decrease of L. innocua in Turkish White Cheese with each inoculum dose was approximately 2 logs during the storage period. L. innocua values were also compared with TAC values. The results had shown that, if pasteurization is not as sufficient as to kill this bacteria in contaminated raw milk, or if there is post-process contamination, Listeria can survive during the manufacture and storage, although they decrease in number. Storage (ripening) period for consumption of cheeses should be at least 90 and 178 days, in low and high inoculum dose, respectively. Physico-chemical properties of cheese as pH, acidity, salt, fat, moisture contents during storage period were determined. Salt concentration, pH value and storage temperature had a cumulative bactericidal effect on microorganisms. In this respect, effect of implementing HACCP method on reducing the Listerial contamination of Turkish White Cheese was determined for checking the quality problems in a cheese plant and for directing the companies as a guide.
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Bardin, Marcela Grigol 1988. "Higiene e cuidados com a genitália em mulheres com vulvovaginites = Hygiene and genital care of women with vulvovaginitis." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/312983.
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Orientadores: Paulo César Giraldo, Cristina Laguna Benetti PintoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas
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Resumo: INTRODUÇÃO: A vaginose bacteriana (VB) e a candidíase vaginal (CV) são as vulvovaginites (VV) mais frequentemente encontradas em mulheres durante o ciclo reprodutivo. Embora os tratamentos dessas VV estejam esclarecidos, a prevenção ainda é pouco estudada. Os hábitos de higiene e cuidados diários com a genitália feminina são fatores que podem influenciar o ecossistema vulvovaginal, facilitando a instalação dessas VV. OBJETIVO: Verificar os hábitos de lavagem, uso de absorventes higiênicos, práticas depilatórias, uso de piercings e tatuagens, tipo indumentária e atividades sexuais em mulheres com VV. MÉTODOS: Estudo de corte transversal utilizou questionário contendo 60 perguntas, divididas nos seguintes domínios: I ¿ Limpeza genital; II ¿ Uso de absorventes higiênicos; III ¿ Práticas depilatórias; IV ¿ Uso de piercings e tatuagens genitais; V ¿ Tipo indumentária e VI ¿ Atividades sexuais. Foram analisadas 307 mulheres de 18 a 45 anos, atendidas nos ambulatórios de um hospital universitário (Universidade Estadual de campinas, Brasil). Realizou-se exame ginecológico para diagnóstico de VB e CV por bacterioscopia e cultura de fungo, além de medir pH e realizar teste de Whiff. Os critérios de exclusão foram: uso de antibiótico até 15 dias antes da inclusão, antecedente de câncer, sorologia positiva para HIV e/ou sífilis e presença doença imunossupressora. Este estudo teve a aprovação do Comitê de Ética em Pesquisa da Unicamp sob número de protocolo 1836/2013 e todas as voluntárias assinaram o termo de consentimento livre e esclarecido previamente à participação neste estudo. A coleta de dados foi realizada no período de março a novembro de 2013. Para a análise estatística, consideraram-se dois grupos principais: mulheres sem e com vulvovaginites (presença de VB, CV e ambas) que foram comparados entre si. Também se realizou uma segunda análise de cada tipo de VV isoladamente (VB, CV e ambas associadas) versus mulheres sem vulvovaginites. Foram empregados os testes de Fischer e Qui-quadrado através do EPI INFO 0.5. Considerou-se nível de significância quando p<,05. RESULTADOS: Entre as 307 participantes, 46% foram diagnosticadas com VV presentes e 54% sem VV. Quando comparados estes grupos, não se encontraram diferenças significativas quanto à idade, IMC, escolaridade, número de gestações, número de partos, estado marital, raça, religião, uso de métodos contraceptivos, tabagismo, tempo fora de casa e queixas de dispareunia. A média de idade foi de 33,6 (±6,8) anos e de escolaridade 10,4 (±3,3) anos de estudo. A presença de VV esteve significativamente associada ao menor uso de produtos para higiene genital tais como sabonete líquido íntimo para higiene diária (p=,04) e lenço úmido para higiene pós-miccional (p=,04) e maior uso de sabonete bactericida para realização da lavagem genital durante o banho (<,0001). As mulheres com VV utilizaram mais calcinhas de tecido sintético (p<,05), apresentaram mais ciclos menstruais (p<,0001) que aquelas sem VV e apresentaram hábitos de uso de absorventes semelhantes. As mulheres com VB praticaram mais o sexo anal nos últimos 30 dias (p<,0001) e usavam mais substâncias erógenas (p<,02) que aquelas sem VV. Não houve diferenças significativas de frequência de relações sexuais, dispareunia, sexo oral e uso de lubrificantes entre os grupos estudados. A análise da depilação genital também não evidenciou diferenças significativas quanto ao método utilizado, motivação, frequência, área de depilação, irritabilidade vulvar, produtos pós-depilatórios e opinião sobre a influência da depilação genital sobre a saúde feminina. Apesar de ser um número baixo, mulheres com CV apresentaram mais tatuagens genitais que os demais grupos (p=,04) e apenas uma mulher apresentou piercing genital. CONCLUSÕES: Alguns hábitos de lavagem da genitália, a presença de ciclos menstruais, o uso de calcinhas de tecido sintético, relações sexuais anais e uso de substâncias erógenas na genitália se associaram à frequência de vulvovaginites. Especialmente estas últimas relacionadas aos hábitos sexuais estiveram associadas à presença de vaginose bacteriana. Os hábitos de uso de absorventes higiênicos e depilatórios não se associaram à presença de VV. Os adornos genitais foram raros, porém encontraram-se mais tatuagens genitais em mulheres com CV
Abstract: INTRODUCTION: Bacterial vaginosis (BV) and vaginal candidiasis (VC) are the most frequently vulvovaginitis (VV) encountered during in women at reproductive cycle. Although the treatments of VV are clear, prevention is still little studied. Hygiene habits and daily care with the female genitalia are factors that can influence the vulvovaginal ecosystem, and might facilitate the installation of these VV. MAIN: To investigate the genital washing habits, use of sanitary pads, genital hair removal, use of piercings and tattoos, clothing type and sexual activity in women with VV. METHODS: Cross-sectional study used a questionnaire containing 60 questions, divided into the following areas: I ¿ Genital Cleaning; II ¿ Use of sanitary pads; III ¿ depilatory practices; IV ¿ Use of genital piercings and tattoos; V ¿ clothing type and VI ¿ Sexual Activities. Were analyzed 307 women from 18 to 45 years, attended at two outpatient clinics of a university hospital (University of Campinas, Brazil). Gynecological exam was performed for collecting vaginal material for BV and VC diagnosis by Gram stain and culture of fungus, as well as measured pH and performed Whiff test. Exclusion criteria were: use of antibiotics within 15 days before enrollment, history of cancer, HIV positive and/or other immunosuppressive disease. This study was approved by the Ethics Committee of UNICAMP Research under protocol number 1836/2013 and all volunteers signed an informed consent form prior to their participation in this study. Data collection was conducted from March to November 2013. For statistical analysis, we considered two main groups: women with and without vulvovaginitis (presence of BV, VC and both) were compared to each other. It was also conducted a second analysis of each group of VV alone (BV, VC and both combined) versus women without vulvovaginitis. Statistical analysis used exact Fischer and chi-square tests by the EPI INFO 0.5. It was considered a significance level of p<.05. RESULTS: Among the 307 participants, 46% were diagnosed with VV and 54% without VV. When comparing these groups, there were no significant differences in age, BMI, duration of study, number of pregnancies, number of births, marital status, race, religion, use of contraceptives, smoking, time away from home and complaints of dyspareunia. The mean age was 33.6 (± 6.8) years of education and 10.4 (± 3.3) years of education. The presence of VV was significantly associated with lower use of genital hygiene products such as liquid soap for daily intimate hygiene (p=.04) and moist napkin as hygiene post urination (p=.04) and, on the other hand, increased use of antibacterial soap for daily genital wash (<.0001). Women with VV used more panties of synthetic fabric (p<.05), had more menstrual cycles (p<.0001) than those without VV and similar use of sanitary pads. Women with BV practiced more anal sex in the last 30 days (p<.0001) and used more erogenous substances (p<.02) than those without VV. There were no significant differences in frequency of sexual intercourse, dyspareunia, oral sex and using lubricants between groups. The analysis of genital hair removal also showed no significant differences in the method used, motivation, frequency, area of hair removal, vulvar irritability, post-depilatory used products, and opinion about the influence of genital waxing on women's health. Despite being a low number, women with genital VC had more tattoos than the other groups (p=.04) and only one woman had genital piercing. CONCLUSIONS: Some habits related to genitalia washing, the presence of menstrual cycles, the use of synthetic fabric underwear, anal intercourse and use of erogenous substances during sexual intercourse were associated with frequency of vulvovaginitis. Especially anal sex on the last 30 days previous to diagnosis and use of erogenous substances during sexual intercourse were specifically associated with the presence of bacterial vaginosis. Use of sanitary pads and hair removal habits were not associated with the presence of VV. The genital adornments were rare but genital tattoos were most common among women with VC
Mestrado
Fisiopatologia Ginecológica
Mestra em Ciências da Saúde
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De, Lamo Castellví Sílvia. "Behaviour of pathogenic gram negative bacteria inoculated in milk and model cheese treated with high hydrostatic pressure." Doctoral thesis, Universitat Autònoma de Barcelona, 2006. http://hdl.handle.net/10803/5672.
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Els efectes de les altes pressions hidrostàtiques i la capacitat per sobreviure, recuperar-se i créixer de tres microorganismes patògens (Yersinia enterocolitica, Escherichia coli Salmonella enterica) van ser investigats en llet desnatada i en un formatge model elaborat amb i sense estàrter. Les mostres inoculades amb aquests microorganismes, van ser tractades a 300, 400 i 500 MPa (exceptuant les mostres inoculades amb soques de S. enterica) durant 10 minuts a 20ºC o a temperatura ambient i van ser analitzades microbiològicament just després d'aplicar el tractament d'altes pressions i als 1, 2, 7, 10 i 15 dies (en el cas dels experiments fets amb llet desnatada) i 1, 7 i 15 dies después del tractament (en el cas de les mostres de formatge model) per estudiar l'evolució i comportament de la població d'aquests microorganismes durant el període de conservació. Les mostres de llet desnatada i de formatge model elaborades amb estàrter, van mostrar una letalitat màxima després de ser tractades a 400 i 500 MPa i no es van poder detectar diferències estadísticament significatives en el comportament baroresistent d'aquests microorganismes, exceptuant el cas de les soques de Y. enterocoliticaÉs important mencionar que les mostres de formatges elaborades sense estàrter van necessitar més pressió per obtenir les mateixes reduccions que en mostres de formatge produïdes amb estàrter. De fet, en aquest cas, el tractament més efectiu va ser 500 MPa per les soques d'E. coli i 400 MPa per les soques de S. enterica. Els patògens inoculats en formatge model produït amb estàrter no van tenir capacitat de recuperar-se i créixer: els recomptes de microorganismes en les mostres tractades van anar disminuint durant el període de conservació a 8 o 12ºC. En canvi, en el cas de la llet desnatada i del formatge model elaborat sense estàrter, totes les mostres tractades van mostrar una tendència a incrementar els seu recomptes cel·lulars durant el període de conservació. Aquests resultats suggereixen que la presència de l'estàrter i el baix pH són els principals factors per controlar la capacitat d'aquests microorganismes de recuperar-se i créixer en aquest tipus de formatge tractat per altes pressions hidrostàtiques.
The effects of high hydrostatic pressure (HHP) treatment, and the ability for survival, repair and growth of three human pathogenic microorganisms (Yersinia enterocolitica, Escherichia coli and Salmonella enterica strains) were investigated in skimmed milk and model cheese made with and without starter culture. Inoculated samples were treated at 300, 400 and 500 MPa (except S. enterica) for 10 min at 20ºC or at room temperature and analysed at 1, 2, 4, 7, 10 and 15 days (in the case of skimmed milk samples) and at 0, 1, 7 and 15 days (in the case of model cheese samples) to study the behaviour of bacterial population over time. Skimmed milk and cheese samples produced with starter culture showed the maximum lethality at 400 and 500 MPa and no significant differences in the baroresistant behaviour of microorganisms were detected, except in the case of Y. enterocolitica strains. Nevertheless, it is important to remark that in cheese produced without starter culture, it was necessary to apply more pressure to obtain the same reduction than in cheese produced with starter culture. In fact, the most effective treatment was mainly 500 MPa, for E. coli strains and 400 MPa for S. enterica strains. Ability to repair and grow was not observed in model cheese produced with starter culture and cell counts of treated samples decreased after 15 days of storage at 8 or 12ºC. Whereas, in skimmed milk and cheese produced without starter, all pressurized samples showed the trend to repair and grow during the storage period. These results suggest that the presence of starter and low pH are the main factors to control the ability to recover and grow of Y. enterocolitica, E. coli and S. enterica strains inoculated in this type of cheese and treated by HHP.
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Peire, Morais Aitana. "The role of male courtship behaviour in prezygotic isolation in Nasonia do wasps finish what bacteria started? /." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2007. http://irs.ub.rug.nl/ppn/301106282.
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Prithiraj, Alicia. "Corrosion behaviour of ferrous and non-ferrous alloys exposed to sulphate - reducing bacteria in industrial heat exchangers." Thesis, Vaal University of Technology, 2018. http://hdl.handle.net/10352/433.
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M.Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of TechnologyCorrosion responses of some carbon steels, stainless steel and copper alloys in the presence of a culture of bacteria (referred to as SRB-Sulphate-reducing bacteria) found in industrial heat exchangers, was studied to recommend best alloys under this service condition, with techno-economic consideration. Water from cooling towers in three plants in a petrochemical processing complex were analysed for SRB presence. Two of the water samples showed positive indication of SRB presence. The mixed cultures obtained from plant one were grown in prepared media and incubated at 35 °C for 18 days. Potentiodynamic polarisation studies in anaerobic conditions were done on the selected alloys in aqueous media with and without the grown SRB. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were then used to study the corrosion morphology and corrosion products formation. The voltamograms show higher icorr for alloys under the SRB compared to the control media, indicating the SRB indeed increased the corrosion rates. The surface analysis showed pitting on steel alloy ASTM A106-B. Localised attack to the grain boundaries on a selective area, was seen on ASTM A516-70 dislodging the grains, and intergranular corrosion was seen throughout the exposed area of ASTM A179. Copper alloys showed pitting on ASTM B111 grade C71500 (70-30), and denickelification on ASTM B111 grade C70600 (90-10), and is a good alternative material for use apart from carbon steel alloys, recording a low corrosion rate of 0.05 mm/year. The EDS analysis supported the findings showing higher weight percent of iron and sulphur on surface of the alloys after exposure to the SRB media. This implies that the presence of the sulphur ion indeed increased the corrosion rate. ASTM A516-70 carbon steel was chosen as a suitable alternative material to the stainless steel in this environment. The Tafel plot recorded a corrosion rate of 1.08 mm/year for ASTM A516-70 when exposed to SRB media.
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Rebata-Landa, Veronica. "Microbial Activity in Sediments: Effects on Soil Behavior." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19720.
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Thesis (Ph.D)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.Committee Chair: Santamarina, J. Carlos; Committee Member: Burns, Susan; Committee Member: Frost, David; Committee Member: Mitchell, James; Committee Member: Rix, Glenn; Committee Member: Sobecky, Patricia.
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Cisneros, Luis. "The Organized Melee: Emergence of Collective Behavior in Concentrated Suspensions of Swimming Bacteria and Associated Phenomena." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195513.
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Suspensions of the aerobic bacteria {\it Bacilus subtilis} develop patterns and flows from the interplay of motility, chemotaxis and buoyancy.In sessile drops, such bioconvectively driven flows carry plumes down the slanted meniscus and concentrate cells at the drop edge, while in pendant drops such self-concentration occurs at the bottom.These dynamics are explained quantitatively by a mathematical model consisting of oxygen diffusion and consumption, chemotaxis, and viscous fluid dynamics.Concentrated regions in both geometries comprise nearly close-packed populations, forming the collective ``Zooming BioNematic'' (ZBN) phase.This state exhibits large-scale orientational coherence, analogous to the molecular alignment of nematic liquid crystals, coupled with remarkable spatial and temporal correlations of velocity and vorticity, as measured by both novel and standard applications of particle imaging velocimetry.To probe mechanisms leading to this phase, response of individual cells to steric stress was explored, finding that they can reverse swimming direction at spatial constrictions without turning the cell body.The consequences of this propensity to flip the flagella are quantified, showing that "forwards" and "backwards" motion are dynamically and morphologically indistinguishable.Finally, experiments and mathematical modeling show that complex flows driven by previously unknown bipolar flagellar arrangements are induced when {\it B. subtilis} are confined in a thin layer of fluid, between asymmetric boundaries.The resulting driven flow circulates around the cell body ranging over several cell diameters, in contrast to the more localized flows surrounding free swimmers.This discovery extends our knowledge of the dynamic geometry of bacteria and their flagella, and reveals new mechanisms for motility-associated molecular transport and inter-cellular communication.
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Pham, Vinh Dang. "Components modulating the predatory and developmental behaviors of the soil bacterium Myxococcus xanthus /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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Hortin, Joshua. "Behavior of Copper Oxide Nanoparticles in Soil Pore Waters as Influenced by Soil Characteristics, Bacteria, and Wheat Roots." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6895.
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The goal of this project was to study the behavior of copper oxide nanoparticles in soil environments. Copper oxide nanoparticles have antimicrobial properties and may also be used in agricultural settings to provide a source of copper for plant health, but accidental or misapplication of these nanoparticles to soil may be damaging to the plant and its associated bacteria.
Dissolved soil organic matter that is present in soil pore waters dissolved nanoparticles, but did not dissolve the expected amounts from a geochemical model because the geochemical model did not take into account surface chemistry or coating of the nanoparticles by dissolved organic matter. Wheat grown in soil pore water increased the solubility of the nanoparticles. The nanoparticles and dissolved copper were harmful to wheat, but dissolved soil organic matter remediated a portion of the damage. These studies were conducted with Utah soils and wheat, a highly valuable Utah crop.
These results suggest that contamination of soils by copper oxide nanoparticles will be partially mitigated by the organic matter content of the soil. Producers of fertilizers and fungicides may use various forms of organic matter to deliver products that are targeted to specific plants or pathogens and avoid damage to non-target organisms.
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Gray, David Steven. "Novel approaches to investigate behaviors of bacteria by atomic force microscopy and circulating tumor cells through microfluidics." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/89951.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 126-138).
The adaptability and apparent ingenuity of renegade and intruding cells within the human body present formidable challenges in warding off disease. As the longevity of humans increases, cancer will afflict greater numbers, and if bacteria continue to grow resistant to conventional antibiotics, new treatment approaches will need to be identified. Through the use of two types of advanced instrumentation, a high-speed atomic force microscope (AFM) and microfluidic devices, further insights into behaviors of bacteria and cancer cells were sought, respectively. Although involving very different types of cells, the projects were characterized by overarching similarities, including the aim of studying the cells at the individual level and the need to attach the cells to a substrate to accomplish this. Ultimately, these studies uncovered phenomenon that without the AFM and microfluidics may have gone unnoticed. Specifically, a new, possible two-phase response of bacteria to an antimicrobial peptide (AmP) was discovered by high-speed AFM, and very large clusters of circulating tumor cells (CTCs) with platelets were captured on the microfluidic device - albeit the mechanism by which this happens remains to be determined. These insights were the result of seeking to understand the response of E. coli to CM15, a particular AmP, and attempting to isolate platelet-CTC complexes with a herringbone microfluidic device functionalized with antibodies that bind to surface markers on activated platelets.
by David Steven Gray.
Ph. D.
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Teratanatorn, Pavintorn. "Binding of bacteria to highly branched poly (N-isopropylacrylamide) modified with antibiotics : comparison of behaviour of linear and highly branched conformation." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/20816/.
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Poly (N-isopropylacrylamide) (PNIPAM) polymers are thermo-responsive and change conformation above their lower critical solution temperature (LCST). However, there is evidence that highly branched PNIPAM can be driven through a conformational change from open chain to globule at temperatures below the LCST by interaction of groups placed on the chain ends with a compatible molecule/ligand. It is less clear how the linear analogue would behave and our hypothesis is that it would collapse but with the chain ends shielded within the globule. In this study we explored the behaviour of a highly branched PNIPAM and a linear analogue that had the antibiotic vancomycin placed at the chain ends. Vancomycin binds to residues in the cell wall of Gram-positive bacteria so binding to bacteria should result in the highly branched PNIPAM undergoing a conformational change. The aim of the work reported in this thesis, therefore, was to compare the behaviour of linear and highly branched PNIPAM functionalised with vancomycin when interacting with Staphylococcus aureus with a view to better understand the role of conformation in polymer responsiveness. The reporting systems employed were the ability of the polymers to cause aggregation of bacteria and the response of the fluorescent solvatochromic dye, nile red. The highly branched PNIPAM (HB-PNIPAM) was synthesised via self-condensing vinyl polymerisation (SCVP)-reversible addition-fragmentation chain transfer (RAFT) polymerisation using 4-vinylbenzyl-1-pyrrolecarbodithioate as the chain transfer monomer. The polymer chain ends were functionalised with vancomycin via activation of carboxylic acids to succinimidyl derivative. A linear analogue of the polymer was synthesised using vinyl benzoic acid as comonomer to provide the same fraction of repeating units and aryl groups, because HB-PNIPAM consists of aryl branching points. The coil-to-globule conformational transition of the two polymers was studied by micro differential scanning calorimetry (microDSC) and turbidimetry. It was found that the LCSTs of highly branched polymers with pyrrole and carboxylic acid chain ends could be measured by turbidimetry (cloud point) and by microDSC. A cloud point for vancomycin-ended PNIPAM could only be detected for the linear version, not the HB-PNIPAM-van. However, the LCST of both polymers could be measured by microDSC. In aggregation tests with bacteria in aqueous suspension, the L-PNIPAM-van and HB-PNIPAM-van behaved very differently. Even though both polymers contained the same amount of vancomycin, only the HB-PNIPAM-van caused aggregation of S. aureus. These observations support a concept that the HB-PNIPAM-van has a core-shell structure above its LCST, with the densely packed core originating from desolvated PNIPAM and the outer shell stemming from solvated polymer that is swollen because of the presence of vancomycin. In contrast, when the L-PNIPAM-van initially bound to S .aureus and desolvation occurred, most of the vancomycin residues become shielded within the globule so are not available to stabilise the collapse and consequently bind more bacteria. It is suggested that the outer shell swelling is stabilised by electrostatic repulsion of adjacent vancomycin residues. However, a further complexity was identified which was the degree of hydrophobicity and charge of the bacterial cells. We also sought to confirm that vancomycin end groups of both linear and highly branched polymers were still functional and able to bind to their targets. The data presented here indicate that as the vancomycin residues on the chain ends of the polymers bind to their targets D-Ala-D-Ala and the two polymers did not differ in this respect. To probe the solvation state of the polymers when interacting with the target for vancomycin, two approaches were taken. First in the presence of the D-Ala-D-Ala peptide, hydration was disrupted by binding to vancomycin so that less energy was required to drive the polymer through its LCST. Second, a solvatochromic dye, nile red, provided information on the environmental polarity of the polymer. The hypothesis was that nile red could provide information on phase transition because loss of water should shift the emission wavelength or fluorescence intensity. It was found that in the presence of 108cfu/ml of S. aureus and HB-PNIPAM-van nile red fluorescence increased with the number of bacteria almost in a dose dependent manner, whereas there was relatively little change in fluorescence with the L-PNIPAM-van. This supports a model of change in the solvation of only the microenvironment around the chain ends of HB-PNIPAM-van, rather than of the whole polymer segment. Finally, we have shown that highly purified vancomycin functionalised L-PNIPAM and HB-PNIPAM, which bind to the cell surface of S. aureus without killing activity. We conclude, therefore, that the binding interaction primarily involves surface-located D-Ala-D-Ala on the bacterial cell wall.
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Leggett, Helen Catherine. "Developments in social evolution and virulence in parasites." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:e69b69ae-440a-4d32-8947-efb4a0c55930.
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The study of social evolution and virulence in parasites is concerned with fitness consequences of trade-offs between parasite life history traits and interactions between parasite species and/or genotypes with their hosts. I develop our understanding of social evolution and virulence in parasites in several ways. (1) I review empirical evidence for the fundamental predictions of virulence-transmission trade-off theory and demonstrate that the fit between theory and data is primarily qualitative rather than quantitative; that parasites differ in their degree of host generalism, and this is likely to impact virulence in four ways. (2) I take a comparative approach to examine the underlying causes of an observed statistical variation in the size of parasite infectious doses across taxa, revealing that mechanisms used by parasites to infect hosts are able to explain variation in both infectious dose and virulence. (3) I formally compare data on human pathogens to explain variation in virulence across taxa, revealing that immune subversion and not growth rate, explains variation in virulence. This allows me to predict that immune subverters and not fast growing parasites are likely to cause the most virulent clinical infections. (4) Using bacteria and their naturally infecting viruses (bacteriophage), I take an experimental approach to investigate the consequences of coinfection for parasite life history traits, and find that viruses cultured under a mix of single infections and coinfections evolved plasticity; they killed hosts more rapidly when coinfecting, and this resulted in high fitness under both single infection and coinfection conditions. (5) I experimentally investigate how selection within and between hosts and patches of hosts affects the fitness and virulence of populations of these viruses. I find that limited host availability favours virulent, faster killing parasites with reduced transmission; suggesting high, rather than low, virulence may be common in spatially structured host-parasite communities.
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Scott, Kyla. "Gut Pathophysiology in Mouse Models of Social Behavior Deficits." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/honors/544.
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Autism spectrum disorders (ASD) encompass neurodevelopment disorders characterized by atypical patterns of development that impact multiple areas of functioning beginning in early childhood. The etiology of ASD is unknown and there are currently no preventative treatment options. Gastrointestinal symptoms are commonly associated comorbidities. The microbiota-gut-brain axis is a multidirectional communication chain that connects the central and enteric nervous system that relates brain function to peripheral intestinal functions. Changes within this axis have been postulated in ASD. For example, the “leaky gut theory” proposes that chronic inflammation is linked to alterations in the bacterial profiles of the gut microbiome and subsequent shifts in the amount and type of short-chain fatty acids produced can affect downstream neuronal development. Short-chain fatty acids are signaling molecules produced by bacteria that can trigger nerve afferents in the gut. Dysbiosis causes altered signaling patterns that can be identified by altered intestinal morphology. In this study, C57BL/6J control mice and three mouse models of social behavioral deficits were used to investigate markers of intestinal pathophysiology. Fecal and intestinal samples were collected from adult wild type control mice and the social deficit groups of BTBR genetic knockout mice, C57BL/6J mice injected with valproic acid, and C57BL/6J mice injected with polyinosinic–polycytidylic acid. Short-chain fatty acid profiles that included acetic, propionic, isobutyric, butyric, isovaleric, and valeric acids were obtained from fecal samples to determine differences between the models and control mice. The profiles of the BTBR genetic knockout and valproic acid models were found to be significantly different from control mice. Additionally, postmortem intestinal ileum samples underwent hematoxylin and eosin identification procedures to determine the thickness of the tunica muscularis and tunica mucosa. The thickness of the tunica muscularis was reduced in the valproic acid group compared to the wild type control mice in early stages of development (p=0.0279). This research may illuminate developmental cues that attribute to autism spectrum disorders and may provide markers to assess future therapeutic treatments.
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Kuba, Cristina Atsumi. "Análise bacteriológica de hortaliças em três sistemas de cultivo em Presidente Prudente SP." Universidade do Oeste Paulista, 2016. http://bdtd.unoeste.br:8080/tede/handle/tede/738.
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Previous issue date: 2016-05-19The aim of this study was to quantitatively evaluate Listeria monocytogenes, Salmonella spp, Escherichia coli and Staphylococcus aureus in garden lettuce (Lactuca sativa) produced in the region of Presidente Prudente, using three cultivation systems: conventional, hydroponic and organic. One hundred and eighty samples of lettuce were collected for six months, sixty in each cultivation system. The lettuces were diluted in fractions 10-1 10-2 and 10-3 and plated on chromogenic agar for Listeria (Aloa Agar - Laborclin ), Baird-Parker agar supplemented with egg yolk (Oxoid ) and potassium tellurite (Laborclin ) for isolation of S. aureus, eosin methylene blue agar (Kasvi ) for isolating thermotolerant fecal coliforms (E. coli) and Rappaport-Vassilaidis broth (Himedia ) and sodium tetrathionate (Himedia ) followed by plating on Rambach agar for isolation of Salmonella. The production systems did not differ with regard to the E. coli (p = 0.582) or L. monocytogenes counts (p = 0.526). The counts of S. aureus in the lettuces cultivated in the organic system were statistically higher than the counts registered in the hydroponic system (p <0.05). The systems evaluated did not differ in relation to the isolation frequencies of the investigated bacterial species. Positive and statistically significant correlations were found between E. coli and S. aureus counts for the hydroponic and conventional systems. The results suggest that lettuces, regardless of the cultivation system, may contain food-borne infectious agents. Thus, improvements in the management system for these crops are recommended in order to strengthen the prevention of infections spread through consumption of raw vegetables.
O objetivo deste estudo foi avaliar quantitativamente Listeria monocytogenes, Salmonella spp, Escherichia coli e Staphylococcus aureus em alfaces crespas (Lactuca sativa) produzidos na região de Presidente Prudente, em três sistemas de cultivo: convencional, hidropônico e orgânico. Durante seis meses, foram coletadas 180 alfaces crespas, sendo 60 de cada sistema de cultivo. As amostras foram diluídas nas frações 10-1 10-2 e 10-3 e semeadas em agar cromogênico para Listeria (Aloa Agar - Laborclin ), agar Baird-Parker suplementado com gema de ovo (Oxoid ) e telurito de potássio (Laborclin ) para isolamento de S. aureus, agar eosina azul de metileno (Kasvi ) para isolamento de coliformes fecais termotolerantes (E. coli) e caldo Rappaport-Vassilaidis (Himedia ) e tetrationato de sódio (Himédia ) seguido de plaqueamento em agar Rambach para isolamento de Salmonella. Os sistemas de produção não diferiram quanto a contagem de E. coli (p = 0,582) e L. monocytogenes (p = 0,526). As contagens de S. aureus das alfaces cultivadas nos sistemas orgânico foram estatisticamente superiores às contagens registradas no sistema hidropônico (p < 0,05). Os sistemas avaliados não diferiram quanto as frequências de isolamento das espécies bacterianas pesquisadas. Correlações positivas e estatisticamente significativas foram detectadas entre contagens de E. coli e S. aureus para os sistemas hidropônico e convencional. Os resultados sugerem que alfaces, independentemente do sistema de cultivo, podem conter agentes infecciosos de veiculação alimentar. Desta forma, são recomendadas melhorias no sistema de manejo desses cultivos a fim de reforçar a prevenção de infecções veiculadas pelo consumo de vegetais crus.
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Mendelson, Neil, Patrick Shipman, Darshan Roy, Liling Chen, and John Thwaites. "The dynamic behavior of bacterial macrofibers growing with one end prevented from rotating: variation in shaft rotation along the fiber's length, and supercoil movement on a solid surface toward the constrained end." BioMed Central, 2003. http://hdl.handle.net/10150/610048.
Full textAbstract:
BACKGROUND:Bacterial macrofibers twist as they grow, writhe, supercoil and wind up into plectonemic structures (helical forms the individual filaments of which cannot be taken apart without unwinding) that eventually carry loops at both of their ends. Terminal loops rotate about the axis of a fiber's shaft in contrary directions at increasing rate as the shaft elongates. Theory suggests that rotation rates should vary linearly along the length of a fiber ranging from maxima at the loop ends to zero at an intermediate point. Blocking rotation at one end of a fiber should lead to a single gradient: zero at the blocked end to maximum at the free end. We tested this conclusion by measuring directly the rotation at various distances along fiber length from the blocked end. The movement of supercoils over a solid surface was also measured in tethered macrofibers.RESULTS:Macrofibers that hung down from a floating wire inserted through a terminal loop grew vertically and produced small plectonemic structures by supercoiling along their length. Using these as markers for shaft rotation we observed a uniform gradient of initial rotation rates with slopes of 25.6degrees/min. mm. and 36.2degrees/min. mm. in two different fibers. Measurements of the distal tip rotation in a third fiber as a function of length showed increases proportional to increases in length with constant of proportionality 79.2 rad/mm. Another fiber tethered to the floor grew horizontally with a length-doubling time of 74 min, made contact periodically with the floor and supercoiled repeatedly. The supercoils moved over the floor toward the tether at approximately 0.06 mm/min, 4 times faster than the fiber growth rate. Over a period of 800 minutes the fiber grew to 23 mm in length and was entirely retracted back to the tether by a process involving 29 supercoils.CONCLUSIONS:The rate at which growing bacterial macrofibers rotated about the axis of the fiber shaft measured at various locations along fibers in structures prevented from rotating at one end reveal that the rate varied linearly from zero at the blocked end to maximum at the distal end. The increasing number of twisting cells in growing fibers caused the distal end to continuously rotate faster. When the free end was intermittently prevented from rotating a torque developed which was relieved by supercoiling. On a solid surface the supercoils moved toward the end permanently blocked from rotating as a result of supercoil rolling over the surface and the formation of new supercoils that reduced fiber length between the initial supercoil and the wire tether. All of the motions are ramifications of cell growth with twist and the highly ordered multicellular state of macrofibers.
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Miranda, Marcelo Pedreira de. "Caracterização do comportamento alimentar de Bucephalogonia xanthophis (Berg) (Hemiptera: Cicadellidae) em citros e suas implicações na transmissão de Xylella fastidosa." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/11/11146/tde-14072008-170900/.
Full textAbstract:
Xylella fastidiosa é uma bactéria limitada ao xilema de plantas, sendo transmitida principalmente por cigarrinhas da subfamília Cicadellinae (Hemiptera: Cicadellidae). No Brasil, é o agente causal da Clorose variegada dos citros (CVC), doença que afeta laranja-doce [Citrus sinensis (L.) Osbeck]. O objetivo deste trabalho foi caracterizar o comportamento alimentar da cicadelíneo vetor Bucephalogonia xanthophis (Berg) em citros e correlacionar suas atividades estiletares com a transmissão de X. fastidiosa. Inicialmente, testes de escolha e análises de excreção de honeydew foram realizadas para determinar os locais e períodos preferidos para alimentação em mudas de citros. B. xanthophis preferiu a haste dos ramos novos, na parte superior da muda. Esta cigarrinha ingeriu seiva do xilema e apresentou maior volume médio de excreção e maior percentual de indivíduos que excretaram durante a fotofase. Assim, estudou-se a penetração estiletar do vetor na haste de brotações cítricas, durante a fotofase, pela técnica de \"Electrical Penetration Graph\" (EPG, sistema DC). Os principais padrões de EPG foram correlacionados com análises histológicas e de \"honeydew\" para determinação da posição exata dos estiletes no tecido vegetal e atividades envolvidas. Seis padrões foram descritos: (S) secreção de bainha salivar e caminhamento dos estiletes através de células da epiderme ou parênquima; (R) estiletes inseridos na planta, porém sem nenhuma atividade aparente; (X) contato dos estiletes com os vasos do xilema; (Xi) ingestão ativa no xilema; (I) breve interrupção durante X ou Xi; (W) retirada dos estiletes da planta. Durante uma prova, a seqüência de eventos com maior probabilidade de ocorrência foi penetração estiletar através da epiderme e parênquima (S) (100% dos insetos), seguida de contato com o xilema (X) (67,6%). Entre os indivíduos que exibem o padrão X, 88,3% passam para Xi. Os vasos do xilema foram localizados pelo inseto após uma média de 2,2 provas. O tempo médio para atingir o xilema (X) e iniciar ingestão (Xi) após o início da primeira prova foi 27.8 min e 34,2 min, respectivamente. Entretanto, verificou-se ingestão prolongada no xilema (Xi > 5 min) somente após 39,8 min, em média. Em um outro estudo, investigou-se a relação dos padrões S, X e Xi com os processos de aquisição e inoculação de X. fastidiosa em citros. B. xanthophis adquiriu X. fastidiosa somente no padrão Xi. Após 1 h de ingestão no xilema, esta cigarrinha transmitiu a bactéria para plantas-teste com uma eficiência de 7,7%. A inoculação ocorreu durante os padrões S, S+X e S+X+Xi, com eficiência de 3,5; 7,1 e 7,4%, respectivamente. Um fato intrigante foi a ocorrência de inoculação de X. fastidiosa pelo inseto antes de atingir os vasos do xilema, durante o padrão S. Contudo, as maiores taxas de transmissão ocorreram após o contato com o xilema (S+X ou S+X+Xi). Por fim, estudou-se o efeito da infecção sintomática e assintomática por X. fastidiosa em plantas cítricas sobre a penetração estiletar de B. xanthophis. O comportamento alimentar foi semelhante em plantas sadias e infectadas sem sintomas. A infecção sintomática não afetou a capacidade de B. xanthophis localizar os vasos do xilema, mas reduziu o tempo gasto por este inseto ingerindo seiva dos mesmos. Estes resultados sugerem que a aquisição de X. fastidiosa pode ser mais eficiente em plantas infectadas assintomáticas do que em plantas com sintomas severos de CVC. As informações sobre penetração estiletar do vetor B. xanthophis em citros são importantes para estudos mais avançados de mecanismos de transmissão de X. fastidiosa, bem como para estabelecer estratégias que visem interferir neste processo.Xylella fastidiosa is a xylem-limited bacterium transmitted mainly by leafhoppers (Hemiptera: Cicadellidae) in the subfamily Cicadellinae. In Brazil, it is the causal agent of Citrus variegated chlorosis, a disease that affects sweet orange [Citrus sinensis (L.) Osbeck]. The goal of this research was to characterize the feeding behavior of the cicadeline vector Bucephalogonia xanthophis (Berg) in citrus and correlate its feeding activities with transmission of X. fastidiosa. Initially, choice tests and honeydew excretion analyses were carried out to determine preferred feeding sites and periods on citrus nursery trees. B. xanthophis preferred the stems of young shoots, in the upper part of the plant. This species ingested sap from the xylem vessels and showed larger excretion volume and higher proportion of excreting individuals during the day. Thus, vector stylet penetration was studied on the stem of citrus shoots in the photophase, by using the Electrical Penetration Graph (EPG, DC system) technique. The main EPG waveforms were correlated with histological and honeydew excretion analyses to determine the precise stylet position in the plant tissue and feeding activities. Six waveforms and proposed activities are described: (S) secretion of salivary sheath and intracellular pathway; (R) stylets inserted into the plant, without any apparent activity; (X) contact of stylets with xylem vessels; (Xi) active xylem ingestion; (I) interruption between X and Xi; and (W) stylet withdrawal from the plant. During a probe, the most likely sequence of events is stylet pathway (S) through epidermal and parenchymal cells (all individuals), followed by contact with xylem (X) (67.6% of all individuals) and then active ingestion (Xi) (88.3% of those that exhibit waveform X). The xylem was reached after an average of 2.2 probes. The mean time to contact the xylem (X) and initiate ingestion (Xi) after onset of the first probe was 27.8 and 34.2 min, respectively. However, sustained xylem ingestion (Xi > 5 min) was established only after 39.8 min, on average. In a second study, the waveforms S, X and Xi were correlated with X. fastidiosa acquisition and inoculation in citrus. Acquisition of X. fastidiosa from infected plants occurred only after onset of the pathogen to 7.7% of test plants. In healthy plants, inoculation took place during waveform Xi (xylem ingestion); but with just 1 h in Xi, B. xanthophis subsequently transmitted waveforms S (salivary sheath formation and stylet pathway), S+X (X= first xylem contact by stylets) and S+X+X1, with efficiencies of 3.5, 7.1 and 7.4%, respectively. Although higher transmission rates were recorded after the first contact with xylem (S+X and S+X+Xi), it is intriguing the fact that inoculation of this xylem-limited bacterium also occurred before that (during S). Finally, the effect of X. fastidiosa infection on the feeding behavior of B. xanthophis was studied by comparing stylet penetration on: a) healthy citrus; b) symptomless infected citrus; c) infected citrus with CVC symptoms. Based on the analysis of 26 EPG parameters, no significant differences were found in stylet penetration on healthy versus asymptomatic infected citrus. Symptomatic infection did not affect the ability of B. xanthophis to locate xylem vessels, but reduced the time spend by this vector ingesting xylem sap. These results suggest that X. fastidiosa acquisition may be more efficient on symptomless infected plants than on citrus with severe CVC symptoms. Information on vector feeding behavior is basic for future studies on transmission mechanisms of X. fastidiosa and to establish control strategies aimed to interfere with this process.