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Adebayo, Olajumoke O. "Evaluation of bacterial polymers as protective agents for sensitive probiotic bacteria." Thesis, University of Wolverhampton, 2018. http://hdl.handle.net/2436/621096.
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Probiotics are live microorganisms which when administered in adequate amounts confer one or more health benefits on the host. Different processing conditions, the acidic condition of the stomach and exposure to hydrolytic enzymes affect the viability and efficacy of probiotic organisms. This study investigated the protective effects of two biopolymers poly-gamma-glutamic acid (γ-PGA) and bacterial cellulose (BC) on probiotics during freeze drying and during exposure to simulated intestinal juices and bile salts. The antibacterial property of Bifidobacterium strains was also investigated against four pathogenic bacteria. γ-PGA, a naturally occurring biopolymer was produced by two bacteria (Bacillus subtilis ATCC 15245 and B. licheniformis ATCC 9945a) in GS and E media, γ-PGA yields of about 14.11g/l were achieved in shake flasks and molecular weight of up to 1620 k Da was recorded, γ-PGA production was scaled up in a fermenter with B. subtilis using GS medium. BC, an edible biopolymer was produced by Gluconacetobacter xylinus ATCC 23770 in HS medium and a modified HS (MHS) medium. A yield of about 1.37g/l was recorded and BC production with MHS medium was used for probiotic application. B. longum NCIMB 8809 B. breve NCIMB 8807 and B. animalis NCIMB 702716 showed the best antimicrobial properties against the investigated pathogens. Survival of Bifidobacterium strains was improved when protected with powdered BC (PBC) although γ-PGA offered better protection than PBC. Viability of B. longum NCIMB 8809, B. breve NCIMB 8807 and B. animalis NCIMB 702716 in simulated gastric juice (SGJ) and simulated intestinal juice with bile salts was improved when protected with 5% γ-PGA and 5% γ-PGA+PBC with a reduction of < 1 Log CFU/ml while a reduction of ≤2 Log CFU/ml was recorded in PBC protected cells. Protecting Bifidobacterium strains with γ-PGA, PBC or a novel γ-PGA + PBC combination is a promising method to deliver probiotic bacteria to the target site in order to confer their health benefits on the host.
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Magennis, Eugene Peter. "Bacterial auto-nemesis : templating polymers for cell sequestration." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/14503/.
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The detection and control of microorganisms such as bacteria is important in a wide range of industries and clinical settings. Detection, binding and removal of such pathogenic contaminants can be achieved through judicious consideration of the targets which are available at or in the bacterial cell. Polymers have the ability to present a number of binding ligands for cell targeting on one macromolecule and so avidity of interaction can be greatly increased. The goal of the project was to test whether polymers generated with bacteria in situ would have their composition significantly altered to determine if a templating process was occurring. It was also anticipated that the templated polymers would have better re-binding properties than those produced in the absence of bacteria. A series of chemical functionalities were analysed for their binding properties to bacteria. The functionalities were chosen with consideration to the cell surface characteristics. Further to identification of the most binding and least binding functionalities the polymers were tested for their cytotoxicity against bacteria and human epithelial cells. Concentration ranges were determined which could facilitate bacterial binding and templating yet minimise the lethality of the processes. Templated polymers of the bacteria were generated using a novel method of atom transfer radical polymerisation (ATRP) which we have termed bacterial activated atom transfer radical polymerisation (b-ATRP). This polymerisation method has maximised the potential for templating processes to occur during the polymerisation. Templated polymers differed in both their composition and their binding behaviour to non-templated polymers. The bacterial organic reduction process has also been demonstrated to have greater scope for use within the organic chemistry field as demonstrated by the use of this system to enable in "click-chemistry" via the reduction of copper.
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Freebairn, David Alexander. "Electrical control of bacterial adherence to conducting polymers." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680117.
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In this thesis, low direct currents (DC) have been shown to successfully reduce bacterial adherence to conducting polymers in unique electrically modified flow devices without the aid of an antimicrobial agent. However, alternating currents (AC) and radio-frequency currents (RF) were not found to be effective. The design and manufacture of these new DC and RF flow devices has been comprehensively documented within, accompanied by relevant standard operating procedures and experimental designs. Additionally, the thesis includes a review of seminal bioelectric literature and discusses the potential for exciting future developments in this multidisciplinary field of research. These findings are ultimately intended to facilitate the design of new indwelling medical devices (IMDs) as well as electrically sterilized polymer surfaces for a wide range of far-reaching applications in industries where bacterial biofilms proliferate
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Kajornatiyudh, Sittiporn. "Bacterial extracellular polymers and flocculation of activated sludges." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/52313.
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The extracellular polymers produced by bacteria play an important role in bacterial aggregation or bacterial flocculation in secondary waste treatment. The mechanisms responsible for this floc formation are thought to be polymer induced adsorption and interparticle bridging among bacterial cells or between bacterial cells and inorganic colloids. The efficiency of the processes following flocculation in the treatment line such as sedimentation, sludge thickening, and sludge dewatering depends on the extent of this bacterial flocculation.
In this research, sludge samples from under various substrate conditions were examined for type, molecular weight, physical characteristics„ and quantity of extracellular polymers so that the general characteristics of the various polymers could be established. An attempt was made to determine if a relationship exists between the state of bacterial aggregation and the polymer characteristics. This research also investigated the sludge physical properties. The effect of various parameters such as pH, divalent cation (mixture and concentration), and mixing (period and intensity) on dewatering properties were studied.
A major goal of this study was to develop a flocculation model for activated sludge. This model could be used to determine if plants can increase the efficiency of waste treatment and sludge thickening and sludge dewatering processes.Ph. D.
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Atabek, Arzu. "Investigating bacterial outer membrane polymers and bacterial interactions with organic molecules using atomic force microscopy." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-082206-162049/.
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Wendels, Sophie. "Synthesis and elaboration of new biobased hemostatic adhesives from bacterial polymers." Thesis, Strasbourg, 2021. http://www.theses.fr/2021STRAE006.
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Les polyuréthanes (PU) sont une des principales familles de polymères démontrant des propriétés variées pour de multiples applications. Ces propriétés leurs ont permis d’être utilisés dans le domaine du biomédical depuis des décennies. Avec le développement actuel de nombreuses molécules issues de la biomasse, les possibilités d’innovation dans les matériaux biosourcés sont multiples. Aujourd’hui, des PUs aux propriétés avancées sont développés. Cependant, il y a toujours un manque de solutions plus respectueuses de l’environnement et efficaces comme adhésifs hémostatiques. Ainsi, ce travail a porté sur l’élaboration d’une nouvelle série d’adhésifs biosourcés PU à partir de différentes biomasses telles que les polymères bactériens et les huiles végétales, mais pas seulement. Plusieurs séries d’adhésifs ont été préparées et caractérisées, et proposent une large gamme de propriétés spécifiques aux adhésifs tels que la viscosité, le temps de réaction, l’adhésion tissulaire et l’éxothermie. De plus, des systèmes correspondant à l’état chimique final des adhésifs au contact des tissus ont été préparés et caractérisés. Selon la formulation, les propriétés physico-chimiques, thermiques et mécaniques peuvent être adaptées à différents tissus. La cytotoxicité et la dégradation, qui sont des paramètres clés pour une utilisation dans le biomédical, ont également été évaluéesPolyurethanes (PUs) are a major family of polymers used in a large range of fields. Moreover, they display a wide spectrum of physico-chemical, mechanical and structural properties. In this regard, they have shown suitable for biomedical applications and are used in this domain since decades. The current variety of biomass available has extended the diversity of starting materials for the elaboration of new biobased macromolecular architectures, allowing the development of biobased PUs with advanced properties. Nowadays, there is a need for more environmentally friendly and effective solutions for tissue adhesive purposes. In this frame, new renewably sourced PU-based hemostatic adhesives have been successfully designed. Chosen biomasses were mainly from bacterial ressources and vegetable oils, but not only. Many different adhesive formulations were obtained and characterized, and the developed adhesives offer a broad range of specific properties such as viscosity, curing time, tissue adhesion and exothermy. PUs, corresponding to the final adhesives chemical state in contact with the tissue, were also prepared and studied. They exhibited tailored physico-chemical, thermal and mechanical properties, close to diverse tissue native mechanical properties. Cytotoxicity and degradation, which are key parameters for biomedical applications, were also investigated
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Boltz, Joshua. "The Kinetics of Particulate Substrate Utilization by Bacterial Films." ScholarWorks@UNO, 2005. http://scholarworks.uno.edu/td/254.
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There is a need to develop a mathematical expression capable of describing the removal of particulate chemical oxygen demand (PCOD) from wastewaters in biological film systems. In this context, organic particles that are maintained in suspension (i.e., not removed during normal settling) are the focus of experimentation, modeling, and discussion. The goal of this research project is to study the kinetics of PCOD removal from wastewaters by bacterial films, or biofilms. To achieve this objective, a bench-scale rotating disc biofilm reactor (RDBR) was operated using methanol (dissolved substrate), Min-U-Sil 10 (inorganic particulates), and Maizena corn starch (organic particulates) dissolved/suspended in the influent stream. The effect of the ratio of biofilm area to volumetric flow rate passing through the RDBR on the concentration of substrate remaining in the final effluent was determined, and the kinetic relationship was established for both dissolved substrate and particle removal. Exocellular polymeric substances (EPS) were extracted and quantified in order to explain the role of biological flocculation, or bioflocculation, in particulate removal. In the literature, Fick's first law and zero-order kinetics have described the diffusion and biochemical reaction of soluble substrate within the bacterial film matrix (when completely penetrated), respectively. The present study confirms this kinetic behavior for various influent methanol concentrations. On the other hand, the removal of particulates, organic and inorganic, adheres to first-order reaction kinetics. These findings, coupled with the identification of EPS, attribute bioflocculation as the primary removal mechanism of particulates. A mass balance on the biofilm reactor allowed for the development of a comprehensive rate expression for substrate consumption by biofilms when both dissolved and particulate substrates are available. Total chemical oxygen demand (TCOD) is comprised of dissolved chemical oxygen demand (DCOD) and PCOD, each of which can be readily determined through laboratory analysis. An equation was developed that accurately describes the disappearance of TCOD by the bioflocculation of PCOD and consumption of DCOD in the bench scale RDBR.
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Zakrisson, Johan. "The mechanics of adhesion polymers and their role in bacterial attachment." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-109524.
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Bacterial resistance to antibiotics is increasing at a high rate in both developing and developed countries. To circumvent the problem of drug-resistant bacterial pathogens, we need to develop new effective methods, substances, and materials that can disarm and prevent them from causing infections. However, to do this we first need to find new possible targets in bacteria to approach and novel strategies to apply.Escherichia coli (E. coli) bacteria is a normal member of the intestinal microflora of humans and mammals, but frequently cause diverse intestinal and external diseases by means of virulence factors, which leads to hundreds of million sick people each year with a high mortality rate. An E. coli bacterial infection starts with adhesion to a host cell using cell surface expressed adhesion polymers, called adhesion pili. Depending on the local environment different types of pili are expressed by the bacteria. For example, bacteria found in the gastrointestinal tract commonly express different pili in comparison to those found in the urinary tract and respiratory tract. These pili, which are vital for bacterial adhesion, thereby serve as a new possible approach in the fight against bacterial infections by targeting and disabling these structures using novel chemicals. However, in order to develop such chemicals, better understanding of these pili is needed.Optical tweezers (OT) can measure and apply forces up to a few hundred pN with sub-pN force resolution and have shown to be an excellent tool for investigating mechanical properties of adhesion pili. It has been found that pili expressed by E. coli have a unique and complex force-extension response that is assumed to be important for the ability of bacteria to initiate and maintain attachment to the host cells. However, their mechanical functions and the advantage of specific mechanical functions, especially in the initial attachment process, have not yet been fully understood.In this work, a detailed description of the pili mechanics and their role during cell adhesion is presented. By using results from optical tweezers force spectroscopy experiments in combination with physical modeling and numerical simulations, we investigated how pili can act as “shock absorbers” through uncoiling and thereby lower the fluid force acting on a bacterium. Our result demonstrate that the dynamic uncoiling capability of the helical part of the adhesion pili modulate the force to fit the optimal lifetime of its adhesin (the protein that binds to the receptor on the host cell), ensuring a high survival probability of the bond.iiiSince the attachment process is in proximity of a surface we also investigated the influence of tether properties and the importance of different surface corrections and additional force components to the Stokes drag force during simulations. The investigation showed that the surface corrections to the Stokes drag force and the Basset force cannot be neglected when simulating survival probability of a bond, since that can overestimate the probability by more than an order of magnitude.Finally, a theoretical and experimental framework for two separate methods was developed. The first method can detect the presence of pili on single cells using optical tweezers. We verified the method using silica microspheres coated with a polymer brush and E. coli bacteria expressing; no pili, P pili, and type 1 pili, respectively. The second method was based on digital holography microscopy. Using the diffraction of semi-transparent object such as red blood cells, we showed that this method can reconstruct the axial position and detect morphological changes of cells.
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Parikh, Sanjai Jagadeep. "A Spectroscopic Study of Bacterial Polymers Mediating Cell Adhesion and Mineral Transformations." Diss., Tucson, Ariz. : University of Arizona, 2006. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1456%5F1%5Fm.pdf&type=application/pdf.
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Flo, Trude Helen. "Receptors involved in cell activation by defined uronic acid polymers and bacterial components." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Medicine, 2001. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-39.
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PAPER 1
In the first paper we show that reducing the average molecular weight from ~350 kDa to <6kDa by acid hydrolysis diminished the cell-stimulating activity of poly-M, measured as TNFproduction from human monocytes. However, the activity of the resulting oligomers (M-blocks) was greatly enhanced when covalently attached to particles (plastic beads or biodegradable albumin particles). Similar results were obtained with detoxified/deacylated LPS (DLPS) and glucuronic acid polymers (C6OXY), but not with G-blocks that by themselves are not active. These results suggest that the supramolecular structure affects the potency of polysaccharide stimuli, and that M-blocks attached to biodegradable albumin particles could possibly be exploited as an immunostimulant for protection against various diseases.
PAPER 2
In paper 2, according to the reviewers suggestion, the designation M-polymers of different molecular size was used in place of poly-M (~350 kDa) and M-blocks (~3 kDa). In this study we demonstrated that M-blocks and DLPS attached to particles engaged different receptors than soluble poly-M and DLPS in activation of monocytes. By using blocking mAbs to CD14, CD11b and CD18, we found that particulate stimuli employed the β2- integrin CD11b/CD18 in addition to the shared CD14 for signaling TNF-production. Moreover, whereas poly-M only bound to CD14-expressing CHO-cells, M-particles preferentially bound to CHO-cells expressing β2-integrins. However, the DLPS- and M-particles failed to activate NF-κB-translocation in CHO-cells co-transfected with CD14 and β2-integrins, suggesting that additional molecules are required for activation of CHO-cells. The major conclusion drawn from this work is that the supramolecular structure, in addition to influence the potency, affects the cellular receptor engagement by carbohydrates like poly-M and DLPS. This points to the importance of comparing the mechanisms involved in activation of immune cells by soluble bacterial components and whole bacteria to achieve a better understanding of inflammatory diseases like sepsis.
PAPER 3
Poly-M activates cells in a CD14-dependent manner, but CD14 is linked to the membrane with a GPI-anchor and mediates activation by interaction with other, signal-transducing molecules, like the TLRs. By using blocking mAbs to TLR2 (generated in our lab, paper 5) and TLR4, we found that both receptors were involved in mediating TNF-production from human monocytes in response to poly-M. Furthermore, TLR4 mutant (C3H/HeJ) and knockout (TLR4-/-) murine macrophages were completely non-responsive to poly-M, whereas TLR2-deficient macrophages showed reduced TNF-responses. These findings indicate that CD14, TLR2 and TLR4 on primary cells all participate in cytokine-induction by poly-M, and that TLR4 may be necessary for activation.
PAPER 4
In addition to CD14, β2-integrins have been implicated in LPS-induced cellular activation, and in this study we compared the involvement of CD14 and β2-integrins in TNF-production and NF-κB-activation induced by LPS and GBS cell wall fragments. With blocking mAbs to CD14 and CD18 we found that LPS and GBS cell walls shared CD14, but in addition the cell walls employed CD11/CD18 in mediating TNF-production from human monocytes. Both stimuli specifically induced NF-κB-translocation in CD14-transfected CHO-cells, but only LPS could activate cells transfected with CD11/CD18. The lack of response to GBS cell walls in CD11/CD18-transfected CHO-cells indicated that the cell walls need CD14 for cell activation. Further in paper 4 we demonstrate the ability of GBS cell walls to activate LPS-hyporesponsiv C3H/HeJ mouse macrophages, suggesting that LPS and GBS cell walls employ different receptors/signaling mechanisms in murine macrophages.
PAPER 5
When it was discovered that human TLR2 and TLR4 are involved in microbial recognition, we started to generate a mouse mAb to human TLR2, and in paper 5 we report the production and characterization of the mAb TL2.1. We subsequently used this mAb to evaluate the role of TLR2 in mediating activation by heat-killed GBS and L monocytogenes. L. monocytogenes, but not GBS, activated TLR2-transfected CHO-cells to IL-6-production, and the response was inhibited by TL2.1. A CD14 mAb and TL2.1 both inhibited TNF-production from monocytes induced by L. monocytogenes, but neither mAb affected the TNF-response triggered by GBS. Our results suggest that CD14 and TLR2 are engaged in cell activation by L. monocytogenes, but that neither receptor seem to be involved in activation by GBS. This study was the first to show that human TLR2 can discriminate between two G+ bacteria.
PAPER 6
In paper 6 we report the generation of a new TLR2 mAb, TL2.3, that stained with the same specificity as TL2.1 (anti-TLR2, paper 5). We used these mAbs to investigate the expression of TLR2 protein in human cells. We found that TLR2 was highly expressed in blood monocytes, less in granulocytes, and not present in lymphocytes. The protein level was measured on quiescent and activated cells by extra- and intracellular flow cytometry, and by immunoprecipitation of TLR2 from metabolic S35-labeled cells. Surprisingly, TLR2 protein was detected in activated B-cells located in lymphoid germinal centers, indicating that subsets of lymphocytes may express TLR2. We further show that TLR2 protein was differentially regulated on monocytes and granulocytes after exposure to LPS, pro- or anti-inflammatory cytokines. However, we could not correlate the regulation of TLR2 to cellular responses, as for instance the three anti-inflammatory cytokines TGFβ, IL-4 and IL-10 all inhibited lipopeptideinduced TNF-production, but either did not affect, reduced, or increased the level of surface TLR2, respectively. Thus, the biological significance of TLR2-regulation remains to be found.
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Brunstedt, Michael R. "Cellular, bacterial and humoral interactions with biomedical polymers under static and flow conditions." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1056993095.
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Swallow, Isabella Diane. "Probes for bacterial ion channels." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:d42d13dd-dd0c-451b-bd00-e06f84350335.
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Using three complementary approaches, this work sought to tackle the widespread problem of antibiotic resistance. To circumvent the resistance mechanisms developed by bacteria, it is necessary to establish drug candidates that act on novel therapeutic targets, such as the ion channels used by bacteria to modulate homeostasis. Examples include the potassium efflux channel, Kef, and the mechanosensitive channel of small conductance, MscS, which are not found in humans. How these targets function must be well understood before drug candidates can be developed, as such, their identification and investigation is often accompanied by the evolution of the analytical techniques used to study them. Membrane protein mass spectrometry is one technique showing potential in the study of ion channels. However, spectra can be clouded by the detergents used to solubilise ion channels from their native membranes. Undertaken herein was the synthesis of some fluorescent glycolipid detergents, which it was hypothesised could be encouraged to dissociate from ion channels via laser-induced excitation within the gas phase of a mass spectrometer, thereby improving the clarity with which spectra can be obtained. For Kef, an unconfirmed mechanism of action had previously been proposed. To explore the suggestion that sterically-demanding central residues are important for channel activation, solid phase peptide synthesis was used to isolate three tripeptide analogues of N-ethylsuccinimido glutathione, a known activator with a high affinity for Kef. A competition fluorescence assay suggested these tripeptides bound to Kef with an affinity lower than predicted, allowing the conclusion that a more detailed assessment of the steric bulk required for activation was necessary before a mechanism of action could be confirmed. Lysophosphatidylcholine has been shown to activate MscS, although it is not known how. Affinity chromatography between MscS and lysophosphatidylcholine was proposed as a means by which specific binding interactions could be investigated. For this technique an amino-derivative of lysophosphatidylcholine was necessary and its challenging synthesis is also detailed herein.
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Smith, Diane Elizabeth. "Adhesion of Mycobacteria: Capture, Fouling, Aggregation." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1542537888485749.
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Tourney, Janette. "The role of bacterial extracellular polymers in cell surface chemistry, metal adsorption and biomineralisation." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/14561.
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This study aimed to characterise the role of bacterial extracellular polymers in surface reactivity, metal adsorption and biomineralisation. This was undertaken using an EPS-producing, thermophilic, bacterial strain, Bacillus licheniformis S-86. Experimental work was undertaken comparing cells with the EPS layer intact (native cells) with cells from which the EPS layer had been extracted (EPS-free cells). The study incorporated surface characterisation by potentiometric titration, infrared analysis and electrophoretic mobility analysis. Investigation of the mechanisms of zinc and nickel adsorption to cell surfaces was undertaken by both macroscopic batch adsorption experiments, and spectroscopic (EXAFS) analysis. Surface complexation modelling of the potentiometric titration data indicated that the native and EPS-free cells contained four proton-active functional groups, with pKa values of 3.3-3.4, 5.3-5.4, 7.4-7.5 and 9.9-10.1. These were tentatively identified as phosphodiester, carboxyl, phosphoryl and hydroxyl/amine groups respectively, and ATR-FTIR analysis supported identification of the pKa 5.3-5.4 site as carboxylic. The site concentrations of the pKa 3.3-3.4 and 9.9-10.1 groups were significantly lower in the EPS-free cells than in the native cells. Both the macroscopic and EXAFS metal adsorption studies indicated that the carboxyl group is of principle importance to Zn complexation, and a lack of temperature-dependent adsorption provides evidence that Zn binds by an outer-sphere mechanism. Results for Ni did not provide a conclusive explanation of the binding mechanism. Biomineralisation experiments indicated that the presence of EPS affects both CaCO3 morphology and polymorphism. The metastable polymorph vaterite appears less stable in the presence of EPS. The results of this study have shown that EPS, and potentially the associated dissolved organic carbon, can significantly affect the surface reactivity of bacterial cells.
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Cavaleiro, Eliana Marisa dos Santos. "Development of polymeric materials to inhibit bacterial quorum sensing." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/9236.
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Bacterial infections are an increasing problem for human health. In fact, an increasing number of infections are caused by bacteria that are resistant to most antibiotics and their combinations. A new solution to fight bacteria and infectious diseases, without promoting antimicrobial resistance, is required. A promise strategy is the disruption or attenuation of bacterial Quorum Sensing (QS), a refined system that bacteria use to communicate. In a QS event, bacteria produce and release specific small chemicals, signal molecules - autoinducers (AIs) - into the environment. AIs regulate gene expression as a function of cell population density. Phenotypes mediated by QS (QS- phenotypes) include virulence factors, toxin production, antibiotic resistance and biofilm formation. In this work, two polymeric materials (linear polymers and molecularly imprinted nanoparticles) were developed and their ability to attenuate QS was evaluated. Both types of polymers should be able to adsorb bacterial signal molecules, limiting their availability in the extracellular environment, with expected disruption of QS. Linear polymers were composed by methyl methacrylate as backbone and itaconic acid or methacrylic acid as functional monomer. IA and MAA monomers were identified by computer modelling to have strong interactions with the AIs produced by Gram-negative bacteria. Cont/d.
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Ma, Luyao. "Biomimetic molecularly imprinted polymers : a new quorum sensing capturing agent to prevent bacterial biofilm formation." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59434.
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Biofilm is a bacterial community that is responsible for most clinical infections and shows increased resistance to the conventional antimicrobials. Biofilm formation is mediated by quorum sensing (QS), by which bacteria produce and recognize autoinducers (AIs) and thereby coordinate their behaviors in a cell-density dependent manner. The purpose of this thesis project was to design and apply molecularly imprinted polymers (MIPs) to capture AIs, interrupt QS, and subsequently inhibit the formation of bacterial biofilms.
Pseudomonas aeruginosa and N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C₁₂-AHL) were selected as the bacterial model and target AI molecule, respectively. Photo-initiated bulk polymerization method was conducted to synthesize MIPs using 3-oxo-C₁₂-AHL as the template, itaconic acid (IA) or 2-hydroxyethyl methacrylate (HEMA) as the functional monomer, ethylene glycol dimethacrylate as the crosslinker, 2,2’-azobis(2-methylpropionitrile) as the initiator and N,N-dimethylformamide as the porogen. Different functional monomers and different molar ratios of template: functional monomer: crosslinker were examined to optimize the adsorption capacity and affinity of the synthesized MIPs.
Equilibrium rebinding study was conducted to evaluate the adsorption performance of MIPs. MIPs captured 55.2%-61.2% of 3-oxo-C₁₂-AHL in 20% acetonitrile. However, none of them showed good adsorption affinity due to the dominant non-specific binding. In 50% acetonitrile, IA-based MIPs (i.e., 1:6:25 and 1:8:25) demonstrated good adsorption affinity with imprinting factor >1.
In biofilm inhibitory studies, P. aeruginosa biofilm was incubated with or without the presence of MIPs for 24 h. Biofilm biomass and sessile cell viability were determined by crystal violet assay and 2,3,5-triphenyl-tetrazolium chloride assay, respectively. Selective HEMA-based polymers (i.e., 1:8:25, 1:6:48 and 1:8:48) significantly (P < 0.05) inhibited the formation of P. aeruginosa biofilms, while all IA-based polymers had no impact on biofilm development. The viability of sessile cells was significantly (P < 0.05) reduced by selective HEMA-based polymers (i.e., 1:6:48 and 1:8:48), but was increased by some IA-based polymers (P < 0.05). Moreover, some HEMA-based polymers (e.g., 1:6:48) showed antimicrobial effect against P. aeruginosa planktonic cells.
The current study investigated the inhibitory effect of MIPs against P. aeruginosa biofilm. However, more studies need to be conducted to optimize the capturing performance of MIPs towards 3-oxo-C₁₂-AHL, thereby increase the anti-biofilm effect.Land and Food Systems, Faculty of
Graduate
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Pérez-Soto, Nicolás. "Taming Vibrio cholerae with cationic polymers : engineering bacterial physiology by interfering with communication and virulence." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8857/.
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The Gram-negative Vibrio cholerae is native to aquatic environments and an important human pathogen causing cholera disease. The induction of virulence in this bacterium is subjected to a wide variety of stimuli including environmental cues and quorum sensing. In this study, non-bactericidal cationic polymers were designed to capture Vibrio cholerae into clusters resulting in physiological changes. Poly(N-(3-aminopropyl) methacrylamide) (P1), poly(N-[3-dimethylamino)propyl] methacrylamide) (P2) or poly(acryloyl hydrazide) imidazole (P3) were synthesised via free radical polymerisation displaying amine groups that cluster cells mediated by electrostatic interactions. This binding resulted in a forced transition from planktonic to a sessile lifestyle. The clustering is accompanied by reduced motility, increased biofilm synthesis and repression of virulence since the expression cholera toxin was down-regulated. This avirulent phenotype was defective to colonise intestinal epithelial cells and the zebrafish digestive tract. Since the cell density increases locally as a result of the clustering, a quorum-sensing-controlled phenotype was observed as the lux operon was actively expressed. Overall, the bacterial physiology was modulated without genetic modification preventing virulence as the pathogen adapt its lifestyle during clustered lifestyle. This thesis highlights the use of polymeric materials as a mean to control pathogens beyond the use antibiotics.
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Schulze, H., H. Wilson, I. Cara, Steven Carter, Edward N. Dyson, R. Elangovan, Stephen Rimmer, and T. T. Bachmann. "Label-Free Electrochemical Sensor for Rapid Bacterial Pathogen Detection Using Vancomycin-Modified Highly Branched Polymers." MDPI, 2021. http://hdl.handle.net/10454/18494.
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YesRapid point of care tests for bacterial infection diagnosis are of great importance to reduce the misuse of antibiotics and burden of antimicrobial resistance. Here, we have successfully combined a new class of non-biological binder molecules with electrochemical impedance spectroscopy (EIS)-based sensor detection for direct, label-free detection of Gram-positive bacteria making use of the specific coil-to-globule conformation change of the vancomycin-modified highly branched polymers immobilized on the surface of gold screen-printed electrodes upon binding to Gram-positive bacteria. Staphylococcus carnosus was detected after just 20 min incubation of the sample solution with the polymer-functionalized electrodes. The polymer conformation change was quantified with two simple 1 min EIS tests before and after incubation with the sample. Tests revealed a concentration dependent signal change within an OD600 range of Staphylococcus carnosus from 0.002 to 0.1 and a clear discrimination between Gram-positive Staphylococcus carnosus and Gram-negative Escherichia coli bacteria. This exhibits a clear advancement in terms of simplified test complexity compared to existing bacteria detection tests. In addition, the polymer-functionalized electrodes showed good storage and operational stability.
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Cavaleiro, Eliana Marisa dos Santos. "Development of polymeric materials to inhibit bacterial quorum sensing." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14887.
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Doutoramento em BiologiaBacterial infections are an increasing problem for human health. In fact, an increasing number of infections are caused by bacteria that are resistant to most antibiotics and their combinations. Therefore, the scientific community is currently searching for new solutions to fight bacteria and infectious diseases, without promoting antimicrobial resistance. One of the most promising strategies is the disruption or attenuation of bacterial Quorum Sensing (QS), a refined system that bacteria use to communicate. In a QS event, bacteria produce and release specific small chemicals, signal molecules - autoinducers (AIs) - into the environment. At the same time that bacterial population grows, the concentration of AIs in the bacterial environment increases. When a threshold concentration of AIs is reached, bacterial cells respond to it by altering their gene expression profile. AIs regulate gene expression as a function of cell population density. Phenotypes mediated by QS (QSphenotypes) include virulence factors, toxin production, antibiotic resistance and biofilm formation. In this work, two polymeric materials (linear polymers and molecularly imprinted nanoparticles) were developed and their ability to attenuate QS was evaluated. Both types of polymers should to be able to adsorb bacterial signal molecules, limiting their availability in the extracellular environment, with expected disruption of QS. Linear polymers were composed by one of two monomers (itaconic acid and methacrylic acid), which are known to possess strong interactions with the bacterial signal molecules. Molecularly imprinted polymer nanoparticles (MIP NPs) are particles with recognition capabilities for the analyte of interest. This ability is attained by including the target analyte at the synthesis stage. Vibrio fischeri and Aeromonas hydrophila were used as model species for the study. Both the linear polymers and MIP NPs, tested free in solutions and coated to surfaces, showed ability to disrupt QS by decreasing bioluminescence of V. fischeri and biofilm formation of A. hydrophila. No significant effect on bacterial growth was detected. The cytotoxicity of the two types of polymers to a fibroblast-like cell line (Vero cells) was also tested in order to evaluate their safety. The results showed that both the linear polymers and MIP NPs were not cytotoxic in the testing conditions. In conclusion, the results reported in this thesis, show that the polymers developed are a promising strategy to disrupt QS and reduce bacterial infection and resistance. In addition, due to their low toxicity, solubility and easy integration by surface coating, the polymers have potential for applications in scenarios where bacterial infection is a problem: medicine, pharmaceutical, food industry and in agriculture or aquaculture.
Infeções bacterianas são um problema recorrente para a saúde pública. A maioria das infeções bacterianas tem aumentado devido ao facto das bactérias se tornarem resistentes aos antibióticos. A procura de estratégias para combater este facto, sem promover a resistência antimicrobiana, tem sido incessante. A atenuação ou até mesmo a disrupção do Quorum Sensing (QS), é uma estratégia promissora para enfrentar este problema. QS é um sistema de comunicação bacteriana, onde há produção e libertação de moléculas sinais específicas, denominadas de Auto Indutores (AIs) para o ambiente. Á medida que a população bacteriana aumenta, aumenta também a concentração de moléculas sinais no ambiente. Quando a concentração destas moléculas atinge um certo limite, há uma alteração a nível da expressão genética. A expressão de determinados genes relacionados com fatores de virulência, produção de toxinas, resistência a antibióticos e formação de biofilmes é intrinsecamente relacionada com QS. Neste estudo foram desenvolvidos dois tipos de polímeros (polímeros lineares e nanopartículas impressas molecularmente) com capacidade para atenuar QS. Ambos os polímeros têm como finalidade a absorção e consequente remoção de moléculas sinais do ambiente, com consequente disrupção de QS. Os polímeros lineares são compostos por dois tipos de monómeros (ácido itacónico e ácido metacrílico) que possuem afinidade para as moléculas sinais. Nanoparticulas impressas molecularmente são partículas específicas para o alvo de interesse, pois este é incluído no processo de síntese. Vibrio fischeri e Aeromonas hydrophila foram os microrganismos escolhidos para este estudo. A eficiência dos polímeros lineares e das nanopartículas foi testada quer em solução quer como revestimento de superfícies, evidenciando as suas capacidade de disrupção de QS através da diminuição da bioluminescência de V. fischeri e da formação de biofilme de A. hydrophila. O crescimento bacteriano não mostrou ser afetado pela presença destes materiais. A citotoxicidade foi avaliada, usando uma linha celular de fibroblastos, de modo a avaliar a biocompatibilidade. Os resultados mostraram que ambos os materiais não são citotóxicos. Em conclusão, este estudo demonstrou que os polímeros desenvolvidos podem ser uma estratégia efetiva de disrupção de QS e redução de infeções e de resistência bacteriana. Devido às suas características, reduzida citotoxicidade, solubilidade e facilidade de integração, estes materiais poderão ser aplicados de diversas formas, especialmente onde há predominância de infeções bacterianas, como ambientes clínicos, farmacêuticos, indústria alimentar, agricultura ou aquacultura.
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Guenther, Denise, Jaoine Valle, Saioa Burgui, Carmen Gil, Cristina Solano, Alejandro Toledo-Arana, Ralf Helbig, Carsten Werner, Inigo Lasa, and Andrés F. Lasagni. "Direct laser interference patterning for decreased bacterial attachment." SPIE, 2016. https://tud.qucosa.de/id/qucosa%3A34805.
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In the past 15 years, many efforts were made to create functionalized artificial surfaces showing special anti-bacterial and anti-biofouling properties. Thereby, the topography of medical relevant materials plays an important role. However, the targeted fabrication of promising surface structures like hole-, lamella- and pyramid-like patterns with feature sizes in the sub-micrometer range in a one-step process is still a challenge. Optical and e-beam lithography, molding and selfassembly layers show a great potential to design topographies for this purpose. At the same time, most of these techniques are based on sequential processes, require masks or molds and thus are very device relevant and time consuming. In this work, we present the Direct Laser Interference Patterning (DLIP) technology as a capable method for the fast, flexible and direct fabrication of periodic micrometer- and submicrometer structures. This method offers the possibility to equip large plain areas and curved devices with 1D, 2D and 3D patterns. Simple 1D (e.g. lines) and complex 3D (e.g. lamella, pillars) patterns with periodic distances from 0.5 μm to 5 μm were fabricated on polymeric materials (polyimide, polystyrene). Subsequently, we characterized the adhesion behavior of Staphylococcus epidermidis and S. aureus bacteria under in vitro and in vivo conditions. The results revealed that the topographies have a significant impact on bacteria adhesion. On the one side, one-dimensional line-like structures especially with dimensions of the bacteria enhanced microbe attachment. While on the other hand, complex three-dimensional patterns prevented biofilm formation even after implantation and contamination in living organisms.
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Andersson, Magnus. "Construction of force measuring optical tweezers instrumentation and investigations of biophysical properties of bacterial adhesion organelles." Doctoral thesis, Umeå : Department of Physics, Umeå Univ, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1425.
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Yan, Xibo. "Heptyl mannoside based polymers and nanocapsules : Towards potent anti-adhesive glycomaterials and nanocarriers." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0011/document.
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Ce travail de thèse est consacré à la préparation de glycopolymères porteurs de groupements pendants mannoside d’heptyle et à l’évaluation de la capacité de ces ligands multivalents à inhiber la fixation bactérienne sur les cellules humaines. Nous avons synthétisé, par polymérisation radicalaire contrôlée, une série de glycopolymères linéaires ou en étoile présentant des masses molaires, des densités en mannoside et des microstructures modulables dans le but d’évaluer l’influence de ces paramètres sur les processus d’interactions avec diverses souches de bactéries E coli (AIEC LF82 et UTI 89). Nous avons tout d’abord mis en évidence par diffusion dynamique et statique de la lumière, la formation d’agrégats entre ces glycopolymères et FimH, la lectine à l’origine de la fixation de souches de bactéries E coli, traduisant des interactions fortes entre les motifs mannosides et les sites de reconnaissance au mannose de la lectine. Nous avons ensuite évalué l’aptitude de ces ligands multivalents à bloquer l’adhésion bactérienne d’AIEC LF82 (impliquée dans la maladie de Crohn) sur des cellules épithéliales intestinales T84. Il a été démontré en conditions in vitro que l’ajout de 10 nM ou 100 nM d’unités mannoside (respectivement en pré- ou post-incubation) réduit de moitié l’adhésion des bactéries sur les cellules épithéliales. L’effet anti-adhésif de ces glycopolymères a été confirmé par des tests ex vivo réalisés sur des intestins isolés de souris transgéniques CEABAC10. Enfin, nous avons exploité la technique de nanoprécipitation pour l’élaboration de nanocapsules de glycopolymères à cœur huileux. Le procédé développé permet la synthèse de nanocapsules de dimensions contrôlées, porteuses de groupements fonctionnels (fluorophores, ligands) ou de particules métalliques et l’encapsulation de molécules actives à cœur en une seule étapeThis PhD work focuses on the preparation of glycopolymers bearing pendent heptyl mannose groups and the evaluation of the capability of such multivalent ligands to inhibit bacterial adhesion to human cells. Aiming at understanding the impact of various structural parameters on glycopolymer/ E coli interactions (AIEC LF82 et UTI 89 strains of E. coli), a series of linear and star-shaped glycopolymers with tunable molecular weight, mannoside density and microstructure (block copolymers, gradient copolymers, random copolymers) has been constructed. The association of the glycopolymers with FimH adhesin, a lectin which possesses a mannose-specific receptor site and is responsible for recognition and binding to host cells, was first confirmed by static and dynamic light scattering experiments. The propensity of the glycopolymers to prevent attachment of E. coli (AIEC LF82 involved in Crohn’s disease) to intestinal epithelial cells (T84 cells) was further investigated through adhesion assays. It was shown that under in vitro conditions, the addition of 10 nM or 100 nM of glycopolymer on a mannose unit basis (in pre-incubation and post-incubation respectively) decreases by half the bacterial adhesion to intestinal epithelial cells. The anti-adhesive effect of these multivalent ligands was further confirmed in ex vivo conditions for colonic loops of transgenic CEABAC10 mice (Crohn’s disease model mouse). Finally we took advantage of the nanoprecipitation process to generate glyconanocapsules with oily core. The employed strategy allowed for preparing well-defined nanocapsules bearing groups of interest (tags, ligands) or metal particles within the shell and loaded with active molecules in the core in one step
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Huang, Dan. "In Situ Infrared Studies of Photooxidation of Ethanol and Bacteria on TiO2-Based Catalysts." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1398093214.
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Caulkins, Juliana Carvalho de Arruda. "Identificação de genes envolvidos na síntese de polihidroxialcanoatos em Burkholderia cepacia linhagem IPT64." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/87/87131/tde-06082009-111247/.
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Os polihidroxialcanoatos (PHAs) são poliésteres acumulados por microrganismos como material de reserva. O conhecimento das vias bioquímicas e enzimas envolvidas na biossíntese e degradação dos PHAs é uma importante ferramenta para auxiliar na produção industrial. A linhagem Burkholderia cepacia IPT64 é capaz de acumular uma blenda composta de P(3HB) e P(3H4PE) a partir de sacarose. Este trabalho está focado em duas das principais enzimas envolvidas na biossíntese de PHAs: a b-cetotiolase (phaA) e a PHA sintase (phaC). A primeira está associada à especificidade pelo substrato, e a segunda é considerada a enzima chave na síntese de PHAs. Neste trabalho a linhagem mutante phaC foi avaliada quanto à atividade enzimática de PHB sintase, que se constatou ter sido perdida. A presença de mais de uma tiolase no genoma de B. cepacia foi detectada. A inativação do gene phaABc identificado anteriormente, bloqueou totalmente a síntese de P(3HB), e não promoveu o aumento da quantidade total de polímero. Este resultado indica que a tiolase identificada é responsável direta do acúmulo de P(3HB). Outra indicação é que não há uma competição das vias de síntese dos dois polímeros P(3HB) e P(3H4PE), já que não houve alteração na quantidade de P(3H4PE) acumulado, mesmo quando P(3HB) deixou de ser acumulado.The polyhydroxyalkanoates (PHAs) are polyesters accumulated by microorganisms as storage compounds. Knowing the biochemistry pathway and enzymes involved in the biosynthesis and degradation of PHAs is an important tool to help industrial production. The Burkholderia cepacia IPT64 strain is able to accumulate a blend of P(3HB) and P(3H4PE) from sucrose. The focus of this work is on the two main enzymes involved in PHA biosynthesis: the b-ketothiolase (phaA) and the PHA synthase (phaC). The first one is associated with substrate specificity, and the second one is considered the key enzyme in PHA synthesis. In this work a mutant strain phaC was evaluated on its PHB synthase enzymatic activity, that was discovered to have been lost. The presence of other thiolases in the B. cepacia genome was detected. The inactivation of phaABc gene identified previously, blocked totally the P(3HB) synthesis, and didnt increase the polymer content. This result indicates that the identified thiolase is directly responsible for P(3HB) accumulation. Another indication is that the synthesis pathways of the two polymers, P(3HB) and P(3H4PE), dont compete with each other, because the content of P(3H4PE) was not altered, even when the P(3HB) was not accumulated.
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Scolari, Vittore Ferdinando. "Physics of bacterial nucleoid organiation and large-scale gene expression." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066649/document.
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L'ADN génomique des bactéries existe dans un complexe dynamique riche en protéines, le "nucléoïde'', très bien organisé à différentes échelles de longueur. Cette thèse décrit notre modélisation et analyse des données en mettant l'accent sur l'organisation du nucléoïde de \textit{E. coli}, et sur comment cette organisation affecte l'expression des gènes. La première partie du travail est une revue des progrès récents expérimentaux et théoriques quantifiant l'organisation physique (la géométrie et le compactage) du chromosome bactérien. En particulier, nous soulignons le rôle que la physique de la matière molle et la physique statistique jouent dans la description de ce système. Une deuxième partie de l'ouvrage traite d'un modèle de la physique des polymères inspiré par deux caractéristiques du nucléoïde: auto-adhérence osmotique et effet des protéines de pontage. Les résultats sont une caractérisation qualitative du diagramme de phase, qui montre que les nucléoïdes forment des domaines distincts sans interactions intra-spécifiques. La thèse couvre également plusieurs approches d'analyse de données pour tester les connexions entre l'organisation du nucléoïde avec l'expression des gènes (RNA-Seq) et des protéines (ChIP-Seq). Cette dernière partie contient une description de l'outil web NuST, qui permet d'effectuer de simples analyses statistiques sur de multiples échelles. En outre, nous présentons une étude de corrélation d'un grand nombre de mesures d'expression génomique dans différentes conditions de croissance, et nous le comparons avec les cartes d'interaction (Hi-C) spatiale entre le chromosomeThe genomic DNA of bacteria exists in a complex and dynamic protein-rich state, which is highly organized at various lengthscales. This thesis describes a work of physical modeling and data analysis focused on the E. coli genome organization, in the form of the "nucleoid'', and on how nucleoid organization affects gene expression.The first part of the work is a review of the recent experimental andt heoretical advances quantifying the physical organization (compactionand geometry) of the bacterial chromosome with its complement of proteins (the nucleoid). In particular, we highlight the role that statistical and soft condensed matter physics play in describing this system of fundamental biological importance.A second part of the work discusses a simple polymer physics model inspired by two main features of the nucleoid: osmotic self-adhesion and protein bridging. Results are summarized by a qualitative characterization of the phase diagram of this model which shows the general feature that distinct domains may form without the need forintra-specific interactions.The thesis also covers several data analysis approaches to test possible connections between the physical organization of the nucleoid with gene expression (RNA-Seq) and protein binding (ChIP-Seq) datasets. This latter part contains a description of the NuST webtool, which consists of a database which collect datasets from past experiments and an implementation of simple multi scale statistical analysis tools. Additionally, we introduce a correlation study of a large number (about 300) of genome-wide expression data-sets, also compared to the outcome to the published genome interaction map (Hi-C)data
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Brown, Elvie Escorro. "Bacterial cellulose/thermoplastic polymer nanocomposites." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Spring2007/e_brown_050207.pdf.
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Cottenye, Nicolas. "Antimicrobial surfaces based on self-assembled nanoreactors : from block copolymer synthesis to bacterial adhesion studies." Phd thesis, Université de Haute Alsace - Mulhouse, 2010. http://tel.archives-ouvertes.fr/tel-00598560.
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The aim of this work is to develop a new strategy for the prevention of biofilm growth. For this purpose, we prepared bioactive surfaces resulting from the surface-immobilization of nanoreactors self-assembled from amphiphilic poly(isobutylene)-block-oligonucleotide copolymers. The block copolymer was synthesized and characterized via appropriate complementary techniques. Self-assembly into vesicles allowed the functional encapsulation of enzymes, as assayed through enzyme activity monitoring, leading to a prodrug-drug system. The self-assembled structures were specifically immobilized on surfaces via base pairing between the oligonucleotide block of the copolymer and the surface tethered complementary nucleotide sequence. Using E.coli strains, we first observed an influence of the two density of oligonucleotides immobilized on the surface on the number of adherent bacteria. This influence may be due to an effect of surface charge density. We then confirmed the well-known role of curli in biofilm cohesion, and we showed gene over-expression associated with curli production on oligonucleotide-modified surfaces. We demonstrated that gene over-expression does not depend on the topographical features of the surface or on the composition of the nucleotide sequences used in this study. Finally, we demonstrated tha the presence of the vesicular structure is able to produce strong anti-adhesive properties of the surface. We assume, from observations of bacterial response in dynamic conditions, that this effect is due to increased bacterial motility on the surface, leading to a high detachment rate. Which is further confirms by a comparable bacterial response observed on agar hydrogel of different hardnesses. This result provides a preliminary outcome, paving the way to new approaches to antimicrobial strategies.
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Kulaga, Emilia. "Antimicrobial coatings for soft materials." Thesis, Mulhouse, 2014. http://www.theses.fr/2014MULH5312/document.
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Les infections bactériennes lorsqu’elles se développent à partir d’implants sont très difficiles à traiter, l’issue courante étant un retrait pur et simple de l’implant incriminé. Dans ce cadre, les revêtements des biomatériaux ont un rôle important à jouer pour, d’une part, prévenir l’adhésion bactérienne et d’autre part, éliminer les bactéries présentes. Ces revêtements antibactériens doivent par ailleurs permettre une intégration tissulaire des biomatériaux aux cellules rencontrées sur le site de l’implantation. Dans ce travail une nouvelle famille de revêtements antibactériens a été développée. Ils contiennent et libèrent de manière contrôlée un agent bioactif. Ils sont constitués de multicouches de polymère plasma d'anhydride maléique déposées à la surface de fibres de polypropylène tressées et constituant le matériau à implanter. Entre chaque dépôt de polymère plasma (agissant comme couche barrière), des nanoparticules d'argent sont piégées formant ainsi des réservoirs d’agent antibactérien. En raison des différences de propriétés mécaniques entre les films minces plasma et le substrat massique élastique (i.e. tissu de fibre de polypropylène), la résistance à la traction génère des fissures dans les couches polymère plasma, qui sont utilisées comme canaux de diffusion pour les substances bioactives (dans notre cas les ions argent). Avant étirement, la libération spontanée des ions argent par simple diffusion aux travers des couches barrières peut être contrôlée en jouant sur le taux de réticulation des couches plasma. Au cours de l'étirement, le contrôle réversible de l'ouverture des fissures permet une libération maîtrisée des ions argent. Dans le domaine des textiles et d'autres biomatériaux souples, cette stratégie est prometteuse en raison des contraintes mécaniques qui se produisent naturellement sur le site de l'implantation.L'impact de différents types de procédures de stérilisation couramment utilisés (autoclave et irradiation par faisceau d’électrons) sur les propriétés du matériau développé a également été étudié. En particulier, l’incidence sur la chimie de surface, la dispersion des nanoparticules d'argent et la formation de fissures sous étirement a été regardée. La méthode de stérilisation par faisceau d’électrons permet de conserver les propriétés finales recherchées. Enfin, les propriétés antibactériennes du nouveau matériau ont été étudiées. L'effet du relargage des ions argent sur des bactéries Escherichia coli planctoniques, l'adhésion bactérienne et la formation de biofilm sur le système étiré et non-étiré a été évalué. L’intégrité membranaire des bactéries adhérées et des bactéries dans les biofilms a été suivie au cours de l'étude comme indicateur de l’état physiologique des bactéries. Les résultats ont suggéré que la sensibilité des bactéries aux concentrations faibles d'ions d'argent libérés aboutit à la formation de différents types de structures de biofilms sur les matériaux étudiés. L’ensemble des résultats obtenus donne une base solide pour le développement de matériaux intelligents capables de contrôler la libération du principe actif sur le site de l'infection. Nos résultats montrent qu’une faible dose d’argent peut suffire à contrôler l’infection en agissant sur la structure des biofilms formésDespite strict operative procedures to minimize microbial contaminations, bacterial infection of implants significantly raises postoperative complications of surgical procedures. One of the promising approaches is to adjust and control antimicrobial properties of the implant surface. New types of antibacterial coatings prepared via plasma polymer functionalization step have been developed. These coatings contain and release in a control way a bioactive agent. Controlled release was achieved by the fabrication of plasma polymer multilayer systems, which consist of two layers of Maleic Anhydride Plasma Polymer deposited on the surface of Polypropylene made surgical mesh. In between plasma polymer layers, silver nanoparticles are trapped as an antibacterial agent reservoir. Owing to differences between mechanical properties of the plasma-polymer thin films and the elastic bulk substrates, tensile strengths generate cracks within the plasma polymer, which might be used as diffusive channels for bioactive substances, here silver ions. The cracks can be controlled mechanically in a reversible way. The tailoring of the spontaneous release of bioactive agent is achieved by the modification of the second plasma polymer deposition conditions. In addition, during mechanical stimulation of the designed material, control over silver ion release is achieved through an elongation-dependent releasing process allowed by the reversible control of the cracks. In the field of textiles and other soft biomaterials, this strategy is promising due to the mechanical stresses that naturally occur at the implant location. In regard of possible application of the developed system as a future biomaterial, the impact of different types of commonly used sterilization procedures on the properties of developed material was studied. The effects of autoclaving and electron beam sterilization methods on the surface chemistry, the dispersion of embedded silver nanoparticles in the plasma polymer and the cracks formation of the developed material was verified. Results showed the compatibility of the developed system with electron beam sterilization method. The antibacterial properties of the new material have been evaluated. The effect of developed system on planktonic bacteria, bacterial adhesion and biofilm formation on stretched and unstretched system was studied. The membrane integrity of the adhered bacteria and bacteria in biofilms was followed during the study as an indicator of the physiologic state of bacteria. Results suggested that the sensitivity of bacteria to low concentrations of released silver ions resulted in the formation of different types of structures of the biofilms on the studied materials. The results give a strong base on the future of intelligent, silver containing materials that control the release at the site of infection. Our results show that low doses of silver may be sufficient to control infection by acting on the structure of bacterial biofilms
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Arumugam, Senthil. "Reconstitution of bacterial cytokinesis: the Z-ring." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-99045.
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Prokaryotic cell division is one of the most fundamental processes in biology, but the dynamics and mechanics are far from being understood. In many bacteria, FtsZ, a tubulin homologue assembles into a ring-like structure – Z-ring at precisely the middle of the cell. This accurate site selection is dependent on the Min proteins. Min D and MinE self-organise into waves in vitro, and oscillate pole to pole in vivo. MinC is thought to couple the Min oscillations to FtsZ by direct interaction. The mechanism of inhibitory action of MinC on FtsZ assembly is not known. Critical to the understanding of regulation of FtsZ by MinC and other proteins and its probable role in force generation is the organisation, structure and the dynamics of the Z-ring. Current models of the FtsZ filament organization in the Z-ring argue between two different structures – (i) short overlapping protofilaments with lateral interactions and (ii) few long annealed protofilaments with or without lateral contacts.
Our observations of the characteristics of polymerization and turnover studies using fluorescence microscopy suggest that the FtsZ filament is a continuous and irresolute bundle. The results are consistent with a structure where the turnover happens throughout, and any specialised structure resulting in a GTP cap like structure can be ruled out. We show that the turnover rates and hydrolysis rates are similar arguing for a model in which subunit leaves as soon as it hydrolyses GTP. On the basis of crystal structures, we cloned the N-terminal of FtsZ, which acts as a C-terminal end capping fragment and is able to interact with monomers. The end-capping fragment, NZ can disassemble the FtsZ polymers, without influencing the GTPase activity, offering a comparable standard for the activity of MinC. On the basis of our observations, we propose a model on how MinC can disassemble FtsZ polymers. Furthermore, our data shows that the Min CDE system is sufficient to cause spatial regulation of FtsZ provided FtsZ is dynamic.
How the Z-ring takes the form of a functional helical or ring-like structure remains unclear. Extensive modelling approaches have tried to explain the ring formation and force generation. Previous studies have qualitatively shown bending of liposome membranes by FtsZ filaments. We hypothesised that the presumably intrinsically curved filaments should respond to pre-curved substrates, and the alignment should be quantifiable. This should ascertain whether or not FtsZ has intrinsic curvature and/or actively induces any force. Thus, we investigated how FtsZ filaments respond to a range of curvatures, which mimic different stages of the division process.
Our results show that the FtsZ filaments possess intrinsic curvatures as well as spontaneous twist. This facilitates the formation of Z-ring by utilizing geometrical cues. Our results are in agreement with consistent helical FtsZ polymers observed in vivo by Cryo-EM or super resolution microscopy. The alignment of filaments over a range of curvature suggests that the filaments have considerable flexibility, which strongly suggests reconsidering possible mechanisms of force generation. Moreover, the developed assay constitutes a valuable platform to further study proteins involved in modifying curvature of FtsZ filaments.
In summary, by reconstituting the FtsZ filament in vitro, we have elucidated the nature of FtsZ filaments. The dynamics of FtsZ filaments allows them to be inhibited by MinC, thus cooperating with the Min waves. The presence of intrinsic curvature and twist facilitates their formation into a ring necessary for the cell to carry out cytokinesis.
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Jesudason, Jeyarajan Joseph. "Synthetic analogues of bacterial polyesters : preparation and properties." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41256.
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The in situ, equimolar, trimethylaluminum/H$ sb2$O catalyst was used for the ring opening polymerization of racemic $ beta$-butyrolactone, $ beta$-heptanolactone and $ beta$-nonanolactone to form synthetic analogues of the naturally occurring family of biodegradable poly((R) -$ beta$-hydroxyalkanoate) polymers. This catalyst was found to produce both a better yield and a higher molecular weight of a high isotactic, primarily crystalline fraction of poly($ beta$-(R,S) -hydroxybutyrate) than the conventional in situ, equimolar triethylaluminum/H$ sb2$O catalyst. A mechanically tougher, less isotactic and less crystalline fraction of lower molecular weight and a largely amorphous fraction of even lower molecular weight were also isolated and characterized.Biodegradation of solid films of synthetic poly($ beta$-(R,S) -hydroxybutyrate) in the presence of an "extracellular" poly($ beta$-(R) -hydroxybutyrate) depolymerase was found to be dependent on accessibility of the enzyme to the (R) linkages along the polymer chain. The semicrystalline fraction was the most susceptible to degradation whereas the high crystallinity fraction showed little degradation and the low crystallinity fraction only showed limited degradation early in the incubation period.
Synthetic poly($ beta$-(R,S) -hydroxyheptanoate) and poly($ beta$-(R,S) -hydroxynonanoate) polyesters were prepared for the first time and the whole product was predominantly isotactic. It was found to have comparable physical properties as the biosynthetic materials, which are only available as terpolymers. Evidence for paracrystalline ordering relating to the organization of the side chains and formation of liquid crystalline-like phases was observed.
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Hillmering, Mikael. "Polymer microfluidic systems for samplepreparation for bacterial detection." Doctoral thesis, KTH, Mikro- och nanosystemteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-151244.
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Sepsis, caused by blood stream infection, is a very serious health condition thatrequires immediate treatment using antibiotics to increase the chances for patientsurvival. A high prevalence of antibiotic resistance among infected patients requiresstrong and toxic antibiotics to ensure effective treatment. A rapid diagnostic devicefor detection of antibiotic resistance genes in pathogens in patient blood would enablean early change to accurate and less toxic antibiotics. Although there is a pressingneed for such devices, rapid diagnostic tests for sepsis do not yet exist.In this thesis, novel advances in microfabrication and lab-on-a-chip devices arepresented. The overall goal is to develop microfluidics and lab-on-a-chip systems forrapid sepsis diagnostics. To approach this goal, novel manufacturing techniques formicrofluidics systems and novel lab-on-a-chip devices for sample preparation havebeen developed.Two key problems for analysis of blood stream infection samples are that lowconcentrations of bacteria are typically present in the blood, and that separation ofbacteria from blood cells is difficult. To ensure that a sufficient amount of bacteria isextracted, large sample volumes need to be processed, and bacteria need to be isolatedwith high efficiency. In this thesis, a particle filter based on inertial microfluidicsenabling high processing flow rates and integration with up- and downstream processesis presented.Another important function for diagnostic lab-on-a-chip devices is DNA amplificationusing polymerase chain reaction (PCR). A common source of failure for PCRon-chip is the formation of bubbles during the analysis. In this thesis, a PCR-on-chipsystem with active degassing enabling fast bubble removal through a semipermeablemembrane is presented.Several novel microfabrication methods were developed. Novel fabrication techniquesusing the polymer PDMS that enable manufacturing of complex lab-on-a-chipdevices containing 3D fluidic networks and fragile structures are presented. Also,a mechanism leading to increased accuracy in photopatterning in thiol-enes, whichenables rapid prototyping of microfluidic devices, is described. Finally, a novel flexibleand gas-tight polymer formulation for microfabrication is presented: rubbery OSTE+.Together, the described achievements lead to improved manufacturing methodsand performances of lab-on-a-chip devices, and may facilitate future development ofdiagnostic devices.QC 20140916
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Bilbruck, John. "Some factors affecting bacterial adhesion to polymer monofilaments." Thesis, University of Brighton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292350.
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Xue, Xuan. "Polymers for quorum sense interference." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13060/.
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The synthetic polymers reported in this thesis are able to bind the small molecule autoinducer-2 (AI-2) in the Quorum Sense (QS) pathways of the marine organism with high affinity, and some of the polymers are also able to sequester rapidly the same bacteria from suspension. Specifically, the Alizarin Red S (AR-S) assay was used to compare binding interactions of boric and boronic acid with diol species, and interactions were further probed by 11B-NMR spectroscopy and Mass spectrometry. Dopamine was considered as a potential AI-2 scavenger for polymeric QS control owing to the high binding affinities for boron. Therefore, poly{N-(3,4-dihydroxyphenethyl) methacrylamide-co-N-[3-(dimethylamino)propyl] methacrylamide} [p(DMAm-c-DMAPMAm)] and poly(3,4-dihydroxy-L-phenylalanine methacrylamide) [p(L-DMAm)] were prepared via Reversible Addition Fragmentation Chain Transfer (RAFT) polymerization and characterized by 1H-NMR spectroscopy. The activities of these catechol polymers and carbohydrate-based poly(β-D-glucosyloxyethyl methacrylate) (p(GlcEMA)) in QS interference was demonstrated by bioluminescence assays with the Vibrio harveyi MM32 strain and by bacterial aggregation experiments. Polymersomes were then investigated as artificial protocells, with a view to establishing polymer vesicle containers as both reservoirs of QS mediated molecules, and of binding QS agents and bacteria. Hydrophobic monomers N-(2-Ethylhexyl) acrylamide [p(2-EHAm)] and N-phenylacrylamide [p(PAm)] were therefore polymerized into block copolymers from p(L-DMAm)-RAFT agents. The membrane permeability of polymersomes was measured via encapsulation and release of dyes, while the morphologies were examined with Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). Polymersomes were also investigated for potency in QS quenching via the bioluminescence assay and bacterial aggregation experiments. Initial studies of a communication feedback loop between bacteria and polymersome-encapsulated QS agents were performed again via bioluminescence assays. The results reveal that the investigated polymersomes exhibit potent activities in QS quenching, and further development might act as components of a synthetic biology approach to combating microbial pathogenicity.
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Fernández, Coll Llorenç. "Secondary channel of the RNA polymerase, a target for transcriptional regulation in bacteria." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/298719.
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Gene expression begins by an enzymatic complex known as RNA polymerase (RNApol). The basic unit (core) of RNApol in bacteria is formed by 5 protein subunits (α2ββ’ω). The three-dimensional structure of the RNApol defines two spaces that play a relevant role during transcription, defined as primary and secondary channel. The holoenzyme needs the binding of a σ subunit to recognise promoter sequences and initiate the transcription process.
Transcription is a dynamic process controlled at different steps. Genetic regulation during transcription initiation has been highly studied, and several mechanisms of regulation exist. However, the aim of this project is to study some aspects of the regulation during transcription elongation. It has been described that the alamone ppGpp, as well as several proteins, such as GreA, GreB or DksA, enter within the secondary channel and interact directly with the catalytic centre of the RNApol. The swap between the different factors that bind to the secondary channel of the RNApol may cause changes in the expression pattern.
It has been postulated that DksA and ppGpp act as cofactors, however, a previous study performed in our research group, indicated that the phenotype of ppGpp and DksA deficiencies were not always identical, letting us suggest that the occupancy degree of the secondary channel of the RNApol may have significant impact in the expression pattern in E. coli. The data obtained clearly indicate that upregulation of some genes, such as fliC, that occurs in absence of DksA, was the result of the vacancy of the secondary channel generated in a dksA strain rather than being the result of DksA having a direct repressor effect. We suggested that in the absence of DksA, the interactions of other proteins, such as GreA, are promoted and responsible of the upregulation observed.
In this project, functional, structural and phylogenetical studies of the protein GreA were performed to determine which amino acids are important for i) the functionality of GreA, ii) the ability to bind to the secondary channel of the RNApol or iii) the capacity to compete with other factors, such as DksA. We have determined that greA overexpression produces a negative effect of the bacterial growth. Moreover, this negative effect is enhanced in absence of DksA, highlighting the hypothesis of a competition between factors that bind into the secondary channel.
The effect of this competition between GreA and DksA was also determined studying the expression of the fliC gene. Our data showed that both, GreA and DksAare required for fliC expression but act at different levels in the regulatory cascade of flagella expression regulation. GreA may control fliC expression during transcription elongation whereas DksA may act during transcription initiation.
Changes in the amount of GreA, could affect the competition between factors that bind to the secondary channel of the RNApol. Therefore, we have determined the expression pattern of greA. Transcriptional studies showed a crosstalk between the different factors that bind into the secondary channel of the RNApol exists.
Finally, transcriptomic studies were performed to determine the effect of ppGpp and DksA on the expression pattern of Salmonella enterica serovar Typhimurium. The results obtained indicate : i) the effect of the possible competence between the factors that interact into the secondary channel of the RNApol and ii) the effect of ppGpp and DksA on the expression of several virulence factors as well as different mobile elements present in Salmonella.El control de l’expressió gènica en bacteris recau principalment sobre un complex enzimàtic anomenat ARN polimerasa (ARNpol). A procariotes, la seva unitat bàsica (core) està formada per 5 subunitats proteiques (a2bb’w). S’han determinat dos canals entre les diferents subunitats de l’ARNpol: el canal primari, on es desenvolupa la transcripció, i el canal secundari, que comunica el medi exterior amb el centre catalític de l’ARNpol. Tot i així, aquest holoenzim necessita la unió d’una subunitat σ per ser capaç de reconèixer una seqüència promotora i iniciar la transcripció. S’han descrit diferents factors, tant proteics com no proteics, que poden interaccionar amb el canal secundari de l’ARNpol i causar alteracions a l’expressió gènica. En aquesta tesi ens hem centrat en la possible competència entre els diferents factors que poden interaccionar amb el canal secundari de l’ARNpol. Estudis anterior duts a terme en el nostre grup d’investigació, ens van permetre postular una possible competència entre els diferents factors que interaccionen amb el canal secundari de l’ARNpol, més concretament entre les proteïnes GreA i DksA. Aquesta competència provocaria alteracions en el patró d’expressió gènica d’Escherichia coli. En aquest treball s’han dut a terme estudis funcionals, estructurals i filogenètics de la proteïna GreA que ens han permès determinar quins aminoàcids, i com a conseqüència quins dominis, podrien ser importants per la funcionalitat de la proteïna, la seva capacitat d’unir-se a l’ARNpol i la seva capacitat de competir amb altres factors. A més, hem estudiat quin efecte té la competència entre els diferents factors que interaccionen amb el canal secundari sobre l’expressió d’un gen diana. Canvis en els nivells de la proteïna GreA, poden afectar la competència pel canal secundari de l’ARNpol Per això hem determinat el patró d’expressió del gen greA, així com l’existència d’una regulació creuada entre les diferents proteïnes que interaccionen amb el canal secundari. Finalment, hem dut a terme un estudi transcriptòmic en Salmonella enterica serovar Typhimurium, amb l’objectiu de determinar quin és l’efecte d’aquesta competència en l’expressió de factors de virulència.
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Bridgett, Michael Jonathan. "The control of bacterial adhesion to polymeric surfaces." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335642.
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Dexter, Sarah Jayne. "Adhesion of mammalian and bacterial cells to modified polymer surfaces." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395586.
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Pereni, Codruta-Ioana. "Encrustation and bacterial adhesion on metallic, ceramic and polymer surfaces." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423284.
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Ramos, Patrícia Locosque. "Taxonomia do gênero Stenotrophomonas através de Multi Locus Sequence Analysis (MLSA)." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/87/87131/tde-26012012-170618/.
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As Stenotrophomonas são comumente encontradas no trato respiratório de pacientes com doenças pulmonares crônicas e também na rizosfera de plantas. Esse gênero apresenta resistência a diversos antibióticos, promove o crescimento de plantas e algumas espécies apresentam a capacidade de fixar o nitrogênio atmosférico. O Multi Locus Sequence Analysis (MLSA) é uma metodologia baseada em genes constitutivos para definição e alocação taxonômica de novas espécies. O objetivo geral do presente trabalho foi caracterizar taxonomicamente uma coleção ampla de Stenotrophomonas composta por isolados endófitos, linhagens-tipo e de referência. Para tanto, foi estabelecido um sistema de classificação e identificação de Stenotrophomonas por meio de MLSA. Foi possível através da metodologia de MLSA definir 9 novas espécies, detectar a presença de um novo gênero e estabelecer um sistema online de taxonomia para Stenotrophomonas.The genus Stenotrophomonas is found in the respiratory treatment of patients with chronic pulmonary and also in the rizhosfera of plants. It presents resistance to several antibiotics, promotes the growth of plants and some species present the ability to fix atmospheric nitrogen. The Multi Locus Sequence Analysis (MLSA) is a methodology based on constitutive genes for definition and taxonomic allocation of new species. The general objective of the present work was to characterize a wide collection constituted by Stenotrophomonas from isolated endophytic, type and reference strains. In such a way, a system of classification and identification of Stenotrophomonas by means of MLSA was established. It was possible through the MLSA methodology to define 9 new species, to detect the presence of a new genus and to establish an online system for Stenotrophomonas taxonomy.
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Rode, Alexander. "Isolierung und Charakterisierung von bakteriellen extrazellulären polymeren Substanzen aus Biofilmen / Isolation and characterization of bacterial extracellular polymeric substances from biofilms." Gerhard-Mercator-Universitaet Duisburg, 2004. http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-09132004-102114/.
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Microorganisms in biofilms are kept together by extracellular polymeric substances (EPS). The EPS are key molecules for the structure, function and organization of biofilms. Chemical and / or physical isolation methods are being used for the quantitative separation of EPS from biofilms. The yield of EPS depends on the method of isolation. Four different methods of EPS isolation were used in this work (separation by stirring and centrifugation, use of a cation exchange resin, extraction with formaldehyde and extraction with formaldehyde and NaOH) on pure culture biofilms of Pseudomonas aeruginosa and biofilms from sewage treatment systems. The isolation by stirring and centrifugation was suitable for pure culture biofilms. If calcium was present in the growth medium stirring and centrifugation alone was not sufficient. The isolation of EPS was successful with the cation exchange method. The method of choice for the isolation of EPS from environmental biofilms was the cation exchange method. EPS from pure culture biofilms of P. aeruginosa and P. fluorescens did not only consist of polysaccharides, but also of significant amounts of proteins. In environmental biofilms humic substances and DNA were found in addition to polysaccharides and proteins. Detailed studies of the EPS from P. aeruginosa showed, that the EPS consisted of 70 % (w/w) of alginate. Alginate showed a clear heterogeneity in relation to charge (acetylated and non-acetylated fraction) and molar mass. Neutral carbohydrates were not found in the EPS after total hydrolysis followed by thin layer chromatography. Proteins amounted to 28 % (w/w) of the EPS. It is assumable that this not only related to enzymes, but also structural proteins (e. g. lectins). Rhamnose lipids (mainly di-rhamno lipid) were also found in the EPS (small amount of 1 % (w/w)); these molecules may also play an important role in the development of the biofilm structure. By increasing the time of biofilm cultivation P. aeruginosa produced (related to cell number) more EPS (mainly alginate). The composition of the EPS was depending on the nutrient medium. In synthetic media high amounts of polysaccharides and almost no proteins (in contrast to rich media) were detected in the EPS. EPS of pure culture biofilms of P. fluorescens contained carbohydrates (57 % (w/w)) and proteins (28 % (w/w)). Acetyl groups (5 % (w/w)) and glucose and galactose after hydrolysis and thin layer chromatography were detected in the EPS. Possibly the exopolysaccharide of P. fluorescens is an acetylated galactoglucan. In the analyzed sludges of waste water treatment proteins followed by carbohydrates made up the main components of the EPS. Humic substances and small amounts of DNA were detected in these EPS. The EPS of aquatic biofilms contained large amounts of humic substances. Uronic acids were not detected in any analyzed environmental biofilm. Therefore acidic polysaccharides in these biofilms cannot play any role in the stabilization of biofilms by cross linking the EPS with multivalent cations. Instead of that, humic substances, nucleic acids and acidic proteins could be responsible for cross linking.
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Pancani, Elisabetta. "Development and advanced characterisation of antibiotic-loaded nanoparticles to fight intracellular bacteria." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS513/document.
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Le traitement des infections intracellulaires est compliqué par la capacité des bactéries à «se cacher» à l’intérieur des cellules de l’hôte, en particulier celles du système immunitaire, entravant ainsi l’action de nombreux agents antimicrobiens. La diffusion croissante de souches résistantes est très inquiétante. Dans ce cadre, les nanoparticules (NPs) constituent une stratégie prometteuse pour administrer de manière optimisée des agents antimicrobiens.Ce travail de thèse, réalisé dans le cadre du projet européen ITN Cyclon Hit, visait à développer et caractériser des NPs biodégradables et biocompatibles chargées en antibiotiques, composés d’acide polylactique (PLA), d’acide poly (lactique-co-glycolique) (PLGA) et de polycaprolactone (PCL) ou de cyclodextrines polymérisées (pCD).Les deux premiers chapitres sont consacrés aux verrous technologiques liés à l'encapsulation de certains médicaments puissants dans les NPs polymériques. Tout d'abord, ces vecteurs ont été utilisés pour la délivrance simultanée d'une combinaison de molécules actives récemment découverte, l'éthionamide (ETH) et son Booster, pour le traitement de la tuberculose. Deuxièmement, ils ont été employés pour relever les défis liés à l'incorporation d'une quinolone de première génération, l'acide pipémidique (PIP), dans le but d'optimiser sa distribution intracellulaire dans des infections telles que la salmonellose.La co-incorporation efficace de l'ETH et du booster a dû surmonter de nombreuses difficultés liées à des problèmes de solubilité, de cristallisation et de biodisponibilité. Nos NPs en PLA et en pCD ont montré leur capacité de co-encapsuler efficacement les deux molécules et tout particulièrement celles en pCD. Elles incorporent les médicaments à la fois dans les cavités des CD et dans des microdomaines hydrophobes. Les NPs en pCD, non toxiques après administration pulmonaire répétée de fortes doses, ont été administrés in vivo par voie endotrachéale directement au site d'infection. Elles ont permis une diminution de 3-log de la charge bactérienne pulmonaire des animaux infectés après seulement 6 administrations. De même, l'incorporation de PIP a été confrontée à des défis liés à la cristallisation de PIP et à sa libération incontrôlée. Malheureusement, le PIP présentait une faible affinité pour tous les matériaux polymériques étudiés et son encapsulation physique était infructueuse. Ainsi, une approche alternative a été développée en couplant le PIP au PCL via une réaction sans catalyseur initiée par le médicament. Le conjugué PCL-PIP se auto-assemble en forme de NPs avec une charge en PIP de 27%. Cependant, le PCL-PIP n'a pas pu être dégradé in vitro, mais l’approche de synthèse de conjugués est séduisante pour obtenir de particules stables et avec un contenu important en PIP.La compréhension approfondie de la structure et de la composition du noyau et de la couronne des nanostructures contenant une ou deux molécules actives est cruciale pour leur optimisation. Les deux derniers chapitres sont donc consacrés à l'application innovante de l'AFM-IR, une méthode nanospectroscopique originale combinant la microscopie à force atomique (AFM) avec la spectroscopie infrarouge (IR), à l'analyse chimique des NPs en PLGA ou à leur détection sans marquage après internalisation dans les cellules.L’AFM-IR est capable de fournir une caractérisation chimique à l'échelle nanométrique (résolution ~10 nm). Une avancée majeure du travail est l'application du mode tapping permettant l'investigation individuelle de chaque NP. Le signal IR spécifique des composants des NPs a été utilisé pour appréhender la composition chimique de leur cœur et couronne ainsi que pour localiser précisément le médicament. De plus, l'AFM-IR en mode contact a permis pour la première fois la localisation sans marquage et l'identification chimique des NP à l'intérieur des cellules. Ce travail ouvre la voie à d'innombrables applications de cette technique dans le domaine de la nanomedecineThe treatment of intracellular infections is very challenging given the ability of bacteria to “hide” inside the cells of the host, especially the ones of the immune system, thus hampering the action of many antimicrobial agents. The battle against these bacteria has been further exacerbated by the increasing diffusion of antimicrobial resistant strains. In this frame, nanoparticles (NPs) are a very promising strategy to overcome the limitations of free antimicrobial agents by administering them in an optimized manner.This PhD work, performed as part of the European Project ITN Cyclon Hit, aimed at the development and advanced characterisation of antibiotic-loaded biodegradable and biocompatible NPs made of poly (lactic acid) (PLA), poly (lactic-co-glycolic) (PLGA) and polycaprolactone (PCL) or of polymerised cyclodextrins (pCDs).The first two chapters are dedicated to the encapsulation of powerful but challenging drugs in polymeric NPs. Firstly, these carriers were employed for the simultaneous delivery of a potent drug combination recently discovered, ethionamide (ETH) and its booster, for tuberculosis therapy. Secondly, they were used to address the challenges related to the incorporation of a first-generation quinolone, pipemidic acid (PIP), with the aim of optimising its intracellular delivery in infections such as salmonellosis.The efficient co-incorporation of ETH and booster had to overcome several technological barriers. These drugs presented solubility, crystallisation and bioavailability-related problems which were overcome thanks to the developed NPs. Our engineered PLA and pCD NPs were both able to efficiently co-encapsulate the two molecules. Among the in depth-characterised formulations, pCDs NPs displayed the best physico-chemical properties and were shown to host the drugs both in the CD cavities and in confined spaces inside NPs crosslinked polymer. The pCD NPs were administered in vivo by endotracheal route directly to the infection site. Empty NPs were shown non-toxic after repeated pulmonary administration of high doses. Moreover, loaded pCD NPs led to a 3-log decrease in the pulmonary bacterial load of infected animals after only 6 administrations. Similarly, the incorporation of PIP faced challenges mainly related to PIP crystallization and burst release. Unfortunately, PIP displayed poor affinity for all the studied polymeric materials and its physical encapsulation was unsuccessful. Thus, an alternative approach was developed by coupling PIP to PCL by using an original catalyst-free drug-initiated reaction. The PCL-PIP conjugate self-assembled in NPs with up to 27 wt% PIP which were thoroughly characterised. However, the conjugate couldn’t be enzymatically degraded. With the design of novel PCL-PIP conjugates, this self-assembly approach could represent a promising strategy.The deep understanding of the structure and composition of complex core-corona nanocarriers containing one or two active molecules is crucial for their optimisation. The last two chapters are devoted to the innovative application of AFM-IR, an original nanospectroscopic method combining atomic force microscopy (AFM) with infrared (IR) spectroscopy, to the chemical analysis of PLGA NPs or to their label-free detection after cell internalisation.AFM-IR is able to provide chemical characterisation at the nanometer scale (resolution ~10nm). One main breakthrough here is the application of the recently developed tapping mode allowing the investigation of single polymeric NPs. The specific IR signal of NPs constituents was used to unravel the chemical composition of their core and corona as well as to precisely locate the drug. Moreover, the AFM-IR in contact mode enabled for the first time the label-free localisation and unambiguous chemical identification of NPs inside cells using the polymer IR specific response as a fingerprint. This work paves the way for countless application of this technique in the field of drug delivery
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Ferguson, Anna Louise. "Interactions of bacterial sigma subunits with core RNA polymerase." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341839.
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Sheppard, Carol Maria. "Characterisation of bacteriophage-encoded inhibitors of the bacterial RNA polymerase." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/10960.
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RNA polymerase (RNAP) is an essential enzyme which catalyses transcription; a highly regulated process. Bacteriophage are viruses which infect bacteria and as a result have evolved a diverse range of mechanisms to regulate the bacterial RNAP to serve the needs of the virus. T7 Gp2 and Xp10 P7 are two bacteriophage-encoded transcription factors that inhibit the activity of the bacterial RNAP. The aim of this study is to investigate the molecular mechanisms of action of Gp2 and P7. Fluorescence anisotropy experiments proved Gp2 to bind to RNAP, independently of the σ- factor, with a 1:1 stoichiometry and a low nanomolar affinity. In vitro transcription assays demonstrated that a negatively charged strip in Gp2 is the major determinant for its inhibitory activity. Furthermore, it was shown that efficient Gp2-mediated inhibition of RNAP also depends upon the highly negatively charged and flexible σ70 specific domain, R1.1. Gp2 and R1.1 both bind in the downstream-DNA binding channel and exert long-range antagonistic effects on RNAP-promoter DNA interactions around the transcription start site. A systematic mutagenesis screen was used to identify residues in P7 necessary for binding to the RNAP; results were interpreted in the context of a newly resolved NMR structure of P7. Electrophoretic mobility shift assays revealed that P7 ‘traps’ a RNAP-promoter DNA complex en route to the transcriptionally-competent complex. Preliminary results from a fluorescence based RNAP-DNA interaction assay suggest that P7 may target RNAP interactions with the -35 promoter element and the ‘discriminator region’. This study has contributed to our understanding of how non-bacterial transcriptional factors can influence bacterial gene expression by modulating RNAP activity. This study has also uncovered vulnerabilities in RNAP, which have the potential to be exploited therapeutically. To this end, these structure-function studies of Gp2 and P7 have provided the basis for the rational design of novel anti-bacterial compounds.
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Sui, Cheng. "Effects of polymeric materials on bacterial aggregation and quorum sensing." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/42853/.
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In order to develop novel antibacterial therapies that combine anti-adhesion, anti-quorum sensing and the delivery of conventional antibiotics, the effects of polymers on bacterial aggregation and quorum sensing (QS) were studied. QS is a term used to describe method by which bacteria use chemical signal molecules to modulate pre-infection behaviour such as surface attachment. Polymers that can interfere with bacterial adhesion or the signal molecules used for QS are therefore a potential means to control bacterial population responses. In this thesis, the ability of the cationic polymers poly (N-[3-(dimethylamino) propyl] methacrylamide) (p(DMAPMAm), P1) and poly (N-dopamine methacrylamide-co-N-[3-(dimethylamino) propyl] methacrylamide) (p(DMAm-co-DMAPMAm), P2) to cluster a range of bacteria, such as Staphylococcus aureus(Gram-positive), Vibrio harveyi, Escherichia coli and Pseudomonas aeruginosa(Gram-negative) under conditions of varying pH and polymer concentration was investigated. It was identified that clustering ability was strongly dependent on the balance between charge and hydrophobicity. The results also suggested that catechol moieties might have a positive effect on adhesive properties. Moreover, the potency of polymers against QS of Vibrio harveyi was assayed via testing bioluminescence. P1 which was able to bind to the surface of bacteria through electrostatic interactions enhanced the expression of QS and P2 which could bind to both the bacteria and QS signals showed the ability to both enhance and reduce light production. Furthermore, polymeric vesicles made of copolymers containing poly (3,4-dihydroxy-L-phenylalanine methacrylamide) (p(L-DMAm)) which displayed similar dual affinity compared toP2 were prepared and their ability to modulate QS responses in Vibrio harveyi was demonstrated. All the vesicles showed higher potency in quenching bioluminescence than their linear polymer analogues. To explore the feasibility of using self-assembled polymers for anti-microbial drug delivery, silver loaded DOPG lipid vesicles were made and were found to interfere with QSwhile reducing bacterial viability when the concentration of Ag+ was above the MIC (0.1 μg/mL). The results overall suggested that combined antimicrobial therapies might be possible using polymers and both QS and cytostatic or cytotoxic agents.
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Southern, Emma. "The role of #sigma#'54 region II in transcription initiation." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302057.
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Phillips, Ronald Lee III. "Poly(para-phenyleneethynylene)s probing the biological interface with biomolecular materials /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26555.
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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Dr. Uwe H.F. Bunz; Committee Member: Dr. Andrew Lyon; Committee Member: Dr. Laren Tolbert; Committee Member: Dr. Nicholas Hud; Committee Member: Dr. Sherry Michele Owen. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Pernagallo, Salvatore. "Biocompatible polymer microarrays for cellular high-content screening." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/7571.
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The global aim of this thesis was to study the use of microarray technology for the screening and identification of biocompatible polymers, to understand physiological phenomena, and the design of biomaterials, implant surfaces and tissue-engineering scaffolds. This work was based upon the polymer microarray platform developed by the Bradley group. Polymer microarrays were successfully applied to find the best polymer supports for: (i) mouse fibroblast cells and used to evaluate cell biocompatibility and cell morphology. Fourteen polyurethanes demonstrated significant cellular adhesion. (ii) Analysis of the adhesion of human erythroleukaemic K562 suspension cells onto biomaterials with particular families of polyurethanes and polyacrylates identified. A DNA microarray study (to access the global gene expression profiles upon cellular binding) demonstrated that interactions between cells and some polyacrylates induced a number of transcriptomic changes. These results suggested that, during these interactions, a chain of cellular changes is triggered, most notably resulting in the downregulation of membrane receptors and ligands. (iii) Identification of polymers with potential applications in the field of stem cell biology. Polymers were identified that showed attachment, promotion and stabilisation of hepatocyte-like cells. A polyurethane support (PU-134) was pinpointed, which significantly improved both hepatocyte-like cell function and “lifespan”. A second project investigated biomaterials that promoted adhesion, growth and function of endothelial progenitor cells. A new polymer matrix was identified which contained the necessary signals to promote endothelial phenotype and function. This has potential application in the creation of blood vessels and the endothelialisation of artificial vessel prostheses and stent coatings for improving angioplasty therapy. (iv) The study of bacterial adhesion, focusing on the adhesion of food-borne pathogenic bacterium Salmonella enterica serovar typhimurium, strain SL1344, and the commensal bacterium Escherichia coli, strain W3110. Several polymers were found to support selective bacterial enrichment, as well as others that minimised bacterial adhesion.
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Martín, Arjol Ignacio. "Polymeric emulsifiers obtained by bacterial transformation from oily wastes in bioreactor." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/135052.
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Cerca del 80% de los aceites y las grasas producidas mundialmente son aceites vegetales y el resto de origen animal. Dicha cantidad de ácidos grasos sirve como fuente para la producción de una serie de compuestos nuevos: diácidos o epóxidos de cadena larga o ácidos grasos omega-hidroxilados.
Pseudomonas aeruginosa 42A2 es un bacilo gramnegativo que produce ácidos grasos trans-hidroxilados (HFA) a partir del ácido oleico cuando es cultivado en un medio mineral. Dichos HFA, los ácidos 10(S)-hidroxi-8(E)-octadecenoico ((10S)-HOME) y 7,10(S,S)-dihidroxi-8(E)-octadecenoico ((7S,10S)-DiHOME), son producidos a través de un sistema de aireación no dispersivo que permite una mayor oxigenación y homogeneidad del medio de cultivo en los que son producidos. Tanto es así que se han conseguido unos valores de productividad para estos HFA de 0.29 y 0.31 g•L-1•h-1, respectivamente.
Éstos han sido purificados a unos niveles superiores del 91% para poder ser polimerizados y obtener estólidos, poliésteres de trans-HFA. Por medio de una búsqueda exhaustiva, se decidió que Novozym 435, lipasa B de Candida antarctica, era la lipasa ideal para realizar dicha polimerización in-vitro.
En una primera aproximación, se sintetizaron estólidos a partir de (10S)-HOME en medio orgánico, n-hexano. Se optimizó las condiciones de reacción y el mayor rendimiento obtenido fue del 30%. Esta nueva generación de estólidos trans ha requerido unas nuevas técnicas analíticas. Estos poliésteres han sido analizados a través de MALDI-TOF-MS utilizando una matriz de DHB neutralizada con LiOH, ya que, el ion 7Li+ ayuda a estabilizar dichos compuestos y por ende obtener espectros de masas menos fragmentados. Dicha técnica estructural ha resultado ser más rápida y barata que una LC-MS convencional. Dímeros del derivado monohidroxilado fueron sintetizados.
En una segunda aproximación, se sintetizaron estólidos a partir de (10S)-HOME y (7S,10S)-DiHOME en medio libres de disolventes orgánicos usando Novozym 435. Rendimientos del 71 y del 94% de conversión, respectivamente, fueron obtenidos después de optimizar los medios de reacción. Estos estólidos fueron analizados por MALDI-TOF-MS con una matriz de DHB saturada en acetonitrilo para incrementar la sensibilidad de los oligómeros de mayor peso molecular. Mediante esta técnica se llevaron a detectar oligómeros de hasta 6 y 7 unidades monoméricas, respectivamente. Así mismo se usó la RMN para determinar la estructura de los compuestos analizados con gran éxito.
Finalmente, se decidió sintetizar etil ésteres de los ácidos (10S)-HOME y (7S,10S)-DiHOME debido a las propiedades aromáticas. Estos ésteres se sintetizaron en medio orgánico, cloroformo, y en un medio libre de disolventes con unos rendimientos totales, en ambos casos. Dichos etil ésteres fueron analizados por MALDI-TOF-MS y RMN para determinar su masa molecular y estructura, respectivamente.
Finalmente, se realizó un estudio de diversas propiedades físico-químicas de estos compuestos obtenidos. La viscosidad y diversos parámetros calorimétricos obtenidos a partir de curvas DSC y TGA fueron determinados para saber de la naturaleza de esta nueva generación de ésteres.About 80% of the oil and fats produced worldwide are vegetable oils and the rest are from animal origin. This amount of fatty acids is used as a source for producing new compounds: long chain diacids or epoxides or omega-hydroxylated fatty acids. Pseudomonas aeruginosa 42A2 is a gramnegative bacillus which produces hydroxy-fatty acids (HFA) when is cultivated in a mineral médium using oleic acid as carbon source. These HFA, 10(S)-hydroxy-8(E)-octadecenoic acid ((10S)-HOME) and 7,10(S,S)-dihidroxi-8(E)-octadecenoic acid ((7S,10S)-DiHOME), are produced with a non-dispersive aeration system that enhanced oxygenation and homogeneity of the culture media. The following volumetric productivity for these HFA were achieved: 0.29 y 0.31 g•l(-1)•h(-1), respectively. These HFA were purified with levels higher than 91% of purity for being later polymerizated and obtaining estolides, polyesters of HFA. For that purpose Novozym 435, lipase B from Candida antarctica, was chosen among other lipases to performance this enzymatic reaction. First of all, (10S)-HOME estolides were synthesized in organic media, n-hexane. Reaction conditions were optimized, reaching a 30% reaction yield. This new family of trans-estolides required adapted analytical techniques. These polyesters were analyzed with MALDI-TOF-MS using a DHB matrix neutralized with LiOH. 7Li+ ion stabilizes such compounds and less fragmented mass spectra were observed. This technique was less time-consuming than LC-MS. Dimers of the monohydroxylated compound were produced. Secondly, estolides from (10S)-HOME y (7S,10S)-DiHOME were synthesized in a solvent-free media using Novozym 435. Reaction yields of 71 and 94% were reached, respectively, after optimizing reaction media. These compounds were analyzed by MALDI-TOF-MS using a DHB matrix saturated in acetonitrile for detecting higher mass oligomers. This technique could detect oligomers composed of 6 and 7 monomeric units, respectively. Moreover, NMR were also used to determine the structure of these polyesters. Thirdly, trans-HFA ethyl esters were synthesized due to their aromatic properties. Such esters were produced in organic media, chloroform, and in a solvent-free media, in both cases with a total conversion. trans-HFA ethyl esters were analyzed by MALDI-TOF-MS and NMR for determing their molecular mass and structure, respectively. Finally, a physicochemical study of these compounds, estolides and ethyl ester, was carried out. Viscosity and some calorimetric parameters from DSC and TGA curves were determined.
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Burrows, Patricia Clare. "Structure-function studies on the major form of bacterial RNA polymerase." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415040.
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Akbar, Sirwan. "Gram negative bacterial biofilm formation and characterisation of extracellular polymeric substances." Thesis, University of Huddersfield, 2016. http://eprints.hud.ac.uk/id/eprint/30236/.
Full textAbstract:
Gram negative bacteria such as Stenotrophomonas maltophilia, Pseudomonas aeruginosa and Citrobacter freundii are often associated with multiple drug resistance and the generation of nosocomial infections. In the current study several clinical strains of theses bacteria (Ps 1, Ps 3, Ps 5, St 18, St 51, St 53 and C. freundii) and two culture collection strains Ps 10421 and St 9203 were evaluated for their ability to generate biofilms and the characteristics of the associated extracellular polysaccharides they produced. The ability of these strains to develop biofilms on a range of media and with a number of carbon sources was investigated. A range of mineral media employing glucose, ethanol and glycerol were developed in such a way as to ensure they did not contain compounds that interfere with extracellular polysaccharide analysis allowing a more in depth analysis of the extracellular polysaccharide generated by the bacteria under investigation. Following an assessment of the biofilm forming potential of all the strains under consideration, three were singled out for particular attention, i.e. Ps 3, St 53 and C. freundii strain isolated during this investigation. Two of strains were chosen for the strength of their biofilm forming potential (Ps 3 and St 53), on the other hand C. freundii was chosen because the scientific literature contains very little published information regarding its extracellular polysaccharide and its biofilm forming characteristics. These bacteria were able to produce biofilm on both hydrophobic (plastic) and hydrophilic (glass) surfaces. In order to get a broader understanding of the biofilm forming capabilities of these bacteria their whole genomes were sequenced and subsequently published. These genomes demonstrated that St 53 and C. freundii both contained the pgaABCD which is known to be associated with biofilm formation. Whilst Ps 3 contains a full complement of pel (PA3058-PA3064), psl (PA2231-2245) and alginate biosynthesis operons (PA3540-3548) related to biofilm formation. In addition all three species contained genes associated with virulence, pathogenicity and antibiotic resistance. The generation and extraction of extracellular polymeric substance generated by these three bacteria underwent a period of optimisations which included an optimisation of both the media and the growth conditions and the extraction process. In particular the use of trichloroacetic acid (TCA) was found to be critical with 0-5% TCA considered optimum for the removal of proteins prior to polysaccharide extraction. This is far less than has been previously employed in studies on lactic acid bacteria, however when used with the Gram negative bacteria investigated here, high levels of TCA degraded the polysaccharide that was being generated preventing its extraction in the quantities required for analysis. Analysis of the polysaccharides produced by St 53, Ps 3, and C. freundii, all demonstrated typical NMR spectra associated with bacterial extracellular polysaccharide. However, the NMR spectra from these polysaccharides also contained peaks typical of the presence of dextran. The use of a fungal dextranase confirmed the presence of a dextran like polymer in the polysaccharide generated by these bacteria. This indicated that all three of these bacteria generated complex polysaccharides with at least two components one mannose rich and the second a dextran like glucose rich polymer. This is the first report of a dextran being associated with the EPS of these bacteria and suggests that the Pel polysaccharide of P. aeruginosa is a dextran. Investigation of bacterial pathogenicity focussed on Ps 3 since P. aeruginosa is the most pathogenic of the three species investigated. The culture collection strain Ps 10421 failed to produce outer membrane vesicles (OMV) without antibiotic treatment, however Ps 3 generated OMV under normal growth conditions generating more when grown on ethanol rather than glucose. In order to investigate the impact of ethanol vs glucose grown culture a wax worm pathogenicity model was employed. This model revealed that ethanol grown cells were more pathogenic than glucose grown cells. This difference could be attributed to the effects of type of carbon sources that induce virulence genes to generate more toxins. Transcriptomic analysis of Ps 3 grown with ethanol vs growth on glucose revealed large differences in gene expression but no definitive evidence of which cellular processes were responsible for this enhanced pathogenicity associated with grown on ethanol.
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Wu, Mei. "Polymer microarrays for microbial high-content screening." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/7664.
Full textAbstract:
Research on the interactions between microbes and polymeric materials constitutes an important part in antimicrobial identification and provides an insight into microbial response on the polymer surfaces. Herein, a high-content screening method with polymer microarray technology was developed to investigate microbe-polymer interactions, especially in studying adhesion/repellence of microbes (bacteria and parasites). Firstly, the polymer microarray approach was used to successfully identify polymers which either selectively captured or prevented the binding of major food-borne pathogen, Salmonella Typhimurium. A parallel study with a lab strain of Escherichia coli was also carried out, revealing polymers which either displayed a common binding activity or which exhibited species discrimination. Likewise, this polymer microarray technology was applied to more bacterial strains, such as Campylobacter, Clostridium, Streptococcus, Klebsiella and their cocktails to discover families of substrates that displayed strong broad-spectrum bacterial non-binding activity. These synthetic polymers represented a novel class of coating materials which can be used to prevent surface colonisation and subsequent formation of bacterial biofilms. The study of protozoan-polymer interactions was also explored in this thesis. Polymers were identified which either bound or prevented parasites (Crysporidium parvum and Giardia lamblia) binding. Material properties, including wettability, surface roughness and polymer composition were analysed to study correlation of parasite binding and the generation of polymer structure function relationships.