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Château, Maarten de. "Functional, structural and evolutionary studies on a family of bacterial surface proteins." Lund : Dept. of Cell and Molecular Biology, Lund University, 1996. http://catalog.hathitrust.org/api/volumes/oclc/38947242.html.
Повний текст джерела
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Lloyd, Diarmuid Padraig. "Microscopic studies of surface growing bacterial populations." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10509.
Повний текст джерелаАнотація:
In this thesis, I present three microscopy studies of surface growing Escherichia coli (E. coli ) microcolonies. All experiments were carried out by growing microcolonies on agarose pads, and imaging their growth using phase contrast, fluorescence and confocal microscopy. In the first project, the importance of spatial structure and growth strategies between competing populations of E. coli was studied. An agarose pad was seeded with bacterial cells and their colonisation success tracked. Cell lag-times and local cell density were found to play important roles in determining the eventual success of a colony. Arrangements of neighbouring cells were found to be partially responsible at high cell densities. These results were reproduced using a simple simulation, which also highlighted the importance of exponential expansion in determining colonisation success. The second project investigates the effect of confinement on growing microcolonies restricted to one plane (2d growth). Colonies were grown in agarose microchannels with different aspect ratios, and in unconfined environments. In particular internal physical colony structure and genealogical structure was studied by using single-cell tracking. Results showed that relatedness between cells was directionally biased (cells tended to be more closely related to cells at their poles, than to their side) regardless of the amount of spatial restriction. Furthermore, confinement caused cells to align with each other more, and induced high cell velocities at the colony edges driven by cell expansion. In the final project, growth of secondary layers in growing colonies of E. coli was studied. Cells initially grew as a monolayer, before invading the agarose bulk, producing a secondary layer. By analysing time-lapse movies, this layer was found to initially expand rapidly well in excess of cell growth rates and initial colony expansion rates, before slowing down. The initial secondary growth rate likely depends on the colony area at agarose invasion. Furthermore, the colony area when colonies invaded the agarose depended on their rate of growth, suggesting a complex interplay between forces exerted by the agarose, and by the colony.
3
Petkova, Petya Stoyanova. "Surface nano-structured materials to control bacterial contamination." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/398122.
Повний текст джерелаАнотація:
The spread of bacteria and infections, initially associated with an increased number of hospital-acquired infections, has now extended into the community causing severe and difficult to treat diseases. Additionally, many of those diseases are evoked by bacteria that have become resistant to antibiotics. Overcoming the ability of bacteria to develop resistance will potentially reduce the burden of these infections on the healthcare systems worldwide and prevent thousands of deaths each year.
The nano-scale particles are promising candidates to fight bacteria, since developing of resistance to their action is less likely to occur. Nanoparticles (NPs) can be incorporated into polymeric matrices to design a wide variety of nanocomposites. Such nano-structures consisting of inorganic and inorganic/organic NPs represent a novel class of materials with a broad range of applications.
This thesis is about the development of antibacterial nano-structured materials aimed at preventing the spread of bacteria. To achieve this, two versatile physicochemical and biotechnological tools, namely sonochemistry and biocatalysis were innovatively combined. Ultrasound irradiation used for the generation of various nano-structures and its combination with biocatalysts (enzymes) opens new perspectives in materials processing, here illustrated by the production of NPs coated medical textiles, water treatment membranes and chronic wound dressings.
The first part of the thesis aims at the development of antibacterial medical textiles to prevent the bacteria transmission and proliferation using two single step approaches for antibacterial NPs coating of textiles. In the first approach antibacterial zinc oxide NPs (ZnO NPs) and chitosan (CS) were deposited simultaneously on cotton fabric by ultrasound irradiation. The obtained hybrid NPs coatings demonstrated durable antibacterial properties after multiple washing cycles. Moreover, the presence of biopolymer in the NP hybrids improved the biocompatibility of the material in comparison with ZnO NPs coating alone.
In the second approach, a simultaneous sonochemical/enzymatic process for durable antibacterial coating of cotton with ZnO NPs was carried out. The enzymatic treatment provides better adhesion of the ZnO NPs and, as a consequence, enhanced coating stability during exploitation. Likewise to the antibacterial coatings obtained in the first approach, the antibacterial efficiency of these textiles was maintained after multiple intensive laundry regimes used in hospitals. The NPs-coated cotton fabrics inhibited the growth of the most medically relevant bacteria species.
In the second part of the thesis, hybrid antibacterial biopolymer/silver NPs and cork matrices, were enzymatically assembled into an antimicrobial material with potential for water remediation. Intrinsically antibacterial amino-functional biopolymers, namely CS and aminocellulose were used as doping agents to stabilize colloidal dispersions of silver NPs (AgNPs), additionally providing the particles with functionalities for covalent immobilization on cork to impart durable antibacterial effect. The biopolymers promoted the antibacterial efficacy of the obtained nanocomposites in conditions simulating a real situation in constructed wetlands.
In the last, third part of the thesis, a bioactive nanocomposite hydrogel for wound treatment was developed. Sonochemically synthesized epigallocatechin gallate nanospheres (EGCG NSs) were incorporated and simultaneously crosslinked enzymatically into a thiolated chitosan hydrogel. The potential of the generated material for chronic wound treatment was evaluated by assessing its antibacterial properties and inhibitory effect on myeloperoxidase and collagenase biomarkers of chronic wound infection. Sustained release of the EGCG NSs from the biopolymer matrix was achieved. The latter, coupled with the good biocompatibility of the hydrogel, suggested its potential for chronic wound management.La propagación de bacterias e infecciones, inicialmente limitada a infecciones adquiridas en el hospital, se ha extendido al resto de la sociedad causando enfermedades muy graves y más difíciles de tratar. Además, muchas de estas enfermedades son provocadas por bacterias que se han hecho resistentes a los antibióticos convencionales. Por lo tanto, limitar la capacidad de estas bacterias para desarrollar resistencia puede potencialmente reducir la alta incidencia de estas infecciones y evitar miles de muertes cada año. Las partículas de escala nanométrica son unas candidatas prometedoras para combatir las bacterias, ya que su mecanismo de acción las hace disminuir las probabilidades en el desarrollo de resistencia. Las nanopartículas (NPs) se pueden incorporar en matrices poliméricas para diseñar una amplia variedad de materiales nanocompuestos. Estas nanoestructuras consisten en NPs orgánicas/inorgánicas e inorgánicas representando una nueva clase de materiales con una amplia gama de aplicaciones. Esta tesis trata sobre el desarrollo de materiales antibacterianos con estructura nanométrica dirigidos a prevenir la propagación de bacterias. Para lograr esto, dos herramientas fisicoquímicas y biotecnológicas versátiles tales como sonoquímica y biocatálisis, se combinaron de manera innovadora. La irradiación por ultrasonido se ha utilizado para la generación de nanoestructuras diversas y su combinación con biocatalizadores (enzimas) abre nuevas perspectivas en el tratamiento de materiales, aquí ilustrados por la producción de textiles médicos recubiertos con NPs, membranas de tratamiento de agua y apósitos para heridas crónicas. La primera parte de la tesis tiene como objetivo el desarrollo de textiles médicos antibacterianos para prevenir la transmisión y proliferación de bacterias utilizando dos estrategias "de un solo paso" para el recubrimiento antibacteriano de estos textiles con NPs. En el primer enfoque NPs antibacterianas de óxido de zinc (ZnO NPs) y quitosano (CS) fueron depositadas simultáneamente sobre tejido de algodón por irradiación de ultrasonido. Los recubrimientos híbridos de NPs obtenidos demostraron propiedades antibacterianas duraderas después de varios lavados exhaustivos. Por otra parte, la presencia de biopolímeros en las NPs híbridas mejoraba la biocompatibilidad del material en comparación con el recubrimiento de solamente de ZnO NPs. En la segunda parte de la tesis, híbridos antibacterianos hechos de biopolímeros y NPs de plata y matrices de corcho, fueron ensamblados enzimáticamente en un material antimicrobiano para su utilización en la remediación de aguas. Biopolímeros antibacterianos aminofuncionalizados (CS y aminocelulosa) se utilizaron como agentes dopantes para estabilizar las dispersiones coloidales de plata (Ag NPs). Además, estas partículas presentan todas las funciones necesarias para su inmovilización covalente en el corcho proporcionando un efecto antibacteriano duradero. Estos biopolímeros aumentaron la eficacia antibacteriana de estos nanocompuestos en condiciones que simulan una situación real en humedales construidos. En la tercera parte de la tesis, se desarrolló un hidrogel nanocompuesto bioactivo para el tratamiento de heridas crónicas. Nanoesferas de galato de epigalocatequina (EGCG NSs) fueron sintetizadas a través de sonoquimica y se incorporaron y simultáneamente reticularon enzimáticamente en un hidrogel de quitosano tiolado. El potencial del material generado para el tratamiento de heridas crónicas fue evaluado por sus propiedades antibacterianas y su efecto inhibidor sobre biomarcadores producidos en heridas crónicas infectadas (mieloperoxidasa y colagenasa). También se consiguió la liberación sostenida de EGCG NSs por parte de la matriz generada, que junto con su buena biocompatibilidad, demostraba su potencial para el tratamiento de heridas crónicas.
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Haynie, Teron D. "Synthesis of Bacterial Surface Glycans for Conjugate Vaccines." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8669.
Повний текст джерелаАнотація:
Bacteria are coated with repeating units of oligosaccharides that exhibit remarkable diversity. Often, glycan units of three or even two sugars are sufficient to identify a species of bacteria. Such specificity makes bacterial surface glycans attractive vaccine targets. However, efforts to create effective vaccines against carbohydrates have been hampered by poor vaccine design as well as the human immune tendency to respond to glycan antigens with non-specific, T-cell independent mechanisms. As a result, carbohydrate vaccines have historically produced only adequate memory responses in healthy individuals and poor responses in the elderly or immunocompromised. To circumvent these issues, a novel conjugate vaccine was developed that utilizes theQβ virus-like particle carrier that displays both a carbohydrate antigen as well as a Natural Killer T cell adjuvant. This unique vaccine has been reported to stimulate the production of high affinity (nanomolar) antibodies against carbohydrate antigens. To further conjugate vaccine research, the present work synthesizes two bacterial surface antigens: a trisaccharide from Streptococcus pneumoniae serotype 23F (Sp23F), and a pentasaccharide from Ruminococcus gnavus (Rg). Sp23F has been characterized as one of the more virulent and disease-causing strains of S. pneumoniae. Rg secretes highly immunostimulatory proteins and is associated with irritable bowel syndrome. The Sp23F antigen is synthesized with an alkyne at the reducing end of the sugar to facilitate coupling to Qβ. A selection reagent for Sp23F is also synthesized to enable the extraction of antibodies and B cells that bind the antigen. In conjunction with providing a conjugate vaccine antigen, the Rg pentasaccharide will be examined as a TLR4 ligand and was therefore synthesized without an alkyne. The Rg conjugate vaccine shows promise in treating irritable bowel syndrome as well as facilitating research into the role Rg plays in the human microbiome.
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Ramos, Isabel Cristina Santos Silva de Faria. "Culturable bacterial community of the estuarine surface microlayer." Master's thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/849.
Повний текст джерелаАнотація:
Mestrado em MicrobiologiaA camada superficial aquática (1-1000 μm) é um ecossistema único, definido como a interface entre a hidrosfera e a atmosfera. É uma camada exposta a altas intensidades de radiação solar Ultra-Violeta, sendo enriquecida com compostos orgânicos e poluentes antropogénicos. Além disso, está sujeita a condições instáveis de temperatura e salinidade. Assim sendo, é razoável colocar-se a hipótese de que esta camada é habitada por comunidades bacterianas distintas e especializadas. Apenas alguns estudos sobre este tema foram publicados e os resultados foram frequentemente divergentes. Apesar do já reconhecido enviesamento introduzido pelas metodologias dependentes do cultivo, tais técnicas permanecem essenciais para a compreensão da fisiologia e ecologia da comunidade bacteriana. Os estuários são ambientes confinados e frequentemente muito poluídos, o que provavelmente favorece a formação de camadas superficiais claramente distintas das águas subjacentes. Portanto, o objectivo deste trabalho foi comparar as comunidades bacterianas cultiváveis da camada superficial aquática e da coluna de água. Foram escolhidos três locais ao longo do estuário Ria de Aveiro atendendo a diferentes parâmetros ambientais e exposição a poluentes. A amostragem foi realizada utilizando o método 'Glass- Plate'. As amostras foram obtidas em maré baixa, durante o dia e noite, em cinco campanhas, tendo em vista a quantificação das unidades formadoras de colónias e subsequente isolamento para caracterização filogenética. Para estes fins, usámos dois meios de cultura: GSP (Pseudomonas Aeromonas Selective Agar Base) e EA (Estuarine Agar). A quantificação das UFC indica que o número de bactérias provenientes da camada superficial (bacterioneuston) é cerca de três vezes mais abundante do que o proveniente da coluna de água (bacterioplâncton). Verifica-se uma diminuição da abundância de bacterioneuston de dia para noite, ao contrário do bacterioplâncton, que tende a aumentar durante o mesmo período. Dos isolados obtidos, o rDNA 16S foi e digerido com a enzima HaeIII. A partir de 402 isolados, foram identificados 72 perfis diferentes. Desses, 21 perfis foram exclusivos da camada superficial e 28 foram exclusivos da coluna de água. Representantes dos diferentes perfis foram analisados por sequenciação e bactérias pertencentes a 5 Filos: Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes e Deinococci-Thermus; e 9 Classes: Gammaproteobacteria, Alphaproteobacteria, Betaproteobacteria, Epsilonproteobacteria, Actinobacteria, Flavobacteria, Sphingobacteria, Deinococci e Bacilli foram identificadas. Os isolados afiliaram com sequências provenientes de ambientes aquáticos bem como de áreas altamente contaminadas. Os resultados apontam para uma comunidade cultivável distinta/particular na microcamada superficial estuarina. ABSTRACT: The sea surface microlayer (SML) is an unique ecosystem, defined as the interfacial film (uppermost 1–1000 μm) between the atmosphere and the ocean. Thereby, it is exposed to high intensities of solar radiation, and is enriched with organic compounds and pollutants from anthropogenic inputs. Also it is subjected to unstable temperature and salinity conditions. Thus, it is proper to hypothesize that the SML is inhabited by distinct and specialized microbial communities. Only a few studies on this topic were published and results wee frequently divergent. Despite the previously recognized biases introduced by culture-dependent methodologies, such techniques remain essential to understand bacterial population’s physiology and ecology. Estuaries are confined and frequently highly polluted environments, which probably favor the formation of distinct surface layers clearly distinct from underlying waters. Therefore, our goal was to compare the culturable bacterial communities occurring in SML and underlying waters (UW). Our work concerned three sampling sites in the estuary Ria de Aveiro, corresponding to different environmental parameters and exposure to pollutants. Sampling was conducted using the so-called ‘Glass-Plate’ method. The UW samples were collected directly into a sterilized glass bottle from a depth of approximately 0.4 m. Samples were obtained at low-tide, during day and night, in five campaigns, regarding the CFU (Colony Forming Units) quantification and subsequent recovery of bacterial isolates. For these purposes we used two culture media: GSP (Pseudomonas Aeromonas Selective Agar Base) and EA (Estuarine Agar). CFU quantification indicates that bacterioneuston is about three times more abundant than bacterioplankton. Generally bacterioneuston abundance decreases from day to night while bacterioplankton usually increases during the same period. From all the obtained isolates the 16S rDNA was amplified using universal primers and digested with the enzyme HaeIII. The profiles were analyzed using the software GelCompar and representatives of each pattern were selected for sequencing. From 402 isolates, 72 different profiles were identified. From those 21 profiles were exclusive from SML samples and 28 were exclusive from UW samples. Sequencing results allowed identifying bacteria belonging to 5 different Phyla: Proteobacteria, Bacteroidetes, Actinobacteria, Firmicutes and Deinococci-Thermus; and 9 Classes: Gammaproteobacteria, Alphaproteobacteria, Betaproteobacteria, Epsilonproteobacteria, Actinobacteria, Flavobacteria, Sphingobacteria, Deinococci e Bacilli. Isolates affiliated with sequences from aquatic environments as well as highly contaminated areas. The results point to a distinct/particular culturable community within the SML of this estuarine environment.
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Auditto, Sanjana. "Synthesis of organic conductive polymers to struggle bacterial infections." Electronic Thesis or Diss., Aix-Marseille, 2022. http://www.theses.fr/2022AIXM0179.
Повний текст джерелаАнотація:
Les biofilms sont à l'origine de nombreux problèmes industriels, sanitaires et domestiques conduisant à d’intenses activités de recherche pour concevoir des solutions pour lutter contre leur formation et développement. Deux voies sont classiquement utilisées pour résoudre ces problèmes, soit l’utilisation de polymères anti-salissures soit des surfaces antibactériennes agissant par effet de contact ou par libération continue de biocides. Par ailleurs, des surfaces sensibles à divers stimuli (microenvironnement, lumière, ondes acoustiques etc.) ont été développées pour libérer de manière contrôlée les agents biocides. De plus, l’action d’un potentiel électrique (effet bioélectrique) a suscité un intérêt pour perturber les biofilms, mais reste sous-exploité. C’est dans ce contexte que s’inscrit ce travail avec le développement de surfaces électrostimulables biocompatibles à partir soit de (i) monocouches auto-assemblées (SAMs) déposées sur électrodes de titane ou d’or, (ii) polymères conducteurs (PCs) fonctionnalisés, pour empêcher l'adhésion/tuer les bactéries. Les SAMs à base de phosphoniums ont démontrées d’intéressantes propriétés antibactériennes, sans libération d’agent biocide, contre des souches Gram positive et négative (S. aureus, K. pneumoniae). D’autres part des films minces d’homo- et copolymères de PCs, à base de pyrrole fonctionnalisés par des phosphoniums, ont été obtenus par électropolymérisation et analysés en modifiant et en appliquant un ensemble de paramètres et testés comme antibactérien. Enfin, des phosphoniums hydrophiles ont été synthétisés et des études préliminaires ont mis en évidence leur intérêt potentiel comme vecteurs de médicamentsBacterial biofilms are in the background of many industrial, health and domestic adverse effects with economic losses leading to intensive research to design solutions to combat their formation and development. Two routes are commonly used to solve these issues, one aiming at preventing the adhesion of bacteria and the other at inhibiting and killing adhered microorganisms. Recent work has been done in that direction with the use of polymer-based antifouling or antibacterial surfaces acting either by contact effect or continuous release of bacterial substances. Besides, responsive surfaces to various stimuli (microenvironment, light, acoustic waves, etc.) have been developed to release biocides in a controlled way. In addition, the use of an electrical potential (bioelectric effect) has aroused interest to disrupt biofilms but remains underexploited. The present work focuses on the development of biocompatible electrostimulable surfaces based on either (i) self-assembled monolayers (SAMs) deposited on titanium or gold electrodes, or (ii) functionalized conductive polymers (CPs), to prevent adhesion and/or kill bacteria. Phosphonium-based SAMs have demonstrated interesting antibacterial properties, without release of biocidal agent, against Gram positive and negative strains (S. aureus, K. pneumoniae). In addition, thin films of homo- and copolymers of phosphonium-based pyrrole CPs were obtained by electropolymerization, and analyzed by modifying and applying a set of parameters and tested as antibacterial coatings. Lastly, hydrophilic phosphoniums have been synthesized and preliminary studies have highlighted their potential use as nanocarriers for drug delivery
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Mitik-Dineva, Natasa. "Bacterial attachment to micro- and nano- structured surfaces." Swinburne Research Bank, 2009. http://hdl.handle.net/1959.3/48547.
Повний текст джерелаАнотація:
The ongoing interest in bacterial interactions with various surfaces, followed by attachment and subsequent biofilm formation, has been driven by the importance of bacterial activities in number of medical, industrial and technological applications. However, bacterial adhesion to surfaces has not been completely understood due to the complexity of parameters involved. The study presented herein investigates the attachment pattern of nine medically and environmentally significant bacteria belonging to different taxonomic lineages: Firmicutes - Bacillus, Gammaproteobacteria, Alphaproteobacteria and Bacteriodetes. Physicochemical assessment techniques such as contact angle and surface charge measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), confocal microscopy (CLSM), as well as X-ray photoelectron spectroscopy (XPS), X-ray fluorescence spectroscopy (XRF) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) analysis were all employed in order to attain better insight into the factors that influence bacterial interactions with surfaces. Bacterial surface characteristics such as surface wettability and charge in addition to substratum surface wettability, tension, charge and chemistry were also considered. However due to the recent interest in designing micro-textured surfaces with antibacterial and/or antifouling effects the prime was given to the influence of micro- and nano-meter scale surface textures on bacterial adhesion. The interactions between selected bacteria and glass, polymer and optical fibre surfaces were studied. Carefully designed methods for surface modification allowed alteration of the topography of glass, polymer and optical fibre surfaces while maintaining other surface parameters near constant. This allowed isolated assessment of only the effects of surface roughness on bacterial adhesion. Obtained results indicated consistent cellular inclination towards the smoother surfaces for all of the tested species. Enhanced bacterial presence on the smoother surfaces was also accompanied by changes in the bacterial metabolic activity as indicated by the elevated levels of secreted extracellular polymeric materials (EPS) and modifications in the cells morphology. The results indicate that nano-scale surface roughness exert greater influence on bacterial adhesion than previously believed and should therefore be considered as a parameter of primary interest alongside other wellrecognized factors that control initial bacterial attachment.
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Ye, Zhou. "Effect of Nanoscale Surface Structures on Microbe-Surface Interactions." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/85387.
Повний текст джерелаАнотація:
Bacteria in nature predominantly grow as biofilms on living and non-living surfaces. The development of biofilms on non-living surfaces is significantly affected by the surface micro/nano topography. The main goal of this dissertation is to study the interaction between microorganisms and nanopatterned surfaces. In order to engineer the surface with well-defined and repeatable nanoscale structures, a new, versatile and scalable nanofabrication method, termed Spun-Wrapped Aligned Nanofiber lithography (SWAN lithography) was developed. This technique enables high throughput fabrication of micro/nano-scale structures on planar and highly non-planar 3D objects with lateral feature size ranging from sub-50 nm to a few microns, which is difficult to achieve by any other method at present. This nanolithography technique was then utilized to fabricate nanostructured electrode surfaces to investigate the role of surface nanostructure size (i.e. 115 nm and 300 nm high) in current production of microbial fuel cells (MFCs). Through comparing the S. oneidensis attachment density and current density (normalized by surface area), we demonstrated the effect of the surface feature size which is independent of the effect on the surface area. In order to better understand the mechanism of microorganism adhesion on nanostructured surfaces, we developed a biophysical model that calculates the total energy of adhered cells as a function of nanostructure size and spacing. Using this model, we predict the attachment density trend for Candida albicans on nanofiber-textured surfaces. The model can be applied at the population level to design surface nanostructures that reduce cell attachment on medical catheters. The biophysical model was also utilized to study the motion of a single Candida albicans yeast cell and to identify the optimal attachment location on nanofiber coated surfaces, thus leading to a better understanding of the cell-substrate interaction upon attachment.Ph. D.
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Panhorst, Kimberly A. "Estimating Bacterial Loadings to Surface Waters from Agricultural Watersheds." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/36433.
Повний текст джерелаАнотація:
Fecal bacteria and pathogens are a major source of surface water impairment. In Virginia alone, approximately 73% of impaired waters are impaired due to fecal coliforms (FC). Because bacteria are a significant cause of water body impairment and existing bacterial models are predominantly based upon laboratory-derived information, bacterial models are needed that describe bacterial die-off and transport processes under field conditions. Before these bacterial models can be developed, more field-derived information is needed regarding bacterial survival and transport. The objectives of this research were to evaluate bacterial survival under field conditions and to develop a comprehensive, spatially variable (distributed) bacterial model that requires little or no calibration. Three field studies were conducted to determine die-off or diminution (settling plus die-off) rates of FC and Escherichia coli (EC) over time in: 1) dairy manure storage ponds and turkey litter storage sheds, 2) pasture and cropland soils to which dairy manure was applied, and 3) beef and dairy fecal deposits. The dairy manure storage ponds were sampled just under the pond surface. The FC and EC diminution (settling plus die-off) rates for dairy manure storage ponds were 0.00478 day-1 and 0.00781 day-1, respectively. The five samples collected for turkey litter in storage were inadequate to draw any conclusions. Bacterial die-off rates in cropland and pastureland soils were found to be statistically different from each other at the α = 0.05 level. The FC and EC die-off rates in cropland soils were 0.01351 day-1 and 0.01734 day-1, respectively, while the FC and EC die-off rates in pastureland soils were 0.02246 day-1 and 0.02796 day-1, respectively. Die-off rates for bacteria from dairy heifer, dairy milker, and beef cow fecal deposits were not statistically different from each other. The resulting die-off rate constants for fecal deposits were 0.01365 day-1 and 0.01985 day-1 for FC and EC, respectively. The EC/FC ratio was also evaluated for the fecal deposits and land-applied manure to determine if a quantifiable relationship was discernable. In general the EC/FC ratio declined over time, but no quantifiable relationship was discerned.
The bacterial model simulates die-off, bacterial partitioning between soil and water, and bacterial transport to surface waters in free (in solution) and sediment-adsorbed forms. Bacterial die-off was modeled using Chick's Law, bacterial partitioning was modeled with a linear isotherm equation, and bacterial transport was modeled using continuity and flow equations. The bacterial model was incorporated into the ANSWERS-2000 model, a continuous, distributed, nonpoint source pollution model. The model was tested using data from two plot studies. Calibration was required to improve runoff and sediment predictions. Bacterial model predictions underpredicted bacterial concentrations in runoff with a maximum underprediction error of 92.9%, but predictions were within an order of magnitude in all cases. Further model evaluation, on a larger watershed with predominantly overland flow, over a longer time period, is recommended, but such data were not available at the time of this assessment. The overall conclusions of this research were 1) FC and EC die-off or diminution under the examined field conditions followed Chick's Law, 2) measured die-off rate constants in the field were much less than those cited in literature for laboratory experiments, and 3) for the conditions simulated for two plot studies, the bacterial model predicted bacterial concentrations in runoff within an order of magnitude.
Master of Science
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Redford, Amanda J. "Interspecies and temporal variation in bacterial leaf surface communities." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1456691.
Повний текст джерела
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Wang, Yiying. "Effect of Aligned Nanoscale Surface Structures on Microbial Adhesion." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/104040.
Повний текст джерелаАнотація:
Microbes in nature live collaboratively in adherent communities, known as biofilms. Biofilms can be contextually beneficial or detrimental. In medical implants, biofilms cause infections leading to additional healthcare costs of billions of dollars. Studies have found that micro/nanoscale surface topography can significantly alter (i.e., promote or hinder) the process of biofilm formation. The formation of biofilm starts with planktonic microbes attach to the surface. To further understand the biophysical underpinning of this process, the effect of aligned nanoscale surface structures on microbial adhesion was studied. To this end, aligned nanofiber coating with controlled fiber diameter and edge-to-edge spacing were manufactured using the Spinneret-based Tunable Engineered Parameters (STEP) techniques. The effect of surface topography on bacterial near-surface motility was studied. The experimental results showed that the bacterial attachment and near-surface motion can be greatly impacted by surface topography. Furthermore, the finding was applied to ureteral stents. The results showed that the aligned nanofiber can significantly reduce the biofilm formation process on ureteral stents.Master of Science
Many microbes in nature live in adherent communities called biofilm. Biofilms contain individual microbes inside polymeric matrix which protect them from environmental stressors such as antibiotics. Biofilms are a significant contributor to the infection of implantable medical devices, which leads to additional healthcare costs of billions of dollars annually in the U.S. alone. Studies have found that sub-micron scale surface topography can significantly promote or hinder biofilm formation; however, the exact mechanism remains poorly understood. To further understand this process, the effect of aligned nanoscale surface structures on microbial adhesion was studied. The formation of microbial biofilm starts with swimming bacteria sensing the liquid-solid interface and attaching to the surface. Microbes are more likely to settle on a surface if a surface is favorable to attach. However, the decision-making process has not been fully understood. Our experimental results showed that the bacterial attachment and near-surface motion can be greatly influenced by surface topography. Furthermore, the finding was applied to ureteral stents, which is a type of medical implants used to maintain the flow of urine in the urinary tract. Ureteral stents serve great for medical purposes, but as foreign bodies, they also lead to urinary tract infection. The results showed that some types of aligned fiber coating increased microbial attachment density, while other types of aligned fiber coating reduced the bacterial surface coverage by up to 80%, which provides directions for future studies.
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Mitchell, Beth Louise. "Characterization of the Physical, Chemical, and Biological Factors that Control the Fate and Transport of Bacteria through Glacial-Outwash Sediments." Miami University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=miami1164820103.
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Rastall, Robert A. "The cell surface biochemistry of Erwinia amylovora." Thesis, University of Greenwich, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258366.
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Kharbouch, Alaa Amin. "A bacterial algorithm for surface mapping using a Markov modulated Markov chain model of bacterial chemotaxis." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36186.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.Includes bibliographical references (p. 83-85).
Bacterial chemotaxis is the locomotory response of bacteria to chemical stimuli. E. coli movement can be described as a biased random walk, and it is known that the general biological or evolutionary function is to increase exposure to some substances and reduce exposure to others. In this thesis we introduce an algorithm for surface mapping, which tracks the motion of a bacteria-like software agent (based on a low-level model of the biochemical network responsible for chemotaxis) on a surface or objective function. Towards that end, a discrete Markov modulated Markov chains model of the chemotaxis pathway is described and used. Results from simulations using one- and two-dimensional test surfaces show that the software agents, referred to as bacterial agents, and the surface mapping algorithm can produce an estimate which shares some broad characteristics with the surface and uncovers some features of it. We also demonstrate that the bacterial agent, when given the ability to reduce the value of the surface at locations it visits (analogous to consuming a substance on a concentration surface), is more effective in reducing the surface integral within a certain period of time when compared to a bacterial agent lacking the ability to sense surface information or respond to it.
by Alaa Amin Kharbouch.
S.M.
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Chacko, Sarah Jane. "Surface attachment behaviour in Rhodobacter sphaeroides." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:943eb194-b147-4cb9-bbc2-a9fd04a45949.
Повний текст джерелаАнотація:
Motility and chemotaxis have been implicated in the process of biofilm formation in a wide range of species. Using a combination of microscopy and image analysis, genetics, microbiology and biochemistry, the initial approach of Rhodobacter sphaeroides cells to a solid surface has been characterised. Interestingly, these data suggest that for R. sphaeroides alterations in motility and swimming behaviour may result in differences in biofilm formation simply by changing the number of cells which reach the surface. This is in contrast to a few other well-studied species where the motility apparatus, the flagellum, has been shown to play an active role in surface sensing and the transition to biofilm growth. Tracking swimming cells and measuring surface attachment revealed that changes in motility affect the ability of cells to attach to a surface, with non-motile cells attaching least and mutants with frequent stops attaching less than smooth swimming cells with few stops. Tracking attaching cells and classifying their method of attachment revealed that flagellar tethering is not essential for R. sphaeroides attachment. Competition assays with fluorescently labelled strains showed that the initial imbalance between motile and non-motile cells remains as microcolonies develop over 48 hours,and the proportion of non-motile cells remains fairly constant. Development on a surface over 48 hours was similar for motile and non-motile strains, including aflagellate strains, once attached. Using parameters calculated by tracking swimming cells to calculate the effective diffusion coefficient in a simple model of cell movement suggested that motion alone could explain the differences in attachment without assuming different cell properties. In particular, aflagellate strains might be hindered from surface attachment by their reduced motility alone. This is interesting since some other bacterial species use the flagellum as a surface sensor.
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Lopez, Hector Matias. "Influence of the coupling between flow and bacteria on the fluid rheology and on bacterial transport." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112168.
Повний текст джерелаАнотація:
Le transport des micro-organismes, comme par exemple les bactéries, par un fluide se retrouve au centre de thématiques de recherche dans des domaines aussi variés que de la biologie, l’écologie, l’ingénierie et la médecine.Ce manuscrit résume mon étude expérimentale du couplage entre le mouvement microscopique de la nage des bactéries et le mouvement advectif de l’écoulement.La première partie du manuscrit porte sur la rhéologie des suspensions d’E. coli sous faible taux de cisaillement. Pour cette condition, j’ai montré que les perturbations hydrodynamiques induites par la nage réduisent fortement la viscosité. Cet effet peut-être si important pour qu’il soit suffisant pour compenser entièrement la perte visqueuse due au cisaillement.La seconde partie traite des expériences d’écoulement réalisées dans un canal capillaire. Pour cette géométrie, j’ai examiné le couplage pour des écoulements caractérisés par un plus fort taux de cisaillement. Le suivi des trajectoires et le dénombrement des bactéries m’ont permis de mettre en évidence l’existence d’une composante de vitesse normal à la direction de l’écoulement. Cette dernière montre que les bactéries suivent des trajectoires hélicoïdales qui s’enroulent autour du centre du capillaire d’une façon antihoraires. Cette nouvelle composante est corrélée à la migration préférentielle des bactéries dans une couche de localisation proche de la paroi du canal.Les couplages rhéotactiques bactéries/fluide que j’ai étudiés doivent avoir des conséquences potentielles sur le transport en géométries plus complexes qui mériteraient une étude particulièreThe question of transfer and spreading of living microorganisms, such as motile bacteria, is of interest in biology and ecology, but also in engineering and medicine.The way in which the background flow affects the behavior of these bacteria and how it impacts the bacterial transport through complex systems and on the macroscopic properties of the fluid remains unclear and little studied.In this thesis, I present an experimental investigation of the coupling between the local bacteria-driven motion and the fluid advection.In a first part, I investigate the rheological response of E. coli suspensions when subjected to weak flows (low shear rates). I show that, in particular conditions, the microscopic perturbations caused by the bacteria highly impact on the macroscopic viscosity of the suspension, leading to a striking viscosity decrease and eventually overcoming the dissipative effects due to viscous loss. I also identify the relevant time scales defining this viscosity decrease.In a second part, I perform experiments in a capillary channel and analyze the coupling for stronger flows (higher shear rates), at which bacteria were found not to impact on the macroscopic viscosity. Instead, by analyzing the bacterial trajectories under flow, I evidence a breakage of the symmetry of this trajectories which, characterized by a preferential migration, causes the localization of the bacteria in a layer that extends over a significant distance from the surface, and thus potentially influencing the bacterial transport in complex systems
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Wilton, Alison Jane. "Iron-regulated surface antigens of Pseudomonas aeruginosa." Thesis, Aston University, 1989. http://publications.aston.ac.uk/12564/.
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Nualnoi, Teerapat. "Detection and in vivo fate of surface-expressed bacterial polysaccharides." Thesis, University of Nevada, Reno, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10126085.
Повний текст джерелаАнотація:
The potential bioterrorism agents, Francisella tularensis and Burkholderia pseudomallei, are the etiologic agents of two life-threatening diseases, termed tularemia and melioidosis, respectively. An early diagnosis and a timely treatment regimen are crucial for successful therapeutic outcomes. However, bacterial isolation, which is known to be time-consuming and have low sensitivity, remains the 'gold standard' for diagnosis of these infections. Therefore, in the first study in this dissertation, we developed an antigen-capture enzyme-linked immunosorbent assay (ELISA) targeting bacterial surface-expressed lipopolysaccharide (LPS) for rapid F. tularensis detection. A murine monoclonal antibody (mAb) specific to F. tularensis LPS, 1A4 IgG3, and its subclass family (1A4 IgG1 and 1A4 IgG2b, bearing the same antigen-binding site as mAb 1A4 IgG3) were isolated and used for assay development. Surface plasmon resonance (SPR) and competition ELISA were used to assess the binding affinities of the mAbs. We found that the assay developed using 1A4 IgG1 or IgG2b had better assay sensitivity compared to when the IgG3 was used. Interestingly, while the assay sensitivity was improved, we also found a decrease in functional affinity as a result of subclass switching. Direct ELISA and SPR suggested that the higher affinity of 1A4 IgG3 might be related to self-association, which correlated to high assay background and low assay sensitivity. Altogether, we demonstrated that IgG subclass switch could improve assay sensitivity by reduction of the assay background (through elimination of IgG3 self-association).
As for melioidosis, a rapid diagnostic targeting B. pseudomallei CPS (Active Melioidosis Detect (AMD™) rapid test) has already been developed and is currently being assessed. However, a rapid immunoassay for differentiation between typical and atypical LPS strains has never been developed. This is important to advance our understanding of the epidemiology and pathology of melioidosis. Thus, in the second project, we developed antigen-capture immunoassays for typical and atypical LPS strain typing using CPS-specific mAb 4C4 for bacterial capture, and mAbs 4C7 and 3A2 for detection of typical and atypical LPS strains, respectively. In this study, two atypical LPS-specific mAbs (3A2 and 5B4) were successfully isolated; SPR results suggested that 3A2 is preferable for the assay. B. pseudomallei (174 strains) was used to evaluate the assay, and the results showed the assays have 98.8% accuracy, suggesting that they are effective and applicable for B. pseudomallei LPS typing.
Additionally, in the present work, we also investigate the in vivo fate of B. pseudomallei CPS using a murine model. The goal of this study was to improve our understanding of the appropriate clinical use of the AMD™ test. We found that CPS has a short serum half-life and is eliminated predominantly through the urine, suggesting that i) the presence of CPS in serum and/or urine may be indicative of active melioidosis, ii) CPS may be used as a marker to monitor and assess melioidosis treatment outcome, and iii) in addition to serum, urine (a noninvasive sample) has the potential to be used as a clinical specimen for the diagnosis of melioidosis.
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Petersson, Christoffer. "Characterisation of surface traits of Helicobacter pylori and their role in the infectious process /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/med805s.pdf.
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Ries, Johannes. "Pneumococcal pili and other cell surface properties affect the infection biology of Streptococcus pneumoniae /." Stockholm, 2007. http://diss.kib.ki.se/2007/978-91-7357-179-1/.
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Summers, Stephen. "The bacterial ecology and function from a sub-surface critical zone." Thesis, Open University, 2013. http://oro.open.ac.uk/54727/.
Повний текст джерелаАнотація:
The rock-soil interface (critical zone) is where a variety of important earth system processes occur, such as the sequestration of CO2 and pedogenesis from rock weathering. This zone is an important sub-surface region of microbial activity in extreme environments because bedrock hydrolyses providing nutrients and cations (Le. Ca2 Mg2., Na) otherwise unavailable to flora and fauna. Yet, the diversity and role of microorganisms in weathering at the critical zone is not well understood. This thesis examines microbial communities in vegetated and unvegetated critical zones near Skorradalur Lake, Iceland. A suite of analyses were carried out to determine the environmental conditions, diversity, function and trophic survival strategy employed by bacteria at the sub-surface critical zone. Molecular analysis of the bacterial 16S rRNA gene indicates that the presence of plants at the soil surface influences the bacterial diversity and composition. Cultivation of microorganisms produced several bacterial isolates; most of which were capable of mineral phosphate solubilisation. However, isolate growth rates and copper tolerance show most isolates inhabit areas of sub-optimal growth potential. Environmental factors such as temperature and pH may influence bacterial divers ity, although the presence of organics may override these other influences. The trophic conditions at sites without higher plants may have a role in bacterial weathering as the availability of organics has resulted in a diverse heterotrophic community capable of utilizing bacterial necromass as a carbon source rather than plant derived carbon. This work has shown for the first time the bacterial diversity of the sub-surface critical zone in this region. Moreover, this bacterial diversity is influenced by plants and the potentially associated organics. Areas devoid of plants harboured a diverse heterotrophic bacterial community that employ weathering as a genera list function. Experiments show that bacteria increase the rate of phosphate weathering, although it may be a generalist function rather than specific to any individual taxon.
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Timol, Zaheer. "Chemical and conformational studies of bacterial cell surface polysaccharide repeating units." Master's thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25484.
Повний текст джерелаАнотація:
Abstract Bacterial cell surface polysaccharides are primarily present as lipopolysaccharides or capsular polysaccharides. They are used by cells for both structure and function and have been shown to be a virulence factor of bacterial pathogens. Cell surface polysaccharides are widely utilised as antigenic components in vaccines and play an important role in the protection against numerous diseases including meningococcal disease and shigellosis. This study is composed of two parts: a computational section, which investigates the capsular polysaccharide (CPS) repeating unit (RU) conformations of meningococcal Y and W CPS vaccines and a second experimental component that involves synthetic studies toward the O-specific polysaccharide (O-SP) RU of Shigella sonnei. The CPS RU of MenY [→6)-α-D-Glc(1→4)-α-D-NeuNAc-(2→] and MenW [→6)-α-D-Gal(1→4)-α-D-NeuNAc-(2→] differ only in the orientation of the C-4 hydroxyl: equatorial in MenY and axial in MenW. However, groups Y and W CPS vaccines have different levels of antibody cross-protection. The purpose of the computational study was to determine if these observed differences may be attributed to CPS RU conformation. Potential of mean force calculations were applied to disaccharide RUs of MenY and MenW, and larger three repeating units (3RU) were simulated with molecular dynamics (MD) in solution. The molecular modelling showed that differences in RU conformation between the meningococcal groups arise primarily due to the structural differences between glucose and galactose; affecting the behaviour and orientation of the 2→6 dihedral linkage. The 2→6 linkages in the MenY 3RU adopt a single preferred orientation and consequently it has a single dominant molecular conformation. In contrast, the 2→6 linkages in the MenW 3RU move frequently between different rotameric conformations resulting in multiple conformational families. These results indicate significant conformational differences between the MenY and MenW CPS RUs, which may account for the different levels of cross-protection observed. The synthetic component was part of a larger study to develop a novel route towards the O-SP RU of S. sonnei for use in biological testing and physicochemical characterisation for vaccine development. The O-SP RU of S. sonnei is →4-α-L-AltNAc-(1→3)-β-D-FucNAc4N(1→. The multi-step synthesis was performed using known methodology as well as methods developed by the research group. The key 2,3-oxazolidinone protected intermediate was successfully synthesised in good yields and due to time constraints the final product synthesised was two steps away from the protected FucNAc4N residue. Additional studies were performed on the 2,3-oxazolidinone intermediate as part of a divergent synthesis strategy toward the AltNAcA residue of S. sonnei. Reactions were conducted whereby β and α derivatives of the 2,3-oxazolidinone intermediate were successfully synthesised in large scale and good yields for further studies to be performed by the group. i
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Ramos, Cruz Ana Raquel. "Characterization of the surface of segmented filamentous bacteria from the unicellular to filamentous stage." Electronic Thesis or Diss., Université Paris Cité, 2024. http://www.theses.fr/2024UNIP5192.
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Hammar, Mårten. "Assembly and adhesive properties of curli : a stationary phase-specific surface organelle in gram-negative enteric bacteria /." Stockholm, 1997. http://diss.kib.ki.se/1997/91-628-2605-0/.
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Ozaktas, Tugba. "Multiple Antibiotic Resistance Of Surface Mucus Dwelling Bacterial Populations In Freshwater Fish." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12609113/index.pdf.
Повний текст джерелаАнотація:
Surface mucus of a freshwater fish, Alburnus alburnus (bleak), caught from Lake Mogan, situated in south of Ankara, was collected in different seasons. The total cultivable bacteria were enumerated by spread plate method on nine different media. Bacteria were isolated based on colony morphologies and pigmentation. A total of sixty bacterial isolates obtained. The mucus-dwelling bacteria were first tested for resistance against ampicillin and kanamycinthen streptomycin and chloramphenicol were added to the experimental set up. The resistance levels of isolates were determined in terms of four antibiotics by tube dilution method. About 90% of the isolates were resistant to chloramphenicol, about 84% to kanamycin, about 88% to streptomycin and about 98% to ampicillin. These high levels of antibiotic resistance are rather interesting from a standpoint that the lake has no record of antibiotics exposure of any sort. The plasmid isolations were carried out to determine if the multiple antibiotic resistance could be attributed to plasmids for starting assumption. But we found no direct relationship between the presence of plasmids and multiple antibiotic resistance. Our study indicated that multiple antibiotic resistance at high levels is among the current phenotypes of the fish mucus-dwelling bacterial populations in Lake Mogan.
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Grouzdev, D. S., M. V. Dziuba, D. V. Kurek, and A. I. Ovchinnikov. "The Method for Protein Display on the Surface of Bacterial Magnetic Nanoparticles." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35488.
Повний текст джерелаАнотація:
In this study, we present a comprehensive approach to the design and development of magnetosomes with antibodies immobilized on their surface by integration in membrane in vitro. Designed fusion proteins Mbb and Mistbb consisted of anchor proteins and BB-domains of Staphylococcus aureus protein A as IgG-binding region were used for development of IgG-binding magnetosomes. The magnetosome membrane protein MamC and membrane protein of Bacillus subtilis Mistic were selected as anchor proteins. Using Response Surface Methodology (RSM), the high level of fusion proteins integration into bacterial nanopar-ticles membrane was achieved. IgG-binding magnetosomes obtained through this strategy could serve as multifunctional platform for displaying various types of antibodies. Such systems could be applied as theranostic agents.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35488
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Arora, Bhupinder S. "Detection of polysaccharides on a bacterial cell surface using Atomic Force Microscopy." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0826103-011111.
Повний текст джерелаАнотація:
Thesis (M.S.)--Worcester Polytechnic Institute.Keywords: Leuconostoc mesenteroides NIRC1542; Atomic Force Microscope; Pseudomonas putida KT2442; Adhesion. Includes bibliographical references (p. 75-83).
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Barrett, Gary. "Towards detection of endotoxin in high-purity water utilising a surface plasmon resonance biosensor." Thesis, Cranfield University, 2000. http://dspace.lib.cranfield.ac.uk/handle/1826/11094.
Повний текст джерелаАнотація:
The aims of this project were to develop a system for monitoring a continuous stream of high grade purified water for potential contamination by bacterial endotoxins. The monitoring system was to be designed so that it could be readily integrated within a closed water purification processing system. The project was viewed as a developmental stage towards the development of a commercial sensor with wide ranging applications within the pharmaceutical and environmental sectors. This text details the development of testing protocols for the examination of ultra pure water using different sensing matrices. The endotoxin structure is comprised of three main sections with specific chemistry. These regions have each been considered as potential areas for detection. The development of surface plasmon resonance (SPR) systems and protocols for the detection of endotoxin was shown both to be possible and practical within given experimental parameters. In order to assess the potential for this sensing within a more established experimental system and to further expand the potential sensing layers for endotoxins, further experiments were carried out using a BIAcore system. The use of the BIAcore allowed the examination of alternative sensing surfaces based on the specific nature of the endotoxin molecule rather than the use of literature based reactants that have previously displayed an affinity for the endotoxin molecules. The methods used within this project have concentrated on the overall chemistry of the endotoxin molecule. The potential binding/complexing agents have been targeted at the three principal regions of the endotoxin structure using the chemical nature of these regions as an attractive surface to the sensing layer.
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Saffie, Jared C. "Microfluidic evaporator chip for concentration of bacterial samples for SERS identification." Thesis, Boston University, 2014. https://hdl.handle.net/2144/21248.
Повний текст джерелаАнотація:
Thesis (M.Sc.Eng.)Sepsis is a serious medical condition in which a person becomes infected with bacteria in his or her bloodstream. The symptoms of sepsis are a result of the immune system’s interaction with the infecting agent. Currently, to diagnose a patient with sepsis, a blood sample must be collected and cultured for 24-48 hours before the infection can be confirmed. In the meantime, a broad-scope antibiotic is administered which may or may not be effective in treating the patient. If the antibiotic is ineffective, a different antibiotic must be chosen. When the results of the blood culture are available, a narrow scope antibiotic, appropriate to treat the infection is administered. However, sepsis has a mortality rate of 18-30% depending on the infecting agent and the treatment is highly time sensitive. Within 24 hours, the syndrome may progress to septic shock and mortality rates reach 50%. Therefore, it is important to quickly and correctly identify the infecting agent and provide immediate targeted treatment. Surface Enhanced Raman Spectroscopy (SERS) can be used to quickly identify and distinguish between different bacterial strains; however it requires higher bacterial concentrations than are present in the blood during the early stages of sepsis. A microfluidic evaporator chip has been developed to concentrate bacteria samples from 4μl to 100nl; the chip has been evaluated for concentration efficiency on Escherichia coli and methicillin-sensitive Staphylococcus aureus. Various blocking methods using bovine serum albumin (BSA) have been tested to reduce bacterial adhesion to the chip and have improved bacterial recovery to around 70% for both strains tested. Ongoing tests are being performed to improve bacterial recovery and sample purity for identification.
2031-01-01
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SURANA, UTTAM CHAND. "BIOCHEMICAL CHARACTERIZATION OF THE BACILLUS SUBTILIS MACROFIBER CELL SURFACE." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184038.
Повний текст джерелаАнотація:
Cell walls of Bacillus subtilis macrofibers have been biochemically analyzed to determine the contribution of various surface polymers in the twist regulation. Helix hand inversion was induced by a variation in either the growth temperature or the nutritional composition of the culture medium. Initial experiments had demonstrated a fivefold difference in the sensitivity of right- and left-handed forms to muramidases indicating modifications of peptidoglycan as a possible mechanism underlaying inversion. An examination of lysozyme susceptibility of purified cell walls and whole cells derived from the two structural forms, however, exhibited no significant difference suggesting loss of the relevant component(s), perhaps biomechanical in nature, during disintegration of macrofibers. The effect of various twist modulators such as trypsin, ammonium sulfate and D-alanine on the development of helical twist in both switchable and "fixed" mutants were studied. The interaction matrices have established D-alanine as the most potent of right-factors. Intestinal alkaline phosphatase is reported as a newly discovered antagonist to the development of leftward twist. Heat inactivation and protein purification experiments strongly indicated that twist modulation was due to the phosphatase activity rather than minor protease contaminants. The chemical composition of cell walls purified from right- and left-handed structures was determined. No twist correlated differences in the overall content of peptidoglycan, teichoic acid and teichuronic acid were detected. Evidence is presented for the absence of correlation between the extent of ester-linked alanine substitution and twist state. These findings suggest that gross changes in wall composition is perhaps not the mechanism for hand inversion. From the profiles of the wall associated proteins, a 200 Kdal band has been identified whose presence is strongly correlated with the development of leftward twist. This polypeptide was found to be highly sensitive to trypsin; a property it shares with a previously proposed left-twist protein. Preliminary evidence for isolation of left-hand specific polyclonal antibodies is also presented. FJ7, a switchable mutant, was successfully transformed with a plasmid containing the Streptococcus transposon Tn917. A small bank of insertional mutants has been constructed for the isolation of mutants impaired in helix hand inversion.
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Daugherty, Patrick Sean. "Screening combinatorial polypeptide libraries using bacterial surface display and fluorescence-activated cell sorting /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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WOLFE, ALAN JEFFREY. "THE RELATIONSHIP OF BACILLUS SUBTILIS PHYSIOLOGY AND HELICAL STRUCTURE AND ORGANIZATION (MACROFIBER, CELL SURFACE, HELIX HAND INVERSION)." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187939.
Повний текст джерелаАнотація:
Helix hand inversion exhibited by Bacillus subtilis macrofibers is induced by changes in culture medium composition. The kinetics of this inversion are compared to those of temperature-induced inversions. D-alanine evokes a similar inversion process. The role of left-twist proteins(s), the existence of "memory", and the asymmetry of left to right versus right to left kinetics are confirmed within the context of these inversion regimes. Initiation time of right to left inversions is correlated to degree of pre-shift twist. Evidence is presented suggesting effective twist of the wall is defined by (1) the average of that twist conformation inserted prior to a shift in culture conditions and that of wall inserted following the shift and (2) the location of left-handed material within the wall. A constant 50 minute delay is observed before initiation of left to right inversions, irregardless of twist. Evidence is presented for a protein in the left to right inversion process. A classification system of macrofiber phenotypes based upon hand and degree of structural organization has been established. Three major classes are identified. Subclasses are shown to be distinguishable. Isotwist phenotypes of seven strains are defined upon a matrix of temperature and medium composition. These plots reveal a fundamental pattern of hand and organization that is present in each of the strains studied. The polarity of the four axes, the range of attainable twist conformations, and the existence of a right-hand maximum in the 12.5% SPl domain remain virtually constant. Major variations include extent of a disorganized band and/or the shifting of conformational range either left or right. Several mutants were transformed into A734, a strain that produces the tightest structures at all four matrix corners. Multiple mutations are responsible for the phenotypes of several strains. Evidence is presented for single genes that express as extreme left-handedness and stress at high temperature, swelling and stress in TB at high temperature, and reduction in structural organization produced in high TB content at low temperature.
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Najem, Joseph Samih. "Droplet Interface Bilayers for Mechano-Electrical Transduction Featuring Bacterial MscL Channels." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/83399.
Повний текст джерелаАнотація:
This dissertation investigates the behavior of the Escherichia Coli mechanosensitive (MS) channel MscL, when incorporated within a droplet interface bilayer (DIB). The activity of MscL channels in an artificial DIB system is demonstrated for the first time in this document. The DIB represents a building block whose repetition can form the basis to a new class of smart materials. The corresponding stimuli-responsive properties can be controlled by the type of biomolecule incorporated into the lipid bilayer, which is in the heart of this material. In the past decade, many research groups have proven the capability of the DIB to host a wide collection of natural and engineered functional biomolecules. However, very little is known about the mechano-electrical transduction capabilities of the DIB. The research present herein specifically seeks to achieve three direct goals: 1) exploring the capabilities of the DIB to serve as a platform for mechano-electrical transduction through the incorporation of bacterial MscL channels, 2) understanding the physics of mechano-electrical transduction in the DIB through the development of theoretical models, and 3) using the developed science to regulate the response of the DIB to a mechanical stimulus.
MscL channels, widely known as osmolyte release valves and fundamental elements of the bacterial cytoplasmic membrane, react to increased tension in the membrane. In the event of hypo-osmotic shocks, several channels residing in the membrane of a small cell can generate a massive permeability response to quickly release ions and small molecules, saving bacteria from lysis. Biophysically, MscL is well studied and characterized primarily through the prominent patch clamp technique. Reliable structural models explaining MscL's gating mechanism are proposed based on its homolog's crystal structure modeling, which lead to extensive experimentation. Under an applied tension of ~10 mN/m, the closed channel which consists of a tight bundle of transmembrane helices, transforms into a ring of greatly tilted helices forming an ~8 A water-filled conductive pore. It has also been established that the hydrophobicity of the tight gate, positioned at the intersection of the inner TM1 domains, determines the activation threshold of the channel. Correspondingly, it was found that by decreasing the hydrophobicity of the gate, the tension threshold could be lowered. This property of MscL made possible the design of various controllable valves, primarily for drug delivery purposes. For all the aforementioned properties and based on its fundamental role of translating cell membrane excessive tensions into electrophysiological activities, MscL makes a great fit as a mechanoelectrical transducer in DIBs.
The approach presented in this document consists of increasing the tension in the lipid bilayer interface through the application of a dynamic mechanical stimulus. Therefore, a novel and simple experimental apparatus is assembled on an inverted microscope, consisting of two micropipettes (filled with PEG-DMA hydrogel) containing Ag/AgCl wires, a cylindrical oil reservoir glued on top of a thin acrylic sheet, and a piezoelectric oscillator actuator. By using this technique, dynamic tension can be applied by oscillating one droplet, producing deformation of both droplets and area changes of the DIB interface. The tension in the artificial membrane will cause the MS channels to gate, resulting in an increase in the conductance levels of the membrane. The increase in bilayer tension is found to be equal to the sum of increase in tensions in both contributing monolayers. Tension increase in the monolayers occurs due to an increase in surface area of the constant volume aqueous droplets supporting the bilayer.
The results show that MS channels are able to gate under an applied dynamic tension. Interestingly, this work has demonstrated that both electrical potential and surface tension need to be controlled to initiate mechanoelectric coupling, a property previously not known for ion channels of this type. Gating events occur consistently at the peak compression, where the tension in the bilayer is maximal. In addition, the experiments show that no activity occurred at low amplitude oscillations (< 62.5um). These two findings basically present an initial proof that gating is occurring and is due to the mechanical excitation, not just a random artifact. The role of the applied potential is also highlighted in this study, where the results show that no gating happens at potentials lower that 80 mV. The third important observation is that the frequency of oscillation has an important impact of the gating probability, where no gating is seen at frequencies higher than 1 Hz or lower than 0.1 Hz.
Each of the previous observations is addressed separately in this research. It was found that the range of frequencies to which MscL would respond to in a DIB could be widened by using asymmetrical sinusoidal signals to stimulate the droplets. By increasing the relaxation time and shorting the compression time, a change in the monolayer's surface area is achieved, thus higher tension increase in the bilayer. It was also found that a high membrane potential assists in the opening of MscL as the droplets are stimulated. This is due to the sensitivity of MscL to the polarity of the signal. By using the right polarity the channel could be regulated to become more susceptible to opening, even at tensions lower than the threshold.
Finally, it was demonstrated, for the first time, that MscL would gate in asymmetric bilayers without the need to apply a high external potential. Asymmetric bilayers, which are usually composed from different lipids in each leaflet, generate an asymmetric potential at the membrane. This asymmetric potential is proven to be enough to cause MscL to gate in DIBs upon stimulation.Ph. D.
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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.
Повний текст джерелаАнотація:
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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Santos, Ana Catarina Gonçalves Carvalho Queiroga. "Novel wild bacterial enzymes for applications in the wool industry." Doctoral thesis, ISA/UTL, 2011. http://hdl.handle.net/10400.5/5191.
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Pouliot, Kimberly Lea. "Surface of Yersinia pestis: LCRV, F1 Production, Invasion and Oxygen: A Dissertation." eScholarship@UMMS, 2007. https://escholarship.umassmed.edu/gsbs_diss/358.
Повний текст джерелаАнотація:
Of the eleven species of bacteria that comprise the genus Yersinia of the family Enterobacteriaceae, three species are pathogenic for humans. Yersinia pseudotuberculosis and Yersinia enterocolitica usually cause a mild, self-limiting mesenteric lymphadenitis or ileitis. Yersinia pestis causes a highly invasive often fatal disease known as plague. All three elaborate a type three secretion system that is essential for virulence and encoded on closely related plasmids. In Y. pestis, all the effectors, structural components and chaperones are encoded on the 70kb plasmid, pCD1.
Of these, LcrV from Y. enterocolitica has been implicated in playing an immunosuppressive role through its interaction with host Toll-like receptor 2 (TLR2) and induction of IL-10. Through expression and purification of recombinant LcrV from Escherichia coliwe show that only high molecular weight species of rLcrV are able to stimulate TLR2. In a highly sensitive subcutaneous mouse infection model we demonstrate no difference in the time to death between TLR2-sufficient or deficient mice. Analysis of cytokine levels between these two genotypes also shows no significant difference between splenic IL-10 and IL-6 or levels of bacteria. We conclusively show that this interaction, if it does occur, plays no significant role in vivo.
In a separate set of experiments, we also determined that the expression of F1, a peptide shown to be responsible for 37°C-dependent inhibition of invasion by Y. pestis in vitro, was significantly decreased under high oxygen conditions. This led us to re-examine the invasion phenotype both in vitro and in vivo. These results give new insights into virulence gene expression in Y. pestis by environmental cues other than temperature.
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Brading, Melanie Gayle. "The influence of fluid dynamics and surface material on pure and binary culture biofilms." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307314.
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Patrone, Julia Beth. "The effects of neisserial surface molecules and initial bacterial dose on interactions with human monocytes." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3862.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Cell Biology & Molecular Genetics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Soimala, Tanawan [Verfasser]. "Hygiene in Ophthalmic Surgery and Bacterial Resistance on the Ocular Surface of Animals / Tanawan Soimala." Berlin : Freie Universität Berlin, 2019. http://d-nb.info/1189659972/34.
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Gloe, Tobias-Elias [Verfasser]. "Carbohydrate Conjugates to Explore Bacterial Adhesion : from Amadori Rearrangement to Surface Functionalization / Tobias-Elias Gloe." Kiel : Universitätsbibliothek Kiel, 2019. http://d-nb.info/1192303695/34.
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Maknojia, Shahnaz Rahim. "Bacterial diversity and nutritional significance of the surface microlayer in Anopheles gambiae (Diptera:Culicidae) larval habitats." Diss., Connect to online resource - MSU authorized users, 2006.
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Seale, Richard Brent, and n/a. "The surface characteristics of spores from thermophilic bacilli isolated from a milk powder production line and their influence on adhesion to surfaces." University of Otago. Department of Food Science, 2009. http://adt.otago.ac.nz./public/adt-NZDU20091001.131237.
Повний текст джерелаАнотація:
Spores of thermophilic bacilli are a common concern during the manufacture of milk powder. Spores are believed to occur in high numbers in milk powder due to their ability to survive pasteurisation, attach to stainless steel surfaces, germinate, grow as biofilms and subsequently enter the product stream and thereby contaminate the final product.
In this study, thirty one thermophilic bacilli isolates were obtained from a New Zealand milk powder production line and identified as either Anoxybacillus flavithermus or Geobacillus spp. using random amplified polymorphic DNA (RAPD) and species-specific PCR. Sporulation media and a polyethylene glycol two-phase separation system were modified to produce high yields of spores free from debris.
The spores of four Geobacillus spp. isolates (CGT-8, D4, E7 and E11) were characterised in terms of structure (electron microscopy), surface charge (zeta potential), hydrophobicity (contact angle and microbial adhesion to hexadecane) and attenuated total reflectance infrared spectroscopy (ATR-IR). Spores from three of the four isolates possessed an exosporium while the fourth did not. However the integrity of the exosporium varied over time. The spores were negatively charged (-10 to -20 mV) at neutral pH and high ionic strength (0.1 M KC1). Both hydrophobicity assays revealed that the spores of the four isolates were relatively hydrophilic while ATR-IR revealed the spores' surfaces consisted of protein and polysaccharides.
The influence of these spore characteristics on adhesion to a variety of substrata under high flow rates was examined using the extended Derjaguin, Landau, Verwey and Overbeek (XDLVO) theory. Spores generally attached in higher numbers to hydrophobic surfaces compared to hydrophilic surfaces, however this observation was more prevalent for isolate D4. This result indicated that a single mechanism could not describe the adhesion of spores from different strains.
A series of glass surfaces with modified characteristics were produced in order to test the antifouling properties on the adhesion of D4 spores. Spores suspended in a high ionic strength medium (0.1 M KC1) attached in greater numbers (1 Log₁₀ CFU cm⁻�) to positively charged and hydrophobic surfaces compared with negatively charged and hydrophilic surfaces. A clean in place (CIP) procedure, reduced spore numbers on hydrophobic and hydrophilic surfaces by 1.5 and by 2.0 Log₁₀ CFU cm⁻�, respectively. When spores were suspended in milk, there was little difference in the number of spores attaching to the different surfaces (ie. 3.5 to 3.8 Log₁₀ CFU cm⁻�), and spore removal from surfaces via a CIP regime was unchanged (1.5 to 2.0 Log₁₀ CFU cm⁻� reduction) compared with spores that attached in simple 1:1 electrolyte media.
The effects of a caustic wash on spore surface characteristics and adhesion was determined. There was a significant reduction in spore viability (2 Log₁₀ CFU mL⁻�) after a 30 min caustic wash at 65 �C in the current study, however surviving spores displayed a greater propensity to attach to stainless steel. Surface characterisation results revealed an increase in hydrophobicity and a greater negative charge on the spores' surface after treatment with NaOH. Surviving spores could potentially recontaminate sections of the plant which are cleaned with this recycled caustic wash solution, thereby seeding surfaces with spores at the beginning of the next processing run.
In conclusion, while surfaces that reduce spore adhesion and enhance removal can be produced, exposure to complex solutions such as milk can reduce the anti-fouling effectiveness of such surfaces to spore adhesion.
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Ribeiro, Cyntia Ferreira. "Influência dos diferentes tratamentos de superfície em discos de titânio comercialmente puro sobre a formação e aderência do biofilme inicial: estudo in situ." Universidade de Taubaté, 2013. http://www.bdtd.unitau.br/tedesimplificado/tde_busca/arquivo.php?codArquivo=595.
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Hipótese do Estudo: O presente estudo hipotetizou que superfícies tratadas de discos de titânio comercialmente puro (Ti c.p.) são mais susceptíveis a aderência bacteriana que as superfícies lisas. Objetivo: O objetivo deste trabalho foi avaliar, in situ, a aderência bacteriana em discos de Ti c.p. submetidos a dois diferentes tratamentos de superfície: duplo ataque ácido e anodização. Metodologia: Sessenta corpos-de-prova de Ti c.p. foram divididos em três grupos: Grupo 1 - discos de Ti c.p. liso (grupo controle); Grupo 2 - discos de Ti c.p. com superfície duplamente condicionada com ácido (Master Pours Implant, Conexão Sistemas Prótese LTDA, SP., Brasil) e o Grupo 3 - discos de Ti c.p. submetidos à irradiação laser (Vulcano Actives, Conexão Sistemas Prótese LTDA, SP., Brasil). Inicialmente foi avaliada a rugosidade superficial (Ra) de todos os corpos-de-prova. Para a avaliação in situ, foram confeccionadas dez moldeiras individuais e em cada uma delas fixados seis discos de titânio, sendo dois de cada grupo. Dez voluntários usaram, por 24 horas, a moldeira contendo os discos de Ti c.p. Após este período três discos de titânio de cada grupo foram levados ao Microscópio Eletrônico de Varredura (MEV) para visualização do biofilme formado. O biofilme foi removido dos 17 discos restantes e, em sete deles, foi realizado o ensaio de MTT para quantificar as bactérias viáveis e em dez a Reação em Cadeia de Polimerase em Tempo Real (PCR Real Time, quantitativo) para quantificação total das bactérias aderidas e do Streptococcus oralis. Resultados: Os dados obtidos foram estatisticamente analisados utilizando Análise de Variância (ANOVA) One Way, seguido do pós-teste de Tamhane. Com relação a Ra, a diferença observada entres os Grupos 3 e 1 foi de 0,652 0,098μm e entre os Grupos 3 e 2 de 0,688 0,099μm. Nas micrografias foi observado biofilme aderido em todos os discos de titânio. O ensaio de MTT não evidenciou diferença significativa entre os grupos Grupo 1 (0,1190,048), 2 (0,1360,079) e 3 (0,1210,074), p=0,89. Os resultados da PCR Real Time não evidenciaram diferença significativa quanto ao número de bactérias entre os grupos estudados, tanto para o Universal (UN), Grupos 1- 372.477 (87.556;889.408), Grupo 2- 294.834 (51.742;648.674) e Grupo 3- 497.393 (150.596;2.333.567) com valor de p=0,88, quanto para o Streptococcus oralis (SO), Grupos 1-3.623(262;31.603), Grupo 2- 477(154;42.292) e Grupo 3- 9.002(1.053;147.154) com valor de p=0,42. Conclusões: Os discos do grupo 1 apresentaram rugosidade superficial igual aos do grupo 2 e ambos uma rugosidade superficial menor que os discos do grupo 3. A adesão bacteriana não foi influenciada pela rugosidade superficial dos discos de titânio. Não foi observada diferença significante na adesão bacteriana entre os grupos estudados, tanto pelo ensaio de MTT, quanto pela PCR real time.Hypothesis of the Study: This study hypothesized that treated surfaces of discs commercially pure titanium (CP Ti) discs are more susceptible to bacterial adhesion than smooth surfaces. Objective: The objective of this study was to evaluate in situ the bacterial adherence in cp Ti discs subjected to two different surface treatments: double etching and anodizing. Methods: Sixty Ti specimens were divided into three groups: Group 1 - smooth cp Ti discs (control group), Group 2 - cp double Ti discs with surface acid etching (Master Pours Implant , Connection Prosthesis Systems LTD, SP., Brazil) and Group 3 - laser irradiated cp Ti discs subjected (Vulcan Actives , Connection Implant Systems LTD, SP., Brazil). Initially we evaluated the surface roughness (Ra) of all specimens. To assess in situ, individual trays were prepared and ten in each set of six disc titanium, two in each group. Ten volunteers wore what for 24 hours, the tray containing discs cpTi After this period three titanium disks from each group were taken to the Scanning Electron Microscope (SEM) to visualize the biofilm. The biofilm was removed from the 17 remaining disks, and seven of them, was held by the colorimetric MTT method to quantify living cells and ten to Real Time Polymerase Chain Reaction (Real Time PCR) for quantification of adhered bacteria and Streptococcus oralis. Results: Data were statistically analyzed using analysis of variance (ANOVA) One Way, followed by post-test Tamhane. With respect to Ra, the difference observed between the groups 3:01 was 0.652 0.098 m and between Groups 3 and 2 of 0.688 0.099 micrometers. In micrographs biofilm attached was observed in all titanium disks. The MTT method showed no significant difference among groups Group 1 (0.119 0.048), 2 (0.136 0.079) and 3 (0.121 0.074), p = 0.89. The Real Time PCR results showed no significant difference in number bacterial between the groups for both the Universal (UN), Group 1- 372.477 (87.556;889.408), Group 2- 294.834 (51.742;648.674) and Group 3- 497.393 (150.596;2.333.567) with p = 0, 88, as for Streptococcus oralis (SO), Group 1- 3.623(262;31.603), Group 2- 477(154;42.292) and Group 3- 9.002(1.053;147.154) with p = 0.42. Conclusions: The disks of group 1 showed surface roughness equal to Group 2 and both had a surface roughness smaller than the disks of group 3. The bacterial adhesion was not influenced by the surface roughness of the titanium disks. There was no significant difference in bacterial adhesion between the groups, both by MTT method, and by real time PCR.
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Hufton, Joseph. "The role of the bacterial cell surface and extracellular macromolecules in U(VI) biosorption and biomineralisation." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/13628/.
Повний текст джерелаАнотація:
Uranium biosorption and biomineralisation are processes exhibited by bacteria that aren’t fully understood at a mechanistic level, making it difficult to consider their use and application in remediation, extraction and reuse. The aim of this study was, therefore, to deconstruct the bacterial cell and characterise the specific roles of cell surface structures and extra polymeric substances, in order to elucidate their contribution to the biosorption and biomineralisation of uranium within live cells. The complexation and precipitation of uranium with extracellular DNA (eDNA) was predominantly mediated by negatively charged phosphate moieties within eDNA. The reaction was dependent on pH, where the formation of a precipitate was reduced as the pH increased. Towards circumneutral pH, acid phosphatase liberated phosphate from eDNA that precipitated uranium as a phosphate-bearing mineral. The biosorption of uranium with bacteria is governed by the interactions with functional groups at the cell surface. The cell wall isolates and lysed cells of B. subtilis 168 exhibited a greater uranium retention capacity in comparison to those from P. putida 33015, live cells and cell membrane isolates from both strains. Carboxyl groups and phosphate groups, from proteins and phosphorylated biopolymers, were responsible uranium biosorption with the cell surface structures. The viability and metabolic activity of live cells of P. putida 33015 and D. radiodurans R1 in the presence of uranium was evaluated. An increase in uranium concentration was directly linked to cell toxicity in both strains. At low concentrations of U(VI) and circumneutral pH, viable cells likely sequestered uranium either through biosorption or through the precipitation of enzymatically generated uranium phosphate minerals that were tethered to the cell surface or within EPS as a tolerance mechanism to cope with uranium toxicity. At higher concentrations of uranium or at low pH where the bacterial growth wasn’t favourable or there was cell death, biosorption to the bacterial biomass present likely occurred.
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Jones, Andrew John Melvill. "The binding of an afimbrial bacterial surface adhesin to glycophorin using aqueous polymer two-phase partitioning." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26420.
Повний текст джерелаАнотація:
Colonisation by many bacteria and viruses is now thought to depend upon their ability to adhere to host cells via proteinacious surface appendages called adhesins. Information relevant to the prevention and cure of many diseases therefore is supplied by knowledge of this adhesive process, especially the chemistry of the binding and the structure of the binding molecules. At this time, the structure of very few adhesin receptors is known. Similarly, the quaternary and primary structure of only a small number of adhesins is currently available. Those associated with Escherichia coli are known in some cases to be arranged as helical coils with repeating proteinacious subunits with molecular weights of 10-30 kDa, however there is conflicting information on the distribution along these coils of the polypeptide involved in adhesion. Thermodynamic binding studies have not yet been used to clarify this problem because of the size of the receptors for the adhesins. This thesis presents a thermodynamic study of the binding between the adhesin from an F41+ E.coli and its receptor, glycophorin, from the human red blood cell membrane using an aqueous polymer two-phase system. The study shows that 2.4±0.8 glycophorin molecules bind to the predominant subunit of this adhesin, suggesting that this subunit has one binding site, since glycophorin dissolves as a dimer. It is proposed that the assay could be used, in addition, to obtain information on the chemical specificity and the thermodynamics of this particular reaction, in order to obtain a broader understanding of the colonisation and infection by this particular pathogen.Science, Faculty of
Chemistry, Department of
Graduate
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Hornung, Michael [Verfasser], Andreas [Akademischer Betreuer] Lübbert, and Jan [Akademischer Betreuer] Pàca. "Optimising the production of bacterial cellulose in surface culture / Michael Hornung. Betreuer: Andreas Lübbert ; Jan Pàca." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2010. http://d-nb.info/1024976912/34.
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Bäckhed, Fredrik. "Role of toll-like receptors in host responses to mucosal bacterial infections /." Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-367-8/.
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Liu, Guansheng, Hua Zhong, Yongbing Jiang, Mark L. Brusseau, Jiesheng Huang, Liangsheng Shi, Zhifeng Liu, Yang Liu, and Guangming Zeng. "Effect of low-concentration rhamnolipid biosurfactant on P seudomonas aeruginosa transport in natural porous media." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/623109.
Повний текст джерелаАнотація:
Enhanced transport of microbes in subsurface is a focus in bioaugmentation applications for remediation of groundwater. In this study, the effect of low-concentration monorhamnolipid biosurfactant on transport of Pseudomonas aeruginosa ATCC 9027 in natural porous media (silica sand and a sandy soil) with or without hexadecane as the nonaqueous phase liquids (NAPLs) was studied with miscible-displacement experiments using artificial groundwater as the background solution. Transport of two types of cells was investigated, glucose-grown and hexadecane-grown cells with lower and higher cell surface hydrophobicity (CSH), respectively. A clean-bed colloid deposition model was used to calculate deposition rate coefficients (k) for quantitative assessment on the effect of the rhamnolipid on the transport. In the absence of NAPLs, significant cell retention was observed in the sand (81% and 82% for glucose-grown and hexadecane-grown cells, respectively). Addition of low-concentration rhamnolipid enhanced cell transport, with 40 mg/L of rhamnolipid reducing retention to 50% and 60% for glucose-grown and hexadecane-grown cells, respectively. The k values for both glucose-grown and hexadecane-grown cells correlated linearly with rhamnolipid-dependent CSH quantitatively measured using a bacterial-adhesion-to-hydrocarbon method. Retention of cells by the soil was nearly complete (>99%). Forty milligrams per liter of rhamnolipid reduced the retention to 95%. The presence of NAPLs in the sand enhanced the retention of hexadecane-grown cells with higher CSH. Transport of cells in the presence of NAPLs was enhanced by rhamnolipid at all concentrations tested, and the relative enhancement was greater than in the absence of NAPLs. This study shows the importance of hydrophobic interaction on bacterial transport in natural porous media and the potential of using low-concentration rhamnolipid for facilitating cell transport in subsurface for bioaugmentation efforts.
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Ruiz, Rueda Olaya. "Nitrifying and denitrifying bacterial communities in the sediment and rhizosphere of a free water surface constructed wetland." Doctoral thesis, Universitat de Girona, 2008. http://hdl.handle.net/10803/7871.
Повний текст джерелаАнотація:
La contínua descàrrega de nutrients, sobretot fosfats i nitrogen, és la major causa d'eutrofització dels ecosistemes aquàtics. Els sistemes de tractament basats en aiguamolls construïts s'han emprat per reduir ells nivells de nitrogen a l'aigua com a alternativa de baix cost als mètodes de depuració convencionals. L'eliminació del nitrogen a aquests sistemes depèn en bona part de la vegetació, i l'alternança de condicions aeròbiques i anaeròbiques per promoure els processos de nitrificació i desnitrificació. En aquest treball hem volgut investigar les activitats microbianes de nitrificació i desnitrificació en relació a dues espècies de plantes macròfites en un sistema d'aiguamolls de tractament de flux superficial (FS-SAC), dissenyat per minimitzar l'impacte de l'alliberament d'aigua carregada de nutrients a la reserva natural dels Aiguamolls de l'Empordà (Girona, Espanya).The continuous delivery of nutrients, mainly phosphate and nitrogen, is the major cause of eutrophication of aquatic environments. Treatment technologies based on constructed wetlands have been applied to reduce the levels of nitrogen as a cost-effective alternative compared to conventional treatment methods. The nitrogen removal efficiency in wetlands relies on the presence of plants and the alternation of aerobic and anaerobic conditions to promote both nitrification and denitrification. Although the role of emergent macrophytes in such systems is largely recognized, their contribution to the overall treatment process has not been quantified very frequently. We have investigated the microbial nitrification and denitrification activities in relation to two plant species in a free water surface constructed wetland (FWS-CW), designed to minimize the impact of nutrient release into the Natural Reserve of Els Aiguamolls de l'Empordà (Girona, Spain).
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Shen, Song, and 沈嵩. "The bacterial and yeast flora of root surface caries in elderly Chinese: clinical and in vitro studies." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31245985.
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