Köln, Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Köln, Univ., Diss., 2002. / Computerdatei im Fernzugriff.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1963. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 79-83).

Köln, Universiẗat, Diss., 2002.

Düsseldorf, Universiẗat, Diss., 2002.

La qualité microbiologique de l’eau potable peut fortement se dégrader au cours de son transport dans les réseaux de distribution en raison notamment du détachement de bactéries présentes au sein de biofilms qui se développent inévitablement à la surface interne des canalisations. Cette étude développe une approche originale consistant à évaluer in situ et en temps réel la stabilité microbiologique d’une eau via l’empreinte spectrale infrarouge (IR) en mode réflexion totale atténuée (ATR) d’un jeune biofilm de référence constitué d’une monocouche de bactéries. Pseudomonas fluorescens a été choisie comme bactérie modèle. Ses signatures spectrales, infrarouge et Raman, ont été étudiées dans un premier temps à l’état planctonique et ce en fonction de la phase de croissance et de l’état d’hydratation. Le suivi in situ, via une cellule IR-ATR à circulation, des premières étapes de l’adhésion bactérienne, a ensuite permis de déterminer les conditions opératoires optimales de formation sur le cristal ATR du biofilm de référence. La structure de ce dernier a été caractérisée par microspectrométrie Raman et microscopie à épifluorescence. Enfin, la réponse du biofilm de référence exposé à des eaux contenant différentes quantités de carbone organique dissous (COD), facteur clé de la biostabilité d’une eau, a été analysée. Cette dernière partie montre très clairement la dynamique de croissance du biofilm et la corrélation entre les changements observés dans le profil spectral du biofilm naissant et les variations de la quantité de COD, et illustre le potentiel que pourrait présenter la méthode proposée en matière de gestion de la qualité microbiologique des eaux de distribution. / Drinking water biostability can evolve during its transport through distribution systems because of several factors. Bacterial biofilms which develop on the inner surface of pipes can detach and can consequently be a major source of contamination. This study evaluates the feasibility to assess, in real time, drinking water biostability by monitoring in situ the evolution of the Attenuated Total Reflectance – Fourier Transform InfraRed (ATR-FTIR) fingerprint of a nascent reference biofilm exposed to water under test. Pseudomonas fluorescens CIP 69.13 was chosen as the reference bacteria to form the monolayer reference biofilm. Its IR and Raman fingerprints were studied, in a first step, in planktonic state in accordance with growth phases and degree of hydration. Then, optimal experimental conditions were determined by following in situ and in real time the first steps of bacterial adhesion thanks to an ATR flow cell. Biofilm structure was characterised by Raman microspectroscopy and epifluorescence microscopy. Finally, the reference biofilm response was analysed when biofilm was exposed to different dissolved organic carbon (DOC) quantities in filtered drinking water. This parameter was chosen because its significant role in bacterial regrowth in drinking water distribution system. The last part clearly shows the dynamic response of biofilm growth and the relationship between the spectral profiles changes and DOC variations. Moreover, it illustrates the potential of the developed method to manage drinking water stability.

Cell-free extracts from Pseudomonas fluorescens NCIMB 11764 catalyzed the degradation of cyanide into products that included C02, formic acid, formamide and ammonia. Cyanide-degrading activity was localized to cytosolic cell fractions and was observed at substrate concentrations as high as 100 mM. Two cyanide degrading activities were identified by: (i) the determination of reaction products stoichiometries, (ii) requirements for NADH and oxygen, and (iii) kinetic analysis. The first activity produced CO2 and NH3 as reaction products, was dependent on oxygen and NADH for activity, and displayed an apparent Km for cyanide of 1.2 mM. The second activity generated formic acid (and NH3) pfus formamide as reaction products, was oxygen independent, and had an apparent Km of 12 mM for cyanide. The first enzymatic activity was identified as cyanide oxygenase whereas the second activity consists of two enzymes, a cyanide nitrilase (dihydratase) and putative cyanide hydratase. In addition to these enzymes, cyanide-grown cells were also induced for formate dehydrogenase (FDH), providing a means of recycling NADH utilized by cyanide oxygenase.

published_or_final_version / Microbiology / Master / Master of Medical Sciences

The role of ecological opportunity in adaptive radiation has been demonstrated by the diversification of the bacterium Pseudomonas fluorescens SBW25 in a spatially structured microcosm. This provides an ideal system for studying the genetics of adaptation and asking questions about the genes that matter in evolution. Previous studies have identified the genes that are necessary for the evolved, biofilm-forming, niche-specialist genotype, the wrinkly spreader (WS). These genes are organised in two operons: the wss operon that encodes the genes for cellulose biosynthesis, and the wsp operon that encodes a chemosensory pathway. The terminal gene in the wsp operon, wspR, encodes a novel response regulator thought to regulate the activity of the wss operon. This gene forms the basis of this study, which assesses the role of regulatory genes in adaptive evolution. The structure-function relationship of WspR is established through the phenotypic analysis of overexpressed wspR random point mutants. On this basis a model of WspR activity is proposed which is tested by molecular genetic analysis. The role of phosphorylation is demonstrated by site-directed mutagenesis, and domain liberation is used to study the interaction of WspR with the other components of the signalling pathway. As the overexpression of certain wspR mutant alleles mimics the evolutionary transition from ancestor to niche-specialist, the fitness effects of such overexpression are measured. It is found that some, but not all, wspR alleles do indeed cause adaptation. It is also found that a phenotypically-plastic genotype, with enhanced fitness, can be created by artificial manipulation, but does not occur naturally; this demonstrates the existence of a constraint on evolution. Sequence analysis of independently-isolated WS genotypes shows no evidence of wspR sequence variation, despite its capacity to enhance fitness. A further proteomic and phenotypic characterisation shows variation between ancestral and WS genotypes, and also between different WS genotypes. This demonstrates that there are different mutational routes to the same adaptation.

Thesis (M. Med. Sc.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 27-37).