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Giannakis, Christos. "Nitrate utilization by cultured cells and bacteroids of Bradyrhizobium japonicum /." Title page, contents and summary only, 1987. http://web4.library.adelaide.edu.au/theses/09A/09ag433.pdf.
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Lodwig, Emma Mary. "Regulation of carbon and nitrogen metabolism in Rhizobium leguminosarum." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368874.
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Meakin, Georgina Emma. "The contribution of Bradyrhizobium japonicum bacteroids to nitrosylleghaemoglobin formation in soybean nodules." Thesis, University of East Anglia, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437637.
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Li, Youzhong, and Youzhong Li@health gov au. "Respiration and nitrogen fixation by bacteroids from soybean root nodules : substrate transport and metabolism in relation to intracellular conditions." The Australian National University. Faculty of Science, 2003. http://thesis.anu.edu.au./public/adt-ANU20040630.114138.
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Bacteroids of B. japonicum from nodules of soybean roots were isolated using differential centrifugation (the standard bench method) and density gradient centrifugation methods (either sucrose- or Percoll-) under anaerobic conditions in which N2 fixation was preserved. The relationships between N2 fixation and respiration, O2 supply, O2 demand, substrate (mainly malate) transport and metabolism in bacteroids were investigated using the flow chamber system. In related experiments, the primary products of N2 fixation which leave the bacteroids were investigated using a 15N-labelling technique in a closed shaken system and other biochemical methods.¶
In the flow chamber experiments, the rates at which O2 was supplied to bacteroids in the chamber were varied by (a) changing the flow rate of reaction medium through the chamber; (b) by changing the [O2 free] in the inflowing reaction medium by using either 3-5% (v/v) or 100% air in the gas mixture above the stirred reaction medium in two reservoir flasks; (c) by successively withdrawing bacteroids from the chamber, thus increasing the supply of O2 per bacteroid to those remaining in the chamber. The results showed that the rate of O2 supply regulates respiratory demand for O2 by bacteroids rather than the O2 concentration present in the reaction system. Respiration is always coupled to N2 fixation. ¶
Uptake of malate by bacteroids withdrawn from the flow chamber was measured under microaerobic conditions. Malate uptake by these N2-fixing bacteroids was lower than that by bacteroids isolated under aerobic conditions, which eliminate N2 fixation of bacteroids, but is closely correlated with bacteroid respiration rates. When respiration was increased by an increase in O2 supply, malate uptake by bacteroids was also increased. This suggested that transport of malate through the bacteroid membrane is also regulated by O2 supply, but indirectly. Higher uptake by bacteroids under aerobic conditions was observed because respiration was enhanced by the high availability of O2, but the fast uptake of malate by bacteroids driven by the abnormal respiration rates may not reflect the reality of malate demand in vivo by bacteroids when N2 fixation by bacteroids is fully coupled. ¶
The results of 15N labelling experiments and other biochemical assays once again demonstrated that ammonia is the principal significant 15N labelled product of N2 fixation accumulated during 30 min in shaken assays with 0.008-0.01 atm O2. Alanine although sometimes found in low concentrations in the flow chamber reactions, was not labelled with 15N in shaken closed system experiments. No evidence could be obtained from the other biochemical assays, either. Therefore, it is concluded that these and earlier results were not due to contamination with host cytosolic enzymes as suggested by Waters et al. (Proc. Natl. Aca. Sci. 95, 1998, pp 12038-12042). ¶
Malate transported into bacteroids is oxidized in a modified TCA cycle present in bacteroids. The results of flow chamber experiments with a sucA mutant (lacking a-ketoglutarate dehydrogenase) showed that respiratory demand for O2 by the mutant bacteroids is regulated by O2 supply in the same way as the wild-type. Despite differences in other symbiotic properties, rates of nitrogen fixation by the mutant bacteroids, based on the bacteroid dry weight, appeared to be the same as in the wild-type. Also N2 fixation was closely coupled with respiration in the same manner in both mutant bacteroids and wild type bacteroids. These results and other supporting data, strongly support the conclusion that there is an alternative pathway of the TCA cycle in bacteroids, which enables the missing step in the mutant to be by-passed with sufficient activity to support metabolism of transported malate.
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Mitsch, Michael James. "Characterization of the NADP+-dependent malic enzyme of Sinorhizobium (Rhizobium) meliloti and investigations into the requirements of malate uptake and malic enzyme activity in bacteroids /." *McMaster only, 2001.
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Le, Roux Marcellous R. "Respiratory and photosynthetic C and N metabolism of nodulated Lupin roots during phosphorus deficiency." University of the Western Cape, 2010. http://hdl.handle.net/11394/8427.
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Philosophiae Doctor - PhDGrowth of symbiotic legume hosts is P limited, because of the high energetic requirements associated with N2 fixation. Attempts to overcome P deficiency in soils where legumes are grown involve addition of P-based fertilisers. However, these are produced from fmite, non-renewable resources that could be exhausted in the next 50-80 years. For this and other prudent reasons, viable alternatives are sought that include producing genetically enhanced plants with better P use efficiency (PUE). There exist some inter- and intraspecific genetic variation for associated traits of PUE in various legumes and these will have to be exploited to realize the development of P efficient cultivars. With the advent of sophisticated molecular tools, good progress has been made to understand the molecular response of some common physiological and morphological functions observed under LP. The research aims here were to investigate the energy costs and the alternative metabolic routes associated with C and N metabolism under LP in legumes, which is very scant in literature. We also investigated the recovery responses of nodulated roots upon P alleviation. Consequently, improvement strategies to produce legume varieties for better adaptation in poor P soils are envisaged. We have demonstrated varying degrees of sensitivity between the amide and ureide legume systems being investigated under short-term LP. The species-specific responses were ascribed to differences related to the agro-climatic origins, nodule morphologies and the type of N containing export product of the different legume types. These different responses also underscore possible different regulatory mechanisms under LP. Lupins were probed further, because of its apparent tolerance to P deficiency. Lupin nodules had between 3 to 5-fold higher Pj concentrations compared with soybeans under LP and HP, respectively. The maintenance of Pj levels, as oppose to a decline in the total P pool, is discussed in relation to its role in maintaining N2 fixation in lupins. Under LP, an effective Pj recycling mechanism in nodules is proposed to occur via the induction of the PEPc- MDH-ME route. This route also enhanced the capacity of root nodules to procure high malate concentrations that are used to fuel bacteroid respiration and N2 fixation. Two distinctly different cMDH proteins, one corresponding to HP and another corresponding to LP, were identified. The high malate concentrations reported here are speculated to have arisen through LP-induced cMDH. Metabolically available Pj decline developed gradually as P deficiency progressed. This coincided with a 15% decline in the %Ndfa. Moreover, under prolonged P deficiency the disproportionate synthesis of organic acids, most notably malate, that occurred at the expense of amino acids was proposed to account for this decline. The recovery in response to alleviation from LP involved alterations in the allocation of respiratory costs to growth and nutrient acquisition. Under LP, smaller nodules were formed and nodule metabolism revolved around accentuating PUE. Thus, there is considerable potential for improvement of P efficiency in legumes through manipulation of root: shoot partitioning.
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Nicoud, Quentin. "Study of terminal bacteroid differentiation features during the legume-rhizobium symbiosis Bradyrhizobium diazoefficiens USDA110 nodulation of Aeschynomene afraspera is associated with atypical terminal bacteroid differentiation and suboptimal symbiotic efficiency Sinorhizobium meliloti functions required for resistance to the antimicrobial NCR peptides and bacteroid differentiation." Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASB007.
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La symbiose rhizobium-légumineuse est une intéraction étroite entre plante et bactérie. Au cours de cette symbiose, la bactérie est hébergée par la plante au sein d’organes symbiotiques où elle fixe l’azote atmosphérique pour la plante. Les espèces de légumineuses du groupe des IRLC et des Dalbergioïdes peuvent contrôler les rhizobia symbiotiques et induire un processus de différenciation particulier grâce à la production massive de peptides riches en cystéines (NCR) spécifiques aux nodosités. In vitro, les peptides NCR cationiques ont des activités de perméabilisation de la membrane sur de nombreuses bactéries. La manière dont les rhizobiums s'adaptent pour résister à ce stress intense reste encore aujourd’hui mal compris. Deux axes de recherche principaux ont été menés au cours de cette thèse, tous deux liés à la compréhension de la réponse des bactéries à la différenciation terminale imposée par les peptides NCR. D'un côté, nous avons analysé certaines fonctions bactériennes pour leur rôle dans la résistance à la NCR au cours de l'interaction modèle entre Medicago truncatula et Sinorhizobium meliloti. Dans ce travail, nous avons principalement évalué les fonctions membranaires telles que la synthèse du LPS, le système de réponse aux stress de l’enveloppe et des fonctions d'importation. Nous avons trouvé de nouvelles fonctions qui pourraient être impliquées dans la résistance à la NCR et la différenciation terminale des bactéroïdes.De l'autre côté, nous avons mené une approche multi-omique couplée à des techniques de biologie cellulaire pour caractériser l'interaction mal adaptée entre Bradyrhizobium diazoefficiens USDA110 et Aeschynomene afraspera. Nous avons découvert de nouvelles particularités dans cette interaction avec notamment une différenciation inhabituelleThe legume-rhizobia symbiosis is a close interaction between a plant and bacteria. During this symbiosis, bacteria are hosted by the plants in symbiotic organs called nodules and in which the symbionts fix atmospheric nitrogen for the plants. Legume species from IRLC and Dalbergioid can control symbiotic rhizobia and mediate a particular differentiation process through the massive production of nodule-specific cysteine-rich (NCR) peptides. In vitro, cationic NCR peptides have membrane-permeabilizing activities on many bacteria. How rhizobia adapt to resist this intense stress remains poorly understood. Two main research axes were driven during this thesis, both linked to the understanding of how bacteria react to terminal differentiation imposed by NCR peptides. On one side, we tried to functionally analyze bacterial functions for their role in NCR resistance during the model interaction between Medicago truncatula and Sinorhizobium meliloti. In this work, we mainly assessed membrane functions such as LPS synthesis, Envelope Stress Response, and import functions. We found novel functions that could be involved in NCR resistance and terminal bacteroid differentiation.On the other side, we conducted a multi-omics approach coupled with cell-biology techniques to characterize the ill-adapted interaction between Bradyrhizobium diazoefficiens USDA110 and Aeschynomene afraspera. We discovered new features in this interaction with an unusual differentiation
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Bourcy, Marie. "DNF2 et SYMCRK : deux gènes impliqués dans le contrôle symbiotique des réactions de défense chez Medicago truncatula." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112041.
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Medicago truncatula forme une association symbiotique avec Sinorhizobium meliloti qui conduit à la formation de nodosités fixatrices d’azote. Les cellules symbiotiques végétales accueillent des centaines de bactéries qui restent viables dans la nodosité et se différencient en bactéroïdes fixateurs d’azote. Dans le but de mieux comprendre les mécanismes moléculaires nécessaires à la mise en place de cette interaction, nous avons recherché de nouveaux gènes de plante requis pour une symbiose effective en utilisant des approches de génétique directe et inverse. Des méthodes de biologie cellulaire et moléculaire ont été utilisées pour caractériser le phénotype des mutants et mieux comprendre la fonction biologique de ces gènes.Le gène symbiotique DNF2 code une phosphatidylinositol phospholipase C putative. Les nodosités formées par le mutant dnf2 contiennent une zone de fixation qui est réduite et dans laquelle les rhizobia ne se différencient pas complètement en bactéroïdes. De plus ces nodosités sénescent rapidement et présentent des réactions similaires à des réponses de défense. Sous certaines conditions d’expérimentation, le phénotype sauvage peut être restauré chez ce mutant ce qui montre le caractère conditionnel du phénotype.Le gène symbiotique SYMCRK code un récepteur kinase riche en cystéine. Le phénotype du mutant symCRK est similaire à celui de dnf2, ce qui suggère que ces deux gènes sont impliqués dans des processus aboutissant à des réponses similaires, probablement la persistance des bactéries dans les cellules végétales ou l’inhibition des réactions de défense de la plante. Les phénotypes Fix- atypiques des mutants dnf2 et symCRK suggèrent que les gènes correspondants sont impliqués dans les processus de répression des défenses de la plante et de persistance des bactéroïdesMedicago truncatula and Sinorhizobium meliloti form a symbiotic association resulting in the formation of nitrogen-fixing nodules. In the nodules, symbiotic plant cells home and maintain hundreds of viable bacteria which are differentiated into bacteroids, the nitrogen-fixing form of rhizobia. In order to better understand the molecular mechanism sustaining this phenomenon, we used a combination of forward and reverse genetics approaches to identify genes required for nitrogen fixation. In addition we have used cell and molecular biology to characterize the phenotype of the corresponding mutants and to gain an insight into the genes functions.The symbiotic gene DNF2 encodes a putative phosphatidylinositol phospholipase C-like protein. Nodules formed by the mutant contain a zone of infected cells reduced to a few cell layers. In this zone, bacteria do not differentiate properly into bacteroids. Mutant nodules senesce rapidly and they exhibit defense-like reactions. The dnf2 symbiotic phenotype has been shown to be dependent on the experimental conditions.The symbiotic gene SYMCRK encodes a cystein-rich receptor kinase. The symCRK phenotype is similar to dnf2 suggesting that the two genes SYMCRK and DNF2 are participating in similar processes. This atypical phenotype amongst Fix- mutants unravels DNF2 and SYMCRK as new actors of bacteroid persistence inside symbiotic plant cells and repression of plant defense
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Lamouche, Florian. "Analyse comparative des mécanismes de différenciation des bactéroïdes au cours des symbioses Bradyrhizobium Aeschynomene." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS036/document.
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En cas de carence azotée, les légumineuses sont capables de mettre en place une symbiose avec des bactéries du sol fixatrices d’azote appelées rhizobia. Cette symbiose a lieu dans un organe appelé nodosité où les bactéries sont endocytées et appelées bactéroïdes. Certains clades de légumineuses imposent un processus de différenciation à leurs bactéroïdes qui agrandissent considérablement et deviennent polyploïdes, menant à des morphotypes bactériens allongés ou sphériques. Au cours de cette thèse, j’ai étudié la différenciation des bactéroïdes de Bradyrhizobium spp. en association avec Aeschynomene spp.. Les bactéroïdes de ces plantes présentent des degrés de différenciation distincts qui dépendent de l’espèce hôte. Mes données suggèrent que les bactéroïdes les plus différenciés sont aussi les plus efficaces. J’ai cherché à savoir quels facteurs procaryotes pourraient être impliqués dans les adaptations des bactéroïdes au processus de différenciation et à leurs divers hôtes, le tout en lien avec cette différence d’efficacité symbiotique au travers d’approches globales sans a priori de type -omiques. Les conditions considérées sont des bactéroïdes de différents morphotypes et des cultures libres de référence. Les fonctions activées en conditions symbiotiques ont été identifiées, ainsi que les gènes spécifiques d’un hôte donné. Des analyses fonctionnelles des gènes d’intérêt ont également été menées. Les mutants bactériens n’ont toutefois pas présenté de phénotype symbiotique drastique, montrant ainsi l’existence de réseaux de gènes complexes menant à la résilience des génomes de rhizobiaIn case of nitrogen starvation, legume plants establish a symbiotic interaction with nitrogen-fixing soil bacteria called rhizobia. This interaction takes place in nodules where the symbionts are internalized and become bacteroids. Some legume clades also impose a differentiation process onto the bacteroids which become enlarged and polyploid, leading to elongated or spherical morphotypes. During my PhD work, I have studied bacteroid differentiation of Bradyrhizobium species in association with Aeschynomene spp.. These bacteroids display distinct differentiation levels depending on the plant host, and my analyses suggest that the most differentiated ones are also the most efficient. I investigated the bacterial factors potentially involved in the adaptations to differentiation and host-specificity, and related to the higher efficiency of the most differentiated bacteroids using global-omics approaches without a priori. The analyzed conditions were bacteroids of distinct morphotypes and free-living reference cultures. Activated functions under symbiotic conditions were identified, as well as host-specific ones. Functional analyses were performed on genes of interest. However, the bacterial mutants did not display drastic symbiotic phenotypes, showing the existence of complex gene networks leading to high resilience of rhizobial genomes
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Nguyen, Van Phuong. "Plant and bacterial functions required for morphological bacteroid differentiation in the Aeschynomene-Bradyrhizobium model." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT158/document.
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Les légumineuses sont capables de développer des organes symbiotiques, les nodules, qui hébergent des bactéries du sol appelées rhizobia. Au sein des nodules les rhizobia intracellulaires se différencient en bactéroïdes capables de réduire l'azote atmosphérique en ammonium au bénéfice de la plante. En contrepartie, la plante alimente la bactérie en sources de carbone. Des études récentes sur le modèle symbiotique Medicago/Sinorhizobium ont montré dans les nodules la forte présence d'une grande diversité de peptides appelés NCR qui sont similaires aux peptides antimicrobiens (AMP) impliqués dans l'immunité innée. Ces NCR sont responsables du maintien de l'homéostasie entre les cellules hôtes et la forte population bactérienne qu'elles contiennent. Bien que certains NCR sont de vrais AMP, capable de tuer des bactéries in vitro, dans les nodules ils induisent plutôt une différenciation terminale caractérisée par une élongation cellulaire, une amplification du génome, une perméabilité membranaire et une perte des capacités de division de la bactérie. Néanmoins le mode d'action des NCR reste à élucider. Au cours de ma thèse j'ai participé à la caractérisation des processus de différenciation dans le modèle Aeschynomene, une légumineuse tropicale, Bradyrhizobium.Dans un premier temps, une nouvelle classe de NCR a été identifiée chez différentes espèces d'Aeschynomene. Ces NCR sont responsables de la différenciation des Bradyrhizobium via un processus similaire à celui décrit chez Medicago. Ces résultats suggèrent une évolution convergente des processus de différenciation chez les Dalbergioïdes (Aeschynomene) et le clade des IRLC (Medicago).Ensuite, pour identifier les fonctions bactériennes requises lors de la différenciation, j'ai criblé 53 mutants Tn5 d'Aeschynomene indica fix- . Huit gènes bactériens dont la mutation inhibe ou affecte le processus de différenciation ont été identifiés. Parmi eux, je me suis focalisé sur la DD-CPase une enzyme de modification du peptidoglycane et sur 2 gènes impliqués dans l'homéostasie du phosphate.La caractérisation du gène DD-CPase1 a permis de démontrer que le remodelage du peptidoglycane est requis pour une différenciation correcte des bactéroïdes chez les plantes hôtes qui produisent des NCR, en général, et chez Aeschynomene en particulier. Ces résultats suggèrent une interaction possible entre DD-CPase1 et des NCR conduisant à l'endoréplication des bactéroïdes.Enfin, j'ai étudié les propriétés physiologiques et symbiotiques des mutants pstC et pstB. Les mutants Tn5 des gènes pstC et pstB de la souche ORS285 de Bradyrhizobium sont sévèrement affectés par la carence en phosphate en culture pure et leurs propriétés symbiotiques (différenciation, réduction de l'azote) sont fortement réduites. Des analyses fonctionnelles plus approfondies de l'opéron Pst devraient permettre une meilleure compréhension du lien entre l'homéostasie du phosphate et l'efficience symbiotique dans l'interaction Aeschynomene-Bradyrhizobium.Mes travaux ont permis d'élargir nos connaissances sur l'évolution de la symbiose en montrant que le modus operandi impliquant des peptides dérivés de l'immunité innée utilisée par certaines légumineuses pour maintenir leur population bactérienne intracellulaire sous contrôle est plus répandue et ancienne qu'on ne le pensait et a été utilisée par l'évolution à plusieurs reprises. De plus différentes cibles bactériennes pouvant participer au processus de différenciation ont également été identifiéesThe legume species are able to form symbiotic organs, the nodules, that house soil bacteria called rhizobia. Within these nodules intracellular rhizobia differentiate into bacteroids, which are able to reduce atmospheric dinitrogen to ammonium for the benefit of the plants. In counterpart, the plants provide carbon sources to the bacteria. Recent studies on symbiotic model Medicago-Sinorhizobium showed that the nodules of M. truncatula produce a massive diversity of peptides called NCRs, which are similar to antimicrobial peptides (AMPs) of innate immune systems. These NCRs are responsible in maintaining the homeostasis between the host cells in the nodules and the large bacterial population they contain. Although many NCRs are genuine AMPs, which kill microbes in vitro, in nodule cells they do not kill the bacteria but induce them into the terminally differentiated bacteroids characterized by cell elongation, genome amplification, membrane permeability and loss of cell division capacity. However, the action mode of NCRs is still an open question. During my PhD thesis I focused on the identification of plant and bacterial functions required for bacteroid differentiation in the Aeschynomene-Bradyrhizobium model.Firstly, a new class of cysteine rich peptides (NCR-like) was identified in tropical aquatic legumes of the Aeschynomene genus, which belong to the Dalbergioid clade. These peptides govern terminal bacteroid differentiation of photosynthetic Bradyrhizobium spp. This mechanism is similar to the one previously described in Medicago suggesting that the endosymbiont differentiation in Dalbergioid and ILRC legumes is convergently evolved.Secondly, in order to identify the bacterial functions involved in bacteroid differentiation, I screened 53 fix- Tn5 mutants of the ORS278 strain on Aeschynomene indica. This screening allowed identify 8 bacterial genes, which inhibit or disorder the bacteroid differentiation. Among these identified genes, I focused on DD-CPase encoding a peptidoglycan-modifying enzyme and two genes pstC and pstB belonging to Pst-system.The characterization of DD-CPase gene demonstrated that the remodeling peptidoglycan enzyme, DD-CPase1, of Bradyrhizobium is required for normal bacteroid differentiation in host legumes that produce NCRs, in general, and in Aeschynomene spp., in particular. This prompts a possibility of direct interaction of DD-CPase1 with NCRs leading to endoreduplication of the bacteroids.Finally, I have investigated the physiological and symbiotic properties of different mutants of pstC and pstB genes. The Tn5 mutants of pstC and pstB genes of Bradyrhizobium sp. strain ORS278 severely affected symbiosis on A. indica and A. evenia. Further functional studies on pst-operon will provide deeper understanding the correlation between phosphate homeostasis and nitrogen fixation efficiency in Aeschynomene-Bradyrhizobium symbiosis.This study broadens our knowledge on the evolution of symbiosis by showing that the modus operandi involving peptides derived from innate immunity used by some legumes to keep their intracellular bacterial population under control is more widespread and ancient than previously thought and has been invented by evolution several times
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Stewart, Linda D. "Bacteroides fragilis in clinical infection." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333836.
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Tumba, Nancy. "Glutamine synthetase in Bacteroides fragilis." Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/14720.
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Includes bibliographical references (p. 78-90).Bactereroides fragilis is a gram-negative, non spore-forming, obligate anaerobe of the human intestinal microbiota. It is, however, an opportunistic pathogen and has been ranked as the most prevalent isolate in cases of anaerobic septicaemia. Similar to most bacteria, ammonium is assimilated in B. fragilis through the action of glutamine synthetase (GS). Glutamine is vital to nitrogen metabolism as it serves as a precursor to many secondary metabolites. GS enzymes are, therefore, vital to the growth of the organism and many prokaryotes are known to possess two or more isoforms of the enzyme. In addition, GS expression and regulation is usually tightly regulated in concert with the availability of nitrogen. Previous studies have identified a single GSIII encoding gene (glnN) in B. fragilis. In this dissertation, an additional ORF coding for a putative GSI enzyme in B. fragilis was identified, isolated and functionally characterized. A putative regulatory protein was also identified and its functional contribution to nitrogen metabolism was determined, in order to extend our understanding of nitrogen assimilation in B. fragilis.
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Steffens, Laura Sione. "DNA repair in bacteroides fragilis." Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/4337.
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Includes abstract.Includes bibliographical leaves (leaves 89-101).
Bacteroides fragilis is a gut commensal in both humans and animals where it benefits the host through metabolizing indigestible compounds, stimulating the immune system and protecting against pathogen colonization. However, it is also an opportunistic pathogen, responsible for approximately half of anaerobic bacteraemias. Metronidazole is used to treat anaerobic infections. It diffuses into the celI as an inactive prodrug where it is reduced to form nitro anion and nitroso and hydroxylamine radicals. These chemically reactive compounds interact with DNA causing strand breaks and base mutations; the damage accumulates and leads to cell death. Mechanisms of metronidazole resistance in B. fragilis include decreased activity of oxidation/reduction enzymes, over-expression of multidrug efflux pumps and the conversion of metronidazole to non-toxic derivatives by nitroimidazole nitroreductases (encoded by nim genes). However, metronidazole resistance could also potentialIy be mediated by the over-expression or enhanced activity of DNA repair proteins. Thus, DNA repair in B. fragilis should be thoroughly investigated.
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Robert, Jean-Claude. "Bactériologie du parodonte de l'enfant : Incidence des Bacteroides gingivalis et autres bacteroides à pigmentation noire." Rennes 1, 1989. http://www.theses.fr/1989REN10A01.
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L'emploi de techniques de microscopie électronique à balayage et en transmission a permis d'examiner les surfaces lactéales et la pénétration des bactéries dans les tissus du parodonte des enfants. La flore parodontale est moins abondante dans le sulcus de l'enfant mais elle présente une grande complexité sans pathologie. Ainsi on retrouve des structures en épis de maïs. Les bactéries pénètrent dans l'épithélium kératinisé ou non, et deans les tissus sous-jacents. Nous avons recherché le milieu adapté à nos germes et éliminé tout milieu sélectif surtout ceux contenant des antibiotiques. Par contre la poussée des Bacteroides à pigmentation noire nécessite la présence de certains facteurs de croissance, l'hémine et la vitamine K. C'est pourquoi nous avons choisi la gélose au sang et surtout le milieu de Todd-Hewitt enrichi. Grâce à l'utilisation d'un anticorps spécifique dans la technique d'immunofluorescence indirecte nous retrtouvons 4,5 fois plus de Bacteroides gingivalis que par culture. L'évaluation de différentes méthodes d'identification met en avidence la fiabilité et la facilité d'utilisation du test API 32 A. On peut affirmer que tous les enfants de 6 ans et plus ont des Bacteroides gingivalis.
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Guefrachi, Ibtissem. "Bacteroid differentiation in Aeschynomene legumes." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112113/document.
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Les Légumineuses ont développé une interaction symbiotique avec des bactéries du sol, les rhizobia, qui fixent l’azote atmosphérique et le transfèrent à la plante sous forme assimilable.Cette interaction a lieu, au sein des nodosités, des organes racinaires où les bactéries intracellulaires se différencient en bactéroïdes. Chez Medicago truncatula, ces bactéroïdes correspondent à un stade de différentiation terminale corrélée à une endoréplication de leur génome, une augmentation de la taille des cellules, une modification des membranes et une faible capacité à se propager. Cette différentiation est induite par des facteurs de la plante appelés NCR (Nodule-specific Cysteine Rich). Les peptides NCRs ressemblent à des défensines, des peptides antimicrobiens ayant une activité antimicrobienne in vitro, tuant des bactéries. Ainsi, un élément clef dans la différenciation des bactéroïdes est la protéine bactérienne BacA, un transporteur membranaire qui confère une résistance contre l’activité antimicrobienne des peptides. Dans le cadre de ce travail de thèse, j’ai montré que l'expression des NCR est soumise à une régulation stricte et qu’ils sont activés dans trois vagues dans les cellules symbiotiques polyploïdes.Les mécanismes de contrôle par la plante sur les rhizobia intracellulaires demeurent à ce jourpeu connus et le seul modèle étudié, au début de ce travail de thèse, restait l'interaction entre M. truncatula et S. meliloti. Je me suis donc intéressée à la symbiose de certaines Légumineuses tropicales du genre Aeschynomene appartenant au clade des Dalbergoïdes où jemontre qu’ils utilisent une classe différente de peptides riches en cystéine (NCR-like) pour induire la différenciation des bactéroïdes. Ce mécanisme est analogue à celui décrit précédemment chez Medicago qui était jusqu'à présent supposé être limitée aux légumineuses appartenant au clade des IRLC. J’ai également montré que Bradyrhizobium, symbionte d’Aeschynomene possèdent un transporteur de type ABC homologues à BacA de Sinorhizobium nommé BclA. Ce gène permet l'importation d'une variété de peptides comprenant des peptides NCR. En l'absence de ce transporteur, les rhizobiums sont incapables de se différencier et de fixer l'azote.Cette étude a permis d'élargir nos connaissances sur l'évolution de la symbiose en montrant qu’au cours de l’évolution, deux clades de Légumineuses relativement éloignés (IRLC et Dalbergoïdes) aient convergé vers l’utilisation de peptides de l’immunité innée afin de contrôler leur symbionte bactérien et d’en tirer un bénéfice maximal au cours de l’interaction symbiotiqueThe ability of legumes to acquire sufficient nitrogen from the symbiosis with Rhizobium relies on the intimate contact between the endosymbiotic, intracellular rhizobia, called bacteroids, and their host cells, the symbiotic nodule cells. A well-studied example is the symbiotic nitrogen fixing bacterium Sinorhizobium meliloti, which nodulates the legume Medicago truncatula. Nodules of M. truncatula produce an enormous diversity of peptides called NCRs which are similar to antimicrobial peptides (AMPs) of innate immune systems. These NCRs are involved in maintaining the homeostasis between the host cells in the nodules and the large bacterial population they contain. Although many NCRs are genuine AMPs which kill microbes in vitro, in nodule cells they do not kill the bacteria but induce them into the terminally differentiated bacteroid state involving cell elongation, genome amplification, membrane fragilization and loss of cell division capacity. Protection against the antimicrobial action of NCRs by the bacterial BacA protein is critical for bacteroid survival in the symbiotic cells and thus for symbiosis. As a part of my PhD thesis, I have shown that the differentiation of the symbiotic cells in M. truncatula is associated with a tremendous transcriptional reprogramming involving hundreds of genes, mainly NCR genes, which are only expressed in these cells. Although the extensive work on the model M. truncatula/S. meliloti, little is known how the plant controls its intracellular population and imposes its differentiation into a functional form, the bacteroids in other symbiotic systems.In my PhD work, I provide several independent pieces of evidence to show that tropical legumes of the Aeschynomene genus which belong to the Dalbergoid legume clade use a different class of cysteine rich peptides (NCR-like) to govern bacteroid differentiation. This mechanism is similar to the one previously described in Medicago which was up to now assumed to be restricted to the advanced IRLC legume clade, to which it belongs. I have also shown that the Bradyrhizobium symbionts of Aeschynomene legumes possess a multidrug transporter, named BclA, which mediates the import of a diversity of peptides including NCR peptides. In the absence of this transporter, the rhizobia do not differentiate and do not fix nitrogen. BclA has a transmembrane domain of the same family as the transmembrane domain of the BacA transporter of Rhizobium and Sinorhizobium species which is known to be required in these rhizobia to respond to the NCR peptides of IRLC legumes. Again this is a mechanism which is analogous to the one described in S. meliloti the symbiont of Medicago.This study broaden our knowledge on the evolution of symbiosis by showing that the modus operandi involving peptides derived from innate immunity used by some legumes to keep their intracellular bacterial population under control is more widespread and ancient than previously thought and has been invented by evolution several times
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Singh, Umadatt. "The adherence properties of Bacteroides gingivalis." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/31013.
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A Bacteroides gingivalis adhesin mediating attachment to red blood cells and buccal epithelial cells was isolated, cloned and characterized. The isolation procedure involved gentle stirring of the cells followed by ammonium sulphate precipitation, ion-exchange and gel chromatography. The native molecule had a Mr in excess of 10⁶ kDa and was made up of subunits with an Mr of 43 kDa. Antisera raised to the adhesin and its subunits reacted with antigens on the surface of B. gingivalis cells. No reaction with fimbriae was seen. The IgG fractions from these antisera inhibited the adherence of B. gingivalis to host tissue. Proteolytic enzymes destroyed binding capability of whole cells and of the purified adhesin but the molecular weight of the haemagglutinin was not altered.
A genomic library of B. gingivalis DNA was created in E. coli JM83. 5500 colonies were screened by a colony immunoassay with anti-S. gingivalis serum and by a direct haemagglutinating assay. 337 clones tested positive by the immunoassay and two clones, 1-3,and 1-49 tested positive for haemagglutinating activity. Both haemagglutinating positive recombinants had inserts of 3.2 kb. One clone, 1-49 was chosen for further characterization. E. coli 1-49 expressed a protein of 43 kDa that was not present in E. coli JM 83 control as seen by SDS-PAGE and Western blot analysis. Anti-1-49 serum inhibited the haemagglutinating activity of B. gingivalis and E. coli 1-49. This serum reacted with surface molecules on B. gingivalis and E. coli 1-49 as seen by immunogold electron microscopy and immunofluorescence, and to the purified haemagglutinin by Western blot analysis. Like the haemagglutinin on B. gingivalis, the haemagglutinating activity of E. coli 1-49 was destroyed by heating and proteolytic enzymes but the apparent size of the molecule as determined by SDS-PAGE was not affected.
A bacterial coaggregating adhesin from B. gingivalis was isolated and characterized.
The isolation procedure involved adsorption of the solubilized adhesin on S. mitis followed by elution with glycine buffer. SDS-PAGE of the boiled adhesin revealed a protein with an Mr of 46 kDa. Proteolytic digestion destroyed all bacterial aggregating activity and hydrolysed the 46 kd protein. Antisera raised to the 46 kDa protein reacted with surface molecules on all strains of B. gingivalis tested. This antiserum inhibited the coaggregation reaction between B. gingivalis and other bacteria.
Vesicles produced by B. gingivalis were found to enhance the binding of S. sanguis to serum coated hydroxy apatite (SeHA). Maximum vesicle mediated binding took place at 37°C and was destroyed by heating.
The lipopolysaccharide from several black pigmented bacteroides were isolated and characterized physically, chemically and immunologically. All of the LPS were of the smooth type and contained the sugars rhamnose, glucose, galactose, glucosamine and galactosamine; no KDO or heptose were found.Science, Faculty of
Microbiology and Immunology, Department of
Graduate
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McCoy, L. J. "Molecular analysis of Bacteroides fragilis virulence." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398111.
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Jobling, Kelly Louise. "Horizontal gene transfer in Bacteroides fragilis." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9637.
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Horizontal gene transfer (HGT) is one of the man driving forces of evolution in prokaryotes, and can also promote within-strain variation of bacterial species. The genomes of three previously sequenced Bacteroides fragilis strains, NCTC9343, 638R and YCH46 displayed evidence of extensive HGT, demonstrated by the presence of 28 divergent capsular polysaccharide-associated biosynthesis loci. The genomes of a further four B. fragilis strains, LS66, GNAB92, RD48 and BE1 were sequenced and analysed. Genomic comparisons of BE1 and GNAB92 with NCTC9343, 638R and YCH46 identified ten new divergent polysaccharide biosynthesis loci. There is consequently, the potential to express 38 different polysaccharides amongst these five strains. Such a high level of variation in capsular polysaccharides, in so few strains has not been previously observed. HGT has occurred in B. fragilis despite the presence of diverse Restriction-Modification systems. The genome sequences of NCTC9343 and 638R contained a gene, ubb, the product of which, BfUbb, has 63% identity to human ubiquitin. The closest DNA sequence homology is to a migratory grasshopper entomopox virus, suggesting acquisition of this gene was via inter-kingdom HGT. The ubb gene was also identified in the newly sequenced genomes of B. fragilis strains LS66 and RD48. BfUbb had a predicted signal sequence; both full-length and processed forms were detected in whole-cell extracts by Western blot analysis. The inability to detect BfUbb in periplasmic extracts isolated from a B. fragilis strain containing an ubb signal sequence deletion construct, supported the periplasmic location of the processed form of the protein and the requirement for the signal peptide for transport from the cytoplasm. BfUbb was also detected in concentrated supernatants containing outer membrane vesicles, suggesting a mechanism by which the protein may be delivered to the host. This is the first example of ubiquitin being produced by a prokaryote. Transduction by bacteriophages is one mechanism by which horizontal gene transfer can occur and can also be a useful tool for genetic manipulation. Fifteen potentially new B. fragilis-specific bacteriophages were isolated from filtered sewage and characterised by phage titres and restriction endonuclease cleavage profiles. Of the fifteen, seven phages appeared to be different to the previously identified phage ФED01. None of the bacteriophages were capable of transduction. B. fragilis is a predominant member of the gastrointestinal microbiota. To survive within this specific niche, bacteria must successfully compete with other organisms for nutrients and space, and withstand attacks from bacteriophages. HGT may aid in the survival of B. fragilis as a commensal.
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Southern, James Arnold. "Molecular genetic studies of bacteroides fragilis." Doctoral thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/21909.
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Bibliography : pages 234-264.Some genetic systems operative in Bacteroides fragilis have been successfully investigated. Firstly the bacteriocin produced by the B.fragilis BF-1 strain was purified and partially characterized. This bacteriocin was found to be cell bound and constitutively produced by the bacteria. The purified bacteriocin was a protein with an apparent Mr of 6400-7200, and was relatively heat stable. The action of the bacteriocin resulted in the lysis of sensitive bacteria. As previous reports indicated that a bacteriocin isolated from the BF-1 strain inhibited the action of RNA-polymerase in-vivo and in-vitro, RNA-polymerase was extracted and partially purified from the bacteriocin sensitive B.fragilis BF-2 strain (described in Appendix 5). This enzyme was essentially similar to that described for other Eubacteriales, but was not inhibited in the in vitro assay by the purified bacteriocin described in this thesis.
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Thomson, Andrew Montgomery. "Gene transfer in rumen Bacteroides species." Thesis, University of Aberdeen, 1990. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU497422.
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Obligately anaerobic bacteria of the genus Bacteroides are important and abundant inhabitants of the rumen and hind gut of mammals. They are the most numerous group in the rumen and play a major role in fibre degradation with the rumen. They are phylogenetically remote from the better studied groups of facultatively anaerobic gut bacteria (eg. enterobacteria), but are closely related to the colonic Bacteroides. Interstrain conjugal transfer of a plasmid, pRRI4 (coding for tetracycline (Tc) resistance), from the multiple plasmid bearing B.ruminicola strain 223/M2/7 to F101, a rifampicin resistant mutant of B.ruminicola B 14, was demonstrated. pRRI4 was demonstrated to be self transmissible and carried the genes coding for TcR in B.ruminicola. Transformation of B.ruminicola F101 to Tc R with pRRI4 was achieved using electroporation at frequencies up to 106 per mug DNA. Four other B.ruminicola strains were not transformed with this plasmid nor was a strain of B.uniformis. Similar procedures gave transformation of B.uniformis strains, but not B.ruminicola strains, with the E.coli:Bacteroides shuttle vectors pDP1 and pE5-2 at frequencies up to 107 per mug DNA. A nuclease assay was developed to determine the nuclease activity of a number of rumen bacteria and high nuclease activity in all B.succinogenes and five B.ruminicola strains was demonstrated. E.coli and B.uniformis strains were also transformed using electroporation by the shuttle vector, pRRI207, which has been constructed from a cryptic B.ruminicola plasmid (pRRI2, 3.4kbp) cut with EcoRI *, an E.coli vector plasmid (pHG165, 3.37kbp) carrying the pUC8 multiple cloning site, and the 4.2kbp Cc-EmRTc R* EcoRI region of pDP1. pRRI207 is capable of transforming B.uniformis, B.distasonis and B.ruminicola to clindamycin (Cc) resistance and E.coli to TcR (only expressed aerobically), and was the only construct from eleven different constructs obtained based on pRRI2 able to do so.
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Han, Yeong-Hwan. "The microaerophilic nature of Wolinella recta, Wolinella curva, Bacteroides ureolyticus, and Bacteroides gracilis." Diss., Virginia Tech, 1991. http://hdl.handle.net/10919/39699.
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Broad relationships among bacteria can be identified by ribosomal RNA analysis, but the resulting groups may not be easily definable by phenotypic characteristics. This is exemplified by the genus Campylobacter, which consists of at least three separate groups that cannot be differentiated readily by phenotypic characteristics.
Examination of the type strains of all Campylobacter species (except Campylobacter pylori), Wolinella recta, Wolinella curva, Bacteroides ureolyticus, and Bacteroides gracilis revealed that sheathed flagella occur only in species of rRNA group II (except W.succinogenes). This is helpful in differentiating this group.
Campylobacters are microaerophilic: they can respire with oxygen but cannot grow at the full level of oxygen found in an air atmosphere (21% O₂). Although W. recta, W. curva, B. ureolyticus, and B. gracilis are closely related to the campylobacters of rRNA group I, they were thought to be anaerobes, incapable of oxygen-dependent growth and of respiring with O₂. However, the present study revealed that they are in fact microaerophiles. They exhibited oxygen-dependent growth but failed to grow at 21% O₂ and grew only very slightly under anaerobic conditions unless provided with electron acceptors such as fumarate and nitrate. They exhibited 0₂ uptake with H₂ or formate as electron donors (W. recta showed only a low O₂ uptake with H₂). Oxygen uptake was inhibited by KCN and 2-heptyl-4-hydroxyquinoline N-oxide. The organisms possessed membrane bound cytochromes (cytochromes b560 and C551-553, and a CO-binding cytochrome c), as well as soluble cytochrome C552 and CO-binding cytochrome c. The cytochromes were reduced by H₂ and formate as electron donors. Proton efflux from cells in anaerobic suspensions containing H₂ or formate occurred upon addition of a pulse of oxygen. With formate as the electron donor, H+/O ratios of W. curva, W. recta, B. ureolyticus, and B. gracilis were 0.75, 1.66,2.06, and 2.04, respectively. With H₂ as the electron donor, H⁺/O ratios of W.curva, B. ureoyticus, and B. gracilis were 1.25, 1.97, and 2.36, respectively; technical difficulties prevented measurement of the ratio in W. recta. Proton translocation was inhibited by the protonophore carbonylcyanide m-chlorophenylhydrazone. The results confirm the relationship of these organisms to campylobacters.Ph. D.
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Veny, Nadia. "Epidémiologie des "Bacteroi͏̈des fragilis" entérotoxinogènes : première étude française." Paris 5, 1994. http://www.theses.fr/1994PA05P052.
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Dallacker-Losensky, Kevin. "Identifizierung von obligaten Anaerobiern der Bacteroides fragilis Gruppe einschließlich Metronidazol-resistenter und Enterotoxin-positiver Stämme mittels MALDI-TOF MS." Doctoral thesis, Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-206555.
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Die klassische Identifizierung von obligat anaeroben Bakterien ist mit einem hohen Labor- und Zeitaufwand verbunden. Um festzustellen, ob die Identifizierung mittels Matrix-unterstützter Laser-Desorption/Ionisation und Massenspektrometrie mit Flugzeitanalysator (Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; MALDI-TOF MS) ein Verfahren ist, um obligate Anaerobier eindeutig zu identifizieren, wurde mit der vorliegenden Arbeit die Identifizierung von unterschiedlichen Spezies der B. fragilis Gruppe mittels MALDI-TOF MS untersucht.
Hierfür wurden 105 obligate Anaerobier der B. fragilis Gruppe aus der Stammsammlung des Institutes für Medizinische Mikrobiologie und Infektionsepidemiologie der Universität Leipzig untersucht. Es fanden sich für die untersuchten Erreger Spektren mit sehr guter Auflösung. Eine Identifizierung und Differenzierung war eindeutig möglich. Unter Verwendung dieser Daten wurde eine Referenzdatenbank erstellt. Die erhaltenen Ergebnisse wurden mittels einer verblindeten Studie überprüft, wobei 52 von 53 (98,1%) der untersuchten Stämme eindeutig identifiziert werden konnten. Dies schließt ebenfalls die Identifizierung und Differenzierung von 15 Metronidazol-sensiblen/ Enterotoxin-negativen, 8 Metronidazol-resistenten/ Enterotoxin-negativen und 8 Metronidazol-sensiblen/ Enterotoxin-positiven B. fragilis Stämmen ein.
Die Identifizierung mittels MALDI-TOF MS ist somit eine zuverlässige Methode zur Identifizierung von obligaten Anaerobiern der B. fragilis Gruppe. Weiterhin finden sich Hinweise, dass ein Nachweis von Resistenz-, Virulenz- und Pathogenitätsfaktoren mittels MALDI-TOF MS bei diesen Erregern möglich ist.
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Unique, Cécile. "Cinétique de l'activité bactéricide de la pipéracilline seule ou associée au sulbactam vis à vis de "Bacteroides fragilis"." Paris 5, 1989. http://www.theses.fr/1989PA05P122.
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Zhang, Guangming. "Identification of Bacteroides fragilis from clinical samples /." Stockholm, 1999. http://diss.kib.ki.se/1999/91-628-3742-7/.
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Manickan, Lakshmy. "Proteomics of bacteroides fragilis and enterobacter cancerogenus." Thesis, Northumbria University, 2010. http://nrl.northumbria.ac.uk/1253/.
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Bacteroides fragilis NCTC 9343 is a Gram-negative anaerobic bacterium with genomic DNA of 5205 Kb and a GC ratio of 43%. It is a commensal organism that can act as an opportunistic pathogen and is commonly present on the mucous membranes. It causes a variety of infections including intra abdominal infections, perirectal abscesses and decubitus ulcers. Enterotoxigenic forms are capable of causing diarrhoea in children and animals. Enterobacter cancerogenus ATCC 35316 is also a Gram-negative facultatively anaerobic bacterium with genomic DNA of 4602 Kb and a GC ratio of 55%. It is a naturally occurring human gut symbiont known to exhibit resistance to antibiotics like aminopenicillins. It has also been reported in cases of severe osteomyelitis and infections of bones and joints. This study aims to analyse the differential expression of proteins in the presence of mucin since it serves as the first site of adherence for the bacteria. The E. cancerogenus and B. fra gilis proteins were extracted and separated by two dimensional electrophoresis from logarithmic phase cultures grown in semi-defined media enriched with or without porcine gastric mucin Types II and III. The gel images were analysed using Bio-Rad PDQuest, Ludesi Redfin and Nonlinear Dynamics SameSpots softwares. It was observed that the presence of mucin in the media affected the expression of a number of proteins in E. cancerogenus and B. fragilis cells. The protein spots of interest were excised, hydrolysed using trypsin and subjected to electrospray ionisation based LC-MS analysis in order to determine the identity of the digested proteins and obtain a better understanding of the interactions of B. fra gilis and E. cancero genus with mucin. The outer membrane protein surface antigen X was found to be up-regulated in both mucin Type II and III enriched media in E. cancerogenus. Some of the other proteins that were differentially regulated in both E. cancerogenus and B. fra gilis included the elongation factor Ts, malate dehydrogenase, triose phosphate isomerase and thiol peroxidase proteins indicating that these proteins may be associated with the ability of bacteria to grow in mucin and may be potential virulence factors. Genes encoding the proteins CAH06598 and CAH09443 from the glycoside hydrolase families 95 and 97 in B. fra gilis strain NCTC9343 were cloned, overexpressed and purified using nickel affinity and gel filtration chromatography. The enzymes were found to be active by performing fluorimetric assays using methyl-umbelliferyl sugar substrates. Diffracting crystals of CAH09443 were obtained from the PACT ANION screens containing polyethylene glycol and sodium malonate as a precipitant. Structure determination was achieved via molecular replacement using the glycoside hydrolase Family 97 α-galactosidase, BtGH97b, from Bacteroides thetaiotaomicron as a starting model. The structure of CAH09443 was shown to be composed of a N-terminal β-super-sandwich domain and a canonical (β/α)₈ barrel, similar to the two other glycoside hydrolase family 97 enzyme structures reported.
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Pheulpin, Patrice. "Construction de vecteurs navettes Escherichia coli - Bacteroides." Lille 1, 1989. http://www.theses.fr/1989LIL10067.
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Un vecteur navette s'exprimant chez e. Coli et bacteroides a été construit par l'association d'un plasmide cryptique de 4,6 kb, d'un plasmide dérivé de pBR 322 et d'un fragment de 4,2 hb du plasmide pBFTM10. Ce plasmide confère la résistance à différents antibiotiques suivant la bactérie où il est inséré. Les régions nécessaires à la réplication chez bacteroides ont été identifiées - un deuxième vecteur navette a été construit, et s'exprime chez e. Coli, b. Distasonis et b. Ruminicola. Ces plasmides peuvent être utiliser pour clouer des gènes de bacteroides chez e. Coli, puis pour étudier leur expression dans des souches de bacteroides hétérologues.
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Abratt, Valerie Rose. "DNA repair in Bacteroides fragilis Bf-2." Doctoral thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/21823.
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Bibliography:pages 157-175.Repair deficient mutants of Bacteroides fragilis have been isolated in order to study the responses of this organism to various DNA damaging agents at the physiological and molecular levels. Two types of mutants were isolated by ethyl methane sulphonate mutagenesis of B.fragilis followed by selection for sensitivity to mitomycin C. One mutant (UVS9) showed sensitivity to both mitomycin C and far-UV irradiation. The other (MTC25) was more sensitive to mitomycin C than UVS9, but showed wild-type resistance to UV radiation. Both mutant strains had wild-type resistance to methyl methane sulphonate.
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Delahooke, Diane Mary. "The biological activity of Bacteroides surface polysaccharides." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/21194.
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Lipopolysaccharide (LPS), a major constituent of Gram-negative bacteria, is implicated as the key factor in the development of the Systemic Inflammatory Response Syndrome (SIRS). LPS can arise from an underlying bacteraemia, but given that the majority of patients with SIRS have no detectable bacteraemia, then LPS derived from the gut must be considered. Bacteroides species outnumber the enterobacteria such as E.coli in the gut by approximately 1000-fold. Although Bacteroides LPS is less endotoxic, by simple arithmetic there must be as much biological potential from the LPS of Bacteroides as from E.coli. This thesis re-examines the biological activity of Bacteroides LPS and its possible role in the development of SIRS. LPSs were extracted from seven Bacteroides species by three different techniques: the phenol-water (PW), the phenol-chloroform-petroleum (PCP) and Triton-Mg2+. The biological activity of these Bacteroides LPSs was compared to that of an E.coli O18K- LPS control. In general, Bacteroides LPSs prepared by the PW method were found to have a significantly higher activity in a mouse lethality model, LAL assay, TNF and IL-8 induction assays, than LPS extracted by the PCP or Triton methods. Bacteroides LPS extracted by the PCP method had consistently low activity in all assays. LPS from B.fragilis NCTC 9343 and B.caccae had a consistently higher activity than LPS from B.vulgatus and B.thetaiotaomicron in most assays. Differences in activity between B.fragilis NCTC 9343 LPS grown in different media was seen. The PW method selected for greater amounts of carbohydrate and KDO and the PCP the least. Further information from sub-population studies, Percoll profiles, chemotype on PAGE and chemical analysis failed to account for differences in biological activity between extraction methods and Bacteroides species.
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Winkelhoff, Arie Jan van. "Black-pigmented bacteroides in human oral diseases." Amsterdam : Free University Press, 1986. http://catalog.hathitrust.org/api/volumes/oclc/15601243.html.
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Blandford, Lucy Emily. "Sequelae of Bacteroides fragilis infection and carriage." Thesis, King's College London (University of London), 2018. https://kclpure.kcl.ac.uk/portal/en/theses/sequelae-of-bacteroides-fragilis-infection-and-carriage(bb202025-6e89-451f-876c-bc4c2d1ae1bc).html.
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B. fragilis is considered an opportunistic pathogen, often isolated from abdominal abscesses, bloodstream infections and peritonitis. B. fragilis can produce multiple capsular polysaccharides including an immunomodulatory, zwitterionic, polysaccharide A (PSA) capable of stimulating anti-inflammatory interleukin-10 (IL-10) production. Conversely, some strains can produce a putative carcinogenic toxin, the metalloprotease Bacteroides fragilis toxin (BFT). BFT has been demonstrated to promote colonic cell proliferation and DNA damage in mammalian cell culture and animal models. An additional putative B. fragilis virulence factor present in select strains is a eukaryotic-like ubiquitin protein (BfUbb). BfUbb is capable of interfering with the host ubiquitination cascade this protein but the consequence of this on host health in unknown. This study describes the robust design and validation of PCR-based assay to target specific bacterial taxa and putative virulence genes. The PCR assay was subsequently used to determine prevalence in a collection of gastrointestinal tissue samples from individuals with and without disease. The bft gene was found to have a significantly higher prevalence in individuals newly diagnosed with polyps/cancer compared with a healthy patient group. This finding further points towards the importance of BFT in colonic tumorigenesis. Contrary to previous CRC literature the prevalence of Fusobacterium and fadA were not significant in the cohorts investigated in this study. Colonic location and histological type of Fusobacterium-positive tumours did not result in any significant associations, but the trends observed support previous suggestions of an association between Fusobacterium species and right-sided colon cancer. Presented here is the first reported determination of B. fragilis capsular PSA promoter orientation in vivo. Furthermore, individuals with IBD had a significantly lower percentage of the B. fragilis population PSA orientated on in comparison with a healthy cohort. Similarly, bft-positivity was significantly associated with a lower proportion of the PSA promoter orientated on. In conclusion, overall the results presented indicate that the common gastrointestinal species, B. fragilis, can have wide ranging effects on gastrointestinal health. Between-strain differences and within-strain antigenic variation were shown to have significant associations with patient populations and argue for a gene-centric, and not taxonomic-centric, approach to microbiome research.
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Depiazzi, L. J. "Virulence of Bacteroides nodosus in ovine footrot." Thesis, Depiazzi, L. J. (1988) Virulence of Bacteroides nodosus in ovine footrot. PhD thesis, Murdoch University, 1988. https://researchrepository.murdoch.edu.au/id/eprint/53226/.
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Virulence, in relation to ovine footrot, was examined in a review which emphasised the primary role of Bacteroides nodosus, an anaerobic strict parasite of ungulates. The association of this parasite with other bacteria in the footrot lesion resulted in complex interactions of host. parasite and environment. However, experimentation showed that the severity of the footrot lesion was associated principally with two different properties of B. nodosus: protease stability and surface translocation, the latter being a probable function of the pilus. The relationship between virulence, extracellular protease and translocation was elucidated in terms of function rather than structure. For example, the severity of footrot lesions was not related specifically to the electrophoretic mobility of protease isoenzymes or outer membrane proteins of B. nodosus.
Although there were only two levels of protease stability, surface translocation, measured as either colony size or degree of cellular twitching, varied continuously between isolates. It was suggested that surface translocation was the basis for a continuous spectrum of virulence observed in ovine footrot. Nevertheless, protease stability was associated specifically with microbial penetration of the epidermal matrix of the hoof , hence justifying a classification of B. nodosus isolates into virulent (stable protease) and benign (unstable protease) strains. Although this classification was considered realistic, the complexity of ovine footrot was emphasised by evidence that twitching motility mediated the effects of both ambient temperature and the footrot microbial flora on the severity of all forms of the disease.
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Ameur, Rabha. "Étude cinétique de la croissance des bactéries du groupe bacteroides fragilis et comparaison de leurs mécanismes de transport du glucose." Lille 1, 1992. http://www.theses.fr/1992LIL10040.
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Les bactéries du genre bacteroides sont anaérobies strictes et saccharolytiques. Dans le colon, elles se développent en très grand nombre à partir des polysaccharides végétaux non dégradés par l'homme. L'étude au biophotomètre du développement de plusieurs espèces dans différents milieux nous a permis de préciser les constantes cinétiques de leur croissance. Nous avons pu constater qu'en conditions d'anaérobiose stricte, les espèces étudiées se développent très rapidement en présence de monosaccharides qui, en mélange, sont utilisés simultanément. Nous avons ensuite étudié plus particulièrement la première étape de la dégradation de ces substrats : leur transport au travers de la membrane cytoplasmique. Cette étude a été approfondie chez bacteroides thetaiotaomicron. L'utilisation des inhibiteurs métaboliques, la recherche du substrat phosphoryle durant le transport et comparaison du transport chez les sphéroplastes et les cellules entières nous ont permis de mettre en évidence deux systèmes : diffusion facilitée et système phosphotransférase. Les constantes cinétiques apparentés km et vmax ont été déterminées. Ce mécanisme semble être constitutif et il n'est pas spécifique du glucose. Récemment, le genre bacteroides a été restreint à l'espèce type bacteroides fragilis et aux espèces apparentées. Nous avons cherché le système du transport du glucose chez les espèces les plus représentatives de ce groupe et nous avons montré que les mécanismes du transport du glucose chez bacteroides sont nombreux et différents en fonction des espèces
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Moore, Jane. "Putative bacteroides fragilis virulence determinants; analysis and comparison." Thesis, Queen's University Belfast, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486575.
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Bacteroidesfragilis forms part of the gastrointestinal microbiota. On release from the gastrointestinal tract this opportunistic pathogen can cause internal abscesses and bacteraemia. Completed genome sequences of B. fragi/is NCTC 9343, 638R and YCH46 recently became available. Therefore the importance of potential virulence factors may be assessed though genotypic and phenotypic comparisons. B. fragilis NCTC 9343 phase variably expresses a large capsule (LC), small capsule (SC) and an antigenically variable electron dense layer (EDL). A small irregular LC like capsule is expressed by B. fragilis 638R, attributed to a stop codon within BF2782 (putative polysaccharide export protein). Phase variable LC expression may be regulated by excision/insertion of a transpos~n, detected in PS-9/I of B. fragilis YCH46. The EDL polysaccharides produced by the 3 strains are divergent. This has no effect on in vivo survival. The conservation of invertible promoter regions (fIX sites) and putative transcriptional regulators, upxZ and upxY, indicates antigenic variation may be important for virulence. Invertases, finA and finB are involved in inversion of the fIX sites. The presence of . finA is conserved but notfinB. A long delay is observed prior to detection of antigenic variation in finB+ B. fragilis NCTC 9343, but not finE B. fragilis LS66. Therefore finB may be repressing inversion of the fix sites. The absence offinB, LC expression, haemagglutination phenotype, or reduced growth rate in a minimal medium does not affect in vivo survival. Iron acquisition and regulatory systems are important for B. fragilis virulence, with the ferric uptake protein, FeoAB, and ferric uptake regulator, Fur, required for B. fragilis survival in vivo. FeoAB is important for growth of B. fragilis in vitro, indicating ferrous iron is an important iron source. The haem uptake protein, HutA, and the peroxide regulon repressor, Per, are not required for B. fragilis survival in vivo.
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Houston, Simon Andrew. "Molecular genetic analysis of Bacteroides fragilis virulence factors." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491954.
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B. fragilis is the most commonly isolated Gram-negative anaerobe from human clinical infections, and is the most common cause of anaerobic bacteraemia. The aim of the current study was to analyse potential virulence factors of B. fragilis, by investigating the contribution of three genes putatively involved in capsule biosynthesis, and by examination of fibrinogen binding and degradation. A novel plasmid DNA transformation protocol exploiting the anti restrictive property of Ocr protein was developed which allowed for the transformation of wild-type and mutant B.fragilis NCTC9343 strains. The current study is the first report of successful DNA transformation in strain NCTC9343 by electroporation. B. jfragilis is capable of within-strain variable expression of micro, small, and large capsules. Data presented herein indicate that the putative transcriptional regulator, upcY, is necessary for expression of the micro capsule polysaccharide biosynthesis locus, PS C/8, the putative wzz-like capsular polysaccharide processing gene, Bf1708, is required for micro capsule biosynthesis, and the putative glycosyltransferase, Bj2782, is necessary for large capsule expression. DNA inversion of the Bj2782 promoter was shown to regulate large capsule production in strain NCTC9343. Fibrinogen is the structural protein used in fibrin abscess formation, a pathological host response to B. ji-agilis intra-abdominal infections. Abscess formation is likely to be important in bacterial containment, preventing dissemination of infection and bacteraemia. All clinical isolates of B. ji-agilis tested degraded human fibrinogen. Fibrinoge~ degradation was related to secreted and outer membrane proteases. B.ji-agilis NCTC9343 bound human fibrinogen. A putative fibrinogen binding protein, Bfl705, after gene cloning and expression, was purified from E. coli and shown to bind human fibrinogen. The fibrinogen binding protein and fibrinogenolytic proteases may be important virulence factors in B. fragilis, allowing the bacteria to slow down, or prevent abscess fom1ation, resulting in dissemination of infection.
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Lutton, Deborah A. "Variability of surface structure expression in Bacteroides fragilis." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334571.
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Chen, Ying. "In vivo metal substitution in bacteroides superoxide dismutase." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44628.
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The effect of various growth conditions on the type of superoxide dismutase (SGD) formed anaerobically in three Bacteriodes species was studied. B. fragilis, B. distasonis, and B. thetaiotaomicron were grown in ironâ restricted media with or without manganese supplementation. Iron availability was decreased by treatment of the media with chelex-100, a metal-chelating resin, and addition of desferrioxamine mesylate (desferal, Ciba-Geigy), an iron chelator. Mn-containing (MnSOD) and Fe-containing superoxide dismutase (EeSOD) activities in cell extracts were differentiated by inhibition with azide and inactivation by H202. The amount of Mn-containing superoxide dismutase was estimated by the fraction of azide- and H202, -resistant activity. Cells grown in untreated media contained approximately 90% FeSOD and 10% MnSOD. Cells grown in Fe-restricted media supplemented with graded amounts of manganese synthesized a progressively larger fraction of MnSOD. Hemin, added to the Fe-restricted media, did not serve as an iron source for FeSOD formation. Superoxide dismutase specific activities varied (3-6 U/mg) in each extract but not as a function of manganese concentration.
Master of Science
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Casanueva, Ana. "Identification of Bacteroides genes involved in Metronidazole resistance." Doctoral thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/4246.
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Includes bibliographical references (leaves [123]-141).Bacteroides species are Gram-negative obligate anacrobes that live in the gastrointestinal tract of mammals and are thought to account for approximately 30% of the colonic microbiota. Certain Bacteroides species, such as B. fragilis and to a lesser extent B. thetaiotaomicron, can become opportunistic pathogens and cause severe infection. The antibiotic of choice for treating such infections is metronidazole, a DNA damaging agent. Metronidazole enters the bacterial cell as an inert prodrug, and is activated by cellular reduction into a cytotoxic compound which is thought to cause DNA strand breaks. Certain metronidazole resistant B. fragilis strains have been described, where the drug was not reduced inside the cell due to decreased activity of the metabolic enzymes which are involved in this process. Little is known about the mechanisms involved in repair of metronidazole damage and the potential for resistance. In this study, two difIerent approaches were used to isolate and analyse Bacteroides genes involved in metronidazole resistance, with emphasis on DNA repair genes. These methods were transposon mutagenesis of Bacteroides, and functional complementation of E. coli metronidazole sensitive mutants with genes from B. fragilis.
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Tessier, Françoise. "Apport de l'immunochimie à la taxonomie des bacteroides du groupe fragilis." Bordeaux 2, 1990. http://www.theses.fr/1990BOR2PND3.
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Hood, Graham. "Physiological response of Rhizobium leguminosarum during bacteroid development." Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/48693/.
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legume-rhizobia symbioses, free-living rhizobia colonise root nodules and develop into N2 fixing specialists known as bacteroids. During bacteroid development, rhizobia must adapt to the nodule environment, consisting of reactive oxygen species, low oxygen, antimicrobial secondary metabolites, low pH and in some nodules, antimicrobial peptides. This study offers a holistic insight into the processes required by R. leguminosarum during bacteroid development in nodules formed on four legumes: Pisum sativum, Vicia faba, Vicia hirsuta and Phaseolus vulgaris. Initially, a high-throughput mutagenesis strategy was used to target genes upregulated during bacteroid development. Screening forty-two mutants on P. sativum identified some moderate phenotypes but more importantly, highlighted functional redundancy between certain gene products. A clear example of functional redundancy was seen between the Mn2+ transporters SitABCD and MntH. Single mutations in sitA or mntH did not cause a symbiotic phenotype whereas the double mutant could not form bacteroids on P. sativum, V. faba or V. hirsuta. Intriguingly, no symbiotic phenotype for the double mutant was observed on P. vulgaris. In addition to Mn2+ transporters, a Mg2+ channel, MgtE, that is essential for growth in Mg2+-limited medium at low pH was identified. As with the Mn2+ transporters, the requirement of MgtE during symbiosis depended upon the species of the hostlegume. Reasons for host-dependent requirement of SitABCD, MntH and MgtE are discussed. The requirement of three O2-responsive regulators that govern regulatory pathways essential to N2 fixation was also investigated. FnrN appears to be the major O2- responsive regulator required for symbiosis but in addition to fnrN, two genes, fixL and fixLc, need to be mutated to prohibit N2 fixation. Other findings include a putative toxin-antitoxin system that hinders N2 fixation when disturbed.
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Gantzer, Christophe. "Persistance du génome d'entérovirus et des bactériophages de Bacteroides fragilis dans les eaux : intérêt de ces marqueurs en tant qu'indicateurs de contamination virale." Nancy 1, 1996. http://docnum.univ-lorraine.fr/public/SCD_T_1996_0388_GANTZER.pdf.
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Au début des années 1990, quelques voix se sont élevées dans la communauté scientifique, en particulier parmi les spécialistes de biologie moléculaire préconisant l'utilisation de la PCR pour le diagnostic virologique du milieu hydrique. Certains postulaient que la détection du génome viral dans une eau, une boue ou un coquillage pouvait apporter la preuve que ce milieu était contaminé par le virus infectieux correspondant. D'autres affirmaient au contraire qu'une «PCR positive» ne pouvait en aucun cas indiquer la présence de virus infectieux, tout au plus pouvait-elle servir de témoin de contamination virale. La présence de génome viral est-elle le témoin d'une présence de virus infectieux ou simplement un témoin d'une contamination virale plus ou moins ancienne ? L'objectif de ce travail est d'apporter des éléments de réponses à cette interrogation et dans ce cadre, nous avons considéré qu'il était fondamental de comparer le comportement du génome et du virus infectieux. Dans le milieu hydrique. En effet, pour que la présence de génome puisse témoigner de celle de virus infectieux, il semble nécessaire que la capacité de survie de ces 2 entités soit identique. La première partie réalisée en milieu hydrique artificiellement contaminé par du coxsackievirus B3 et du bactériophage de Bacteroides fragilis montre que : - une incubation à forte température (> 55°C) se traduit par l'inactivation rapide du virus infectieux, alors que le génome reste présent jusqu'à des températures de 95°C ; - en milieu PBS à 25°C, la survie du génome est deux fois supérieure à celle du virus infectieux et du phage de Bacteroides fragilis. La présence de Na-montmorillonite augmente la persistance du génome d'un facteur 2, alors qu'elle n'augmente celle du virus infectieux que de quelques jours ; - en eau d'adduction (chlore résiduel 0,08 rng. L-1), la persistance du génome est là encore supérieure d'un facteur 2 à celle du virus infectieux, mais est comparable à celle du phage de Bacteroides fragilis. Cependant contrairement au phage, le génome et le virus infectieux sont sensibles aux faibles doses de chlore résiduel ; - en eau de forage, la persistance du génome est équivalente à celle du virus infectieux, alors que le phage survit 2 fois plus longtemps. En milieu PBS et en eau d'adduction, le génome ne constitue qu'un indicateur de contamination virale au même titre que le phage de Bacteroides fragilis. Cependant, il semble qu'en eau de forage la détection de génome peut témoigner de la présence de virus infectieux. La deuxième partie consiste à rechercher le génome d' entérovirus, les phages de Bacteroides fragilis et les coliphages somatiques comparativement aux entérovirus infectieux dans des eaux usées traitées de qualité différente. Les résultats montrent que : - la détection d'entérovirus infectieux, de génome d'entérovirus et de phage de Bacteroides fragilis doit s'effectuer après concentration des eaux usées traitées ; - la densité en coliphage somatique est suffisante pour l'analyse directe des eaux ; - la détection de génome entéroviral ne constitue qu'un indicateur de contamination virale ; - les phages de Bacteroides fragilis semblent constituer le meilleur indicateur de présence d'entérovirus contrairement aux coliphages qui ne sont que des indicateurs d'efficacité de traitement. Le génome entéroviral qui présente une fréquence de détection analogue à celle des phages des Bacteroides fragilis semble lui aussi constituer un bon indicateur de contamination entérovirale.
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Eley, A. R. "The response of Bacteroides species to beta-lactam antibiotics." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356555.
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Parry, Frances Louise. "Identification of pre-synaptic processing proteins from Bacteroides fragilis." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5031.
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The repair of DNA double-strand breaks (DSBs) is required for the survival of all organisms. In bacteria, DNA DSBs can occur during normal housekeeping processes such as DNA replication or by exogenous damage due to chemicals or radiation. DSBs will compromise the integrity of the genome if left un-repaired, and can be fatal to an organism. Repair of DSBs by homologous recombination (HR) replicates missing chromosomal regions before joining of the separated DNA ends. In Escherichia coli the HR repair steps are; pre-synapsis, synapsis and post-synapsis. In the pre-synaptic stage a DSB is processed into a 3′ single-strand overhang, the substrate required for strand invasion in the synapsis stage and the eventual repair of the DSB. At present there are three identified pre-synapsis systems involved in recombination in bacteria; represented by the AdnAB, AddAB and the RecBCD protein complexes. Each system functions in a similar manner but differ in the physical composition of the machinery. This project investigated the pre-synaptic system of Bacteroides fragilis NCTC9343. Genes encoding putative pre-synapsis proteins were initially identified through analysis of the NCTC9343 genome. The function of these proteins was investigated in vivo by rescue of a repair-deficient strain of E. coli. This demonstrated that Bacteroides fragilis encodes a two component system, where both genes products are required to work in concert for pre-synaptic processing of DSBs. The identified genes were BF2192 and BF2191, and have been renamed addA and addB, respectively. To further examine the role of the AddAB proteins in DSB repair, a Bacteroides fragilis strain with a deletion of addAB was constructed and shown to be extremely sensitive to DNA damaging agents. The AddAB complex was purified and found to be an ATP-dependant helicase and exonuclease that acted on double-stranded DNA ends. In conclusion, this project has identified the proteins involved in pre-synaptic processing of DSBs in B. fragilis NCTC9343, consisting of AddAB homologues, and shown their protective role in repair of DNA damage.
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Franklund, Clifton Victor. "Glucose Uptake by the Cellulolytic Rumen Anaerobe Bacteroides Succinogenes." Thesis, North Dakota State University, 1986. https://hdl.handle.net/10365/28338.
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Glucose uptake by the cellulclytic rumen anaerobe, Bacteroides succinogenes S85, was measured under conditions that maintained anaerobiosis and osmotic stability. This organism was found to possess a highly specific, active transport mechanism for glucose. Evidence for a phosphoenol-pyruvate:g1ucose phosphotransferase system was not detected. Compounds that inhibit electron transport systems (non-heme iron chelators, and sulfhydryl reagents) were effective inhibitors of glucose uptake. The strongest inhibitors were compounds (proton and metal ionophores) that interfere with maintenance of the proton motive force. Compounds which interfere with ATP synthesis also inhibited glucose uptake, but a role for ATP in energizing uptake could not be inferred from these results. Oxygen prevented glucose uptake (75% inhibition), reflecting possible active sulfhydryl centers (above) or autooxidation of electron transport components. The results suggest the fumarate reductase-coupled electron transport system of B. succinogenes can generate a proton motive force that is used to energize glucose uptake. Na+ and Li+. but not K+, stimulated glucose uptake and may partly account for the growth requirement of B. succinogenes for Na+. However, the data were insufficient to conclude that glucose uptake occurs by a Na+ symport mechanism. Spheroplasts of B. succinogenes transported glucose as well as whole cells, indicating glucose uptake is not dependent on a periplasmic glucose binding protein. A variety of sugars including the nonmetabolizable analog, [inversely proportional symbol]-methylglucoside. did not inhibit glucose uptake. Only cellobiose and 2-deoxyglucose were active and neither behaved as a competitive inhibitor. Metabolism of both sugars was probably responsible for the inhibition. Cellobiose-grcwn B. succinogenes showed a reduced ability to transport glucose compared to glucose-grown cells. This may indicate regulation of synthesis of the glucose carrier protein by cellobiose through a mechanism other than catabolite repression. Differences in the ability to transport glucose were detected between transition cells (transition from lag to log phase of growth) and log-phase cells. However, the differences were not due to different glucose transport mechanisms. Alterations in the structural integrity of the cell envelope, as reflected by osmotic- and cold-sensitivity features of transition and log cells, may have affected the glucose uptake abilities in these cell types.
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Vingadassalom, Didier. "Etude fonctionnelle du facteur sigma principal de Bacteroides fragilis." Paris 6, 2006. http://www.theses.fr/2006PA066224.
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Bacteroides fragilis est un germe anaérobie du tractus intestinal de l’homme. Les promoteurs végétatifs de B. Fragilis sont reconnus par un facteur sigma principal particulier (SigA), restreint aux phyla Bacteroidetes et Chlorobium. SigA possède un court segment basique, à la place de la région N-terminale 1. 1 acide retrouvée chez tous les autres facteurs sigma principaux connus. Il contient des résidus "signature" dans les régions conservées 2 à 4, impliquées dans la reconnaissance des promoteurs et l’interaction avec l’ARN polymérase-cœur. Le segment basique de SigA conditionne le positionnement de l’enzyme sur le promoteur et l’étendue de la bulle de transcription. Le rôle de plusieurs résidus dans la formation du complexe ouvert de transcription et l’interaction avec la séquence consensus -33 des promoteurs de B. Fragilis est décrit. Cette thèse révèle l’existence d’un couple facteur sigma/promoteur unique au sein d’un lignage majeur qui est apparu tôt dans l’évolution bactérienne.
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Hamilton, Michelle Ann Elizabeth. "The relationship between plasmid presence, antibiotic resistance and surface structures in Bacteroides." Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/28187.
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Podglajen, Isabelle. "La résistance de "Bactaroides fragilis" aux carbapènèmes." Paris 11, 1994. http://www.theses.fr/1994PA114827.
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Pérez, de Rozas Ruiz de Gauna Ana Mª. "Utilización de cepas de bacteroides spp. como probiótico en conejos." Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/285643.
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La utilización de antimicrobianos, de forma metafiláxica, para mantener la salud de los animales en las granjas de producción, puede ser problemático en un futuro próximo, debido a las altas tasas de resistencias que se están observando. Esta situación obliga a replantearse medidas alternativas, las más habituales basadas en el uso de prebióticos, probióticos o la combinación de ambos (simbióticos).
El objetivo principal de este trabajo ha sido el de seleccionar cepas de diferentes especies del género Bacteroides para ser utilizadas en conejos como probiótico.
El género Bacteroides constituye uno de los principales componentes de la microbiota intestinal de los mamíferos (hasta 1011 UFC/g heces, en humanos). Degradan moléculas complejas, especialmente carbohidratos, y juegan un papel importante en el control de la colonización del tracto digestivo por parte de patógenos; también, en algún caso, pueden actuar como patógenos oportunistas. Están implicados además en la maduración del sistema inmunitario asociado a la mucosa intestinal.
Los Bacteroides spp. podrían tener actividad probiótica por dos mecanismos diferentes: bien produciendo sustancias inhibidoras del crecimiento de otros componentes de la microbiota intestinal (bacteriocinas, metabolitos secundarios…), bien estimulando al sistema inmune, incrementando las defensas de forma inespecífica (inmuno-moduladores).
Basándonos en la colección de Bacteroides spp. del CReSA, en este trabajo se han realizado estudios in vitro para seleccionar cepas, con ausencia de características negativas y presencia de características positivas, que pudieran utilizarse en estudios in vivo, en gazapos durante la fase de lactación, y poder analizar su rol como posible probiótico.
La presencia de resistencias a determinados antibióticos, especialmente de marcadores transferibles, ha sido la característica más restrictiva a la hora de seleccionar las cepas a analizar in vivo.
Después de seleccionar cuatro cepas, se procedió al estudio in vivo, en una granja comercial, examinando el efecto sobre la microbiota intestinal y diferentes parámetros inmunitarios. De los resultados obtenidos podemos inferir que algunas de las cepas probadas pueden ser candidatos para el desarrollo de un probiótico para conejo.The metaphylactic use of antimicrobials to maintain the health of animals in food production farms can be problematic in the near future, due to the high rate of resistances observed. This situation forces to looking for alternative measures, the most common based on the use of prebiotics, probiotics or a combination of both (symbiotic). The main objective of this work was to select strains of different species of the Bacteroides genus that could be used as probiotic in rabbits. Bacteroides genus is one of the main components of the mammalian intestinal microbiota (1011 CFU/g feces, in humans). These bacteria degrade complex molecules, especially carbohydrates, and play an important role in the control of the colonization of the digestive tract by pathogens; but, in some cases, they can act as opportunistic pathogens. Furthermore, they are involved in the maturation of the immune system associated with intestinal mucosa. The Bacteroides spp. could have probiotic activity in two different ways: producing inhibitory substances against other components of intestinal microbiota (bacteriocins, secondary metabolites…) or stimulating the immune system, increasing the nonspecific defenses of host (immune-modulators). Using the collection of Bacteroides spp. of CReSA, in this work different in vitro studies were conducted to select strains, looking for the absence of negative characteristics and the presence of positive characteristics, to be used for the in vivo studies on rabbits during the lactation period and to analyze their role as probiotic. The presence of resistances against antimicrobials, especially when transferable markers were present, was the most restrictive characteristic for the selection of the strains that were analyzed in vivo. After the selection of four strains, the in vivo study on a commercial farm was conducted, examining the effect on the intestinal microbiota and on different immune parameters. By the analysis of the obtained results can be inferred that some of the tested strains may be candidates for the development of probiotics for rabbit.
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Edwards, Richard. "Mechanisms of resistance to β-lactam antibiotics in Bacteroides species." Thesis, University of Nottingham, 1995. http://eprints.nottingham.ac.uk/13956/.
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Mechanisms responsible for resistance to β-Iactam antibiotics were investigated in clinical isolates of Bacteroides spp., the most common anaerobic Gram negative pathogen. Among 108 isolates of Bacteroides spp. obtained from clinical material in Nottingham, 69 (64%) were identified as Bacteroides fragilis. Approximately one-fifth of the Bacteroides spp. produced elevated levels of β-Iactamases, and many of these strains showed increased resistance to β-Iactam antibiotics usually regarded as β-Iactamase stable. Four β-Iactamase types were identified: Type one was represented by zinc dependent metallo-β-lactamases that hydrolysed cefoxitin, latamoxef and imipenem. Type two displayed intermediate to high specific activity in tests with nitrocefin as substrate and hydrolysed cefoxitin and latamoxef, but not imipenem. Type three exhibited intermediate levels of specific activity and caused reduced susceptibility to cefoxitin, latamoxef and imipenem, although they hydrolysed these antibiotics inefficiently. Type four probably represented enhanced production of the β-Iactamases characteristic of most bacteroides strains. Organisms producing this enzyme normally remained susceptible to cefoxitin, latamoxef and imipenem, and the enzyme was fully susceptible to β-Iactamase inhibitors, including clavulanic acid. Several strains were detected that exhibited reduced susceptibility to imipenem that was not related to metallo-β-Iactamases production. In contrast, one strain that produced a metallo-β-lactamase remained fully sensitive to imipenem as judged by conventional titration. Investigation of isolates producing metallo-β-lactamase and several similar ones encountered in an earlier study showed a correlation between the degree of resistance to imipenem and specific imipenemase activity. In an attempt to elucidate reduced susceptibilty to imipenem that was not related to metallo-β-lactamase production, cell envelope properties and penicillin-binding proteins (PBPs) of selected strains were investigated. Studies of outer membrane proteins and lipopolysaccharide composition of B.fragilis strains unexpectedly showed that metallo-β-Iactamase producers displayed unusual cell envelope profiles. Those strains that showed reduced susceptibility that was not associated with β-Iactamase appeared to be normal, although two of these strains displayed abnormally high crypticity values. Between three and six PBPs were visualised in tests with 3H-benzylpenicillin. PBPs 1 to 3 were present in all strains, but were observed in imipenem-resistant strains only when tests were carried out in the presence of β-lactamase inhibitors. Competitive binding experiments indicated that imipenem showed affinity for the high molecular weight PBPs of sensitive B.fragilis. The low molecular weight PBPs 4 to 6 were detected intermittently and only in certain strains, notably those that exhibited reduced susceptibility to imipenem. PBP 6 was found only in strains showing non-enzymic resistance. The results suggest that several different types of resistance to β-lactam antibiotics are circulating in clinical isolates of Bacteroides spp. in Nottingham: firstly, strains that produce a metallo-β-lactamase that hydrolyses 'β-lactamase-stable' compounds, including imipenem; secondly, strains producing enzymes that hydrolyse cefoxitin and latamoxef, but not imipenem; thirdly, strains that possess a permeability barrier that affects imipenem as well as other β-Iactam antibiotics; fourthly, strains with altered penicillin-binding proteins; and fifthly strains that produce raised amounts of 'normal' β-lactamase. The latter strains slowly hydrolyse imlpenem and other β-lactam compounds and this may be a factor in the reduced susceptibility to these agents. Clinical isolates that possess these resistance mechanisms may appear susceptible according to conventional break-point criteria in vitro. Never the less, they exhibit considerably reduced susceptibility to β-Iactam agents and the therapeutic implications of this need investigating. At present such strains represent a relatively small proportion of clinical isolates of Bacteroides spp., but the prevalence of resistance needs to be carefully monitored.
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Kay, Helen Moira. "Some properties of the extracellular vesicles of Bacteroides gingivalis W50." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306532.
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