At the end of 1995 work was completed on a low level intersecting foul sewer for the upper Pymme' s Brook catchment (north London), known as the East Barnet foul water sewerage scheme. Commissioned by Thames Water Utilities Limited (TWUL), it was intended that this would both resolve flooding problems in the area, and address environmental concerns raised by the Environment Agency (EA). The key element of the scheme was the removal of seven combined sewer overflows (CSOs) that the EA had defined as 'unsatisfactory'. Consequently, the present study assesses the scheme's impact on the brook's environmental status, and considers the results in light of the pollutant generation, transport and dispersal properties of the catchment. The pollutant generation, transport and dispersal processes operating in the catchment were explored at a range of spatial and temporal scales, in order to assess the contributions made by a range of urban non-point sources of pollution (CSOs, misconnections and urban runofl), under differing weather conditions, and to determine the way in which they interacted to control water quality. Considerable temporal and spatial variability was identified in the quality of both the brook, and the effluents discharging to it. A first flush of contamination was noted for both solid and dissolved pollutants, during many of the studied storm events; although the studied determinants (pH, conductivity, suspended solids, biochemical oxygen demand, dissolved oxygen, ammonia-N, chloride and E. coli count) responded to storm driven processes in different ways. A holistic approach was adopted to define the environmental status of the studied watercourse; incorporating its benthic macro-invertebrate community structure (BMWP score and ASPT), bacteriology (E. coli count) and water chemistry. Temporal change was then identified in each data set by performing an ANOVA between years, and between the periods prior to, during and after the scheme's construction. The scheme's impact on catchment hydrology was also explored by assessing temporal changes in the catchment's unit hydrograph parameters, using both linear regression for, and ANOVA between the periods related to the scheme's construction. In addition, regression analysis was used to explore the relationship between climatically induced hydrological change and both BMWP score and water column E. coli count, in which both variables were related to the mean discharge recorded at the EA's Silver Street gauging station on a range of temporal scales. It was concluded that climatically driven hydrological change was the major factor in determining the environmental status ofPymme's Brook, whereas the East Barnet foul water sewerage scheme produced only a limited improvement. This was because as well as removing several pollutant sources, the scheme had a hydrological effect that negated some of the expected improvements in water qUality. In addition, the large number and variety of pollutant sources operating in the catchment meant that a scheme designed to address just one element of the problem was unlikely to have a wtifonnly positive effect. Consequently, the magnitude of the temporal changes observed varied between the eight sites sampled in a way that was determined by a combination of the sensitivity of the benthic macro-invertebrate community inhabiting a site, the contamination processes prevalent within its local catchment area and its location within the catchment as a whole. Methodological recommendations for the future are made.

A wide variety of proteins which are synthesised in the cytoplasm of E. coli are subsequently directed either to non-cytoplasmic compartments or transported to the extracellular medium. Proteins which are exported from the cytoplasm are thought to interact with a complex cellular machinery and a number of mutations affecting this secretion machinery have been isolated. In this study, the export of the outer membrane protein TonA was used as a model system to examine the effect on protein translocation of two temperature sensitive secretion mutants, secA and secY. Initial analysis of the effect of secAts mutations on bulk envelope protein synthesis confirmed the key role of SecA in protein transport, including many proteins assembled into the inner membrane. Analysis of the rate of processing of preTonA, pulse-labelled at the restrictive temperature and chased at the permissive temperature revealed differences between SecA and SecY mutants. In particular these data indicate that SecA and SecY may interact sequentially to promote protein export and that SecA may be required to maintain preTonA in a translocationally competent form prior to interaction with SecY. In order to investigate the nature of a specific "export" signal within a protein to be exported, the possibility of using the novel secretion signal at the C-terminus of E. coli haemolysin to direct chimeric protein into the medium was also investigated. The C-terminal signal was successfully fused to a hybrid protein containing a few residues of ss-galactosidase and the majority of E. coli outer membrane protein OmpF lacking its own NH2-terminal signal sequence. The chimeric protein is specifically translocated across the inner and outer membranes and is released into the medium. Consistent with a transport system which bypasses the periplasm, other studies indicated that haemolysin transport is secA independent but may involve secY. Finally, the localisation of haemolysin and several outer membrane proteins synthesised in spheroplasts was also examined in the hope of gaining some further insight into the route taken by proteins which reach the outer membrane or the external medium.

No description available.

Les systèmes toxine-antitoxines (TA) sont abondants dans la majorité des génomes bactériens séquencés à ce jour. Ces systèmes codent une toxine stable qui inhibe soit la transcription, soit la traduction, et une antitoxine qui contrecarre l’effet de la toxine par formation d’un complexe avec celle-ci. L’antitoxine est instable suite à sa dégradation continue par les protéases ATP-dépendantes. Afin de maintenir un ratio antitoxine : toxine constant en condition normale de croissance, l’expression des systèmes TA est régulée négativement au niveau transcriptionnel par le complexe toxine-antitoxine. Au début de notre travail, cinq systèmes TA étaient identifiés dans le chromosome d’E. coli. Il avait été montré par notre laboratoire que parmi ces systèmes, seul yefM-yoeB était activé en condition de surproduction de la protéase ATP-dépendante Lon. Ce résultat était surprenant puisque Lon était connue pour dégrader également l’antitoxine RelB du système chromosomique relBE. Un des objectifs de notre travail était de comprendre les mécanismes sous-jacents à cette spécificité. Nous avons montré que l’antitoxine YefM était dégradée à la fois par Lon et les protéases ClpAP et ClpXP. Nous avons également montré qu’en condition de surproduction de Lon, YefM était fortement instable (t1/2~ 10 min. vs 60 min en condition normale). Cette instabilité accrue permet donc l’activation du système yefM-yoeB, c’est-à-dire la libération de la toxine YoeB du complexe qu’elle forme avec YefM. Nous avons également avons montré que le t1/2 de RelB n’était pas affecté par la surproduction de Lon, ce qui explique pourquoi le système relBE n’est pas activé dans ces conditions. Notre hypothèse était qu’un cofacteur soit nécessaire à la dégradation de RelB par Lon et que celui-ci serait limitant dans nos conditions expérimentales. Le crible génétique que nous avons réalisé n’a cependant pas permis d’identifier de cofacteur de dégradation ni de régulateur transcriptionnel en trans du système relBE. Un deuxième volet de notre travail de thèse a consisté en l’étude de la fonction des systèmes TA chromosomiques. L’hypothèse prévalente au début de notre travail était que les systèmes TA soient intégrés dans les voies adaptatives de réponses au stress. Cependant, le résultat de leur activation était controversé. L’hypothèse du groupe de Gerdes était que leur activation mène à un état bactériostatique réversible alors que le groupe d’Engelberg-Kulka montrait que le système mazEF était un système de mort programmée. Afin d’éclaircir le rôle des cinq systèmes TA dans la physiologie d’E. coli, nous avons testé l’effet de nombreux stress sur la croissance et la viabilité de souches sauvages et de souches délétées de ces systèmes. Aucune des conditions que nous avons testées n’a entraîné une diminution de la viabilité excluant de manière définitive l’hypothèse de la mort programmée. De plus, l’inhibition de croissance causée par ces différents stress s’est avérée être indépendante des cinq systèmes, de même que la phase de récupération suivant les différents stress. Enfin, nos expériences de compétition ont clairement démontré que les cinq systèmes ne procuraient aucun avantage sélectif aux bactéries dans des conditions de compétition en carence nutritive. Les systèmes TA étudiés dans ce travail ne jouent donc aucun rôle dans l’adaptation aux stress que nous avons testé puisqu’ils n’améliorent ni l’aptitude (fitness), ni la compétitivité des bactéries dans ces conditions.

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Le cancer colorectal est un des cancers les plus fréquents en France. Les patients présentant une inflammation chronique de l'intestin sont à haut risque de développer un cancer colorectal. Il a récemment été démontré que certaines bactéries de l'espèce Escherichia coli pouvaient être impliquées dans la genèse de maladies inflammatoires intestinales, par des mécanismes d'adhésion et d'invasion aux cellules épithéliales intestinales faisant intervenir le récepteur CEACAM6, marqueur tumoral reconnu dans le cancer colorectal. Nous avons montré que certaines bactéries de l'espèce E. coli colonisaient la muqueuse colique de patients atteints de cancer colorectal et possédaient des propriétésd'adhésion et d'invasion dans les cellules épithéliales intestinales. Ces souches synthétisent des cyclomodulines variées susceptibles de jouer un rôle dans la carcinogenèse colique, et colonisent davantage les tumeurs les plus évoluées. Une corrélation a été observée entre la colonisation de la muqueuse colique par un clone unique de ces E. coli et l'expression du récepteur CEACAM6. Nous avons montré in vitro que certains clones de pouvaient induire l'expression de CEACAM6 par des cellules épithéliales intestinales en culture. Enfin, sur modèle animal transgénique exprimant le récepteur humain CEACAM6, ces mêmes clones ont montré des capacités de colonisation très supérieures à desE. coli non pathogènes, et l'induction d'une surexpression de marqueurs de prolifération au niveau de la muqueuse colique. Les E. coli associés à la muqueuse colique pourraient ainsi participer à la promotion du cancer colorectal via l'induction d'une surexpression du récepteur CEACAM6 et d'une hyperprolifération des cellules épithéliales. / No abstract available

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2017-07-17T14:33:57Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação de Mestrado - Suelene Suassuna Silvestre Alencar.pdf: 1698152 bytes, checksum: 7bc449edbb1386a1875057dc6f3f376f (MD5) / Made available in DSpace on 2017-07-17T14:33:58Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação de Mestrado - Suelene Suassuna Silvestre Alencar.pdf: 1698152 bytes, checksum: 7bc449edbb1386a1875057dc6f3f376f (MD5) Previous issue date: 2001-01-10 / Estudo realizado com o objetivo de avaliar a translocação bacteriana (TB) do trato gastrointestinal para órgãos viscerais em ratos submetidos à ligadura do ducto colédoco e submetidos à administração por via oral (gavagem) de E.coli marcada com 99mTecnécio (99mTc-E.coli). Quatro grupos de ratos foram estudados: grupo I (n=10) ligadura do colédoco, grupo II (n=10) controle ou “sham operation”, grupo III (n=12) ligadura do colédoco e gavagem com 99mTcE.coli e grupo IV (n=5) controle ou “sham operation”e gavagem com 99mTc-E.coli. Usando técnica asséptica e sob anestesia, os ratos foram submetidos à laparotomia. Nos ratos dos grupos I e III realizou-se ligadura do colédoco com fio de seda nº 3 zeros e nos ratos dos grupos II e IV apenas manipulação do colédoco com pinça de Adison (sham operation). Após sete dias de observação, os animais dos grupos I e II foram mortos e ressecados fígado, baço, linfonodos mesentéricos e pulmões para exame microbiológico (meios Agar-sangue e Agar Mac Conkey) e exame histopatológico (coloração H.E. e Tricrômico de Masson) por análise morfométrica. O nível de bilirrubina nos grupos ictéricos foi elevado em relação aos do grupo controle. A incidência de bactérias translocadas foi maior no grupo I comparada ao controle p 0,05. Nos animais dos grupos III e IV, após sete dias de observação, foi administrada por via oral (gavagem) 99mTcE.coli e após 24 Hs, os ratos de ambos os grupos foram mortos e seus órgãos retirados para contagem da radioatividade em cintilador gama. Os resultados não mostraram diferença estatisticamente significativa na captação da -E.coli entre os dois grupos (p 0,05). Porém a análise das interações grupo x órgão mostrou diferença entre os grupos ictérico e controle para os órgãos: fígado e pulmão. Os dados disponíveis permitem concluir que em ratos ictéricos por ligadura do colédoco ocorreu translocação de bactérias detectáveis por exame microbiológico. Não ocorreu translocação de bactérias com 99mTc no modelo proposto. / This study was designed to evaluate the bacterial translocation (TB) from the gastrointestinal tract to visceral organs in rats submitted to laparotomy and common bile duct ligation (CBDL). Four groups of rats were studied: group I (n = 10) CBDL; group II (n=10) control or “sham operation”; group III (n= 12) CBDL and 99mTc-E.coli and group IV (n=5) control or “sham operation” e 99mTc-E.coli. All the animals were operated with aseptic technic under intraperitoneal anesthesia with pentobarbital sodium (200mg/Kg). On 7th postoperative day the animals of groups I and II were killed with a letal dosis of anesthetic and the liver, spleen, mesenteric lynfonodes and lungs were ressecated to microbiological (Agar-blood and Agar-Mac Conkey) and histological examination (H.E. and Masson Trichromic) through morphometric analysis. On 7th postoperative day the animals of III and IV groups were submitted to 99mTc-E.coli gavage and after 24 hr they were killed and their organs were ressected. After that, the bacterial radioactivity was mensured through an Automatic count of Gama Radioative – model ANSR (Abott Laboratories). The bilirrubin levels of the jaundiced rats were elevated compared with the control groups. The incidence of bacterial translocation was higher in group I compared with control group (p 0,05). The results showed no significant differences among the jaundiced and control groups to the liver and lungs. The data allow to conclude that in jaundiced rat with ligated bile duct occurred bacterial translocation through microbiological analyses. The model proposed showed no bacterial translocation by the labeled 99mTc technic.

No description available.

No description available.

No description available.