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ALENCAR, Suelene Suassuna Silvestre de. "Translocação e bactérias marcadas com 99m técnécio na icterícia obstrutiva experimental em ratos." Universidade Federal de Pernambuco, 2001. https://repositorio.ufpe.br/handle/123456789/19708.
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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.
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Aoyama, Takashi. "Essential Structure of E.coli Promoter." 京都大学 (Kyoto University), 1987. http://hdl.handle.net/2433/86456.
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Harrington, Lesley. "Genes controlling anaerobic metabolism in E.coli." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/40623.
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Gene fusion technology has been exploited in this project to study the regulation of genes involved in the switch from aerobic to anaerobic metabolism in E.coli. Protein or operon fusions were created when the appropriate transducing phage inserted in frame with a target gene. XplacMu was found to be the most versatile vector, being capable of translocating the lac genes, minus their transcriptional and translational signals, to any site in the chromosome. The expression of p-galactosidase from these fusions will reflect both the transcriptional and translational activity of the target gene in response to a particular stimulus, in this case the presence or absence of molecular oxygen. Insertion of XplacMu into the control sequence of an anaerobically or aerobically regulated gene was detected by its anaerobic Lac+/aerobic Lac- (or vice versa) phenotype. Secondary mutagenesis of such fusions defines those control proteins involved in the switch by screening for a Lac+/Lac+ or Lac~/Lac? phenotype following TnlO mutagenesis. A library of fusion strains was identified by map position and phenotype and control of the anaerobically regulated fusions was further investigated. As the Fnr protein is essential for anaerobic respiration the regulation of the fusions by this pleiotropic activator protein was monitored. The expression of two fusion strains was regulated by another gene, designated adhC. The pleiotropic nature of this locus may be indicative of a second activator protein involved in the regulation of fermentative pathways. The cloning and subsequent genetic manipulation of this gene was simplified by constructing an adhC :: XplacHu fusion. Dual regulation by Fnr and AdhC was investigated, as was the regulation of anaerobic Lac+ fusions unaffected by either activator. The interrelationship of the various pathways of anaerobic metabolism was considered together with putative effector metabolites of the regulatory proteins involved.
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Holmström, Emelie. "Ni (II) absoption with recombinant E.coli." Thesis, KTH, Skolan för bioteknologi (BIO), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-149310.
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Ren, Xiaojing, and 任晓晶. "Modeling pattern formation of swimming E.coli." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B43704001.
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Lee, Hoyoung. "Evolution of macrolide antibiotics in E.coli /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Ren, Xiaojing. "Modeling pattern formation of swimming E.coli." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43704001.
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Neelakanta, Girish. "Genome variations in commensal and pathogenic E.coli." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974330329.
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Barbosa, Joana Cristina Pacheco. "Lichenicidin: regulation, expression and bioengineering in E.coli." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/9548.
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Mestrado em Biotecnologia MolecularA lichenicidina e um lantibiotico de classe II, naturalmente produzido por B. licheniformis I89. E constituida por dois peptidos denominados Blia e Blib. Este lantibiotico foi o primeiro a ser expresso completamente in vivo num hospedeiro Gram negativo (Escherichia coli). Neste trabalho, pretendeu-se avaliar o impacto da proteina LicR na biossintese da lichenicidina usando um sistema de expressao heterologa em E. coli. A estirpe de E. coli que nao contem o gene licR parece apresentar uma maior producao de lichenicidin do que a estirpe que contem todo o conjunto de genes envolvidos na sintese da lichenicidin. Assim, LicR parece nao apresentar qualquer funcao regulatoria em E. coli ou esta nao podera ser descrita segundo os mecanismos habituais de regulacao da producao de lantibioticos. Paralelamente um sistema de expressao foi construido para produzir cada um dos peptidos da lichenicidina separadamente, tendo sido comparados os niveis de producao de cada um dos peptidos. Este sistema foi usado com sucesso para produzir o peptido BliƒÀ mas nao apresentando qualquer vantagem sobre os sistemas ao nivel da producao. Finalmente, uma biblioteca de mutagenese do peptido Bliƒ¿ foi construida em E. coli e os clones obtidos foram analisados; a maioria dos clones obtidos apresentou bioatividade reduzida ou nula contra Micrococcus luteus. Alguns destes clones foram sequenciados para determinar qual(ais) a(s) mutacao(oes) presente(s) no gene licA1.
Lichenicidin is a class II lantibiotic, naturally produced by Bacillus licheniformis I89 strain. It is composed by two peptides: Bliα and Bliβ. This was the first lantibiotic to be fully produced in vivo using a Gram negative host (Escherichia coli). Herein, the impact of LicR protein in lichenicidin biosynthesis was assessed, using an E. coli heterologous expression system. It was shown that the E. coli strain without the licR gene presented increased lichenicidin production, when compared with the strain containing the entire gene cluster. Thus, if LicR presents some regulatory function in E. coli, its role cannot be described according to the usually proposed regulation mechanisms involved in lantibiotic production. Also, an expression system was constructed to produce each lichenicidin peptide independently and this expression system was compared with other available systems in terms of production levels. The system was successfully used to obtain Bliβ peptide. However it did not show any advantage over the systems previously developed. Ultimately, a mutagenesis library of Bliα was constructed in E. coli and the clones were analyzed; the majority of the clones showed low or null bioactivity against Micrococcus luteus. Some of these clones were sequenced to determine which mutation(s) was present in the licA1 gene.
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Green, Andrew. "The impact of combined sewer overflow removal on the environmental status of a small urban watercourse (Pymme's Brook, North London)." Thesis, University of Hertfordshire, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323428.
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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.
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Feng, Mei. "Physiological state specific modelling of recombinant E.coli fermentations." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394639.
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Macpherson, Cindy Josephine. "Plasmid-mediated regulation of the E.coli cell cycle." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624602.
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Zahra, Rabaab. "CAG.CTG trinucleotide repeat instability in the E.coli chromosome." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/11667.
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In order to identify the molecular basis of genetic instability, a polymerization-independent strategy is developed to generate expanded repeat arrays. The repeat tracts are integrated in the 5’end of lacZ gene in the Escherichia coli chromosome. Using this model system, instability is studied in wild type E. coli and in strains deficient in cellular pathways such as DNA repair, replication and recombination. The work demonstrates that instability (expansion and contraction) in wild type cells is length and orientation dependent. Longer tracts are more unstable than shorter ones and the orientation where CAG repeats are on the leading strand template is more unstable than the opposite where CTG repeats are on the leading strand template. This orientation-dependence of CAG·CTG trinucleotide repeat instability is determined by the proofreading subunit of DNA polymerase II (DnaQ) in the presence of the hairpin nuclease SbcCD. The analysis of the sizes of deletions observed in wild type and mutant cells is consistent with the formation of secondary structures in vivo. The mismatch repair pathway does not affect the instability of CTG repeats in the E. coli chromosome but influences the CAG orientation. It is suggested that MutS stabilizes CAG repeats by initiating a “repair” process and protecting hairpins from SbcCD, which can cleave hairpins in the presence of MutL and MutH. Finally, the roles of two helicases, Rep and UvrD are analyzed. A mutation in rep helicase strongly destabilizes CTG repeats with no effect on the CAG orientation UvrD mutants show instability in both orientations. The increase in instability in the uvrD mutant depends on RecF in the CTG orientation.
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Eriksson, Jenny, Sofia Fasth, Cecilia Orrenius, Plavsic Milica, Andersson Linnéa Yuan, and Marcus Westholm. "Goodbye E.coli : Alternativa endotoxinfria produktionssystem till Escherichia coli." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-411969.
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Affibody is interested in replacing Escherichia coli as the production system for Affibody®-molecules in order to reduce the amount of resources needed for the purification step. The aim of this report is to present relevant endotoxin-free alternatives that would suit production. Affibody®-molecules are proteins that have similar specificity as antibodies used in biopharmaceuticals, but have the advantage of being smaller. Since E. coli is the current production organism, the product is contaminated with immunogenic endotoxins which cause a high demand of resources during the purification process, something Affibody wants to reduce. The results presented in this report were achieved by means of a systematic literature study, divided into one general phase and two specific search phases. In the general literature search phase we were solely concerned with finding endotoxin-free expression systems. In the specific search phases the expression systems found were narrowed down in two steps based on criteria such as potential of scale-up > 1000 L, approval from the European Medicines Agency and the Food and Drug Administration, cost and productivity. Finally, only three candidates remained that met all requirements. The information found pertaining to the expression systems was presented in a spreadsheet, as were the different sources used. The nominated endotoxin-free candidates suggested to replace E. coli are Pichia pastoris, Chinese Hamster Ovary (CHO) cells and the Baculovirus Expression Vector System (BEVS). The candidates were then weighed against each other in an analysis based on the given criteria. We concluded that all three candidates satisfy the criteria and are suitable replacements for Affibody to use instead of E. coli.
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Milunov, Dimitrije. "External real time control of E.coli range expansion." Electronic Thesis or Diss., Université Paris Cité, 2023. http://www.theses.fr/2023UNIP7078.
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Les progrès de la microfluidique, de la technologie sensorielle et de la biologie synthétique et moléculaire ont permis l'émergence d'un nouveau domaine scientifique dans lequel les principes fondamentaux de la théorie du contrôle peuvent être appliqués pour contrôler et réguler de manière externe les bioprocessus cellulaires : la cybernétique. Jusqu'à présent, la cybernétique a été capable de contrôler avec succès des réseaux génétiques complexes, multi-stables et adaptatifs au niveau de la population et de la cellule unique, mais les défis du contrôle de systèmes biologiques de type multi-agent composés de multiples composants interactifs n'ont pas encore été relevés. Dans cette étude, nous nous sommes concentrés sur des colonies denses d'E. coli, semblables à des biofilms, qui ont été cultivées à l'intérieur d'un dispositif microfluidique multicouche dont la géométrie permet la croissance des colonies dans une seule direction. De même que pour les biofilms, il est largement connu que les colonies denses d'E.coli présentent des niveaux remarquables d'organisation spatiale qui sont la conséquence de l'interaction complexe entre les gradients nutritifs et chimiques et les interactions métaboliques entre les différentes couches de la colonie. Ces interactions rendent les colonies denses et les biofilms plus résistants aux traitements antimicrobiens, ce qui les rend difficiles à éradiquer. La question de savoir si et dans quelle mesure nous pouvons contrôler ce système de l'extérieur reste ouverte. Pour répondre à cette question, nous avons d'abord analysé quantitativement les modèles de croissance à l'intérieur de la colonie pour comprendre la dynamique du système. Nous avons utilisé trois stratégies différentes pour perturber la colonie et voir l'impact sur les modèles de croissance spatiale - la modulation de l'ARN polymérase par un promoteur inductible et la modulation biochimique des ressources cellulaires par des changements de nutriments et des antibiotiques. Comme les cellules ne sont pas mobiles, la vitesse d'invasion de la colonie peut être considérée comme un descripteur global de la dynamique de croissance spatiale de la colonie. En gardant cela à l'esprit, nous avons finalement utilisé la compréhension de la dynamique des systèmes, la connaissance de la réponse des colonies à divers stimuli et une plateforme de contrôle faite sur mesure pour contrôler de manière externe la vitesse d'invasion de la colonieAdvances in microfluidics, sensory technology and synthetic and molecular biology enabled the rise of a novel scientific field in which fundamentals of control theory can be applied to externally control and regulate cellular bioprocesses-cybergenetics. So far, cybergenetics was able to successfully control complex multi-stable and adaptive gene networks at the population and the single cell level, but challenges in the control of biological multiagent-like system composed of multiple interactive components have not yet been addressed. In this study we focused on dense biofilm like colonies of E.coli which were grown inside the multilayered microfluidic device whose geometry enabled the growth of the colonies in one direction. Similarly to biofilms, it is widely known that dense E.coli colonies exhibit remarkable levels of spatial organization that come as a consequence of the complex interplay between nutrient and chemical gradients and metabolic interactions between different layers of the colony. These interactions make both dense colonies and biofilms more resistant to antimicrobial agents treatment consequently making them difficult to eradicate. Thus can we and at which extent we could externally control this system remains an open question. To answer this we firstly quantitively analyzed the growth patterns inside the colony to understand the dynamics of the system. We used three different strategies to perturb the colony and to see the impact on the spatial growth patterns - modulation of RNA polymerase by inducible promoter and biochemical modulation of the cellular resources by nutrient change and antibiotics. Since the cells were nonmotile, the invasion speed of the colony could be regarded as a global descriptor of the colony spatial growth dynamics. Thus having this in mind we finally used the understanding of the systems dynamics, knowledge of colonies response to various stimulus and a custom made control platform to externally control the invasion speed of the colony
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Molle, Virginie. "The whiD and bldM loci of Streptomyces coelicolor A3(2)." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327448.
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Durany, Türk Olga. "Producció de Fuculosa-1-Fosfat aldolasa recombinant en E.coli." Doctoral thesis, Universitat Autònoma de Barcelona, 2003. http://hdl.handle.net/10803/5302.
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En l'actualitat es coneix un gran ventall d'enzims naturals capaços de catalitzar la formació d'enllaços caboni-carboni amb estereoquímica definida que obren noves perspectives en el camp de la síntesi asimètrica aportant solucions sintètiques en camps difícils d'abordar des de la perspectiva de la síntesi orgànica convencional. Aquests enzims són bàsicament aldolases i transcetolases. En concret es coneix una família de quatre aldolases depenents de DHAP que catalitzen la formació d'un enllaç C-C amb generació de dos nous centres quirals amb estereoquímica definida i complementària: segons l'aldolasa utilitzada s'obtindrà de forma específica un dels quatre diaestereoisòmers possibles. Aquesta família d'aldolases ha despertat un gran interès com a eina sintètica.El projecte en que s'emmarca aquesta tesi aposta per l'estudi d'aquest grup de biocatalitzadors i pretén contribuir al desenvolupament pràctic de les aldolases centrant-se en els aspectes de producció dels enzims i en el desenvolupament de metodologia per a la seva utilització en síntesi quiral.
En aquesta memòria de tesi doctoral s'estudia la millora de producció de l'aldolasa Fuc-1-PA en E.coli, com enzim model d'aquesta família d'aldolases depenents de DHAP. L'objectiu és definir un procés optimitzat i reproduïble per a la seva obtenció a escala productiva. Amb aquest objectiu global, es consideren els principals aspectes que condicionen la sobreexpressió de proteïnes recombinants E.coli. Primer, s'estudia la influència de la composició del medi de cultiu en el creixement i sobreexpressió recombinant. Segon, es treballa en el desenvolupament d'una estratègia de cultiu semicontínua adequada per assolir cultius d'alta densitat cel.lular de forma reproduïble. Un cop fixades les condicions d'operació per al creixement segons aquesta estratègia semicontínua, és possible definir els criteris d'inducció per maximitzar la producció de Fuc-1-PA al procés. Finalment, s'aborda la millora genètica del procés provant un nou sistema d'expressió recombinant desenvolupat pensant en la seva aplicació a escala de producció.
Nowadays, a considerable number of wild-type enzymes catalazing formation of stereo chemically defined C-C bond as natural function have been discovered. These enzymes have opened new possibilities in quiral chemistry field as they could mean a solution for problems impossible to be solved right now with conventional organic chemistry alternatives. These enzymes are, basically, aldolases and transketolases. It is important to point here out that it is known a four members DHAP dependent aldolases family which is able to catalyze the formation of a new C-C bond which results in the formation of two new quiral centers with complementary and perfectly defined stereochemistry. Hanging on the aldolase employed in the new C-C bond synthesis it is obtained specifically one of the four possibles diastereoysomers. This family has been considered really interesting as synthetic tool.
The project this thesis work is related to, is focused on the study of these biocatalyzers group and its main goal is the practical knowledge of aldolases: learn new techniques for maximize their production and make it possible their final application as quiral synthetic tools.
In this work, improvements in Fuculose-1-phosphate aldolase production are studied, as enzyme model of this four members family. The final goal fixed for this work is define a optimizated and reproducible process for its production at industrial scale. To obtain this final goal, here are studied the most important points affecting recombinant proteins production in E. coli. First, study of growth media composition influence in growth and recombinant overexpression. Second, search of a new semi-continues fermentation strategy which allows obtain high cell density cultures in a reproducible way. Once, growth conditions have been fixed related to this new semi continues fermentation strategy, it is possible to work on induction criteria definition in order to maximize Fuc-1-FA production. Finally, work has been focused on genetic improvement of the process. We have tested a new recombinant expression system for industrial scale application: ORT expression System.
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Elderkin, Sarah Louise. "Functional analysis of the E.coli phage shock protein PspA." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407101.
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Fox, Simon George. "Expression of catalytic antibody C3 esterase scFv in E.coli." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322119.
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Duboff, James Steven. "The role of indole in plasmid replication in E.coli." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607877.
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Warner, Stuart A. "Roles of recombination in trinucleotide repeat instability in E.coli." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/13211.
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Almeida, Diana Margarida Silva. "Contaminação microbiológica de alimentos : o caso particular de E.coli." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/11459.
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Mestrado em BioquímicaQuando alimentos contaminados por Escherichia coli (E. coli) são ingeridos, podem manifestar-se várias doenças provocadas pela bactéria ou por toxinas por ela produzidas. Para além de poder constituir uma ameaça à saúde do consumidor, a presença de E. coli em alimentos pode ser indicativa de contaminação fecal e de processos de higienização inadequados. Pelas suas características nutricionais, pH e água disponível, a carne picada é um alimento particularmente suscetível a contaminação microbiológica, principalmente pela bactéria E. coli. Devido a este facto, é exigido por decreto-lei descrito na Portaria 699:2008 “Ministérios da economia e da inovação e da agricultura, do desenvolvimento rural e das pescas”, que os estabelecimentos comerciais de venda de carnes realizem mensalmente ensaios de enumeração desta bactéria em amostras de carne picada, devendo ser avaliadas 5 amostras por cada estabelecimento. De acordo com esta legislação, o conjunto das amostras é considerado insatisfatório se alguma delas apresentar concentrações de E. coli superiores a 5,0 x 102 UFC/g ou se mais do que 2 amostras apresentarem concentrações entre 5,0 x 101 e 5,0 x 102 UFC/g. Desta forma, numa primeira parte do trabalho do presente estágio (que englobou o período de outubro de 2012 a maio de 2013), foi feita uma avaliação da incidência de E. coli em carnes picadas provenientes de 22 talhos diferentes, da região de Aveiro, no período de julho de 2011 a fevereiro de 2013. No conjunto dos 22 talhos, foram encontrados níveis da bactéria E. coli em não conformidade com a legislação vigente em 25% das avaliações mensais das amostras de carne picada. Em 2 dos 22 talhos, foi verificado um número máximo de 9 meses em que as amostras apresentaram resultados insatisfatórios, enquanto em apenas um talho foi verificada a conformidade das amostras em todos os meses considerados neste estudo. Nos vários estabelecimentos, em cada mês considerado, foram verificadas apenas algumas correlações entre valores indicativos de higienização inadequada de superfícies e manipuladores, e amostras de carne picada em não-conformidade. Tal averiguação é indicativa de que a maioria das contaminações tem origem em processos anteriores à chegada da carne ao estabelecimento, como o processo de abate dos animais, processamento das carcaças e/ou aplicação de temperaturas inadequadas durante o armazenamento e transporte da carne. Uma segunda parte do trabalho no laboratório YourLAB Segurança Alimentar consistiu em avaliar a presença de microrganismos indicadores e microrganismos patogénicos, em alimentos confecionados e frescos, recolhidos entre julho de 2011 e fevereiro de 2013 em diversos estabelecimentos distintos. Não foram detetados microrganismos patogénicos nas amostras de refeições e produtos alimentares analisados, com as exceções de uma amostra de requeijão em que foi detetada e confirmada a presença de Salmonella spp, e de algumas das amostras analisadas ao longo do período considerado, em que foi detetada a presença de esporos de Clostridium sulfito-redutores. Destas últimas amostras fazem parte produtos confecionados como um pastel bola de Berlim e frango estufado com batata e legumes, e produtos frescos, ou ainda crus, como croissants de ovo e de chocolate congelados. Relativamente a microrganismos indicadores, foram encontradas algumas amostras (de produtos confecionados e produtos frescos) insatisfatórias de acordo com os valores guia publicados em Portugal, pelo Instituto Nacional de Saúde de Dr. Ricardo Jorge, podendo indicar a ocorrência de contaminação fecal, uma confeção inadequada do produto, e/ou uma contaminação pós-confeção.
When food contaminated with Escherichia coli (E. coli) is ingested, several diseases caused by the bacteria itself or by the toxins it produces may occur. Moreover, the presence of E. coli in foods may be indicative of inadequate hygiene processes. Minced meat is particularly susceptible to microbiological contamination by E. coli, due mostly to their available nutrients and water, and aw. Therefore, the Portuguese law expressed in Portaria 699:2008 – “Ministérios da economia e da inovação e da agricultura, do desenvolvimento rural e das pescas”, requires the enumeration of this bacteria in 5 samples of minced meat, each month, in each commercial establishment. Accord to this law, the samples are in non compliance if more than two samples exhibit a concentration of E. coli between 5,0 x 101 e 5,0 x 102 CFU/g, or if any sample exceed the value 5,0 x 102 CFU/g. In the first part in this study, an assessment of the incidence of E. coli in minced meat was carried out for 22 different butchers, in the Aveiro region, from July of 2011 to February of 2013. Considering all collection sits, 25% of the samples have shown to be in non-compliance with current legislation. The number of occurrences of non-conforming minced meat samples reached a maximum of 9 in 2 of the 22 the butchers, whereas only one butcher showed all results satisfactory during the study period. The possibility of unacceptable values of E. coli in ground beef correlated with unsatisfactory values in surface and handlers swabs (indicative of poor sanitation) was investigated, but found not the be the case. This finding is indicative that most of the contamination originates in processes prior to the arrival of the meat at the butcher store, like the process of slaughter and application of inappropriate temperatures during storage and transportation of meat. A second part of the study work carried out in the laboratory YourLAB S. A., consisted in the assessment of the indicator microorganisms incidence and the presence of pathogenic microorganisms in several types of fresh and cooked food samples, collected in various commercial establishments between July 2011 and February of 2013. No pathogens were detected in meal and other food samples, with the exceptions of one sample of cottage cheese in which was confirmed the presence of Salmonella spp. and the presence of sulphite-reducing Clostridium spores in some samples over the period considered. Those samples included cooked products like a cake “bola de berlim” and stewed chicken with potatoes and vegetables, and fresh products such as frozen croissants. Unsatisfactory values of indicator microorganisms were found in some samples of both cooked and fresh products, according to the table of guide values published in Portugal, by the “Instituto Nacional de Saúde Dr. Ricardo Jorge”, indicating fecal contamination, inadequate cooking or a post-processing infection.
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Sjöberg, Gustav. "MFA för att öka produktiviteten av 3HB av rekombinant E.coli." Thesis, KTH, Skolan för bioteknologi (BIO), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-163703.
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Balbi, Kevin Jon. "Patterns of short-term genome evolution in E.coli and Shigellae." Thesis, University of Bath, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512374.
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The time-dependence of molecular evolution, specifically over short timescales, has been shown to be a major confounding factor in the analysis of nucleotide changes between closely related strains or species. The assumption that selection works extremely quickly to purge all of the deleterious changes is at odds with the Nearly Neutral model of evolution, whereby the majority of changes are only mildly deleterious and therefore impose only a minor fitness cost so they are relatively rapidly purged only in populations with large effective population sizes. The aim of this project was to explore the patterns of nucleotide changes evident between the core genomes of nine E. coli and Shigella strains, with the latter having adopted a specific ecological niche in the recent evolutionary past. The Shigellae and E. coli show little difference in their extant genome compositions, in terms of nucleotide composition and genome size, however there are a markedly higher number of pseudogenes and insertion sequences present in the Shigella genomes. The polymorphism profiles of the core genomes reveal a time-dependency of dN/dS, Ti/Tv, +AT/+GC and the Metabolic cost of Amino acid changes, the nucleotide data showing a clear separation of the E. coli from the Shigellae, with the latter showing trends indicative of weaker purifying selection. Additionally these differences are evident when examining the nucleotide ratios (+AT/+GC & Ti/Tv) along the core genome, also revealing patterns of evolution associated with genome position. A simulation based approach reveals different projected nucleotide contents for the E. coli and Shigellae genomes further highlighting their different evolutionary paths as evident from the polymorphism profiles. The methods employed and developed in this study provide a useful and effective toolset for examining the evolution of bacterial genomes over short timescales, especially in light of the availability of multiple whole genome sequences for a given 'species'.
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Loftus, Katherine Marie. "Studies of the Structure and Function of E.coli Aspartate Transcarbamoylase." Thesis, Boston College, 2006. http://hdl.handle.net/2345/580.
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Thesis advisor: Evan R. KantrowitzE.coli Aspartate transcarbamoylase (ATCase) is the allosteric enzyme that catalyzes the committed step of the de novo pyrimidine biosynthesis pathway. ATCase facilitates the reaction between L-aspartate and carbamoyl phosphate to form N-carbamoyl-L-aspartate and inorganic phosphate. The holoenzyme is a dodecamer, consisting of two trimers of catalytic chains, and three dimers of regulatory chains. ATCase is regulated homotropically by its substrates, and heterotropically by the nucleotides ATP, CTP, and UTP. These nucleotides bind to the regulatory chains, and alter the activity of the enzyme at the catalytic site. ATP activates the rate of ATCase's reaction, while CTP inhibits it. Additionally, UTP and CTP act together to inhibit the enzyme synergistically, each nucleotide enhancing the inhibitory effects of the other. Two classes of CTP binding sites have been observed, one class with a high affinity for CTP, and one with a low affinity. It has been theorized that the asymmetry of the binding sites is intrinsic to each of the three regulatory dimers. It has been hypothesized that the second observed class of CTP binding sites, are actually sites intended for UTP. To test this hypothesis, and to gain more information about heterotropic regulation of ATCase and signal transmission in allosteric enzymes, the construction of a hybrid regulatory dimer was proposed. In the successfully constructed hybrid, each of the three regulatory dimers in ATCase would contain one regulatory chain with compromised nucleotide binding. This project reports several attempts at constructing the proposed hybrid, but ultimately the hybrid enzyme was not attained. This project also reports preliminary work on the characterization of the catalytic chain mutant D141A. This residue is conserved in ATCase over a wide array of species, and thus was mutated in order to ascertain its significance
Thesis (BS) — Boston College, 2006
Submitted to: Boston College. College of Arts and Sciences
Discipline: Chemistry
Discipline: College Honors Program
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Лохматова, Т. М., Р. П. Боровик, and О. В. Чеботар. "Чутливість музейного штаму E.coli до комбінацій антимікробних засобів з емоксипіном." Thesis, Сумський державний університет, 2016. http://essuir.sumdu.edu.ua/handle/123456789/45033.
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Відомо, що вірулентні штами E. coli можуть викликати гастроентерити, запалення сечової системи, менінгит у новонарождених та інші тяжкі інфекції. Одним з шляхів підвищення ефективності лікування цих інфекцій може бути комбінування протимікробних засобів, у спектрі дії яких є кишкова паличка, з речовинами, що мають нестандартні механізмами впливу на мікробну клітину. Серед таких речовин – похідні 3-гідроксипіридину, наприклад емоксипін, який у зв’язку з його антиоксидантними властивостями застосовують у медицині за «неінфекційними» показаннями..
Мета роботи – вивчити чутливість музейного штаму E. coli АТСС 25922 до відомих антимікробних препаратів у комбінації з емоксипіном.
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Si, Yang. "Fluorescent Nanomaterials for Bioimaging and Biosensing : Application on E.coli Bacteria." Thesis, Cachan, Ecole normale supérieure, 2015. http://www.theses.fr/2015DENS0038/document.
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Les bactéries sont les organismes les plus abondants dans le monde. Des études sur les bactéries peuvent être bénéfiques pour la recherche médicale, la qualité des ressources en eau et l'industrie alimentaire. La détection et le marquage fluorescent est une des méthodes les plus utilisées pour des objectifs bioanalytiques. Dans la recherche de marqueurs luminescents et stables, des nouvelles nanoparticules fluorescentes et auto-stabilisées à base de polymères (FNPs, 60 nm) et des chaînes de polymères fluorescents (FPCs, 5nm) ont été développées. Dans un premier chapitre, une méthodologie pour insérer ces FNPs dans la bactérie E.coli a été développée. Pour contrôler si les FNPs sont en effet internalisé, nous avons développé un protocole basé sur l'extinction de luminescence des FNPs par le bleu de méthylène. Dans un second chapitre, les biotines conjuguées de FNPs peuvent être utilisées pour étudier les protéines membranaires spécifiques. En utilisant un lien streptavidine-biotine, un "sandwich" est formé pour construire un pont entre des particules, des anticorps spécifiques et des bactéries. Les images de fluorescence SPR et les images SEM ont démontré l'interaction de la biotine conjuguée de FNPs avec la bactérie E.coli. Dans un troisième chapitre, les chaînes de polymères fluorescents de couleur verte (GFPCs) peuvent facilement entrer dans des bactéries E.coli. Les GFPCs peuvent marquer le cyctoplasme mais pas l'ADN. Les chaînes de polymères fluorescents de couleur rouge (RFPCs) peuvent marquer facilement et efficacement la membrane de bactérie E.coli. Les deux FPCs sont extrêmement brillantes et non toxiques, les chaînes sont solubles dans l'eau. Ce sont de nouveaux matériaux fluorescents pour le marquage interne et externe des bactéries. Dans le dernier chapitre, il est démontré que les FANPs sont sensibles au pH et peuvent être utilisées pour mesurer la croissance de la bactérie E.coli. Les nano-objets détectent rapidement et précisément la croissance des cellules. En effet, leur fluorescence est sensible au changement de pH résultant du métabolisme cellulaire. De plus, ces particules permettent une surveillance en continu d'un grand nombre d'échantillons pour des applications de criblage à haut débit. Les nanomatériaux présentés dans ce manuscrit sont des outils prometteurs pour les applications en biocapteurs et bioimagerie en raison de leur luminosité/brillance et photostabilité élevées ainsi que les possibilités de post-fonctionnalisationBacteria are the most abundant organisms in the world. Investigations and studies on bacteria can be beneficial to medical research, water resources research and food industry. Fluorescent sensing and labeling are commonly used for bioanalytical purposes. In the quest for very bright and stable labels, novel polymer-based, self-stabilized, fluorescent nanoparticles (FNPs, 60 nm) and fluorescent polymer chains (FPCs, 5 nm) have been developed. In the first part, a methodology to insert these FNPs into E.coli bacteria was developed. To control if the FNPs are indeed internalized, we developed a protocol based upon FNPs luminescence quenching by methylene blue. In the second part, a "sandwich" system is built. By using a streptavidin-biotin link, a bridge between particles (FNP), specific antibodies and bacteria is built. SPR, fluorescent images and SEM images demonstrated the interaction of biotin conjugated FNPs with E.coli bacteria. In the third part, interactions of fluorescent polymer chains with bacteria are investigated. Green fluorescent polymer chains (GFPCs) can easily enter into E.coli bacteria. GFPCs can label the cytoplasm but not the DNA. Red fluorescent polymer chains (RFPCs) can label the membrane of E.coli bacteria easily and efficiently. Both FPCs are highly water-soluble, bright and non-toxic, they are novel fluorescent labels for internal and external biological labeling of bacteria. In the last part, it is demonstrated that pH sensitive FANPs can be used to measure the growth of E.coli. They detect rapidly and accurately bacterial growth by signaling the change of pH resulting from cellular metabolism. Moreover, these particles allow for continuous monitoring a large number of samples for high-throughput screening applications. The studied fluorescent nanomaterials are promising tools for biosensing and bioimaging applications due to their brightness, high photostability and rich functionalisation ability
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Burger, Adélle. "The E.coli RNA degradosome analysis of molecular chaperones and enolase." Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1004009.
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Normal mRNA turnover is essential for genetic regulation within cells. The E. coli RNA degradosome, a large multi-component protein complex which originates through specific protein interactions, has been referred to as the “RNA decay machine” and is responsible for mRNA turnover. The degradosome functions to process RNA and its key components have been identified. The scaffold protein is RNase E and it tethers the degradosome to the cytoplasmic membrane. Polynucleotide phosphorylase (PNPase), ATP-dependent RNA helicase (RhlB helicase) and the glycolytic enzyme enolase associate with RNase E to form the degradosome. Polyphosphate kinase associates with the degradosome in substoichiometric amounts, as do the molecular chaperones DnaK and GroEL. The role of DnaK as well as that of enolase in the RNA degradosome is unknown. Very limited research has been conducted on the components of the RNA degradosome under conditions of stress. The aim of this study was to understand the role played by enolase in the assembly of the degradosome under conditions of stress, as well as investigating the protein levels of molecular chaperones under these conditions. The RNA degradosome was successfully purified through its scaffold protein using nickel-affinity chromatography. In vivo studies were performed to investigate the protein levels of DnaK and GroEL present in the degradosome under conditions of heat stress, and whether GroEL could functionally replace DnaK in the degradosome. To investigate the recruitment of enolase to the degradosome under heat stress, a subcellular fractionation was performed to determine the localization of enolase upon heat shock in vivo. The elevated temperature resulted in an increased concentration of enolase in the membrane fraction. To determine whether there is an interaction between enolase and DnaK, enolase activity assays were conducted in vitro. The effect of DnaK on enolase activity was measured upon quantifying DnaK and adding it to the enolase assays. For the first time it was observed that the activity of enolase increased with the addition of substoichiometric amounts of DnaK. This indicates that DnaK may be interacting with the RNA degradosome via enolase.
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Cassels, Eoin. "Characterisation of the E.coli and Pseudomonas aeruginosa TolA-TolB interaction." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3890/.
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The Tol-Pal complex of Gram-negative bacteria is a highly conserved family of interacting proteins that span the periplasm, from inner to outer membrane. Despite decades of work on this protein complex, only the structure of a small part of the Tol complex in E.coli (TolB, Pal, TolB-Pal complex, TolA domain 3) as well as part of TolA from Pseudomonas aeruginosa have been resolved, and the native function of the Tol-Pal system remains elusive. A key interaction of the Tol-Pal system is between TolA and TolB. These two proteins bridge the periplasm, linking the inner membrane complex of TolQ, TolR and TolA with the outer membrane through the outer membrane bound Pal and periplasmic TolB. The structure of the TolA-TolB complex is not known, and although the TolA binding epitope of TolB has been localised to the intrinsically disordered N-terminus of TolB, the binding site on TolA is also unknown (Bonsor et al. 2009). The aim of this work is to address a number of questions regarding a fundamental part of the Tol-Pal system: the interaction between TolA and TolB. This thesis reports that not only is the short 22 residue N-terminus of TolB important for its interaction with TolA domain 3, but that it is the sole site of interaction between E.coli TolA and TolB. This was shown by engineering the E.coli TolB N-terminus onto another protein to create a novel interaction with E.coli TolA. In addition, a synthetic peptide of the N-terminus of TolB binding TolA can recapitulate and serve as a model for the native interaction. This work also reports that the TolA-TolB interaction is conserved between Pseudomonas aeruginosa TolA and TolB, and that the N-terminus is also important for this interaction, the first work to suggest this. Finally, through use of nuclear magnetic resonance spectroscopy, residues perturbed on Pseudomonas aeruginosa TolA domain 3 through the binding of a synthetic peptide representing Pseudomonas aeruginosa TolB have been mapped onto the TolA protein to determine the potential binding site of TolB on TolA, something which until now has been unknown.
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Garrido, Franco Marta. "Structural and functional studies of pyridoxine 5'-phostate synthase from e.coli." Doctoral thesis, Universitat Autònoma de Barcelona, 2002. http://hdl.handle.net/10803/3469.
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El piridoxal 5'-fosfato es la forma biocatalíticamente activa de la vitamina B6, siendo uno de los cofactores más versátiles de la naturaleza, el cuál tiene un papel central en el metabolismo de aminoácidos. Mientras que la mayoria de microorganismos y plantas pueden sintetizar la vitamina B6 de novo, los mamíferos se ven obligados a obtener uno de sus vitámeros a través de la dieta. La maquinaria biosintética de Escherichia coli es, de lejos, la mejor caracterizada y consiste en cuatro proteínas pdx. PdxJ, también conocida como piridoxina 5'-fosfato sintasa, es la enzima clave en esta via. Cataliza el último paso, la complicada reacción de cierre del anillo entre 1-deoxi-D-xilulosa-5-fosfato y aminoacetona-3-fosfato para formar piridoxina 5'-fosfato. La comparación de secuencias de PdxJ entre espécies revela que existe un alto grado de conservación indicando así la enorme importancia fisiológica de esta enzima.Con el uso de un derivado de mercurio fue posible el resolver la estructura cristalina de la enzima de E. coli por el método del "single isomorphous replacement with anomalous scattering" y el refinar la estructura a 2.0 Å de resolución. El monómero corresponde al plegamiento TIM o barril (_/_)8, con la incorporación de tres hélices extra que median los contactos entre intersubunidades en el octámero. El octámero representa el estado fisiológicamente relevante, que fué observado tanto en el cristal como en solución, y que esta organizado como un tetrámero de dímeros activos. La caracterización de la estructura cristalográfica de la enzima con sustratos, análogos de sustrato y productos unidos permitió la identificación del centro activo y la propuesta de un mecanismo detallado. Los rasgos catalíticos más remarcables son: (1) el cierre del centro activo una vez se han unido los sustratos, de manera que el bolsillo de unión queda aislado del solvente y los intermediarios de la reacción quedan así estabilizados; (2) la existencia de dos sitios de unión de fosfato bien definidos; (3) y un canal de agua que penetra el núcleo del barril _ y permite liberar las moléculas de agua formadas durante la reacción.
La cantidad de información presentada debería permitir el diseño de inhibidores de la piridoxina 5'-fosfato sintasa basados en su estructura. Es interesante el destacar que entre las bacterias que contienen el gen pdxJ se encuentran unos cuantos patógenos bien conocidos. La resistencia de bacterias contra antibióticos está aumentando cada vez más, hecho que se está convirtiendo en un auténtico problema. Por este motivo, es necesario el desarrollar medicamentos antibacterianos con un alto grado de especificidad y la piridoxina 5'-fosfato sintasa parece ser una diana muy prometedora.
Pyridoxal 5'-phosphate is the biocatalytically active form of vitamin B6, being one of nature's most versatile cofactors that plays a central role in the metabolism of amino acids. Whereas microorganisms and plants can synthetise vitamin B6 de novo, mammals have to obtain one of the B6 vitamers with their diet. The Escherichia coli biosynthetic machinery is the, by far, best characterised and it consists in four pdx proteins. PdxJ, also referred to as pyridoxine 5'-phosphate synthase, is the key enzyme in this pathway. It catalyses the last step, the complicated ring-closure reaction between 1-deoxy-D-xylulose-5-phosphate and aminoacetone-3-phosphate yielding pyridoxine 5'-phosphate. Sequence comparison of PdxJ from different species revealed a remarkable high degree of conservation indicating the paramount physiological importance of this enzyme.
With the use of one mercury heavy-atom derivative, it was possible to solve the crystal structure of the E. coli enzyme by the single isomorphous replacement method with anomalous scattering and to refine the structure at 2.0 Å resolution. The monomer folds as a TIM or (_/_)8 barrel, with the incorporation of three extra helices that mediate intersubunits contacts within the octamer. The octamer represents the physiological relevant state that was observed in the crystal and in solution, and that is organised as a tetramer of active dimers. Characterisation of the enzyme crystal structure with bound substrates, substrate analogues, and products allowed the identification of the active site and the proposal of a detailed reaction mechanism. The most important catalytic features are: (1) active site closure upon substrate binding, in order to isolate the specificity pocket from the solvent und thus stabilise the reaction intermediates; (2) the existence of two well-defined phosphate binding sites; (3) and a water channel that penetrates the _ barrel core and allows the release of waters in the closed state.
The amount of information here presented should permit the structure-based design of pyridoxine 5'-phosphate synthase inhibitors. Interestingly, among bacteria that contain the pdxJ gene there are several well-known pathogens. More and more, the bacterial resistance against antibiotics is increasing and therefore becoming a real problem. Thus, it is necessary the development of highly specific antibacterial drugs and pyridoxine 5'-phosphate synthase seems to be a promising novel target.
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Schmidt, Bastian. "Veränderungen im LPS-Muster von E.coli Shigella durch cld pHS_-1tn2." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980061172.
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Gudzuhn, Andrej. "Virulenzfaktoren von E.coli aus gewaschenen Kolonbiopsien von Patienten mit kolorektalen Neoplasien." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=972574433.
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Odeyemi, Babatunde O. "Hydrodynamic cavitation : effects of cavitation on inactivation of Escherichia coli (E.coli)." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/11009.
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Bartolo, Natalie Di. "In vitro folding and assembly of the E.Coli ABC transporter BTUCD." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492472.
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Most studies of membrane protein folding have focused on a-helical monomeric proteins. The next major challenge is to extend these folding studies to incorporate oligomeric membrane proteins, for which there is a paucity of information available on their folding and assembly. The folding of multisubunit proteins is a biologically important and far-reaching area of research since the majority of proteins exist as protein-protein complexes. In order to understand these proteins it is important to be able to recreate their folding and assembly in vitro starting with simple model protein complexes. Work in this thesis takes advantage of the modular organisation of BtuCD and methods are described to prepare the individual building blocks of the protein complex.
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Bruneaux, Luke Julien. "Multiple Unnecessary Protein Sources and Cost to Growth Rate in E.coli." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11041.
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The fitness and macromolecular composition of the gram-negative bacterium E.coli are governed by a seemingly insurmountable level of complexity. However, simple phenomenological measures may be found that describe its systems-level response to a variety of inputs. This thesis explores phenomenological approaches providing accurate quantitative descriptions of complex systems in E.coli. Chapter 1 examines the relationship between unnecessary protein production and growth rate in E.coli. It was previously unknown whether the negative effects on growth rate due to multiple unnecessary protein fractions would add linearly or collectively to produce a nonlinear response. Within the regime of this thesis, it appears that the interplay between growth rate and protein is consistent with a non-interacting model. We do not need to account for complex interaction between system components. Appendix A describes a novel technique for real-time measurement of messenger RNA in single living E.coli cells. Using this technique, one may accurately describe the transcriptional response of gene networks in single cells.Physics
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Lim, Ping Ping. "Structure-function analysis of the #beta# subunit of E.coli RNA polymerase." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306106.
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Gokce, Isa. "Expression of CFTR and its transmembrane domains in E.coli and yeast." Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299633.
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Liang, Yi. "Studies of E.Coli YIDC and other factors for membrane protein insertion." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1110228536.
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Gudzuhn, Andrej. "Virulenzfaktoren von E.coli aus gewaschenen Kolonbiopsien von Patienten mit kolorektalen Neoplasien." Doctoral thesis, Humboldt-Universität zu Berlin, Medizinische Fakultät - Universitätsklinikum Charité, 2004. http://dx.doi.org/10.18452/15059.
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Hintergrund: Die Pathogenese nicht-familiärer kolorektaler Neoplasien ist heute noch nicht bekannt. Die Besonderheiten der Epidemiologie der Erkrankung sprechen für die Beteiligung von Umweltfaktoren, wie sozioökonomischer Faktoren, der Ernährung oder der bakteriellen Flora des Darmes. Eine intrazelluläre, von E.coli dominierte Flora wurde in Kolonbiopsien dieser Patienten beschrieben. Methoden: Es wurden Virulenzfaktoren von Escherichia coli untersucht, die aus gewaschenen koloskopischen Biopsien von 43 Patienten mit kolorektalen Adenomen und Karzinomen isoliert worden waren. 100 Stämme wurden mittels PCR auf Gene für folgende Virulenzfaktoren untersucht: s-Fimbrien (sfa), pyelonephritisassoziierter Pilus (pap), Hämolysin A (hlyA), hitzestabiles und -labiles Toxin (ST, LT, EAST), Intimin (eae), Verotoxin (stx), Invasionsplasmid (ipa), cytolethal distending toxin (cdt) und cytotoxic necrotizing factor 1 (cnf1). Für die Kontrollgruppe wurden E.coli aus Biopsien von 55 Patienten mit chronisch-entzündlichen Darmerkrankungen (CED) und unspezifischer Kolitis, von 16 Patienten mit Colon irritabile (IBS) und aus Stuhlproben von 29 gesunden Probanden isoliert und untersucht. Ergebnisse: Bei 69% der Patienten mit kolorektalen Karzinomen und bei 58% der Patienten mit kolorektalen Adenomen wurde mindestens einer der Virulenzfaktoren gefunden, dagegen nur bei 25 bis 39% der IBS- und CED- Patienten sowie der gesunden Probanden (pBackground: Pathogenesis of non-hereditary colorectal neoplasia is poorly understood. The differences in regional incidence indicate an influence of environmental factors, as socio-economic conditions, nutrition and intestinal flora. An intracellular flora with a predominance of Escherichia coli in colon biopsies has been described in these patients. Methods: We studied virulence factors of Escherichia coli isolated from washed colonoscopic biopsies of 43 patients with colorectal carcinoma and adenoma. 100 strains of E.coli were isolated and used for detection of a broad range of virulence genes by PCR encoding: s-fimbriae (sfa), pyelonephritis-associated pili (pap), hemolysin A (hlyA), heatstable and heatlable toxins (ST, LT, EAST), verotoxin (stx), invasionplasmidantigen (ipaH), intimin (eae), cytolethal distending toxin (cdt) and cytotoxic necrotizing factor 1 (cnf1). E.coli from biopsies of 55 patients with inflammatory bowel disease (IBD) and non-specific colitis, of 16 patients with irritable bowel syndrom (IBS) and from stool samples of 29 healthy individuals were isolated and examined as controls. Results: The prevalence of virulent strains bearing at least one of the tested genes was 69% in colorectal carcinoma and 58% in colorectal adenoma, but only 25 to 39% of IBD and IBS patients and healthy individuals (p
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Schmidt, Bastian. "Veränderungen im LPS-Muster von E.coli Shigella durch cld pHS-2." Doctoral thesis, Humboldt-Universität zu Berlin, Medizinische Fakultät - Universitätsklinikum Charité, 2006. http://dx.doi.org/10.18452/15463.
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Bei neun von vierzehn Serogruppen der Subspezies E. coli Flexneri (SF) konnte ein pHS-2-Plasmid nachgewiesen werden. Es besteht eine positive Korrelation zwischen pHS-2-positiven SF und dem Auftreten einer Reaktiven Arthritis, eine Komplikation der bakteriellen Ruhr. Verschiedene Autoren führen das gehäufte Auftreten der Reaktiven Arthritis bei pHS-2-positiven SF auf eine erhöhte Serumresistenz zurück, die den Bakterien durch das cld(pHS-2)-Gen vermittelt wird. Das cld(pHS-2)-Gen als längstes aller 18 "open reading frames" auf dem pHS-2-Plasmid kodiert für ein 35 kD großes Protein, das aufgrund seiner Funktion als "chain length determinant" (Cld(pHS-2)) bezeichnet wurde. Cld(pHS-2) ist maßgeblich an der Produktion von Lipopolysacchariden vom VL-Typ beteiligt. LPS vom VL-Typ produzieren O-Seitenketten mit mehr als 70 bis 80 Oligosaccharideinheiten und sollen die bakterielle Membran vor einer Komplementbindung und Serum-Antikörpern schützen, wodurch den Bakterien eine erhöhte Serumresistenz vermittelt werde. In dieser Arbeit wurde cld(pHS-2) in einen pHS-2-negativen Stamm der SF Serogruppe 6 integriert, um nachzuweisen, dass cld(pHS-2) das LPS-Muster pHS-2-negativer SF in charakteristischer Weise modifiziert. Während der Expressionsnachweis von cld(pHS-2) als Einzelprotein misslang, war eine Expression von cld(pHS-2) als Fusionsprotein in SF Serogruppe 6 erfolgreich. Im Vergleich zu pHS-2-negativen SF war unsere SF Serogruppe 6-Mutante nun in der Lage, LPS vom VL-Typ in Form einer zusätzlichen Bande mit ca. 80 Oligosaccharideinheiten zu produzieren. Diese phänotypische Veränderung war zwar nur gering ausgeprägt, konnte jedoch den spezifischen Einfluss von cld(pHS-2) als Fusionsprotein auf das LPS-Muster pHS-2-negativer SF nachweisen.In nine out of fourteen serogroups of E. Coli Flexneri (SF) a pHS-2 plasmid has been isolated. There is a positive correlation between pHS-2-positive SF and the occurence of reactive arthritis (ReA) which is a complication of bacterial dysentery. Different authors reduce the widespread appearance of ReA by pHS-2-positive SF to an increased serum resistance caused by a cld(pHS-2)-gene. The cld(pHS-2)-gene ist the longest of 18 open reading frames in pHS-2 and it is the coding for a 35 kD protein which has been identified as a chain length determinant because of its function. Cld(pHS-2) plays a decisive role in the production of lipopolysaccharides (LPS) of the VL-type. LPS of the VL-type produce O antigen with more than 70-80 repeat units, and protect the bacterial outer membrane from complement factors and serum antibodies by a higher serum resistance. In this research the cld(pHS-2)-gene was integrated in a pHS-2-negative SF serogroup 6 to prove that cld(pHS-2) is able to modify the LPS pattern (destribution) of pHS-2-negative SF in a characteristic manner. The expression of cld(pHS-2) in SF serogroup 6 as an isolated protein failed, but the expression of cld(pHS-2) as a fusion protein was successful. In contrast to the pHS-2-negative SF our SF serogroup 6 mutant was able to produce LPS of the VL-type with 80-90 repeat units. Despite the slight effect, a specific influence of cld(pHS-2) as a fusion protein on LPS pattern and the bacterial phaenotype has to be confirmed.
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Camilleri, Raymond Stephen. "Molecular genetic and biochemical studies of the D1-processing protease of Arabidopsis Thaliana." Thesis, Royal Holloway, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322223.
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Scott, Christopher John. "Investigation of expression methodologies for the dissection of the catalytic mechanism of interleukin-1#beta#-converting enzyme." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325991.
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Mesquita, M. M. F. "Bacterial and bacteriophage investigations using the mussel Mytilus edulis." Thesis, University of Newcastle Upon Tyne, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380755.
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Chapman, Peter Alan. "Purification of the verotoxins of Escherichia coli and production of antitoxins for use in a diagnostic test." Thesis, University of Sheffield, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244433.
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Casadei, Maria Aurelia. "The effect of high hydrostatic pressure on Escherichia coli membrane structure and function." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312583.
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Jin, Kai. "Studies of the scale-up of production and recovery of recombinant proteins formed as inclusion bodies." Thesis, University College London (University of London), 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324597.
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Baker, Karen Anne. "Mechanisms of protein translocation in Escherichia coli." Thesis, University of Leicester, 1987. http://hdl.handle.net/2381/34434.
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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.
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Saviolli, Juliana Yuri. "Pesquisa e Caracterização de Escherichia coli patogênica (E.coli produtora de toxina Shiga - STEC; E.coli aviária patogênica - APEC) de fragatas (Fregata magnificens) da Costa do Estado de São Paulo." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/10/10133/tde-10082010-143759/.
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O presente trabalho objetivou pesquisar e caracterizar Escherichia coli patogênica (E. coli produtora de toxina Shiga STEC; E. coli aviária patogênica - APEC) em fragatas (Fregata magnificens) da costa do Estado de São Paulo e, desta forma, contribuir para a compreensão de aspectos epidemiológicos deste importante grupo de enfermidades zoonóticas bacterianas, as colibaciloses. Para tanto, foram realizadas três expedições científicas aos dois sítios de nidificação de fragatas no estado de São Paulo, Ilha Principal do Arquipélago de Alcatrazes (24°06´S 45°41´W) e Ilha de Castilho (25°16´S 47°57´W), nas quais foi colhido um total de 42 amostras de \"swabs\", sendo 21 cloacais e 21 de coanas, oriundos de 18 filhotes de sexo indeterminado, 2 fêmeas adultas e 1 macho adulto de fragatas. Das 42 amostras clinicas estudadas, foram identificadas 18 com crescimento de E.coli. Destas, foram isoladas 67 cepas, que foram então submetidas à pesquisa de genes de virulência e caracterização de grupos filogenéticos através da técnica de PCR. Em seguida, as cepas que exibiram fatores de virulência foram analisadas através de sorotipagem. Para investigar os padrões de resistência e sensibilidade a antimicrobianos, foram realizados antibiogramas para 18 tipos distintos de antimicrobianos para uma cepa de cada amostra selecionada de E. coli. Os resultados alcançados mostraram que foi possível identificar 15 diferentes perfis de virulência, com positividade para os seguintes genes: fimH (98,3%), malX (52,4%), traT (31,1%), cvaC (22,9%), fyuA (19,6%), ibeA (19,6%), aer (13,1%) e papC (13,1%). A maioria dos isolados de fragatas foi caracterizado entre os grupos filogenéticos D e B2, e os principais sorotipos encontrados foram O1:H6, O2:H7, O25:H4, e O102:H10. Em relação à resistência a antimicrobianos, 60,1%% dos isolados foram sensível aos 18 diferentes antimicrobianos testados; por outro lado, o antimicrobiano que apresentou maior resistência foi a Tetraciclina, que se revelou inefetiva em 20,1% das amostras pesquisados. Até o momento não foram identificadas cepas de STEC nos indivíduos pesquisados; por outro lado, os isolados albergam genes que caracterizam as ExPEC. Tais resultados mostram que a maioria das cepas isoladas é potencialmente patogênica para as aves, podendo representar significativo risco para sanidade das aves marinhas, além de se configurar como agentes zoonóticos relevantes, enfatizando a importância de se investigar a eventual participação das aves selvagens, em especial as marinhas, na cadeia epidemiológica de doenças ocasionadas por E. coli. Tais informações poderão nortear as pesquisas de doenças selecionadas nas populações das fragatas, assim como embasar a adoção de eventuais ações em relação a aspectos de saúde animal e humana, que tenham as fragatas como um dos elos.The present study is to investigate and characterize pathogenic Escherichia coli (E. coli Shiga toxin-producing - STEC avian pathogenic E. coli - APEC) on frigates (Fregata magnificens) from the coast of São Paulo and contribute to the understanding of epidemiological aspects in this important group of zoonotic bacterial diseases, the colibacillosis. To this, there were three scientific expeditions to two nesting sites of frigates in the state of Sao Paulo, the main island of Alcatraz (24 ° 06\'S - 45 ° 41\'W) and Castilho´s island (25 ° 16\'S - 47 ° 57\'W), in which it was collected a total of 42 samples of swabs, and 21 cloacal and choanal 21, coming from 18 offspring of indeterminate sex, 2 adult females and 1 adult male frigate. Of the 42 clinical samples studied, 18 were identified with growth of E.coli. Of these, 67 strains were isolated, which were then tested for virulence genes and characterization of phylogenetic groups by PCR technique. Then the strains that exhibited virulence factors were analyzed by serotyping. To investigate the patterns of resistance and sensitivity to antimicrobial susceptibility tests were performed for 18 different types of antimicrobials for one strain of each selected sample of E. coli. The results showed that it was possible to identify 15 different profiles of virulence, tested positive for the following genes: fimH (98.3%), malX (52.4%) traT (31.1%), cvaC (22.9 %), fyuA (19.6%), ibeA (19.6%), aer (13.1%) and papC (13.1%). Most isolates of frigates was characterized between phylogenetic groups D and B2, and the main serotypes were O1:H6, O2:H7, O25:H4, and O102:H10. For resistance to antibiotics, 60.1%% of the isolates were sensitive to 18 different antimicrobial agents tested on the other hand, the antimicrobial with the highest resistance was to tetracycline, which has proved ineffective in 20.1% of the samples studied. So far not been identified in STEC strains studied subjects on the other hand, isolates harbor genes that characterize ExPEC. These results show that most of the strains are potentially pathogenic to birds and may represent significant risk to health of sea birds, including how to configure agents relevant, emphasizing the importance of investigating the possible involvement of wild birds, especially navies in the epidemiological chain of diseases caused by E.coli. Such information could guide the research of selected diseases in populations of the frigates, as well as basing the adoption of any action in relation to aspects of animal and human health, which have the frigates as a link.
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Khandaker, MD Shahjahan Ali. "Economic analysis of diseases caused by VTEC (verotoxin producing e.coli) in Australia /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17335.pdf.
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Chahar, Sanjay [Verfasser]. "Functional characterization and molecular evolution of E.coli DNA methyltransferase (EcoDam) / Sanjay Chahar." Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2010. http://d-nb.info/1034988166/34.
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