Tesi: "Escherichia coli"

1

Schnepel, Jörn. "Klonierung, Expression und Charakterisierung kryptischer Fibronektin-Proteinasen". [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=969330472.

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2

Rang, Camilla. "Molecular and physiological characteristics of Escherichia coli growth in vitro and in the gastrointestinal tract of mice". Göteborg : [Dept. of General and Marine Microbiology, Göteborg University], 1997. http://catalog.hathitrust.org/api/volumes/oclc/38988157.html.

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3

Rosko, Jerko. "Osmotaxis in Escherichia coli". Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28947.

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Bacterial motility, and in particular repulsion or attraction towards specific chemicals, has been a subject of investigation for over 100 years, resulting in detailed understanding of bacterial chemotaxis and the corresponding sensory network in many bacterial species including Escherichia coli. E. Coli swims by rotating a bundle of flagellar filaments, each powered by an individual rotary motor located in the cell membrane. When all motors rotate counter-clockwise (CCW), a stable bundle forms and propels the cell forward. When one or more motors switch to clock-wise (CW) rotation, their respective filaments fall out of the bundle, leading to the cell changing orientation. Upon switching back to CCW, the bundle reforms and propels the cell in a new direction. Chemotaxis is performed by the bacterium through prolonging runs by suppressing CW rotation when moving towards nutrients and facilitating reorientation by increasing CW bias when close to a source of a harmful substance. Chemicals are sensed through interaction with membrane bound chemosensors. These proteins can interact with a very specific set of chemicals and the concentrations they are able to sense are in the range between 10-⁶ and 10-² M. However, experiments have shown that the osmotic pressure exerted by large (> 10-¹ M) concentrations of solutes, which have no specificity for binding to chemosensors (e.g. sucrose), is able to send a signal down the chemotactic network. Additionally, clearing of bacterial density away from sources of high osmolarity has been previously observed in experiments with agar plates. This behaviour has been termed osmotaxis. The aim of this doctoral thesis work is to understand how different environmental cues influence the tactic response and ultimately, combine at the network output to direct bacterial swimming. As tactic responses to chemical stimuli have been extensively studied, I focus purely on the response to non-specific osmotic stimuli, using sucrose to elevate osmolarity. I monitor the chemotactic network output, the rotation of a single bacterial flagellar motor, using Back Focal Plane Interferometry over a variety of osmotic conditions. Additionally, in collaboration with Vincent Martinez, I studied the effect of elevated osmolality on swimming speed of large (104) bacterial populations, using differential dynamic microscopy (DDM). I have found that sudden increases in media osmolarity lead to changes of both motor speed and motor clockwise bias, which is the fraction of time it spends rotating clockwise. Changes in CW Bias proceed in two phases. Initially, after elevating the osmolarity, CW Bias drops to zero, indicating that the motor is exclusively in the ‘cell run’ mode. This phase lasts from 2-5 minutes depending on the magnitude of the change in solute concentration. What follows then is a distinct second phase where the CW Bias is elevated with respect to the initial levels and this phase lasts longer than 15-20 minutes. In comparison, for defined chemical stimuli, the motor output resets after several seconds, a behaviour termed perfect adaptation. For changes of 100 mOsm/kg and 200 mOsm/kg in magnitude the motors speed up, often by as much as a factor of two, before experiencing a gradual slow down. Despite the slow down, motors still rotate faster 15-20 minutes after the change in osmolarity, than they did before. For changes of 400 mOsm/Kg in magnitude the motors decrease sharply in speed, coming to a near halt, recovering after 5 minutes and eventually, on average, speeding up. DDM studies of free swimming bacteria have shown that elevated osmolality leads to higher swimming speeds, in agreement with single motor data. Using theoretical models of bacterial swimming from the literature, it is discussed how this motor output, although different to what is expected for chemotaxis, is able to drive bacteria away from regions of space with high osmolalities. Additionally, I have started extending the work done with sucrose, to another solute often used to elevate osmolality, sodium chloride. While sucrose is outer membrane impermeable, NaCl can cross the outer membrane into the periplasmic space. Another layer of complexity is that NaCl has some specificty for the chemoreceptors. The preliminary results are shown and qualitatively agree with those obtain with sucrose.

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4

Rosser, Tracy. "Pathogenic potential of Escherichia coli O26 and sorbitol-fermenting Escherichia coli O157:NM". Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4427.

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Verocytotoxin-producing Escherichia coli (VTEC) are important human pathogens that may cause diarrhoea, haemorrhagic colitis and haemolytic uremic syndrome (HUS). Worldwide, non-sorbitol-fermenting (NSF) VTEC O157:H7 is the most common serogroup associated with HUS but several non-O157:H7 serogroups have emerged as causes of this disease. This research investigated the pathogenic potential of two non-O157:H7 serogroups: O26 and sorbitol-fermenting (SF) O157:NM. While VTEC O26 have emerged as a significant cause of HUS in continental Europe, human infections associated with this pathogen are uncommon in Scotland and generally only result in simple diarrhoea. The study characterised E. coli O26 isolates recovered from human infections in Europe and Scotland and isolates collected from Scottish cattle with the objectives to identify factors which may allow strains to cause more serious clinical disease and to investigate the potential of bovine VTEC O26 in Scotland to cause human infection. MLST analysis of housekeeping genes found little genetic variation in the genomic ‘backbone’ among the vast majority of E. coli O26 isolates. The gene for verocytotoxin 2 (vtx2) alone was carried by VTEC O26 isolates recovered from patients in continental Europe but was found in no Scottish human isolate, where the majority of isolates did not harbour a vtx gene. It was demonstrated that among the European VTEC O26 human isolates, 67% carried a specific allele within the promoter region for LEE1 and 87% harboured the tccP2 gene. In contrast, no Scottish VTEC O26 human isolate carried this allele or the tccP2 gene. The impact these genotypic characteristics have on the pathogenic potential of a strain remains uncertain. There were no clear differences in verocytotoxin titres, levels of LEEencoded protein secretion or levels of adherence to Caco-2 cells between VTEC O26 isolates recovered from human infections of varying severity. However, levels of LEE-encoded protein secretion from cattle isolates were generally higher than those from many of the human isolates. The differences in pathogenic potential between isolates are likely to be due to horizontally acquired DNA, including vtx2 carriage and the O-island-phage-associated effector protein repertoire. Further work is required to determine if the differences identified may also impact on shedding levels from cattle and therefore the likelihood of transmission to humans. Since 1988, SF VTEC O157:NM strains have emerged and have been associated with a higher incidence of progression to HUS than NSF VTEC O157:H7. This study investigated bacterial factors that may account for the increased pathogenic potential of SF VTEC O157:NM. While no evidence of toxin or toxin expression differences between the two VTEC O157 groups was found, the SF VTEC O157:NM strains adhered at significantly higher levels to a human colonic cell line. Under the conditions tested, curli were shown to be the main factor responsible for the increased adherence to Caco-2 cells. The capacity of SF VTEC O157:NM strains to express curli at 37C may have relevance to the epidemiology of human infections as curliated strains could promote higher levels of colonization and inflammation in the human intestine. In turn this could lead to increased toxin exposure and an increased likelihood of progression to HUS.

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5

Solecki, Olivia. "Explaining the urban and rural differences of Escherichia coli 0157 human infection in Grampian". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2008. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25203.

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6

Wu, Gilbert Kar Po. "Signal transduction responses to enteropathogenic Escherichia coli and Shiga toxin-producing Escherichia coli infections". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0007/MQ46054.pdf.

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7

Hesterberg, Micaela. "Charakterisierung einer unbekannten Redoxgruppe sowie der Konformation der NADH:Ubichinon-Oxidoreduktase (Komplex I) aus Escherichia coli". [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964821672.

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8

Grabowski, Gabriele. "Untersuchungen zum Mechanismus der Katalyse und zu In-vivo-Selektionssystemen für die Anreicherung von Mutanten der Restriktionsendonuklease EcoRI mit veränderter DNA-Bindungs- oder Spaltspezifität". [S.l. : s.n.], 1998. http://deposit.ddb.de/cgi-bin/dokserv?idn=954823028.

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9

Uhland, Kerstin. "Biochemische und genetische Charakterisierung der Trehalasen TreA und TreF von Escherichia coli". [S.l. : s.n.], 1997. http://deposit.ddb.de/cgi-bin/dokserv?idn=958497885.

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10

Franke, Sylvia. "Das Kupfer-transportierende CusCFBA-Efflux-System aus Escherichia coli". [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=967128110.

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11

Schneider, Frank. "Beta-Alaninaufnahme und Pantothensäureexkretion durch Escherichia coli". [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968826105.

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12

Schauer, Stefan. "Die Glutamyl-tRNA-Reduktase aus Escherichia coli rekombinante Produktion, Enzymmechanismus und biochemische Charakterisierung /". [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=97070304X.

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13

Niu, Lili. "Escherichia coli proteomics and bioinformatics". [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1240.

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14

Kelemen, Peter. "Quantitativer Nachweis chlorungsvorgeschädigter Escherichia coli". Frankfurt a.M, 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=964197170.

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15

Zundel, Michael. "Ribosome Degradation in Escherichia coli". Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/152.

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Upon termination of translation, the fate of ribosomes is determined largely by the rate at which cells are growing. During periods of exponential growth, ribosomes are rapidly recycled, translation is re-initiated, and the ribosomes are extremely stable. However, when nutrient sources become limiting, and ribosomes are not actively translating, they may become substrates for degradation. While this phenomenon is well known, details of how the process is initiated and what are the signals for degradation have, until now, remained elusive. Here, I present in vitro and in vivo data showing that free ribosome subunits are the targets of degradative enzymes, whereas 70S particles that remain associated are protected from such degradation. Conditions that increase the formation of subunits both in vitro and in vivo lead to enhanced degradation. Thus, the simple presence of free 50S and 30S subunits is sufficient to serve as the mechanism that initiates ribosome degradation. In order to identify RNases involved in ribosome degradation, both in vitro and in vivo assays were developed. Together, they have provided evidence for a multi-step degradation process involving both endo- and exoribonucleases. Examination of extracts from strains deficient in known RNases revealed that the endoribonucleases, RNase E and RNase G, may be involved in the initial cleavages. The resulting fragments, some of which are small enough oligoribonucleotides that they remain part of the acid-soluble fraction are degraded to mononucleotides primarily by the 3'-5' exoribonucleases, RNase R and polynucleotide phosphorylase.

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16

Champion, Matthew Maurice. "Functional proteomics in Escherichia coli". Texas A&M University, 2005. http://hdl.handle.net/1969.1/3194.

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Cells respond to their environment with programmed changes in gene expression. Cataloging these changes at the protein level is key towards understanding the physiology of an organism. Multi-subunit and multi-protein complexes are also important and pathogenic and physiologic processes. In order to identify expressed proteins and potential protein complexes, we utilized a combination of non-denaturing chromatography and peptide mass fingerprinting. This approach allows us to identify the components of protein mixtures, as well as information lost in traditional proteomics, such as subunit associations. Applying this methodology to cells at both mid-exponential and stationary phase growth conditions, we identified several thousand proteins from each cell-state of E. coli corresponding to hundreds of unique gene products. The copurification of proteins when fractionated at varying pHs could suggest the components of higher order complexes. This non-denaturing proteomic approach should provide physiological data unavailable by other means. The components of several known cellular complexes were also evident in this analysis. To characterize proteins associated with nucleic acid binding, we also performed proteome analysis on log and stationary phase cells grown in LB separated over heparin chromatography at neutral pH, which enriches for these proteins. The complete analysis of these identifications is discussed.

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17

Skoog, Karl. "Cell division in Escherichia coli". Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-62908.

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The Gram-negative bacterium Escherichia coli is a model system to describe the biochemistry and cell biology of cell division in bacteria. This process can be divided into three major steps. The first step involves the replication of the DNA, followed by an elongation step in which the cells become twice as long. In the last step the elongated cell constricts in the middle and the two daughter cells are separated. The cell division process in E. coli has been extensively studied for at least 50 years and a lot is known, however many details are still vague. New proteins involved in the process continue to be identified and the number of these proteins as well as the interactions among them are not yet fully known. It is therefore not completely understood how the contraction proceeds to form two daughter cells. In this thesis, I have carried out experiments that contribute to our understanding of cell division in E. coli. Using fluorescence microscopy I show that the contraction of the inner membrane in dividing E. coli proceeds in a linear fashion and that the periplasm closes after the cytoplasm. I have also analyzed the oligomeric state of two proteins involved in the cell division and I show that the early cell division protein ZipA can dimerize. This could explain how this protein can bundle FtsZ protofilaments, as it could bridge two protofilaments. Penicillin-binding protein 5 (PBP5) has been found to localize to the septum and it has been suggested to be connected to cell division. I have found that PBP5 forms a homo-oligomeric complex, most likely a dimer. The dimer can be modeled in a back-to-back conformation with the catalytic domains being flexible. This allows PBP5 to reach for pentapeptides of the peptidoglycan at different distances from the membrane. An understanding of the mechanisms used by the cell division proteins and their protein: protein interactions can be a first step towards determining new antibiotic targets.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: Manuscript.

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18

Robertson, Fiona E. "Starvation-survival in Escherichia coli". Thesis, University of Warwick, 1996. http://wrap.warwick.ac.uk/63636/.

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The population dynamics of carbon-starved E. coli K12 cultures was investigated. It was found that less cell lysis occurred when cells were previously grown in low glucose concentrations. Exponential-phase cells grown previously in 0.05% (w/v) glucose had survival rates comparable with their stationary-phase counterparts, suggesting that the rate of growth is more important in determining the outcome of starvation than the phase of batch culture growth. Long-termstarved cells (18-24 months) showed very little protein, DNA and RNA synthesis. Methionine was shown to alter the de novo synthesis protein profiles of longterm- starved cells and growth was seen to occur in the presence of methionine. This suggests that radio-labelling of proteins with 35S-methionine in these cells should be interpreted with care as the cells have been subjected to a nutrient upshift. Radio-labelling of proteins with 3H-leucine did not have the same effect. The ATP content of cells during prolonged incubation was shown to decrease in the first 48 hours incubation, increase until 5-7 days incubation then decrease after 7-8 days. After 13 days a slow, steady increase occurred. The ATP content of cells incubated for 16 days was higher than that of 48 hour-incubated cells. The physiology of long-term-starved cells was investigated with respect to their permeability to routine bacteriological stains ( e.g. DAPI, saffranin, Geimsa) and it was found that very few of these dyes were able to penetrate the cells, indicating that a decrease in cell permeability may be an important factor in survival as is seen in endospores of Bacillus species and swarmer cells of Rhodomicrobium vannielii and Caulobacter crescentus. Resistance of long-term starved cells to heat and biocide challenge was increased in comparison with exponential- and short-term (48 hour) stationary-phase cells and the resistance to biocides was shown to be retained through subsequent generations. Examination of the nucleoids of long-term-starved cells revealed that a more condensed form was present in cultures incubated for over 14 days, suggesting that dehydration of the DNA had occurred, similar to the situation found in endospores of Bacillus species and suggestive of dormancy. Analysis of outer-membrane proteins and lipopolysaccharide of long-term-starved cells showed that alterations occurred to the surface of the cells and it was demonstrated that hydrophobicity changes occurred. Hydrophobicity reached a maximum after 48 hours incubation then subsequently declined between days 2 and 3 which corresponded with an increase in cell numbers. Cell surface hydrophobicity was shown to be a potential method for separating heterogeneous, carbon-starved populations into homogeneous subpopulations. The data suggest that E. coli produces a dormant survival cell type which is morphologically and physiologically distinct from the parent cell.

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19

Burton, Claire Louise. "Norepinephrine, iron and Escherichia coli". Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342475.

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20

Kershaw, Christopher John. "Copper homeostasis in Escherichia coli". Thesis, University of Birmingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419690.

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21

Storey, A. "Exonuclease V of Escherichia coli". Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374741.

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22

Burke, Denis Anthony. "Ulcerative colitis and Escherichia coli". Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309075.

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23

McClellan, J. A. "Studies on Escherichia coli-mutabile". Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355195.

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24

Esteves, de Matos Ferrer Raquel Sofia NegraÌƒo Sequeira. "Metabolic quiescence in Escherichia coli". Thesis, University of Warwick, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397740.

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25

MacLean, Morag. "Methylglyoxal detoxification in Escherichia coli". Thesis, University of Aberdeen, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287604.

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Methylglyoxal is a naturally occurring toxic electrophile which, in E. coli, can be detoxified by several routes. This study has focused on the glutathione-dependent glyoxalase system. The genes encoding glyoxalase I (gloA) and glyoxalase II (gloB) were identified in the E. coli genome and cloned into the multi-copy plasmid pHG165. A null mutant in glyoxalase I (ΔgloA::KanR) was also created. Cells overexpressing glyoxalase I exhibit elevated rates of detoxification and enhanced tolerance of methylglyoxal. Analysis of the ΔgloA mutant has revealed that growth and viability are quite normal, unless the cell is challenged with methylglyoxal either added exogenously or synthesized by the cells. The mutant strain has a low rate of detoxification of methylglyoxal; only 20 -30 % of the level of the detoxification compared to the parent strain. Thus, the glutathione-dependent glyoxalase system was shown to be the dominant pathway for the methylglyoxal detoxification in E. coli. Glyoxalase I mutant cells rapidly lose viability when exposed to methylglyoxal as cell viability parallels the rate of detoxification. Glyoxalase I is the rate determining step in this pathway as overexpression of glyoxalase II does not affect the overall rate of metabolism of methylglyoxal. Methylglyoxal-elicited potassium efflux via the E. coli potassium channel KefB is enhanced in strains overexpressing glyoxalase I. Activation of KefB is diminished in the absence of functional glyoxalase I or in a strain overexpressing glyoxalase II. S-lactoylglutathione is the product of glyoxalase I and the substrate for glyoxalase II. This glutathione adduct is the major activator of the KefB and KefC systems. The glyoxalase I substrate, hemithiolacetal, could partially activate KefB and KefC when they were overexpressed on a multi-copy plasmid.

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26

Rembacken, Björn Joakim. "Escherichia coli and ulcerative colitis". Thesis, University of Leicester, 2003. http://hdl.handle.net/2381/29440.

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27

Blake, Catherine E. "Illegitimate recombination in Escherichia coli". Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/15058.

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The factors affecting deletion of long DNA palindromes from high copy number cloning vectors are investigated with particular reference to the mode of deletion and it is shown that the deletion of a 571 bp palindrome deleted from pMS7 using 3 bp repeats. A shorter 109 bp palindrome deleted from a related plasmid using 7 bp direct repeats and the mode of deletion is unaffected by the genotype of the host strain. There also appears to be a bias for the deletion of palindromic sequences on the lagging strand of a replication fork. It is also shown that in a wild-type E. coli strain there is inhibition of plasmid multimerization if the plasmids carry long palindromic sequences. It is proposed that the lack of plasmid multimers in this background is a result of the removal of palindromic sequences form the plasmids by the SbcCD protein of E. coli. In an sbcCD strain, plasmid DNA bearing long palindromes is not detected in a monomeric form, instead the DNA is present in multimeric forms, predominantly dimers. The ability to form plasmid multimers in this background may help to stabilise the palindromic sequences. The behaviour of palindromic sequences carried on plasmids is also investigated in recA sbcCD strains with a view to the correct choice of E. coli strain for the cloning of long palindromic sequences. Finally, the influence of an sbcCD mutation on the formation of araB-lacZ cistron fusion is investigated. The SbcCd proteins are thought to have a role in the processing of secondary structures formed by palindromic sequences. The formation of araB-lacZ fusions occurs via a strand transfer complex involving a complex genome rearrangement and secondary structure. Although an sbcCD mutation did not affect the kinetics or sequences specificity of fusion formation it is possible that SbcCD might have a role in processing the strand transfer complex which is not easily detected.

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28

Davis, Elaine Olive. "Xylose transport in Escherichia coli". Thesis, University of Cambridge, 1986. https://www.repository.cam.ac.uk/handle/1810/270399.

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29

Saragosti, Jonathan. "Chimiotactisme collectif de Escherichia coli". Paris 6, 2010. http://www.theses.fr/2010PA066329.

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La bactérie Escherichia coli nage dans les liquides au moyen de ses flagelles en suivant une trajectoire qui est une marche aléatoire ˆ trois dimensions. Celle-ci est biaisée en réponse ˆ des gradients chimiques. Ce microorganisme chimiotactique peut ainsi s'orienter vers les sources de nourriture et établir une communication avec ses congénères lorsqu'il sécrète des molécules attractives. Dans des géométries confinées, où les gradients chimiques peuvent persister, les bactéries s'attirent ainsi mutuellement alors que la population dans son ensemble migre la recherche de nutriments. On observe alors des fronts de migration dont la dynamique complexe a fait l'objet de nombreux travaux théoriques initiés par Keller et Segel. Ce travail de thèse a consisté tout d'abord en la réalisation d'un montage expérimental permettant une étude quantitative de ces phénomènes. La bonne reproductibilité des expériences nous a permis d'une part de caractériser ce comportement collectif dans différentes conditions, mais aussi d'obtenir des informations sur les mouvements individuels au sein des fronts de migration. En particulier, nous avons pu mettre en évidence une modulation chimiotactique et active de la réorientation de ces bactéries le long de leurs trajectoires dans des gradients chimiques. En l'absence de ces gradients, nous montrons qu'un mécanisme effectif de diffusion rotationnelle permet de donner une description de ces phases de réorientation aléatoire. Tout au long de cette thèse, nous avons confronté nos résultats ˆ un modèle cinétique original qui intègre les observations expérimentales faites aux échelles individuelle et collective dans la description de ces phénomènes.

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30

Broadhead, Richard Ian. "Metabolic flexibility in Escherichia coli". Thesis, University of Aberdeen, 1998. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU104201.

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This study of the relationship between heterologous protein production and bacterial growth has shown that foreign protein can account for as much as 30% of the total cell protein without the specific growth rate being affected. Higher levels of foreign protein production are achieved at lower growth rates. Foreign protein is synthesised without any increase in ribosome number or ribosome activity occurring in the recombinant cells relative to their parent strain, i.e. the capacity of parental and recombinant cells to synthesise protein is the same. These observations are explained in terms of a model in which Escherichia coli proteins are be divided into two types. Type I proteins are involved in the processes of transcription and translation. Type 2 proteins are those which serve other purposes. The model suggests that the synthesis of type 2 proteins will be decreased in order to accommodate foreign protein production. This implies that some Escherichia coli proteins are overproduced relative to the amount of that protein that is essential to the cell to maintain growth. Two dimensional electrophoresis showed that there was a decrease in some host cell protein levels between parental and recombinant cells. An increase in the levels of molecular chaperone proteins in recombinant cells grown under some conditions was observed. These data are explained in terms of our current understanding of the regulation of molecular chaperone production. The data obtained are discussed in relation to our current understanding of the growth of bacteria and the reported effects of high levels of foreign protein production on bacterial physiology.

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31

Slade, Kristin M. Pielak Gary J. "Protein diffusion in Escherichia coli". Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2508.

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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2009.
Title from electronic title page (viewed Oct. 5, 2009). " ... in partial fulfillment of the requirements for the degree of Doctorate of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.

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32

Fox, Sian L. "Verocytotoxin expression in Escherichia coli". Thesis, University of Warwick, 1992. http://wrap.warwick.ac.uk/110785/.

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In order to examine the physiology of verotoxin (VT) production in vitro, it was necessary to develop an assay to enable specific measurement of VTl and VT2 expression. Initial efforts focussed on quantifying VTl and VT2 messenger RNA synthesis. RNA extraction and electrophoresis was consistently achieved, however, subsequent probing of Northern filters was not successful. A gene fusion between the slt-ll operon and the transposon vector TnphoA, such that expression of the phoA gene was brought under the control of the 5/MI promoter, was then developed. The presence and site of insertion of TnphoA within the s/MI operon was confirmed by restriction and sequence analysis, and a single copy fusion derivative within the VT2-producing E. coli strain E32511 was then obtained by exchange recombination. Use of the resulting single copy fusion derivative (E32511 SLF22/1) and a plasmid encoded slt-\. fïnphoA fusion (pSC105) demonstrated significant differences in the synthesis, secretion and localisation abilities of VTl and VT2 during growth under aerobic, anaerobic and iron limiting conditions. These characteristics could have important implications on the relative abilities of the two toxins to cause disease in vivo.

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33

McAuliffe, Laura. "Stress responses of Escherichia coli". Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248098.

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34

Harding, Amanda. "Mechanisms of acid protection mediated by periplasmic chaperones in Escherichia coli". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25744.

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35

Ozyamak, Ertan. "The analysis of methylglyoxal detoxification and stress responses in Escherichia coli". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources. Restricted: no access until Nov. 20, 2011, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=59008.

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36

Silva, Mídana Felismino da. "Escherichia coli e a resistência antibiótica: uma análise do padrão de evolução da resistência da Escherichia coli aos antibióticos no distrito de Castelo Branco, de 2006 a 2008". Master's thesis, Universidade da Beira Interior, 2009. http://hdl.handle.net/10400.6/1048.

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Abstract (sommario):

O aumento inabalável da resistência da E. coli aos antibióticos e as diferenças geográficas na sua prevalência levam com que seja imprescindíveis os estudos locais de prevalências e das tendências evolutivas das resistências. Objectivo: Analisar a prevalência e as tendências evolutivas da resistência da E. coli no distrito de Castelo Branco de Janeiro de 2006 a Dezembro de 2008 Método: Trata-se de um estudo descritivo com uma abordagem quantitativa. Foram analisadas todos os resultados dos testes de sensibilidade aos antibióticos efectuados nos laboratórios de microbiologia do Centro Hospitalar da Cova da Beira e do Hospital Amato Lusitano, obtidos mediante sistemas automatizados para identificação e antibiograma (VITEK®) durante aquele período. Os isolados foram incluídos com base no perfil de sensibilidade e no tempo de isolamento. Resultados: Foram estudados 1138 isolados no HAL e 1714 no CHCB. Observou-se uma elevada taxa de resistência da E. coli à penicilina (> 40%) em ambos os hospitais durante os três anos em causa. Entre os isolados no CHCB observou-se uma tendência decrescente nas taxas de resistências entre 2007 e 2008, à excepção da taxa de resistência à ciprofloxacina que tende a aumentar. Relativamente a resistência dos isolados no HAL, observou-se uma tendência à estabilizar porém, as taxas de resistência à ampicilina e à gentamicina tendem a aumentar. No CHCB observou-se também uma reemergência dos isolados da E. coli produtores de ESBL. No HAL, apesar de se verificar uma ligeira diminuição na sua taxa de prevalência, esta ainda permanece elevada. Conclusão: O presente trabalho revelou as diferenças nas variações evolutivas das taxas de prevalência da resistência da E. coli entre duas regiões do distrito de Castelo Branco à semelhança das encontradas em outras investigações em diferentes regiões e países. Comprovando a necessidade de desenvolvimento de um compromisso local constante, no combate as resistências bem como na adaptação dos protocolos de tratamentos às realidades locais.
Background: The unwavering increase of resistance of E. coli to antibiotics and the geographical differences in its prevalence entail the necessity for local studies of its prevalence and trends of resistance. Objective: To assess the prevalence and trends of resistance of E. coli in the district of Castelo Branco from January 2006 to December 2008. Method: This is a descriptive study with a quantitative approach. All the results of tests of sensitivity to antibiotics made in the microbiology laboratories of Cova da Beira Hospital Center and the Hospital Amato Lusitano, obtained by automated systems for identification and antibiogram (Vitek ® ) during that period was analyzed. The isolates were included based on the profile of sensitivity and time of isolation. Results: The total of 1138 Isolates in HAL and 1714 in CHCB were studied. There was a high rate of resistance of E. coli to penicillin (> 40%) in both hospitals throughout the three year period. Among the isolates in CHCB there was a decreasing trend in resistance rates except for the rate of resistance to ciprofloxacin which tends to increase. Among the isolates in HAL there was a tendency to stabilize but the rates of resistance to ampicilin and gentamicin tends to increase. In CHCB there was also a reemerging of the isolates of ESBLproducing E. coli. In HAL, although there was a slight decrease, its prevalence rate remains high. Conclusion: This study revealed differences in evolutionary changes in the prevalence of resistance of E. coli between two regions in the district of Castelo Branco as founded in the other investigations in different regions and countries. This demonstrates the need for development of a constant local effort in combating the resistance and adaptation of therapeutics protocols to local realities.

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Nemec, Michelle D. Drummond Massengale Andrea Rene. "Analysis of Escherichia coli populations in a large watershed". Waco, Tex. : Baylor University, 2008. http://hdl.handle.net/2104/5174.

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Robelek, Rudolf. "Untersuchungen zur Transkriptionsantitermination in Escherichia coli". [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965257223.

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39

Landgraf, Frank Thomas. "Expression von Holophytochrom in Escherichia coli". [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968412157.

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40

Dadgar, Ashraf. "Detection of enterohemorrhagic Escherichia coli (EHEC)". Thesis, Uppsala University, Department of Medical Biochemistry and Microbiology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6011.

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Abstract (sommario):

Escherichia coli is a natural inhabitant of the intestines of both humans and animals, but there are also several pathogenic types of E. coli which cause disease in humans.

Strains of enterohemorrhagic E. coli (EHEC) have been associated with outbreaks of diarrhea, hemorrhagic colitis and hemolytic uremic syndrome in humans. Most clinical signs of disease arise as a consequence of the production of shigatoxin 1 and 2 or combination of these toxins. Other major virulence factors include EHEC hemolysin and intimin, the product of the eae gene that is involved in attaching and effacing adherence phenotype. EHEC has also been associated with uncomplicated diarrhea.

The capacity to control EHEC disease and to limit the scale of outbreaks is dependent upon prompt diagnosis and identification of the source of infection.

The principal reservoirs of EHEC are cattle and food products, which presumably have come into contact with domestic animal manure and/or are inadequately pasteurised, these are important vehicles of infection.

In the present study, the PCR technique with primers detecting the verocytotoxin genes was shown to be a possible method to screen for and identify EHEC.

In summary stx genes were detected in 16 samples of 228 sampels and the eae gene was detected in 2 samples using PCR.

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41

Ibwala, Nsatam-Yamumi. "Escherichia coli :hémagglutination, hémolyse et adhésion". Doctoral thesis, Universite Libre de Bruxelles, 1989. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/213209.

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42

Martin, Mathew Paul. "Mechanistic studies of Escherichia coli transketolase". Thesis, University of Exeter, 2008. http://hdl.handle.net/10036/88813.

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The enzyme transketolase is found in nature as part of the Pentose Phosphate Pathway to rearrange large sugar phosphates. It also is an important enzyme for carboncarbon bond formation for industrial biocatalysis. The work presented in this thesis describes the purification, crystallisation, characterisation and structural determination of the recombinant Escherichia coli transketolase complexed with the substrate hydroxypyruvate and potential inhibitor fluoropyruvate. The native transketolase and the transketolase-hydroxypyruvate structures were solved to a 1.18 and 1.05 Å resolution respectively. The transketolase structures show a chain of ordered water molecules spanning a distance of 20 Å between the two active sites. The water molecules are linked via a network of hydrogen bonds and they are proposed to facilitate proton transfer between the two-thiamine pyrophosphate molecules, thereby providing a method of communication between the two active sites of the enzyme. The transketolase-hydroxypyruvate structure shows the hydroxypyruvate substrate forming a covalent bond to the thiamine pyrophosphate thereby creating a a,b-dihydroxyethyl–thiamine pyrophosphate complex within the enzyme active site. The novel transketolase-fluoropyruvate structure solved to a 1.60 Å resolution, it produced a snapshot image of the ketol donor prior to formation of the active enamine intermediate. The trapped fluoropyruvate molecule is shown to form an angle that varies from the accepted Burgi-Dunitz angle of 109.5° for nucleophilic attack. However, this is inconclusive due to the low occupancy of the fluoropyruvate. In addition, kinetic studies were performed on the recombinant E. coli transketolase to investigate the inhibitory role of fluoropyruvate during the enzymatic reaction. The active site recombinant E. coli transketolase mutants H26Y and D469Y have been also been purified and characterised. The mutant H26Y complexed with fluoropyruvate was crystallised and its structure determined to 1.66 Å resolution. This structure has given an insight into why this mutation results in the formation of the opposite D-enantiomer of erythrulose rather than the L-erythrulose produced by the wild-type transketolase enzyme. The thesis also includes the purification, crystallisation, characterisation and Xray diffraction studies of the commercially useful oxygenating enzyme, 2,5- diketocamphane 1,2-monooxygenase from Pseudomonas putida. The recombinant dimeric oxygenase component of this enzyme has been crystallised and its structure solved to 1.4 Å resolution.

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Baptist, Guillaume. "Réseaux de régulation chez Escherichia coli". Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00772446.

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L'adaptation d'une bactérie aux changements de son environnement est contrôlée par un réseau de régulation large et complexe, faisant intervenir de nombreux acteurs et modules différents. Dans ce travail, nous avons étudiés un module de régulation spécifique, contrôlant l'adaptation de la bactérie Escherichia coli à un changement de sources de carbone. Dans un milieu contenant du glucose et de l'acétate, la croissance est divisée en deux phases : les bactéries utilisent préférentiellement le glucose et commencent à métaboliser l'acétate qu'après l'épuisement du glucose. En effet, la présence du glucose réprime la transcription d'un gène nécessaire à la croissance sur acétate, le gène acs (codant pour l'acétyl-CoA synthétase). Le mécanisme régulateur fait intervenir le facteur de transcription Crp-AMPc et le système de transfert de phosphate (PTS), qui permet l'import du glucose. Plusieurs modèles décrivent en détail la cascade de réactions moléculaires à l'origine de cette " répression catabolique ". Cependant, certaines de nos observations expérimentales ne sont pas correctement prédites par les modèles actuels. Ces modèles doivent être révisés ou complétés. L'outil majeur que nous employons pour les expériences est la fusion transcriptionnelle : une région promotrice fusionnée en amont d'un gène rapporteur (GFP, luciferase). Avec ces constructions, nous mesurons la dynamique de l'expression génique dans différentes souches (mutants) et différentes conditions environnementales. Les observations à l'échelle de la population sont corroborées par des mesures similaires à l'échelle de la cellule unique. Nous utilisons cette même technologie pour construire de petits systèmes synthétiques qui sondent davantage le phénomène de répression catabolique. Nous avons ainsi créé un interrupteur génétique dont le fonctionnement est contrôlé par le flux glycolytique et nous avons construit un petit système de communication intercellulaire basé sur la molécule AMPc. Enfin, nous proposons une manière originale de mesurer l'état métabolique des cellules en utilisant la dépendance énergétique de la luciferase.

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Baaghil, Suzanne. "Mechanistic studies of Escherichia coli bacterioferritin". Thesis, University of East Anglia, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398799.

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45

Moore, Tim. "The RdgC protein of Escherichia coli". Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250574.

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46

Ince, J. E. "Formation of ethylene by Escherichia coli". Thesis, University of Kent, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355189.

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47

McHugh, Jonathan. "The fur modulon of Escherichia coli". Thesis, University of Reading, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288684.

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48

Timms, Andrew Robert. "Spontaneous mutagenesis in stressed Escherichia coli". Thesis, Open University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244410.

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49

Orchard, Lisa Marguerite Denise. "The 1-phosphofructokinase of Escherichia coli". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259621.

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Maiden, M. C. J. M. "Arabinose-proton symport in Escherichia coli". Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383815.

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Tesi sul tema "Escherichia coli"

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