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Tesi sul tema "Escherichia coli Genetics"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 6 settembre 2023

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1

Baldwin, Thomas John. "Disease mechanism of enteropathogenic Escherichia coli". Thesis, University of Leicester, 1990. http://hdl.handle.net/2381/34445.

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Colonization of gut mucosal surfaces by enteropathogenic Escherichia coli (EPEC) elicits a severe persistant diarrhoea in infants and young children without elaboration of enterotoxins or tissue invasion. The formation of a distinct ultrastructural lesion involving intimate adherence to cell surfaces, loss of microvilli and membrane perturbations, however, has for some time been recognized as an important component of pathogenesis, but the processes involved in lesion formation and its relevance to the disease state remained obscure. In this study intimate adherence of EPEC to surfaces of cultured cells has been shown to elicit specific changes reminiscent of cellular activation by various hormones and growth factors via signal transduction pathways. The formation of two second messengers, 1,4,5-inositol trisphosphate and diacylglycerol by the activity of phospholipase C (PLC) on membrane phosphatidylinositol lipids is known to promote release of calcium from intracellular stores and to activate protein kinase C (PKC) respectively. Therefore the observed intracellular calcium elevation, calcium-dependent actin accretion at sites of bacterial attachment, release of glycosyl-phosphatidylinositol (GPI) anchored proteins, eventual loss of host cell viability, and phosphorylation of target cell proteins on EPEC infection of cultured cells, are consistent with a mechanism of diarrhoeagenesis that involves activation of a host cell signal transduction pathway terminating in PLC activity. I propose that the rapid onset of severe secretory diarrhoea associated with EPEC infections is induced by phosphorylation of particular ion transport proteins in the microvillus membrane, mediated by calcium-dependent kinases and PKC. In addition reduction in the surface area of infected regions of the gut, which may itself enhance hypersecretion by preventing absorption, can be explained by calcium-dependent breakdown of the microvillus cytoskeleton.

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2

Lim, C. K. "Cloning of Streptomyces genes in Escherichia coli". Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373850.

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3

Chua, K.-L. "Plasmid recombination in Escherichia coli K-12". Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383777.

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4

Morgan, Brian Alexander. "The regulation of rpoBC in Escherichia coli". Thesis, University of Edinburgh, 1986. http://hdl.handle.net/1842/15431.

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5

Agostinho, Juliana Maria Avanci [UNESP]. "Diversidade genética, fatores de virulência e perfis de susceptibilidade a antimicrobianos de isolados de Escherichia coli provenientes do útero, da boca e das fezes de cadelas com piometra". Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/108413.

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Made available in DSpace on 2014-08-13T14:50:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-07-26Bitstream added on 2014-08-13T18:01:12Z : No. of bitstreams: 1 000735330_20140826.pdf: 26004 bytes, checksum: 80491d16dd561bc066d6dacbdc900451 (MD5)
A piometra canina é uma enfermidade caracterizada pela inflamação do útero com acúmulo de exsudatos, acometendo principalmente fêmeas adultas. Ocorre na fase lútea do ciclo estral em decorrência de alterações hormonais e infecção bacteriana. É reconhecida como uma das principais causas de morte em cadelas e a Escherichia coli é o principal patógeno associado a esta doença. O objetivo deste estudo foi isolar e identificar cepas de E. coli provenientes de conteúdo intra uterino, boca e fezes de cadelas diagnosticadas com piometra, estudar a prevalência de genes codificadores de fatores de virulência uropatogênicos das cepas obtidas testando ainda a semelhança genética entre as cepas isoladas de conteúdo intra uterino e boca e avaliar a susceptibilidade “in vitro” das bactérias isoladas frente a 12 agentes antimicrobianos. Setenta cepas de E. coli, 25 provenientes do conteúdo intra uterino, 26 provenientes da boca e 19 provenientes das fezes, isoladas de 6 cadelas foram examinadas por PCR. Entre as cepas examinadas, 67 (95,7%) foram positivas para o gene fim, 19 (27,1%) foram positivas para iss, 18 (25,7%) foram positivas para hly , 13 (18,5%) foram positivas para iuc e 12 (17,1%) foram positivas para usp. Três animais apresentaram grande similaridade entre as cepas de E. coli isoladas do conteúdo intra uterino e da boca, através da análise da diversidade genética realizada mediante emprego da técnica REP-PCR, ERIC-PCR e BOX-PCR. Resistência antimicrobiana predominante foi detectada para cefalotina (67,1%), ampicilina (65,7%), tetraciclina (61,4%) e nitrofurantoina (58,5%) entre as cepas isoladas. Resistência a múltiplos antimicrobianos foi detectada em 12 (48,0%) dos isolados do conteúdo intra uterino, em 22 (84,6%) dos isolados da boca e em 14 (73,6%) dos isolados das fezes...
Canine pyometra is a disease characterized by the inflammation of the uterus with accumulation of purulent discharge, affecting mainly adult animals. Occurs in the luteus phase of the estrus cycle in result of hormone alterations and generally is associated with bacterial infections. It is recognized as one of the main causes of disease and death in the bitch and Escherichia coli is the major pathogen associated with this disease. The aim of this study was to research, isolation and identification of Escherichia coli strains from intrauterine contents, mouth and feces of bitches diagnosed with pyometra, studying the prevalence of uropathogenic virulence factors genes in strains isolated, still testing the genetic similarity among strains isolated from intrauterine contents and mouth and evaluate the susceptibility in vitro of the isolated bacteria to 12 antimicrobial drugs. Seventy E. coli strains, 25 from intrauterine contents, 26 from mouth and 19 from feces isolated from six bitches were examined by PCR. Among the strains 67 (95.7%) were positive for fim, 19 (27.1%) were positive for iss, 18 (25.7%) were positive for hly, 13 (18.5%) were positive for iuc and 12 (17.1%) were positive for usp. Multiple antimicrobial resistance was detected for cephalothin (68.0%), nalidixic acid (56.0%) and ampicillin (56.0%) among the pyomera E. coli isolates. Multidrug resistance was found in 12 (48.0%) of the isolates from pyometra, in 22 (84.6%) of the isolates from mouth and in 14 (73.6%) of the isolates from feces...

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6

Sendy, Bandar. "Studies on transcription in Escherichia coli". Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7576/.

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The expression of genes is tightly controlled, predominantly at the point of transcription. RNA polymerase (RNAP) must first bind to a deoxyribonucleic acid (DNA) promoter upstream of a gene to transcribe it. However, the ability of RNAP binding is dictated by the core promoter DNA sequence, the presence of transcription activator or repressor proteins and numerous other factors. The strength of promoters has been indirectly measured. Only a few studies have attempted to directly address the RNAP flux through transcription units, and further studies are still required. In the current study, the aim was to directly correlate RNAP gene transcription with the strength of core promoter elements. To do that, I employed the direct method of chromatin immunoprecipitation (ChIP), followed by quantification of immunoprecipitated DNA. For promoter regions, this method directly measures the occupancy by RNAP; for regions within transcription units, the flux of the RNAP was deduced. A range of semisynthetic promoters, with different combinations of core promoter elements to obtain different levels of expression, was used to validate our method. This direct method enabled the calculation of “promoter competitivity”, “promoter occupancy index” (POI), RNAP “escape index” (EI), “fragment occupancy percentage” (FOP) and the time interval between transcribing RNAPs (Tint). On the basis of Tint, the number of RNAPs crossing any DNA sequence of interest per second (polymerase per second; PoPS) was calculated. Surprisingly, the results of the present study revealed that the RNAPs are well separated during transcription of the \(lac\) operon.

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7

Ennis, Don Gregory. "Genetics of SOS mutagenesis". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184602.

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Previous genetic evidence suggested that RecA was required in SOS mutagenesis for its regulatory role and perhaps some other nonregulatory role (Mount, 1977; Blanco et al., 1982). I undertook a genetic study which confirmed the above studies and provided further evidence that RecA protein appeared to have a dual "role in mutagenesis; first, the cleavage of LexA repressor for the derepression of specific SOS genes and second, one or more additional role(s). For these studies a new phage mutagenesis assay was developed which allows rapid scoring of SOS mutagenesis in a large number of host mutants. I next conducted a genetic analysis to determine if the newly defined RecA mutagenesis function was separable by mutation from the numerous other phenotypes which are known to be influenced by RecA protein. From the study of recA mutants it appears that the RecA mutagenesis function(s) is genetically separable from the following RecA phenotypes: LexA cleavage, lambda cI repressor cleavage, UV resistance and homologous recombination. In addition, I discovered that the LexA cleavage function and lambda cI cleavage function is also separable. I also studied in some detail the novel genetic properties that I uncovered for recA432 mutant strains. recA432 was defined as a mutagenesis defective allele (Kato and Shinoura, 1977). LexA cleavage in recA432 cells was more easily induced that in recA⁺ cells, causing lethal filamentation of these mutant cells even at very low UV doses. I concluded that the basis for the Mut⁻ phenotype was this strain's propensity to lethally filament, which complicated the detection of mutant cells. In another set of experiments, I examined the regulatory requirements for SOS mutagenesis and Weigle phage-reactivation; I wanted to determine which SOS operons must be derepressed for this process. lexA(Ind⁻) mutant cells are defective in mutagenesis because they cannot derepress specific SOS genes required in this process. I found that the selective derepression of umuDC was sufficient to restore mutagenesis to these lexA(Ind⁻) mutants; however, derepression of umuDC and recA was required for phage reactivation.

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8

Woodgate, R. "A mechanism for UV mutagenesis in Escherichia coli". Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375858.

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9

Hallewell, Jennyka, e University of Lethbridge Faculty of Arts and Science. "Shiga toxin-producing bacteriophage in Escherichia coli O157:H7". Thesis, Lethbridge, Alta. : University of Lethbridge, Deptartment of Biochemistry, 2008, 2008. http://hdl.handle.net/10133/776.

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Shiga toxin-producing E. coli (STEC) including E. coli O157:H7 are potential food and water borne zoonotic bacterial pathogens capable of causing outbreaks of severe illness in humans. The virulence of E. coli O157:H7 strains may be related to the type of Stx produced and several Stx2 variants have been identified which appear to differ in their ability to cause disease. Two lineages exist within O157 strains where lineage I is associated mainly with human and bovine isolates and lineage II is associated mainly with bovine isolates. The goal of this study was to identify and characterize a lineage II EC970520 Stx2c phage and determine if variations in the phage compared to Stx2 phage found within the lineage I strain, EDL933, can result in differences in virulence observed between the lineages. This study suggests: 1) that the lineage II strain EC970520 contains a highly heterogeneous Stx2c variant phage; 2) that location of integration of the phage within the genome of a bacterium may be important for host selection; 3) that EC970520 Stx2c phage genes are lineage II specific but only a subset of EDL933 phage genes are lineage I specific; 4) that differences in the stability of phages within bacteria contribute to the evolution of new pathogens; 5) that variation in phage genes can be used to detect different strains of E. coli O157:H7 and other STEC; and 6)that the type of phage may result in phenotypic differences between lineages and occurrence of human disease. Results of this study indicate that lineage II strains may be less virulent than lineage I strains due to specific genetic differences and the ability to release phage which is important to the evolution of new pathogenic strains.
xv, 162 leaves : ill. ; 29 cm.

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10

Miao, Yuanying, e 缪元颖. "The localization of E. coli persistent gene products". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45554791.

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11

Ho, Joanne Ming-Li. "Towards Sense Codon Reassignment in Escherichia Coli". Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:26718706.

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Expansion of the genetic code through engineering of the translation machinery has vastly increased the chemical repertoire of the proteome. Incorporation of non-canonical amino acids (ncAAs) entails use of engineered aminoacyl-tRNA synthetase (AARS)•transfer RNA (tRNA) pairs that do not interact with the canonical aminoacylation machinery. Although engineered AARSs are selected for their ability to utilize ncAAs and discriminate against the twenty canonical amino acids, many utilize other ncAAs – a phenomenon known as polyspecificity. Specific incorporation of multiple ncAAs in a single polypeptide requires knowledge of the polyspecificities of engineered and wild-type AARSs, which this thesis explores. Recoding of the UAG and UGA stop codons has facilitated the incorporation of more than 150 ncAAs. Given the abundance of degenerate sense codons, potentially many more ncAAs can be incorporated. This thesis investigates the malleability of sense codons, and presents the findings from two engineered systems that change the amino acid designations of sense codons. In bacteria, an mRNA minihelix (selenocysteine insertion sequence, SECIS) recruits a dedicated elongation factor SelB that incorporates selenocysteine (Sec) at a UGA stop codon. Replacement of the UGA codon revealed that at least 58 of the 64 codons could be recoded to Sec, thus demonstrating that the Sec machinery is able to outcompete cognate aminoacyl-tRNAs. Next, an engineered pyrrolysyl-tRNA synthetase developed to incorporate 3-iodo-L-phenylalanine (3-I-Phe) was used to reassign sense codons in wild-type E. coli. To quantify the amino acids incorporated at a specific serine AGU codon in a super-folder GFP reporter protein, a selected reaction monitoring (SRM) experiment was performed – the incorporation yields (65±17% 3-I-Phe, 33±17% serine, 1±1% phenylalanine, and 1±1% threonine) revealed the intricacies of tRNA competition during aminoacylation and decoding. Reassignments of other serine (AGC, UCG) and leucine (CUG, UUG, UUA) codons were less efficient, thus providing a guideline for the choice of sense codons to reassign in future studies. Since the engineered AARS•tRNA pair so efficiently reassigns a serine AGU codon in wild-type E. coli, it should provide complete reassignment in genomically recoded organisms that feature an “open” codon.
Medical Sciences

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12

Picksley, S. M. "Inducible recombination and DNA repair in Escherichia coli K12". Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332729.

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13

Taylor, L. "The recB and recC gene products of Escherichia coli". Thesis, University of Newcastle Upon Tyne, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355080.

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14

Dave, Emma. "The physiology of the Escherichia coli pyruvate dehydrogenase complex". Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364242.

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15

Doyle, Noel James. "Plasmid mediated error prone DNA repair in Escherichia coli". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262031.

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16

Pickett, M. A. "Regulatory aspects of the gua operon of Escherichia coli". Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381272.

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17

Malloch, Richard Anthony. "Ribonuclease III processing of Escherichia coli rpoBC messenger RNA". Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/15259.

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18

Stumpf, Jeffrey D. "Polyphosphate kinase regulates DNA polymerase IV in Escherichia coli". [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3253637.

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Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2007.
Title from PDF t.p. (viewed Nov. 19, 2008). Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 0748. Adviser: Patricia L. Foster.

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19

Cowan, Peter J. "Controlled production of tryptophan by genetically-manipulated strains of Escherichia coli". Connect to thesis, 1992. http://repository.unimelb.edu.au/10187/1020.

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The tryptophan productivity of the genetically-manipulated strain JP4153 was increased 2.5-fold by introducing pMU78, a medium copy-number plasmid carrying a feedback-resistant trp operon. JP4153(pMU78) produced 23.5 g/l of tryptophan at a rate of 0.7 g/l/h when grown at 37 degrees C in a defined glucose and ammonium salts medium in a bench-scale fermentor.
During prolonged cultivation in the presence of antibiotic, the recombinant strain generated faster-growing, production-defective variants, which harboure mutated derivatives of pMU78. Insertion sequences were responsible for the two predominant types of mutation. The plasmid element ISI02 mediated deletions extending into the promoter-proximal region of the plasmid-borne trp operon. ISI0-Right, a chromosomal element, inserted into the promoter/trpE region of the plasmid. Three methods were employed to increase the structural stability of JP4153(pMU78) during the course of the production process. First, the growth of seed cultures was carried out at 30 degrees C, the permissive temperature for the trpS378 mutation carried by the host strain. Second, the seed culture medium was modified by the addition of yeast extract, which appeared to reduce the selective disadvantage conferred by the plasmid. Third, ISI02was deleted from pMU78 to create pMU88. (For complete abstract open document)

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20

Park, Simon Fearon. "The biochemistry and genetics of osmoregulation in Escherichia coli". Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254420.

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21

Xiao, Minfeng, e 肖敏鳳. "The regulatory mechanisms and physiological functions of an outer membrane protein opmpW during anaerobic adaptation in Escherichia coli". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/206531.

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ompW encodes a widespread outer-membrane porin protein in Gram-negative bacteria. It has been implicated in bacterial responses to various antibiotics and environmental substances such as antibiotics, drugs and mouse mucus etc. Little is known, however, about its regulation and physiological roles during bacterial stress responses. Recently, comparative genomics studies revealed that the ompW gene is a core regulon of the global transcription factor FNR (Fumarate Nitrate Reduction) which mediates the transition from aerobic to anaerobic lifestyle of facultative bacteria. Anaerobiosis represents a predominant challenge encountered by many bacteria in their natural ecological niches and human hosts. This thesis thus aims to elucidate the molecular mechanism of FNR-dependent regulation of ompW expression and its relevance to the anaerobic adaption of the model facultative bacterium E. coli. Regulation of ompW expression by several other key physiological signals related to the anaerobiosis of E. coli, as well as the physiological significance, is also explored systematically. In the first half of the thesis, FNR-dependent regulation of ompW is confirmed by in vivo transcriptional activity assay, and then further confirmed at mRNA and protein level by RT-qPCR and western blotting. EMSA combined with transcriptional activity assay reveals that FNR directly binds with two sites centered at -81.5 and -126.5 bp respectively on ompW promoter (PompW). While binding to the -81.5 site by FNR activates the transcription of ompW, interaction with the -126.5 site represses it, and repression through the -126.5 site is dependent on primary occupancy of the -81.5 site by FNR. Based on these molecular mechanisms, a novel regulatory model of ompW expression during anaerobic adaptation of E. coli is proposed. Growth competition assay further confirmed the physiological significance of this fine-tuned regulation of ompW by FNR in facilitating the fitness and adaptation of E. coli during the transition from aerobic to micro-aerobic and anaerobic lifestyles. In the second half of the thesis, it is demonstrated that two other physiological signals related to the anaerobiosis of E. coli participate in the regulation of ompW, i.e. carbon and electron sources. The molecular mechanisms of how the relevant transcription factors, namely CRP and NarXL, mediate ompW transcription were elucidated: CRP activates the transcription of ompW by binding with the -42.5 site on PompW when glucose is absent; NarL represses the expression of ompW via its binding with the -18.5 site on PompW in the presence of nitrate (the most preferred electron source of E. coli during anaerobic growth). Fumarate is estimated to enter the central channel of OmpW and rescues OmpW-mediated colicin S4 killing of E. coli, suggesting OmpW is a receptor for fumarate and revealing its role in facilitating C4-dicarboxylates utilization. In summary, my study reveals a previously unrecognized, highly co-ordinated and dynamic regulation network for the expression of the widely distributed Gram-negative bacterial minor porin protein OmpW. Given the high conservancy of both the ompW gene and its promoter regions in several pathogenic bacterial species, my study contributes to the understanding of the pathogenicity of these species in the host relevant environment of anaerobiosis.
published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy

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22

Huen, Shing-yan Michael, e 禤承恩. "A mechanistic study of lambdaphage-mediated recombination in E. coli". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B35321854.

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23

Sule, Preeti. "Phenotypic and Genotypic Effects of FlhC Mediated Gene Regulation in Escherichia Coli O157:H7". Diss., North Dakota State University, 2011. https://hdl.handle.net/10365/29205.

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Escherichia coli (E.coli) 0157:H7, a pathogen belonging to the enterohemorrhagic group of E.coli, has long been a concern to human health. The pathogen causes a myriad of symptoms in humans, ranging from diarrhea and malaise to renal failure. Human infection with the spread of the pathogen is mainly attributed to consumption of contaminated food material such as meat. Decontamination of meat via sprays have to date been the most commonly practiced method to reduce contamination, which now has little relevance in the face of developing resistance by the pathogen. In the following study we investigated FlhC mediated gene regulation in E. coli 0157:H7 on the surface of meat, in an attempt to recognize FlhC regulated targets, which may ultimately serve as targets for the development of novel decontaminating sprays. Microarray experiments were conducted to compare gene expression levels between a parental E. coli 0157:H7 strain and its isogenic flhC mutant, both grown on meat. Putative FlhC targets were then grouped based on their function. Realtime PCR experiment was done to confirm the regulation. Additionally, experiments were done to investigate the phenotypic effects of the regulation. To test the effect of FlhC on biofilm formation, an ATP based assay was first developed in E.coli K-12, which has been detailed in the following dissertation. This assay was used to quantify biofilm biomass in E. coli 0157. Microarray experiments revealed 287 genes as being down regulated by FlhC. These genes belonged to functions relating to cell division, metabolism, biofilm formation and pathogenicity. Real-time PCR confirmed the regulation of 87% of the tested genes. An additional 13 genes were tested with real-time PCR. These belonged to the same functional groups, but were either not spotted on the microarray chips or had missing data points and were hence not included in the analysis. All 13 of these genes appeared to be regulated by FlhC. The phenotypic experiments performed elucidated that the FlhC mutants divided to 20 times higher cell densities, formed five times more biofilm biomass and were twice as pathogenic in a chicken embryo lethality assay, when compared to the parental strain. The following dissertation also reports the development of a combination assay for the quantification of biofilm that takes advantage of the previously mentioned ATP assay and the PhenotypeMicroarray TM (PM) system. The assay was developed using the parental E. coli strain AJW678 and later applied to its isogenic flhD mutant to elaborate on the differences in nutritional requirements between the two strains during biofilm formation. Metabolic modeling and statistical testing was also applied to the data obtained. This assay will be used in the future to study biofilm formation by the parental strain E. coli 0157:H7 strain and its isogenic FlhC mutants on single carbon sources, hence identifying potential metabolites which differentially support biofilm formation in the parental and the mutant strain.

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24

Bendezu, Felipe Oseas. "CELL SHAPE DETERMINATION IN ESCHERICHIA COLI". Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1215459479.

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25

Leong, Mei-kid, e 梁美潔. "Development of an effective method to tag escherichia coli chromosomalgenes by recombineering". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30430811.

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26

黃雅誼 e Nga-yi Queenie Wong. "DNA engineering utilizing thymidylate synthase A (thyA) selection system in Escherichia coli". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31226851.

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27

Paton, Adrienne Webster. "Molecular characterization of variant shiga-like toxin genes of Escherichia coli /". Title page, contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09php3118.pdf.

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28

Crickmore, Neil. "Analysis of a cell division gene cluster in "Escherichia coli"". Thesis, University of Warwick, 1987. http://wrap.warwick.ac.uk/2468/.

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Several genes, essential for cell growth and division in Escherichia coli, have been mapped to the 76 minute region of the chromosome. DNA sequencing of part of this region revealed three cell division genes (ftsY, ftsE, and ftsX) in a putative operon. A fourth gene (orf4) was also identified that was transcribed in the opposite direction to the putative operon. The genes rpof, f am, dnaM and ftsS have also been mapped to this region, but their location, relative to the putative operon, was unknown. In this study the fam and rpoU genes were independently cloned and shown to be allelic. The dnaM gene was also found to be an allele of rpoH, and the gene was found to lie immediately downstream of the putative cell division operon. The restriction map of the area was extended, and the distance between the putative operon and the nearest known gene clockwise on the chromosome map (pit), was determined. The ftsS gene was found to be an allele of ftsX. Two promoters were identified within the putative operon, one proximal to ftsY and the other proximal to ftsE. A combination of S1 and primer extension mapping, of the mRNA transcripts, identified the transcriptional start sites of these two promoters. A polycistronic message was also identified encoding all three cell division genes, suggesting at least some degree of co-ordinated expression. In conclusion, the transcriptional organisation of the 76 minute, essential gene cluster has been determined, and evidence has been presented. that there is some degree of co-ordinated expression of the component genes.

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29

Anton, I. A. "Studies on the shikimate dehydrogenase gene of Escherichia coli". Thesis, University of Glasgow, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234808.

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30

Stanley, Peter. "Studies on the mutator gene mutS of Escherichia coli K-12". Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328271.

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31

Ralph, Edward T. "Molecular characterisation of FNR, the anaerobic transcription regulator of Escherichia coli". Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323194.

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32

Musuri, Periasamy Vigneshbabu. "Co-ordination of replication initiation with transcriptional regulation in Escherichia coli". Thesis, State University of New York at Buffalo, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10013540.

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Abstract (sommario):

In Escherichia coli, replication initiates when the DnaA-ATP protein assembles at the origin oriC. Hda protein in complex with the beta sliding clamp protein (? clamp) on DNA, functions in altering the nucleotide bound form of the replication initiator DnaA protein from DnaA-ATP to DnaA-ADP in a process termed as Regulatory Inactivation of DnaA (RIDA). DnaA also functions as a transcription factor of several genes including the aerobic ribonucleotide reductase nrdAB genes. In this study, I have exploited the cold sensitive growth phenotype due to loss of Hda function and its suppressors to understand the Hda function beyond initiation of replication. I describe the global transcriptional changes in strains lacking Hda and suppressed by two different modes. Loss of Hda function results in reduced expression of nrdAB genes, altered thiol status of the cell, SOS induction and increase in iron import due to de-repression of the Fur regulon. Strains lacking Hda function have increased requirement for the RpoH mediated heat shock response that affects the activity of NrdAB. I have shown that oversupply of ? clamp results in a slow growth phenotype which is more pronounced at low temperatures. Six mutant ? clamps suppress this slow growth phenotype. One of the mutant clamp that has the E202K mutation displays a hyper-Hda phenotypes such as hydroxyurea resistance and increase in nrdAB expression. These phenotypes were dependent on Hda but independent of SOS response. Finally, the slow growth phenotype due to overexpression of ? clamp can be compensated by co-overproducing Hda. This leads to a model where ? clamp could recruit Hda as a response to replication defects independent of SOS response.

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33

Dorrell, Nicholas. "Characterisation of a gene for photorepair in Escherichia coli K-12". Thesis, University of Bath, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357241.

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34

Agostinho, Juliana Maria Avanci. "Diversidade genética, fatores de virulência e perfis de susceptibilidade a antimicrobianos de isolados de Escherichia coli provenientes do útero, da boca e das fezes de cadelas com piometra /". Jaboticabal, 2013. http://hdl.handle.net/11449/108413.

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Abstract (sommario):

Orientador: José Moacir Marin
Banca: Janete Apparecida Desidério
Banca: Maria de Fátima Martins
Resumo: A piometra canina é uma enfermidade caracterizada pela inflamação do útero com acúmulo de exsudatos, acometendo principalmente fêmeas adultas. Ocorre na fase lútea do ciclo estral em decorrência de alterações hormonais e infecção bacteriana. É reconhecida como uma das principais causas de morte em cadelas e a Escherichia coli é o principal patógeno associado a esta doença. O objetivo deste estudo foi isolar e identificar cepas de E. coli provenientes de conteúdo intra uterino, boca e fezes de cadelas diagnosticadas com piometra, estudar a prevalência de genes codificadores de fatores de virulência uropatogênicos das cepas obtidas testando ainda a semelhança genética entre as cepas isoladas de conteúdo intra uterino e boca e avaliar a susceptibilidade "in vitro" das bactérias isoladas frente a 12 agentes antimicrobianos. Setenta cepas de E. coli, 25 provenientes do conteúdo intra uterino, 26 provenientes da boca e 19 provenientes das fezes, isoladas de 6 cadelas foram examinadas por PCR. Entre as cepas examinadas, 67 (95,7%) foram positivas para o gene fim, 19 (27,1%) foram positivas para iss, 18 (25,7%) foram positivas para hly , 13 (18,5%) foram positivas para iuc e 12 (17,1%) foram positivas para usp. Três animais apresentaram grande similaridade entre as cepas de E. coli isoladas do conteúdo intra uterino e da boca, através da análise da diversidade genética realizada mediante emprego da técnica REP-PCR, ERIC-PCR e BOX-PCR. Resistência antimicrobiana predominante foi detectada para cefalotina (67,1%), ampicilina (65,7%), tetraciclina (61,4%) e nitrofurantoina (58,5%) entre as cepas isoladas. Resistência a múltiplos antimicrobianos foi detectada em 12 (48,0%) dos isolados do conteúdo intra uterino, em 22 (84,6%) dos isolados da boca e em 14 (73,6%) dos isolados das fezes...
Abstract: Canine pyometra is a disease characterized by the inflammation of the uterus with accumulation of purulent discharge, affecting mainly adult animals. Occurs in the luteus phase of the estrus cycle in result of hormone alterations and generally is associated with bacterial infections. It is recognized as one of the main causes of disease and death in the bitch and Escherichia coli is the major pathogen associated with this disease. The aim of this study was to research, isolation and identification of Escherichia coli strains from intrauterine contents, mouth and feces of bitches diagnosed with pyometra, studying the prevalence of uropathogenic virulence factors genes in strains isolated, still testing the genetic similarity among strains isolated from intrauterine contents and mouth and evaluate the susceptibility "in vitro" of the isolated bacteria to 12 antimicrobial drugs. Seventy E. coli strains, 25 from intrauterine contents, 26 from mouth and 19 from feces isolated from six bitches were examined by PCR. Among the strains 67 (95.7%) were positive for fim, 19 (27.1%) were positive for iss, 18 (25.7%) were positive for hly, 13 (18.5%) were positive for iuc and 12 (17.1%) were positive for usp. Multiple antimicrobial resistance was detected for cephalothin (68.0%), nalidixic acid (56.0%) and ampicillin (56.0%) among the pyomera E. coli isolates. Multidrug resistance was found in 12 (48.0%) of the isolates from pyometra, in 22 (84.6%) of the isolates from mouth and in 14 (73.6%) of the isolates from feces...
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35

Leung, Hang-mei Polly, e 梁杏媚. "Epidemiology and molecular genetics of verocytotoxigenic escherichia coli in Hong Kong". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B31245663.

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36

Kempsell, K. "The regulation of glutamate and melibiose utilisation in Escherichia coli". Thesis, University of Aberdeen, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384465.

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Abstract (sommario):

Wild type cells of Escherichia coli K-12 are unable to grow on glutamate as the sole source of carbon. Glutamate-utilising mutants have been isolated previously and found to exhibit enhanced glutamate transport. Mutations at two loci gltS and gltR and possibly a third gltC were previously shown by other workers to mediate enhanced glutamate permeability. The gltR locus was suggested to be a negative regulatory for the gltS gene. A mutation at the gltS locus, the gltSo mutation increases the activity of a Na⁺-stimulated glutamate transport system GltI. The regulation of the GltI system was investigated by the isolation of MudX gene fusions which abolished Na⁺-stimulated glutamate transport. Two fusions with 'strong' and 'weak' B-galactosidase activities were isolated. These were both found to map at the gltS locus. Subsequent mapping exercises, suggested that the MudX fusions may be located in separate genes. Transcription of the 'strong' fusion was found to be impaired in the presence of the phs mutation. This is a mutation in the rpoA gene which encodes the -subunit of RNA polymerase. Glutamate-utilising suppressor mutants were isolated in both the MudX gene fusion strains. The suppressor mutations were found to map at the gltR locus. This was found to be the map location of a second glutamate transport system GltII. Thus, the gltR locus was found not to be the location of a negative regulator for the gltS gene. The melAB operon encodes the proteins for melibiose transport and utilisation. No regulatory locus has previously been reported for this transport system. The regulation of the melAB operon was investigated by cloning the melAB promoter into an lacZ expression vector. The region upstream from the melAB promoter was subsequently found to encode a trans-acting positive regulatory necessary for melAB expression. Transcription from the melAB promoter was also found to be impaired by the phs mutation. The results presented in this study substantiate previous observations that the phs mutation causes a generalised transcription defect.

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37

Blakely, Garry William. "The regulation and stability of insertion sequence IS1 in Escherichia coli K12". Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335291.

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38

Walters, Robin George. "The organisation, expression and function of the UVRC gene of Escherichia coli". Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237558.

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39

McFarlane, Ramsay James. "Molecular mechanisms of recombinogenic recircularization of linear plasmid DNA in escherichia coli". Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384995.

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40

Moffat, K. G. "The molecular cloning of the mutT gene of Escherichia coli K-12". Thesis, Cranfield University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373991.

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41

Huen, Shing-yan Michael. "A mechanistic study of lambdaphage-mediated recombination in E. coli". Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B35321854.

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42

Wendel, Brian Michael. "Completion of DNA Replication in Escherichia coli". PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4406.

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Abstract (sommario):

To maintain genomic integrity, all cells must accurately duplicate their genetic material in order to provide intact and complete copies to each daughter cell following cell division. Successful inheritance of chromosomal information without changing even a single nucleotide requires accurate and robust DNA replication. This requires that cells tightly control replication initiation from the origin(s), processive elongation of the replisome, and the completion of DNA replication by resolving convergent replication forks ensuring that each sequence is duplicated without alteration. Unlike initiation and elongation, the process by which replication forks converge and are resolved into two discrete, inheritable DNA molecules is not well understood. This process must be remarkably efficient, occurring thousands of times per cell division in human cells, and is likely to be a fundamental step in regulating genome stability in all cells. In this dissertation I address how DNA replication completes in the model system Escherichia coli. To achieve this, I examined candidate mutants for impairments in the completion of DNA replication. By evaluating growth, viability, chromosomal copy number, and plasmid stability I identified a requirement for the proteins RecBCD, ExoI, and SbcCD in the completion reaction. SbcCD and ExoI act before RecBCD in the completion reaction and process the DNA intermediates arising as replication forks converge. These enzymes act in the completion reaction without recombination or RecA, but in the absence of the normal process recombination is required to complete DNA replication via an aberrant pathway that results in genomic instability.

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43

Nelson, Adam Michael. "Genomic analysis of pathogen evolution virulence gene acquisition and genetic erosion in Escherichia coli /". Diss., Connect to online resource - MSU authorized users, 2008.

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44

Benson, Fiona Elizabeth. "Molecular cloning and analysis of the ruv gene of Escherichia coli K12". Thesis, University of Nottingham, 1988. http://eprints.nottingham.ac.uk/30593/.

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Abstract (sommario):

Mutations in the ruv gene of Escherichia coli K-12 result in an increased sensitivity to agents that damage DNA. Studies presented in this thesis demonstrate that the ruv gene product is required for conjugational recombination in certain genetic backgrounds. From this it was inferred that the role of the ruv gene product was in the recombination repair of daughter strand gaps and double strand breaks in damaged DNA. In addition, the ruv gene product is shown to be required for the efficient recovery of F' transconjugants in certain genetic backgrounds, suggesting that recombination between transferred F' and the recipient chromosome may be an obligatory event in these strains. Expression of ruv is regulated as part of the SOS response to DNA damage, by the lexA and recA gene products. The ruv gene product appears not to have any major role in its own regulation, however the basal level of expression of other SOS genes is increased in strains carrying ruv mutations. The ruv gene has been cloned on a 10.4kb HindIII fragment into the low copy number vector pHSG4l5, to give plasmid pPVA101, which has been demonstrated to complement the UV sensitivity of strains carrying any of the 10 different ruv mutations tested. Analysis of the proteins synthesised by pPVA101, its deletion derivatives, and derivatives with Tnl1000 insertions inactivating the ruv gene, allowed the identification of the ruv coding region, and suggested that the ruv gene encoded a 4lkd protein. In addition, regions of the cloned DNA coding for two further proteins of approximately 24kd and 33kd were identified. The sites of insertion of Mud(Ap)Rlac and Tn10 elements in the ruv gene were mapped, which allowed the direction of transcription to be determined, and suggested that the 4lkd protein may be cotranscribed with the 24kd protein from a promoter upstream of the smaller protein. This was substantiated by the demonstration that two of the ruv mutations studied were chromosomal inversions, one of which had its end point within the coding region for the 24kd protein, and by the isolation of an SOS inducible promoter derived from the region upstream of the 24kd protein. The nucleotide sequence of the ruv region revealed two open reading frames, designated ruvA and ruvB, with coding potential for proteins of 22087 daltons and 37177 daltons respectively, corresponding to the proteins with molecular weights estimated as 24kd and 41kd from SOS-polyacrylamide gels. A possible promoter, and two sequences with homology to the LexA binding site consensus sequence were identified upstream of the coding region of the 22kd protein. An amino acid sequence within the proposed RuvB protein was identified with homology to ATP binding sites of other proteins 950involved in DNA metabolism.

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45

Luo, Xuebin. "Structural Analysis of the Genes Encoding the Oxalocrotonate Branch of the Pseudomonas putida TOL Plasmid pDKI meta-cleavage Pathway and the Expression of the xy1G Gene Product in Escherichia coli". Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc500659/.

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Abstract (sommario):

Three overlapping DNA fragments from the lower operon of Pseudomonas putida TOL plasmid pDK1, covering the xy1IH genes and downstream flanking region, were cloned into pUC19. They include a 2.8 kbp XhoI fragment, a 2.7 kbp PstI fragment and a 2.0 kbp EcoRI-HindIII fragment. They were subjected to DNA sequence analysis. The xy1I (4-oxalocrotonate decarboxylase) and xy1H (4-oxalocrotonate tautomerase) genes were found to possess coding regions of 792 and 189 nucleotides, respectively. A possible transcriptional terminator resembling E. coli rho-independent terminators was identified downstream of the translational stop of xy1H. An additional stem and loop structure was found in the intergenic region between xy1I and xy1H. The individual ORF's of the oxalocrotonate branch (xy1G, xy1I and xy1H) have been cloned into pUC18/19. The expression of the xy1G gene in E. coli was successfully assayed spectrophotometrically.

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46

Baertlein, Dawn Marie August. "Identification of phosphate starvation inducible mineral phosphate solubilization genes in Escherichia coli". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184606.

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Abstract (sommario):

Under conditions of phosphate starvation Escherichia coli can solubilize mineral phosphates, such as dicalcium phosphate, to orthophosphate which is then available for uptake and cell growth processes. lac operon fusions were created using MudX phage, and mineral phosphate solubilization (Mps) mutants were identified by their inability to solubilize mineral phosphate on plate assays. Four of these mutants have been mapped on the E. coli chromosome via Hfr matings and are located at two distinct portions of the chromosome; between 23 and 50 minutes and between 60 and 90 minutes. One mutant in each region has phosphate starvation inducible (Psi) promoter activity. One of these mutants (DB1047) was mapped to between 69 and 75 minutes via F' matings, and fine structure mapped to 75 minutes by hybridization with λ clones from a genomic library of Escherichia coli. DB1047 was characterized more closely and found to exhibit pleiotropy with regard to several membrane related traits. Evidence that this is a single insertional event comes from the simultaneous loss of all traits tested in spontaneous revertants. Additionally, a Tn5 mutant was identified that was identical for these traits. Our data strongly support the hypothesis that the mutation carried by DB1047 is in the ompB locus. This locus consists of the two regulatory cotranscribed genes, ompR and envZ. This locus is involved in regulation of transcription of the ompC and ompF genes for outer membrane porin proteins, and is located at 75 minutes on the chromosome as is the DB1047 mutation. DB1047 lacks the outer membrane porin OmpF, a phenotype previously attributed to envZ mutants. However, the ompR321 mutant resembles DB1047 in reduced ability to solubilize phosphate. Additional supporting evidence for the DB1047 mutation belonging to the ompB locus comes from the most recent report that mutations in the himA gene, which I found to be deficient in the ability to solubilize phosphate, also affect the regulation of production of the outer membrane porin OmpF.

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47

Ossanna, Nina. "Isolation and characterization of SOS constitutive mutations in Escherichia coli". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184398.

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Abstract (sommario):

Early events occurring during induction of the SOS response in Escherichia coli are poorly understood. In order to understand the early steps in SOS induction more fully, we have isolated several mutations which constitutively express the SOS regulon. Using a Mud(Apᴿ,lac) fusion to the SOS regulated gene sulA, we isolated Lac⁺ colonies as mutants in which RecA protein is constitutively activated for repressor cleavage. The mutations map to four loci: dam, lig, uvrD and recA. The extent of constitutive SOS induction in these mutants varied greatly, indicating different levels or types of signal in the cell. The mutations isolated demonstrate two early steps in SOS induction. The first step in SOS induction is signal generation and includes mutations found in dam, lig and uvrD genes. The mutant gene products presumably alter DNA metabolism to produce an inducing signal. These non-lethal mutations lead to sub-induction and probably generate very specific signals, such as abnormally unwound DNA in the case of DNA helicase II mutants or unsealed DNA nicks that result from deficient ligation in lig mutants. Greater induction may require quantitatively more signal or different types of signal generated by severe defects leading to cell death. These mutations also show that signal is a variable quantity, allowing the cell to fine tune the levels of SOS repair activity according to the amount or type of signal (damage) perceived. In some cases (such as dam mutations), blocking the SOS response by lexA(Ind⁻) alleles leads to cell death. In this type of constitutively activated strain, the increased level of repair from SOS induction is required to allow the cell to tolerate potentially lethal DNA structures generated by the mutant gene product. The second step in induction is the interaction of signal with RecA protein and is shown by isolating 8 recA mutants. Mutant recA alleles caused the strongest SOS induction in any mutants obtained, similar to the level found in strains lacking repressor (lexA(Def) mutants). This full induction in the absence of lethal DNA damage underscores the pivotal role of RecA protein in regulating the SOS response.

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48

Lozano, Gabriela Cazonato. "Avaliação do papel de genes envolvidos na mobilização de poli-3-hidroxibutirato em linhagens recombinantes de Escherichia coli". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/87/87131/tde-17052014-093733/.

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Abstract (sommario):

O P3HB é um tipo de poliéster sintetizado por bactérias como reserva de carbono e energia, e mobilizado na escassez destes. Um estudo com mutantes de Burkholderia sacchari, indicou o envolvimento de PhaZa1 e LonA na mobilização de P3HB. Este estudo avaliou o papel de PhaZa1 e LonA neste processo. A complementação heteróloga dos mutantes de B. sacchari, a partir dos genes phaZa1 e lonA de Ralstonia eutropha, restabeleceu a capacidade de mobilização dessas cepas, confirmando o envolvimento de seus produtos no processo. A partir de cepas recombinantes de Escherichia coli, abrigando tanto os genes de acúmulo de P3HB como de mobilização de R. eutropha, obteve-se cepas abrigando os genes phaZa1 e lonA isoladamente e outra abrigando os dois genes simultaneamente. Quando separados, tanto phaZa1 quanto lonA, não apresentaram papel significante na mobilização porém, quando os dois genes são expressos simultaneamente, as taxas de mobilização atingem mais de 50%, indicando que deva ter uma interação entre PhaZa1 e LonA para que o processo de mobilização seja efetivo.
The P3HB is a type of polyester synthesized by bacteria like carbon and energy source, and is mobilizated when there is a shortage of these. A study with mutants of Burkholderia sacchari, showed the involvement of PhaZa1 and LonA in mobilization of P3HB. The present study evaluated the role of PhaZa1 and LonA in this process. The heterologous complementation of mutants of B. sacchari, with phaZa1 and lonA genes from Ralstonia eutropha, reestablished the mobilization capacity in these strains, confirming the involvement of their products in this process. From the recombinant strain of Escherichia coli, harboring accumulation and mobilization genes from R. eutropha, we obtained strains harboring phaZa1 and lonA genes singly and another harboring both genes simultaneously. When expressed singly, both phaZa1 as lonA, had no significant role in mobilization but, when both genes were expressed simultaneously, the rates of mobilization reached more than 50%, appointing that an interaction must occur between PhaZa1 and LonA for the mobilization process to be effective.

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49

Whitby, Matthew Conway. "Molecular and biochemical analysis of the recR operon of Escherichia coli K-12". Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335405.

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50

Hufton, Simon Evan. "A structure-function analysis of the Escherichia coli vitamin Bâ†1â†2 receptor". Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317422.

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