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Dissertationen zum Thema „Bacterial genetics“

Autor: Grafiati
Veröffentlicht am 4. Juni 2021
Zuletzt aktualisiert am 1. August 2024

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1

Martins, Thaísa Zanetoni. „Mutagênese sítio-dirigida da ORF XAC0024 de Xanthomonas citri subsp. citri e suas implicações no desenvolvimento do cancro cítrico /“. Jaboticabal, 2016. http://hdl.handle.net/11449/138238.

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Orientador: Jesus Aparecido Ferro
Coorientador: Helen Alves Penha
Banca: Fabrício José Jaciani
Banca: Flávia Maria de Souza Carvalho
Resumo: O cancro cítrico tem como agente causal a bactéria Xanthomonas citri subsp. citri (Xac), que afeta diferentes espécies de citros economicamente importantes. É uma doença ainda sem método curativo, e pela sua relevância e dano econômico, faz-se necessário o entendimento em termos moleculares da interação Xac-citros para o desenvolvimento de estratégias que controlem a doença. O objetivo do presente trabalho foi investigar os efeitos da deleção da ORF XAC0024 presente no genoma da Xac isolado 306, que codifica uma proteína hipotética conservada e que apresenta vários domínios putativos, entre eles o domínio peptidase M23. A hipótese é que esta proteína pode estar envolvida com a patogenicidade e/ou virulência da bactéria. Para obter o mutante ΔXAC0024 foi utilizada a técnica de mutagênese sítio-dirigida, seguida de recombinação homóloga com o vetor suicida pOK1. O mutante ΔXAC0024 foi analisado em relação às características de patogenicidade, crescimento in vivo e in vitro, capacidade de autoagregação, produção de biofilme e produção de goma xantana. O teste de patogenicidade e a curva de crescimento in vivo foram realizados em limão cravo utilizando o método de infiltração por seringa para a inoculação da bactéria. Os sintomas do desenvolvimento da doença foram registrados por fotografia digital até o 25º dia após a inoculação (dai) e a curva de crescimento in vivo também foi determinada até o 25º dai. A curva de crescimento in vitro e a agregação célula-a-célula foram analisa... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The bacteria Xanthomonas citri subsp. citri (Xac) is the causal agent of citrus canker, a disease that affects different species of economically important citrus. There is no a curative method for this disease, and do to its relevance and economic damage, it is necessary to understand at molecular level the Xac-citrus interaction in order to develop strategies to control the disease. The objective of this study was to investigate the effects of the deletion of the ORF XAC0024 present in the genome of Xac strain 306, which encodes a conserved hypothetical protein and has several putative domains, including peptidase M23 domain. It is hypothesized that this protein may be involved in the pathogenicity and / or virulence of the bacterium. For the ΔXAC0024 mutant was used for site-directed mutagenesis technique, followed by homologous recombination with the suicide vector pOK1. The ΔXAC0024 mutant was analyzed in relation to pathogenicity characteristics, growth in vivo and in vitro, self-aggregation capacity, biofilm production and production of xanthan gum. The pathogenicity test and in vivo growth curves were performed on Rangpur lime using syringe-infiltration method for the inoculation of bacteria. Symptoms of the disease development were recorded by digital photography to the 25° day after inoculation (dai) and in vivo growth curve was also determined to give the 25°. The growth curve in vitro and cell-to-cell aggregation were analyzed in liquid culture medium NB. Biofilm p... (Complete abstract click electronic access below)
Mestre
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2

Cock, J. M. „Bacterial nitrate reductase genes“. Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355501.

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3

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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4

Leiman, Sara. „Genetics and Regulation of Bacterial Biofilms“. Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17463954.

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Bacterial biofilm formation, the construction of dense, protective, multicellular communities, is a widely conserved behavior. In some bacteria, such as the Gram-positive model organism Bacillus subtilis, the genetics controlling biofilm formation are well understood. In other bacteria, however, including the Gram-negative opportunistic pathogen Pseudomonas aeruginosa, the identities or roles of many biofilm genes remain unknown. Importantly, many proposed applications of biofilm research, particularly in the medical field, require knowledge not only of biofilm assembly but also of biofilm disassembly, the latter being a recent and underdeveloped area of study. It was previously reported that B. subtilis biofilms disassemble late in their life cycle due to the incorporation of four D-amino acids (D-leucine, D-methionine, D-tryptophan, and D-tyrosine, or D-LMWY) into peptidoglycan. It was further argued that D-LMWY specifically inhibits and disassembles the biofilms of diverse bacterial species, including B. subtilis and P. aeruginosa. Here I present a contrasting report. I describe how what had been perceived as D-LMWY-mediated biofilm inhibition is actually D-tyrosine-mediated toxicity. B. subtilis is sensitive to growth inhibition by D-tyrosine due to the absence of D-tyrosyl tRNATyr deacylase (Dtd), an enzyme that prevents the misincorporation of D-tyrosine and other D-amino acids into nascent proteins. By repairing the gene for Dtd, I was able to render B. subtilis resistant to both growth inhibition and biofilm inhibition by D-tyrosine and D-LMWY. In parallel, I recovered spontaneous mutants of B. subtilis that survive in the presence of D-LMWY. These isolates harbored mutations in pathways that regulate tRNATyr charging. Three of these mutations enhanced the expression of the gene (tyrS) for tyrosyl-tRNATyr synthetase (TyrRS), while a separate mutation improved the stereoselectivity of TyrRS. I concluded that these spontaneous D-LMWY resistance mutations were compensating for the absence of Dtd. In addition to my research on B. subtilis biofilm regulation, I demonstrated a new, non-destructive screening approach for identifying P. aeruginosa biofilm genes. Using this screen, I was able to recover a wide range of known biofilm genes as well as the new biofilm gene candidates ptsP, PA14_16550, and PA14_69700. These three genes are the focus of an ongoing study dedicated to characterizing P. aeruginosa biofilm formation, particularly as it relates to the secondary messenger cyclic di-GMP. In summary, this dissertation covers aspects of biofilm formation and dispersal in two bacterial species. My work offers mechanistic insight into D-amino acid resistance, resolves the relationship between D-amino acids and biofilms, and establishes a new tool for understanding the complexities of biofilm genetics and regulation.
Biology, Molecular and Cellular
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5

Parahitiyawa, Nipuna Bandara. „Phylogenetic aspects of oral bacterial microbiome“. Thesis, Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43278486.

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6

Rollie, Clare. „Memories are made of this : investigating the CRISPR-Cas adaption mechanism“. Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/10814.

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CRISPR-Cas is an adaptive immune system unique to prokaryotes, which prevents infection by foreign genetic elements. Key to the function of CRISPR-Cas immunity is the ability to adapt to new threats in incorporating short segments, termed spacers, of invading DNA into the clustered regularly interspaced short palindromic repeat (CRISPR) array of the host. Spacers constitute immunological memories, used by CRISPR-associated (Cas) proteins to mount a sequence-specific attack on subsequent infections. The immunisation of the host is called CRISPR adaption. Adaption requires the integration of new spacers at a precise site in the CRISPR array. Two proteins, Cas1 and Cas2, are essential for adaptation; however, the mechanisms of spacer integration remain poorly understood. The work described here focused on understanding adaptation in Sulfolobus solfataricus. Using biochemical assays, I aimed to characterise the activity of the Cas1 and Cas2 proteins in this organism in order to understand their role in the insertion of new spacers. Additionally, I aimed to investigate how the expression of CRISPR-Cas components is regulated in this organism in response to viral infection. The results presented here show that expression of Cas1 was strongly upregulated in response to infection. A Csa3 protein from S. solfataricus was found to bind to the promoter for transcription of cas1, implying a role in the regulation observed. I reconstituted in vitro both the integration reaction performed by Cas1 and Cas2 proteins of S. solfataricus and the reverse of this reaction, disintegration. Cas1 was shown to impose sequence specificity on these reactions, selecting sites similar to the leader-repeat junction of the CRISPR locus. Finally, I demonstrated that, in addition to the intrinsic specificity of Cas1, there was a requirement for an additional host factor for site-specific integration in S. solfataricus.
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7

Tsang, J. S. H. „The physiology and genetics of bacterial dehalogenases“. Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380588.

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8

Koh, Cheng Gee. „New approaches for mapping bacterial genomes“. Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240188.

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9

Cook, Marisa Anne. „Replicons derived from endogenously isolated plasmids used to classify plasmids occurring in marine sediment bacteria“. Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/25736.

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10

Okuklu, Burcu Güneş Hatice. „Investigation of chromosomal and plasmid dna profiles of lactococcus lactics ssp. lactis/“. [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezler/master/biyoloji/T000396.pdf.

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Thesis (Master)--İzmir Institute of Technology, İzmir, 2005
Keywords: Lactococcus lactis ssp. lactis, chromosome profiling, pulsed field gel electrophoresis, plasmid profiling, plasmid stability. Includes bibliographical references (leaves 58-63)
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11

Davidson, Seana Kelyn. „Biology of the bryostatins in the marine bryozoan Bugula neritina : symbiosis, cryptic speciation and chemical defense /“. Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p3035405.

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12

Hartford, Trudy. „An evaluation of DNA pairing in bacterial systematics“. Thesis, University of Leicester, 1990. http://hdl.handle.net/2381/35384.

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The main aim of this work was to evaluate the use of DNA-DNA pairing techniques in bacterial systematics. The genus Listeria was chosen for the study because of the small number of biochemical differences between the seven species. Also there has been a limited amount of nucleic acid studies carried out on the group using an endonuclease technique (Rocourt et al., 1982), therefore some comparisons of the two techniques were possible. Using optical DNA-DNA reassociation on a spectrophotometer with 23 Listeria strains from the seven species, a complete matrix of DNA-DNA homology values was produced. The data were analysed for reproducibility and second order kinetics. Possible distortion of the derived taxonomic structure due to choice of reference strains was investigated by analysing the structure obtained from the complete matrix and comparing it to results obtained from incomplete 'strip' matrices. An analysis was made on a published matrix of complete DNA relationships (Nakamura and Swezey, 1983a; Hartford and Sneath, 1988) as well as on the data from Listeria species produced in this study. Great distortion in apparent taxonomic structure can result unless reference strains are widely spaced and representative of the clusters present. Problems caused by the choice of reference strains and the use of incomplete matrices was also explored by generating a random normal swarm of OTUs and illustrating the often bizarre effects obtained by using incomplete data sets in bacterial systematics. DNA-DNA pairing data from a selection of published work were examined for experimental error. The average error from replications lay between 3 and 8.6 %, but the data were very limited.
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13

Loman, Nicholas James. „Comparative bacterial genomics“. Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/2839/.

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For the most part, diagnostic clinical microbiology still relies on 19th century ideas and techniques, particularly microscopy and laboratory culture. In this thesis I investigate the utility of a new approach, whole-genome sequencing (WGS), to tackle current issues in infectious disease. I present four studies. The first demonstrates the utility of WGS in a hospital outbreak of Acinetobacter baumannii. The second study uses WGS to examine the evolution of drug resistance following antibiotic treatment. I then explore the use of WGS prospectively during an international outbreak of food-borne Escherichia coli infection, which caused over 50 deaths. The final study compares the performance of benchtop sequencers applied to the genome of this outbreak strain and touches on the issue of whether WGS is ready for routine use by clinical and public health laboratories. In conclusion, through this programme of work, I provide ample evidence that whole-genome sequencing of bacterial pathogens has great potential in clinical and public health microbiology. However, a number of technical and logistical challenges have yet to be addressed before such approaches can become routine.
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14

余慧儀 und Wai-yee Annie Yu. „Epidemiological and emm gene analysis of non-m-typeable group A streptococcus isolates from Hong Kong“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31969987.

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15

Ramesar, Rajkumar Sewcharan. „Developmental genetic studies on Thiobacillus ferrooxidans“. Doctoral thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/26235.

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Thiobacillus ferrooxidans is an industrially important bacterium which is used in bioleaching operations. The work reported in this investigation extends current knowledge of the genetics of this organism. Conjugation was attempted as a means for plasmid DNA transfer to T. ferrooxidans. Recombinant T. ferrooxidans plasmids, pDER401 and pDER405, were shown to code for mobilization and replication functions in Escherichia coli and Thiobacillus novellus strains. The plasmids were mobilizable at high frequency by the IncP plasmid, R68.45. Attempts to transfer the T. ferrooxidans recombinant plasmids directly from E. coli to T. ferrooxidans were unsuccessful. In multistage mating experiments, plasmid DNA was transferred from E. coli to T. novellus, and from T. novellus to Thiobacillus intermedius. However, in subsequent matings, plasmid transfer from these thiobacilli to T. ferrooxidans could not be shown. A genomic library of T. ferrooxidans ATCC 33020 was constructed in the plasmid vector, pEcoR251, for the purpose of cloning a recA-like gene from this organism. The library consisted of approximately 1,78 X 10⁴ clones carrying chromosomal DNA fragments of about 3-12 kilobases (kb). The library was successfully screened for functional complementation of E. coli auxotrophic mutants. Clones that conferred resistance to methyl methane sulfonate (MMS), a DNA-damaging agent, were isolated in an E. coli recA⁻ mutant. In an attempt to clone a homologous marker, T. ferrooxidans ATCC 33020 was mutated to rifampicin resistance (Rifʳ) and DNA from the mutant strain was used in the construction of plasmid- and cosmid-based libraries. The plasmid library contained approximately 1,35 X 10⁴ clones with inserts of about 1-13 kb. The cosmid library consisted of approximately 8.2 X 10³ colonies, 4.0 X 10⁴ in vitro packaged cosmids, and an amplified in vivo-packaged cosmid lysate containing approximately 1.82 X 10¹¹ infectious particles, carrying inserts of about 35-55 kb. Complementation of E. coli auxotrophic mutants was observed with the plasmid and cosmid library of the T. ferrooxidans Rifʳ strain. Screening both libraries for a Rifʳ marker was unsuccessful. Three recombinant plasmids, pRSR100, pRSR101, and pRSR102, each containing the functional analogue of the E. coli recA gene, were isolated from the plasmid-based genomic library of T. ferrooxidans ATCC 33020. The plasmid, pRSR100, was used for further characterization of the cloned recA-like gene. pRSR100 complemented defects in DNA repair and homologous recombination in an E. coli recA- strain. Antiserum raised against E. coli RecA⁻ protein reacted with two protein bands with an apparent Mᵣ of approximately 40 000 and 38 000 in extracts of the recA deletion mutant, E. coli JK696, containing pRSR100. A single band with an apparent Mᵣ of approximately 40 000 was detected in T. ferrooxidans cell extracts with the E. coli RecA antiserum. The nucleotide sequence of the T. ferrooxidans recA gene has been determined. No SOS box characteristic of LexA- regulated promoters could be identified in the 196-bp region upstream of the coding region. The T. ferrooxidans recA gene specifies a protein of 346 amino acids that has 66% and 69% homology to the RecA proteins of E. coli and P. aeruginosa, respectively. Most amino acids that have been identified as being of functional importance in the E. coli RecA protein are conserved in the T. ferrooxidans RecA protein. Although some amino acids that have been associated with ATPase and constitutive protease activity have been substituted, the cloned protein has retained these activities. The cloned recA gene was expressed in E. coli from both the λ Pᵣ and lac promoters. However, no expression from the 2.2 kb T. ferrooxidans DNA preceding the gene was evident.
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Leung, Kei-chun Jane. „Purification of a transcriptional regulator of the dehalogenase IVa gene of Burkholderia species MBA4“. Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38734709.

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17

Leung, Kei-chun Jane, und 梁奇珍. „Purification of a transcriptional regulator of the dehalogenase IVa gene of Burkholderia species MBA4“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38734709.

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18

Deng, Liyu, und 鄧麗瑜. „Exploration of the transcription factors that regulate the expression of the haloacid operon in Burkholderia caribensis MBA4“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208618.

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Bacterial dehalogenase is a key enzyme involved in bioremediation of halogenated organic compounds. A dehalogenase, Deh4a, was isolated from the Gram-negative bacterium Burkholderia caribensis MBA4, which can utilize haloacetic acids as carbon source. The haloacid operon in MBA4 was identified and characterized. It is composed of the structural genes forDeh4a and a transporter Deh4p. Transcription of this operon is negatively regulated, but the mechanism and the relevant regulator are still poorly understood. In this study, magnetic DNA affinity chromatography and Tn5transposon mutagenesis were employed to explore the regulatory factors that affected the expression of this haloacid operon. A process that uses lysates from glycolate-grown cells, magnetic DNA affinity chromatography and LC-MS/MS has identified a TetR family transcriptional regulator, TetR8620, which binds to the promoter region of deh4a. Disruption of the TetR8620 gene in mutant Ins8620 abolished the formation of a slow migrating complex in electrophoretic mobility shift assay (EMSA) using lysates from glycolate-grown cells. Moreover, expressions of deh4a were enhanced in bothglycolate- and MCA- grown Ins8620. The addition of recombinant histidine-tagged TetR8620 to lysates of Ins8620 resumed the formation of a retardation complex, but different from that using purified His-tagged TetR8620.This suggested that TetR8620 is responsible for formation of retardation complexes, and an additional protein might be involved. To investigate other putative factors that interact with TetR8620, purified His-tagged TetR8620 was immobilized with Ni-NTA agarose and used for isolation of interacting proteins. Chemical cross-linking of the purified fraction with BS3established that TetR8620 interacts with a proteinof30 kDa. Separation of the cross-linked complex in SDS-PAGE gel also showed that a protein with similar MW was specifically pulled down. These results suggest that TetR8620 was interacting with a ~30 kDa protein. Protein identification using mass spectrometry assay proposed that this protein is probably a universal stress protein UspA encoding by peg.3485 or acetyl-glutamate kinase (EC 2.7.2.8) encoding by peg.714 in MBA4. Tn5transposon mutagenesis was also employed to explore the factors that regulate the haloacid operon ofMBA4. A derivative of MBA4, MK06, which contains a kanamycin resistant gene (kan) with a deh4apromoter was constructed. Kanamycin resistancy of this derivative was MCA inducible. Transposon mutagenesis was conducted on this derivative, and Tn-containing mutants were isolated as tetracycline resistant colonies on pyruvate plates. These colonies were further selected on their resistance tokanamycin in pyruvate plates. Gene peg.6589 encoding a putative transcriptional regulator, DehR1, was disrupted by Tn insertion. While the production of dehalogenase was still MCA-inducible, this mutant has partially relieved the repression of the haloacid operon in media containing pyruvate. Moreover, constitutive production of DehR1 in MBA4 decreased the transcript levels of deh4ain medium containing pyruvate or MCA. This study has identified two transcription factors, TetR8620 and DehR1, which regulate the expression of Deh4a negatively. TetR8620 is a DNA-binding protein that interacts with the deh4apromoter. Results from this study imply that the regulation of the haloacid operon in MBA4 is likely to be under the control of multiple factors.
published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy
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19

Osborn, Andrew Mark. „Evolutionary analysis of bacterial mercury resistance in natural environments“. Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262489.

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20

Osbourn, Susanne Elizabeth Vana. „The evolution of the Tn21 subgroup of bacterial transposons“. Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284317.

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21

Scragg, Ian G. „The specificity of intracellular protein degradation in bacterial cells“. Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/14370.

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22

Marcinkiewicz, Ashley. „Bacterial and phage interactions influencing Vibrio parahaemolyticus ecology“. Thesis, University of New Hampshire, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10127507.

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Vibrio parahaemolyticus, a human pathogenic bacterium, is a naturally occurring member of the microbiome of the Eastern oyster. As the nature of this symbiosis in unknown, the oyster presents the opportunity to investigate how microbial communities interact with a host as part of the ecology of an emergent pathogen of importance. To define how members of the oyster bacterial microbiome correlate with V. parahaemolyticus, I performed marker-based metagenetic sequencing analyses to identify and quantify the bacterial community in individual oysters after culturally-quantifying V. parahaemolyticus abundance. I concluded that despite shared environmental exposures, individual oysters from the same collection site varied both in microbiome community and V. parahaemolyticus abundance, and there may be an interaction with V. parahaemolyticus and Bacillus species. In addition, to elucidate the ecological origins of pathogenic New England ST36 populations, I performed whole genome sequencing and phylogenetic analyses. I concluded ST36 strains formed distinct subpopulations that correlated both with geographic region and unique phage content that can be used as a biomarker for more refined strain traceback. Furthermore, these subpopulations indicated there may have been multiple invasions of this non-native pathogen into the Atlantic coast.

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Papapostolou, Anastasia. „Role of Genetics in Subgingival and Supragingival Bacterial Colonization“. The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243453546.

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24

Bone, E. J. „Biochemistry and genetics of sporulation in Bacillus subtilis“. Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377250.

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25

Pierce, Eric John. „Bacterial toxins as probes for membrane glycolipids in mammalian cells“. Thesis, University of Leicester, 1985. http://hdl.handle.net/2381/35129.

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Cholera toxin which binds specifically and with high affinity to a glycolipid; ganglioside GM1, has been used as a probe to study glycolipid-protein interactions in the plasma membranes of BALB/c 3T3 mouse fibroblasts and mouse lymphocytes. Evidence is presented that: i) a proportion of cholera toxin bound to GM1 of BALB/c 3T3 cells withstood extraction with Triton X-100 at 0C and remained associated with the cytoskeleton; ii) at 37C, cholera toxin-GM1 complexes were completely extracted with Triton X-100. The resulting complexes existed in a macromolecular form that did not involve other membrane components; iii) antibody-induced capping of GM1-cholera toxin complexes in mouse lymphocytes had characteristics in common with cell surface immunoglobulin- and Con A-capping systems. Immuno- fluorescence studies revealed that in all three systems, capping was accompanied by the redistribution of cytoskeletal components and was inhibited by drugs that inhibit microfilament, but not microtubule, function. These findings suggest that capping in these systems occurs by contractile mechanisms with common features and further suggest that, under certain circumstances, some form of trans-membrane linkage exists between GM1 and the cytoplasm. The role of gangliosides as receptors for tetanus toxin in rat brain membranes was investigated Tris-acetate buffer, pH 6.0 and in a more "physiological" buffer. In agreement with the findings of previous workers, the binding of 125I-labelled tetanus toxin to rat brain membranes in Tris- acetate buffer, pH 6.0 was of high affinity and readily inhibited by gangliosides. The receptors were sensitive to sialidase but less so to heat or protease. In contrast, toxin binding to rat brain membranes in Krebs-Ringer buffer, pH 7.4 involved high and lower affinity components. These receptors were fewer, and markedly sensitive to proteases, heat and sialidase. Binding was not readily inhibited by ganglioside so protein, rather than ganglioside, is likely to represent the high affinity binding site detected in Krebs- Ringer buffer.
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Poole, Deborah Marie. „Molecular analysis of plant cell wall hydrolases of bacterial origin“. Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238939.

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Omrani, M. D. „Molecular biology of a novel type of bacterial transport system“. Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265584.

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28

Pinyon, Rebecca A. „Isolation and characterisation of novel non-ribosomal peptide synthetase genes from the entomopathogenic Xenorhabdus bovienii T228“. Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09php659.pdf.

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29

Huen, Shing-yan Michael, und 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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30

Wang-Holmes, Jenny. „Molecular systematics and biodiversity of planctomycetes / Jenny Wang-Holmes (Jian-Hua Wang)“. [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18395.pdf.

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31

Campbell, Alan L. (Alan Lee). „The Genetics of Pigmentation in Corynebacterium poinsettiae ATCC 9682“. Thesis, North Texas State University, 1986. https://digital.library.unt.edu/ark:/67531/metadc330778/.

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Corynebacterium poinsettiae mutant strains blocked in carotenoid biosynthesis were obtained by treatment with the mutagen N-methyl-N1-nitro-N-nitrosoguanidine. Additional carotenoid (Crt) mutant strains were obtained from a previous study conducted in our laboratory. Fifty-nine Crt mutants affected in carotenoid biosynthesis were examined by a normal phase high performance liquid chromatography (HPLC) system. Pigment extracts of Crt mutants and C. poinsettiae wild type strains were resolved by an isocratic system with hexane:acetone:dicholoromethane, 11.35:1.73:1.00 (by vol.) as the eluting solvent. In addition to the five major peaks, twelve minor peaks were observed in the wild type C. poinsettiae strain used in this study. Crt mutant and wild type strain peak heights were measured from the individual chromatograms and the peak height data set created was analyzed using the Statistical Analysis System program to perform a cluster analysis. The cluster analysis revealed five carotenoid mutant groups. Carotenoid pigments which accumulated or were absent in each of the cluster groups are reported. Cluster group 1 mutants (CrtA) are blocked in the dehydrogenase(s) which is(are) responsible for the dehydrogenations between phytoene and lycopene. Cluster group 2 mutants (CrtB) appear to be blocked at a second dehydrogenase specific for the dehydrogenation from C.p. 470 to C.p. 496. Cluster group 3 mutants (CrtC) are blocked at a cyclization step in the pathway which involves cyclization of C.p. 496 to C.p. 470 and which may cyclize C.p. 473 to C.p. 450. The genes CrtA and CrtB map only 0.5 map units from each other while CrtA and CrtC map 2.1 map units from one another. Mutants which accumulate end products but which lack certain precursors indicate a branched pathway for pigment biosynthesis exists in this organism. Media for the formation, fusion and regeneration of C. poinsettiae protoplasts are reported and a protocol for the use of these media in genetic crosses of strains blocked in carotenoid biosynthesis is described. While isolating antibiotic resistant mutants useful in genetic analyses, novobiocin resistant mutants were observed to have a distinctly different colony pigment phenotype as compared to the wild type strain. HPLC chromatograms of a novobiocin resistant strain showed a distinctly different carotenoid pigment profile. The results provide evidence for differential gene expression in the carotenoid biosynthetic pathway when these mutants are grown in the presence of novobiocin.
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Wong, Chi-wai Bonnie. „Essentiality of methionine aminopeptidase in staphylococcus aureus“. Thesis, Click to view the E-thesis via HKUTO, 2004. http://sunzi.lib.hku.hk/hkuto/record/B31479212.

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33

Kirke, David F. „Protein-nucleic acid interactions regulating bacterial quorum sensing“. Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364668.

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34

Tegmark, Wisell Karin. „Regulation of virulence gene expression in Staphylococcus aureus /“. Stockholm : [Karolinska Univ. Press], 2000. http://diss.kib.ki.se/2000/91-89428-01-3/.

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35

Cheung, Lai-wan, und 張麗雲. „Evaluation of gene targets for identification of tsukamurella species“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206512.

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Using DNA-DNA hybridization as the reference method, the usefulness of six gene targets, secA, ssrA, rpoB, 16S rRNA, groEL and gyrB sequencing for identification of 28 strains isolated from human and snake, and five control strains of Tsukamurella species were evaluated. Phenotypic identification methods, using API 20C AUX and API 50 CH identification kits were also performed and analyzed. Among the 28 test strains, DNA-DNA hybridization confirmed that there were 13 strains of T. tyrosinosolvens, 15 strains of T. paurometabola. Phenotypic identification failed to differentiate the control strains T. inchonensis and T. tyrosinosolvens, indicating phenotypic characteristics are not useful to identify Tsukamurella to species levels. As for genotypic identification, 16S rRNA gene sequencing showed that there was >97% sequence similarity among the 28 test strains and the five control strains, revealing that 16S rRNA gene sequencing is not useful to identify Tsukamurella to species levels. The other five gene loci, secA, ssrA, gyrB, groEL and rpoB were found to be having more sequence variation than 16S rRNA gene, and the discriminatory power of secA gene was found to be the highest among the other four housekeeping genes. The present study also showed that combination of secA and ssrA genes analysis can achieve the best discriminatory power for Tsukamurella identification and the results are concordant with DDH result. More test strains from other clinical important Tsukamurella species such as T. paurometabola, T. strandjordae and T. inchonensis could further verify the usefulness of these gene targets for speciation of Tsukamurella species in future studies.
published_or_final_version
Microbiology
Master
Master of Medical Sciences
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Yu, Tin-Wein. „Physical and functional studies of polyketide synthase genes of Streptomyces“. Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260005.

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Lisle, Warren Derek. „Studies of the integrated functions of the phage T4 encoded Stp peptide“. Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298107.

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Chaithong, Thararat. „A molecular genetic investigation of enterotoxigenic factors in Bacillus cereus“. Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248351.

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39

Malik, A. N. „Genetic studies with Pseudomonas syringae pathovar pisi“. Thesis, University of Greenwich, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354390.

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40

Hill, Russell. „Gene cloning studies in two nocardioform bacteria“. Doctoral thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/21896.

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Bibliography: pages 147-177.
Nocardioforms are Gram-positive, aerobic actinomycetes and are a metabolically diverse group which produce antibiotics, useful enzymes, are important in the biotransformation of organic compounds and the decomposition of organic wastes and are important medically. A gene cloning vector designated pLR591 was constructed from the broad host range, multicopy Streptomyces plasmid pIJ702 and the positive selection Escherichia coli plasmid pEcoR251. This plasmid has useful features for the construction of actinomycete genomic libraries. Cloning of DNA into the unique Bg1II endonuclease site of pLR591 inactivated the lethal EcoRI gene derived from pEcoR251, thereby selecting for recombinant plasmids containing inserted DNA. The thiostrepton resistance gene derived from pIJ702 was shown to be functional in Streptomyces lividans enabling selection of recombinant pLR591 plasmids containing foreign DNA in S. lividans. The vector pLR591 therefore functions as a positive selection Streptomyces-E. coli shuttle vector facilitating construction of actinomycete genomic libraries in E. coli and subsequent transfer of recombinant plasmids into S. lividans.
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Perwez, Tariq. „The mobB protein of broad-host-range plasmid R1162 has two distinct functions, stabilization of relaxosome and enhancement of transfer /“. Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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42

Zhang, Xiaohong. „Cloning, sequencing, expression, and inactivation of the aminodehydroquinate dehydratase gene in Amycolatopsis mediterranei S699 /“. Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/8602.

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43

Yu, Wai-yee Annie. „Epidemiological and emm gene analysis of non-m-typeable group A streptococcus isolates from Hong Kong“. Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23340204.

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44

Leung, Ka-ling. „Novel molecular targets of Burkholderia pseudomallei /“. Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23440144.

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45

Purdy, Shona Thomson. „The biochemistry and genetics of sorbitol metabolism in clostridium pasteurianum“. Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/870.

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46

Gibbons, Sarah Jane. „Population genetics of Wuchereria bancrofti and its bacterial endosymbiont Wolbachia“. Thesis, University of Liverpool, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485943.

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Wuchereria bancrofli is a filarial parasite responsible for 90% of lymphatic filariasis worldwide. Currently a mass drug administration programme, The Global Programme for the Elimination of Lymphatic Filariasis (GPELF) is underway, through the administration of three drugs: diethylcarbamazine (DEC), albendazole and ivermectin, to eliminate lymphatic filariasis as a global he~lth problem. The major aims of the research described in this thesis, were to investigate the genetic diversity of W. bancrofli and their endosymbiotic bacteria Wolbachia and to investigate the presence of putative resistance benzimidazole alleles of W. bancrofli p-tubulin. Attempts were made to isolate W. bancrofli microsatellites using a novel magnetic bead isolation technique. This technique was not successful in identifying microsatellites of w.bancrofli due to overwhelming contamination with human microsatellite DNA. Wolbachia endosymbionts are vertically transmitted and show congruent phylogenies with their nematode hosts, therefore the diversity of W. bancrofli Wolbachia was explored as an indirect marker of w.bancrofli diversity. To investigate the diversity of Wolbachia, genes of the major surface protein (wsp) and cell-division protein (jisZ) were sequenced from W. bancrofli collected from different geographical endemic areas (Burkina Faso, Malawi, Sri Lanka) and were phylogeneticallyanalysed. Although sequence data generated in this study indicates that identical haplotypes of Wolbachia do exist in W. bancrofli samples from different geographical areas, a large amount of diversity was observed in both wsp and flsZ gene sequences in individual W. bancrofli and pooled samples from within these sites. Unweighted Pair Group Method with Arithmetic mean (upGMA) phylogenetic trees generated indicate that Wolbachia is divided into two distinct clades with elevated rates of sequence evolution, especially at non-synonymous sites. Due to the mass drug administration programme currently underway to eliminate lymphatic filariasis, combined with previous reports of benzimidazole resistance (as indicated by Schwab et al. (2006) by the presence of mutation TYR200 in Burkina Faso) experiments to screen for putative resistance benzimidazole alleles in W. bancrofli p-tubulin were investigated. Results demonstrate that the resistanceassociated mutation of benzimidazole at either codon 167 or 200 of the p-tubulin gene was not observed in W. bancrofli samples in patients with varying drug histories from Burkina Faso and Sri Lanka, in contrast to published reports from identical sample sites (village of Tangonko, Burkina Faso). Overall the absence of resistance observed in the study is encouraging for the future of mass drug administration, although further research is required to explain the dynamics of putative resistant alleles under pressure of MDA.
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Nakajima, Erika. „Investigação de proteínas candidatas vacinais contra leptospirose. Apresentação de antígenos na forma de proteínas recombinantes purificadas ou como vacinas vivas em salmonelas atenuadas“. Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/87/87131/tde-02032011-173909/.

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A leptospirose é uma doença endêmica causada por Leptospiras. O genoma da Leptospira interrogans sorovar Copenhageni foi analisado para seleção de potenciais antígenos vacinais. Oito genes foram selecionados e clonados para expressão e purificação dos antígenos. A salmonela SL3261 foi usada como carregadora dos genes de leptospira em vetor pAEsox para expressão das proteínas in vivo. As salmonelas recombinantes induziram resposta imune quando administradas em camundongos por via intraperitoneal. Hamsters foram imunizados com as salmonelas, observando-se que a SLLIC10191 induziu proteção parcial no desafio com L. interrogans sorovar Pomona. Vetores híbridos foram construídos para expressão simultânea de dois antígenos em salmonelas in vivo. Observamos indução de anticorpos específicos, porém, os ensaios de desafio não foram conclusivos. Vários parâmetros do desafio com sorovar Copenhageni foram estudados, como contagem das bactérias e ajuste de dose, variação de virulência por passagens em cultivo e interferência da idade dos animais.
Leptospirosis is an endemic disease caused by Leptospira. The genome of Leptospira interrogans serovar Copenhageni was analyzed for screening potential vaccine antigens. Eight genes were selected and cloned for expression and purification. Salmonella SL3261 was used as carrier of the genes of leptospira in pAEsox vector for in vivo proteins expression of proteins in vivo. Recombinant Salmonella induced immune response when administered intraperitoneally in mice intraperitoneally. Hamsters were immunized with salmonella, resulting we observed that the SLLIC10191 induced partial protection against on challenge with L. interrogans serovar Pomona. Hybrid vectors were constructed for expression of two antigens simultaneously by salmonella in vivo. We observed induction of specific antibodies, however, the challenge tests were not conclusive. Several parameters of the challenge assay with serovar Copenhageni were studied, such as the counting of bacteria count and dose adjustment, changes in virulence by passages in culture and interference backgroundof from the age of animals.
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Stevens, James B. „The molecular genetics of iron uptake in rhizobium leguminosarum“. Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323075.

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49

Kacharia, Fenil Rashmin. „Investigating the Origin and Functions of a Novel Small RNA in Escherichia coli“. PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/3106.

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Non-coding small RNAs (sRNAs) regulate various cellular processes in bacteria. They bind to a chaperone protein Hfq for stability and regulate gene expression by base-pairing with target mRNAs. Although the importance of sRNAs in bacteria has been well established, the mode of origination of novel sRNA genes is still elusive, mainly because the rapid rate of evolution of sRNAs obscures their original sources. To overcome this impediment, we identified a recently formed sRNA (EcsR2) in E. coli, and show that it evolved from a degraded bacteriophage gene. Our analyses also revealed that young sRNAs such as EcsR2 are expressed at low levels and evolve at a rapid rate in comparison to older sRNAs, thereby uncovering a novel process that potentially facilitates newly emerging (and probably mildly deleterious) sRNAs to persist in bacterial genomes. We also show that even though EcsR2 is slightly deleterious to E. coli, it could bind to Hfq and mRNAs to regulate the expression of several genes. Interestingly, while EcsR2 expression is induced by glucose, the expression of its putative targets are regulated by the transcription factor CRP in response to glucose, indicating that EcsR2 has been incorporated into the carbon regulatory network in E. coli. Collectively, this work provides evidence for the emergence, evolution and functions of a novel "young" sRNA in bacteria.
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50

Roberts, Daniel Paul. „Molecular mechanisms of pathogenesis incited by Erwinia carotovora subsp. carotovora“. Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/71251.

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Erwinia carotovora subsp. Carotovora (Ecc) incites soft-rot on many plants. It is believed that soft-rot is due to the concerted activity of extracellular enzymes. Recombinant DNA techniques were used to study the molecular basis of pathogenesis incited by Ecc. Specifically, a clone library of Ecc strain EC14 DNA in plasmid pBR322 was constructed and transformed into Escherichia coli strain HB101. Some of the E. coli strains that contain these hybrid plasmids produce pectinases or cellulase(s). Plasmid pDR1 contains a 3.4 kilobase (kb) EC14 DNA fragment and mediates the production of endo-pectate lyases with isoelectric points (pI) of 9.5 and 7.5 in strain HB101. The pI 9.5 enzyme is believed to be the major extracellular pectolytic enzyme in soft-rot while the pI 7.5 enzyme has no documented counterpart in EC14. Subclone and transposon tn5 analyses of pDR1 indicate that 1.5 kb is necessary for the production of the pI 9.5 and pI 7.5 enzymes and that these enzymes are produced independently of other EC14 pectate lyase enzymes. Plasmid pDR30 contains a 2.1 kb EC14 DNA insert that mediates the production of an endo-polygalacturonase and an exo-pectate lyase in HB101. The exo-pectate lyase encoded by pDR30 produces an inducer of endo-pectate lyase synthesis as a reaction product. The endo-polygalacturonase encoded by pDR30 is thought to play a role in plant cell wall pectic polymer degradation. Restriction endonuclease and Southern hybrididizatian analyses indicate that the EC14 genes on plasmids pDR1 and pDR30 are not part of the same operon. Escherichia coli strain HB101 containing plasmid pDR1 or plasmid pDR30 is unable to macerate potato tuber slices. However, HB101 containing plasmids pDR1 and pDR30 can cause limited maceration of potato tuber slices. There appears to be a genetic interaction between plasmids pDR1 and pDR30 in maceration of potato tuber tissue. However, the EC14 gene(s) contained on plasmid pDR1 are transcribed independently of the EC14 genes contained on plasmid pDR30. It is possible that transcription of certain pectolytic enzymes independent of other pectolytic enzymes provides a flexible system for plant cell wall pectic polymer degradation.
Ph. D.
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