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Title: Regulation of gene expression in Campylocacter jejuni
Author: Jagannathan, Aparna.
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 2001
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The flagellum of Campy/obaeter jejuni is a major virulence determinant, dependent on about 40 flagellar genes that are co-ordinately expressed. However, the existence of a flagellar regulon in C. jejuni and the genes that may control it are so far undefined. To elucidate this, three putative global regulatory gene homologues, rpoN, fliA and flgR encoding the alternative sigma factors, 0'54, 0'28 and the 0'54 -associated transcriptional activator FlgR respectively, were selected. The genes were cloned and mutated by inverse PCR mutagenesis. Kanamycin resistant mutants were constructed by allelic replacement in two C. jejuni strains, NCTC 11168 and NCTC 11828. Electron microscopic studies showed that the rpoN and flgR mutants were nonflagellate; the fliA mutant had truncated flagella. Immunoblotting confirmed lack of flagellin expression in the rpoN and flgR mutants and partial flagellin expression in the fliA mutant. Thus neither the flaB gene with a 0'54 promoter encoding the minor flagellin, nor the flaA gene with a 0'28 promoter encoding the major flagellin are expressed in the rpoN andflgR mutants. These observations confirm the roles of rpoN,flgR andfliA gene homologues in flagellar expression in C.jejuni. Promoter analysis of all the flagellar genes in C. jejuni shows that rpoN and flgR are essential regulatory genes in the putative flagellar regulon of C. jejuni. Microarray hybridisations and analyses reveal that mutation of the rpoN and/or flgR genes affects regulation of expression of several flagellar genes. These analyses shed light on the distinct difference in flagellar regulon between enteric bacteria and C. jejuni and outline the flagellar regulon of the latter. Studies were also carried out with two putative flagellar regulatory genes, Inr and regX3. However, mutations in these genes did not affect the nature of the flagella.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available