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Title: Chromosomal DNA variation in Bordetella species
Author: Leigh, Antonia F.
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1993
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Previous studies had shown that a probe, containing a hin DNA invertase gene from S. typhimurium, hybridised to a B. pertussis chromosomal DNA fragment. This B. pertussis fragment was sequenced in this study. Analysis of the DNA and deduced protein sequence showed no homology to DNA invertases nor to other sequences except limited homology to insertion sequence transposases. Reanalysis of the hybridisation of the hin DNA fragment probe to chromosomal Bordetella DNA showed greater homology to a different fragment. It was deduced that this hybridisation may have been due to flagellin sequences present in the probe. A PCR-amplified hin probe derived from S. typhimurium DNA was therefore produced consisting only of hin DNA. This probe hybridised to tandem repeat sequences in B. pertussis DNA. These are known to be insertion sequences. It is hypothesised that the hybridisations to the DNA of the other Bordetella strains in this study were also due to limited homology to insertion sequences. A PCR-amplified S. typhimurium HI flagellin gene, and an oligonucleotide consisting of conserved N-terminal flagellin sequences, were also used as probes. They hybridised to the DNA of all four Bordetella strains although only two are recognised as expressing flagella. The two non-motile human pathogens B. pertussis and B. parapertussis thus both probably contain flagellin genes that are not expressed. The methylation state of various phases and modes of the Bordetella DNA was examined. Previous studies had suggested that B. pertussis strains in the virulent phase were modified, possibly by methylation. Results in this study showed the presence of Dcm methylation in the DNA of some of the phase avirulent strains of B. pertussis and also under modulated conditions in a virulent phase I strain. This might suggest that other additional modes of phase variation and regulation of virulence factors exist in addition to those already recognised.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available