Genetic approaches to virulence factor expression in Campylobacter jejuni

Arain, Taraq Mahmood (1991) Genetic approaches to virulence factor expression in Campylobacter jejuni. PhD thesis, University of Glasgow.

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Abstract

A modification of a blood-containing agar medium used for cultivation of Campylobacter jejuni is described which promoted or enhanced the haemolytic activity of this organism. Of several types of blood tested, sheep erythrocytes were most sensitive to the actions of the C.jejuni haemolytic factor. A procedure is also reported for the assay of haemolysin released after ultrasonic disintegration of C.jejuni cells. Of 40 strains representative of the C.jejuni /coii group, all exhibited the capacity for haemolysin production. Tentative evidence for a relationship between this haemolysin and the B-lysin of Staphylococcus aureus was not confirmed at the genetic level. A link between the ability to lyse erythrocytes and a microbial requirement for iron was not established. The ability of C.jejuni cell extracts to induce the death of cultured mammalian cells was also assessed by a standard trypan blue assay and by relation to a technique detecting the activity of dehydrogenase enzymes in active mitochondria. Reported also is an evaluation of a reversed phase latex agglutination technique for the detection and assay of the C.jejuni enterotoxin. Two statistically complete libraries of random C.jejuni chromosomal DNA sequences were generated in Escherichia coli, one based in a plasmid shuttle vector and the other in a cosmid vector. Attempts to isolate the gene encoding the Campylobacter haemolysin from both of these genetic libraries proved unsuccessful. Several clones were identified, however, which hybridized with a mixed oligonucleotide probe complementary to a highly conserved region of the mature polypeptide of Vibrio cholerae enterotoxin and E.coli heat-labile toxin. Attempts were made at the isolation of transposon- generated mutants of C.jejuni. Transfer of Tn5, Tn70 and TnphoA from several delivery vectors to the Campylobacter chromosome using protocols employing conjugation or electroporation were, however, unsuccessful. Electroporation experiments did, nevertheless, provide indications for a natural transformation system which allowed entry of DNA into the C.jejuni cell without the requirement for an artificially induced state of competence.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J G Coote
Keywords: Microbiology
Date of Award: 1991
Depositing User: Enlighten Team
Unique ID: glathesis:1991-72076
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 17 May 2019 13:07
Last Modified: 17 May 2019 13:07
URI: http://theses.gla.ac.uk/id/eprint/72076

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