Campylobacter jejuni is an enteric bacterium that causes human gastroenteritis worldwide. Some C. jejuni strains exhibiting human ganglioside-like lipooligosaccharide (LOS) structures, such as GM1 ganglioside, can induce an autoimmune neuropathy of the peripheral nervous system known as the Guillain-Barré syndrome (GBS). This GBS-inducible determinant is encoded by a gene cluster, which shows a high degree of variation among C. jejuni strains. The experiments presented in this thesis were conducted to give a better insight into the LOS synthesis genes in relation to the pathophysiology of C. jejuni. Firstly, a C. jejuni strain without GM1-like molecules was shown to be able to take up large DNA fragments, including LOS synthesis genes, from a strain expressing GM1-like molecules and consequently be transformed into a number of potential GBS-inducible transformants, which exhibited a high degree of genetic and phenotypic diversity. The ability of C. jejuni to take up and integrate foreign DNA explains the genome plasticity observed in this pathogen. Secondly, while attempting to analyse transcription of the LOS gene cluster, neither published methods nor any commercially available kits for RNA isolation could produce DNA-free RNA from C. jejuni. Combinations of these methods were trialled and only the combination of RNAzolB, TURBO DNase treatment, and acid phenol extraction was able to produce DNA-free RNA. The RNA isolated from most C. jejuni strains showed different RNA patterns to that of other bacteria. In addition the RNA from C. jejuni seemed closely associated with DNA compaired to RNA from other organisms. This might be caused by species-specific DNA conformation or chromatin structure. Thirdly, bidirectional transcription was observed in the LOS gene cluster. Both DNA strands were transcribed but transcription of the non-coding strands was at a lower rate, and both sense and antisense transcripts of each LOS gene tested were responsive to acid stress. This unusual transcription might have a potential effect on the expression of the GBS-inducing determinant. Finally, one of the LOS genes, the htrB gene, was further analysed. It was shown that expression of the htrB gene affects morphology, viability, growth ability, and sensitivity to stress environments. These results showed that the LOS molecule of C. jejuni is involved in many processes and is an important molecule for survival.
| Identifer | oai:union.ndltd.org:ADTP/210279 |
| Date | January 2006 |
| Creators | Phongsisay, Vongsavanh, vongsavang@yahoo.com.au |
| Publisher | RMIT University. Applied Sciences |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://www.rmit.edu.au/help/disclaimer, Copyright Vongsavanh Phongsisay |
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