Characterisation of the genetic diversity in the lipooligosaccharide core biosynthesis region of campylobacter jejuni
thesisposted on 15.12.2014, 10:38 authored by Gemma Louise Marsden
Lipooligosaccharides (LOS) are an important constituent of the bacterial outer membrane involved in maintaining cellular structural integrity. In Campylobacter jejuni LOS is postulated to have a role in the virulence of this important gastrointestinal pathogen. The ability of C. jejuni to vary LOS structure and the molecular mimicry of host gangliosides by LOS epitopes suggests a role in the avoidance of host defence mechanisms. Molecular mimicry may form the immunopathological basis for an association with Guillain Barre syndrome. LOS structures differ between strains due to gene content, sequence and tract variation in the LOS biosynthesis gene cluster. Studies have examined the extent of gene content variation in the LOS gene cluster and showed gene content in this region can vary extensively. The aim of this work was to search for novel gene content and further investigate the role of LOS in C. jejuni..;Both PCR and microarray-based methods were developed to classify 50 clinical strains by LOS gene content. Several strains had gene content that did not appear to correlate with any known class and further detailed analysis highlighted that variation is grater than previously supposed. Sequencing revealed two strains that contained capsule polysaccharide biosynthesis genes within the LOS biosynthesis cluster. The presence of capsule genes within the LOS biosynthesis cluster highlights the potential for recombination between these variable polysaccharide loci and further extends the possibility of interaction between the capsule and LOS polysaccharides.;A LOS large deletion mutant was constructed in the genome strain, NCTC 11168 removing the genes between wlaA and wlaT. This mutant shared characteristics of other deep rough mutants being slow growing and sensitive to antibiotics and detergents. Construction of this mutant confirmed the minimal LOS core biosynthesis gene content for bacterial viability and showed the importance of LOS for this bacterium through a role for LOS in host cell invasion.