The genetic basis of lipopolysaccharide bioynthesis in Campylobacter jejuni

Lipopolysaccharide (LPS) and lipooligosaccharide (LOS) molecules are important in the pathogenesis of many Gram negative bacteria. In the enteric pathogen Campylobacter jejuni LPS and LOS molecules are endotoxic, have been suggested as adhesins and are implicated in the development of the auto-immune disorder Guillian Barre syndrome. The aim of this study was to therefore investigate the genetic basis of LPS/LOS biosynthesis, structural variation and function in C. jejuni. A bioinformatic approach was used to identify and characterize LPS/LOS biosynthesis genes in the genome sequence of C. jejuni NCTC 11168 to enable a model of core oligosaccharide biosynthesis to be proposed. Structural variation occurs between LOS/LPS molecules produced by different strains of C. jejuni. The genetic basis of this inter-strain variation was investigated and both conserved and polymorphic genes were identified. Cloning and DNA sequence analysis of some polymorphic genes enabled tentative functions to be proposed. The functions of two genes, one conserved (waaF) and one polymorphic (wlaJ) were further investigated. Studies on wlaJ did not reveal the precise role of this gene in LPS/LOS biosynthesis. However, the function of waaF as encoding a heptosyltransferase involved with inner core biosynthesis was confirmed using complementation and mutational analysis. Significantly, analysis of waaF in C. jejuni NCTC 11828 confirmed that the O-chain molecule produced by this strain is not linked to the core oligosaccharide, and is therefore an independent lipid bound capsular polysaccharide.