Campylobacter jejuniLipooligosaccharides: Structures and Biosynthesis

Abstract

This chapter reviews the structure, biosynthesis, and genetic determination of Campylobacter jejuni lipooligosaccharides (LOSs), with particular reference to the core oligosaccharide region. In particular, the genetic bases for variation of the outer core are discussed, including gene content variation between LOS loci and mechanisms generating LOS core region variation. Although the chapter predominantly addresses the biosynthesis of the variable LOS outer core of C. jejuni, the biosynthesis and genetic determination of the inner core lipid A region is also examined. Variation in LOS structures is due to diversity of the constituent sugars (number of carbon atoms, ring form, isomeric form, anomeric configuration, etc.), the derivatization of the sugars with noncarbohydrate moieties, and the linkages between the individual sugars (or monosaccharides). The formation of these linkages is determined by the glycosyltransferases and other transferases encoded in the LOS biosynthesis locus. Sugar availability for incorporation into LOS is often determined by enzymes from the LOS biosynthesis locus that are involved in synthesis of sugar intermediates such as cytidine monophosphate-5-N-acetylneuraminic acid (CMPNeu5Ac). There is evidence of recombination occurring within the LOS locus to create mosaics of different classes. Functions can be assigned to 12 of the 13 open reading frames (ORFs) present in the LOS biosynthesis locus of OH4384, the only exception being ORF 12a. The variety of capsular polysaccharide (CPS) structures and biosynthesis loci observed in C. jejuni suggests that it would contribute as much as the LOS repertoire to an open pan-glycome.