Genetics behind the biosynthesis of nonulosonic acid containing lipooligosaccharides inCampylobacter coli

Abstract

ABSTRACTCampylobacter jejuniandCampylobacter coliare the most common cause of bacterial gastroenteritis in the world. Ganglioside mimicry byC. jejunilipooligosaccharide (LOS) is the triggering factor of Guillain-Barré syndrome (GBS), an acute polyneuropathy. Sialyltransferases from the glycosyltransferase (GT) family 42 are essential for the expression of ganglioside mimics inC. jejuni. Recently, two novel GT-42 genes,cstIVandcstV, have been identified inC. coli.Despite being present in ∼11% of currently availableC. coligenomes, the biological role ofcstIVandcstVis unknown. In the present study, mutation studies in two strains expressing eithercstIVorcstVwere performed and mass spectrometry was used to investigate differences in the chemical composition of LOS. Attempts were made to identify donor and acceptor molecules usingin vitroactivity tests with recombinant GT-42 enzymes. Here, we show that CstIV and CstV are involved inC. coliLOS biosynthesis. In particular,cstVis associated with LOS sialylation, whilecstIVis linked to the addition of a diacetylated nonulosonic acid residue.IMPORTANCEDespite being a major foodborne pathogen,Campylobacter coliglycobiology has been largely neglected. The genetic makeup of theC. colilipooligosaccharide biosynthesis locus was largely unknown until recently.C. coliharbour a large set of genes associated to lipooligosaccharide biosynthesis, including several putative glycosyltransferases involved in the synthesis of sialylated lipooligosaccharide inCampylobacter jejuni. In the present study,C. coliwas found to express lipooligosaccharide structures containing sialic acid and other nonulosonate acids. These findings have a strong impact in understandingC. coliecology, host-pathogen interaction, and pathogenesis.