A phase-variable capsule is involved in virulence of Campylobacter jejuni 81-176

Campylobacter jejuni strain 81-176 (HS36, 23) synthesizes two distinct glyc an structures, as visualized by immunoblotting of proteinase K-digested who le-cell preparations. A site-specific insertional mutant in the kpsM gene r esults in loss of expression of a high-molecular-weight (HMW) glycan (appar ent M-r 26 kDa to > 85 kDa) and increased resolution of a second ladder-lik e glycan (apparent M-r 26-50 kDa). The kpsM mutant of 81-176 is no longer t ypeable in either HS23 or HS36 antisera, indicating that the HMW glycan str ucture is the serodeterminant of HS23 and HS36. Both the kpsM-dependent HMW glycan and the kpsM-independent ladder-like structure appear to be capsula r in nature, as both are attached to phospholipid rather than lipid A. Addi tionally, the 81-176 kpsM gene can complement a deletion in Escherichia col i kpsM, allowing the expression of an alpha2,8 polysialic acid capsule in E . coli. Loss of the HMW glycan in 81-176 kpsM also increases the surface hy drophobicity and serum sensitivity of the bacterium. The kpsM mutant is als o significantly reduced in invasion of INT407 cells and reduced in virulenc e in a ferret diarrhoeal disease model. The expression of the kpsM-dependen t capsule undergoes phase variation at a high frequency.