Isolation of rfb gene clusters directing the synthesis of O polysaccharides consisting of mannose homopolymers and serological analysis of lipopolysaccharides.

Four serotypes of two genera, Escherichia coli O8 and O9 and Klebsiella O3 and O5, produce the O polysaccharides consisting of mannose homopolymers. Previously, we reported the isolation and expression of E. coli O9 rfb in E. coli K-12 strains (Kido et al, J. Bacteriol., 171: 3629-3633, 1989). In this study, R' plasmids carrying his-rfb region of the other three strains were isolated and expressed in E. coli K-12 strain. Serological study of lipopolysaccharides (LPS) synthesized in E. coli K-12 strain was carried out. His-linked rfb genes from E. coli O9 and Klebsiella O3 directed the synthesis of O polysaccharides with the same antigenicity as those of the parental strains in E. coli K-12 strain. On the other hand, rfb genes from E. coli O8 and Klebsiella O5 directed the synthesis of O polysaccharides which were antigenically not identical but partially common to those of the parental strains. A rough strain derived from E. coli O8 synthesized LPS which showed the identical antigenicity as the wild strain when the his-rfb region of E. coli O8 was introduced. The results suggest that some genes located distantly from his are additionally required to complete the synthesis of O polysaccharides of E. coli O8 and Klebsiella O5.