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 08 and 09 and Klebsiella 03 and 05, produce the 0 polysaccharides consisting of mannose homopolymers. Previously we reported the isolation and expression of E. coli 09 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 09 and Klebsiella 03 directed the synthesis of 0 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 08 and Klebsiella 05 directed the synthesis of 0 polysaccharides which were antigenically not identical but partially common to those of the parental strains. A rough strain derived from E. coli 08 synthesized LPS which showed the identical antigenicity as the wild strain when the his-rfb region of E. coli 08 was introduced. The results suggest that some genes located distantly from his are additionally required to complete the synthesis of 0 polysaccharides of E. coli 08 and Klebsiella 05.