Lipopolysaccharide O-antigen biosynthesis in Shigella dysenteriae serotype 1: analysis of the plasmid-carried rfp determinant.

Abstract The O-antigen polysaccharide of the lipopolysaccharide of Shigella dysenteriae serotype 1 is encoded by determinants located on a 9 kb plasmid ( rfp ) and on the chromosome near the his locus ( rfb ). Molecular genetic and biochemical studies of the rfp determinant reported here show that the rfp region contains two genes, rfpA and rfpB , lying in an operon. rfpB was demonstrated to encode a membrane bound galactosyl transferase. The low G+C content of rfp DNA suggests that it did not originate in Shigella .