Previous study showed that some Gram-negative bacteria possess human blood group activity. Among them, Escherichia coli O86 has high blood group B activity and weak blood group A activity. This is due to the cell surface O-antigen structure, which resembles that of human blood group B antigen. In this study, we sequenced the entire E. coli O86 antigen gene cluster and identified all the genes responsible for O-antigen biosynthesis by ...