Structure of the O antigen of Escherichia coli K-12 and the sequence of its rfb gene cluster

E. coli K-12 gene organization belongs to the congregation of rfb gene cluster, which has segments homologous to those of Dysenteriae and Flexneri. Study of DNA sequences and comparison with other sequences reveal the presence of conserved, powerful regulatory regions within E. coli and S. enterica clones K-12 O16. O antigen synthesis is rfb-dependent for the conversion of Glc NAc to UndP and resembles that of Dysentriae and Flexneri.