Structure and gene cluster of the O-antigen of Escherichia coli O19ab

The O-polysaccharide (O-antigen) of Escherichia coli O19ab was studied by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy. The following structure of the linear pentasaccharide repeating unit was established:→2)-α-L-Rhap-(1→2)-α-L-Rhap-(1→2)-α-L-Rhap-(1→2)-α-D-Glcp-(1→3)-α-D-GlcpNAc6Ac-(1→where the degree of O-acetylation of GlcNAc is ∼33%. The O-antigen gene cluster of E. coli O19ab was sequenced. The gene functions were tentatively assigned by comparison with sequences in the available databases and found to be in full agreement with the E. coli O19ab-antigen structure.