Structure and gene cluster of the O-antigen of Escherichia coli O156 containing a pyruvic acid acetal

• O156 strains belong to Shiga toxin-producing E. coli (STEC).
• The O156-polysaccharide includes a pyruvic acid acetal on a Gal residue.
• The structure of the O-polysaccharide of E. coli O156 was elucidated.
• The O156-antigen gene cluster is consistent with the O-polysaccharide structure.

The lipopolysaccharide of Escherichia coli O156 was degraded under mild acidic and alkaline conditions and the resulting polysaccharides were studied by sugar analysis and 1H and 13C NMR spectroscopy. The following structure of the pentasaccharide repeating unit of the O-polysaccharide was established:Figure optionsDownload as PowerPoint slidewhere Rpyr indicates R-configurated pyruvic acid acetal. Minor O-acetyl groups also were present and tentatively localized on the Gal residues. The gene cluster for biosynthesis of the O-antigen of E. coli O156 was analyzed and shown to be consistent with the O-polysaccharide structure.

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