Structure and gene cluster of the O-antigen of Enterobacter cloacae G3421

• The O-polysaccharide structure of Enterobacter cloacae G3421 was established.
• It shares a trisaccharide fragment with the O-polysaccharide of Shigella boydii type 18.
• Solvolysis with trifluoroacetic acid was applied for selective cleavage of linkages.
• The O-antigen gene cluster of E. cloacae G3421 was sequenced and genes were annotated.

The O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Enterobacter cloacae G3421 and studied by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy. In addition, partial solvolysis with anhydrous trifluoroacetic acid was applied, which cleaved selectively the α-l-rhamnopyranosidic linkages. The following structure of the branched hexasaccharide repeating unit was established.Figure optionsDownload as PowerPoint slideThe O-polysaccharide studied shares the β-l-Rhap-(1→4)-α-l-Rhap-(1→2)-α-l-Rhap trisaccharide fragment with the O-polysaccharide of Shigella boydii type 18. The O-antigen gene cluster of E. cloacae G3421 was sequenced. Functions of genes in the cluster, including those for glycosyltransferases, were tentatively assigned by a comparison with sequences in the available databases and found to be consistent with the O-polysaccharide structure.

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