Structure and genetics of the O-antigen of Enterobacter cloacae G3054 containing di-N-acetylpseudaminic acid

•E. cloacae is a pathogen causing respiratory, urinary, and surgical site infections.•The OPS structure of E. cloacae G3054 was established.•The gene cluster of E. cloacae G3054 has been sequenced and genes were annotated.

Mild acid degradation of the lipopolysaccharide of Enterobacter cloacae G3054 resulted in the cleavage of the O-polysaccharide at the linkage of residues of 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-l-manno-non-2-ulosonic acid (di-N-acetylpseudaminic acid, Pse5Ac7Ac) in the main chain. The resultant oligosaccharide and an alkali-treated lipopolysaccharide were studied by sugar analysis along with 1H and 13C NMR spectroscopy, and the following structure of the branched pentasaccharide O-unit of the O-polysaccharide was established:Figure optionsDownload full-size imageDownload as PowerPoint slideThe O-antigen gene cluster of E. cloacae G3054 between conserved genes galF and gnd was sequenced. Most genes necessary for the O-antigen synthesis were found in the cluster and their functions were tentatively assigned by comparison with sequences in the available databases.

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