Structure and gene cluster of the o–antigen of Escherichia coli o96

•Chemical structure of the O96 polysaccharide was established.•The O-antigen gene cluster includes seven genes and is located between galF and gnd.•The O96-antigen structure and gene cluster are similar to those of E. coli O170.

Mild acid degradation of the lipopolysaccharide of Escherichia coli O96 afforded a mixture of two polysaccharides. The following structure of the pentasaccharide repeating unit of the major polymer was established by sugar analysis, Smith degradation, and 1H and 13C NMR spectroscopy:Figure optionsDownload full-size imageDownload as PowerPoint slideThe O-antigen gene cluster of E. coli O96 between conserved galF and gnd genes was found to be consistent with this structure, and hence, the major polysaccharide represents the O96-antigen. The O96-antigen structure and gene cluster are similar to those of E. coli O170, and two proteins encoded in the gene clusters of both bacteria were putatively assigned a function of galactofuranosyltransferases. The minor polymer has the same structure as a peptidoglycan-related polysaccharide reported earlier in Providencia alcalifeciens O45 and several other O-serogoups of this species (Ovchinnikova OG, Liu B, Kocharova NA, Shashkov AS, Kondakova AN, Siwinska M, Feng L, Rozalski A, Wang L, Knirel YA. Biochemistry (Moscow) 2012;77:609-15)→4)-β-d-GlcpNAc-(1→4)-β-d-GlcpNAc3(Rlac-lAla)-(1→where Rlac-lAla indicates (R)-1-[(S)-1-carboxyethylaminocarbonyl]ethyl.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide