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

Abstract

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 (1)H and (13)C NMR spectroscopy: [Formula: see text]. The 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.

Keywords: Bacterial polysaccharide structure; Escherichia coli; O-antigen; O-polysaccharide; O–antigen gene cluster; Peptidoglycan-related polysaccharide.