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

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 C-13 NMR spectroscopy: -> 4)-alpha-D-GlcpNAc-(1 -> 4)-beta-D-GlcpNAc-(1 -> 5)-beta-D-Galf-(1 -> 3)-beta-D-GlcpNac-(1 -> 4 up arrow 1 beta-D-Galf 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 O96antigen 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)-beta-D-GlcpNAc-(1 -> 4)-beta-D-GlcpNAc3(Rlac-LAla)-(1 -> where Rlac-LAla indicates (R)-1-[(S)-1-carboxyethylaminocarbonyl]ethyl. (C) 2015 Elsevier Ltd. All rights reserved.