Structure elucidation and gene cluster characterization of the O-antigen of Vibrio cholerae O68 containing (2S,4R)-2,4-dihydroxypentanoic acid

Abstract

The O-polysaccharide (O-antigen, OPS) of Vibrio cholerae O68 was studied using chemical analyses and 1D and 2D NMR spectroscopy. The following structure of the tetrasaccharide repeating unit of the OPS was established:▪where Dhpa indicates (2S,4R)-2,4-dihydroxypentanoic acid existing mainly in the form of 1,4-lactone. Recently, (2R,4S)- and (2R,4R)-isomers of Dhpa have been found in the OPS of Providencia alcalifaciens O8 and O31, respectively. Functions of genes in the O-antigen gene cluster of Vibrio cholerae O68 were predicted according to the OPS structure established. These data provide a molecular basis for classification of V. cholerae strains.