Structural studies of the O-antigenic polysaccharide from Plesiomonas shigelloides strain AM36565

The structure of the repeating unit of the O-antigenic polysaccharide from Plesiomonas shigelloides strain AM36565 has been determined. Component analysis and 1H and 13C NMR spectroscopy experiments were employed to elucidate the structure. Inter-residue correlations were determined by 1H,13C heteronuclear multiple-bond correlation, 1H,1H-NOESY, and 1H,13C-HSQC–1H,1H-NOESY experiments. The O-antigen polysaccharide is composed of repeating units with the following structure: →3)-α-l-Rhap-(1→2)-α-l-Rhap-(1→4)[β-d-GalpNAc-(1→3)]-α-d-GlcpNAc-(1→, in which the monosaccharide side-chain substitutes the backbone in half of the repeating units. A matrix-assisted laser desorption/ionization mass spectrometry experiment suggested that the polysaccharide consists of two regions, one with tetrasaccharide repeating units and one with trisaccharide repeating units.