Structure of the O-specific polysaccharide from the legume endosymbiotic bacterium Ochrobactrum cytisi strain ESC1T

• Structure of the O-polysaccharide of Ochrobactrum cytisi ESC1T was established.
• OPS is built of disaccharide units composed of d-Fuc and d-GalNAc.
• Galactosamine can be partly decorated with R-pyruvyl or O-methyl residues.

The O-specific polysaccharide was obtained from the lipopolysaccharide of the legume-endosymbiotic bacterium Ochrobactrum cytisi strain ESC1T and studied by chemical analyses and 1D and 2D NMR spectroscopy. The polysaccharide was found to have a disaccharide repeating unit containing α-d-fucose and β-N-acetyl-d-galactosamine residues connected via (1→3)-glycosidic bonds, resulting in the following structure:→3)-α-d-Fucp-(1→3)-β-d-GalpNAc-(1→The d-GalpNAc residue was nonstoichiometrically substituted with a 4-O-methyl group (∼10%) or with a 4,6-O-(1-carboxy)-ethylidene residue (pyruvyl group) (∼10%).

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