Structural heterogeneity in the lipopolysaccharides of Pseudomonas syringae with O-polysaccharide chains having different repeating units

Studies by sugar and methylation analyses, Smith degradation, and H-1 and C-13 NMR! spectroscopy revealed a structural heterogeneity in the O-polysaccharides of Pseudomonas syringae pvs. coronafaciens IMV 9030 and atrofaciens IMV 8281 owing to the presence of different types of repeating units. In strain IMV 9030, the major repeating units are a linear a-L-rhamnose trisaccharide and a tetrasaccharide (A, n = 0 or 1). A minor repeating unit is a branched pentasaccharide with an a-L-rhamnose main chain and a lateral 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc) residue (B, X = 2, n = 1). In strain IMV 8281, all repeating units are branched and differ in size and position of substitution of one of the alpha -L-rhamnose, residues (tetrasaccharide, B, X = 3, n = 0; pentasaccharides, B, X = 2 or 3, n = 1). A -->2)-alpha -L-Rhap-(1-[-->2)-alpha -L-Rhap-(1-](n)-->3)-alpha -L-Rhap-(1 -->3)-alpha -L-Rhqp-(1 --> [GRAPHICS] Reinvestigation of the structure of the branched O-polysaccharide of P. syringae pv. tomato IPGR 140 showed that, together with the major tetrasaccharide repeating unit (B, X = 3, n = 0) [Knirel, Y. A., et al. Carbohydr. Res. 1993, 243, 199-204], it has a minor pentasaccharide repeating unit (B, X = 3, n = 1). (C) 2001 Elsevier Science Ltd. All rights reserved.