Structure of the O polysaccharide and immunochemical relationships between the lipopolysaccharides of Pseudomonas syringae pathovar tomato and pathovar maculicola.

O polysaccharides (OPS) of the lipopolysaccharides (LPS) of Pseudomonas syringae pathovar tomato GSPB 483 and pathovar maculicola IMV 381 were studied by 1H-NMR and 13C-NMR spectroscopy, including two-dimensional COSY, rotating-frame NOE spectroscopy (ROESY), and H-detected 1H,13C heteronuclear multiple-quantum coherence (HMQC) experiments. The OPS from both strains were shown to be chemically identical. Two structurally different types of repeating units (O repeats 1 and 2) were elucidated in each OPS. The minor O repeat is a pentasaccharide having the structure 2. The same structure has been reported earlier for some other OPS of P. syringae. The major O repeat is a hexasaccharide with the novel structure 1 which is distinguished from 2 by the presence of the second lateral residue of 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc) and by a different position of substitution of one of the L-rhamnose (Rha) residues in the backbone. [structures: see text] Structural and serological diversity of OPS of strains belonging to P. syringae pv. tomato and pv. maculicola and phylogenetic relatedness of the strains are discussed.