O polysaccharides (OPS) of the lipopolysaccharides (LPS) of Pseudomonas syringae pathovar tomato GSPB 483 and pathovar maculicola IMV 381 were studied by 1 H-NMR and 13 C-NMR spectroscopy, including two-dimensional COSY, rotating-frame NOE spectroscopy (ROESY), and H-detected 1 H, 13 C 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.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. Immunochemical studies of LPS of P. syringae revealed correlation between the chemical structures of OPS and the specificity of mAbs against various strains of P. syringae [5Ϫ8]. These findings enabled us to shed some light on the molecular basis of the immunospecificity of P. syringae LPS and to infer the serogroup-specific and serotype-specific OPS-associated epitopes. One of the mAbs, Ps4e 1 (formerly Ps4a), produced against P. syringae pv. syringae (holci) IMV 8300, was shown to be specific in ELISA [8] to OPS with pentasaccharide O repeats containing four L-Rha residues in the backbone and one lateral residue of 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc) (structure 3) [2]. This LPS phenotype is characterised by the serological formula O4a,4e,4e 1 . However, mAb Ps4e 1 did not

The core structure of the lipopolysaccharide (LPS) isolated from a rough strain of the phytopathogenic bacterium Pseudomonas syringae pv. phaseolicola, GSPB 711, was investigated by sugar and methylation analyses, Fourier transform ion‐cyclotron resonance ESI MS, and one‐ and two‐dimensional 1H‐, 13C‐ and 31P‐NMR spectroscopy. Strong alkaline deacylation of the LPS resulted in two core‐lipid A backbone undecasaccharide pentakisphosphates in the ratio ≈ 2.5 : 1, which corresponded to outer core glycoforms 1 and 2 terminated with either l‐rhamnose or 3‐deoxy‐d‐manno‐oct‐2‐ulosonic acid (Kdo), respectively. Mild acid degradation of the LPS gave the major glycoform 1 core octasaccharide and a minor truncated glycoform 2 core heptasaccharide, which resulted from the cleavage of the terminal Kdo residues. The inner core of P. syringae is distinguished by a high degree of phosphorylation of l‐glycero‐d‐manno‐heptose residues with phosphate, diphosphate and ethanolamine diphosphate groups. The glycoform 1 core is structurally similar but not identical to one of the core glycoforms of the human pathogenic bacterium Pseudomonas aeruginosa. The outer core composition and structure may be useful as a chemotaxonomic marker for the P. syringae group of bacteria, whereas a more conserved inner core structure appears to be representative for the whole genus Pseudomonas.

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The O-specific polysaccharide of Pseudomonas fluorescens biovar B, strain IMV 247, was studied by acid hydrolysis, GLC-MS and 1H and 13C NMR spectroscopy, including 1D and 2D NOE, 2D hybrid TOCSY and ROESY (TORO), and 2D H-detected heteronuclear multiple-bond correlation (HMBC) experiments. The polysaccharide was found to contain L-rhamnose, 3.6-dideoxy-3-[(S)-3-hydroxybutyramido]-D-glucose (D-Qui3NHb), 2-acetamido- 2,4,6-trideoxy-4-[(S)-3-hydroxybutyramido-D-glucose (D-QuiNAc4NHb) and 2-acetamido-2- deoxy-D-galacturonic acid (D-GalNAcA). Partial acid hydrolysis of the polysaccharide resulted in a non-reducing GalNAcA-->QuiNAc4NHb disaccharide with the 3-hydroxybutyryl group glycosylated intramolecularly by the QuiN4N residue. The following structure of the tetrasaccharide repeating unit of the polysaccharide was established:-->4) -alpha-D-GalpNAcA-(1-->3)- alpha-D-QuipNAc4NHb-(1-->2)-beta-D-Quip3NHb-(1-->2)-alpha-L- Rhap(1-->.

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