Immunochemical Characterization of O Polysaccharides Composing the a-D-Rhamnose Backbone of Lipopolysaccharide of Pseudomonas syringae and Classification of Bacteria

Murine monoclonal antibodies (MAbs) reacting with Pseudomonas syringae lipopolysaccharide (LPS) O poly-saccharides (OPS) composed of tetra- and tri-a-D-rhamnose repeats in the backbone [3)D-Rha(a1-3)D-Rha (a1-2)D-Rha(a1-2)D-Rha(a1] and [3)D-Rha(a1-3)D-Rha(a1-2)D-Rha(a1] were generated and used for immu-nochemical analysis and for serological classification of the bacteria. A total of 195 of 358 P. syringae strains tested representing 21 pathovars were shown to share a common epitope, 1a, and were classified into sero-group O1. All strains with pathovars aptata, glycinea, japonica, phaseolicola, and pisi, most of the strains with pathovars atrofaciens and striafaciens, and half of the strains with pathovar syringae were classified into sero-types O1a*, O1b, O1c, and O1d within serogroup O1. Serogroup-specific epitope 1a was inferred to be related to the (a1-2)D-Rha(a1-3) site of the OPS backbone. The serotype-specific epitopes 1b, 1c, 1d, and 1a * were in-ferred as relating to the immunodominant lateral (a1-3)D-Rha, (b1-4)D-GlcNAc, and (a1-4)D-Fuc substituents and backbone-located site (a1-3)D-Rha(a1-2), respectively, of OPSs that share the common tetra-D-rhamnose repeats in the backbone. A total of 7.3 % of the strains studied, all with pathovars morsprunorum and lapsa, were classified as serotypes O2a and O2d within serogroup O2. Serotype-specific epitope 2a was inferred as being related to the backbone-located site D-Rha(a1-3)D-Rha and epitope 2d to the immunodominant lateral (a1-4)D-Fuc residue of OPS consisting of tri-D-rhamnose repeats in the backbone. Epitope 2d alternated wit