DISTRIBUTION OF PSEUDOMONAS-SYRINGAE PATHOVARS INTO 23 O-SEROGROUPS

Serological reactions of Pseudomonas syringae and Pseudomonas viridifl ava were studied by Ouchterlony double diffusion, A total of 55 polycl onal antisera, containing anti-lipopolysaccharide (anti-LPS) precipita ting antibodies, were cross-tested against antigenic suspensions of 51 strains. Twenty-three O serogroups were defined, primarily on the rea ction of the type strains, Two families of O serogroups showed antigen ic crossreactivities (PHA, MOP1, MOP2, MOP3, HEL1, HEL2, and SYR1; PER SAVTOM1, PERSAVTOM2, DEL, POR, and SYR2), Ten O serogroups showed a cl earcut specificity: APTPIS, TAB, VIR1, VIR2, VIR3, SYR3, SYR4, SYR5, H US, and LAC. The last serogroup (RIB) contained strains with rough col ony morphology and side chain-deficient LPSs, as evidenced by sodium d odecyl sulfate-polyacrylamide gel electrophoresis. The LPS basis of th e O serogroups was demonstrated by immunoblotting, Serological referen ce strains were designated for all of the O serogroups, and correspond ence was established between the O serogroups studied and seven previo us serogroups (L, T, Pastushenko and I, D. Simonovich, Mikrobiol, Zh, 41:222-229 and 330-339, 1979). A total of 355 strains of P. syringae ( sensu late) belonging to 15 pathovars, not including pathovar syringae , were typed into the 23 described O serogroups, O serogroups were ass igned after double-diffusion reactions, with each strain compared with serological references, The utility of O serogrouping to study P. syr ingae pathovar structure and diversity is discussed.