SEROLOGICAL CHARACTERIZATION OF FLUORESCENT PSEUDOMONAS STRAINS CROSS-REACTING WITH ANTIBODIES AGAINST ERWINIA-CHRYSANTHEMI

Sixteen bacterial strains, cross-reacting with antibodies against Erwi nia chrysanthemi (Ech), were isolated from potato peel extracts, ditch water, and the rhizosphere of wheat, onion, sugar beet and chicory us ing the immunofluorescence colony-staining procedure. Based on fatty a cid profiles, isolates were classified as belonging to the Pseudomonas fluorescens group. These strains, together with two previously isolat ed cross-reacting P. fluorescens strains, cross-reacted with polyclona l antibodies against Ech in immunofluorescence cell-staining, Ouchterl ony double diffusion, and ELISA. Seventeen strains also reacted strong ly with monoclonal antibodies against the lipopolysaccharides (LPS) of Ech in ELISA. Cell envelopes (CE) and proteinase-K-treated CE (mainly LPS) of cross-reacting bacteria were further characterized with SDS-P AGE and Western blotting. Based on CE protein and LPS patterns, the cr oss-reacting bacteria were classified into two groups, each existing o f two subgroups. Both CE and proteinase-K-resistant antigens strongly cross-reacted on immunoblots with antisera against a wild type strain of Ech. With an antiserum against a LPS O-chain lacking mutant of Ech only protein bands but no proteinase-K-resistant antigens were detecte d on immunoblots. These data suggest that in all cases the highly anti genic LPS 0-chain is responsible for the cross-reactions.