Plasmids of Pseudomonas syringae: no evidence of a role in toxin production or pathogenicity

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Abstract
Forty strains of Pseudomonas syringae were analyzed for the presence of plasmids. Of the 21 strains known to produce syringomycin 9 contained plasmids, and of the 10 strains known to produce syringotoxin all contained at least one plasmid. Seven of the remaining nine strains produced a toxin which has not been identified. Of these strains two were shown to contain plasmids. These results suggest that strains exist which do not contain plasmids but produce syringomycin or an unidentified toxin. The same cannot be said for the syringotoxin-producing strains, since all strains examined contained plasmids. In addition, four plasmids have been eliminated from two syringomycin-producing strains with no effect on toxin production or pathogenicity. At present there is no evidence to suggest that any of the plasmids observed in this study are involved with toxin production or pathogenicity.