Indicator Technique for Antimetabolic Toxin Production by Phytopathogenic Species of Pseudomonas

A simple bacteriological technique involving inhibition zone production on a lawn of Escherichia coli was developed to detect antimetabolite toxin production by phytopathogenic species of Pseudomonas. It was established that the mechanism of E. coli inhibition paralleled that of phytotoxin-induced chlorosis of plant tissue. Derivatives of Pseudomonas tabaci and Pseudomonas phaseolicola which did not produce antimetabolite were readily identified by use of this technique. The presence of plasmid DNA in P. tabaci strains was demonstrated, but no physical evidence for plasmid involvement in tabtoxin production was found. The role of antimetabolite production in the pathogenicity of P. phaseolicola was also investigated. The method was extended to show that strains of P. maculicola, P. syringae, and P. coronofaciens also produce antimetabolites.