Plasmid-Mediated Resistance to Streptomycin inXanthomonas campestrispv.vesicatoria

Abstract

Fifty-five percent of 548 strains of Xanthomonas campestris pv. vesicatoria from pepper and tomato grew on media containing 100 .mu.g/ml of streptomycin sulfate. A DNA library of resistant strain BV5-4a was constructed in the cosmid vector pLAFR3. A clone containing an insert of 17 kb conferred resistance to streptomycin after conjugative transfer to a sensitive strain of X. c. vesicatoria. The 4.9-kb insert DNA of a subclone encoding wild-type resistance to streptomycin was labeled and used as a probe in Southern hybridization analyses. The streptomycin-resistance locus was found to be on a plasmid of 68 kb. The subclone DNA hybridized with enzyme-digested genomic or plasmid DNA of three of 17 other resistant strains of X. c. vesicatoria as well as with the DNA from streptomycin-resistant strains Psp 34 and Psp 36 of Pseudomonas syringae pv. papulans. No hybridization occurred with DNA from Erwinia amylovora strain UCBPP 829 or p. cichorii strain Pc 83-1, which also are resistant to streptomycin.