Tn5-Induced Mutations in the Enterobacterial Phytopathogen Erwinia chrysanthemi

Escherichia coli (2492/pJB4JI) matings with Erwinia chrysanthemi produced kanamycin resistant (Km) transconjugants, a majority of which were gentamicin sensitive (Gm). A small proportion (about 0.8%) of the Km Gm clones were either auxotrophic or failed to catabolize galacturonate (Gtu). The R plasmid (pJB4JI) DNA was detected in the parent E. coli strain and in a Km Gm transconjugant, but not in Km GmE. chrysanthemi strains carrying Tn5-induced mutations. In Hfr crosses, Km (Tn5) was found linked with most mutations. A majority (>95%) of prototrophic recombinants were Km, except for Leu and Arg recombinants which were 30 to 50% Km. Spontaneous revertants were obtained for all markers except car, gtu, lys, thr, and trp. Prototrophic revertants, with the exception of Met, Leu, or His clones, were Km. We conclude from both genetic and physical data that Tn5 transposed from pJB4JI into different sites on the chromosome of E. chrysanthemi.