Tn5-Induced Mutations in the Enterobacterial Phytopathogen Erwinia chrysanthemi

Escherichia coli (2492/pJB4JI) matings with Erwinia chrysanthemi produced kanamycin resistant (Km^r) transconjugants, a majority of which were gentamicin sensitive (Gm^s). A small proportion (about 0.8%) of the Km^r Gm^s 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^r Gm^r transconjugant, but not in Km^r Gm^sE. chrysanthemi strains carrying Tn5-induced mutations. In Hfr crosses, Km^r (Tn5) was found linked with most mutations. A majority (>95%) of prototrophic recombinants were Km^s, except for Leu⁺ and Arg⁺ recombinants which were 30 to 50% Km^s. 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^s. We conclude from both genetic and physical data that Tn5 transposed from pJB4JI into different sites on the chromosome of E. chrysanthemi.