Transposon Tn5 mutagenesis of Pseudomonas fluorescens to isolate mutants deficient in antibacterial activity

Pseudomonas fluorescens was subjected to insertion mutagenesis studies using the transposon Tn5‐GM to generate mutants deficient in antibacterial activity minus mutants. The transposon located on the temperature‐sensitive plasmid pCHR84 was conjugally transferred into the non‐pathogenic pseudomonad using the triparental mating procedure. Random integration of Tn5‐GM into the chromosome of P. fluorescens was achieved by heat ttreatment of the transformed cells at 42°C. Approximately 2% of transconjugants revealed an auxotrophic phenotype indicating efficient integration of the employed transposon into the chromosome of P. fluorescens. One transposon insertion mutant was obtained showing an antibacterial activity minus phenotype. This mutant (MM‐7) was found to be defective in the production of an unidentified antibacterial compound against B. subtilis. These results introduce Tn5 transposon mutagenesis as a new useful tool for the molecular analysis of P. fluorescens.