A mutant sex factor ofPseudomonas aeruginosa

SUMMARY A mutant with the properties of a recipient has been isolated from the P. aeruginosa donor strain PAT (FP 2 + ) following treatment with the acridine-mustard ICR-191. While this strain displays the properties expected of a female or recipient in a number of genetic tests, the FP 2 determined property of mercury resistance is retained by the strain, suggesting that it may carry the FP2 factor in a mutated form. Treatment of the donor strain PAT (FP2 + ) with acridine-mustard has produced mutant male strains with the ability to form recombinants with other male strains at frequencies similar to that obtained in FP2+ × FP2 − matings. This characteristic has been shown to be due to a mutation in the FP2 factor which is dominant to the wild-type function. The isolation of stable male strains carrying both the mutant and wild type forms of the sex factor suggests that more than one copy of the FP 2 factor occurs in P. aeruginosa strain PAT donors.