Investigation of the mating system ofPseudodomonas aeruginosastrain I VI. Mercury resistance associated with the sex factor (FP)

Abstract

SUMMARYResistance to mercury has been shown to be associated with the presence of the sex factor (FP) inPseudomonas aeniginosa. The resistance is expressed in all infected cells even though they do not necessarily function as donors.For selection of freshly infected recipients when streptomycin or nalidixic acid were used for contra-selection of the donors, the level of mercury had to be reduced to betweenm/20000 andm/40000 when 500 units of streptomycin were present per ml and tom/40000 when 1·0 mg of nalidixic acid was included in each ml of medium. Normally donor strains would grow in the presence of Hg ions at a concentration ofm/2000, which is 10–20 times greater than the concentration in the two selective media.The kinetics of transfer of the sex factor were investigated and it was shown that transfer began almost as soon as the cells were mixed and was completed in 20 min when 5 min were allowed for pairing.