STABILITY AND CONJUGAL TRANSFER KINETICS OF A TOL PLASMID IN PSEUDOMONAS-AERUGINOSA PAO-1162

Batch mating experiments were employed to study the kinetics of the co njugal transfer of a TOL plasmid, using the transconjugant strain Pseu domonas aeruginosa PAO 1162 (TOL) as the plasmid donor and Pseudomonas putida PB 2442 and Pseudomonas aeruginosa PAO 1162N as the plasmid re cipients. Transfer rates from PAO 1162 (TOL) to PAO 1162N and PB 2442 measured for exponentially grown PAO 1162 (TOL) were 1.81 x 10(-14) (s tandard error (S.E.) 1.25 X 10(-15)) ml cell(-1)min(-1) and 3.32 x 10( -13) (S.E. 4.42 x 10(-14)) ml cell(-1)min(-1), respectively. The insta bility of the TOL plasmid in PAO 1162 (TOL) was evaluated under condit ions that were non-selective for maintenance of the TOL catabolic func tions. The measured rates of instability were 6.7 10(-6) to 8.3 10(-6) min(-1), and the loss of the catabolic functions was mainly caused by structural instability of the plasmid.