[Pseudomonas aeruginosa plasmids controlling resistance to ultraviolet irradiation and increased mutability]

11 out of 35 different resistance (R) plasmids increased the survival of Pseudomonas aeruginosa exposed to ultraviolet irradiation (UV) in the wild-type and uvr and polA mutants but failed to alter the UV-response of a recA mutant. The two most thoroughly studied plasmids, pBS12 and pBS31 protect both uvr+ and uvr- strains from the lethal effect of methyl methane sulphonate and also enhance the UV-induced mutability of the wild-type strain. Sodium arsenite was shown to completely inhibit the UV-protection effect, mediated by pBS12 and pBS31 plasmids. It is suggested that the plasmids pBS12 and pBS31 contain genes, the functioning of which increases significantly the level of resistance of P. aeruginosa cells to UV-irradiation and their mutability, when recA+-dependent arsenite-sensitive pathway of dark DNA reparation is active. The conclusion was made that the genes enhancing resistance of bacteria to UV-irradiation and their mutability are wide-spread among R plasmids of P. aeruginosa belonging to the group of P-2 incompatibility.