Loss of Ultraviolet Light Protection and Enhanced Ultraviolet Light-induced Mutability in Pseudomonas aeruginosa Carrying Mutant R Plasmids

Two mutants of the R plasmid pMG2, selected on the basis of loss of enhanced ultraviolet light (u.v.)-induced mutability, no longer protected a wild type, a uvr rec + type mutant, or a polA type mutant of Pseudomonas aeruginosa against the lethal effects of u.v. For one of the R plasmid mutants tested, pPL2, a plasmid-determined DNA polymerase was no longer detected. The properties of these mutants support the hypothesis that a plasmid gene function responsible for enhanced u.v.-induced mutability also confers u.v.-protection on the host cells. Furthermore a plasmid-determined DNA polymerase plays a major role in producing these effects. On the basis of the effects of sodium arsenite on plasmid u.v.-protection and enhanced u.v.-induced mutability in strain trpf1, it is proposed that a recA-dependent, arsenite-sensitive repair pathway is present in P. aeruginosa.