The CAM-OCT plasmid enhances UV responses of Pseudomonas aeruginosa recA mutants.
The effect of the CAM-OCT plasmid on responses to UV irradiation of Pseudomonas aeruginosa recA mutants was characterized. Mutant alleles examined included rec-1, rec-2, and recA7::Tn501. The plasmid substantially enhanced both survival and mutagenesis of RecA- cells after treatment with UV light. Survival of the RecA-(CAM-OCT) cells after UV irradiation was intermediate between that seen in the wild-type P. aeruginosa PAO1 and the increased survival seen in PAO1(CAM-OCT) cells. Mutability was quantitated by the reversion to carbenicillin resistance of strains carrying a bla(Am) mutation on a derivative of plasmid RP1. UV-induced mutagenesis of CAM-OCT carrying recA mutants occurred at levels comparable to that seen in PAO1(CAM-OCT). The ability of CAM-OCT plasmid to suppress the recombination deficiency in recA mutants was tested by assaying for bacteriophage F116L-generalized transduction of a Tn7 insertion in the alkane utilization genes of CAM-OCT. Transduction of the Tn7 insertion was not detected in RecA-(CAM-OCT) strains but was easily seen in PAO1(CAM-OCT), indicating that the plasmid does not encode a recA analog. The results indicate that the CAM-OCT UV response genes are expressed in RecA- cells, which differs from results seen with other UV response-enhancing plasmids. The results suggest that CAM-OCT either encodes several UV responses genes itself or induces chromosomal UV response genes by an alternate mechanism.
McBeth
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DL
Department of Microbiology, City University of New York Medical School/Sophie Davis School of Biomedical Education, City College, New York 10031.
D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000235:genetics; D005838:Genotype; D009154:Mutation; D010957:Plasmids; D011549:Pseudomonas / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000254:growth & development / Q000528:radiation effects; D011938:Rec A Recombinases / Q000235:genetics*; D014161:Transduction, Genetic; D014466:Ultraviolet Rays
D011938:Rec A Recombinases