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Plasmid modification of radiation and chemical-mutagen sensitivity in Pseudomonas aeruginosa
Abstract:
The R factor pMG2 protects Pseudomonas aeruginosa against the lethal effects of ultraviolet (u.v.) and gamma irradiation, and methyl methanesulphonate and N-methyl-N'-nitro-N-nitrosoguanidine treatment. Enhanced survival occurs in strains of uvr+ rec+ (wild-type) genotype and a variety of uvr rec+ type mutants. No protection occurs in a rec A-type mutant. The plasmid also enhances u.v.-induced mutagenesis. These effects appear to be due to host-cell controlled plasmid-determined DNA repair function(s). Studies on P. aeruginosa strains deficient in DNA polymerase I (polyA) suggest that a plasmid-determined repair resynthesis function may be responsible for increased u.v.-survival and enhanced u.v.-mutability in pMG2-containing bacteria.
Insights
The R factor pMG2 enhances Pseudomonas aeruginosa survival against radiation and chemical mutagens by providing DNA repair functions. This plasmid also boosts ultraviolet-induced mutagenesis, indicating a complex role in bacterial DNA damage response.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Pseudomonas aeruginosa is a significant opportunistic pathogen.
- Bacterial DNA repair mechanisms are crucial for survival against environmental mutagens.
- Plasmids can confer advantageous traits, including resistance and repair capabilities.
Purpose of the Study:
- To investigate the protective effects of the R factor pMG2 against DNA damaging agents in Pseudomonas aeruginosa.
- To elucidate the role of plasmid-mediated DNA repair in bacterial survival and mutagenesis.
- To identify the genetic basis of pMG2-mediated protection.
Main Methods:
- Exposure of Pseudomonas aeruginosa strains with and without pMG2 to ultraviolet (UV) and gamma irradiation, methyl methanesulphonate, and N-methyl-N'-nitro-N-nitrosoguanidine.
- Assessing bacterial survival rates across different genetic backgrounds (wild-type, uvr mutants, recA mutants).
- Evaluating UV-induced mutagenesis in the presence and absence of the pMG2 plasmid.
Main Results:
- The R factor pMG2 significantly enhanced survival of Pseudomonas aeruginosa against UV, gamma irradiation, and chemical mutagens.
- Protection was dependent on host cell recA gene function; no protection was observed in recA mutants.
- pMG2 also enhanced UV-induced mutagenesis.
- Studies involving DNA polymerase I deficient strains suggested a plasmid-determined repair resynthesis function.
Conclusions:
- The R factor pMG2 confers resistance to DNA damaging agents in Pseudomonas aeruginosa through plasmid-determined DNA repair pathways.
- These pathways involve host-cell controlled functions, likely including DNA repair resynthesis.
- pMG2 plays a dual role, enhancing both survival and mutagenesis under DNA-damaging conditions.