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Pure exogenous singlet oxygen: nonmutagenicity in bacteria
T A Dahl1, W R Midden, P E Hartman
1Department of Biology, Johns Hopkins University, Baltimore, MD 21218.
Mutation Research
|September 1, 1988
Summary
Singlet oxygen, a reactive form of oxygen, was tested for its ability to cause mutations in bacteria. Despite its toxicity, pure singlet oxygen did not induce mutations in various bacterial strains, suggesting it does not significantly damage bacterial DNA.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Singlet oxygen (¹ΔgO₂) is a highly reactive excited state of molecular oxygen.
- While implicated in biological effects, its mutagenic potential remains unclear.
- Previous studies lacked definitive evidence due to ambiguous reactive species.
Purpose of the Study:
- To investigate the mutagenicity of pure exogenous singlet oxygen in bacteria.
- To determine if singlet oxygen causes DNA damage leading to mutations.
- To clarify the role of singlet oxygen in genetic alterations.
Main Methods:
- Exposure of 26 Salmonella typhimurium histidine-auxotrophic strains to pure singlet oxygen.
- Assays for base-pair substitutions, frameshift mutations, and deletions.
- Testing in strains with varying DNA-repair capacities and specific mutations (hisG46, hisG428).
- Utilized 8-azaguanine forward mutation assay and lambda prophage induction test in E. coli K12.
Main Results:
- No evidence of mutagenicity was found across 26 Salmonella typhimurium strains, even at high bacterial death rates.
- Specific assays for base-pair substitutions, frameshift mutations, small deletions, and large duplications were negative.
- No induction of lambda prophage in E. coli K12 was observed.
- The frequency of small in-phase deletions remained at spontaneous levels.
Conclusions:
- Pure singlet oxygen, generated externally, does not significantly mutagenize bacterial DNA.
- It does not cause base-pair substitutions, frameshifts, deletions, or duplications.
- Singlet oxygen does not appear to induce DNA damage that triggers the SOS response.