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New Escherichia coli WP2 tester strains highly sensitive to reversion by oxidative mutagens
M Blanco1, A Urios, A Martínez
1Instituto de Investigaciones Citológicas, Fundación Valenciana de Investigaciones Biomédicas, Amadeo de Saboya 4, 46010 Valencia, Spain.blanco@ochoa.fib.es
Abstract:
New Escherichia coli strains have been added to the WP2 mutagenicity test for the specific detection of oxidative mutagens. Strain IC203 derives from WP2 uvrA/pKM101 and is highly sensitive to oxidative stress due to a deficiency in the OxyR function. Following exposure to t-butyl hydroperoxide (BuOOH) or menadione (MD), but not to 4-nitroquinoline 1-oxide (4NQO), strain IC203 (oxyR) shows increased mutability with respect to the oxyR+ parent. The advantage that the OxyR deficiency confers on IC203 strain in detecting oxidative mutagens is not obtained with strains deficient in either katG or ahpCF, two OxyR-regulated genes. Strain IC206, a derivative of WP2 uvrA carrying a deletion of the umuDC genes and deficient in the MutY glycosylase, has also been added to the WP2 test for the detection of SOS-independent mutations promoted by 8-oxoguanine lesions. Induction of these mutations was observed after treatment with BuOOH, but not after MD or 4NQO exposure. The two new strains, IC203 and IC206, can be useful for the screening of mutations resulting from oxidative stress as well as in studies on antioxidants preventing mutagenesis.
Insights
New Escherichia coli strains, IC203 and IC206, enhance mutagenicity testing for oxidative mutagens and 8-oxoguanine lesions. These strains improve the detection of oxidative stress-induced mutations and aid antioxidant research.
Area of Science:
- Microbiology
- Genetics
- Toxicology
Background:
- The WP2 mutagenicity test is a standard assay for detecting DNA damage.
- Specific detection of oxidative mutagens and SOS-independent mutations requires specialized strains.
- OxyR, KatG, AhpCF, and MutY are key proteins involved in oxidative stress response and DNA repair.
Purpose of the Study:
- To introduce new Escherichia coli strains for enhanced detection of oxidative mutagens.
- To develop a strain for identifying SOS-independent mutations caused by 8-oxoguanine lesions.
- To facilitate studies on antioxidants and their role in preventing mutagenesis.
Main Methods:
- Development of strain IC203, an OxyR-deficient derivative of WP2 uvrA/pKM101.
- Development of strain IC206, a WP2 uvrA derivative lacking umuDC genes and deficient in MutY glycosylase.
- Exposure of strains to oxidative agents like t-butyl hydroperoxide (BuOOH) and menadione (MD), and a non-oxidative mutagen 4-nitroquinoline 1-oxide (4NQO).
Main Results:
- Strain IC203 showed increased mutability upon exposure to BuOOH and MD, indicating sensitivity to oxidative stress.
- OxyR deficiency, but not deficiencies in KatG or AhpCF, enhanced oxidative mutagen detection in strain IC203.
- Strain IC206 detected SOS-independent mutations after BuOOH treatment, specifically linked to 8-oxoguanine lesions.
Conclusions:
- The new strains IC203 and IC206 significantly improve the specificity of the WP2 mutagenicity test for oxidative mutagens.
- Strain IC203 is valuable for detecting oxidative mutagens, while IC206 is effective for identifying 8-oxoguanine-induced mutations.
- These strains serve as important tools for screening oxidative stress effects and evaluating antioxidant efficacy in mutagenesis studies.
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