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Assessment of oxidative DNA damage in the oxyR-deficient SOS chromotest strain Escherichia coli PQ300. Environ Mol Mutagen 1992;20(4):297-306



Pubmed ID




Scopus ID

2-s2.0-0026452921   16 Citations


The SOS chromotest is a simple short-term genotoxicity assay measuring the induction of gene sfiA in Escherichia coli K-12. The recent availability of SOS tester strains with additional mutations in DNA repair or protection systems allows testing of DNA damaging compounds for genotoxic specificity. E. coli PQ300 differs from the standard SOS tester strain PQ37 in that it contains an additional mutation in gene oxyR that renders it more sensitive to oxidative genotoxins. The generation of reactive oxygen intermediates (ROI) by hydroperoxides (H2O2, t-butyl hydroperoxide, cumene hydroperoxide), gamma-radiation, glucose oxidase, and xanthine oxidase resulted in a more vigorous SOS response in strain PQ300 compared to strain PQ37. PQ300 was also more sensitive than PQ37 for the detection of reducing agents such as ascorbic acid, cysteine, and glutathione, which also alter the redox status of the bacterial cells. However, intercalating agents (adriamycin, bleomycin, and mitomycin C) and the UV- and radiomimetic compound 4-nitroquinoline-1-oxide whose DNA damaging potential are known also to involve ROI did not show significant differences between strains PQ37 and PQ300. It is concluded that the oxyR-deficient strain PQ300 is useful for detecting certain classes of genotoxins that change the oxidative/antioxidative balance of tester bacteria in the SOS chromotest.

Author List

Müller J, Janz S


Siegfried Janz MD Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

DNA Damage
Escherichia coli
Free Radicals
Hydrogen Peroxide
Mutagenicity Tests
Reactive Oxygen Species
Superoxide Dismutase