Oxidative mutagens specific for A-T base pairs induce forward mutations to L-arabinose resistance in Salmonella typhimurium.

Strain TA102 of S. typhimurium is a new histidine-requiring mutant, particularly suited to the detection of oxidative mutagens acting at A.T base pairs. 10 oxidizing chemicals, previously tested in strain TA102, were used to evaluate the mutagenic sensitivity of the L-arabinose forward mutation assay of S. typhimurium with respect to those types of mutagens. The mutagenicity of each compound was determined by liquid test, measuring both the frequency of mutants among the survivors and the absolute number of mutants growing in selective plates with traces of D-glucose. Strain BA13 with a wild-type lipopolysaccharide barrier was used as compared to the deep rough derivative strain BA9. The chemicals studied were: bleomycin, t-butyl hydroperoxide, chromium trioxide, cumene hydroperoxide, formaldehyde, glyoxal, glutaraldehyde, hydrogen peroxide, paraquat, and phenylhydrazine. Additionally, ultrasonic oscillation was used as a presumable non-mutagenic lethal control treatment. The L-arabinose forward mutation assay detected the mutagenic activity of all the chemicals under study with a high degree of sensitivity, including paraquat which is unable to revert strain TA102. Positive responses were obtained at doses equivalent to or 10 times lower than the doses detected by strain TA102. The results support the idea that the L-arabinose forward mutation assay could replace the set of specific tester strains used by the histidine reverse mutation assay in general screening for genetic toxins.