Genetic toxicity of methyl methanethiosulfonate on Salmonella typhimurium, Saccharomyces cerevisiae and Nicotiana tabacum.

The genetic toxicity of methyl methanethiosulfonate (MMT), a hydrolytic derivative of the insecticide methomyl, or lannate (Du Pont), was studied in Salmonella typhimurium, Saccharomyces cerevisiae and Nicotiana tabacum. At low concentrations, a lethal action was observed in all 3 models. Nuclear genetic effects of the product were not detected on the Xanthi x NC 95 hybrid of N. tabacum or on the diploid strain D7 of S. cerevisiae. At the cytoplasmic level, an effect on chloroplasts was observed on tobacco, but MMT did not induce cytoplasmic 'petites' in yeast. Ames tests with and without metabolic activations by S9 mix and/or fecalase were negative. MMT cannot be considered to be mutagenic on these models; consequently it is unlikely to be genotoxic in man, although these experiments do not exclude eventual co-genetic effects.