Genotoxicity of Water Extracts from Sewage Effluents in the Kanagawa Prefecture, Japan Using the Novel <i>umu</i>Tester Strain

The genotoxic activities of effluents from drainage water treatment plants were examined by using the novel umu tester strain NM8001, which lacks MutMst genes. To enhance the sensitivity of the LacZ assay, a BugBuster mix protein extraction reagent and TokyoGreen-β Gal for a fluorescence-galactosidase substrate were applied. Of the 24 sampling locations present in Kanagawa prefecture, Japan, water extracts from nine sampling points showed apparent genotoxic activities without metabolic activation. In contrast, water extracts from the upper sites of these water treatment plants did not show any significant genotoxic activities. The selected samples with genotoxic activity did not show significant mutagenicity toward Ames strains TA98 and TA100. Genotoxicity was also well correlated with the activity of a classical umu strain of TA1535/pSK1002;these findings indicate that the genotoxicity induced by oxidative damage was not a significant component of the genotoxicity.