Increase of sensitivity and validity of the SOS/umu-test after replacement of the beta-galactosidase reporter gene with luciferase.

The SOS/umu-test with Salmonella typhimurium TA1535/pSK1002 as tester strain is a rapid and valuable bacterial assay for screening of umuC-dependent mutagenic potential of chemical compounds and chemicals relevant to environmental pollution. The initial assay was modified by replacing the beta-galactosidase reporter gene with luciferase. Thereby, the sensitivity of the umu-test was increased significantly and the susceptibility to intensively coloured solutions was reduced. The alternative enzyme assay in the modified umu-test (umu-Luc) represents an independent method which allows to confirm the colorimetric results obtained with the original SOS/umu-test system (umu-Gal) by measuring the beta-galactosidase activity. It has been proved that for several genotoxins an increased induction rate could be achieved by applying the new umu-Luc test.