Water quality – Determination of the genotoxicity of water and waste water – Salmonella/microsome fluctuation test (Ames fluctuation test)“

The Ames Fluctuation Test is a method for the determination of the genotoxic potential of water, waste water and test substances in aqueous solution. The principle of the test corresponds to Bacterial Reverse Mutation Test OECD 471. Testorganisms are Salmonella typhimurium TA 98 and TA 100 in a fluctuation assay. The usage of this combination of strains enables the the deteremination genotoxicity of chemicals causing point mutations (base pair substitutions and frameshift mutations) in genes coding for enzymes that are involved in the biosynthesis of the amino acid histidine.

The bacteria are exposed under defined conditions to various concentrations of the test substance (water/ waste water sample). During a 100 min lasting exposure period genotoxic agents contained in the test sample induce mutations in one or both marker genes of the bacterial strains used (hisG46 for TA 100 and hisD3052 for TA 98) Induction of mutations will cause a concentration-related increase in the number of „revertant“ bacteria. Identification of revertants in the Ames Fluctuation Test is performed on 384 well-microtiter plates. This modification of OECD 471 Reverse Mutation Test facilitates the determination of the incidence of reverse mutations.