Genotoxicity of water —  ISO 13829: 2000. Water quality. Determination of the genotoxicity of water and waste water using the umu-test.  

            This standard specifies the procedure to determine the genotoxicity of water used in the umu test. The assay is based on the detection of genotoxicity by increasing the expression of the SOS system, associated with the umuC gene.

            In this test the test organism is exposed to the evaluated product with and without a metabolic activating system using microplates. After 4 hours of incubation the induction of the umuC gene is compared with the spontaneous activation of the control cultures not exposed to the product. The genetically modified bacterium Salmonella typhimurium TA1535/pSK1002 is used in the test. This bacterium carries the plasmid psK1002 that owns the umu-lacZ gene and an ampicillin resistance gene that allows the selection of the bacteria for its resistance to ampicillin.

            The bacterium is exposed under controlled conditions to different concentrations of the evaluated product. The test is based on the ability of genotoxic products to induce the umuC gene in the Salmonella strain in response to DNA-induced lesions. Only one strain of bacteria is required for its ability to respond to different genotoxic substances. The test must be performed in the presence and absence of S9 activator.

            The induction of the umuC gene is a measure of the genotoxic potential of the evaluated product. This umuC gene is linked to the lac-Z gene of β-galactosidase and its induction can be evaluated by determining β-galactosidase activity.