Mutagenesis microbial tests

COMPARISON OF REVERSE AND FORWARD MICROBIAL MUTAGENESIS ASSAYS Test System Mutations/10 surviving cells/yg... 

Three primary tests are incorporated in the health effects area. The microbial mutagenesis assay is based on the property of selected Salmonella typhimurium mutants to revert from a histidine requiring state to prototrophy due to exposre to various classes of mutagens. The test can detect nanogram quantities of mutagens and has been adapted to mimic some mammalian metabolic processes by the addition of a mammalian liver microsomal fraction. The test is used as a primary screen to determine the mutagenic activity of complex mixtures or component fractions. 

Other microbial mutation, repair and recombination assays have also been used in chemical screening, however, the data base for carcinogenicity-mutagenicity correlation established with these in vitro test systems is relatively limited at this time.62-70 At present, the Ames Salmonella assay appears to be the most generally applicable screen for the detection of chemical mutagens. No other mutagenesis assay has been shown to respond to such a wide group of chemical types as the Salmonella mutants. 

Microbial studies have demonstrated a link between carcinogenesis and mutagenesis and will be reviewed briefly with reference to the individual metals tested. 

H. S. Rosenkranz, W. T. Speck, and B. Gutter, Microbial assay procedures Experience with two systems, in In Vitro Activation in Mutagenesis Testing (F. J. de Serres, J. R. Foots, J. R. Bond, and R. M. Philpot, eds.), pp. 337-363, Elsevier/North-Holland, Amsterdam (1976). 

In studies with crude oils and effluents from synthetic fuel technology, we have used additional microbial assays to validate the results from Salmonella. Table 9 summarizes the comparative mutagenesis of selected test fractions in a variety of mutagenicity assays. 

Results with the selected test fractions have been given in detail and are shown qualitatively in Table 9. In general, the additional microbial assays reinforce the screening results with Salmonella. Discrepancies exist, however, in the mechanism of mutagenesis involved and the requirements(s) for metabolic activation. 

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