MODIFIED SUSPENSION AMES TEST FOR TESTING PROTEINACEOUS SUBSTANCES - AN INITIAL STEP

The basic Salmonella/microsome assay (Ames test) is a valuable primary tool by which to discriminate mutagens from non-mutagens. For a varie ty of chemical test substances this test is easily conducted according to international guidelines for genotoxicity testing. However, the te sting of proteinaceous substances in the basic Ames test may generate false positives owing to the presence of growth-promoting constituents in the test sample, such as histidine or its precursors. It was hypot hesized that the growth-promoting capacities of biological test sample s might be overcome by testing according to the 'suspension variant' o f the Ames test, which uses very rich growth conditions thereby overwh elming any growth-enhancing constituents present in a biological test sample. This hypothesis appeared to be correct, although several impor tant modifications had to be made to the suspension assay. The most im portant aspect of this 'new suspension Ames test' appeared to be the p lating of overnight regrown bacteria in the poorest way possible (by o mitting histidine and nutrient broth from the overlay agar). This stud y may comprise an initial step in the development of a modified suspen sion Ames test for testing proteinaceous substances.