[Problems concerned with microbial mutagenicity tests].

Mutagenicity tests using microorganisms are the Salmonella-typhimurium test (Ames), the test with a polymerase A deficient Escherichia coli, the Saccharomyces cerevisiae D3 system and the Neurospora crassa test. Differences in results of Ames-test may be due to differences preserving the tester strains, the choice of solvent and the dosage of the test compounds, last not least is the production of S-9. The polymerase A deficient Escherichia coli system seems easier to handle than the Saccharomyces cerevisiae- or Neurospora crassa-test. The metabolic activation with different forms of S-9 is needed in the Salmonella- and the Escherichia coli-system. Nevertheless it is not possible to decide if a substance is carcinogenic for human beings or animals with microbial mutagenicity tests only.