SIMPLIFIED METHOD FOR THE INDUCTION OF 8-AZAGUANINE RESISTANCE IN SALMONELLA-TYPHIMURIUM

The selection of induced 8-azaguanine (8-AG) resistant mutants, recently developed as a test system in S. typhimurium, was adapted to the plate incorporation assay technique usually employed in the Ames test. The sensitivity of the procedure was checked by testing known mutagenic compounds (ethyl methanesulfonate (EMS), N-methyl-N''-nitro-N-nitrosoguanidine (MNNG), 2-nitrofluorene (2-NF), 4-nitroquinoline-1-oxide (4NQO), mitomycin C (MMC)) and comparing the increases in mutant numbers with those obtained in the Ames test. A lower sensitivity of the 8-AG system, more notable for strains lacking R factor plasmid, was shown. Five chemicals (Natulan, Paraquat, Diquat, 4-chloro-benzotrifluoride (4-Cl-BTF), 3-nitro-4-chloro-benzotrifluoride (3-n-4-Cl-BTF)), not mutagenic in the Ames test but known or suspected to be mutagenic or carcinogenic in other systems, were also checked. Of them, the herbicides Paraquat and Diquat, were positive in the 8-AG resistance test.