METABOLIC-ACTIVATION AND INACTIVATION OF METANIL-YELLOW AND ORANGE-IIIN THE SALMONELLA-TYPHIMURIUM HIS(-) REVERSION ASSAY

Among a variety of experimental protocols used, the combined use of 0. 5% dextrose in bottom agar and 1 mu mol of flavin mononucleotide (FMN) in preincubation mixtures without fraction S9 mix resulted in the hig hest level of induced Salmonella typhimurium his(-) reversions with bo th dyes metanil yellow and orange II with strain TA100. Strain TA98 yi elded notably lower levels of reversions under the same conditions. Th e presence of uninduced hamster Liver S9 fraction resulted in a weak m utagenic response while Aroclor 1254-induced rat liver S9 fraction res ulted in the complete absence of mutagenicity with both strains and wi th both dyes.