Comparative aflatoxin B1 mutagenesis of Salmonella typhimurium TA 100 in metabolic and photoactivation systems.

Salmonella typhimurium TA 100 was mutagenized with photoactivated aflatoxin B1 (AFB1) and AFB2. Levels of mutagenesis induced by AFB1 correlated with levels of in vitro covalent binding of [3H]AFB1 to calf thymus DNA. The same phenomenon was observed with AFB2. Photoactivated AFB1 induced lethality in the mutagenized cultures, and AFB2 failed to do so. Extraction of nucleic acids from cultures mutagenized by photoactivated or metabolically activated [3H]AFB1 revealed that: (a) in situ levels of [3H]AFB1 binding to DNA were proportional to induction of mutational and lethal events in both cases; (b) mammalian metabolism and photoactivation produced AFB1:DNA lesions possessing comparable lethality and mutagenicity; and (c) [3H]AFB1 binding levels to bacterial RNA did not correlate with mutagenesis and lethality.