Comparative Aflatoxin B₁ Mutagenesis of Salmonella typhimurium TA100 in Metabolic and Photoactivation Systems

Salmonella typhimurium TA100 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.