The genetic toxicology of metal compounds: I. Induction of λ prophage in E coli WP2S(λ)

A number of metal compounds have been shown to be human carcinogens. Others, while not proven human carcinogens, are able to cause tumors in laboratory animals. Short-term bacterial assays for genotoxic effects have not been successful in predicting the carcinogenicity of metal compounds. We report here the ability of some metal compounds to cause the induction of λ prophage in E coli WP2_S(λ). By far the strongest inducing ability was observed with K2CrO4, followed by Pb(N0₃)₂ > MnCl₂ > Ni(OOCCH₃)₂ > CrCl₂ > NaWO₄ > Na₂MoO₄ > KMnO₄. With the exception of chromate, long-term exposures in a narrow, subtoxic dose range were required in order to demonstrate phage induction. A new microtiter assay for λ prophage induction, which incorporates these features, is described. This system also was able to detect very small amounts of organic carcinogens.