Prophage lambda induction of Escherichia coli K12 envA uvrB: a highly sensitive test for potential carcinogens.

Abstract

A simple, inexpensive and sensitive test for potential carcinogens based on the property of carcinogens to induce prophage .lambda. is described. By using chemicals activated with [rat] microsomal enzymes and E. coli K12 permeable (envA) tester bacteria also deficient in DNA repair (uvrB), the range of carcinogens detected in a lysogenic induction test (inductest) was extended. Evidence that after activation, carcinogenic polycyclic hydrocarbons such as benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene induce prophage .lambda. was provided. Three variants of the test were developed (inductests I, II and III), which are as sensitive as the mutagenicity test of Ames et al. Inductests II and III provide a quantitative estimation of the inducing activity of a carcinogen. With the latter test, one can determine the cellular toxic effect of a carcinogen and the kinetics of appearance and disappearance of active metabolites. For 2 series of chemicals, aflatoxins and benz[a]anthracenes, there is a good correlation between their carcinogenic activity in rodents and their prophage inducing activity in bacteria. The fact that the majority of the cell population is induced makes it possible to test the inducing activity of carcinogens at the biochemical level, e.g., by measuring .lambda. repressor inactivation.