The use of rec-bacteria for testing of carcinogenic substances

A series of rec-Escherichia coli strains were tested for their sensitivity to four known carcinogenic compounds by examination of a zone of inhibited bacterial growth around a central well containing the test chemical. The mutants recA-, recB-, recC-, and recA- recB- recC- were all more sensitive to the mutagens than the parental strain AB1157. The recB- recC- strain was examined with a larger series of compounds and was found to respond to many of the substances in a similar way as the Salmonella typhimurium strains of Ames but with some notable exceptions. Nitrosamines, with rat liver microsomal activation, could be detected at lower levels and a group of aromatic amino compounds failed to react with these rec-E. coli. An unusual feature of these rec-mutants is their sensitivity to mixtures of nitrosamines and 2-acetyl amino-fluorene in the absence of microsomal activation.