Rapid Detection of Mutagens by Induction of Luciferase-Bearing Prophage in Escherichia coli

Mutagenicity in bacteria is highly correlated with carcinogenicity in humans, and many industrial wastes and manufacturing sites contain mutagenic components. This has stimulated interest in rapid screening assays for genotoxic agents. We describe a rapid and sensitive bacterial test for detecting DNA-damaging agents, based on bioluminescence reporting of prophage λ induction. A promoterless cassette bearing genes encoding bacterial luciferase was transposed randomly into the λ chromosome from the suicide plasmid pUTmini-Tn5luxAB, and Escherichia coli JM101 was lysogenized with the resulting phages. In the lysogens, the luciferase genes are expressed from phage promoters, which allows rapid detection of DNA-damage-triggered prophage induction with a simple whole-cell luciferase assay. One lysogen was selected among several for its high ratio of induced to spontaneous luciferase activity upon exposure to mitomycin C. Within 4 h, the assay detects ethyl methanesulfonate, methyl methanesulfonate, and mitomycin C with sensitivity comparable to those of assays requiring more time, although not all tested mutagens were detected. The test is also automatable and generates very little waste, which makes it a potentially valuable tool for rapid screening and process monitoring.