A BIOSENSOR FOR ENVIRONMENTAL GENOTOXIN SCREENING BASED ON AN SOS LUXASSAY IN RECOMBINANT ESCHERICHIA-COLI-CELLS

A genetically controlled luminescent bacterial reporter assay, the SOS lux test, was developed for rapid detection of environmental genotoxi ns, The bioassay is based on the recombinant plasmid pPLS-1, which was constructed as a derivative of pBR322, carrying the promoterless luxC DABFE genes of Photobacterium leiognathi downstream of a truncated cda gene from ColD with a strong SOS promoter, E. coli recA(+) strains co ntaining this construction are inducible to high levels of light produ ction in the presence of substances or agents that cause damage to the DNA of the cells. The light signal, reflecting the SOS-inducing poten cy, is recorded from the growing culture within 1 s, and the test resu lts are available within 1 to 2 h, Induction of bioluminescence was de monstrated by treatment of E. coli C600(pPLS-1) with 6 genotoxic chemi cals (mitomycin C, N-methyl-N'-nitro-N-nitrosoguanidine, nalidixic aci d, dimethylsulfate, hydrogen peroxide, and formaldehyde) and with UV a nd gamma radiation. A clear dose-response relationship was established for all eight genotoxins. The sensitivity of the SOS lux test is simi lar to that of other bioassays for genotoxicity or mutagenicity, such as the SOS chromotest, umu test, and Ames mutatest. These results indi cate that the SOS lux test is potentially useful for the in situ and c ontinuous detection of genotoxins.