IMPROVEMENT OF SOS UMU TEST AS A SHORT-TERM DETECTION OF MUTAGENS

A short-term system to detect environmental mutagens is presented by using a plasmid (pSK 1002) carring a fused gene umuC-lacZ introduced into Salmonella typhimurium TA 1535. The principle of this test is that when mutagens in sample attack the DNA in the tester strain, beta-galactosidase is produced in propotion to the amount of the mutagens and then reacts with omicron-nitrophenyl-beta-D-galactopyranoside (ONPG) to produce omicron-nitrophenol which can be detected at 420 nm. This method showed 12 times higher sensitivity than the previous method when AF-2 was used as test compound, and major improvements made by us are as follows ; (1) in order to determine the amount of produced enzyme, the volume of culture treated with the test compound was increased from 0.25 ml to 1.0 ml, (2) the poly(oxyethylene) (23)dodecyl ether and toluene were selected as loosening reagents of the cell membrane, and (3) one ml of ONPG (4 mg.l-1) and 45 min of reaction time were adopted. This method was applied to mutangenicity test of river waters to which clorine and chlorine-alternative disinfectants such as, chloramine, chlorine dioxide, and ozone were added.