A method for the mutagenicity test of biodegradation products produced by microorganisms in river water was developed for the screening of the degradation of organic compounds in an environment. Microorganisms in river water were collected on the membrane filter, which was prepared by autoclaving for three times at 2-minute intervals to remove the surface-active agents coated on the filter. The modified Davis medium was suitable for the medium for the biodegradation test taking into account the growth of microorganisms, the preferential utilization of the chemicals as nutrients, and the effect of the medium component on Ames test following the biodegradation test. While the mutagenicity of 4-nitroquinoline-1-oxide disappeared during incubation with microorganisms, 8-nitroquinoline was shown to be mutagenic after incubation for 3 d, suggesting the conversion of 8-nitroquinoline to mutagenic metabolites.
