The purpose of this research is to establish a method of detecting and evaluating presence of mutagens in water environments.
The mutagenicity test used in this research is the liquid-cultivation method of the Bacillus subtilis rec-assay, which is based on the principle that the difference of survival between the wild-type strain of the bacteria, H17 (Rec⁺), and the recombination-deficient mutant, M45 (Rec^-), when being exposed to mutagens. The rec-assay liquid-cultivation method detects mutagens as a DNA damaging agent and has high sensitivity to various mutagens and good reproducibility.
On the other hand, in order to evaluate DNA damaging strength of test samples from the results of the rec-assay liquid-cultivation method, it is required to define an appropriate DNA damaging indicator. In this paper, therefore, more proper indicators which agreed to the principle of the rec-assay and avoided introduction of personal errors from evaluation of the results, were newly developed by applying the Probit theory and the Target and Hit theory.

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