Influence of bacterial growth of the overnight culture on the captan- and folpet-induced reversion in the Ames test.

The influence of the stage of bacterial growth of the overnight culture on captan- and folpet-induced reversion in the Ames test was investigated. Tests were performed in order to determine both the number of viable bacteria at different intervals of bacterial growth--in the presence or absence of captan and folpet--and also the number of revertants. Captan or folpet were tested at 5 micrograms per plate, a concentration which had previously showed a mutagenic effect to the TA100 strain. The highest induced reversion was obtained when the bacterial culture used had entered the stationary-phase after 10-14 h, with a titre of at least 10(8) viable cells per ml.