The resistance of E. coli cultivated in low concentrations of dichlorvos to N-methyl-N'-nitro-N-nitrosoguanidine induced mutagenesis.

Cultivation of E. coli B/r strain WP2 in low concentrations of either 4-nitroquinoline N-oxide (4NQO) or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) had no effect on the mutagenic or cytotoxic consequences of subsequent challenge with dichlorvos (DCV). However, although the sensitivity of E. coli cells taken from cultures grown in low concentrations of DCV to the effects of 4NQO was unchanged, the cells were more resistant to the mutagenic (but not cytotoxic) consequences of MNNG challenge. This phenomenon was not observed in WP2 derivatives deficient in either error-free (uvrA-) or error-prone (lexA-) DNA-repair, suggesting that a factor common to both these repair pathways may be involved.