Preferential effect of dichlorvos (Vapona) on bacteria deficient in DNA polymerase.

an insecticide in agriculture (9, 10), as an antimosquito agent for eradicating malaria (3, 4, 11, 17), as a disinfectant of commercial aircraft (16), and for the control of flea infections (10). Hence, human exposure to and inhalation of this pesticide occurs frequently. As normally used, this substance has not exhibited acute toxicity except for the occasional lowering of plasma cholinesterase levels (2-4, 6, 10, 12, 19, 21, 22). However, it was shown recently that DDVP and related phosphoric acid esters reacted with purified DNA and that this reaction was due to the methylation of guanine residues of DNA (8, 15). If the reaction were also to occur in vivo, then DDVP could present a real hazard to health in view of the established relationship between the ability of agents to alkylate DNA and their potential carcinogenicity and mutagenicity. In this report it is shown (Tables 1 and 2) that bacteria (Escherichia coli) deficient in DNA polymerase are more sensitive to DDVP than are the parents from which they were derived. This is a property also exhibited by other DNA-alkylating agents (Table 2, Group 2) that are known to be carcinogens as well. On the other hand, substances that do not act on the cellular DNA did not inhibit the DNA polymerase-deficient strain preferentially (Table 2, Group 1). DNA polymerase has been implicated in the DNA repair process (1, 7); bacterial strains lacking this enzyme are more sensitive than their parents to agents that react with the cellular DNA (1, 5, 18, 20), presumably, because they are unable to repair efficiently the damage to their DNA. The present data suggest that DDVP reacts with the DNA of living cells-a reaction which already has been demonstrated in vitro