The effect of nitrapyrin and chloropicolinic acid on ammonium oxidation by Nitrosomonas europaea

Abstract Both nitrapyrin and 6-chloropicolinic acid inhibited nitrite production when added to stationary-phase and exponentially growing cells of Nitrosomonas europaea at a concentration of 2.17 μM. Nitrapyrin inhibited growth immediately, but there was a lag before inhibition by chloropicolinic acid added to growing cells, and induction of a lag phase when this was added to stationary phase cells. There was no effect on the subsequent specific oxidation rate.