The effect of 2-chloro, 6-(trichloromethyl) pyridine on the chemoautotrophic metabolism of nitrifying bacteria

Abstract

N-SERVE, 2-chloro, 6-(trichloromethyl)pyridine, shown to be a potent inhibitor of the ammonia oxidase system ofNitrosomonas was not effective at all in theNitrobacter nitrite oxidizing system at concentrations which had caused complete inhibition of ammonia oxidation, i.e. 1 – 1.5 ppm of the chemical. Very little inhibition of nitrite oxidation by intact cells was observed even in the presence of 50 ppm N-SERVE. Concentrations of 80 to 175 ppm, however, inhibited the nitrite oxidation by 60 to 75 percent. The cell-free nitrite oxidizing system of the chemoautotroph was found to be virtually unaffected by these unusually high concentrations of the inhibitor and 175 ppm concentration caused only a 10 percent inhibition.

As in theNitrosomonas systems, N-SERVE proved to be inhibitory for the cytochrome oxidase present in the cell-free extracts ofNitrobacter but, again, levels from 80 – 175 ppm of the inhibitor were required for a 50 percent inhibition of the enzyme. The nitrite activating enzyme “nitrite-cytochromec reductase” was scarcely affected by these levels of N-SERVE. As a matter of fact, a slight stimulation of enzyme activity was observed.

Copper ions, as in the case ofNitrosomonas, effectively reversed the N-SERVE inhibition of theNitrobacter cytochrome oxidase system.