CELL-FREE NITRIFICATION BY NITROBACTER

Abstract

Investigations of the biochemistry of the nitrite oxidation step in nitrification have been carried out using extracts of cells of Nitrobacter agilis. The extracts carry out a rapid oxidation of nitrite, converting all the substrate to nitrate with no evidence of the formation of any intermediary substances. The enzymatic nitrification is stimulated by Fe whereas Zn, Mg, Mo and Cu fail to bring about an increase in activity. The rate of oxidation can be measured by the utilization of nitrite, the appearance of nitrate or the consumption of O2. The reaction proceeds optimally at pH 7.5-8.0. The nitrifying enzyme is bound to the particulate structures found in the extract. Low concentrations of cyanide and several other inhibitors bring about a diminution in the rate of the cell-free nitrite oxidation.