Ammonia or Ammonium Ion as Substrate for Oxidation by Nitrosomonas europaea Cells and Extracts

Abstract
The effect of pH on the K m values for ammonia was studied in its oxidation by Nitrosomonas cells and cell-free extracts. The K m values decreased markedly with increasing pH, suggesting (NH 3 ) rather than (NH 4 + ) as the actual substrate for oxidation.