Transformations of ammonia and the environmental impact of nitrifying bacteria

In the sequence of events leading from ammonia to N₂ during the process of biotransformation of inorganic nitrogen compounds, the weakest link, with respect to our knowledge and understanding of the organisms involved, is nitrification. In particular, this is true for the oxidation of ammonia to nitrite. The enzymes have not been thoroughly studied, and the enzymatic mechanisms have not been identified. Almost any biochemical and physiological aspect studied proved to be controversial, and major ecological questions still remain unanswered. Unless the structure and function of the various components of the process are worked out, progress in developing means for controlling nitrification will depend mainly on laborious trial and error and not on knowledgeable manipulation of this group of bacteria.