ABSTRACT
It is as well to point out at the start of this review that although compared to Escherichia coli relatively little work has been done on the physiology and biochemistry of the ammonia-oxidizing bacteria, these bacteria are in fact of very great importance in many microbial processes. The prevention of ammonia oxidation to nitrate in soils can be advantageous because ammonia is less readily leached from soils than the anionic nitrate ion and is thus available to the plant for a longer period of time; also with ammonia, the plant does not have to use reductant to reduce nitrate to ammonia. Nitrates and nitrites leached from soils can give rise to intense eutrophication in bodies of fresh water into which the run-off water flows. A special feature of the growth of Nitrosomonas is that they must derive all their reducing power from ammonia oxidation to achieve reductive carbon dioxide assimilation.
