Chemoautotrophic Ammonia-Oxidizing Bacteria, with Special Reference to Ammonia and Hydroxylamine Oxidation by Nitrosomonas.

Abstract

Ammonia and nitrite-oxidizing bacteria contribute to nitrification, a part of the nitrogen cycle in natural environments. These bacteria are important since they decompose accumulated inorganic nitrogen compounds and toxic substances such as nitrogen oxides and consume (fix) of CO2, a factor implicated in global warming. Nitrosomonas europaea, a chemoautotrophic ammonia-oxidizing bacterium which contributes to the first stage of nitrification has been studied in detail. It oxidizes ammonia as the sole nitrogen source of nitrite via hydroxylamine as an intermendiate. It grows under completely inorganic conditions using energy (65kcal) produced by the oxidation of ammonia and atmospheric CO2, its sole carbon source. Its growth rate is thus quite low and no extensive biochemical studies have been conducted. This paper reviews recent studies on the ammonia-oxidizing system (ammonia and hydroxylamine oxidation) in Nitrosomonas europaea. Data obtained with two strains of Nitrosomonas including a pure isolated strain of Nitrosomonas sp. TK794 are presented.