부산대학교 도서관

Nitrogen is naturally present in the environment in organic, inorganic, and gaseous forms. The reduced forms of nitrogen are used by nitrifying bacteria, which form a heterogeneous group comprising different genera and species highly specialized in nitrification. The ammonia oxidation by autotrophic nitrifying bacteria provides them with energy and produces nitrite, then nitrate. The best known and most studied representatives of nitrifying bacteria pertain to the genera Nitrosomonas, Nitrosococcus, and so on, which oxidize ammonia to nitrite, and Nitrobacter, Nitrospira, and so on, which oxidize nitrite to nitrate. Most of these microorganisms are chemolithoautotrophic, with some exceptions which are mixotrophic such as Nitrobacter, which can use acetate as a carbon source. Besides, there is an anammox process in which there is anaerobic oxidation of ammonia combined with nitrite reduction. This chapter summarizes the current knowledge on bacterial ammonia oxidation research and focuses on discussing the biochemical, genetics, and regulatory aspects of the bacterial metabolism of ammonia.