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Nitrite oxidoreductase (NOR or NXR) is an enzyme involved in nitrification.It is the last step in the process of aerobic ammonia oxidation, which is carried out by two groups of nitrifying bacteria: ammonia oxidizers such as Nitrosospira, Nitrosomonas, and Nitrosococcus convert ammonia to nitrite, while nitrite oxidizers such as Nitrobacter and Nitrospira oxidize nitrite to nitrate.
Nitrifying bacteria are chemolithotrophic organisms that include species of genera such as Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrospina, Nitrospira and Nitrococcus. These bacteria get their energy from the oxidation of inorganic nitrogen compounds. [1] Types include ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB).
The process of nitrification begins with the first stage of ammonia oxidation, where ammonia (NH 3) or ammonium (NH 4 +) get converted into nitrite (NO 2-). This first stage is sometimes known as nitritation. It is performed by two groups of organisms, ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA [2]).
Additionally, ammonium and nitrite oxidation are key processes in N cycling in anoxic environments. Ammonium oxidation is the first step in nitrification and ammonia-oxidizing bacteria (AOB) converts NH 3 to NO 2 −. [6] Followed by nitrite oxidation by nitrite-oxidizing bacteria (NOB), which converts NO 2 − to NO 3 −. [6]
The conversion of nitrite to nitrate is facilitated by nitrite-oxidizing bacteria. The genus Nitrobacter is widely distributed in both aquatic and terrestrial environments. [ 2 ] Nitrifying bacteria have an optimum growth between 77 and 86 °F (25 and 30 °C), and cannot survive past the upper limit of 120 °F (49 °C) or the lower limit of 32 ...
Nitrobacter winogradskyi is a gram-negative nitrite-oxidizing bacteria from the genus of Nitrobacter. [2] [3] It is a chemolithoautotroph that derives energy by oxidation of nitrite. Nitrobacter winogradskyi is rod-shaped and is involved in the biological nitrification process that occurs within the nitrogen cycle.
Because anammox bacteria convert ammonium and nitrite directly to N 2 anaerobically, this process does not require aeration and other electron donors. Nevertheless, oxygen is still required for the production of nitrite by ammonia-oxidizing bacteria.
Comammox (COMplete AMMonia OXidation) is the name attributed to an organism that can convert ammonia into nitrite and then into nitrate through the process of nitrification. [1] Nitrification has traditionally been thought to be a two-step process, where ammonia-oxidizing bacteria and archaea oxidize ammonia to nitrite and then nitrite ...