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The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation ...
Nitrification. Nitrification is the biological oxidation of ammonia to nitrate via the intermediary nitrite. Nitrification is an important step in the nitrogen cycle in soil. The process of complete nitrification may occur through separate organisms [1] or entirely within one organism, as in comammox bacteria.
e. A biogeochemical cycle, or more generally a cycle of matter, [1] is the movement and transformation of chemical elements and compounds between living organisms, the atmosphere, and the Earth's crust. Major biogeochemical cycles include the carbon cycle, the nitrogen cycle and the water cycle. In each cycle, the chemical element or molecule ...
Anammox, an abbreviation for "anaerobic ammonium oxidation", is a globally important microbial process of the nitrogen cycle [1] that takes place in many natural environments. The bacteria mediating this process were identified in 1999, and were a great surprise for the scientific community. [2] In the anammox reaction, nitrite and ammonium ...
Impacts of anthropogenic inputs on the nitrogen cycle. Between 1600 and 1990, global reactive nitrogen (Nr) creation had increased nearly 50%. [6] During this period, atmospheric emissions of Nr species reportedly increased 250% and deposition to marine and terrestrial ecosystems increased over 200%. [6]
Denitrification. Nitrogen cycle. Denitrification is a microbially facilitated process where nitrate (NO 3−) is reduced and ultimately produces molecular nitrogen (N 2) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitrification as a type of respiration that reduces oxidized forms of ...
Nitrogenase. Nitrogenases are enzymes (EC 1.18.6.1 EC 1.19.6.1) that are produced by certain bacteria, such as cyanobacteria (blue-green bacteria) and rhizobacteria. These enzymes are responsible for the reduction of nitrogen (N 2) to ammonia (NH 3). Nitrogenases are the only family of enzymes known to catalyze this reaction, which is a step in ...
Morphology and characteristics. Nitrobacter are gram-negative bacteria and are either rod-shaped, pear-shaped or pleomorphic. [1][2] They are typically 0.5–0.9 μm in width and 1.0–2.0 μm in length and have an intra-cytomembrane polar cap. [5][2] Due to the presence of cytochromes c, they are often yellow in cell suspensions. [5]