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Nitrogen fixation

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**Historical Discovery and Development**:
– Discovered by Jean-Baptiste Boussingault in 1838.
– Process described by Hermann Hellriegel and Hermann Wilfarthde in 1880.
– Fully described by Dutch microbiologist Martinus Beijerinck.
– Role of nitrogen-fixing bacteria discovered by Herman Hellriegel and Herman Wilfarth in 1886-1888.
– Beijerinck showed Azotobacter chroococcum can fix atmospheric nitrogen in 1901.

**Biological Nitrogen Fixation**:
– Biological nitrogen fixation (BNF) converts atmospheric nitrogen to ammonia.
– Nitrogenase enzyme catalyzes the overall reaction for BNF.
– Process occurs at FeMoco metal cluster.
– Nitrogenases are rapidly degraded by oxygen.
– Nitrogen-fixing organisms exist mainly in anaerobic conditions.

**Microorganisms and Environmental Impact**:
– Diazotrophs are widespread in domain Bacteria.
– Cyanobacteria play key roles in the carbon and nitrogen cycle.
Nitrogen fixation occurs in both soils and aquatic systems.
– Marine cyanobacterium Trichodesmium accounts for a significant portion of marine nitrogen fixation.
– Methanogens contribute significantly to nitrogen fixation in soils.

**Agricultural Significance and Processes**:
Nitrogen fixation is essential for the biosynthesis of organic compounds.
– Crucial for agriculture and fertilizer production.
– Symbiotic relationships exist between nitrogen-fixing bacteria and plant groups.
– Legumes in Fabaceae family contribute to nitrogen fixation.
– CRISPRi-dCas9 systems have been used to study gene function during nitrogen fixation.

**Industrial Processes and Research**:
– Haber-Bosch process is the dominant method for ammonia production.
– Research on catalysts for nitrogen fixation aims to reduce energy requirements.
– Lightning contributes to the natural nitrogen fixation process.
– Efforts continue to improve catalytic processes for nitrogen fixation.
– Network analysis has revealed ecological links between N-fixing bacteria and wood-decaying fungi.

Nitrogen fixation (Wikipedia)

Nitrogen fixation is a chemical process by which molecular nitrogen (N
), which has a strong triple covalent bond, is converted into ammonia (NH
) or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. The nitrogen in air is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or diazotrophy is an important microbe-mediated process that converts dinitrogen (N2) gas to ammonia (NH3) using the nitrogenase protein complex (Nif).

Nitrogen fixation is essential to life because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing organic compounds, such as amino acids and proteins, nucleoside triphosphates and nucleic acids. As part of the nitrogen cycle, it is essential for agriculture and the manufacture of fertilizer. It is also, indirectly, relevant to the manufacture of all nitrogen chemical compounds, which include some explosives, pharmaceuticals, and dyes.

Nitrogen fixation is carried out naturally in soil by microorganisms termed diazotrophs that include bacteria, such as Azotobacter and Rhizobia, and archaea. Some nitrogen-fixing bacteria have symbiotic relationships with plant groups, especially legumes. Looser non-symbiotic relationships between diazotrophs and plants are often referred to as associative, as seen in nitrogen fixation on rice roots. Nitrogen fixation occurs between some termites and fungi. It occurs naturally in the air by means of NOx production by lightning.

All biological reactions involving the process of nitrogen fixation are catalyzed by enzymes called nitrogenases. These enzymes contain iron, often with a second metal, usually molybdenum but sometimes vanadium.

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