Nitrogen fixation

Nitrogen fixation is a chemical process by which molecular dinitrogen (N
₂) is converted into ammonia (NH
₃).^[1] It occurs both biologically and abiologically in chemical industries. Biological nitrogen fixation or diazotrophy is catalyzed by enzymes called nitrogenases.^[2] These enzyme complexes are encoded by the Nif genes (or Nif homologs) and contain iron, often with a second metal (usually molybdenum, but sometimes vanadium).^[3]

Some nitrogen-fixing bacteria have symbiotic relationships with plants, especially legumes, mosses and aquatic ferns such as Azolla.^[4] 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.^[5] It occurs naturally in the air by means of NO_x production by lightning.^[6]^[7]

Fixed nitrogen is essential to life on Earth. Organic compounds such as DNA and proteins contain nitrogen. Industrial nitrogen fixation underpins the manufacture of all nitrogenous industrial products, which include fertilizers, pharmaceuticals, textiles, dyes and explosives.

^ Einsle O, Rees DC (2020). "Structural Enzymology of Nitrogenase Enzymes". Chemical Reviews. 120 (12): 4969–5004. doi:10.1021/acs.chemrev.0c00067. PMC 8606229. PMID 32538623.
^ Burris RH, Wilson PW (June 1945). "Biological Nitrogen Fixation". Annual Review of Biochemistry. 14 (1): 685–708. doi:10.1146/annurev.bi.14.070145.003345. ISSN 0066-4154.
^ Wagner SC (2011). "Biological Nitrogen Fixation". Nature Education Knowledge. 3 (10): 15. Archived from the original on 13 September 2018. Retrieved 29 January 2019.
^ Zahran HH (December 1999). "Rhizobium-legume symbiosis and nitrogen fixation under severe conditions and in an arid climate". Microbiology and Molecular Biology Reviews. 63 (4): 968–89, table of contents. doi:10.1128/MMBR.63.4.968-989.1999. PMC 98982. PMID 10585971.
^ Sapountzis P, de Verges J, Rousk K, Cilliers M, Vorster BJ, Poulsen M (2016). "Potential for Nitrogen Fixation in the Fungus-Growing Termite Symbiosis". Frontiers in Microbiology. 7: 1993. doi:10.3389/fmicb.2016.01993. PMC 5156715. PMID 28018322.
^ Slosson E (1919). Creative Chemistry. New York, NY: The Century Co. pp. 19–37.
^ Hill RD, Rinker RG, Wilson HD (1979). "Atmospheric Nitrogen Fixation by Lightning". J. Atmos. Sci. 37 (1): 179–192. Bibcode:1980JAtS...37..179H. doi:10.1175/1520-0469(1980)037<0179:ANFBL>2.0.CO;2.

[Rees-1] Einsle O, Rees DC (2020). "Structural Enzymology of Nitrogenase Enzymes". Chemical Reviews. 120 (12): 4969–5004. doi:10.1021/acs.chemrev.0c00067. PMC 8606229. PMID 32538623.

[2] Burris RH, Wilson PW (June 1945). "Biological Nitrogen Fixation". Annual Review of Biochemistry. 14 (1): 685–708. doi:10.1146/annurev.bi.14.070145.003345. ISSN 0066-4154.

[Wagner-3] Wagner SC (2011). "Biological Nitrogen Fixation". Nature Education Knowledge. 3 (10): 15. Archived from the original on 13 September 2018. Retrieved 29 January 2019.

[Zahran-4] Zahran HH (December 1999). "Rhizobium-legume symbiosis and nitrogen fixation under severe conditions and in an arid climate". Microbiology and Molecular Biology Reviews. 63 (4): 968–89, table of contents. doi:10.1128/MMBR.63.4.968-989.1999. PMC 98982. PMID 10585971.

[Sapountzis-5] Sapountzis P, de Verges J, Rousk K, Cilliers M, Vorster BJ, Poulsen M (2016). "Potential for Nitrogen Fixation in the Fungus-Growing Termite Symbiosis". Frontiers in Microbiology. 7: 1993. doi:10.3389/fmicb.2016.01993. PMC 5156715. PMID 28018322.

[6] Slosson E (1919). Creative Chemistry. New York, NY: The Century Co. pp. 19–37.

[7] Hill RD, Rinker RG, Wilson HD (1979). "Atmospheric Nitrogen Fixation by Lightning". J. Atmos. Sci. 37 (1): 179–192. Bibcode:1980JAtS...37..179H. doi:10.1175/1520-0469(1980)037<0179:ANFBL>2.0.CO;2.

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