Nitrogen fixation, biological

Houndean Lodge, 1 Houndean Rise, Lewes, East Sussex BN7 lEG, UK Former Director, ARC Unit of Nitrogen Fixation 

Thus nitrogen fixation is fundamental to the persistence of the biosphere as we know it today.It is also fundamentally important to world agriculture and 

In 1960 a group of microbial biochemists in the Central Research Laboratories of the Dupont de Nemours Chemical Corporation, USA, broke through a barrier that had impeded researchers for at least two decades. They extracted from a species of nitrogen-fixing bacteria a solution containing the enzyme which is responsible for the activation of dinitrogen. It was called nitrogenase, and, in appropriate conditions, it bound N2 from the atmosphere and reduced it to ammonia. 

Biological nitrogen fixation presented a chemical enigma. The two major industrial procedures employed to cause atmospheric dinitrogen to enter chemical combination, like the few available laboratory methods, required drastic conditions. The obsolete Birkeland-Eyde process required exposure of dinitro- 

The biosynthesis of amino acids first requires access to a nitrogen source. In 1888, Hermann Hellriegel (1831-1895) and Hermann Wilfarth (1853-1904) discovered the process of nitrogen fixation by nodular bacteria in the root nodules of the Leguminosae. [26] 

This was one of the far-reaching discoveries in biochemistry, since nitrogen fixation is of similar importance to life on Earth as photosynthesis. Although the atmosphere consists of 78% of molecular nitrogen, its access for chemical conversion is not simple. 

Nitrogen fixation takes place in bacteria Uving in symbiosis, such as Rhizo-bium meliloti in Leguminosae, but also in free hving bacteria like Azotobacter vinelandii (aerobic soil bacteria) or Clostridium pasteurianum (anaerobic soil bacteria). In this way, at ambient temperature and pressure. Nature produces around 1.7 x 10 tonnes of ammonia per annum. [27] 

In 1930, Hermann Bortels (1902-1979) recognised that nitrogen fixation is a molybdenum-dependent process. Obviously, the nitrogenases from Rhizobium meliloti, Azotobacter vinelandii and Clostridium pasteurianum have a similar constitution. In 1966, Leonard E. Mortenson identified for the first time an Fe- and a MoFe-protein as parts of the nitrogenase enzyme system. The exact structure of the nitrogenase-molybdenum-iron protein from Azotobacter vinelandii [28] was clarified in 1992, and that from Clostridium pasteurianum [29] in 1993, both by Douglas C. Rees. [30] The Fe-protein is a y2-dimer with a molar mass of some 60,000 Daltons, and the MoFe-protein is an ca. 

The Fe-protein binds over two cysteine residues a cube-like [Fe4S4]-cluster, ADP and two [Mg(H20)4]++. The MoFe-protein contains as cofactor a so-caUed P-duster, from a Fe4S4-cube and an Fe4S3-fragment. Beside the P-cluster, the 

Plants are amazingly successful in utilizing carbon from the relatively small amounts of carbon dioxide in the air, but they have never developed the ability to utilize atmospheric nitrogen, which is abundant in the air (78%). Only plants of the legumes group (bean family), which include lupines, peas, peanuts, etc., can utilize atmospheric nitrogen. Nitrogen fixation to ammonia by adequate catalysts at room temperature is presently only a dream. 

In these more entrophic marsh areas, periphytic mats are much less abundant, lack a visible 

Detailed information on nitrogen cycling can be found in the following papers Reddy et al. (1993,1999) Koch et al. (1994) Qualls and Richardson (2003) White and Reddy (1999,2000,2001, 

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Howard J B and Rees D C 1996 Structural basis of biological nitrogen fixation Chem. Rev. 96 2965-82... 

Non-enzvmatic simulation of nitrogenase reactions and the mechanism of biological nitrogen fixation. G. N. Schrauzer, Angew. Chem., Int. Ed. Engl., 1975, 14, 514-522 (36). 

Nitrogen fixation is any process in which N2 in the atmosphere reacts to form any nitrogen compound. Biological nitrogen fixation is the enzyme-catalyzed reduction of N2 to NH3, NH4, or any organic nitrogen compound. 

Biological nitrogen fixation as a result of agricultural practices (e.g., planting clover so as to replenish nitrogen on farmlands). 

Granhall, U. (1981). Biological nitrogen fixation in relation to environmental factors and functioning of natural ecosystems. In "Terrestrial Nitrogen Cycles" (F. E. Clark and T. Rosswall, eds). Ecological Bulletin 33, 131-145. Swedish Natural Science Research Council, Stockholm. 

S. J. Pirt, Principles of Microbe and Cell Cultivation, Blackwell, Oxford (1975). J. R. Postgate, New advances and future potential in biological nitrogen fixation. Journal of Applied Bacteriology 57 185 (1974). 

R. M. Boddey, S. Urquiaga, V. Reis, and J. Doberreiner, Biological nitrogen fixation a.ssociated with sugar cane. Plant Soil 137 111 (1991). 

James B. Howard and Douglas C. Rees. Structural Basis of Biological Nitrogen Fixation. Chemical Review. 96 (1996) 2965-2982. Source for nitrogen fixation today. 

Quantum Chemical Investigations into the Problem of Biological Nitrogen Fixation Sellmann-Type Metal-Sulfur Model Complexes Markus Reiher and Bernd A. Hess... 

Biologically active carbon, 7 7 803 Biological media, drug stability in, 9 53 Biological nanomachines, 7 7 45 Biological nitrogen fixation, 77 295-311, 316... 

Hille, R. (2005) Molybdenum-containing hydroxylases, Arch. Biochem. Biophys., 433, 107-116. Howard, J.B. and Rees, D.C. (2006) How many metals does it take to fix N2 A mechanistic overview of biological nitrogen fixation, Proc. Natl. Acad. Sci. U.S.A., 103, 17088-17093. Knowles, J.R. (1991) Enzyme catalysis not different, just better, Nature, 350, 121-124. 

Structural basis of biological nitrogen fixation, Phil. Trans. R. Soc., 363, 971-984. Schrock, R.R. (2005) Catalytic reduction of dinitrogen to ammonia at a single molybdenum center,... 

The other hypothesis suggested earlier was that ammonia rather than hydroxylamine was the product of biological nitrogen fixation. Winogradsky [9] had suggested this, and although the idea was perfectly logical, the evidence was indirect and minimal. 

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