Nitrogen fixation by bacteria

Nitrogen fixation by bacteria involves the reduction of N2 to NH3 (equation 28.14) catalysed by nitrogenases concomitant with this process is the hydrolysis of ATP which is an energy-releasing process. 

Free-living bacteria in Temperate Zones fix only 2 to 3 kg N ha yr In the tropics, however, there is increasing evidence that nitrogen fixation by bacteria, particularly those growing in associative symbioses may be important. In Brazil, the nitrogen-fixing bacterium Azotobacter paspali lives in association with roots of the tropical forage plant Paspalum notatum. This association fixes 90 kg N ha yr [29]. 

Moreover, the lipo-chitooligosaccharides, also known as nod factors, permit nitrogen fixation by which plants and symbiotic Rhizobia bacteria can reduce atmospheric nitrogen to the ammonia that is utihzed by the plant, thus making available nitrogen compounds to other living organisms. 

Ludden, P.W. and G.P. Roberts. The biochemistry and genetics of nitrogen fixation by photosynthetic bacteria. In Anoxygenic Photosynthetic Bacteria, Kluwer Academic Publishers, Dordrecht, The Netherlands,... 

Nitrogen fixation by some bacteria and algae, e.g., Klebsiella, Azotobacter, Nitrifying Rhizobium... 

Teal, J.M. Valiela, I., and Berio, D. (1979) Nitrogen fixation by rhizosphere and free-living bacteria in salt marsh sediments. Limnol. Oceanogr. 24, 126-132. 

In aquatic habitats, cyanobacteria are the principal nitrogen fixers. Rates of nitrogen fixation by cyanobacteria are generally one or two orders of magnitude higher than those by free-living, nonphotosynthetic soil bacteria. Under favorable conditions, cyanobacteria may fix up to 1600 kg of N/ha/year in a rice paddy. 

Welsh, D. T., Bourgues, S., deWit, R., and Herbert, R. A. (1996b). Seasonal variations in nitrogen-fixation (acetylene reduction) and sulphate-reduction rates in the rhizosphere of Zostera noltii Nitrogen fixation by sulphate reducing bacteria. Mar. Biol. 125, 619-628. 

Nitrogen fixation by sediment bacteria and cyanobacteria in algal turfs... 

Lechene, C. P., Luyten, Y., McMahon, G., and Distel, D. L. (2007). Quantitative imaging of nitrogen fixation by individual bacteria within animal cells. Science 317, 1563—1566. 

Molybdenum (Mo) deficiencies have been reported from many countries around the world, mainly in acidic soils. Sandy soils are Mo-deficient more often than are loam or clay soils. Most Mo deficiencies are associated with legume crops, because Mo is an essential constituent of enzymes necessary for fixation of nitrogen (N) by bacteria growing symbiotically with legumes. Molybdenum is also required in other enzyme systems in all plants. 

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]... 

Isotopic compositions of Mo and Fe measured by MC-ICP-MS indicate that during assimilation of Mo and Fe via nitrogen fixation by Azotobacter vindandii, the lighter isotope of Mo ( Mo versus Mo) is preferentially assimilated by the bacteria with a fractionation factor between assimilated and dissolved Mo of0.9997 [2]. In contrast, the heavier isotope of Fe ( Fe versus Fe) was removed from solution by the bacteria with a fractionation factor of 1.0011. Fractionation of Mo isotopes results from kinetic effects involving metal-binding ligands, whereas Fe... 

Henriksson, E. (1951). Nitrogen fixation by a bacteria-freesymbioticMoj ocstrain isolated from Collema. Physiol. Plant. 4, 542-545. 

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