Nitrogen fixation, cyanobacteria

In cyanobacteria nitrogen fixation occurs in the heterocysts, specialized cells with thickened cell envelopes. They supply NH4+ to other cells in the filament of which they are a part. 

Cyanoacetic acid, 2 138, 139 and esters, 2 7 244-245 Cyanoacrylate adhesives, 2 539-540 Cyanoacrylate vapors, 22 102 Cyanobacteria, in nitrogen fixation, 2 7 302 Cyanobacterial associations, in nitrogen fixation, 27 299-300 Cyanocobalamin, 7 238 25 803-804 Cyanoethene. See Acrylonitrile (AN) l-Cyanoethyl-2-ethyl-4-methylimidazole (2EMZ-CN) curing catalyst, 20 17 2V-Cyanoethylated toluenediamines, 25 197... 

Marino R, Howarth RW, Chan F, Cole JJ, Likens GE (2003) Sulfate inhibition of molybdenum-dependent nitrogen fixation by planktonic cyanobacteria under seawater conditions a non-reversible effect. Hydrobiol 500 277-293... 

Bothe, H., Kentemich, T. and Heping, D. (1991) Recent aspects on the hydrogenase-nitroge-nase relationship in cyanobacteria. In M. Polsinelli, R. Materassi and M. Vincenzini (eds). Nitrogen Fixation. Dordrecht Kluwer Academic Publishers, pp. 367-75. 

Haselkorn, R. and Buikema, W. J. (1992) Nitrogen fixation in cyanobacteria. In G. Stacey, R. H. Burris and H. J. Evans (eds). Biological Nitrogen Fixation. London, Great Britain Chapman and Hall, pp. 166-90. 

There is a peak of N2 fixation coincident with the early cyanobacterial bloom, shown by the increase in acetylene reducing activity in the figure. Nitrogen fixation by the colonial cyanobacteria is slower but lasts longer. 

Only certain prokaryotes can fix atmospheric nitrogen. These include the cyanobacteria of soils and fresh and salt waters, other kinds of free-living soil bacteria such as Azotobacter species, and the nitrogen-fixing bacteria that live as symbionts in the root nodules of leguminous plants. The first important product of nitrogen fixation is ammonia, which can be used by all organisms either directly or after its conversion to other soluble compounds such as nitrites, nitrates, or amino acids. 

Nitrogen fixation is the conversion of N2 gas into ammonia, a process carried out by some soil bacteria, cyanobacteria and the symbiotic bacteria Rhizobium that invade the root nodules of leguminous plants. This process is carried out by the nitrogenase complex, which consists of a reductase and an iron-molybdenum-containing nitrogenase. At least 16 ATP molecules are hydrolyzed to form two molecules of ammonia. Leghemoglobin is used to protect the nitrogenase in the Rhizobium from inactivation by 02. 

The photoheterotrophic microorganisms are represented by cyanobacteria such as Nostoc sp. and Anabaena variabilis. They are capable of photosynthesis using sunlight and carbon dioxide in a similar manner as the photoautotrophs. They are also capable of nitrogen fixation mediated by a nitrogenase enzyme, and this is where the carbon is needed, according to the formula... 

Nitrogenases are also extremely labile in an O2 environment. Cyanobacteria have adopted two strategies to overcome the O2 sensitivity of the nitrogenase reaction, either temporal or spatial separation of O2 evolution and H2 production. Temporal separation has been achieved mainly in non-heterocystous unicellular cyanobacteria such as Gloeothece sp. strain ATCC 27152 and Plectonema boryanum. Nitrogen fixation occurs only in darkness, during which respiration of the carbohydrates, syn... 

Gallon, J. R. and Chaplin, A. E. 1988. Recent studies on N2 fixation by nonheterocystous cyanobacteria. In Bothe F. J., de Bruijin F. J., Newton, W. E. (eds) Nitrogen Fixation Hundreds Years After. Gustav Fischer, Stuttgart, Germany, p. 183. 

Scherer, S., Almon, H. Boger, P. 1988. Interactions of photosynthesis, respiration, and nitrogen fixation in cyanobacteria. Photosyn. Res. 15, 95-114. 

Free gaseous H2 is biologically produced during anaerobic fermentations and also as a side product of photosynthesis coupled with nitrogen fixation by cyanobacteria and by Rhizobium legume associations. Most of the H2 produced is utilized anaerobically to reduce NO, SO -, Fe(III), and Mn(IV) or... 

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. 

Lesser, M. P., Falcon, L. I., Rodriguez-Roman, A., Enriquez, S., Hoegh-Guldberg, O., and Iglesias-Prieto, R. (2007). Nitrogen fixation by symbiotic cyanobacteria provides a source of nitrogen for the scleractinian coral Montastraea cavernosa. Mar. Ecol. Prog. Ser. 346, 143—152. 

Needoba, J. A., Foster, R. A., Sakamoto, C., Zehr, J. P., and Johnson, K. S. (2007). Nitrogen fixation by uniceUular diazotrophic cyanobacteria in the temperate ohgotrophic North Pacific Ocean. 

Paerl, H. W., Fitzpatrick, M., and Bebout, B. M. (1996). Seasonal nitrogen fixation dynamics in a marine microbial mat Potential roles of cyanobacteria and microheterotrophs. Limnol. Oceanogr. 41, 419-427. 

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