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Nitrifying bacteria

Nitrifying bacteria are chemoautotrophic bacteria that grow at the expense of inorganic nitrogen compounds.[1] Many species of nitrifying bacteria have complex internal membrane systems that are the location for key enzymes in nitrification: ammonia monooxygenase which oxidizes ammonia to hydroxylamine, and nitrite oxidoreductase, which oxidizes nitrite to nitrate.



Nitrifying bacteria are widespread in soil and water, and are found in highest numbers where considerable amounts of ammonia are present (areas with extensive protein decomposition, and sewage treatment plants).[2] Nitrifying bacteria thrive in lakes and streams with high inputs of sewage and wastewater because of the high ammonia content.

Oxidation of ammonia to nitrate

Nitrification in nature is the result of actions of two groups of organisms, the nitrosifyers (ammonia-oxidizing bacteria) and nitrifying bacteria (nitrite-oxidizing, nitrate producing bacteria)[3]

Nitrosifying bacteria
1. NH3 + O2 + 2e- + 2H+ → NH2OH + H2O
2. NH2OH + H2O + 1/2 O2 → NO2- +2 H2O + H+
Nitrifying bacteria
NO2- + 1/2 O2 → NO3-

Nitrifying bacteria that oxidize ammonia (nitrosifyers)
Characteristics Genus Phylogenetic group DNA (mol% GC) Habitats
Gram-negative short to long rods, motile (polar flagella)or nonmotile; peripheral membrane systems Nitrosomonas Beta 45-53 Soil, Sewage, freshwater, Marine
Large cocci, motile, vesicular or peripheral membranes Nitrosococcus Gamma 49-50 Freshwater, Marine
Spirals, motile (peritrichous flagella); no obvious membrane system Nitrosospira Beta 54 Soil
Pleomorphic, lobular, compartmented cells; motile (peritrichous flagella) Nitrosolobus Beta 54 Soil
Nitrifying bacteria that oxidize nitrite
Characteristics Genus Phylogenetic group DNA (mol% GC) Habitats
Short rods, reproduce by budding, occasionally motile (single subterminal flagella) or non-motile; membrane system arranged as a polar cap Nitrobacter Alpha 59-62 Soil, Freshwater, Marine
Long, slender rods, nonmotile, no obvious membrane system Nitrospina Delta 58 Marine
Large Cocci, motile (one or two subterminal flagellum) membrane system randomly arranged in tubes Nitrococcus Gamma 61 Marine
Helical to vibroid-shaped cells; nonmotile; no internal membranes Nitrospira Nitrospirae 50 Marine, Soil

See also


  1. ^ Mancinelli RL (1996). "The nature of nitrogen: an overview". Life support & biosphere science : international journal of earth space 3 (1-2): 17-24. PMID 11539154.
  2. ^ Belser LW (1979). "Population ecology of nitrifying bacteria". Annu. Rev. Microbiol. 33: 309-33. doi:10.1146/annurev.mi.33.100179.001521. PMID 386925.
  3. ^ Ward BB (1996). "Nitrification and ammonification in aquatic systems". Life support & biosphere science : international journal of earth space 3 (1-2): 25-9. PMID 11539155.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Nitrifying_bacteria". A list of authors is available in Wikipedia.
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