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'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.

Contents

Ecology

Oxidation of ammonia to nitrate

See also

References

Ecology

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 high imputs 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 → NO_2- +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

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'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''	''Nitrospira'' group	50	Marine, Soil

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See also

★ Denitrification

★ Nitrification

★ Nitrogen cycle

★ Nitrogen deficiency

★ Nitrogen fixation

References

1. The nature of nitrogen: an overview, Mancinelli RL, , , Life support & biosphere science : international journal of earth space, 1996
2. Population ecology of nitrifying bacteria, Belser LW, , , Annu. Rev. Microbiol., 1979
3. Nitrification and ammonification in aquatic systems, Ward BB, , , Life support & biosphere science : international journal of earth space, 1996