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.
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 → 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
References
- ↑ 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.
- ↑ Belser LW (1979). "Population ecology of nitrifying bacteria". Annu. Rev. Microbiol. 33: 309–33. doi:10.1146/annurev.mi.33.100179.001521. PMID 386925.
- ↑ 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.