関: Nitrosomonas

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ellipsoidal soil bacteria (同)genus Nitrosomonas
(microbiology) single-celled or noncellular spherical or spiral or rod-shaped organisms lacking chlorophyll that reproduce by fission; important as pathogens and for biochemical properties; taxonomy is difficult; often considered to be plants (同)bacterium

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/04/24 19:56:06」(JST)

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Nitrifying bacteria are chemoautotrophic or chemolithotrophs depending on the genera (Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrococcus) bacteria that grow by consuming 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 the environment, 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 a two-step oxidation process of ammonium (NH4+ or ammonia NH3) to nitrate (NO3-) catalyzed by two ubiquitous bacterial groups. The first reaction is oxidation ammonium to nitrite by ammonium oxidizing bacteria (AOB) represented by Nitrosomonas species. The second reaction is oxidation nitrite (NO2-) to nitrate by nitrite-oxidizing bacteria (NOB), represented by Nitrobacter species ^[3]^[4] . First step nitrification - molecular mechanism

Figure 1. Molecular mechanism of ammonium oxidation by AOB

Ammonia oxidation in autotrophic nitrification is a complex process that requires several enzymes, proteins and presence of oxygen. The key enzymes, necessary to obtaining energy during oxidation ammonium to nitrite are ammonia monooxygenase (AMO) and hydroxylamine oxidoreductase (HAO). First is a transmembrane copper protein which catalyzes the oxidation of ammonium to hydroxylamine (1.1) taking two electrons directly from the quinone pool. This reaction requires O₂. In the second step (1.2), a trimeric multiheme c-type HAO converts hydroxylamine into nitrite in the periplasm with production of four electrons. The stream of four electron are channelled through cytochrome c₅₅₄ to a membrane-bound cytochrome c₅₅₂. Two of the electrons are routed back to AMO, where they are used for the oxidation of ammonia (quinol pool). Rest two electrons are used to generate a proton motive force and reduce NAD(P) through reverse electron transport.^[5] (Figure 1.)

NH₃ + O₂ → NO−
2 + 3H⁺ + 2e⁻ (1)

NH₃ + O₂ + 2H⁺ + 2e⁻ → NH₂OH + H₂O (1.1)

NH₂OH + H₂O → NO−
2 + 5H⁺ + 4e⁻ (1.2)

Second step nitrification - molecular mechanism

Nitrite produced in first step autotrophic nitrification is oxidized to nitrate by nitrite oxidoreductase (NXR)(2). It is a membrane-associated iron-sulfur molybdoprotein, and is part of an electron transfer chain which channels electrons from nitrite to molecular oxygen. The molecular mechanism of oxidation nitrite is less described than oxidation ammonium. In new research (e.g. Woźnica A. et al., 2013)^[6] proposed new hypothetical model of NOB electron transport chain and NXR mechanism (Figure 2.). It should be noted that, in contrast to earlier models ^[7] the NXR acts on the outside of the plasma membrane, directly contributing to postulated by Spieck ^[8] and coworkers mechanism of proton gradient generation. Nevertheless, the molecular mechanism of nitrite oxidation is an open question.

NO−
2 + H₂O → NO−
3 + 2H⁺ + 2e⁻ (2)

Characteristic of ammonia and nitrite oxidizing bacteria ^[3]^[9]

Nitrifying bacteria that oxidize ammonia

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

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: 309–333. doi:10.1146/annurev.mi.33.100179.001521. PMID 386925.
^ ^a ^b Schaechter M. „Encyclopedia of Microbiology”, AP, Amsterdam 2009
^ 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.
^ Byung Hong Kim, Geoffrey Michael Gadd (2008). Bacterial Physiology and Metabolism. Cambridge University Press.
^ Woznica A. et al (2013). "Stimulatory Effect of Xenobiotics on Oxidative Electron Transport of Chemolithotrophic Nitrifying Bacteria Used as Biosensing Element". PLOS ONE 8 (1).
^ Ferguson SJ, Nicholls DG (2002). Bioenergetic III. Academic Press.
^ Spieck E. et al. (1998). "Isolation and immunocytochemical location of the nitrite-oxidizing system in Nitrospira moscoviensis". Arch Microbiol 169: 225–230.
^ Michael H. Gerardi (2002). Nitrification and Denitrification in the Activated Sludge Process. John Wiley & Sons,.

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English Journal

Quantification of the effects of various soil fumigation treatments on nitrogen mineralization and nitrification in laboratory incubation and field studies.

Yan D, Wang Q, Mao L, Li W, Xie H, Guo M, Cao A.SourceDepartment of Pesticides, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, People's Republic of China.
Chemosphere.Chemosphere.2013 Jan;90(3):1210-5. doi: 10.1016/j.chemosphere.2012.09.041. Epub 2012 Oct 11.
Better quantification of nitrogen mineralization and nitrification after fumigation would indicate if any adjustment is needed in fertilizer application. The effects of chloropicrin (Pic), 1,3-dichloropropene (1,3-D), dimethyl disulfide (DMDS) and metham sodium (MS) fumigation on soil nitrogen dynam
PMID 23062947

Effects of temperatures near the freezing point on N(2) O emissions, denitrification and on the abundance and structure of nitrifying and denitrifying soil communities.

Wertz S, Goyer C, Zebarth BJ, Burton DL, Tatti E, Chantigny MH, Filion M.SourceAgriculture and Agri-Food Canada, Potato Research Centre, Fredericton, NB, Canada.
FEMS microbiology ecology.FEMS Microbiol Ecol.2013 Jan;83(1):242-54. doi: 10.1111/j.1574-6941.2012.01468.x. Epub 2012 Aug 29.
Climate warming in temperate regions may lead to decreased soil temperatures over winter as a result of reduced snow cover. We examined the effects of temperatures near the freezing point on N(2) O emissions, denitrification, and on the abundance and structure of soil nitrifiers and denitrifiers. So
PMID 22882277

Japanese Journal

固定化亜硝酸菌群による高濃度窒素含有排水処理と生態学的考察

山崎博人,吉屋愛恵,根來宗孝,福永公寿
環境技術 = Environmental conservation engineering 42(6), 362-369, 2013-06-20
NAID 10031174474

固定化亜硝酸菌群による高濃度窒素含有排水処理と生態学的考察

山﨑博人,吉屋愛恵,根來宗孝 [他]
環境技術 42(6), 362-369, 2013-06
NAID 40019708087

Community Structure and In Situ Activity of Nitrifying Bacteria in Phragmites Root-Associated Biofilms

OKABE SATOSHI,NAKAMURA YOSHIYUKI,SATOH HISASHI
Microbes and environments 27(3), 242-249, 2012-09-01
… The amount of oxygen released by Phragmites roots and the community structure and in situ activity of nitrifying bacteria in the root biofilms were analyzed by the combined use of 16S rRNA gene-cloning analysis, quantitative PCR (qPCR) assay and microelectrodes. …
NAID 10030869175