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Nitrite Oxidoreductase
Nitrite oxidoreductase (NOR or NXR) is an enzyme involved in nitrification. It is the last step in the process of aerobic ammonia oxidation, which is carried out by two groups of nitrifying bacteria: ammonia oxidizers such as '' Nitrosospira'', ''Nitrosomonas'' and '' Nitrosococcus'' convert ammonia to nitrite, while nitrite oxidizers such as ''Nitrobacter'' and ''Nitrospira'' oxidize nitrite to nitrate. The enzyme is bound to the inner cytoplasmic surface of the bacterial membrane and contains multiple subunits, iron-sulfur centers and a molybdenum cofactor. The enzyme is relatively abundant, making up 10-30% of the total protein in these bacteria and forms densely packed structures on the membrane surface. ;Reaction : + acceptor + reduced\ acceptor See also *Microbial metabolism Microbial metabolism is the means by which a microbe obtains the energy and nutrients (e.g. carbon) it needs to live and reproduce. Microbes use many different types of metabolic strategies and spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrification
''Nitrification'' is the biological oxidation of ammonia to nitrite followed by the oxidation of the nitrite to nitrate occurring through separate organisms or direct ammonia oxidation to nitrate in comammox bacteria. The transformation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil. Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea. Microbiology Ammonia oxidation The oxidation of ammonia into nitrite (also known as nitritation) is performed by two groups of organisms, ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). AOB AOB can be found among the Betaproteobacteria and Gammaproteobacteria. Since discovery of AOA in 2005, two isolates have been cultivated: ''Nitrosopumilus maritimus'' and ''Nitrososphaera viennensis''. In soils the most studied AOB belong to the genera '' Nitrosomonas'' and '' Nitrococcus''. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrifying Bacteria
Nitrifying bacteria are chemolithotrophic organisms that include species of genera such as '' Nitrosomonas'', ''Nitrosococcus'', '' Nitrobacter'', '' Nitrospina'', '' Nitrospira'' and '' Nitrococcus''. These bacteria get their energy from the oxidation of inorganic nitrogen compounds. Types include ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). 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), hydroxylamine oxidoreductase (which oxidizes hydroxylamine to nitric oxide - which is further oxidized to nitrite by a currently unidentified enzyme), and nitrite oxidoreductase (which oxidizes nitrite to nitrate). Ecology Nitrifying bacteria are present in distinct taxonomical groups and are found in highest numbers where considerable amounts of ammonia are present (such as areas with extensive protein decomposition, and sewa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrosomonas
''Nitrosomonas'' is a genus of Gram-negative bacteria, belonging to the Betaproteobacteria. It is one of the five genera of ammonia-oxidizing bacteria and, as an obligate chemolithoautotroph, uses ammonia (NH3) as an energy source and carbon dioxide (CO2) as a carbon source in presence of oxygen. ''Nitrosomonas'' are important in the global biogeochemical nitrogen cycle, since they increase the bioavailability of nitrogen to plants and in the denitrification, which is important for the release of nitrous oxide, a powerful greenhouse gas. This microbe is photophobic, and usually generate a biofilm matrix, or form clumps with other microbes, to avoid light. ''Nitrosomonas'' can be divided into six lineages: the first one includes the species '' Nitrosomonas europea'', '' Nitrosomonas eutropha'', '' Nitrosomonas halophila'', and '' Nitrosomonas mobilis.'' The second lineage presents the species '' Nitrosomonas communis'', ''N. sp. I'' and ''N. sp. II,'' meanwhile the third lineag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrosococcus
''Nitrosococcus'' is a genus of Gram-negative bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ....George M. Garrity: '' Bergey's Manual of Systematic Bacteriology''. 2. Auflage. Springer, New York, 2005, Volume 2: ''The Proteobacteria, Part B: The Gammaproteobacteria'' References Chromatiales Bacteria genera {{Chromatiales-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrobacter
''Nitrobacter'' is a genus comprising rod-shaped, gram-negative, and chemoautotrophic bacteria. The name ''Nitrobacter'' derives from the Latin neuter gender noun ''nitrum, nitri'', alkalis; the Ancient Greek noun βακτηρία'','' βακτηρίᾱς'','' rod. They are non-motile and reproduce via budding or binary fission. ''Nitrobacter'' cells are obligate aerobes and have a doubling time of about 13 hours. ''Nitrobacter'' play an important role in the nitrogen cycle by oxidizing nitrite into nitrate in soil and marine systems. Unlike plants, where electron transfer in photosynthesis provides the energy for carbon fixation, ''Nitrobacter'' uses energy from the oxidation of nitrite ions, NO2−, into nitrate ions, NO3−, to fulfill their energy needs. ''Nitrobacter'' fix carbon dioxide via the Calvin cycle for their carbon requirements. ''Nitrobacter'' belongs to the Alphaproteobacteria class of the Pseudomonadota. Morphology and characteristics ''Nitrobacter'' are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrospira
''Nitrospira'' (from Latin: nitro, meaning "nitrate" and Greek: spira, meaning "spiral") translate into “a nitrate spiral” is a genus of bacteria within the monophyletic clade of the Nitrospirota phylum. The first member of this genus was described 1986 by Watson et al. isolated from the Gulf of Maine. The bacterium was named ''Nitrospira marina''. Populations were initially thought to be limited to marine ecosystems, but it was later discovered to be well-suited for numerous habitats, including activated sludge of wastewater treatment systems, natural biological marine settings (such as the Seine River in France and beaches in Cape Cod), water circulation biofilters in aquarium tanks, terrestrial systems, fresh and salt water ecosystems, and hot springs. Nitrospira is a ubiquitous bacterium that plays a role in the nitrogen cycle by performing nitrite oxidation in the second step of nitrification. ''Nitrospira'' live in a wide array of environments including but not limited ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molybdenum
Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lead ores. Molybdenum minerals have been known throughout history, but the element was discovered (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 by Carl Wilhelm Scheele. The metal was first isolated in 1781 by Peter Jacob Hjelm. Molybdenum does not occur naturally as a free metal on Earth; it is found only in various oxidation states in minerals. The free element, a silvery metal with a grey cast, has the sixth-highest melting point of any element. It readily forms hard, stable carbides in alloys, and for this reason most of the world production of the element (about 80%) is used in steel alloys, including high-strength alloys and superalloys. Most molybdenum compounds have low solubility ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microbial Metabolism
Microbial metabolism is the means by which a microbe obtains the energy and nutrients (e.g. carbon) it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles. Types All microbial metabolisms can be arranged according to three principles: 1. How the organism obtains carbon for synthesizing cell mass:Morris, J. et al. (2019). "Biology: How Life Works", 3rd edition, W. H. Freeman. * autotrophic – carbon is obtained from carbon dioxide () * heterotrophic – carbon is obtained from organic compounds * mixotrophic – carbon is obtained from both organic compounds and by fixing carbon dioxide 2. How the organism obtains reducin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferredoxin—nitrite Reductase
In enzymology, a ferredoxin—nitrite reductase () is an enzyme that catalyzes the chemical reaction :NH3 + 2 H2O + 6 oxidized ferredoxin \rightleftharpoons nitrite + 6 reduced ferredoxin + 7 H+ The 3 substrates of this enzyme are NH3, H2O, and oxidized ferredoxin, whereas its 3 products are nitrite, reduced ferredoxin, and H+. This enzyme belongs to the family of oxidoreductases, specifically those acting on other nitrogenous compounds as donors with an iron-sulfur protein as acceptor. The systematic name of this enzyme class is ammonia:ferredoxin oxidoreductase. This enzyme participates in nitrogen metabolism and nitrogen assimilation. It has 3 cofactors: iron, Siroheme, and Iron-sulfur. This enzyme can use many different isoforms of ferredoxin. In photosynthesizing tissues, it uses ferredoxin that is reduced by PSI and in the root it uses a form of ferredoxin (FdIII) that has a less negative midpoint potential and can be reduced easily by NADPH. Structural stu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrogen Assimilation
Nitrogen assimilation is the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment. Organisms like plants, fungi and certain bacteria that can fix nitrogen gas (N2) depend on the ability to assimilate nitrate or ammonia for their needs. Other organisms, like animals, depend entirely on organic nitrogen from their food. Nitrogen assimilation in plants Plants absorb nitrogen from the soil in the form of nitrate (NO3−) and ammonium (NH4+). In aerobic soils where nitrification can occur, nitrate is usually the predominant form of available nitrogen that is absorbed. However this is not always the case as ammonia can predominate in grasslands and in flooded, anaerobic soils like rice paddies. Plant roots themselves can affect the abundance of various forms of nitrogen by changing the pH and secreting organic compounds or oxygen. This influences microbial activities like the inter-conversion of various nitrogen species, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
