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Denitrification
Denitrification is a microbially facilitated process where nitrate (NO3−) is reduced and ultimately produces molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitrification as a type of respiration that reduces oxidized forms of nitrogen in response to the oxidation of an electron donor such as organic matter. The preferred nitrogen electron acceptors in order of most to least thermodynamically favorable include nitrate (NO3−), nitrite (NO2−), nitric oxide (NO), nitrous oxide (N2O) finally resulting in the production of dinitrogen (N2) completing the nitrogen cycle. Denitrifying microbes require a very low oxygen concentration of less than 10%, as well as organic C for energy. Since denitrification can remove NO3−, reducing its leaching to groundwater, it can be strategically used to treat sewage or animal residues of high nitrogen content. Denitrification can leak N2O, which is an o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dissimilatory Nitrate Reduction To Ammonium
Dissimilatory nitrate reduction to ammonium (DNRA), also known as nitrate/nitrite ammonification, is the result of anaerobic respiration by chemoorganoheterotrophic microbes using nitrate (NO3−) as an electron acceptor for respiration. In anaerobic conditions microbes which undertake DNRA oxidise organic matter and use nitrate (rather than oxygen) as an electron acceptor, reducing it to nitrite, then ammonium (NO3−→NO2−→NH4+). Dissimilatory nitrate reduction to ammonium is more common in prokaryotes but may also occur in eukaryotic microorganisms. DNRA is a component of the terrestrial and oceanic nitrogen cycle. Unlike denitrification, it acts to conserve bioavailable nitrogen in the system, producing soluble ammonium rather than unreactive dinitrogen gas. Background and process Cellular process Dissimilatory nitrate reduction to ammonium is a two step process, reducing NO3− to NO2− then NO2− to NH4+, though the reaction may begin with NO2− directly. Each st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrogen Cycle
The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmospheric nitrogen, making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paracoccus Denitrificans
''Paracoccus denitrificans'', is a coccoid bacterium known for its nitrate reducing properties, its ability to replicate under conditions of hypergravity and for being a relative of the eukaryotic mitochondrion (endosymbiotic theory). Description ''Paracoccus denitrificans'', is a gram-negative, coccus, non-motile, denitrifying (nitrate-reducing) bacterium. It is typically a rod-shaped bacterium but assumes spherical shapes during the stationary phase. Like all gram-negative bacteria, it has a double membrane with a cell wall. Formerly known as ''Micrococcus denitrificans'', it was first isolated in 1910 by Martinus Beijerinck, a Dutch microbiologist. The bacterium was reclassified in 1969 to ''Paracoccus denitrificans'' by D.H. Davis. The genome of ''P. denitrificans'' was sequenced in 2004. Ecology and ecological applications Metabolically ''Paracoccus denitrificans'' is very flexible and has been recorded in soil in both aerobic or anaerobic environments. The microbe a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrogen Cycle
The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmospheric nitrogen, making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrous-oxide Reductase
In enzymology, a nitrous oxide reductase also known as nitrogen:acceptor oxidoreductase (N2O-forming) is an enzyme that catalyzes the final step in bacterial denitrification, the reduction of nitrous oxide to dinitrogen. : N2O + 2 reduced cytochome ''c'' N2 + H2O + 2 cytochrome ''c'' It plays a critical role in preventing release of a potent greenhouse gas into the atmosphere. Function N2O is an inorganic metabolite of the prokaryotic cell during denitrification. Thus, denitrifiers comprise the principal group of N2O producers, with roles played also by nitrifiers, methanotrophic bacteria, and fungi. Among them, only denitrifying prokaryotes have the ability to convert N2O to N2. Conversion of N2O into N2 is the last step of a complete nitrate denitrification process and is an autonomous form of respiration. N2O is generated in the denitrifying cell by the activity of respiratory NO reductase. Some microbial communities have only capability of N2O reduction to N2 and doe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrous Oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has a slightly sweet scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen. Nitrous oxide has significant medical uses, especially in surgery and dentistry, for its anaesthetic and pain-reducing effects. Its colloquial name, "laughing gas", coined by Humphry Davy, is due to the euphoric effects upon inhaling it, a property that has led to its recreational use as a dissociative anaesthetic. It is on the World Health Organization's List of Essential Medicines. It is also used as an oxidiser in rocket propellants, and in motor racing to increase the power output of engines. Nitrous oxide's atmospheric concentration reached 333 parts per billion (ppb) in 2020, increasing at a rat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N2, a colorless and odorless diatomic gas. N2 forms about 78% of Earth's atmosphere, making it the most abundant uncombined element. Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins), in the nucleic acids ( DNA and RNA) and in the energy transfer molecule adenosine triphosphate. The human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes the movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere. Many indus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitric-oxide Reductase
Nitric oxide reductase, an enzyme, catalyzes the reduction of nitric oxide (NO) to nitrous oxide (N2O). The enzyme participates in nitrogen metabolism and in the microbial defense against nitric oxide toxicity. The catalyzed reaction may be dependent on different participating small molecules: Cytochrome c (EC: 1.7.2.5, Nitric oxide reductase (cytochrome c)), NADPH (EC:1.7.1.14), or Menaquinone (EC:1.7.5.2). Nomenclature Nitric oxide reductase was assigned Enzyme Commission number (EC) 1.7.2.5. Enzyme Commission numbers are the standard naming system used for enzymes. The EC identifies the class, subclass, sub-subclass, and serial number of the enzyme. Nitric oxide reductase is in Class 1, therefore it is an oxidoreductases. Nitric oxide reductase belongs to the family of oxidoreductases, specifically those acting on other nitrogenous compounds as donors with other acceptors. The systematic name of this enzyme class is nitrous-oxide:acceptor oxidoreductase (NO-forming). ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrate Reductase
Nitrate reductases are molybdoenzymes that reduce nitrate (NO) to nitrite (NO). This reaction is critical for the production of protein in most crop plants, as nitrate is the predominant source of nitrogen in fertilized soils. Types Eukaryotic Eukaryotic nitrate reductases are part of the sulfite oxidase family of molybdoenzymes. They transfer electrons from NADH or NADPH to nitrate. Prokaryotic Prokaryotic nitrate reductases belong to the DMSO reductase family of molybdoenzymes and have been classified into three groups, assimilatory nitrate reductases (Nas), respiratory nitrate reductase (Nar), and periplasmic nitrate reductases (Nap). The active site of these enzymes is a Mo ion that is bound to the four thiolate functions of two pterin molecules. The coordination sphere of the Mo is completed by one amino-acid side chain and oxygen and/or sulfur ligands. The exact environment of the Mo ion in certain of these enzymes (oxygen versus sulfur as a sixth molybdenum li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bradyrhizobium Japonicum
''Bradyrhizobium japonicum'' is a species of legume- root nodulating, microsymbiotic nitrogen-fixing bacteria. The species is one of many Gram-negative, rod-shaped bacteria commonly referred to as rhizobia. Within that broad classification, which has three groups, taxonomy studies using DNA sequencing indicate that ''B. japonicum'' belongs within homology group II. Uses Agriculture ''B. japonicum'' is added to legume seed to improve crop yields, particularly in areas where the bacterium is not native (e.g. Arkansas soils). Often the inoculate is adhered to the seeds prior to planting using a sugar solution. Research A strain of ''B. japonicum'', USDA110, has been in use as a model organism since 1957. It is widely used to study molecular genetics, plant physiology, and plant ecology due to its relatively superior symbiotic nitrogen-fixation activity with soybean (i.e. compared to other rhizobia species). Its entire genome was sequenced in 2002, revealing that the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into plant tissue. By feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system. They also influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and microbes. Ecosystems are controlled by external and internal Environmental factor, factors. External factors such as climate, parent material which forms the soil and topography, control the overall structure of an ecosystem but are not themselves influe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. There are two classes of redox reactions: * ''Electron-transfer'' – Only one (usually) electron flows from the reducing agent to the oxidant. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. * ''Atom transfer'' – An atom transfers from one substrate to another. For example, in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are commonly associated with the formation of oxides, other chemical species can serve the same function. In hydrogenation, C=C (and other) bonds ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
