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Denitration
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 ozone-de ... [...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 atmosphere, atmospheric, terrestrial ecosystem, 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 nitrogen fixation, 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 w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit the air, soil, water, Hot spring, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the nitrogen fixation, fixation of nitrogen from the Earth's atmosphere, atmosphere. The nutrient cycle includes the decomposition of cadaver, dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ecosystem
An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and energy flows. Ecosystems are controlled by external and internal Environmental factor, factors. External factors—including climate—control the ecosystem's structure, but are not influenced by it. By contrast, internal factors control and are controlled by ecosystem processes; these include decomposition, the types of species present, root competition, shading, disturbance, and succession. While external factors generally determine which Resource (biology), resource inputs an ecosystem has, their availability within the ecosystem is controlled by internal factors. Ecosystems are wikt:dynamic, dynamic, subject to periodic disturbances and always in the process of recovering from past disturbances. The tendency of an ecosystem to remain clo ... [...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 only have the capability of N2O reduction to N2 and ... [...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] |
Nitrite Reductase
Nitrite reductase refers to any of several classes of enzymes that catalyze the reduction of nitrite. There are two classes of NIR's. A multi haem enzyme reduces NO2− to a variety of products. Copper containing enzymes carry out a single electron transfer to produce nitric oxide. Iron based There are several types of iron based enzymes. Cytochrome cd1, or ''Pseudomonas'' cytochrome oxidase contains two c and two d type hemes with two polypeptide chains. Different forms of this reductase catalyze the formation of nitric oxide or nitrous oxide. A version of this compound was originally called errocytochrome c-551:oxidoreductase It was initially considered an oxidase. It catalyzes the reduction of NO2− to NO. This tetraheme enzyme has two Protein subunit">subunits, each containing a c-type and a d-type heme. The reduced d hemes bind nitrite and convert it to product. Cytochrome c nitrite reductase (ccNIR) is a multiheme enzyme that converts nitrite to ammonia on each ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitrate Reductase
Nitrate reductases are molybdoenzymes that reduce nitrate () to nitrite (). 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 molybdenum ion that is bound to the four thiolate functional groups of two pterin molecules. The coordination sphere of the molybdenum ion is completed by one amino-acid side chain and oxygen and/or sulfur ligands. In Nap, the molybdenum is covalently attached to the protein by a cysteine side cha ... [...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 species ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alcaligenes Faecalis
''Alcaligenes faecalis'' is a species of Gram-negative, rod-shaped bacteria commonly found in the environment. It was originally named for its first discovery in feces, but was later found to be common in soil, water, and environments in association with humans. While opportunistic infections do occur, the bacterium is generally considered nonpathogenic. When an opportunistic infection does occur, it is usually observed in the form of a urinary tract infection. ''A. faecalis'' has been used for the production of nonstandard amino acids. Description ''A. faecalis'' is a Gram-negative bacterium which appears rod-shaped and motile under a microscope. It is positive by the oxidase test and catalase test, but negative by the nitrate reductase test. It is alpha-hemolytic and requires oxygen. ''A. faecalis'' can be grown at 37 °C, and forms colonies that lack pigmentation. Metabolism The bacterium degrades urea, creating ammonia which increases the pH of the environment. Alt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and non-coding genes. During gene expression (the synthesis of Gene product, RNA or protein from a gene), DNA is first transcription (biology), copied into RNA. RNA can be non-coding RNA, directly functional or be the intermediate protein biosynthesis, template for the synthesis of a protein. The transmission of genes to an organism's offspring, is the basis of the inheritance of phenotypic traits from one generation to the next. These genes make up different DNA sequences, together called a genotype, that is specific to every given individual, within the gene pool of the population (biology), population of a given species. The genotype, along with environmental and developmental factors, ultimately determines the phenotype ... [...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, and then to 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 nitrogen 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− direc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonium
Ammonium is a modified form of ammonia that has an extra hydrogen atom. It is a positively charged (cationic) polyatomic ion, molecular ion with the chemical formula or . It is formed by the protonation, addition of a proton (a hydrogen nucleus) to ammonia (). Ammonium is also a general name for positively charged (protonated) substituted amines and quaternary ammonium cations (), where one or more hydrogen atoms are replaced by Organic compound, organic or other groups (indicated by R). Not only is ammonium a source of nitrogen and a key metabolite for many living organisms, but it is an integral part of the global nitrogen cycle. As such, human impact in recent years could have an effect on the biological communities that depend on it. Acid–base properties The ammonium ion is generated when ammonia, a weak base, reacts with Brønsted–Lowry acid–base theory, Brønsted acids (proton donors): : The ammonium ion is mildly acidic, reacting with Brønsted bases to return ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
