Ammonification

This is a process in which organic nitrogen is converted into ammonia. Nitrogen in living and 

Some of the ammonia thus produced is released from alkaline environments to the atmosphere, where it is relatively inaccessible to biological systems. This form of nitrogen (and others in the atmosphere) is subject to chemical and photochemical transformations, after which they can be returned to the litho- and hydrosphere through water deposition. 

Numerous plants and microorganisms can assimilate ammonium ions by incorporating them into amino acids and other nitrogen-containing biochemicals. Animals acquire all of their amino acids when they eat plants (or other animals). When plants or animals die (or release waste), the nitrogen is returned to the soil. The usual forms of nitrogen returned to the soil in animal wastes or in the output of the decomposers are ammonia, urea, or uric acid. 

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Ammonification (organic nitrogen NH3) Many microbes, especially bacteria... 

Ammonification is the breaking down of organic nitrogen compounds into NH3 or NHT... 

Besides nitrogen fixation, the only other major source of reduced nitrogen is the decomposition of soil or aquatic organic matter. This process is called ammonification. Heterotrophic bacteria are principally responsible for this. These organisms utilize organic compounds from dead plant or animal matter as a carbon source, and leave behind NH3 and NHJ, which can then be recycled by the biosphere. In some instances heterotrophic bacteria may incorporate a complete organic molecule into their own biomass. The majority of the NH3 produced in this way stays within the biosphere however, a small portion of it will be volatilized. In addition to this source, the breakdown of animal excreta also contributes to atmospheric... 

Seitz H-J, H Cypionka (1986) Chemolithotrophic growth of Desulfovibrio desulfuricans with hydrogen coupled to ammonification with nitrate or nitrite. Arch Microbiol 146 63-67. 

The low temperatures and low soil pH that usually prevail at higher altitudes and latitudes (e.g., heathlands) restrain nitrification and (to a lesser extent) ammonification (92). Studies of N relations in temperate and boreal ecosystems have dem-... 

Measurements other than respiration rate can also be used as indicators of soil microbial activity. These include measurements of the rate of multienzyme processes such as arginine ammonification rate (Alef and Kleiner 1995) fluorescein diacetate (FDA) hydrolysis rate (Alef 1995) and measurement of key endocellular enzymes such as dehydrogenase (Tabatabai 1994). 

Alef K, Kleiner D (1995) Arginine ammonification. In Alef K, Nannipieri P (eds) Methods in applied soil microbiology and biochemistry. Academic Press, London, pp 238-240... 

Lipman CB, Burgess PS (1914) The effects of copper, zinc, iron and lead salts on ammonification and nitrification in soils. University of California Publications in Agricultural Science 1 127-139... 

Burger M, Jackson LE (2003) Microbial immobilization of ammonium and nitrate in relation to ammonification and nitrification rates in organic and conventional cropping systems. Soil Biol Biochem 35 29-36... 

Autotrophic activity. Because of the low C N ratio and its declining value as carbonaceous residues are degraded there is substantial ammonification. With all mean treatment times greater than the doubling time of Nitrobacter sp. nitrification will occur provided that oxygen is not limiting. Smith and Evans (19) found that with DO levels above 15% of saturation, nitrification continued until the culture was limited by a fall in pH level. Up to 40% of the slurry ammonia was oxidised. The autotrophic activity never achieved steady state and cycled between periods of activity when the pH value was above about 5.5 and periods of inactivity when the pH value fell below 5.5. Complete nitrification of all ammonia only occurred if the pH value was controlled at about 7 by the addition of alkali. When the DO level was held within the range of 1 to 15% of saturation a system of simultaneous nitrification and denitrification was established. The reduction of nitrate allowed the pH value to remain above 6 and nitrification to continue. Thus more than 70% of the ammonia was oxidised. If the DO level was held below 0.1% of saturation, nitrification was inhibited (unpublished). 

A simplified depiction of the marine nitrogen cycie iiiustrating redox and phase transitions mediated by microbes. The boxes contain the nitrogen species and its oxidation number. The arrows represent transformation reactions as foiiows (1) nitrogen fixation, (2) soiubiiization, (3) ammonification,... 

Ammonification. This process proceeds in steps (1) The breakage of the peptide linkage between amino acids A and B, followed by (2) The deamination of the amino acids and formation of NHJ. The electron carrier (e.g., NAD+, NADP+) involved in such reactions depends on the type of protein undergoing degradation and the species of organism mediating the reaction. These reactions are catalyzed by enzymes. 

In the water column, ammonification and nitrification can sometimes lead to the formation of subsurface ammonium and nitrite concentration maxima that are usually located toward the base of the euphotic zone in stratified water columns. This is called the primary nitrite maximum. Some of this nitrite is also contributed by releases... 

In suboxic waters, a secondary ammonium maximum can also be present. It typically lies just above the secondary nitrite maximum. This secondary maximum is supported by high rates of ammonification. Because the waters are suboxic, nitrification rates are slow permitting the buildup of ammonium. 

Ammonification The microbial process by which dissolved organic nitrogen is converted to ammonium. 

Primary nitrite maximum Subsurface concentration maximum in nitrite found toward the base of the euphotic zone in stratified water columns. Mainly caused by ammonification and nitrification. 

The involvement of HA during bacterial conversion of nitrate to NH3 (known also as the nitrate ammonification phase of the nitrogen cycle) has been studied at the molecular level as part of an effort to delineate the mechanism of conversion of nitrite to NH3 by a group of multiheme cytochromes of bacterial origin. The overall reduction reaction is depicted in equation 3 for cytochrome c-nitrite reductase " ... 

Measured ammonification, nitrification, and denitrification of the soil in GEM, and its nonrecombinant parent. 

Nitrate and Ammonium. The transformations of nitrogen species may occur under suitable microbial catalysis (5, 36). Nitrate reduction may result in formation of either elemental nitrogen or ammonium. Mass balances over a whole lake have indicated the importance of the denitrification process for the elimination of nitrogen from lakes (37). The conditions for the dis-similative ammonification of nitrate are poorly known (36). Ammonium is also released by the mineralization of biomass. 

In 1888, Beijerinck published a series of reports entitled Die bakterien der Paplionacen-Knollchen which he called Bacillus radicicola. At about the same time (1885-1891) Bertholet, Warington and Winogradsky had isolated the main microorganisms from soil and water responsible for ammonification, nitrification and denitrification. 

The nitrogen supplies on land consist of the assimilable nitrogen in the soil VS2 0.19-104tkm-2, in plants (12 1091), and living organisms (0.2 1091). A diversity of nitrogen fluxes is formed here of the processes of nitrification, denitrification, ammonification, fixation, and river run-off. The intensities of these fluxes depend on climatic conditions, temperature regime, moisture, as well as the chemical and physical properties of soil. Many qualitative and quantitative characteristics of these dependences have been described in the literature (Hellebrandt et al., 2003). Let us consider some of them. 

Beek and Frissel (1973) Growth of nitrifier and ammonifer bacteria by Michaelis-Menten kinetics NH4 oxidation by first-order kinetics with environmental variables mineralization of proteins, sugars, cellulose, lignin, and living biomass by first-order kinetics immobilization by first-order kinetics including considerations for microbial biomass and C/N ratio NH3 volatilization by diffusion NH4 clay fixation by equilibrium model. 

Lin, Q. and Brookes, P. C. (1999b). Arginine ammonification as a method to estimate soil microbial biomass and microbial community structure. Soil Biol. Biochem. 31,1985-1997. 

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