Bacteria nitrite reducing

Most recently, a highly unusual membrane composition was reported from anaerobic ammonium-oxidising (anammox) bacteria. In these bacteria, nitrite is reduced, nitrogen gas generated, and carbon dioxide is converted into organic carbon, as the consequence of ammonia reduction. This central energygenerating process can be described as ... 

Similar mechanisms operate in the action of nitrate reductase and nitrite reductase. Both of these substances are produced from ammonia by oxidation. Plants and soil bacteria can reduce these compounds to provide ammonia for metabolism. The common agricultural fertilizer ammonium nitrate, NH4NO3, provides reduced nitrogen for plant growth directly, and by providing a substrate for nitrate reduction. NADH or NADPH is the electron donor for nitrate reductase, depending on the organism. 

Most studies in the microbial metabolism of nitroaromatic compounds used aerobic microorganisms. In most cases no mineralization of nitroaromatics occurs, and only superficial modifications of the structures are reported. However, under anaerobic sulfate-reducing conditions, the nitroaromatic compounds reportedly undergo a series of reductions with the formation of amino compounds. For example, trinitrotoluene under sulfate-reducing conditions is reduced to triaminotoluene by the enzyme nitrite reductase, which is commonly found in many Desulfovibrio spp. The removal of ammonia from triaminotoluene is achieved by reductive deamination catalyzed by the enzyme reductive deaminase, with the production of ammonia and toluene. Some sulfate reducers can metabolize toluene to (X) sub 2. Similar metabolic processes could be applied to other nitroaromatic compounds like nitrobenzene, nitrobenzoic acids, nitrophenols, and aniline. Many methanogenic bacteria can reduce nitroaromatic compounds to amino compounds. 

The ability of some bacteria to reduce nitrite fnr-ther to ammonia (Jorgensen and Sorensen 1985 Sorensen 1987) can be expressed by the following eqnation ... 

Oral bacteria can reduce nitrate to nitrite which, under the acidic conditions of the stomach, can react with amines in foods to form carcinogenic N-nitrosamines. In addition to dietary sources, a significant amount of nitrate is formed endogenously by the metabolism of nitric oxide—1 mg/kg body weight/day (about the same as the average dietary intake), increasing 20-fold in response to inflammation and immune stimulation, and nitrate is secreted in saliva. 

When organics containing reduced nitrogen are degraded, they usually produce ammonium, which is in equilibrium with ammonia. As the pK for NH3 NH4" is 9.3, the ammonium ion is the primary form present in virtually all biological treatment systems, as they operate at pH < 8.5 and usually in the pH range of 6.5-7.5. In aerobic reactions, ammonium is oxidized by nitrifying bacteria (nitrosomonas) to nitrite... 

In 1973, the first naturally occurring isobacteriochlorin, iron-containing siroheme, was isolated1 from a sulfite reductase of Escherichia coli. Later it was also discovered in sulfite and nitrite reductases of numerous bacteria and plants.2 Iron-free sirohydrochlorins (also called factor II) were discovered in vitamin B12 producing bacteria.3-4 Together with factor III. a sirohydrochlorin methylated in the 20-position, the reduced forms of factor II and factor III were identified as biosynthetic intermediates in the biosynthesis of vitamin B12.5... 

Nitrite is a weak reducing agent and is oxidized to nitrate by strong chemical oxidants or by nitrifying bacteria. It also oxidizes reduced substances. 

J. T. Sears, R. Muller, and M. A. Reinsel. Inhibition of sulfate-reducing bacteria via nitrite production. Patent WO 9612867, 1996. 

The nitrite test can be used to detect the presence of nitrate-reducing bacteria in the urine (such as E. coli). The leukocyte esterase test is a rapid dipstick test to detect pyuria. 

The nitrate (NOp content in crops is one of the most important indicators of farm production quality. Nitrate content in food is strictly regulated because of its toxicity, especially in young children. The actual toxin is not the nitrate ion itself but rather the nitrite ion (NOp, which is formed when nitrate is reduced by intestinal bacteria, notably Escherichia coli. In adults, nitrate is absorbed high in the digestive tract before reduction can take place. In infants, whose stomachs are less acidic, E. coli can colonize higher up the digestive tract and therefore reduce the NOJ to NCp before it is absorbed. 

A biosensor for nitrite [24] was recently proposed for monitoring nitrite concentration in activated sludge exposed to oxic/anoxic cycles. The biosensor contains bacteria reducing only N02 into N20, which is subsequently monitored by a built-in electrochemical sensor. Up to 90% of the response is obtained in about 1 min, and the detection limit is around 5 mg L1, a concentration sufficient for treatment process monitoring. Unfortunately, the maximum operational lifetime of the N02 biosensor is 6 weeks and some problems may occur with time. 

Recent research has identified some other microbial routes for denitrification that are not heterotrophic. One, called the anammox reaction, involves the oxidation of ammonium to N2 using either nitrite or nitrate as the electron donor. The second has bacteria using Mn " to reduce nitrate to N2. As noted earlier, N2 is generated by the oxidation of ammonium using Mn02 as the electron acceptor. [Denitrification may also be supported by Fe " (aq) oxidation.] These reactions are summarized in Table 12.2. The overall consequence of these reactions is that ammonium does not accumulate in the pore waters where Mn respiration and denitrification are occurring. 

Cytochrome c nitrite reductase (bacteria) Reduces HA and NH2OCH3 to ammonia (NH3) 10, 23... 

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