Catabolic nitrate reduction

Temperature Catabolic nitrate reduction rates are influenced by temperature, similar to any biological reactions. The increase in biological activity as soil temperatnre increases resnlts in an exponential increase of DNRA and denitrification rates. From the resnlts reported in several stndies, it can be concluded that the catabolic nitrate redaction rates increased... 

A wide range of techniques are used to determine catabolic nitrate reduction rates. These include mass balance methods using input-outputs, acetylene inhibition techniques, dinitrogen production rates, nitrate consumption rates, nitrate pore water profiles, and stable isotope tracer techniques. The limitations and advantages of these methods are discussed by Seitzinger (1988) and Herbert (1999). 

The initial action of simazine and atrazine is the increase of nucleic acid synthesis. This increases protein synthesis and, thereby, the absorption of nitrate. However, nitrate reduction can occur only if sufficient carbohydrate is present for the formation of NADH. An increase in glucose catabolism increases the quantity of a-ketoglutaric acid. As a result of this assumed mechanism, nitrogen assimilation is increased at the expense of carbohydrates if there is not sufficient carbohydrate present, because the temperature is high and the light poor, or the nitrogen supply is good and, in this case, the. r-triazine effect is absent. 

In wetlands, nitrate is used by microbes and plants as a nitrogen source or as an electron acceptor to support catabolic activities of select heterotrophic bacteria. As early as 1882, Maquenne reported the following observations on nitrate reduction in soils ... 

The xanthine oxidoreductases are large, complex molybdo-flavoproteins with roles in the catabolism of purines, for example, oxidizing hypoxanthine to xanthine and xanthine to uric acid (equation 9). Xanthine oxidase can also catalyze the reduction of nitrate to nitrite (or in the presence superoxide, peroxynitrite) and the reduction of nitrite to nitric oxide. Peroxynitrite, a powerfiil and destructive oxidant, has been implicated in diseases such as arthritis, atherosclerosis, multiple sclerosis, and Alzheimer s and Parkinson s diseases. The microbicidal role of milk and intestinal xanthine oxidase may also involve the generation of peroxynitrite in the gut. The high levels of the enzyme in the mammary glands of pregnant... 

As the demand for electron acceptors increases, facultative microbes can utilize oxidized forms of Mn(IV) and Fe(III) as electron acceptors during the catabolic breakdown of organic matter (Figure 5.31). Manganese and iron cycles in wetlands are discussed in detail in Chapter 10. The carbon flow during Mn and Fe reduction has not been studied as extensively as other electron acceptors (oxygen, nitrate, sulfate, and carbon dioxide). 

---