Biological Denitrification

Denitrification is the major biological process through which fixed nitrogen (N) is returned from the soil to the atmosphere. The general requirements for denitrification are the presence of bacteria possessing the metabolic capacity; suitable electron donors such as organic carbon compounds, reduced sulphur compounds, or molecular hydrogen; anaerobic conditions or restricted oxygen availability; and N oxides. The capacity to denitrify has been reported to be present in about 23 genera of bacteria. This chapter presents a list of denitrifying genera including 13 genera for which there is confirmed or multiple documentation. Most denitrifying bacteria are chemoheterotrophs. Denitrification supports bacterial life through respiration. It is well established that denitrification in soil is strongly dependent on the availability of organic compounds as electron donors and as sources of cellular material. Nitrate reduction during denitrification in soil is an enzyme catalyzed reaction.