nitrogen metabolism energy metabolism nitrate reduction (denitrification) Denitrification is the process of reducing nitrate and nitrite, highly oxidised forms of nitrogen available for consumption by many groups of organisms, into gaseous nitrogen, which is far less accessible to life forms but makes up the bulk of atmosphere. Denitrification can be thought of as the opposite of nitrogen fixation. In general, denitrification occurs when oxygen is depleted, and bacteria turn to nitrate in order to respire organic matter. Denitrification proceeds through some combination of the following steps: nitrate -> nitrite -> nitric oxide -> nitrous oxide -> dinitrogen gas. KEGG:map00910 PMID:7508388 pathway GO:0019333 UPa:UPA00652 nitrate respiration KEGG:map01120 MetaCyc:DENITRIFICATION-PWY nitrate reduction