Denitrifying bacteria
Denitrifying bacteria are a diverse group of bacteria that encompass many different phyla. This group of bacteria, together with denitrifying fungi and archaea, is capable of performing denitrification as part of the nitrogen cycle. Denitrification is performed by a variety of denitrifying bacteria that are widely distributed in soils and sediments and that use oxidized nitrogen compounds such as nitrate and nitrite in the absence of oxygen as a terminal electron acceptor. They metabolize nitrogenous compounds using various enzymes, including nitrate reductase (NAR), nitrite reductase (NIR), nitric oxide reductase (NOR) and nitrous oxide reductase (NOS), turning nitrogen oxides back to nitrogen gas (N2) or nitrous oxide (N2O). The reducing power can be supplied by organic carbon compounds (termed "heterotrophic denitrification") or inorganic substances such as hydrogen, reduced iron, or sulfur species (termed "autotrophic denitrification"). Some microbes can use either organic or inorganic sources of reducing power (termed "mixotrophs").