Which organisms are responsible for releasing nitrogen gas from compounds like nitrates or nitrites in the soil back into the atmosphere?

The process of releasing nitrogen gas (N₂) from compounds like nitrates (NO_3^-) or nitrites (NO₂^-) in the soil is called denitrification, and it is carried out by certain types of bacteria. These bacteria are called denitrifiers, and they use the nitrogen in these compounds as an electron acceptor in their metabolic processes. During denitrification, nitrate or nitrite is first converted to nitric oxide (NO), which can then be further converted to nitrogen gas (N₂) and nitrous oxide (N₂O). The nitrogen gas is then released back into the atmosphere, completing the nitrogen cycle. Denitrification is an important process in the nitrogen cycle because it helps to prevent the buildup of excess nitrogen in the soil, which can lead to environmental problems like eutrophication.