Which bacteria types provide the atmosphere with N2?

Denitrifying bacteria are responsible for converting nitrogenous compounds in the soil back into nitrogen gas (N2), which is then released into the atmosphere. This process, known as denitrification, is a crucial part of the nitrogen cycle, allowing nitrogen to return to the atmosphere after being used in various biological processes.

During denitrification, these bacteria utilize nitrates and nitrites as electron acceptors, reducing them ultimately to nitrogen gas. This process helps maintain the balance of nitrogen in the ecosystem, preventing the accumulation of nitrogen compounds in the soil and water, which can lead to pollution and other ecological issues.

While nitrogen-fixing bacteria do play an essential role in the nitrogen cycle by converting atmospheric nitrogen (N2) into ammonia, they are not the organisms responsible for returning N2 to the atmosphere. Pathogenic bacteria are typically associated with diseases and do not play a role in the nitrogen cycle. Photosynthetic bacteria generally capture energy and do not contribute significantly to nitrogen gas production.