Which transformation do denitrifying bacteria perform in the nitrogen cycle?

Which transformation do denitrifying bacteria perform in the nitrogen cycle?

• A. Convert nitrate to molecular nitrogen
• B. Convert ammonia to nitrate
• C. Fix nitrogen gas
• D. Oxidize nitrite to nitrate

Answer: (A)

Denitrifying bacteria use nitrate as an alternative electron acceptor when oxygen is scarce, carrying out denitrification. In this process, nitrate (NO3−) is reduced to molecular nitrogen (N2), returning nitrogen to the atmosphere and reducing fixed nitrogen in the environment. That’s why converting nitrate to nitrogen gas is the transformation performed by denitrifying bacteria. By contrast, converting ammonia to nitrate is nitrification, fixing nitrogen gas is nitrogen fixation, and oxidizing nitrite to nitrate is a step of nitrification, not denitrification.

Denitrifying bacteria use nitrate as an alternative electron acceptor when oxygen is scarce, carrying out denitrification. In this process, nitrate (NO3−) is reduced to molecular nitrogen (N2), returning nitrogen to the atmosphere and reducing fixed nitrogen in the environment. That’s why converting nitrate to nitrogen gas is the transformation performed by denitrifying bacteria. By contrast, converting ammonia to nitrate is nitrification, fixing nitrogen gas is nitrogen fixation, and oxidizing nitrite to nitrate is a step of nitrification, not denitrification.