In the nitrogen cycle, which compound is produced when ammonia is oxidized by nitrifying bacteria?

In the nitrogen cycle, which compound is produced when ammonia is oxidized by nitrifying bacteria?

• A. Ammonia
• B. Nitrite
• C. Nitrate
• D. Nitrous oxide

Answer: (B)

Nitrification includes two oxidation steps under aerobic conditions. The first step is carried out by ammonia-oxidizing bacteria, which convert ammonia (NH3/NH4+) into nitrite (NO2−). This change in nitrogen’s oxidation state—from -3 in ammonia to +3 in nitrite—reflects the oxidation process. The next step then converts nitrite to nitrate (NO3−) by nitrite-oxidizing bacteria. So when ammonia is first oxidized, the immediate product is nitrite. Ammonia is the starting substrate, nitrate is formed later, and nitrous oxide is not the standard product of this primary oxidation.

Nitrification includes two oxidation steps under aerobic conditions. The first step is carried out by ammonia-oxidizing bacteria, which convert ammonia (NH3/NH4+) into nitrite (NO2−). This change in nitrogen’s oxidation state—from -3 in ammonia to +3 in nitrite—reflects the oxidation process. The next step then converts nitrite to nitrate (NO3−) by nitrite-oxidizing bacteria. So when ammonia is first oxidized, the immediate product is nitrite. Ammonia is the starting substrate, nitrate is formed later, and nitrous oxide is not the standard product of this primary oxidation.