Explanation

Nitrifying bacteria (one of the chemosynthetic bacteria) oxidize ammonia to nitrates and obtain energy for the preparation of food. This oxidation occurs in two steps. In the first step, ammonia is oxidized to nitrite by nitrite bacteria (e.g., Nitrosomonas and Nitrosococuus). In the second step, nitrate is oxidised to nitrate by nitrate bacteria (e.g., Nitrocystis and Nitrobacter).