Question

Which bacteria convert ammonia to nitrite?

• A. Nitrobacter
• B. Pseudomonas
• C. Nitrosomonas
• D. Thiobacillus

Answer 1

The correct option is C Nitrosomonas

Ammonia is first oxidised to nitrite by the bacteria Nitrosomonas and/or Nitrococcus. The nitrite is further oxidised to nitrate with the help of the bacterium Nitrobacter. These steps are called nitrification. These nitrifying bacteria are chemoautotrophs.
Denitrification is the reduction of nitrates back into nitrogen gas ($N_2$), completing the nitrogen cycle. This process is performed by bacterial species such as Pseudomonas.