Answer:
Both Nitrosomonas and Nitrobacter. (Ans. D)
Step-by-step explanation:
Nitrifying Bacterium: Nitrifying Bacteria are small group of aerobic bacteria which belongs to family Nitrobacteraceae. They use inorganic chemical as an energy source.
They are the important microorganisms in nitrogen cycle because they are converting soil ammonia to nitrates compounds which are used by plants.
The nitrification process requires two distinct bacteria to complete the process:
Bacteria which converts Ammonia to Nitrites is called Nitrosomonas. Bacteria that converts Nitrites to Nitrates is called Nitrobacter.
Both bacteria Nitrosomonas and Nitrobacter are chemoautotrophic organism present in soil and water.