Question

Which bacterium is responsible for the reduction of nitrates into nitrogen in soil?
A.Nitrosomonas
B.Pseudomonas
C.Rhizobium
D.None of the above

Answer 1

Hint:The process of reduction of nitrates into nitrogen in the soil with the help of facultative anaerobic bacteria is called denitrification. This type of respiration reduces oxidized forms of nitrogen into nitrate, nitrite, nitric oxide, nitrous oxide ultimately resulting in dinitrogen. The microbes require less than 10% of oxygen concentration for processing. The process can take place in aerobic as well as anaerobic conditions.

Complete step by step answer:Option A- Nitrosomonas
Also known as nitrifying bacteria. They play an important role by providing nitrogen to the plants and help in carbon dioxide fixation.
Option B- Pseudomonas
Pseudomonas aeruginosa is also known as denitrifying bacteria that reduce nitrates into nitrogen in the soil. It takes part in the biodegradation of such toxic compounds present in soil and water.
Option C- Rhizobium
It is a nitrogen-fixing bacteria in root nodules of legume plants that convert dinitrogen into ammonia. It increases soil fertility and productivity. Ammonia is absorbed into organic compounds rapidly due to its toxic nature.
Option D- None of the above

Thus, the correct option is option B- Pseudomonas aeruginosa.

Note:Factors affecting this process are soil temperature, pH, soil texture, oxygen, mineral and moisture content along with the concentration of nitrate in the soil. It is used in sewage treatment as well as industrial wastewater treatment. It is an important ecosystem service in coastal environments. The drawback of this process is that it leaks nitrous oxide which is ozone-depleting gas and takes part in the greenhouse effect. Another disadvantage is that the crop yields decrease as nitrogen gets lost in the atmosphere.