Which organisms do participate in the nitrogen cycle?

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pacorz eNotes educator| Certified Educator

Just about all the major classes of living things participate in the nitrogen cycle. Nitrogen is a major component of the Earth's atmosphere, where is exists as dinitrogen, or N2, gas. Nitrogen gas can be converted to nitrates such as nitrogen monoxide (NO) or nitrogen dioxide (NO2) by Rhizobium species of bacteria, which live in nodules on the roots of plants of the Legume family. Lightning can also cause the same conversion from N2 to nitrate to occur.

Plants take up nitrates from the soil and incorporate them into their structure.  Animals consume the plants and absorb the nitrates along with other nutrients. Some of the nitrates are incorporated into the animal's body, and some are eliminated, mostly in the form of ammonia (NH3) in the urine. The stored nitrogen eventually returns to the earth when the animal dies. The nitrogen in urine and in carcasses is processed by bacteria of the Nitrosomonas and Nitrobacter genera, which turn the ammonia compounds back into nitrate compounds. These nitrates may either be taken up by plants and used again, or be further altered by other denitrifying bacteria, which can turn the nitrates into N2 gas and release it back to the atmosphere, completing the cycle.

sid-sarfraz | Student

Which organisms do participate in the nitrogen cycle?


Nitrogen cycle is basically a process through which nitrogen gas is converted into compounds that can be absorbed by plants and animals. As nitrogen is important for all human beings to live, grow and reproduce. It is used by cells in the living organisms.

Microorganisms like bacteria are important in the nitrogen cycle. Some of the bacteria are mentioned below:-

  • Cynobacteria 
  • Methylomonas
  • Rhizobium/Frankia
  • Chromatium
  • Clostridium

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