Posted 5 years ago by Matt Richardson

The Nitrogen Cycle of Microbes and Men  

Level: Junior Apprentice

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Nitrogen (N) is an essential component of DNARNA, and proteins, the building blocks of life. All organisms require nitrogen to live and grow. Although the majority of the air we breathe is N2, most of the nitrogen in the atmosphere is unavailable for use by organisms. This is because the strong triple bond between the N atoms in N2 molecules makes it relatively inert. In fact, in order for plants and animals to be able to use nitrogen, N2gas must first be converted to more a chemically available form such as ammonium (NH4+), nitrate (NO3), or organic nitrogen (e.g. urea – (NH2)2CO). The inert nature of N2 means that biologically available nitrogen is often in short supply in natural ecosystems, limiting plant growth and biomass accumulation.

Key Concepts

  • The nitrogen cycle is the set of biogeochemical processes by which nitrogen undergoes chemical reactions, changes form, and moves through difference reservoirs on earth, including living organisms.
  • Nitrogen is required for all organisms to live and grow because it is the essential component of DNARNA, and protein. However, most organisms cannot use atmospheric nitrogen, the largest reservoir.
  • The five processes in the nitrogen cycle — fixation, uptake, mineralizationnitrification, and denitrification — are all driven by microorganisms.
  • Humans influence the global nitrogen cycle primarily through the use of nitrogen-based fertilizers.


Copied from:

Harrison, John Arthur. Vision Learning. “The Nitrogen Cycle of Microbes and Men.” Accessed June 10, 2013.

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