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Modern Changes in the Nitrogen Cycle: Insights from the Fall 2010 Discussion Group

This discussion leads us through the complexities of the nitrogen cycle, highlighting modern changes and their implications. Nitrogen, as the fifth most abundant element, plays a crucial role in the synthesis of nucleic acids and proteins. The biogeochemistry involves microbial mediation and long-term cycling, with N2 gas largely unavailable to organisms - its fixed forms like nitrate and ammonium often limiting primary productivity. We will explore nitrogen fixation, denitrification, and the role of prokaryotes in reducing N2 to usable forms within various ecosystems.

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Modern Changes in the Nitrogen Cycle: Insights from the Fall 2010 Discussion Group

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  1. Biogeochemical Cycling – Fall 2010 Theme Modern Changes in the Nitrogen Cycle Friday Discussion Group Discussion Leader: Priya Ganguli 12 November, 2010

  2. N 5th most abundant element in solar system • Essential for synthesis of nucleic acids and proteins • For every 100 atoms of C in cells, need 2 to 20 atoms of N • Biogeochemistry of N primarily oxidation-reduction and microbially mediated • Secondarily influenced by long-term cycling through geosphere • N2 largely unavailable to organisms • NO3- and HN4+ (fixed forms) often limit primary productivity in both marine & terrestrial ecosystems

  3. Nitrogen Fixation prokaryotes in bacterial and archaeal domains reduce N2 gas to ammonium ion (NH4+)

  4. nitrate (NO3-) reduction coupled to anaerobic oxidation of Corg • N2 gas • (denitrification) • or • NH4+ • (dissimilatory nitrate reduction to ammonium) (DNRA) electron acceptors from Baker MA, Dahm CN, Valett HM, 2000

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