Nitrogen fixation

Biological nitrogen fixation is the conversion of atmospheric dinitrogen gas (N2) into bioavailable nitrogen.  I study the ecology of nitrogen fixation in oceanic gyre ecosystems including its spatial-temporal distributions, its contribution to new production, and the attribution of rates to microorganisms.

The diel periodicity shown by the nitrogenase enzyme within cyanobacteria stimulates many questions about how photosynthetic nitrogen-fixing microorganisms juggle their various metabolic processes and deal with the oxygen sensitivity of the nitrogenase enzyme

I also work on the methods used to measure nitrogen fixation.  There are several gaseous-based measurements of N2 fixation including 15N-N2 uptake, acetylene reduction, and hydrogen production.  Hydrogen is of particular interest because it is an inherent component of nitrogen fixation and provides an opportunity to conduct high-resolution real-time measurements.  Some of my early work on nitrogen fixation measured natural emissions of hydrogen by cyanobacteria and dissolved hydrogen concentrations in the ocean.  Since then, I have progressed to manipulating samples by replacing dinitrogen with argon, and analyzing the amplified hydrogen production.  This technique is referred to as Argon Induced Hydrogen Production (AIHP) method

Schematic of hydrogen cycling associated with biological nitrogen fixation (Wilson et al., 2010)