Usingpure cultures to define the site preference of nitrous oxideproduced by microbial nitrification anddenitrification

Sutka, R.L., J. Breznak, N.E. Ostrom, P.H. Ostrom, A.J. Pitt, and H. Gandhi

Presented at the All Scientist Meeting (2004-10-08 )

Nitrous oxide (N₂O) is largely produced by microbial activities in soil and water.  An important step to mitigating future emissions is defining the relative importance of nitrification and denitrification to the production of N₂O in the environment.  Here we describe how isotopomers (the intramolecular distribution of nitrogen isotopes) can be used to differentiate between N₂O produced via nitrification and denitrification.  The results from our pure cultures demonstrate that the site preference of N₂O produced during nitrification is approximately 33 ‰ and denitrification is 0 ‰.  Defining the site preference of nitrous oxide (N₂O) produced in pure culture studies is crucial to interpreting field data.  In the future, we will apply the information from pure cultures to estimating the relative importance of denitrification vs. nitrification in soils at LTER sites including KBS, Luquillo, Sevilleta and Colorado Shortgrass Steppe.