Environmental regulation of denitrifying activity in soil producing nitrous oxide and the expression of denitrifier genes in the soil bacteria

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We propose to study the influence of environmental triggers on the temporal production of N2O, the number and expression of denitrifier genes and their role in regulating denitrification and N2O emissions. The soil environmental conditions or triggers that are of primary interest are the addition of electron donor (carbon), the addition of electron acceptor (N oxides), moisture and temperature fluctuation.  Several short-term objectives for this grant application have been identified: 1) Utilizing a tunable diode laser - trace gas analyzer (TDL-TGA), to study the role of carbon, nitrogen, thermal and hydrologic events as triggers of denitrification and N2O emissions. 2) Utilizing state-of-the-art molecular tools, to quantify the rapid temporal response of the number and expression of key denitrification genes in soil to environmental conditions, and their role in regulating denitrification and N2O emissions. 3) To build a culture library of denitrifiers and primers for the denitrification genes in soils under potato production, assessing the representativeness of primers currently being utilized to examine rapid and longer-term temporal responses. 4) To examine the impact of soil characteristics influenced by long-term (decadal) soil processes (organic matter content, soil structure/architecture) as expressed in soil landscapes vs. those influenced by short-term (daily/seasonal) processes (carbon, nitrogen, temperature and moisture additions) on the number of gene copies and gene expression of key denitrifier genes in intact soil cores from a potato cropping system in N.B.