Effect of Simple and Complex Carbon Sources on Denitrifier Abundance, Gene Expression, and Nitrous Oxide Emissions in an Agricultural Soil

Soil denitrification is a source of the greenhouse gas nitrous oxide (N2O). Carbon availability influences N2O emissions, but its effect on bacterial denitrifier communities is not well understood. The objective of this work was to determine the effect of simple and complex carbon on denitrifier abundance, gene expression and N2O emissions in an agricultural soil using molecular and biochemical measurements. The addition of glucose or crop residues (barley, red clover or soybean) increased nosZ gene bearing denitrifier abundance while Pseudomonas mandelii and related species (nirSP) only responded to glucose addition. The expression of nosZ and nirSP denitrifier communities and N2 O emission increased in response to carbon addition. There was a positive correlation between N2O emission and gene expression of nosZ and nirSP denitrifiers after 48 h suggesting that denitrifier activity was more important than denitrifier abundance in regulating N2O emissions under the conditions used.