Glucose effects on denitrifier abundance, denitrification gene mrna levels, and denitrification activity in an anoxic soil microcosm

摘要

Organic carbon availability influences nitrous oxide (N_2O) emissions but its effect on denitrifier communities is not understood. Changes in denitrifier abundance, denitrification gene mRNA levels and denitrification activity were followed in anoxicsoil microcosms in the presence and absence of glucose with non-limiting nitrate concentration for 48 h. nosZ and nirS_p (Pseudomonas mandelii and closely-related spp.) genes (qPCR) and mRNA levels (qRT-PCR) were quantified. Abundance of nosZ and nirS_pwere unaffected by glucose addition and were stable over the duration of the incubation with average values of 4.3 X10~8 and 8.1 X10~8 gene number/g dry soil, respectively. nirS_p mRNA levels were increased by glucose addition. Glucose addition resultedin induction of nirS_p mRNA levels after 4 h, with a 2.5 fold increase in transcripts compared with 0 h, to 2.4 X10~4 transcripts /g dry soil. In contrast, nosZ mRNA levels were not affected by glucose addition and averaged 2.3 X10~6 transcripts /g dry soil. Glucose addition increased cumulative N_2O emissions, with final values of 4.9 and 0.9 mg N_2O-N /kg dry soil for the glucose amended and non-amended soils, respectively, at 48 hr. The increase in N_2O emissions resulting from glucose addition in this study were not clearly accompanied by significant changes in abundance or denitrification gene mRNA levels for the targeted bacterial communities.