Unraveling community structure, ecophysiology, and regulation of new acid-tolerant denitrifiers driving high N2O emissions from cryoturbated peat soil in acidic tundra

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Cryoturbated peat circles in arctic tundra are ‘hot spots’ of N2O emission, while adjacent unturbated peat sites are not. Such permafrost-affected systems are projected to react to global warming and harbor new acid-tolerant denitrifiers. Although denitrification is a major source of N2O in peatlands, and denitrifiers contribute to the control of N2O emissions, the ecophysiology and spatial distribution of active denitrifiers in cryoturbated and unturbated peat is essentially unknown. Thus, the vertical and horizontal distribution of active denitrifiers associated with N2O emissions, and the effect of experimental warming on such organisms will be addressed by structural gene and transcript directed barcoded amplicon pyrosequencing and qPCR, most probable numbers, total cell counts, microcosms, and N2O-flux measurements in the field. Dissimilatory nitrate reducers (DNRA) might release N2O and will likewise be assessed. New active key structural genes of denitrifiers and the relative importance of Bacteria, Archaea, and Fungi will be determined by the ‘double RNA approach’ and ‘subtractive transcriptomics’. ‘Differentiating pyrosequencing based RNA and DNA stable isotope probing’ will be applied to elucidate 16S rRNA genes concomitant to structural genes of active organic acid assimilating denitrifiers and DNRA. The regulation of new denitrifiers by temperature, O2, and pH will be evaluated in microcosms by structural gene and transcript directed qPCR together with process analyses. New denitrifiers will be isolated and characterized by a directed cultivation strategy.