Sulfate-reducing microorganisms in low-sulfate peatlands: overlooked key players in the interwined biogeochemical cycles of peat soils?

Eingeladen durch Marcus A. Horn, Ecological Microbiology.

Methane emission from peatlands contributes substantially to global warming but is significantly reduced by sulfate reduction, which is mainly fuelled by globally increasing aerial sulfur pollution and apparently by an anoxic sulfur cycle in peatlands. However, the biology behind sulfate reduction in peatlands is not well understood. Comparative stable isotope probing in the presence and absence of sulfate revealed that a Desulfosporosinus species, which constitutes only 0.006% of the total microbial community, is a major sulfate reducer in the long-term experimental field site Schlöppnerbrunnen II. The small Desulfosporosinus population has the potential to reduce sulfate in situ at a rate of up to 36.8 nmol (g soil w. wt.)^–1 day^–1, sufficient to account for a substantial part of sulfate reduction in the peat soil.

These results indicate that rare biosphere members can contribute significantly to biogeochemical cycles despite their low abundance. Additional sulfate reducers in the studied peatland might be represented by novel deep-branching lineages of the functional marker genes dsrAB [encoding subunit A and B of the dissimilatory (bi)sulfite reductase], which were shown to be widespread in peatlands of Central Europe. Microarray and qPCR analyses of the Schlöppnerbrunnen II peatland revealed that these novel dsrAB lineages dominated a temporally stable but spatially structured dsrAB community and represented ‘core’ members (up to 1–2% relative abundance) of the autochthonous microbial community. Our results provide first insights into the ecology of sulfate reducing microorganisms in low-sulfate peatlands – a habitat that is considered a major unknown concerning its carbon storage/release-function in the upcoming climate change.

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