A 'rare biosphere' microorganism contributes to sulfate reduction in a peatland

ISME J. 2010 Dec;4(12):1591-602. doi: 10.1038/ismej.2010.75. Epub 2010 Jun 10.


Methane emission from peatlands contributes substantially to global warming but is significantly reduced by sulfate reduction, which is fuelled by globally increasing aerial sulfur pollution. However, the biology behind sulfate reduction in terrestrial ecosystems is not well understood and the key players for this process as well as their abundance remained unidentified. Comparative 16S rRNA gene stable isotope probing (SIP) in the presence and absence of sulfate indicated that a Desulfosporosinus species, which constitutes only 0.006% of the total microbial community 16S rRNA genes, is an important sulfate reducer in a long-term experimental peatland field site. Parallel SIP using dsrAB (encoding subunit A and B of the dissimilatory (bi)sulfite reductase) identified no additional sulfate reducers under the conditions tested. For the identified Desulfosporosinus species a high cell-specific sulfate reduction rate of up to 341 fmol SO₄²⁻ cell⁻¹ day⁻¹ was estimated. Thus, the small Desulfosporosinus population has the potential to reduce sulfate in situ at a rate of 4.0-36.8 nmol (g soil w. wt.)⁻¹ day⁻¹, sufficient to account for a considerable part of sulfate reduction in the peat soil. Modeling of sulfate diffusion to such highly active cells identified no limitation in sulfate supply even at bulk concentrations as low as 10 μM. Collectively, these data show that the identified Desulfosporosinus species, despite being a member of the 'rare biosphere', contributes to an important biogeochemical process that diverts the carbon flow in peatlands from methane to CO₂ and, thus, alters their contribution to global warming.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Ecosystem
  • Genes, Bacterial
  • Methane / metabolism
  • Oxidation-Reduction
  • Oxidoreductases Acting on Sulfur Group Donors / genetics
  • Peptococcaceae / classification
  • Peptococcaceae / enzymology
  • Peptococcaceae / genetics*
  • Phylogeny
  • RNA, Ribosomal, 16S / genetics
  • Soil / chemistry*
  • Soil Microbiology*
  • Sulfates / metabolism*
  • Sulfur / metabolism
  • Sulfur-Reducing Bacteria / classification
  • Sulfur-Reducing Bacteria / enzymology
  • Sulfur-Reducing Bacteria / genetics*


  • Bacterial Proteins
  • RNA, Ribosomal, 16S
  • Soil
  • Sulfates
  • Sulfur
  • Oxidoreductases Acting on Sulfur Group Donors
  • Methane