A ‘rare biosphere’ microorganism contributes to sulfate reduction in a peatland

Abstract

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 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 stable isotope probing 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.

The biogeography of abundant and rare bacterioplankton in the lakes and reservoirs of China

“…The few abundant taxa account for most of the biomass and carbon cycling, whereas some rare species may be important for the cycling of Biogeography of abundant and rare bacterioplankton L Liu et al certain elements (Pedrós-Alió, 2012). An example from a peatland indicated that rare taxon Desulfosporosinus could contribute most of the sulfate reduction in the peat (Pester et al, 2010). Moreover, abundant and rare bacteria may have different ecological strategies.…”

Insights in the ecology and evolutionary history of the Miscellaneous Crenarchaeotic Group lineage

“…In this concept initially developed for macroorganisms, keystone species are commonly understood as the 'backbone' of the community on which the stability of the entire system depends (Paine, 1969). Recently, prokaryotes involved in major biogeochemical processes such as sulfates reducers (Pester et al, 2010) or primary degraders of refractory substrates (Ze et al, 2012) have been regarded as keystone species. Our results suggest that members of the MCG lineage might have a keystone role in archaeal sediment communities.…”

Microbial minorities modulate methane consumption through niche partitioning

“…Type Ia MOB related to the ones found in our study have been demonstrated to be responsible for methane consumption in many important methane-emitting habitats such as rice paddies (Bodelier et al, 2000), arctic wetlands (Graef et al, 2011), landfills (Chen et al, 2007), lake sediments (Dumont et al, 2011) and floodplains , which has been ascribed to their specific traits enabling them to be very responsive to the periodic availability of methane and other nutrients (Steenbergh et al, 2010;Bodelier et al, 2012). Recent studies assigning species-specific contributions to important biogeochemical cycles using stable isotopes also indicated a disproportionate role of single rare microbial species to globally important processes (Musat et al, 2008;Pester et al, 2010;Peter et al, 2011), strongly suggesting that the traits of the organisms involved will be fundamental to the variability and dynamics in the biogeos p e c ie s n ic h e s function Figure 7 Graphical representation of the three dimensions involved in BEF relationships. The curve of the speciesfunction relationship will depend on the number of niches present, allowing species to be active and contribute to function.…”