Wetlands are important carbon sinks but at the same time a major global source of the greenhouse gas methane. How wetland microorganisms will respond to global warming and increasing aerial sulfur pollution in the upcoming decades to centuries is one of the largest unknowns. Although regarded primarily as methanogenic environments, a hidden sulfur cycle exerts important ecosystem functions in wetlands. Dissimilatory sulfate reduction is thermodynamically favorable relative to methanogenic processes and often occurs in wetlands at rates comparable to marine surface sediments, despite significantly lower sulfate concentrations. The underlying interspecies resource competition thus effectively controls gross production of methane in wetlands.
Our previous work revealed that rare Desulfosporosinus species have the potential to substantially contribute to sulfate reduction in an acidic peatland. To further our understanding of sulfate reducer ecophysiology in peatlands, anoxic microcosms were supplemented with typical degradation intermediates of organic matter at in situ concentrations and incubated under methanogenic or sulfate-reducing conditions. Highly parallel 16S rRNA gene and cDNA amplicon sequencing, quantitative real-time PCR, and metatranscriptomics are used to analyze microbial community dynamics, interactions, and activities. In addition, we are reconstructing and analyzing the genomes of wetland microorganisms, such as the rare Desulfosporosinus, by metagenomics of native soil and active microbes as enriched by DNA stable isotope probing and single cell genomics. This holistic approach will yield new insights into the ecophysiology, interspecies interactions, and genomic repertoire of keystone members of the wetland biosphere.
This research was funded by the Austrian Science Fund (FWF) P18836-B17 and P23117-B17 and by sequencing grants from the Joint Genome Institute (JGI) Proposal IDs 257 and 605