Peatlands are a type of wetlands where accumulation of organic matter exceeds its decomposition. They are primarily distributed in northern latitudes and store more carbon than any other terrestrial ecosystem (~455 Pg). Methane (CH4) production is one of the most important microbially-driven processes relevant to the global influence of peatlands in carbon cycling and atmospheric change. Multiple factors have been found to affect CH4 production in peatlands. However, little is known about the Archaea performing this process. Geochemical, molecular, culturing and genomics techniques have allowed us to pursue questions about the diversity, abundance, distribution, and adaptations of methanoarchaea inhabiting peatlands.
Novel methanoarchaeal groups dominated 16S rRNA gene surveys in bogs and fens from upstate NY. NY bogs were almost completely dominated by a novel group in the order Methanomicrobiales, named E2, while a minerotrophic fen was codominated by a sister group, named E1, plus members of the Methanosaetacea family. Further evidence from vertical profiles suggested the differential abundance of E1 versus E2 correlated with fen to bog transitions. These ecological patterns were further evaluated in a broader set of bogs and fens from North America and Europe. Two patterns of community composition were observed amongst sites: a bog to fen ecological pattern for sites in temperate latitudes, and a temperate to boreal/subartic latitudinal pattern. Our results suggest that methanoarchaeal composition can be influenced by local (fen versus bog) and regional (latitude) regimes. Recent culturing efforts have succeeded in isolating a representative of E2 and E1: Methanoregula boonei and Methanosphaerula palustris, respectively. The evaluation of the physiology and genomic composition of our novel methanogens are providing initial clues on their adaptations to the different gradients found amongst peatlands.
These observations provide an initial understanding of methanoarchaeal communities, and propose that ecological and latitudinal patterns should be considered for better predicting the effects of global climate change on peatland methanogenesis.