Spatial and temporal niche separation of Methanomassiliicoccales phylotypes in temperate fens

The hydrogen-dependent and methylotrophic order Methanomassiliicoccales is widespread in temperate peatlands, consisting of several phylotypes with a dominant occurrence of the wetland cluster phylotype amplicon sequence variants in the studied peat types. The hydrogen-dependent and methylotrophic order Methanomassiliicoccales consists of the families Methanomethylophilaceae and Methanomassiliicoccaceae. While Methanomethylophilaceae are comparatively well studied, there is a lack of knowledge on Methanomassiliicoccaceae. In this 16S rRNA gene amplicon sequencing-based study we investigated the temporal and spatial dynamics of the Methanomassiliicoccales in drained and rewetted sites of three common temperate fen peatlands. A 2.5-year monitoring of the fen microbiome composition at three peat depths revealed a dynamic methanogen and Methanomassiliicoccales composition across space and time. Four Methanomassiliicoccales phylotypes were found and they were differentially distributed between the fen types. The wetland cluster phylotype was omnipresent and dominant in abundance in all sites along all depths. The Methanomassiliicoccus phylotype was highly abundant in topsoil while the AB364942 phylotype was exclusively found in deeper regions of the rewetted percolation fen. The phylotype affiliated with Methanomassiliicoccales strain U3.2.1 was only detected in the rewetted percolation fen. We discuss the distribution of the four phylotypes with implications for their ecophysiology, where oxygen tolerance and substrate spectrum might play major roles. In conclusion, the Methanomassiliicoccales are widespread and account for a significant proportion of methanogens, which might suggest their importance for methane emissions from peatlands.

Automated summary

This study investigated the temporal and spatial dynamics of the hydrogen-dependent and methylotrophic order Methanomassiliicoccales in temperate peatlands using 16S rRNA gene amplicon sequencing. The results showed that there were four phylotypes of Methanomassiliicoccales, and their distribution patterns suggested that oxygen tolerance and substrate spectrum may play important roles in their ecophysiology. Overall, this study highlights the significance of Methanomassiliicoccales for methane emissions from peatlands.