Spatial and temporal niche separation of Methanomassiliicoccales phylotypes in temperate fens

Abstract

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 in 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 Methanomassiliicoccales 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 discussed the distribution of the four phylotypes with implications to their ecophysiology, where oxygen tolerance and substrate spectrum might play major roles. In conclusion, the Methanomassiliicoccales are widespread and do account for a significant proportion of methanogens, which might suggest their importance for methane emissions from peatlands.

Unraveling microbial processes involved in carbon and nitrogen cycling and greenhouse gas emissions in rewetted peatlands by molecular biology

“…While the focus on CH 4 is dominant and processes related to this GHG are well characterized on a genetic and molecular level compared to other processes, uncertainties remain on CH 4 emissions from rewetted peatlands. Findings altogether illustrate the variability in responses of CH 4 -cycling communities and functions post-rewetting, which appear to be governed by a variety of factors and are peatland specific (Weil et al 2023). Relationships between peat depth, decomposition state in relation to availability of substrates for CH 4 related microbial processes still need to be further investigated.…”

“…Higher proportions of SO 4 2− reducers were detected after long-term rewetting compared to drained states (He et al 2015 ; Weil et al 2020 ) due to restored waterlogged and anaerobic conditions. Genes involved in SO 4 2− reduction were stratified across the peat profile based on gene abundance (i.e., lower relative abundance in top layer due to presence of oxygen; Emsens et al 2020 ).…”

“…Findings from biodiversity studies employing 16S rRNA amplicon sequencing can serve as indicators to assess the recovery of pristine-like conditions concerning dominant anaerobic microbial communities post-rewetting. A study in rewetted fens showed an increased relative abundance of anaerobic microbial groups compared to pristine peatlands (Weil et al 2020 ). However, in another peatland, the anaerobic microbial community did not fully recover, likely related to a not fully restored vegetation cover and low accumulation of new peat 7–16 years after rewetting (Urbanová and Bárta 2020 ).…”

“…In addition, the presence of iron oxides led to a rise in CH 4 production in incubations of eutrophic peats upon inundation, likely due to the increased relative abundances of methanogens (de Jong et al 2020 ). In coastal rewetted fens, CH 4 production decreased after inflow of brackish water containing sulfate, which stimulates high abundance of sulfate reducers and suppressing methanogens abundance and activity (due to competition for the same substrates such as hydrogen and acetate) but not their abundance (Weil et al 2020 ; Gutekunst et al 2022 ). pH has also been identified as an important control of methanogenesis in peatlands, as it impacts the chemical status of substrates for methanogenesis (acetate vs. acetic acid).…”

Editorial: Theme issue on the ecology of soil microorganisms

“…Their microbiology is, unfortunately, only partly understood. Weil et al ( 2023 ) show that bacterial communities are vertically stratified even considering members of a single archaeal order. While there are concerns that GHG fluxes may increase from peatlands, this may not necessarily be the case since their production can be limited by the availability of terminal electron acceptors (Song et al 2023 ).…”