Permafrost peatlands in the Arctic store large amounts of organic carbon originating from mosses and vascular plants. A diverse community of microorganisms with members from all three domains of life (Bacteria, Archaea and Eukarya) make up a microbial foodweb that degrade the organic matter to produce the greenhouse gases CH4 and CO2.
We have studied the microbial network in Arctic brown-moss peat using a combination of 16S rRNA gene amplicon sequencing, genome-centric metagenomics, (meta)transcriptomics, targeted metabolomics and pure culture studies to detail the members of the foodweb, their function and their response to temperature change.
In the anoxic layer, the majority of Bacteria belong to the phyla Actinobacteria, Bacteriodetes, Firmicutes and Proteobacteria, participating in hydrolysis and fermentation of polysaccharides. Species within archaeal orders Methanobacteriales, Methanomicrobiales and Methanosarcinales produce methane from acetate, formate, H2/CO2 and methylamines. There are comparably few eukaryotes, the majority of which belong to the phylum Cercozoa. Methane oxidizing bacteria belonging to the genus Methylobacter act as the bacterial filter for CH4 in the peat. Analysis of assembled genomes revealed that within the mentioned taxa, there are multiple species with a potential to utilize the same substrates, suggesting that resource competition occurs at each step of the decomposition chain.
After one month of incubation at temperatures ranging from 1–30 °C, the community composition remained intact. Changes in gene expression patterns show that the microbiota adapted quickly to the new conditions, altering the pathways of organic carbon decomposition. Consequently, the CH4 production rate increased substantially with temperature. However, our experiments indicate that the biological CH4 filter is able to adapt quickly to increases in both temperature and substrate availability due to a fast and comprehensive regulatory response, potentially mitigating CH4 releases to the atmosphere.