Large areas in Northern Russia are covered by extensive mires, which represent a complex mosaic of ombrotrophic raised bogs, minerotrophic and eutrophic fens, all in a close proximity to each other. In this paper, we compared microbial diversity patterns in the surface peat layers of the neighbouring raised bogs and eutrophic fens that are located within two geographically remote mire sites in Vologda region using 16S rRNA gene sequencing. Regardless of location, the microbial communities in raised bogs were highly similar to each other but were clearly distinct from those in eutrophic fens. Bogs were dominated by the Acidobacteria (30%-40% of total 16S rRNA gene reads), which belong to the orders Acidobacteriales and Bryobacterales. Other bog-specific bacteria included the Phycisphaera-like group WD2101 and the families Isosphaeraceae and Gemmataceae of the Planctomycetes, orders Opitutales and Pedosphaerales of the Verrucomicrobia and a particular group of alphaproteobacteria within the Rhizobiales. In contrast, fens hosted Anaerolineae-affiliated Chloroflexi, Vicinamibacteria- and Blastocatellia-affiliated Acidobacteria, Rokubacteria, uncultivated group OM190 of the Planctomycetes and several groups of betaproteobacteria. The Patescibacteria were detected in both types of wetlands but their relative abundance was higher in fens. A number of key parameters that define the distribution of particular bacterial groups in mires were identified.
Keywords: Acidobacteria; Chloroflexi; Planctomycetes; Verrucomicrobia; eutrophic fens; high-throughput 16S rRNA gene sequencing; microbial diversity; northern mires; raised bogs.