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Phycisphaera-like WD2101 'soil group' is one of the as-yet-uncultivated phylogenetic clades within the phylum Planctomycetes. Members of this clade are commonly detected in various terrestrial habitats. This study shows that WD2101 represented one of the major planctomycete groups in 10 boreal peatlands, comprising up to 76% and 36% of all Planctomycetes-affiliated 16S rRNA gene reads in raised bogs and eutrophic fens respectively. These types of peatlands displayed clearly distinct intragroup diversity of WD2101-affiliated planctomycetes. The first isolate of this enigmatic planctomycete group, strain M1803, was obtained from a humic lake surrounded by Sphagnum peat bogs. Strain M1803 displayed 89.2% 16S rRNA gene similarity to Tepidisphaera mucosa and was represented by motile cocci that divided by binary fission and grew under micro-oxic conditions. The complete 7.19 Mb genome of strain M1803 contained an array of genes encoding Planctomycetal type bacterial microcompartment organelle likely involved in L-rhamnose metabolism, suggesting participation of M1803-like planctomycetes in polysaccharide degradation in peatlands. The corresponding cellular microcompartments were revealed in ultrathin cell sections. Strain M1803 was classified as a novel genus and species, Humisphaera borealis gen. nov., sp. nov., affiliated with the formerly recognized WD2101 'soil group'.
SummaryThe first representative of the phylum Planctomycetes, Planctomyces bekefii, was described nearly one century ago. This morphologically conspicuous freshwater bacterium is a rare example of as‐yet‐uncultivated prokaryotes with validly published names and unknown identity. We report the results of molecular identification of this elusive bacterium, which was detected in a eutrophic boreal lake in Northern Russia. By using high‐performance cell sorting, P. bekefii‐like cell rosettes were selectively enriched from lake water. The retrieved 16S rRNA gene sequence was nearly identical to those in dozens of metagenomes assembled from freshwater lakes during cyanobacterial blooms and was phylogenetically placed within a large group of environmental sequences originating from various freshwater habitats worldwide. In contrast, 16S rRNA gene sequence similarity to all currently described members of the order Planctomycetales was only 83%–92%. The metagenome assembled for P. bekefii reached 43% genome coverage and showed the potential for degradation of peptides, pectins, and sulfated polysaccharides. Tracing the seasonal dynamics of P. bekefii by Illumina paired‐end sequencing of 16S rRNA gene fragments and by fluorescence in situ hybridization revealed that these bacteria only transiently surpass the detection limit, with a characteristic population peak of up to 104 cells ml−1 following cyanobacterial blooms.
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.
We investigated communities of oribatid mites in five peat bogs in the north-west of the East European plain. We aimed to determine the extent to which geographic factors (latitude, separation distance), local environment (Sphagnum moss species, ground water level, biogeochemistry) and local habitat complexity (diversity of vascular plants and bryophytes in the surrounding plant community) influence diversity and community composition of Oribatida. There was a significant north-to-south increase in Oribatida abundance. In the variance partitioning, spatial factors explained 33.1 % of variability in abundance across samples; none of the environmental factors were significant. Across all bogs, Oribatida species richness and community composition were similar in Sphagnum rubellum and Sphagnum magellanicum, but significantly different and less diverse in Sphagnum cuspidatum. Sphagnum microhabitat explained 52.2 % of variability in Oribatida species richness, whereas spatial variables explained only 8.7 %. There was no distance decay in community similarity between bogs with increased geographical distance. The environmental variables explained 34.9 % of the variance in community structure, with vascular plants diversity, bryophytes diversity, and ground water level all contributing significantly; spatial variables explained 15.1 % of the total variance. Overall, only 50 % of the Oribatida community variance was explained by the spatial structure and environmental variables. We discuss relative importance of spatial and local environmental factors, and make general inferences about the formation of fauna in Sphagnum bogs.
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