Bacterial communities in Sphagnum-dominated peatlands

This research is carried out in close collaboration with Dr. Svetlana N. Dedysh and her group (Laboratory of Wetland Microbiology, Winogradsky Institute of Microbiology RAS, Moscow, Russia). Northern peatlands play a key role in the global carbon and water budget. A large proportion of them consist of Sphagnum-dominated ombrotrophic bogs, which are characterized by low pH values of 3.5 to 5 and extremely low rates of plant debris decomposition. The bacterial diversity in these ecosystems remains poorly described. Over the last two years, we compared the bacterial community composition in the surface (0–5 cm depth) and subsurface (45–50 cm) peat layers of an acidic (pH 4.0) Sphagnum-dominated wetland, using 454 pyrosequencing of 16S rRNA genes [6]. The denoised sequences (37,229 reads) were affiliated with 27 bacterial phyla and corresponded to 1,269 operational taxonomic units (OTUs) determined at 97% sequence identity. OTU richness was higher in the surface layer (882 OTUs) than in the anoxic subsurface peat (483 OTUs), with only 96 OTUs common to both datasets. Abundant OTUs were affiliated with the Acidobacteria. They were represented by more than one-third of all sequences, in both surface and subsurface peat. Other major OTUs were affiliated with the Alphaproteobacteria, Actinobacteria, Verrucomicrobia, Planctomycetes, Deltaproteo-bacteria, and Gammaproteobacteria

Figure 3. Bacterial community composition in surface (green bars) and subsurface (brown bars) peat. (A) Depth profile of Sphagnum-dominated peat bog. (B) Major taxa detected with a relative sequence abundance ≥ 0.5% are displayed. Column “other bacteria” indicates the relative sequence abundance of all the rare phyla and candidate divisions [each < 0.5%] and taxonomically unclassified sequences. The error bars indicate the standard deviation of relative sequence abundances between four subsamples. The number of 454 reads assigned to a particular taxon was significantly different between surface and subsurface peat based on two-tailed t-test (< 0.05), except for those four taxa indicated by asterisk (taken from Serkebaeva et al. 2012, DOI: 10.1371/journal.pone.0063994).

The taxonomic patterns of the abundant OTUs were uniform across all subsamples taken from the same peat layer. In contrast, the taxonomic patterns of rare OTUs were different from those of the abundant OTUs and varied greatly among subsamples, in both surface and subsurface peat. In addition to the bacterial taxa listed above, rare OTUs were affiliated with the following groups: Armatimonadetes, Bacteroidetes, Chlamydia, Chloroflexi, Cyanobacteria, Elusimicrobia, Fibrobacteres, Firmicutes, Gemmatimonadetes, Spirochaetes, AD3, WS1, WS4, WS5, WYO, OD1, OP3, BRC1, TM6, TM7, WPS-2, and FCPU426. The rare groups represented population sizes between 103 and 105 cells per gram of wet peat. Most members of poorly studied phyla, such as the Acidobacteria, Verrucomicrobia, Planctomycetes and the candidate division TM6, showed a clear preference for growth in either aerobic or anaerobic conditions. For example, OTUs related to the recently described Telmatocola sphagniphila [7] were detected primarily in the oxic surface layer. Apparently, the bacterial communities in surface and subsurface layers of northern peatlands are highly diverse and taxonomically distinct, reflecting the different abiotic conditions that occur along the peat profile [6].

References:

[6] Serkebaeva, Y.M., Kim, Y., Liesack, W., Dedysh S.N. (2013) Pyrosequencing-based assessment of the Bacteria diversity in surface and subsurface peat layers of a northern wetland, with focus on poorly studied phyla and candidate divisions. PLoS ONE 8(5): e63994. doi:10.1371/journal.pone.0063994. 

[7] Kulichevskaya, I.S., Serkebaeva, Y.M., Kim, Y., Rijpstra, W.I.C., Damste, J.S.S., Liesack, W., Dedysh, S.N. (2012) Telmatocola sphagniphila gen. nov., sp. nov., a novel dendriform planctomycete from northern wetlands. Front. Microbiol. 3: e146. doi: 10.3389/ fmicb.2012.00146. 

 

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