Phylogenetic composition of bacterial communities in small boreal lakes and ombrotrophic bogs of the upper Volga basin

摘要

Fluorescent in situ hybridization (FISH) with rRNA-specific oligonucleotide probes was used to assess the numbers and phylogenetic diversity of prokaryotic microorganisms in the water of small boreal lakes and peatland catchments of the swampy upper Volga basin. The abundance of bacterioplankton in lake water was found to vary from 1. 6 to 8. 7 × 10~6 cells ml~(-1), with the highest values detected in neutral eutrophic lakes. The total cell numbers in the peat of ombrotrophic bogs were 3. 9-4. 3 × 10~8 cells g~(-1) of wet peat. The proportion of bacteria identified by the group-specific probes decreased from 79-85% in neutral (pH 6. 6-6. 9) mesotrophic and eutrophic lakes to 65-69% in acidic (pH 4. 4-5. 5) dystrophic lakes and to 51-58% in the peat of acidic (pH 3. 6-3. 9) ombrotrophic bogs. The diversity of bacterial communities was highest in lakes with neutral water. These communities were dominated by members of the phylum Actinobacteria (31-44% of the total bacterial number), while the contribution of Alphaproteobacteria (16-19%), Bacteroidetes (6-16%), Betaproteobacteria (6-7%), Planctomycetes (2-8%), and Gammaproteobacteria (4-5%) was also significant. In acidic dystrophic lakes, Actinobacteria (25-35%) and Betaproteobacteria (25-34%) predominated, while peatland catchments were dominated by the Alphaproteobacteria (20-23%). The presence of acidobacteria and some planctomycetes common for bogs in the water of acidic dystrophic lakes, as well as the high proportion of bacteria (31-49%) that were not identified by the group-specific probes, suggest the impact of microbial processes in peatland catchments on the microbial composition of the receiving waters.