Vertical variations and associated ecological function of bacterial communities from Sphagnum to underlying sediments in Dajiuhu Peatland

Abstract

To investigate vertical changes of bacterial communities from living plants to the associated sediments and bacterial biogeochemical roles in peatland ecosystem, samples of different part of individual Sphagnum palustre and the different layers of the underlying sediments were collected from Dajiuhu Peatland in central China. All samples were subject to 16S rRNA gene clone libraries and quantitive PCR analysis. Even though bacteria vary in abundance at the same order of magnitude in all samples, they show great profile difference in composition from the top part of S. palustre to the low layer of the sediments. Cyanobacteria and alpha-Proteobacteria dominate at the top part whereas Acidobacteria at the middle part of S. palustre. Alpha-Proteobacteria and Acidobacteria are the dominant phyla at the bottom part of S. palustre and in the surface peat sediment. In contrast, bacterial communities in the subsurface sediments are dominated by Acidobacteria. These profile distributions of different bacterial communities are closely related to their ecological functions in the peatland ecosystem. Specifically, most Cyanobacteria were observed at the top green part of S. palustre, a horizon where the active photosynthesis of the moss occurs, which infers their endosymbiosis. In contrast, Acidobacteria, dominant in the subsurface sediments, are able to decompose the specific compounds on the cell wall of Sphagnum moss and thus might play an important role in the formation of the peatland, including the acidic condition. Methane oxidizing process might have been underestimated in Sphagnum peatland due to the identification of Methylocystaceae in all parts of the moss investigated here. The vertical difference in bacterial composition and bacterial ecological functions presented here sheds light on the understanding of biogeochemical processes, in particular the CH4 flux, in peat ecosystems.