Shifts in a bacterial community composition of a mesotrophic peatland after wildfire

Abstract

The structural changes in the bacterial community composition of the Galitskii Mokh mesotrophic peatland (Tver oblast) after the 2010 wildfire were analyzed. Burned sites demonstrated an increase in peat water pH and mineralization, with elevated nitrate and sulfate concentrations, which resulted in doubling of the numbers of culturable sulfate reducers. Although the rate of methane oxidation by peat samples from burned sites decreased, methane emission did not increase. Enumeration of bacterial phylogenetic groups by fluorescent in situ hybridization revealed doubling of the numbers of Alphaproteobacteria and Bacteroidetes in burned areas compared to an undamaged site, while a reverse pattern was observed for Deltaproteobacteria and Planctomycetes. Comparative analysis of the 16S rRNA clone libraries revealed shifts in the bacterial community composition in the peat from burned sites. Slowly growing bacteria of the phyla Verrucomicrobia and Planctomycetes were replaced by fast-growing colonizers from the Proteobacteria. The originally diverse Actinobacterial community was replaced by the one dominated by the phylotypes related to thermophilic Aciditerrimonas ferrireducens. In the Acidobacteria, a typical group of peat-inhabiting bacteria, the subgroups 3, 6, and 17 were replaced by subgroups 7 and 10. These changes in the structure of peatland microbial communities could result in disturbances of some biospheric functions of these ecosystems.