Metagenomic Analysis of the Microbial Community in the Underground Coal Fire Area (Kemerovo Region, Russia) Revealed Predominance of Thermophilic Members of the Phyla Deinococcus-Thermus, Aquificae, and Firmicutes

Abstract

Abstract Underground burning of coal seams accompanied by release of gases leads to development of local thermal ecosystems. We investigated the microbial community of the ground heated to 72°C in the release area of hot gases resulting from underground combustion of coal mining waste at the Bungurskiy-Severny coal deposit in the Kemerovo region of Russia. Analysis of the composition of the microbial community by 16S rRNA gene profiling revealed predominance of thermophilic bacteria of the phyla Deinococcus-Thermus, Aquificae, and Firmicutes. As a result of metagenomic analysis, 18 genomes of the main members of the microbial community were assembled, including the complete genomes of Hydrogenobacter thermophiles, a member of the candidate genus UBA11096 of the phylum Aquificae (RBS10-58), Thermoflexus hugenholtzii, and Thermus antranikianii. Analysis of the RBS10-58 genome indicates that this bacterium can autotrophically fix carbon in the reductive tricarboxylic acid cycle and obtain energy via oxidation of hydrogen and sulfur compounds with oxygen or nitrate as electron acceptors. Genome analysis of the two dominant Firmicutes species, Hydrogenibacillus schlegelii and an uncultured member of the class Thermaerobacteria, showed that these bacteria could grow aerobically by oxidizing hydrogen and carbon monoxide. Overall, the community was dominated by aerobic bacteria capable of growing autotrophically and obtaining energy via oxidation of the main components of coal gases, hydrogen and carbon monoxide. Thermus antranikianii, which makes up about a half of the microbial community, probably uses organic matter produced by autotrophic members of Firmicutes and Aquificae.