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.
Highlights
Studies of thermophilic microorganisms have expanded our knowledge of microbial diversity, evolution, and mechanisms of adaptation to extreme environmental conditions (Urbieta et al, 2015; Counts et al, 2017)
The highenergy compounds contained in coal gases, such as hydrogen and CO, can be used by microorganisms as substrates, while oxygen is used as an electron acceptor, which enables formation of specific communities of thermophilic microorganisms
Start new paragraph here we studied the soil microbial community associated with the zone of underground coal combustion and the release of hot coal gases at the dumps of the Bungurskiy-Severny coal deposit in the Novokuznetsk district of the Kemerovo region (Russia)
Summary
Studies of thermophilic microorganisms have expanded our knowledge of microbial diversity, evolution, and mechanisms of adaptation to extreme environmental conditions (Urbieta et al, 2015; Counts et al, 2017). Underground burning of coal seams is a widespread natural phenomenon and has been observed in Australia, Germany, the United States, China, Russia, India, and other countries (Stracher and Taylor, 2004). Such underground fires can last for centuries; for example, the coal seam in Dudweiler (Saarland, Germany) has been burning since 1668. In addition to CO2, coal gases contain mainly hydrogen, CO, and gaseous hydrocarbons (Stracher and Taylor, 2004; Engle et al, 2012). Local extreme ecosystems developing in areas where hot coal gases come to the surface are characterized by high temperatures (>50°C) and the presence of toxic substances (Tammy et al, 2005). Relatively little is known about the composition of microbial communities of such ecosystems and the genetic potential of their microorganisms
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