Application of Microbial Mats for the Isolation of Spore-Forming Prokaryotes from Deep Biosphere

Deep biosphere is an prolific source of novel prokaryotes. A phylogenetically distant lineage of Firmicutes was reported in 2019 as a new genus Thermoanaerosсeptrum. Ecology of this group remains uncertain, since the only known species, T. fracticalcis, gains energy from the use of fumarate, and the source of the latter in groundwater is not apparent. The organism is incapable of using any of the oxidized sulfur species (sulfate, sulfite, thiosulfate, or elemental sulfur) as an electron acceptor for respiration, although the proteins required for dissimilatory sulfate reduction are present in the genome. Research on T. fracticalcis ecology is complicated by the fact that the organism constitutes a minor component of the microbial community. The present work was aimed at the use of microbial mats formed at the head of a deep thermal borehole to obtain spore-forming sulfidogens. The isolated pure culture, Thermoanaerosсeptrum sp. BuN1, reduced sulfate and exhibited saccharolytic activity. It could grow within a broad pH range (3.5 to 9). Strain BuN1 was a moderate thermophile growing within the range from 37 to 60°C, with an optimum at 50°C.