Microorganisms of Two Thermal Pools on Kunashir Island, Russia

SIMPLE SUMMARY: The Kuril Islands are a part of the Circum-Pacific Belt of volcanoes and have many hot springs. Nonetheless, due to the border regime, these islands are difficult to access, and microbial communities of the geothermal springs of these islands have hardly been studied microbiologically and have not been studied metagenomically at all. Here we conducted the first metagenomic study on two thermophilic microbial communities of Kunashir Island. Faust Lake is hot (48 °C) and highly acidic (pH 2.0), whereas the Tretyakovsky Thermal Spring is also hot (52 °C) but weakly acidic (pH 6.0). We demonstrated that water pH affects the composition of the microbial communities. ABSTRACT: The Kuril Archipelago is a part of the Circum-Pacific Belt (Ring of Fire). These islands have numerous thermal springs. There are very few studies on these microbial communities, and none of them have been conducted by modern molecular biological methods. Here we performed the first metagenomic study on two thermophilic microbial communities of Kunashir Island. Faust Lake is hot (48 °C) and highly acidic (pH 2.0). We constructed 28 metagenome-assembled genomes as well as 17 16S ribosomal RNA sequences. We found that bottom sediments of Faust Lake are dominated by a single species of red algae belonging to the Cyanidiaceae family. Archaeans in Faust Lake are more diverse than bacteria but less abundant. The Tretyakovsky Thermal Spring is also hot (52 °C) but only weakly acidic (pH 6.0). It has much higher microbial diversity (233 metagenome-assembled genomes; 93 16S ribosomal RNAs) and is dominated by bacteria, with only several archaeans and one fungus. Despite their geographic proximity, these two thermal springs were found to not share any species. A comparison of these two lakes with other thermal springs of the Circum-Pacific Belt revealed that only a few members of the communities are shared among different locations.