Barcoding monocultures of microeukaryotes from Lake Baikal to expand the database for molecular taxonomy

Lake Baikal, Earth's oldest and deepest freshwater lake, is a crucial habitat for an astonishing array of life forms, including numerous microorganisms. For over eight decades, scientists have examined the composition and dynamics of microbial communities using traditional morphological methods. In the last three decades, molecular techniques have expanded our understanding of them. However, the correspondence between the results obtained by these methods is still hard to reach. The major challenge in the analysis of high-throughput barcoding data is the scarcity of relevant sequences in reference databases, which leads to imprecise taxonomic identification.
In this work, we obtained three monocultures of Baikal microeukaryotes from Baikal plankton using the serial dilution method. The cultures were characterized by light microscopy and by Sanger sequencing of standard barcode fragments of 18S rRNA genes. The obtained sequences are available in the NCBI GenBank database under accession numbers PV231105, PV211307, and PQ565538.
The data obtained indicated that the cultures corresponded to two Chrysophyceae strains: Spumella sp. and Paraphysomonas sp. Both 18S sequences were unique in GenBank. The third culture corresponded to a ciliate Cyclidium sp., and the sequence has not been published for Baikal but was completely identical to a Cyclidium sp. isolate MMP-2020a from Harbin, China, and the closest taxonomically defined isolate belongs to Cyclidium marinum.
Cultivating and then sequencing monocultures is a laborious yet promising way to enrich databases for Baikal microeukaryotes.
The work was supported by the Russian Ministry of Science of Higher Education within the project #FZZE-2026-0004.