Identification of Lake Baikal Plankton Dinoflagellates from the Genera Gyrodinium and Gymnodinium Using Single-Cell PCR

Most of eukaryotes is represented by unicellular organisms (protists) which are still poorly investigated owing to a number of methodological problems. In this study, single-cell PCR was used for the analysis of two unarmoured dinoflagellate species from Lake Baikal. DNA fragments from living and fixed Gymnodinium baicalense and Gyrodinium helveticum cells were successfully sequenced, which indicates the usefulness of the method in the study of uncultivated dinoflagellates. However, this approach is too laborious to be introduced into traditional monitoring studies. The data obtained confirmed the earlier suggestion that the Baikal population of heterotrophic species G. helveticum was wrongly described as an endemic species of Lake Baikal, Gymnodinium coeruleum. The sequences of 28S rRNA gene fragment and ITS2 region were determined for the first time for G. helveticum. Phylogenetic trees inferred from the 28S rRNA and 18S rRNA genes confirm the assignment of G. helveticum to the genus Gyrodinium. Analysis of 18S rRNA gene fragments from the GenBank database revealed a large number of unknown eukaryotes from different water reservoirs similar to G. helveticum. This is could be because of the existence of cryptic diversity within morphospecies G. helveticum, as well as the existence of yet unknown species from the genus Gyrodinium. Our analysis stimulates more intensive study of G. helveticum phylogeography in particular and the diversity of Gyrodinium in general.