ИСТИНА

Potentially toxic marine planktonic dinoflagellates represent an ecologically important group of single-cell eukaryotes which show pronounced physiological adaptability to various types of environmental stress. These protists respond to harsh conditions by activation of their defensive mechanisms, which can differ from those of large multicellular forms. The dinoflagellates Prorocentrum minimum (or P. cordatum) in the Baltic Sea have recently become good model objects in the environmental and cell biology studies of unicellular eukaryotes. The goal of this paper is to demonstrate what cell and molecular mechanisms underpin the fast and effective adaptations of these protists in the brackishwater habitats. We focused on cell metabolism, ion channel research, and on the effects of different levels of salinity and elevated temperature on cell mortality, cell cycle pattern, RNA synthesis, and DNA replication in P. minimum. It appears that P. minimum can utilize urea as a source of organic nitrogen but also as a source of carbon. Moreover, urea inhibits assimilation of nitrate (the “classic” source of nitrogen) and can be the preferable substrate in the coastal brackish waters. Dinoflagellates show elevated biosynthetic activity and low cell-death level at critical salinity 5-8 ‰. We infer that this potentially toxic, bloom forming dinoflagellate species displays great colonizing ability across new ecosystems likely due to high physiological plasticity and pronounced adaptation potential at different levels of biological organization, from molecules and cells to populations. Funded by the Russian Science Foundation, project 16-14-10116.