Effectiveness of Microalgae and Cyanobacteria Cryopreservation (for the Strains from the All-Russian Collection of Microorganisms)

The efficiency of cryopreservation of cyanobacteria and eukaryotic microalgae of different taxonomic groups, including charophyte, chlorophyte and ochrophyte microalgae, was assessed using 24 strains of the algological part of the All-Russian Collection of Microorganisms (VKM) as an example. Microalgae cultures differing in cell size, morphological organization of the thallus, reproduction method, presence and size of mucous membranes, and ability to form dormant cells were selected for comparative study. Two types of cryoprotectors (methanol and dimethyl sulfoxide), two types of nutrient media (slant agar and liquid medium), and three methods for determining the survival of microalgae after cryopreservation were tested. It was shown that a two-step cryopreservation protocol using both cryoprotectants (methanol and dimethyl sulfoxide) was successfully applied to all 24 studied strains, regardless of their taxonomic affiliation and morphological features. Based on the results of the experiment, a standard operating procedure for cryopreservation of microalgae was developed, including a liquid culture medium with dimethyl sulfoxide, as well as two methods for determining the survival of microalgae after cryopreservation - growth in a liquid medium and streaks on agar. The proposed protocol not only ensures the preservation of cell viability and the possibility of further use of the strain as a morphologically and genetically representative sample, but also minimizes time and resource costs, as well as the risk of contamination of cultures.