Publication details

Post rapid freezing growth of Antarctic strain of Heterococcus sp. monitored by cell viability and chlorophyll fluorescence

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Year of publication 2018
Type Article in Periodical
Magazine / Source Cryobiology
MU Faculty or unit

Faculty of Science

Keywords Antarctica; Cold stress; Cryoresistance; Ribitol; Terrestrial alga
Description The soil microalgae of the genus Heterococcus are found in cold environments and have been reported for the terrestrial ecosystems of several Sub-Antarctic and Antarctic Islands. This study focused on resistance of Heterococcus sp. to sub-zero temperature. Heterococcus sp. was isolated from soil samples from James Ross Island, Antarctica. Culture of Heterococcus sp. grown in liquid medium were used to study ribitol effects at sub-zero temperatures on the species resistance to rapid freezing (RF, immersion of a sample into liquid nitrogen) and consequent cultivation on agar. Before the experiment, Heterococcus sp. was cultured in liquid medium for 11 months and then treated in ribitol concentrations of 32 or 50 mM for 2h. Then, 1ml samples were frozen to minus 196°C in liquid nitrogen (day 0) and inoculated on BBM agar after thawing. Number of living and dead cells was evaluated and the cell viability (PV was calculated repeatedly using the optical microscopy approach. The addition of ribitol caused a noticable increase in PV on days 9, 12, 14 (with a PV of 25–45% in ribitol-treated samples compared to 10% in the untreated control). In the following period (d 16–19), the positive effect of ribitol on Pv was less pronounced but still statistically significant. To evaluate the negative effects of RF on chlorophyll fluorescence parameters, the potential yield of photochemical reactions in PS II (FV/FM), and the effective quantum yield of photochemical reactions in PS II (PhiPSII) were measured immediately before and after RF. Consequently, FV/FM and PhiPSII of agar inoculates were measured repeatedly for 30 d cultivation in 3 d interval. Both..
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