Interspecific differences in cryoresistance of lichen symbiotic algae of genus Trebouxia assessed by cell viability and chlorophyll fluorescence.

摘要: Abstract Unicellular algae of genus Trebouxia are the most frequent symbiotic photobionts found in lichen species adapted to extreme environments. When lichenised, they cope well with freezing temperature polar regions, high-mountains environments and were successfully tested open-space experiments. sp. is considered potential model for exobiological The aim this paper evaluate cryoresistence when isolated from thalli cultivated on media. In our study, six algal strains exposed repeated freezing/thawing cycles. (freshly Lasallia pustulata ), erici , asymmetrica glomerata irregularis jamesii culture collection cooled 25 −40 °C at two different rates. also shock frozen liquid nitrogen. After treatment, inoculated a BBM agar 7 days. Then, cell viability was assessed as relative share living cells. Potential quantum yield photochemical reactions PS II ( F V / M effective Φ PSII ) measured. While slow cooling rate (0.5 °C min −1 did not cause any change viability, fast (6.0 °C min caused species-specific decrease all parameters. pronounced interspecific differences cryoresistance after consequent cultivation. T. exhibited low cells (18.9% 34.7%) full suppression photosynthetic processes, other had over 60%, unaffected values . This indicated high degree strains. These could be used detailed investigation underlying physiological mechanisms models astrobiological tests taken Earth facilities.