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@article{985473,
author = {Hájek, Josef and Váczi, Peter and Barták, Miloš and Jahnová, Lucie},
article_number = {3},
doi = {http://dx.doi.org/10.1016/j.cryobiol.2012.02.002},
keywords = {Freezing temperature; Sub-zero temperature; Cooling protocols; Lichenised algae; Quantum yield},
language = {eng},
issn = {0011-2240},
journal = {Cryobiology},
title = {Interspecific differences in cryoresistance of lichen symbiotic algae of genus Trebouxia assessed by cell viability and chlorophyll fluorescence.},
volume = {64},
year = {2012}
}
TY - JOUR
ID - 985473
AU - Hájek, Josef - Váczi, Peter - Barták, Miloš - Jahnová, Lucie
PY - 2012
TI - Interspecific differences in cryoresistance of lichen symbiotic algae of genus Trebouxia assessed by cell viability and chlorophyll fluorescence.
JF - Cryobiology
VL - 64
IS - 3
SP - 215-222
EP - 215-222
SN - 00112240
KW - Freezing temperature
KW - Sub-zero temperature
KW - Cooling protocols
KW - Lichenised algae
KW - Quantum yield
N2 - 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 of polar regions, high-mountains environments and were successfully tested in open-space experiments. Trebouxia sp. is considered potential model species for exobiological experiments. The aim of this paper is to evaluate cryoresistence of Trebouxia sp. when isolated from lichen thalli and cultivated on media. In our study, six algal strains were exposed to repeated freezing/thawing cycles. The strains of Trebouxia sp. (freshly isolated from lichen Lasallia pustulata), Trebouxia erici, Trebouxia asymmetrica, Trebouxia glomerata, Trebouxia irregularis, and Trebouxia jamesii from culture collection were cooled from 25 to minus 40 deg C at two different rates. The strains were also shock frozen in liquid nitrogen. After repeated treatment, the strains were inoculated and cultivated on a BBM agar for 7 days. Then, cell viability was assessed as relative share of living cells. Potential quantum yield of photochemical reactions in PS II (FV/FM), and effective quantum yield of photochemical reactions in PS II (FiPSII) were measured. While the slow cooling rate (0.5 deg C/min) did not cause any change in viability, FV/FM, and FiPSII, the fast cooling rate (6.0 deg C/min) caused species-specific decrease in all parameters. The most pronounced interspecific differences in cryoresistance were found after shock freezing and consequent cultivation. While T. asymmetrica and T. jamesii exhibited low viability of living cells (18.9% and 34.7%) and full suppression of photosynthetic processes, the other strains had viability over 60%, and unaffected values of FV/FM, and FiPSII. This indicated a high degree of cryoresistance of T. glomerata, T. erici, T. irregularis and Trebouxia sp. strains. These strains could be used for detailed investigation of underlying physiological mechanisms and as models for astrobiological tests taken in the Earth facilities.
ER -
HÁJEK, Josef, Peter VÁCZI, Miloš BARTÁK a Lucie JAHNOVÁ. Interspecific differences in cryoresistance of lichen symbiotic algae of genus Trebouxia assessed by cell viability and chlorophyll fluorescence. \textit{Cryobiology}. 2012, roč.~64, č.~3, s.~215-222. ISSN~0011-2240. Dostupné z: https://dx.doi.org/10.1016/j.cryobiol.2012.02.002.
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