Author(s): S. V. Osipova; N. A. Bondarenko; L. A. Obolkina; A. P. Permyakov; L. V. Dudareva; O. A. Timoshkin
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Abstract: Until recently, researchers concentrated their efforts on studying Polar ice communities. Due to the structural peculiarities of freshwater ice, it was considered an impossible location for any life, although some interstitial ice communities were discovered in Pyrenean and Alpine lakes (Felip et al., 1995), as well as plant aggregations on the lower surface of ice cover of Amur River (Yur’ev, Lebedev, 1988). There were several investigations on ice algae from Belaya River and Lake Kandry-Kul (Shkundina, 1988), St. Lawrence River (Frenette et al., 2008). Our study on ice communities in the ultra-pure water of Lake Baikal (Obolkina et al., 2000; Timoshkin et al., 2000; and others) brought us to a conclusion that they are a principal factor in the life of the lake, because they are species-rich and active in spite of the low temperature and the seasonal occurrence of the habitat. Typical species of the ice communities in Lake Baikal are planktonic diatoms and dinoflagellates as well as benthic green algae. The results of the present work show that the content of unsaturated fatty acids (> 75%) in a freshwater hydrophytic green alga Ulothrix zonata (Weber et Mohr) Kuetzing from Baikal ice community is typical for psychrophilic organisms. It has been statistically proven that synthesis of unsaturated fatty acids 16:1 (n-9), 20:5 (n-3) and 22:6 (n-3) decreases as the temperature rises providing evidence of the principal role of these fatty acids in the chilling tolerance of the species. Moreover, immuno-detection in the protein microsomal fraction of U. zonata revealed proteins immunologically related to aquaporins PIP subfamily of higher plants. Their concentration in the ice algae exceeds that of the summer population. Enhanced synthesis of PUFAs and proteins immunologically related to aquaporins seems to play an important role in facilitating cold resistance of algae in Lake Baikal.
Year: 2010