| Popis: |
Environment in Polar Regions is characterized by many extremes. Low temperatures, lack of fluid water, irregular nutrient and light supply, fluctuations in daily and annual cycles could seem unfavourable for life. In spite of this, diatoms (Bacillariophyceae) are one of groups of microorganisms that apparently well adapted to such environment and dominate in a wide range of polar habitats. For many organisms, dormancy is a strategy to overcome unfriendly conditions, but morphologically distinct resting stages are observed rarely in diatoms. In this study, the tolerance of polar and temperate diatoms to freezing was experimentally tested and the difference in survivability of vegetative and resting cells was assessed. Diatom strains for the experiments were isolated in 2014 using natural samples from the Maritime Antarctica (James Ross Island, Vega Island) and the Arctic (Spitsbergen). Further strains were acquired from culture collections of microorganisms (CCCryo and BCCM). Resting cells were induced by incubation under nitrogen and light limitation in lower temperature. The vegetative and resting cells of 26 strains were exposed to six different freezing treatments (including those simulating natural conditions) to -4 řC, -20 řC, -40 řC and -180 řC (liquid nitrogen). Treatments differed also in... |
