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首页> 外文期刊>Protoplasma: An International Journal of Cell Biology >The conjugating green alga Zygnema sp. (Zygnematophyceae) from the Arctic shows high frost tolerance in mature cells (pre-akinetes)
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The conjugating green alga Zygnema sp. (Zygnematophyceae) from the Arctic shows high frost tolerance in mature cells (pre-akinetes)

机译：共轭绿藻Zygnema sp。 （Zygnematophyceeae）来自北极显示成熟细胞中的高霜耐受性（Pre-akinetes）

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摘要

Green algae of the genus Zygnema form extensive mats and produce large amounts of biomass in shallow freshwater habitats. Environmental stresses including freezing may perturb these mats, which usually have only annual character. To estimate the limits of survival at subzero temperatures, freezing resistance of young Zygnema sp. (strain MP2011Skan) cells and pre-akinetes was investigated. Young, 2-week-old cultures were exposed to temperatures of 0 to - 14 °C at 2-K steps, whereas 8-month-old cultures were frozen from - 10 to - 70 °C at 10-K intervals. Cell viability after freezing was determined by 0.1% auramineO vital fluorescence staining and measurements of the effective quantumyield of photosystemII (Ф_(PSII)). At - 8 °C, the young vegetative cells were unable to recover from severe frost damage. But temperatures even slightly below zero (- 2 °C) negatively affected the cells' physiology. Single pre-akinetes could survive even at - 70 °C, but their LT50 value was - 26.2 °C. Severe freezing cytorrhysis was observed via cryo-microscopy at - 10 °C, a temperature found to be lethal for young cells. The ultrastructure of young cells appeared unchanged at - 2 °C, but severe damage to biomembranes and formation of small foamy vacuoles was observed at - 10 °C. Pre-akinetes did not show ultrastructural changes at - 20 °C; however, vacuolization increased, and gas bubbles appeared at - 70 °C. Our results demonstrate that the formation of pre-akinetes increases freezing resistance. This adaptation is crucial for surviving the harsh temperature conditions prevailing in the High Arctic in winter and a key feature in seasonal dynamics of Zygnema sp.
机译：Zygnema属的绿藻形成宽阔的垫子，在浅淡水栖息地中产生大量生物量。在包括冻结的环境压力可能会扰乱这些垫子，这通常只有年度性格。估算亚零温度的存活率，幼苗SP的冷冻抗性。 （菌株MP2011SKAN）细胞和预先形成。在2-k步骤下，年轻，2周龄的培养物暴露在0至-14°C的温度下，而8个月的培养物以10-k间隔从-10至-70°C中冷冻。冷冻后的细胞活力由0.1％AuRamineo的生命荧光染色和测量的光照系统（Ф_（psii））测定。在-8℃下，年轻的营养细胞无法从严重的霜冻损伤中恢复。但温度甚至略低于零（ - 2°C）对细胞的生理学产生负面影响。单个预ki​​netes即使在-70°C时也可以存活，但它们的LT50值为-26.2°C。通过低温显微镜在-10℃下观察到严重的冷冻筛选，发现患有幼小细胞的温度。幼细细胞的超微结构在​​-2℃下显得不变，但在-10℃下观察到生物膜的严重损伤和形成小泡沫泡沫泡。 Pre-AWINETES没有显示在20°C的超微结构变化;然而，漂浮液体增加，气泡出现在-70℃。我们的结果表明，预先形成的形成增加了抗寒性。这种适应对于幸存在冬季高北极的苛刻温度条件以及Zygnema SP的季节性动态的关键特征至关重要。

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