Glacier and ice sheet surfaces host diverse communities of microorganisms whose activity (or inactivity) influences biogeochemical cycles and ice melting. Supraglacial microbes endure various environmental extremes including resource scarcity, frequent temperature fluctuations above and below the freezing point of water, and high UV irradiance during summer followed by months of total darkness during winter. One strategy that enables microbial life to persist through environmental extremes is dormancy, which despite being prevalent among microbial communities in natural settings, has not been directly measured and quantified in glacier surface ecosystems. Here, we use a combination of metabarcoding and metatranscriptomic analyses, as well as cell-specific activity (BONCAT) incubations to assess the diversity and activity of microbial communities from glacial surfaces in Iceland and Greenland. We also present a new ecological model for glacier microorganisms and simulate physiological state-changes in the glacial microbial community under idealized (i) freezing, (ii) thawing, and (iii) freeze–thaw conditions. We show that a high proportion (>50%) of bacterial cells are translationally active in-situ on snow and ice surfaces, with Actinomycetota, Pseudomonadota, and Planctomycetota dominating the total and active community compositions, and that glacier microorganisms, even when frozen, could resume translational activity within 24 h after thawing. Our data suggest that glacial microorganisms respond rapidly to dynamic and changing conditions typical of their natural environment. We deduce that the biology and biogeochemistry of glacier surfaces are shaped by processes occurring over short (i.e., daily) timescales, and thus are susceptible to change following the expected alterations to the melt-regime of glaciers driven by climate change. A better understanding of the activity of microorganisms on glacier surfaces is critical in addressing the growing concern of climate change in Polar regions, as well as for their use as analogues to life in potentially habitable icy worlds.

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冰川表面活跃和休眠的微生物

冰川和冰盖表面拥有各种微生物群落，它们的活动（或不活动）影响生物地球化学循环和冰融化。冰上微生物忍受各种极端环境，包括资源稀缺、水冰点以上和以下的频繁温度波动，以及夏季的高紫外线辐照度和冬季数月的完全黑暗。使微生物生命能够在极端环境中持续存在的一种策略是休眠，尽管休眠在自然环境中的微生物群落中普遍存在，但尚未在冰川表面生态系统中直接测量和量化。在这里，我们结合使用元条形码和宏转录组学分析，以及细胞特异性活性 (BONCAT) 孵化，以评估冰岛和格陵兰冰川表面微生物群落的多样性和活性。我们还提出了一个新的冰川微生物生态模型，并模拟了理想化 (i) 冻结、(ii) 解冻和 (iii) 冻融条件下冰川微生物群落的生理状态变化。我们表明，高比例（>50%）的细菌细胞在冰雪表面上具有原位翻译活性，其中放线菌、假单胞菌和 Planctomycetota 主导了总体和活跃的群落组成，并且冰川微生物，即使在冻结时，解冻后 24 小时内可恢复翻译活动。我们的数据表明，冰川微生物对其自然环境典型的动态和变化条件做出快速反应。我们推断冰川表面的生物学和生物地球化学是由短时间（即每天）发生的过程形成的，因此很容易随着气候变化驱动的冰川融化状态的预期变化而发生变化。更好地了解微生物在冰川表面的活动对于解决人们对极地地区气候变化的日益关注以及将它们用作可能适合居住的冰冷世界中的生命的类比至关重要。因此很容易随着气候变化驱动的冰川融化机制的预期变化而发生变化。更好地了解微生物在冰川表面的活动对于解决人们对极地地区气候变化的日益关注以及将它们用作可能适合居住的冰冷世界中的生命的类比至关重要。因此很容易随着气候变化驱动的冰川融化机制的预期变化而发生变化。更好地了解微生物在冰川表面的活动对于解决人们对极地地区气候变化的日益关注以及将它们用作可能适合居住的冰冷世界中的生命的类比至关重要。