Zhang Qing, Leng Hope T, Li Hongquan, Arrigo Kevin R, Prakash Manu
Department of Bioengineering, Stanford University, Stanford, CA 94305.
Department of Earth System Science, Stanford University, Stanford, CA 94305.
Proc Natl Acad Sci U S A. 2025 Sep 16;122(37):e2423725122. doi: 10.1073/pnas.2423725122. Epub 2025 Sep 9.
Despite periods of permanent darkness and extensive ice coverage in polar environments, photosynthetic ice diatoms display a remarkable capability of living inside the ice matrix. How these organisms navigate such hostile conditions with limited light and extreme cold remains unknown. Using a custom subzero temperature microscope during an Arctic expedition, we present the finding of motility at record-low temperatures in a Eukaryotic cell. By characterizing the gliding motility of several ice diatom species, collected from ice cores in the Chukchi Sea, we record that they retain motility at temperatures as low as [Formula: see text]15 C. Remarkably, ice diatoms can glide on ice substrates, a capability absent in temperate diatoms of the same genus. This unique ability arises from adaptations in extracellular mucilage that allow ice diatoms to adhere to ice, essential for gliding. Even on glass substrates where both cell types retain motility at freezing temperatures, ice diatoms move an order of magnitude faster, with their optimal motility shifting toward colder temperatures. Combining field and laboratory experiments with thermo-hydrodynamic modeling, we reveal adaptive strategies that enable gliding motility in cold environments. These strategies involve increasing internal energy efficiency with minimal changes in heat capacity and activation enthalpy, and reducing external dissipation by minimizing the temperature sensitivity of mucilage viscosity. The finding of diatoms' ice gliding motility opens new routes for understanding their survival within a harsh ecological niche and their migratory responses to environmental changes. Our work highlights the robust adaptability of ice diatoms in one of Earth's most extreme settings.
尽管极地环境存在长期黑暗和广泛的冰层覆盖，但光合冰藻展现出在冰基质中生存的非凡能力。这些生物如何在有限光照和极端寒冷的恶劣条件下生存仍是未知之谜。在一次北极探险中，我们使用定制的低温显微镜，发现了真核细胞在创纪录低温下的运动能力。通过对从楚科奇海冰芯采集的几种冰藻的滑行运动进行表征，我们记录到它们在低至零下15摄氏度的温度下仍能保持运动能力。值得注意的是，冰藻能够在冰基质上滑行，而同一属的温带硅藻则没有这种能力。这种独特能力源于细胞外黏液的适应性变化，使冰藻能够附着在冰上，这对滑行至关重要。即使在两种细胞类型在冷冻温度下都能保持运动能力的玻璃基质上，冰藻的移动速度也快一个数量级，其最佳运动状态向更低温度转移。通过将野外和实验室实验与热流体动力学建模相结合，我们揭示了使冰藻在寒冷环境中实现滑行运动的适应性策略。这些策略包括在热容量和活化焓变化最小的情况下提高内部能量效率，以及通过最小化黏液粘度的温度敏感性来减少外部耗散。冰藻冰上滑行运动的发现为理解它们在恶劣生态位中的生存以及对环境变化的迁移反应开辟了新途径。我们的研究突出了冰藻在地球最极端环境之一中的强大适应性。
