Antarctica is an ideal analogue for studying the limits of life. Despite severe temperature fluctuations and desiccating conditions, life is commonly found colonizing the structural cavities within Antarctic rocks (i.e., endoliths). Previous studies have speculated that the slow cycling of endoliths in the McMurdo Dry Valleys may be the limit of life on Earth. However, very little is known about the in situ activities of these communities—especially in regions outside the McMurdo Dry Valleys where endoliths are thought to be cycling carbon very slowly (e.g., hundreds of years). Here, we show that East Antarctic endoliths found on nunataks are cycling carbon quickly and are therefore quite active. Through radiocarbon (¹⁴C) analyses of the viable cell membrane (as phospholipid-derived fatty acids [PLFA]), we found that the Δ¹⁴C composition of these microbial communities was on average predominantly modern, with a few samples signaling older carbon in the system. These findings indicate that endoliths inhabiting inland Antarctic nunataks are cycling carbon on decadal timescales, which support the notion that endoliths in Antarctica are cycling carbon quickly. This work provides new insights into the potential variability of Antarctic endolith activities and demonstrates that, despite the climatic extremes that exist farther inland on the most inhospitable continent on Earth, indigenous life can thrive.

中文翻译：

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南极东部的石内微生物碳循环

南极洲是研究生命极限的理想模拟地。尽管有剧烈的温度波动和干燥条件，但在南极岩石（即内石）内的结构空腔中仍普遍发现有生命存在。先前的研究推测，麦克默多干谷内石的缓慢循环可能是地球上生命的极限。然而，人们对这些群落的原地活动知之甚少——尤其是在麦克默多干谷以外的地区，人们认为内石循环碳的速度非常缓慢（例如，数百年）。在这里，我们展示了在 nunatak 上发现的东南极内石正在快速循环碳，因此非常活跃。通过放射性碳 ( ¹⁴C) 对活细胞膜（如磷脂衍生的脂肪酸 [PLFA]）的分析，我们发现这些微生物群落的 Δ ¹⁴ C 组成平均而言主要是现代的，少数样品表明系统中的碳较旧。这些研究结果表明，栖息在南极内陆海螺中的内石正在十年时间尺度上循环碳，这支持南极洲内石正在快速循环碳的观点。这项工作为南极内岩活动的潜在变异性提供了新的见解，并表明，尽管地球上最荒凉的大陆上更远的内陆存在极端气候，但土著生命可以蓬勃发展。