Documenting anaerobic microbial metabolisms in hypersaline perennially ice-covered lakes in Antarctica further refines the environmental limits to life and may reveal rare biogeochemical mechanisms and/or novel microbial catalysts of elemental cycling. We assessed rates of sulfate reduction, methanogenesis, and anaerobic oxidation of methane using radiotracers and generated 16S rRNA gene libraries from the microbial communities inhabiting the deep calcium-chloride-rich brine and sediments of Lake Vanda, McMurdo Dry Valleys, Antarctica. Sulfate reduction rates were observed in surface sediments but not in the brine overlying the sediments. Methane formation through the methylotrophic, acetoclastic, and hydrogenotrophic pathways was quantified using ¹⁴C-labeled methylamine, acetate, and CO₂, respectively, and methanogenesis was detected in both the brine and the sediments. Hydrogenotrophic methanogenesis rates were the highest of all substrates tested in the sediments, while methylotrophic methanogenesis was highest in the brines. Anaerobic oxidation of methane was below the limit of detection in both the brines and sediments. The major taxa of Bacteria and Archaea detected were most similar to organisms previously observed in hypersaline environments and included examples related to known sulfate-reducing bacteria other than Deltaproteobacteria (surprisingly, sulfate-reducing Deltaproteobacteria were not observed in this study), and both methanogenic and methanotrophic Archaea. These data indicate an active microbial community in the anoxic brine of Lake Vanda that while similar in terms of community structure and metabolism to other brine habitats, is uniquely evolved to survive in this extreme environment.

中文翻译：

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多年生冰雪覆盖的湖泊高盐深水和沉积物中的硫酸盐还原和甲烷生成

在南极常年被冰覆盖的高盐湖中记录厌氧微生物的代谢，进一步完善了生活的环境限制，并可能揭示了罕见的生物地球化学机制和/或元素循环的新型微生物催化剂。我们使用放射性示踪剂评估了甲烷的硫酸盐还原，甲烷生成和厌氧氧化的速率，并从微生物群落生成了16S rRNA基因文库，这些微生物群落居住在南极麦克凡多干谷的旺达湖中，富含氯化钙的浓盐水和沉积物。在表层沉积物中观察到硫酸盐还原速率，但在沉积物上方的盐水中未观察到硫酸盐还原速率。使用¹⁴ C标记的甲胺，乙酸盐和CO ₂定量分析了甲基营养，乙酰碎裂和氢营养途径中的甲烷形成分别在盐水和沉积物中检测到甲烷生成。在沉积物中测试的所有底物中，氢营养型甲烷生成率最高，而盐水中的甲基营养型甲烷生成率最高。在盐水和沉积物中，甲烷的厌氧氧化均低于检出限。检测到的细菌和古细菌的主要类群与以前在高盐环境中观察到的生物最相似，并包括与除三角洲变形菌之外的其他已知的减少硫酸盐还原菌有关的例子（令人惊讶的是，在本研究中未观察到减少硫酸盐的三角洲变形菌），并且产甲烷和甲烷营养古生菌。这些数据表明，旺达湖缺氧盐水中有一个活跃的微生物群落，尽管其群落结构和新陈代谢与其他盐水生境相似，但在这种极端环境下可以生存。