Below their ice shells, icy moons may offer a source of chemical energy that could support microbial life in the absence of light. In the Arctic, past and present glacial retreat leads to isostatic uplift of sediments through which cold and methane-saturated groundwater travels. This fluid reaches the surface and freezes as hill-shaped icings during winter, producing dark ice-water interfaces above water ponds containing chemical energy sources. In one such system characterized by elevated methane concentrations - the Lagoon Pingo in Adventdalen, Svalbard (~10 mg/L CH4, <0.3 mg/L O2, -0.25°C, pH 7.9), we studied amplicons of the bacterial and archaeal (microbial) 16S rRNA gene and transcripts in the water pond and overlaying ice. We show that active chemolithoautotrophic sulfur-oxidizing microorganisms (Sulfurimonas, Thiomicrorhabdus) dominated a niche at the bottom of the ice in contact with the anoxic water reservoir. There, the growing ice offers surfaces interfacing with water, and hosts favorable physico-chemical conditions for sulfide oxidation. Detection of anaerobic methanotrophs further suggests that the ice led to a steady-state dark and cold methane sink under the ice throughout winter, in two steps: first methane is oxidized to carbon dioxide and sulfates concomitantly reduced to sulfides by the activity of ANME-1a and SEEP-SRB1 consortia, in a second time energy from sulfides is used by sulfur- oxidizing microorganisms to fix carbon dioxide into organic carbon. Our results underline ice- covered and dark ecosystems as a hitherto overlooked oasis of microbial life and emphasize the need to study microbial communities in icy habitats.

中文翻译：

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化能自养细菌在北极冷泉的暗水-冰界面处繁衍生息。


在冰壳下面，冰冷的卫星可能提供化学能源，可以在没有光的情况下支持微生物的生命。在北极，过去和现在的冰川退缩导致沉积物均衡抬升，寒冷且甲烷饱和的地下水流经沉积物。这种流体到达地表，在冬季冻结成山形的冰，在含有化学能源的水池上方产生黑色的冰水界面。在一个以甲烷浓度升高为特征的系统中，即位于斯瓦尔巴群岛 Adventdalen 的 Lagoon Pingo（~10 mg/L CH4，<0.3 mg/L O2，-0.25°C，pH 7.9），我们研究了细菌和水池和覆盖冰中的古菌（微生物）16S rRNA 基因和转录本。我们发现，活跃的化能自养硫氧化微生物（硫单胞菌、硫微杆菌）在与缺氧水库接触的冰底部占据主导地位。在那里，不断生长的冰提供了与水接触的表面，并为硫化物氧化提供了有利的物理化学条件。对厌氧甲烷氧化菌的检测进一步表明，整个冬季，冰导致冰下稳态黑暗和寒冷的甲烷下沉，分两个步骤：首先，甲烷被氧化为二氧化碳和硫酸盐，同时通过 ANME-1a 的活性还原为硫化物和SEEP-SRB1联盟，硫氧化微生物第二次利用硫化物的能量将二氧化碳固定为有机碳。我们的研究结果强调了冰雪覆盖的黑暗生态系统是迄今为止被忽视的微生物生命绿洲，并强调了研究冰冷栖息地中微生物群落的必要性。