Radiometric measurement of primary (PP) and secondary production (SP) in Rotmoosferner cryoconites sampled for metagenome sequencing on 14 September 2010

<b>Table 1.</b> Radiometric measurement of primary (PP) and secondary production (SP) in Rotmoosferner cryoconites sampled for metagenome sequencing on 14 September 2010. Values are the mean of triplicate incubations, and cryoconites with a positive ratio of SP:PP consistent with net heterotrophy are highlighted in bold. <strong>Abstract</strong> Cryoconite is a microbe–mineral aggregate which darkens the ice surface of glaciers. Microbial process and marker gene PCR-dependent measurements reveal active and diverse cryoconite microbial communities on polar glaciers. Here, we provide the first report of a cryoconite metagenome and culture-independent study of alpine cryoconite microbial diversity. We assembled 1.2 Gbp of metagenomic DNA sequenced using an Illumina HiScanSQ from cryoconite holes across the ablation zone of Rotmoosferner in the Austrian Alps. The metagenome revealed a bacterially-dominated community, with <em>Proteobacteria</em> (62% of bacterial-assigned contigs) and <em>Bacteroidetes</em> (14%) considerably more abundant than <em>Cyanobacteria</em> (2.5%). Streptophyte DNA dominated the eukaryotic metagenome. Functional genes linked to N, Fe, S and P cycling illustrated an acquisitive trend and a nitrogen cycle based upon efficient ammonia recycling. A comparison of 32 metagenome datasets revealed a similarity in functional profiles between the cryoconite and metagenomes characterized from other cold microbe–mineral aggregates. Overall, the metagenomic snapshot reveals the cryoconite ecosystem of this alpine glacier as dependent on scavenging carbon and nutrients from allochthonous sources, in particular mosses transported by wind from ice-marginal habitats, consistent with net heterotrophy indicated by productivity measurements. A transition from singular snapshots of cryoconite metagenomes to comparative analyses is advocated.

表1。2010年9月14日用于宏基因组测序（metagenome sequencing）采样的罗特莫斯费纳冰川（Rotmoosferner）冰尘（cryoconite）的初级生产力（PP）与次级生产力（SP）辐射测量结果。数值为三次重复培养的平均值，SP:PP比值为正且符合净异养特性的冰尘样本以粗体标注。
摘要：冰尘（cryoconite）是一种微生物-矿物团聚体，可使冰川冰面变暗。基于微生物过程与标记基因的聚合酶链式反应（PCR，polymerase chain reaction）检测结果显示，极地冰川上存在活跃且多样的冰尘微生物群落。本研究首次发布冰尘宏基因组（metagenome）研究成果，并对阿尔卑斯冰尘微生物多样性开展了非培养依赖型研究。我们对取自奥地利阿尔卑斯山罗特莫斯费纳冰川消融区各处冰尘孔洞的样本进行测序，使用Illumina HiScanSQ平台共组装得到1.2 Gbp的宏基因组DNA序列。宏基因组分析显示群落以细菌为主，其中变形菌门（Proteobacteria，占细菌注释重叠群的62%）与拟杆菌门（Bacteroidetes，占14%）的丰度远高于蓝细菌门（Cyanobacteria，占2.5%）。真核生物宏基因组中以链形植物类群（Streptophyte）的DNA占主导。与氮（N）、铁（Fe）、硫（S）和磷（P）循环相关的功能基因体现出资源获取型代谢趋势，以及一套基于高效氨回收的氮循环系统。对32组宏基因组数据集的比较分析显示，本研究中的冰尘样本与其他寒冷环境微生物-矿物团聚体的宏基因组在功能特征上具有相似性。总体而言，此次宏基因组快照分析显示，该阿尔卑斯冰川的冰尘生态系统依赖从外源环境获取碳与营养物质，尤其是从冰缘生境经风力搬运而来的苔藓，这与生产力测量结果所揭示的净异养特性相一致。本研究倡导从单一的冰尘宏基因组快照研究转向比较分析研究。