The Arctic environment is particularly affected by global warming, and a clear trend of the ice retreat is observed worldwide. In proglacial systems, the newly exposed terrain represents different environmental and nutrient conditions compared to later soil stages. Therefore, proglacial systems show several environmental gradients along the soil succession where microorganisms are active protagonists of the soil and carbon pool formation through nitrogen fixation and rock weathering. We studied the microbial succession of three Arctic proglacial systems located in Svalbard (Midtre Lovénbreen), Sweden (Storglaciären), and Greenland (foreland close to Kangerlussuaq). We analyzed 65 whole shotgun metagenomic soil samples for a total of more than 400 Gb of sequencing data. Microbial succession showed common trends typical of proglacial systems with increasing diversity observed along the forefield chronosequence. Microbial trends were explained by the distance from the ice edge in the Midtre Lovénbreen and Storglaciären forefields and by total nitrogen (TN) and total organic carbon (TOC) in the Greenland proglacial system. Furthermore, we focused specifically on genes associated with nitrogen fixation and biotic rock weathering processes, such as nitrogenase genes, obcA genes, and genes involved in cyanide and siderophore synthesis and transport. Whereas we confirmed the presence of these genes in known nitrogen-fixing and/or rock weathering organisms (e.g., Nostoc, Burkholderia), in this study, we also detected organisms that, even if often found in soil and proglacial systems, have never been related to nitrogen-fixing or rock weathering processes before (e.g., Fimbriiglobus, Streptomyces). The different genera showed different gene trends within and among the studied systems, indicating a community constituted by a plurality of organisms involved in nitrogen fixation and biotic rock weathering, and where the latter were driven by different organisms at different soil succession stages.

北极环境尤其受全球变暖影响，全球范围内冰层消退趋势明显。在冰期前系统中，新暴露的地形代表与后期土壤阶段不同的环境和营养条件。因此，冰期系统沿着土壤演替显示出几个环境梯度，其中微生物是土壤的活性主角，并通过固氮和岩石风化形成碳库。我们研究了位于斯瓦尔巴群岛（Midtre Lovénbreen）、瑞典（Storglaciären）和格陵兰岛（靠近康克鲁斯瓦克的前陆）的三个北极前冰川系统的微生物演替。我们分析了 65 个完整的鸟枪法宏基因组土壤样本，总共超过 400 Gb 的测序数据。微生物演替显示出冰期前系统典型的共同趋势，沿着前场时间序列观察到多样性不断增加。微生物趋势可以通过 Midtre Lovénbreen 和 Storglaciären 前田距冰缘的距离以及格陵兰前冰川系统中的总氮 (TN) 和总有机碳 (TOC) 来解释。此外，我们特别关注与固氮和生物岩风化过程相关的基因，例如固氮酶基因， OBCA基因，以及参与氰化物和铁载体合成和运输的基因。然而我们证实了这些基因存在于已知的固氮和/或岩石风化生物体中（例如，发菜,伯克霍尔德杆菌），在这项研究中，我们还检测到了一些生物体，即使经常在土壤和前冰川系统中发现，但以前从未与固氮或岩石风化过程相关（例如,球毛菌,链霉菌属）。不同属在研究系统内部和系统之间表现出不同的基因趋势，表明由参与固氮和生物岩石风化的多种生物体构成的群落，并且后者是由不同土壤演替阶段的不同生物体驱动的。