Centre for Microbial Ecology and Genomics, Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria 0002, South Africa.
Department of Microbiology, Monash Biomedicine Discovery Institute, Clayton VIC 3800, Australia;
Proc Natl Acad Sci U S A. 2021 Nov 9;118(45). doi: 10.1073/pnas.2025322118.
Numerous diverse microorganisms reside in the cold desert soils of continental Antarctica, though we lack a holistic understanding of the metabolic processes that sustain them. Here, we profile the composition, capabilities, and activities of the microbial communities in 16 physicochemically diverse mountainous and glacial soils. We assembled 451 metagenome-assembled genomes from 18 microbial phyla and inferred through Bayesian divergence analysis that the dominant lineages present are likely native to Antarctica. In support of earlier findings, metagenomic analysis revealed that the most abundant and prevalent microorganisms are metabolically versatile aerobes that use atmospheric hydrogen to support aerobic respiration and sometimes carbon fixation. Surprisingly, however, hydrogen oxidation in this region was catalyzed primarily by a phylogenetically and structurally distinct enzyme, the group 1l [NiFe]-hydrogenase, encoded by nine bacterial phyla. Through gas chromatography, we provide evidence that both Antarctic soil communities and an axenic Bacteroidota isolate () oxidize atmospheric hydrogen using this enzyme. Based on ex situ rates at environmentally representative temperatures, hydrogen oxidation is theoretically sufficient for soil communities to meet energy requirements and, through metabolic water production, sustain hydration. Diverse carbon monoxide oxidizers and abundant methanotrophs were also active in the soils. We also recovered genomes of microorganisms capable of oxidizing edaphic inorganic nitrogen, sulfur, and iron compounds and harvesting solar energy via microbial rhodopsins and conventional photosystems. Obligately symbiotic bacteria, including Patescibacteria, Chlamydiae, and predatory Bdellovibrionota, were also present. We conclude that microbial diversity in Antarctic soils reflects the coexistence of metabolically flexible mixotrophs with metabolically constrained specialists.
大量不同的微生物栖息在南极洲大陆的寒冷荒漠土壤中，但我们缺乏对维持它们生存的代谢过程的整体理解。在这里，我们描绘了 16 种物理化学性质多样的山地和冰川土壤中微生物群落的组成、功能和活性。我们从 18 个微生物门组装了 451 个宏基因组组装基因组，并通过贝叶斯分歧分析推断出，目前存在的优势谱系可能是南极洲的本地种。支持早期的研究结果，宏基因组分析表明，最丰富和普遍的微生物是代谢多样的好氧微生物，它们利用大气中的氢气来支持有氧呼吸，有时还进行碳固定。然而，令人惊讶的是，该地区的氢气氧化主要由一种系统发育和结构上不同的酶——第 1l 组 [NiFe]-氢化酶所催化，该酶由 9 个细菌门编码。通过气相色谱，我们提供了证据表明，南极土壤群落和一个无菌的拟杆菌门（）都使用这种酶氧化大气中的氢气。根据在环境代表性温度下的现场速率，氢气氧化理论上足以满足土壤群落的能量需求，并通过代谢水的产生来维持水合作用。多样的一氧化碳氧化菌和丰富的甲烷营养菌在土壤中也很活跃。我们还回收了能够氧化土壤无机氮、硫和铁化合物以及通过微生物视紫红质和传统光合系统获取太阳能的微生物基因组。还有一些专性共生菌，包括 Patescibacteria、Chlamydiae 和捕食性 Bdellovibrionota，也存在于土壤中。我们得出结论，南极土壤中的微生物多样性反映了代谢灵活的混合营养体与代谢受限的专性生物共存的现象。
