Amen Rahma, Ganzert Lars, Friedl Thomas, Rybalka Nataliya, Wagner Dirk
GFZ Helmholtz Centre for Geosciences, Section Geomicrobiology, Potsdam, Germany.
Department of Zoology, Faculty of Science, Aswan University, Aswan, Egypt.
Front Microbiol. 2025 May 21;16:1576898. doi: 10.3389/fmicb.2025.1576898. eCollection 2025.
In the extremely dry and oligotrophic soils of East Antarctica, where low temperatures and humidity result in minimal biological turnover rates, extracellular DNA (eDNA) can persist over extended timescales. Differentiating between sequences from living, potentially active cells (intracellular DNA, or iDNA) and those from ancient, non-living organisms (eDNA) is crucial for accurately assessing the current microbial community and understanding historical microbial dynamics.
This study was conducted along a chronosequence in the Larsemann Hills, East Antarctica, where soil samples were collected from sites at varying distances from the glacier. By employing DNA separation methods, we distinguished iDNA, which represents living cells, from eDNA derived from dead organisms. High-throughput sequencing was used to characterize bacterial and eukaryotic communities across different successional stages.
The DNA separation approach revealed distinct bacterial and eukaryotic community structures along the glacier transect. Actinobacteria were consistently abundant across all sites, while other phyla such as Chloroflexi, Gemmatimonadetes, and Proteobacteria thrived in extreme, nutrient-poor environments. Early successional stages were characterized by the simultaneous colonization of green algae Trebouxiophyceae and cryophilic fungi, alongside nitrogen-fixing bacteria, which contributed to initial soil development. The study also identified three distinct modes of microbial distribution, reflecting varying degrees of activity and adaptability.
Our findings provide new insights into microbial dynamics in extreme habitats and propose new hypotheses for microbial colonization in newly exposed soils. Moreover, they contribute to the ongoing debate in microbial ecology regarding the viability of dormant or dead cells and emphasize the need for refining DNA-based methods and exploring functional pathways to deepen our understanding of microbial succession in polar regions.
在东南极洲极度干燥且贫营养的土壤中，低温和低湿度导致生物周转率极低，细胞外DNA（eDNA）能够在很长的时间尺度上持续存在。区分来自活的、可能具有活性的细胞的序列（细胞内DNA，即iDNA）和来自古老的、无生命的生物体的序列（eDNA），对于准确评估当前的微生物群落以及理解历史微生物动态至关重要。
本研究沿着东南极洲拉斯曼丘陵的一个时间序列进行，在该区域从距离冰川不同距离的地点采集土壤样本。通过采用DNA分离方法，我们将代表活细胞的iDNA与源自死生物体的eDNA区分开来。利用高通量测序来表征不同演替阶段的细菌和真核生物群落。
DNA分离方法揭示了沿冰川样带不同的细菌和真核生物群落结构。放线菌在所有地点一直都很丰富，而其他门类如绿弯菌门、芽单胞菌门和变形菌门则在极端、营养贫乏的环境中大量繁殖。早期演替阶段的特征是绿藻中的 trebouxiphyceae 和嗜冷真菌与固氮细菌同时定殖，这有助于土壤的初步发育。该研究还确定了三种不同的微生物分布模式，反映了不同程度的活性和适应性。
我们的研究结果为极端栖息地的微生物动态提供了新的见解，并为新暴露土壤中的微生物定殖提出了新的假设。此外，它们有助于微生物生态学中关于休眠或死细胞活力的持续争论，并强调需要改进基于DNA的方法和探索功能途径，以加深我们对极地地区微生物演替的理解。
