George Scott F, Fierer Noah, Levy Joseph S, Adams Byron
Department of Biology, Brigham Young University, Provo, UT, United States.
Department of Ecology and Evolutionary Biology and Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, United States.
Front Microbiol. 2021 Jan 27;12:616730. doi: 10.3389/fmicb.2021.616730. eCollection 2021.
Ice-free soils in the McMurdo Dry Valleys select for taxa able to cope with challenging environmental conditions, including extreme chemical water activity gradients, freeze-thaw cycling, desiccation, and solar radiation regimes. The low biotic complexity of Dry Valley soils makes them well suited to investigate environmental and spatial influences on bacterial community structure. Water tracks are annually wetted habitats in the cold-arid soils of Antarctica that form briefly each summer with moisture sourced from snow melt, ground ice thaw, and atmospheric deposition via deliquescence and vapor flow into brines. Compared to neighboring arid soils, water tracks are highly saline and relatively moist habitats. They represent a considerable area (∼5-10 km) of the Dry Valley terrestrial ecosystem, an area that is expected to increase with ongoing climate change. The goal of this study was to determine how variation in the environmental conditions of water tracks influences the composition and diversity of microbial communities. We found significant differences in microbial community composition between on- and off-water track samples, and across two distinct locations. Of the tested environmental variables, soil salinity was the best predictor of community composition, with members of the phylum being relatively more abundant at higher salinities and the phylum showing the opposite pattern. There was also a significant, inverse relationship between salinity and bacterial diversity. Our results suggest water track formation significantly alters dry soil microbial communities, likely influencing subsequent ecosystem functioning. We highlight how Dry Valley water tracks could be a useful model system for understanding the potential habitability of transiently wetted environments found on the surface of Mars.
麦克默多干谷的无冰土壤选择了能够应对具有挑战性环境条件的分类群，这些条件包括极端的化学水活度梯度、冻融循环、干燥和太阳辐射状况。干谷土壤的生物复杂性较低，这使其非常适合研究环境和空间对细菌群落结构的影响。水道是南极寒冷干旱土壤中每年都会被水浸湿的栖息地，每年夏天短暂形成，其水分来源包括融雪、地下冰融化以及通过潮解和蒸汽流入盐水的大气沉降。与邻近的干旱土壤相比，水道是盐分高且相对湿润的栖息地。它们占干谷陆地生态系统相当大的面积（约5 - 10公里），预计随着气候变化的持续，这一面积还会增加。本研究的目的是确定水道环境条件的变化如何影响微生物群落的组成和多样性。我们发现水道上和水道外的样本之间以及两个不同地点的微生物群落组成存在显著差异。在测试的环境变量中，土壤盐度是群落组成的最佳预测指标，在较高盐度下， 门的成员相对更为丰富，而 门则呈现相反的模式。盐度与细菌多样性之间也存在显著的负相关关系。我们的结果表明，水道的形成显著改变了干燥土壤中的微生物群落，可能会影响随后的生态系统功能。我们强调了干谷水道如何能够成为一个有用的模型系统，用于理解火星表面短暂湿润环境的潜在宜居性。
