Over the past 150 million years, the Chilean Atacama Desert has been transformed into one of the most inhospitable landscapes by geophysical changes, which makes it an ideal Mars analog that has been explored for decades. However, a heavy rainfall that occurred in the Atacama in 2017 provides a unique opportunity to study the response of resident extremophiles to rapid environmental change associated with excessive water and salt shock. Here we combine mineral/salt composition measurements, amendment cell culture experiments, and next-generation sequencing analyses to study the variations in salts and microbial communities along a latitudinal aridity gradient of the Atacama Desert. In addition, we examine the reshuffling of Atacama microbiomes after the rainfall event. Analysis of microbial community composition revealed that soils within the southern arid desert were consistently dominated by Actinobacteria, Chloroflexi, Proteobacteria, Firmicutes, Bacteroidetes, Gemmatimonadetes, Planctomycetes, and Acidobacteria, and Verrucomicrobia. Intriguingly, the hyperarid microbial consortia exhibited a similar pattern to the more southern desert. Salts at the shallow subsurface were dissolved and leached down to a deeper layer, challenging indigenous microorganisms with the increasing osmotic stress. Microbial viability was found to change with aridity and rainfall events. This study sheds light on the structure of xerotolerant, halotolerant, and radioresistant microbiomes from the hyperarid northern desert to the less arid southern transition region, as well as their response to changes in water availability.

在过去的 1.5 亿年中，智利阿塔卡马沙漠因地球物理变化而变成了最荒凉的景观之一，这使其成为探索了数十年的理想火星模拟物。然而，2017 年发生在阿塔卡马的暴雨为研究常驻极端微生物对与过度水和盐冲击相关的快速环境变化的反应提供了独特的机会。在这里，我们结合矿物/盐成分测量、修正细胞培养实验和下一代测序分析来研究沿阿塔卡马沙漠纬度干旱梯度的盐和微生物群落的变化。此外，我们研究了降雨事件后阿塔卡马微生物组的重新洗牌。对微生物群落组成的分析表明，南部干旱沙漠内的土壤始终以放线菌、绿曲菌、变形菌、厚壁菌门、拟杆菌门、Gemmatimonadetes、Planctomycetes、酸杆菌门和疣微菌为主。有趣的是，超干旱微生物群落表现出与更南部沙漠相似的模式。浅表层下的盐分被溶解并浸出到更深层，随着渗透压力的增加，对本土微生物提出了挑战。发现微生物活力随干旱和降雨事件而变化。这项研究揭示了从极度干旱的北部沙漠到不太干旱的南部过渡地区的耐旱、耐盐和抗辐射微生物群落的结构，以及它们对水供应变化的反应。