Temporal Microbial Community Dynamics within a Unique Acid Saline Lake

Lake Magic is an extremely acidic, hypersaline lake found in Western Australia, with the highest concentrations of aluminium and silica in the world. Previous studies of Lake Magic diversity have revealed that the lake hosts acid-tolerant and halotolerant bacterial species. However, they have not canvassed microbial population dynamics across flooding, evapo-concentration and desiccation stages. In this study, we used amplicon sequencing and potential function prediction on sediment and salt mat samples. We observed that the bacterial and fungal diversity in Lake Magic is strongly driven by carbon, temperature, pH and salt concentrations at the different stages of the lake. We also saw that the fungal diversity decreased as the environmental conditions became more extreme. In addition, bacterial species were dominant over archaeal species, perhaps because bacteria better tolerate the extreme variation in conditions. On the other hand, bacterial diversity was very dynamic. It was the highest during early flooding stage and decreased during more stressful conditions. We observed in the sediment, an increase in acid-tolerant and halotolerant species involved in various functions, such as sulphur and iron metabolism, i.e. species involved in buffering the external environment. Thus, due to activity within the microbial community, the environmental conditions in the sediment do not change to the same degree as conditions in the salt mat, resulting in the sediment becoming a safe haven for microbes, which are able to thrive during the extreme conditions of the evapo-concentration and desiccation stages.

魔法湖（Lake Magic）是一处位于西澳大利亚的极强酸性高盐湖泊，其水体中铝与硅的浓度位列全球首位。此前针对该湖微生物多样性的研究已证实，魔法湖栖息有耐酸与耐盐的细菌类群。然而过往研究尚未覆盖该湖在洪水泛滥、蒸发浓缩与干燥脱水三个阶段中的微生物种群动态变化。本研究针对沉积物与盐垫样本开展了扩增子测序（amplicon sequencing）与潜在功能预测分析。研究结果显示，在湖泊的不同演化阶段，魔法湖的细菌与真菌多样性主要受碳源含量、温度、pH值及盐浓度的调控。同时观测到，随着环境条件愈发严苛，真菌多样性呈持续下降趋势。此外，细菌类群的丰度显著高于古菌类群，这或许是因为细菌更能耐受环境条件的剧烈波动。与之相对的是，细菌多样性呈现出极强的动态性：在洪水泛滥初期达到峰值，而在环境胁迫加剧的阶段则逐步降低。我们在沉积物样本中发现，参与硫代谢、铁代谢等多种功能的耐酸与耐盐类群丰度有所提升——这类类群可通过代谢活动缓冲外部环境的极端变化。因此，依托微生物群落的代谢活动，沉积物的环境变化幅度远小于盐垫，进而成为微生物的安全庇护所，使其可在蒸发浓缩与干燥脱水的极端环境中存活并繁衍。