LExEn: Water Stress Dynamics in Anhydrophilic Microbial Mats

生命存在和繁衍的最基本标准是水的存在。极端微生物（嗜热菌、嗜热菌、嗜酸菌、嗜盐菌、嗜碱菌）只要有充足的水，就能在恶劣的环境中繁衍生息。相比之下，无亲水性植物对间歇暴露于液相或气相水，以及细胞成分缺乏单层水覆盖的长期水胁迫都表现出很高的耐受性。在这些条件下，细胞还可能受到极端温度、太阳照射和高盐度的影响。现存的嗜水生物对急性干燥的生存和恢复反应可能为理解其他可能存在各种形式水的行星和卫星（即火星和木卫二）上生命过程的关键控制提供关键信息。这项研究将调查和描述微生物垫的能力，这些被认为是地球上第一个现存生物群落的现代类似物，以干燥的形式在水压力下生存。微生物席在陆地和水生生态系统中无处不在，具有自我维持的特征，并且往往是地球上一些最极端（即温度、光照、营养枯竭）环境中唯一具有功能的生物群落。利用跨学科（生态学、生理学、分子生物学）和合作团队的方法，我们将确定水的可用性和水的短缺如何决定在极端环境下的毡群落的分布、活动和结构，受全球气候梯度的影响，从极地到温带再到热带气候。该研究结果将适用于基于缺水条件下的发展、生存和进化来了解行星生命极限的生态学、分子和生物地球化学研究。

The most fundamental criterion for the existence and proliferation of life is the presence of water. Extremophiles (thermophiles, pychrophiles, barophiles, acidophiles, halophiles, alkalphiles) can colonize and grow actively in environments, albeit harsh ones, as long as water is abundant. In contrast, anhydrophiles, exhibit a high tolerance for both intermittent exposure to liquid or gas-phase-water, and long term water stress where cellular components lack a monolayer coverage of water. Under these conditions cells may also be subjected to extremes of temperature, solar irradiation, and hypersalinity. The survival and recovery responses of extant anhydrophiles to acute desiccation may provides information critical to understanding key controls of life processes on other planets and moons where various forms of water may exist (i.e. Mars and Europa). This study will investigate and characterize the ability of microbial mats, which are believed to be modern day analogs of Earth's first extant biotic communities, to survive water stress in the form of desiccation. Microbial mats are ubiquitous, self-sustaining, features in terrestrial and aquatic ecosystems and are often the only functional biotic communities in some of the most extreme (i.e. temperature, irradiance, nutrient deplete) environments on Earth. Using an interdisciplinary (ecology, physiology, molecular biology) and collaborative team approach, we will determine how water availability and water deficit determine the distribution, activities and structure of mat communities in extreme environments subject to a global climatic gradient, ranging from polar to temperate to tropical clines. The results from this research will be applicable to ecological, molecular and biogeochemical studies aimed at understanding the limit of planetary life based on development, survival and evolution under water-deprived conditions.