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.
