Abstract: Life, or at least life as we know it, depends on water. Water is the solvent in which the cytoplasmic enzymatic machinery functions. However, life on Earth has adapted to a variety of environments with low water activity. Availability of water can be reduced both by the presence of salts and other solutes in the cells' surroundings (‘osmotic water stress’) and by drought (‘matric water stress’). As biological membranes are permeable to water, intracellular water activity equals that of the outside medium. A water activity of 0.60–0.62...
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Topics: 
Environmental chemistry