Desiccation is the removal of water from a biological system. Usually this is accomplished by exposure to dry heat. Most biological systems are adversely affected by the loss of water. Microorganisms are no exception to this, except for those that have evolved defensive measures to escape the loss of viability typically associated with water loss.

Desiccation also results from the freezing of water, such as in the polar regions on Earth. Water is present at these regions, but is unavailable.

Microorganisms depend on water for their structure and function. Cell membranes are organized with the water-loving portions of the membrane lipids positioned towards the exterior and the water-hating portions pointing inward. The loss of water can throw this structure into disarray. Furthermore, the interior of microorganisms such as