Crowe, J.H.*; Crowe, L.M.: Anhydrobiosis: A Unique Biological State

Anhydrobiosis (“life without water”) is a wide-spread phenomenon in all major groups of lower organisms. Anhydrobiotic organisms often contain as little as 2% water content. They persist in the dry state for lengthy periods, but when they are returned to water they rapidly rehydrate and resume active metabolism. The mechanisms underlying their ability to survive in this unique state are becoming well understood; virtually all such organisms produce disaccharides at high concentrations, most notably a disaccharide of glucose, trehalose. Trehalose has the ability to stabilize dry membranes and proteins, and, it is emerging, intact cells in the absence of water. This stabilization involves direct interaction between the sugar and hydrophilic residues in biomolecules, an interaction that confers upon the molecule a physical state that resembles the fully hydrated state. This interaction, which has come to be called the “water replacement mechanism” appears to be required for the stabilization. Recently, these findings have been applied to mammalian cells, and it is becoming possible to reduce these cells to a dry state, with excellent recovery, findings that are likely to have applications in clinical medicine. In the dry state, anhydrobiotic organisms show an arrest of metabolism, during which they appear not to age. When the cells are rehydrated, they resume active metabolism, but the life span is not shortened by the length of time spent in anhydrobiosis. The same appears to be true of mammalian cells dried with trehalose. We suggest that such an effective extension of the life span should have profound ecological and philosophical implications.