RESUMO
Water is usually thought to be required for the living state, but many organisms can withstand anhydrobiosis When essentially all of their body water has been removed. The mechanisms for survival to this Kind of stress could be similar in microbes, plants and animals. One common feature is the accumulation of sugars by anhydrobiotic organisms. Trehalose, which is one of the most effective saccharides in preventing phase transition events in the lipid bilayer, is accumulated by anhydrobiotic organisms in large amounts. It lowers membrane phase transitions in dry yeast cells, thus preventing imbibitional damages when cells are rehydrated. Yeast cells have a trehalose carrier in the plasma membrane which endows them with the ability to protect both sides of the membrane. Kinetic analysis of the trehalose transport activity in Saccharomyces cerevisiae cells revealed the exoistence of a multicomponent system with a constitutive low-affinity uptake component and a high-affinity H+ - trehalose symporter regulated by glucose repression.