Tardigrades, often called water bears, are microscopic organisms legendary for surviving conditions that would obliterate almost any other lifeform. They can withstand temperatures near absolute zero, intense solar radiation, atmospheric pressures six times deeper than the ocean floor, and complete desiccation. The key to this incredible resilience is a physiological state known as anhydrobiosis, where the tardigrade expels up to 95 percent of its body water, slows its metabolism to near zero, and curls into a dried shriveled ball called a tun.
For decades, scientists believed tardigrades relied primarily on trehalose—a protective sugar used by brine shrimp—to survive dehydration. However, recent genomic research revealed that tardigrades rely on a unique class of proteins called Tardigrade Disordered Proteins (TDPs). Unlike standard proteins that possess fixed three-dimensional structures required for function, TDPs are intrinsically disordered proteins (IDPs) that remain flexible and unstructured in liquid water.
As water evaporates from the tardigrade's cells during desiccation, the concentration of IDPs increases rapidly. This change triggers a phase transition known as vitrification, transforming the interior of the cell into an amorphous, glasslike solid state. This biostasis matrix physically traps delicate cellular components, enzymes, and DNA in place, preventing them from unfolding, breaking, or fusing together during dry spells.
Upon reexposure to water, the glass matrix dissolves instantly, returning the proteins to their flexible state and allowing the tardigrade to rehydrate and walk away unharmed within hours.