Tardigrades, or water bears, are some of the smallest and toughest animals we have ever discovered. They are even able to survive in space.
Researchers from the University of Tokyo have discovered a new mechanism explaining how tardigrades are able to survive extreme dehydration.
A variety of tardigrade species, also known as water bears, are capable of surviving in environments hostile to most other life forms. Researchers describe a new mechanism explaining tardigrades’ ability to endure extreme dehydration without dying in their study. The researchers studied proteins involved in forming a gel during cellular dehydration. Cells would otherwise be killed by mechanical stress, but this gel supports and protects them. Human cultured cells and insect cells have also shown limited functionality of these proteins.
Despite their small size, tardigrades often attract attention. The public has been amazed at their ability to survive situations that would kill most organisms. Humans might be able to become more resilient to extreme temperatures, pressures, and even dehydration if we decode their secrets. While this is only science fiction, for now, researchers are also fascinated by the microscopic creatures and are seeking to understand their robustness, as this could lead to other benefits in the future.
Some tardigrades can survive without water for decades, despite the water being essential to all life. Associate Professor Takekazu Kunieda, head of the Department of Biological Sciences at the University of Tokyo, explained that the key is how their cells cope with dehydration’s stress. “It’s thought that as water leaves a cell, some kind of protein must help the cell maintain physical strength to avoid collapsing in on itself.” The researchers tested several different kinds and found that tardigrade cells are protected against dehydration by cytoplasmic-abundant heat-soluble (CAHS) proteins.
CAHS proteins are capable of sensing dehydration in the cells they encapsulate, which is when they take action. As CAHS proteins dry out, they form gel-like filaments which support the shape of the cells as they lose their water. This process is reversible, which means the filaments recede slowly as the tardigrade cells become hydrated again, without undue stress. However, even when isolated from tardigrade cells, the proteins showed the same kind of action.
The lab’s graduate student, Akihiro Tanaka, described some of the challenges he faced in trying to understand how CAHS proteins behave in insects and humans. Before they could visualize the proteins, the scientists had to stain them so that they would appear under their microscopes. Staining normally requires solutions containing water, which obviously complicates experiments that aim to control the concentration of water. Due to this, methanol was chosen as the solution.
It is possible that dry preservation of cells and organisms will have a wide range of applications in the future. Researchers hope that their new knowledge will help them preserve cell materials and biomolecules in a dry state better. In this way, materials used for research, medicines with short expiration dates, or whole organs for transplantation might have a longer shelf life.
The first step toward achieving this goal is to isolate and activate these unique proteins. More than 300 other proteins will be analyzed by Kunieda and his team, some of which may play a role in these bears’ life-saving abilities.
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