Nature is home to numerous wonderful organisms, each blessed with a set of unique features that ensures their survival against harsh elements. One prime example is the water bear, an eight-limbed, water-dwelling micro-animal that inhabits a range of diverse ecosystems, from mountaintops to tropical forests and even in the depths of oceans. Also known as tardigrades, these microscopic invertebrates are known for their ability to survive the most extreme natural conditions, including extended desiccation, incredibly low and high temperatures of around −272.222 °C (−458.000 °F) and 149 °C (or 300 °F), near-100 percent fluid loss, powerful ionizing radiation and even possibly the vacuum present in outer space.
Discovered back in 1773, tardigrades have been the subject of numerous scientific research. A recent project, for instance, has revealed that these tiny organisms turn into glass to protect themselves against extreme desiccation. When faced with severe natural conditions, they produce a particular type of “bioglass” that in turn preserves the essential molecules and proteins present inside, until they are restored back to life. According to the scientists, the discovery could pave the way for special drought-resistant crops as well as longer-lasting vaccines.
A few months back, a team, led by Juan de Pablo from the University of Chicago, shed more light on the type of glass produced internally by water bears to combat dehydration. While the scientists are still working to unravel the exact mechanism behind the process, their research has revealed that the glass ensures the organisms’ survival even when they have lost nearly 97-percent of body water. What is more, this new type of glass could help enhance the efficiency of a variety of electronic devices, including optical fibers, light-emitting diodes and photovoltaic cells. Speaking about the breakthough, de Pablo said:
When you remove the water, they very quickly coat themselves in large amounts of glassy molecules. That’s how they stay in this state of suspended animation. We have been able to generate new glasses with new and unknown properties through this combination of experiment, theory, and computation.
As part of yet another research, biologist Thomas Boothby and his team from the University of North Carolina at Chapel Hill have come one step closer to untangling the mysteries surrounding these microscopic organisms. For the first time ever, the scientists have managed to identify the tardigrade-specific genes responsible for the production of the bioglass. The genes, according to the researchers, code specific types of proteins known as intrisically disordered proteins (IDPs), which in turn create the highly-specialized glass.
The research, recently presented at the American Society for Cell Biology, focuses on the intrinsically disordered proteins. As their name suggests, these proteins are incredibly flexible and shapeless during normal conditions. With the coming of extremely dryness, however, they get produced in larger amounts, following which they rearrange themselves into solid bioglass. These glass-like structures envelope essential cellular components, molecules and other proteins, thus preventing from falling apart during severe desiccation.
When exposed to water again, the glass melts, restoring the organisms back to life. For the research, the team used genetic engineering to lower the levels of IDPs present in the water bears. As expected, the organisms exhibited reduced capacity to withstand dehydration, but remained fairly uneffected by other harsh elements, such as extreme cold. This indicates that the creatures possess different features for survival against different types of extreme stresses and conditions. To further test their efficacy, the scientists injected these proteins into human epithelial cells (or HeLa). They explained:
[W]e found that when expressed in HeLa cells, desiccation induced a relocalization of these IDPs, which under hydrated conditions appeared diffuse throughout cells’ cytoplasm, to specific cytoplasmic organelles – suggesting that individual proteins are targeted to different parts of cells, perhaps protecting specific cellular compartments. We found in vitro these proteins formed biological glasses when dried.
What is more, the team genetically programmed certain species of yeast and bacteria to generate IDPs. When placed under prolonged desiccation, these microscopic organisms were found to be more capable of surviving the extreme dry conditions. Once fully studied, the mechanism could help develop healthy, drought-tolerant crops. As Boothby has pointed out, it could also be used to prevent certain enzymes from drying out, thus reducing the amount of money spent on storing vaccines. The team added:
[A]round 80 percent of the costs of vaccination programs in developing countries comes from having to keep vaccines cold… The enzyme [lactate dehydrogenase] loses its activity when dried out. But when the researchers mixed the enzyme with the glass proteins before drying, the enzyme bounced back to normal activity when rehydrated. Mixing in water bear proteins after drying didn’t help, indicating that the glass proteins need to encase other molecules to protect them.