Tardigrades, tiny, eight-legged creatures that look like alien bears, are tougher than any animal on Earth. These little guys can withstand massive amounts of radiation, about 1,000 times the lethal level for humans, and survive in harsh environments that no other living organism can withstand. A newly discovered species of tardigrades reveals new information on how the tiny animal manages to repair damage to its DNA when exposed to high levels of gamma radiation.
There are about 1,500 known species of tardigrades, known as water bears, but much remains to be known about how the hardy invertebrates protect themselves from radiation. The new study specifically examines one type, named Hypsibius henanensis, uncovering clues behind the molecular mechanism that gives tardigrades their superpowers. The results may inform new ways to help reduce radiation exposure to astronauts in space, and make long-term spaceflight easier for humans.
“The extreme environmental resistance of extremophiles such as tardigrades is a treasure trove of unexplored molecular mechanisms for stress resistance,” said Lei Li, a researcher at the Chinese Academy of Science, and lead author of the paper, in a statement. “Effective research on these mechanisms of radiotolerance … will improve our understanding of cellular survival under extreme conditions.”
The scientists behind the study, published on Thursday at Science, they sequenced the genome of a species of tardigrade, which they had discovered six years ago in the Henan province of China. When exposed to radiation, tardigrade species activate a complex defense system that not only protects their DNA from damage but also repairs any breaks that occur.
A well-known defense mechanism of tardigrades is their ability to enter a deathly hibernation state in which they use all eight of their limbs and curl up into a ball while draining almost all of their internal water (water bears. it would be great Dune’s fictional planet, Arrakis). This state of dehydration, among other defenses, allows them to survive in extreme conditions for decades or perhaps longer, surviving in freezing temperatures, intense radiation, or the confinement of space.
Newly discovered species, Hypsibius henanensishas a total of 14,701 genes, 30% of which are unique to tardigrades. Through a series of experiments, scientists exposed their newly discovered water bears to doses of 200 and 2,000 gray radiation, and, in response, they found that 2,801 genes involved in DNA repair, cell division, and immune responses became active ( “gray” is the standard unit for measuring radiation doses). One of those genes, TRID1, summons a protein (called 53BP1) to damaged areas to help repair double-strand breaks in DNA.
Water bear species also call on other genes to help with their incredible resilience, including DODA1, which produces antioxidant pigments commonly found in bacteria, plants, and fungi to clean up reactive chemicals caused by radiation exposure. Another gene, BCS1, protects tardigrades’ cells from mitochondrial damage.
“Tardigrades are found almost everywhere on Earth from the depths of the ocean to the tops of tall mountains,” Thomas Boothby, an assistant professor in the Department of Biological Sciences at the University of Wyoming, who was not involved in the study, told Gizmodo. “Tardigrades have been found on every continent, including Antarctica. Their ability to tolerate extreme stress may have helped their growth in various biomes. “
In 2021, Boothby sent water bears into space, putting them in extreme conditions aboard the International Space Station to better understand how they endure extreme environments. “It is important to understand how tardigrades live in space and under the conditions of spaceflight as this can help us develop treatments and measures to combat the stress and dysfunction experienced by humans during long-duration flight,” said Boothby. “This is critical to promoting a safe and productive human presence in space and expanding our space economy.”
Tardigrades have long fascinated scientists, especially within the context of spaceflight. Identifying the ways in which tiny creatures survive in the pressure, gravity and high levels of radiation, could help researchers identify ways to protect humans from the effects of long-duration spaceflight.
“Better understanding the unique strategies tardigrades employ to cope with extreme stressors, including those such as the radiation found during spaceflight, will help us understand how to protect humans from these stresses,” Boothby said. “This would be important for safe and productive deep space or long-duration space travel.”
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