In the moss-covered slopes of China’s Funiu Mountain, scientists have discovered a new species of tardigrade that may hold the key to protecting humans from the harmful effects of radiation.
The tiny eight-legged creatures, known as water bears, are renowned for their ability to survive extreme conditions that would be lethal to most life forms. Now, a team of researchers has identified the genetic mechanisms that allow these microorganisms to withstand radiation levels nearly 1,000 times higher than the lethal dose for humans.
A new tardigrade
Despite their small size, tardigrades have a unique appearance. They resemble a squishy pillow with eight legs, four on each side, with finger-like little claws at the end of each leg. Their endearing looks have earned them the nickname “moss piglets.”
Tardigrades are the ultimate survivors. They can survive extreme temperatures, dehydration, and even the vacuum of space by entering a state called cryptobiosis. They can remain in this state for years, waiting for the environment to become favorable again. Once conditions improve, they rehydrate and resume their normal activities.
Around six years ago, Lingqiang Zhang, a molecular and cellular biologist at the Beijing Institute of Lifeomics, and his colleagues collected moss samples from Funiu Mountain in China’s Henan province. Under the microscope, they identified a new species of tardigrade, which they named Hypsibius henanensis. Genome sequencing revealed that this species has 14,701 genes, 30% of which are unique to tardigrades.
When exposed to high doses of gamma radiation — 200 and 2,000 grays — the researchers observed that 2,801 genes became more active. These genes are involved in DNA repair, cell division, and immune responses.
“It’s like when in wartime, when factories are refitted to just make munitions,” Bob Goldstein, a cell biologist at the University of North Carolina at Chapel Hill, told Nature. “We’re fascinated by how an organism would change their gene expression to a point where they’re making that much transcript for specific genes.”
One gene, called TRID1, encodes a protein that helps repair double-strand breaks in DNA by recruiting specialized proteins to the damage sites. Another gene, DODA1, appears to have been acquired from bacteria through horizontal gene transfer. DODA1 enables the tardigrade to produce antioxidant pigments called betalains, which can neutralize harmful reactive chemicals generated by radiation.
Implications for Human Health and Space Exploration
The researchers tested one of the tardigrade’s betalains on human cells and found that it significantly improved their survival rate after radiation exposure. This could become a big deal if the tardigrade’s compounds can be converted into a therapy, which could particularly benefit cancer patients undergoing chemotherapy.
“This discovery may help improve the stress tolerance of human cells, benefiting patients undergoing radiation therapy,” Zhang told Nature.
There are over 1,000 species of tardigrades, and they live in almost every environment that you can think of, from deep oceans to mountaintops. Their ability to withstand such stresses has made them scientists’ pet favorite when it comes to space exploration.
“Better understanding the unique strategies mounted by tardigrades to cope with extreme stresses, including those such as radiation that are experienced during spaceflight, will help us understand how we might safeguard humans against these stresses,” Thomas Boothby, an assistant professor at the University of Wyoming who was not involved in the study, told Gizmodo. “This would be important for safe and productive deep space or long-term manned space missions.”
Exploiting tardigrade resilience could have far-reaching applications, from protecting astronauts during long-duration space missions to developing new treatments for patients undergoing radiation therapy. It might also aid in cleaning up nuclear pollution and improving the shelf life of medicines.
“Extreme environmental resistance of extremophiles such as tardigrades is a treasure trove of unexplored molecular mechanisms of stress resistance,” wrote Lei Li, a researcher at the Chinese Academy of Sciences and lead author of the study. “Functional research on these radiotolerance mechanisms… will further broaden our understanding of cellular survival under extreme conditions.”
The findings appeared in the journal Science.
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