Slow-walking water bears, small creatures with eight legs resembling space bears, are stronger than any monster on Earth. These tiny creatures can withstand massive amounts of radiation, nearly 1000 times higher than the lethal level for humans, and survive in harsh environments that no other creature can endure. A recently discovered species of water bear reveals new insights into how this microscopic animal is able to repair the damage to its DNA when exposed to high doses of gamma rays.
There are approximately 1500 known species of water bears, also known as tardigrades, but much is still to be learned about the mechanisms through which these resilient invertebrates protect themselves from radiation. A new study specifically looks at one species named Hypsibius henanensis, to uncover evidence behind the molecular mechanisms that give slow-walking water bears their superpowers. The results could provide new ways to help mitigate the effects of radiation on space travelers in space and facilitate long-term human space missions.
Lee Li, a researcher at the Chinese Academy of Sciences and the lead author of the study, stated: “The extreme environmental resistance of extreme organisms like slow-walking water bears is a treasure trove of unexplored molecular mechanisms for stress resistance.” “Functional research on radiation tolerance mechanisms… will enhance our understanding of cell survival under harsh conditions.”
The scientists behind the study, published on Thursday in Science, sequenced the genome of tardigrade species discovered about six years ago in the Chinese province of Henan. When exposed to radiation, these tardigrade species activate a sophisticated defense system that not only protects their DNA from damage but also repairs any breaks that may occur.
The most famous defense mechanism of slow-walking water bears is their ability to enter a state of suspended animation resembling death, where they retract their eight limbs and curl into a ball, while nearly depleting all their internal water supplies (water bears). This desiccation state allows them, among other defensive measures, to survive in the harshest conditions for decades or even longer, and withstand freezing temperatures, intense radiation, or the vacuum of space.
The recently discovered species Hypsibius henanensis has a total of 14,701 genes, with 30% dedicated to slow-walking water bears. Through a series of experiments, scientists exposed the newly discovered water bears to doses ranging from 200 to 2000 gray of radiation, and found that 2801 genes involved in DNA repair, cell division, and immune responses became active (“gray” is a standard unit for measuring radiation doses). One of these genes, TRID1, calls for a protein (called 53BP1) at damage sites to aid in repairing double-strand breaks in DNA.
Water bear species also invoke other genes to aid in their remarkable resilience, including DODA1, which produces antioxidant pigments typically found in bacteria, plants, and fungi to clean up reactive chemical species resulting from radiation exposure. Another gene, BCS1, protects slow-walking water bear cells from mitochondrial damage.
Thomas Boothby, an assistant professor in the Department of Molecular Biology at the University of Wyoming, who was not involved in the study, told Gizmodo: “Tardigrades are found almost everywhere on Earth, from deep ocean environments to towering mountain peaks.” “Water bears have been found on every continent, including Antarctica. Their ability to withstand extreme pressures may have helped in their extensive colonization of various habitats.”
In 2021, Boothby sent water bears into space to expose them to harsh conditions aboard the International Space Station to better understand their resilience to challenging environments. Boothby stated: “Understanding how water bears survive in space and under spaceflight conditions is important because it can help us develop treatments and countermeasures for the stresses and imbalances that humans face during long space missions.” “This is necessary to enhance safe and productive human presence in space and to expand our space economy.”
Water bears have intrigued scientists for a long time, especially in the context of space travel. Identifying the ways in which these tiny creatures survive in stressful environments, with microgravity and high radiation levels, can help researchers determine ways to protect humans from the effects of long-term space missions.
Boothby said: “A better understanding of the unique strategies employed by slow-walking water bears to deal with extreme pressures, including those like radiation they encounter during space travel, will help us understand how we can protect humans from these pressures.” “This will be important for a safe and productive deep-space environment or long-duration manned space missions.”
