Then and Now: Sandeep Eswarappa’s Tardigrade Research Blasts Off into Space

More than a decade ago, Sandeep Eswarappa, then a postdoctoral researcher at the Cleveland Clinic, fell in love with tardigrades, often called water bears, when he learned that they are among the hardiest known animals. So, when he set up his lab at the Indian Institute of Science (IISc) in 2015, he and his team scoured the campus looking for these eight-legged, pinhead-sized creatures.

Not only did the researchers discover a new species of tardigrade lurking in their own backyard, but they also found that the creatures survived and fluoresced under high doses of ultraviolet (UV) light.¹ Extracting and applying the fluorescent paste from these animals to other tardigrade species or nematode worms protected them from lethal doses of UV rays. “It was like applying a sunscreen agent on the skin,” Eswarappa told The Scientist in 2021.

For The Scientist’s 40^th anniversary, we reached out to Eswarappa again to see what paths his scientific work has taken over the last five years. Encouraged by their initial finding of tardigrades’ UV resistance, Eswarappa and his team reached out to the Indian Space Research Organisation (ISRO), which culminated in the tardigrades making it all the way to the International Space Station (ISS) and back. Studying these space-returned tardigrades could offer molecular insights into ways to confer protection in harsh conditions, advancing fundamental genetics knowledge and offering potential applications in food and medicine preservation in space-like environments.

Tardigrades’ Journey from an Institutional Campus to Space

Eswarappa’s 2020 study describing the tardigrade species’ UV resistance garnered his team a significant spotlight. “For us, it just was a fun story we published,” said Eswarappa. “We never thought that it [would] attract so much media attention at that time.”

This publicity only strengthened his resolve to better understand the creatures’ stress tolerance. He approached ISRO, which granted him funding to study the tardigrades’ resistance to stress. He also set up collaborations at the physics department at IISc to house the creatures at extremely low temperatures and pressure and to expose them to significantly higher radiation than they would encounter on Earth.

When the water bears survived all these stressful environments, Eswarappa knew his team was onto something. Last year, armed with this data, he reached out to ISRO, where experts were preparing for the Axiom-4 mission, with intense discussions about what scientific experiments astronauts on the ISS would conduct next. “They selected our experiment to perform, and we sent our candidates to ISS,” said Eswarappa.

So, the researchers prepared their tardigrades for the long journey. They dehydrated the creatures, coaxing them to enter a dormant “tun” state, where tardigrades reduce their metabolism to nearly zero.² In this state, the tardigrades retract their legs, dry out, and curl themselves into a ball that can survive for years without food or water. “This is their natural mechanism to protect themselves,” Eswarappa explained.

Once the tardigrades made it to the ISS, Eswarappa and his team watched a live stream of astronaut Shubhanshu Shukla adding water to the creatures. “After one hour he observed the [tardigrades] under the microscope, [and] we were all kind of scared. [We thought], ‘What if they don't show any activity. What if they're all dead?’” recalled Eswarappa.

But all was well. “It was very fulfilling to see the real-time moment of tardigrades at ISS. We were watching from our laptop in the lab, so that was very, very memorable,” said Eswarappa.

Decoding Tools that Help Tardigrades Survive Extreme Environments

Once the tardigrades returned to Earth from their space trip, Eswarappa and his team set out to investigate how space travel had changed them. The team is in the process of comparing the reproduction and gene activity of these tardigrades with those that remained on Earth, hoping to obtain clues into their space-tolerance properties.

Eswarappa noted that with several fundamental facts about this tardigrade species established, including their extreme survival properties, he now hopes to understand the molecular mechanisms that confer their survival advantage. “How do they protect themselves from such strong radiation? Do they have a strong DNA repair mechanism? Do they have DNA-protective proteins or molecules?” asked Eswarappa. “We plan to go to the molecular level from now on, and we are planning some experiments in that direction.”

Looking back, Eswarappa never thought this project—which he started simply for fun—would reach this juncture. “When I conceived the idea of working with tardigrades, I never thought that it [would] be a serious science study. Forget about space, [I never thought] it will go to any publication,” he said. “It’s amazing that that led to our journey to the space station and back here.”