Why are “water bears” indestructible? Scientists think they have found an answer

(CNN) — Tardigrades, also known as water bears, typically live in some of the most challenging environments on Earth. These microscopic animals are so unusual that they were transported to the International Space Station for research.

When the going gets tough, these surprisingly resilient creatures are able to enter a form of suspended animation, called a “tun state,” for decades. Now, researchers say they've discovered the mysterious mechanism that activates survival mode in animals, and the work could have implications for humans, according to a new study.

The microscopic tardigrade, or water bear, is shown in its active state. Blickwinkel/Alamy photo album

Under stress in extreme cold or other extreme environmental conditions, tardigrades' bodies produce unstable oxygen free radicals and an unpaired electron, also known as reactive oxygen species, that can damage the body's proteins and DNA if they accumulate in excess. (Yes, this oxidative stress is the same physiological event that humans experience cWhen they are stressed And why health experts suggest eating plenty of blueberries and other antioxidant foods when you're having a tough week at work.

The survival mechanism is activated when cysteine, one of the amino acids that make up proteins in the body, comes into contact with these oxygen free radicals and is oxidized, according to the researchers. This process is the signal that lets the tardigrade know that it is time to move into protection mode. Free radicals become, so to speak, the hammer with which the fire alarm glass is broken.

The results were published on January 17 in the journal One plus.

This discovery could eventually help develop materials that can respond to extreme conditions like deep space or treatments that can disarm cancer cells, said Amanda Smithers, lead author of the study and a postdoctoral researcher at Dana-Farber Cancer Institute and Harvard Medical School. In Boston.

The illustration shows the tardigrade in its inactive state when it goes into protective “control” mode against stressors. RoyaltyStockPhoto/RF Scientific Image Library/Getty Images

“Eureka moment”

in Unforgiving habitats As diverse as Antarctica, mountain peaks and deep-sea vents, tardigrades encounter Extreme temperature Or drought will retract their eight arms and reduce the amount of water they store.

Tardigrades shrink to a quarter of their normal size. The invertebrates are usually fairly linear and thick in appearance, transform into protective dry balls in their toon state, and lurk in environments that would kill most other life forms.

Smithers and researchers at the University of North Carolina at Chapel Hill and Marshall University in Huntington, West Virginia, began looking into this phenomenon thanks to a growing body of literature suggesting that cysteine ​​was involved in initiating the morphogenesis process, Smithers said.

“When we looked at the list of all these crazy conditions that tardigrades can live in (space, vacuum, high salt concentration, like when the ocean starts to evaporate), the one thing that really connected all of these things was the species,” Smithers said. Reactive oxygen. “It was actually a eureka moment.”

Over the past decade, researchers have begun to realize that reactive oxygen species — free radicals that were once considered quite a “problem,” Smithers said — may be “really important for our bodies to function and be able to adapt to different stresses.”

Previous studies said that instead of free radicals helping to initiate the adjustment process as protection against stressors, tardigrades protected themselves from free radicals. Smithers and his colleagues found that the body's production of free radicals is instead part of the process of helping the tardigrade protect itself by curling up into a hard ball resistant to extreme heat, cold, or other environmental factors.

“We came up with the idea that maybe these species are signaling the tardigrades to go into their seizure mode,” he said.

First, an informal experience

Before creating the longer process used in the study, Smithers invited a student to help him conduct a quick experiment to test his initial hypothesis about reactive oxygen species and their role in initiating ton formation.

Microscopic invertebrates live in environments as diverse as Antarctica, deep-sea vents, mountaintops, and tropical forests. Two active water bears are on display. Amanda Smithers

Smithers asked the student to go to the pharmacy and buy peroxide, a common free radical. While Smithers watched the experiment via FaceTime, the student dropped some peroxide on a water bear to see what would happen.

“All of a sudden, he started stiffening up. His paws started going into his body. He started shrinking. It became the perfect tone that we knew what to expect,” Smithers said.

How could the secret of tardigrades help humans?

Research is not only done to find out how animals cope in the harsh environments in which they often live. Smithers said the findings could help researchers develop materials that can respond to extreme conditions, such as engineered firefighter gear that can create a protective layer when conditions get too harsh, or develop better chemical treatments to destroy malignant cells by disabling the protective measures they create. Cancer cells are difficult to kill.

This finding excites Dr. William R. Miller, a research assistant professor at Baker University in Baldwin City, Kansas. Miller, who has studied and written about tardigrades, was not involved in this research.

“It would be great to find other ways in which these mechanisms can be used to control cancer,” Miller said.

Miller commented that he was impressed by Smithers' ability to imagine ways in which tardigrade research could be implemented in cancer research and other fields. He said it takes “another level of mind and thought to find the transfer of one technology or set of things to another technology that is very far away. “We need more of that.”

Jenna Schnewer A freelance writer, editor, and audio producer based in Anchorage, Alaska, who focuses (primarily) on science, art, and travel.