Water Bears’ DNA Makes Them Practically Indestructible

Tanaka S, Sagara H, Kunieda.
Tanaka S, Sagara H, Kunieda. / Tanaka S, Sagara H, Kunieda.

Burn it. Freeze it. Chuck it into space. Water bear don’t care. The water bear, also known as the tardigrade or moss piglet, is one of the weirdest and toughest creatures on the planet. Now new research published in the journal Nature Communications suggests we might someday be able to borrow its resilience to use in our own flimsy, floppy bodies.

Tardigrades are extremophiles—that is, they can keep trucking in unbelievably hostile environments, from scorching deserts to the vacuum of space. This astonishing near-indestructibility has, understandably, made them especially appealing to scientists, who have been working for years to pick apart the genetic basis of the microscopic creatures’ badassery. But the more we learn about these creatures, the weirder they seem to get.

In 2015, a group of researchers reported one possible source of the tardigrade’s toughness: burglary. While looking at the genome of the tardigrade species Hypsibius dujardini, the team said they found all kinds of genes that belonged to other organisms, including fungi and bacteria. Horizontal gene transfer (when one organism swipes genes from another) is not unheard of, but H. dujardini appeared to have taken it to the next level, with a full 17 percent of its genes yoinked from other species.

Even for the moss piglet, this seemed kind of, well, extreme. When other scientists tried to replicate the original team’s results, they found only tiny amounts of horizontal gene transfer—about 1 or 2 percent. They said the original team’s samples had likely been contaminated. #tardigate ensued. The tardigrade remained a tiny, scrappy enigma.

Scientists kept at it. The latest research, published today, may have cracked some of the mystery. Researchers in Japan examined the genome of an especially hardy water bear named Ramazzottius varieornatus. In comparing the tardigrade’s genetic codes with those of worms and flies, they found way more genes related to surviving stressful conditions.

In the video below, by researcher Daiki D. Horikawa, you can see R. varieornatus encounter one stressful condition: a lack of water. The tardigrade dries out and shrinks up, seemingly dead. But it isn't. Given a drop of water, it plumps right up, stretches its little legs, and begins to move around.

Then the team took the study to the next level. They found a resilience-boosting protein they called Damage suppressor (Dsup) that appears to be completely unique to tardigrades. Then they inserted Dsup into human cells, which then became more resistant to damage from x-ray radiation.

There’s a lot here to get excited about, says Sujai Kumar, a genome informatician at the University of Edinburgh and a co-author on the #tardigate-triggering study. “The Japanese team's genome sequencing methodology is exemplary,” he tells mental_floss. The depth and breadth of their investigation have yielded a huge quantity of information that will continue to help other researchers unravel the tardigrade mystery.

Even better, Kumar says, were the Japanese researchers’ “really cool” studies in human cells. “Although not quite at the level of a superheroine origin story,” he says, “this is a great example of a gene from an extremotolerant species conferring a 'super power' to a human cell, and is an exciting finding.”

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