WHY won't water bears die? Extreme temperatures. Radiation. Even the vacuum of space. Now research has revealed what makes the microscopic creatures indestructible.
They rely on good looks for survival.
The water bear - otherwise known as a tardigrade - is built like a tank.
Its survival abilities can only be compared to that of fictional super heroes.
But a study published in the science journal Molecular Cell today reveals all.
It's long been suggested the chubby little critter could activate a sugar called trehalose. This reinforces cell walls to protect them from damage.
But it seems that idea was barking up the wrong tree.
Turns out, the water bear turns itself into glass.
The study discovered the new protein after observing tardigrades didn't use trehalose as previously thought. The water bear's only recorded 2 per cent of their body weight as trehalose, while other creatures that use its reinforcing properties - such as brine shrimp - measured as much as 20 per cent.
But dried-out water bears did have another protein.
And this protein is odd.
The researchers say the microscopic creature floods its body with the protein to replace water.
Once crystallised, it essentially turns the water bear into a glass figurine. This buttresses its body, protecting and preserving its cell structure at the same time.
It can remain that way - in suspended animation - for up to 30 years.
Named tardigrade proteins, they don't have the orderly 3D amino-acid structures of other proteins. They're messy. Floppy.
But they somehow manage to encapsulate cells in a protective coating.
Later, when the water bear is wet again, the glass protein matrix melts away - leaving the cells intact.
Biologist and study co-author Thomas Boothby of University of North Carolina says: "It's a really interesting question about how a protein without a defined three-dimensional structure can actually carry out its function in a cell."
The discovery of the tardigrade protein's properties was tested by putting them inside yeast.
The results were similar. The yeast became much more tolerant to being dried out.
In fact, researchers say the water bear's magic pill can boost the resilience of other organisms by up to 100 times.
This has enormous potential use, the researchers say.
Spliced into plants, it could be used to make crops far more drought tolerant.
If introduced to delicate vaccines, these may no longer need careful refrigeration.
Surviving dissication isn't the water bear's only amazing survival characteristic.
Japanese researchers last year identified a radiation shield protecting their DNA.
They say the damage suppressor protein can be used to boost human resistance to X-ray radiation by 40 per cent.
The study also uncovered the water bear genome produced 16 antioxidant enzymes, where most animals make just 10, and contain for versions of DNA repair genes were most others only have one.
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