Scientists discover how the water bear survives in such extreme conditions

Pablo Tucker
March 20, 2017

Tardigrades are microscopic animals, otherwise known as water bears, that are known for their freaky characteristics, including the ability to stay dried out, and bisexual mating tendencies. They're also able to withstand complete dehydration - and scientists have finally figured out how they do it. When tardigrades dry out they retract their legs and heads within their cuticle forming a ball like shape known as a "tun". These are called tardigrade-specific intrinsically disordered proteins (TDPs).

They published their findings in the journal Molecular Cell. But scientists have wondered how that was possible, particularly for tardigrades that spend a decade or more as dried-out tuns. These ancient and surprisingly adorable microscopic creatures are capable of withstanding the worst that nature can throw at them, making them a valuable organism for scientific inquiry.

This sugar is found in other types of animals and in plants, and is known to play a role in tolerance to dry conditions.

Tardigrades are small creatures that can only be seen via a microscope.

Tardigrades live on damp moss and algae around the world. Their global travels often get them into trouble, and they have managed to evolve an incredible array of life-saving tricks.

The ultra-tough tardigrades can survive in a number of harsh conditions including the vacuum of space and intense radiation. They can stay in this configuration for up to a decade or longer, and then spring back to life once water is available. Yeasts or brine shrimps have a sugar called trehelose which helps them cope with extreme dryness, but previous studies discovered that water bears do not have trehelose present in their bodies. Furthermore, a look into the creatures' genome has shown that they don't have the gene for the enzyme required to make trehelose. The absence of this compound in tardigrades suggested a different strategy, prompting Thomas Boothby and his team from UNC to figure it out.

The scientists first looked at the various genes that were active in tardigrades under different conditions: unstressed, drying out and frozen. They found a group of proteins known as IDPs or disordered proteins. Unlike other known proteins, TDPs are jelly-like in the water and do not become well-defined three-dimensional structures.

Tardigrades are not the only organisms that can survive drying.

To verify that the TDPs were what gave the tardigrades their unique abilities, the researchers put those genes into yeast and bacteria. "In addition, the proteins that these genes encode can be used to protect other biological material-like bacteria, yeast, and certain enzymes-from desiccation". "The glassy solids that they form are thought to coat desiccation sensitive molecules and physically prevent them from breaking apart, unfolding, or fusing". Boothby cited it as an example of convergent evolution, which is when evolution comes up with similar solutions multiple times. These TDP genes form "non-crystalline amorphous solids (vitrify) upon desiccation, and this vitrified state mirrors their protective capabilities".

The researchers believe that TDPs have a range of potential uses, including protecting crops from drought, and safeguarding medications that usually require cold storage.

More speculatively, these proteins might work in the cells of larger animals, and possibly even humans - the key word being might. Scientists claimed that the proteins found in tardigrades might bring benefits to humans.

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