water bear
March 17, 2017

Scientists discover how the water bear survives in such extreme conditions

Tardigrades, the odd microscopic animals also referred to as water bears, are known for the puppet-like appearance and capacity to persist despite extreme environments and states

According to a new report in the journal Cell, water bears' uncanny survival ability can be attributed to a unique group of proteins, which the study team called tardigrade-specific intrinsically disordered proteins (TDPs).

The study helps explain why tiny animals are able to withstand harsh radiation, temperatures approaching Absolute Zero, extreme desiccation, and other bizarre circumstances.

"The big takeaway from our study is that tardigrades have evolved unique genes that allow them to survive drying out," study author Thomas Boothby, a postdoctoral fellow at the University of North Carolina, Chapel Hill, said in a statement. "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 Tardigrade's Big Secret

For some time, it was thought that a glucose known as trehelose gave tardigrades the capability to put up with an extreme lack of water. Trehelose is discovered in a quantity of other organisms that can make it through extreme dessiccation, including yeast and some nematode worms.

However, biochemical analyses of tardigrades have discovered trehelose at low amounts or not at all, and genetic analyses have not shown a gene for the enzyme necessary to make this sugar.

"The question has been, 'If tardigrades aren't relying on trehelose to survive desiccation, what do they use instead?'" Boothby said.

To reach their conclusion, the study team looked at which genes were productive in various circumstances: normal, desiccated and frozen. They determined which genes were turned up and expressed at substantial levels when the animals started to dry out. The proteins these genes made, the TDPs, are in a category of proteins known as intrinsically disordered proteins (IDPs). In contrast to most proteins, IDPs do not have fixed three-dimensional framework.

As soon as they found the TDP genes expressed at high amounts during the drying-out period in a single species of tardigrade, the team investigated two other species and saw the same genes. One species, which had the genes excited all the time, was able to survive a desiccation much more quickly than the others.

To confirm these particular TDPs were what offered tardigrades their particular abilities, they put the genes encoding them into yeast and bacteria, and saw these proteins were able to safeguard these other microorganisms.

Boothby said these proteins could have a number of potential uses, including protecting crops from cold and drought.


Image credit: Power and Syred/Science Source