An image of a tardigrade (http://www.mikro-foto.de)

Tardigrades are amazing. These eight-legged micro-organisms – also called water bears – are extremophiles, meaning that while they might live in a mossy corner of your garden, they can also survive in extremely hostile climes: temperatures ranging from near absolute zero to well over 100C and pressures found in the deepest ocean.

This makes them well suited to space, particularly given their high tolerance for cosmic radiation. Chances are that tardigrades are currently living on the moon, deposited there by an Israeli spacecraft as part of a “lunar library” back in 2019 (see Kit Chapman on page 18). That’s not to say that they’re crawling around. Instead, they will have entered a form of suspended animation, adopting a dehydrated spore-like state. But should anyone administer a drop of reviving water, they could well spring back to life.

Tardigrades have a raft of strange biological adaptations, which we’re only beginning to understand. They contain a unique DNA damage suppressor protein that protects their genetic material from the radicals formed when high energy ionising radiation interacts with water. They also contain an unusual amount of intrinsically disordered proteins. (Most proteins, in contrast, adopt a fixed 3D shape.)

Recently, Martin Blackledge and his team at the Institute of Structural Biology in France may have discovered a reason why they produce quite so much disordered protein. When one of these proteins was cooled or dehydrated, it formed a fibrous gel. Intriguingly, this gel protected other, more structured proteins, allowing them to stay folded and functional in the absence of the aqueous conditions normally needed to maintain their shape.

For now, these observations have only been made with proteins isolated from the tardigrades, so how (or if) the protective mechanisms work within living organisms is still a puzzle. But it does provide yet another example of the water bears’ bizarre biochemistry. It also leads to the tantalising idea that the mechanisms used by tardigrades to protect themselves from harsh conditions could be utilised to prolong the shelf-life of protein-based therapeutics.

This piece is from the Witness section of New Humanist spring 2022. Subscribe here.