Secret to Eternal Life Revealed!
What if I told you that the key to a long life was not a healthy diet, exercise and ample amounts of sleep, but rather, to extract almost all the water from your body and enter a shrivelled, low-energy state in which all bodily functions are essentially ceased.
Doesn’t sound right?
Well, in truth, this tactic doesn’t really apply to humans. It is, however, a phenomenal survival strategy employed by tardigrades, a group of eight-legged micro-animals. Also called water bears, they’re just visible to the human eye, at about half the length of an average grain of salt.
Tardigrades have of recent, attained cult status for their extraordinary hardiness. Faced with thirty years locked in a freezer, temperatures up to 150°C, harmful doses of ionising radiation and even being propelled into the vacuum of space, tardigrades come out on top. This incredible survivability means that tardigrades can be found just about anywhere – from your backyard to the bottom of the ocean.
Tardigrades: just add water
Tardigrades owe their near-indestructible nature to a process called anhydrobiosis, from the Greek meaning ‘life without water’. Reminiscent of a grape’s transformation into a raisin, anhydrobiosis involves expelling up to 99% of the normal volume of water found inside a tardigrade. In this ‘tun’ state, tardigrades curl upon themselves, with metabolism lowered to essentially undetectable levels.
With metabolic activity so significantly decreased, the need for water as a reactant disintegrates, and prolonged dry spells are no longer threats to survival. Previously, the secretion of a sugar called trehalose was thought to be crucial to this process. Recent research by Thomas Boothby of the University of North Carolina has all but disproved this theory, as expression of trehalose was found to be extremely low or not expressed at all in dehydrated tardigrades.
Instead, he identified a cluster of genes similar to trehalose, that were unique to tardigrades. The protein products of these genes, called tardigrade-specific intrinsically disordered proteins (TDPs), form a glass-like matrix which surrounds important cellular structures, proteins and DNA, protecting them, kind of like display cases protecting fragile artefacts in a museum. The TDP matrix affixes the molecules, stopping their unfolding, aggregation or dismantling. Upon contact with water, the tardigrades are resurrected from their tun state as the matrix dissolves, and they return to business as usual – reproducing and running rife in practically any environment they please.
One small step for tardigrades, one giant leap for mankind
Scientific fascination with tardigrades extends beyond torturing them and subjecting them to a series of traumatic conditions. Tardigrade literally means ‘slow steppers’, and ironically, various applications based on the anhydrobiotic model of tardigrades might produce rapid advances in agriculture, healthcare and even space exploration.
For example, the same group of researchers found that transferring the TDP gene cluster into certain bacteria has conferred them increased tolerance to periods without water, like tardigrades. Introducing these transformed bacteria and their new genome into plants could produce highly drought-resistant crops, that could be irrigated in fertile soil, then transferred to land once too arid for any vegetation to survive.
Tardigrades also show promise to transform the access of remote populations to crucial medicines. For example, many vaccines need to remain refrigerated throughout all stages of their transport, creating a significant logistical constraint which hikes up the cost of their delivery. Boothby hopes that principles of dehydration modelled on tardigrades could be applied to these vaccines, allowing them to be stored at room temperature and increasing their availability in more far-flung regions.
As for space travel? Astrobiologist Lukasz Kaczmarek of the Adam Mickiewicz University has found that anhydrobiosis may not just suspend metabolism in tardigrades, but also ageing. Remarkably, it appears that tardigrades emerge from decade-long dehydration with essentially the same biological age as when they entered into this state. Through this ‘Sleeping Beauty Model’, Kaczmarek foresees a possibility to ‘time-freeze’ astronauts that are sent to explore planets many light years away, without their biological death clock hanging over them.
As unique creatures with an array of biological quirks, tardigrades are often viewed merely as a novelty, or an interesting scientific enigma. However, in the wake of these discoveries, the emerging secrets of the tardigrade may herald the transformation of human life as we know it. From near-immortality to interplanetary travel, a new frontier of tardigrade technology seems to be on the horizon.