tter grades you know them you love them and you couldn't kill one even if you tried and believe me we have tried over Decades of research we have subjected tardigrades to some of the most extreme conditions imaginable they've been shot from a gun at 900 m/s they've survived the coldest temperatures in the universe being boiled at 150° Centigrade subjected to pressures of 400 times that of normal atmospheric pressure they've been stored in a freezer for over 30 years and then finally fin were left in space and blasted with Cosmic radiation and none of this seems to have phased them in the slightest the underlying reason for why these adorable microorganisms are just such Elite survivalists comes inherent to their biology but as of a study published last month we finally think we know how they're doing it and if the lessons learned from it can be adapted into our own biology they could stop us getting diseases like cancer survive on off-world habitats with weak or no atmosphere like the moon or Mars enable us to travel into deep space through the universe's high levels of radiation and maybe even let us survive cryosleep so we can live out our true sci-fi future fantasies tardigrades may just be the best survivors on the planet but of course the story of how we came to know these microscopic super survivors is just as fascinating as the extremes that they've endured in 1773 German biologist Johan goz peered into a microscope and saw something strange unlike other microscopic animals he studied which preferred to swim wriggle or beat their all like fella to move around he saw a small wrinkly creature making its way across a micro algae using eight Stumpy legs each tipped with tiny claws with a deep sigh of German reverence and foresight into the hearts and minds of an Internet generation 300 years in the future he announced he had just discovered the water bear a name that instantly indoctrinated this creature into a place in all of our hearts a creature so tiny it fits in between the grooves of a fingerprint it wasn't until 3 years later in an act of unusually poor branding for Italians that Abott and biologist Lazaro fanari gave them the more official tardigrada meaning slow Walker based on their unusual choice of moving around in 1842 Tarter grades again caught the attention of science as Louie deer a French zoologist and agronomist began to run experiments where he observed tardigrades being actively adorable in their natural environments moist mosses and lyans what was strange was when he accidentally underwatered the Tarter grad's habitat one day and it dried out under the warmth of the microscope lamp he watched as the tardigrades actively slowed to a crawl as if moving in suspended animation he came back a few hours later and swore that his test subjects had disappeared panning around frantically the micro environment he realized it was now covered instead in small dark debris The Remains he assumed of the tardigrades repeating the experimental conditions as the second sample dried out deer observed his tardigrade family slowly transform from inquisitive water bears into shriveled desiccated balls a phrase you should never utter on the internet in this state later called a ton all movement stopped the creatures seemed utterly dead but when doer left a sample to rehydrate in the room something remarkable happened the tardigrades slowly stirred back to life something impossible for normal organisms or cells as extreme dehydration leads to cell collapse breaking the internal Machinery of a cell usually Beyond repair doer however found that he could keep his tardra suspended for between a few days up to several months and could expose them to hot cold high pressure and still reliably they would pop back to life as if nothing ever happened in his thesis Memoir on the organization and natural relationships of tardigrades which sounds like a political Manifesto for these tiny survivalists deer documents one of the first ever cases of cryptobiosis crypto meaning hidden and biosis meaning life a physiological state in which metabolic activity is reduced to an almost undetectable level the world's smallest zombie jerky in this state at gr's metabolism Slows To as low as 0. 01% of its normal rate that's 10,000 times slower to put that in perspective if you usually consume 2,000 calories a day this would represent a drop in your caloric intake to 0. 2 calories you would be capable of surviving on about 1 tenth of a McDonald's fry or about 10 grains of rice per day but the question is shriveling into a ton like some sort of microscopic raisin is impressive in itself but it hardly explains how tardigrades can brush off lethal doses of radiation extreme dehydration or the cellular damage that should arise from Ice Crystals forming within their cells what is actually happening Beyond this simple transformation before we answer that question though I have to quickly thank today's sponsor who is preventing me 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to the video in a 2017 study led by Thomas boothby and his team at the University of North Carolina researchers were determined to get to the bottom of how Tarter grades were surviving in extreme temperatures and conditions that would prove fatal to basically all other forms of life on the planet when we expose organisms to extreme environments like the vacuum of space or Ultra cold temperatures water becomes a major problem water makes up 60 to 80% of most organisms and it is the solvent that enables life's Machinery to function but at temperatures below freezing water turns into a formidable enemy as water freezes to ice it expands by about 9% if ice forms inside of a cell it can rupture the cell's membrane or damage internal cellular structures low temperatures can also make the lipid by layer of the cell membrane brittle and cause breaks in DNA as a result Nature has evolved to avoid freezing at all costs and while we can freeze and Thor some individual cells such as reproductive cells like eggs and sperm with minimal damage to the disappointment of all of the Walt Disney's body is secretly Frozen beneath Disneyland conspiracy theorists unfortunately freezing entire bodies still poses significant challenges except in some very rare examples some species have evolved antifreeze like properties to survive the slightly less adorable Antarctic toothfish the snow flea and the wood frog use natural antifreeze compounds to lower the freezing point of their bodily fluids to protect internal cellular structures but these adaptations are limited to temperatures just below freezing far from the extremes and this is where tardigrades really stand apart they didn't just survive slightly Sub-Zero conditions or mild dehyd ation in their ton State these microscopic creatures can survive down to temperatures as low as - 270° c a range so cold that Atomic movement almost entirely halts researchers had previously found that as a tardigrade encounters extreme conditions it begins preemptively to slowly dehydrate itself this process isn't instantaneous by any means it can take several hours but it means that the tardigrade can lose 97% of its total water content this significantly reduces the likelihood of ice crystals damaging cells while also Contracting the grd's body to minimize its surface area and exposure to the Hazardous environment but that doesn't explain how the tardigrade doesn't then succumb to the cell collapse of extreme dehydration boothby and his team were intrigued by the idea that a hidden mechanism was slowly allowing these tiny water bears to cheat death they set out to solve this puzzle starting by examining what happens at the molecular level when tardigrades enter their ton state to do this they looked at the proteins being produced in these extreme conditions and what they found was unexpected rather than typical proteins that fold neatly into specific shapes they discovered a class of proteins with no fixed structure free floating like loose threads inside the cell in normal conditions these proteins seemed reasonably unremarkable but under stress when the tardigrade was drying out they slowly started to transform and solidify forming a glass-like matrix inside the tardra cells here the best description I can come up with is it's like dipping hand Solo in carbonite protein damage occurs normally within a cell due to denaturing either when the cell is too hot too cold or too mechanically stressed protein structures break and then don't go back together this is what's happening for example when you fry an egg the nicely coiled natural proteins break and unravel so are no longer ordered and transparent and instead start to SC at light in all directions appearing white these newly discovered proteins in the tardigrade cell now called tardigrade specific intrinsicly disordered proteins or tdps which I find particularly catchy this process combined with a then later discovered cytoplasmic abundant heat soluble or cach protein discovered later in 2021 formed a further protective gel-like Network preventing the mechanical stress of dehydration or extreme temperature from breaking the general proteins within tardigrade cells in order to prove their theory that this is how the Todd grade was gleaning some level of extreme environment resistance boothby and his team wanted to see if tdps were truly the key to tardigrade survival boothby and his team took the genes responsible for producing these proteins and inserted them into other organisms specifically yeast and bacteria these organisms which normally cannot survive desiccation was suddenly able to endure extreme drying just like the Tarter grades the tdps worked the same way in these foreign organisms creating that protective glass-like shield and proving that these proteins were a key component of the tardigrades Arsenal but that wasn't the end of the story while tdps Safeguard cellular structures they cannot prevent the ionizing effect of radiation from breaking DNA strands the median lethal dose or ld50 is approximately 0.
6 to 0. 9 gray for mice it's about 2. 5 to 4.
