Dehydrate to survive!

What sort of creatures might be able to survive in space? Alan Tunnacliffe explains it might be those who can live without water...
03 December 2013

Interview with 

Alan Tunnacliffe, Chemical Engineering and Biotechnology, University of Cambridge


Our next guest is Alan Tunnacliffe who is from Chemical Engineering and Some yeastBiotechnology at the University of Cambridge. He works actually on things that can survive in really quite bizarre environments,  including space.

Alan - Well, we work on organisms, creatures, that can survive desiccation. So, that means they can dry out, they can lose essentially all their water, and that sounds like a pretty bad  thing to happen which it would be for us, we'd die pretty quickly if we started drying out. But there are some creatures that can do this. They can lose all their water and survive and then you just add water again and they  come back to life and carry on as though nothing had happened.

Chris - What are they?

Alan - A wide range  of things - lots of microorganisms, lots of bacteria , yeast for example, which you might see a little bit later on or perhaps....

Ginny - Yeah, in fact, let's get it setup now. So, we're going to show you how you can bring some animals, some creatures back to life. So, we've gotten these little pots, just some normal fast-acting bread yeast and a little bit of sugar to give them some food. What we're going to do is we're going to add some water to them, rehydrate it, and we've got them in film canisters. Now, young people amongst you might not recognise these. They're remarkably hard to get a hold of these days,  now, everyone has digital cameras. This is what you use to get film in and they're very useful for science experiments.

Dave - So, I'm just filling them up with water nicely. I'm going to put the lids on and then we will leave them for a bit. See if we can reanimate that yeast.

Ginny - So, we've given them some nice warm water and we're going to put them in the bath of warm water. Do you want to put the bowl on the front just so no one can miss it if something exciting happens?

Chris- I'm glad it's in front of Alan. So, these creatures that can do this, why have they evolved to dry out?

Alan - Well, it's part of the natural environment. If you think about a yeast living on a surface of some fruit, then they're going to experience drying conditions. It's quite hot in the sun, the wind blows around them and takes all the water away. So, they need to be able to cope with this low level of water and survive.

Chris- So, when something does dry up, what actually happens to the organisms when their cells lose all their water?

Alan - Well, we need water to have any biology at all. So, they basically shut down.  They go into a state to suspend the animation. It's as though they - they even stop ageing. So, animals will do this and they have a natural lifetime and when you dry them, that stops and they stop ageing at that point. When you rehydrate them, they will continue ageing and then they will live out what's left with their natural lifespan after that point.

Chris - So, what is the relevance of these creatures to space?

Alan - Good question. The point is that there's not much water in space. So, if you were thinking about organisms moving from one place in the solar system to another, from Earth to Mars, or the other way around perhaps, an organism like a yeast is not going to build itself a spaceship. So, it needs to be able to survive that journey without the presence of water. So, if it can survive drying, there is a good chance it'll be able to survive the journey through space because the other thing that happens when you have this drying process, when you get this sort of shutdown of all the biology in the organism, is they become very resistant to stresses. So, a dried yeast for example is able to survive vacuum as in space. It's able to survive very, very low temperatures even close to absolute zero which you'd  find space. So, that's exactly what you would like the organism to be able to do to become very stress resistant.

Chris - A lot of radiation in space though, doesn't it?

Alan - Yes, that's the problem. So, you need to be able to shield the organism from radiation, but that may be possible.

Chris - Dare I ask, has anyone actually tried seeing if there are organisms capable of surviving in space?

Alan - Yes, indeed. So, people have sent up various organisms. For example, bacterial spores and some dried little animals of the type that that we work on, water bears and rotifers and things and you can put them on satellites or the   International Space Station and have them exposed to space conditions. There have been bacterial spores going around the Earth for several years and yet, surviving that process. So, they can survive.

Chris - So, it's like C. diff can survive in the hospital and these things can even survive in orbit. So, when NASA and other agencies, say, they take steps to make sure that what they put into space and sent to Mars doesn't pose a microbiological threat - in other words, they go to enormous lengths to clean satellites and other objects off, then that's reasonable practice.

Alan - Yes, if you don't want to contaminate the environment that you're visiting, it's a good idea to do that.

Chris -   Ginny...

Ginny - So, I've got a question here. Alan Scott who actually got in touch on Facebook and he asked, "Could we engineer DNA to send to a planet if we found one with the right conditions? Would it survive and could it then seed life?"

Alan - So, yeah. If you take the right steps to protect the DNA from radiation as we just heard, you could in fact get DNA from one place to another.


Chris - I think out experiment just worked

Alan - It didn't quite launched into space, but it's...

Chris - Now, it looks like Alan has thrown up on the table in front of him. Ginny, what's going on?

Ginny - So, what happened...


Chris - There's the other one.

Ginny - I'm just going to pass some tissues to our guests so they can tidy up if they need to. So, what happened there? Well, our yeast was coming back to life. Once it had the water in there and had some sugar, it could rehydrate. It could start to grow again. What yeast does when it grows is it produces a gas. So, it's produced carbon dioxide that's built up in this little film canister and then film canisters are pretty good. They can keep quite high pressure, but at some point, they can't hold it in anymore. The lid popped off and we got a nice big explosion.

Dave - A fountain of yeasty broth.

Chris - So, there's one theory Alan that says, that life got started here on Earth because something delivered life to Earth. Do you believe in that?

Alan -  It could've happened. People talk about the life on Earth arriving too early in a way. It may be as much as only 500 million years after the Earth was formed and some people think that's too early. So, how could that have happened? Well, we might got a helping hand by life being seeded from elsewhere, perhaps from Mars.

Chris - Is there any evidence that things could get into rocks and things and then survive being blasted off of  the surface of one planet across space and then land on another and not get destroyed?

Alan - Not quite that, but people have done experiments with bacteria which have been buried inside rocks and they've tried to mimic what would happen if you had a meteor impact and blasted that rock into space. People have shown that the bacteria that they've used survived that process. So, possibly, yes.

Chris - Anyone got any questions?

Jeff - I'm Jeff also from Cambridge. What's the largest size of creature that can survive being dried and brought back to life again?

Alan - There's a creature called polypedilum vanderplanki which is basically...

Chris - Easy for you to say.

Alan - Well, it's not a very attractive organism in a sense, it's just a midge,  just very boring, but it's interesting. It comes from Africa and its larval stage is able to survive desiccation.  The larvae are quite big. They're about ½ cm in length, something like that and that's the largest one I know of that can survive desiccation. The problem is, once you get larger and larger, there's a physical stresses on something as it dries out. It gets really sort of brittle and crumbly. So, if you tried to do that with say, a human being, we just wouldn't survive physical stresses of drying. We'd just crumble.

Chris - Dave and Ginny have got an experiment coming up......

Carl - Hello. I'm Carl. I'm also from Cambridge. You say that water is necessary for life, but isn't that just life as we know it? Could there be different life in space that doesn't depend on water?

Alan - Absolutely, yeah, I mean, everything we say is from a sample of one, right? All we know about is life on this planet. And so, who knows? There could be other types of life out there.

Ginny - I've got a question in from John Michael Williams who wants to know whether the very high levels of iron on Mars might prevent life there.

Alan - Just looking at what happens on Earth again which is the only example we have, there are lots of organisms that can survive and grow in fact in the presence of elements - lots of iron and other types of heavy elements. They've evolve ways to live with that. So, in principle, no, that's not a problem.

David - David from Cambridge. When I was at school, we were taught that all life derived its energy ultimately from the sun and life wouldn't be possible without that. We've since discovered sulphur-eating bacteria in under sea vents; has this changed our opinion on the chances of finding life in other places in the solar system and beyond?

Alan - Yes, I think it has in the sense that people think about Mars as our closest neighbour and we're interested in the idea of life on Mars because we think there was water on the surface, water on the planet at some point in its history. And therefore, life may have evolved on Mars during its early life. The question is, what happened to it? Well, it's possible that the life, if it did evolve on Mars is still there, but surviving not on the surface, but underground. So, we know that if you look at the Earth again, we can see bacteria which survive, grow, live quite happily several kilometres under the surface of the Earth. So, they live within the rocks and there's enough water there for them to survive and get by, it's a bit warmer down there. Actually, the temperature that it gets very hot as you go towards the centre of the Earth is a limiting factor of how far bacteria can survive down there. So, if you think about Mars then maybe it also gets a little bit warmer as you get towards core. So, there may be liquid water underground. And so, if life did evolve on Mars, there's no reason why it shouldn't still be there, but not on the surface where we're looking for it, but maybe some distance underground.

Chris - Is it possible then that we'll be able to work out how to put humans into a suspended animation state, a bit like they do in sci-fi films, so you can go on long space journeys so that we can head off to Mars or wherever else we want to go?

Alan - Well, not by drying them. That's not going to work. We're actually trying to do that with human cells actually, so you could dry a human cell which you can grow in laboratory but not a whole human being. Maybe you could use freezing instead.  That's probably the best way to go.

Chris - Especially in this weather. Any other questions from you guys?

Helen - Hi. Helen from Cambridge. What's the longest period of time that anything has been desiccated and then successfully reanimated that you know of?

Alan - It depends on the organism. So, if you're thinking about these little animals that we work with which are tiny little invertebrates, anything from 10 to 100 years. But those are only the well-documented examples because you're relying on having museum specimens and so on that you know the age of and that you can look at carefully. There is evidence that some microorganisms, some bacteria may be able to survive for much longer periods. Some people claim even 200 million years which I think that's not really well substantiated. But we're talking about long periods of time, certainly enough time we think to transit between planets in the solar system.

Robin - Hi. I'm Robin from Cambridge. I just have a question with desiccation. Is there any change in the organism in that time when they are kind of shutdown or do you just come back exactly as you were?

Alan - We think that the organism is basically unchanged. For biochemistry to happen which is how things break down, degrade, how you get older, you need water. So, if you take all that water away, those biochemical processes, including ageing and other processes can not take place.

Melanie - Hi. I'm Melanie from Cambridge. All the kind of things you've talked about so far for going between planets, it's kind of just suspended. Do you think there's any chance that you could have life which actively lives not attached to a planet?

Alan - As far as we know it, and we had a question about other forms of life, but the form of life that we know requires liquid water. So, you'd need to have a situation where you could guarantee liquid water. And the temperatures that you find in space are way too low for that to happen. So, you would need a protected environment like a spaceship in order for life to survive in space.

Chris - What about a planet that doesn't have a star and just goes wandering through space because we've found some of those now? I mean, Didier Queloz in the recent month, we've heard a report another one being found of just a planet with no star. It's just wandering through space.

Didier - I mean, we don't know exactly how much they are, all these planets, but clearly, in the mechanism to produce the planetary systems in some cases, we can be unlucky and because of the big interactions between planets, you may have a change in the orbit and some of them can just be thrown away into space. So, there must be such a planet going around that is very cold, extremely cold. That's why we don't see them because they're so cold that they do not emit anything.

Chris - Any other questions from you guys? There's one just at the back over here...

Carlo - Good evening. It's Carlo from Cambridge. I would like to ask, how gravity may affect living forms or is there a gravity range where we believe life can develop?

Alan - People have put living creatures into space in a spaceship - humans of course, but also, other creatures and there are some processes which may be slightly affected so development of the organism from an egg to a fully grown organism might be affected somewhat. But basically, most of the things seem to happen okay. If you were a bacterium, you're probably not going to notice too much that you're in a microgravity environment.

Dave - I guess, the bigger you are, the more gravity affects you. So, the narrower range of gravities which you function on. So, if you're an elephant and you went to some planet twice as big as Earth then you'd have trouble.

Alan - Well, you'd have to adapt to microgravity I think which is the question. And so, if you're an organism which has evolved to live on a planet with significant gravity, you're going to find it quite difficult. Astronauts that go into space have problems with their bone density and muscle tone and so on. So, yeah it would prove quite challenging I think.

Chris - A weighty question. Anything else from you guys?

Brian - I'm Brian from Cambridge. When we send an astronaut up into space they have a closed environment for maintaining water in, is that 100 percent? Is there a limit to how long you can send an astronauts into space, preserving the water they've got or do you need to send up a water supply to keep them going?

Alan - Gosh what a great question. So, I imagine, you could do this for quite a long time, people are talking about very long missions indeed, missions to other stars and things. To do that, you would have to be able to recycle your water and maybe yes, even regenerate it to some extent.

Sam - I'm Sam from St. Ives. If there was a planet with an atmosphere with gravity, if the planet moved, would the atmosphere move with it or would it stay in a cloud?

Chris - That's one for you Didier.

Didier - Actually, because the gravity, the atmosphere, it's a bit like Earth. It's a bit difficult to get out of these planets. We need a rocket to get out of the planet. So, the atmosphere is kind of glued by the gravity to the planet as well. It's exactly the same. The only part of the atmosphere that can get away if you have a very light molecules and some of them maybe hydrogen or maybe helium which is used for balloon and then just this one can just escape in some conditions. But most of the gas, they're just trapped like us to the planet.

Alan - Can I just ask a question, Didier?

Didier - Are you allowed to do that?

Alan - This is the only chance I'm going to get to ask this question. So, gas is escaping from the planet, right? So, why doesn't our atmosphere just all disappear into space?

Didier - It's a matter of two actions. One of them is called gravity. So, if you get the planet light, not strong enough, we don't have gravity then we're going to lose the atmosphere. It's a bit like what happened with Mars which is a very small planet compared to the Earth. And then the other situation when you can get trapped is you're too close to the sun, but then there is interaction in the upper atmosphere between what's called the solar wind. Because there is interaction, the sun is producing particles and not only radiation but also particles and then you interact.

It's like blowing wind that slowly kind of grind and blow out the atmosphere. If the atmosphere is very thick but the planet is very close, if you get enough time, it can completely peel off the atmosphere and we do believe that we have known some very wierd, you may have heard of a planet, rocky planet made of lava orbiting the star in one day. So, they're so close. I mean, they can almost touch the stars and we do believe that these planets must've been bigger and kind of have lost their atmosphere because of the impact of the sun.

Chris - Lovely! Any more questions?

Victoria - Hello. It's Victoria from Cambridge. If we're talking about exophiles and changes in pressure, if we took some of the bacteria and the creatures that are living in hydrothermal vents deep under the sea, and we brought them back up to the surface, would they survive or would the change in pressure be too great?

Alan - That is a problem. These so-called barophiles, these organisms which like living at high pressures.

Chris - Like in our lab.

Alan - A different kind of pressure. Yeah, if you try to bring them up to the surface where the pressures are what for us are normal, that for them of course, it's not normal. So, you could think about these so-called extremophiles living in these crazy extreme conditions. But of course to them, living there, those are the normal conditions. And what we live in is an extreme environment to them. That's why it's difficult to work on those organisms because you have to try to replicate the conditions that they would normally live to be able to study them.


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