The Infinite Monkey Cage - Microbes: Secret Rulers of the World?

Episode Date: January 7, 2019

Microbes: Secret Rulers of the World?Brian Cox and Robin Ince return for a new series of the hugely popular, award-winning science/comedy show. This week they are joined by comedian Ed Byrne, oceanographer Dr Jon Copley and planetary scientist Prof Monica Grady to ask whether the real master-race on planet Earth is not human but microbe. They'll be looking at how microbes are found in every extreme environment on the planet, how and when they first arrived on the Earth and why the hunt is on to find evidence of microbes in space.

In our new podcast, Nature Answers, rural stories from a changing planet, we are traveling with you to Uganda and Ghana to meet the people on the front lines of climate change. We will share stories of how they are thriving using lessons learned from nature. And good news, it is working. Learn more by listening to Nature Answers wherever you get your podcasts. This is the first radio ad you can smell. The new Cinnabon pull apart only at Wendy's. It's ooey gooey and just five bucks with a small coffee all day long. Taxes extra at participating Wendy's until May 5th. Terms and conditions apply. BBC Sounds. Music, radio, podcasts.

Welcome to the first Monkey Cage of 2019. This is a very special year for lovers of science and lovers of conspiracy theories. Or is it? Something for everyone who enjoys an entirely pointless Twitter spat. 50 years ago, human beings walked on the moon, or did they? And 50 years ago, the US Air Force closed Operation Blue Book, the investigation into unidentified flying objects, concluding there was no evidence of extraterrestrial life or technology, entirely ignoring the fact that the moon is a spaceship. Where did you read that? I actually learned that from an excellent book called our mysterious

spaceship moon which is 35 pounds on ebay so at that price it must be correct did you see that clip on youtube where buzz aldrin met that moon hoaxer no what do you mean i mean that i'm going to demonstrate the conservation of momentum to you there we go and that is how a physicist threatens you with a punch. Yes, this is, although Robin doesn't think so, a science show. Yes, this is a science show. We have no listeners who believe that multicellular organisms capable

of building a spacecraft have visited Earth. Or if we do, they can write in afterwards and complain to our usual complaint address, which is monkeys at slash dev slash null. That's a Unix joke. Because the Unix operating system was also invented in 1969 at Bell Labs in the United States.

However, we do have a panel who believe it's possible for a unicellular alien to exist beyond Earth, but within our solar system, because today's episode of Monkey Cage is about microbes, masters of Earth and, quite possibly, masters of the universe, though I would imagine Hasbro would have made a lot less money if He-Man had been a microbe doll. So, with us to discuss the wonder of unicellular life,

we have a distinguished panel of half-human, half-microbes, and they are... I'm John Copley. I'm Associate Professor of Ocean Exploration at the University of Southampton. And I think the next place we're going to find exciting microbes is in the hitherto unimagined organ of an undiscovered deep-sea animal, where they'll be enabling that animal to do something incredible. Beat that.

I'm Monica Grady. I'm Professor of Planetary and Space Sciences at The Open University. And to be honest, some microbe in some animal at the bottom of the ocean just leaves me, well, you know, not excited at all. I know where the smart money is. The smart money is on microbes on Mars.

And I'll tell you something else. She-woman rather than he-man. Microbes as mistresses. I think that's what we should look for. My name is Ed Byrne. I'm a stand-up comedian, except when I'm on shows like this, when I'm a sit-down comedian. I believe that the next place where the new exciting microbe will be found will be in the sinus cavity of one of my two sons, because that is where every microbe known to man has managed to find itself over this whole winter. It'll just be there, something new, something exciting

that will form another way to form a different virulent strain of snot. And this is our panel. I've got to admit, I think Ed is right. There is something incredible. It's only when you're a parent you really realise how many different varieties of snot there are. And just the glueyness. I had no idea when we had children

just what an open door to the world diseases I was letting into my house. They are just vectors in cute faces. They're just... I used to know things. I used to know who the new hot young comedians were. I even used to know who does some hot new music.

Now I know what ear infection is going round. Oh yes, I hear that's a nasty one. That's where I am now. Anyway, I really shouldn't have started by talking about this, so we've gone downhill very, very quickly. I take all responsibility. It was me who started it, really. But really, who's to blame? Other microbes. Well, and the presenter of the programme. And science itself, Brian. Monica, we like definitions, so can we start with the definition what do we mean by microbe well

we mean something very small microscopic in size we generally mean something that's only got one cell so unicellular it's got all the bits in it that it needs to to, to grow, to reproduce, to take in nutrition. The sort of classic ones are things like an amoeba. You get unicellular plants, unicellular animals, and that's what microbes are, small things. And John, you were actually the person who suggested the title of the show, you know, Rulers of the World. So why, you know, these things which are

so small, these unicellular organisms, how do they rule the world? Well, microbes have had the planet themselves for an awfully long time before Johnny-come-lately life forms like us appeared. So microbes probably appeared maybe around about 4 billion years ago in the 4.6 billion year history of our world. And animals probably appeared about only 570, I think a recent paper said maybe 588 million years ago. So for an awfully long time, microbes had the place to themselves. They're the great engineers of the life support system that we all depend on. And not just creating it, but also maintaining it over those billions of years. And they influence everything from potentially maybe even our our health and behavior and they have also influenced

human history over time as well so why is it that you know that's a very long period of time for just evolution to go this is fine this unicellular that's fine what do we know what events it takes for evolution to then take things off to such a variety of different forms of shapes and organisms multicellular organisms there are a lot of building blocks that have to be in place before you can get kind of complex multicellular life like us there's a lot of different metabolic pathways the atmosphere is very different from what it was in the early history of the Earth. An awful lot needed to happen before you could get anything like us.

So is the leap from nothing to microbe as big as the leap from microbe to multicellular? Ooh. Ooh. You know, really good question, Ed. Really good question. I didn't realise how profound I was being. Genuinely just curious. I mean, from my perspective, you start off with your building blocks, your atoms, your molecules, carbon dioxide, water, whatever,

and then they make more complex molecules, and then somehow those complex molecules become an organism, and they've bound themselves they have a membrane to separate themselves from everywhere else and they can reproduce and pass information on forwards so those two two things having a membrane and translating information are really really big things so for my money to go from building blocks to microbes is a much, much bigger step than going from microbes to humans. I think Hal Dane said, didn't he, that that's the mystery. The mystery is in going from an atom to a cell.

Once you've done that, then you can kind of understand the rest. But which raises an interesting question, actually, about why we only expect to find microbes somewhere like Mars, given that, as you say, in your opinion, the real difficulty is from going from geology to biochemistry in the first place. Well, I mean, one of the main things that we know about life on Earth is that it needs water. And so we take that as a given. If we're going to find life anywhere, we're going to need something that deals with water. And there are places in the solar system where there is water or has been water. Mars is one of them. Some of the satellites of

the giant planets are other ones. However, water isn't unique. Well, no, that's not true. Water is unique. But it's a liquid. It acts as a solvent. And that's all life needs. It needs something to be able to transfer nutrients and gases and to hold a body rigid. Any old solvent would do. But water happens to be liquid over a range of temperature of 100 degrees.

It can dissolve a whole lot of stuff there's no other solvent can do that so we say right okay you need water for life so let's look for water john many many biologists would say that because as you said life began on earth pretty much as soon as it could so perhaps for 3.84 billion years ago um that that's an easier step perhaps than going through the eukaryotic cell and onwards to multicellular life and what's your view of the the the well the question is do you think it may be inevitable given the right conditions as monica said with water and perhaps geological activity that life becomes essentially inevitable there's a suggestion that maybe with the right ingredients in place it it is in some way

inevitable it may be some consequence of the physical chemistry of of some of the transition metals that are involved in catalyzing various reactions and so on and once you've got everything in place i mean it did appear to happen as you mentioned quite quickly in the early history of the earth and yet it is in terms of complexity it, it is the big leap from nothing to microbe, really is a big step. And then since then, I mean, what excites me about the microbes here on Earth is their ubiquity. So we find them everywhere from 20 miles, 32 kilometers up in the stratosphere. They can survive those conditions before they come back down to Earth. You know, where it's cold, it's dry, they're not protected very much from radiation

from space. It's very much like the conditions on Mars. And yet we can find them in these things called lignite deposits, which is a sort of fossilized peat. And that occurs in some places two and a half kilometers below the ocean floor. and there are microbes living there as well. So now they are everywhere, and they're thriving in so many different ways. They're like the Brian Cox of life. You're everywhere, man. You're ubiquitous. In certain circles. When we talk about microbial life,

as we kind of alluded to in the introduction though as well the idea of that there's microbes and there's us and then actually we were saying so 50 is that right that we are how much of of us is microbial life and how true is that of most or even all living things so yes it we we used to think that it was about we were outnumbered in terms of cells sort of 10 to 1 by microbes but more recent workers said no it's about it is about one to one uh so yeah i mean plants live in partnership with microbes animals live in partnership with microbes so when we say we're half micro but we're not i mean that's not we're all human aren't we but it

requires being how does it divide up and what if i accidentally flush out all my microbes what's going to happen then so yes why when jeff goldblum got into the teleporter why did he only fuse with the fly why wasn't he genetically absorbed by the microbes and just a big half human half microbe. Or a fungus. But it wouldn't have been as much fun, would it? I suppose it would have been a mushroom. LAUGHTER It would have been a different show. It would have been a very, very different film. And you couldn't see what had happened to all the microbes when you went into the transporter,

because they might also have become half of a fly microbe as well as half of a human microbe. There was a whole other story happening, a million other stories happening at the same time. I think that that film about a man and a fly being transported in a mass transporter may have had scientific flaws. Yeah.

And this is... LAUGHTER That line, I think I was a fly who dreamt he was a man, is very different, isn't it, where I think I was a mushroom who dreamt he was a man. It's very different, isn't it, where I think I was a mushroom who dreamt he was a man. It just doesn't have the same melodramatic impact, does it?

But you can't be a fly microbe, can you? Because fly cells are eukaryotic. So you couldn't be a prokaryotic fly, could you? Well, you could be a microbe that lives on a fly. But are they different to the microbe? So here's the thing. So we've got microbes living on us and inside us, but not directly inside our cells,

although in a sense we have. Because inside our cells, we have these things called mitochondria, which are the powerhouse of our cells, and they are probably the ghosts of something called alpha proteobacteria. Back about 2.5 billion years ago, an alpha proteobacterium got together with an archaean

and formed some kind of new kind of cell. And so these structures inside us, these mitochondria, they really look like proteobacteria, and that's probably their origin. So I think Lynn Margulis was one of the great champions of this idea of this sort of symbiotic relationship developing more complex life. And she said, you know, the world wasn't conquered by combat. It was conquered by networking.

I just love the fact that you use the word ghost as well. It's like people weren't disturbed enough by how much of their bodies are actually diseases, essentially. I mean, really, I don't. But also parts of our own cells were essentially haunted but it's startling how they do look like uh like these things uh so the first time i ever did something called transmission electron microscopy which is a way of looking inside cells we all remember the first time you never want to get your first time but it's an incredibly fiddly thing you have to take this little bit of tissue

and you have to kind of shave these very very fine sort of slices off of it to then put under the microscope and it is like planing a piece of wood under a microscope to try and get a lovely ribbon of wood off of it and you're swearing all the time because they're breaking or they're too thick or whatever eventually you get one after

hours you've dulled your diamond knife and you've got to pay another five thousand pounds to get a new one eventually you get one you stick it in the microscope and and suddenly it becomes this incredibly large landscape when you switch on the electron beam and you you can look at this thing in in great detail and you start to explore it and apparently what all the rookies do and i did this myself first time out is you find a cell you find a mitochondrion and you go oh my god it looks like the textbook and you zoom in on it at 80 000 times magnification and take a picture of it even if it's not what you're interested in so you remember you mentioned lynn margolis there so the the theory is that the the origin of our cells the complex cell with the nucleus and the mitochondria and so on,

was this event where a bacterium got inside something else, an archaean, you think? Possibly, possibly. There may have had to be a little bit of preparation. It may have to have sort of, you know, protected its own genetic material with some sort of nuclear membrane before another prokaryote came along,

but it's a possibility. Because I find that... Some sort of nuclear membrane before another prokaryote came along but uh it's possibility because i find that some sort of dating then i mean i find it a remarkable thought because this is perhaps the most widely accepted theory isn't it for the origin of multicellular life that it was a merger of two microbes at some point and is it suggestion it's almost a single it's called a fateful encounter, isn't it? It's almost a single event. A single event. And there could have been definite advantages from doing this. So one of the things that happened in the early history of the Earth

was, to start with, there was no oxygen in the atmosphere. And then eventually, a form of photosynthesis that produces oxygen arose, and oxygen started to trickle into the atmosphere. But it's really toxic to all the life that was around then and then respiration which is the way of taking a food molecule and breaking it down in lots more steps than fermentation which is the other way of breaking down a food molecule you get more energy out of it and it produces simpler waste products

carbon dioxide easier to handle than alcohols and acids um oxygen you know that uses oxygen at the end of it and that's great because you take something that's a problem and then life finds a use for it and so bringing in something that does that inside a cell that helps to control this toxic oxygen that life's you know now challenged with that's that's you know gradually trickling into and building up in the environment it amazes me though and when i when i first read about this that that really this story is that a single event in some ocean presumably somewhere two and a half billion years ago ish is is the root of all complex life on earth a single merger between two cells it is a remarkable idea isn't it oh oh but there's a hand up over there. Yes.

I mean, it might only have happened, you know, one merger might have been the successful thing that went on, but it didn't necessarily only happen once. It might have happened several times, many, many times over millennia, and the fusion wasn't successful or didn't go on. So, yeah, there was eventually something evolved. And that's the whole deal with evolution. You have to build something that's going to be able to cope with its environment.

It took a while. It took a while, didn't it? But that every all of life then did still come from the one that caught the single one that caught is still pretty much in that single that idea of everybody able to trace themselves back to genghis khan the last universal common ancestor yeah well here we're talking about the origins of one of those three trunks in the tree of life that the cells that are like ours there's still the other two uh as well and tracing that tree of life back to where those three trunks come together gets really difficult because what we can do today is we can look at all the living things that are like at the end of all the branches of the tree and we can compare their genes and we

can see you know how similar they are genetically and from that we might think we can deduce when they shared common ancestors and start to trace back, you know, the roots towards the roots of the tree. But microbes do some weird stuff that makes that very difficult. So usually we, you know, we assume we get our genetic material from our parents. So for example, if we were to do some genetic tests and Ed, you know, I end up sharing more genes in common with you than say Brian, Then we might deduce that you and I had a common ancestor more recently in our past, in family history, than I did with Brian. But what microbes can do is two microbes that are completely different,

that are not related, can bump into each other and can kind of exchange genetic material between themselves, almost like just by shaking hands. So now it looks like they share genetic material, but it's not come from a common ancestry. It's just because they bumped into each other and they swapped some genetic material between them. So that means, you know, that's what we call horizontal gene transfer instead of vertical heredity. And it means that really confuses things when we try and trace back towards the roots of the tree of life.

Or they can mix their genes without reproducing with each other. Yeah, they can exchange genetic material. So this happens all the time. It happened quite recently, we think, with Clostridium botulinum, which is the nasty microbe that produces a neurotoxin that causes botulism. Well, a new form of botulism has now been detected and completed for a microbe, a microbe, an enterococcus microbe, one of the things that lives in a lot of guts. It turned up in a cow pat in South Carolina. And clearly the gene for this toxin has probably, by this kind of transfer, ended up in this different type of microbe. So they're swapping

these genes around. And it means when we try and trace back down to the base, the roots of the tree of life, a lot of this horizontal gene transfer is taking place. And instead of a tree, it becomes like a big sort of ball of sort of wibbly-wobbly, horizontally transfer-y stuff. Wibbly-wobbly ball. Or a hedge. Let me write that down. Or a hedge. I think you have very clearly shown there why some people would decide to go with theoretical

physics rather than biology. And eventually we found it in a cow pat. We'd had to look in a load of them. But then we all went, hooray! As we threw the cow pat into the air. It was a day of merriment, dance and eventually food poisoning. I do, by the way, I think

you're more closely related to Brian because you've both got great hair. What are you talking about? I think you've both got the great hair gene. I have great hair? You barely have hair. That's what I'm saying. got the great hair, Jean. Great hair? You barely have hair. No, that's what I'm saying. It's great hair. Great hair.

No, great hair. Do you know what? I've never realised... Do you know what? Why don't you pronounce the T? Because otherwise... What I love there is the fact that, you know, every now and again you see the true narcissism of the comedian.

Great hair! I'll never get any of those TV jobs if people listen and think I have grey hair. That's what I thought you said as well. We both thought you said grey hair. Will you have your hair grey so people think you're a human boy? Grey streaks. It's interesting,

when we talk about microbes, it's sort of almost tempting to think of them as primitive organisms, but that would be wrong, wouldn't it? Because they evolve at the same rate as everything else. So can you give us some sense of how diverse and complicated they are? Oh, gosh. They're all around us. And we don't necessarily need a microscope to see what they're up to.

So they do lots of different things and they come in lots of different forms. So, for example, I mentioned the sort of architects of our planet's life support system. One of the things that we need, in addition to building our molecules out of carbon, is we need nitrogen. It's in our proteins, it's in our DNA, it's in our RNA. But a lot of the nitrogen, most of it in the atmosphere, is not in a form that we can use. So we rely on microbes to carry out something called nitrogen fixing to make it available for other life forms. So if you go to a lawn and you find a clover and very carefully take it out of the ground with its roots intact, you might see, if you look closely, little knobbly bits on the roots of the clover. And if you squeeze it,

there'll be this sort of pinkish blood that emerges. And that pink, it's actually a form of haemoglobin produced by bacteria living in these nodules on the roots. And that's to lock up the oxygen to keep it away from the nitrogen fixing that they're doing for the plant. So that's a way you can kind of see microbes doing their thing around you. And then I go out walking my dog in the countryside on some quite peaty ground. And I'll sometimes see these sort of little ponds puddles and there'll be what looks sometimes a little bit like an oil sheen on the surface of the puddles and you think oh that's terrible you know someone spilled some oil here and then you look at it closely you think well hang on it's not quite that rainbow colour it's a bit more sort of just a silvery colour and if you poke it it breaks up into jagged bits not like

an oil slick and it's actually a raft of manganese oxidizing bacteria that are living on the surface of that little puddle so they're all around us and we can learn to see the signs again this is another bit where people listening at home thinking do i want to do theoretical physics or do i want to go to more biological am i a pokey squeezy kind of person or am i a kind of chalky equationy kind of person that's amazing sorry the the nitrogen fixing bacteria that certain plants have but that's where then then the whole basis of crop rotation comes from is that because the fact that you have to every cycle plant something that has the nitrogen fixing bacteria then replenishes the soil which they didn't know that that's what it

was doing it they just knew that they when they when they discovered't know that that's what it was doing it. They just knew that when they discovered crop rotation, that they planted certain plants, that somehow the soil fixed itself. And it's, why does it do it? It is one of those ones you go, the most stodged atheist, you kind of go, why does that do that, though? There must be a plan! No, there isn't. It's evolution.

I know it. You have to then go, no, you're right. But there is a lovely moment when I suddenly saw you as a 13-year-old boy in school being taught crop rotation, thinking, when on earth is this going to be useful? And some decades later, you find yourself on Radio 4 and go, now, thank you very much, Mrs Forbes, for that lesson. I didn't learn about crop rotation until much later in life.

It was the great moment when he found he could use that knowledge, and then he accidentally tries to use it as an argument for the existence of God on a science show. He blew it at the last minute. For the record, I was not trying to argue for the existence of God. I was merely trying to argue for how sometimes you discover

something like that, and you have to actively fight the fact that it makes you think that way. Oh, whenever I'm rotating my crops, that's when I see Odin. Monica, let's move on quickly. Now, in terms of microbial life, trying to find evidence, because that's what I presume at the moment in terms of trying to find life beyond the planet

earth microbial life is the thing which we're focusing on would that be correct yeah that's true I mean what John's been saying about different types of microbes they all live in different sorts of environments so some of them can live in boiling water some of them can live in water that's below freezing point because it's got so much salt dissolved in it some of them can live in water that's below freezing point because it's got so much salt dissolved in it. Some of them can survive huge pressures, living very deep below the surface of the Earth. Some of them can survive very, very high radiation fluxes. So we know microbes are practically indestructible.

We know they formed very early on in Earth's history. And we know that places like Mars were formed from the same ingredients as the Earth. So everything's there. The stage is set for microbes to have evolved on Mars. And there are some arguments that say that, well, hang on a minute. 4.5 billion years ago, when the planets were forming on the Earth, it was boiling hot. It was the surface of the Earth was molten, the atmosphere was made of steam

and very high hydrogen content, and nothing could survive. Okay, yeah, Mars was like that for a bit, but Mars cooled much more quickly. And so it could be that actually life got going on Mars before it got going on Earth. So actually, you know, because of transfer of materials, we know we've got meteorites from Mars,

and we could have had these microbes coming from Mars, hitching a ride on meteorites and seeding the Earth. We have a lot of Jeff Wayne fans listening to this. Since the last time... Do we know what the chances of anything coming from Mars are at the moment? Are they still what they have been before? I think they're about a million to one. They are still a million to one.

That is good to know. That is good to know. Following the statistical discourses written by Terry Pratchett, we know that million to one chances happen nine times out of ten there's an argument isn't there so so there's some eminent scientist man fred hoyle had the idea for a while didn't he it's called panspermia isn't it that's something different panspermia is life coming from uh out there to us okay, beyond the solar system. So panspermia is very specifically beyond the solar system.

And this is what Fred Hoyle used to explain life on Earth. Now, to me, that makes no sense at all, because you've still got the problem of where did life form beyond the solar system? You know, let's keep it simple, and let's have life getting going in the solar system you know let's just you know let's keep it simple and let's have life getting going in the solar system and you know i don't know whether life got going on mars and seeded the earth it's it's something that we hope we'll find out you know in the next 15 or so years when we bring samples directly back from mars that's it's it's not quite panspermia i think let's let's say it's an evolutionary uh offspring of panspermia how I think, let's say, it's an evolutionary offspring of panspermia.

How do we search for microbes? How would we recognise them? So if we drill into some subsurface water deposit, let's say, on Mars, what experiments are we doing? Well, you're going to be looking for signatures. I mean, unless you actually drill a hole on Mars and see some worms, then you're going to have to look for something fossilised, you're going to have to look for something fossilised, you're going to have to look for particular chemical signatures,

combinations of chemical signatures. And, you know, only if we're extremely lucky are we likely to find, you know, something that is a recognisable fossil microbe. And does that assume that the metabolism would be similar to life on earth or if it's radically different would we recognize it? Well again it's difficult enough to recognize fossilized bacteria on earth you know the stuff from the Pilbara was caused huge and still does

cause huge controversy you know are these things are they actually fossilized bacteria or are they simply traces where fluids have flowed through the rock and left left an imprint behind so is that one of the the oldest rock deposits is that what you're referring to it's a very old rock deposit um and the it is in the pilbara isn't it the bill shop stuff yeah there's also uh an even older deposit on greenland uh there was a what people assumed was a stromatolite there um 3.7 billion years old and very recently a paper saying oh hang on a minute you could possibly have produced these structures by a non-living process it's very hard to tell and even some of the chemical signatures that we usually associate

with life aren't there may be some non-living processes that can produce the same kind of signatures so i think nasa have recently come up with something called a ladder of life which is sort of you know different layers of evidence you might hope to build up and it's not supposed to be definitive it's really to stimulate discussion haven't you just like in the last 20 years discovered how many microbes there are in for instance a drop of seawater so you've only just realized in the last 20 years we've been able to detect microbes that are alive in water now. And we're discussing detecting microbes

that have been fossilised from water on Mars that existed millions of years ago. A third of the age of the universe ago. When we're looking at them today, we can identify their dna you know because they are alive you know looking for past traces of life when that's gone when it's just other things left behind yes it's absolutely much harder and and it is really 20 30 years that we've had these tools i mean i i went to sea for the first time on a research expedition 25 years ago

and we were studying hot springs on the ocean floor and we had a microbiologist on board and he'd previously been studying microbes in cows guts and we were at sea springs on the ocean floor and we had a microbiologist on board. And he'd previously been studying microbes in cows' guts and we were at sea for seven weeks and I don't think anything grew on his Petri dishes because these things don't. I think only about 0.1% of microbes in the environment are easy to culture in the laboratory. But now we have molecular probes to identify them.

So, you know, there's a lot going on in the living world, let alone in the past. So, Monica, how do you, if you're looking at a sample, say, an emeter, or whatever it might be, what are the different levels of testing in terms of, because there have been close calls, haven't there? There have been beliefs, oh, it looks like maybe we found microbe, or maybe it's just in the

newspapers, I don't know, in the science world you might be not, but... Well, in 1996, a group of scientists found a structure within a rock that had come from mars and they identified it as a fossilized bacterium that had been found on mars and the evidence they used was that the rock came from mars the mineral grains that it was in were from mars this thing had obviously been in the rock when it was fossilised, and there was carbon associated with it. Now, all those things were true,

but it still doesn't add up to that fossil being coming from Mars. I mean, this rock had spent 13,000 years in Antarctica, and many other meteorites from Antarctica have biological fossils in them, because we know that fossilisation doesn't take long. You know, those of you who've gone throwing things in like Mother Shipton's well in Knaresborough and seen it fossilised, and we know about stalactites in caves, they don't take long to form, so it doesn't take long for something to fossilise.

So it's very difficult. You're going to have to rely on chemical signatures, isotopic signatures, not just shape. You can't rely on shape but it's all in the context of where it's come where it's actually come from i don't know i don't know whether we're just being unduly optimistic that we're going to find this i don't know it's going to be very difficult is it better not to look for microbes and like up the game and look for sea monkeys or something well you know we've got all these infinite monkeys that are kept in a cage and goodness knows whether any of them have ever been to mars

but i think if there was anything higher more evolved on mars like meerkats or something like that um they would have been seen i mean i did try to discuss the possibility that on Mars there are lava caves, okay? So if you think there are huge volcanoes, and when the lava flows down the volcanoes, you can get big tubes of lava, which have then become hollowed out. And so in these caves, they're protected from the radiation on Mars' surface. And we do know there's a mission at Mars at the moment called the Trace Gas Orbiter, which is looking for methane. Now, methane shouldn't be stable because it is destroyed very quickly. But methane is produced by cows and termites.

And I have tried to posit that there are herds of cows in the lava tubes producing methane. But I haven't actually managed to get this into a peer-reviewed publication. You've got to just admit that that's not likely, just for the record. For the record, it's incredibly unlikely it's very very unlikely And there's probably not meerkats either No. They would have tried to sell us car insurance by now if there was

You did mention that this is one of the most tantalising measurements isn't it from the Trace Gas Observatory there's seasonal methane changes on Mars which some people take to be a potential biosignature. Yeah. I mean, one of the things is methane is destroyed very rapidly in the atmosphere because of the radiation, the sun's radiation.

And so something is putting it back there. Now, there are plenty of non-biological processes that will do this in terms of perhaps the impact of an asteroid coming down, heating part of the surface, melting ice and releasing any methane that's been trapped in there from weathering of some of the basalts that are on the surface of Mars. So there are non-biological explanations. But it's such a strange signal. It comes and goes. It doesn't seem... It seems to be... I think I can't remember.

I think there's more of it in the summer rather than there is in the winter. And so it's really interesting. And this is what the Trace Gas Orbiter is going to be looking for. John, what are the most extreme environments that we've detected microbes so the current record for thermo tolerance is uh an archaean that can survive reproduce at 122 degrees c so temperature wise that's pretty impressive so boiling water does not kill yeah this arcane yeah i mean it's living in the deep ocean where water doesn't boil at that temperature,

but there may be similar ones in hot springs or Yellowstone and places like that approaching that as well. I'm just going to... Just about archaea, because we haven't really... Just for completeness, the bacteria and archaea.

So the archaea, they were only recognised, really, a few decades ago. Can you describe just very briefly the difference? Because everyone knows about bacteria, but archaea is a word that many people have never heard of. Well, the difference is to perhaps seem a little bit subtle. There's a difference in what the outer coating of the cell is made of between the bacteria and the archaea. That's probably one of the big differences. There are a few other metabolic differences. And also what the archaea can do.

I think most of the methane-producing microbes that we're familiar with are archaea. So there's definitely differences like that as well. Isn't there some idea that they split very early on in the history of life on Earth? They're almost different forms of life. Potentially. And then we are closer to archaea than we are to the bacteria. And it is down at that messy root of the tree of life where it's hard for us from the ends of these branches

to peer back down there and see what's really going on. So where do viruses sit in these trees? Oh, don't ask. No idea. He said beforehand, don't bring up viruses. Don't ask. Oh sit in these? Oh, don't ask. He said beforehand, don't bring up viruses. Oh, did you? He said he doesn't know anything about them. Oh, right. Okay. Not him personally. What about prions, then? No, we're here to talk about

unicellular life and viruses aren't cells. We can leave them to one side. We can't let you just say that viruses aren't cells. What are they, then? We have a very strict set of rules on this show, and that's one of the things you can't say.

No, but it's intriguing, isn't it? Because actually, just colloquially, you just think, yeah, well, they're a cell. Packages of genetic material. They can't survive by themselves, is that right? Can't reproduce. Can't reproduce. Can't reproduce. They're the hermit crab of the microblog.

Every time I hear Archaea, I just think of a tiny little microbial group of cubs and brownies. Anyway, we've only got time for a couple more questions. One thing is, we kind of talked about this a little bit, but it's still fascinating. We've only got time for a couple more questions. One thing is, we kind of talked about this a little bit, but it's still fascinating. If the microbial content of a human body or other mammalian life form, let's start with that,

was removed, is that even an imaginable situation? So people have done experiments with fruit flies and with mice to look at what happens if we don't have gut microbes, for example. In the case of mice, some researchers in Japan can raise mice without microbes in the guts, and they found that those mice, I think, produced twice as much stress hormone when they were placed in a stressful situation compared with normal mice. So now there is a lot of interest in how our gut microbes do actually influence our physical and even potentially our mental health. And then very recently, there was a study on fruit flies

by a team led by someone at the California Institute of Technology and they found that fruit flies lacking a particular bacterium in their microbiome were hyperactive. They raced about, walking about, about 50% faster than fruit flies usually do and it's a particular enzyme produced by one particular strain of bacteria that kind of puts the brakes on that hyperactive behaviour. Ed, how do you feel now you've found out you're 50% microbe? At the end of this show, how are you...

I have to say that my... Listening to the fascinating discussion that I have been listening to, I feel like my 50% microbial content is really the only thing that earns me my place at this table. I feel like that's the only thing I go, well, I feel like I should be here, for I am part microbe. Yeah, 50% apparently. Representing the microbes.

Yes. So, I just wanted to ask, Monica, we've talked about Mars. Just very briefly, across the solar system where are the other places that we think we may find life well europa is a literally a hot favorite john has referred um already to the hydrothermal vents on the base of the ocean floor that he has explored and it could be that on the base of the ocean floor on europa there are these hydrothermal vents where there are a whole load of microbes surviving and fauna not flora because there's no light light there so they don't photosynthesize so europa is one place

and saladus is another place it seems to have streams of vapor coming from it. But anywhere that these beasts can get away from radiation, any little niche where they can find the nutrients they require, I think microbes will be able to survive. So, for instance, on the moon, which we used to think was completely dry and lifeless, we know there is quite a lot of ice in some of the craters in the moon. Same on Mercury. Even though it's so close to the sun,

there are parts of Mercury that don't ever receive the sun's rays, which are really, really cold. And, you know, there are these cold spots, and so things might exist in the ice. So I think almost anywhere, I reckon, like if you dig a shovel in the earth, almost anywhere on earth, even in really arid places like the Atacama, you find things, and I bet the solar system's like that.

So in this picture of the solar system with material being transferred around it, so almost microbes, you can't imagine microbes raining down on pretty much everything in the solar system with material being transferred around it so almost microbes you can't imagine microbes raining down on pretty much everything in the solar system and irrespective of where that where they originated you could imagine perhaps them surviving in these places we could live in a living solar system yeah i mean it does it does make us think that perhaps we are a spaceship on our way to somewhere else. Does it make me think that? That could have been such a poetic end to the show. Oh, no.

Bearing in mind the fact that microbes were around for billions of years before we came along, and the fact that we are 50% microbe, is it not possible that we are merely, this is just life finding away, and that we are merely conveyances for microbes. That we are nothing more than vessels for microbes to communicate themselves better throughout the galaxy. The microbes are just waiting for us to perfect space travel so they can move on to another planet. So they are indeed, then, the masters of the universe.

They are. We are just their vessels. You've actually described one of the biggest revelations in modern biology. Man, I keep getting on these things. It's this idea that organisms are actually a partnership between multicellular life form, animal or plant, and microbes. That's essential to their survival. This is actually how they've evolved. They've evolved together in this kind of tandem, tangoo like dance uh you know when conditions change your animal your plant

doesn't necessarily have to evolve new adaptations through genetic changes it might be able to swap for a different microbial partner that can help it cope with new conditions but in return we are the vessels for those microbes or as those higher life or more complex life forms so it's very much how we're looking at and then where's the organism you know and this is what you were saying robin where where do we stop where do the microbes begin what i love now is that you've moved on so much that next year someone go you're going to british comedy awards tonight ed nah and clashes with the nobel prize and i'm up for one of those as well so i can't go sorry um nobody's ever asked me if i'm going to the British Company of Works We've also asked the audience a question as usual and this week we asked them

what's the smallest thing that makes you scared? Mine says Robin Ince The smallest thing that makes you scared Brian Cox's brain cell That wasn't designed to make him feel good Somebody here has written Michael Gove And they've actually signed us

Right Honourable Theresa May MP A plank A plank With a C and a K at the end A plank length Somebody's written for the smallest thing that makes you scared, my wife's moral compass. By the way, where it says name, they've just written,

I'd rather not say. Somebody who knows what side their bread is buttered on. Carrying on the light-hearted theme, my lifespan in relation to the entire history of time. And at this point, we move into the Beckett part of the evening. Well, that makes Pat Daly's answer quite boring in comparison, which is simply, moths, eggs. I'm not scared of moths the eggs

that's what really gets me well because they're the ones that you know those are always those urban myths you hear about yeah and he wouldn't get his hair cut or anything and anyway

it ended up he had moth's eggs inside it and they all hatched and came out of his eyes anyway so I love those stories who's that an impression of? oh just like someone

who's really into different like stories about you know and they just said don't look back at the cards don't look back at the car, don't look back at the car, and she looked back and there was a bloke who pulled someone's head off. He was banging it on the roof, wasn't he? And the babysitter turned out that the murderer was inside

the house, wasn't he? And the Sony Award for Best Non-Specific Impression. Next week, oh, by the way, thank you very much to our fantastic panel, who are John Copley, Monica Grady and Ed Byrne, who I would like to say has very beautiful, luxuriant brunette hair. Thank you.

Next week, we're looking at the future of humanity and whether it's worth bothering with. Should we just stop now and give it to another species? I think it's time the octopus had a go, to be quite honest. What is our greatest threat? Is it climate change, artificial intelligence or whatever lives in a mysterious spaceship moon? Conservation of momentum is the biggest risk to you.

He wants a fight. Good night. In the infinite monkey cage. Turned out nice again. Before you go, let me just squeeze in here and tell you about the Flip podcast from BBC Radio 4. Each month, there's a new book set to listen to from people like Rhys James, May Martin and Joe Lycett. Subscribe to the Flip podcast on BBC Sounds.

In our new podcast, Nature Answers, rural stories from a changing planet, we are travelling with you to Uganda and Ghana to meet the people on the front lines of climate change. We will share stories of how they are thriving using lessons learned from nature. And good news, it is working. Learn more by listening to Nature Answers wherever you get your podcasts.